Direct Visualization of Microscale Dynamics of Water Droplets on under-Oil-Hydrophilic Membranes by Using Synchrotron White-Beam X-ray Microimaging Techniques

Abstract

Despite considerable academical and practical interests on separation of water-in-oil emulsion via special wettable membranes, fundamental understanding on microscale dynamics of water droplets on under-oil-hydrophilic membranes (UOHMs) at early stages during separation is still very preliminary due to temporal and spatial resolution of existing visualization techniques. To this end, we here succeed in a direct microscopic visualization of separation processes of water droplets on the UOHMs by employing a high-speed, two-dimensional synchrotron white-beam X-ray microimaging technique. During the separation of water-in-oil emulsion, microscale dynamic behaviors of water droplets on hydrophilic membrane surfaces immersed in the different oil media (i.e., hexane, kerosene, and light and heavy mineral oils) and oil films between water droplets and membrane surfaces are visualized and analyzed.