Arsenic(As)contamination of groundwater is a serious global issue requiring effective and sustainable remediation strategies.For long-term As immobilization,this study explores the potential of in-situ magnetite preci...Arsenic(As)contamination of groundwater is a serious global issue requiring effective and sustainable remediation strategies.For long-term As immobilization,this study explores the potential of in-situ magnetite precipitation,induced by anaerobic nitrate-reducing Fe(II)-oxidizing(NRFO)bacteria.A nitrate-intercalated layered double hydroxide(NO_(3)^(-)MgFe LDH)was introduced to provide nitrate as an electron acceptor for Fe(II)bio-oxidation and serve as an iron-based precursor in magnetite formation.The experimental results showed that NO_(3)^(-)MgFe LDH was transformed into green rust(GR)in the presence of Fe(II)and HCO_(3)^(-).Meanwhile,0.5 g/L of NO_(3)^(-)MgFe LDH released cumulatively about 1.21 mM of nitrate within 12 h,promoting the transformation of GR into magnetite induced by Acidovorax sp.BoFeN1.As a result,the aqueous As concentration decreased from 2 mg/L to<0.008 mg/L,with approximately 70%of As confined in recalcitrant Fe oxides,suggesting high potential for long-term As immobilization.Environmental factors influenced the transformation process:a lower Fe(II)concentration(0.5 mM)delayed GR formation,while varying HCO_(3)^(-)concentrations(2.5-10 mM)had minimal effect.Subsequently,an elevated As level(5 mg/L)inhibited the bio-formation of magnetite,leading to lepidocrocite as the dominant mineral phase.Given the stability of magnetite,this study provides a cost-effective and environmentally friendly strategy for the durable in-situ remediation of As-contaminated groundwater.展开更多
Layered Double Hydroxides MgFe-LDH and MgAl-LDH have been prepared by th e method involving separate nucleation and ageing steps. The structure analyses for these two materials show that the values of the parameters b...Layered Double Hydroxides MgFe-LDH and MgAl-LDH have been prepared by th e method involving separate nucleation and ageing steps. The structure analyses for these two materials show that the values of the parameters both a and c of M gAl-LDH are smaller than that of MgFe-LDH though their structures are simila r, and MgAl-LDH with higher crystallinity is more easily formed than MgFe-LD H in the same preparing conditions. The IR analyses manifest that the structures of layer sheets and the orderings of the anions in the interlayer regions of Mg Al-LDH are more regular than that of MgFe-LDH. The temperature programmed XR D analyses reveal that the diffraction peak of 003 reflections for MgAl-LDH co uld be seen after calcining at 300℃, while this peak for MgFe-LDH disappears after calcining at 200℃. Together with the TG-DTA analysis it can be conclu ded that the thermal stability of MgAl-LDH is obviously higher than that of Mg Fe-LDH.展开更多
基金Project(2023YFC3207000)supported by the National Key Research and Development Program of ChinaProject(2024RC1008)supported by the Science&Technology Innovation Program of Hunan Province,China。
文摘Arsenic(As)contamination of groundwater is a serious global issue requiring effective and sustainable remediation strategies.For long-term As immobilization,this study explores the potential of in-situ magnetite precipitation,induced by anaerobic nitrate-reducing Fe(II)-oxidizing(NRFO)bacteria.A nitrate-intercalated layered double hydroxide(NO_(3)^(-)MgFe LDH)was introduced to provide nitrate as an electron acceptor for Fe(II)bio-oxidation and serve as an iron-based precursor in magnetite formation.The experimental results showed that NO_(3)^(-)MgFe LDH was transformed into green rust(GR)in the presence of Fe(II)and HCO_(3)^(-).Meanwhile,0.5 g/L of NO_(3)^(-)MgFe LDH released cumulatively about 1.21 mM of nitrate within 12 h,promoting the transformation of GR into magnetite induced by Acidovorax sp.BoFeN1.As a result,the aqueous As concentration decreased from 2 mg/L to<0.008 mg/L,with approximately 70%of As confined in recalcitrant Fe oxides,suggesting high potential for long-term As immobilization.Environmental factors influenced the transformation process:a lower Fe(II)concentration(0.5 mM)delayed GR formation,while varying HCO_(3)^(-)concentrations(2.5-10 mM)had minimal effect.Subsequently,an elevated As level(5 mg/L)inhibited the bio-formation of magnetite,leading to lepidocrocite as the dominant mineral phase.Given the stability of magnetite,this study provides a cost-effective and environmentally friendly strategy for the durable in-situ remediation of As-contaminated groundwater.
文摘Layered Double Hydroxides MgFe-LDH and MgAl-LDH have been prepared by th e method involving separate nucleation and ageing steps. The structure analyses for these two materials show that the values of the parameters both a and c of M gAl-LDH are smaller than that of MgFe-LDH though their structures are simila r, and MgAl-LDH with higher crystallinity is more easily formed than MgFe-LD H in the same preparing conditions. The IR analyses manifest that the structures of layer sheets and the orderings of the anions in the interlayer regions of Mg Al-LDH are more regular than that of MgFe-LDH. The temperature programmed XR D analyses reveal that the diffraction peak of 003 reflections for MgAl-LDH co uld be seen after calcining at 300℃, while this peak for MgFe-LDH disappears after calcining at 200℃. Together with the TG-DTA analysis it can be conclu ded that the thermal stability of MgAl-LDH is obviously higher than that of Mg Fe-LDH.
