Study On Magnesia Catalysts For Treatment Of Organic Wastewater By Catalytic Ozonation

With the rapid development of industry in China,the problem of wastewater discharge,which contains high COD,high concentration,heave color,high toxicity and wide variety of organic matters,became more and more serious.Phenol is one of the most difficult degraded organic compounds.An effective method of organic wastewater is needed to solve these problems.In this paper,a kind of highly efficient catalysts based on MgO has been prepared for the catalytic ozonation for purification of phenol wastewater.The effect of various process conditions on the removal of phenol in wastewater was investigated,and the mechanism of catalytic ozonation treatment of wastewater was studied.Firstly,magnesium oxide/activated carbon（MgO/AC）composites have been prepared by equal volume impregnation method in this work.Then prepared catalysts have been used for catalytic ozonation of phenol and characterized by IR,XRD,and XPS et al.Magnesium oxide was bonded on the AC surface in the form of nanocrystalline particles.This work studied the effect of catalyst loading,pH and others factors on the catalytic ozonation performance.The COD removal rate could reach 83.5%under the following conditions that 210 mg·L^-1of initial phenolconcentration,43 mg·L^-1of O₃ concentration,pH of 5.51,500 mg of catalyst dosage,1%loading amount of MgO.The alkalinity of MgO effectively alleviates the pH changes in the reaction system and provides additional active sites for the production of hydroxyl radicals,which is beneficial to the degradation of organic pollutants.The intermediate products were determined and possible degradation pathways were proposed.It provides a simple method to prepare efficient catalysts for catalytic ozonation.Secondly,the hollow rod-like magnesium oxide supported CoO_xcatalyst was prepared by coprecipitation method for catalytic ozonation of phenol wastewater.The catalysts were characterized by XRD,TEM,CO₂-TPD and XPS et al.Structure and physicochemical properties of the catalysts were analyzed.The COD removal rate could reach 79.8%at the initial concentration of 210 mg·L^-1for phenol,43 mg·L^-1of ozone concentration,pH of 5.51,500 mg of catalyst dosage,1 to 50 of the molar ratiosfor Co to Mg.The catalyst which prepared by sodium carbonate has the largest surface area and the best catalytic performance.The catalyst can adsorb phenol,regulate pH change in solution,and provide a large number of active sites for the catalytic ozonation process,which is beneficial to the free radical type reaction.The catalyst can be reused at least five times without reducing the COD removal rate.The prepared CoO_x/MgO catalyst also showed excellent catalytic performance for the removal and degradation of ciprofloxacin,norfloxacin and salicylic acid.Finally,the prepared catalysts,MgO/AC and CoO_x/MgO,were used to treat wastewater A from a pharmaceutical factory.The removal rate of COD can reach 59.7%and 38.0%under the initial wastewater ACOD concentration of 337 mg·L^-1and the solutionpH of 8.34,respectively.The synergy effect on MgO/AC or CoO_x/MgO catalytic ozonation was verified.A feasible treatment method has been provided for the treatment of actual wastewater.The experimental results showed that catalyze ozonation for the treatment of wastewater can be effectively catalyzed by the prepared MgO/AC and CoO_x/MgO.It provides theoretical and experimental basis for efficient treatment of wastewater.