Mineralization and electroreduction-recycling of toxic Pb2+ ions using memory-effect of layered double hydroxide structure with ultrahigh capacity

Lead (Pb) as one of the most widespread toxic heavy metals in both water distribution systems and in surface water, it still remains a challenge to quickly and completely remove/recycle Pb ions from these systems. Herein, the obtained Mg2Fe-mixed metal oxides (Mg2Fe-MMO) through calcination of Mg2Fe-Cl-layered double hydroxide (Mg2Fe-Cl-LDH) showed extremely high mineralized capacity for Pb ions with removal figures of 2406 mg/g. This performance is superior to most reported materials, and can rapidly purify Pb2+ at 1 ppm to safe levels (12 ppb). X-ray absorption fine structure (XAFS) studies revealed a transformation from MgFe-MMO to defective Mg2Fe-CO3-LDH with the Pb ions sequestering OH− from Mg2Fe-CO3-LDH to form a solid precipitate. Moreover, the mineralized products could be recycled by electrolysis to obtain metallic lead, providing a new opportunity for pollution remediation and the recovery of metal lead. This work provides a new route for Pb ions removal from wastewater and the potential for utilization of the recycled Pb resource.