Evaluation of a Novel Polymeric Flocculant for Enhanced Water Recovery of Mature Fine Tailings
This thesis explores the feasibility of using a novel degradable cationic flocculant, poly(PLA4ChMA), for enhanced dewatering of mature fine tailings (MFT). Previous research indicated that this material provided improved flocculation of 5.0 wt.% MFT diluted in deionized water compared to commercial anionic polymers, with continued dewatering of the sediment occurring as the polymer undergoes partial hydrolytic degradation. However, the elevated dosages (10,000 ppm) required would make the polymer costly to implement on an industrial scale. With this motivation, the impact of MFT composition and the use of process water is explored while comparing the settling performance of poly(PLA4ChMA) to commercially available alternatives such as anionic FLOPAM A3338. While consolidation of 5.0 wt.% MFT diluted with process water could be achieved using 500 ppm poly(PLA4ChMA), the final compaction levels after polymer degradation were similar to those achieved with the non-degradable FLOPAM A3338. Furthermore, the initial (24 h) compaction and clarity were better with FLOPAM A3338, which also provided faster settling rates (5-8 m/h) than those observed with poly(PLA4ChMA) at 10,000 ppm (<0.4 m/h). Attempts to increase poly(PLA4ChMA) molecular weight did not offer improvements in the settling properties at comparable dosages to those used with FLOPAM A3338. A series of flocculation-filtration experiments were also conducted to compare the performance of the polymers with undiluted MFT. While faster rates of water release were observed with cationic flocculants compared to FLOPAM A3338, no improvement in overall compaction of the tailings was measured with poly(PLA4ChMA), either before or after degradation. Slower rates of water release were measured with poly(PLA4ChMA) following degradation, indicating that the cleavage of the cationic functionality from the polymer during degradation has a negative impact on its performance. Thus, the improved dewatering observed with poly(PLA4ChMA) in dilute MFT suspensions does not extend to conditions that would be encountered in the field.