Novel Vanadium supported onto mixed Molybdenum-Titanium Pillared Clay catalysts for the low temperature SCR-NO by NH3 Chem. Eng. J. (IF 6.735) Pub Date : 2017-02-10 Jihene Arfaoui, Abdelhamid Ghorbel, Carolina Petitto, Gerard Delahay
Adsorption and desorption of U(VI) on different-size graphene oxide Chem. Eng. J. (IF 6.735) Pub Date : 2018-04-09 Xia Liu, Ju Sun, Xuetao Xu, Ahmed Alsaedi, Tasawar Hayat, Jiaxing Li
Remediation of hydrocarbon–heavy metal co-contaminated soil by electrokinetics combined with biostimulation Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-20 Yongsong Ma, Xi Li, Hongmin Mao, Bing Wang, Peijie Wang
Successful remediation of organics and heavy metals compound pollution is challenging, and their removal using conventional techniques is often difficult. This study developed an enhanced electrokinetics technology to decontaminate a hydrocarbon–heavy metal co-contaminated soil by applying biostimulation and selective membranes (cationic and anionic). A 30-day experiment was conducted in the laboratory to remediate the soil co-contaminated with total petroleum hydrocarbon (TPH) (9075 mg/kg) and Ni (446.6 mg/kg). The results demonstrated that the addition of anion- and cation-exchange membranes maintained soil pH stability. BioEK remediation under pH control improved microbial growth, microbial degradation of petroleum and reduced biological toxicity. Microbial action immobilized metals (e.g., reduction in exchangeable Ni and the increase in residual Ni). The degradation rate of TPH in contaminated soil was linearly correlated with the increase in TPH degradation population (P<0.05). Under the optimum operating conditions, electro-bioremediation achieved 77.4% TPH degradation and 58.5% Ni removal after 30 days. Thus, the application of EK with the use of anion- and cation-exchange membranes improved microbial growth and biodegradation, and indigenous bacteria could effectively reduce metal toxicity. The proposed technique can effectively remediate the soil contaminated by heavy metal and organic pollutants.
An efficient high-throughput grafting procedure for enhancing carbon fiber-to-matrix interactions in composites Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-20 Daniel J. Eyckens, Filip Stojcevski, Andreas J. Hendlmeier, Chantelle L. Arnold, James D. Randall, Magenta D. Perus, Linden Servinis, Thomas R. Gengenbach, Baris Demir, Tiffany R. Walsh, Luke C. Henderson
It is widely acknowledged that the integrity of the fiber-to-matrix interface inherent to carbon fiber reinforced composites has scope for improvement. One promising and highly-researched strategy is the use of surface manipulation of carbon fibers to enhance their mechanical performance under shear. The complexity of commonly used surface treatments, such as plasma and oxidative etching, require modification of existing manufacturing infrastructure and thus their broad adoption in a manufacturing context has been limited. Herein we show that simply impregnating the carbon fibers with aryl diazonium salts and subjecting them to external stimuli, such as mild heating (100 °C), can induce surface modification which can deliver improvements of up to 150% in interfacial shear strength (IFSS) in epoxy resins. Interrogation of the fiber-to-matrix interface using molecular dynamics simulations suggests that the surface grafted molecules imparts a ‘dragging effect’ though the polymer phase and that the surface concentration of these compounds is critical to enhancing IFSS. This process obviates the practical limitations of current functionalization procedures for carbon fibers and requires infrastructure that is already routinely available on fiber manufacturing lines.
Chlorpyrifos and 3,5,6-trichloro-2-pyridinol degradation in zero valent iron coupled anaerobic system: performances and mechanisms Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-20 Fei Zhang, Jun Hou, Lingzhan Miao, Juan Chen, Yi Xu, Guoxiang You, Songqi Liu, Jingjie Ma
Pesticide contaminants, such as chlorpyrifos (CP) and its more toxic metabolite 3,5,6-trichloro-2-pyridinol (TCP) in farmland drainage have attracted extensive concerns around the world, and are in urgent need of treatment. In this work, three groups of anaerobic reactors packed with zero valent iron (mono-ZVI system), ZVI coupled with anaerobic sludge (coupled system) and anaerobic sludge (mono-cell system) were continuously operated to investigate their performances on CP, TCP and chemical oxygen demand (COD) removal, as well as the reaction mechanisms of ZVI coupling with anaerobic microorganisms. Results showed that the removal efficiencies of CP and COD in coupled system were both around 95%. The corresponding results were 80% and 82% in mono-cell system, and the unstable values in mono-ZVI system were around 86% and 70%. The TCP residual concentration was the lowest in coupled system. The results of X-ray photoelectron spectrometer (XPS) and the photo images of ZVI at the end of reaction implied that the presence of sludge and the interaction between microorganisms and ZVI protected iron shavings from excessive corrosion. Moreover, the addition of ZVI promoted the electron transfer in the anaerobic system, which was proved by the higher value of electron transport system (ETS) activity and Cytochrome C (Cyt C) content of sludge with 250 mg (g h)-1 and 20.71 nmol L-1 in coupled system, compared to 200 mg (g h)-1 and 17.56 nmol L-1 in mono-cell system. The improvement of extracellular polymeric substances (EPS) and anaerobic sludge granulation in the coupled system were on account of the existence of ZVI. It was obvious that the key enzymes and microbial species functioned in COD, CP and TCP degradation were enriched in coupled system.
Selective separation of cesium contaminated clays from pristine clays by flotation Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-20 Huagui Zhang, Suparit Tangparitkul, Brogan Hendry, Joseph Harper, Yun Kon Kim, Timothy N. Hunter, Jae W. Lee, David Harbottle
The ongoing boom of industrialization is conflicted by concerns regarding increased levels of environmental contamination, in particular the uncontrolled release of heavy metal ions and radionuclides into soils and groundwater systems. The extent of contamination can be substantial, hence ways to remediate and reduce the volume of waste for further treatment and ultimate disposal are highly desired. In the current study, flotation has been considered as an engineering solution to rapidly separate cesium contaminated clays from low-level contaminated and pristine clays. Cesium (Cs+) sorption by montmorillonite clay particles was considered over a range of ionic concentrations (0.01 to 500 mM), showing a multistage sorption isotherm that can be interpreted using a two-site model, which considers both interlayer ion-exchange and specific ion sorption on the clay basal planes at higher cesium concentrations. Assessment by X-ray photoelectron spectroscopy (XPS) and zeta potential confirmed the increased surface contamination with increasing Cs+ concentration, with the surface enrichment sufficiently altering the surface chemistry of the contaminated clays for them to favourably interact with the flotation collector, ethylhexadecyldimethyl-ammonium-bromide (EDAB). Within a critical concentration range of EDAB, the cesium contaminated clays were separated from pristine clays using flotation, with recovery efficiencies of ∼75% for the contaminated clays, compared to less than 25% for the pristine clays. When contaminated and pristine clays were blended, separation by flotation once again demonstrated excellent selectivity for the contaminated clays. The current study highlights the potential for flotation to rapidly treat contaminated clay rich soils and significantly reduce the volume of contaminated solids for further treatment or ultimate disposal.
Novel power-to-syngas concept for plasma catalytic reforming coupled with water electrolysis Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-20 Kai Li, Jing-Lin Liu, Xiao-Song Li, Hao-Yu Lian, Xiaobing Zhu, Annemie Bogaerts, Ai-Min Zhu
We propose a novel Power to Synthesis Gas (P2SG) approach, composed of two high-efficiency and renewable electricity-driven units, i.e., plasma catalytic reforming (PCR) and water electrolysis (WE), to produce high-quality syngas from CH4, CO2 and H2O. As WE technology is already commercial, we mainly focus on the PCR unit, consisting of gliding arc plasma and Ni-based catalyst, for oxidative dry reforming of methane. An energy efficiency of 78.9% and energy cost of 1.0 kWh/Nm3 at a CH4 conversion of 99% and a CO2 conversion of 79% are obtained. Considering an energy efficiency of 80% for WE, the P2SG system yields an overall energy efficiency of 79.3% and energy cost of 1.8 kWh/Nm3. High-quality syngas is produced without the need for post-treatment units, featuring the ideal stoichiometric number of 2, with concentration of 94.6 vol.%, and a desired CO2 fraction of 1.9 vol.% for methanol synthesis. The PCR unit has the advantage of fast response to adapting to fluctuation of renewable electricity, avoiding local hot spots in the catalyst bed and coking, in contrast to conventional catalytic processes. Moreover, pure O2 from the WE unit is directly utilized by the PCR unit for oxidative dry reforming of methane, and thus, no air separation unit, like in conventional processes, is required. This work demonstrates the viability of the P2SG approach for large-scale energy storage of renewable electricity via electricity-to-fuel conversion.
Enhanced nitrate removal and high selectivity towards dinitrogen for groundwater remediation using biochar-supported nano zero-valent iron Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-20 Anlei Wei, Jing Ma, Jingjing Chen, Yan Zhang, Jinxi Song, Xiangyang Yu
We prepared nano zero-valent iron/biochar composites (nZVI/BC) to remove nitrate from groundwater with harmless products. Results show nZVI/BCs derived from different mass ratios of Fe(0) to biochar exhibited different nitrate removal efficiencies, and the mass ratio of 1:2 developed the nZVI/BC with optimum nitrate removal. The nZVI/BC maintained preferable nitrate removal (75.0%-97.0%) over a wide pH range 2-12. Nitrate removal amount declined due to serious corrosion and clogging of nZVI/BC’s surface when initial nitrate concentration exceeded 40 mg/L. The nitrate removal process followed a first-order kinetic reaction. As regards real groundwater, the nZVI/BC removed more nitrate than both pure Fe(0) nanoparticles and biochar. Mass balance analysis revealed 60.2% of removed nitrate selectively became dinitrogen. X-ray photoelectron spectroscopy measurements suggested that nitrate-oxidized Fe(0) resulted in significant increase of magnetite on the surface of nZVI/BC. The redox potential and pH of long duration in reaction changed around -210 mV and 8-9, respectively. These changes facilitated the selective reduction of nitrate to dinitrogen. We also proposed that biochar may provide favorable circumstances for nitrate reduction by directly mediating redox potential, pH and electron transfer, which establishes a possible mechanism for the enhanced removal and selective reduction of nitrate. Our study suggests that nZVI/BC would be a promising alternative for the remediation of nitrate-contaminated groundwater.
Enhanced Oxidation Resistance of NaBH4-treated Mackinawite (FeS): Application to Cr(VI) and As(III) removal Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-20 Young-Soo Han, Chang-Mi Lee, Chul-Min Chon, Jeong An Kwon, Ji-Hyun Park, Yeon-Jeong Shin, Dong-Hee Lim
Sulfide minerals are important in immobilizing toxic contaminants in reducing environments. Iron sulfide (FeS) is ubiquitous in anoxic conditions and is a good scavenger of various organic and redox sensitive contaminants and heavy metals. Despite its contaminant removal capabilities, FeS has not been used as a practical adsorbent in contaminant removal due to its rapid oxidation under atmospheric conditions. To increase its applicability, we developed a method of modifying FeS by the addition of NaBH4 to form the less oxygen-sensitive NaBH4–FeS. We conducted oxidation tests using laboratory batch testing and real-time synchrotron X-ray absorption spectroscopy (XAS). The Fe K-edge XAS results showed that the oxidation rate of NaBH4–FeS was eight times slower than that of unmodified FeS while maintaining comparable contaminant removal capacities for Cr(VI) and As(III). The results of mechanistic density functional theory (DFT) calculations demonstrated that the oxidation of FeS occurred through electron transfer from sulfur of FeS to an oxidizing agent of oxygen, and that the hydride ion provided by NaBH4 retarded electron transfer from the FeS surface.
