Structural investigation of tailings flocculation and consolidation via quantitative 3D dual fluorescence/reflectance confocal microscopy.

ABSTRACT

HYPOTHESIS: Mechanistic understanding of particle-flocculant interactions and its link to the resulting floc structure is essential for developing tailings treatments with enhanced consolidation rates. A noninvasive, in-situ visualization of the floc formation and the consequent sediment microstructure via tri-dimensional laser scanning confocal microscopy (LSCM) can enable establishing the quantitative link between the flocculation conditions and bulk properties of the resulting sediment structures. EXPERIMENTS A dual fluorescence/reflectance confocal imaging protocol is developed to non-invasively detect morphological changes in dense oil sands tailings during flocculation with an anionic polymer and the subsequent sediment compaction stages for three different polymer dosages. The image reconstruction is developed to quantify the organics/clay volume fractions in the sediment and the floc network characteristics through the pseudo fractal dimension which are related to the bulk rheological properties following a 5-day densification period. FINDINGS: In-situ imaging of the flocculation process gives insights into the variable floc density and size at different stages of mixing. The acquired 3D images of the flocculated sediment reveal that bitumen remains within the flocs. The increase in the polymer dosage results in the reduction of the sediment fractality and strength attributed to the possible formation of more swelled floc structures. Clay reflectance detection is validated using a model kaolinite clay dispersion. The developed methodology may ultimately be used as a guiding tool for standard screening of the new flocculants and flocculation protocols for various mineral tailings systems.