Dual-functional lignin-encapsulated Zn-O-Fe synergistic chitosan-carbon aerogel spheres for integrated seawater desalination and wastewater treatment

The escalating severity of global water scarcity and pollution necessitates the development of efficient and sustainable treatment technologies. Solar-driven interfacial evaporation presents an environmentally friendly, low-energy solution for both seawater desalination and wastewater treatment. In this study, we introduce a multifunctional integrated spherical evaporator composed of lignin-wrapped ZnFe 2 O 4 /chitosan‑carbon aerogel spheres (ZFO/CLCA), employing renewable chitosan as a three-dimensional flexible framework. By integrating ZnFe 2 O 4 , a visible-light-active semiconductor, with sodium lignosulfonate, known for its excellent photothermal conversion capabilities, we constructed a three-component organic hybrid featuring an in-situ formed hierarchical porous structure through a one-step carbonization process. The resulting ZFO/CLCA material demonstrates a high density of interconnected multiscale pores, a substantial specific surface area, and broad-spectrum absorption (93.48% across 250–2500 nm). Under simulated solar irradiation (1 kW m −2 ), this material exhibits an evaporation rate of 2.33 kg m −2  h −1 and a solar-to-steam conversion efficiency of 94.54%. The distinctive through-hole structure effectively prevents surface salt accumulation in high-salinity environments (3.5–20 wt% NaCl) via concentration-gradient-driven ion reverse diffusion, maintaining excellent long-term stability over 12 h of continuous operation. Importantly, during photothermal evaporation, the material concurrently catalyzes the degradation of organic pollutants, achieving an 87.10% degradation rate of tetracycline (100 mg L −1 ). In the context of real industrial wastewater treatment containing high salt concentrations and antibiotics, the evaporator produces clean effluent that complies with discharge standards. This study highlights a multifunctional spherical carbon aerogel evaporator that integrates efficient photothermal evaporation, salt resistance, and catalytic degradation, thereby, establishing a promising material platform for integrated solar-driven water treatment systems with both scientific significance and practical application potential.