Removal of arsenate from aqueous solutions by transformation of cerussite to mimetite

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Water pollution by arsenic is a growing concern due to its toxicity and health effects, prompting research on its immobilization. A novel method for removing arsenate ions from water using synthetic or natural cerussite powder (PbCO3) is proposed. Laboratory experiments over three months at pH 2-8 show that in the presence of chloride ions, cerussite transforms into Pb(AsO4)(3)Cl (mimetite), and in their absence, into Pb(AsO4)(3)OH. Arsenate is removed as lead carbonate dissolves and mimetite precipitates, achieving a removal efficiency of 57-99.9 %. Repeated treatments can enhance this efficiency to over 99 %, with the cerussite powder being reusable. Atomic Force Microscopy experiments show that mimetite formation is surface-controlled, and cerussite reacts with arsenate through a dissolution-precipitation mechanism, partially armouring the cerussite surface. Repeating the experiments with cerussite in the presence of other cations (Mn, Fe, Ni, Cu, Zn, Cd, Al) or anions (CO32- , SO42- , PO43- , F-) showed that their presence has no significant effect on the progress and efficiency of the process. Only Al may slightly reduce the effectiveness. Reaction with solutions with an initial concentration of 5 mg As/L resulted in a 99.9 % reduction in As content. Similar observations were noted in experiments using natural arsenic-enriched waters (similar to 0.1 mg As/L), though the reaction proceeded more slowly, requiring additional time for arsenate removal to reach completion. These findings suggest that cerussite removes arsenate from water by gradually being replaced with mimetite crystals. While challenges remain in optimizing this method, it has the potential to become a novel technology for arsenic-contaminated water remediation.