Oil-water separation techniques

In this type of emulsion, water is the internal dispersed or discontinuous phase, while oil is the external or continuous phase. Separation by the different gravity of the two phases is a very slow process, but can be accelerated by the assistance of chemicals. The chemicals used are termed demulsifiers, emulsion breakers or wetting agents. These additives are surfactants, which migrate to the oil/water interface. They adsorb on the oil films surrounding water droplets and break the oil films. Then, water droplets aggregate to form water drops large enough to gravitationally separate them from the oil. Non-ionic surfactants having both lipophilic and hydrophilic groups are mainly used as demulsifiers.