Study On Degradation Of Reactive Red X-3B As Azo Dyestuff By Fenton Reagent

The textile dyeing industry is one of largest industry sectors with the water and wastewater emissions in China. According to the material statistics, the wastewater emissions amount to more than 900 million tons at the textile dyeing industry every year, occupies industrial wastewater emissions sixth in China. Dyeing wastewater is 80% of the textile industry wastewater. At present, the average wastewater treatment rate of the textile dyeing industry was only 70%; the pass rate only was 30%. The large quantities dyeing wastewater of untreated or non-standard treated directly discharged, not only has a direct threat to people's health, but also seriously undermining water, soil and ecology, will cause unimaginable consequences. Dyeing wastewater with volume big, color depth, water quality changes big, high content of toxic organic compounds, complex and bio-refractory, is recognized one of the intractable industrial wastewater in the world. Fenton reagent has a super oxidation and appeared to be applicable for the treatment of bio-refractory wastewater, so Fenton reaction has become one of effective means in the treatment and control of wastewater.Fenton reagent was used to treat reactive red X-3B dyed wastewater. In order to confirm the optimum response condition, the main factors influencing efficiency were investigated one by one. When T=25℃, pH=3.0, the concentrations of H₂O₂ and Fe²⁺ were 1.6mmol/L and 0.08mmol/L, respectively, the experimental results indicated that the removal rate of COD_Cr could reach 67.8% and the degradation rate of Reactive red X-3B was 92.9% under the concentration of the raw wastewater reactive red X-3B is 200mg/L. In addition, studies on the effects of treatment by reaction temperature, photosource and its intensity, results showed that: at normal temperature, the reaction temperature change did not affect results; UV-Fenton reagent is synergy, combination can significantly improve the rate of degradation, with the UV intensity and the increase in the degradation rate correspondingly increased.In the actual wastewater treatment, water samples will usually contain some anions and soluble metal ions, such as Cl^-, S^2- SO₄^2-, NO₃^- Cu²⁺, Mn²⁺, Mg²⁺, Zn²⁺, and so on, these inorganic ions perhaps to a certain extent, Fenton reagent on the catalytic oxidation performance impact. In this paper, the effect of some inorganic ions on Fenton reaction was studied by choosing some representative inorganic ions, and the mechanism was discussed. Experimental results showed that S^2- had great influence on catalysis ability of Fenton reagent; H₂PO₄^- and Cl^-suppressed the decomposition of reactive red X-3B in the following sequence H₂PO₄^-> Cl^-; Cu²⁺ and Mn²⁺ also lowered the treatment efficiency to some extent; SO₄^2-, NO₃^-, Mg²⁺, Zn²⁺ almost had not effect on the degradation rate of reactive red X-3B.Kinetics is one of the important research contents on the Fenton reagent catalytic oxidation degradation of organic compounds. Through the kinetics study, the reaction rate can be calculated on organic compounds degradation by Fenton reagent, Fenton method better applied to the actual industrial wastewater provide valuable experimental data, In this paper, on the basis of the rules of catalytic decomposition of reactive red X-3B, the relationship between the remained concentration of reactive red X-3B and reaction time was analyzed by the monoacid regression equation, derived the apparent kinetic model.Finally, through determination Cl^- and NO₃^- concentrations change in the reaction process and UV-Vis spectrum analysis, degradation products of reactive red X-3B were conjectured and degradation pathway of reactive red X-3B was discussed. It provided the theoretical basis for the application of Fenton reagent in the treatment of dyeing wastewater and better understand the oxidation mechanism of reactive red X-3B by hydroxyl radical.