Nanogradient Hydrophilic/Hydrophobic Organosilica Membranes Developed by Atmospheric-Pressure Plasma to Enhance Pervaporation Performance.
Nanogradient Hydrophilic/Hydrophobic Organosilica Membranes Developed by Atmospheric-Pressure Plasma to Enhance Pervaporation Performance.
复制标题
由大气压等离子体开发的纳米梯度亲水/疏水有机二氧化硅膜可增强渗透汽化性能。
作者：
Shunnzo Aoyama;Hiroki Nagasawa;M. Kanezashi;T. Tsuru
有机硅膜由于其可调的分子筛分特性和优异的水热稳定性而成为渗透蒸发脱水的有希望的候选者。在此，我们报告了一种使用常压水蒸气等离子体的简单改性，以提高有机二氧化硅膜的渗透汽化性能。采用水蒸气等离子体对端甲基有机硅膜表面进行处理，制备了一种适用于渗透蒸发脱水的超薄分离活性层。水蒸气等离子体使甲基氧化分解形成硅醇基，提高了表面亲水性。等离子体修饰层的厚度为几纳米，由于硅醇基团的缩合而具有类似二氧化硅的结构。等离子体修饰的有机硅膜由于形成了孔径约为0.4 nm的高度交联的硅氧烷网络而具有更好的分子筛分性能。由于纳米厚的分离活性层具有控制孔径和增强的亲水性，该膜在醇脱水过程中也表现出良好的过电选择性。在90 wt %的水溶液中，在50℃脱水条件下，等离子体修饰膜具有较高的水透性，其水透比为517-3050，水透比为10-6 mol m-2 s-1 Pa-1，水透比为517-3050，水透比为10- 000，是硅基膜的最高透选择性之一。此外，等离子体修饰膜对H2O/MeOH混合物表现出高效的脱水性能。在50℃条件下，90 wt %的MeOH水溶液脱水时，水通过率和水/MeOH通过率分别为（2.3 ~ 3.0）× 10-6 mol m-2 s-1 Pa-1和31-143，超过了传统膜（聚合物膜、硅基膜和沸石膜）的渗透选择性权衡。结果表明，等离子体辅助方法可以在常压和室温下通过改性提高有机硅膜的渗透汽化性能。
Organosilica membranes are a promising candidate for pervaporation dehydration owing to their tunable molecular sieving characteristics and excellent hydrothermal stability. Herein, we report a facile modification using an atmospheric-pressure water vapor plasma to enhance the pervaporation performance of organosilica membranes. The surface of methyl-terminated organosilica membranes was treated by water vapor plasma to develop an ultrathin separation active layer suitable for pervaporation dehydration. The surface hydrophilicity was increased by water vapor plasma due to oxidative decomposition of methyl groups to form silanol groups. The plasma-modified layer had a thickness of several nanometers and had a silica-like structure due to the condensation of silanol groups. The plasma-modified organosilica membranes exhibited an improved molecular sieving property owing to the formation of highly cross-linked siloxane networks with a pore size of approximately 0.4 nm. The membranes also exhibited an excellent permselectivity in the dehydration of alcohols due to the nanometer-thick separation active layer with controlled pore size and increased hydrophilicity. The plasma-modified membranes showed high H2O permeance exceeding 10-6 mol m-2 s-1 Pa-1 with permeance ratios for H2O/EtOH and H2O/IPA of 517-3050 and >10 000, respectively, in the dehydration of 90 wt % aqueous solutions at 50 °C, which is among the highest permselectivities for silica-based membranes. Furthermore, the plasma-modified membranes displayed highly efficient dehydration performance for a H2O/MeOH mixture. The H2O permeance and H2O/MeOH permeance ratio in the dehydration of a 90 wt % MeOH aqueous solution at 50 °C were (2.3-3.0) × 10-6 mol m-2 s-1 Pa-1 and 31-143, respectively, which exceeded the permeance-selectivity trade-off of conventional membranes including polymeric, silica-based, and zeolite membranes. The results indicate that the proposed plasma-assisted approach can enhance the pervaporation performance of organosilica membranes via the modification under atmospheric pressure and at room temperature.