MEDIUM-CONSISTENCY OZONE BLEACHING WITH ENZYME PRETREATMENT

Several elemental chlorine-free bleaching sequences with ozone and low levels of chlorine dioxide were evaluated. The sequences focused on m edium-consistency ozone bleaching with xylanase pretreatment. Oxygen-d elignified softwood kraft pulp was bleached with either ZED or XZED se quences. Brightness, viscosity, and kappa number were determined and e ffluent characteristics evaluated. The use of xylanase pretreatment re sulted in significant brightness gains and kappa number reduction. Thi s reduction in kappa number can also be used to decrease the ozone cha rge.