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Xuefei Zhou - One of the best experts on this subject based on the ideXlab platform.
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enhanced oxidative and adsorptive removal of diclofenac in heterogeneous fenton like reaction with sulfide modified nanoscale zerovalent iron
Environmental Science & Technology, 2018Co-Authors: David Jassby, Jan Filip, Xuefei Zhou, Shikun Song, Hongying Zhao, Eleni Petala, Yalei ZhangAbstract:Sulfidation of nanoscale zerovalent iron (nZVI) has shown some fundamental improvements on reactivity and selectivity toward pollutants in dissolved-oxygen (DO)-stimulated Fenton-like reaction systems (DO/S-nZVI system). However, the pristine microstructure of sulfide-modified nanoscale zerovalent iron (S-nZVI) remains uncovered. In addition, the relationship between pollutant removal and the oxidation of the S-nZVI is largely unknown. The present study confirms that Sulfidation not only imparts sulfide and sulfate groups onto the surface of the nanoparticle (both on the oxide shell and on flake-like structures) but also introduces sulfur into the Fe(0) core region. Sulfidation greatly inhibits the four-electron transfer pathway between Fe(0) and oxygen but facilitates the electron transfer from Fe(0) to surface-bound Fe(III) and consecutive single-electron transfer for the generation of H2O2 and hydroxyl radical. In the DO/S-nZVI system, slight Sulfidation (S/Fe molar ratio = 0.1) is able to nearly doubl...
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Enhanced Oxidative and Adsorptive Removal of Diclofenac in Heterogeneous Fenton-like Reaction with Sulfide Modified Nanoscale Zerovalent Iron
2018Co-Authors: David Jassby, Jan Filip, Xuefei Zhou, Shikun Song, Hongying Zhao, Eleni Petala, Yalei ZhangAbstract:Sulfidation of nanoscale zerovalent iron (nZVI) has shown some fundamental improvements on reactivity and selectivity toward pollutants in dissolved-oxygen (DO)-stimulated Fenton-like reaction systems (DO/S-nZVI system). However, the pristine microstructure of sulfide-modified nanoscale zerovalent iron (S-nZVI) remains uncovered. In addition, the relationship between pollutant removal and the oxidation of the S-nZVI is largely unknown. The present study confirms that Sulfidation not only imparts sulfide and sulfate groups onto the surface of the nanoparticle (both on the oxide shell and on flake-like structures) but also introduces sulfur into the Fe(0) core region. Sulfidation greatly inhibits the four-electron transfer pathway between Fe(0) and oxygen but facilitates the electron transfer from Fe(0) to surface-bound Fe(III) and consecutive single-electron transfer for the generation of H2O2 and hydroxyl radical. In the DO/S-nZVI system, slight Sulfidation (S/Fe molar ratio = 0.1) is able to nearly double the oxidative removal efficacy of diclofenac (DCF) (from 17.8 to 34.2%), whereas moderate degree of Sulfidation (S/Fe molar ratio = 0.3) significantly enhances both oxidation and adsorption of DCF. Furthermore, on the basis of the oxidation model of S-nZVI, the DCF removal process can be divided into two steps, which are well modeled by parabolic and logarithmic law separately. This study bridges the knowledge gap between pollutant removal and the oxidation process of chemically modified iron-based nanomaterials
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optimal design and characterization of sulfide modified nanoscale zerovalent iron for diclofenac removal
Applied Catalysis B-environmental, 2017Co-Authors: Shikun Song, Yalei Zhang, Adeyemi S Adeleye, Xuefei ZhouAbstract:Abstract Noble metal catalyzed nanoscale zerovalent iron (nZVI) has shown some promise in degrading pharmaceuticals, but it still suffers from inactivation caused by common anions. In this study, Sulfidation was adopted to enhance diclofenac (DCF, an emerging groundwater pollutant) removal under aerobic conditions in the presence of common anions. X-ray adsorption near edge structure (XANES) analysis shows that dithionite is not only able to sulfurize nZVI, but also stimulates the crystal growth of Fe(0) and restrains FeOOH formation to some degree. Except in CaCl2 solution, certain extent of Sulfidation can inhibit the aggregation and sedimentation of nZVI in aqueous media with common ions and anions. While pristine nZVI achieves only 21.2% DCF removal, the optimal sulfide-modified nZVI (S-nZVI) shows 73.5% DCF removal under near neutral condition (pH ∼6.5), and the maximum removal could reach 85.9% at pH 4.5. Mechanism study shows that a heterogeneous layer composed of iron sulfide and iron oxide restricts the direct reaction between oxygen and Fe(0), but facilitates electron transfer from Fe(0) core to Fe(III), producing considerable amount of surface bound Fe(II). Electron Paramagnetic Resonance spectroscope (EPR) analysis and quenching experiments further demonstrate that Sulfidation catalyzes dissolved molecular oxygen activation through one-electron transfer. Moreover, Sulfidation can lower the negative impact of common anions and humic acid on DCF removal, and S-nZVI is capable of removing DCF in simulated groundwater efficiently. This study provides fundamental understanding on the sulfur catalyzed oxidation of DCF under aerobic conditions.
