Arsenic removal from real-life groundwater by adsorption on laterite soil

The adsorption characteristics of arsenic on laterite soil, a low-cost natural adsorbent, were studied in the laboratory scale using real-life sample. The studies were conducted by both batch and continuous mode. Laterite soil was found to be an efficient adsorbent for arsenic removal from the groundwater collected from arsenic affected area. The initial concentration of arsenic in the sample was 0.33 ppm. Under optimized conditions the laterite soil could remove up to 98% of total arsenic. The optimum adsorbent dose was 20 g/l and the equilibrium time was 30 min. Isotherm studies showed that the process is favorable and spontaneous. The kinetics showed that the removal of arsenic by laterite soil is a pseudo-second-order reaction. In the column study the flow rate was maintained at 1.49 m3/(m2 h). Using 10 cm column depth, the breakthrough and exhaust time found were 6.75 h and 19.0 h, respectively. Height of adsorption zone was 9.85 cm, the rate at which the adsorption zone was moving through the bed was 0.80 cm/h, and the percentage of the total column saturated at breakthrough was 47.12%. The value of adsorption rate coefficient (K) and the adsorption capacity coefficient (N) were 1.21 l/(mg h) and 69.22 mg/l, respectively. Aqueous NaOH (1 M) could regenerate the adsorbent, and the regenerated adsorbent showed higher efficiency.