Arsenic removal from groundwater using acid-activated laterite

Abstract

Groundwater arsenic contamination has been a global threat due to its pernicious health impacts on people. Many studies have revealed the status of severe arsenic contamination and its health hazards in many districts in Terai region of Nepal. Of the many technologies available for arsenic treatment, very few are suitable for rural terai region, and the most widely used Kanchan Arsenic Filters (KAF) have shown inefficient performance by recent studies, depicting the need for enhancement of existing filters or finding better alternatives. This study suggests a better method of arsenic treatment using laterite soil as an efficient adsorbent. Batch study done with adsorbent (treated laterite dose kept in between (0–40) g/L at lab temperature (25 ± 2) °C) showed the most efficient/optimum particle size for treated laterite as 0.165 mm, adsorbent dose 40 g/L and detention time 4 h with initial arsenic concentration of 1000 μg/L. The maximum removal of As(III) (98.84%) and As(V) (99.66%) was observed near pH value of 8 and 3 respectively. The overall reaction was observed to follow pseudo second-order kinetics and Langmuir isotherm curve was best fit for the process data with the highest regression coefficient (R2 = 0.99). Fixed-bed column study was also conducted to access the quality and applicability of laterite soil as filter media for a newly proposed system. The modification viability of existing filter by adding beds of activated carbon and acid-activated laterite for enhancing performance are discussed as well as its application in a new filter system is proposed.