With the growing awareness of environmental protection and the increasing demand for rare earth elements(REEs),it has become necessary to efficiently remove and recover REEs from mine wastewater.In this study,jarosite...With the growing awareness of environmental protection and the increasing demand for rare earth elements(REEs),it has become necessary to efficiently remove and recover REEs from mine wastewater.In this study,jarosite(Jar)and schwertmannite(Sch)were biosynthesized using Acidithiobacillus ferrooxidans for the adsorption of REEs.Additionally,the adsorption capacities of Jar and Sch for La^(3+),Ce^(3+),Pr^(3+),Nd^(3+),Sm^(3+),Gd^(3+),Dy^(3+),and Y^(3+)in mine wastewater were improved by mechanical activation.XRD,FTIR,BET,and SEM-EDS analyses revealed that mechanical activation did not alter the phase of the material,but increased the amount of surface-OH and SO42−groups,as well as the specific surface area.This significantly enhanced the adsorption performance of Jar and Sch for REEs.The optimum adsorption time and pH were determined through batch adsorption experiments.Besides,the adsorption kinetics were studied and found to align well with the pseudo-second-order model.Furthermore,the thermodynamic parameters(ΔG^(Θ),ΔH^(Θ)andΔS^(Θ))and adsorption isotherms were analyzed.The results indicated that mechanically activated schwertmannite(M-Sch)exhibited superior adsorption performance for REEs compared to mechanically activated jarosite(M-Jar).Moreover,M-Sch was reusable and exhibited high adsorption efficiency of REEs in actual mine wastewater,exceeding 92%.展开更多
Schwertmannite, a common iron-derived mineral, is known for its high efficiency in adsorbing As from water and reducing the mobility and availability of As in soils. However,few studies have examined the critical peri...Schwertmannite, a common iron-derived mineral, is known for its high efficiency in adsorbing As from water and reducing the mobility and availability of As in soils. However,few studies have examined the critical period for the effectiveness of schwertmannite in hindering As uptake by rice plants, particularly its impact on the uptake and transport of As across different growth stages of rice. In this study, hydroponic experiments were performed to explore the absorption and translocation of As(500 μg/L As(Ⅲ) or As(Ⅴ)), when combined with schwertmannite, in rice during all growth stages. The results showed that As concentration in roots, stems and leaves increased with rice growth, while the addition of schwertmannite reduced the As concentration in all parts of rice, compared to the control without schwertmannite. Besides, schwertmannite application mitigated the harmful impact of As on rice yield, and reduced As levels in grains by 66 %-90 % compared to treatments with only As(Ⅲ) or As(Ⅴ). The heading stage is identified as a critical period for applying schwertmannite to reduce As uptake in rice. Specifically, during the heading stages,the plants uptake 85 %-91 % of the As contents in the absence of schwertmannite. However,adding schwertmannite retained about 84 %-90 % of As content, significantly reducing its absorption by rice plants at this stage. Therefore, maintaining As adsorption by schwertmannite up to the heading stage is beneficial to effectively reduce As uptake in rice and lower As concentration in rice grains.展开更多
Potential health risks related to environmental endocrine disruptors(EEDs)have aroused research hotspots at the forefront of water treatment technologies.Herein,nitrogen-doped titanium dioxide/schwertmannite nanocompo...Potential health risks related to environmental endocrine disruptors(EEDs)have aroused research hotspots at the forefront of water treatment technologies.Herein,nitrogen-doped titanium dioxide/schwertmannite nanocomposites(N-TiO_(2)/SCH)have been successfully developed as heterogeneous catalysts for the degradation of typical EEDs via photo-Fenton processes.Due to the sustainable Fe(Ⅲ)/Fe(Ⅱ)conversion induced by photoelectrons,as-prepared N-TiO_(2)/SCH nanocomposites exhibit much enhanced efficiency for the degradation of bisphenol A(BPA;ca.100% within 60 min under visible irradiation)in a wide pH range of 3.0-7.8,which is significantly higher than that of the pristine schwertmannite(ca.74.5%)or N-TiO_(2)(ca.10.8%).In this photo-Fenton system,the efficient degradation of BPA is mainly attributed to the oxidation by hydroxyl radical(·OH)and singlet oxygen(^(1)O_(2)).Moreover,the possible catalytic mechanisms and reaction pathway of BPA degradation are systematically investigated based on analytical and photoelectrochemical analyses.This work not only provides a feasible means for the development of novel heterogeneous photo-Fenton catalysts,but also lays a theoretical foundation for the potential application of mineral-based materials in wastewater treatment.展开更多
