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
Nano-MgFe2O4-Fe2O3 magnetic powders were synthesized by citrate gel under microwave irradiation. The structure,particle size distribution,electromagnetic characteristics of nano-MgFe2O4-Fe2O3 were characterized by usi...Nano-MgFe2O4-Fe2O3 magnetic powders were synthesized by citrate gel under microwave irradiation. The structure,particle size distribution,electromagnetic characteristics of nano-MgFe2O4-Fe2O3 were characterized by using TG-DTA, X-ray, electronic microscope, nano-size measurement and electromagnetism measurement apparatus?The results show that the product is a mixture of MgFe2O4 and Fe2O3 with average size of 44 nm, tanδ for the product is 0.265 and 0.610 at frequency of 1.0 GHz and 1.8 GHz respectively.展开更多
MgFe2O4 nanoparticles were hydrothermally synthesized at 150 ℃ using iron nitrate [Fe(NO3)3·9H2O], magnesium nitrate [Mg(NO3)2·6H2O] and sodium hydroxide (NaOH) as starting materials by carefully controllin...MgFe2O4 nanoparticles were hydrothermally synthesized at 150 ℃ using iron nitrate [Fe(NO3)3·9H2O], magnesium nitrate [Mg(NO3)2·6H2O] and sodium hydroxide (NaOH) as starting materials by carefully controlling the reaction conditions. The influences of several factors such as presence or absence of Na+, molar ratio of Fe3+ / Mg2+, concentration of mental ions, temperature and reaction time on resultant products were investigated in the hydrothermal process. The sample was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and its magnetic properties were measured using vibrating sample magnetometer (VSM).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Nano-MgFe2O4-Fe2O3 magnetic powders were synthesized by citrate gel under microwave irradiation. The structure,particle size distribution,electromagnetic characteristics of nano-MgFe2O4-Fe2O3 were characterized by using TG-DTA, X-ray, electronic microscope, nano-size measurement and electromagnetism measurement apparatus?The results show that the product is a mixture of MgFe2O4 and Fe2O3 with average size of 44 nm, tanδ for the product is 0.265 and 0.610 at frequency of 1.0 GHz and 1.8 GHz respectively.
文摘MgFe2O4 nanoparticles were hydrothermally synthesized at 150 ℃ using iron nitrate [Fe(NO3)3·9H2O], magnesium nitrate [Mg(NO3)2·6H2O] and sodium hydroxide (NaOH) as starting materials by carefully controlling the reaction conditions. The influences of several factors such as presence or absence of Na+, molar ratio of Fe3+ / Mg2+, concentration of mental ions, temperature and reaction time on resultant products were investigated in the hydrothermal process. The sample was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and its magnetic properties were measured using vibrating sample magnetometer (VSM).
