LED illumination-assisted activation of peroxydisulfate by heterogeneous Cu₂S under alkaline condition for efficient...

The copper-based materials were considered as promising catalysts for the activation of peroxydisulfate (PDS), but the study on the Cu₂S-activated PDS under LED illumination and alkaline condition was little reported. In this work, Cu₂S, a simple and readily available heterogeneous catalyst, was employed to enhance the activation of PDS under alkaline condition through LED illumination. The results indicated that under LED illumination, the degradation rate of tetracycline (TC) during the first 15 min was 3.55 times higher than that of the darkness. A series of important influencing factors were optimized, including anions, humic acid and complex water matrices. The results showed that the Cu₂S/PDS/LED system exhibited excellent adaptability. Besides, the Cu₂S maintained a good stability. The quenching experiments and electron spin resonance analysis demonstrated that the electron transfer and singlet oxygen were two primary pathways for the degradation of TC, and also other species such as sulfate and hydroxyl radicals played important roles. Furthermore, X-ray photoelectron spectroscopy characterization and a series of experiments confirmed that the Cu⁺ was the primary catalytic active sites, while the reductive sulfur species could directly activate PDS and accelerate the circulation of Cu²⁺/Cu⁺. The toxicity test proved that the toxicity of TC was decreased after the degradation. This study not only highlighted the potential of the Cu₂S/PDS/LED system for efficient TC degradation under alkaline condition but also provided new insight for the development of Cu-based catalytic technology.