Arsenic in groundwater and its sorption by kimberlite tailings

Abstract

The experiments were conducted to investigate the sorption of arsenic from the groundwater onto kimberlite tailings, the mineral waste from diamond mining, in two phases ‐ batch studies and column studies. In batch studies, the effects of different factors such as pH, adsorbent dose and adsorbent size on the performance of kimberlite tailings were investigated. Adsorption kinetics and equilibrium isotherm studies were also carried out. The adsorption capacity of kimberlite tailings was calculated as 0.25 mg/g of adsorbent. In column studies, the performance of fixed‐bed kimberlite tailings was studied and the adsorption capacity was found to be 0.27 mg/g of adsorbent. Film diffusion was found to be the rate‐limiting factor for the removal of arsenic by kimberlite tailings. Adsorption of arsenic was found to be pH dependent and higher removal efficiencies were observed near neutral pH range. The arsenic uptake increased with increase in adsorbent dose. Spent kimberlite tailings could be regenerated with dilute NaOH. The proposed treatment methodology was applied to the groundwater samples collected from various places of North 24‐Parganas district situated in West Bengal, India. The samples were analyzed for the presence of total arsenic. The arsenic contamination of groundwater was found to be location specific in North 24‐Parganas district. The maximum arsenic concentration at certain places was found to be many folds more than the WHO recommended limits. The treatment of arsenic contaminated water samples with kimberlite tailings showed 90–94% removal in 12 hours. The present study can be used as a basis for designing and developing filter columns, which can be attached to the tube wells for low cost and effective removal of arsenic.