High-Efficiency Pb2+ Removal by Hydroxy-Sodalite for Point-of-Use Drinking Water Purification

Abstract

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 lake 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.

Keywords: Pb removal, hydroxy-sodalite, Drinking water, point-of-use.