Superhydrophobic sponge-like chitosan/CNTs/silica composite for selective oil absorption and efficient separation of water-in-oil emulsion

Developing state-of-the-art materials with durability, superhydrophobicity, and superoleophilicity is essential for effective cleanup of oil spills and the treatment of oily wastewater. In this study, a novel superhydrophobic/ superoleophilic chitosan-based composite was created by incorporating carbon nanotubes (CNTs) into a chitosan (CS) matrix and depositing superhydrophobic SiO2 nanoparticles, forming a sponge-like absorbent (SHSiO2@3CNTs/CS) for selective oil absorption and efficient oil/water separation. The optimal CNTs incorporation was comprehensively investigated to enhance the structural stability and mechanical strength of the chitosan/ CNTs/silica composite. The size and loading of in-situ-grown SiO2 nanoparticles on the chitosan/CNTs composite surface were identified as crucial factors in achieving surface superhydrophobicity. The optimized SHSiO2@3CNTs/CS, with its three-dimensional porous structure, exhibited not only superhydrophobicity and superoleophilicity, but also high chemical stability, excellent resistance to high temperature and friction. Notably, the SH-SiO2@3CNTs/CS composite effectively absorbed oil with a capacity of up to 18.24 times its own weight and selectively separated oil/water mixtures and water-in-oil emulsions, achieving a separation efficiency of exceeding 97 % under vacuum pump conditions. This study not only introduces a novel approach for developing superoleophilic chitosan-based sponge-like composite materials, but also presents a promising strategy for selective oil absorption and efficient separation of water-in-oil emulsions.