Synthesis of novel zeolite-supported zinc-cobalt bimetallic catalyst by co-precipitation-calcination method for efficient activation of persulfate to degrade tetracycline hydrochloride

Abstract

Addressing the challenges posed by the high cost and limited efficiency of traditional Chinese medicine wastewater treatment, the development of a cost-effective and highly efficient catalyst for activating persulfate (PMS) to degrade organic pollutants holds significant practical importance. This research successfully synthesized a zinc-cobalt bimetallic catalyst supported on sepiolite (Zn-Co@SEP). The verification was performed using various characterization techniques, including Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), and X-ray Photoelectron Spectroscopy (XPS). XRD and SEM results both indicate that Zn-Co@SEP has excellent crystallinity, with active metal particles uniformly distributed on the surface of sepiolite nanofibers and consistent particle size. Additionally, the BET method determined the specific surface area of Zn-Co@SEP to be 5.533 m²/g. The introduction of sepiolite as a carrier provided additional active sites, facilitating the redox cycling of Co²⁺/Co³⁺ and Zn²⁺/Zn³⁺, which continuously generated reactive species. Zn-Co@SEP exhibited remarkable catalytic activity towards PMS, achieving a degradation efficiency of over 93% for TC (50 mg/L) within just 30 min in the Zn-Co@SEP/PMS system. The study systematically investigated the influence of Zn-Co@SEP dosage, PMS dosage, TC concentration, pH, and temperature on the degradation efficiency of the catalytic system. Notably, the Zn-Co@SEP/PMS system maintained high degradation rates for TC across a wide pH range (3–11) and demonstrated robust stability and recyclability, retaining a degradation rate of 89.56% after four cycles of reuse. Further experimental evidence from free radical quenching studies, electron paramagnetic resonance (EPR) experiments, and oxidative capacity potential (OCPT) results underscored the involvement of multiple radicals (¹O₂, SO₄⁻•, O₂⁻•, •OH) and electron transfer pathways in promoting TC degradation. In conclusion, this research contributes new insights into the synthesis of efficient PMS catalysts tailored for the degradation of antibiotic wastewater, addressing a critical need in environmental remediation.