Spectrophotometric determination of hydrogen peroxide in water by oxidative decolorization of azo dyes using Fenton system

In this study, based on the oxidative decolorization of three azo dyes (Orange G (OG), Acid Orange 7 (AO7) and Reactive Black 5 (RB5)) with hydroxyl radicals generated in Fenton system, we have successfully established three types of azo dyes spectrophotometric methods for measuring aqueous hydrogen peroxide (H2O2) concentration. The decolorization extent of OG, AO7 and RB5 at the corresponding characteristic wavelengths of 478 nm, 484 nm and 597 nm are proportion to the concentration of H2O2 in aqueous solutions. Under the selected reaction conditions, three well linear correlations between the depletion of azo dyes and the H2O2 concentration are established in the range of 0.45–175 μmol L−1 of OG, 0.36–120 μmol L−1 of AO7 and 0.44–175 μmol L−1 of RB5, respectively. These proposed spectrophotometric methods are enough accurate to measure low concentrations of H2O2 in practical water samples and monitor the variations of H2O2 concentration during the phenol degradation in the Cu(II)/HCO3−/H2O2 process. [Display omitted] •The methods were based on the oxidative decolorization of azo dyes in Fenton system.•The methods didn't need any difficult or time–consuming operations for H2O2 analysis.•The methods were effective to tolerate the effect of trace reducing agents in water.•The methods were accurate for measuring H2O2 concentration in Fenton-like system.