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.

A critical review on arsenic removal from water using iron-based adsorbents

“…An in situ remediation for arsenic from groundwater by using an aquifer iron coating method was considered as an effective and simple way for arsenic remediation in rural and remote areas where groundwater is used as the main water resource for drinking. 182 A continuous injection of FeSO 4 and NaClO solutions for 96 h led to the formation of a uniform a-FeOOH (30-50 nm) coating on the surface of the sand. During this process, ferrous iron can also be adsorbed and subsequently oxidized to form new ferric hydroxide particles, which can be used to adsorb arsenic from water.…”

“…The process of adsorption/co-precipitation with ne goethite particles resulted in arsenic immobilization. 182 Titanium dioxide (TiO 2 ) is a famous photocatalyst that offers a relatively inexpensive and environmentally safe way to achieve oxidation of As(III) to As(V). 183 TiO 2 nanoparticles doped with 10% Fe adsorbent could effectively oxidize As(III) to As(V).…”

In-situ arsenic remediation by aquifer iron coating: Field trial in the Datong basin, China

“…Therefore, to overcome these problems encountered in natural groundwater aquifers, it requires not only to promote the formation of Fe(III) oxides/hydroxides, but also to transfer As(III) into As(V) to improve As adsorption onto Fe(III) oxides/hydroxides. Our previous study has confirm that Fe(III) oxides/hydroxides coating onto quartz sands has achieved As removal from groundwater [21]. However, for the implications of this method in natural aquifers, some concerns remains to be clearly answered.…”

Arsenic: A Review of the Element’s Toxicity, Plant Interactions, and Potential Methods of Remediation

“…A simulation of this technique involving added arsenic yielded promising results, with all of the aqueous arsenic being removed. 89 Another approach to establishing new techniques is to combine bioremediation techniques with phytoremediation to reduce the level of a target contaminant. Called phytobial remediation, these hybrid methods are designed to utilize both types of technique in a way that they complement each other's limitations.…”