Kaolin aerated flocs formation assisted by polymer-coated microbubbles

Aerated kaolin floc formation was studied in a continuous-flow, laboratory-scale system, and the flocs were separated from aqueous solution by flotation. Microbubbles were generated by the depressurisation of dissolved air in water, and flocculation was achieved in a Floc Generator Reactor (FGR). An aerated floc characterisation (AFC) technique was utilised for characterising the aggregates formed. Flocculation–flotation studies were performed using a non-ionic polymer (920SH SNF-Floerger®) added to a suspension flow (4 L/min) at an air/solid rate (A/S) of 0.02 mg/mg. The main results revealed the existence of an extra flocculation mechanism resulting from interactions between particles, bubbles and polymer-coated air microbubbles. The latter acted as “flocculation nuclei”, where particles aggregated by a sort of “bridge” with the polymer-coated-bubbles. These polymer-coated bubbles can interact with other bubbles, particles and/or flocs resulting in a large amount of bubbles (of different sizes, depending on coalescence) to the floc structures improving the rising rates of the aerated flocs. It is believed that these findings will contribute to the understanding of the formation of the light, aerated flocs and the rapid flocculation–flotation process for solid/liquid separation.

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► A flocculation mechanism between particles, bubbles and polymer-coated air bubbles.
► Important interactions in the formation of kaolin aerated flocs were investigated.
► Adhesion an entrapped of polymer-coated microbubbles were observed in the aeroflocs.