title: In situ treatment of arsenic contaminated groundwater by aquifer iron coating: Experimental study.
abstract: In situ arsenic removal from groundwater by an aquifer iron coating method has great potential to be a cost effective and simple groundwater remediation technology, especially in rural and remote areas where groundwater is used as the main water source for drinking. The in situ arsenic removal technology was first optimized by simulating arsenic removal in various quartz sand columns under anoxic conditions. The effectiveness was then evaluated in an actual high-arsenic groundwater environment. The arsenic removal mechanism by the coated iron oxide/hydroxide was investigated under different conditions using scanning electron microscopy (SEM)/X-ray absorption spectroscopy, electron probe microanalysis, and Fourier transformation infrared spectroscopy. Aquifer iron coating method was developed via a 4-step alternating injection of oxidant, iron salt and oxygen-free water. A continuous injection of 5.0 mmol/L FeSO4 and 2.5 mmol/L NaClO for 96 h can form a uniform goethite coating on the surface of quartz sand without causing clogging. At a flow rate of 7.2 mL/min of the injection reagents, arsenic (as Na2HAsO4) and tracer fluorescein sodium to pass through the iron-coated quartz sand column were approximately at 126 and 7 column pore volumes, respectively. The retardation factor of arsenic was 23.0, and the adsorption capacity was 0.11 mol As per mol Fe. In situ arsenic removal from groundwater in an aquifer was achieved by simultaneous injections of As(V) and Fe(II) reagents. Arsenic fixation resulted from a process of adsorption/co-precipitation with fine goethite particles by way of bidentate binuclear complexes. Therefore, the study results indicate that the high arsenic removal efficiency of the in situ aquifer iron coating technology likely resulted from the expanded specific surface area of the small goethite particles, which enhanced arsenic sorption capability and/or from co-precipitation of arsenic on the surface of goethite particles.
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, 430074 Wuhan, China. Electronic address: xjxie@cug.edu.cn.
authors.forename: Xianjun
authors.initials: X
authors.lastname: Xie
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, 430074 Wuhan, China. Electronic address: yx.wang@cug.edu.cn.
authors.forename: Yanxin
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, 430074 Wuhan, China.
authors.forename: Kunfu
authors.initials: K
authors.lastname: Pi
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, 430074 Wuhan, China; Pacific Northwest National Laboratory, Richland, WA 99354, USA.
authors.forename: Chongxuan
authors.initials: C
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, 430074 Wuhan, China.
authors.forename: Junxia
authors.initials: J
authors.lastname: Li
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, 430074 Wuhan, China.
authors.forename: Yaqing
authors.initials: Y
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, 430074 Wuhan, China.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, 430074 Wuhan, China.
authors.forename: Mengyu
authors.initials: M
authors.lastname: Duan
mesh_terms: D001151:Arsenic / Q000032:analysis* / Q000737:chemistry; D052918:Environmental Restoration and Remediation / Q000379:methods*; D060587:Groundwater / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry
chemical_list: D014874:Water Pollutants, Chemical; D007501:Iron; D001151:Arsenic
keywords: Arsenic contamination; Groundwater; In situ immobilization; Iron coating