The heterogeneous photo-Fenton reaction is an effective technique in combating organic contaminants for both soil and water remediation,and extensive studies have focused on enhancing its efficiency and reducing its c...The heterogeneous photo-Fenton reaction is an effective technique in combating organic contaminants for both soil and water remediation,and extensive studies have focused on enhancing its efficiency and reducing its costs.In this work,we developed novel photoFenton catalysts by simply milling commercially available TiO_2(P25)with Schwertmannite(Sh),a natural iron-oxyhydroxysulfate nanomineral.We expect that the photo-generated electrons from TiO_2could continuously migrate to Sh,which then could enhance the separation of electron-hole pairs on TiO_2and accelerate the reduction of Fe(III)to Fe(II)on Sh,leading to high degradation efficiency of the target organic contaminants.SEM and TEM results showed the distribution of TiO_2on Sh surface for the nanocomposites(TiO_2/Sh).Under simulated sunlight irradiation,the much higher content of Fe(II)was determined on TiO_2/Sh than on Sh via a common method in the iron ore,and the consumption of H_2O_2and the production of·OH were more significant in the TiO_2/Sh system than those in the TiO_2and Sh systems.These results well support our hypothesis that the photo-generated electrons could migrate from TiO_2to Sh on the composites,and can also explain the much higher degradation efficiency of Rhodamine B(RhB)in the TiO_2/Sh system.Besides,TiO_2/Sh had lower Fe dissolution as compared with Sh,and retained high catalytic stability after four repeated cycles.Above merits of the TiO_2/Sh composites,in combining with their simple synthesis method and low-cost property,indicated that they should have promising applications as heterogeneous photo-Fenton catalysts.展开更多
Schwertmannite is an amorphous iron(III)-oxyhydroxysulfate that forms in acid mine drainage(AMD) environments. The characteristic of high heavy metal adsorption capability makes schwertmannite a potentially useful, en...Schwertmannite is an amorphous iron(III)-oxyhydroxysulfate that forms in acid mine drainage(AMD) environments. The characteristic of high heavy metal adsorption capability makes schwertmannite a potentially useful, environmentally friendly material in wastewater treatment. Unstable schwertmannite is prone to recrystallization.Understanding the mechanisms that induce schwertmannite labilization and affect its capacity to remove heavy metals are of great environmental and geochemical significance.Thiocyanate(SCNˉ) is a hazardous pseudohalide that is also normally found in AMD.However, little is known about the impact of Fe(III)-binding ligand SCNˉ on schwertmannite stability and its subsequent capacity to bind trace elements. Here, we investigated the adsorption of SCNˉ on schwertmannite and subsequent mineral transformation to characterize this little-known process. The appearance of Fe2+indicated that the interactions between schwertmannite and SCNˉ may involve complexation and reduction reactions. Results showed that the majority of the adsorbed-SCNˉ was immobilized on schwertmannite during the 60-days transformation. The transformation rates of schwertmannite increased with increasing concentrations of SCNˉ. Goethite was detected as the dominant transformation product with or without SCNˉ. The mechanisms of SCNˉ-promoted dissolution of schwertmannite can be described as follows:(1) formation of Fe(III)–NCS complexes on the schwertmannite surface and in solution, a process which increases the reactivity of solid phase Fe(III);(2) the extraction of Fe(III) from schwertmannite by SCNˉ and subsequent schwertmannite dissolution; and(3) the formation of secondary minerals from extracted Fe(III). These findings may improve AMD treatment strategies and provide insight into the use and potential reuse of schwertmannite as a trace element sorbent.展开更多
The massive amount of sludge generated by the classic Fenton process, which has often been hypothesized to consist of ferric hydroxide, remains a major obstacle to its large-scale application. Therefore, reutilization...The massive amount of sludge generated by the classic Fenton process, which has often been hypothesized to consist of ferric hydroxide, remains a major obstacle to its large-scale application. Therefore, reutilization of Fenton sludge has recently gained more attention.Understanding the formation, transformation, and properties of Fenton sludge combined with the stages of the Fenton reaction is pivotal, but not well illustrated yet. In this study,SEM-EDS, FT-IR, XRD, and XPS were applied to study the morphology, crystallinity,elemental composition, and valence state of Fenton sludge. The authors report that schwertmannite and 2-line ferrihydrite were generated and transformed in the oxidation phase and the neutralization phase of the Fenton process. SO_4^(2-) in the solution decreased by8.7%–26.0% at different molar ratios of Fe(II) to H_2 O_2; meanwhile, iron ion precipitated completely at pH 3.70 with the formation of schwertmannite containing sulfate groups in the Fenton sludge. The structural sulfate(Fe-SO_4) in schwertmannite was released from the precipitate with the addition of OH-, and the production of Fenton sludge decreased with increasing pH when pH > 3.70. Goethite was found to form when the final p H was adjusted to 12 or at a reaction temperature of 80°C. Moreover, the possible thermal transformation to goethite and hematite indicated that Fenton sludge can be reused as a raw material for synthesizing more stable iron(hydro)oxides. The results provide useful insights into the formation and transformation of Fenton sludge, with implications for regulating the crystal type of Fenton sludge for further reuse.展开更多
