Corner Capillary Rise As a Mechanism for Slurry Dewatering

Slurries of tailings produced by the mining industry represent an environmental threat not only for their inadequate management, contamination of soils and bioaccumulation of heavy metals, but also for the intensive use of water resources. Dewatering of these slurries is an important factor in reducing the environmental footprint of the mining activity. Partial dewatering is typically carried out by adding a thickening agent, resulting in a concentrated slurry. However, water recovery from concentrated slurries is often energy-intensive. This work explores the use of capillary-driven flows in sharp corners as a passive process for dewatering slurries. That is, capillary flows in the angle formed at the point of intersection between two solid surfaces (corner flow) to reduce the local concentration of the slurry particles within the liquid as it rises in a vertical column. Laboratory tests were conducted to test the premise of the proposed process, using kaolin and dolomite slurries at different concentrations as model systems. The process was analyzed by image processing to determine relative concentration profiles during the slurry rise. Results showed that there is a direct influence of the slurry concentration on the system capability to dewater while affecting the dynamics of liquid rise. At high concentrations, no appreciable particle moved into the corner flow and only water was extracted. Likewise, for both systems it is observed that, as the concentration of the slurry increases the particles tend to agglomerate near the corner region of the system. Therefore, a local decrease was observed in concentration near the contact line (outermost region of the system). Finally, size exclusion near the corner for kaolin was observed due to interparticle interactions and house-of-cards structure. This was tested by adding salt to disrupt structuring in the slurry, which increased the uniformity of the particle distribution in the rising slurry. This research is the first, to the best of our knowledge, to explore corner flow with fine particle systems and provides insights for potential new engineering solutions to enhance slurry dewatering processes.