Wenqing Qin - One of the best experts on this subject based on the ideXlab platform.
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effects of sodium salts on the Sulfidation of lead smelting slag
Minerals Engineering, 2017Co-Authors: Junwei Han, Wei Liu, Wenqing Qin, Tianfu Zhang, Ziyong Chang, Kai XueAbstract:Abstract The effects of sodium salts on the Sulfidation behavior, phase transformation, ZnS particle growth, and zinc floatability of lead smelting slag (LSS) were investigated by roasting experiments and flotation tests. The roasting results indicated that sodium salt additives could enhance the reactivity of zinc Sulfidation and the percentage of liquid phase and thus promoted the Sulfidation of LSS and the growth of ZnS particles. However, with the increase in temperature, the positive effects were reduced because the reactivity of the Sulfidation and the percentage of liquid phase were not the determining factors at high temperatures. The effect of Na2CO3 was stronger than Na2SO4, while Na2SO4 was stronger than NaCl on the Sulfidation of zinc and the growth of ZnS particles. The addition of Na2CO3 or Na2SO4 favored the conversion of marmatite to wurtzite, which could be evaporated at temperatures above 1000 °C. Flotation test results revealed that sodium salt additives had different influences on the zinc grade and recovery at different temperatures. Na2CO3 was the best additive in roasting for increase in zinc grade, due to the formation of metallic iron rather than iron sulfides.
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mechanism study on the Sulfidation of zno with sulfur and iron oxide at high temperature
Scientific Reports, 2017Co-Authors: Junwei Han, Wei Liu, Fen Jiao, Tianfu Zhang, Kai Xue, Wenqing QinAbstract:The mechanism of ZnO Sulfidation with sulfur and iron oxide at high temperatures was studied. The thermodynamic analysis, Sulfidation behavior of zinc, phase transformations, morphology changes, and surface properties were investigated by HSC 5.0 combined with FactSage 7.0, ICP, XRD, optical microscopy coupled with SEM-EDS, and XPS. The results indicate that increasing temperature and adding iron oxide can not only improve the Sulfidation of ZnO but also promote the formation and growth of ZnS crystals. Fe2O3 captured the sulfur in the initial Sulfidation process as iron sulfides, which then acted as the sulfurizing agent in the late period, thus reducing sulfur escape at high temperatures. The addition of carbon can not only enhance the Sulfidation but increase sulfur utilization rate and eliminate the generation of SO2. The surfaces of marmatite and synthetic zinc sulfides contain high oxygen due to oxidation and oxygen adsorption. Hydroxyl easily absorbs on the surface of iron-bearing zinc sulfide (Zn1−xFexS). The oxidation of synthetic Zn1−xFexS is easier than marmatite in air.
