Melamine modified POM@MOF composites (WCo@C) for enhanced activation of peroxymonosulfate to efficiently degrade tetracycline

Abstract

Tetracycline (TC) antibiotics in aquatic environments pose severe ecological and health risks due to their difficult biodegradability and environmental accumulation. Persulfate-based advanced oxidation process (PS-AOP) has been proven to be a promising method for TC degradation in wastewater treatment but requires efficient, stable catalysts. Herein, three melamine-modified POM@MOF composites WCo@C-1, WCo@C-5 and WCo@C-10 (WCo-PMOFs and melamine in mass ratios of 1:1, 1:5, and1:10, respectively) were synthesized by calcining a mixture of WCo-PMOFs and melamine, which were used as catalysts for peroxymonosulfate (PMS) activation to degrade TC efficiently. The results demonstrated that the TC degradation rate by WCo @ C-10 activated persulfate (PMS) reached 95.83 % within 2 h superior to that of WCo@C-1 and WCo@C-5 under the same experimental conditions. Notably, the WCo@C-10/PMS system exhibited exceptional cycling stability, maintaining a degradation efficiency of 83.51 % even after four consecutive cycles. The X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS) characterization results indicate that the WCo@C-10 composite material exhibits outstanding catalytic performance. This characteristic is mainly attributed to the significant improvement in the material's dispersion and its having the smallest impedance arc radius among a series of materials, which reflects a lower charge transfer resistance and excellent electrical conductivity. These characteristics synergistically promote the efficient conversion of Co(III) to Co(II). The quenching experiment combined with electron paramagnetic resonance (EPR) analysis confirmed that superoxide radicals (O₂^·-) and singlet oxygen (¹O₂) are the main reactive oxygen species in this system. This study provides a new idea for designing efficient PMS-based advanced oxidation systems.