Catalytic Ozonation Of Phenolic Wastewater By Cuo Loaded On Al₂O₃

Highly toxic phenols are a kind of prototype poison and can be venenous to all creatures.The treatment of phenolic wastewater is one of the highlights in industrial wastewater treatment. Heterogeneous catalytic ozonation is a potential advanced oxidation technology in recent years. It not only can improve the efficiency of ozone oxidation, but also can enhance the removal rate of target contaminants effectively. In this paper, aiming at the problem of direct oxidation of ozone with selectivity, good effect of CuO/Al2O3 catalyst is prepared.CuO/Al2O3 catalytic ozonation process is built and analyzed with actual phenolic wastewater as the target.Catalysts CuO/Al2O3 are prepared by impregnate-sedimentation method. In the process of preparing catalyst various influencing factors which are impregnation liquid concentration,the type and concentration of precipitator, solid-liquid ratio of dipping,calcination temperature are reviewed in order to obtain the best preparation conditions. Catalyst which is prepared under those conditions is used repeatedly and then the catalyst activity reduced. It is because that the pollutants can cover the active point on the surface of the catalyst. In the experiments catalyst used six times repeatedly are activated by two methods. Whether cleaning or roasting, catalyst activity can be obviously improved. And in the whole process of using repeatedly, catalyst quantity has little change and physical-chemical property is stable.In the experiment catalysts CuO/Al2O3 was characterized by modern analysis method with FTIR, XRD, SEM, BET and XPS to analyze surface groups, crystal structure, microstructure,specific surface area and element composition. The catalyst with a large specific surface area and rich pore structure has good crystallinity and distributes uniformly which are conducive to the catalytic ozone oxidation reaction and improvement of the reaction efficiency. In the catalyst the main forms of element are CuO, Al2O3 and a small amount of substance formed by Al-O-Cu keys.In the experiments CuO/Al2O3 catalytic ozonation process is built with actual phenolic wastewater as the target. Air is gas source of ozone generator to produce ozone. In the experiment some influence factors which are ozone flow, catalyst dosing quantity and initial pH value are investigated to determine the optimum reaction conditions and get the best removal rate. In addition,salinity,hardness and the concentration of ammonia nitrogen in wastewater in a certain range have little effect on phenol removal rate. The addition of catalyst can effectively increase the phenol removal rate. Because the catalyst can adsorb more ozone dissolved in the liquid phase and contacted fully with the active point on the catalyst surface, promoting the decomposition of ozone to produce hydroxy free radicals.Compared with the separate ozone oxidation system, the final phenol removal rate, COD and TOC removal rate with 98.7%, 50% and 30% respectively, increasing 30%, 16% and 15%.Catalyst adsorption and air flow have a small contribution to removal of phenol wastewater.In the paper CuO/Al2O3 catalytic ozonation of phenolic wastewater follows the hydroxy free radical mechanism and conforms with the pseudo first order kinetics equation. The reaction rate constant is 0.3159s-1.