Selective flotation of inherently hydrophobic minerals by controlling the air/solution interfacial tension

Abstract

Selective wettability and floatability of several inherently hydrophobic minerals have been investigated using aqueous methanol solutions of various surface tensions. The relationship between the critical surface tension of wetting, γ c , and of floatability, γ cf , of the samples is examined. Experimental evidence is provided to show that a flotation feed cannot be represented by an uniquely defined γ cf value. It is appropriate to specify for an inherently hydrophobic solid a critical surface tension range of floatability with upper and lower limits, γ cmf and γ clf respectively. The particles which are predominated by cleavage or crystal faces determine the lower limit, while those with some threshold degree of ionic character determine the upper limit. Examples of separation tests presented demonstrate that in the case of equality between γ c values of two inherently floatable solids (or their γ clf values), a difference in γ cmf values determines the efficiency of their separation. It is also shown that the interfacial tension of maximum separation efficiency may be predicted from the individual surface tension of floatability curves which may be represented by second-order functions.