Sustainable lignocellulosic-based sponge with Janus salt-tolerant structure for efficient solar steam generation

Solar Vapor Generation (SVG) is a new green production technology that is gaining increasing attention for obtaining fresh water from seawater or wastewater. Currently, the evaporator substrates face challenges such as complex fabrication processes, high cost, and poor biodegradability. Lignocellulosic sponge (LS), as a sustainable material, exhibits characteristics such as hydrophilicity, excellent insulation properties, lightweight nature, and low cost. It is considered a highly promising material for evaporators. In this study, LS was modified to create an efficient evaporator with excellent salt resistance. The polyvinyl alcohol/carbon black (PVA/CB) gel-based photothermal coating was introduced to enhance the water evaporation rate significantly on the surface of the lignocellulosic sponge. Subsequently, a polydimethylsiloxane (PDMS) coating was sprayed on the interfacial steam generator surface to form a hydrophobic layer, effectively resisting salt accumulation on the evaporator surface. Simultaneously, the incorporation of degreased cotton as a one-dimensional water pathway enhanced the salt ion backflow and prevented salt crystallization at the hydrophilic/hydrophobic interface. The resulting porous sponge-based photothermal evaporator (PCP-LS) achieved a high evaporation rate of up to 3.2 kg m⁻² h⁻¹ and demonstrated stable operation in high-concentration saltwater (20wt%). PCP-LS, as a cost-effective, easily fabricated, salt-tolerant, and environmentally friendly solar evaporator, holds great potential in seawater/wastewater treatment.