Structurally integrated lignin-derived biochar/CuFeO2 aerogel for salt-resistant solar-driven interfacial evaporation and wastewater purification

The growing scarcity of freshwater demands sustainable and efficient purification technologies. Although solar-driven interfacial evaporation offers a low-energy solution, existing photothermal materials frequently suffer from limited light absorption, salt accumulation, and limited functionality. To address these challenges, we designed and fabricated a bifunctional bilayer aerogel evaporator using lignin-derived biochar and cellulose. The fabricated evaporator comprised a bottom hydrophilic cellulose aerogel for efficient water transport and a top carbonized lignin layer, which demonstrated broad-spectrum light absorption (>89 %) and effective solar-to-thermal conversion. Furthermore, CuFeO 2 photocatalysts were integrated onto the biochar via hydrothermal synthesis, endowing the evaporator with pollutant degradation capability. This performance is attributed to the strong interfacial electron transfer between the multi-metal redox cycle and the carbon carrier. Under 1 kW m −2 irradiation, the device achieved a 2.19 kg m −2 h −1 evaporation rate and 94.52 % solar-to-vapor efficiency, alongside robust salt resistance and a 78.4 % tetracycline degradation rate. Outdoor tests confirmed that the evaporator retained a high evaporation rate of 2.06 kg m −2 h −1 and degraded 92.1 % of pollutants in wastewater under actual, low-intensity sunlight, thereby underscoring its practical potential. This work therefore presents an integrated design that offers a promising strategy for efficient solar water purification and wastewater treatment.