Conversion and pre-concentration of SWRO reject brine into high solubility liquid salts (HSLS) by using electrodialysis metathesis Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-10 Qing-Bai Chen, Hang Ren, Zhenhua Tian, Luqin Sun, Jianyou Wang
An electrodialysis metathesis (EDM) technology aimed at efficiently converting and pre-concentrating SWRO reject brine into high solubility liquid salts was proposed. In terms of process influence factors, effects of surface flow velocity, applied voltage and number of repeating units were investigated. Results showed that the applicable range of surface flow velocity should be set to 2.20-2.95 cm/s. 6 V (2 V per repeating unit) seems appropriate for the operation. Increasing the number of repeating units in a certain region (≥3) would be beneficial. For the ion migration analysis at optimized conditions, it is found that the ions leakage and co-ions migration were extremely weak. In the multiple batches pre-concentrating process, the TDS values of concentrating solutions gradually increased from 0 to about 200g/L after 72 hours, and scaling phenomenon was not found. This process thus provides a suitable way for producing high concentration liquid salts with high solubility feature.
Design and performance evaluation of novel colliding pulse jet for dust filter cleaning Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-11 Jianlong Li, Daishe Wu, Quanquan Wu, Min Luo, Jiangsheng Li
Pleated filter cartridges with high pleat ratios and large filter surface are found to have great instances of patchy cleaning. In order to improve the intensity and uniformity of filter cleaning, a novel colliding pulse-jet cleaning method was designed and tested in this study. An experimental pulse-jet cleaning dust collector (the filtration chamber is 1225 × 750 × 1000 mm (width × depth × height)) was built with two nozzles installed over the filter cartridge (ϕ320 × ϕ240 × 660 mm) and on the cartridge bottom. The nozzle outlet pressure, pulse jet performance (intensity and uniformity), and compressed air consumption were studied. The effect of the trigger time difference between the top and bottom pulse jets on the performance was researched. This study demonstrated that the non-time-differenced colliding pulse-jet mode increased the pulse-jet intensity obviously to 2.56 times compared with the top-jet-only mode with some more air consumption (about 1.85 times than that in top-jet-only mode), but the pulse-jet uniformity slightly worsened. The pulse-jet intensity could be enhanced remarkably to 5.49 times if the colliding pulse jet was controlled in the strategy of varying trigger time difference, with the uniformity also increased obviously.
Production of high-purity fucose from the seaweed of Undaria pinnatifida through acid-hydrolysis and simulated-moving bed purification Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-11 Seok-Bin Hong, Jae-Hwan Choi, Yong Keun Chang, Sungyong Mun
An efficient process suitable for a large-scale production of fucose from the seaweed of Undaria pinnatifida was developed in this study. The developed process consisted of a hydrolysis, a series of pretreatment processing for decolorization and deionization, and a final-stage purification using a well-designed simulated-moving bed (SMB) process. First, the optimal acid concentration and reaction time for the seaweed hydrolysis were investigated. The hydrolysate resulting from such investigation was then used to determine the optimal operating conditions for the pretreatment step consisting of an activated-carbon treatment, an electrodialysis, and an ion-exchange processing, which were performed to accomplish decolorization and deionization. On the basis of the optimal conditions that were obtained from the preceding experiments, a series of hydrolysis and pretreatment operations were carried out to secure a sufficiently large amount of decolorized and deionized hydrolysate. This was then moved on to the final purification step based on the use of the SMB process, which was designed such that the detailed recovery of fucose with a very high purity in a continuous mode could be ensured. The results showed that the purity of fucose, which reached 15.4% after the completion of the pretreatment processing, was markedly increased to nearly 100% through the SMB processing. It was also confirmed that the overall loss of fucose amounted to 22.9%, and most of the fucose loss occurred during the electrodialysis and ion-exchange procedures whereas there was almost no loss during the SMB processing.
Experiments on filtering nano-aerosols from vehicular and atmospheric pollutants under dominant diffusion using nanofiber filter Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-11 Wallace Woon-Fong Leung, Yuen Ting Chau
Nano-aerosols of size 100nm and below are manifested everywhere in various urban micro-environments. In outdoor, the vehicular emission during traffic jam can release nano-aerosols with concentration above 200million/m3 (200/cm3). Superimposed on vehicular emission are smog particles, around 10-50nm, generated from the photochemical reaction of hydrocarbon and NOx in the presence of sunlight. These nano-aerosols, by virtue of their small sizes, can be inhaled readily into our bodies leading possibly to various chronic diseases. Air-borne viruses from influenza to epidemic viruses, which can lead to acute sickness and even death, are also in the same size range of 100nm. Despite microfibers are being commonly used today in filters, there has been limited studies on filtration of real aerosols using microfiber filters, let alone nanofibrous filters, as most studies used simulated aerosols (e.g. sodium chloride) or test dust. Also, in standard sodium chloride test, only monodispersed aerosol size is allowed to challenge the filter. On the other hand, in reality aerosols of all sizes challenge simultaneously the filter. In this study, we have used nanofiber filter to filter polydispersed aerosols from the micro-environment near busy traffic area where aerosols comprise of both vehicular and atmospheric pollutants with size range between 10 and 400nm. A portable test filter was used for the measurements and the test results are compared to the theoretical correlation from Payet with diffusion correction at small Peclet number (Pe). We have found good comparison between test results with theoretical correlations using equivalent aerodynamic diameter for the aerosols with face velocity from 1 to 11 cm/s. A new dimensionless specific filter resistance (also established independently by Buckingham-π approach) is defined for the first time. It measures the flow drag on fibers to the amount of fibers present in the filter, the lower is the specific filter resistance the better is the filter. For our test condition, it is approximately 1-1.2. We have also improved the filtration efficiency of the filter by increasing the fiber basis weight by stacking up two layers of nanofibers. We have demonstrated that the efficiency increases while both the quality factor and specific filter resistance remain constant. We have also investigated the single fiber efficiency due to diffusion and found that at low velocity and low Peclet number (Pe<10), the test results agree well with the theoretical prediction. On the other hand, at higher face velocity (>0.07m/s) and large Peclet number (>10), there are small deviations from the theory which is probably due to the smaller aerosols collecting by the larger aerosols upstream of the filter for polydispersed aerosol distribution challenging the filter. This has not been seen previously as tests conducted were mostly using monodispersed aerosol size distribution for which aerosol-aerosol interaction was absent.
Statistical methodology for scale-up of an anti-solvent crystallization process in the pharmaceutical industry Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-11 Ameessa Tulcidas, Susana Nascimento, Bruno Santos, Carlos Alvarez, Sylwin Pawlowski, Fernando Rocha
The scale-up of crystallization processes is a challenging step in production of active pharmaceutical ingredients (APIs). When moving from lab to industrial scale, the mixing conditions tend to modify due to the different geometry and agitation performance, which is particularly important in anti-solvent crystallizations where the size of the crystals depends on the mixing and incorporation of the anti-solvent in the solution. In this work, the results obtained in anti-solvent lab-scale crystallization experiments were used to develop multivariate statistical models predicting Particle Size Distribution (PSD) parameters (Dv10, Dv50 and Dv90) in function of predictors such as percentage of volume, power per volume and tip speed. Firstly, the collinearity among the predictors was assessed by Variance Inflation Factor (VIF) diagnosis. Subsequently, least squares method was employed to find correlations among the predictors and output variables. The optimization of the models was executed by testing quadratic, logarithmic and square root terms of the predictors and removing the least statistically significant regression coefficient. The quality of the fitting was evaluated in terms of adjusted R2 (R2adj). The modelled Dv10, Dv50 and Dv90 values presented a good fitting to the experimental data, with R2adj higher than 0.79, either when using power per volume or tip speed along the percentage of volume as predictors. Afterwards, the particle size distribution parameters of industrial scale production were predicted using the previously developed models. The deviations between predicted and experimental values were lower than 17%. This demonstrates that multivariate statistical models developed in lab-scale conditions can be successfully used to predict particle size distribution in industrial-size vessels.
Effect of the inlet duct angle on the performance of cyclone separators Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-11 Marek Wasilewski, Lakhbir Singh Brar
This study analyzed the effect of the angle of the inlet duct bend on the separation efficiency and pressure drop in cyclone separators. The design of the inlet to the cyclone chamber is a significant parameter that has been analyzed to date only in a few research studies. Following the literature review of this subject, 20 bend angles (10 in the vertical plane and 10 in the horizontal plane) were proposed and analyzed by means of the computational fluid dynamics code Fluent V18.2. As a closure model to the Reynolds-averaged Navier–Stokes equation, the Reynolds stress model was used, as it solves the transport equations for Reynold’s stresses and the dissipation rate - this model is capable of accounting highly curved streamlines prevailing inside the cyclone separators. The discrete phase model with one-way coupling was used, in which the trajectory of solid particles was calculated based on Lagrangian formulation. Conclusive results indicate that the bend angle (in both planes) marginally affects the collection efficiency (the maximum difference being 3.1%), whereas its effect on Eu is highly significant (the difference being 5,700%) - all the comparisons were made with respect to the base variant at 0° angle.
CFD Simulation of Hollow Fiber Supported NaA Zeolite Membrane Modules Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-08 Jiacheng Wang, Xuechao Gao, Guozhao Ji, Xuehong Gu
NaA zeolite membranes have exhibited excellent performance in pervaporation dehydration of organic solvents. However, the industrial applications based on tubular NaA zeolite membranes are limited due to the high fabrication cost and low permeation flux. Hollow fiber supported zeolite membranes have great advantages of high permeation flux and large packing density, which are beneficial to further reduce the membrane cost. For practical application, it is of great significance to design membrane modules with optimized geometric configuration for the hollow fibers. Here, a hollow fiber membrane module equipped with seven bundles of hollow fiber NaA zeolite membranes and several baffles was designed by computational fluid dynamics (CFD) technique. The effect of baffles on flow field distribution of the membrane module was investigated. The results showed that the membrane module with two radial baffles and four axial baffles not only showed uniform flow distributions inside the module, but also improved the axial velocities along the hollow fibers, which could alleviate concentration polarization. The improved separation efficiency of the membrane module was further confirmed by the experimental characterization.
