The effect of alkali type in temporal rheological behaviour of refractory bio-oxidised flotation concentrate has been investigated. Generally, the results showed that interfacial chemistry, particle leaching behaviour, pulp chemistry and rheological behaviour are alkali-type dependent. The magnitudes of the zeta potentials observed were markedly low, indicative of significant electrical double layer screening. Quicklime modified bio-oxidised pulp was electropositive at high pH whilst the caustic soda modified pulps showed deprotonated particles. The predominant chemical species leached at pH 10.5 were Ca and S, independent of pH modifier. Significant back precipitation of species such as Ca and S ions were mainly observed when quicklime was deployed. This was coupled with very low leaching efficacy from the mineral ores compared with the use of sodium hydroxide. In all cases, non-Newtonian, plastic, thixotropic rheological behaviour was displayed. In addition, shear thickening and thinning behaviour was displayed by the pulps upon pH modification with quicklime and sodium hydroxide, respectively. The results suggested emergence of van der Waals and non-DLVO attractive forces such as adsorbed Ca(II) ion-particle bridging, surface nucleation and cementation for the stronger rheology of quicklime modified pulps, in contrast with caustic soda modified pulps.
CITATION:Asamoah, R K and Addai-Mensah, J, 2019. Effect of Alkaline Type in Controlling Interfacial Chemistry, Rheology and Leaching Behaviour of Gold Concentrates, in Proceedings MetPlant 2019, pp 377382 (The Australasian Institute of Mining and Metallurgy: Melbourne).