Degradation pathways of crystal violet by Fenton and Fenton-like systems: Condition optimization and intermediate separation and identification

摘要

The main advantage of Fenton's reagent (FR) over other ~·OH systems is its simplicity. FR has the potential for widespread use in treating wastewater, but compared to other ~·OH systems, little information on the dye degradation pathways of FR exists. The degradation of crystal violet (CV), a triphenylmethane dye, by FR was determined as a function of reagent concentration and ratio and pH in the batch treatment. The experimental results showed the optimum Fe~(2+)/H_2O_2 ratio to be 0.5mM:50mM and the optimum Fe~(3+)/H_2O_2 ratio to be 1 mM:50mM. Optimal pH was about 3. To obtain a better understanding of the mechanistic details of Fenton reagent's degradation of CV dye, the intermediates of the process were separated, identified, and characterized by HPLC-PDA-ESI-MS and GC-MS techniques in this study. Indications were that the probable degradation pathways were N-de-methylation and cleavage of the conjugated chromophore structure. The intermediates were generated in the order of the reaction time and relative concentration, indicating that the N-de-methylation degradation of CV dye is a major reaction pathway. The reaction mechanisms proposed in this research should prove useful for future application of the technology to the decolorization of dyes.