Improved Dewatering of Mature Fine Tailings Using High Molecular Weight Polyacrylamide Grafted From an Activated Carbon Surface by Surface-Initiated ATRP

The remediation of mature fine tailings remains a critical challenge in oil sand processing due to the inability to dewater the tailings effectively. In this study, high molecular weight polyacrylamide (PAM) (106 g/mol) was grafted from the surface of hydrophobic activated carbon using surface-initiated atom transfer radical polymerization (SI-ATRP) to enhance tailings dewatering. Grafting was done using two SI-ATRP methods, standard and activators regenerated by electron transfer, to evaluate each method's ability to form high molecular weight brushes from a prefunctionalized activated carbon surface that was oxidized and attached with ATRP initiators. Size exclusion chromatography showed that the grafted PAM brushes achieved molecular weights greater than 106 g/mol, while thermogravimetric analysis showed that they had activated carbon contents of 0.5-5.8 wt%. The dewatering performance of the resulting high molecular weight PAM from activated carbon was evaluated against neat PAM by performing settling tests on dilute mature fine tailings. In summary, this work demonstrates the successful grafting of high molecular weight PAM from activated carbon, improving the dewatering of mature fine tailings shown by the increase of solids content up to 50 wt% compared to neat PAM, which only reached 20 wt%. This work advances the application of hybrid flocculants and paves the way for improved water recovery and sustainable tailings management.