Ordered mesoporous Zn-based supported sorbent synthesized by a new method for high-efficiency desulfurization of hot coal gas Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-20 Mengmeng Wu, Lei Shi, Teik-Thye Lim, Andrei Veksha, Feng Yu, Huiling Fan, Jie Mi
A new approach (microwave-hydrothermal plus oxidation) was proposed for the preparation of the Zn-based sorbents supported on the ordered mesoporous Si-based material. The hydrothermal synthesis and oxidation conditions of the sorbent precursor (ZnS/MCM41 mesophase) with Zn(AC)2 and thioacetamide (TAA) as the Zn and S sources, respectively, were optimized. The sorbents were evaluated in a fixed bed using the simulate gas of 2000 ppm H2S, 39% H2, 27% CO, 12% CO2, and N2 as balance gas. The structure of the sorbents was characterized by means of XRD, N2 adsoprtion, SEM, EDX, and TEM analysis. The results indicate that the optimal microwave-hydrothermal conditions are 400 W, 2.5 h, and 1:3 (the mole ratio of the Zn(AC)2 to TAA). The oxidation of ZnS in the sorbent precursor to ZnO is invalid at 550 °C due to unfavorable reaction kinetics. Both the fresh and used sorbents show ordered hexagonal mesoporous structure. It is confirmed that Zn2SiO4 present in the fresh and regenerated sorbents could be consumed during the desulfurization process via the reaction (Zn2SiO4 + 2H2S→ 2ZnS + SiO2 +2H2O), giving a positive effect on the desulfurization of the sorbents. The optimized Zn-based mesoporous sorbent (actual Zn content: 20.3%) exhibits superior (high breakthrough sulfur capacity: 5.4-5.7%) and stable desulfurization ability during five sulfidation/regeneration cycles. In addition, sulifidation reaction only leads to low-degree plugging of the pore structure of the regenerated sorbents, and the regeneration reaction could restore (at least mostly) the aforementioned changes in the pore properties.
Effect of the wavelength on the pathways of 2-MIB and geosmin photocatalytic oxidation in the presence of Fe-N co-doped TiO2 Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-20 Rongfang Yuan, Shaona Wang, Dan Liu, Xia Shao, Beihai Zhou
In this study, 2-methylisoborneol (2-MIB) and geosmin (GSM) were degraded through photocatalytic oxidation process. For 2-MIB degradation under visible light irradiation, the highest removal rate was obtained in the presence of the 0.001% Fe – 0.5% N co-doped TiO2 calcined at 500°C. The removal rates of 2-MIB and GSM were significantly affected by the wavelength of the lamp used during the oxidation, with the effective order of 254 nm > 365 nm > 420 nm > 475 nm. Higher steady-state concentration of ·OH, which was obtained at shorter wavelength, led to higher T&O removal efficiency. The degradation intermediates of 2-MIB and GSM during the photocatalytic oxidation, including a series of alcohols, aldehydes and ketones, were associated with the dehydration and ring-opening pathways. In most cases, for 2-MIB photocatalytic degradation, intermediates with ring structure were yielded under visible light, while the chain compounds tended to be generated under UV irradiation. However, intermediate products of GSM were not varied from each other significantly when the wavelength changed. The abundances of the GSM degradation intermediates were larger than those of the 2-MIB degradation intermediates because GSM was easier to be oxidized than 2-MIB. The apparent degradation rates of 2-MIB and GSM in real water were lower than those in deionized water, and the humic substances in real water were decomposed into low-molecular weight substances.
New Design on Li-ion Battery Anode of Ternary Complex Metal/Metal Oxide@CNT: A Case Study of Hierarchical NiCo-NiCo2O4@CNTs Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-21 Chunyan Ding, Wang Lijuan, Weiwei Zhou, Dong Wang, Yu Du, Guangwu Wen
Urgent and heavy demand of high energy/power density lithium-ion batteries (LIBs) challenges the ultimate limit of commercial anodes. Herein, enlightened by the extra capacity on transition metal oxides (TMO) anodes derived from the transition metal (TM) catalytic effect on reversible solid-electrolyte interface (SEI) films, a ternary composite consisting of TM, TMO, and carbon matrix, namely TM/TMO/carbon, is proposed as a novel and high-efficiency anode prototype. In this electrode design, TMO not only serve as active material but also pulverizes the TM nanoparticles via the conversion reaction during cycling. Pulverized TM nanoparticles can activate and/or promote the reversible transformation of SEI films more efficiently. And carbon matrix ensures the electronic conductivity and integrity of the overall electrode during multiple electrochemical reactions. As a proof-of-concept demonstration, NiCo-NiCo2O4@carbon nanotubes (NC-NCO@CNTs) is synthesized by a bottom-up strategy via in-situ growth on a simplified chemical vapor deposition (CVD) process. As designed, the NC-NCO@CNTs keeps gaining extra capacity upon cycling, delivering an unceasingly increased capacity up to 1324 mAh g-1 (500 mA g-1), splendid rate performance (945 mAh g-1 at 1000 mA g-1, 696 mAh g-1 at 2000 mA g-1), and ultralong lifespan (2200 cycles). Detailed electrochemical investigation reveals a transformation of lithium storage mechanism from battery-type conversion reaction to pseudocapacitive electrochemical interfacial reaction arising from SEI films. It is believed that our work offers a novel and effective prototype for designing high energy/power density anodes for LIBs.
A flexible 3D graphene@CNT@MoS2 hybrid foam anode for high- performance lithium-ion battery Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-21 Jing Ren, Rui-Peng Ren, Yong-Kang Lv
A three-dimensional (3D) flexible hybrid foam composed of graphene foam@carbon nanotubes decorated with MoS2 nanoparticles is synthesized for flexible anode applications in lithium-ion battery. The inner layer of graphene foam (GF), serving as a 3D skeleton of the hybrid foam, which enlarges the electrode/electrolyte contact, shortens the diffusion distance of Li+ ions and provides enough internal void space to accommodate the large volume change of MoS2 nanoparticles. The middle carbon nanotubes (CNT) layer wrapped on the graphene foam is more conductive to facilitate electron/ion transport within the hybrid foam and can further enhance the flexibility of the hybrid foam. The outer layer of active MoS2 nanoparticles can provide high specific capacity. Owing to these advantages, the flexible GF@CNT@MoS2 electrodes delivers a specific capacity of 935 mAh g-1 at a current density of 0.1 A g-1, high reversible capacity of 606 mAh g-1 after 200 cycles at 0.2 A g-1.
Adsorption for phosphate by crosslinked/non-crosslinked-chitosan-Fe(III) complex sorbents: Characteristic and mechanism Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-21 Boaiqi Zhang, Nan Chen, Chuanping Feng, Zhenya Zhang
Fe(III)-doped chitosan (CTS-Fe) and crosslinked Fe(III)-chitosan (CTS-Fe-CL) composites were developed for the removal of phosphorus from aqueous solution. The characteristics of adsorbents, performance on adsorption and pathway of phosphate transformation were investigated in batch studies. The SEM images and hardness tests showed that CTS-Fe-CL exhibited a three-layer structure with well-developed pore size, while CTS-Fe had more compact structure and stronger strength than CTS-Fe-CL. The low pH value was favorable for the adsorption of phosphate on the chitosan-Fe complex. Moreover, raw CTS-Fe showed better adsorption capacity than after crosslinking in a wide pH range. XPS and FTIR analyses demonstrated that under acidic conditions, the route of the adsorption process was the reaction between phosphate and functional groups (NH2 and NH3+) by electrostatic attraction and iron hydrolysates by ligand exchange, respectively. In addition, Fe(III) could release large quantities of hydrogen ions during the hydrolysis reaction process, which could enhance the protonation and electrostatic attraction under acidic conditions. Owing to the increase of challenging OH− ions, the electrostatic attraction weakened and ligand exchange was the dominant mechanism for phosphate adsorption under alkaline conditions. Moreover, the maximum phosphate adsorption capacity for CTS-Fe and CTS-Fe-CL was 15.7 and 10.2 mg-P g−1 at 303 K, respectively. The present study revealed the phosphate adsorption mechanism on Fe-modified chitosan under different pH conditions.
Insight on the generation of reactive oxygen species in the CaO2/Fe(II) Fenton system and the hydroxyl radical advancing strategy Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-21 Yunfei Xue, Qian Sui, Mark L. Brusseau, Xiang Zhang, Zhaofu Qiu, Shuguang Lyu
Calcium peroxide (CaO2) is a stable hydrogen peroxide (H2O2) carrier, and the CaO2/Fe(II) system has been applied for treatment of various pollutants. It is commonly reported in the literature that hydroxyl radical (HO●) and superoxide radical anions (O2●-) are the two main reactive oxygen species (ROSs) generated in the CaO2/Fe(II) system. However, many of the reported results were deduced from degradation performance rather than specific testing of radical generation. Thus, the specific generation of ROSs and the influence of system conditions on ROSs yield is still unclear. To our knowledge, this is the first study specifically focusing on the generation of HO● and O2●- in the CaO2/Fe(II) system. Experimental conditions were optimized to investigate the production of HO● and O2●-. The results showed the influences of CaO2, Fe(II), and solution pH on HO● and O2●- generation, and the HO● generation efficiency was reported for the first time. In addition, the ROSs generation pathways in the CaO2/Fe(II) system were elucidated. A strategy for enhancing HO● yield is developed, based on the continuously dosing Fe(II). This proposed strategy has implications for the effective application of in situ chemical oxidation employing CaO2/Fe(II) for groundwater remediation.
Hydrophobic 3D Fe/N/S doped graphene network as oxygen electrocatalyst to achieve unique performance of zinc-air battery Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-21 Yimai Chen, Hui Wang, Fusheng Liu, Hengjun Gai, Shan Ji, Vladimir Linkov, Rongfang Wang
Electrocatalysts’ activity in oxygen reduction reaction can be regarded as crucial indicator for their expected performance in metal-air battery, where catalyst selection is limited by low conductivity and insufficient electrochemical activity of available materials. This drawback could be addressed by the development of three-dimensional (3D) hierarchically structured carbon. In this study, hydrophobic 3D Fe/N/S doped graphene network is synthesized as electrocatalysts for zinc-air batteries in molten mixed salts (NaCl/FeCl2). It was observed that NaCl could seal maximum possible quantity of N in 3D-N/S. This is accompanied by more pyridinic-N and graphitic-N groups being tailor made in 3D-Fe/N/S. When assembled as air breathing cathodes in zinc-air batteries, 3D-Fe/N/S material demonstrated open-circuit potential (OCP) of 1.507 V, which was more than 1.492 V in case of 3D-N/S and 1.489 V of 20 % Pt/C. Similar pattern occurred at discharge current density 50 mA cm-2 where a discharge voltage of 1.079 V observed in 3D-Fe/N/S was higer than 1.043 V of Pt/C and 1.040 V of 3D-N/S. Corresponding discharge power density maintained the same order, 3D-Fe/N/S (53.929 mW cm-2)＞Pt/C (52.158 mW cm-2)＞3D-N/S (52.002 mW cm-2), rendering hydrophobic FeNx and N/S doped 3D-Fe/N/S better zinc-air battery electrode material than 20 % Pt/C.
oA Quantitative-Structure-Activity-Relationship (QSAR) model for the reaction rate constants of organic compounds during the ozonation process at different temperatures Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-19 Zhiwen Cheng, Bowen Yang, Qincheng Chen, Xiaoping Gao, Yujia Tan, Yuning Ma, Zhemin Shen
The ozonation process is an effective method for removing hazardous wastes in water. To better characterize and understand the factors influencing the reaction rate constants of organic compounds during the ozonation process, a quantitative-structure-activity-relationship (QSAR) model was developed using the principal component analysis and multiple linear regression (PCA-MLR) method. In principal component analysis, five of the seven components were found to mechanistically and statistically affect the reaction rate constants. Component 1 was represented by the number of oxygen atoms (nO) and minimum value of bond order (BOn), component 2 was represented by the energy of the highest occupied molecular orbital (EHOMO), and component 3 and 4 were dominated by the largest change in the charge of each atom during nucleophilic attack (f(+)x) and the energy of the lowest unoccupied molecular orbital (ELUMO), respectively. The temperature (T) was the most important factor for component 7. The optimal model was lnkO3=4.102+0.007T-3.419BOn+1.765f(+)x+5.698ELUMO-4.016EHOMO-0.241nO, with the following evaluation index values: squared correlation coefficient (R2) = 0.916, internal validation (q2) = 0.895 and external validation (Qext2) = 0.962. Based on these evaluation indices, Y-randomization validation and the definition of the applicability domain, the optimal model was stable, robust and predictive. We anticipate that our work will provide a credible theoretical foundation for estimating the reaction rate constants for degradation of high-molecular weight organic compounds during ozonation over a temperature range from 25 to 60 °C.
