Chengyi Zhang,Yingxin Mu,Song Zhao,Wen Zhang,Yuxin Wang
Lithium extraction from brines with the high Mg 2+ /Li + ratio is crucial for sustainable lithium resource and environmental protection. This study incorporated the classic tributylphosphate (TBP)/FeCl 3 system into the polyvinyl chloride (PVC) based polymer inclusion membrane (PIM) to extract Li + from the solution which is rich of Mg 2+ (The initial Mg 2+ /Li + molar ratio is 15). The morphology and composition of PIMs were characterized systematically, and the content of TBP/FeCl 3 carrier in the PIM was optimized. Compared to liquid-liquid extraction, the extraction ratio of Li + for PIM extraction increases by 20% and the separation factor of Li + over Mg 2+ increases by 5%. Besides, the loss ratio of Fe 3+ after one loop of liquid-liquid extraction is 17.79%, which is close to that of PIM extraction after three loops (18.30%), demonstrating that the PIM showed a good stability. Furthermore, the separation factor of Li + over Mg 2+ for the PIM with 50 wt% TBP/FeCl 3 is as high as 176 and the initial flux for Li + is 8.12 × 10 −4 mol m −2 h −1 . This study displays a TBP/FeCl 3 based PIM with high selectivity for Li + , providing a possible membrane technology for lithium extraction from brines.
Huanhuan Wu,Yakai Lin,Wenyan Feng,Tianyin Liu,Lin Wang,Hong Yao,Xiaolin Wang
In order to utilize lithium from brines with high Mg 2+ /Li + ratio, a positively charged nanofiltration (NF) membrane was prepared by grafting amine-functionalized ionic liquid 1-(3-aminopropyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([MimAP][Tf 2 N]) onto the surface of polyamide (PA) membrane. The effects of [MimAP][Tf 2 N] contents on the chemical composition, surface morphology , surface charges and separation properties of the modified PA membranes were discussed. The results of chemical composition analyses indicated reaction of the amine group of [MimAP][Tf 2 N] with the residual acyl chloride groups, which was existed on the surface of the nascent PA membrane. The surfaces of all the modified PA membranes were positively charged at pH = 6.4 due to the quaternary ammonium group of [MimAP][Tf 2 N]. In the separation process, the resulting membrane presented high water permeance (37.8 L/(m 2 ⋅h)) and mono-/divalent cation selectivity (Li + and Mg 2+ ) with much higher MgCl 2 rejection (83.8%) than LiCl rejection (24.4%). For a simulative brine with a Mg 2+ /Li + ratio of 20, the rejections to Mg 2+ and Li + by the optimized membrane (NF-IL-2.0%) were around 81.9% and −45.2%, respectively, where the permeate with the Mg 2+ /Li + ratio of 3.5 was obtained and the selectivity ( S Li,Mg ) was 8.12. Additionally, the optimized membrane exhibited a stable performance for Mg 2+ /Li + separation. Therefore, there is a very possibility for utilization of lithium from brine with high Mg 2+ /Li + ratio by using the optimized NF membrane.
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