Solar-regenerable bio-waste-derived ceramic–carbon aerogel for sustainable tetracycline removal via coupled adsorption–photothermal–photocatalytic processes

Antibiotic-contaminated wastewater requires treatment materials that can remove parent pollutants, promote mineralization, and be recovered and regenerated with limited chemical input. Here, a solar-regenerable bio-waste-derived ceramic–carbon aerogel was fabricated from rice-husk-derived silica and carbon, together with g-C₃N₄-derived nitrogen-containing domains, through sol–gel assembly, freeze-drying, and carbonization. The optimized ceramic–carbon aerogel (CCA-3) exhibited a hierarchical porous structure with a BET surface area of 512 ± 15 m² g⁻¹ , a pore volume of 1.18 ± 0.04 cm³ g⁻¹ , a porosity of approximately 97.8%, and a thermal conductivity of 0.028 W m⁻¹ K⁻¹ . CCA-3 showed an experimental equilibrium adsorption capacity of approximately 278 mg g⁻¹ , while nonlinear Langmuir fitting gave a maximum capacity of 328.4 ± 15.2 mg g⁻¹ . Under simulated solar irradiation, CCA-3 achieved 94.6% irradiation-stage aqueous tetracycline disappearance within 90 min and approximately 65% total organic carbon removal after 120 min. The combined scavenger, oxygen-controlled, ESR, photophysical, and electrochemical results were consistent with contributions from O₂•⁻, photogenerated holes, interfacial charge extraction, and localized photothermal heating. In a simulated hospital-effluent matrix, approximately 74% irradiation-stage TC removal was retained. After ten adsorption–irradiation cycles, TC removal decreased from approximately 94.5–84.0%, while the aerogel retained 96.8% of its initial mass and 86.8% of its compressive stress at 10% strain. These results demonstrate the potential of CCA-3 as a recoverable and solar-assisted platform for coupled adsorption, pollutant transformation, and thermal management.