Solar Evaporation-Induced Mass-Transfer Enhancement in a Biomass-Derived Dual-Network Aerogel for Selective Enrichment of Rare-Earth Ions

Low-concentration rare-earth industrial wastewater contains low target-ion concentrations and high concentrations of coexisting salts, which limit mass transfer in conventional static adsorption. A biomass-derived dual-network photothermal aerogel (CB@DCP) was developed, and a solar interfacial evaporation-assisted strategy was proposed to intensify mass transfer for selective rare-earth enrichment. CB@DCP comprises carboxymethyl chitosan, oxidized β-cyclodextrin, poly(vinyl alcohol), and carbon black, providing interconnected hierarchical pores, coordination sites, and broadband photothermal conversion. Under 1.0 kW m–2 irradiation, CB@DCP achieved an evaporation rate of 2.19 kg m–2 h–1. Using Nd3+ as a model ion, the dynamic enrichment process achieved an adsorption capacity of approximately 190 mg g–1, compared with 136 mg g–1 under the corresponding static adsorption condition, a 39.7% enhancement. In actual rare-earth industrial wastewater, La3+, Ce3+, Nd3+, and Gd3+ were preferentially enriched, with 85% Gd3+ extraction. These results demonstrate that photothermal evaporation facilitates dynamic rare-earth enrichment by combining evaporation-induced concentration with enhanced ion transport.