Surface oxygen vacancy inducing peroxymonosulfate activation through electron donation of pollutants over cobalt-zinc ferrite for water purification
Graphical abstract
Introduction
The extensive use of pesticides, pharmaceuticals, personal care products, dyes and other industrial chemicals has led to the release of increasing amounts of refractory organic pollutants [1], such as environmental hormone bisphenol A (BPA) [2], antihistamine drug diphenhydramine (DP) [3], synthetic dye rhodamine B (RhB) [4] and insecticide precursor 2-chlorophenol (2-CP) [5] into our water environment [6]. Most of these pollutants, even at trace concentrations, are potentially harmful and toxic to the eco-environment and to human beings, even carcinogenic, teratogenic and endocrine disruptive [7]. The traditionally conceived solution is to thoroughly degrade or mineralize these pollutants, but conventional water treatment plants cannot effectively achieve this goal [8], consume even more energy and waste organic resources (organic pollutants and their intermediate products). To effectively solve the problem of pollutant elimination for water purification, we propose the concept of utilizing the intrinsic energy of organic pollutants in a sustainable process of pollutant conversion.
The use of peroxymonosulfate (PMS, [O3SOIOIIH]−) activation technology to eliminate organic contaminants is one concept among emerging advanced oxidation processes (AOPs) [[9], [10], [11], [12]]. Hydroxyl radicals (OH, E0(OH/H2O) = 2.81 VNHE), sulfate radicals (SO4−, E0(SO4−/SO42−) = 2.43 VNHE) and singlet oxygen (1O2) produced by the activation of PMS are candidates for the main active species for destruction of pollutant structures during this process [[13], [14], [15], [16], [17], [18], [19], [20], [21], [22]]. Similar to the Fenton reaction for activating hydrogen peroxide (H2O2), the homogeneous reaction process for PMS activation is limited to acidic pH values and results in undesirable metal-sludge accumulation [23,24]. Heterogeneous catalysts, such as Co3O4, Fe3O4, and Fe2O3, have been developed to activate PMS, while the existence of a rate limiting step of high-valence metal species reduction greatly restrains the performance of PMS activation [25]. Moreover, this step requires oxidation and consumption of additional PMS to promote electron circulation in the metal species, resulting in a low PMS utilization efficiency. The most commonly used method for accelerating this step is external assistance [9], such as UV light [26], electricity [27] and other reductive reagents [28], but external assistance greatly increases energy and resource consumption and introduces new competitive substances for trapping free radicals, which are not conducive for the reaction.
Recently, we have found that organic pollutants, such as BPA, 2-CP and their organic radical intermediates, can replace H2O2 as electron donors in the Fenton-like reaction through the construction of surface electron-rich/poor micro-areas on the catalyst [[29], [30], [31]], greatly improving the activity of the catalytic system and the utilization of H2O2 without any external assistance; however, such modification of the catalyst is difficult to achieve in the PMS activation system due to the structural complexity of PMS and the diversity of the produced active species, which often disturb the oriented transfer of electrons. It is necessary to construct more distinct and powerful electron-rich sites and electron traps to activate PMS and consume organic pollutants.
Oxygen vacancy (VO) is a kind of anion defect consisting of a lower formation energy on oxide surface produced by lattice oxygen detachment under specific conditions. VO species are often used in photocatalysis because the VO-induced localized states can extend the light response to visible or infrared light and efficiently trap charge carriers, enhancing photo catalytic activity [32,33]. In fact, in most redox-based reactions, the oxygen vacancies are equivalent to the electron transfer stations that can accept and donate free electrons. The absence of lattice oxygen gives VO a tendency to capture relatively unrestricted O atoms from the environment; therefore, during the activation of PMS, VO may efficiently trap one of the O atoms of PMS ([O3SOIOIIH]−) and achieve electron oriented transfer, further driving the conversion of pollutants.
