Enhanced dewatering of oil sands tailings by a novel water-soluble cationic polymer

Abstract

This work investigates how poly(vinylbenzyl trimethylammonium chloride)–poly(VBTMAC)–flocculates oil sands mature fine tailings (MFT). This water-soluble cationic polymer contains pendant benzene rings that make it partially hydrophobic. The positive charges on the poly(VBTMAC) backbone neutralize the negatively-charged MFT clays while the hydrophobic benzene rings help expel the water trapped in the aggregates. Vinylbenzyl trimethylammonium chloride can be polymerized to produce long chains (comparable to anionic polyacrylamide) with fast polymerization rates. Focused beam reflectance measurement (FBRM) experiments showed that larger aggregates were formed using higher molecular weight poly(VBTMAC), which is evidence of the bridging mechanism. The flocculation performance of poly(VBTMAC) was tested against commercially available anionic polyacrylamides for undiluted MFT by measuring the extent of dewatering in filtration tests and the rheological properties of the sediments. Our results showed that poly(VBTMAC) is a better flocculant in terms of ease of production, fast dewatering rate, and formation of sediments with high shear strength, but required substantially higher dosages to perform better than commercially available anionic polyacrylamides.