Oxidative removal of Fast Green FCF and ponceaux 4R dyes by H2O2/NaHCO3, UV and H2O2/UV processes: A comparative study

Abstract

In this work, we explored the use of reactive oxygen species generated by either bicarbonate activated hydrogen peroxide (BAP), UV and UV/H2O2 system for degradation of triarylmethane dye, Fast Green FCF (FG), and azo dye Ponceau 4R (P4R). The degradation rate constant is supposed to be a pseudo-first-order. By bicarbonate activated peroxide (BAP) system which generates hydroxyl radicals and superoxide anion radical (O2-) able to attack the dyes molecules, in 20 min the conversions ware up to 65% for FG and 50% for P4R, respectively. The most efficient degradation is achieved through UV irradiation in the presence of hydrogen peroxide, where the kinetic constants increase by an order of magnitude for both dyes. The total organic carbon (TOC) data showed that for chemical oxidation of FG, the mineralization degree is 86% instead in the case of P4R, the chemical oxidation with BAP system does not lead to mineralization (mineralization degree is about 5%). In the mixture, the degradation of dyes in the BAP system occurs with higher rates for both dyes; in the photolysis, the degradation of FG is slightly increased in the mixture, while the degradation of P4R is much slower. In the case of the UV/H2O2 system, the degradation of both dyes is slower in the mixture. The results obtained by HPLC-MS led to the identification of some organic intermediates and a plausible reaction mechanism for FG and P4R degradation process was proposed.