Swelling reduction of polyvinylidenefluoride hollow fiber membrane incorporated with silicoaluminophosphate-34 zeotype filler for membrane gas absorption Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-07 N.A. Ahmad, C.P. Leo, A.L. Ahmad, M. Nur Izwanne
CO2 gas absorption is important in fuel purification and carbon capture. By incorporating a porous membrane with a large surface area in membrane gas absorption (MGA) system, the CO2 transfer between feed gas and liquid absorbent can be greatly improved. However, the absorption flux usually drops in the long-term operation due to membrane wetting by the common liquid absorbent, amine. Membrane wetting can lead to membrane swelling which induce the growth of mass transfer resistance. In this work, silicoaluminophosphate-34 (SAPO-34) zeolite was incorporated into polyvinylidene fluoride (PVDF) hollow fiber membrane to reduce flux decline caused by membrane swelling. The membrane porosity and pore size increased with increasing SAPO-34 loading. Nevertheless, significant changes in water contact angle or liquid entry pressure were not shown. PVDF hollow fiber membrane incorporated with 3 wt% of SAPO-34 showed slightly higher CO2 absorption flux to PVDF hollow fiber membrane in MGA with distilled water as the absorbent. However, the CO2 absorption flux of this PVDF/SAPO-34 membrane was greatly improved of about 140 % higher than the CO2 absorption flux of the neat membrane when diethanolamine was used as the absorption. The CO2 absorption flux of PVDF hollow fiber membrane dropped about 60 % after 96 hours. Although these membranes showed a similar water contact angle after being wetted by water or amine, they swelled differently. PVDF hollow fiber membrane swelled nearly 71.0 % after being wetted by amine, but only swelled about 2 % after being wetted by water. The incorporation of SAPO-34 into PVDF hollow fiber membrane reduced swelling by amine, down to 47.7 %. The swelling reduction could be a major cause of absorption improvement shown by PVDF/SAPO-34 hollow fiber membrane in MGA using diethanolamine.
Conversion of water-organic solution of sodium naphtenates into naphtenic acids and alkali by electrodialysis with bipolar membranes Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-07 Aslan Achoh, Victor Zabolotsky, Stanislav Melnikov
The process of recovery of sodium naphtenates into naphtenic acids and sodium alkali using electrodialysis with bipolar membranes is investigated. The values of current efficiency for naphtenic acid and alkali, as well as energy consumption for the process, are determined. It is shown that the main problems with the development of electro-membrane technology for producing naphtenic acids from petroleum and petroleum products are associated with micelle formation of a mixture of naphtenic acids with sodium naphtenate in the pH = 6.5–8 range, which leads to a sharp increase in the viscosity and electrical resistance of solutions. Introduction of the cation-exchanger and sodium sulfate to the intermembrane space of naphtenthe salt chamber can significantly improve the technical and economic characteristics of the process - for example, the specific energy consumption decrease from 0.86 kWh∙L–1 down 0.38 kWh∙L–1, which is more than two times lower than the original three-chamber cell. At the same time, the production of naphtenic acids remains on the same level which is 17 L∙m-2∙h-1.
Stepwise synthesis of oligoamide coating on a porous support: Fabrication of a membrane with controllable transport properties Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-07 Paramita Manna, Alberto Tiraferri, Marco Sangermano, Roy Bernstein, Roni Kasher
Porous polymeric membranes are widely used in potable water purification, wastewater treatment, the food and pharmaceutical industries, and haemodialysis. However, producing specialized membranes with diverse transport properties is challenging. A method for fabricating membranes with controllable transport properties is described here by stepwise synthesis of aromatic oligoamide on a porous polymeric support. The use of aromatic oligoamide affords good water permeance due to its hydrophilic character. Alternate couplings of trimesoyl chloride and meta-phenylenediamine yielded an oligoamide dendrimer that was covalently bonded to the support. The water permeance and molecular weight cutoff (MWCO) of the synthesized membranes were controlled (with values of 4.6 to 543 L·m−2·h−1·bar−1 and 22.6 to 332 kDa, respectively) by adjusting the number of oligoamide synthesis cycles in the range of 2.5 – 20.5. The oligoamide membrane with 5.5 synthetic cycles showed a high rejection of the negatively charged rose bengal dye (95% rejection) with high flux (126.4 ± 4.2 L·m−2h−1 at 5.2 bar), as compared with other membranes reported in the literature. The fabricated membranes are potentially highly useful for the separation of macromolecules with specific ranges of molecular weight, for industrial separations that require membranes with tunable MWCO ranges, or for the separation of charged macromolecules.
Hybrid electrostatic filtration systems for fly ash particles emission control. A review Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-07 A. Jaworek, AT. Sobczyk, A. Krupa, A. Marchewicz, T. Czech, L. Śliwiński
The removal of submicron and nanoparticles from flue gases emitted by coal fired boilers is the subject of extensive studies in recent years. Electrostatic precipitators and fibrous filters are the most commonly used gas-cleaning devices for the removal of these particles in power plants and industry. However, the collection efficiency of electrostatic precipitators decreases for particles smaller than 1 micron. Fibrous filters provide higher filtration efficiency for particles of this size, but the pressure drop is higher, and additional energy is needed to supply the outlet fan. Recently, special attention of engineers has been given to hybrid constructions, which apply electrostatic fields and forces in order to improve the performances of bag filters. There are three types of such solutions, which have been investigated in the literature: (1) electrically energized filter, in which fibres of the filter are energized by an electric field; (2) hybrid electrostatic filter, which applies electrostatic charging of particles before their filtration by bag filter; and (3) hybrid electrostatic precipitator, which uses a conventional electrostatic precipitator for the removal of coarse particles, and a subsequent bag filter for the removal of fine particles leaving the precipitator. All of these constructions allow the collection efficiency for PM2.5 particles to be increased and the pressure drop across the bag filter to be reduced. In this paper, various hybrid electrostatic filtration systems have been reviewed and their performances compared with respect to collection efficiency, pressure drop and dust cake dislodging.
Reduced Thermal Rearrangement Temperature via Formation of Zeolitic Imidazolate Framework (ZIF)-8-based Nanocomposites for Hydrogen Purification Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-08 Susilo Japip, Sugiarto Erifin, Tai-Shung Chung
Thermally rearranged polymers are a class of heterocyclic microporous polymers generated by in situ thermal rearrangement (TR) of ortho-hydroxy polyamides or polyimides at elevated temperatures to produce polybenzoxazole (PBO). Poly(hydroxyamide) (PHA) was selected as a model polymer to generate amide-derived PBO (APBO) owing to its lower TR temperature. A nano-size zeolitic imidazolate framework of ZIF-8 was synthesized and incorporated into the PHA matrix to form PHA-ZIF8 nanocomposites. Due to the presence of ZIF-8 inside the PHA matrix, interchain interactions in the PHA matrix may be inhibited that results in a reduced TR temperature for PHA conversion into APBO. Differential scanning calorimetry (DSC) confirmed that the TR temperature of PHA-ZIF8 nanocomposites decreases as a function of ZIF-8 loading. In addition, the conversion of PHA into APBO and the structural integrity of ZIF-8 before and after TR were visualized by Fourier-transform infra-red (FTIR) spectroscopy and X-ray diffractometer (XRD), respectively. Subsequent measurements of gas transport properties of both PHA-ZIF8 and APBO-ZIF8 nanocomposites revealed that the synergistic amalgamation of TR and formation of nanocomposites can boost hydrogen separation performance, particularly H2/CH4, of APBO-ZIF8-35% close to the 2008 upper-bound.
An extended standard blocking filtration law for exploring membrane pore internal fouling due to rate-determining adsorption Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-06 Kang Xiao, Yinghui Mo, Jianyu Sun, Mingyu Wang, Shuai Liang, Xiaomao Wang, Xia Huang, T. David Waite
Membrane internal fouling due to foulant adsorption onto the pore walls is a critical aspect of fouling. The classical “standard blocking law” for internal fouling simplistically assumes instantaneous adsorption such that the adsorbed amount grows linearly with the filtered liquid volume, which is inadequate to describe realistic internal fouling with varied adsorption rates. In this study, an extended standard blocking law for scenarios involving time dependent adsorption is proposed and yields an expression of the form dR/dV∼RN (where R is filtration resistance and V is filtrate volume). Two ultimate scenarios of the law, i.e. the 1st-kind for sufficiently fast adsorption with the characteristic exponent N ≈ 1.5 (similar to the classical standard blocking) and the 2nd-kind for sufficiently slow adsorption with N ≈ 2.5 are experimentally verified via microfiltration of model polysaccharide (alginate) solutions using hydrophobic and hydrophilic membranes. Transition between the 1st-kind and 2nd-kind laws is related to the rates of adsorption versus filtrational mass transfer. The extended law provides an improved tool to evaluate internal fouling, particularly that associated with adsorption of hydrophilic matter (such as polysaccharides) into hydrophilic membranes.
Optimisation of Wet pressure Drop in Nonwoven Fibrous, Knitted, and Open-cell foam Filters Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-06 V. Golkarfard, A.J.C. King, S. Abishek, R. Mead-Hunter, G. Kasper, B.J. Mullins
This work investigates the relationship between wet (multi-phase) pressure drop, saturation and filter face velocity in mist (or coalescing) filters in order to evaluate optimum operating conditions. Three different structural types of oleophobic filter media (fibrous, knitted and open-cell foam), with equivalent clean filtration efficiency and pressure drop, were investigated numerically over a wide range of inlet velocities (0.05 to 2 m.s-1). The numerical results indicate the balance between saturation/flow resistance and pressure drop of the filter media with increasing velocity. Experiments were also conducted to validate the trends found in simulations. Both the numerical and experimental results show a local optimum in the pressure drop profile, due to flow regime transition. This effect has not previously been documented due to a lack of parametric studies in this region. This region may be an optimal operating regime for some applications.
