Adsorption process of Octadecylamine Hydrochloride on KCl crystal surface in various salt saturated solutions: Kinetics, isotherm model and thermodynamics properties

Majority of potash production around the word is still conducted through froth flotation, during the process of which the adsorption of collector on salt crystal surface is one of key points determining the accomplishment of flotation. In this work, the adsorption kinetics and isotherm models of one common collector, Octadecylamine Hydrochloride (ODA), on KCl surface in different saturated salt solutions at different temperature is studied for details. The results show that the adsorption equilibrium time is 4 h for ODA adsorbed on KCl surface in all systems at 25 degrees C. High temperature can increase the adsorption quantity, however, the presence of Mg2+ will decrease it. This may be attributed to the property of 'water structure maker' for Mg2+ in solutions. The pseudo second-order model is appropriate to describe the adsorption kinetics for all studied systems. The adsorption isotherm of ODA on KCl surface is much more close to the Langmuir isotherm model than the Freundlich isotherm model. The adsorption process for all the systems need additional energy and the energy requirement increases with the temperature decreasing. In addition, the adsorption in all systems also presents an exothermic process. The randomness at the solid-solution interface becomes less in the KCl-MgCl2 and KCl-NaCl-MgCl2 saturated solutions than in KCl saturated solution. This work provides detailed information of adsorption process of ODA on KCl surface, which may constitute a step forwards in our understanding of froth flotation of KCl and help to improve the flotation recovery at low temperature. (C) 2016 Elsevier B.V. All rights reserved.