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selective Sulfidation of lead smelter slag with pyrite and flotation behavior of synthetic zns
Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2016Co-Authors: Junwei Han, Wei Liu, Fen Jiao, Tianfu Zhang, Dawei Wang, Wenqing QinAbstract:The selective Sulfidation of lead smelter slag with pyrite in the presence of carbon and Na salts, and the flotation behavior of synthetic ZnS were studied. The effects of temperature, time, pyrite dosage, Na salts, and carbon additions were investigated based on thermodynamic calculation, and correspondingly, the growth mechanism of ZnS particles was studied at high temperatures. The results indicated that the zinc in lead smelter slag was selectively converted into zinc sulfides by Sulfidation roasting. The Sulfidation degree of zinc was increased until the temperature, time, pyrite, and carbon dosages reached their optimum values, under which it was more than 95 pct. The growth of ZnS particles largely depended upon roasting temperature, and the ZnS grains were significantly increased above 1373 K (1100 °C) due to the formation of a liquid phase. After the roasting, the zinc sulfides generated had a good floatability, and 88.34 pct of zinc was recovered by conventional flotation.
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selective Sulfidation of lead smelter slag with sulfur
Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2016Co-Authors: Junwei Han, Wei Liu, Fen Jiao, Dawei Wang, Wenqing QinAbstract:The selective Sulfidation of lead smelter slag with sulfur was studied. The effects of temperature, sulfur dosage, carbon, and Na salts additions were investigated based on thermodynamic calculation. The results indicated that more than 96 pct of zinc in the slag could be converted into sulfides. Increasing temperature, sulfur dosage, or Na salts dosage was conducive to the Sulfidation of the zinc oxides in the slag. High temperature and excess Na salts would result in the more consumption of carbon and sulfur. Carbon addition not only promoted the selective Sulfidation but reduced the sulfur dosage and eliminated the generation of SO2. Iron oxides had a buffering role on the sulfur efficient utilization. The transformation of sphalerite to wurtzite was feasible under reducing condition at high temperature, especially above 1273 K (1000 °C). The growth of ZnS particles largely depended upon the roasting temperature. They were significantly increased when the temperature was above 1273 K (1000 °C), which was attributed to the formation of a liquid phase.
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Sulfidation roasting of lead and zinc carbonate with sulphur by temperature gradient method
Journal of Central South University, 2015Co-Authors: Yong-xing Zheng, Wei Liu, Wenqing Qin, Fen Jiao, Junwei Han, Kang Yang, Hong-lin LuoAbstract:In order to enhance the lead and zinc recovery from the refractory Pb-Zn oxide ore, a new technology was developed based on Sulfidation roasting with sulphur by temperature gradient method. The solid-liquid reaction system was established and the Sulfidation thermodynamics of lead and zinc carbonate was calculated with the software HSC 5.0. The effects of roasting temperature, molar ratio of sulphur to lead and zinc carbonate and reaction time in the first step roasting, and holding temperature and time in the second roasting on the Sulfidation extent were studied at a laboratory-scale. The experimental results show that the Sulfidation extents of lead and zinc are 96.50% and 97.29% under the optimal conditions, respectively, and the artificial galena, sphalerite and wurtzite were formed. By the novel sulfidizing process, it is expected that the sulphides can be recovered by conventional flotation technology.
J W Niemantsverdriet - One of the best experts on this subject based on the ideXlab platform.
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basic reaction steps in the Sulfidation of crystalline tungsten oxides
Journal of Physical Chemistry B, 2002Co-Authors: A J Van Der Vlies, Gurram Kishan, J W Niemantsverdriet, Roel Prins, Th WeberAbstract:The Sulfidation of crystalline m-WO3 and WO3·H2O and the thermal decomposition of (NH4)2WO2S2 to an {WOS2} oxysulfide and (NH4)2WS4 to {WS3} were studied by means of temperature-programmed Sulfidation (TPS), X-ray photoelectron spectroscopy (XPS), thermogravimetrical analysis (TGA), and laser Raman spectroscopy. Several basic steps of the Sulfidation reaction could be resolved and explained in terms of the structures of crystalline m-WO3 and WO3·H2O. The Sulfidation reaction starts at low temperatures with a reduction of the crystalline oxides by reaction with H2S without incorporation of sulfur. Only after this reduction does an exchange of terminal O2- ligands of the oxides for S2- take place. In subsequent W−S redox reactions S22- ligands form, which leads to oxysulfidic intermediates. The {WOS2} oxysulfide phase serves as a reference of structural features of oxysulfides. The presence of oxygen at bridging and terminal positions as well as of disulfide ligands seems to be a common structural property ...