Chlorination of Bromacil: Kinetics and disinfection by-products Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-06 Chen-Yan Hu, Yan-Guo Deng, Yi-Li Lin, Yuan-Zhang Hou
Bromacil, a nonselective uracil compound, is applied to field crops, such as citrus and pineapple, to control annual and perennial grass weeds. In this study, the degradation kinetics and effects of influencing factors on the formation of disinfection by-products (DBPs) during bromacil chlorination were investigated. The reaction between chlorine and bromacil followed second-order kinetics, and the degradation kinetic model for bromacil chlorination was established. The rate constants of the reactions between bromacil and HOCl and ClO− were calculated as 4.33 (±1.40) ×101 and 3.21 (±0.47) ×102 M−1s−1, respectively. The presence of Br− in water resulted in the formation of HOBr and accelerated the rate of bromacil degradation during chlorination. The rate constant was calculated as 6.34 (±0.09)×104 M−1s−1for the reaction between bromacil and HOBr at 25°C. The apparent second-order rate constant (kapp) increased with increase in temperature and pH, and the activation energy was calculated as 37.83 kJ/mol using the Arrhenius equation. Because the structure of bromacil comprises bromine atoms, brominated DBPs, including dibromochloromethane (DBCM) and bromodichloromethane (BDCM), formed abundantly during bromacil chlorination. The formation of bromoform (BF), BDCM, and DBCM increased with the reaction time, whereas the formation of chloroform (CF) increased until day 4 and then decreased. The yields of all the detected DBPs increased with the increase in pH from 5 to 8. With increasing bromide concentration, the formation of CF and BDCM gradually decreased, where as that of BF considerably increased, resulting in relatively stable bromine utilization factor in the bromide to chlorine ratio of 0.00-0.10 during bromacil chlorination.
Effect of humic acid concentration on pharmaceutically active compounds (PhACs) Rejection by direct contact membrane distillation (DCMD) Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-07 Carolina Fonseca Couto, Míriam Cristina Santos Amaral, Liséte Celina Lange, Lucilaine Valeria de Souza Santos
In this study, a direct contact membrane distillation process was used to achieve rejection of 25 pharmaceutically active compounds (PhACs) in water. The influence of natural organic matter (NOM), a common contaminant in waters that are used for water supply, on PhACs removal was investigated. Humic acid was used as an organic model in order to represent major constituents of NOM. Results indicated that flux decline slightly increased from 0 to 8% as HA feed concentration increased from 0 to 80 mg L-1. Flux decline was mainly associated with membrane fouling which added hydraulic resistance to the transfer of liquid water. Pore wetting was observed when HA concentration increased, which indicated changes in the hydrophobic character of the membrane. MD process showed a rejection of ≥ 99% for the 25 assessed PhACs for all HA concentration evaluated even at high permeate recovery rate (60%), whereas, 24 PhACs presented concentrations below limit detection. The retention of PhACs by MD membrane occurs predominantly by membrane rejection which is mainly governed by volatility and, to a lesser extent, by hydrophobia. The adsorption contribution to PhACs retention was low (<8%) and was significantly associated with positively charged compounds. Although the feed side of the membrane became hydrophilic due to the HA deposit, the PhACs retention by DCMD was not affected, which reinforces the robustness of the process and the ability to produce safe water. Thus, in general, DCMD is less influenced by the feed composition than nanofiltration or reverse osmosis, implicating in higher PhACs rejections.
Hydrothermal stability and permeation properties of TiO2-ZrO2 (5/5) nanofiltration membranes at high temperatures Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-06 Sofiatun Anisah, Masakoto Kanezashi, Hiroki Nagasawa, Toshinori Tsuru
The hydrothermal stability of TiO2-ZrO2 nanofiltration (NF) membranes fired at 200, 400, and 550 °C was examined at 90 °C for 4-100 h, followed by an evaluation of the NF performance at 25 °C. After hot-water treatment, the water permeability (Lp) of a membrane fired at 200 °C had slightly increased, while that of membranes fired at 400 and 550 °C had drastically decreased. Meanwhile, the values for molecular weight cut-off (MWCO) were decreased for all membranes. The Lp and MWCO changed during the initial 20 h and remained constant for as long as 100 h, confirming the stability in an aqueous solution at 90 °C. The permeation properties of water and neutral solutes were evaluated for temperatures that ranged from 25 to 85 °C. The water permeability and permeate flux increased with an increase in temperature, while the rejection of solutes decreased. Based on analysis using the Spiegler-Kedem equations, the reflection coefficient was constant irrespective of permeation temperature, while both water and solute permeability were increased with an increase in the permeation temperature, which revealed that the permeation mechanism of water and neutral solutes is an activated process. In addition, the activation energies of solute permeability were found to be higher than those of water permeability.
Enhancing CO2 separation performance of Pebax® MH-1657 with aromatic carboxylic acids Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-05 Shadi Meshkat, Serge Kaliaguine, Denis Rodrigue
In this work, two aromatic carboxylic acids (benzoic acid and isophthalic acid) are proposed to modify the permeability of poly(amide-b-ethylene oxide) or Pebax for CO2 separation membranes. The effect of acid content on the gas separation performance of flat membranes was investigated using CO2, CH4 and N2 at different pressures (4-10 bar) and temperatures (35-65°C). The results show that both aromatic acids substantially improved the CO2 permeability (about 120% above neat Pebax) due to the strong interaction between Pebax and the carboxylic groups of the acids, while CH4 and N2 permeability only slightly increase due to the restricted polymer chain mobility. This behavior led to enhanced CO2/N2 and CO2/CH4 selectivity by about 55% and 80%, respectively. Fourier transform infrared spectroscopy (FTIR) confirmed the coordinative interaction between the amide group of Pebax with the carboxyl functional group of the acids. The membranes thermal and mechanical stability were also determined by thermogravimetric (TGA and DSC) and dynamic mechanical (DMA) analyses. Finally, benzoic acid was found to be of interest since it contributed to superior thermal and mechanical strength as well as enhanced CO2 separation properties.
An exciting opportunity for zeolite adsorbent design in separation of C4 olefins through adsorptive separation Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-05 Hilman Ibnu Mahdi, Oki Muraza
High production for C4 olefins as a byproduct in naphtha crackers has stimulated researchers to explore different separation options. Adsorptive separation has been targeted to separate C4 olefins. In this review, challenges and opportunities in the adsorptive separation of C4 olefins using microporous zeolites are scrutinized and elaborated. C4 olefins such as 1-butene, 2-butene, isobutene and butadiene are highly demanded in the petrochemical industry. Their similar properties require highly intensive distillation processes. Adsorptive separation offers lower energy cost, however in the past 70 years, there are limited studies on microporous zeolites for C4 olefins separation. This review highlights the criteria to produce cost-effective adsorbents with shorter synthesis time, cheaper organic structure directing agent (OSDA), potentially higher capacity and improved regenerability properties. Among more than 200 frameworks, FAU, DDR and CHA are some potential frameworks which have been explored for separation of C4 olefins. Recent development of these frameworks and their applications in C4 olefins are carefully studied. It is expected that this review paper will stimulate further exploration of selected zeolites for adsorptive separation of C4 olefins and open plethora applications in related separations.
Fabrication of Ag3VO4 decorated phosphorus and sulphur co-doped graphitic carbon nitride as a high-dispersed photocatalyst for phenol mineralization and E. Coli disinfection Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-04 Pankaj Raizada, Anita Sudhaik, Pardeep Singh, Pooja Shandilya, Adesh K. Saini, Vinod Kumar Gupta, Ji-Ho Lim, Hanbo Jung, Ahmad Hosseini-Bandegharaei
In this work, we have successfully anchored Ag3VO4 (AV) onto P and S co-doped g-C3N4 (PSGCN) to prepare high-dispersible AV/PSGCN photocatalyst via a deposition-precipitation method. The P and S co-doped g-C3N4 was synthesized via thermal polycondensation using hexachlorotriphosphazene (HCCP) and thiourea as precursors. AV/PSGCN was characterized using various spectral techniques. The atomic force analysis indicated that the thickness of AV/PSGCN was less than 3.0 nm. The zeta potential and Tyndall effect experiments ascertained formation of the well-dispersed suspension of AV/PSGCN in water. The co-doping resulted in lowering optical band gap of g-C3N4. The photoluminescence and electrochemical impedance analysis indicated suppression in recombination of photogenerated electron and hole pairs in AV/PSGCN. The photodegradation of phenol followed pseudo-first order kinetics. Hydroxyl radicals and holes were the two main reactive species for photodegradation of phenol. The COD, HPLC and LC-MS analyses confirmed mineralization of phenol in 6 h. Unlike conventional slurry type photo-reactors, AV/PSGCN was not magnetically agitated during photocatalytic reactions. AV/PSGCN exhibited significant antibacterial activity for E.Coli disinfection. The photodegradation of phenol and bacterial disinfection occurred through hole and hydroxyl radical formation mechanism.
In situ synthesis of Z-scheme BiPO4/BiOCl0.9I0.1 heterostructure with multiple vacancies and valence for efficient photocatalytic degradation of organic pollutant Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-04 Peng Yue, Guoqiang Zhang, Xingzhong Cao, Baoyi Wang, Yanfeng Zhang, Yu Wei
Design and construction of Z-scheme photocatalyst has been attracted much attention, which is a great challenge to develop highly efficient photocatalyst without the external redox mediators. Herein, a novel efficient redox-mediator-free Z-scheme BiPO4/BiOCl0.9I0.1 heterojunction is synthesized in situ via a mild 90°C water bath reaction. The as-synthesized BiPO4/BiOCl0.9I0.1 heterostructure exhibits outstanding photocatalytic performance for degradation of phenol and Rhodamine B, approximately 2.6 and 4.3 times higher than that of BiOCl0.9I0.1, respectively. The BiPO4/BiOCl0.9I0.1 heterostructure have multiple vacancies and valence, such as Bi5+, Bi3+, Bi(3-x)+, I-, I3-, and IO3-, which could facilitate the charge separation and transfer in the photocatalytic process. The higher photocatalytic activity of redox-mediator-free Z-scheme BiPO4/BiOCl0.9I0.1 heterostructure could be attributed to the strong redox ability, multiple charge transfer channels via the various defects, and tight contact due to in situ synthesis. The finding provides some new insights for the design of effective direct Z-scheme photocatalyst with multiple defects.