Schwertmannite is an important Fe(Ⅲ)-oxyhydroxysulfate in acid mine drainage (AMD) polluted areas and its stability depends on surrounding environmental factors and previously bound elements.The treatment and neutral...Schwertmannite is an important Fe(Ⅲ)-oxyhydroxysulfate in acid mine drainage (AMD) polluted areas and its stability depends on surrounding environmental factors and previously bound elements.The treatment and neutralization of AMD normally involve the use of lime,which leads to the discharge of abundant Ca in the mining area.Such an environmental disturbance brings up an important and less considered problem of how the reductive transformation of schwertmannite associated with coexisting Ca occurred.Here,the Fe(Ⅱ)-mediated transformation of Ca-adsorbed schwertmannite and subsequent Ca repartitioning behaviors were investigated.Results showed that adsorbed Ca had a weak inhibitory effect on Fe(Ⅱ)-mediated schwertmannite transformation.Release of SO_(4)2-and SEM images both indicated that transformation rates of schwertmannite decreased under the influence of adsorbed Ca.XRD patterns indicated that adsorbed Ca altered schwertmannite transformation pathways and product compositions upon treatment with 0.4 mmol/L Fe(Ⅱ).The end products of Sch notably contained both goethite and lepidocrocite;however,transformation products of SchCa only contained goethite all along.Approximately 33.5%of the surface adsorbed-Ca was released into solution within 6 hr after Fe(Ⅱ) injection.Aqueous Ca behaved in a“first release and then im-mobilization”manner,which indicated dissolution and secondary mineralization drove Ca migration during the Fe(Ⅱ)-mediated transformation of SchCa.Adsorbed Ca blocked the surface sites for subsequent Fe(Ⅱ) adsorption,limited the Fe(Ⅱ)-Fe(Ⅲ) ETAE,and decreased the transformation rates.This work sheds light on the complex geochemical behavior of schwertmannite under the influences of environmental perturbations in AMD environments.展开更多
Here we reported an effective method to solve the rate-limiting steps, such as the reduction of Fe^(3+) to Fe^(2+) and an invalid decomposition of H2O2 in a conventional Fenton-like reaction. A magnetic heterogeneous ...Here we reported an effective method to solve the rate-limiting steps, such as the reduction of Fe^(3+) to Fe^(2+) and an invalid decomposition of H2O2 in a conventional Fenton-like reaction. A magnetic heterogeneous photocatalyst, Fe3O4-schwertmannite(Fe3O4-sch) was successfully developed by adding Fe3O4 in the formation process of schwertmannite. Fe3O4-sch shows excellent electrons transfer ability and high utilization efficiency of H2O2(98.5%). The catalytic activity of Fe3O4-sch was studied through the degradation of phenol in the heterogeneous photo-Fenton process. Phenol degradation at a wide pH(3-9) was up to 98% within 6 min under visible light illumination with the Fe3O4-sch as heterogeneous Fenton catalyst, which was higher than that using pure schwertmannite or Fe3O4. The excellent photocatalytic performance of Fe3O4-sch is ascribed to the effective recycling between ≡Fe^(3+) and ≡Fe^(2+) by the photo-generated electron, and also profit from the formation of the "Z-Scheme" system. According to the relevant data, photocatalytic mechanism of Fe3O4-sch for degrading phenol was proposed. This study not only provides an efficient way of enhancing heterogeneous Fenton reaction, but also gives potential application for iron oxyhydroxysulfate mineral.展开更多
Schwertmannite, a ubiquitous mineral present in iron oxyhydroxides formed in iron- and sulfate-rich acid media, favors incorporation of some toxic anions in its structure. We reported an iron-oxidizing bacterial strai...Schwertmannite, a ubiquitous mineral present in iron oxyhydroxides formed in iron- and sulfate-rich acid media, favors incorporation of some toxic anions in its structure. We reported an iron-oxidizing bacterial strain HX3 from a municipal sludge that facilitates the formation of pure schwertmannite in cultures. Ferrous iron oxidation by the isolated strain HX3 was optimum at an initial pH of 2.0-3.3 and temperature of 28-35°C. Pure schwertmannite was found through bacterial oxidation of ferrous iron at an initial pH 2.8and temperature 28°C. Following 16 S rDNA gene sequence analysis the bacterial strain HX3 was identified as Acidithiobacillus ferrooxidans. The arsenic-resistance A. ferrooxidans HX3 showed the potential of environmental application in arsenic removal from the As（Ⅲ）- and iron-rich acid sulfate waters directly by As（Ⅲ） adsorption or the formation of schwertmannite in the environment.展开更多
