Xu Jinyan, Chen Bajin, Yin Lu, Zhang Liang, Li Yongjin, You Jichun
Key Laboratory of Organosilicon Chemistry and Material Technology, Ministry of Education, College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 311121, China.
Transfar Zhilian Co., Ltd., Xiaoshan, Hangzhou 311215, China.
Membranes (Basel). 2022 Feb 28;12(3):278. doi: 10.3390/membranes12030278.
To break the trade-off effect between permeability and selectivity in separation, wrinkled carbon nanotubes@polylactic acid (CNTs@PLLA) composite membranes were successfully fabricated in this work. On pre-deformed PLLA membranes, CNTs were loaded by filtrating their suspension, followed by releasing the PLLA upon heating based on its shape memory effect. The asynchronous deformations of CNTs and PLLA layers produced wrinkled CNTs@PLLA composite membranes. Relative to the reference without wrinkles, the attained wrinkled composite membranes exhibit much higher flux (~12 times) without any loss of rejection ratio during the separation of water-in-hexadecane emulsion. The significant improvement of separation performance can be attributed to the following issues: Firstly, the existence of wrinkles results in higher surface roughness, providing an additional driving force for separation resulting from the enlarged contact-angle difference between water and oil; Secondly, the shrinkage of the supporting PLLA layer during recovery induces the preferred alignment of CNTs along the wrinkle direction, which is the reason for the orientated slit pores with enhanced overlap of neighboring pores in the film-thickness direction; Finally, a wrinkled surface significantly increases the available area for separation. The synergism of the effects discussed above contributes to much higher permeability and comparable selectivity relative to the reference.
为了打破分离过程中渗透率和选择性之间的权衡效应，本研究成功制备了皱纹状碳纳米管@聚乳酸（CNTs@PLLA）复合膜。在预变形的聚乳酸膜上，通过过滤碳纳米管悬浮液加载碳纳米管，然后基于聚乳酸的形状记忆效应在加热时释放聚乳酸。碳纳米管层和聚乳酸层的异步变形产生了皱纹状的CNTs@PLLA复合膜。相对于没有皱纹的参考膜，所得的皱纹复合膜在分离十六烷包水乳液时表现出高得多的通量（约12倍），而截留率没有任何损失。分离性能的显著提高可归因于以下几点：首先，皱纹的存在导致更高的表面粗糙度，由于水和油之间扩大的接触角差异，为分离提供了额外的驱动力；其次，支撑聚乳酸层在恢复过程中的收缩导致碳纳米管沿皱纹方向优先排列，这是薄膜厚度方向上相邻孔重叠增强的定向狭缝孔的原因；最后，皱纹表面显著增加了分离的可用面积。相对于参考膜，上述效应的协同作用导致了更高的渗透率和相当的选择性。
