Industrial scaleup of enzyme-enhanced deinking of nonimpact printed toners

The mixed office waste (MOW) portion of presently under-utilized mixed recovered paper grade contains more than 70% uncoated free sheet, mainly printed with difficult-to-deink toners. Both the cost and difficulty of removing toners from MOW have limited upgrading MOW into printing and writing grades. This paper presents the results of an industrial-scale investigation exploring the benefits of enzyme-enhanced deinking. Since residual toner inks are the primary contaminant remaining in deinked marked pulp, 100% laser-printed white office postconsumer waste was used for these trials. The results of three deinking trials - two enzyme trials and a control - are presented. The control was similar to the enzyme trials with the exception that a heat-killed enzyme preparation was substituted for the active enzyme. Results showed increased ink removal is achieved at a low level of a commercially available enzyme preparation in combination with a surfactant. The enzyme-enhanced trials also displayed improved drainage and comparable strength when compared with the control. There were no significant differences in the quality and treatability of the process water from the various trials. Effluent samples from these trials were lower in oxygen demand and toxicity than effluents from the control.