High performance, pH-resistant membranes for efficient lithium recovery from spent batteries

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Conventional polyamide membranes degrade under extreme pH, hindering efficient lithium recovery from spent batteries.
• Developing robust nanofiltration membranes with superior pH stability is a critical challenge for resource recycling.

Purpose of the Study:

• To synthesize a high-performance nanofiltration membrane with excellent pH resistance for cation separation.
• To evaluate the stability and separation performance of the novel membrane under harsh acidic and basic conditions.

Main Methods:

• Interfacial quaternization reaction between 1,4,7,10-Tetraazacyclododecane (TAD) and 1,3,5-Tris(bromomethyl)benzene (TBMB) to form thin film composite membranes (TFCMs).
• Immersion tests in concentrated acids (H2SO4, HNO3, HCl) and bases (NaOH) for up to 70 days.
• Performance evaluation including separation flux and rejection rates (e.g., Co2+) under extreme pH conditions and continuous nanofiltration of battery leachate.

Main Results:

• The synthesized TAD-TBMB TFCMs demonstrated remarkable pH stability, maintaining performance after 70 days in 3 M acid/base solutions, significantly outperforming commercial membranes.
• Achieved high separation performance with a flux of 11.3 LMHB and 97% Co2+ rejection in 2 M H2SO4, attributed to size sieving and charge repulsion.
• The membrane remained stable during 30 days of continuous nanofiltration of 2 M H2SO4 and spent battery leachate.

Conclusions:

• The TAD-TBMB TFCM offers a highly stable and effective solution for cation separation in extreme pH environments.
• This membrane technology holds significant promise for enhancing lithium recovery processes from spent batteries and other recycling applications.
• The robust chemical structure of TAD-TBMB TFCMs ensures long-term operational stability in challenging chemical conditions.