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Intrinsically Lithium-SelectiveNanofiltration MembranesEnabled by 1,3,5-Tris(aminomethyl)benzene
Journal article

Intrinsically Lithium-SelectiveNanofiltration MembranesEnabled by 1,3,5-Tris(aminomethyl)benzene

Amir Aghaei, Hossein Varghaei, Vahid Rad, Aria Khalili, Xiwen Hu, Masoud Soroush, Jae-Young Cho and Mohtada Sadrzadeh
ACS applied engineering materials, Forthcoming
10 Jul 2026
DOI: https://doi.org/10.1021/acsaenm.6c00660
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Abstract

Materials Science, Multidisciplinary Science & Technology Materials Science Technology
Rising demand for lithium, driven by its essential role in energy storage technologies, necessitates efficient, selective recovery from saline brines. However, Li+/Mg2+ separation remains challenging due to their similar hydrated sizes and the high Li+/Mg2+ ratios in natural brines. In this study, we proposed a method to fabricate intrinsically lithium-selective nanofiltration (NF) membranes by incorporating 1,3,5-tris(aminomethyl)benzene (TAB) as an aqueous-phase monomer in interfacial polymerization. Thin-film composite (TFC) membranes were prepared using varying ratios of piperazine (PIP) and TAB, forming polyamide (PA) selective layers with tunable structure and charge properties. The incorporation of TAB, a rigid aromatic triamine, promotes the formation of a densely cross-linked network via stable covalent amide bonds while increasing the density of protonatable amine groups. This results in enhanced positive surface charge and improved Mg2+ rejection via Donnan exclusion, without requiring postfabrication modification. The membrane prepared with a combined PIP-TAB system exhibited a significantly enhanced Li+/Mg2+ selectivity of 118.7, achieving 97.9% Mg2+ rejection and -149.2% Li+ rejection, compared to a selectivity of 25.4 for the conventional PIP-only membrane. A higher selectivity of 172.3 was achieved using TAB as the sole aqueous-phase monomer; however, this came at the expense of reduced water permeability (1.6 L m-2 h-1 bar-1), compared to 5.4 and 4.6 L m-2 h-1 bar-1 for the PIP and PIP-TAB membranes, respectively. This work introduces a design strategy for high-performance NF membranes, offering a scalable and efficient approach for lithium recovery from complex brine systems.

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