Waste to treasure: Superwetting foam enhanced by bamboo powder for sustainable on-demand oil-water separation.

Low-cost and sustainable superwetting materials are urgently required for oily wastewater treatment. Many poly(vinylidene fluoride) (PVDF)-based materials have been designed for oil-water separation. However, their fabrication processes frequently require toxic organic solvents and high-cost materials (e.g., carbon tubes and graphene). In this study, a highly porous and superhydrophobic bamboo powders (BP)-enhanced PVDF foam (SBPF) was fabricated via an organic solvent-free process. The SBPF exhibits efficient adsorption and recovery for various oils and organic solvents. Moreover, the SBPF shows high adsorption and separation performance under ultraviolet exposure and turbulent environments. It can also be used for water-in-oil emulsions separation, with a high separation efficiency more than 99.3 % under gravity. Interestingly, the amphiphilic PVDF-BP foam (ABPF) shows underwater superoleophobicity and underoil superhydrophobicity after delignification of SBPF. Owing to the conversion of wettability, it presents a high performance in treatment of both surfactant-stabilied water-in-oil and oil-in-water emulsions with the high separation efficiency achieving more than 99.6 % and 99.5 % respectively under gravity. In addition, the ABPF shows a high separation performance even after ten cycles. Hence, this fabricated organic solvent-free foams are promising candidates for sustainable on-demand separation of oils or organic solvents and water in complex environments.