| A temperature-sensitive polymer, Poly N-isopropylacrylamide (poly(NIPAM)), was synthesized and used as a flocculant to treat kaolinite clay suspensions and as an aid to process low-grade oil sand ores. In the settling of clay suspensions, two procedures referred to as procedures A and B, respectively, were employed. In both procedures, the polymer was first mixed with kaolinite suspensions at room temperature. In procedure A, settling tests were carried out at room temperature, i.e., without changing the mixing temperature. In procedure B, the prepared suspensions were heated to 40°C and then settling tests were carried out at this higher temperature. The results showed that procedure B resulted in significantly higher settling rates and smaller sediment volumes. While used as an aid in a low-grade oil sand ore processing, the polymer exhibited a similar behavior in the flocculation of fine particles in the ore, i.e. by adding the polymer at room temperature but operating the bitumen extraction at 40°C, significantly higher bitumen recoveries and faster tailings settling rates were achieved.;To understand the role of the polymer in the settling of clay suspensions, the long-range interaction and adhesion forces between kaolinite particles in aqueous solutions in the presence of the polymer were directly measured using an' atomic force microscope (AFM). The force measurements were carried out at both room temperature and 40°C by following similar temperature-changing procedures as used in the settling tests. At 40°C, stronger adhesion and weaker long-range repulsive forces were measured. The retracting force profiles obtained at different temperatures confirmed the conformation change of the polymer with temperature. |
