SEDIMENTATION OF FLOCCULATED ALUMINA SUSPENSIONS - GAMMA-RAY MEASUREMENTS AND COMPARISON WITH MODEL PREDICTIONS

A gamma-ray absorption technique has been used to measure the evolution of volume fraction profiles during transient settling of flocculated alumina suspensions. The experimental system consisted of a submicron, polydisperse alumina powder immersed in an organic solvent (decalin) with fatty acids of varying molecular weights adsorbed at the alumina/decalin interface. The interaction energy at particle contact was determined by the thickness of the adsorbed layer. The volume fraction profiles measured were compared with model predictions and it was found that the model only partly describes the settling process. Further, the experimental results showed that the permeability of aggregated particle networks at low volume fractions is larger than expected from simplistic permeability models.