Studies Of Photocatalytic Degradation Of Acetic Acid On TiO₂ Particles And Thin Films

The TiO2 photocatalytic degradation method is now arousing more and more interest in photochemistry and environmental protection field because TiO2 has many advantages such as good photo-stability, high photocatalytic activity, low cost, nonpoison, simple equipment, and so on. At present, there are more than 300 kinds of pollutant organics, which can be degraded by photocatalysis method. The furfural is a widely used chemical product. While during the producing of furfural, the wastewater must be discharged by the factories. Photocatalysis degradation is a much more substantial and promising method in researching the feasibility of the furfural wastewater being processed by this method because the other industrial wastewater treatment methods cannot be used with good results.The paper chooses the main pollutant of the furfural wastewater－acetic acid as the researching material being processed by photocatalysis degradation method.The high performance liquid chromatographic method is employed for determining acetic acid with symmetry 5μm C18(4.6×150mm)column and mobile phase of 0.0020 mol/L H2SO4 at a flow rate of 1.0 ml/min .Detection is made by a UV detector at 210 nm with external standard calibration. The merits of the method are rapidness of the analysis, good selection of the compounds and high-sensitivity.The impact factors of photocatalytic degradation include the initial concentration of organic compounds, photocatalyst dosage, temperature, amount of air, initial pH value, reaction time, intensity and wavelength of the photo-illumination and mixed impure types etc.Under the mercury lamp illumination with the intensity of 9.06×104 Lx, the optimum photocatalysis conditions of 25 mg/L, 500 ml acetic acid solution on TiO2 powder are 700 mg TiO2, 35±2oC temperature, 0.5 ml/min air flow and pH=4.2. The photocatalytic degradation rate of acetic acid and TOC are 100% and 51.1% respectively in 160 min. The acetic acid in aqueous solution would be mineralized with the longer time.We can get a line equation with better linear relation, 1/ V0= 15.85 (1/ C0) +2.61,correlation coefficient r=0.994, the values of apparent adsorbing balance constant K and surface reaction rate constant k are 0.165 L/mg and 0.383 mg/L·min respectively. Then we can conclude that at the experimental condition the photocatalysis procedure of acetic acid can be described with the Langmuir- Hinshelwood(L-H)kinetic model. Although we can get the better efficiency of photocatalysis of acetic acid on TiO2 powder in water suspension, reusing of TiO2 powder is difficult, which somewhat restricts the actual utilization of this method. Preparing high efficiency photocatalytic thin films is the researching key to resolve the problem of separation TiO2 from solution.The methods for preparing TiO2 thin films include electron beam sputtering, chemical vapor deposit, sol-gel, hydrolysis-precipitation, liquid-phase deposit and so on. The sol-gel method is the usually used method. At present, the research of using hydrolysis of TiCl4 to prepare the thin film is very rare, but this method demands low temperature. The composites of the thin film are homogeneous and the particles on the thin film are nanosized with the small ranges. The technology of the method is simple so that it can be easy used for preparing the big area thin films. In this paper, TiO2 thin films had been prepared on glass substrates using hydrolysis of TiCl4 by the method of soaking in the TiO2 colloid and lifting the substrates from the TiO2 colloid. The TiO2 thin films were investigated by X-ray diffraction (XRD); scan electron microscopy (SEM), energy dispersion spectroscopy (EDS) and weighting method to characterize the particle size, surface properties. UV adsorption spectroscopy and visible light transmission rate were employed to investigate the optical characterization of the thin films. The results show that the weight of the thin films is in good linear correlation with the coating layers. The thin films coated 4 layers with 0...