乳化剂对动态膜分离油水乳化液过程的影响

Impact of emulsifier on separation of oil-in-water emulsion by dynamic membrane

利用管状陶瓷膜基氧化锆动态膜分离油水乳化液,研究了4种工业常见乳化剂[斯盘80 (SP-80)、十二烷基磺酸钠(SDS)、十二烷基硫酸钠(SLS)和十二烷基苯磺酸钠(SDBS)]对分离过程的影响。利用正交实验方法考察了乳化剂种类和浓度、乳化液温度和流量以及操作压力对过程的影响。正交实验结果表明,在SDS、1.0g/L、50℃、120L/h和0.14MPa操作条件下,油水混合物稳定渗透通量最大。单因素实验结果表明,当乳化剂浓度增大时,稳定渗透通量减小;当乳化液温度升高时,稳定渗透通量先增加后降低。无机盐离子Na+、Ca2+和Al3+的存在均可使稳定渗透通量增加。当Al3+大于0.75g/L时,乳化液的稳定性被完全破坏,更有利于提高渗透通量。基于实验结果,采用分子模拟方法研究了不同实验条件下乳化剂的乳化效果,分析了SDS的油水界面形成能(E)和水的界面扩散系数(D)与乳化剂浓度和乳化液温度的关系。模拟结果表明,E和D绝对值均随着乳化剂浓度和乳化液温度增加而增大。实验和模拟结果均表明,乳化剂的乳化效果决定了油滴的平均粒径,基于油水分离的堵塞机理,也由此影响了稳定渗透通量。模拟结果从微观角度解释了实验现象,研究结果可为动态膜处理油水乳化液的工业应用提供依据。

Ceramic tube supported zirconium dioxide dynamic membrane was applied to the separation of oil-in-water emulsion by crossflow microfiltration. Effects of four industrial emulsifiers, i.e., span 80 (SP- 80), sodium dodecyl sulfate (SDS), sodium dodecyl sulfate (SLS) and sodium dodecyl benzene sulfonate (SDBS) were investigated. The influence of emulsifier type and concentration, emulsion temperature and flow rate and operating pressure on the process were investigated by orthogonal experiment. The results show that the maximum steady permeate flux exists under operating conditions of SDS, 1.0g/L, 50?C, 120L/ h and 0.14MPa. Single factor experimental results show that the steady permeation flux decreases with the increase of emulsifier concentration, and increases first and then decreases with the increase of emulsion temperature. Inorganic salt ions, Na^+, Ca^2+ and Al^3+ can cause a stability loss of emulsion. As the Al^3+ is more than 0.75g/L, the stability of the emulsion is completely destroyed, which was more beneficial to improving the permeability flux. Based on the experimental results, molecular simulation method was adopted to study the emulsification under experimental operating conditions. Relationship between oilwater interface formation energy (E) of SDS and water interface diffusion coefficient (D) with emulsifier concentration and emulsion temperature was analyzed. Simulation results show that the absolute values of the E and D gradually increase with the increase of concentration and temperature. The experimental and numerical results show that the emulsifying effect of the emulsifier determines the average oil drop size within an emulsion and affects the stable permeation flux according to the plugging mechanism in the separation of oil-in-water emulsion. The simulation results have successfully explained the experimental permeation phenomena from a microscopic perspective. This fundamental research can provide a basis for industrial application of dynamic membrane treatment of oil-water.