The adsorption and post adsorption behavior of schwertmannite with various oxyanions were investigated for clean-up contaminated water with hazardous oxyanions and safe disposal of spent schwertmannite. The result of ...The adsorption and post adsorption behavior of schwertmannite with various oxyanions were investigated for clean-up contaminated water with hazardous oxyanions and safe disposal of spent schwertmannite. The result of adsorption experiments showed that the maximum capacities of oxyanions adsorption onto schwertmannite are 1.023, 0.934, 0.723 and 0.313 mmol/g for arsenate, phosphate, chromate and selenate, respectively. Based on the differences in the adsorption capacities, the selectivity of oxyanion adsorption on schwertmannite decreases as the order: arsenate ≥ phosphate > chromate >> selenate. Change in the Zeta potential after adsorption by arsenate, phosphate and chromate were very different from those after adsorption by selenate and of the original schwertmannite. This difference implies that the adsorption mechanism on schwertmannite with arsenate, phosphate and chromate is different from that with selenate and sulfate. Arsenate, phosphate, and chromate ions form inner-sphere complexes with the surface of schwertmannite, while selenate and sulfate ions form outer-sphere complexes with the surface of schwertmannite. Based on a comparison with anion adsorption, strong base anions form inner-sphere complexes, which induce a strong adsorption with schwertmannite as well as it is conducive to high adsorption capacity. From the results of aging experiments, schwertmannite with sulfate and selenate changed to a more stable phase, goethite, in a short time, whereas there is no change in the XRD patterns of schwertmannite with arsenate and phosphate after 30 days. The stability of schwertmannite after the adsorption increased in the following order: sulfate ≌ selenate «chromate ≌ arsenate. The solubility of schwertmannite with different oxyanions was calculated according to solid solution theory. The solubility of schwertmannite decreased after adsorption of oxyanions with high selectivity. It is concluded that oxyanions with high selectivity can stabilize schwertmannite by decreasing the solubility of the schwertmannite after adsorption of the oxyanions.展开更多
Schwertmannite(Sh), a poorly crystalline iron(hydr)oxide that usually appears in acid mine drainage, plays a significant role in the immobilization of As(V). In this study, the effects of UV irradiation and oxalate on...Schwertmannite(Sh), a poorly crystalline iron(hydr)oxide that usually appears in acid mine drainage, plays a significant role in the immobilization of As(V). In this study, the effects of UV irradiation and oxalate on the dissolution of Sh with structurally incorporated As(V) [Sh-As(V)] and the subsequent mobilization of As(V) were investigated at pH 3.0. In the dark, more total dissolved Fe was produced(the maximum value was 33.2 mg/L) in the suspensions of Sh-As(V) with oxalate than in those without oxalate. UV irradiation slightly enhanced the mobilization of As(V) for the system of Sh-As(V)-1 and Sh-As(V)-2 in the absence of oxalate compared with that in the dark. However, in the presence of oxalate, UV irradiation caused the concentration of mobilized As(V) to decline by 630-875% compared with that in the dark. This study enhanced our understanding of the mobilization of As(V) and demonstrated that UV irradiation could contribute to the immobilization of As(V) on Sh in aqueous environments containing oxalate.展开更多
Due to continuing mining activities,Cd(II)and As(III)contamination in acid mine drainage(AMD)has become a major environmental challenge.Currently,there is increasing focus on the use of biochar to mitigate AMD polluti...Due to continuing mining activities,Cd(II)and As(III)contamination in acid mine drainage(AMD)has become a major environmental challenge.Currently,there is increasing focus on the use of biochar to mitigate AMD pollution.However,the impact of biochar on the process of Fe(II)oxidation by Acidithiobacillus ferrooxidans(A.ferrooxidans)in AMD systems has not been determined.In this study,we investigated the effects of introducing biochar and biochar-leachate on Fe(II)biooxidation by A.ferrooxidans and on the removal of Cd(II)and As(III)from an AMD system.The results showed that the biochar-leachate had a promoting effect on Fe(II)biooxidation by A.ferrooxidans.Conversely,biochar inhibited this process,and the inhibition increased with increasing biochar dose.Under both conditions(c(A.ferrooxidans)=1.4×107 copies mL-1,m(FeSO4·7H2O):m(biochar)=20:1;c(A.ferrooxidans)=7.0×107 copies mL-1,m(F eSO4·7H2O):m(biochar)=5:1),the biooxidation capacity of A.ferrooxidans was severely inhibited,with Fe(II)oxidation efficiency reaching a value of only~20%after 84 h.The results confirmed that this inhibition might have occurred because a large fraction of the A.ferrooxidans present in the system adsorbed to the biochar,which weakened bacterial activity.In addition,mineral characterization analysis showed that the introduction of biochar changed the A.ferrooxidans biooxidation products from schwertmannite to jarosite,and the specific surface area increased after the minerals combined with biochar.Coprecipitation experiments of As(III)and Cd(II)showed that Cd(II)was adsorbed by the biochar over the first 12 h of reaction,with a removal efficiency of~26%.As(III)was adsorbed by the generated schwertmannite over 24 h,with a removal efficiency of~100%.These findings have positive implications for the removal of As(III)and Cd(II)from AMD.展开更多
