Aqueous solutions of phenol were oxidized by hydrogen peroxide assisted by microwave(MW)irradiation.A simple kinetic model for the overall degradation of phenol in the presence of excess H_(2)O_(2) is proposed in which the degradation rate of phenol is expressed as a linear function of the concentrations of phenol and H_(2)O_(2).A detailed parametric study showed that the degradation rate of phenol increased with increasing[H_(2)O_(2)]until saturation was observed.Phenol degradation followed apparent zero-order kinetics under MW radiation or H_(2)O_(2) oxidation.However,after 90 min of irradiation,the observed kinetics shifted to pseudo first order.The overall reaction rates were significantly enhanced in the combined MW/H_(2)O_(2) system,mainly because microwave could accelerate H_(2)O_(2) to generate hydroxyl radical(·OH)and other reactive oxygen intermediates.The observed synergetic effects of the MW/H_(2)O_(2) process resulted in an increased in the net reaction rate by a factor of 5.75.When hydrogen peroxide is present in a large stoichiometric excess,the time required to achieve complete mineralization is reduced significantly.