Effect of heat-stable salts on absorption/desorption performance of aqueous monoethanolamine (MEA) solution during carbon dioxide capture process Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-03 Hao Ling, Sen Liu, Hongxia Gao, Zhiwu Liang
In order to study the effect of heat-stable salts (HSSs) on the CO2 absorption performance of amine solution, the CO2 absorption/desorption rates and cyclic CO2 capacity of 30 wt% (monoethanolamine) MEA solutions in the presence of various acidic degradation products were comprehensively investigated systematically by an improved rate-based screening method. In addition, the initial pH values and CO2 equilibrium solubility were also evaluated. These acidic degradation products considered were formic acid, acetic acid, propionic acid, butyric acid, glycolic acid, oxalic acid, lactic acid, malonic acid and bicine. The experimental results indicated that the carboxylic acids with different chemical structures can reduce the initial pH values, equilibrium solubility of CO2, absorption rate and cyclic CO2 solubility, but promote the CO2 desorption rate of aqueous MEA solution. Furthermore, a countermeasure was proposed to maintain absorption performance and reduce the energy requirement of solvent regeneration for an MEA amine-treating unit. The obtained results can provide a guidance for developing corresponding countermeasure for heat-stable salts control and removal in the CO2 absorption-stripping process using amine solutions.
Preparation and characterization of an antifouling poly (phenyl sulfone) ultrafiltration membrane by vapor-induced phase separation technique Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-04 Amin Dehban, Ali Kargari, Farzin Zokaee Ashtiani
In this paper, anti-fouling poly (phenyl sulfone) ultrafiltration membranes were fabricated through the NIPS (V-0) and VIPS-NIPS (V-15 through V-60) technique. The effect of VIPS conditions on the structure and performance of the membranes has been investigated. Scanning electron microscopy (SEM) and liquid-liquid displacement porosimetry (LLDP) methods were used for membrane characterization. Pure water flux and BSA retention were also used for evaluation of separation performance of the fabricated membranes. The results revealed that by increasing VIPS time, pore size and permeate flux of the membranes were both increased except for V-30 membrane where both the pore size and PWF were decreased. BSA retention has an opposite behavior. By increasing VIPS time from 0 to 15 s, the PWF increased from 17.12 to 20.79 L/m2.h. At a VIPS time of 30 s, PWF reduced to 15.60 L/m2.h, and by further increase of VIPS time to 60 s, the flux increased to 37.69 L/m2.h. BSA retention showed a closer dependency to pore size of the membranes i.e. it decreased from 71.32% to 55.68% by increasing VIPS time from 0 to 15 s, then increased to 63.27% for V-30 membrane, and finally decreased to 52.69% at a VIPS of 60 s. It is noteworthy that the increase of VIPS time from 0 to 15 s leads to an increase in mean pore radius from 0.96 to 1.44 nm and then a decreases to 1.04 nm for a VIPS time of 30 s and finally to 1.39 nm with an increase of VIPS time to 60 s.
Separation of Pt(IV), Pd(II), Ru(III) and Rh(III) from model chloride solutions by liquid-liquid extraction with phosphonium ionic liquids Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-11-30 Martyna Rzelewska-Piekut, Magdalena Regel-Rosocka
The recovery of metals from waste is profitable not only from an economic but also from an ecological point of view. The natural resources of metals (especially platinum group metals - PGM) are limited, while the amount of waste containing the desired metals is still growing. The purpose of the work is the use of quaternary phosphonium salts, i.e. Cyphos IL 101 (trihexyl(tetradecyl)phosphonium chloride), Cyphos IL 102 (trihexyl(tetradecyl)phosphonium bromide) and Cyphos IL 104 (trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate), for the separation of palladium(II), platinum(IV), rhodium(III) and ruthenium(III) from their multi-component model mixtures of composition based on real solutions after leaching of PGM-containing wastes (e.g. automobile catalytic converters). Though, Pd(II) could not be separated from Pt(IV) by one-stage extraction, separation of Pd(II) from Pt(IV) was possible by stripping with 0.1 M thiourea in 0.5 M HCl. The extraction of Rh(III) from the four-component solution practically did not occur (Rh(III) stayed in raffinate), therefore Pt(IV) and Pd(II) could be selectively separated from Rh(III). As a result of the work, a separation procedure of successful separatation of Pd(II), Pt(IV), Ru(III) Rh(III) from four-component solutions has been developed based on two stages of extraction with ionic liquid solution (trihexyl(tetradecyl)phosphonium chloride) and two stages of stripping.
Experimental investigation of the ideal selectivity of MFI-ZSM-5 zeolite-type membranes for a first evaluation of the separation of hydrogen isotopologues from helium Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-12-01 R. Antunes, A. Böhmländer, A. Bükki-Deme, B. Krasch, M.M. Cruz, L. Frances
In future fusion power plants, the tritium (T) breeding inside the reactor is a key aspect to ensure the so-called tritium self-sufficiency. The continuous availability of the fuel for further fusion reactions requires the continuous separation of small molecules such as hydrogen isotopologues (e.g., HT) from helium. Pressure-driven separation with membranes is a promising method to fulfill these requirements, especially if molecular-sieving membranes are available to separate these gas species. In this work, the single gas permeances of He, H2 and D2 were measured with a MFI-ZSM-5 zeolite-type tubular membrane. These experiments were performed in the membrane’s temperature range: 298 - 398 K . At these temperatures, a transition in the transport regime was observed at 360 K , which is attributed to the transition from surface-diffusion dominant to gas-translational diffusion dominant. Using the measured permeances, the permselectivities for H2/He and D2/He were calculated. In the temperature range tested, the permselectivities exceed the Knudsen selectivity, indicating that the membrane is of rather high-quality. Instead, the H2/D2 permeances ratio was around the Knudsen ratio (i.e., ∼ 1.41 ). Moreover, the permeances of the binary mixture H2/D2, at the whole concentration range, were also measured at 298 K to study the isotopic effects on the transport through the MFI-ZSM-5 membrane. We found that the mixed gas behaves macroscopically as a hydrogen isotopologue molecule, and its permeance falls with M eff - 0.5 , where M eff is the effective mass of the mixture determined by the concentrations of H2 and D2. Using this result, the Q2 permeances and the Q2/He permselectivities (where Q = H, D, T) for the other hydrogen isotopologues (i.e., HD, HT, DT and T2) were also calculated.
Non-additive separation selectivity enhancement in poly(4-methyl-2-pentyne) in relation to C1-C4-alkanes Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-11-29 V. Zhmakin, M. Shalygin, V. Khotimskiy, S. Matson, V. Teplyakov
This study examines the fundamental and practical aspects of C1-C4 hydrocarbons separation (pure or in binary or ternary mixtures), using highly permeable glassy 1,2-disubstituted polyacetylenes. Poly(4-methyl-2-pentyne) (PMP) was chosen as the main object of study. An attempt is made here to carry out a systematic comparative study of the PMP permeability target parameters using correlation detection and a thermodynamic gas/polymer model. A non-isothermal application method was used, which allowed us to work with each gas individually and with various mixtures to obtain an experimental value for the dependence on temperature of the permeability of C1, C3, C4 hydrocarbons. This is the first time that this method has been used for the study of glassy polymers with high free volume. An interesting phenomenon of an increase in non-additive separation selectivity α was shown (for a value of α of between ∼10 and ∼8000 units) with increase of butane activity (p/psat) from 0.02 to 0.94 in the feed gas mixture. In the current study, an explanation is given for the increase in non-additive selectivity for PMP membrane separation. Modelling was carried out of the separation process of a binary butane/methane mixture using this non-additive phenomenon, which gives rise to concentrated components.
Selective recovery of indium from iron-rich solutions using an Aliquat 336 iodide supported ionic liquid phase (SILP) Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-11-30 Stijn Van Roosendael, Mercedes Regadío, Joris Roosen, Koen Binnemans
Selective recovery of valuable metals from secondary (waste) sources is essential for better resource efficiency. However, low-grade waste streams typically have complex and variable compositions and low concentrations of valuable metals. Therefore, development of novel technologies, able to deal with these complex and variable waste streams, is necessary. In this work, we present a process for the separation and purification of indium from iron-rich matrix solutions making use of a supported ionic liquid phase (SILP). The SILP used in this study was synthesized by impregnating Amberlite XAD–16N with the iodide form of the quaternary ammonium salt Aliquat 336. The SILP was characterized by infrared spectroscopy, elemental analysis, density, specific surface area and porosity and it was tested for the selective recovery of indium. Adsorption was preceded by the addition of an excess of iodide anions to the solution, to form indium iodide species, which were extracted to the ionic liquid of the SILP. A high selectivity for indium over iron could be achieved because iron iodide species are not stable in aqueous medium. The reaction kinetics and several adsorption parameters, including anion concentration, adsorbent mass, stripping and reusability of the adsorbent were investigated, using synthetic binary iron-indium solutions containing iron in large excess in comparison with indium, as is typically the case in low-grade ores or industrial process residues. Finally, the developed indium recovery process was validated on a real leachate of goethite residue. A pure indium solution of 49 mg·L–1 was obtained with an indium-over-iron mass ratio of 7.9 and a selectivity factor equal to 5400.
Improved CO2 flux by dissolution of oxide ions into the molten carbonate phase of dual-phase CO2 separation membranes Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-11-30 Wen Xing, Zuoan Li, Thijs Peters, Marie-Laure Fontaine, Michael McCann, Anna Evans, Truls Norby, Rune Bredesen
In a solid-liquid dual-phase CO2 separation membrane, the native ions in the molten alkali carbonate, including carbonate anions and metal cations can transport CO2 in a process that is charge–compensated by electronic species (electrons or holes), oxide ions, or hydroxide ions, depending on materials and conditions. This strongly affects the design of experiments for assessing the performance of these membranes, and further determines the routes for integration of these membranes in industrial applications. Here we report how dissolved oxides in the liquid carbonate improve the CO2 flux of the membrane due to an enhanced charge–compensating oxygen ion transport. A qualitative understanding of the magnitude and role of oxide ion conductivity in the molten phase and in the solid support as a function of the temperature is provided. Employing a solid matrix of ceria, and dissolving CsVO3 and MoO3 oxides in the molten carbonate phase led to an almost doubled CO2 flux at 550 °C under dry ambient conditions. When the sweep gas contained 2.5% H2O, the CO2 flux was increased further due to formation of hydroxide ions in the molten carbonate acting as charge compensating species. Also, as a consequence of permeation controlled by ions in the liquid phase, the CO2 flux increased with the pore volume of the solid matrix.