Herein, a special catalyst for PMS activation and pollutant conversion consisting of surface oxygen vacancy-rich ZnFe0.8Co0.4O2.4 nanoparticles is synthesized by lattice-doping Co into ZnFe2O4 spinel using the sol-gel combustion method. ZnFe0.8Co0.4O2.4 can efficiently utilize the intrinsic energy of organic pollutants in the process of pollutant conversion, thus exhibiting excellent PMS activation and refractory pollutant degradation with good stability and wide adaptability. In the PMS activation system of ZnFe0.8Co0.4O2.4, pollutants can be completely converted in a few minutes, accompanied by the generation of hydrogen (H2) and active free radicals (•OH and SO4−). The formation of a large number of surface oxygen vacancies with unpaired electrons was verified and characterized by X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR) and temperature programmed reduction (H2-TPR) techniques. The oxygen vacancy-activity relationship and the interfacial reaction process between PMS, pollutants and catalysts were revealed by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), in situ Raman spectroscopy and spin-trapping EPR analysis. Mechanisms have been proposed for the characteristic activation of PMS, the electron donating role of pollutants, the dual-pathway degradation of pollutants and H2 generation in the ZnFe0.8Co0.4O2.4 system.
Section snippets
Cobalt-zinc ferrite preparation
Spinel nanoparticle catalysts were synthesized using a sol-gel combustion method. Information about chemicals and reagents of this study are reported in Text S1 (Supplementary Information). In a typical synthesis procedure for ZnFe0.8Co0.4O2.4, diluted nitric acid solution was prepared by mixing 60 mL deionized water and 4 mL nitric acid. Five millimoles (5.0 mmol) Zn(CH3COO)2·2H2O, 7.0 mmol Fe(NO3)3·9H2O and 3.0 mmol Co(CH3COO)2·4H2O were accurately weighed and dissolved in the nitric acid
Characterization of catalysts
The SEM image of ZnFe0.8Co0.4O2.4 (Fig. S2a) revealed that the catalyst particles were predominantly in the shape of spherical nanoparticles with some short rod-like shape. The BET surface area of ZnFe0.8Co0.4O2.4 was obtained as 10.59 m2 g−1, which was slightly smaller than that (14.01 m2 g−1) of ZnFe2O4 (Fig. S2b), implying a decrease in specific surface area after doping with Co. The TEM image (Fig. S2c) further demonstrated that ZnFe0.8Co0.4O2.4 exhibited a nearly nano-hexagonal shape with
Conclusion
In summary, we developed an efficient surface oxygen vacancy (VO)-rich cobalt-zinc ferrite water purification system for PMS activation and pollutant degradation, and elucidated the underlying solid-liquid interfacial mechanisms. In addition to the fact that the pollutants were rapidly eliminated in just a few minutes in the surface oxygen vacancy-rich ZnFe0.8Co0.4O2.4/PMS system, H2 was produced during the reaction process without any external assistance due to the surface electron-rich/poor
CRediT authorship contribution statement
Hongxiang Zhang: Methodology, Data curation, Formal analysis, Writing - original draft. Chenwei Li: Investigation, Writing - review & editing. Lai Lyu: Supervision, Conceptualization, Visualization, Formal analysis, Writing - review & editing. Chun Hu: Supervision, Validation, Resources, Funding acquisition, Project administration.
Declaration of Competing Interest
The authors declare no competing financial interest.
Acknowledgments
This work was financially supported by the Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme (Young Scholar), the Pearl River Talent Recruitment Program of Guangdong Province, the National Natural Science Foundation of China (51838005, 51808140, 51538013and 21722702), the National Key Research and Development Plan of China (2016YFA0203200), the Natural Science Foundation of Guangdong Province (2018A030313487) and the Young Innovative Talent Project in Higher
References (56)
- et al.
Photocatalytic diphenhydramine degradation under different radiation sources: kinetic studies and energetic comparison
Appl. Catal. B: Environ.
(2018) - et al.
In situ generation and efficient activation of H2O2 for pollutant degradation over CoMoS2 nanosphere-embedded rGO nanosheets and its interfacial reaction mechanism
J. Colloid. Interf. Sci.
(2019) - et al.
