Laterite-A Potential Alternative for Removal of Groundwater Arsenic

Arsenic removal by heat treated laterite from contaminated water was investigated through batch adsorption experiments. The removal rate was dependent on the initial arsenic concentrations and a high initial rate of removal followed by a slower subsequent removal rate with a gradual approach to a steady-state condition. Rate kinetics was studied using both first-order and pseudo-second order models, and intraparticle diffusion from the solution to the adsorption sites was considered as major rate controlling step. Adsorption equilibrium data pointed to favorable adsorption of arsenic onto laterite and fitted with both Langmuir and Freundlich models. Thermodynamic data suggested chemical nature of the adsorption. Experimental data were used to estimate the life-time of laterite as a column packing-adsorber with the simplest assumptions and for typical initial concentration (∼0.30 mg L^-1 arsenic) it was 74 days maximum while to achieve WHO safe limit (0.01 mg L^-1). Laterite is a natural substance and can be collected very cheaply, so its utilization for arsenic removal is expected to be economical and feasible. It might be a promising alternative of other proposed arsenic removal media for the arsenic-affected region of the world.