Heat-treated laterite as an efficient and low-cost adsorbent for the removal of arsenic

Abstract

Arsenic removal capacity of heat-treated lat erite, collected from Kampong Thom province, Cambodia, has been investigated. Laterite is a local material and readily available in many parts of Cambodia. It is easily prepared as an absorbent and the cost of preparation is low compared to commercial adsorbent. Characterization study by BET showed that the heating treatment increases the surface area of the laterites. This was confirmed by FESEM study which showed that heating treatment creates tiny cracks on the surface of the laterite particles. EDX study showed t hat the late rite contained iron (37.33%), aluminum (1.25%), silicon (2.45%) and manganese (1.1S%). Heating treatment decomposes t he organic compound present in laterite, thus resulted in the decreasing of carbon and oxygen content from 11.59% to 3.52% and 45.71% to 34.94% respectively. For the removal capacity of arsenic, parameters such as the effects of pH, temperature, adsorbent dose, adsorbent particle size, agitation speed and initial concentration were examined. The maximum adsorption capacity of arsenic by heated laterite was found to be 0.21 mg g" based on Langmuir adsorption isotherm. The removal was observed to be particle size independent which represents less than 0.06% difference of arsenic removal between t he smallest (0.07 - 0.10 mm) and the largest (0.60 - 1.00 mm) size of adsorbent particle. Kinetic results of arsenic removal showed that the uptake of arsenic was rapid in the first hour and slower thereafter. Kinetic data of arsenic adsorption followed the pseudo-second order equation (R' = 0.99) . Thermodynamic study estimated t hat the adsorption was spontaneous, favorable and endothermic reaction.