title: The effects of iron(II) on the kinetics of arsenic oxidation and sorption on manganese oxides.
abstract: In this study, As(III) oxidation kinetics by a poorly-crystalline phyllomanganate (δ-MnO2) in the presence and absence of dissolved Fe(II) was investigated using stirred-flow and batch experiments. Chemically synthetic δ-MnO2 was reacted with four influent solutions, containing the same As(III) concentration but different Fe(II) concentrations, at pH 6. The results show an initial rapid As(III) oxidation by δ-MnO2, which is followed by an appreciably slow reaction after 8h. In the presence of Fe(II), As(III) oxidation is inhibited due to the competitive oxidation of Fe(II) as well as the formation of Fe(III)-(hydr)oxides on the δ-MnO2 surface. However, the sorption of As(III), As(V) and Mn(II) are increased, for the newly formed Fe(III)-(hydr)oxides provide additional sorption sites. This study suggests that the competitive oxidation of Fe(II) and consequently the precipitation of Fe(III) compounds on the δ-MnO2 surface play an important role in As(III) oxidation and As sequestration. Understanding these processes would be helpful in developing in situ strategies for remediation of As-contaminated waters and soils.
authors.affiliation: Environmental Soil Chemistry Research Group, Delaware Environmental Institute, University of Delaware, Newark, DE 19716, United States.
authors.forename: Yun
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Environmental Soil Chemistry Research Group, Delaware Environmental Institute, University of Delaware, Newark, DE 19716, United States; Key Laboratory of Surficial Geochemistry, Ministry of Education, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210046, People's Republic of China. Electronic address: liwei_isg@nju.edu.cn.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.affiliation: Environmental Soil Chemistry Research Group, Delaware Environmental Institute, University of Delaware, Newark, DE 19716, United States.
authors.forename: Donald L
authors.initials: DL
authors.lastname: Sparks
mesh_terms: D000327:Adsorption; D001151:Arsenic / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry*; D007700:Kinetics; D017895:Manganese Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010084:Oxidation-Reduction; D010087:Oxides / Q000138:chemical synthesis / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D005296:Ferrous Compounds; D017895:Manganese Compounds; D010087:Oxides; C027424:manganese oxide; D001151:Arsenic
keywords: Arsenic; Iron; Kinetics; Oxidation; Sorption; Stirred-flow; δ-MnO(2)