Elucidation of degradation mechanism of reactive blue 171 dye by ceric ammonium nitrate

Abstract

Oxidative degradation of azo chromophore based C. I. Reactive Blue 171 dye having recalcitrant triazine and naphthalene rings in the structure was attempted using ceric ammonium nitrate (CAN) as an oxidant. The extent of decolorization was evaluated, which was found to be maximum (93.1%) at pH 6.5 and CAN dosage 0.19 mM for 50 mg/L dye solution in 1 h. The COD removal was 30.9%. The kinetic study of dye degradation exhibited pseudo-firstorder kinetics. The effect of temperature was described by the Arrhenius equation and the activation energy was found to be 33.8 kJ/mol. The intermediates formed by the CAN treatment were analyzed by TLC, FTIR and HPLC, which indicated the breaking of bonds of the dye. GC/MS analysis indicated formation of smaller sulfonate fragments by azo bond cleavage. The degradation pathway for the dye pollutant has been predicted based on the characterization of the degradation products formed. Phytotoxicity, as analyzed by ANOVA, indicated results comparable with distilled water, revealing extensive reduction in toxicity of the dye upon CAN treatment. Thus, oxidative treatment with CAN gives effective decolorization, partial mineralization and extensive reduction in the toxicity of the dye RB 171, which allows safe reuse of the treated dye solution for irrigation purpose.