Elaboration of the Demulsification Process of W/O Emulsion with Three-Dimensional Electric Spiral Plate-Type Microchannel

Abstract

Rapid and efficient demulsification (destabilizing of an emulsion) processes of a water in oil (W/O) emulsion were carried out in a three-dimensional electric spiral plate-type microchannel (3D-ESPM). In this experiment, the demulsifying efficiency of emulsions by 3D-ESPM was compared with that by gravity settling, the factors influencing demulsifying efficiency were investigated, and the induction period, cut size and residence time in the demulsification process were studied. The results showed that in contrast to the gravity settling method, 3D-ESPM can directly separate the disperse phase (water) instead of the continuous phase (oil). The maximum demulsifying efficiency of W/O emulsion in a single pass through the 3D-ESPM reached 90.3%, with a microchannel height of 200 μm, electric field intensity of 250 V /cm, microchannel angle of 180°, microchannel with 18 plates and a flow rate of 2 mL /min. An induction period of 0.6 s during the demulsification process was simulated with experimental data fitting. When the residence time of emulsion in 3D-ESPM was longer than the induction period, its demulsifying efficiency increased as the increase of the flow velocity due to the droplet coalescence effects of Dean vortices in the spiral microchannel. For this device a cut size of droplets of 4.5 μm was deduced. Our results showed that the demulsification process of W/O emulsion was intensified by 3D-ESPM based on the coupling effect between electric field-induced droplets migration and microfluidic hydrodynamic trapping.

Emulsion Liquid Membrane Extraction of Bisphenol A with Three-dimensional Spiral Plate-type Microchannel

“…Therefore, the membrane, oil phase between external and internal water phase, should be stable in this short period, and less quantity of emulsifier SP80 was used to stable the W/O emulsion. In our experiments, only 33.33 mg/L SP80 was used, and the detailed emulsion preparation method could refer to our former work [13,14]. The W/O emulsions prepared were pumped through the 3D and no significant demulsification was observed.…”

“…The W/O emulsions prepared were pumped through the 3D and no significant demulsification was observed. Also, we had reported [14] that the 3D could demulsify the W/O emulsion only by adding a 40-100 V•cm -1 DC electric field. emulsifier dosage for the emulsion used in the 3D-SPM extraction process could be decreased by 90%, which is easy for recycling the emulsion and friendly for the environment.…”

“…At both ends along the arrangement line, there were two pieces of stainless steel end plates, which were 5 mm in-depth and with two orifices of entrance and exit. For the manufacturing details of 3D-SPM, please refer to our previous article [10,13,14].…”

“…Where J is the stability of the emulsion, (mL) is the volume of the residual emulsion after standing, V total (mL) is the total volume of emulsion collected before standing, the volume of water phase after standing, V kerosene (mL) is the volume of oil phase after standing. The emulsion prepared with this method can be stable for at least 2 hours with stability over 90% [13,14]. was prepared by dissolving 0.05 g analytical grade BPA in 5mL of methanol and then the volume of 500 mL.…”

“…In this research, to further improve the extraction efficiency of BPA with ELMs, we used 100-200 µm 3D-PSM as a contactor for ELMs extracting BPA from aqueous solutions, and explore the optimization condition to short the resident time for extraction. The 3D-PSM had been reported [13,14] to demulsify the W/O emulsion efficiently by adding a DC electric field. And with this research, we focus on the effect of flow rate ratios, Qa/Qe the height of microchannel H, and plate numbers P, on the BPA extraction η, and try to find a simple continuous process for ELMs extraction.…”