Specific anion effects on adsorption and packing of octadecylamine hydrochloride molecules at the air/water interface

Abstract

The spread of collector molecules on bubble surfaces in salt solution is a fundamental phenomenon in the froth flotation of soluble salts, such as KCl, and consideration of ionic effects on adsorption behavior and packing of collector molecules at the air/solution interface is appropriate for study. In this work, specific anion effects on the adsorption and packing of one common collector (octadecylamine hydrochloride, ODA) at the air/water interface were investigated by employing a combination of surface pressure measurements, sum frequency vibrational spectroscopy (SFVS) and molecular dynamics simulations (MDS). The results from experiments and MDS showed that the addition of external anions disturb the arrangement of ODA molecules due to the penetration of these anions from the water subphase into the ODA monolayer at the air/water interface. During monolayer compression, the penetrated anions might be driven back to the water subphase by electrostatic forces and the added compression force. These anions could screen the charge of -NH 3 groups resulting in a reduction of the minimum area of the ODA molecule (A min ) for the solid phase state of the monolayer. With the exception of the sulfate anion, the added anions increase hydrogen bonding of interfacial water molecules at the air/water interface. These results allow for a better understanding of the anionic effect on adsorption and packing of ODA molecules at the air/water interface, and might therefore provide new insights into froth flotation of soluble salts and should help to improve soluble salt flotation technology.

Sum-Frequency Vibrational Spectroscopic Study of the Cation−π Interaction: Amine and Guanidine

“…It agrees well with the previous study that reported that protonated amine interacts much more favorably with aromatic molecules than the neutral amine. 12,45 The marked difference in the CH range of the spectra from that of a neat ODA monolayer indicates that the indole molecules disrupted the ODA monolayer significantly, 28,46 demonstrating again the high permeability of the indole molecule into the membrane.…”

Self-assembly mechanism, physicochemical analyses and application performance investigations of branched alkyl glycosides with alcohol ether carboxylic acids of varied epoxide numbers

“…The elongation of the alkyl chain further diminishes the curvature of the surfactant monomolecular film, leading to the formation of larger aggregates, indicative of heightened molecular stacking. 39,40 Generally, an increase in ethylene oxide addition increases the CMC of the surfactant and decreases the maximum adsorption capacity. However, the higher the ethylene oxide addition, the higher the surface activity efficiency of the surfactant.…”

Emerging Trends of Computational Chemistry and Molecular Modeling in Froth Flotation: A Review

“…MD simulations were utilized to better understand the adsorption and packing of octadecylamine hydrochloride (ODA) collector molecules at the air/ water interface in the presence of various ions in the solution. 392 Some anions (e.g., I − and SO 4 2−…”

“…MD simulations were utilized to better understand the adsorption and packing of octadecylamine hydrochloride (ODA) collector molecules at the air/water interface in the presence of various ions in the solution . Some anions (e.g., I – and SO 4 2– ) are shown to penetrate the ODA monolayer at the air/water interface due to their larger size and greater polarizability and disrupt the arrangement of the ODA molecule.…”