High-performance polyurea nanofiltration membrane for waste lithium-ion batteries recycling: Leveraging synergistic control of bulk and interfacial monomer diffusion

Abstract

The development of high-performance nanofiltration (NF) membranes with extreme chemical stability is urgently needed for the recovery of spent lithium. In this study, a series of polyurea membranes with high lithium recovery efficiency and pH stability were fabricated by zone-regulated interfacial polymerization (IP). The reaction inhibitor Cu²⁺ in the bulk aqueous phase reduces IP intensity by reversibly binding to the amino groups of polyethyleneimine monomers through chelate bonds. Meanwhile, surfactant promote the uniform diffusion of macromolecular aqueous monomers at the phase interface. The milder polymerization reaction and the more stable phase interface endow the polyurea membrane (NF_{10k PEI-SDS-Cu}²⁺) with higher water permeance (2.1 L m⁻² h⁻¹ bar⁻¹), desirable MgCl₂ rejection (94.7 %), and excellent fabrication repeatability. Moreover, the membrane demonstrates stable separation selectivity for Co²⁺/Li⁺ and SO₄²⁻/Li⁺ under conditions of 0.05 mol L⁻¹ H₂SO₄ and 2 mol L⁻¹ LiOH, respectively. Our study provides a facile method for constructing NF membranes with extreme pH stability and confirms the feasibility of membrane-based lithium recovery.