超疏水蒸馏膜的功能改性研究进展

Research Progress on Functional Modification of Superhydrophobic Distillation Membranes

膜蒸馏技术因具有操作压力低、温差小、蒸馏液纯净、脱盐率高、可直接分离出结晶产物等优点而备受关注。但缺乏优异疏水性能的蒸馏膜是限制其应用的一个重要因素。迄今为止,科研人员在膜材料的疏水理论研究与超疏水蒸馏膜的功能改性方面开展了大量工作,研究者通过向膜面引入含硅或碳的纳米颗粒来提高膜面粗糙度,选用含氟的改性添加剂降低表面能,采用不同溶剂分散原材料并选择不同的成膜方式,使制备出的蒸馏膜疏水性能有了大幅度提高。本文归纳总结了近年来超疏水蒸馏膜功能改性方法的研究进展,并对改性效果进行了对比分析。分类研究结果表明,表面涂覆法适用于不同类型的基膜,可实现对膜骨架和膜表面的同时改性,既增大膜通量又提高膜的抗污染性能,操作简单,可以应用于大规模生产。与涂覆法相比,静电纺丝掺杂法改性的膜可以最大程度地保持稳定性,在提高耐透水性的同时可以减小改性物质对通量的影响,但其应用范围受到基膜的限制。化学沉积法可获得有梯度的沉积物或混合镀层,相比于涂覆法更容易控制涂层的组成和厚度,可进行更加精准的膜表面改性过程。等离子体等非传统方法多为几种方法的联用,从改性剂材料、操作过程、操作条件等方面均为蒸馏膜的改性开辟了新方向。本文分类分析了不同改性方法采用的疏水添加剂、分散剂、操作方法与操作条件,并对比了不同方法改性后的膜通量、孔隙率、脱盐率、过滤周期等指标,结合过滤方式评价了不同改性方法的优缺点,展望了超疏水改性蒸馏膜商业化应用面临的问题及发展前景,旨在为开发成本低廉、操作简单、膜通量高、抗污染能力强的超疏水蒸馏膜提供参考。

Membrane distillation technology has attracted much attention because of its advantages such as low operating pressure,small temperature difference,pure distillation liquid,highsalt rejection rate and direct separation of crystal products.However,the lack of distillation membranes with excellent hydrophobic properties is an important factor limiting its application.So far,researchers have carried out a lot of work in the hydrophobic theory research of membrane materials and functional modification of superhydrophobic distillation membranes,and made great progress in developing new modification methods and finding new modification additives.Based on the contact angle model,the researchers improved the surface roughness by introducing nanoparticles containing silicon or carbon into the membrane surface,selected modified additives containing fluorine groups to reduce the surface energy,dispersed raw materials with different solvents and selected different film-forming met-hods,which greatly improved the hydrophobic performance of the prepared distillation membrane.In this paper,the research progress of functional modification of superhydrophobic distillation membranes in recent years is reviewed,and the modification effect is compared and discussed.The results of classification research show that the surface coating method is suitable for different types of base membranes,which can realize the simultaneous modification of membrane skeleton and its surface,not only increase the membrane flux but also improve the antifouling property.The operation is simple and can be applied to large-scale production.Compared with the coating method,the membrane modified by the electrostatic spinning doping method can maintain the stability to the maximum extent,improve the water permeability and reduce the influence of the modified substances on the flux,but the application range is limited by the base membranes.The chemical deposition method can obtain gradient deposits or mixed coatings.Compared with the coating method,it is easier to control the composition and thickness of the coating,and can carry out a more accurate film surface modification process.Unconventional methods such as plasma are mostly the combination of several methods,which has opened up a new direction for the modification of distillation membranes from the aspects of modifier materials,operating process,operating conditions,etc.The hydrophobic additives,dispersants,operating methods and conditions used in different modification processes are classified and analyzed,and the membrane flux,porosity,salt rejection rate,filtration pe-riod and other indicators after modification by different methods are compared.The advantages and disadvantages of different modification met-hods are evaluated in combination with the filtration methods,and the problems and development prospects of commercial application of superhydrophobic modified distillation membranes are prospected,aiming to provide beneficial help for the development of superhydrophobic distillation membranes with low cost,simple operation,high membrane flux and strong anti-pollution ability.