Ping Xu,Wei Wang,Xiaoming Qian,Haibo Wang,Changsheng Guo,Nan Li,Zhiwei Xu,Kunyue Teng,Zhen Wang
To effectively separate Mg 2+ and Li + from salt lake brine with high Mg 2+ /Li + mass ratio, a positive charged nanofiltration membrane with abundant -NH 3 + and -NH 2 + was designed and fabricated via interfacial polymerization between polyethyleneimine (PEI) and trimesoyl chloride (TMC) on the polyethersulfone ultrafiltration membrane. Zeta potential test revealed that at pH below 9.3, the resulting membrane exhibited a high positive charge due to a large amount of unreacted amine groups on the PEI branch. In the separation process, Donnan exclusion effect dominated the separation performance of resulting membranes for Mg 2+ and Li + . The results showed that the Mg 2+ /Li + mass ratio declined from initial 20 to 1.3 and the separation factor S Mg , Li was as low as 0.05 with a pure water permeation of 5.02 L/(m 2 hbar) after filtration with resulting NF membrane. The difference between the rejection for Mg 2+ and Li + reached up to 76%. Compared with membrane in previous studies, the separation performance for Mg 2+ and Li + of positive charged NF membrane prepared in this work increased more than one time. This research demonstrated the potential of positive charged PEI-TMC composite NF membrane for the separation of Mg 2+ and Li + from salt lake brine with high Mg 2+ /Li + mass ratio.
Chenxi Tian,Da Lei,Yongchao Qian,Xiang-Yu Kong,Zhong Liu
The development of advanced membranes with precise ion selectivity is essential for efficient Li + /Mg 2+ separation. In this study, we synthesized a novel Lys-TMC membrane via a nucleophilic addition reaction between Lysine and trimesoyl chloride (TMC), yielding in a negatively charged surface interconnected by amide bonds. We systematically investigated the effects of varying Lys:TMC ratios on the membrane’s chemical structure, surface morphology, and ion separation performance. Our results revealed that the degree of cross-linking increases initially with the Lysine content, reaching an optimum at a Lys:TMC ratio of 10:1, where the membrane exhibited prominent Turing patterns on its surface. These patterns were critical for achieving effective ion separation. In contrast, excessive Lysine led to spontaneous polymerization, resulting in irregular ‘stone-like’ structures and the loss of Turing patterns. The optimally cross-linked Lys-TMC membrane displayed superior Li + /Mg 2+ separation performance, highlighting the crucial role of controlled cross-linking and Turing structure formation in enhancing ion selectivity. This work provides a mechanistic understanding of the relationship between Turing structure formation and ion sieving performance, offering a promising strategy for designing advanced separation membranes.
Xintong Li,Yongna Guo,Xin Ma,Chao Zhang,Jia Yang,Shuai Wang
Herein, a series of α -hydroxyalkyl phosphinic acids were designed and first introduced in Mn 2+ extraction and Mn 2+ -Mg 2+ separation. The extraction tests indicate that the α -hydroxy-2-ethylhexyl phosphinic acid ( α -H-2-EHA) possesses superior extraction ability compared to di-2-ethylhexyl phosphinic acid (P204) for Mn 2+ and Mg 2+ , and the partition coefficient ( β ) is 28.2 at a saponification ratio of 30%. The results of quantum chemical calculation, FT-IR spectrum and slope analysis method reveal that the α -H-2-EHA can form stable four-membered ring structure with metal ions during the extraction process through P–OH and P O bonds. Furthermore, the HOMO composition results suggest that α -OH might also promote the interaction between extractant and metal ions. Finally, a three-stage countercurrent extraction—washing—stripping process was proposed and Mn 2+ can be enriched from 11.2 g/L to 36.6 g/L, with Mg 2+ decreased from 30.3 g/L to 0.6 g/L, which provides an efficient strategy for the preparation of high-purity manganese.
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