Study On Influencing Factors And Kinetics Of Ultrasonic Activated Persulfate Degradation Of Methyl Orange

Azo dyes are widely used in dyeing,leather and textile industries.Azo dyes have the advantages of low cost and good coloring in the production process.But the discharge of dye wastewater was harmful to the environment,and it may even cause cancer and distortion of organisms or other adverse consequences.Azo dyes have excellent light resistance,it can inhibit the growth of bacteria,and the structure was very stable.The mechanism of the traditional advanced oxidation process was to degrade organics by the generated oxidation species（hydroxyl radicals）.Hydroxyl radicals has strong oxidizability and can degrade pollutants without selectivity.With the deepening of research,The researchers found that sulfate radical（SO₄^-·）has a longer existence time than hydroxyl radical,and more importantly,the redox potential of SO₄^-·is not lower than·OH.Therefore,the advanced oxidation technology with sulfate radical as oxidation species has been widely concerned.In the experiment,methyl orange of azo dye was taken as the research object,and ultrasound activated persulfate was used to oxidize and degrade methyl orange,and the effect of thermal assistance on the degradation of methyl orange was analyzed.The effects of various factors on the degradation of methyl orange was studied,and the experimental results was analyzed,and the main reasons for the degradation of methyl orange were studied.The main results of this experiment are as follows:（1）Adding PS of 3 mmol/L to the reaction system to degrade methyl orange,the degradation rate of methyl orange at 60 min was 52.22%.When the ultrasound intensity was 0.54 W/cm²,the degradation rate of methyl orange was 16.7%.The degradation effect of methyl orange by US alone was not significant,but the degradation rate of methyl orange with the increase of ultrasonic power（0.22～0.54 W/cm²）and the decrease of initial concentration of methyl orange（40～10 mg/L）was improved.（2）In US/PS system,when the initial concentration of methyl orange solution was40 mg/L,the concentration of sodium persulfate（PS）was 3 mmol/L,and the ultrasound intensity was 0.54 W/cm²,the degradation rate of methyl orange reached 87.38%,which were 70.68%and 35.16%higher than that for US and PS alone,and synergy index S=2.05.It was found that the degradation rates of methyl orange increased with the increase of ultrasound intensity（0.22～0.54 W/cm²）and persulfate concentration（0.5～3 mmol/L）,and the degradation rates of methyl orange was better in acid condition.Under the same conditions,the degradation of TOC was worse than that of methyl orange.The addition of radical scavenger for methanol and tert-butanol could reduce the degradation rates of methyl orange.Besides,the presence of methanol had a more obvious inhibition effect than that of tert-butanol on methyl orange,indicating that the degradation of methyl orange was mainly caused by sulfate radicals in the combined US/PS process.（3）The experimental results show that heat can assist US/PS system to improve the degradation rate of methyl orange.The degradation rates of methyl orange can be improved more significantly by the combined process.When the initial concentration of methyl orange was 40 mg/L,the concentration of sodium persulfate（PS）was 3 mmol/L,the ultrasonic intensity was 0.54 W/cm²,and the temperature of the system was maintained at 60℃in a circulating water bath.When treated for 60 min,the degradation rate of methyl orange was 96.08%.Thermal assistance can shorten the reaction time,reduce the amount of persulfate and reduce the energy loss.