Combined CdS nanoparticles-assisted photocatalysis and periphytic biological processes for nitrate removal Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-19 Ningyuan Zhu, Jun Tang, Cilai Tang, Pengfei Duan, Lunguang Yao, Yonghong Wu, Dionysios D. Dionysiou
The concept of improving in-situ nitrate removal was demonstrated in a CdS nanoparticles (NPs)-assisted periphyton bioelectrochemical system (PCdS-BES). Compared to the control (periphyton bioelectrochemical system, P-BES), nitrate reduction to nitrogen gas by the PCdS-BES was enhanced by 1.5 times on day 7 under stimulated sunlight irradiation (20 W m-2), avoiding nitrous oxide emission. The presence of CdS NPs optimized the community structure of periphyton, enhanced its activities (represented by catalase (CAT) and ATPase), stimulated more extracellular polymeric substance (EPS) production and increased the relative abundance of electroactive bacteria strains (e.g. Xanthomonadaceae, Hyphomonadaceae and Sphingobacteriales). The enhancement of nitrate reduction under irradiation was primarily attributed to the synergistic effect of EPS, electroactive bacteria strains and CdS NPs. Specifically, CdS NPs provided photoexcited electrons under light irradiation. The EPS facilitated the stability of CdS NPs in the periphyton matrix and separation of photo-induced electron-hole on the surface of CdS NPs. EPS served as extracellular electron transfer mediators for electron transfer from CdS NPs to microorganisms. The electroactive bacteria were beneficial to the acquisition of electrons produced by CdS NPs under irradiation, promoting catalytic nitrate reduction. This study gives an insight into the mechanism of nitrate reduction via the synergistic action of photoexcited electrons, EPS and electroactive bacteria. The successful combination of photocatalyst (i.e. CdS NP) and microbial community in BES also provides a promising approach for nitrate removal.
A numerical modelling study of SO2 adsorption on activated carbons with new rate equations Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-18 Ziyi Li, Yingshu Liu, Haihong Wang, Chuen-Jinn Tsai, Xiong Yang, Yi Xing, Chuanzhao Zhang, Penny Xiao, Paul A. Webley
Modelling dynamic adsorption of sulfur dioxide (SO2) on activated carbons (ACs) is significant in guiding practical desulphurization processes and making highly efficient use of adsorbents in terms of the adsorption rate which largely depends on particle size. In this work, models derived from the Vermeulen and an improved linear driving force (LDF) rate equation were studied for the first time on SO2 adsorption over AC particles with different sizes. For larger particles (≥ 3 ≥ 3 mm), breakthrough curves predicted by the Vermeulen equation showed good agreement with experimental data, demonstrating that intraparticle diffusion resistance varied with particle size, feed concentration, adsorption time and location. For smaller particles (1 mm), a correction on the volume-averaged adsorption capacity as a function of adsorption time and saturation in the rate equation was developed to avoid the underestimation of adsorption rate due to the inappropriate parabolic concentration profile inherent in the conventional LDF model. By providing a concentration gradient and adsorption rate closer to actual values, the improved LDF equation was confirmed to provide excellent prediction results on 1-mm particles. Different modelling characteristics of the two models indicates varying effects of intraparticle diffusion on adsorption rate with particle size regarding the specificity of SO2 physisorption on ACs.
Effects of Fe(II) on Cd(II) immobilization by Mn(III)-rich δ-MnO2 Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-18 Qian Sun, Pei-Xin Cui, Ting-Ting Fan, Song Wu, Mengqiang Zhu, Marcelo Eduardo Alves, Dong-Mei Zhou, Yu-Jun Wang
Manganese (Mn) oxides have high Cd(II) sorption affinities and could effectively immobilize Cd(II) in soil and aquatic systems. However, coexisting Fe(II) can react with Mn oxides at oxic-suboxic interfaces, thereby affecting Cd(II) immobilization by Mn oxides. Mn(IV)-rich Mn oxides in the environment are readily to be reduced to Mn(III)-rich Mn oxides by natural organic matter. Herein, we determined the effects of Fe(II) on Cd(II) immobilization by Mn(III)-rich δ-MnO2 (denoted as HE-MnO2) at pH 5.5 and 7.5. Results show that Fe(II) decreased Cd(II) retention on HE-MnO2 at pH 5.5 but had no effects at pH 7.5 due to the high Cd(II) adsorption affinity of HE-MnO2 at high pH. Poorly crystalline Fe oxides, likely ferrihydrite, uniformly precipitated on HE-MnO2 surfaces upon Fe(II) addition at both pHs. β-MnOOH formed at the high initial Fe(II) concentration at pH 7.5. Cd(II) was mainly adsorbed on HE-MnO2 rather than the newly formed Fe oxides and β-MnOOH which had low Cd(II) adsorption capacities. The decrease of Cd(II) sorption in the presence of Fe(II) could be explained by the reduction of HE-MnO2, the precipitation of Fe oxides on HE-MnO2, and the competition of generated Mn(II) for the sorption sites. Cd(II) formed double-corner sharing (DCS) and double-edge sharing (DES) complexes with Mn(III) edge sites on HE-MnO2. After the addition of Fe(II), Cd(II) formed only DCS complexes with Mn(III) edge sites. The alternation of the surface complexes caused by Fe(II) promoted Cd(II) desorption from HE-MnO2. This work suggests that Fe(II) can decrease the removal efficiency of Cd(II) by Mn(III)-rich δ-MnO2 at oxic-suboxic interfaces in the environment.
One-pot synthesis of monolithic Mn-Ce-Zr ternary mixed oxides catalyst for the catalytic combustion of chlorobenzene Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-18 Gaoyuan Long, Mengxia Chen, Yajun Li, Jiafeng Ding, Runze Sun, Yanfang Zhou, Xiuying Huang, Gaorui Han, Weirong Zhao
Mn-based catalysts have been widely investigated for the disposal of chlorinated volatile organic compounds (CVOCs), due to their excellent catalytic performances. In this study, Ce-Zr co-modified monolithic Mn-based oxide catalysts were synthesized by one-pot solution combustion method. All the samples were tested with chlorobenzene (CB), as a model molecule of CVOCs. The Mn-Ce-Zr catalyst retained high surface area, small particle size and high redox properties, and exhibited superior catalytic activity with T90% at 390 °C. The superior catalytic activity of Mn-Ce-Zr catalyst originated from the larger specific surface area, the higher Mn4+ cation and surface oxygen contents, as well as the greater oxygen mobility and manganese reducibility. The catalytic activity declined slightly during the life test and the reduced activity could be partially regenerated by introducing water vapor. H2-TPR results indicated that the blockage of active sites by strongly adsorbed chlorine species contributed to the deactivation. By-products generated during CB oxidation included phenol, 2-butene, 2-butenal, acetone, trichloromethane, etc., no highly toxic polychlorinated aromatic compounds were detected. CB oxidation was initiated by CCl bond cleavage followed with ring-open reactions. This work developed a monolithic Mn-Ce-Zr ternary mixed oxides catalyst with striking activity and stability and provided some insightful understandings for designing industrial catalysts.
Three-dimensional hierarchical porous Na3V2(PO4)3/C structure with high rate capability and cycling stability for sodium-ion batteries Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-18 Rui Ling, Shu Cai, Dongli Xie, Xin Li, Mingjing Wang, Yishu Lin, Song Jiang, Kaier Shen, Kunzhou Xiong, Xiaohong Sun
Na3V2(PO4)3 (NVP) with an open NASICON structure has drawn worldwide attention as a potential cathode material for sodium-ion batteries (SIBs) owing to its high theoretical capacity. However, the inherently poor electronic conductivity of NVP severely restricts its electrochemical performance, particularly for rate capability and long cycle performance. Herein, high performance NVP/C cathode (denoted as NVP/C-T) is demonstrated by designing and synthesizing three-dimensional (3D) hierarchical porous NVP architecture via a facile hydrothermal technique. In this hierarchical porous structure, ultrathin NVP nanosheets capped with in-situ carbon layers are interlinked to form hierarchical pores, convenient nanochannels and 3D conductive carbon framework. This delicate structure not only provides adequate void for the intimate contact between electrode/electrolyte, shortens ionic diffusion distances, ensures the ultrafast electron transfer but also strengthens the structural stability of electrode material. The as-prepared NVP/C-T cathode exhibits a high reversible initial capacity (114.8 mAh g-1 at 1 C approaching the theoretical capacity), excellent rate performance (89.3 mAh g-1 at 60 C and 73.2 mAh g-1 at 80 C) and long life span (93.3 mAh g-1 after 8000 cycles at 20 C). In addition, the electrochemical properties of symmetric full cell constructed with NVP/C-T // NVP/C-T are also studied and high initial charge capacity (101.8 mAh g-1 at 0.25 C) and high stability (70.1 mAh g-1 at 2 C after 200 cycles) are achieved. Significantly, the design of the 3D hierarchical porous nanocrystal@C strategy and scalable synthesis method may pave a way to develop high performance SIBs.
Effect of solution chemistry on the reactivity and electron selectivity of zerovalent iron toward Se(VI) removal Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-17 Junlian Qiao, Yadan Song, Yuankui Sun, Xiaohong Guan
Both the reactivity and electron selectivity (ES) of zerovalent iron (ZVI) are critical for successful application of ZVI. In this study, taking Se(VI) as a probe contaminant, the influence of pH (3.0-10.0) and coexisting ions (e.g., Ca2+, Mg2+, Cl-, SiO32-, SO42-, and PO43-) on the reactivity and ES of ZVI were comprehensively investigated. It was demonstrated that, the ES of ZVI was low in general and merely 0.9-12.1% of electrons donated by ZVI were effectively used for Se(VI) reduction under different conditions. Both Se(VI) removal rate and ES were significantly influenced by pH and both of them achieved maximum at pH 5.0, while further increasing or decreasing pH values would deteriorate the ZVI performance. Depending on the types and concentrations, coexisting ions could exert different effects on ZVI reactivity and ES, negatively, negligibly or positively. For example, relative to Cl-, Ca2+, Mg2+, and SiO32- did not show any significant influence on Se(VI) removal rate but could enhance ES by 3.0-50.3%. The presence of SO42- and PO43- hindered Se(VI) removal rate during their tested concentration range, while they could enhance ES at a low concentration level and depress ES at high concentration levels. X-ray absorption fine structure analysis revealed that, pH and coexisting ions could influence the transformation of ZVI corrosion products and thereby impact the electron transfer from ZVI to Se species at the water-particle interface.
