Enhancement of solar water evaporation in copper-sodium humate/SA/PAM hydrogels via an environmental heat field

Photothermal 3D hydrogels have shown great potential for solar-driven desalination. In this study, an integrated 3D photothermal hydrogel evaporator was developed to enhance evaporation performance by leveraging a solar-induced environmental heat field and a concave evaporation surface. The photothermal hydrogel matrix was fabricated by incorporating sodium humate-based photothermal particles (synthesized through the chelation of sodium humate and Cu 2+ ) into a sodium alginate/polyacrylamide hydrogel network. The resulting 3D hydrogel evaporator, featuring a tree-ring structure, achieved a stable evaporation rate of 2.23 kg m −2  h −1 in deionized water for 3 h under one-sun irradiation and demonstrated robust performance in various water bodies, including strong brine and sewage. To further enhance energy input, a commercial photothermal enclosure was integrated to create a surrounding heat field under sunlight. By combining energy from the photothermal particles and the solar-induced heat field, the evaporator with a concave evaporation surface achieved an exceptional evaporation rate of 3.69 kg m −2  h −1 under one-sun irradiation, corresponding to a theoretical solar energy utilization efficiency of 193 %, representing a 65 % improvement compared to pre-integration levels. This work presents a novel strategy for designing high-efficiency solar evaporators, offering significant advancements in sustainable desalination technologies.