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correlation between hydrodesulfurization activity and order of ni and mo Sulfidation in planar silica supported nimo catalysts the influence of chelating agents
Journal of Catalysis, 2001Co-Authors: L Coulier, V H J De Beer, J A R Van Veen, J W NiemantsverdrietAbstract:Abstract Surface science models of silica-supported NiMo catalysts have been prepared to study the formation of the active phase (“NiMoS”) in hydrotreating catalysts. Combination of XPS and thiophene hydrodesulfurization (HDS) measurements shows that the key step in the formation of the NiMoS phase is the order in which Ni and Mo precursors transfer to the sulfidic state. In NiMo systems prepared by conventional methods the Sulfidation of Ni precedes that of Mo. However, complexing Ni to chelating agents like nitrilotriacetic acid, ethylenediamine, ethylenediaminetetraacetic acid (EDTA), and 1,2-cyclohexanediaminetetraacetic acid (CyDTA) retard the Sulfidation of Ni. For EDTA and CyDTA the Ni Sulfidation is delayed to temperatures where MoS 2 is already formed. These catalysts show the highest activity in thiophene HDS, indicating that complete Sulfidation of Mo preceding that of Ni provides the ideal circumstances for NiMoS formation.
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Sulfidation and thiophene hydrodesulfurization activity of nickel tungsten sulfide model catalysts prepared without and with chelating agents
Journal of Catalysis, 2000Co-Authors: Gurram Kishan, L Coulier, V H J De Beer, J A R Van Veen, J W NiemantsverdrietAbstract:Silica-supported NiWS catalysts with a high activity for thiophene hydrodesulfurization are obtained when chelating agents such as 1,2-cyclohexanediamine-N,N,N′,N′-tetraacetic acid (CyDTA), ethylenediaminetetraacetic acid, or nitrilotriacetic acid are added in the impregnation stage. X-ray photoelectron spectroscopy has been used to follow the state of Ni and W during the temperature programmed Sulfidation of Ni–W model catalysts prepared with and without chelating agents on planar SiO2 films on silicon substrates. Fully sulfided catalysts have been tested in thiophene hydrodesulfurization. The activity increases with increasing Ni content and reaches a plateau at a Ni : W atomic ratio of 0.66. In NiW catalysts prepared without additives the Sulfidation of Ni precedes that of W. However, Ni sulfide formed at low temperatures changes its structure at high temperatures where WS2 is present, as indicated by the Ni XPS binding energy, which we tentatively attribute to redispersion of sulfidic Ni over WS2. Chelating agents stabilize Ni against sulfide formation at low temperature, the effect being strongest when CyDTA is applied. CyDTA retards the Sulfidation of Ni to temperatures where all W has already been sulfided. This complete reversal in the order in which the two elements convert to sulfides is seen as the key step in preparing highly active NiWS HDS catalysts.
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basic reaction steps in the Sulfidation of crystalline moo3 to mos2 as studied by x ray photoelectron and infrared emission spectroscopy
The Journal of Physical Chemistry, 1996Co-Authors: Th Weber, J C Muijsers, J H M C Van Wolput, C P J Verhagen, J W NiemantsverdrietAbstract:The Sulfidation of crystalline MoO3 and the thermal decomposition of (NH4)2MoO2S2 to MoS2 via an {MoOS2} oxysulfide intermediate have been studied by means of monochromatic X-ray photoelectron spectroscopy (XPS) and infrared emission spectroscopy (IRES). Several basic steps of the Sulfidation reaction could be resolved and explained in terms of the structure of crystalline MoO3. The Sulfidation reaction starts at low temperatures with an exchange of terminal O2- ligands of the oxide for S2- by reaction with H2S from the sulfiding atmosphere. In subsequent Mo−S redox reactions, bridging S22- ligands and Mo5+ centers are formed. Lattice relaxation and further sulfur uptake are the main processes before, at temperatures above 200 °C, direct reactions with H2 occur, during which the Mo5+ centers are converted into the 4+ oxidation state. The decomposition experiments with (NH4)2MoO2S2 show that terminal O2- ligands serve as the reactive sites. The conversion of terminal MoOt to MoS entities and the subsequent...
