Control of slime coatings by the use of anionic phosphates: A fundamental study

A model system comprising of chemically-dissimilar and oppositely-charged m etal oxides has been used to investigate the removal of small particles fro m surfaces and, particularly, the role of interaction forces in this proces s. Techniques including reflectometry, rheology, microelectrophoresis, acou stophoresis and atomic force microscopy have been utilised. Silica particle s adsorbed onto titania surfaces were removed by the addition of phosphate. The phosphate was shown to adsorb selectively to the titania. Desorption o f the silica particles has been attributed to the ability of the phosphate to modify the interaction forces between the metal oxides. Phosphate was fo und to alter the electrostatic force between silica and titania from attrac tive to repulsive. It also introduced an additional repulsive force, which has been ascribed to the presence of a steric barrier. In addition, signifi cant reductions in the adhesive and frictional forces acting between silica and titania were observed. The implications of the findings for 'slimes' c ontrol during the separation of mineral ores are discussed. (C) 2000 Elsevi er Science Ltd. All rights reserved.