Triazine-based hyper-cross-linked polymers with inorganic-organic hybrid framework derived porous carbons for CO2 capture Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-17 Lishu Shao, Yafei Sang, Jianhan Huang, You-Nian Liu
Herein, octaphenylcyclotetrasiloxane was used as the substrate, cyanuric chloride was applied as the cross-linker, and a series of novel hyper-cross-linked polymers with organic-inorganic hybrid framework and spherical morphology was fabricated by a typical Friedel-Crafts reaction. These polymers were used as the excellent precursors for the synthesis of N-doped porous carbons. After KOH-activation carbonization, the spherical morphology of the polymers was retained while the porosity was significantly enhanced. Interestingly, the Brunauer-Emmett-Teller surface area (SBET), total pore volume (Vtotal), micropore volume (Vmicro), and Vmicro/Vtotal of the carbons could be finely tuned in the range of 237-2058 m2/g, 0.12-1.08 cm3/g, 0.10-0.93 cm3/g, and 79.4-88.5%, respectively, and the microporosity was distinctly improved as the carbonization temperature increased. These carbons owned decent CO2 uptake (80-263 mg/g), HCP2b-K700 had the highest CO2 uptake of 263 mg/g at 273 K and 1.0 bar and it arrived at 590 mg/g at 298 K and 10 bar. These carbons had moderate isosteric heat of adsorption (20.3-41.8 kJ/mol) and acceptable CO2/N2 selectivity (IAST: 10.8-43.7). The porous carbons developed therein had high surface area and outstanding microporosity, endowed them with promising application prospect in CO2 capture and sequestration.
Management of nitrogen and phosphorus internal loading from polluted river sediment using Phoslock® and modified zeolite with intensive tubificid oligochaetes bioturbation Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-17 Hongbin Yin, Jincan Zhu, Wanying Tang
In situ sediment remediation using modified clay has become increasingly popular in aquatic ecosystem management. In this study, two modified clays, Phoslock® and modified zeolite, were used together to co-manage nitrogen and phosphorus loading from a polluted river sediment and intermittent aeration was used as an aid for this remediation. After 120 days of core incubation, results indicated that the two clays alone cannot effectively control all the total and soluble nitrogen and phosphorus concentrations in the overlying water all the time. However, the combined use of clays with intermittent aeration can effectively reduce the nutrient concentrations throughout the experiment. Sediment phosphate flux can be largely inhibited solely by clays or when combined with aeration. Meanwhile, the ammonium flux can only be inhibited effectively for 60 days and is not statically different from control after 120 days. Surprisingly, intensive bioturbation can create a vertical movement of the applied clays in sediment with time, which enhances the phosphorus and nitrogen retention capacity of the subsurface sediment. Phosphorus fractionation analysis indicated that around 50% of mobile phosphorus was reduced in a 4–6 cm sediment layer after 120 days. In contrast, the extractable ammonium and nitrate content in treated sediment increased 2 to 3 times in this layer. The short-term bioturbation experiment confirmed that bioturbation did not have a large effect on P control efficiency of the clay-treated sediment. Conversely, bioturbation can enhance ammonium release from sediment and the following gradual burial effect can have a negative effect on nitrogen removal from overlying water over time. These results indicate that intensive bioturbation should be considered in polluted river sediment remediation.
Visible-light-driven photocatalytic degradation of 4-CP and the synergistic reduction of Cr(VI) on one-pot synthesized amorphous Nb2O5 nanorods/graphene heterostructured composites Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-17 Juan Yang, Jingyi Hao, Siyu Xu, Jun Dai, Yan Wang, Xinchang Pang
In this study, Nb2O5 nanorods/graphene composites (NbO NRs/GR) are prepared by one-pot alkaline hydrothermal process, utilizing the new roles of graphene oxide (GO) as the structure-directing and morphology-controlling agent for the growth of NbO NRs. Compared to blank NbO, NbO/GR composites exhibit significantly improved photocatalytic activity for 4-CP degradation under visible-light irradiation, although 4-CP and NbO do not absorb visible light themselves. The in-situ formation of surface complexes between 4-CP and NbO and the subsequent charge transfer based on LMCT mechanism can be responsible for the visible photocatalytic activity. And meanwhile, the photoelectrons transferred to GR surface from in-situ formed complex (NbO/4-CP) via NbO NRs can initiate the synergistic Cr(VI) reduction. The GR contents and NbO crystalline phase have great effects on the photocatalytic activity of NbO/GR composites toward simultaneous 4-CP degradation and Cr(VI) reduction. The amorphous NbO/GR composite with 4.0 wt% GR (NbO-400/GR-4.0%) shows the highest photocatalytic activity. The influences of various experimental conditions (including the surface fluorination of NbO/GR, the initial concentrations of 4-CP and Cr(VI), pH, reaction atmosphere, and adding radical scavengers) on the visible photocatalytic activities are investigated in detail. According to the catalytic activity, UV-vis DRS and FT-IR spectra of NbO/4-CP or NbO/GR/4-CP, and photocurrent response in aqueous 4-CP solution, the formation of the surface complex is evidenced and the visible-light catalytic mechanism based on LMCT process is proposed.
Radical assisted iron impregnation on preparing sewage sludge derived Fe/carbon as highly stable catalyst for heterogeneous Fenton reaction Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-17 Haifeng Wen, Lin Gu, Haixiang Yu, Xingbo Qiao, Daofang Zhang, Jianfeng Ye
Radical induced sewage sludge pretreatment has been developed to enhance sludge stabilization and dewaterability. Except for anaerobic digestion, the reutilization of the oxidized sludge residuals is still a challenging issue for wastewater treatment plant. In the view of favorable role in sludge disintegration, the pretreated sludge precursors, which was obtained by sequential radical oxidation and iron impregnation, was carbonized to prepare the carbon encapsulated Fe nanoparticles (Fe NPs), which could then behave as highly stable and active heterogeneous Fenton-like catalyst to degrade Black-T. By contrast, the carbonized products derived from direct iron impregnation were also prepared as a control method. The effect of H2O2/Fe2+ on zeta potential, particle size, morphology and texture structure of the pretreated sludge precursors and their corresponding influence on the carbonized materials were systematically evaluated. Results showed that radicals’ activation could facilitate the iron impregnation on sewage sludge by rupturing the microbial aggregate and making them more accessible to subsequent microbial fragments. Compared to direct iron impregnation, the carbonized products featured much higher iron insertion rate and the uniformly dispersed Fe NPs encapsulated into porous carbons, which in turn enables catalysts exhibiting more efficient catalytic activity in continuous heterogeneous Fenton-like degradation and resistance to metal leaching.
Surface-nucleated heterogeneous growth of zeolitic imidazolate framework-A unique precursor towards catalytic ceramic membranes: synthesis, characterization and organics degradation Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-17 Yueping Bao, Wen-Da Oh, Teik-Thye Lim, Rong Wang, Richard David Webster, Xiao Hu
A novel Co3O4 nanocatalyst functionalized Al2O3 ceramic membrane (CoFCM) with a honeycomb structure was prepared via an optimized surface-nucleated zeolitic imidazolate framework (ZIF-67) growth method. The Co3O4 hollow structure which was confirmed via chemical characterizations (XRD, FTIR, Raman and XPS), was formed on the membrane surface by direct one-step calcination of ZIF-67 membrane. The CoFCM was characterized by various techniques including the field emission scanning electron microscopy and atomic force microscopy. The results reveal the formation of well-defined Co3O4 layer on the porous Al2O3 ceramic membrane with 1.5 - 2 µm thickness. The growth mechanism of CoFCM was further proposed via XPS and the catalytic activity of CoFCM was investigated for the removal of sulfamethoxazole (SMX). The membrane performance was examined under a home-made dead-end mode. Results indicate that CoFCM has a rougher surface with an initial membrane resistance of 1.19 ×1011 m-1 and performs outstanding catalytic activities. The pure water permeability of CoFCM is 3024 L m-2 h-1 bar-1, which is comparable to that of the pristine ceramic membrane (< 10% difference). The SMX removal efficiency achieved to > 90% in 90 min with an Oxone addition of 0.1 g L-1. Meanwhile, the membrane showed excellent durability by retaining > 95% of initial flux for at least 3 operational cycles with a low cobalt ion leaching via Oxone-assisted cleaning. Furthermore, the reaction mechanism of Oxone activation by CoFCM was proposed from the results of the electron paramagnetic resonance (EPR) and radical scavenger experiments.
Fabrication of two-dimensional Ni2P/ZnIn2S4 heterostructures for enhanced photocatalytic hydrogen evolution Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-17 Xu-li Li, Xiao-jing Wang, Jia-yu Zhu, Yu-pei Li, Jun Zhao, Fa-tang Li
Promoting electron-hole separation and migration and lowering the overpotential of hydrogen evolution reactions are two effective solutions for improving photocatalytic hydrogen performance. Suitable co-catalyst and appropriate interfacial contacts can effectively lower overpotential and can also construct an electric field at the interface to increase the separation efficiency of the carriers. In this work, we design and fabricate a 2D-2D type of Ni2P co-catalyst modified with ZnIn2S4 for boosting the performance of photocatalytic hydrogen evolution. As a co-catalyst, the 2D Ni2P nanosheets exhibit a lower overpotential and smaller charge transfer resistance in hydrogen evolution reactions, and is much improved in both respects compared to Ni2P nanoparticles. Based on this, 2D/2D Ni2P/ZnIn2S4 nanohybrids with large contact regions and shorter transmission distances of the charges were fabricated, which effectively improve the separation of photo induced carriers and the interfacial charge transfer. By taking advantage of the above features, the fabricated 2D-2D Ni2P/ZnIn2S4hybrid exhibits a superior hydrogen evolution rate of 2066μmol·h-1·g-1 under visible light irradiation, and the apparent quantum yield was 7.7% at 420±20 nm. This activity far exceeds performance of the 0D/2D Ni2P/ZnIn2S4 hybrid, and is ascribed to better charge separation and accelerated surface reactions of the Ni2P nanosheets.
A 3D Coral-like Structured NaVPO4F/C Constructed by a Novel Synthesis Route as High-performance Cathode Material for Sodium-Ion Battery Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-17 Pingyuan Feng, Wei Wang, Jie Hou, Kangli Wang, Shijie Cheng, Kai Jiang
A novel bottom-up synthesis route based on hydrogen bonds has been developed to prepare NaVPO4F/C (NVPF/C) composite as the cathode material for sodium ion batteries (SIBs). NVPF grains are anchored through effective hydrogen bonds between the fluorine ions and hydrogen atoms inside the sol-gel template, which endows the final product an interconnected and porous three-dimensional (3D) coral-like structure composed by oriented packing of uniform nanoparticles (15-20 nm). The as-prepared NVPF/C exhibits excellent rate capability and extraordinary cyclic stability. The corresponding discharge capacities at 1, 2, 5, 10, 20, 30 and 50 C range from 106, 102, 99, 98, 93, 90 to 88 mAh g−1 respectively. At 5 C, it releases an initial capacity of 100 mAh g-1, and still maintains 70 mAh g-1 after 2500 cycles, corresponding to a very low capacity fading of 0.012% per cycle. The uniform nanometers sized (15-20 nm) fundamental particles and nanopores (3-8 nm) of as-prepared NVPF/C endow the efficient transfer of both electrons and sodium ions. This work implies that the novel 3D coral-like structured NVPF/C is a very promising high-performance cathode for SIBs, and the new synthetic method can also be amplied to prepare other fluorine contained polyanion-type materials.
