Green Upcycling of Crop Residue into Activated Carbon in Designing Photothermal/Adsorptive Membrane for Solar-Driven Desalination and Simultaneous Volatile Organic Compound Removal

The growing freshwater scarcity and decline in air quality pose serious threats to the natural biosphere and human well-being. Developing functional materials for water purification through upcycling agricultural waste like crop residues, which are often burned in open fields and cause air pollution, offers an eco-friendly and sustainable solution for the global freshwater crisis. Solar-driven interfacial water evaporation (SIWE) presents a green and efficient method for freshwater production from seawater/wastewater. However, the presence of volatile organic compounds (VOCs) in wastewater limits its practicality as they co-evaporate with water molecules, leading to secondary pollution. Herein, we report a three-layered photothermal/adsorptive membrane (PCP-m), in which crop residue-derived activated carbon (CRAC) is sandwiched between a PVDF support and a PVA hydrogel layer, exhibiting desalination and simultaneous removal of VOCs like phenol, p-nitrophenol, and p-cresol. Under 1 sun illumination, PCP-m achieves an evaporation efficiency of 86.4% and maintains it even at higher intensities. The PVA hydrogel layer in PCP-m promotes mechanical strength, leaching resistance, and stability in harsh chemical conditions while ensuring even water distribution for Marangoni-driven site-specific salt rejection, enabling effective long-term desalination. Moreover, the superior VOC capturing capacity of CRAC enables PCP-m to achieve exceptional VOC removal efficiency (>95%) for phenol, even at high concentrations (100 mg L^-1) or higher solar intensity (3 kW m^-2). This work presents an efficient and environmentally conscious strategy for seawater desalination and simultaneous VOC removal through SIWE.