Effect Of Magnetic Field On Photocatalytic Reaction

Environmental pollution and energy shortages have constrained the human sustainable development.Therefore,seeking a clean,energy-saving,and highly efficient chemical process has become the most pressing need today.TiO₂photocatalyst has been recognized as an environmentally friendly photocatalytic material with good development prospects due to its high chemical stability,corrosion resistance and thermal stability,but the biggest drawback of using photocatalysis for this purpose is that the matching between the TiO₂ bandgap energy and the solar spectrum is less.Therefore,its potential and sustainable technologies have not yet been fully developed.This article is based on the above reasons,from the internal and external conditions of the two perspectives,to fully explore the main factors affecting the photocatalytic TiO₂,and through the doping of different magnetic permeability ion synthesis composite catalyst,exploring if its external field-the magnetic field conditions changes,what happen to catalytic performance.The specific work is as follows:（1）Based on the principle of orthogonal test,the catalyst particle size,catalyst amount,solution pH and the strength of the magnetic field—The four factors were set to three levels respectively,which constituted nine groups of photocatalytic experiments with different conditions.The three different particle size TiO₂ samples are mainly anatase structure,and their specific surface area decreases with the increase of particle size,and the regularity of morphology decreases.The photocatalytic analysis was performed by selecting the degradation data of 60 min UV irradiation.Through visual calculation and analysis of variance,the order of importance of the four factors can be obtained as follows:the particle size is the most important,the magnetic field intensity and the amount of catalyst are more important,and the pH value is minimal.Therefore,combining the two to derive the best combination of experiments:25 nm TiO₂,150 mg,pH=7,magnetic field intensity of0.1 T.（2）Using the TiO₂ particle size of 25 nm as a carrier,the composite catalysts with different doping proportions were prepared by impregnation and marked as 0.5%,1.0%,2.0%,5.0%M/TiO₂(M=La³⁺;Ni²⁺;Cu²⁺).Through the characterization,it was found that the oxides corresponding to the doping ions showed a highly dispersed state on the surface of the TiO₂ sample,and the actual doping ratio at the high doping concentration was basically consistent with the theoretical doping value.In addition,the specific surface area of the catalysts corresponding to the three doping series was less than that before doping.The type of the adsorption-desorption isotherm was type IV,and the hysteresis loop was H3,which represented the narrow hole formed by the accumulation of particles.At the same time,due to the different magnetic permeability of the doped ions,the photocatalysts formed by the composite catalyst under the action of a magnetic field exhibit different rules.（3）Photocatalytic experiments were carried out under the condition of 0.2 T for the three series of samples.The photocatalytic effects of the best doping proportions(1.0%La³⁺/TiO₂;0.5%Ni²⁺/TiO₂)in both antimony doping and nickel doping were similar.It is less than the photocatalytic effect of pure TiO₂,while the best doping ratio of Cu doped sample(0.5%Cu²⁺/TiO₂)is basically consistent with the photocatalytic efficiency of pure TiO₂.In general,the photocatalytic activity of the three best doping ratios in the magnetic field conditions is stronger than that in the absence of the magnetic field,but changes in the applied magnetic field strength from0.05 T to 0.3 T,1.0%La³⁺/TiO₂ The photocatalytic activity of the photocatalysts shows a law of first rise and then fall.The maximum first-order kinetics constant is at0.2 T.The photocatalytic activity of 0.5%Ni²⁺/TiO₂ is always degraded,and the corresponding magnetic field strength at the optimum photocatalytic performance is0.05 T.The photocatalytic behavior of 0.5%Cu²⁺/TiO₂ is consistent with 1.0%La³⁺/TiO₂,but the photocatalytic performance of copper-doped samples at 0.3 T is much better than that of antimony-doped samples.