Preparation Of Transition Metal Catalysts For Ozone Catalytic Oxidation Of Refractory Organics And Reactor Simulation

In China,the annual discharged volume of industrial wastewater with complex components is huge,which is difficult to deal by traditional biochemical methods.Thus,it is in urgent need of inventing a cheap and effective method to remove the refractory organic matter.In this work,catalyst for the catalytic ozonation in advanced treatment technology based on industrial wastewater is investigated.Different transition metal catalysts were prepared by excess impregnation using ?-Al2O3 balls with diameters of 3 to 5 mm as carriers.The COD value before and after treatment of methine blue dye wastewater was used to evaluate the catalyst.The transition metal and the preparation conditions of catalysts were screened.The results showed that the trimetallic catalyst with transition metal Cu added in the Mn-Ce bimetallic catalyst system works best.The catalysts prepared under the conditions of Cu,Mn and Ce metal with the ratio of 2:2:2 and 3:1:3 have the best effect.The best impregnation time for the preparation of the catalyst was 12 h,the best calcination temperature was 450 ?,the best holding time was 3 h,and the best impregnating solution pH was 13.Ozone catalytic oxidation experiments were carried out on methylene blue dye wastewater and phenol-ketone industrial wastewater,and the catalyst was evaluated by the COD value before and after the wastewater treatment.Compare with wastewater treatment at different ozone dosages and liquid flow rates.It was found that the smaller the liquid phase velocity is,the larger the ozone dosage is,and the more favorable is the ozone catalytic reaction.The higher the removal rate of organic matters in the wastewater is,the more the color is removed,and basically becomes colorless after 200 mg/L.The catalysts prepared under the condition of 3:1:3 ratio of Cu,Mn,and Ce metal have the best COD removal efficiency for methylene blue wastewater,and the removal rate of 300 mg/L ozone dosage can reach 60.61%.The Mn and Ce ratio of 2:2 bimetallic catalyst treatment of phenol industrial wastewater the best effect,300 mg/L ozone dosage removal rate of up to 44.25%.The same catalyst has a single component dye wastewater,and the treatment effect is far better than the industrial wastewater with complex components and many organic substances.Two-dimensional model was built by software of Fluent in Ansys series.The flow field was simulated for the experimental reactor model and the industrial bubble column model.The experimental reactor was a two-dimensional model with high 1000 mm and wide 50 mm.The inlet speed of the liquid phase was 4 L/h and the inlet speed of gas phase was 0.35 L/min.The industrial bubble column model was a two-dimensional model with high 5.5 m and wide 3 m.The inlet speed of liquid phase was 80 m3/h,and the inlet speed of gas phase was 400 m3/h.The VOF multiphase flow model was selected,and it was laminar flow.The catalyst inside the reactor was regarded as a porous medium.Select a variable time step for calculation.The effects of gas flow rate,liquid flow rate,reactor height and diameter ratio,gas distributor,ozone dosage and gas concentration on the flow field of gas holdup,pressure,velocity and phase inside the reactor were studied.The results show that the gas-liquid phase velocities of the two models are relatively reasonable,the number of distributor holes 6 or 8 is the most appropriate,the height and diameter of the experimental reactor are relatively reasonable,and the bubble column size should be designed according to the actual treatment volume.When the dosage of ozone was 200 mg/L,the optimum gas concentration in the reactor was 30 mg/L,and the optimum gas concentration in the industrial bubble column was 50 mg/L.The concentration of ozone produced by air sources is low,so oxygen sources are used industrially.