Adsorption of arsenate and arsenite on titanium dioxide suspensions.

Adsorption of arsenate (As(V)) and arsenite (As(III)) to two commercially available titanium dioxide (TiO2) suspensions, Hombikat UV100 and Degussa P25, was investigated as a function of pH and initial concentration of adsorbate ions. The BET surface area and zeta potential values of TiO2 were also measured to understand the difference in adsorption behavior of two suspensions. Both As(V) and As(III) adsorb more onto Hombikat UV100 particles than Degussa P25 particles. Adsorption of As(V) onto TiO2 suspensions was more than As(III) at pH 4 while the adsorption capacity of As(III) was more at pH 9. The electrostatic factors between surface charge of TiO2 particles and arsenic species were used to explain adsorption behavior of As(V) and As(III) at different pH. The Langmuir and Freundlich isotherm equations were used to interpret the nature of adsorption of arsenic onto TiO2 suspensions. The usefulness of adsorption data in removing arsenic in water is briefly discussed.