Sallakhniknezhad Reza, Khorsi Manijeh, Niknejad Ali Sallakh, Bazgir Saeed, Kargari Ali, Sazegar Mohsen, Rasouli Mohsen, Chae Soryong
School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China.
Department of Chemical Engineering, Science and Research Branch, Islamic Azad University, Tehran 1477893855, Iran.
Membranes (Basel). 2021 Dec 9;11(12):969. doi: 10.3390/membranes11120969.
Insufficient mechanical strength and wide pore size distribution of nanofibrous membranes are the key hindrances for their concrete applications in membrane distillation. In this work, various post-treatment methods such as dilute solvent welding, vapor welding, and cold-/hot-pressing processes were used to enhance the physical properties of styrene-acrylonitrile (SAN) nanofiber membranes fabricated by the modified electrospinning process. The effects of injection rate of welding solution and a working distance during the welding process with air-assisted spraying on characteristics of SAN nanofiber membranes were investigated. The welding process was made less time-consuming by optimizing system parameters of the electroblowing process to simultaneously exploit residual solvents of fibers and hot solvent vapor to reduce exposure time. As a result, the welded SAN membranes showed considerable enhancement in mechanical robustness and membrane integrity with a negligible reduction in surface hydrophobicity. The hot-pressed SAN membranes obtained the highest mechanical strength and smallest mean pore size. The modified SAN membranes were used for the desalination of synthetic seawater in a direct contact membrane distillation (DCMD). As a result, it was found that the modified SAN membranes performed well (>99.9% removal of salts) for desalination of synthetic seawater (35 g/L NaCl) during 30 h operation without membrane wetting. The cold-/hot-pressing processes were able to improve mechanical strength and boost liquid entry pressure (LEP) of water. In contrast, the welding processes were preferred to increase membrane flexibility and permeation.
纳米纤维膜的机械强度不足和孔径分布较宽是其在膜蒸馏中具体应用的关键障碍。在这项工作中，采用了各种后处理方法，如稀溶剂焊接、蒸汽焊接和冷/热压工艺，以增强通过改进的静电纺丝工艺制备的苯乙烯 - 丙烯腈（SAN）纳米纤维膜的物理性能。研究了空气辅助喷涂焊接过程中焊接溶液的注入速率和工作距离对SAN纳米纤维膜特性的影响。通过优化电吹工艺的系统参数，使焊接过程耗时更少，同时利用纤维的残留溶剂和热溶剂蒸汽来减少暴露时间。结果，焊接后的SAN膜在机械强度和膜完整性方面有显著提高，而表面疏水性的降低可忽略不计。热压后的SAN膜获得了最高的机械强度和最小的平均孔径。改性后的SAN膜用于直接接触膜蒸馏（DCMD）中合成海水的脱盐。结果发现，改性后的SAN膜在30小时运行期间对合成海水（35 g/L NaCl）脱盐性能良好（盐去除率>99.9%），且无膜润湿现象。冷/热压工艺能够提高机械强度并提高水的液体进入压力（LEP）。相比之下，焊接工艺更有利于提高膜的柔韧性和渗透性。
