Study On Ozone Catalytic Oxidation Of Organic Wastewater By Honeycomb Activated Carbon Catalyst

Industrial organic wastewater is difficult to be treated by conventional biochemical methods because of its complex composition and high toxicity.Ozone catalytic oxidation technology is simple in operation,high in treatment efficiency,and has a good effect on the treatment of industrial organic wastewater.The development of new heterogeneous catalysts has become a research hotspot.In this paper,catalysts of different active components were prepared,the process conditions of ozone catalytic oxidation were optimized,and the reaction mechanism of honeycomb activated carbon based catalyst ozone catalytic oxidation was explored.Six catalysts Fe-La/HAC,Fe-Ce/HAC,Cu-La/HAC,Cu-Ce/HAC,Zn-La/HAC and Zn-Ce/HAC were prepared using 100 well/square foot honeycomb activated carbon（HAC）as support.Using methylene blue as the target pollutant,the catalytic activity of the catalyst was evaluated.Combined with XPS and H₂-TPR characterization,the active groups were determined as Cu and La.The transition element Cu had higher catalytic activity,and the addition of rare earth element La could reduce the dissolution concentration of the active component.The effect of catalyst on COD removal rate of methylene blue wastewater under different preparation conditions was investigated by changing Cu and La loading,roasting temperature and roasting time.The results showed that the optimum preparation conditions of honeycomb activated carbon catalyst were as follows:Cu supported 1.0 wt.%,La supported 1.0 wt.%,calcination temperature 400℃,calcination time 2 h.Three Cu-La/AC catalysts were prepared using columnar activated carbon（AC）with diameters of 1 mm,2 mm and 4 mm as supports.Compared with the treatment effect of Cu-La/HAC catalyst on methylene blue wastewater,the catalytic activity of Cu-La/HAC catalyst prepared with honeycomb activated carbon carrier is between 1mm and 2 mm Cu-La/AC catalyst,indicating that honeycomb activated carbon as the catalyst carrier has better performance.The effects of different process conditions on the COD removal rate of methylene blue wastewater were investigated.The optimized process conditions were as follows:hydraulic retention time 15 min,ozone dosage 80mg/L and initial p H 8.3.In the range of 10～30℃,the increase of temperature will improve the COD removal rate.The COD removal rate of methylene blue wastewater is 85.19%,methylene blue removal rate is 95.43%.For the treatment of the organic wastewater containing cyanide which is more difficult to degrade and more toxic,the total cyanide removal rate of the organic wastewater containing cyanide is 88.60%and the COD removal rate is77.78%under O₃:COD=3.6:4.05.The mechanism of Cu-La/HAC catalyst ozonation was investigated.The removal rate of methylene blue decreased by 17.37%and 30.56%respectively by quenching·OH in the liquid phase and on the catalyst surface,which confirmed the existence of·OH in the system.Sodium dihydrogen phosphate inhibits the degradation of methylene blue by combining with the hydroxyl group on the surface of Cu-La/HAC catalyst,indicating that the hydroxyl group on the surface of catalyst is the active site for the decomposition of O₃into·OH.In ozone catalytic oxidation,·OH and O₃act together,and the reaction follows the synergistic mechanism.