ABSTRACT
Paper recycling requires the collection of wastepaper and the cleaning of cellulose fibers from ink and other additives introduced during paper production and printing
processes. The de-inking separation is accomplished through pulping, in the first step, and then screening, washing, flotation, and bleaching in the following steps [1]. The goal of pulping is to disintegrate the complex paper matrix and release cellulose fibers from the ink and mineral filler. The fiber is then recovered in a combination of separation steps. Ink particles (as well as hydrophobized mineral filler particles) can be successfully removed from the paper pulp by flotation. This is due to the 'natural' hydrophobicity of many inks and attractive interactions between air bubbles and ink particles. Although this general strategy was recognized a long time ago, probably at the beginning of paper recycling activities, no direct measurement of the forces involved between the particulates in de-inking flotation systems has been reported in the technical literature, mainly due to the lack of appropriate instrumentation. Several surface-chemistry laboratories using atomic force microscopy (AFM) are now studying this issue associated with de-inking flotation [2-4].
