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 Kf 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.