Synthesis optimization of (h 0 h)-oriented silicalite-1 membranes for butane isomer separation Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-02-13 Amei Wu, Congyong Tang, Shenglai Zhong, Bin Wang, Junjing Zhou, Rongfei Zhou
A water-based mixing process for fabricating ZIF-8/PEG mixed matrix membranes with efficient desulfurization performance Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-02-15 Xiaolong Han, Tingting Hu, Ye Wang, Huiyong Chen, Yuqi Wang, Ruiqing Yao, Xiaoxun Ma, Jiding Li, Xifei Li
Enhanced performance of superhydrophobic polypropylene membrane with modified antifouling surface for high salinity water treatment Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-02-19 Yingqi Wang, Gaohong He, Yushan Shao, Daishuang Zhang, Xuehua Ruan, Wu Xiao, Xiangcun Li, Xuemei Wu, Xiaobin Jiang
In this work, the superhydrophobic polypropylene (PP) composite membranes with modified surface were successfully fabricated by loading the SiO2 nanoparticles and attaching low surface energy 1H,1H,2H,2H-perfluorodecyltriethoxysilane. The impact of deposited nanoparticle size on the surface roughness, heterogeneous nucleation barrier and critical nucleus size versus the loaded nanoparticle size (d∗nuclear/d) was simulated by the model combining the surface roughness and superhydrophobility with the critical nucleation energy. The optimized loaded nanoparticles size maintained the proper roughness and d∗nuclear/d to ensure the desired performance of antifouling. The improved superhydrophobic surface enhanced the anti-wetting ability of the membrane for vacuum membrane distillation (VMD) purpose. The resulting modified membrane possessed good anti-wetting ability and stable anti-fouling performance during long-term continuous and batch operation of VMD treating high salinity water system. The fouling rate of the fabricated membrane was decreased to 20% of the one of the original membrane under 15 wt% high salinity feed condition.
ZIF-8 heterogeneous nucleation and growth mechanism on Zn(II)-doped polydopamine for composite membrane fabrication Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-02-27 Xuehua Ruan, Xinfang Zhang, Ziyuan Zhou, Xiaobin Jiang, Yan Dai, Xiaoming Yan, Gaohong He
Continuous ZIF-8 membranes have showed great potential for gas separation. The prospect is subjected to two pivotal issues: shorten the time to construct the ZIF-8 selective layer and tightly bond ZIF-8 layer onto the substrate. In our previous work, Zn(II)-doped polydopamine (Zn-PDA) linkage layer was proposed and effectual to solve these problems. In this research, the mechanism likely to support the improvements is studied intensively. The dominant factor is that Zn(II) ions can be chelating and depositing sufficiently in the linkage layer. The strongly alkaline condition for dopamine polymerization is also beneficial to Zn(II) chelation and deposition, which has been confirmed by DFT simulation, together with characterization tests, e.g., XPS, FTIR, and Zn(OH)2 precipitation for Zn(II)–O coordination. Phenolic hydroxyl groups are deprotonated in the strongly alkaline environment with high Mulliken charge (−0.515 & −0.524 e) and become strong chelation sites to Zn(II). Subsequently, Zn(II) clusters extensively filled in the PDA linkage layer are acting as the starting sites for ZIF-8 heterogeneous nucleation and growth. The correspondence between Zn(II) clusters probed by EDX and nascent ZIF-8 crystals visualized by FE-SEM can support this phenomenon clearly. On the whole, the abundant starting sites in Zn-PDA enhanced ZIF-8 growth, and ZIF-8 growth from the rooting-in Zn(II) clusters created an indented and hinged boundary for tightly bonding ZIF-8 layer onto the substrate.
Thermodynamic study on carbon dioxide absorption in aqueous solutions of choline-based amino acid ionic liquids Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-03-16 Biao Li, Yifeng Chen, Zhuhong Yang, Xiaoyan Ji, Xiaohua Lu
Five choline-based amino acid ionic liquids ([Cho][AA]s) are prepared by neutralization between choline hydroxide and amino acids with different molecular weight and alkalinity. Solubility of CO2 in 30 wt% aqueous solutions of these five [Cho][AA]s has been measured at temperatures from 303.15 to 333.15 K and pressures up to 7 bar. Based on the zwitterion mechanism, the solubility of CO2 in aqueous [Cho][AA]s solutions is correlated with a reaction equilibrium thermodynamic model (RETM). The corresponding thermodynamic parameters, such as Henry’s law constants, reaction equilibrium constants, and enthalpy of physical dissolution and chemical reaction are all calculated and compared to evaluate the CO2 absorption performance in aqueous solutions of five [Cho][AA]s. Meanwhile, the recyclability of the aqueous solution with 30 wt% [Cho][Lys] has been also investigated.
Nafion/PEG hybrid membrane for CO2 separation: Effect of PEG on membrane micro-structure and performance Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-03-27 Zhongde Dai, Hesham Aboukeila, Luca Ansaloni, Jing Deng, Marco Giacinti Baschetti, Liyuan Deng
In the present work, PEGDME with different molecular weight (Mn ∼ 250 and 500 g/mol) was added into Nafion-based membranes as CO2-philic additive, aiming at improving their CO2 capture performance. The physical, chemical and morphological characteristics of the hybrid membranes were thoroughly investigated using different techniques, including TGA, XRD, SEM and FTIR. The gas transport properties were studied by means of mixed gas permeation tests at different relative humidity conditions. CO2 permeability is greatly enhanced upon the addition of the PEGDME. The addition of 40 wt% PEGDME 250 into the Nafion matrix shows a CO2 permeability of 57.4 Barrer at the dry state, which is 36 folds higher than the pristine Nafion. The presence of water vapor in the gaseous streams further enhances the CO2 permeability and CO2/N2 selectivity, reaching a value of 446 Barrer and 37, respectively, under fully saturated conditions. However, the further increase of the PEGDME content in the Nafion matrix leads to undesirable micro phase separation (defects were observed from the morphological analysis), causing serious loss of the selectivity. Finally, in order to improve the theoretical understanding of the transport mechanism, a modified Maxwell model was successfully applied to describe the separation performances of the resulted Nafion/PEGDME hybrid membrane. The model results suggest that an interconnected CO2-philic structure is obtained upon the addition of PEGMDE and water to the ionomer matrix, forming preferential pathways for gas permeation able to enhance the membrane performance.
Absorption of SO2 with calcium-based solution in a rotating packed bed Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-03-29 Liangliang Zhang, Shuying Wu, Yue Gao, Baochang Sun, Yong Luo, Haikui Zou, Guangwen Chu, Jianfeng Chen
In this work, the absorption performance of SO2 into calcium-based solution was studied in a rotating packed bed (RPB). Experiments were carried out to examine the effect of various operating parameters on the desulfurization efficiency, such as absorbent pH value, gravity level of RPB, gas-liquid ratio, gas treatment amount and inlet SO2 concentration. It was found that the SO2 removal efficiency increased with the increasing of absorbent pH value and RPB gravity level, and decreased with the increasing of the gas-liquid ratio and inlet SO2 concentration. SO2 removal efficiency was about 88% for the metal packing and 82% for the plastic packing under the optimal operating conditions when the SO2 inlet concentration was 900 mg/m3. Moreover, volumetric mass transfer coefficient (KGa) in RPB of this absorption process was calculated. It was found that KGa was 7.83–19.34 s−1 in RPB, almost 1 order of magnitude higher than that in packed tower and impinging stream gas-liquid reactor.
A multifunctional chromatographic material modified with aminopolycarboxylic acid agent Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-03-31 Ning Zhang, Bin Chen, Rong Li, Chen Li, An Fan, Fei Huang
A novel chromatographic material, aminopolycarboxylic-modified silica, was developed by two different synthetic routes, followed by characterization of the prepared material. The methods were compared and discussed based on binding capacity of ligand, chromatographic experiments and metal ion-chelating capacity of the material. Versatility of this chromatographic material including ion-exchange and affinity behaviors for proteins as well as chelating property for metal ions were investigated. The results showed that the material was prepared successfully, and synthetic method II was more favorable to the preparation of the material. This novel chromatographic material displayed good chromatographic behaviors for the separation of proteins, as well as outstanding chelating property for metal ions. Versatility of the material can effectively expand the applications of this functional material in different research fields.
ZIF-8 nanoparticles with tunable size for enhanced CO2 capture of Pebax based MMMs Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-04-04 Wenji Zheng, Rui Ding, Kai Yang, Yan Dai, Xiaoming Yan, Gaohong He
Poly (ether-block-amide) (Pebax) based mixed matrix membranes (MMMs) were prepared by using size-tunable ZIF-8 nanoparticles as fillers. ZIF-8 nanoparticles with sizes of 40, 60, 90 and 110 nm (ZIF-8-40, ZIF-8-60, ZIF-8-90 and ZIF-8-110) were synthesized in microemulsion by controlling the ratio of Zn2+ to Hmim (1:16, 1:8, 1:5, 1:2). And they were distributed uniformly in Pebax matrix without obvious agglomerations and defects at the loading of 0–20 wt.%, which was confirmed by field-emission scanning electron microscopy (FE-SEM). The incorporation of ZIF-8 resulted in a significant improvement in CO2 permeability and the CO2/N2 selectivity increased with the BET surface area of ZIF-8 increasing. The enhanced permeability is attributed to an improvement in the free volume of the polymer induced by larger sized ZIF-8, while the increased selectivity results from the high specific surface area of large sized ZIF-8, which can provide more active sites for CO2 capture and great mass transfer resistance for N2. At 5 wt.% loading of ZIF-8-90, the MMM presents the best separation performance with CO2 permeability of 99.7 Barrer and CO2/N2 selectivity of 59.6, both of which are increased by about 25% by comparison to the pure Pebax membrane. The present study provides an effective way to obtain size-controlled ZIF-8 fillers and high separation performances of Pebax based MMMs.
Cost-effective synthesis of activated carbons with high surface areas for electrodes of non-aqueous electric double layer capacitors Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-04-07 Takeshi Mori, Shinichiroh Iwamura, Isao Ogino, Shin R. Mukai
Activated carbons for electrodes of non-aqueous electric double layer capacitors were prepared from composites of poly(methymethacrylate) particles and phenolic resins. Their surface areas can be increased up to 3000 m2 g−1 through simple CO2 activation. Through the characterization of pore properties of the resulting carbons, it was found that the activation process appears to be composed of two steps. The pore properties of the activated carbons were optimized to maximize their performances as electrodes for non-aqueous electric double layer capacitor electrodes.
