Microwave-induced efficient degradation of tetracycline using magnetic ZnFe₂O₄ nanoparticles anchored on C/SiO₂

In response to the ecological and health risks posed by Tetracycline Hydrochloride (TCH) residues in the environment, this study develops a microwave-induced catalytic system using ZnFe₂O₄/C/SiO₂ nanocomposites for efficient TCH degradation. The composites were prepared by anchoring ZnFe₂O₄ nanoparticles onto a rice husk-derived C/SiO₂ support, leveraging both the thermal and non-thermal effects of microwave irradiation to synergistically enhance catalytic performance. Our results showed that the porous structure of C/SiO₂ effectively dispersed ZnFe₂O₄ nanoparticles, reduced agglomeration, and significantly improved microwave absorption by balancing dielectric loss and magnetic loss, with a reflection loss reaching -41.97 dB. Under optimized conditions (microwave power: 1000 W, catalyst dosage: 100 mg, reaction time: 21 min), the degradation rate of 60 ppm TCH exceeded 99%. Free radical trapping and EPR analyses confirmed that holes (h⁺) are the dominant active species responsible for degradation, and oxygen vacancies promote electron-hole separation. Recycling experiments showed that the catalyst maintained a degradation efficiency of over 75% after four cycles, indicating good stability. This study offers an efficient and sustainable microwave catalytic technology for organic wastewater treatment, with the added environmental benefit of utilizing agricultural waste.