Achieving the efficacious and rapid separation of mixed water/oil streams has emerged as a fundamental imperative in order to facilitate extraction of fossil fuels by methods such as cyclic steam stimulation as well as to mitigate the potentially calamitous impact of oil spills in natural aquatic environments. Here, we demonstrate functionalized ZnO nanotetrapodal membranes combining the micrometer-scale texturation of underlying stainless steel meshes with the nanoscale texturation of an enmeshed interconnected porous network of ZnO tetrapods, the conformal adhesion afforded by an amorphous silica layer, and the low surface energy of surface-deposited perfluorinated sulfonate layers. The membranes exhibit pronounced differential wettability and selectively permeate water whilst retaining oil. The multivariate design space of the architectures has been evaluated to determine the mesh size and ZnO loading that yield the highest separation efficiencies. Oil content in recovered water is reduced to <300 ppm while maintaining a flux rate of greater than 325 L/(m 2 •h). The functioning of the membranes can be understood in terms of the creation of differential Cassie−Baxter nonwetting and Wenzel wetting regimes for oil and water, respectively.

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An increasing global population and a sharply upward trajectory of per capita energy consumption continue to drive the demand for fossil fuels, which remain integral to energy grids and the global transportation infrastructure. The oil and gas industry is increasingly reliant on unconventional deposits such as heavy crude oil and bitumen for reasons of accessibility, scale, and geopolitics. Unconventional deposits such as the Canadian Oil Sands in Northern Alberta contain more than one-third of the world’s viscous oil reserves and are vital linchpins to meet the energy needs of rapidly industrializing populations. Heavy oil is typically recovered from subsurface deposits using thermal recovery approaches such as steam-assisted gravity drainage (SAGD). In this perspective article, we discuss several aspects of materials science challenges in the utilization of heavy crude oil with an emphasis on the needs of the Canadian Oil Sands. In particular, we discuss surface modification and materials’ design approaches essential to operations under extreme environments of high temperatures and pressures and the presence of corrosive species. The demanding conditions for materials and surfaces are directly traceable to the high viscosity, low surface tension, and substantial sulfur content of heavy crude oil, which necessitates extensive energy-intensive thermal processes, warrants dilution/emulsification to ease the flow of rheologically challenging fluids, and engenders the need to protect corrodible components. Geopolitical reasons have further led to a considerable geographic separation between extraction sites and advanced refineries capable of processing heavy oils to a diverse slate of products, thus necessitating a massive midstream infrastructure for transportation of these rheologically challenging fluids. Innovations in fluid handling, bitumen processing, and midstream transportation are critical to the economic viability of heavy oil. Here, we discuss foundational principles, recent technological advancements, and unmet needs emphasizing candidate solutions for thermal insulation, membrane-assisted separations, corrosion protection, and midstream bitumen transportation. This perspective seeks to highlight illustrative materials’ technology developments spanning the range from nanocomposite coatings and cement sheaths for thermal insulation to the utilization of orthogonal wettability to engender separation of water–oil emulsions stabilized by endogenous surfactants extracted during SAGD, size-exclusion membranes for fractionation of bitumen, omniphobic coatings for drag reduction in pipelines and to ease oil handling in containers, solid prills obtained from partial bitumen solidification to enable solid-state transport with reduced risk of damage from spills, and nanocomposite coatings incorporating multiple modes of corrosion inhibition. Future outlooks for onsite partial upgradation are also described, which could potentially bypass the use of refineries for some fractions, enable access to a broader cross-se...

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Dual purposed ZnO tetrapods promote photopolymerization of methacrylates and provide surface roughness for superhydrophobicity. Large area photochemical fabrication of hybrid coating is demonstrated for liquid/liquid separation applications.