Arsenic(III) immobilization on rice husk silica

Silica was prepared by burning rice husk in a muffle furnace at 500°C and immobilization (adsorption) of As(III) by the rice husk silica from aqueous solution was examined. Batch adsorption test showed that extent of As(III) adsorption depended on initial As(III) concentration, contact time and pH. Equilibrium adsorption was attained in 180 min, with maximum adsorption occurring at pH 8. Equilibrium adsorption data were well described by the Langmuir and Freundlich isotherm models. Langmuir constants Q° and b were 1.89 and 0.1, and Freundlich constants K_f and 1/n were 0.17 and 0.9, respectively. Adsorption of As(III) by rice husk silica followed pseudo-second-order kinetics. Rice husk silica is effective in the adsorption of As(III) from water and is a potentially suitable filter medium for removing As(III) from groundwater at wells or in households.