废水处理用类荷叶表面微纳米结构超疏水微孔膜的制备及膜蒸馏机理研究

Membrane distillation (MD) is an important solution for the treatment and reuse of wastewater with higher concentration. In MD process, volatile components are extracted through the micropores of hydrophobic membranes and the solution can be concentrated to near saturation under the driving force of evporation pressure difference betweent the two sides of the membrane. High performance hydrophobic membrane is urgently needed to overcome the obstacles of existed hydrophobic membranes. The obstacles including low hydrophobicity, low flux, fouling and wetting..This application stands on the basis that some natural and synthetical surfaces which have lotus-leaf like nano-micro two scale structures possess good hydrophobicity and self-cleaning property. Super-hydrophobic surfaces with lotus-leaf like micro-structure will be constructed on the surface of traditional hydrophobic polyvinylidene fluoride membranes. Membrane preparation and micro-structure control method will be constructed on the basis of dry-wet phase inversion process. The effect of casting solution composition and phase inversion parameters on the micro-structure of the membranes will be studied. The forming and developing mechanism of the micro-protuberance of the super-hydrophobic surfaces will be detected. The quantitative connection between the micro-structure and properties of the prepared membranes will be constructed. The effect of membrane surface micro-structure on the heat and mass transfer mechanisms of MD process will be studied. A mathematical model including parameters relative to the membrane structure will be constructed to describe the heat and mass transfer process.

膜蒸馏可实现废水中易挥发组分提取和废水高度浓缩，是实现废水资源化、节水减排的重要技术。但膜蒸馏用疏水膜仍存在的疏水性不足、通量低、易污染和亲水化等问题，迫切需要结合膜蒸馏特性开发高性能超疏水膜。.本申请利用荷叶等天然生物表面具有超疏水性的微结构原理，通过聚合物稀溶液涂覆-相转化法，在疏水性聚偏氟乙烯微孔基膜表面构建具有类荷叶微结构（规则分布微、纳米结构微突）的超疏水复合膜。研究涂覆液组成、相转化制膜方法对复合膜表面微结构的影响规律，探索膜面微突的形成原理与成长规律，建立涂覆液组成及制膜工艺参数与复合膜表面微结构、膜性能（疏水性、膜蒸馏性能等）的关联关系，确立类荷叶微结构超疏水复合膜的制备及微结构控制方法、原则，研制出高性能的膜蒸馏用超疏水膜。在此基础上，研究膜面微结构对膜蒸馏传热传质过程的影响规律、原理，尝试将超疏水膜结构因数引入膜蒸馏传质传热模型，构建包含膜面微结构因数的膜蒸馏机理。

膜蒸馏可实现废水中易挥发组分提取和废水高度浓缩，是实现废水资源化、节水减排的重要技术。但膜蒸馏用疏水膜仍存在的疏水性不足、通量低、易污染和亲水化等问题，迫切需要结合膜蒸馏特性开发高性能超疏水膜。.本申请利用荷叶等天然生物表面具有超疏水性的微结构原理，通过聚合物稀溶液涂覆-相转化法，在疏水性聚偏氟乙烯微孔基膜表面构建具有类荷叶微结构（规则分布微、纳米结构微突）的超疏水复合膜。研究涂覆液组成、相转化制膜方法对复合膜表面微结构的影响规律，探索膜面微突的形成原理与成长规律，建立涂覆液组成及制膜工艺参数与复合膜表面微结构、膜性能（疏水性、膜蒸馏性能等）的关联关系，确立类荷叶微结构超疏水复合膜的制备及微结构控制方法、原则，研制出高性能的膜蒸馏用超疏水膜。研究结果表明，聚合物稀溶液在基膜表面的浸润时间、温度影响其在基膜表面的附着及后续相分离进程；聚合物稀溶液临近浊点（相分离点）组成时，其在基膜表面附着——相分离，聚合物分子链的预成形胶束更易在基膜表面形成均匀的双重微突结构，从而经相分离后形成超疏水结构。利用此法制备的复合膜，其表面纯水接触角达到160°以上；通过调节该稀溶液近浊点组成，可显著降低复合层厚度，有效降低气体传输阻力，从而使该膜具备较佳的膜蒸馏传质速率，膜蒸馏通量可达到50kg/m2h以上。在此基础上，结合膜蒸馏过程传质特性，建立了基于过程强化的膜蒸馏过程传热传质机理研究，初步建立了适于该过程的膜蒸馏传热传质理论模型，模型计算得膜蒸馏过程通量与实验值误差低于7%。