Flotation deinking of toner-printed papers

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Flotation deinking of toner-printed papers

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Title: Flotation deinking of toner-printed papers
Author: Schmidt, Dale C. (Dale Charles), 1965-
Abstract: The role of electrostatic properties and particle shape on toner flotation is investigated. Toner electrostatic properties, as measured by the zeta potential, are found to have little correlation on floatability due to the strong hydrophobicity of the toner surface. Flotation experiments in a Hallimond tube and in a single bubble flotation tube show that model toner spheres and are more readily floated than similar volume disks. High-speed motion pictures of particle/bubble interactions in a flowtube show differences in disk and sphere behavior. Spheres are deflected away from the bubble by flow but usually attach if they contact the bubble surface. Disks often collide with the bubble edge-on but immediately bounce off, seldom attaching to the bubble due to the very short contact time. Alternatively, disks (particularly small disk fragments) turn to the side as they approach the bubble but seldom attach due to a large thin-film drainage area.To describe the motion of large disks around a bubble, a simple hydrodynamic model is constructed and used to conduct a parametric study of the effect of disk size and initial orientation on the efficiency of collision, $E\sb{c},$ attachment, $E\sb{a},$ and collection, $E=E\sb{c}E\sb{a},$ and to compare these results with those computed for spheres. Initial disk orientation is shown to significantly affect collision and attachment efficiencies, and a mean value of each is calculated by taking the average over a range of equally spaced initial disk orientations assumed to be equally probable. Large disk-to-bubble radius ratios ($>$0.1) are found always to yield greater collision efficiencies than those for equivalent spherical particles. An equivalent sphere is one with an equal disk volume, computed on the basis of a diameter-to-thickness aspect ratio of 40. Attachment efficiencies of large disks, on the other hand, are always lower than the values obtained for equivalent spheres. The decrease in $E\sb{a}$ is always greater than the increase in E$\sb{c},$ so that the predicted collection efficiency E for disks is always less than that for spheres. These predictions for disks vs. spheres are in qualitative agreement with experimental observations.
Description: Thesis (Ph. D.)--University of Washington, 1996
URI: http://hdl.handle.net/1773/9828

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