Demulsification of Oil-in-Water (O/W) Emulsion in Bidirectional Pulsed Electric Field

The research about electric demulsification of oil-in-water (O/W) emulsion is not enough at present, especially compared with that about electric demulsification of water-in-oil (W/O) emulsion. As an easy and novel method, a bidirectional pulsed electric field (BPEF) was investigated to demulsify the O/W emulsion in this work. Here we report that BPEF could actuate O/W emulsion to form rotational flow and drove oil droplets to form oil-droplet chains and to coalescence. In order to interpret the mutual attraction and coalescence of oil drops in BPEF, we put forward the hypothesis that charges on an oil drop surface would redistribute in BPEF, and we built the charge redistribution model according to the adsorption phenomenon of oil droplets. The behavior of oil drops in BPEF could be successfully explained in terms of the hypothesis and the model. The charge redistribution on an oil droplet surface could be evaluated by the two parameters we proposed. An amended potential redistribution formula of an oil drop surface was also obtained according to the model. The O/W emulsions were successfully demulsified by BPEF in the experiments. It showed that BPEF could be a significant method for electric demulsification of O/W emulsions.