WET AIR OXIDATION OF PHENOL - FACTORS THAT MAY INFLUENCE GLOBAL KINETICS

Wet air oxidation is presented as a technique for removal of organic p ollutants found in waste water streams. The oxidation of phenol has be en achieved at moderate temperatures (T=473 K) and pressures (3.0 MPa total pressure) with up to 95% destruction in less than 30 minutes. An increase in either oxygen concentration or temperature has a positive influence on reaction rate, with temperature following an Arrhenius d ependence. The influence of pH is shown to be complex. For a 0.01 mol( -1) phenol solution significant destruction was obtained; however, whe n the initial pH was modified to either less than two or between neutr ality and ten, practically no change in phenol concentration was obser ved. When oxidation is carried out in strong alkali media (pH>12) reac tion rate is enhanced significantly. Addition of small quantities of h ydrogen peroxide resulted in enhanced rates of oxidation even at low t emperatures (373 K). When hydrogen peroxide is added, oxygen plays a n egligible role in the initial reaction, only becoming significant once the hydrogen peroxide has been consumed. The nature and geometry of t he reactor has been found to play an important role in free radical te rmination steps, with metal surfaces likely to enhance significantly d ecomposition of organic radicals.