Preparation Of MgO/CeO 2 Nanocomposites And Their Catalytic Degradation Of Phenol By Ozone

As an important chemical raw material,phenol is widely used in the industrial production,its environmental toxicity will cause serious harm to human,animals and plants.As the catalytic ozone oxidation technology response fast,degradation completely,does not produce secondary pollution,it get a lot of attention in the field of water treatment.In this paper,MgO/Ce02 nano composite catalysts were prepared by coprecipitation method,the performance of the catalysts was evaluated by XRD,SEM,BET and TG-DSC.The performance of its catalytic ozone degradation of phenol was evaluated.The technological conditions of MgO/Ce02 catalytic ozone degradation of phenol were investigated.The mechanism of catalytic oxidation of ozone and the kinetics of phenol degradation were discussed.The results show:?The optimum conditions for the preparation of MgO/CeO2 nanocomposite catalyst are as follows:calcination temperature is 550 ?,molar ratio of Mg/Ce is 1:3.When the calcination temperature is 550?,the crystallinity and particle size of MgO/CeO2 are more suitable,and the removal rate of phenol by catalytic ozonation is 25.34%and 8.83%higher than that of 450? and 650?,respectively.When the ratio of MgO and CeO2 is different,the growth pattern of crystal will change,the morphology and grain size of the composite catalyst will change.When the content of magnesium oxide is less,the cerium oxide is octahedral,the aspect ratio is larger,the grain size is smaller than that of pure Ce02,and the magnesium oxide is no longer the film,and is attached to the surface of cerium oxide with small granular form.When the content of magnesium oxide is more,magnesium oxide is massive,cerium oxide is attached to the surface of magnesium oxide with small particles.When the molar ratio of Mg/Ce is 1:3,the specific surface area of the composite catalyst is 90.1m2/g,which is 2 times higher than that of 34.3m2/g when the mole ratio of Mg/Ce is 3:1.The removal rate of phenol in the catalytic ozonation experiment,the former is 10.37%higher than that of the latter.MgO/CeO2 nano composite catalyst has better catalytic performance than CeO2 and MgO.The phenol removal rate in catalytic ozonation experiments is 8.39%and 4.75%higher than that of MgO and CeO2 respectively.?The optimum conditions for the degradation of phenol wastewater by MgO/CeO2 catalytic ozone oxidation are as follows:the dosage of ozone is 6.34mg/min,the dosage of catalyst is 50mg/L,and the initial pH was 11.Under these conditions,and the reaction temperature is 20?,the removal rate of phenol was 86.56%at 20min.When the reaction temperature is 10?50?,the removal rate of phenol increases with the increase of reaction temperature.The repeating utilization factor of MgO/CeO2 catalyst was investigated,used in every 30 minutes,after repeated use 10 times,the removal rate of phenol in catalytic ozonation was only reduced by about 7%,the catalyst has good stability.?·OH exist in the system of MgO/CeO2 catalytic ozonation of phenol.After 40mg/L tert-butyl alcohol was added to the reaction system,the phenol removal rate was 36.72%lower than that without adding tert-butyl alcohol after 20min.The Rc values in the ozone oxidation and MgO/CeO2 catalytic ozonation systems were 2.42×10-6 and 3.21 × 10-6,respectively.The concentration of ·OH in the catalytic ozone oxidation system was 1.33 times that of the ozone oxidation system,indicating that in the catalytic ozonation system,the MgO/CeO2 catalyst can promote the decomposition of ozone,and produce more ·OH.The system follows the hydroxyl radical reaction mechanism.The reaction kinetic model of the MgO/CeO2 catalytic ozonation of phenol was obtained by fitting the experimental data of the factors affecting the ozonation of phenol.The average relative error between the theoretical data and the experimental data was 9.51%,which could simulate the process of MgO/CeO2 catalytic ozonation of phenol.