Study On Heterogeneous Catalytic Ozonation In Reactive Dye Wastewater

Reactive brilliant Red X-3B is a widely used commercial dyestuff, which has bright color, high solubility in water and reasonable price. Because of its good solubility in water and molecular stability, traditional wastewater treatment methods, such as flocculation and activated sludge process, can't work well with Reactive brilliant Red X-3B wastewater. It is suggested in this paper that ozonation and catalytic ozonation processes be applied to treat the wastewater.In the study of ozonation alone, gas volume into the reactor was 6.5L/min, with 50min as reacting time. By detecting the color, UV-VIS adsorption, COD_Cr and pH value of the effluent, it was known that at the end of ozonation, the original stable dyestuff molecules had been oxidized and degraded. COD_Cr removal rate and decoloration rate were 25.14% and 99.90%, respectively. The pH value in the reacting system was also found to decrease from 6.28 to 2.83. In heterogeneous catalytic ozonation, all catalysts were prepared using impregnation method, withγ-Al₂O₃ as their supports. Several catalysts with single active component were compared on their catalytic effects of dye wastewater treatment. The results showed that Ni/Al₂O₃ +O₃ > Co/Al₂O₃ +O₃ > Fe/Al₂O₃+O₃ > Mn/Al₂O₃ + O₃ > Cu/Al₂O₃ + O₃ > Ce/ Al₂O₃ +O₃. Co and Ni were chosen as the two most active components in preparing a bi-component catalyst withγ-Al₂O₃ as the support.The bi-component catalyst was then used in the treatment of aqueous solutions of reactive brilliant red X-3B by ozone catalytic oxidation process. Investigations on the X-3B degradation showed that the catalytic effects were deeply influenced by the catalyst preparation conditions, such as soaking time, mole ratio of Ni, calcinating temperature and calcinating time. The optimized preparation conditions were: soaking time 8.5h, the mole composition of Ni in the active components 0.67, the calcinating temperature and time are 300℃and 5 hrs, respectively. The physical properties and the structures of the catalysts were also characterized by XRD and SEM methods.The addition of the third component to the ozone oxidation catalyst for dyestuff wastewater treatment was also researched in this paper. The experimental results showed that after 50 min reaction, the third additive effect of the catalyst: K≈La>Ce>Na. However for the first 40 minutes in the reaction La was obviously more superior to K in enhancing catalytic effect. So La was selected as an additive for the optimal catalyst.The choice of the support had a great impact on the activity of a catalyst. The catalysts were prepared using the above optimal conditions, with activated carbon andγ-Al₂O₃ as the carrier in experiments, respectively. COD_Cr removal rate of catalytic ozonation with activated carbon andγ-Al₂O₃ as the carrier after 50 min of reaction was 69.49% and 83.65%, respectively. It can be seen that effect of catalytic ozonation withγ-Al₂O₃ as the support was better than that of activated carbon.