Polyurea Membranes for lithium recovery from waste batteries

In a study featured in the Journal of Membrane Science, Prof. WAN Yinhua and their research team at the Institute of Process Engineering (IPE) of the Chinese Academy of Sciences have introduced an innovative zone-regulated interfacial polymerization strategy. This approach aims to produce nanofiltration (NF) membranes that are resistant to both acids and alkalis while offering exceptional separation selectivity for lithium recovery from discarded lithium batteries.

With the rapid growth of the new energy industry, there is an increasing demand for lithium resources, underscoring the importance of efficiently recycling used lithium batteries. The development of environmentally friendly and efficient nanofiltration (NF) technology has emerged as a crucial step towards sustainable lithium recovery.

However, traditional polyamide NF membranes are hindered by structural degradation when exposed to acidic and alkaline conditions, leading to compromised separation performance.

A compelling solution is found in polyurea (PU) membranes, renowned for their chemical stability and utility in specialized separation processes. Yet, the utilization of polyethyleneimine (PEI) as the aqueous phase monomer in PU production presents challenges. The abundance of reactive sites in PEI leads to highly intense interfacial polymerization, resulting in inconsistent membrane structures and limited reproducibility, obstructing its potential for large-scale lithium recovery applications.

The approach outlined in this research involves controlling the diffusion behavior of monomers in the bulk solution and at the phase interface by employing the reaction inhibitor Cu²⁺ and the surfactant sodium dodecyl sulfate (SDS), respectively.

“We use Cu²⁺ to regulate the diffusion and reactivity of PEI, while SDS ensures even distribution at the phase interface, improving membrane integrity. Together, Cu²⁺ and SDS enable the formation of a thinner, more uniform PU separation layer,” explained Prof. WAN.

This method effectively manages the dispersion and interaction of monomers in both bulk solutions and at the interface, leading to a more consistent polymerization process. Additionally, it helps to reduce the rapid reactivity of hyperbranched monomers, thereby enhancing batch-to-batch stability and membrane uniformity.

The chemical stability of PU membranes is outstanding, enabling them to maintain separation selectivity even in highly acidic and alkaline conditions encountered during lithium recovery from waste batteries. These membranes offer reliable performance in extreme pH environments by effectively balancing charge and side effects.

“Our zone-regulated interfacial polymerization strategy showcases the importance of controlling monomer diffusion behavior to improve membrane performance and manufacturing stability. This study expands the scope of PU membranes in the energy sector, offering a robust solution for sustainable lithium recovery,” said Prof. LUO Jianquan, the author of the study.

This study represents a major advancement in recycling technology and membrane science, supporting global initiatives for sustainable resource utilization in the rapidly expanding new energy sector.

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