Efficient degradation of organic pollutants with sodium percarbonate by activation with CuFeS2 prepared from precursors of different valence states

Four chalcopyrite (CuFeS2) catalysts were fabricated by a one-pot hydrothermal method using different copper and iron precursors at different valence states. The prepared CuFeS2 samples were then evaluated for the oxidative degradation of Congo red (CR) using sodium percarbonate (SPC) as the oxidant. The sample of CuFeS2-1, which was prepared from Cu (I) and Fe (II) precursors, exhibited the highest CR removal efficiency of 96.6% among the four CuFeS2 samples. Using CuFeS2-1 as the optimum catalyst, the effects of operation and environmental factors on the removal efficiency of CR were investigated in detail. Mechanism studies showed that CO3•− was the main reactive oxidative species in the reaction process, while O2•− and low-valent sulfur species together promoted the regeneration of Fe (II) and Cu (I) sites on the catalyst. Furthermore, density functional theory (DFT) calculations were used in combination with liquid chromatography-mass spectrometer (LC-MS) to propose the plausible degradation pathway. Finally, toxicity prediction showed that most of the degradation products showed decreased toxicity compared to the parent CR, and toxicity evaluation with Vigna radiata further revealed the declined toxicity.