DEINKING

Increasingly, large volumes of used paper are recovered for recycling. Before the recovered paper can be used to manufacture new ‘white’ grades of paper, like the production of graphic papers, the printing inks have to be removed to increase the whiteness and purity. A chemical process using alkali and detergents is used. The recovered paper is first dissolved in water and separated from the non-fibre impurities. The fibres are then progressively cleaned in order to obtain the pulp and during this stage the ink is removed in a flotation process where air is blown into the solution. The ink adheres to bubbles of air and rises to the surface from where it is separated.
After the ink is removed, the fibre may be bleached, usually with hydrogen peroxide.

THE DEINKING PROCESS