A low cost hydrophobic kaolin hollow fiber membrane (h-KHFM) for arsenic removal from aqueous solution via direct contact membrane distillation Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-04-09 Siti Khadijah Hubadillah, Mohd Hafiz Dzarfan Othman, A.F. Ismail, Mukhlis A. Rahman, Juhana Jaafar
In this work, a low cost hydrophobic kaolin hollow fiber membranes (h-KHFM) was successfully prepared by phase inversion/sintering technique followed by a modification via grafting with fluoroalkylsilane (FAS) molecules. The influence of sintering temperature varied from 1200 to 1500 °C on the hydrophobization and separation performance of kaolin hollow fiber membrane (KHFM) was investigated through direct contact membrane distillation (DCMD) system towards synthetic arsenic wastewater. The results reveal that h-KHFM prepared at a sintering temperature of 1300° °C induced a high contact angle value of 145°, an excellent LEPw value of 2 bar, and an average pore size of 0.32 µm. As a consequence, a high permeate flux of 28 kg/m2 h for As(III) and 25 kg/m2 h for As(V) with 100% arsenic rejection was obtained at a feed temperature of 60 °C and has met the required standard of maximum contaminant level (MCL) of 10 ppb. In addition, arsenic concentrations of up to 1000 ppm with various pH values of arsenic were also investigated using h-KHFM sintered at 1300 °C and there was no arsenic detected in the permeate.
Absorption of n-butane in imidazolium and phosphonium ionic liquids and application to separation of hydrocarbon gases Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-04-16 Takashi Makino, Mitsuhiro Kanakubo
In this report, the density, viscosity, and heat capacity of the tetraalkylphosphonium ionic liquids, containing newly synthesized trihexyltetradecylphosphonium p-dodecylbenzenesulfonate and bis(2-ethylhexyl)sulfobutanedioate, were measured at atmospheric pressure. Then, the n-butane absorption in the dialkylimidazolium and tetraalkylphosphonium ionic liquids were investigated at the n-butane pressure of 0.101 MPa and the temperatures of (298.15–353.15) K. In a series of bis(trifluoromethanesulfonyl)amide ionic liquids, the trihexyltetradecylphosphonium salt absorbed the largest amount of n-butane, followed by the triethyloctylphosphonium, 1-methyl-3-octylimidazolium, and 1-butyl-3-methylimidazolium salts. On the other hand, in the trihexyltetradecylphosphonium ionic liquids, the bis(2-ethylhexyl)sulfobutanedioate and p-dodecylbenzenesulfonate salts had the higher solubilities of n-butane than the bis(trifluoromethanesulfonyl)amide salt. In addition, the solubilities of water vapor in the trihexyltetradecylphosphonium salt were measured at 298.2 K and atmospheric pressure. Trihexyltetradecylphosphonium bis(trifluoromethanesulfonyl)amide was the most free from the moisture. We further performed the continuous gas absorption experiments of n-heptane and toluene using the present tetraalkylphosphonium ionic liquids. They removed successfully the vapors of hydrocarbons despite the very dilute concentrations of hydrocarbons, less than 1500 ppm. The initial absorption rates were calculated to discuss the absorption kinetics in the tetraalkylphosphonium ionic liquids.
Recovery of gold ions from discarded mobile phone leachate by solvent extraction and polymer inclusion membrane (PIM) based separation using an amic acid extractant Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-04-16 Fukiko Kubota, Riho Kono, Wataru Yoshida, Maha Sharaf, Spas D. Kolev, Masahiro Goto
This paper reports on the selective separation and recovery of gold ions from leachates of discarded mobile phones using liquid-liquid extraction and a polymer inclusion membrane (PIM) transport system. The collected mobile phones were crushed by a mill and the obtained powder was calcinated. After leaching with aqua regia, the metal composition of the leachate was analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES). The analysis results confirmed that the mobile phone waste contained 397 g/ton of gold. Liquid-liquid extraction and PIM-based separation procedures for the selective recovery of gold(III) from synthetic and actual leachates were developed. The extracting organic solution and the PIM incorporated the newly synthesized extractant N-[N,N-di(2-ethylhexyl)aminocarbonylmethyl]glycine (D2EHAG) which exhibited high selectivity for the gold(III) ion over the other metal ions present in much higher concentrations in the leachates. The compositions of the feed and receiving solutions in both the liquid-liquid and PIM based extraction and back-extraction of the gold(III) ions were optimized. It was established that optimal extraction required a HCl concentration in the feed solution of 2 mol/L and that a receiving solution containing 0.1 M thiourea in 1 M HCl was capable of back-extracting gold(III) quantitatively. Membrane transport experiments with a synthetic leachate as the feed solution demonstrated that 96% of the gold(III) ions was selectively transported into the receiving solution of the transport cell thus leaving all other metal ions in the leachate.
ZIFs-modified GO plates for enhanced CO2 separation performance of ethyl cellulose based mixed matrix membranesf Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-04-30 Kai Yang, Yan Dai, Wenji Zheng, Xuehua Ruan, Hao Li, Gaohong He
Graphene oxide (GO) has been employed as filler in mixed matrix membranes (MMMs) to enhance gas selectivity as its high-aspect ratio structure makes the path of gas diffusion longer and tortuous, improving diffusivity selectivity of gases with different molecular sizes. However, the stacking and folding structure of GO nano-sheets leads to gas barrier effects which reduce gas permeability. In this paper, a strategy of modifying continuous ZIF-8 layer with ultra-microporosity and high gas permeability on the surface of GO nano-sheets was proposed to increase the size and connectivity of gas transfer passage. ZIF-8@GO nano-sheets were successfully prepared by two-step ultrasonic synthesis method of growing ZIF-8 on GO surface at room temperature and the flexibility of nano-sheets could be easily tuned by different reaction times. CO2 permeability of ethyl cellulose (EC)/ZIF-8@GO MMMs achieves continuous enhancement with the increased loading of ZIF-8@GO compared with pure GO based MMMs which shows rare effective improvement in CO2 permeability. EC/ZIF-8@GO membrane containing 20 wt% fillers exhibits CO2 permeability of 203.3 Barrer together with CO2/N2 selectivity of 33.4, increased by 139% and 65% from that of pristine EC membrane respectively, and this performance is also higher than that of MMMs containing independent GO or ZIF-8. Having distinct improvement of CO2 separation performance, the modification strategy using ultra-porosity MOFs to enhance gas transfer of 2D nano-sheets is promising for fabrication of high performance CO2 separation membranes.
Incorporating attapulgite nanorods into graphene oxide nanofiltration membranes for efficient dyes wastewater treatment Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-04-30 Cai-Yun Wang, Wen-Juan Zeng, Ting-Ting Jiang, Xi Chen, Xiao-Liang Zhang
Graphene oxide/attapulgite (GO/APT) composite membranes were successfully fabricated by the vacuum-assisted filtration for efficient dyes wastewater treatment. By characterization of FTIR, XPS, Raman, XRD and FESEM, APT nanorods were confirmed to be incorporated into GO laminar layers via grafting modification, which would influence GO interlayer distance (d-spacing), membrane surface microstructure (laminate morphology, structure, and hydrophilicity) and even water separation performance. Comparison of those of pristine GO membrane, the calculated d-spacing of GO/APT membranes gradually increased from 0.90 nm to 1.07 nm, while water contact angles decreased from 71.0° to 43.3° with the increasing APT/GO ratios. Moreover, GO/APT membranes exhibited rough hierarchical microstructure and higher surface hydrophilicity, which was in conjunction with larger interlayer spacing to synergistically improve separation performance. The water permeated flux increased from 3.4 of pristine GO membrane to 13.3 L m−2 h−1 of GO/APT membrane with preserving high rejection nearly to 100% for 7.5 mg L−1 Rh B wastewater under optimized conditions. Similarly, membrane thickness, dye concentrations and separating species in feed solutions were also found to affect membrane separation performance. Dye molecules were efficiently rejected through GO/APT nanofiltration membranes by the synergistic separation mechanism: size exclusion effect because of the unimpeded water channels formed into 3D network laminate structure, and electrostatic interactions between the oxygen-containing functional groups on membrane surface and charged molecules. Such these GO/APT membranes demonstrated efficiently separation properties and thus provided new insight into the potential applications in water purification and dyes wastewater treatment.
Graphic synthesis method for multi-technique integration separation sequences of multi-input refinery gases Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-05-01 Xuehua Ruan, Hongyan Xiao, Xiaobin Jiang, Xiaoming Yan, Yan Dai, Gaohong He
In petroleum and chemical industries, many valuable species are depleted into various refinery gases. In order to fractionate and reclaim these valuable components efficiently and sufficiently, it is necessary to integrate diverse separation techniques together. The major obstacle to synthesize and optimize such a multi-component and multi-input process is the combinatorial explosion. In this research, graphic synthesis method is established to construct the multi-technique integration processes, in which the optimum or near-optimum sequence would be programmed to couple high efficient separation unit operations together to improve efficiency. As the support, three technical measures are summarized: the pseudo-ternary mixtures of H2, light hydrocarbons and fuel gases are proposed to depict refinery gases, after ranking species with their separation characteristics and belongings in products, so that the composition space can be visualized into triangular coordinate system; the dominant feed ranges for the pivotal separation units, i.e., adsorption, condensation, glassy and rubbery polymeric membranes, are determined after efficiency analysis, in which the represented technique is more efficient than the others for the composition matched feedstock; the shortcut calculation and the visualized representation with vectors in triangular coordinate system are created to quickly estimate separation operations, owing to their selectivity unique to a certain component group. Without laborious work to screen numerous sequences, this method programs recovery strategies and synthesizes processes appropriately and quickly.
