Degradation Mechanism of Methylene Blue in a Heterogeneous Fenton-like Reaction Catalyzed by Ferrocene

Abstract

Ferrocene (Fc) was used to catalyze a heterogeneous Fenton reaction for the degradation of methylene blue (MB). The high catalytic activity and stability of Fc in the Fc/Fenton-like system are confirmed. MB removal percentage could still maintain at 99.50% after Fc was successively used for three cycles and only 1.12% of Fc dissolved with 100% discoloration of MB, indicating the good reusability and stability of Fc. The reaction rate can be accelerated by improving the dosage of the catalyst and the temperature, and the degradation of MB was found to follow the pseudo-first-order kinetic model and the activated reaction energy was calculated to be 82.71 kJ/mol. MB was determined to be degraded through three different pathways simultaneously during the Fc/Fenton-like process, forming Cl–, NO3–, SO42–, and lower molecular weight intermediates: C–N and C–S broke to form the previous rarely reported benzothiazole (determined by liquid chromatography–mass spectrometry), C–N broke to form phenol, and -OH and -HSO3 connected to MB.