Elucidation of kinetics of photolysis of phenol

Photolysis of phenol has been carried out in a batch reactor using 8W (253.7 nm) UV lamp at initial concentrations of 600 ppm, 400 ppm, 300 ppm, 200 ppm, and 100 ppm in aqueous solution. The transmittance (T) was found to be unity for 600 ppm and was decreasing for other concentrations. The rate of degradation was found to be constant and was independent of optical density (D) and T for 600 ppm. At all other concentrations, the rate varied non-linearly with time, moles, D and T. Equation based on the combination of Stark-Einstein law and Lambert-Beer Law is found to explain the rate of degradation satisfactorily at all concentrations. The order of the reaction was found to vary from zero to one depending upon the mole or optical density. An effectiveness factor, defined as the ratio of the rate of reaction during falling period of T to that at the constant T has been found to explain degradation from 600 ppm to 10 ppm satisfactorily.