Investigation of KCl crystal/NaCl-KCl saturated brine interface and octadecylamine deposition with the use of AFM

The deposition of octadecylamine (ODA) at the KCl crystal/NaCl-KCl brine interface was investigated using atomic force microscopy (AFM). The AFM images of freshly cleaved KCl specimens immersed in a KCl-NaCl saturated brine at room temperature reveal the disappearance with time of the atomic steps and formation of cubic NaCl crystals. These crystals were found to form when the specimen was withdrawn from the saturated solution. Depending on the way of contacting the specimens with the octadecylamine dispersion, the AFM images show huge differences in the deposition patterns of ODA on KCl crystals. Adequate dispersion was found to help the formation of quite uniform ODA coverage. The coverage was several monolayers thick when air/brine/solid contact took place suggesting that in the potash flotation, the collector is likely to be carried to the solid surfaces by air bubbles. The presence of methyl-isobutyl carbinol (MIBC) enhanced the dispersion of ODA in brine, thus helping more uniform deposition of the surfactant on the KCl crystal surface.