Removal of arsenic(III) from drinking water by adsorption with titanium and ferrous oxide nanoparticles

Abstract

Adsorption isotherms and reaction kinetics of arsenic(III) removal from drinking water by adsorption with varying amount of titanium and ferrous oxide [namely Ti(OH)4, TiO2, Fe3O4 and Fe2O3] were evaluated in the present paper. Arsenic(III) can be average removed over 92 % by these titanium or ferrous adsorbents within 2 h in near neutral solution (include in weak acid and weak alkaline solution). The reaction rate was speedy at initial stage of adsorption but the further time reaction rate was steeply decreased. The removal efficiency of arsenic(III) slightly increased with increasing solution pH to an adsorption maximum at around pH 8 but steep decreased with further increasing solution pH. Adsorption kinetics data were found to be best described by the modified pseudo-second-order kinetics model for titanium adsorbents [Ti(OH)4 and TiO2] but second-order kinetics model for ferrous oxide adsorbents (Fe3O4 and Fe2O3). Langmuir and Freundlich isotherms all fit the data but not very well. Maximum adsorption capacity (mg/g) calculated from the slope and the intercept of the graph of Dubinin-Radushkevich (D-R) isotherm were found to be 19.22 mg/g of Ti(OH)4, 4.64 mg/g of TiO2 and 66.42 mg/g of Fe 3O4, respectively. Results of adsorption isotherms and reaction kinetics suggested the adsorption of arsenic(III) on titanium and ferrous oxide nano-particles were controlled by chemical process at low concentration but physical in high range.