Novel regenerable solid sorbents based on lithium orthosilicate for carbon dioxide capture at high temperatures Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-05-08 Soo Chool Lee, Min Joo Kim, Yong Mok Kwon, Ho Jin Chae, Min Sun Cho, Yong Ki Park, Hwi Min Seo, Jae Chang Kim
Purification of industrial grade lithium chloride for the recovery of high purity battery grade lithium carbonate Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-05-09 Nicholas Linneen, Ramesh Bhave, Douglas Woerner
Due to lithium’s high energy along with other exceptional characteristics, lithium demand across many industries is rising, specifically for Li-batteries. Therefore, a sufficient supply of high purity lithium is vital in order for these significant technologies to develop. In the current work, industrial grade lithium chloride has been successfully treated with four simple precipitation steps to obtain a high purity battery grade lithium carbonate of >99.95%. The LiCl starting solutions contained K, Na, Mg, Ca, Cu, Ni, and Fe chloride contaminants and solutions of 2.5 to 10 M were simulated. The heavier metals and the majority of Mg were removed in a single step with an increase in pH. The removal of Ca and remaining Mg was executed by sodium oxalate addition where the calcium levels of the 10 M were able to be reduced to 5–6 ppm in solution. It appeared that the higher molarity and ionic strength of the LiCl solution aided in obtained higher degrees of impurity removal. Finally, high purity Li2CO3 was obtained by first precipitating from brine solution, followed by a second purification step with pressurized CO2. The second step allowed for the removal of entrapped Na and K after the first precipitation, resulting in >99.95 wt% purity Li2CO3.
Recovery of platinum by solvent extraction and direct electrodeposition using ionic liquid Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-06-06 Masahiko Matsumiya, Yueqi Song, Yusuke Tsuchida, Hisashi Ota, Katsuhiko Tsunashima
The diluent characteristics and the wide electrochemical window of the ionic liquid (IL), triethyl-n-hexyl phosphonium bis(trifluoromethyl-sulfonyl)amide; [P2225][NTf2], has been exploited for the extraction of Pt(IV) using tri-n-octylamine (TOA, R3N, R = (CH2)7CH3) hydrochloride, followed by direct electrodeposition as Pt metal from organic phase. The extraction mechanism of Pt(IV) with [R3N·HCl]/[P2225][NTf2] has been investigated from the slope analysis. As a result, it was revealed that the extraction mechanism of Pt(IV) was based on the following anion exchange extraction; [PtCl62−]aq + 2[R3N·HCl]org ⇔ [R3NH]2[PtCl6]org + 2[Cl−]aq (R = (CH2)7CH3) The viscosity and the ionic conductivity for the [R3NH]2[PtCl6] were satisfied by Vogel-Fulcher-Tamman (VFT) equation and each best-fit parameter can be estimated in this study. The electrochemical behavior for [R3NH]2[PtCl6] in IL was investigated by Electrochemical Quartz Crystal Microbalance (EQCM) at 373 K. It was revealed that the cathodic reaction: Pt(IV) + 2e− → Pt(II) was estimated from 0 V to −0.87 V and Pt(II) + 2e− → Pt(0) was proceeded from −0.87 V to −1.13 V considering from Mapp = 178.5 evaluated by CV/EQCM. Moreover, the alternation of Δηρ (product of viscosity and density) was corresponded to the locally decrease of the viscosity of IL near the electrode. Finally, the potentiostatic electrodeposition of [R3NH]2[PtCl6] allowed us to recover the blackish electrodeposits, which were identified as most of Pt metal by EDX and XRD analyses.
Antifouling zwitterion embedded forward osmosis thin film composite membrane for highly concentrated oily wastewater treatment Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-07-07 W.J. Lee, P.S. Goh, W.J. Lau, C.S. Ong, A.F. Ismail
The raising oil consumption in oil and gas industries has exacerbated the disposal of oil waste into various water streams. This phenomenon has called for treatments to prevent threats to the human and environment. With some great advantages such as lower membrane fouling rate, lower energy requirement and higher water recovery rate compared to the conventional pressure-driven membrane processes, forward osmosis (FO) has been recognized as a potential candidate for oily wastewater treatment. In this study, a poly[3-(N-2-methacryloylxyethyl-N,N-dimethyl)-ammonatopropanesulfonate] (PMAPS) incorporated thin film composite (TFC) membrane with excellent anti-fouling properties was fabricated for oily wastewater through forward osmosis process. PMAPS was blended with polyethersulfone (PES) dope solution and cast into PES support layer. Interfacial polymerization (IP) technique was applied to form a thin polyamide (PA) layer atop of the PES support layer. The PMAPS incorporated TFC membranes were characterized for their morphology and surface hydrophilicity. The resultant 1% PMAPS-TFC membrane exhibited high water flux of 15.79 ± 0.3 L/m2.h and oil flux of 12.54 ± 0.8 L/m2.h when tested in FO mode for oil removal from oily wastewater using 1000 ppm emulsified oily solution as feed solution and 2 M NaCl as draw solution. The oil rejection up to 99% was also obtained. Most significantly, PMAPS incorporated TFC membrane outperformed neat TFC membrane with lower fouling propensity for oily waste treatment. When treating 10000 ppm oil emulsion, PMAPS-TFC was able to achieve average flux recovery rate of 97% while neat TFC only able to achieve 70.8% of average flux recovery rate.
Effect of a Li2SiO3 phase in lithium silicate-based sorbents for CO2 capture at high temperatures Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-07-26 Yong Mok Kwon, Ho Jin Chae, Min Sun Cho, Yong Ki Park, Hwi Min Seo, Soo Chool Lee, Jae Chang Kim
The Li4SiO4 sorbent is considered one of the most promising CO2 acceptor materials at high temperatures, but it has the disadvantage of poor CO2 capture performance due to aggregation. In this study, a novel lithium silicate-based sorbent containing both Li4SiO4 phase and Li2SiO3 phase was developed to overcome the decrease of CO2 capture capacity of the sorbent for CO2 capture in the high temperature range of 550–700 °C. This sorbent was simply prepared by physical mixing of Li2CO3 and SiO2 (Ludox®) in a 1.8:1 M ratio. The effect of the developed lithium silicate-based sorbent on CO2 capture was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and temperature-programmed desorption (TPD) analysis. The novel lithium silicate-based sorbent exhibited a high CO2 capture capacity (∼250 mg CO2/g sorbent) during multiple cycles at a regeneration temperature of 700 °C. In addition, we found that the CO2 capture performance was affected by Li2SiO3 phase in the lithium silicate-based sorbents. This is because the Li2SiO3 in the sorbent helps prevent growth of particle size and aggregation.
Visible-light photocatalytic fuel cell with Z-scheme g-C3N4/Fe0/TiO2 anode and WO3 cathode efficiently degrades Berberine Chloride and stably generates electricity Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-11-29 Kané Rabé, Lifen Liu, Noor Ahmed Nahyoon, Yizhen Zhang, Ahmed Mahmoud Idris
A visible-light Z-scheme g-C3N4/Fe0/TiO2 anodic catalyst was tested with cathodic WO3 in photocatalytic Fuel Cell (PFC) that efficiently degrades berberine chloride and simultaneously generate electricity at pH 2,5,7 and 13. The Stainless-steel mesh electrodes loaded with prepared catalyst were irradiated by visible-light in single chamber PFC. The highest removal of berberine Chloride, cell voltage, and power density were 91%, 0.8 V, and 16.4 W/m2 at a current density of 2.02 mA/cm2, respectively after 90 min irradiation in 0.05 M Na2SO4 electrolyte, with 10 Ω external resistance. The impacts of pH and initial concentration of BEC on photocatalytic degradation and cell voltage were evaluated. The cell current density is enhanced while the photocatalyst activity increased. The constructed PFC maintained high-performance after 5 uses. Its use in degrading wide spectrum refractory pollutants and generate electricity is expected for the proved catalyst design, paired electrodes and high PFC performance for practical wastewater treatment.
Ceramic Membranes with Mussel-inspired and Nanostructured Coatings for Water-in-oil Emulsions Separation Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-11-28 Nengwen Gao, Zhi-Kang Xu
The effective removing water from water-in-oil emulsions is of great importance in fuel oil production and waste oil recovery. Ceramic membranes with excellent mechanical, and chemical stability have been increasingly used in the treatment of water-in-oil emulsions. However, membrane fouling is still a challenge needed to be solved due to the intrinsic hydrophilic property of these ceramic membranes. Herein, mussel-inspired and nanostructured coatings have been fabricated to modify the ceramic membrane with superhydrophobic/oleophilic surfaces. First, polydopamine (PDA) is deposited on the ceramic membrane surface using CuSO4/H2O2 as a trigger. Then, the formed PDA coating acts as a platform to induce the metallization of Ag ions into Ag nanoparticles. Subsequently hexadecanethiol (HDT) is grafted on the obtained membranes. The membrane morphologies, chemistry and wettability after each step of surface modification are characterized. CuSO4/H2O2 accelerates the deposition process of PDA on ceramic membrane surface with much more uniformity. Hierarchical nanostructure by silver nanoparticles is formed on PDA coated membranes. And the synergistic effect of surface hierarchical structure and HDT modification leads to the membrane surface's superhydrophobicity in air and a non-adhesive behavior to the water droplet under oil. The final modified membranes also show good stability in a series of solvents, and show excellent antifouling property in the filtration of water-in-oil emulsions. This modification method provides a facile and efficient strategy for preparing durable antifouling ceramic membranes for the treatment of organic solvents.
Critical Flux and Fouling Mechanism in Cross Flow Microfiltration of Oil Emulsion: Effect of Viscosity and Bidispersity Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-11-28 Henry J. Tanudjaja, Jia Wei Chew
Membrane-based filtration is promising for applications in the food industry, for example, for processing dairy products, but membrane fouling restricts the efficiency of the process. The deposition of the main constituents in skim milk of casein, lactose and milk fat globules onto the membrane due to the permeate drag is inevitable, which necessitates a mechanistic study of the fouling phenomena. The Direct Observation through the Membrane (DOTM) technique was used to understand the effects of viscosity and bidispersity on the microfiltration of oil emulsions. Deposits at the feed-membrane interface clearly slowed down as the feed viscosity increased. The higher drag to the crossflow as a result of the higher viscosity caused more oil droplets to foul the membrane. However, although both casein and lactose increased the feed and permeate viscosity, the presence of lactose did not alter the fouling phenomena of a moving cake layer of oil droplets much, but the presence of casein caused the oil droplets to deposit instead as clusters. For casein, other than the viscosity effect, it also resulted in a bidisperse suspension, with the smaller particulates promoting membrane fouling. Agreement between the experimental data and the shear-induced diffusion model was good at the lower cross-flow velocities (CFVs) but poorer at higher CFVs, which indicate that the effect of viscosity appeared negligible at the lower CFVs but more dominant at the higher CFVs. The DLVO model agreed with the Jcrit and TMP results. This study sheds light on the membrane fouling phenomena for viscous feeds, and are expected to be useful particularly for food applications.
