A thermodynamic approach to ion flotation. I. Kinetics of cupric ion flotation with alkylsulfates

A thermodynamic approach was taken to model the removal of cupric ion from sodium dodecylsulfate(SDS)–Cu, sodium tetradecylsulfate (STS)–Cu and sodium hexadecylsulfate (SHS)–Cu ion flotation systems. The surface tensions of these solutions were found to vary linearly with the alkylsulfate concentration. From these linear equations, it was determined that in copper–alkylsulfate systems the Gibbs free energy of adsorption changes by −2.16 kJ mol−1 for each additional CH2 group on the alkyl chain. Estimated mass transfer coefficients indicated that adsorption should approach or reach equilibrium in the batch ion flotation tests reported here. The Gibbs adsorption equation was then used to estimate the adsorption densities of copper as a function of time, from the surface tension data. The cupric ion removal kinetics predicted from the surface tension data were consistent with the experimentally measured kinetics, provided a term for backflux of colligend was included, and the bubble size was allowed to increase with increasing surface tension.