Effect of Composition and Morphology on Self-Weight Settling of Laterite Ore Slurries

Abstract

Knowledge of slurry settling is essential for geotechnical engineering applications such as coastal land reclamation and mine waste disposal. In the presence of charged solids and ion-rich liquids, complex physicochemical interactions govern the behavior of slurries. The main objective of this study was to develop a fundamental understanding of self- weight settling of laterite ore slurries. To capture the influence of geology and the environment, samples were obtained from mining operations in different parts of the globe. Based on laboratory testing, the investigated ores were found to be either oxide-rich with goethite, gibbsite, meghamite and hematite making at least 90% of the material or clay-rich with chrysotile, cholritic intergrade, and siliceous minerals accounting for more than 50% of the sample. The dominance of salt forming ions such as Na ? ,K ? , Ca 2? ,M g 2? ,C l - ,N O 3 - , HCO3 - and SO4 2- in the pore waters indicated the influence of seawater on the waters used for slurry preparation. The oxide-rich ores in low ionic waters resulted in flocculated fabrics whereas the clay-rich ores in high ionic waters led to cardhouse microstructures. The aggregated fabrics with low tortuousity and fewer dead ends resulted in a high settling rate and amount (ki = 10 -1 to 10 -2 cm/s and SP = 62 to 49%) whereas the cardhouse mor- phologies with high tortuousity and lower pore connectivity exhibited a slow and low settling (ki = 10 -3 to 10 -4 cm/s and SP = 37 to 17%). The initial hydraulic conductivity was found to be directly proportional to settling potential.