Demulsification

the reverse of emulsification; the destruction of emulsions, that is, of disperse systems comprising two immiscible liquids, one of which is uniformly distributed as fine drops in the other.

In demulsification the emulsion drops increase as a result of coalescence (fusion) during Brownian motion, sedimentation (precipitation), or mixing. Demulsification leads to the complete or partial separation into layers of the liquids forming the emulsion. It occurs when the action of the emulsion stabilizers (emulsifiers) ceases to be effective, that is, the protective coating that they form on the surfaces of drops is destroyed or loses the ability to prevent coalescence. In industry and the laboratory demulsification is effected mechanically (by centrifuging, filtering through porous materials, and stirring), by heating or freezing, by the action of an electric field, by salting out (adding electrolytes), and by adding special reagents-demulsifiers, which neutralize the action of emulsifiers by reacting with them chemically or expelling them from the surfaces of the emulsion drops. Usually demulsifiers are surface-active agents with greater surface activity than the emulsifier of the given emulsion but with less stabilizing capacity.

Demulsification is extensively used in dewatering and desalting crude petroleum, in many processes in chemical technology, in butter production, and in other processes.