Catalytic decomposition of 2-chlorophenol using an ultrasonic-assisted Fe3O4-TiO2@MWCNT system: influence factors, pathway and mechanism study
J. Colloid. Interf. Sci.
(2018) - et al.
Occurrence and removal of pharmaceuticals and personal care products (PPCPs) in an advanced wastewater reclamation plant
Water Res.
(2011) - et al.
Sulfate radical induced degradation of beta 2-adrenoceptor agonists salbutamol and terbutaline: phenoxyl radical dependent mechanisms
Water Res.
(2017) - et al.
Iron encapsulated in boron and nitrogen codoped carbon nanotubes as synergistic catalysts for Fenton-like reaction
Water Res.
(2016) - et al.
Activation of peroxymonosulfate on visible light irradiated TiO2 via a charge transfer complex path
Chem. Eng. J.
(2018) - et al.
Bread-making synthesis of hierarchically Co@C nanoarchitecture in heteroatom doped porous carbons for oxidative degradation of emerging contaminants
Appl. Catal. B: Environ.
(2018) - et al.
Visible light-induced catalytic activation of peroxymonosulfate using heterogeneous surface complexes of amino acids on TiO2
Appl. Catal. B:Environ.
(2018) - et al.
Generation of sulfate radical through heterogeneous catalysis for organic contaminants removal: current development, challenges and prospects
Appl. Catal. B: Environ
(2016)
A novel Fe(II)/citrate/UV/peroxymonosulfate process for micropollutant degradation: optimization by response surface methodology and effects of water matrices
Chemosphere
Degradation of 2,4,5-trichlorophenoxyacetic acid by a novel Electro-Fe(II)/Oxone process using iron sheet as the sacrificial anode
Water Res.
Fenton-like degradation of 2,4-dichlorophenol using Fe3O4 magnetic nanoparticles
Appl. Catal. B: Environ.
Investigation on Fe-Co binary metal oxides supported on activated semi-coke for NO reduction by CO
Appl. Catal. B: Environ.
Pt enhanced the photo-Fenton activity of ZnFe2O4/α-Fe2O3 heterostructure synthesized via one-step hydrothermal method
J. Colloids Interface Sci.
Synthesis of a Bi2O2CO3/ZnFe2O4 heterojunction with enhanced photocatalytic activity for visible light irradiation-induced NO removal
Appl. Catal. B: Environ.
Reduction property and catalytic activity of Ce1-XNiXO2 mixed oxide catalysts for CH4 oxidation
Appl. Catal. A Gen.
NO oxidation over Ni-Co perovskite catalysts
Chem. Eng. J.
Catalytic removal NO by CO over LaNi0.5M0.5O3 (M = Co, Mn, Cu) perovskite oxide catalysts: tune surface chemical composition to improve N-2 selectivity
Chem. Eng. J.
Pathways of the photocatalytic reaction of acetate in H2O and D2O: a combined EPR and ATR-FTIR study
J. Catal.
FTIR spectroscopic characterization of Cu(II) coordination compounds with exopolysaccharide pullulan and its derivatives
J. Mol. Struct.
Highly efficient activation of peroxymonosulfate by natural negatively-charged kaolinite with abundant hydroxyl groups for the degradation of atrazine
Appl. Catal. B: Environ.
Heterogeneous activation of peroxymonosulfate by a novel magnetic 3D gamma-MnO2@ZnFe2O4/rGO nanohybrid as a robust catalyst for phenol degradation
Appl. Catal. B: Environ.
Fate of endocrine-disruptor, pharmaceutical, and personal care product chemicals during simulated drinking water treatment processes
Environ. Sci. Technol.
Environmental toxins – exposure to bisphenol A advances puberty
Nature
The challenge of micropollutants in aquatic systems
Science
Oxidation of organic compounds in water by unactivated peroxymonosulfate
Environ. Sci. Technol.
Selective oxidation of arsenite by peroxymonosulfate with high utilization efficiency of oxidant
Environ. Sci. Technol.
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