REACTION-MECHANISMS AND KINETICS OF CHEMICAL PRETREATMENT OF BIORESISTANT ORGANIC-MOLECULES BY WET AIR OXIDATION

The partial wet air oxidation of aqueous solutions of p-coumaric acid and polyethylene glycol, two model organic pollutants typically found in wastewaters of agricultural origin and polymer-manufacturing respec tively, has been investigated at temperatures from 373 K to 513 K and oxygen partial pressures from 0.2 MPa to 3 MPa. Reaction intermediates have been identified and their concentration profiles have been deter mined using liquid chromatography as the main analytical technique, an d reaction mechanisms and pathways have been postulated. The impact of various heterogeneous catalysts, such as metal oxides and noble metal s, on the kinetics and mechanisms of the reaction has also been studie d. Conversion of these model compounds through various oxidation inter mediates to end-products, such as carboxylic acids, could be easily ac hieved even under mild operating conditions, while further total oxida tion proved to be difficult even under more severe conditions. Catalys ts were found to be, in general, capable of increasing the rates of bo th partial and total uncatalysed oxidation. The stability of some of t he catalysts used has also been studied with respect to metal leaching and deactivation. The implications for complete removal of bioresista nt organic pollutants by partial wet oxidation followed by a biologica l treatment step are also discussed. (C) 1997 IAWQ. Published by Elsev ier Science Ltd.