Mechanism research for degradation of azo dying wastewater based on persulfate activated by sulphite
For the advanced treatment of azo dyeing wastewater, a novel advanced oxidation technology was studied for the the production of active species based on persulfate activated by sulfite using methyl orange (MO) as the target pollutant, and its activation mechanism, oxidation theory and kinetic were analyzed. Through the degradation comparison of the- -22 , S2O8, SO3three systems and ESR and other technical characterization, it is revealed that persulfate can be activated by sulfite significantly producing sulfate radicals to destroy the conjugated system of MO azo double bond, which has a better decolorization and degradation effects. The effects of the molar ratio of sulfite to persulfate, dosage of persulfate, initial pH on the degradation of MO were investigated. The results showed that the percent removal rate of MO reached 96.1% under the conditions: the initial pH of 3.0, the molar ratio of sulfite to persulfate of 1:1, the dosage of persulfate of 20mmol/L at the reaction time of 300min. It is further found that the system has a wide range of adaptation to the initial pH (3.0~11.0). The response surface based on Box-behnken model was simulated and the analysis of variance was two times the response surface model up to significant level, contributing factor on the degradation of MO as follows: initial dosage of persulfate > pH value >molar ratio. The oxidation process analyzed by kinetics under the different initial concentrations was- -22 SO3 /S2O8-4 found that it fits well perso second-order reaction kinetics. The reaction kinetic constants vary from 1.8212×10 ~-2.4649×10-41 min. On the other hand, the increasing of temperature can promote the removal of MO, according to the perso second-order reaction rate constants at different temperatures were calculated Arrhenius activation energy Eaoxidation process (44.9kJ/mol), its value is relatively low compared with the conventional metal activation method, which reveals it has a potential commercial value in the treatment of toxic and harmful industrial organic wastewater.
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