THE ROLE OF THE HYDROXYL RADICAL IN PEROXIDE BLEACHING PROCESSES

The kinetics of N,N-dimethyl-4-nitrosoaniline (DMNA) oxidation in alkaline and acidic hydrogen peroxide have been studied at 50-degrees-C. Based on the premise that DMNA is a specific acceptor for the hydroxyl radical during the oxidation process, the effects of transition metal ions and stabilizing agents on steady state concentrations of the radical species have been determined. Using these kinetic formulations, it has been inferred that the hydroxyl radical has little influence on alkaline peroxide bleaching of mechanical wood pulp at low consistency. However, using a two-stage acid/alkali peroxide bleaching process a correlation exists between the calculated relative hydroxyl radical concentration in the acidic stage and the final pulp brightness after the alkaline stage.