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.