Bubbles facilitate ODA adsorption and improve flotation recovery at low temperature during KCl flotation

Understanding the adsorption process of collectors and the interaction between bubbles and mineral particles during KCl froth flotation are still weaknesses in our interpretation of the mechanism of flotation. In this study, we investigated in detail the adsorption kinetics and adsorption isotherm of a commonly used collector, octadecylamine hydrochloride (ODA), at the surface of KCl crystals. The effects of bubbling and temperature are discussed systematically. Our results indicated that the adsorption of ODA onto the surface of KCl crystals can be facilitated by bubbles, and that the adsorption kinetics of this process can be interpreted according to a pseudo-second order model. Both the Langmuir and Freundlich isotherm models were found to fit the adsorption isotherm of ODA on KCl crystal surface inappropriately, implying that the adsorption of ODA upon KCl crystal surfaces is a more complex process than typical monolayer, or multilayer, adsorption. This might be because the adsorption of ODA on KCl crystal surfaces takes place through an aggregated intermediate, rather than through the direct interaction of dispersed molecules. We note that the quantity of ODA adsorbed at 0 °C increased markedly with increasing numbers of bubbles. Micro-flotation tests suggested that increasing the gas flow rate effectively improved flotation recovery at 0 °C, consistent with the adsorption behavior. These results provide complementary information on the adsorption behavior of ODA at the surface of KCl crystals and on the effect of bubbles during froth flotation, which could help to design new flotation process and improve flotation recovery of KCl at low temperatures.