http://nova.newcastle.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:278 Experiments have been conducted in a shear cell in order to provide insight into the separation of floes by size and density in a hydrocyclone. The size of the aggregates was measured after shearing at a rate comparable to that found within a typical hydrocyclone. Two types of coal tailings from the Hunter Valley, NSW Australia with average sizes of about 0.4 mu m and 10 mu m were investigated. The size of aggregates after shearing was measured for a range of different polymeric flocculants of varying molecular weight and charge density. Under certain conditions 90% of the aggregates from the submicron tailings have size greater than 38 mu m after shear at 1200 s(-1) for 30 s. The aggregates produced from the 10 mu m tailings had over 90% larger than 82 mu m with the flocculants tested. The size of the aggregates remained sufficiently large after shearing to be suitable for hydrocyclone dewatering. The density of the aggregates was calculated from the aggregate size and mass fractal dimension. The small difference between the density of the aggregates and water was found to be the factor limiting their velocity under the applied centrifugal acceleration. (c) 2005 Elsevier B.V All rights reserved. 2010-04-27T05:58:48.794Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:658 The addition of silica particles (4.3, 19, 43, 105, and 285 nm) to stable alumina dispersions (310nm) was found to aggregate the alumina causing the large aggregates to settle out. The oppositely charged silica particles adsorb onto the alumina particle surface resulting in charge neutralisation, bridging and aggregation. The effect of particle size ratio and surface coverage on the amount of silica required to produce the clearest supernatant was investigated. It was found that as the silica particle size increases the number of particles needed for optimum aggregation decreased, although the total amount of silica (wt.%) increased. Below a particle size ratio of about 0.025, the number of silica particles exceeded the calculated half surface coverage number, while at particle size ratios near 1.0 the number of silica particles needed was only about 25% of that calculated for half surface coverage. The median point of the range of concentrations that produced clear supernatants correlated with zero zeta potential. 2010-04-27T05:42:09.876Z ]]>