Surface-Engineered Nanofiltration Membranes for Sustainable Lithium Recovery from Real Brine: Addressing Fouling and Scaling Challenges

Nanofiltration (NF) membranes hold great promise for lithium (Li) recovery from brines, with numerous studies focusing on improving Li/Mg separation performance. However, real brine environments pose significant challenges, as fouling and scaling severely hinder Li recovery efficiency. Despite their critical impact, these challenges have received limited attention. This study addresses these issues through surface engineering of polyamide (PA) NF membranes, achieving a positively charged, ultra-smooth surface. The engineered membrane demonstrated exceptional fouling and scaling resistance during real brine treatment, exhibiting only a 12% flux decline over 12 hours, compared to 28% and 20% for the control and commercial NF270 membranes, respectively. This superior antifouling performance enabled sustained high Li flux (>80 mM·m⁻ 2 ·h⁻ 1 ) while reducing the Mg/Li mass ratio from 4.1 in the feed to 1.4 in the permeate. Additionally, the membrane displayed remarkable resistance to scaling in synthetic brine containing high concentrations of Ca 2+ and SO 4 2 ⁻. Systematic evaluations in both synthetic and real brines revealed that the enhanced process stability arises from the synergistic effects of reduced surface roughness and optimized surface charge, which together minimize foulant adhesion and mitigate scaling. These findings mark a significant advancement toward the practical implementation of membrane-based Li recovery, underscoring the critical importance of addressing fouling and scaling in real brine environments.