Study of biodegradation properties of phthalate esters in aqueous culture conditions

Several kinds of esters are widely used in synthetic lubricants. The evaluation of their influence on the environment is a matter of considerable interest. This paper studies the ultimate aerobic biodegradation of several phthalates, such as dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), di-n-octyl phthalate (DOP) and di(2-ethylhexyl) phthalate (DEHP), and their degrading kinetics by quantitative assessment of the carbon dioxide produced. The production of CO2 was chosen as the evaluation parameter to determine the biodegradability of phthalates in aqueous solution. A kinetic model was established to describe the biodegradation process of phthalates. The results indicated that biodegradation of phthalates followed the first-order kinetic equation; the rate constant (kb) of biodegradation decreased as the carbon number of the alkyl chain increased, and linear phthalates had better biodegradability than branch phthalate. When the initial concentration was over 200 mg/L, a lag phase was evident during the degradation of phthalates, which was prolonged with increased carbon number in the alkyl chain. Easily biodegradable organics, such as glucose, had a favorable effect on the aerobic biodegradation of phthalates. Copyright © 2006 John Wiley & Sons, Ltd.