Persulfate Activation by Zero-Valent Co-Fe Functionalized Reduced Cobalt Ferrite for the Mineralization of Pharmaceuticals in Wastewater

Abstract

A novel reduced cobalt ferrite nanoparticle catalyst (rCoFe2O4) was synthesized via a modified co-precipitation method to enhance persulfate (PS) activation through surface Co⁰/Co²⁺ and Fe⁰/Fe²⁺ redox-active sites. Comprehensive characterization confirmed successful synthesis of the material, which exhibited a well-defined crystalline structure and a high specific surface area. X-ray photoelectron spectroscopy performed before and after reaction indicated that zerovalent cobalt and iron on the catalyst surface contributed to PS activation and reactive species generation. The catalyst achieved rapid doxycycline (Dox) degradation, with a maximum removal efficiency of 96.4% within 2 h, and near-complete mineralization within 6 h. Mineralization was further evaluated using total organic carbon analysis and carbon mass balance, including CO₂ formation. Radical quenching experiments and electron paramagnetic resonance analysis indicated that •OH was the dominant reactive species, while SO₄•⁻ also contributed to Dox degradation. Liquid chromatography-mass spectrometry was used to identify intermediate products and to propose a transformation pathway from initial ringopening reactions to final mineralization. The catalyst also showed good durability, with less than a 10% decline in performance and negligible Co and Fe leaching over five consecutive cycles. Overall, these findings suggest that rCoFe2O4 is a promising heterogeneous catalyst for the treatment of pharmaceutical contaminants in water.