BIOLOGICAL DEINKING TECHNOLOGY FOR THE RECYCLING OF OFFICE WASTE PAPERS

Results of the enzymatic deinking approach were demonstrated on a labo ratory scale to provide a good quality deinked pulp from laser-printed alkaline office paper wastes. It has been suggested that, for alkalin e papers, the majority of inks are localised on the paper coatings and fillers consisting mainly of CaCO3. Enzyme treatment improved by stoc k acidification and dissolution of CaCO3 prior to flotation resulted i n effective detachment and dispersion of toner specks ensuring a high deinking effectiveness. Highly dispersed toner particles separation wa s promoted by acidic flotation in the presence of a surfactant, hydroc arbon oil, applied to improve microink agglomeration and hydrophobicit y of the toner particles and agglomerates. A minimal level of visible dirt was observed for optimised enzyme-treated and acidically floated pulps. Both enzyme preparations significantly favoured deinking effect iveness relative to control stocks. Only minor differences were observ ed between cellulase and resinase (lipase) preparations. The lowering of pH prior to flotation considerably improved the cleanliness not onl y of the enzyme-treated, but also the control pulps relative to alkali ne floated stocks. The addition of an appropriate surfactant, such as hydrocarbon oil proved to be a necessary factor to prevent redepositio n of microink particles on the fibre surfaces and promote the separati on of highly dispersed toner particles from the fibre network. (C) 199 8 Elsevier Science Ltd. All rights reserved.