Evidences of arsenic (III) precipitation on iron (III) oxy-hydroxides from the combination of Raman spectroscopy, density functional theory calculations, and extended X-ray absorption fine structure spectroscopy

Iron oxy-hydroxides are especially important soil constituents related to natural arsenic attenuation in the environment. Many studies have applied spectroscopic techniques and theoretical calculations to elucidate the molecular structure of arsenic sorbed on iron oxy-hydroxides (S herman & R andall 2003; Kubicki 2005; Kubicki et al. 2007). The general conclusion has been that As(V) is mainly bonded to Fe oxy-hydroxides through bidentate-binuclear inner-sphere complexation. On the other hand, there is no consensus regarding the mechanisms of As(III) sorption. Both outer and inner sphere complexation are suggested from EXAFS analyses.