Preparation Of Pyridine N-Oxide Coordination Compouds And Study On Their Catalytic Properties In Dye Decolorization

With the development of the economy,there is a substantial increase in the volume of the waste water,especially in dyeing and printing field.It makes 60% in the total general water discharge.According to the specific process,the methods of waste water treatment mainly include three branches,which are physical,biological and chemical methods.The physical method usually refers to the simple interfacial adsorption of the wastes in water;and the chemical process usually refers to the oxidative degradation of wastes in water with strong oxidizing agents.During the biological process,the aerobic enzyme and anaerobic enzyme are used for the oxidative degradation with high efficiency.But due to the harsh condition of this process and the instability of the biological activity of enzymes,the study of biomimetic catalyst,which is cheap and could be used as the chemical catalyst under mild conditions,become a trend in recent years.Metal organic complexes are widely used in catalytic field due to their structural diversity and good catalytic property.Metal complexes usually contain the organic ligands and metal ions,and the kind of the metal ions and the structure of the ligands have great effect on the property of the complexes.Clearly,homogeneous catalysts are easy to use with high efficiency.But they could not be recycled and would make second pollution.Therefore,the immobilization of homogeneous catalyst attracts much attention.Owing to the high electron density of the oxygen atom which directly connected with nitrogen of the bipyridine n-oxide,the ligands of bipyridine n-oxide are easier to form unique complexes with metal ions,which showed better catalytic activity than pyridine complexes.In this paper,three isomeric bipyridine n-oxide compounds were synthesized firstly,and then they were used as the ligands to coordinate with CuCl₂,CoCl₂ and MnCl₂,respectively to form nine complexes.The structures were characterized by ¹H NMR,IR,EA and ICP.The nine complexes were used as catalyst in degradation of KN-R 19 with hydrogen peroxide as oxygenant.The connections between the catalytic activity and the metal ions or the structure of the ligands were also studied.The results showed that theL₃ complexes present the best activity of three ligands,and the Co²⁺ complexes give the best result.So the comparation shows the CoL₃ is the best choice.For CoL₃,the optional catalytic degradation process is: the system contains 30 m L dye solution?500 mg/L?,14 mL 1 mol/L buffer solution?Na₂CO₃/NaHCO₃,pH=10.2?,56 mL distilled water,hydrogen peroxide solution to make its concentration 0.1 mol/L,and 10 mg CoL₃.The decolorization rate is up to 95 % in 15 min.The microcapsule method was used for supporting the catalyst CoL₃.CoL₃ and magnetic powder were dispersed in gelatin,then glutaric dialdehyde woked as crossing-link agent to form the microcapsule.The microcapsule also could be used as catalyst in degradation of KN-R 19,and under the outside magnetic field they ccould be collected and reused.It showed that the magnetic microcapsule still kept over 90% rate after 5 cycles;and after 8 cycles,the decolorization rate was still over 60%.