Statistical Evaluation of UV/TiO2/H2O2 and Fe2+/H2O2 Process for the Treatment of Coloured Wastewater; A Comparative Study

I. Grčić, D. Vujević and N. Koprivanac

Abstract
In this work, two types of advanced oxidation processes; photocatalytic oxidation, UV/TiO2/H2O2 and classic Fenton oxidation, Fe2+/H2O2, have been applied for the treatment of a model wastewater containing reactive azo dyes, C.I. Reactive Violet 2 (RV2) and C.I. Reactive Yellow 3 (RY3). In order to evaluate the effect of the initial concentration of catalysts, γ(TiO2) or [Fe2+], initial concentration of oxidant, [H2O2] or the initial oxidant/catalyst mole ratio [H2O2]/[Fe2+] and pH on apparent mineralization and decolourization rates, a response surface method (RSM) D-optimal design was used. Mineralization was described by pseudo-first-order kinetics with the highest observed rate constants; km,UV = 0.0065 min–1 in the case of UV/TiO2/H2O2 process and km,F = 0.0213 min–1 in the case of Fenton process. A kinetic model describing decolourization on wavelengths of maximum absorbance for studied dyes, λmaxRV2 550 nm, and λmaxRY3 385 nm, was composed of two first-order in-series reactions with corresponding decolourization rates. The effects of each factor on the efficiency of the applied processes were found to be significant.

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Keywords
wastewater treatment, reactive azo dyes, photocatalytic oxidation, Fenton oxidation, response surface method (RSM), D-optimal design