Study On Preparation And Properties Of Modified TiO₂ Photocatalyst

Humans are facing issue of organic pollutants.The traditional physical chemistry or biological method is difficult to effectively remove it.TiO₂ photocatalytic oxidation technology as an advanced method is a promising method to remove all kinds of organic pollutants in water,which is efficient and friendly for organic pollutant degradation in water.TiO₂ nanopowder?such as comercial Degussa P25 TiO₂?shows high photocatalytic activity for degradation of organic pollutants in water,but TiO₂ nanopowder dispersed in water becomes colloid and difficult to recycle,which limits its practical application.It is urgent to develop a high preformance photocatalyst.TiO₂ was prepared by homogeneous precipitation hydrothermal method using urea and titanium sulfate as precursors.Methyl orange?MO?is used as model of organic pollutants in water.The effects of pH,storage time of aqueous titanium sulfate and preparation conditions on the photocatalytic performance of titanium dioxide were investigated.The results show that the TiO₂ prepared by hydrothermal reaction at 160 oC for 20 h and calcination at 800 oC using aqueous titanium sulfate of pH-0.51 and storage 60 d,exhibited excellent photocatalytic performance.Moreover,the as-prepared TiO₂ has large particles size,and can be recovered easily after catalysis.Infrared?IR?,X-ray powder diffraction?XRD?analysis showed that the longer the storage time of titanium sulfate aqueous solution,the more the hydroxyl number of the TiO₂ surface,the higher crystallinity,which may be responsible for excellent photocatalytic performance of the as-prepared TiO₂.In order to further improve the photocatalytic activity of the TiO₂,photocatalytic performance of silver phosphate,carbon and carbon nitrogen modified TiO₂ was investigated.It was found that doping a small amount?1wt%?of silver phosphate or carbon?n?TiO₂?/n?C?= 200?significantly improve the photocatalytic activity of the TiO₂,especially when the TiO₂ was modified with 1wt% Ag3PO4.Under reaction conditions of 1.5 g/L 1wt%Ag3PO4/TiO₂,150 mL 20 mg/L aqueous methyl orange solution was thoroughly degradated in 50 minutes,whereas 150 mL 20 mg/L aqueous methyl orange solution was degradated only 81.6% under same reaction conditions.Moreover,the 1wt%Ag3PO4/TiO₂ catalyst shows good stability.The catalyst exhibited excellent photocatalytic activity after 4 cycles.XRD results show that silver phosphate,carbon are highly dispersed on TiO₂.UV Vis diffuse reflectance?UV-Vis DRS?analysis shows that the absorption peak of silver phosphate,carbon modified TiO₂ was red shifted,which is responsible for the improved photocatalytic activity.In this paper,the reaction conditions of photocatalytic degradation of methyl orange over 1wt%Ag3PO4/TiO₂ catalyst were optimized.The optimum reactions are 20 mg/L aqueous methyl orange,1.5g/L catalyst.