Electrochemical/peroxydisulfate/Fe3+ Treatment of Landfill Leachate Nanofiltration Concentrate after Ultrafiltration Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-17 Yu-Hong Cui, Wei-Jun Xue, Sui-Qin Yang, Jia-Ling Tu, Xiao-Lei Guo, Zheng-Qian Liu
Landfill leachate nanofiltration concentrate after ultrafiltration was treated. The experiments were carried out in an electrolytic cell which had an anode chamber and a cathode chamber and could be separated by a proton exchange membrane. Different electrochemical processes combined with peroxydisulfate/Fe3+ (PS/Fe3+) were compared and the reactions in anode chamber and cathode chamber were discussed. The Anode/PS/Fe3+-Cathode/PS/Fe3+ process shows the best effect on COD removal and color removal. The 3D-EEMFS results indicate that Anode/PS/Fe3+-Cathode/PS/Fe3+ process has the best effect on the destruction of organics. In anode chamber, the total COD removal is ascribed to (1) the oxidation by SO4•- produced from PS activation by original metal ions in the target solution, (2) direct and indirect oxidations by anode, and (3) coagulation caused by Fe3+ after pH adjustment. In cathode chamber, the total COD removal is due to (1) the oxidation by SO4•- produced from PS activation by the regenerated Fe2+ from Fe3+ reduction on cathode, and (2) coagulation caused by Fe3+ after pH adjustment. An optimal experimental condition with current of 80 mA, Fe3+ dosage of 15 mM and PS dosage of 37.5 mM is obtained for Anode/PS/Fe3+-Cathode/PS/Fe3+ process. The energy consumption between Anode/PS/Fe3+-Cathode/PS/Fe3+ (4.42 kWh/kgCOD) and (Anode+Cathode)/PS/Fe3+ (4.57 kWh/kgCOD) is similar when 55% of COD is removed. However, the toxicity increase in Anode/PS/Fe3+-Cathode/PS/Fe3+ process is obviously less than that in (Anode+Cathode)/PS/Fe3+ process.
Sulfur-doped g-C3N4 nanosheets with carbon vacancies: General synthesis and improved activity for simulated solar-light photocatalytic nitrogen fixation Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-17 Shihai Cao, Bin Fan, Yanchao Feng, Huan Chen, Fang Jiang, Xin Wang
Ultrathin sulfur-doped g-C3N4 porous nanosheets (SCNNSs) with large lateral size and carbon vacancies were obtained by directly collecting the gaseous product of thiourea under a self-generated NH3 atmosphere. The NH3 atmosphere promoted the formation of sulfur doped g-C3N4 nanosheets with a hierarchical pore structure and a high specific surface area. Carbon vacancies were also generated in the SCNNSs without notably changing the overall chemical structure. The obtained SCNNSs-550 showed a photocatalytic nitrogen fixation rate of 5.99 mM h−1 gCat−1 under simulated sunlight irradiation within 4 hours, which is 2.8 times as high as that of bulk SCN. This superior photocatalytic performance of SCNNSs was attributed to the porous sheet structure with sulfur doping and carbon vacancies, which provide many active sites for surface reactions and increase the charge-carrier separation rate. This novel synthetic method provides a simple and efficient way to dope non-metals and form a defect structure in g-C3N4 for excellent photocatalytic performance.
A temperature-induced conductive coating via layer-by-layer assembly of functionalized graphene oxide and carbon nanotubes for a flexible, adjustable response time flame sensor Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-17 Wenhua Chen, Pengju Liu, Yuan Liu, Qi Wang, Wenfeng Duan
A multilayered coating of Phenoxycyclophosphazene-functionalized graphene oxide (FGO) and chitosan-functionalized carbon nanotubes (CNTs) for wood pulp paper (WPP) is designed by a facile layer-by-layer assembly method. The obtained FGO/CNTs coated WPP shows enhanced mechanical properties as well as improved flame retardancy without deteriorating the intrinsic flexibility of WPP. Meanwhile, the electrical resistance of the hybrid FGO/CNTs structure is highly sensitive to flame and temperature, which makes the coated WPP an ideal fire sensor. The as-prepared flexible FGO/CNTs coated WPP sensor exhibits excellent shape retentivity and flame retardancy when burnt by ethanol flame or heat treated, and can detect fire by sensing the elevated temperature in several seconds before igniting the combustible materials. Besides, the response time is adjustable by varying the content of CNTs in constructing the hybrid conductive network. These results suggest that the novel design of multilayer coating of FGO/CNTs on WPP has great potential in the applications of advanced fire alarm systems.
Photocatalytic activity enhanced by synergistic effects of nano-silver and ZnSe quantum dots co-loaded with bulk g-C3N4 for Ceftriaxone sodium degradation in aquatic environment Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-17 Yanyan Zhao, Xuhua Liang, Huanxian Shi, Yongbo Wang, Yingkun Ren, Enzhou Liu, Xu Zhang, Jun Fan, Xiaoyun Hu
The development of novel semiconductor with highly efficient photocatalytic activity for completely degrading organic pollutants in the aquatic environment is a dominating goal of modern chemistry. Herein, a novel composite with excellent photocatalytic activity was firstly synthesized by loading small size of ZnSe quantum dot (QDs) and nano-Ag onto the surface of the bulk g-C3N4 (CN). The novel composite (ZnSe-Ag/CN) was used to degrade Ceftriaxone sodium in the aquatic environment at low concentrations under visible light irradiation, and the 7%-ZnSe-Ag/CN composite displayed superior photocatalytic activity, approximately 89.24% of Ceftriaxone sodium has been degraded under visible light irradiation for 90 min, which was approximately 10.14-folds, 2.72-folds, 2.09-folds and 1.39-folds higher than pure ZnSe QDs, CN, 7%-Ag/CN and 5%-ZnSe/CN sample, respectively. Based on the adsorption test, the UV–vis diffuse reflectance spectra (DRS), the N2 adsorption–desorption isotherm, the photoluminescence spectra, the transient photocurrent response and the electrochemical impedance spectroscopy (EIS) measurements, the enhanced photocatalytic activity of the ZnSe-Ag/CN composite could be attributed to the excellent adsorbability, expansion of the light-harvesting scope, as well as the efficient separation of photogenerated electron-hole pairs. Meanwhile, the ZnSe-Ag/CN composite could produce a large amount of the hydroxyl radicals (•OH) during the photocatalytic degradation process. Furthermore, a possible pathway of Ceftriaxone sodium degradation was proposed according to the detailed analyses of the produced intermediates to better understand the reaction process. Therefore, this work offers a new strategy for designing novel photocatalyst with excellent photocatalytic activity to remediation of water contamination.
Visible-light photocatalytic oxidation of gas-phase Hg0 by colored TiO2 nanoparticle-sensitized Bi5O7I nanorods: Enhanced interfacial charge transfer based on heterojunction Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-17 Haoqiang Cheng, Jiang Wu, Fengguo Tian, Qizhen Liu, Xuemei Qi, Qingwei Li, Weiguo Pan, Zhaozhao Li, Jie Wei
A series of colored TiO2/Bi5O7I composites were successfully fabricated. The physicochemical properties of the as-prepared TiO2/Bi5O7I heterostructures were investigated by XRD, SEM, TEM, HRTEM, FT-IR, BET, UV–vis DRS, XPS and PL characterization. The characterization indicates that colored TiO2 nanoparticles are tightly anchored to the Bi5O7I nanorods to form heterojunctions. The photocatalytic activity of the sample was examined by photocatalytic oxidation of gas-phase Hg0 under visible-light irradiation. The results show that TiO2/Bi5O7I composites exhibits highly enhanced visible light photocatalytic activity compared to pure Bi5O7I. Hg0 removal rate of TiO2/Bi5O7I composite is up to 89%. Compared with the pure Bi5O7I, the as-prepared composite photocatalyst enhanced the visible light absorption and increased the specific surface area. More importantly, the heterostructure formed in the composite effectively promotes the charge transfer, ultimately improves the photocatalytic activity. Meanwhile, the cyclic experiments were performed to confirm the stability of TiO2/Bi5O7I composites. The influence of various flue gas components (O2, NO and SO2) on the performance of photocatalytic removal of Hg0 was studied. Based on characterization and experiments, the reasonable charge transfer and photocatalytic reaction mechanism were proposed.
Inhibition kinetics of ammonium oxidizing bacteria under Cu(II) and As(III) stresses during the nitritation process Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-10 Chong-Jian Tang, Cheng-Shan Duan, Peng Liu, Xilin Chai, Xiaobo Min, Shuo Wang, Ruiyang Xiao, Zongsu Wei
Nitritation processes with ammonium oxidizing bacteria (AOB) frequently suffer inhibition from heavy metals in municipal wastewater treatment. In the present study, two typical heavy metals, Cu(II) and As(III), were selected to assess their inhibition effect during the nitritation process. Specific ammonium conversion rate (SACR), specific oxygen uptake rate (SOUR), and specific nitrite production rate (SNPR) in batch tests were first applied to evaluate nitritation kinetics, and simulated by the classic Haldane substrate inhibition kinetic model. The presence of Cu(II) stress imposed a more pronounced inhibition on nitritation process than As(III) with half inhibition concentrations of 6.7 and 86.6 mg L-1, respectively. The kinetic result showed that Cu(II) acts as an uncompetitive inhibitor on nitritation process with reduced affinity (KS) and specific activity (Vmax) values. The difference in the inhibition kinetics between Cu(II) and As(III) can be accounted by the oxidation of As(III) to As(V) and subsequent competition by dissolved oxygen under nitritation condition. Our result indicated that the SNPR method exhibits great performance in describing and modelling the inhibition kinetics of Cu(II) and As(III) on AOB nitritation process.
Activation of persulfate by modified drinking water treatment residuals for sulfamethoxazole degradation Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-10 Chengdu Qi, Gang Yu, Jun Huang, Bin Wang, Yujue Wang, Shubo Deng
In this work, drinking water treatment residuals (WTRs), an iron–rich safety byproducts, was modified via facile reduction calcination and subsequently proved as an effective persulfate (PS) activator for degradation of sulfamethoxazole (SMX). Various parameters affecting SMX degradation efficiency were tested, and the results showed that 80% of SMX (50 μM) was removed within 60 min in the presence of 2.0 mM PS and 0.2 g L–1 modified WTRs at pH 5.3 under ambient temperature. Radical scavenging and electron spin–resonance spectroscopy tests indicated that sulfate radical was a much more powerful active oxygen specie than hydroxyl radical for the SMX degradation in the WTRs/PS system. To understand the proposed activation mechanism, X–ray diffraction and X–ray photoelectron spectroscopy were applied to reveal the change of modified WTRs before and after use. This process confirmed that the activation mechanism was in situ homogenous and heterogeneous reaction simultaneously. Furthermore, liquid chromatography coupled with ion trap time–of–flight mass spectrometry was applied to identify the intermediates of SMX to understand the possible pathway. This work provides a novel value–added reuse approach for WTRs as an efficient and cost–effective heterogeneous activator for PS.