基金Project(2022YFC2105300) supported by the National Key Research and Development Program of ChinaProject(52274288) supported by the National Natural Science Foundation of China。
文摘With the growing awareness of environmental protection and the increasing demand for rare earth elements(REEs),it has become necessary to efficiently remove and recover REEs from mine wastewater.In this study,jarosite(Jar)and schwertmannite(Sch)were biosynthesized using Acidithiobacillus ferrooxidans for the adsorption of REEs.Additionally,the adsorption capacities of Jar and Sch for La^(3+),Ce^(3+),Pr^(3+),Nd^(3+),Sm^(3+),Gd^(3+),Dy^(3+),and Y^(3+)in mine wastewater were improved by mechanical activation.XRD,FTIR,BET,and SEM-EDS analyses revealed that mechanical activation did not alter the phase of the material,but increased the amount of surface-OH and SO42−groups,as well as the specific surface area.This significantly enhanced the adsorption performance of Jar and Sch for REEs.The optimum adsorption time and pH were determined through batch adsorption experiments.Besides,the adsorption kinetics were studied and found to align well with the pseudo-second-order model.Furthermore,the thermodynamic parameters(ΔG^(Θ),ΔH^(Θ)andΔS^(Θ))and adsorption isotherms were analyzed.The results indicated that mechanically activated schwertmannite(M-Sch)exhibited superior adsorption performance for REEs compared to mechanically activated jarosite(M-Jar).Moreover,M-Sch was reusable and exhibited high adsorption efficiency of REEs in actual mine wastewater,exceeding 92%.
基金supported by the National Natural Science Foundation of China(Nos.22336003 and 42177222)the National Key Research and Development Program of China(No.2023YFC3707600).
文摘Schwertmannite, a common iron-derived mineral, is known for its high efficiency in adsorbing As from water and reducing the mobility and availability of As in soils. However,few studies have examined the critical period for the effectiveness of schwertmannite in hindering As uptake by rice plants, particularly its impact on the uptake and transport of As across different growth stages of rice. In this study, hydroponic experiments were performed to explore the absorption and translocation of As(500 μg/L As(Ⅲ) or As(Ⅴ)), when combined with schwertmannite, in rice during all growth stages. The results showed that As concentration in roots, stems and leaves increased with rice growth, while the addition of schwertmannite reduced the As concentration in all parts of rice, compared to the control without schwertmannite. Besides, schwertmannite application mitigated the harmful impact of As on rice yield, and reduced As levels in grains by 66 %-90 % compared to treatments with only As(Ⅲ) or As(Ⅴ). The heading stage is identified as a critical period for applying schwertmannite to reduce As uptake in rice. Specifically, during the heading stages,the plants uptake 85 %-91 % of the As contents in the absence of schwertmannite. However,adding schwertmannite retained about 84 %-90 % of As content, significantly reducing its absorption by rice plants at this stage. Therefore, maintaining As adsorption by schwertmannite up to the heading stage is beneficial to effectively reduce As uptake in rice and lower As concentration in rice grains.
基金supported by the Open Project Program of the State Key Laboratory of Photocatalysis on Energy and Environment,Fuzhou University(No.SKLPEE-202008)the Special Fund for Scientific and Technological Innovation of Fujian Agriculture and Forestry University(No.CXZX2019073G)。
文摘Potential health risks related to environmental endocrine disruptors(EEDs)have aroused research hotspots at the forefront of water treatment technologies.Herein,nitrogen-doped titanium dioxide/schwertmannite nanocomposites(N-TiO_(2)/SCH)have been successfully developed as heterogeneous catalysts for the degradation of typical EEDs via photo-Fenton processes.Due to the sustainable Fe(Ⅲ)/Fe(Ⅱ)conversion induced by photoelectrons,as-prepared N-TiO_(2)/SCH nanocomposites exhibit much enhanced efficiency for the degradation of bisphenol A(BPA;ca.100% within 60 min under visible irradiation)in a wide pH range of 3.0-7.8,which is significantly higher than that of the pristine schwertmannite(ca.74.5%)or N-TiO_(2)(ca.10.8%).In this photo-Fenton system,the efficient degradation of BPA is mainly attributed to the oxidation by hydroxyl radical(·OH)and singlet oxygen(^(1)O_(2)).Moreover,the possible catalytic mechanisms and reaction pathway of BPA degradation are systematically investigated based on analytical and photoelectrochemical analyses.This work not only provides a feasible means for the development of novel heterogeneous photo-Fenton catalysts,but also lays a theoretical foundation for the potential application of mineral-based materials in wastewater treatment.
