High performance, pH-resistant membranes for efficient lithium recovery from spent batteries
Yafei Su, Huawen Peng, Xufei Liu, Jiapeng Li, Qiang Zhao
Abstract
Cation separation under extreme pH is crucial for lithium recovery from spent batteries, but conventional polyamide membranes suffer from pH-induced hydrolysis. Preparation of high performance nanofiltration membranes with excellent pH-resistance remains a challenge. Here we synthesize a high performance nanofiltration membrane (1,4,7,10-Tetraazacyclododecane (TAD)−1,3,5-Tris(bromomethyl)benzene (TBMB) thin film composite membranes (TFCMs)) with excellent pH-stability through interfacial quaternization reaction between TAD and TBMB. Due to the high stability of “C-N” bonds in TAD-TBMB TFCMs, its separation performance is stable even after 70 days immersion in concentrated acid (3 M H2SO4, HNO3, or HCl) and base (3 M NaOH), which is at least 15 times more stable than benchmark commercial membranes. The membrane shows an overall separation performance (11.3 L m−2 h−1 bar−1 (LMHB), RCo2+: 97% in 2 M H2SO4) due to the size sieving and the intensified charge repulsion, outperforming many of the state-of-the-art membranes. Finally, the TAD-TBMB TFCM remains stable during 30-days continuous nanofiltration of 2 M H2SO4 and leachate (2 M H2SO4, ions: 6.2 g L−1) from spent batteries. A highly pH-resistant membrane was prepared by interfacial quaternization reaction, which shows the highest separation performance among analogous membranes and 70-days stability in concentrated acid/base. Meanwhile, Li2CO3 with purity of 99.1% was recovered from acid leachate of spent batteries.