Study On The Selectivity Of Active Substances Produced In The Photocatalytic Process Of TiO₂

In recent years,with the rapid development of science and technology,the problem of environmental pollution is increasingly serious.At present,the organic pollutants represented by organic dyes have become the hot and difficult point of ecological environment treatment.However,there are many problems in traditional governance methods,which can not meet our needs for a better life.Nano semiconductor photocatalytic materials,represented by TiO₂,are widely used in environmental treatment and organic dye wastewater treatment due to their high degradation efficiency and no secondary pollution.Although there are extensive investigations on the photocatalytic performance of TiO₂ crystalline components,there are few reports on the mechanism of TiO₂ oxidation and the selective generation of active substances.In this paper,the degradation mechanism of TiO₂ photocatalysts with different crystalline components and the selective formation of active radicals were studied.?1?TiO₂ with different crystal components was prepared by aerobic treatment.TiO₂with different crystal components was characterized by X-ray powder diffraction?XRD?,Raman spectrum,specific surface analysis and UV diffuse reflection.The results show that when the temperature increases,the composition of rutile phase becomes higher,the specific surface becomes smaller and the width of valence band becomes smaller.Therefore,the composition ratio of anatase and rutile can be controlled by calcining at different temperatures.?2?The effect of rutile and anatase rich on the selectivity and tunability of photocatalytic degradation was studied by using methyl orange methylene blue?MO-MB?solution with pH=3 as the model system;In the process of photocatalytic reaction,the degradation rate and selectivity of MB and mo were observed after adding isopropanol?·OH capture agent?,p-benzoquinone(O₂^·-capture agent)and triethanolamine?h⁺capture agent?,and the surface fixed O₂^·-was detected by fluorescence spectrum.The change of valence state of titanium was characterized by XPS,and the singlet oxygen was detected by EPR.The results show that:Rutile rich TiO₂ catalyst shows high selectivity for photocatalytic degradation of MB,and its selectivity is twice that of anatase rich TiO₂;·OH and h⁺have little contribution to the selective degradation,and O₂^·-has significant influence on the photocatalytic activity and selectivity;rutile rich TiO₂ is easier to form fixed O₂^·-than anatase rich TiO₂;by controlling the crystal phase of TiO₂ catalyst;regulating the solid-state TiO₂ The formation of O₂^·-was localized to control the possibility of photocatalytic selectivity.?3?A new method of photodegradation based on oxygen exposure was used to remove nonylphenol ethoxylate phosphate?TXP-10?,which was a model organic compound,with TiO₂ as photocatalyst.NBT molecular probe was used to analyze the relative amount of O₂^·-generated by TiO₂ photocatalyst with different oxygen exposure and different crystal phase composition;Under different light intensity and oxygen exposure,it can capture·OH and h⁺in the process of photocatalytic reaction;determine the change of TXP-10 in the degradation process by infrared spectrum;evaluate the change of scale inhibition performance of txp-10with degradation time.The results show that rutile is more sensitive to oxygen exposure,and the larger the oxygen exposure is,the more oxygen is produced;it is more sensitive to light intensity;the hydrophobic alkyl chain and aromatic ring are converted into hydrophilic derivatives containing carboxyl group;with the extension of photocatalytic reaction time,the resulting compounds lose surface activity and the anti precipitation rate is reduced.