基金financially supported by the National Natural Science Foundation of China (No. 41572031)the Science and Technology Planning Project of Guangdong Province, China (No. 2017B030314175)+1 种基金the National Program for Support of Top-notch Young ProfessionalsChina scholarship council
文摘The heterogeneous photo-Fenton reaction is an effective technique in combating organic contaminants for both soil and water remediation,and extensive studies have focused on enhancing its efficiency and reducing its costs.In this work,we developed novel photoFenton catalysts by simply milling commercially available TiO_2(P25)with Schwertmannite(Sh),a natural iron-oxyhydroxysulfate nanomineral.We expect that the photo-generated electrons from TiO_2could continuously migrate to Sh,which then could enhance the separation of electron-hole pairs on TiO_2and accelerate the reduction of Fe(III)to Fe(II)on Sh,leading to high degradation efficiency of the target organic contaminants.SEM and TEM results showed the distribution of TiO_2on Sh surface for the nanocomposites(TiO_2/Sh).Under simulated sunlight irradiation,the much higher content of Fe(II)was determined on TiO_2/Sh than on Sh via a common method in the iron ore,and the consumption of H_2O_2and the production of·OH were more significant in the TiO_2/Sh system than those in the TiO_2and Sh systems.These results well support our hypothesis that the photo-generated electrons could migrate from TiO_2to Sh on the composites,and can also explain the much higher degradation efficiency of Rhodamine B(RhB)in the TiO_2/Sh system.Besides,TiO_2/Sh had lower Fe dissolution as compared with Sh,and retained high catalytic stability after four repeated cycles.Above merits of the TiO_2/Sh composites,in combining with their simple synthesis method and low-cost property,indicated that they should have promising applications as heterogeneous photo-Fenton catalysts.
基金supported by the National Natural Science Foundation of China (Nos. 41330639 and 41720104004)the National Key Research and Development Program of China (No. 2017YFD0801000)
文摘Schwertmannite is an amorphous iron(III)-oxyhydroxysulfate that forms in acid mine drainage(AMD) environments. The characteristic of high heavy metal adsorption capability makes schwertmannite a potentially useful, environmentally friendly material in wastewater treatment. Unstable schwertmannite is prone to recrystallization.Understanding the mechanisms that induce schwertmannite labilization and affect its capacity to remove heavy metals are of great environmental and geochemical significance.Thiocyanate(SCNˉ) is a hazardous pseudohalide that is also normally found in AMD.However, little is known about the impact of Fe(III)-binding ligand SCNˉ on schwertmannite stability and its subsequent capacity to bind trace elements. Here, we investigated the adsorption of SCNˉ on schwertmannite and subsequent mineral transformation to characterize this little-known process. The appearance of Fe2+indicated that the interactions between schwertmannite and SCNˉ may involve complexation and reduction reactions. Results showed that the majority of the adsorbed-SCNˉ was immobilized on schwertmannite during the 60-days transformation. The transformation rates of schwertmannite increased with increasing concentrations of SCNˉ. Goethite was detected as the dominant transformation product with or without SCNˉ. The mechanisms of SCNˉ-promoted dissolution of schwertmannite can be described as follows:(1) formation of Fe(III)–NCS complexes on the schwertmannite surface and in solution, a process which increases the reactivity of solid phase Fe(III);(2) the extraction of Fe(III) from schwertmannite by SCNˉ and subsequent schwertmannite dissolution; and(3) the formation of secondary minerals from extracted Fe(III). These findings may improve AMD treatment strategies and provide insight into the use and potential reuse of schwertmannite as a trace element sorbent.
基金supported by the National Natural Science Foundation of China(No.21876130)the Shanghai Natural Science Foundation(No.18ZR1440800)
文摘The massive amount of sludge generated by the classic Fenton process, which has often been hypothesized to consist of ferric hydroxide, remains a major obstacle to its large-scale application. Therefore, reutilization of Fenton sludge has recently gained more attention.Understanding the formation, transformation, and properties of Fenton sludge combined with the stages of the Fenton reaction is pivotal, but not well illustrated yet. In this study,SEM-EDS, FT-IR, XRD, and XPS were applied to study the morphology, crystallinity,elemental composition, and valence state of Fenton sludge. The authors report that schwertmannite and 2-line ferrihydrite were generated and transformed in the oxidation phase and the neutralization phase of the Fenton process. SO_4^(2-) in the solution decreased by8.7%–26.0% at different molar ratios of Fe(II) to H_2 O_2; meanwhile, iron ion precipitated completely at pH 3.70 with the formation of schwertmannite containing sulfate groups in the Fenton sludge. The structural sulfate(Fe-SO_4) in schwertmannite was released from the precipitate with the addition of OH-, and the production of Fenton sludge decreased with increasing pH when pH > 3.70. Goethite was found to form when the final p H was adjusted to 12 or at a reaction temperature of 80°C. Moreover, the possible thermal transformation to goethite and hematite indicated that Fenton sludge can be reused as a raw material for synthesizing more stable iron(hydro)oxides. The results provide useful insights into the formation and transformation of Fenton sludge, with implications for regulating the crystal type of Fenton sludge for further reuse.
