High-activity carrier-based catalysts from iron tailings: activating peroxymonosulfate for tetracycline hydrochloride degradation—the link between active sites and pollutant degradation

Abstract

This study focuses on overcoming the obstacles encountered during peroxymonosulfate (PMS) activation utilizing iron ore residues. The passive constituents within these residues frequently obscure the reactive elements, consequently diminishing PMS activation performance. Conventional enhancement techniques employ alkaline extraction for inert component elimination and thermal treatment for structural modification, typically yielding less than a twofold augmentation in active component concentration. By applying a “reverse leaching-carrier reconstruction” strategy, we developed the MFT@0.02Co catalyst through a modified sol–gel-calcination process with citric acid. This method extracts active components from iron tailings and uses residual inert components as carriers. The MFT@0.02Co composite catalyst has a porous structure and high specific surface area (BET surface area increased 16.87 times), with Co₂FeO₄ as the active component, enhancing PMS activation and reactive oxygen species (ROS) generation. It achieved 96.29% tetracycline hydrochloride (TC) degradation within 30 minutes and retained over 83% efficiency after five cycles. Co serves as the active center for breaking the O–O bonds in PMS to generate sulfate radicals (SO₄˙⁻), hydroxyl radicals (˙OH), and superoxide radicals (O₂˙⁻). Fe replenishes electrons lost by Co during this process. Trace elements like Ca, Mg, and Ti create oxygen vacancies during calcination, boosting singlet oxygen (¹O₂) production. A 10 g granular MFT@0.02Co catalyst, mixed with water glass (Na₂SiO₃) and biochar, maintained over 74% TC degradation efficiency in a fixed-bed reactor after treating 20 L of wastewater. This study provides a cost-effective and eco-friendly solution for industrial PMS-based advanced oxidation processes.