Bubble contact angle variation of sulphide minerals in relation to their self-induced flotation

Standard method for captive bubble contact angle measurements in distilled water usually yield no finite contact angles on common sulphide minerals such as chalcopyrite, galena and chalcocite although samples from such minerals have been shown to float in the absence of a collecting agent. The current study documents a case, where small but stable contact angles have been obtained on these minerals. Measured angles ranged from 0 to 36° for chalcopyrite, 0–21° for galena and 0–24° for chalcocite. During the initial period, volumes of attached air bubbles have been noted to decrease. A pronounced pH dependence has been notable from the results. High contact angles have been distinctly associated with low pH and relatively short induction periods. These effects are attributable to increased stability of elemental sulphur. Development of hydrophobicity on these minerals is in general agreement with the results of small-scale tests on their self-induced flotation. The correlation for chalcopyrite has been most notable for the acidic pH range. No correlation has been observed between the contact angle variation and flotation behavior of galena.