Study On Photocatalytic Oxidation Of 2-chlorophenl With TiO₂ Thin Film Supported By Feather Zeolite

Ultraviolet photocatalytic oxidation mediated by illuminated TiO₂ has received considerable attention as one of the most potential advanced oxidation technologies. It can mineralise a wide rang of organic pollutants such as chlorophenols which are difficult to remove by simple biodegradation in water completely to CO₂, H₂O with high reaction rate and high removal efficiency.Selecting 2-chlorophenol as targeted pollutant, 125W high pressure mercury vapour lamp as UV light source, the effects of TiO₂ concentration, pH value, and initial 2-chlorophenol concentration to photocatalytic reaction are studied using a selfmade photocatalytic reactor. The intermediates and mechanism of photocatalytic degradation of 2-chlorophenol are analyzed by GC-MS. The kinetics of photocatalytic degradation of reactant in slurry system are described as C=Kt TOC=K/t, which are typical of zero-order reaction. The results of experiments show that the optimum catalyst concentration is 0.30 g L^-1, the activity of photocatalysis reaches highest value when pH<3, and the relationship between reaction rate and initial 2-chlorophenol concentration is of inverse correlation. The Cl substituent restrains the photocatalytic oxidation of 2-chlorophenol. O-dichlorobenzene, benzene, (p-) benzoquinone and catechol are detected in the reaction solution by GC-MS.Thin TiO₂ films supported zeolites are prepared by Solid State Dispersion (deionized water and ethanol as dispersant respectively) and Sol-gel method under 300℃, 400℃, 500℃, 600℃. These supported catalysts are characterized by BET surface area, XRD, TiO₂ loading and SEM. For the reason that zeolite has good adsorptive capacity and particular internal structure which can form electrostaticfields in the photocatalytic degradation of 2-chlorophenol, the reaction system of TiO₂ thin film has higher photocatalytic activity than slurry TiO₂, and TiO₂ supported zeolite prepared by Sol-gel at 400℃ is the most active one among these catalysts. The form of L-H adsorption isotherm is found suitable to describe the kinetics ofreaction which can be simplified as TOCt=TOCoe^kt. Intermediatesformed during degradation can have competive adsorptive effect to 2-chlorophenol, and then the disappearance of 2-chlorophenol does not follow an apparent first-order rate. TiO₂ film falls off continually from support when it is used in solution. The phtocatalytic efficiency of TiO₂ film used repeatedly for 11 times decreases to 66.39% (reaction time = 60 min) of the first time, but still excels the of TiO₂ powder.