Hydrogen peroxide is colorless transparent liquid and a strong oxidizer. But because it is not stable, the actual amount is greater than theoretical dosage. When it’s used alone, the degradation effect is often not ideal. Methylene blue is a kind of aromatic heterocyclic compounds. It’s soluble in water, ethanol and insoluble in ether. Aqueous solution is blue in the oxidizing environment, but in reducing agent of zinc, ammonia water it can be restored into a colorless form. Methylene blue is widely used in chemical indicator, hemp, silk fabric, paper, bamboo, wood dyeing and the shading. It can also be used in the manufacture of ink and dyeing of organisms, bacteria and organization. At the same time, the methylene blue also has oxidability and its degradation is more difficult.

 

Based on the difficult degradation of methylene blue solution as the simulated printing and dyeing wastewater, this article discussed sodium tungstate-hydrogen peroxide system catalytic oxidation and degradation of methylene blue. The experiment can be divided into the following steps:

1. Use deionized water to prepare 0.01 mol/L sodium tungstate solution and 10 mg/L of methylene blue simulated printing and dyeing wastewater respectively. 

2. Take 100 ml methylene blue solution to a beaker, adding suitable amount of sodium tungstate solution. After sulfuric acid or sodium hydroxide solution adjusting the pH of the solution, slowly stir it in constant temperature magnetic stirrer. 

3. When reaching the set temperature, add a certain amount of hydrogen peroxide solution. Start the time and take samples in interval time. Test its absorbance in 660 mm of methylene blue maximum absorption wavelength.

4. Water samples before and after treatment were taken photometry and ultraviolet visible from curve analysis of the degradation products.

5. Use Cu electrode as working electrode, Pt electrodes as auxiliary electrode, saturated calomel as reference electrode. Measure water samples before processing, hydrogen peroxide water samples and sodium tungstate - hydrogen peroxide water samples respectively.

 

The results showed that the degradation rate of methylene blue was near 100% after 40min of reaction in sodium tungstate-hydrogen peroxide system. The optimum conditions for 100mL methylene blue (10mg/L) degradation were as follows: reaction temperature 60℃, sodium tungstate(0.01mol/L) dosage7.0mL, 30% hydrogen peroxide solution dosage 3.5mL. The degradation of methylene blue was effective in a wide range of pH value 1~14. Sodium tungstate-hydrogen peroxide system has an obvious catalyzing and degrading effect of methylene blue simulating dyeing-wastewater.