Cellulase deinking of fresh and aged recycled newsprint/magazines (ONP/OMG)

Three commercial cellulases were evaluated for their effects on deinking of both fresh and artificially aged old newsprint (ONP) mixed with fresh old magazines (OMG) at a ratio of 7:3. The enzymes were added at the beginning of the repulping stage followed by incubation for up to 3 h. Although these enzymes were able to detach a significant amount of ink from the ONP/OMG, cellulase deinking was less efficient than either sulphite or alkaline deinking chemistry. None of the three cellulase enzymes tested were able to deink aged ONP/OMG, and a poor deinkability was also observed by using either sulphite or alkaline chemistry. However, combining enzymes with sulphite chemistry significantly enhanced sulphite deinking and provided a potential strategy to achieve effective deinking of aged newsprint at neutral pH.