Removing submicrometer-sized oil droplets from water is still one of the leading challenges in the separation of emulsions. In the oil and gas industry, emulsions are handled in one of two distinctive ways: the stabilization of emulsions is altogether precluded by the addition of appropriate demulsifiers or emulsions are separated after extraction. During the extraction of hydrocarbons, it is possible to use preventive measures that greatly mitigate the formation of emulsions. However, the increased usage of unconventional extractive processes such as steam-assisted gravity drainage (SAG-D) where emulsions form easily as a result of natural surfactants, makes such preventive measures impractical and can furthermore reduce the efficacy of the extractive processes. Engineering the separation of emulsions has thus emerged as a critical imperative. The separation of emulsions has further resonance in addressing oil spills in marine environments. In this work, we demonstrate that a mesostructured substrate with hierarchical texturation shows drastic differences in the wettability of water and oil. The mesostructured substrates are prepared using a scalable process in which ZnO nanotetrapods, prepared by oxidizing zinc metal at high-temperature, are spray coated onto a stainless-steel mesh that exhibits microscale texturation. The ability of such meshes to separate the water and oil fractions of SAG-D emulsions and the flux rates attainable for such a separation process have been evaluated as a function of mesh pore size and ZnO loading. The use of high temperatures was necessary for the separation given the operating conditions under which the emulsions are extracted and handled. Such high temperatures are required to break apart complex emulsions. Based on the results obtained, membranes with small pore sizes are necessary to significantly reduce the quantity of water present in the emulsions. The flux rate also showed a great variance between high and low permeation temperatures as well as high and low ZnO concentrations.
