Sonny Astani Department of Civil and Environmental Engineering, University of Southern California, 3620 S. Vermont Avenue, Los Angeles, California 90089, United States.
Environ Sci Technol. 2024 Oct 15;58(41):18404-18413. doi: 10.1021/acs.est.4c05865. Epub 2024 Oct 3.
Water treatment membranes play crucial roles in applications such as desalination, wastewater treatment, and potable water reuse. In a prior study, we introduced a novel method, combining electrical impedance spectroscopy with dynamic mechanical analysis, to quantify single-layer homogeneous membrane compaction up to 12.5 psi. Now we extend the method's capabilities to quantify real-time compaction of multilayer heterogeneous nanofiltration and reverse osmosis (RO) membranes up to 330 psi. Our findings demonstrate that membrane compaction does not solely occur in the support/backing layer. The air pockets between the polysulfone support and the polyester backing layers, which were not discussed previously, account for up to 18% and 14% of total membrane compaction for the nanofiltration and RO membranes. For the nanofiltration membrane, the majority of compaction (up to 45%) occurs in the void spaces of the backing layer, while for the RO membrane, the majority of compaction (up to 40%) occurs in the solid material of the backing layer. We also confirm, with experimental results, the importance of using compressive testing instead of tensile testing to accurately characterize compaction. Membrane fatigue is characterized by experimental trends including: increasing irrevocable compaction, increasing creep/instantaneous compaction ratios, and increasing strains in hysteresis experiments.
水处理膜在海水淡化、废水处理和饮用水再利用等应用中发挥着关键作用。在之前的研究中，我们引入了一种新的方法，将电阻抗谱与动态力学分析相结合，以量化高达 12.5psi 的单层均质膜压实。现在，我们扩展了该方法的能力，以实时量化高达 330psi 的多层异质纳滤和反渗透（RO）膜的压实情况。我们的研究结果表明，膜压实不仅发生在支撑/背衬层中。之前未讨论过的聚砜支撑层和聚酯背衬层之间的气隙占纳滤膜和 RO 膜总压实量的 18%和 14%。对于纳滤膜，高达 45%的压实发生在背衬层的空隙中，而对于 RO 膜，高达 40%的压实发生在背衬层的固体材料中。我们还通过实验结果证实了使用压缩测试而不是拉伸测试来准确描述压实情况的重要性。膜疲劳的特征是实验趋势，包括：不可恢复的压实增加、蠕变/瞬时压实比增加以及滞后实验中的应变增加。
