Investigating the use of excess Gibbs energy to predict the hydrophobicity of a mineral treated with a collector

Abstract

The paper sets out to determine whether there is any evidence to support the hypothesis that the hydrophobicity of a mineral particle treated with a collector may be strongly related to the fact that the alkyl chain associated with the collector adsorbed on a mineral particle behaves in the same way as any hydrocarbon would behave in an aqueous medium. Such a mixture is classified as a non-ideal mixture which is a concept widely used in chemical engineering in the study of many separation processes. Non-ideal mixtures are quantified by determining the activity coefficient of the hydrocarbon and hence its partial molar excess Gibbs energy in the mixture. In the absence of a turbulent environment hydrophobicity of a mineral particle is responsible for flotation recovery in, for example, a microflotation cell. It is also indicated by a contact angle measurement. Using data from published literature of the behaviour of collectors with different alkyl chain lengths the paper has demonstrated that there is a strong linear relationship between partial molar excess Gibbs energy of the alkyl moiety of the collector and the flotation recovery and the contact angle for, inter alia, a xanthate-galena and an amine-quartz system. These relationships seem to provide good evidence that the extent to which a collector will enhance recovery of a mineral is strongly related to the partial molar excess Gibbs energy of the alkyl chain or, in other words, the extent to which the alkyl group associated with the mineral particle represents a significant contribution to the force driving a particle from the aqueous(water) phase to the gas (bubble) phase.