ZSM-5沸石分子筛膜的制备及脱盐性能研究

淡水资源日益短缺，发展膜法海水淡化技术是满足世界淡水供应需求的重要途径，但是寻找合适的膜材料依然是人类面临的挑战。ZSM-5沸石分子筛膜（简称沸石膜）具有规则的孔道结构、合适的孔径尺寸（0.51~0.56 nm）以及可调变的硅铝比，在有机物脱水分离应用中展示了优异的选择性及良好的渗透性和稳定性。基于其孔径尺寸介于水分子和盐离子之间，其在海水淡化脱盐领域也具有应用潜力。在大孔α-Al₂O₃载体上采用二次生长法制备了ZSM-5沸石膜，考察了晶化时间与合成液的硅铝比对ZSM-5沸石膜成膜和渗透蒸发脱盐性能的影响，并采用XRD、SEM、EDS与水接触角表征了合成膜的相结构与结晶度、骨架组成表面特性等膜的结构性质。结果表明：通过二次水热法采用合成液摩尔配比为n（Al₂O₃）∶n（SiO₂）∶n（Na₂O）∶n（NaF）∶n（H₂O）=0.05∶1∶0.21∶1.01∶55的合成液在175℃下晶化48 h为最佳的合成条件，制备了Si/Al比为10、接触角为17.5°的亲水纯相致密ZSM-5沸石膜，并在75℃下对3.5%（质量）的NaCl水溶液进行了渗透蒸发测试，水的通量和盐离子截留率达到8.35 kg·m^-2·h^-1和99.99%，且性能在60 h的时间依存性测试后依然稳定，表现出了很高的海水淡化工业应用潜力。

Preparation of ZSM-5 zeolite membrane and its application in desalination

Freshwater resources are increasingly scarce, and membrane desalination technologies continue to develop to meet the world's freshwater supply needs. However, development of high performance membranes for this technology is still under way. ZSM-5 zeolite membrane has been widely used in dehydration of organics due to the uniformed pore structure, suitable pore size (0.51—0.56 nm) and adjustable Si/Al ratio. Considering its pore size is between the size of water molecules and most of the salts, it exhibits excellent selectivity and good permeability and stability in the application of organic matter dehydration and separation. In this work, ZSM-5 zeolite membrane was synthesized on the macroporous α-Al₂O₃ support using secondary growth method. The effects of crystallization time and Si/Al ratio of synthetic solution on membrane formation and desalination performance of ZSM-5 zeolite membrane were investigated. XRD, SEM, EDS and water contact angle characterizations were used to examine the phase structure and crystallinity, framework structure composition of the membranes. The results showed that, high performance ZSM-5 zeolite membrane with Si/Al ratio of 10 and contact angle of 17.5° was obtained with recipe of n(Al₂O₃)∶n(SiO₂)∶n(Na₂O)∶n(NaF)∶n(H₂O) = 0.05∶ 1∶0.21∶1.01∶55 at 175℃ for 48 h. The synthesized membrane was used for seawater desalination by pervaporation, and a high water flux of 8.35 kg·m^-2·h^-1 with ion rejection of 99.99% was obtained for the desalination of 3.5%(mass) NaCl aqueous solution at 75℃, indicating the ZSM-5 zeolite membrane possesses great potential for seawater desalination.