基于脂环族酰氯单体制备用于镁锂分离的纳滤膜

Preparation of nanofiltration membranes based on alicyclic chloride monomers for magnesium-lithium separation

纳滤(nanofiltration,NF)膜在盐湖提锂中潜力巨大,但低渗透性和低选择性问题阻碍了其进一步发展.选用具有一定空间构象的脂环族酰氯单体1,3,5-环己三甲酰氯(1,3,5-cyclohexyl triformyl chloride,HTC)用作油相单体,通过与水相单体聚乙烯亚胺(polyethyleneimine,PEI)的界面聚合(interfacial polymerization,IP)反应制备用于镁锂分离的纳滤膜.通过调整分离层内部结构和优化膜表面化学性质,提升纳滤膜整体性能.研究结果表明,以HTC为有机相单体制备的纳滤膜比传统的以均苯三甲酰氯(trimesoyl chloride,TMC)制备的纳滤膜具有更大的孔径和厚度以及更好的润湿性,且渗透性和镁锂分离因子均优于传统纳滤膜;制备PEI-HTC纳滤膜的最优条件为:相对分子质量为1800 u(1 u=1 Da)、质量浓度为0.1 g/L的PEI水溶液和0.01 g/L的HTC-正已烷溶液反应60 s;以最优条件制备的PEI-HTC纳滤膜的渗透性为47.30 L/(m^(2)·h·MPa),是传统纳滤膜的2倍,PEI-HTC纳滤膜的分离因子为12.37,是传统纳滤膜的1.61倍.长期运行下,PEI-HTC纳滤膜保持了良好的选择性和结构稳定性,在盐湖提锂中有较大的应用价值.

Nanofiltration(NF)membranes have great potential for lithium extraction from salt lakes,however,issues like low permeability and low selectivity have impeded further development.This study introduces 1,3,5-cyclohexane tricarbonyl chloride(HTC),an alicyclic chloride monomer with a certain spatial conformation,as the oilphase monomer for preparing NF membranes via interfacial polymerization(IP)reaction with polyethyleneimine(PEI)as the aqueous-phase monomer.The overall performance of NF membranes is improved by adjusting the internal structure of the separation layer and optimizing the chemical properties of the membrane surface.The research results show that the NF membranes fabricated using HTC as the organic phase monomer exhibit larger pore size and thickness,and superior wettability than traditional NF membranes synthesized with trimethyl chloride(TMC).Moreover,the permeability and magnesium-lithium separation factors are superior to traditional NF membranes.The permeability of the PEI-HTC NF membrane prepared under optimal conditions is 47.30 L/(m^(2)·h·MPa),doubling that of traditional NF membranes.The separation factor of the PEI-HTC NF membrane is 12.37,being 1.61 times that of traditional NF membranes.Under long-term operation,the PEI-HTC NF membrane maintains good selectivity and excellent structural stability,demonstrating great potential for application in lithium extraction from salt lakes.