基金supported by the National Natural Science Foundation of China (Nos.42007363,41977277)Scientific Research Project of Chongqing Technology and Business University (No.KFJJ2019051)+3 种基金Science and Technology Research Projects of Chongqing Education Commission (No.KJQN202000814)Chongqing Science and Technology Commission of China (No.cstc2019jcyj-msxmX0647)Foundation for High-level Talents of Chongqing University of Arts and Sciences (No.R2018CH11)Innovation Group of New Technologies for Industrial Pollution Control of Chongqing Education Commission (No.CXQT19023)。
文摘Schwertmannite is an important Fe(Ⅲ)-oxyhydroxysulfate in acid mine drainage (AMD) polluted areas and its stability depends on surrounding environmental factors and previously bound elements.The treatment and neutralization of AMD normally involve the use of lime,which leads to the discharge of abundant Ca in the mining area.Such an environmental disturbance brings up an important and less considered problem of how the reductive transformation of schwertmannite associated with coexisting Ca occurred.Here,the Fe(Ⅱ)-mediated transformation of Ca-adsorbed schwertmannite and subsequent Ca repartitioning behaviors were investigated.Results showed that adsorbed Ca had a weak inhibitory effect on Fe(Ⅱ)-mediated schwertmannite transformation.Release of SO_(4)2-and SEM images both indicated that transformation rates of schwertmannite decreased under the influence of adsorbed Ca.XRD patterns indicated that adsorbed Ca altered schwertmannite transformation pathways and product compositions upon treatment with 0.4 mmol/L Fe(Ⅱ).The end products of Sch notably contained both goethite and lepidocrocite;however,transformation products of SchCa only contained goethite all along.Approximately 33.5%of the surface adsorbed-Ca was released into solution within 6 hr after Fe(Ⅱ) injection.Aqueous Ca behaved in a“first release and then im-mobilization”manner,which indicated dissolution and secondary mineralization drove Ca migration during the Fe(Ⅱ)-mediated transformation of SchCa.Adsorbed Ca blocked the surface sites for subsequent Fe(Ⅱ) adsorption,limited the Fe(Ⅱ)-Fe(Ⅲ) ETAE,and decreased the transformation rates.This work sheds light on the complex geochemical behavior of schwertmannite under the influences of environmental perturbations in AMD environments.
基金supported by National Natural Science Foun-dation of China (Nos. 21637003 and 41977338)。
文摘Here we reported an effective method to solve the rate-limiting steps, such as the reduction of Fe^(3+) to Fe^(2+) and an invalid decomposition of H2O2 in a conventional Fenton-like reaction. A magnetic heterogeneous photocatalyst, Fe3O4-schwertmannite(Fe3O4-sch) was successfully developed by adding Fe3O4 in the formation process of schwertmannite. Fe3O4-sch shows excellent electrons transfer ability and high utilization efficiency of H2O2(98.5%). The catalytic activity of Fe3O4-sch was studied through the degradation of phenol in the heterogeneous photo-Fenton process. Phenol degradation at a wide pH(3-9) was up to 98% within 6 min under visible light illumination with the Fe3O4-sch as heterogeneous Fenton catalyst, which was higher than that using pure schwertmannite or Fe3O4. The excellent photocatalytic performance of Fe3O4-sch is ascribed to the effective recycling between ≡Fe^(3+) and ≡Fe^(2+) by the photo-generated electron, and also profit from the formation of the "Z-Scheme" system. According to the relevant data, photocatalytic mechanism of Fe3O4-sch for degrading phenol was proposed. This study not only provides an efficient way of enhancing heterogeneous Fenton reaction, but also gives potential application for iron oxyhydroxysulfate mineral.
基金supported by the National Natural Science Foundation of China (Nos. 40902018, 31372133)the Jiangsu Key Laboratory of Environmental Material and Environmental Engineering (No. K13058)
文摘Schwertmannite, a ubiquitous mineral present in iron oxyhydroxides formed in iron- and sulfate-rich acid media, favors incorporation of some toxic anions in its structure. We reported an iron-oxidizing bacterial strain HX3 from a municipal sludge that facilitates the formation of pure schwertmannite in cultures. Ferrous iron oxidation by the isolated strain HX3 was optimum at an initial pH of 2.0-3.3 and temperature of 28-35°C. Pure schwertmannite was found through bacterial oxidation of ferrous iron at an initial pH 2.8and temperature 28°C. Following 16 S rDNA gene sequence analysis the bacterial strain HX3 was identified as Acidithiobacillus ferrooxidans. The arsenic-resistance A. ferrooxidans HX3 showed the potential of environmental application in arsenic removal from the As（Ⅲ）- and iron-rich acid sulfate waters directly by As（Ⅲ） adsorption or the formation of schwertmannite in the environment.