Highly Efficient Electrodes for Supercapacitors using Silver-plated Carbon Nanofibers with Enhanced Mechanical Flexibility and Long-term Stability Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-10 Yong Il Kim, Edmund Samuel, Bhavana Joshi, Min-Woo Kim, Tae Gun Kim, Mark T. Swihart, Sam S. Yoon
Highly flexible freestanding carbon nanofibers were electroplated with silver for use in supercapacitor applications. The brittle carbon nanofibers were encased within bendable silver shells to provide superior flexibility and resilience of the supercapacitors. The enhanced electrical conductivity derived from the silver shell structure dramatically increased the capacitance of the supercapacitor. The silver shell also conferred structural stability to the carbon core, thus furnishing stable, long-term electrode performance. Nearly 100% of the specific capacitance was retained after N = 10,000 galvanostatic charge-discharge cycles. The mechanical endurance or stability of the fabricated electrode was evaluated using 1,000 bending cycles, demonstrating that the electrode performance remained unchanged. Cyclic voltammetry and galvanostatic discharge curves were measured at various scan rates and current densities. The fabricated electrodes were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy, which clearly illustrated the carbon-core and silver-shell structure.
Heterogeneous activation of peroxymonosulfate by LaFeO3 for diclofenac degradation: DFT-assisted mechanistic study and degradation pathways Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-10 YongFang Rao, Yufei Zhang, Fuman Han, Huichao Guo, Yu Huang, Ruoyu Li, Fei Qi, Jun Ma
A perovskite oxide, LaFeO3 (LFO), was synthesized and evaluated as a heterogeneous catalyst to activate peroxymonosulfate (PMS) for the oxidative degradation of diclofenac (DCF), a non-steroidal anti-inflammatory drug. It was observed that the catalytic activity of LFO was much higher than that of Fe2O3. LFO catalyzed PMS to degrade DCF with a turnover frequency (2.02×10-3 min-1) which is 17-fold higher than that of Fe2O3. Both sulfate and hydroxyl radicals were identified during LFO-activated PMS process by electron spin resonance (ESR). Radical competitive reactions indicate sulfate radicals played a major role in DCF degradation by LFO/PMS process. The PMS decomposition can be attributed to the formation of an inner-sphere complexation between the Fe (III) sites on LFO surface and PMS. Theoretical calculations illustrated the strong interaction between PMS and Fe (III) and electron transfer from PMS to Fe (III). Hydrogen temperature-programmed reduction (H2-TPR) indicates that the LFO perovskite oxide is capable of facilitating an easier reduction of Fe (III) to mediate a redox process. Oxygen temperature-programmed desorption (O2-TPD) suggests much more oxygen vacancies exist in LFO than in Fe2O3. Oxygen vacancies are favorable for the formation of chemical bond between Fe (III) and PMS and the activation of PMS. In situ ATR-FTIR analysis of LFO surface during PMS decomposition implies Fe (III) – Fe(II) – Fe (III) redox cycle was believed to account for the generation of sulfate radical. The intermediates generated during DCF degradation were identified and the possible degradation pathways were advanced in LFO/PMS system.
Influence of titanium dioxide nanoparticles on functionalities of constructed wetlands for wastewater treatment Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-10 Xiangyu Yang, Yi Chen, Xiaobo Liu, Fucheng Guo, Xiaoxuan Su, Qiang He
Titanium dioxide nanoparticles (TiO2 NPs) have been widely used in industrial and commercial products, resulting in potential environmental risks. However, the impacts of these nanoparticles on wastewater treatment in ecological systems are less known. In this study, short- and long-term effects of TiO2 NPs on contaminant removal in constructed wetlands (CWs) were investigated. The results showed that short-term exposure to TiO2 NPs (1 and 50 mg/L) induced marginal adverse effects on treatment performance (COD, TN, NH4+-N, and TP) of CWs, while N removal evidently declined under prolonged exposure to TiO2 NPs. Furthermore, metagenomics and enzyme activities analyses suggested that the reduced N removal efficiency could possibly be due to the decrease in the relative abundance of nitrifiers (Nitrospira and Nitrosomonas) and inhibition of ammonia monooxygenase activity. In contrast, long-term exposure to TiO2 NPs promoted net photosynthesis rate, stomatal conductance, transpiration rate and root activity of Phragmites australis, indicating a positive impact of TiO2 NPs on plant physiology. Overall, the findings of this study suggested that long-term exposure to TiO2 NPs at an environmentally relevant concentration (1 mg/L) significantly altered the functionalities of microorganisms and plants, which in turn impaired the wastewater treatment performance of CWs.
Multiphase flow studies for microscale hydrodynamics in the structured packed column Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-11 Rajesh K. Singh, Janine E. Galvin, Xin Sun
Post combustion carbon capture by solvent absorption in a structured packed column is a promising technology for mitigating greenhouse gas emissions. Computational fluid dynamic (CFD) modelling of such a column is a challenging multiscale problem due to the range in length and time scales. The microscale hydrodynamics play a key role in the overall column efficiency with the interfacial area significantly influencing the mass transfer between the gas and liquid phases. In this context, multiphase flow simulations using the volume of fluid (VOF) method in a representative elementary unit (REU) of the packed column can provide fundamental insights into the microscale hydrodynamics, such as, interfacial area and liquid holdup. The present study systematically examines the impact of various factors (e.g., physical properties and contact angle) on the interfacial area. The results are compared with existing correlations and a scaling analysis is also performed. The solvent physical properties are characterized by the Kapitza number (Ka), a dimensionless number that depends only on fluid properties. So that the Ka number decreases with increasing viscosity. At a fixed liquid load, the interfacial area and liquid holdup are observed to increase with decreasing Ka number. The impact of contact angle (i.e., solid surface characteristics) is effectively investigated by modifying the wall boundary conditions. The interfacial area and liquid holdup are found to decrease with increasing contact angle. Subsequently, a phenomenological correlation for interfacial area is proposed that includes the impact of these parameters. This correlation may be used to predict the interfacial area for gas-liquid flow in a structured packing for rivulet to fully wetted flow regimes.
Efficient Visible-Light Driven Photocatalyst, Silver (meta)vanadate: Synthesis, Morphology and Modification Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-11 Jiayin Guo, Jie Liang, Xingzhong Yuan, Longbo Jiang, Guangming Zeng, Hanbo Yu, Jin Zhang
As a fascinating visible-light driven photocatalyst, silver (meta)vanadate with the merits of narrow band gap, well crystallization and easy preparation has been a hotspot in the field of photocatalysis. Generally, pristine silver (meta)vanadate suffers from photocorrosion, high recombination rate of photogenerated e--h+ pairs, poor quantum yield and insufficient sunlight absorption, resulting in poor photocatalytic performance. Typically, heterojunction structure construction, noble metal loading, and cocatalyst binding have been explored to improve the photocatalytic performance of silver (meta)vanadate by enhancing stability, accelerating charge separation and transportation, prolonging the lifetime of charge carriers and increasing light absorption. Therefore, this review provided insights into the recent progress in the development of efficient modified silver (meta)vanadate and their application in photocatalytic degradation of pollutant, water splitting, and bacteria disinfection. Meanwhile, this review summarized the synthetic methods commonly used in silver (meta)vanadate synthesis. Moreover, as the photocatalytic activity is structure-dependent, the relationship between morphology and photocatalytic property of silver (meta)vanadate was discussed in this review. Finally, the current challenges and the crucial issues of modified silver (meta)vanadate that are in urgent need of being addressed in future research are presented. It is expected that this review could provide meaningful knowledge to help rationally design and fabricate highly-efficient silver (meta)vanadate-based photocatalysts.
Facile fluorine-free one step fabrication of superhydrophobic aluminum surface towards self-cleaning and marine anticorrosion Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-11 Binbin Zhang, Qingjun Zhu, Yantao Li, Baorong Hou
Service performance and safety of aluminum materials are restricted by the proneness to marine corrosion. The facile and low cost fabrication of fluorine-free superhydrophobic aluminum surfaces for anticorrosion is still a challenging issue. Herein, we report a handy and versatile fabrication of nonfluorinated Allium giganteum-like superhydrophobic aluminum surfaces via one step electrodeposition approach. The surface topographies, wettability and chemical compositions were detailed characterized and discussed. In addition, we investigated the self-cleaning and low surface adhesion ability of the as-fabricated electrodeposited superhydrophobic surface. The electrochemical impedance spectra was performed to reveal the corrosion resistance and inhibition efficiency of the as-prepared superhydrophobic surface. The air-exposure and 3.5 wt.% NaCl immersion tests suggest a good lasting quality of the surface. We believe the facile fabrication of fluorine-free superhydrophobic surface can meliorate many shortcomings of achieving superhydrophobicity and broaden the potential applications of aluminum-based materials towards marine-related fields.
Enhanced activation of persulfate by carbohydrate-derived carbon cryogels for effective removal of organic pollutants Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-11 Liang Liang, Minghua Zhou, Weilu Yang, Lili Jiang
Nanocarbons are promising alternatives to metal-based catalysts in advanced oxidation processes for wastewater treatment. Herein, carbon cryogels were prepared through the hydrothermal carbonization (HTC) of glucose directed by polyaniline (PANI) and their catalytic performances towards persulfate (PS) activation for the degradation of organic pollutants were investigated. When the polymerization temperature of PANI was increased from 0 to 80 °C, carbon cryogels exhibited increased total pore volume (0.23 to 0.33 cm3 g−1) and decreased average particle diameter (132 to 63 nm), which further enhanced their adsorption and catalytic activity for PS activation. The excellent catalytic activity of carbon cryogels for PS activation was universal in the degradation of different organic pollutants, comparable to various metal catalysts and reported metal-free catalyst, applied to a wide pH range (pH 3–9), and easily regenerated through calcination, proving that it had potential practical application for organic wastewater treatment. Radical quenching and electron paramagnetic resonance (EPR) experiments demonstrated the nonradical pathway in catalytic oxidation of orange acid 7 (AO7) on carbon cryogels. It was found that the reaction rate of catalytic oxidation of AO7 was positively correlated with the meso-/macropore volume and negatively with particle diameter of carbon cryogels. Finally, the catalytic process for organic pollutants on carbon cryogels was suggested.
Continuous and Controlled Directional Water Transportation on a Hydrophobic/Superhydrophobic Patterned Surface Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-11 Chen Xu, Rui Feng, Fei Song, Jia-Min Wu, Yu-Qiong Luo, Xiu-Li Wang, Yu-Zhong Wang
Directional transportation of water flow, which is frequently seen in nature, is of not only great importance to organisms but also crucial demand for advanced science and technologies. Numerous contributions have been dedicated to the motion manipulation of single drops on chemically heterogeneous surfaces, which have hydrophilic/superhydrophobic patterns in general. Drop retention is therefore difficult to avoid due to the hydrophilic regions, and continuous transportation of water flow still remains a challenge. Here, a hydrophobic/superhydrophobic patterned surface, featured with chemical homogeneity, is developed via a simple coating on a morphologically heterogeneous surface. Such surface can guide the continuous water motions, and relationship between the surface patterns and the motion controllability is clarified. Additionally, the potential application of the patterned films is explored as a micro-mixing device for different drops. The finding and results are essential for advancing more applications of microfluidics and microchips.
A Loose hybrid nanofiltration membrane fabricated via chelating-assisted in-situ growth of Co/Ni LDHs for dye wastewater treatment Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-12 Shuang Zhao, Hongtai Zhu, Zhan Wang, Peng Song, Min Ban, Xufeng Song
A nano-filtration membrane with a loose LDHs/polymer hybrid layer which aimed at the desalination of textile wastewater was fabricated by chelating-assisted in-situ growth of layered double hydroxides (LDHs) on the organic substrate. The positively charged polyethyleneimine (PEI) with excellent chelating ability to metal ions was initially deposited on the hydrolyzed polyacrylonitrile (PAN) membrane surface by electrostatic interaction. Then, Co2+ ions were immobilized on the modified membrane though chelating reaction to form a Co2+/PEI complex layer, which provided a Co2+ source for the in-situ growth of Co/Ni LDHs at a lower temperature. Besides, the LDHs/PEI hybrid membrane prepared at optimized condition achieved a sufficient permeability (198.6 L/(m2·h·MPa)), high rejection for dyes (methyl blue 97.9 % and acid fuchsin 97.5%) and low salt rejection (less than 3%). Meanwhile, this membrane possessed good hydrophilicity, satisfactory antifouling performance (flux recovery ratio was 89.5% for humic acid (HA)) and remarkable long-term stability. The loose LDHs/polymer hybrid layer was conducive to the transport of ions and water molecules, since the ridge-and-valley surface structure enhanced the steric hindrance effect and consequently increased the rejection of macromolecules. Therefore, this surface modification strategy can be applied to construct a ridge-and-valley porous structure on substrate for desalination of textile wastewater.
