Flocculation and dewatering of oil sands tailings with a novel functionalized polyolefin flocculant

Abstract

• Use of novel partially-hydrophobic graft polymer flocculant for mineral tailings treatment. • Grafts of PMA with different molecular weights and densities were attached to EPDM backbones. • Use of a central composite experimental design to assess the effect of polymer architecture on flocculation and dewatering performance. • The performance of the graft copolymers was quantified by initial settling rate (ISR), capillary suction time (CST), supernatant turbidity, and sediment solids content. This work investigates the impact of the molecular weight and grafting density of partially hydrolyzed poly(methyl acrylate) grafted onto ethylene-propylene-diene copolymer backbones (EPDM -g- HPMA) on the flocculation and dewatering of oil sands mature fine tailings through a central composite experimental design by measuring initial settling rate, capillary suction time, supernatant turbidity, and sediment solids content. Flocculants with high molecular weight grafts and low grafting densities reduced the initial settling rates, decreased supernatant turbidities, and increased the solids content of the flocculated sediments. The capillary suction time, however, depended mostly on the charge density and on the hydrophobicity of the grafted copolymer. The effect of the EPDM backbone molecular weight was also investigated. Shorter backbones resulted in flocculants that dispersed more easily in water and settled the sediments faster. In addition, they decreased the supernatant turbidity and increased the solids content in the sediments. EPDM -g- HPMA flocculants with graft molecular weight of 179 kDa and grafting density of 13% are outstanding filtration aids, helping generate sediments with 43% solids content and outperforming a reference commercial polyacrylamide flocculant.