Mahdhi Noureddine, Alsaiari Norah Salem, Amari Abdelfattah, Chakhoum Mohamed Ali
Laboratory Materials Organizations and Properties, Tunis El Manar University, Tunis 2092, Tunisia.
Department of Chemistry, College of Science, Princess Nourah Bint Abdulrahman University, Riyadh 11671, Saudi Arabia.
Polymers (Basel). 2022 Jul 17;14(14):2908. doi: 10.3390/polym14142908.
In this study, a novel concept of nanofiltration process of drinking water based on capillary-driven nanofiltration is demonstrated using a bio-based nanocomposites' nanofilter as free power: a green and sustainable solution. Based on Lifshitz and Young-Laplace theories, we show that the chitosan (CS), cellulose acetate (CLA), and Polyvinylidene fluoride (PVDF) polymer matrixes demonstrate hydrophobic behavior, which leads to the draining of water from nanopores when negative capillary pressure is applied and consequently prevents the capillary-driven nanofiltration process. By incorporating 10%, 20%, and 30% volume fraction of titanium dioxide (TiO) nanoparticles (NPs) to the polymers' matrixes, we demonstrate a wetting conversion from hydrophobic to hydrophilic behavior of these polymer nanocomposites. Subsequently, the threshold volume fraction of the TiO NPs for the conversion from draining (hydrophobic) to filling (hydrophilic) by capillary pressure were found to be equal to 5.1%, 10.9%, and 13.9%, respectively, for CS/TiO, CLA/TiO, and PVDF/TiO nanocomposites. Then, we demonstrated the negligible effect of the gravity force on capillary rise as well as the capillary-driven flow for nanoscale pore size. For nanofilters with the same effective nanopore radius, porosity, pore shape factor, and tortuosity, results from the modified Lucas-Washburn model show that the capillary rise as well as the capillary-driven water volume increase with increased volume fraction of the TiO NPs for all nanocomposite nanofilter. Interestingly, the capillary-driven water volume was in range (5.26-6.39) L/h·m with 30% volume fraction of TiO NPs, which support our idea for capillary-driven nanofiltration as zero energy consumption nano-filtration process. Correspondingly, the biodegradable CS/TiO and CLA/TiO nanocomposites nanofilter demonstrate capillary-driven water volume higher, ~1.5 and ~1.2 times, respectively, more than the synthetic PVDF/TiO nanocomposite.
在本研究中，使用基于生物基纳米复合材料的纳米过滤器作为自由动力，展示了一种基于毛细管驱动纳滤的饮用水纳滤过程的新概念：一种绿色且可持续的解决方案。基于 Lifshitz 和 Young-Laplace 理论，我们表明壳聚糖（CS）、醋酸纤维素（CLA）和聚偏氟乙烯（PVDF）聚合物基体表现出疏水行为，当施加负毛细管压力时，这会导致纳米孔中的水排出，从而阻止毛细管驱动的纳滤过程。通过将 10%、20% 和 30% 体积分数的二氧化钛（TiO₂）纳米颗粒（NPs）掺入聚合物基体中，我们证明了这些聚合物纳米复合材料的润湿性从疏水行为转变为亲水行为。随后，对于 CS/TiO₂、CLA/TiO₂ 和 PVDF/TiO₂ 纳米复合材料，发现通过毛细管压力从排水（疏水）转变为填充（亲水）的 TiO₂ NPs 的阈值体积分数分别等于 5.1%、10.9% 和 13.9%。然后，我们证明了重力对毛细管上升以及纳米级孔径的毛细管驱动流的影响可忽略不计。对于具有相同有效纳米孔半径、孔隙率、孔形状因子和曲折度的纳米过滤器，修正后的 Lucas-Washburn 模型结果表明，对于所有纳米复合纳米过滤器，毛细管上升以及毛细管驱动的水量随 TiO₂ NPs 体积分数的增加而增加。有趣的是，在 TiO₂ NPs 体积分数为 30% 时，毛细管驱动的水量在（5.26 - 6.39）L/h·m 范围内，这支持了我们将毛细管驱动纳滤作为零能耗纳滤过程的想法。相应地，可生物降解的 CS/TiO₂ 和 CLA/TiO₂ 纳米复合材料纳米过滤器表现出的毛细管驱动水量分别比合成的 PVDF/TiO₂ 纳米复合材料高约 1.5 倍和 1.2 倍。
