Synergistic adsorption and photocatalytic degradation of tetracycline by a functionalized Fe3O4/CuWO4/biochar Z-scheme composite

The effective removal of tetracycline (TC) from aquatic environments remains a critical challenge due to its persistence and ecological risks. In this study, a novel magnetic photocatalyst (MCB) was synthesized by loading Fe 3 O 4 and CuWO 4 onto biochar, aiming to integrate adsorption enrichment with Z-scheme visible-light photocatalysis. The biochar (BC) framework exhibited a high specific surface area (117.70 m 2  g −1 ), enabling efficient TC capture with an adsorption rate of 81.19 % and a Langmuir-derived maximum capacity of 225.28 mg g −1 at 35 °C. Kinetic modeling revealed a pseudo-second-order chemisorption mechanism, while thermodynamic analysis confirmed that the adsorption process was spontaneous and endothermic. The Z-scheme heterojunction formed between CuWO 4 and Fe 3 O 4 effectively promoted photogenerated charge carrier separation and enhanced redox potential, facilitating the production of reactive species. The incorporation of BC introduces additional electron transfer-active sites, thereby markedly enhancing the charge transport rate. Electron spin resonance and scavenger experiments verified h + , •OH and •O 2 − as the dominant oxidative agents. As a result, 0.6-MCB achieved a total TC removal efficiency of 92.83 % and a TOC removal rate of 85.57 %, indicating strong mineralization performance. After five cycles, it maintained 79.45 % removal efficiency, demonstrating good recyclability and structural stability. Toxicity analysis demonstrated that the degradation process significantly reduces both the toxicity and teratogenicity of TC and its intermediates, thereby underscoring the environmental safety and practical applicability of 0.6-MCB. This work provides a promising material platform for sustainable antibiotic removal in wastewater treatment.