Evaluation of the Use of Limestones for the Removal of Arsenic from Groundwater

Arsenic contamination in aquifers poses a significant global health risk due to its toxicity and widespread presence in groundwater used for drinking. Although several approaches for arsenic removal exist, many are either expensive or logistically difficult. This study assesses the efficacy of native limestones from two arsenic-contaminated regions in Mexico as a sustainable treatment alternative. Tested in batch and column experiments using synthetic solutions, as well as natural and arsenic-enriched groundwater, the limestones were characterized mineralogically (XRD) and chemically (XRF). Surface area, particle size, average pore volume in rocks, and competing anions (i.e., bicarbonate and sulfate) in groundwaters played important roles in removal performance. The results show that smaller particle sizes improve arsenic retention. Up to 87.6% of the arsenic was removed from groundwater containing 1.29 mg/L of arsenic when treated with rock particles smaller than 0.062 mm. Natural groundwater, however, in general, exhibited lower efficiency than synthetic solutions due to anion interference. Although site-specific evaluations are essential, these results indicate that limestone may be a cost-effective and locally accessible solution for addressing arsenic (As) contamination in regions with abundant limestone outcrops.