Nanofiltration membrane with a reactive, positively charged nanofiber interlayer for recycling lithium from waste batteries

With the development of new energy powered vehicles, the shortage of lithium resources has become more urgent. The recovery and extraction of lithium resources from waste lithium iron phosphate batteries can achieve the sustainable development of the new energy industry, alleviate the imbalance between the supply of and demand for lithium resources, and greatly reduce the environmental pressure brought by the future battery retirement tide. In this work, a poly(ethylene vinyl alcohol) nanofiber was employed to construct a positive interlayer via co-crosslinking with PEI and sprayed on a PES substrate, on which a positive polyamide nanofiltration layer was formed via interfacial polymerization with 1,3,5-benzenetricarbonyl chloride. The abundant interconnected pores of nanofibers provided high water flux. Meanwhile, the dual positively charged layer had a synergistic effect on cation rejection. The nanofiber interlayer greatly improved the roughness and effectively enhanced the hydrophilicity of the membrane surface. The optimized nanofiltration membrane exhibited a pure water flux of 36.73 L m-2 h-1, a high Fe3+ rejection of 99.36%, and a Li+/Fe3+ separation factor of up to 115. Its excellent separation performance was maintained under acidic conditions, revealing its great potential in recycling lithium from waste batteries.