Understanding Two-step Polymer Flocculation of Oil Sands Tailings
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Abstract
In this study, a two-step flocculation method by combining anionic and cationic polymeric flocculants on the treatment of oil sands tailings was investigated. Compared to conventional flocculation by using a single anionic or cationic polymer, which has been a widely exploited procedure for flocculation of oil sands tailings and mineral tailings, the two-step flocculation with anionic Magnafloc 1011 (MF) and cationic chitosan showed an enhanced capacity in the treatment of oil sands tailings by improving the quality of released water, i.e. high clarity and low solid content, yet retaining a high settling efficiency. This improved flocculation performance is attributed to combined flocculation effects induced by bridging effect of the anionic polymer and charge neutralization of cationic polymer. The replacement of chitosan by a synthesized temperature responsive polymer, chitosan-g-PMEOMA (CgM), resulted in more water release and better consolidation. The CgM polymer chains adsorbed on solids at temperatures below the low critical solution temperature (LCST) become more hydrophobic at temperatures above LCST which results in particle aggregation by hydrophobic attraction. This work provides useful information and insights into the development of effective technologies for oil sands tailings treatment and settling of colloidal suspensions.