Biodegradation of phenol by Pseudomonas putida (NICM 2174), a potential biodegradent of phenol has been investigated for its degrading potential under different conditions. Pseudomonas putida (NICM 2174) cells immobilized in chitosan were used to degrade phenol. Adsorption of phenol by the chitosan immobilized matrix played an important role in reducing the toxicity of phenol. In the present work, results of the batch equilibrium adsorption of phenol on chitosan from its aqueous solution at different particle sizes (0.177 mm, 0.384 mm, 1.651 mm) and initial concentration of phenol (20,40,60, 80, 100, 120, 140, 160, 180, 200 mg/l) have been reported. The adsorption isotherms are described by Langmuir, Freundlich and Redlich-Peterson types of equations. These indicate favourable adsorption with chitosan. From the adsorption isotherms, the adsorption capacity, energy of adsorption, number of layers and the rate constants were evaluated. In batch kinetic studies the factors affecting the rate of biodegradation of phenol, were initial phenol concentration (0.100 g/l, 0.200 g/l, 0.300 g/l), temperature (30°C, 34°C, 38°C) and pH (7.0, 8.0, 9.0). Biodegradation kinetic data indicated the applicability of Lagergren equation. The process followed ®rst order rate kinetics. The biodegradation data generally ®t the Lagergren equation and the intraparticle diffusion rate equation from which adsorption rate constants, diffusion rate constants and diffusion coef®cients were determined. Intraparticle diffusion was found to be the rate-limiting step. Cell growth contributed signi®cantly to phenol removal rates especially when the degradation medium was supplemented with a utilizable carbon source.
