Green Upcycling of Crop Residue into Activated Carbon in Designing Photothermal/Adsorptive Membrane for Solar-Driven Desalination and Simultaneous Volatile Organic Compound Removal
Lokesh Kumar Rathore, Vishal Nagar, Gopika Pranghol, Ashok Bera
Abstract
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.