基于液固界面效应的滤膜破乳及机理研究

A large amount of oil wastewater is produced from petroleum, mechanical processing and other industries. Much of them discharged into the water and the soil does very harm to the survival environment. Therefore separating oil from the oil wastewater is becoming a world problem. The separation of emulsified oil wastewater is the most difficult in all oil wastewater treatments. Membrane wastewater treatment technology has the advantages of low energy consumption, simple, no pollution and so on. However the traditional osmosis membrane method has the disadvantage of low efficiency. The oil and water separation based on the membrane wettability can greatly improve the treatment efficiency and has become a research hotspot. The research mainly focuses on the free oil separation from the wastewater, and seldom involves the emulsified oil wastewater. Furthermore, the demulsification and its mechanism by wetting on a membrane are even more rarely involved. In this study, a new oil and water separation method through demulsification based on liquid-solid interfacial effects of a filter membrane and then free oil separation from the emulsified oil wastewater by a membrane wettability control is proposed. The aims of the study are to explore the mechanism on the demulsification, to achieve influence factors and rules, and to give an optimized scheme for high efficiency demulsification. The main contents to be completed of this study include: 1) interfacial behavior and mechanical analysis of emulsified oil droplet aggregation, adsorption and wetting on a membrane surface; 2) wetting behavior and mechanism of oil droplets on a membrane surface under water; 3) behavior and mechanism of demulsification and coalescence of emulsified oil droplets on a membrane surface; 4) the design and optimization of high efficiency demulsification and oil-water separation filtration system.

石油、机加工等行业会产生含油废水，大量含油废水直接排放至水体、土壤中，破坏了生态环境，油水分离已成为一个世界性问题。含油废水中乳化油处理难度最大，其中膜处理技术具有能耗低、简单、无二次污染等优点。传统反渗透膜等膜方法具有效率低的缺点，通过滤膜润湿性控制实现油水分离的方法可大大提高处理效率，已成为了当前的研究热点。滤膜润湿油水分离的研究目前主要针对游离态的油水分离，针对乳化液的研究较少，其中对于破乳及相关机理的研究更少涉及。研究提出先进行基于界面效应的乳化液滤膜破乳，再进行润湿分离的思路，以探明相关界面效应及机理、获得滤膜破乳的影响因素及影响规律为目标，提出高效滤膜破乳的优化方案。拟完成的研究内容包括：1）乳化油滴在滤膜表面聚集、吸附的界面行为及力学分析；2）水下油滴在滤膜表面的润湿行为及机理；3）滤膜表面乳化油滴聚并破乳行为及机理；4）高效破乳及油水分离过滤系统的设计和优化。

石油化工、机械加工等行业会产生大量含油废水，含油废水直接排放至水体、土壤中，破坏了生态环境，油水分离已成为一个世界性问题。含油废水中乳化油处理难度最大，其中膜处理技术具有能耗低、简单、无二次污染等优点。传统反渗透膜等膜方法具有效率低的缺点，通过滤膜润湿性控制实现油水分离的方法可大大提高处理效率，已越来越成为乳化液破乳处理的重要方法，其研究具有重要理论和现实意义。项目主要以油水乳化液为研究对象，以实现高效滤膜破乳和油水分离为目标，开展乳化液滴向滤膜表面趋近、在滤膜表面润湿及聚并破乳等过程所涉及的界面效应及相关机理研究，并在此基础上完成乳液高效破乳的系统方案设计。首先，项目提出基于静电场、张力梯度场等构建溶液胶体微粒向液固界面运动的长程诱导力，实现了液固界面附近更大范围胶体微粒向界面的快速驱动，所提张力梯度场方法相对传统的界面力方法可实现胶体微粒趋近速度2个数量级的提高；通过实验和分子动力学仿真等研究获得了长程诱导力、静电力、双电层力等对乳化液滴向液固界面聚集的影响因素及影响规律，实现了乳化液滴向滤膜表面的高效聚集和吸附，探明了胶体微粒在张力梯度等力场中的运动机理。其次，项目提出并研究了基于纤维结构及润湿梯度构建实现液滴在纤维表面的自驱运动，获得了基于锥形等纤维尺寸变化的结构梯度和润湿梯度实现液滴自驱的原理、乳化液滴通过纤维滤孔的界面力学机理，以及液滴间的相互作用、聚并和润湿破乳机理，形成了实现乳化液滴破乳的系统理论，该理论为基于纤维滤膜的破乳设计奠定了坚实基础。最后，项目提出了基于静电、张力梯度构建、多相组分喷涂等纤维表面润湿改性的多种滤膜表面涂层制备方案，通过一种双组分纤维滤膜的方案设计，分别实现油包水和水包油乳化液的高效破乳和油水分离。