Advances in oil sludge separation technology and mechanism at normal temperature: A review

The rapid increase in the global economy and expansion of industry has contributed to the rapid depletion of conventional resources. Oily sludge is a hazardous waste inevitably generated during oil extraction and oil refining. The efficient separation and recycling of its petroleum hydrocarbons has been an important challenge for the petrochemical industry. Despite the rapid advancement of oil sludge normal temperature separation technology, with the popularity of polymer-driven oil and tertiary oil recovery methods, the nature of oil sludge varies and emulsion complexity increases, necessitating urgent investigations into the intrinsic difficulties, process enhancements, and future directions of oil sludge normal temperature separation. The causes of sludge separation challenges including the macroscopic components of the sludge and microscopic interfacial interactions during treatment are systematically summarized. And the main oil sludge separation processes, mechanisms and application scenarios at normal temperature are systematically described in this work. Aiming at the problems of low index of single pathway, high solid content in recovered oil and cumbersome compounding process in oil sludge separation, a few new technologies of oil sludge at normal temperature are proposed, including biosurfactant treatment of oil sludge, environmentally responsive ionic liquid microemulsion treatment of oil sludge, environmentally responsive emulsion treatment of oil sludge, and environmentally responsive magnetic nanoparticle solution disposal of oil sludge. It also suggests new approaches to the oil sludge disposal process, such as targeted regulation of the oil sludge emulsion interface, combined process design of environmentally responsive agents, elaboration of the integrated mechanism of action of oil sludge emulsification and demulsification, and standardization of the oil sludge separation assessment system. The resolution of the above fundamental scientific and technological problems will provide a strong guarantee for the reduction of environmental pollution and the promotion of high-quality development of the petrochemical industry.