The sorption of inorganic arsenic on modified sepiolite: the effect of hydrated iron(III) oxide

Abstract

The sorption of inorganic arsenic species, As(III) and As(V), from water by sepiolite modified with hydrated iron(III) oxide was investigated at 25 degrees C through batch studies. The influence of the initial pH value, the initial As concentration, the contact time and the type of water on the sorption capacity was investigated. Two types of water were used, deionised and groundwater. The maximal sorption capacity for As(III) dissolved in deionised water was observed at an initial and final pH value 7.0, while the bonding of As(V) was observed to be almost pH independent for pH value in the range from 2.0 to 7.0, while a significant decrease in the sorption capacity was observed at pH values above 7.0. The sorption capacity at initial pH 7.0 was about 10 mg g(-1) for As(III) and 4.2 mg g(-1) for As(V) in deionised water. The capacity in groundwater was decreased by 40 % for As(III) and by 20 % for As(V). The Langmuir model and pseudo-second order kinetic model revealed good agreement with the experimental results. The results showed that Fe(III)-modified sepiolite exhibits significant affinity for arsenic removal and it has the potential for application in water purification processes.