Degradation Of Methyl Orange Wastewater By Hydroxyl Radical And Ozone

The discharge of textile printing and dyeing industrial wastewater is increasing year by year in the total discharge of industrial wastewater around the country. The annual discharge of printing and dyeing wastewater could reach to 2,300,000,000 t to 3,000,000,000 t according to the investigation into the first national sources of pollution discharge coefficient production in 2007. Azo dyes account for the majority of textile production, and have been in widespread use in the textile, food, paper making, printing, leather and cosmetic industries. There are azo refractory organics in dyeing wastewater which are intractable complex polluted wastewater. They can cause mutation, cancerization and be serious harm to human health, if discharged directly into receiving waters. At present some of the traditional methods can not treat with the complex wastewater quality, and an effective technology or method is in urgent need to improve treatment efficiency. Therefore, it has an important significance for research of the control technology to seek an effective way of dyeing wastewater treatment.Methyl orange with typical azo structure was used to simulated wastewater. The degradation processes of methyl orange by hydroxyl radical and ozonation were investigated. The effects of pH, initial methyl orange concentration, reaction time, temperature, concentration of hydroxyl radical, concentration of ozone and flow of ozone on the degradation of methyl orange were studied. The ozonation mechanism of methyl orange was analyzed by using UV-Visible, Fourier Transform Infrared Spectroscopy (FTIR) and Gas Chromatography and Mass Spectroscopy (GC-MS). And the reaction mechanism was explored.The results of the degradation efficiency of methyl orange by hydroxyl radical indicated that the initial pH of methyl orange had significant impact on the ratio of degradation. The acidity and increasing the concentration of hydroxyl radical solution are favorable for degradation of methyl orange. The CODCr removal ratio and decolorization ratio of 200 mg/L methyl orange got to 88.9% and 89.9% with in 15 minutes when pH and temperature were 1.5 and 20℃.The results of the degradation efficiency of methyl orange by ozonation declared that the hydroxyl radical inhibitor tert-Butyl alcohol affected the removal of methyl orange to some degree, which proved that the ozone molecule was cooperated with the hydroxyl radical to remove methyl orange in the oxidation process. The decolorization ratio and CODCr removal ratio of 100 mg/L methyl orange got to 99.0% and 52.9% with in 25 minutes when the concentration of ozone was 106 mg/L and the flow of ozone was 60 mL/min. And the chromophores of methyl orange was attacked easily by ozone, the further oxidation of organic matter was relatively difficult. Moreover the decolorization of methyl orange followed the first-order kinetics and R was 0.993. The ozonation mechanism of methyl orange was analyzed by using UV-Visible, Fourier Transform Infrared Spectroscopy (FTIR) and Gas Chromatography and Mass Spectroscopy (GC-MS), which indicated that the dye molecules were oxidized and transformed into phenol, aldehyde, quinone, acid and amide, eventually into H2O and CO2.