Advances in special wettable materials for adsorption separation of high-viscosity crude oil/water mixtures

Effective separation of highly viscous crude oil/water mixtures remains a worldwide challenge. Employing special wettable materials with adsorptive properties as an emerging separation strategy has attracted extensive attention in the treatment of crude oil spillage. Such a separation technique combines excellent wettability materials and their adsorption performance to achieve energy efficient removal or recovery of high viscosity crude oil. Particularly, special wettable adsorption materials with thermal properties provide novel ideas and directions for the construction of rapid, green, economic and all-weather crude oil/water adsorption separation materials. Negatively, the high viscosity of crude oil makes most special wettable adsorption separation materials and surfaces extremely susceptible to adhesion and contamination in practical applications, leading to rapid functional failure. Moreover, such an adsorption separation strategy towards high-viscosity crude oil/water mixture separation has rarely been summarized. Consequently, there are still some potential challenges in separation selectivity and adsorption capacity of special wettable adsorption separation materials which urgently need to be summarized to guide the future development. In this review, the special wettability theories and construction principles of adsorption separation materials are first introduced. Then, the composition and classification of crude oil/water mixtures, particularly focusing on enhancing the separation selectivity and adsorption capacity of adsorption separation materials, are comprehensively and systematically discussed via regulating surface wettability, designing pore structures and reducing crude oil viscosity. Meanwhile, the separation mechanisms, construction ideas, fabrication strategies, separation performances, practical applications, and the advantages and disadvantages of special wettable adsorption separation materials are also analyzed. Finally, the challenges and future prospects for adsorption separation of high-viscosity crude oil/water mixtures are expounded.