Abstract
On-site treatment of pesticide waste is necessary to prevent surface and ground water from being polluted. A treatment method using photocatalyst (titanium dioxide) is proposed. In the study, kinetics of photocatalytic decomposition of herbicide 2, 4-D-butyl under solar-simulated irradiation was investigated. The following results were obtained.
(1) The rates of photocatalytic decomposition are described by a simple Langmuir form, r=kKC/ (1+KC) and the rate equation can be approximated by first-order kinetics with respect to the concentration of 2, 4-D-butyl below 2.1×10-6 mol·l-1 (0.58 ppm).
(2) The rate constants k are proportional to both the square root of the concentration of titanium dioxide and that of light-intensity.
(3) The equilibrium constants of adsorption K are constant under the experimental conditions examined.
(4) Above 300 mg·l-1 of the concentration of titanium dioxide, more than 90 % decomposition occurs within the depth of 0.5 cm in the reactor.
