Comparison of azo dye AR88 degradation efficiency using various oxidant systems

Abstract

The degradation and mineralization of azo dyes, Acid Red 88 (AR88), were studied by several oxidant methods, including UV, H2O2, O3, UV/O3, UV/H2O2, O3/H2O2, and UV/O3/H2O2, and the production yields of the hydroxyl radicals (•OH) in each oxidation process were also determined. The results showed it could not produce a perceptible of •OH using single UV, H2O2, or O3 method; however, the combined ones involving O3, i.e. O3/H2O2, UV/O3, UV/O3/H2O2, all showed high generation of •OH, which resulted in good degradation performance of AR88. Among the seven oxidation methods, UV/O3/H2O2 was proved to be the best for generation of •OH with an average generation rate up to 1.13 mg L−1 min−1 in 30 min and also the most effective system for degradation and mineralization of AR88 with a total organic carbon (TOC) removal efficiency of 88% in 30 min after reaction. It was found that the pH value decreased as the increase of TOC and AR88 removal efficiencies during the mineralization process. The degradation intermediates including benzene, naphthalene, naphthalene sulfonic acid, and phthalic acid were detected using gas chromatography–mass spectrometry.