Abstract: The demulsification effect and characters of O/W emulsion in DC electric field are studied.According to the stratification phenomena in the experiments,the whole demulsification process of O/W emulsion can be divided into three stages:water layer formation,re-emulsification with transverse diffusion and uplift-stabilization.The higher the voltage given,the faster the stratification.Some evidences confirm that O/W emulsion system with surfactant will appear surface tension gradient in the demulsification process.The current together with the surface tension gradient cause different demulsification processes and current variation for different emulsions.Due to the impact of Brown movement,DC electric field exhibits poor effect on the oil droplets with a diameter less than 7 μm.When the initial oil content of the emulsion is 3 000 mg·L-1 and DC voltage is between 20-30 V,the lowest oil content after demulsification can reach 60 mg·L-1.
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