Flocculation Efficiency and Spatial Distribution of Water in Oil Sands Tailings Flocculated with a Partially Hydrophobic Graft Copolymer.

This work investigates the effect of partially hydrophobic grafted polymers on flocculation and dewatering of oil sands mature fine tailings. Here, we combine confocal microscopy and rheology to investigate how the graft density of ethylene-propylene-diene grafted with hydrolyzed poly(methyl acrylate) (EPDM-g-HPMA) affects its dispersion in water and flocculation efficiency in terms of sediment solids content and long-term dewatering of oil sands tailings. Increasing the graft density from 30 to 50% makes the flocculant easier to disperse, increases the rate of initial dewatering, and also enhances the viscoelastic response of the flocculated sediments. Conversely, the long-term rheological properties of the flocculated sediments were similar for all flocculants. Tri-dimensional microscopic details of the spatial distribution of water within the flocculated sludge provide novel insights into the performance of the flocculants. Increasing the graft density in EPDM-g-HPMA traps more water within the individual flocs and, consequently, decreases the post-flocculation dewatering rate. Our systematic approach confirms the importance of the spatial distribution of water in the flocculated sediment, which depends on how the flocculant is dispersed and how it retains water in the flocs.