The development of a novel non‐leaching flocculant, derived from activated carbon and polyacrylamide

Canadian oil sands are the third largest oil reserves in the world, containing an estimated 28.3 billion m3 of recoverable bitumen. Extraction of bitumen via surface mining and water‐based extraction leads to the formation of tailings ponds, which contain slow settling mature fine tailings (MFT). These MFT can take hundreds of years to settle on their own. Polymer flocculants are used to improve the settling rate of the MFT. This requires a significant amount of polymer, which may itself have environmental impacts. Here, we describe development of a solid‐state flocculant using activated carbon (AC) as a backbone for polyacrylamide (PAM) flocculant branches, with the intention that this solid‐state flocculant would reduce the amount of polymer applied, replacing the bulk of the material with hydrophobic AC, and limit leaching of these materials. The development of this flocculant is achieved by bromination of AC followed by reaction with cis‐octadecen‐1‐ol at the carbon surface. Subsequently, PAM was attached to the alkene of the enol via thermally induced radical polymerization. This AC‐PAM demonstrated effective flocculation of 5% MFTs at a minimum dosage of 120,000 ppm with an initial settling rate of 33 m/h. Thermogravimetric analysis determined that the AC‐PAM had 2% PAM content, indicating that the system only uses 2400 ppm polymer, which is a significant reduction when compared to the typical 20,000 ppm of PAM otherwise required to flocculate 5% MFTs. This demonstrates a marked reduction in the polymer required to flocculate MFTs, reducing potential environment impact.