The Study Of Dye Sensitized Phototransformation-chemiluminescence Of Chlorophenols

Chlorophenols are the common pollutants which are difficult to degrade in the environment. Because they exist in many kinds of industrial wastewater (e.g. in herbicide, oil refining, paper-making and plastic production processes), there has been a growing concern related to the damage due to the presence of chlorophenols. In the previous studies, it was found that chemiluminescence phenomenon could be produced when the photosensitized degradation products of chlorophenols reacted with bromosuccinimide (NBS). And the chemiluminescence intensity was closely related to the concentration of the chlorophenols. Therefore, the method of determining chlorophenols with flowing injection chemiluminescence (FIA-CL) had been established. However, the flowing system is too complicated and it is hard to explain the reaction mechanism. Thus, this paper studies the electrochemiluminescence (ECL) after the sample solution of chlorophenol is pre-transformed with dye sensitized photodegradation process. Then the paper discusses the mechanism of this reaction. The main contents are outlined below:1. The paper initially studied the factors that affects the ECL intensity, including light sources, photosensitizers, pH, surfactants, voltage, flowing rate and electrodes etc. 2,4-DCP was taken as a model compound. It was found that the strongest ECL can be obtained when the sample solution (pH=7.00) containing 2.50×10-5 mol·L-1 fluorescein as photosensitizer, 2.00×10?3 mol·L-1 CTAB was injected into a carrier of 0.05 mol·L-1 sodium borate.2. It was found that the singlet oxygen was very important in the process of phototrasformation. The solvent system has a great influence to the process of photosensitize. However, the reaction intermediates were stable in the acid and media solution, but not basic. The reaction intermediates were proved to be peroxide compounds by post column chemiluminescence detection. The research found that the oxygen in the solution was very important during the process of electrochemiluminescence and more oxygen help to increase the ECL intensity. The ECL has become stronger when adding the typical coreactant Na2S2O8. Consequently, we inferred that there exist an ECL coreatant, which may be O2·- got by deoxidizing from O2, then the O2·- reacted with the reaction intermediates which may be peroxide compounds, and the products reacted with fluorescein to generate excited state fluorescein, at last the excited state fluorescein emitted fluorescence emission.