Solar-heated mono-domain-structured ferrimagnetic cellulosic sponge fabricated by using bidirectional freeze casting for energy-efficient liquid adsorption

Liquid adsorption has a wide range of industrial and environmental applications. In recent years, interest in liquid adsorption technology that leverages porous materials has surged, primarily driven by these materials’ substantial surface area and adjustable wettability. However, high tortuous structures of conventional porous materials impede the flow of liquids, limiting their applicability in situations requiring rapid liquid adsorption such as oil spill cleanups. This study proposed two strategies for rapid liquid adsorption. We introduced a polydimethylsiloxane (PDMS) wedge to control ice crystal growth by generating a dual temperature gradient. This led to a mono-domain lamellar structure composed of vertically aligned channels. Cubic iron oxide nanoparticles (CION) were also utilized to enhance solar heating, that enabled rapid adsorption, even of high-viscosity liquids, without an external power supply unit for heating sorbents. The application of a solar-heated ferrimagnetic cellulosic sponge with precisely controlled channels facilitates the rapid removal of high-viscosity oils, which have traditionally been challenging for large-scale oil spill cleanups in oceans.