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Sulfidation study of molybdenum oxide using moo3 sio2 si 100 model catalysts and mo3iv sulfur cluster compounds
Journal of Catalysis, 1995Co-Authors: J C Muijsers, Thomas Weber, R M Van Hardeveld, H W Zandbergen, J W NiemantsverdrietAbstract:Monochromatic XPS spectra of the temperature-dependent Sulfidation of MoO{sub 3}/SiO{sub 2}/Si(100) model catalysts are compared with spectra of Mo-S cluster compounds in particular with those of (NH{sub 4}){sub 2}[MO{sub 3}S{sub 13}]{center_dot}H{sub 2}O and its thermal decomposition products. XPS is used to identify different states of sulfur and molybdenum occurring during Sulfidation. The spectra show the presence of bridging disulfide ligands and of substantial amounts of Mo{sup v} in an early stage of the Sulfidation. These findings suggest that the initial reaction of the MoO{sub 3}-type precursor with the H{sub 2}S/H{sub 2} atmosphere consists of two elementary steps, namely an O-S exchange followed by an Mo-S redox process. 31 refs., 6 figs., 1 tab.
Dehai Wang - One of the best experts on this subject based on the ideXlab platform.
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effects of addition of mo on the Sulfidation properties of fe based sorbents supported on fly ash during hot coal gas desulfurization
Chemical Engineering Journal, 2011Co-Authors: Dehai Wang, Liping Chang, Dongmei WangAbstract:Abstract This paper studies the influence of the addition of Mo on the Sulfidation performance of Fe-based sorbent supported on fly ash for hot coal gas desulfurization. Sorbent samples were prepared using physical mixing method with different Mo oxide content. The Sulfidation experiments were carried out in the temperature range of 400–600 °C. Gas compositions were analyzed using a GC. The structure and morphology of sorbent samples before and after Sulfidation were examined by using SEM, XRD and compressive strength was also measured. The experimental results show that the fly ash supporter has some capability for sulfur removal from the hot coal gas. The addition of Mo may effectively improve the desulfurization efficiency and increase the compressive strength of iron-based sorbents.
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removal of sulfur at high temperatures using iron based sorbents supported on fine coal ash
Fuel, 2010Co-Authors: Liping Chang, Dehai Wang, T F Wall, Jianglong YuAbstract:Abstract This paper deals with the simultaneous removal of H 2 S and COS in the temperature range of 400–650 °C at 1 bar by using iron-based sorbents. The iron-based sorbents were prepared using iron oxide and cerium oxide with coal fine ash as the support. Simulated coal gas was used in the Sulfidation experiments and 5% O 2 in N 2 gas was used for regeneration of sorbents. Both Sulfidation and regeneration experiments have been carried out using a fixed-bed quartz reactor. The product gases were analyzed using a GC equipped with a TCD and a FPD. The results demonstrated that both H 2 S and COS can be effectively reduced using the iron-based sorbents supported on fine coal ash. XRD analysis shows that Fe 1− x S phase has formed during Sulfidation indicating a high sulfur capacity of the sorbent. The mechanism of the removal of COS simultaneously with H 2 S is also discussed.
Yalei Zhang - One of the best experts on this subject based on the ideXlab platform.
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enhanced oxidative and adsorptive removal of diclofenac in heterogeneous fenton like reaction with sulfide modified nanoscale zerovalent iron
Environmental Science & Technology, 2018Co-Authors: David Jassby, Jan Filip, Xuefei Zhou, Shikun Song, Hongying Zhao, Eleni Petala, Yalei ZhangAbstract:Sulfidation of nanoscale zerovalent iron (nZVI) has shown some fundamental improvements on reactivity and selectivity toward pollutants in dissolved-oxygen (DO)-stimulated Fenton-like reaction systems (DO/S-nZVI system). However, the pristine microstructure of sulfide-modified nanoscale zerovalent iron (S-nZVI) remains uncovered. In addition, the relationship between pollutant removal and the oxidation of the S-nZVI is largely unknown. The present study confirms that Sulfidation not only imparts sulfide and sulfate groups onto the surface of the nanoparticle (both on the oxide shell and on flake-like structures) but also introduces sulfur into the Fe(0) core region. Sulfidation greatly inhibits the four-electron transfer pathway between Fe(0) and oxygen but facilitates the electron transfer from Fe(0) to surface-bound Fe(III) and consecutive single-electron transfer for the generation of H2O2 and hydroxyl radical. In the DO/S-nZVI system, slight Sulfidation (S/Fe molar ratio = 0.1) is able to nearly doubl...
