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Abstract
Demulsification is an indispensable step in the application of emulsion liquid membrane (ELM) separation process. In this work, a novel microwave demulsification method is first applied in the ELM system to study the phenomenon of breaking water-in-oil (W/O) emulsion. The mechanism of microwave heating is essentially that of dielectric heating. After exposing the emulsion to the microwave electromagnetic (EM) field, molecular rotation, and ionic conduction due to the penetration of EM into the emulsion are responsible for the internal heating. Thus, the application of microwave radiation results in the acceleration of separation of emulsion. In this work, the effects of emulsion conditions and microwave operating conditions on the demulsification rate and the separation efficiency of W/O emulsion were systematically studied. The results exhibited that both the demulsification rate and the separation efficiency increased with the increase in droplet size and the concentrations of the carrier (D2EHPA) and acid. However, they decreased with the increase in surfactant (Span 80) concentration and the oil phase-to-aqueous phase volume ratio (O/A). As for the effect of electrolyte concentration, it exhibited a peculiar maximum phenomenon. Both the demulsification rate and the separation efficiency were maximum when the concentration of electrolyte was about 0.5 M. The optimum microwave irradiation power and exposure time were suggested to be 420 W and 12 sec, respectively.
ACKNOWLEDGMENT
Financial support for this work from the National Science Council of the Republic of China (Grant No. NSC-82-0402-E035-070) is gratefully acknowledged.
