Zhou Zongyao, Wang Qun, Qin Yiwen, Hu Yunxia
State Key Laboratory of Separation Membranes and Membrane Processes, National Center for International Research on Membrane Science and Technology, School of Materials Science and Engineering, Tiangong University, Tianjin 300387, P. R. China.
College of Chemical and Biological Engineering, Shandong University of Science and Technology, Qingdao 266590, P. R. China.
Environ Sci Technol. 2023 Apr 11;57(14):5999-6007. doi: 10.1021/acs.est.2c09009. Epub 2023 Mar 30.
A free-standing polyamide (PA) film is fabricated via in situ release from a thin-film composite (TFC) membrane achieved through the removal of the polysulfone support. The structure parameter of the PA film is measured to be 24.2 ± 12.6 μm, which is about 87-fold of its film thickness. A significant decline in water flux of the PA film from an ideal forward osmosis membrane is observed. We find that the decline is predominantly influenced by the internal concentration polarization (ICP) of the PA film based on our experimental measurements and theoretical calculations. We propose that the asymmetric hollow structures of the PA layer with dense crusts and cavities may be the underlying cause of the occurrence of the ICP. More importantly, the structure parameter of the PA film can be reduced and its ICP effect can be mitigated by tuning its structures with fewer and shorter cavities. Our results for the first time provide experimental evidence to prove that the PA layer of the TFC membrane has the ICP effect, which could potentially provide fundamental insights into the influence of structural properties of PA on the membrane separation performance.
通过去除聚砜支撑体，从薄膜复合（TFC）膜原位释放制备了一种独立的聚酰胺（PA）膜。测得PA膜的结构参数为24.2±12.6μm，约为其膜厚度的87倍。观察到PA膜作为理想的正向渗透膜时水通量显著下降。基于我们的实验测量和理论计算，我们发现这种下降主要受PA膜内部浓差极化（ICP）的影响。我们提出，具有致密外壳和空洞的PA层不对称中空结构可能是ICP发生的潜在原因。更重要的是，通过调整PA膜结构，减少空洞数量并缩短空洞长度，可以降低其结构参数并减轻ICP效应。我们的结果首次提供了实验证据，证明TFC膜的PA层具有ICP效应，这可能为PA结构特性对膜分离性能的影响提供基本见解。
