Arsenic adsorption onto hematite and goethite

Surface complexation reactions on mineral affect the fate and the transport of arsenic in environmental systems and the global cycle of this element. In this work, the sorption of As(V) on two commercial iron oxides (hematite and goethite) was studied as a function of different physico-chemical parameters such as pH and ionic strength. The main trend observed in the variation of the arsenic sorbed with the pH is a strong retention in acidic pH and the decrease of the sorption on both sorbents at alkaline pH values. The sorption experiments for these iron oxides show that there is no effect of the ionic strength on arsenate adsorption suggesting the formation of an inner sphere surface complex. At pH values corresponding to natural pH water, both hematite and goethite are able to adsorb more than 80% of arsenic, whatever the initial concentration may be. The iron oxides used in this work should be suitable candidates as sorbents for As(V) removal technologies.