Spunlace Cotton Nonwoven-Reinforced Sodium Alginate/Bamboo Charcoal Photothermal Hydrogel Evaporator for Solar-Driven Water Purification

Solar-driven interfacial evaporation offers a low-energy and sustainable route for seawater desalination and the purification of complex water matrices. However, freestanding hydrogel evaporators often suffer from insufficient mechanical robustness and interfacial salt accumulation under high-salinity conditions. Herein, a spunlace cotton nonwoven/sodium alginate/bamboo charcoal (SC/SA/BC) composite interfacial evaporator was fabricated through a facile impregnation–ionic crosslinking strategy, using a spunlace cotton nonwoven (SC) as the reinforcing scaffold, sodium alginate (SA) as the hydrophilic hydrogel matrix, and bamboo charcoal powder (BC) as the photothermal component. The Ca2+-crosslinked SA network immobilized the bamboo charcoal particles and formed continuous hydrated mass-transport pathways, while the spunlace fibrous network provided capillary water-supply channels and robust mechanical support. Consequently, SC/SA/BC exhibited substantially improved mechanical performance compared with the freestanding SA/BC hydrogel. Under 1 sun irradiation using a 3.5 wt% NaCl solution, SC/SA/BC achieved an evaporation rate of approximately 1.80 kg m−2 h−1 and maintained stable performance during 8 h of continuous operation. The evaporation–condensation process markedly reduced the concentrations of major ions in natural seawater and effectively retained nonvolatile dyes. Through the synergistic integration of a spunlace fibrous scaffold, a hydrated hydrogel network, and a bamboo-charcoal-based photothermal component, the proposed evaporator simultaneously achieved mechanical reinforcement, sustained water supply, efficient photothermal conversion, and salt-tolerant operation. This work provides a promising strategy for constructing structurally stable and readily fabricated solar interfacial evaporation materials.