Mechanism Of Oxidation Of MnO₂ Quinoneimine Class

MnO₂ is a kind of amphoteric oxide.It is widely used due to its strong adsorption,non-toxic harmless,environmental protection and abundant reserves.Besides chemical adsorption,redox reactions will take place between MnO₂ and quinoneimine,so that unstable complexes will be produced.During the reactions,colorless and soluble Mn³⁺complex is generated which is instable and changes into salmon pink materials gradually.The reaction has a good prospect because of no pre-processing,simple preparation,low cost.Acidic methylorange is a kind of dyes of quinoneimine.Therefore,it is significant to study the reaction mechanism of MnO₂ and quinoneimine.In this paper,IR and X ray diffraction was selected as test methods to analyze the crystal of MnO₂.It was drawn that the MnO₂ was beta-MnO₂.N-caprylic alcohol was selected as material of degradation.The effect of MnO₂ and N-caprylic alcohol was studied under different qualities of MnO₂,reaction time and light source.Finally,it was concluded that MnO₂ has no photocatalytic properties.Toluidine blue,azure I and methylene blue were selected as the quinoneimine dyes.Based on the results of single factor experiments,the best pH of MnO₂ degradation quinoneimine was 3.The quality of MnO₂ is 1g/L in the degradation of toluidine blue and azure I,The quality of MnO₂ is 1.5 g/L in the degradation of methylene from single factor experiment.The UV-vis spectra of the solution at 0 min,30 min and 60 min were detected.The results showed that in the process of degradation of MnO₂ and the dyes of quinoneimine,a new absorption peak was indicated between 400nm?500nm.The composition of the reaction system was tested in order to explore the reason for the generation of the new material.And Mn²⁺ and Mn³⁺ were found in the reaction system.By adding Mn²⁺ to the raw solution of quinoneimine,The UV spectrum showed there was no reaction between Mn²⁺ and quinoneimine.Therefore,it was determined that the new substance was generated from the effect of Mn³⁺ and quinoneimine.In conclusion,there is a common reaction mechanism between MnO₂ and quinoneimine substances.Firstly,Mn²⁺ and derivatives are produced by the reaction of MnO₂ and quinoneimine dyes.Sencondly,Mn³⁺ will be produced by the reaction of MnO₂ and Mn²⁺,then it will react with the derivatives.In this reacion,a unstable complexes can be produced,which will be eventually transformed into a new substance.