Study On The Oxidative Degradation Of Azo Dyes By Solid Oxidants In Different Activation Systems

In this paper,three kinds of activation systems（Fe（Ⅲ）-OA,Fe（Ⅲ）-EDTA and TAED）were used to catalyze the degradation of azo dye reactive red 195 by four oxidants（H₂O₂,SPS,SPC,SPB）respectively.The properties of the activation system,the concentration of oxidant,reaction conditions（such as temperature,pH value and irradiation）,and the effects of inorganic salts and surfactants on the degradation of dyes were mainly investigated.The mechanism of oxidation degradation of dyes in the above systems was analyzed by means of the determination of total organic carbon（TOC）,UV-Vis spectroscopy,ESR and free radical identification experiments.Finally,the degradation of azo dyes by oxidants in different activation systems was compared.The results showed that the three activation systems showed significant activation to the four oxidants,and accelerated the degradation of the dye.For Fe（Ⅲ）-OA and Fe（Ⅲ）-EDTA systems,the degradation of dyes could be promoted by increasing the concentration of oxidants,oxalic acid or EDTA and Fe³⁺,raising the reaction temperature or introducing irradiation.However,both inorganic salts and surfactants inhibit the degradation of dyes.The TAED system ould activate the four kinds of oxidants to azo dyes oxidation degradation reaction.The increase of TAED concentration,temperature and pH value could obviously promote the degradation reaction of dyes.However,it had little dependence on the irradiation and had good activation under alkaline conditions.The activation mechanism of TAED system was significantly different from that of Fe（Ⅲ）-OA and Fe（Ⅲ）-EDTA systems.TAED system was difficult to produce free radicals with high oxidation resistance to dyes,which limited the mineralization of dyes.The Fe（Ⅲ）-OA and Fe（Ⅲ）-EDTA systems exhibited better activation than TAED system under the conditions of radiation and acidity,while the TAED system was better in the absence of radiation and alkaline conditions.What’s more,three kinds of solid oxidants could exhibit the same oxidation degradation ability as H₂O₂ in the three activation systems.They were safer and easier to use,which maked it possible to replace H₂O₂.