Study On The Efficiency And Mechanism Of Cobalt-based Catalyst For Persulfate Degradation Of Dye Wastewater

With the rapid development of printing and dyeing,food,medicine,cosmetics and other industries,dyes are discharged into water bodies in various ways,causing serious water pollution problems.However,the dye wastewater is characterized by high chrominance,high ammonia nitrogen content,complex water quality,carcinogenicity,teratogenicity and difficult degradation.Once it is directly discharged into the water,it will even affect human health in all aspects and pose a great threat to the environment and human health.The removal of dye molecules from wastewater has become an urgent problem at present.In recent years,the advanced oxidation process based on sulfate radical(SO4-·)has attracted more and more attention in the treatment of dye wastewater due to its higher oxidation efficiency,wider p H range,longer service life and non-selective oxidation.Sulfate radical is usually formed by PMS activation,and heterogeneous cobalt catalytic activation is the first choice for PMS activation.Therefore,the design and development of highly efficient and environmentally friendly heterogeneous cobalt catalysts have undoubtedly become the focus of current research in the field of catalytic activation of PMS.Cobalt catalysts can be designed as oxides,sulfides,hydroxides and phosphates.Many studies have shown that the catalytic activation performance of cobalt catalysts depends greatly on the physical and chemical properties such as the composition,structure and morphology of the catalysts.Therefore,in this study,two catalysts,cobalt aluminum hydrotalcite(Co Al LDH)nanosheets and 3d flower magnesium cobaltate,were developed and used as catalysts to activate PMS to degrade Rhodamine B(Rh B),a common azo industrial dye,and the catalytic performance of the two catalysts to activate PMS was evaluated.(1)Co Al hydrotalcite nanosheets were prepared by hydrothermal treatment of Co Al hydrotalcite with lye;The lye water heat treatment did not affect the crystal structure,surface element type,content and valence state of the material,but the surface structure of the nano-sheet could expose more active sites and make the catalyst contact with PMS and pollutants more effectively,thus significantly improving the catalytic activation performance of the PMS.The optimum catalytic degradation performance was obtained when the initial concentration of Rhodamine B was 80 mg/L,catalyst concentration was 0.10 g/L,PMS concentration was 0.10 g/L,initial p H was 7.0 and reaction temperature was 25 °C.When the initial concentration of Rhodamine B was 80 mg/L,catalyst concentration was 0.10 g/L,PMS concentration was 0.10 g/L,initial p H was 7.0 and reaction temperature was 25 °C,the catalytic degradation performance of Rhodamine B was the best.The results of quenching experiment and EPR analysis showed that 1O2 and SO4·-played a major role in the degradation of Rhodamine B.In addition,the Co Al-LDH catalyst has high reusability and good stability,which can be recycled at least 4 times,and has high practical application potential.(2)Magnesium cobaltate catalyst was prepared by hydrothermal method using SDBS surfactant as template,and the physicochemical properties of the catalyst were analyzed by XRD,SEM,EDS and XPS.The catalytic performance of Rhodamine B(Rh B)was investigated by degradation experiments.The results show that magnesium cobaltate-SDBs presents a three-dimensional flower structure assembled by nanoparticles,which has a large surface area and exposed active sites,greatly improving its catalytic activation performance for PMS.In addition,when the initial concentration of Rhodamine B is 80 mg/L,catalyst concentration is 0.10 g/L,PMS concentration is 0.10 g/L,initial p H is 7.0 and reaction temperature is 25 °C,the catalyst has the best degradation performance of Rhodamine B.The quenching experiment and EPR analysis showed that the main degradation of Rhodamine B in magnesium cobaltate /PMS system was activated oxygen species such as 1O2 and SO4·-.In addition,magnesium cobaltate catalyst has high reusability and good stability,which can be recycled at least 4 times,and has high practical application potential.