title: Effect of dissolved oxygen concentration on iron efficiency: Removal of three chloroacetic acids.
abstract: The monochloroacetic, dichloroacetic and trichloroacetic acid (MCAA, DCAA and TCAA) removed by metallic iron under controlled dissolved oxygen conditions (0, 0.75, 1.52, 2.59, 3.47 or 7.09 mg/L DO) was investigated in well-mixed batch systems. The removal of CAAs increased first and then decreased with increasing DO concentration. Compared with anoxic condition, the reduction of MCAA and DCAA was substantially enhanced in the presence of O2, while TCAA reduction was significantly inhibited above 2.59 mg/L. The 1.52 mg/L DO was optimum for the formation of final product, acetic acid. Chlorine mass balances were 69-102%, and carbon mass balances were 92-105%. With sufficient mass transfer from bulk to the particle surface, the degradation of CAAs was limited by their reduction or migration rate within iron particles, which were dependent on the change of reducing agents and corrosion coatings. Under anoxic conditions, the reduction of CAAs was mainly inhibited by the available reducing agents in the conductive layer. Under low oxic conditions, the increasing reducing agents and thin lepidocrocite layer were favorable for CAA dechlorination. Under high oxic conditions, the redundant oxygen competing for reducing agents and significant lepidocrocite growth became the major restricting factors. Various CAA removal mechanisms could be potentially applied to explaining the effect of DO concentration on iron efficiency for contaminant reduction in water and wastewater treatment.
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, PR China.
authors.forename: Shun
authors.initials: S
authors.lastname: Tang
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, PR China.
authors.forename: Xiao-mao
authors.initials: XM
authors.lastname: Wang
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, PR China.
authors.forename: Yu-qin
authors.initials: YQ
authors.lastname: Mao
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, PR China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, PR China. Electronic address: yanghw@tsinghua.edu.cn.
authors.forename: Hong-wei
authors.initials: HW
authors.lastname: Yang
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, PR China; Environmental Programs, The Pennsylvania State University, 777 West Harrisburg Pike, Middletown, PA 17057, USA.
authors.forename: Yuefeng F
authors.initials: YF
authors.lastname: Xie
mesh_terms: D000085:Acetates / Q000737:chemistry*; D003999:Dichloroacetic Acid / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D010100:Oxygen / Q000032:analysis*; D014238:Trichloroacetic Acid / Q000737:chemistry*; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification
chemical_list: D000085:Acetates; D014874:Water Pollutants, Chemical; C006972:chloroacetic acid; D014238:Trichloroacetic Acid; D003999:Dichloroacetic Acid; D007501:Iron; D010100:Oxygen
keywords: Chloroacetic acids; Corrosion products; Dissolved oxygen (DO); Iron; Removal mechanism