Ming Yang,Ni Yao,Xiaoxi Li,Jianyong Yu,Shichao Zhang,Bin Ding
Distillation membranes with hydrophobic surfaces and defined pores are considered a promising solution for seawater desalination. Most existing distillation membranes exhibit three-dimensional (3D) stacking bulk structures, where the zigzag water-repellent channels often lead to limited permeability and high energy costs. Here, we created two-dimensional nanowebs directly from the polymer/sol solution to construct dual-asymmetric Janus membranes. By tailoring the phase separation rate, the polymer phase evolved into continuous hydrophilic webs in situ weld on the microporous hydrophobic layer. The webs possess true-nanoscale architectures (internal fiber diameter of ∼20 nm, pore size of ∼140 nm) with enhanced roughness, serving as a superspreading surface to reach a water contact angle of 0° in 1.7 s. Benefiting from the architecture and wettability dual asymmetries, the obtained Janus membrane shows high-efficiency desalination performance (salt rejection >99%, flux of 11 kg m–2 h–1, and energy efficiency of 79%) with a thickness of 6.7 μm. Such a fascinating nanofibrous web-based Janus membrane may inspire the design of advanced liquid separation materials.
Guangming Tan,Xiangyang Xue,Zhigao Zhu,Jiansheng Li
Membrane distillation holds promise for further recovery of reverse osmosis (RO)-concentrated seawater to realize zero-liquid discharge; however, severe scaling induced by high-concentration salts and fouling triggered by a naturally occurring substance would result in severe wetting of the hydrophobic distillation membrane. To retard membrane wetting during the concentration process, the membrane’s interfacial structure and the seawater’s ingredients were systematically investigated to improve the membrane’s durability. The results demonstrated that the dual-layer membrane with hierarchically rough beads-on-a-string structured fibers could enlarge the water evaporation area on the membrane surface to improve membrane water flux, and superhydrophobicity can reduce the contact area between the salt and membrane surface to prevent membrane scaling. Significantly, the membrane’s durability can be further improved by adjusting the seawater ingredients. This finding revealed that the scaling resulting from Ca2+ and Mg2+ when they exist alone is more severe than when they exist together. Therefore, eliminating the dominant Ca2+, Mg2+, and naturally occurring substance in seawater and maintaining it in a neutral state can stably concentrate the seawater with a high water recovery of ∼85%. The regulation of the membrane interface integrated with optimal seawater ingredients is essential for the application of membrane distillation in the treatment of RO-concentrated seawater.
危险品化学品经营许可证（带存储）