A review of demulsification technique and mechanism for emulsion liquid membrane applications

The present paper on Emulsion Liquid Membrane (ELM) focuses on the process of water and oil separation in the emulsion or better known as demulsification. The success of demulsification allows the reuse of the membrane phase which highly likely to reduce the cost of the system. Else, this process is used to recover the extracted solute from the internal phase. Although the number of reports on ELM application, formulation and stability have grown over the years but, reports that specifically discuss demulsification process lacks attention. The interest of this article is to report the current progress and known mechanism of demulsification of primary emulsion in ELM via several methods. Basically, the demulsification process of ELM can be categorized into 3 types; physical, chemical or combination of both. Meanwhile, flocculation, Ostwald Ripening and coalescence are the main reasons for phase separation between water and oil in the emulsion. Unfortunately, the presence of surfactant and formation of highly stable emulsion in the system made the demulsification process impossible or at a very slow rate. Further discussion on the role of surfactant, emulsion properties, types of demulsification methods available and the effect of membrane phase reuse can be found in this article.