EFFECT OF SALT ON THE FLOCCULATION BEHAVIOR OF NANOPARTICLES IN OIL SANDS FINE TAILINGS

Currently, two commercial plants, operating in the Athabasca region of Alberta, produce approximately 20 percent of Canada's petroleum requi rements from oil sands. Surface mined oil sand is treated in a water b ased separation process that yields large volumes of clay tailings wit h poor settling and compaction characteristics. Clay particles, suspen ded in the pond water, interact with salts, dissolved from the oil san ds ore, to produce mature fine tailings (MFT) containing only 20 to 50 w/w% solids. As a result, large sedimentation ponds are required to p roduce enough process water to recycle for the plant. Tailings pond dy kes can only be constructed during a short summer season. Consequently , the capability to predict production rate and final volume of MFT is essential for mine planning and tailings disposal operations. Previou s research has demonstrated that a small fraction of nano sized clay p articles (20 to 300 nm) effectively controls the bulk properties of MF T. These particles are present in the original ore and become mobilize d into the water phase during the oil separation process. In this work , the nano sized particles have been separated from the bulk tailings and subjected to a fundamental study of their flocculation behavior in model tailings water. Photon correlation spectroscopy and a deuterium NMR method were used to follow particle flocculation and gelation pro cesses. These results were correlated with particle settling data meas ured under the same conditions. It was determined that the nano partic les form fractal flocs that eventually interact to give a thixotropic gel. The ultimate sediment volume produced is almost entirely dependen t on the original concentration of nano particles while the rate of wa ter release is governed primarily by electrolyte concentration.