title: Removal of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) from water by coagulation: mechanisms and influencing factors.
abstract: In this study, alum (Al2(SO4)3⋅18H2O), ferric chloride (FeCl3⋅6H2O) and polyaluminium chloride (PACl) were used to remove perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) from water. The influencing factors, including pH and natural organic matter (NOM), were investigated. A positive correlation was found between the size of the flocs and the removal efficiency of PFOX (X=S and A). The removal ratios of PFOS and PFOA were 32% and ∼12%, respectively, when 50 mg/L of FeCl3⋅6H2O was added as the coagulant at the initial pH. Coagulation achieved high removal ratios for PFOX under acidic conditions (∼47.6% and 94.7% for PFOA and PFOS at pH 4, respectively). In addition, increasing NOM concentrations decreased the removal rates of PFOX because of the existence of competitive adsorption between NOM molecules and PFOX on the surface of the coagulants and flocs. The combination of adsorption by powdered activated carbon (PAC) and coagulation increased the removal ratios up to >90% for PFOX at the initial concentration of 1mg/L, implying that the adsorption enhanced coagulation. Meantime, the experiments with natural water showed that coagulation is a feasible method to remove PFOS and PFOA from surface water.
authors.affiliation: State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, PR China.
authors.forename: Yueping
authors.initials: Y
authors.lastname: Bao
authors.affiliation: State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, PR China. Electronic address: junfengn@bnu.edu.cn.
authors.forename: Junfeng
authors.initials: J
authors.lastname: Niu
authors.affiliation: State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, PR China.
authors.forename: Zesheng
authors.initials: Z
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, PR China.
authors.forename: Ding
authors.initials: D
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, PR China.
authors.forename: Jianghong
authors.initials: J
authors.lastname: Shi
authors.affiliation: Environment Research Institute, Shandong University, Jinan 250100, PR China.
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Sun
authors.affiliation: College of Agricultural and Environmental Sciences, Department of Crop and Soil Sciences, University of Georgia, Griffin, GA 30223, United States.
authors.forename: Qingguo
authors.initials: Q
authors.lastname: Huang
keywords: Coagulation; Mechanism; Natural organic matter; PFOA; PFOS