Cost-Effective multifunctional bilayer structural hydrogel evaporator for stable solar desalination and wastewater treatment

Solar-driven interfacial evaporation (SIE) has the advantages of zero-carbon and convenient operation, and has a wide range of applications in desalination and brine concentration. SIE using hydrogels can effectively break the thermodynamic evaporation limit of pure water. However, most organic hydrogels were difficult to withstand long-term high temperature, high humidity and solar radiation, which seriously restricted their application and popularization. In this work, the solar-driven interfacial hydrogel evaporator with bilayer structure (BSHE) was constructed using the cost-effective natural 1-D inorganic nanofiber minerals (palygorskite) as the main material and carbon nanotube as the photothermal conversion material. A series of BSHEs were synthesized through adjustments to the process parameters and feedstock ratios, and their evaporation performance was investigated to achieve stable water transmission and long-term efficient evaporation. The evaporation rate and efficiency of the BSHE could reach 2.88 kg m-2h- 1 and 97.5 % (1 kW m-2). More importantly, the BSHE could also isolate the transfer of pollutants in the water during evaporation to obtain safe and pure drinking water. BSHE features a cost-effective and streamlined manufacturing procedure, effectively reducing the threshold of product use and providing a new approach to promote large-scale solar water purification and desalination.