Synergistic effects and mechanisms of hydroxyl radical-mediated oxidative degradation of sulfamethoxazole by Fe(II)-EDTA catalyzed calcium peroxide: Implications for remediation of antibiotic-contaminated water Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-12 Amina, Xiongyuan Si, Kang Wu, Youbin Si, Balal Yousaf
In this study, a modified Fenton system using calcium peroxide (CaO2) powder, as an effective source of hydrogen peroxide (H₂O₂), for the degradation of sulfamethoxazole (SMX) in aqueous solution was investigated. Our results indicated that degradation of SMX in Fe(II)-EDTA catalyzed CaO2 system was readily more efficient than in Fe(II) catalyzed CaO2 system. The SMX degradation efficiency was found maximum at pH 6.0 and SMX degradation was suppressed as the initial solution pH was increased. Nevertheless overall removal efficiency in this system was favorable near to neutral pH. In addition, it was observed that the higher bicarbonates (HCO3‾) contents had a considerable scavenging ability to SMX degradation while low concentration exhibited auspicious role. The presence of chlorides (Cl‾), nitrates (NO3‾), sulfates (SO42‾), and humic acid (HA) could improve SMX removal in this Fenton-like system. Furthermore, chemical probe and radical scavenging activity confirmed the formation of hydroxyl (HO•) and superoxide (O2‾•) radicals, and also described that the SMX degradation was predominantly due to the HO•-induced oxidative destruction. Electron paramagnetic resonance (EPR) studies for different systems, different pH values and different reaction times were carried out to determine the HO• radical intensities. EPR results showed that HO• intensities were higher in Fe(II)-EDTA catalyzed CaO2 system, at pH 6.0 and at 90s reaction time, respectively. Intermediate products of SMX were identified and possible mechanism of SMX degradation was suggested. In conclusion, this work provided comprehensive knowledge for the use of Fe(II)-EDTA catalyzed CaO₂ system for remediation of SMX contaminated sites.
One-step synthesis of Co-doped UiO-66 nanoparticle with enhanced removal efficiency of tetracycline: simultaneous adsorption and photocatalysis Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-09 Jiao Cao, Zhao-hui Yang, Wei-ping Xiong, Yao-yu Zhou, Yan-rong Peng, Xin Li, Cheng-yun Zhou, Rui Xu, Yan-ru Zhang
In this study, a novel recyclable Co-doped UiO-66 nanoparticle was synthesized by a one-step solvothermal method. A high adsorption capacity of 224.1 mg g-1 was obtained by the CoUiO-1 nanoparticle, then the adsorbed tetracycline (TC) molecules could be removed more than 94% of initial concentration under simulative sunlight irradiation. The adsorptive ability and photocatalytic performance of CoUiO-1 nanoparticle were about 7.6 and 6.9 times higher than the pristine UiO-66, respectively. The adsorption capacity of CoUiO-1 nanoparticle was sensitive to adsorbent dosage, coexisting ions, solution pH values and initial TC concentrations. Pseudo-second-order and Freundlich models fitted well with the adsorption process. Thermodynamic study indicated the TC adsorption on CoUiO-1 nanoparticle was a spontaneous and exothermic process. TC photodegradation experiment showed that the Co-doped modification expanded light absorption and facilitated charge separation of UiO-66, which was beneficial to enhance photocatalytic performance. The mechanism of TC photodegradation by Co-doped UiO-66 nanoparticle was investigated. Moreover, a plausible degradation pathway for TC was proposed. The high removal efficiencies of CoUiO-1 nanoparticle were obtained towards real samples including tap water, river water and pharmaceutical wastewater. Therefore, the novel Co-doped MOFs photocatalytic adsorbent showed great potential in wastewater treatment.
A Robust Hierarchical 3D Si/CNTs Composite with Void and Carbon Shell as Li-ion Battery Anodes Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-09 Hui Zhang, Xiaofeng Zhang, Hong Jin, Ping Zong, Yu Bai, Fei Ma, Hui Xu, Kun Lian
To target the low conductance and expansion issues of Si based anodes for li-ion batteries, a 3D structural composite constructed by CNTs framework distributedly anchored with double-carbon coated silicon nanoparticles has been designed, fabricated and characterized. The crosslinked CNT framework provided electrical conductive pathway as well as void-space to accommodate the expansion of silicon nanoparticles. The double layered carbon coating was formed under the assistance of the sulfur sacrificing agent giving protection on the silicon particle surface. The Si/CNTs@(S)-C electrodes exhibited a high reversible capacity of 943 mAhg-1 after 1000 cycles at a C/5 rate. The excellent cycling performance is attributed to the unique structure which can stabilize the silicon particle during volume expansion and keep the electrical connection at the same time.
Biogenic manganese oxide: an efficient peroxymonosulfate activation catalyst for tetracycline and phenol degradation in water Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-09 Na Tian, Xike Tian, Yulun Nie, Chao Yang, Zhaoxin Zhou, Yong Li
From the view of environment and easy availability, to develop the most efficient manganese oxide for peroxymonosulfate (PMS) activation is of great importance for the degradation of recalcitrant organic pollutants. In this study, biogenic manganese oxide (BioMnOx) exhibited an unprecedented efficiency than the most efficient 3D α-Mn2O3 prepared by chemical method. 100% of phenol degradation at 40 min and 99.4% of tetracycline removal at 60 min were achieved over BioMnOx with PMS, which was 3-fold faster than 3D α-Mn2O3. BioMnOx also has an excellent long-term stability and good performance toward the pollutants degradation at a wide pH range of 3.0-9.0. Most importantly, 1O2 was identified as the primary reactive species in BioMnOx/PMS system based on the trapping experiment and EPR analysis. The PMS activation over BioMnOx should follow a self-decomposition and energy quenching mechanism instead of electron transfer process as confirmed by the XPS analysis. Finally, the degradation pathways of tetracycline and phenol by 1O2 over BioMnOx were proposed according to HPLC and HPLC-MS results, which are greatly different from that by •OH oxidation in the literature.
MnO2 enhances electrocatalytic hydrodechlorination by Pd/Ni foam electrodes and reduces Pd needs Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-09 Zimo Lou, Jiasheng Zhou, Mei Sun, Jiang Xu, Kunlun Yang, Dan Lv, Yaping Zhao, Xinhua Xu
A Pd/MnO2/Ni foam electrode with hierarchical structure was synthesized via electrodeposition for efficient electrocatalytic hydrodechlorination. Compared with the ordinary Pd/Ni foam electrode, the introduction of MnO2 greatly enhanced the catalytic reactivity and reduced the dose of precious metal Pd. Only a quarter of Pd was required for the Pd/MnO2/Ni foam compared to the Pd/Ni electrode to achieve complete dechlorination of 2,4-dichlorobenzoic acid (2,4-DCBA) within 120 min. Various characterizations suggested that MnO2 covered the surface of the Ni foam and increased the specific surface area of the electrode, while Pd nanoparticles were subsequently deposited on MnO2. The atomic H∗-based indirect dechlorination was the dominant pathway while only approximately 13% of 2,4-DCBA was removed by direct electron transfer. Atomic H∗ adsorbed on Pd acted as the key active species for the dechlorination of 2,4-DCBA by the Pd/MnO2/Ni foam electrode in this study. The introduction of MnO2 would promote the water dissociation and the hydrogen evolution reaction, and provide Pd with more atomic H∗. Pd/MnO2/Ni foam exhibited good stability and reusability according to the XPS spectra and consecutive electrocatalytic experiments, which suggested its long-term potential for efficient removal of chlorinated contaminants. This work demonstrated a new strategy to design efficient electrocatalysts with less precious metal.
Fe3O4@LAS/RGO Composites with a Multiple Transmission-Absorption Mechanism and Enhanced Electromagnetic Wave Absorption Performance Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-09 Yanan Yang, Long Xia, Tao Zhang, Bin Shi, Longnan Huang, Bo Zhong, Xinyu Zhang, Huatao Wang, Jian Zhang, Guangwu Wen
For the first time, Fe3O4@LAS/RGO composites with uniform size and extraordinary electromagnetic wave absorption properties were successfully synthesized by a simple three-step method. The Fe3O4 nanospheres with a diameter of about 200 nm are tightly attached by the lithium aluminum silicate (LAS) glass-ceramic particles with a diameter of about 20 nm and evenly distributed among the graphene sheets. The method of coating a microwave absorber with a wave-transparent material introduces a multiple transmission-absorption mechanism for the material to effectively improve impedance matching. The input impedance Zin value (∼1.0) of Fe3O4@LAS/RGO is better and more stable than the Zin value (∼1.2) of Fe3O4/RGO. The RL values of Fe3O4@LAS/RGO could reach -65 dB at 12.4 GHz with a thickness of only 2.1 mm and the absorption bandwidth with RL values less than -10 dB (over 90% electromagnetic wave absorption) is up to 4 GHz at the corresponding thickness. The intrinsic properties of the component of Fe3O4@LAS/RGO composites and the composite structure of the material lead to a variety of microwave absorption mechanisms acting together to improve the microwave absorption properties of the composites.
Comparative study of glyphosate removal on goethite and magnetite: adsorption and photo-degradation Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-09 Ying Yang, Qinzu Deng, Wei Yan, Chuanyong Jing, Yongli Zhang
Glyphosate (PMG) has been demonstrated to be strongly adsorbed on iron oxides, but few studies have been made on the subsequent degradation process. As the mechanism and process of PMG degradation plays a crucial role on its existence in the environment, this study aims to investigate the comparative adsorption and photo-degradation of PMG on goethite and magnetite. The results show that the Langmuir adsorption capacity of goethite (7.9 mg/g) was higher than that of magnetite (6.7 mg/g) at pH=7. Further clarifying of Zeta potential and attenuated total reflectance Fourier-transform infrared spectroscopy measurements revealed that PMG was absorbed through the coordination of phosphonate moiety. In contrast, PMG degradation due to the photo-catalysis effectiveness of magnetite (kapp=1.2 h-1) was significantly higher than that of goethite (kapp=0.4 h-1) at pH=7. This phenomenon was primarily due to the greater release of the dissolved iron in magnetite which led to the promotion of reactive oxygen species generation in the magnetite/UV system. DFT results show that the formation of Fe-O-P bonds in the presence of iron oxide would change the electron density distribution around the phosphorus center of PMG, and potentially made the C-P bond more assailable to ROS. Furthermore, electron spin resonance results identified the existence of •OH and O2•-, and further tests by adding radical captures proved the domination of •OH in degrading PMG. In addition, intermediate identification of PMG revealed that amino acid, carboxyl acid and other inorganic ions were the main products in the process of photo-degradation. Therefore, it is concluded that the comparative exploration of goethite and magnetite on PMG degradation provides an integrated insight into the similar fate of PMG heterogeneous photo-degradation in the environment.
