直流电场下O/W体系中油滴的迁移行为及油水分离效果研究

Migration behavior of oil droplets and oi l-water separation of an oil-in-water(O/W)emulsion in a DC electric field

首先利用电化学工作站和生物显微镜研究了直流电场下水包油(O/W)乳化体系中油滴的迁移行为,然后分析了电场强度、油滴粒径等因素对油滴迁移行为的影响规律,结果表明:直流电场下,油滴会发生定向迁移,但迁移过程中不会发生聚并;油滴迁移速率随着电场强度的增大而增大,随着平均粒径的减小而变小。直流电场可破坏油滴表面稳定的电荷结构,导致油滴表面电荷分布不均,从而促使油滴在电场中发生定向迁移,并在阳极表面发生破乳、聚并,实现与水相的分离。最后,对直流电场作用下乳化含油体系的油水分离效果进行了实验验证,结果表明,对初始含油量为89.2 mg/L的模拟乳化废水而言,在一定条件下进行处理后,其出水含油量低于5 mg/L,除油率高达95.3%。

The migration behavior of oil droplets in an oil-in-water(O/W)emulsion under a DC electric field has been studied by means of an electrochemical workstation and an optical microscope.The influence of electric field strength and oil droplet size on the migration behavior of the oil droplets was also investigated.The results showed that the oil droplets began to migrate towards the anode when a DC electric field was applied.However,it should be noted that the oil droplets did not coalesce during the migration process.The migration rate of oil droplets increased with increasing electric field intensity.As the particle size decreased,the migration rate slowed down.The application of a DC electric field destroys the stability of the surface charge structure of the oil droplets,resulting in an unbalanced distribution of surface charges,which leads to the directional migration of the oil droplets.Specifically,the mechanism of demulsification and separation of the O/W emulsion can be described as:1)the migration of the oil droplets towards the anode driven by the electric field;2)demulsification and coalescence of the oil droplets on the anode surface;3)floatation of the oil droplets caused by their lower density and their subsequent separation from the water.The oil-water separation effect of a DC electric field was verified by experiment.The oil content of the model wastewater was 89.2 mg/L.After treatment,the oil content could be reduced to less than 5 mg/L and the corresponding removal ratio was higher than 95.3%.This method has many advantages for oil-water separation,such as low energy consumption,no addition of chemical reagents,no secondary pollution,and a high degree of device integration,which enhance its prospects for commercial application.