Preparation Of Cellulose-based Composite Catalysts And Its Application In Degradation Of Acid Orange Ⅱ

With the development of printing and dyeing industry,the composition of printing and dyeing wastewater becamemore complex.The traditional treatment methods such as coagulation sedimentation,membrane technology,biological method,adsorption method are ineffective to completely remove the dyes from the wastewater.Recently advanced oxidation technology proved to be highly effective in dealing with the high concentration of refractory organic pollutants.Persulfate oxidation technology has been widely used because of its wide range of p H,strong oxidizing ability and little inactivation factors.The previous research showed that among the activation method of transition metal,cobalt based catalyst are effective,lower energy consumption and widely used methods of activating persulfate.Recently,many kinds of catalysts consisting of cobalt oxide supported on graphene oxide have been prepared and have shown very good catalytic performance.However,due to the hydrophilic nature of the catalyst and very small particle size,its recovery still remains unsolved problem.Therefore,it is imperative to find a catalyst with high catalytic activity and convenient recovery.Cellulose is a kind of biodegradable natural environmental material available in abundance.Compared with the artificial synthetic material,cellulose has many advantages like it’s a renewable,low cost and naturally occurring in abundance.As a derivative of cellulose,the oxidized cellulose also has advantages of high strength,good regeneration,biodegradable and no toxicity.The previous researches show that the composite of oxidized cellulose and other materials can significantly improve the mechanical properties of the composites.In this paper,Co₃O₄ was first supported on graphene oxide（GO）,and oxidized cellulose（TOCNs）was doped into it by inorganic/organic blending modification to synthesized self-precipitation recoverable composite catalyst（Co₃O₄/GO/TOCNs）about 5 mm in size.In this study the performance of the catalyst was analyzed by measuring its mechanical stability,recyclability,the effect of the inorganic ions on the reaction system and the modification of the activated carbon.（1）Preparation and characterization of self-precipitated catalyst（Co₃O₄/GO/TOCNs）The oxidized graphite and oxidized cellulose were prepared by modified Hummers method and TEMPO method.Then Co₃O₄/GO was prepared by hot melt method of n-hexanol.Finally,oxidized cellulose（TOCNs）was doped into it by inorganic/organic blending modification to prepare the new composite catalyst Co₃O₄/GO/TOCNs with a diameter of about 5 mm.The prepared materials were characterized by XRD,FT-IR,SEM and TEM.The results show that the Co₃O₄/GO/TOCNs composite catalyst has been successfully prepared and the nanometer Co₃O₄ can evenly be distributed on the supportmaterial.（2）Catalytic performance and stability of Co₃O₄/GO/TOCNs.The degradation of acid orange Ⅱ catalyzed by Co₃O₄/GO/TOCNs with PMS,and the catalyst’s recyclability were studied.Several operational parameters,such as catalyst amount,oxidant amount,p H,temperature,and oxidation rate,affected the degradation of acid orange II.Complete dye degradation was achieved within six（6）minutes when using PMS dose（2 mmol/L）,catalyst mass（0.5 g/L）,PH（7）for 0.2 mmol/L acid orange Ⅱ at 25℃.The apparent degradation kinetics of acid orange Ⅱ by Co₃O₄/GO/TOCNs catalyzed using PMS was investigated in detail.Interestingly,activation energy was 20.612 k J/mol,which is lower than that of the traditional Fenton oxidation technology.This indicated that the ability of degradation of acid orange Ⅱ in Co₃O₄/GO/TOCNs/PMS system was higher than that of traditional Fenton oxidation technology.After 6 rounds of regeneration of the catalyst,the catalyst exhibited stable performance,because the reaction still can be finished within 12 min and the cobalt dissolution rate was kept under 0.05 mg/L during the recycling process.（3）The effect of inorganic ions on degradation of acid orange Ⅱ in Co₃O₄/GO/TOCNs/PMS system.The results showed that H₂PO₄^-promoted the degradation of acid orange Ⅱ;effect of HCO₃^-was positive at first but converted to negative during high concentration;Cl-was negative at first but converted to positive during high concentration;the NO₃^-had a slight inhibitory effect on the degradation rate of acid orange Ⅱ.（4）Research on modification of Co₃O₄/GO/TOCNs by activated carbon and its catalytic performance.The Co₃O₄/GO/TOCNs/AC catalyst was prepared by the modification of Co₃O₄/GO/TOCNs onto activated carbon by the inorganic/organic blending modification method.The degradation of acid orange Ⅱ catalyzed by Co₃O₄/GO/TOCNs/AC using PMS and the recyclability of the catalyst was studied.The results showed that the amount of cobalt in Co₃O₄/GO/TOCNs/AC was only 40% of that of Co₃O₄/GO/TOCNs in the same catalytic effect as that of Co₃O₄/GO/TOCNs.After 6 rounds of regeneration of the catalyst,the catalyst exhibited stable performance,because the reaction still can be finished within 14 min.