Titanium-based nanocomposite materials for arsenic removal from water: A review

Abstract

Arsenic is highly carcinogenic element and less concentration of this chemical element makes natural water unsafe for human consumption. Versatile techniques including adsorption method have been established to remove the arsenic from water. However, adsorption is found to be one of effective method for the remediation of arsenic from contaminated water. Different types of natural adsorbents i.e. clays, waste materials, carbon based material have been studied widely for the adsorption of arsenic. Recently, nanotechnology is considered to be one of the best technology for waste water treatment. Therefore researchers have synthesized several types of nanoadsorbents and investigated them for the removal of various pollutants including arsenic from water. Now days, attention is paid on development of nanocomposite materials which are proven as competent arsenic adsorbent candidate as compared to other adsorbents due to dominant structural and surface features. Various metal/metal oxide based nanocomposites have been developed and studied for arsenic removal from aqueous media. It has been reported that TiO₂ based nanocomposite exhibit stong affinity for both inorganic form of arsenic. Therefore, in this review numerous metal or metal oxide based titania nanocomposites i.e. TiO₂-αFe₂O₃, NHITO, Ce-Ti oxide, Zr-TiO_2, RGO-MFT etc. have been discussed in details for the water treatment containing arsenic. This review also presents an overview of low cost adsorbents, titania based nanoadsorbent and hybrid titania nanostructures for the removal of arsenic. In this review paper the particle size, surface area and adsorption efficiency of these titania based materials at different pH are also been presented in tabulated form. It provides the opportunity to choose best titania based nanocomposites for the treatment of arsenic polluted water.

Keywords: Chemistry; Engineering; Environmental science; Materials science.

Fig. 1

Low cost adsorbent for the removal of arsenic.

Fig. 2

(a) Individually added alumina chitosan bead (AlCB) and titania chitosan bead (TICB) to form mixed batch system (b) mixed impregnated chitosan bead preparation (MICB) by mixing chitosan, alumina and titania.

Fig. 3

Schematic representation of adsorption of As (V) on meso- Ti$O_2$ /α$F{e}_2{O}_3.$ H₃AsO₃ (As III) oxidized into As (V) i.e. HAsO₄⁻² and H₂AsO₄⁻².

Fig. 4

Suggested mechanism of photoxidation of arsenite on V₂O₅/TiO₂ nanocomposites. Electrons and holes are generated which convert oxygen and hydroxyl into O₂•/OH• radicals that cause the oxidation of As (III) into As (V).