Development of an Anti-Organic Fouling Photothermal Membrane for Sustainable Freshwater Generation from Wastewater

Passive freshwater generation via photothermal membranes represents a sustainable and eco-friendly solution for the water crisis. Herein, we describe a unique method for producing organic fouling-resistant Ag-CNTs/PVDF photothermal membranes using CNTs (multi-walled Carbon Nanotubes) decorated with silver (Ag) nanoparticles deposited on the hydrophilic polyvinylidene difluoride (PVDF) substrate via vacuum filtration. CNTs were decorated with different loads of silver nanoparticles via a wet-impregnation technique. The prepared Ag-CNTs nanocomposites were fully characterized, and the fabricated anti-fouling Ag-CNTs/PVDF photothermal membranes with different loadings of Ag-CNTs nanocomposite were investigated for their surface morphology, roughness, light absorption, surface temperature, contact angle measurement, water evaporation, and antifouling performances. The optimized Ag-CNTs/PVDF photothermal membrane achieved 95% solar light absorption at a surface temperature of 82 ℃ ± 0.5 with significant hydrophobic behavior due to the plasmonic impact of silver nanoparticles. The evaporation rate reached 1.2 kg.m^− 2.h^− 1 using 3.5% NaCl solution (simulated to seawater) with a solar thermal conversion efficiency of 75.6% ± 2.0. The optimized Ag-CNTs/PVDF photothermal membrane showed relative stability in the evaporation rate compared to other membranes using 100 mg.L^− 1 humic acid solution for 600 min after one week under natural evaporation with the same solution. The developed membrane showed an effective water evaporation rate with organic matter resistance that makes it highly recommended for application to any water source with the capability of resisting harsh conditions of the environment and with continuous freshwater generation.