The separation and enrichment of molecules with part amphipathy using a novel ultrasonic emulsion-enrichment method

Separation and enrichment of part amphiphilic compounds that have both hydrophilic and hydrophobic functional groups from dilute aqueous solutions or surface water, are frequently encountered. In this work, a novel ultrasonic emulsion-enrichment method is proposed by taking advantage of the weak surface-active property of these compounds. It is a universal and platform technology with benefits of low cost and easy operation, compared to conventional methods such as extraction, adsorption, membrane and microbubble-based methods. The principle of this method is to generate emulsions rapidly in an ultrasonic microreactor and adsorb the part amphiphilic compounds onto the droplet interfaces. During demulsification naturally, they can be enriched into a thin layer. Rhodamine B was chosen as a model material with weak surface activity. Detailed emulsification process, separation/enrichment phenomenon and performance were presented and discussed. The result showed that the concentration of the enriched layer was about 7–244 times of that in the bulk layer. When the concentration was reduced from 25 mg/L to 1 mg/L, the enrichment effect slightly decreased. In addition, this method was applied to other compounds (1H-benzotriazole, bisphenol A, bisphenol F and bovine serum protein). Similar excellent performance was also achieved.