Adsorption Mechanism of Mixed Long-chain Amines and Alcohols on Silicate Minerals

The mechanism of adsorption of long chain alkyl primary amines and co-adsorption of amines and alcohols on silicate minerals (quartz and feldspar) were studied using FTIR (DRIFT and IRRAS) and XPS spectroscopy methods at neutral pH 6-7. The spectroscopic data were correlated with zeta-potential and Hallimond flotation results. The influence of long chain alcohols on the adsorption of amines in mixed amine-alcohol is also examined.

The infrared studies revealed that the amine cation form strong hydrogen bonds with the surface silanol groups. The XPS spectra revealed the presence of molecular amine together with the protonated amine on silicate surface. Based on these observations, a model of successive two-dimensional and three-dimensional precipitation was suggested to explain amine adsorption on a silicate surface. The co-adsorption of long chain alcohols with amine cations leads to formation of a closer packed surface layer with synergistic enhancement of amine adsorption. The enhanced adsorption and hence higher flotation recoveries is discussed in the light of our experimental results.