Removal of arsenic from aqueous solution by synthetic hematite

Abstract

A hematite was synthesized and subjected to batch equilibration of arsenic and it’s desorption processes that control the mobility, toxicity and availability of arsenic in the water environment. The pH_pzc of the synthesized hematite as determined by mass and potentiometric titration techniques were 9.18 and 9.20 respectively. The effect of background electrolyte concentration affected the pH_pzc values. Adsorption of As(III) was influenced by ionic strength and pH of the adsorbate medium. Maximum adsorption was obtained at pH 7.8. The adsorption data fitted well into Langmuir, Freundlich and Temkin isotherms with correlation coefficient, r² values of 0.96, 0.94, and 0.92 respectively. The n< 1 value obtained from Freundlich plot was an indication of favorable adsorption of As(III) over the entire range of concentrations studied. From the kinetic studies, a significant amount of As(III) was sorbed within 240 min. About 53% and 81% of the amount at 100% coverage were sorbed at 120 and 240 min respectively. Desorption of As(III) is pH dependent with 86% maximum desorption at pH 1 and 7% at pH 6.

Keywords: Hematite, arsenic, adsorption kinetics, desorption, pH

International Journal of Natural and Applied Sciences, 6(2): 246-254, 2010