Mechanism of Adsorption of Long-Chain Alkylamines on Silicates. A Spectroscopic Study. 1. Quartz

Abstract

The mechanism of adsorption of long-chain alkylamines at pH 6-7 onto quartz was studied using FTIR and XPS spectroscopy. The spectroscopic data were correlated with potential and Hallimond flotation results. For the first time it was shown that (1) amine cation in the first monolayer is H-bonded with surface silanol group and this H-bond becomes stronger after the break in the adsorption characteristics (isotherm, potential, floatability); (2) at the break the origin of the adsorbed amine species changes qualitatively, and along with alkylammonium ion attached to deprotonated silanol group, molecular amine appears at the surface and, as a result, monolayer thick patches of well-oriented and densely packed adsorbed amine species form rendering the surface highly hydrophobic; and (3) at higher amine concentration, bulk precipitation of molecular amine takes place. The counterion was found to influence both these steps. A model of successive two-dimensional and three-dimensional precipitation was suggested to explain amine adsorption on a silicate surface.

Developments in numerical treatments for large data sets of XPS images

“…As expected, [21] two contributions have to be introduced to account for the N 1s signal. One N component is found at a binding energy shift of 2.3 eV in agreement with ammonium species, [22] whereas the other one appearing, upon illumination, at lower energy is attributed to amine species in agreement with Eqn (1). As depicted in Figure 7 c), this ammonium-like N1s component is spatially correlated with Cl-enriched zones (Figure 7 e).…”

Adsorption of N-Tallow 1,3-Propanediamine–Dioleate Collector on Albite and Quartz Minerals, and Selective Flotation of Albite from Greek Stefania Feldspar Ore

“…It has been cited in the literature extensively that the amines are sensitive to fine particles (slimes) and desliming is an essential step prior to silicate flotation with amines. Our recent spectroscopic studies of amine interaction on silicate surfaces showed that the ammonium groups adsorb through hydrogen bonding on surface silanol groups as well as electrostatic interactions (29,30). The infrared spectra (DRIFT) of quartz and albite treated with increasing amine concentration showed a progressive diminishing of silanol groups, signifying amine interaction with silanols through hydrogen bonding.…”

Adsorption mechanism of mixed cationic/anionic collectors in feldspar-quartz flotation system

“…The oxyhydryl collectors adsorb on oxide, silicate and salt-type minerals either physically by electrostatic interactions and/or chemically, while the amine collectors adsorb on silicates purely by electrostatic interactions. However, our spectroscopic studies [26,27] of the adsorption of primary alkyl amine on silicate surface revealed that the ammonium head groups are H-bonded to the negatively charged silanols as H | ≡Si-O· · ·H-N + H 2 -R and establishing the following equilibrium when the local concentration approaches a critical value:…”