Superhydrophobic Photothermal Halloysite-Based Sponge for Oil–Water Separation and Fast Recovery of High-Viscosity Crude Oil Spill

Frequent oil spills and oily water pose a severe threat to ecosystems. Besides, efficient cleanup and recovery of high-viscosity marine crude oil remain a global challenge. Herein, a superhydrophobic halloysite-based oil-adsorption sponge (k-HNTs@MS2) with a photothermal conversion property was fabricated via a one-step calcination technique and a dip-coating method. Briefly, melamine sponges (MS) were calcined in argon and then dip-coated with halloysite nanotubes (HNTs) modified with 3-aminopropyltriethoxysilane (KH-550) in a PDMS/n-hexane solution. Due to the three-dimensional porous skeleton structure of the sponge and the low surface energy coating on the surface, the as-prepared k-HNTs@MS2-1 exhibited outstanding superhydrophobicity (WCA > 155°), high oil absorption capacity (18.4-37.0 g g-1), and excellent separation efficiency (>99.2%) for various oil-water mixtures. Notably, the modified sponge can use the photothermal effect to rapidly heat up and reduce the viscosity of crude oil. This enabled k-HNTs@MS2-1 to absorb more than 8 times its own weight (8.9 g g-1) of crude oil under simulated sunlight illumination of 1.0 sun (1.0 kW m-2). This work might offer a multifunctional solution for oil-water separation and cleaning up large-area viscous crude oil spills, leveraging the unique combination of superhydrophobicity, high oil absorption capacity, and photothermal conversion properties.