Study On Photocatalytic Oxidation Of Dye Wastewater Using TiO₂-C_o3O₄Catalyzed Peroxymonosulfate System

This research subject, sponsored by CDJRC (10210002), is part of a major creativeresearch subject (10210005) of CDJZR.Cobalt/peroxymonosulfate (Co/PMS) is a transition metal-mediated decompositionof peroxide system established on Fenton oxidation process. It is one of mostextensively researched advanced oxidation technology recently, which can degradevarious organic pollutants effectively. The cobalt species dissolved in water fromheterogeneous Co/PMS are lower then homogeneous Co/PMS, which are harmful to theenvironment. Cobaltosic oxide the most frequently used catalyst in heterogeneousCo/PMS, and it has a wide range of applications.Composite metal oxides always has higher catalytic activity than single metaloxide. the titanium dioxide-cobaltosic oxide composite catalyst was synthesized bysolution impregnation-high temperature calcination method in this paper, which has anexperimental research of degradation of dye water in heterogeneous activation ofperoxymonosulfate by titanium dioxide-cobaltosic oxide composite catalyst under UVradiation with Rhodamine B as target pollutant. Three aspects have been studied in thispaper:⑴cobaltosic oxide and titanium dioxide-cobaltosic oxide composite catalystwere synthesized by hydrothermal and solution impregnation-high temperaturecalcination method respectively. The activity of composite catalyst was evaluated andthe catalyst was characterized by X-ray power diffraction (XRD), fourier transforminfrared spectroscopy (FT-IR), scanning electron microscopy (SEM)，EDS and BETmethods.⑵The characteristics of decolorization were studied by single factorexperiments, and the mechanism of UV/TiO2-Co3O4/PMS system was preliminarystudied by different systems.⑶The Dynamic Behavior of Rhodamine B in oxidationdegradation was studied under UV/TiO2-Co3O4/PMS system.The following results were achieved in this paper based on former experimentresearch：①The catalyst with Ti:Co(molar ratio)=1:3at calcinations temperature400℃for2hours has the highest catalytic activity with favorable sedimentation, referred to TC.TC composite catalyst could be used repeatly,which with high crtstallinity. However, Tiand Co could be flowed off in a certain extent.②The degradation of Rhodamine B in different systems showed that SO4fromperoxymonosulfate actived by TiO2-Co3O4played a major role in decoloration ofRhodamine B. The presence of TiO2increased the content of surface hydroxyl oxygen,which favored the formation of CoOH+complexes, then decolorization rate could reach 82.83%in5minutes which was more shorter than UV/Co3O4/PMS system. Thedecoloration ability of TC was11.1%more than Co3O4in UV/catalyst/PMS/RhBsystem. Compareing TC and compounds of TiO2and Co3O4, the activity of TC wasbetter than compounds. However, the reusability and stability of catalyst were poor.Thedecolorization rate and time was76.61%and2h when TC was used repeatly, owing tolose of TiO2.③The decoloration of Rhodamine B in UV/TC/PMS was12.09%more thanTC/PMS. The decolorization of Rhodamine B reached75%when the initial pH wasbetween2to9, and the reaction was easy to carry in acidic condition than alkaline. Theinitial concentration of peroxymonosulfate was the key of SO4-yield and usage rate.The decoloration of Rhodamine B increased from47.88%to82.83%as PMSconcentration increased from0.2mM to0.4mM, and Rhodamine B could be completelydecolored if PMS concentration increased countinusly. The best concentration of TCand RhB were0.5g/L and50mg/L,respectively. High catalyst dosage and Rhodamineconcentration are not in favor of degration for pollutants. The degradation was increasedby12.09%under UV light.④Under the condition of UV, pH=3.57, the reaction order of degradation ofRhodamine B by peroxymonosulfate actived by TiO2-Co3O4was3.013, and apparentkinetic equation was V=4.5×10-5×P0.924×A1.565×B0.524, the concentration ofperoxymonosulfate had the greatest influence on the reaction rate.The major creative parts and learning values are as the followings:①TiO2-Co3O4composite catalyst was creatively synthesized. The TiO2which wascovered on the surface of Co3O4increased the activity of catalyst. By controlling theload of TiO2, the activity of Co3O4was used xompletely.