Kinetics of photodegradation and ozonation of pentachlorophenol.
The oxidation of 2,3,4,5,6-pentachlorophenol (PCP) has been carried out by a photodecomposition process using a polychromatic UV irradiation, and by an ozonation process. In the photodegradation process, the pH accelerated the decomposition rate and the approximate first-order rate constants were evaluated, with values between 0.16+/-0.005 min(-1) at pH=3 and 0.26+/-0.007 min(-1) at pH=9. A more rigorous kinetic study led to the determination of the quantum yields of the reaction, with values of 200+/-7x10(-3) mol/Eins for pH=3 and 22+/-1.1x10(-3) mol/Eins for pH=9. In the ozonation process, the rate constants for the reaction between ozone and PCP were determined by means of a competition kinetics, with values in the range from 0.67x10(5) to 314x10(5) l/mols. The specific rate constants for the un-dissociated and dissociated forms of PCP were also calculated. Finally, in both processes, the intermediate reaction products were identified, the most important being tetrachlorocatechol, tetrachlorohydroquinone and tetra-p-chlorobenzoquinone. Free chloride ion released, which was favored at high pHs, was also followed in both processes.
Javier Benitez
F
F
Departamento de Ingeniería Química y Energética, Universidad de Extremadura, Avda. de Elvas, s/n 06071, Badajoz, Spain. javben@unex.es
Acero
Juan L
JL
Real
Francisco J
FJ
García
Juan
J
D006863:Hydrogen-Ion Concentration; D007306:Insecticides / Q000737:chemistry*; D007700:Kinetics; D010083:Oxidants, Photochemical / Q000737:chemistry; D010126:Ozone / Q000737:chemistry; D010416:Pentachlorophenol / Q000737:chemistry*; D010777:Photochemistry; D014466:Ultraviolet Rays; D014873:Water Pollutants / Q000032:analysis*
D007306:Insecticides; D010083:Oxidants, Photochemical; D014873:Water Pollutants; D010126:Ozone; D010416:Pentachlorophenol