EFFECT OF FREQUENCY IN AC HIGH-VOLTAGE ON COALESCENCE OF WATER-IN-OIL EMULSION STABILIZED WITH SORBITAN MONOOLEATE TYPE NONIONIC SURFACTANT

The liquid surfactant membrane has advantages superior to those of other types of liquid membranes, but its biggest bottleneck lies in the demulsification process for separating the stripping solution from the organic phase containing surfactant and carrier. This paper is concerned with the electrostatic coalescence of the W/O emulsion stabilized with surfactant in an a.c. high-voltage current applied between two insulated flat electrodes. Effects of the dispersed phase hold-up, the applied voltage and the frequency of the phase separation rate were studied. The separation rate was larger for lower initial hold-up of the dispersed phase. When the initial hold-up was less than 40 %, the coagulation stage preceded the coalescence stage and the separation rate decreased. The separation rate increased approximately with the second order of the applied voltage. It also increased with frequency and tended to become constant at frequencies in the range of 1000 to 2000 Hz. The water content of the separated oil phase decreased with increase in frequency.