Emulsion liquid membrane for heavy metal removal: An overview on emulsion stabilization and destabilization

Extraction processes using emulsion liquid membrane (ELM) have received significant attention due to their potential as an effective technique for treatment of industrial liquid wastes. However, the need to obtain desired level of stability is very important in order to overcome the obstacle of the application of ELM at industrial scale. The small droplet diameter of emulsion is a key criterion that will provide a stable emulsion and a larger mass transfer area. Two important factors related to the stability of emulsion such as method of emulsification and mechanism of emulsion breaking is discussed in detail. Various emulsification methods such as mechanical agitation and ultrasound emulsification, as well as the emulsion formulation which includes composition, selection of agent, and operation parameters on emulsion stabilization were presented. Emulsion destabilization in term of emulsion breakdown mechanisms such as coalescence, swelling and leakage was also discussed.

► Recent studies to improve emulsion stability on heavy metals extraction by ELM. ► Mechanical and ultrasound emulsification to produce stable emulsion. ► Composition, agent selection, and operation parameter effects on emulsion stability. ► Emulsion breakdown mechanisms including coalescence, swelling and leakage.