Assessment of Groundwater Fluoride Contamination and Its Removal using Chemically Activated Agricultural Waste-Based Adsorbents

Groundwater is the primary source of drinking water in rural areas, but fluoride contamination poses significant health risks when present above permissible limits. This study investigates the sustainable removal of fluoride using activated carbon (AC) derived from agricultural wastes, namely rice husk (RH) and potato peel (PP), activated with phosphoric acid. Batch adsorption experiments were carried out using synthetic fluoride solutions and groundwater collected from hand pumps and tube wells in the Banasthali (Niwai) region of Rajasthan. Fluoride concentrations in the groundwater ranged from 0.10 to 5.71 mg/L, with several samples exceeding the permissible limit of 1.5 mg/L. RH-AC achieved a maximum fluoride removal of 79%, compared with 54.17% for PP-AC at an initial fluoride concentration of 5 mg/L. The adsorption behaviour was best fitted by the Freundlich isotherm, while the pseudo-second-order model provided the best fit for the adsorption kinetics. The findings identify rice husk-based activated carbon (RH-AC) as a promising, low-cost adsorbent for fluoride removal from contaminated water. Using agricultural waste for this purpose may offer a practical route to water treatment while supporting SDGs 3 (Good Health and Well-being), 6 (Clean Water and Sanitation) and 12 (Responsible Consumption and Production).