Use of xylanase in the totally chlorine-free bleaching of eucalyptus kraft pulp

Environmental pressures are forcing the pulp and paper industry to develop new technologies that reduce or eliminate the presence of various contaminants in bleaching plant effluents. Oxygen delignification techniques, replacement of elemental chlorine with chlorine dioxide, ozone, hydrogen peroxide and new bleaching agents as well as the use of xylanase enzymes for biobleaching, reduce or eliminate the production of chlorinated organic substances. This paper compares the sequence XOZP with OZP in the bleaching of Eucalyptus globulus kraft pulps. It has been studied the influence of enzymatic treatment on the consumption of bleaching agents: ozone and hydrogen peroxide. Chemical, physical, optical and refining properties of pulps, as well as COD and colour of effluent are studied as well. The xylanase treatment is positive and it is possible to manufacture fully bleached pulps at high brightness and viscosity without using chlorine compounds at a low ozone and hydrogen peroxide consumption.