Tungsten disulfide particles driving ferric ions reduction for the enhancement of calcium peroxide fenton-like reaction

Abstract

The conventional Fenton method is confined to the inefficient Fe3+/Fe2+ cycle in narrow pH range and disproportionation of H2O2. Herein, we utilized powder tungsten disulfide (WS2) as an assistant catalyst to improve high-low valent iron circulation, and calcium peroxide (CaO2) was used to replace H2O2, thus enhanced the oxidization of typical antibiotic metronidazole (MTZ) in water. The degradation ratio of MTZ achieved 94.3 % after 10 min in the system of WS2/Fe3+/CaO2 with optimum conditions (2 mmol/L CaO2, 1.5 mmol/L Fe3+, 1.5 g/L WS2 and initial pH 7), and the reaction rate constants of two stages (quick and slow) were both higher than that of Fe3+/CaO2. Even after five cycles, more than 80 % of MTZ was still degraded, indicating a benign stability of WS2. And the synergetic system could perform quite well within the wide pH range (3–11). X-ray photoelectron spectroscopy analysis suggested that unsaturated S on the exterior of WS2 exposed reductive W4+, thereby promoting the reduction of Fe3+ and H2O2 decomposition. Hydroxyl radicals (⋅OH) was confirmed as the predominant reactive oxygen species (ROS) through electron paramagnetic resonance and quenching tests, which also certified that the addition of WS2 could accelerate ROS production. The degradation intermediates of MTZ were identified by mass spectrometry, and their biotoxicities were evaluated through computational toxicology software. The proposed WS2/Fe3+/CaO2 process exhibited good performance in different water matrix and real waterbodies, proving a promising potential for improved Fenton technology.