The relationship between enthalpy of immersion and flotation response

Abstract

The enthalpy of immersion is the heat change arising from the replacement of the solid-gas interface with the solid-liquid interface when a solid surface is immersed in a liquid. Although immersion calorimetry has been established as a reliable means of determining wettability of solid surfaces, it has found only limited applications in flotation research where wettability of mineral ores is a key variable. In this study, precision solution calorimetry was employed to measure the enthalpies of immersion of different minerals in water. These values were then related to the first-order flotation rate constants as determined by microflotation. The same measurements were also made on sulphide minerals whose surfaces were modified using different percentage coverages of potassium amyl xanthate collector.It was found that there was a strong inverse relationship between the enthalpy of immersion of the minerals studied and their wettability as indicated by their rates of flotation in a microflotation cell. In addition, a critical enthalpy of immersion (CEI) value was observed, above which no flotation occurred. The variance in the inverse relationship between enthalpy of immersion and rate of flotation decreased when the data was normalized with respect to particle density which was the only variable in the flotation studies with respect to bubble-particle encounter efficiency. These results have shown that the enthalpy of immersion is an excellent indicator of both the natural mineral hydrophobicity and of the extent to which collectors render a mineral hydrophobic. This technique has considerable potential to be used as a highly sensitive measure of mineral surface wettability in predicting flotation performance.