Regulating Fe(III) spin state by anchoring iron on titanium dioxide for enhancing photo-Fenton treatment of tetracycline wastewater

Abstract

Tetracycline (TC) wastewater can hardly be treated effectively by conventional processes due to its stable chemical structure and its refractoriness to biodegradation. Photo-Fenton technology based on iron-based catalyst exhibits excellent capacity on organic wastewater treatment, but current iron-based catalyst materials exist crucial problems such as slow regeneration of Fe(II) and low utilization of H2O2. In this study, Fe atom was anchored on TiO2 to regulate the spin state of Fe to prepare a new efficient photo-Fenton material. The results showed that the removal of TC by Fe2O3-TiO2(high spin, HS) can reach 94.7%, while the removal of TC by Fe-TiO2(low spin, LS) was only 83.0%. The Fe2O3-TiO2(HS) maintained high photo-Fenton activity after five cycles, and the TC removal rate still reached 91.8%. Fe2O3-TiO2(HS) had a narrow bandgap and excellent photogenerated charge separation properties, which facilitates the generation of photogenerated charges, improves the electron transfer, and accelerates the redox cycle of Fe(III)/Fe(II). The electrons in the 3d orbital of Fe2O3-TiO2(HS) are more easily to cross the antibonding orbital of the H2O2, which is conducive to the adsorption of H2O2 and generation of ·OH to accelerate TC degradation. This study provides a new photo-Fenton material for the treatment of TC wastewater and offers a new strategy for the development of photo-Fenton.