文摘The adsorption and post adsorption behavior of schwertmannite with various oxyanions were investigated for clean-up contaminated water with hazardous oxyanions and safe disposal of spent schwertmannite. The result of adsorption experiments showed that the maximum capacities of oxyanions adsorption onto schwertmannite are 1.023, 0.934, 0.723 and 0.313 mmol/g for arsenate, phosphate, chromate and selenate, respectively. Based on the differences in the adsorption capacities, the selectivity of oxyanion adsorption on schwertmannite decreases as the order: arsenate ≥ phosphate > chromate >> selenate. Change in the Zeta potential after adsorption by arsenate, phosphate and chromate were very different from those after adsorption by selenate and of the original schwertmannite. This difference implies that the adsorption mechanism on schwertmannite with arsenate, phosphate and chromate is different from that with selenate and sulfate. Arsenate, phosphate, and chromate ions form inner-sphere complexes with the surface of schwertmannite, while selenate and sulfate ions form outer-sphere complexes with the surface of schwertmannite. Based on a comparison with anion adsorption, strong base anions form inner-sphere complexes, which induce a strong adsorption with schwertmannite as well as it is conducive to high adsorption capacity. From the results of aging experiments, schwertmannite with sulfate and selenate changed to a more stable phase, goethite, in a short time, whereas there is no change in the XRD patterns of schwertmannite with arsenate and phosphate after 30 days. The stability of schwertmannite after the adsorption increased in the following order: sulfate ≌ selenate «chromate ≌ arsenate. The solubility of schwertmannite with different oxyanions was calculated according to solid solution theory. The solubility of schwertmannite decreased after adsorption of oxyanions with high selectivity. It is concluded that oxyanions with high selectivity can stabilize schwertmannite by decreasing the solubility of the schwertmannite after adsorption of the oxyanions.
基金supported by the Science and Technology Plans of Tianjin (No. 15PTSYJC00230)Tianjin Research Program of Application Foundation and Advanced Technology (No. 17JCQNJC08000)the National Natural Science Foundation of China (Nos. 41373114 and 41201487)
文摘Schwertmannite(Sh), a poorly crystalline iron(hydr)oxide that usually appears in acid mine drainage, plays a significant role in the immobilization of As(V). In this study, the effects of UV irradiation and oxalate on the dissolution of Sh with structurally incorporated As(V) [Sh-As(V)] and the subsequent mobilization of As(V) were investigated at pH 3.0. In the dark, more total dissolved Fe was produced(the maximum value was 33.2 mg/L) in the suspensions of Sh-As(V) with oxalate than in those without oxalate. UV irradiation slightly enhanced the mobilization of As(V) for the system of Sh-As(V)-1 and Sh-As(V)-2 in the absence of oxalate compared with that in the dark. However, in the presence of oxalate, UV irradiation caused the concentration of mobilized As(V) to decline by 630-875% compared with that in the dark. This study enhanced our understanding of the mobilization of As(V) and demonstrated that UV irradiation could contribute to the immobilization of As(V) on Sh in aqueous environments containing oxalate.
基金supported by the National Natural Science Foundation of China(42377248,41977338)the Shanxi Province“1331 Project”funded project(20211331-15)the Natural Science Foundation of Shanxi Province,China(No.202103021224139),and the Shanxi Agricultural University school-enterprise cooperation project(QT004).
文摘Due to continuing mining activities,Cd(II)and As(III)contamination in acid mine drainage(AMD)has become a major environmental challenge.Currently,there is increasing focus on the use of biochar to mitigate AMD pollution.However,the impact of biochar on the process of Fe(II)oxidation by Acidithiobacillus ferrooxidans(A.ferrooxidans)in AMD systems has not been determined.In this study,we investigated the effects of introducing biochar and biochar-leachate on Fe(II)biooxidation by A.ferrooxidans and on the removal of Cd(II)and As(III)from an AMD system.The results showed that the biochar-leachate had a promoting effect on Fe(II)biooxidation by A.ferrooxidans.Conversely,biochar inhibited this process,and the inhibition increased with increasing biochar dose.Under both conditions(c(A.ferrooxidans)=1.4×107 copies mL-1,m(FeSO4·7H2O):m(biochar)=20:1;c(A.ferrooxidans)=7.0×107 copies mL-1,m(F eSO4·7H2O):m(biochar)=5:1),the biooxidation capacity of A.ferrooxidans was severely inhibited,with Fe(II)oxidation efficiency reaching a value of only~20%after 84 h.The results confirmed that this inhibition might have occurred because a large fraction of the A.ferrooxidans present in the system adsorbed to the biochar,which weakened bacterial activity.In addition,mineral characterization analysis showed that the introduction of biochar changed the A.ferrooxidans biooxidation products from schwertmannite to jarosite,and the specific surface area increased after the minerals combined with biochar.Coprecipitation experiments of As(III)and Cd(II)showed that Cd(II)was adsorbed by the biochar over the first 12 h of reaction,with a removal efficiency of~26%.As(III)was adsorbed by the generated schwertmannite over 24 h,with a removal efficiency of~100%.These findings have positive implications for the removal of As(III)and Cd(II)from AMD.
