A bionic stem-shaped copper-doped aniline-pyrrole copolymer composite photothermal sponge evaporator for seawater desalination and sewage treatment

Abstract

Sustainable solutions are needed for global freshwater shortages. Solar-driven interfacial water evaporation technology for saltwater desalination and wastewater purification is promising due to its low-carbon and energy-efficient nature. In this study, we develop a high-performance solar evaporator based on a copper nanoparticle (CuNPs)-modified poly (aniline-co-pyrrole)/polyvinyl alcohol (CuNPs@PANI-PPy/PVA) composite sponge. The material consists of a porous polyvinyl alcohol (PVA) sponge substrate composited with a CuNPs@PANI-PPy photothermal layer, which leverages a metal-polymer synergistic effect to overcome the limitations of single-component photothermal materials, including narrow absorption of sunlight and low solar energy utilization efficiency. Moreover, a bionic stem-shaped evaporator structure that does not need to float on the water surface was designed to achieve directional capillary water delivery, ensuring that there is always an adequate water supply at the evaporation interface while preventing heat loss downward due to excessive water supply.The CuNPs@PANI-PPy/PVA sponge achieves an exceptional evaporation rate of 3.84 kg m-2 h-1 with a remarkable energy efficiency of 98.9% under 1 sun irradiation. Furthermore, the evaporator demonstrated outstanding salt resistance; the evaporator maintained a remarkable average evaporation rate of 3.63 kg m-2 h-1 in a 15 wt% NaCl solution. Additionally, the material exhibited excellent purification capabilities for both saline water and organic dye-contaminated wastewater. Therefore, this work proposes a method that combines conductive copolymers with metal nanoparticles to design highly efficient and durable solar photothermal materials, and optimizes the structure of the evaporator based on a bionic stem design, providing a feasible approach for scalable practical desalination projects.