Photocatalytic oxidation of isoflurane, an anesthetic gas: the influence of operating parameters Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-09 Henrietta Essie Whyte, Cécile Raillard, Albert Subrenat, Valérie Hequet
Photocatalytic oxidation (PCO) is a technology that has been suggested as an alternative energy efficient method to improve Indoor Air Quality (IAQ) in several indoor air spaces. In the past few years, several studies have been made to assess the feasibility of PCO for the removal of VOCs that are commonly found in most indoor environments like homes and schools. There are however little or no studies on other indoor environments like hospitals. In hospital operating rooms, anesthetic gases such as isoflurane are known to be one of the main pollutants found in the air. The present work therefore studies the efficiency of PCO to remove isoflurane by studying the influence of three operating parameters on the degradation process. The operating parameters investigated were air velocity, light intensity and initial concentration. The experiments were carried out in a closed-loop multi pass reactor. The kinetic degradation curve of isoflurane showed two distinct phases; the first phase where the degradation occurred slowly and a second phase where the degradation accelerated and fit a first order decay model. Two quantitative indicators, the induction time and the single pass removal efficiency were chosen to compare the influence of the parameters on the first and second phases respectively. Increasing the air velocity led to longer induction periods and lower single pass removal efficiencies. Induction period was decreased when light intensity was increased and removal efficiencies increased by half order. Lower induction periods and better removal efficiencies were obtained at lower concentrations. Although some intermediates were identified, their low concentrations mean they may not pose significant negative effects to human health.
In-situ hydrothermal growth of Zn4Si2O7(OH)2·H2O anchored on 3D N, S-enriched carbon derived from plant biomass for flexible solid-state asymmetrical supercapacitors Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-09 Yifu Zhang, Hanmei Jiang, Qiushi Wang, Changgong Meng
Zinc silicates are an appealing feature for electrode materials in Li-ion battery owing to their layered structure providing a well-defined and facile Li ion transportation route. However, the poor conductivity of zinc silicates limits their wide application as electrode materials, and furthermore zinc silicates have not been explored to apply to supercapacitor. Herein, three-dimensional N, S-doped C-Zn4Si2O7(OH)2·H2O (3D C-ZnSi) have been developed by a hydrothermal process from a highly available and recyclable plant biomass - bamboo leaves, composed of organic compound and silica, for the application to supercapacitor. This is about zinc silicate first applied to supercapacitor. The as-prepared electrode materials have extensive pores inherited from biological structures of bamboo leaves, including micropores, mesopores and macropores. Owing to the existence of hierarchical pores, the single electrode presents excellent capacitance of 450 mF cm−2 at 5 mV·s−1, and excellent cyclic performance with the retention of 83% after 10000 cycles. Furthermore, the as-assembled 3D C-ZnSi//activated carbon (3D C-ZnSi//AC) flexible solid-state asymmetric supercapacitor can achieve a maximum energy density of 0.69 Wh m−2. Additionally, the device exhibits high cycle stability for 6900 cycles with the retention of 80%. This study shows the possibility for 3D N,S doped C-Zn4Si2O7(OH)2·H2O as one of the most promising candidates for high performance energy storage devices.
MXene Debris Modified Eggshell Membrane as Separator for High-Performance Lithium-Sulfur Batteries Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-09 Lingxia Yin, Guiyin Xu, Ping Nie, Hui Dou, Xiaogang Zhang
A functional separator (MXene/ESM) to suppress the lithium polysulfides shuttling via coating MXene debris on one surface of a biodegradable eggshell membrane (ESM) is designed to enhance the electrochemical performance of Li-S batteries. The excellent electronic conductivity of the porous MXene debris, and the good mechanical strength, superior thermal stability as well as large electrolyte infiltration of ESM make MXene/ESM an ideal separator for high-performance Li-S batteries. The strong chemisorption induced from both Ti-S bond formed between Ti atom in MXene and the lithium polysulfides by the Lewis acid-base interaction and affinity of O and N containing functional groups on ESM to the lithium polysulfides greatly prevents the shuttling effect of the polysulfides. Compared with a commercial polypropylene separator, the Li-S battery with the MXene/ESM separator containing a KJC/S cathode and a Li metal anode displays greatly improved cycling stability with a capacity retention of 74% after 250 cycles at 0.5 C, while the Li-S battery with a polypropylene separator remains only 11%. The rate performance of Li-S battery with the MXene/ESM separator has also been enhanced compared to that with a polypropylene separator. Specifically, the Li-S battery with the MXene/ESM separator has a discharge capacity of 1321 mAh g-1 at 0.1 C, 1112 mAh g-1 at 0.2 C, 1003 mAh g-1 at 0.5 C and 948 mAh g-1 at 1 C.
Techno-economic assessment of surrogate-based real-time control and monitoring of secondary effluent ozonation at pilot scale Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-05 Michael Chys, Wim T.M. Audenaert, Harald Stapel, Achim Ried, Arne Wieland, Marjoleine Weemaes, Herman Van Langenhove, Ingmar Nopens, Kristof Demeestere, Stijn W.H. Van Hulle
During secondary effluent ozonation, real-time control of the ozone dose based on the water quality is essential to minimize operational costs and by-product formation (i.e. two of the main hurdles hindering a fast implementation of the technology). In this pilot-scale study, the ozone dose was controlled via online UV absorbance (UVA254) measurements. Only one sensor was used although a ΔUVA254-based control strategy was applied. The practical implications of online spectral sensors and the effect of effluent dynamics in terms of load (i.e. Dissolved Organic Carbon or DOC concentration) and composition (i.e. reactivity) was studied in relation to the applied control strategies. The one sensor approach - presented for the first time to the best of the authors’ knowledge - reduced the negative impact of sensor fouling. The use of manual and ultrasonic cleaning is recommended as it results in significantly less fouling (i.e. a factor of 6 difference). Additionally, the variable effluent reactivity showed to be more influential than the effluent load in determining the ozone dose. The use of ΔUVA254 ensured the supply of the required ozone doses during varying water quality and weather conditions, and at lower operational costs than more common control strategies (up to 22% of savings). Flow or load proportional strategies were not able to cope with the dynamic ozone demand of the effluent. However, the required additional response time of the ΔUVA254-strategy might be a disadvantage and could be tackled using hybrid control approaches including load-based dosing (i.e. O3:DOC ratio based) and the use of a combined feedback-feedforward system.
Catalytic activity of different iron oxides: Insight from pollutant degradation and hydroxyl radical formation in heterogeneous Fenton-like systems Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-05 Ling Zhao, Zhi-Rong Lin, Xiao-hong Ma, Yuan-Hua Dong
The catalytic performance of iron oxides in 2,4,4’-trichlobiphenyl (PCB28) degradation following an order of goethite > magnetite > hydrated iron(III) oxide > hematite was observed in four iron oxides catalyzed Fenton-like reactions, which was not consistent with the stoichiometric efficiency of ·OH generation. This result indicates that ·OH was not the sole active species responsible for PCB28 degradation in four iron oxides catalyzed Fenton-like systems. The reductive degradation of hexachloroethane (HCE) was 76.8%, 58.7%, 46.1% and 37.6% for magnetite, goethite, hematite and hydrated iron(III) oxide, respectively, further suggesting that both oxidative species (·OH) and reductive species (HO2·) simultaneously contributed on PCB28 degradation. The addition of tert-butyl alcohol (·OH scavenger) decreased the amount of 7-hydroxycoumarin (7-HC, ·OH indicator) by 42%, 77%, 97%, and 97% for magnetite, goethite, hematite, and hydrated iron(III) oxide, respectively. Meanwhile, the addition of p-benzoquinone (HO2· scavenger) only reduced the amount of 7-HC by 77%, 27%, and 33.5% for magnetite, hematite, and hydrated iron(III) oxide, respectively; but increased the amount of 7-HC by 126.7% in the goethite/H2O2 system. This result indicates that the mechanism of ·OH generation from H2O2 catalyzed by four iron oxides was different. For goethite, the surface lattice iron was primarily responsible for activating H2O2 to form reactive species (·OH and HO2·) and thereby degrade pollutants on the oxide surface. For magnetite, both the surface lattice iron and the dissolved Fe in solution played an equally important role in catalyzing H2O2 decomposition to form and propagate reactive species for pollutant degradation. For hematite and hydrated iron(III) oxide, the solution phase chain reaction effectively propagated by dissolved Fe should be the primary catalytic mechanism although the chain reaction was initiated by the surface processes.
Effect of Na, K, Ca and P-impurities on diesel oxidation catalysts (DOCs) Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-05 Paola Anguita, Jesús Manuel García-Vargas, François Gaillard, Eduard Iojoiu, Sonia Gil, Anne Giroir-Fendler
In order to reach the limits of CO2 emissions set by Kyoto protocol, the use of biofuels is gaining momentum. However, the biofuels contains alkali and alkaline earth metals (Na, K and Ca) and phosphorus (P) species, which could decrease the efficiency of the after-treatment system. The main aim of this study is to increase the knowledge of the effect of impurities contain on biofuel on the catalytic activity of the diesel oxidation catalysts (DOCs). Both reference (PtPd/CeZrO2/La-Al2O3) and modified catalysts were synthesized, characterized by several techniques and tested, concerning their physico-chemical, redox and catalytic properties. Based on the characterization results, the catalyst crystalline structure did not change after the impurities incorporation, however, the specific surface area was decreased in all cases. NO adsorption strength was increased due to the low electronegativity of Na, K and Ca species, according to H2-TPR and NO-TPD analyses. XPS analysis confirmed the formation of cerium phosphate, which can stabilize the Ce3+ oxidation state related to its higher Ce3+/Ce4+ ratio, diminishing the catalytic redox activity. The physico-chemical and redox properties modifications after Na, K and Ca impurities addition diminished the CO and NO removal, however, the C3H6 conversion was improved. Besides, both CO and C3H6 oxidation were enhanced, while the NO to NO2 conversion decreased in presence of P species.
Z-scheme 2D/3D g-C3N4@ZnO with enhanced photocatalytic activity for cephalexin oxidation under solar light Chem. Eng. J. (IF 6.735) Pub Date : 2018-07-05 Ning Li, Yu Tian, Jianhui Zhao, Jun Zhang, Wei Zuo, Lingchao Kong, Hao Cui
In this study, a newly-designed Z-scheme g-C3N4@ZnO heterostructure was synthesized by 3D ZnO controllable deposition on 2D g-C3N4 nanosheets using thermal atomic layer deposition. The activity of 2D/3D g-C3N4@ZnO was evaluated by photocatalytic degradation of cephalexin under simulated sunlight. Results showed that the g-C3N4@ZnO photocatalyst achieved 98.9% degradation and 72.8% mineralization of cephalexin within 60 min of illumination. This degradation process fitted to the pseudo first order dynamic model with reaction rate constant of 0.0735 min-1, 5.4 and 8.1 times higher than that of pure g-C3N4 and ZnO, respectively. Consecutive degradation experiments revealed the excellent stability and recyclability of 2D/3D g-C3N4@ZnO photocatalyst. Mechanism exploration found the enhanced photocatalytic activity was mainly ascribed to the strong oxidizability of active species generated on Z-scheme g-C3N4@ZnO. Besides, the oxidative species, especially h+ and ·OHplayed significant roles in the degradation process. Moreover, the degradation intermediates were identified through HPLC/MS/MS analysis and the possible pathway of cephalexin decomposition was proposed accordingly. The Z-scheme 2D/3D g-C3N4@ZnO was also proved effective for contaminants removal in real sewage. This study provided a new platform for controllable creation of Z-scheme photocatalysts with broad application prospects in contaminants remediation from aquatic environment under solar light.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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