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Enhanced Oxidative and Adsorptive Removal of Diclofenac in Heterogeneous Fenton-like Reaction with Sulfide Modified Nanoscale Zerovalent Iron
2018Co-Authors: David Jassby, Jan Filip, Xuefei Zhou, Shikun Song, Hongying Zhao, Eleni Petala, Yalei ZhangAbstract:Sulfidation of nanoscale zerovalent iron (nZVI) has shown some fundamental improvements on reactivity and selectivity toward pollutants in dissolved-oxygen (DO)-stimulated Fenton-like reaction systems (DO/S-nZVI system). However, the pristine microstructure of sulfide-modified nanoscale zerovalent iron (S-nZVI) remains uncovered. In addition, the relationship between pollutant removal and the oxidation of the S-nZVI is largely unknown. The present study confirms that Sulfidation not only imparts sulfide and sulfate groups onto the surface of the nanoparticle (both on the oxide shell and on flake-like structures) but also introduces sulfur into the Fe(0) core region. Sulfidation greatly inhibits the four-electron transfer pathway between Fe(0) and oxygen but facilitates the electron transfer from Fe(0) to surface-bound Fe(III) and consecutive single-electron transfer for the generation of H2O2 and hydroxyl radical. In the DO/S-nZVI system, slight Sulfidation (S/Fe molar ratio = 0.1) is able to nearly double the oxidative removal efficacy of diclofenac (DCF) (from 17.8 to 34.2%), whereas moderate degree of Sulfidation (S/Fe molar ratio = 0.3) significantly enhances both oxidation and adsorption of DCF. Furthermore, on the basis of the oxidation model of S-nZVI, the DCF removal process can be divided into two steps, which are well modeled by parabolic and logarithmic law separately. This study bridges the knowledge gap between pollutant removal and the oxidation process of chemically modified iron-based nanomaterials
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optimal design and characterization of sulfide modified nanoscale zerovalent iron for diclofenac removal
Applied Catalysis B-environmental, 2017Co-Authors: Shikun Song, Yalei Zhang, Adeyemi S Adeleye, Xuefei ZhouAbstract:Abstract Noble metal catalyzed nanoscale zerovalent iron (nZVI) has shown some promise in degrading pharmaceuticals, but it still suffers from inactivation caused by common anions. In this study, Sulfidation was adopted to enhance diclofenac (DCF, an emerging groundwater pollutant) removal under aerobic conditions in the presence of common anions. X-ray adsorption near edge structure (XANES) analysis shows that dithionite is not only able to sulfurize nZVI, but also stimulates the crystal growth of Fe(0) and restrains FeOOH formation to some degree. Except in CaCl2 solution, certain extent of Sulfidation can inhibit the aggregation and sedimentation of nZVI in aqueous media with common ions and anions. While pristine nZVI achieves only 21.2% DCF removal, the optimal sulfide-modified nZVI (S-nZVI) shows 73.5% DCF removal under near neutral condition (pH ∼6.5), and the maximum removal could reach 85.9% at pH 4.5. Mechanism study shows that a heterogeneous layer composed of iron sulfide and iron oxide restricts the direct reaction between oxygen and Fe(0), but facilitates electron transfer from Fe(0) core to Fe(III), producing considerable amount of surface bound Fe(II). Electron Paramagnetic Resonance spectroscope (EPR) analysis and quenching experiments further demonstrate that Sulfidation catalyzes dissolved molecular oxygen activation through one-electron transfer. Moreover, Sulfidation can lower the negative impact of common anions and humic acid on DCF removal, and S-nZVI is capable of removing DCF in simulated groundwater efficiently. This study provides fundamental understanding on the sulfur catalyzed oxidation of DCF under aerobic conditions.
