Hydrodynamic Particle Volume and Its Relationship to Mixed Office Waste Paper Flotation Efficiency. Part I, 1995 Pulping Conference Proceedings

Ruth M. Vidotti

Donna A. Johnson

Edward V. Thompson

University of Maine

Laser printed standard sheets of paper were re-pulped and a portion of the repulped furnish treated with a cellulase enzyme to "clean" the toner particles. The original "untreated" portion contained the usual mixture of clean and hairy toner particles, while the "cleaned" portion contained only clean toner particles. Image analysis results indicate the distributions of toner particle sizes are essentially identical in both portions (samples). Both samples were fractionated using a Bauer-McNett fiber classifier to produce four fractions with size ranges of 100-200, 200-300, 300-420, and > 20µm. Image analysis results show large differences between the distribution of toner particles for the untreated and cleaned samples, especially for the 300-420 and > 420 µm fractions. In particular, the cleaned fractions are much sharper and the peak of the distribution is centered in the appropriate size range, while the untreated fractions are much broader with considerable percentages of small particles. Microscopic examinations of the untreated repulped furnish and Bauer-McNett fractions were performed to determine the ratio of clean to hairy particles present. It is shown that small, hairy particles are preferentially held up by larger size screens and account for the broad distributions of the larger size fractions of the untreated furnishes. Since image analysis or visual observation measures only the size of the black toner particle and not any fibers attached to it, it is hypothesized that hairy particles possess a larger "hydrodynamic volume" or size, and this is what determines in which Bauer-McNett fraction the toner/fiber agglomerate will appear.