Removal of oil spills from aqueous systems by polymer sorbents

This review deals with the applicability of polymeric sorbents in removing spilled free oil from water surfaces. The theoretical framework covers the sorption ability of polymeric materials in general, respecting their size and morphology; however, the main focus is on polyolefins, primarily various grades of polyethylene (PE) and polypropylene (PP), including PE and PP waste. The core motivation associated with recycling polyethylene LDPE is the low interest in plastic convertors and the limited marketability of these commodities. The scientific focus in this area is on the development of new products having at least two general features: i) a specific application that does not require high mechanical performance, and ii) the material has a unique functionality that is not significantly influenced by using a recyclate against the use of the pristine polymer. Recycled polyolefins fully satisfied these requirements. This review pays special attention to the theoretical aspects of polymeric sorbents. Specific features of sorbents are analyzed depending on their geometry and morphology, involving powders, membranes/mats, and 3D foams (sponges)/gels. The wettability and sorption mechanisms regarding the chemical composition of materials, their surface topology, and internal porosity are discussed in detail. The presented manuscript emphasizes the close connection between materials' behavior and properties, which is crucial for efficient oil/water separation and the theoretical modeling of adsorption and absorption processes. The focus on the physical aspects of materials from a theoretical point of view is highlighted, enabling a complex understanding of the oil/water separation processes.