Novel n–n Type CoCr₂O₄/NiFe₂O₄ Heterojunction Photocatalyst: Internal Magnetic Field Control of Photocatalytic Activity, Mechanism Insight and Pathway for Tetracycline Hydrochloride Degradation

Abstract Herein, a series of CoCr₂O₄/wt%NiFe₂O₄(CCO/wt%NFO) composites are successfully synthesized by a simple solution combustion method combined with mechanical grinding techniques. The preparation of CCO/wt%NFO composites result in an estimation of its photocatalysis performance by removing tetracycline hydrochloride (TC) as a model of antibiotic pollutants. The results show that the percentage of NFO by mass have a great influence on the morphology and the photocatalysis performance of CCO/wt%NFO composites. Superior photocatalysis performance is observed in CCO/25%NFO composites prepared at percentage of NFO is 25%. The photocatalyst used with CCO/25%NFO composites result in a removal ratio of 81% for TC. The generation of hydroxyl radical (•OH), superoxide anion radical (•O₂⁻) and holes (h⁺) is largely responsible for degrading TC through photocatalysis in the presence of CCO/wt%NFO composites. The optimal operating conditions involve the initial concentration of TC and pH of TC being 50 mg L⁻¹ and pH = 13, respectively. Furthermore, CCO/wt%NFO is highly reusable and stable during the photocatalytic removal process. The degradation pathway, toxicity, and photocatalytic mechanism of CCO/25%NFO composites for the degradation of TC are extensively examined through mass spectrometry, toxicity analysis, and energy band theory.