The role of oxalic acid in the ozone bleaching kinetics of an XO-kraft pulp

The effect of oxalic acid on the reaction kinetics of ozone with a Eucalypt us globulus kraft pulp was studied. Xylanase treatment (X) and oxygen delig nification (O) were carried out on the pulp before the kinetic study. Ozone treatment was carried out in a special batch reactor at low consistency (0 .5% o.d.p.). The main variables were ozone consumption and oxalic acid dose s, and the measured responses were kappa number, viscosity and brightness. The positive, effect of oxalic acid was shown. First order kinetics for bot h cellulose degradation and lignin removal were observed. For chromophore d egradation, the kinetics were also first order. The addition of oxalic acid increased the rate of delignification and decreased that of cellulose degr adation during ozone bleaching.