Development of Composite Filters with High Efficiency, Low Pressure Drop, and High Holding Capacity PM2.5 Filtration Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-11-28 De-Qiang Chang, Chi-Yu Tien, Chein-Yu Peng, Min Tang, Sheng-Chieh Chen
Many efforts are being made to develop filters with high efficiency and high holding capacity but remaining a low pressure drop. A two-layer composite filter to achieve the goal was developed, in which the first layer was a charged coarse fibers to provide large void space for particle loading and the second was a thin layer of charged melt-blown with finer fibers to enhance the overall efficiency. Experimental results showed that although the new composite media had a lower initial efficiency than the other two HEPA filters (PTFE and glass fiber filter), its figure of merit (FOM) was the highest. Besides, the composite media had a better holding capacity for PM2.5 than the other two. At a fixed mass load, i.e., 2 g m-2, the PTFE (ΔP=380 Pa) and glass fiber (ΔP=165 Pa) required around 7.6 and 3.3 times more power, respectively, than the composite media (ΔP=50 Pa). Due to the low charge level of the coarse fiber layer and the fine fiber diameter of the melt-blown layer, resulted in no efficiency reduction along the loading process. Theoretical analysis showed that the charge shielding and the loss of efficiency in the successive top-down layers were timely compensated by the efficiency increase caused by the loading effects, which made the composite media a much uniform deposition of PM2.5 in layers. This was the main reason resulting in the high holding capacity and low pressure drop of the current composite media which acted like a perfect depth filtration media.
Comparative performance assessment of flat sheet and hollow fiber DCMD processes using CFD modeling Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-11-28 Pelin Yazgan-Birgi, Mohamed I. Hassan Ali, Hassan A. Arafat
The effects of select system parameters on the performance of direct contact membrane distillation (DCMD), in terms of permeate flux (J) and temperature polarization coefficient (TPC), were investigated and compared for flat-sheet (FS) and hollow-fiber (HF) modules. Three-dimensional (3D) computational fluid dynamics (CFD) models were developed and validated using experimental data. Then, a two-level full factorial design tool was used to design the simulation runs to investigate the effects of four selected process parameters on flux and TPC. These are:; feed inlet temperature (Tf), permeate inlet temperature (Tp) and Reynolds number on the feed (Ref) and permeate (Rep) sides. The effect of each factor and the interactions thereof were assessed based on data obtained from the CFD models.Although all four parameters showed a significant influence on flux and TPC, their interactions had different effects on the HF and FS modules. For instance, since the permeate stream temperature increases much faster along the permeate channel in the HF module than in the FS module, Rep has a more substantial impact in the HF module. At higher Rep values, higher Tf results in further enhancement in permeate flux in the HF module. Furthermore, the CFD model results indicate that the FS module generally showed better performance, in terms of permeate flux, than the HF module under the same DCMD process conditions. In the CFD model runs which yielded the highest flux in both HF and FS modules, the permeate outlet temperatures from the HF and FS modules were 21.72 °C and 18.53 °C, respectively, under the same operating conditions. Generally, the HF module exhibited about 21% lower flux than the FS module.
Azeotropic distillation for 1-propanol dehydration with diisopropyl ether as entrainer: equilibrium data and process simulation Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-11-27 Jordi Pla-Franco, Estela Lladosa, Sonia Loras, Juan B. Montón
Azeotropic distillation process is widely used to separate non-ideal binary mixtures into their constituent pure components. 1-Propanol dehydration was used as case study and diisopropyl ether was analysed as possible entrainer in an azeotropic distillation. The separation of some alcohols from their aqueous solution is a challenging task because these aqueous mixture forms minimum boiling azeotrope. In this way, isobaric vapor-liquid and vapour-liquid-liquid equilibrium data were measured for the 1-propanol+ water + diisopropyl ether ternary mixture at 101.3 kPa. The data were correlated by NRTL and UNIQUAC models. A separation sequence (a decanter and a single-feed distillation column) for 1-propanol dehydration using diisopropyl ether was proposed. The simulation of the separation sequence was carried out satisfactorily by Aspen Hysys® using the thermodynamic model NRTL with the binary parameters obtained in this work. Moreover, the effect of temperature decantation was investigated in order to reduce the energy demand of the process.
Synthesis and characterization of a plat sheet potassium ion sieve membrane and its performances for separation potassium Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-11-26 Sha-Sha An, Jie Liu, Ji-Hong Wang, Mu-Cun Wang, Zhi-Yong Ji, Shan-Shan Qi, Jun-Sheng Yuan
Most of the ion exchange membranes distinguished monovalent ions from the multivalent ions according to the charge difference, but scarcely had selectivity to the specific ions. In order to effectively separate potassium ions from seawater containing more than 30 times sodium ions, potassium ion-sieve composite membranes with specific selectivity to potassium ions had been synthesized in this paper. The potassium ion sieve was successfully synthesized on the flat α-Al2O3 membrane by secondary hydrothermal method to form potassium ion sieve composite membrane. Then, the results of SEM, XRD and EDS showed that the potassium ion sieve had been successfully bonded with base membrane. The results of electrodialysis experiments showed that the ionic perm-selectivity were α (K/Na) =7.62, α (K/Mg) =68.43 and α (K/Ca) =162.92 respectively, which indicated that the composite membrane had special selectivity for potassium ions. The composite membrane had been evaluated under different voltages and temperatures. As the voltage increased, the ion flux and the perm-selectivity to potassium were all improved. Moreover, with the increase of temperature, the ion flux increased but the selectivity to potassium decreased. The separation performance of the composite membrane was studied by using equimolar solution (containing K+, Na+, Ca2+, Mg2+), seawater and twice concentrated seawater as the test solutions, and the results had exhibited that the composite membrane had good application performance in extracting potassium from seawater.
Selective removal of nitrate ion using a novel activated carbon composite carbon electrode in capacitive deionization Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-11-26 Ling Gan, Yifan Wu, Haiou Song, Shupeng Zhang, Chang Lu, Shuang Yang, Zheng Wang, Bicun Jiang, Changming Wang, Aimin Li
Two double-layer composite electrodes were fabricated by coating anion exchange resin (A520E) and carboxyl-functionalized multi-walled carbon nanotubes (MWCNTs-COOH) onto activated carbon electrodes. Subsequently, an asymmetric capacitive deionization reactor was assembled to evaluate performance of the selective electro-adsorption of nitrate in 2 mM chloride and 1 mM nitrate solutions. In the experiment, the total amount of anions adsorbed in reactor reached 48.80 mmol/m2, with nitrate accounting for 54.07% in particular. It was confirmed that A520E/AC/GP electrode enhanced nitrate selectivity, and MWCNTs-COOH/AC/GP electrode increased the adsorption capacity. An investigation of desorption of anions showed nitrate was electrostatically adsorbed on electrode and then ion exchanged on the resin layer. When the applied voltage increased from 1.0 to 1.6 V, the total amounts of adsorbed anions increased, while the molar fraction of nitrate decreased. Desalination tests performed using different binary solutions of anions, revealed that the order of desalination capacities for anions is NO3- >SO42-> F- ≈ Cl-. A highly linear relationship between the amounts of total adsorbed ions and desorbed chloride ions on resin electrode indicated the same effect of changing solution conditions (i.e., concentration of ions) on adsorption by ion exchange and the electric field.
Prediction of breakthrough behaviors using logistic, hyperbolic tangent and double exponential models in the fixed-bed column Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-11-22 Qili Hu, Yanhua Xie, Chuanping Feng, Zhenya Zhang
In this work, the logistic, hyperbolic tangent and double exponential models were proposed to describe the breakthrough behaviors in the fixed-bed column. Introduction of the parameter n into the above three models resulted in the corresponding modified breakthrough models. The physical meanings of the parameters in these models were explicated. The maximum specific growth rate μmax, lag time λ, inflection point ti and half-operating time t50 were defined to better reflect symmetry and curvature of the breakthrough curve. The breakthrough models established using μmax and λ mainly focused on the adsorption rate instead of adsorption capacity. Many attempts were made to reveal the mathematical relationships between the logistic, hyperbolic tangent and double exponential models. The obtained results indicated that the new breakthrough models could describe the two different adsorption systems very well. These empirical models provided an alternative method for the description of the breakthrough curve.
The Genius of Gibbsian Surface Excess (GSE) Framework for Fluid (Gas or Liquid) - Solid Adsorption: A Powerful Practical Tool Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-11-22 Shivaji Sircar
The GSE is the only experimental variable to unambiguously quantify the extent of multicomponent fluid (gas or liquid)-solid adsorption. It can be directly used to describe all practically important thermodynamic and dynamic characteristics of an adsorption system as well as to formulate the relevant mass and heat conservation equations needed for design of adsorptive processes for separation and purification of fluid mixtures.
Exploration of the Formation of Self-forming Dynamic Membrane in An Upflow Anaerobic Sludge Blanket Reactor Sep. Purif. Technol. (IF 3.927) Pub Date : 2018-11-22 Muhammad Ahmar Siddiqui, Ji Dai, Dao Guan, Guanghao Chen
Self-forming dynamic membrane bioreactor (SFDMBR) technology has drawn increased attention recently, especially for its potential application in anaerobic conditions to retain slow growing sludge in the system. To attain maximum sludge retention, quick development of a self-forming dynamic membrane (SFDM) is deemed necessary. A lab-scale upflow anaerobic sludge blanket (UASB) reactor with a side-stream anaerobic SFDMBR was used in this study to investigate the factors affecting the successful formation of a SFDM and identify the indicators of success. The SFDM formed successfully within 60 to 90 minutes to produce permeates of less than 10 NTU after system optimization. The short formation period and low permeate turbidity provide strong support for the potential of retaining a large amount of sludge in the UASB reactor. The thickness and wet density of the SFDM increased continuously with the decrease in surface area during the formation period. Extracellular polymeric substances (EPS) played an essential role in SFDM formation. Humic acid was the dominant EPS in the sludge, but it did not significantly affect the SFDM formation. Even though polysaccharides only represented 3.7% of the total EPS in sludge, it accumulated on the supporting material as a percentage of the total EPS increased significantly from 6.2% after 60 minutes to 10.8% after 720 minutes. Therefore, polysaccharides were the primary reason for the formation of the SFDM. β-polysaccharides were more important because it mainly accumulated on the fiber of the supporting material.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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