Solar-driven interfacial evaporation-assisted adsorption of Gd (III) using phosphorylated nanocellulose composite hydrogel membranes

Solar interfacial evaporation was coupled with Gd 3+ enrichment and adsorption. • CPM achieved a high evaporation rate of 2.29 kg m −2  h −1 under 1 kW m −2 irradiation. • The membrane showed good salt tolerance and self-cleaning capability. • Phosphate and carboxyl groups enabled selective Gd 3+ capture via Gd O coordination. Efficient purification and resource recovery from wastewater containing low concentrations of rare-earth ions remain challenging for conventional treatment technologies. Solar-driven interfacial evaporation has emerged as a sustainable and promising approach for wastewater treatment. However, its potential for rare-earth ion enrichment and recovery remains largely unexplored. Herein, we developed a phosphorylated nanocellulose/sodium carboxymethyl cellulose/multi-walled carbon nanotube composite hydrogel membrane (CPM) as the multifunctional photothermal material for solar-driven interfacial evaporation-assisted Gd (III) removal and recovery from wastewater. In CPM, multi-walled carbon nanotubes endow the membrane with broadband light absorption and efficient photothermal conversion capability, while phosphorylated nanocellulose and sodium carboxymethyl cellulose jointly construct the hydrophilic layered hydrogel network rich in oxygen-containing coordination sites, including phosphate, carboxyl, and hydroxyl groups, which serve as effective Gd (III)-binding sites. Under one-sun illumination, the CPM evaporator achieved an apparent photothermal conversion efficiency exceeding 120%, a stable water evaporation rate of 2.2 kg m −2  h −1 , and a maximum Gd (III) adsorption capacity of approximately 80 mg g −1 . Moreover, solar irradiation accelerated the adsorption kinetics by driving the interfacial enrichment of Gd (III). This work integrates interfacial evaporation, rare-earth ion enrichment, and in situ adsorption, offering a promising route for the purification and resource recovery of low-concentration rare-earth-containing wastewater. Download: Download high-res image (141KB) Download: Download full-size image