Preparation Of Cobalt-based Fenton-like Catalysts And Study On Their Degradation Performance For Rhodamine B

Due to the rapid development of society,a large number of water pollution problems are threatening human health and life.People have developed a variety of technologies for water pollution treatment,among which advanced oxidation processes（AOPs）were widely used because of their remarkable catalytic properties.In this thesis,three different heterogeneous cobalt-based catalysts were synthesized for the activation of peroxymonosulfate（PMS）to degrade organic pollutants in Fenton-like oxidation reactions,and their catalytic degradation properties of rhodamine B were studied respectively.In the second chapter,Co/Co₉S₈@N-S-C composite Fenton-like catalyst was prepared by a two-step calcination process,which activated PMS to degrade rhodamine B（Rh B）under dark conditions.The experimental results showed that the catalyst can degrade about 99.8%of Rh B within 25 minutes,showing good degradation performance.Co/Co₉S₈@N-S-C can activate PMS to produce sulfate radicals,which played a main role in the degradation process.Co₉S₈ participated in PMS activation in which Co²⁺was involved in sulfate radical formation,while sulfur species facilitated the conversion of Co³⁺to Co²⁺.In addition,pyridinic N,carbon atoms adjacent to pyridinic N,C=O groups,and C-S-C also contributed to PMS activation.The optimum reaction conditions were obtained by exploring different concentrations of PMS,and the influence of inorganic anions on the degradation performance of the catalyst was also discussed.Based on the results of literature research and trapping agent experiments,the mechanism of Co/Co₉S₈@N-S-C composite to activate PMS to degrade Rh B in Fenton-like reaction was proposed.Finally,the cyclic experiments showed that the catalyst has good cyclic stability.In the third chapter,Co-modified Bi₂O₃/Bi OCl composites were synthesized by solvothermal method,and Rh B was degraded by activating PMS under the irradiation of halogen tungsten lamp.The experimental results showed that the degradation efficiency of Rh B increased from 47.6%to 98.5%in 25 minutes after the introduction of cobalt,compared with Bi OCl alone.The experimental results showed that the catalyst has good catalytic performance for Rh B in the p H range of 4.5 to 9,indicating that the catalyst has good applicability.Through literature review and scavenger experiments,the active species in the reaction process were determined and the reasonable reaction mechanism was proposed.The cyclic experiments showed that the cyclic stability of the catalyst needs to be improved.In the fourth chapter,a new coordination polymer with Co–O₆ units and abundant N and C sources was synthesized by a Schiff-base reaction of 3,4-dihydroxybenzaldehyde（DB）and p-phenylenediamine（PPDA）and then connected with the Co–O coordination bonding.Subsequently,the Co coordination polymer precursor with the formed Na Cl salts were thermally annealed into abundant Co@N-C nanostructures,which were used for Fenton-like degradation reaction.Co nanoparticles with the size of 20-50 nm were encased in N-doped graphite shells,which reduced the leakage of Co ions.The experimental results showed that the Co@N-C core-shell nanostructures can degrade about 99%of Rh B within 27 minutes under dark conditions,showing excellent degradation performance.The trapping agent experiments showed that the degradation reaction was a process of interaction of free radicals and non-free radicals.¹O₂ played a main role in the catalytic reaction process,SO₄^·-and·OH also participated in the reaction.The applicability of the catalyst was investigated by studying the effect of initial solution p H and common inorganic anions on the degradation performance.The cyclic experiment results showed that the catalyst has good cyclic stability.In this thesis,three kinds of highly efficient cobalt-based heterogeneous catalysts were prepared by calcination and solvothermal method for Fenton-like catalytic reactions.The experimental results showed that the three catalysts showed good catalytic activity,and have great practical application prospects.