High-efficiency Pb²⁺ removal by hydroxy-sodalite for point-of-use drinking water purification

The development of cost-effective point-of-use (POU) devices that effectively remove lead (Pb) from drinking water is imperative in mitigating the threat of Pb contamination to public health in underdeveloped regions. Herein, we have successfully transformed inexpensive natural kaolinite as hydroxy-sodalite (HySOD) via a simple hydrothermal process, achieving an impressive yield of 91.5 %. Remarkably, HySOD demonstrates excellent selectivity and affinity towards Pb²⁺ with an adsorption capacity of 476 mg/g in a single Pb²⁺ system and a high distribution coefficient of 5.0 × 10⁷ mL/g in multi-cations system, several orders of magnitude higher than other cations, showing remarkable Pb²⁺ removal efficiency. Mechanism studies reveal that the preeminent Pb²⁺ capture capacity of HySOD is mainly attributed to the fast surface chemisorption effects and spontaneous phase change from Na₈Al₆Si₆O₂₄(OH)₂·2H₂O to Pb₄Al₆Si₆O₂₄(OH)₂·5H₂O caused by cation exchange effects. Through a continuous filtration test, a simplified HySOD-loaded POU device is employed to treat Pb-contaminated water with the Pb²⁺ concentration of 200 μg/L. At a high water flux of 477 L/m²/h, the Pb²⁺ effluent concentration is swiftly reduced below 10 μg/L, well meeting the security standard for drinking water. Overall, this work introduces a remarkable Pb²⁺ removal material, showing significant application potential for POU drinking water purification.