PHOTOCATALYTIC DECOMPOSITION OF CATECHOL IN AQUEOUS MEDIA UNDER MILD CONDITIONS

The photocatalytic decomposition of catechol as a pollutant in water was investigated. Catechol is a widely used intermediate that finds applications in a range of industries. It is significantly soluble in water but quite resistant to biological degradation. A batch vertical reactor was used in which a 250 W, UV lamp was immersed symmetrically with the advantage of receiving total emitted photons. The reactor was conic in the bottom section, providing no dead zone with the aid of circulating stream. It was also jacketed with external circulating stream of cooling water, to adjust the temperature. The well known powder of titanium dioxide (anatase) was used as the catalyst. The effects of some parameters including catalyst concentration, pH and temperature were studied to find the optimum relevant values. Data showed a maximum catechol conversion at catalyst concentration of about 10 mg/L and pH about 4.5. The conversion of catechol was increased with temperature and could reach more than 25% after about 180 min irradiation at 303 K. Based on experimental data, obtained under optimum and mild conditions, an empirical kinetic model was proposed for initial rate as a function of catechol concentration. This model includes the two competing observed decomposition paths, under the effects of only UV light and UV/TiO2. A power law model and the Langmuir-Hinshelwood model have good agreements with the results respectively. This model is able to justify the observed dependence of the catechol initial decomposition rate on its initial concentration.

کلیدواژه ها:

Photocatalysis ، UV/ TiO2 ، Catechol ، Pollutant decomposition