Photocatalytic Degradation Of Organic Waste Water On Surface Modified Nanometer Size Titanium Dioxide

Photocatalysis oxidation technology was usually adopted for its high efficiency, low energy consumption,simple operation,mild reaction conditions,wide application range,and little secondary pollution.Nano-TiO₂ could be widely applied in photocatalysis degradation because of its advantages of large specific surface area,non-toxicity,low cost,and long service life. The usage of Nano-TiO₂ was limited by its strong polar,high surface free energy and easily reunitation,and the effective action area of nano-TiO₂ was decreased because nano-TiO₂ was not easy to disperse in water and organic media.Meanwhile, nano-TiO₂ photocatalysts had band gaps of 3.2 ev,the photocatalytic process could be induced by UV light irradiation.The extreme low surface coverage of organic pollutants on the catalyst TiO₂ was the key factor that resulted in the low adsorption and photocatalytic efficiency.The surface of Nano-TiO₂ should be modified to improve its treatment effect.Printing and dyeing industry porduced a large ammount of industrial wastewater.It had the characteristics of higher concentration,deeply tinct,strong toxicity and it was difficultly to be decomposed.Phenol compounds were common pollutants,especially as priority pollutants,and they were difficult to degraded in environment.Surface modification led not only lead to an increase in the light utilization,but also improved the surface coverage.Both of these factors were crucial for the photocatalytic activity of heterogeneous photocatalysis.The conclusions of this study were:(1) To establish a new technology of nano-TiO₂ surface modificationThe surface of nanometer size TiO₂ was simply and fast modified by chemical adsorption in saturated solution of 5-sulfosalicylic acid.After surface modification,a stable,yellow surface complex was formed quickly.(2) The advantages of nanometer size titanium dioxide surface modified with 5-sulfosalicylic acid were:a.Enhancing the wettability of nano-TiO₂ powder surface;b.Good dispersive capacity in polar and non-polar solvent;c.Enhancing the surface coverage ofbenzenoid pollutants on TiO₂ through phenyl group interaction;d.Expanding the wavelength response range from ultraviolet to visible region.e.Improving photoproduction hydroxyl radical yield of nano-TiO₂ surface modified with 5-sulfosalicylic acid by visible light.(3) A new photocatalyst was provided on photodegration of methyl violet by visible light.Comparing with the treatment effects of methyl violet on nano-TiO₂ and nano-TiO₂ surface modified with 5-sulfosalicylic acid with different light irradiation (avoid light,ultraviolet lamp,high pressure mercury lamp and sunlight dysprosium lamp).The removal rates of methyl violet on nano-TiO₂ surface modified with 5-sulfosalicylic acid were all higher than mano-TiO₂.The photocatalysis degradation rate of methyl violet on nano-TiO₂ surface modified with 5-sulfosalicylic acid with sunlight dysprosium lamp irradiation was highest.On optimal photodegradation conditions,including initial pH 9.0,methyl violet 60mg/l,catalyst 8.0g/l,irradiation time 100 min with sunlight dysprosium lamp,the degradation efficiency of methyl violet was 91.3%.(4) A new method was established to photodegrade of p-nitrophenol.The influences of nano-TiO₂ surface modified with 5-sulfosalicylic acid and its dosage,pH value,and p-nitrophenol concentration on the photodegradation were investigated.On optimal photodegradation conditions,including initial pH 4.0,p-nitrophenol 20mg/l, catalyst 60mg,irradiation time 60min with sunlight dysprosium lamp,the degradation efficiency of p-nitrophenol was increased from 50.6%to 92.6%.This photodegradational method was better than the other methods.(5) Photoproduced hydroxyl radical production was detected by alizarin violet ultraviolet spectrophotometry.Irradiation with sunlight dysprosium lamp or high pressure mercury lamp,the production of hydroxyl radical by nano-TiO₂ surface modified With 5-sulfosalicylic acid was higher than it by nano-TiO₂.