Iron oxide and its modified forms as an adsorbent for arsenic removal: A comprehensive recent advancement

Arsenic, one of the elements having most terrible impact on the human being, is threatening the world continuously. It exists in the combined form in rocks under earth which on dissolution contaminates ground water. The contamination has led to a massive epidemic in East and South-East Asia, and the problem is more dangerous for Bangladesh and adjoining province, Bengal of India, where more than 100 million people are currently affected by arsenic contaminated ground water. Arsenic exists in water as oxyacids in two oxidation states, As(III) and As(V), the former is more toxic. Various techniques are under use for the removal of both forms of arsenic but most of these are not suitable for As(III) form. Adsorption has been proved most preferable technique for the removal of both forms of arsenic. Various types of solid materials had been used as adsorbent but nanomaterials have been reported more effective. However, some of these materials are toxic, difficult to separate after adsorption, and ineffective in the presence of water constraints. Iron oxides and its modified forms overcome all these shortcomings. Arsenic adsorption using various types of iron oxides has been surveyed and their sorption efficiencies have been compared herein. The effect of presence of other competitive ions in water has also been discussed. The valuable literature available on arsenic remediation, latest advancement, implementation of iron oxides in filters, and future perspective along with safe disposal of sludge produced have been incorporated. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.