Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product

Abstract

A low cost by-product material namely Sulphuric acid Acidified Laterite (ALS), generated during the production of Ferric Aluminium Sulphate (FAS) by acid leaching treatment, was employed as an adsorbent for the removal of arsenic from aqueous solution. In addition raw laterite was used for comparison purposes in the arsenic adsorption experiments. The raw and Acidified Laterite were chemically and physically characterised (elemental analysis, surface chemistry, pore texture parameters, PZC, and SEM observation). Arsenic adsorption batch and kinetics experiments were undertaken, and process parameters such as; pH, dose, particle size, and initial arsenic concentration were investigated. Adsorption isotherm and kinetics data were modelled using the pseudo first and pseudo second order kinetic models. The maximum loading capacities of raw laterite for arsenite and arsenate ions were 127.8μgg−1 and 301.2μgg−1, respectively. By contrast, the maximum loading capacities of Acidified Laterite for arsenite and arsenate ions are 171.7μgg−1 and 923.6μgg−1, respectively. It was found that the higher surface area and presence of residual sulphate surface groups on the ALS explained the increase in the adsorption capacities. Overall the results indicated that the laterite adsorbents proved to be effective materials for the treatment of arsenic-bearing aqueous solutions.