Study On Photocatalytic Degradation Of Parachlorophenol

Chlorophenols are a series of important chemical raw materials. They are notonly often used as raw materials of pesticides, bactericides, fungicides andpharmaceutical industry, but also used in the preservatives and disinfectants of wood,vegetables, leather, coatings, etc. They are also intermediate products produced in alot of industrial synthesis. Chlorophenols are carcinogenic, teratogenic, mutagenic,nonbiodegradable and highly toxic. Photodegradation is one of the most importantnatural degradation process of such substances in environmental waters. In this study,parachlorophenol was taken as a model pollutant. In order to improve the theoreticalstudy on photodegradation behavior of chlorophenols in the environment, andprovided reference to the prevention and treatment of waste water containingchlorophenols, the direct photolysis of parachlorophenol and photodegradationbehavior with coexisting substances were studied. In this article, some works carriedout were shown as below.Parachlorophenol direct photolysis degradation experiments were conductedunder xenon lamp, mercury lamp and sunlight. The results confirmed that directphotolysis of parachlorophenol can be occur quickly when the wavelength of theradiation light is less than300nm, but almost no direct photolysis under sunlight.Photodegradation of parachlorophenol coexisting with humic acid and Fe²⁺werestudied respectively, using a xenon lamp as the light source to simulate sunlight. Theresults show that, parachlorophenol photodegradation actually slowed under xenonlamp, after adding humic acid or FeSO₄. TiO₂, which is a typical photocatalyst, wasalso used as an additive in the photodegradation experiment under xenon lamp. Theresults show that TiO₂might make a certain impact on the degradation products.Adding Fe2O3or polyaniline into TiO₂failed to improve the catalytic activity of TiO₂.This study also demonstrated parachlorophenol photolysis behavior under variousconditions is basically in line with the first-order kinetics, and the intermediateproduct were Cl^-, para-benzoquinone, hydroquinone and an unknown polar substancewhose peak is in front of water peak.