Study On Catalytic Degradation Of Organic Pollutants By Cobalt-Based Advanced Oxidation Processes

With the improvement of society’s demand for quality of life and the emphasis on sustainable development,water pollution has become one of the serious problems to be solved urgently.Among the emerging water treatment technologies,the advanced oxidation processes（SR-AOPs）in which sulfate radical（SO₄·^-）plays a leading role has attracted wide attention because of its high oxidation potential,strong anti-interference,long half-life,and easy operation.It has been reported that SO₄·^-can be generated by activating peroxymonosulfate（PMS）.Among the existing activation methods,the activation effect of transition metal oxides on PMS is very significant.Therefore,transition metal oxides such as Co,Fe,Cu,and Mn have been widely used for PMS activation.Among them,cobalt oxide has the best activation effect on PMS.However,there are still some problems in the practical application of cobalt-based catalysts,such as:（1）The active sites of the catalytic materials are limited,resulting in insufficient catalytic activity and it is difficult to efficiently degrade organic pollutants;（2）The catalyst structure is unstable,and the cobalt leaching is serious,resulting in poor recyclability of the materials and secondary pollution of water bodies.In order to solve the above problems,two different cobalt-based catalyst/PMS systems have been constructed in this paper.The specific design schemes are as follows:1.Preparation and catalytic mechanism of highly efficient cobalt selenite（Co Se O₃）In view of the problems of insufficient activity and poor cycle stability of cobalt-based catalysts.Taking Co Se O₃（CS）as the research object in this part,a series of structurally stable and oxygen vacancy(O_vac)-rich catalytic materials CS-X（X=120,150,180,and 200°C）are synthesized by a simple hydrothermal and calcination process.For the first time,an efficient Co Se O₃/PMS system was constructed and used in the degradation experiments of various aromatic dyes and antibiotics.The results show that the selenite network significantly improves the structural stability of the catalyst,exposes abundant active sites,and promotes the charge transfer efficiency,thereby enhancing the catalytic performance of the material.In addition,high-temperature calcination induces oxygen vacancy defects on the surface of the material,which provide additional active sites for the adsorption and degradation of pollutants,promote the generation of singlet oxygen（¹O₂）,and further enhance the catalytic activity of Co Se O₃.In the cycling experiment,after five degradation reactions,the Co Se O₃/PMS system can still completely degrade malachite green within 3 minutes,proving that Co Se O₃has high catalytic activity,structural stability,and reusability.Based on the above advantages,the efficient Co Se O₃/PMS system constructed in this paper will have potential value in practical applications.2.Preparation and properties of cobalt hydroxide carbonate（Co₂（OH）₂CO₃） rich in surface oxygen vacancies and cobalt hydroxyl groupsOn the basis of ensuring the stability of the material,in order to further enhance the catalytic activity of cobalt-based catalysts,in this work,cobalt hydroxide carbonate（Co₂（OH）₂CO₃）nanorods rich in surface oxygen vacancies(O_vac)and cobalt hydroxyl groups were synthesized by a simple glycol-assisted hydrothermal method,and their catalytic performance of activating peroxymonosulfate（PMS）to degrade pollutants was systematically studied.Firstly,the highly active≡Co-OH⁺pre-formed on the catalyst surface,as a rate-determining step,can shorten the activation time of PMS,thereby improving the catalytic degradation efficiency of pollutants.Secondly,the abundant oxygen vacancies introduced by the solvothermal reduction reaction not only provide additional active sites,but also participate in the activation of PMS,thus providing abundant singlet oxygen（¹O₂）for the degradation of pollutants.Based on the above structural control,Co₂（OH）₂CO₃has excellent catalytic performance.The Co₂（OH）₂CO₃/PMS system can completely degrade 9 organic pollutants in only 6 minutes at room temperature.In addition,the catalytic system also has excellent anti-interference ability,and can effectively degrade organic pollutants in a wide p H range and in the presence of environmental interferences.To sum up,this study provides an efficient catalyst for the field of environmental remediation,and further demonstrates the superiority of AOPs in wastewater treatment.