The effects of chrysotile mineralogical properties on the rheology of chrysotile suspensions

Chrysotile (serpentine) is a phyllosilicate mineral that occurs as a major gangue mineral in many ores (e.g. Mt. Keith nickel sulphide ore, Western Australia). It is believed that the distinctive morphology and electrical surface charge of chrysotile particles are central to the problematic rheological behaviour and low solids throughput typically experienced in the processing of such ores. This study investigates the effects of both these factors on the rheology of chrysotile suspensions.Chrysotile particles were found to carry a net positive charge over the range pH 2–11, with an apparent point of zero charge at pH 8.23. This is a direct result of the convoluted mineral structure of chrysotile fibres, which comprise a positively charged brucite outer layer. The disparity in the point of zero charge and range of maximum yield stress for chrysotile is consistent with the anisotropic nature of chrysotile particles. The long, thin fibres are easily entangled to form suspensions with much higher plastic viscosities and Bingham yield stresses than non-fibrous particles.Although chrysotile shape and surface charge are fundamental to the rheology of chrysotile suspensions, it was found that shape plays a more significant role.

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► Effect of chrysotile morphology and surface charge on rheology.
► Net p.z.c. at pH 8.23 and ’net’ positive zeta potential over range pH 2–11.
► Peak range of yield stress (pH 5–9) corresponds to range of positive zeta potential.
► Higher yield stresses than non-fibrous minerals (quartz) even at lower solids concentration (< 0.8% solids volume).
► Rheology of chrysotile largely due to fibrous morphology.