@article{Gong2026, 
author = {Xinyu Gong and Dingxin Xu and Miaofei Huang and Yuxin Li and Hanlu Jiang and Kuang Yu and Zhen Chen and Yang Su},
title = {Counter-ion controlled ionic sieving in graphene oxide/polyelectrolyte membrane for Li+/Mg2+ separation from low-quality brines},
year = {2026},
journal = {Nano Research},
keywords = {two-dimensional materials, nanochannel, Li+/Mg2+ separation, low-quality brine, counter-ion adsorption},
url = {https://www.sciopen.com/article/10.26599/NR.2026.94908964},
doi = {10.26599/NR.2026.94908964},
abstract = {Precise control of the interlayer spacing of graphene oxide (GO) membranes at the sub-nanometer scale offers size-exclusion-based separation of Li+/Mg2+, a critical step towards efficient lithium resource management and energy sustainability. While previous GO-based membranes have shown high Mg2+ rejections, their performance was largely limited to static diffusion settings or diluted solutions where Donnan exclusion dominates. Here, we report a GO membrane intercalated with a uniform polyelectrolyte layer. The membrane shows substantially enhanced MgCl2 rejection over a wide concentration range, while allowing LiCl permeation under pressure-driven filtration. This enables direct lithium recovery from low-quality brines with high MgCl2 concentrations and high Mg2+/Li+ ratios. Mechanistic study reveals that the adsorption of halide counter-ions onto the charged GO channel walls narrowed the interlayer spacing and enabled size-exclusion-based ionic separation. At higher ionic concentrations, a partial exchange of these adsorbed counter-ions with those in the second hydration shell of Mg2+ allowed moderate Mg2+ permeation. We further demonstrate a streamlined GO-based membrane filtration process, which rejects 99.53% Mg2+ from a low-quality brine, effectively upgrading it towards a high-quality lithium source, and highlighting the potential of this approach for sustainable lithium production.}
}