Complexation of arsenate with ferric ion in aqueous solutions

Abstract

Interactions between arsenic and iron play an important role in arsenic removal from water. For the purpose of understanding the complexation of arsenate with ferric ion, arsenate solutions were prepared to react with ferric ion under various pH and temperature conditions. The formation of ferric–arsenate complex was examined using UV-Vis spectroscopy. The complex substance was proposed to exist as FeH₂AsO₄²⁺ and FeHAsO₄⁺, which transformed into gel-like material under higher pH (pH ≥ 2.38) or higher temperature (T ≥ 90 °C). The solid phase of gel-like material was verified as poorly crystallized ferric arsenate by XRF, XRD and FTIR. Moreover, the competitive complexation of ferric between sulfate and arsenate was also concerned. This study is beneficial for the better understanding of the fate and solubility of arsenic and ferric in water.