Morphology Control And Photocatalytic Properties Analysis Of Nano-scale Titania Prepared By Hydrothermal Method

With the development of society,groundwater resources are exploited uncontrolled and industrial wastewater is discharged unrestricted.In reality,we need to pay more attention to the protection of water resources and the treatment of wastewater.After decades of development,semiconductor photocatalytic technology has shown remarkable effect in the field of dye removal from wastewater.Among many semiconductor photocatalysts,TiO₂ is almost the only material suitable for industrial use because of its high stability and low cost.It is also a promising material.At present,the two main factors restricting the development of TiO₂ photocatalytic materials are the low photocatalytic activity and the low utilization rate of solar energy.In this paper,TiO₂ with special morphology was prepared to improve its photocatalytic activity and N-doping was introduced to improve the utilization rate of solar light.A series of single factor experiments were carried out to determine the optimum process parameters for the preparation of TiO₂.And the reasons for the formation of special morphology of titanium dioxide were analysised.The specific work was as follows:（1）Mesoporous spherical TiO₂ was synthesized by one-step hydrothermal calcination method using Ti（SO₄）₂ and TiCl₃ as titanium sources.The effects of titanium source ratio,hydrothermal temperature,hydrothermal time,calcination temperature and calcination time on photocatalytic properties were studied by a series of single factor experiments.The preparation process was simple,high efficiency and no need to add organic additives to make it disperse,at the same time the sample with good dispersion and high photocatalytic performance could be obtained.The grain sizes of the sample were 29.0 nm,and the specific surface area of the sample was 99.201 m²/g.The degradation rate of methyl orange was 98.74%in visible light.The sample prepared with Ti（SO₄）₂ as titanium sources was anatase phase TiO₂,and the grain sizes of the sample were 32.2 nm,the specific surface area of the sample was 80.7 m²/g,and the average pore sizes of the sample were 11.3 nm.The degradation rate of methyl orange was 82.59%in visible light.The sample prepared with TiCl₃ as titanium sources was rutile-anatase mixed phase TiO₂ with a mixture ratio of 24:1.The grain sizes of the sample were 117.1 nm,the specific surface area of the sample was21.1 m²/g.The differences in crystal phase,grain size and morphology of TiO₂ prepared with different titanium sources were analyzed and the reasons for its formation were explored.The advantages of mesoporous spherical TiO₂ prepared by mixed titanium source compared with TiO₂ prepared with single titanium source were analyzed.（2）The mesoporous slice anatase TiO₂ exposed（001）face was prepared by two-step hydrothermal method.The optimum preparation process was determined by a series of single factor experiments.The specific surface area was 42.3 m²/g and the average pore diameter was 10.0 nm.The degradation rate of methyl orange almost reached 92.5%in visible light for 2 h.The adsorption of fluoride ions on the surface of titanium dioxide could reduce the energy of（001）and（101）face,and made the（001）face more stable than that of（101）face.Therefore,the growth rate of TiO₂ in[001]direction and[101]direction was changed,and finally the slice TiO₂ was obtained.The addition of hydrazine hydrate with strong reducibility led to an increase in the surface defects of the slice TiO₂,resulting in the doping of nitrogen.And the specific surface area of the slice TiO₂ was greatly increased at the same time.