Comparison of azo dye AR88 degradation efficiency using various oxidant systems

The degradation and mineralization of azo dyes, Acid Red 88 (AR88), were studied by several oxidant methods, including UV, H2O2, O-3, UV/O-3, UV/H2O2, O-3/H2O2, and UV/O-3/H2O2, and the production yields of the hydroxyl radicals (center dot OH) in each oxidation process were also determined. The results showed it could not produce a perceptible of center dot OH using single UV, H2O2, or O-3 method; however, the combined ones involving O-3, i.e. O-3/H2O2, UV/O-3, UV/O-3/H2O2, all showed high generation of center dot OH, which resulted in good degradation performance of AR88. Among the seven oxidation methods, UV/O-3/H2O2 was proved to be the best for generation of center dot OH with an average generation rate up to 1.13mgL(-1)min(-1) in 30min and also the most effective system for degradation and mineralization of AR88 with a total organic carbon (TOC) removal efficiency of 88% in 30min 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.