INTERACTIONS BETWEEN SULFIDE MINERALS AND ALKYLXANTHATE IONS .3. A VIBRATION SPECTROSCOPIC, CALORIMETRIC AND ATOMIC-ABSORPTION SPECTROPHOTOMETRIC STUDY OF THE INTERACTION BETWEEN GALENA AND ETHYLXANTHATE IONS IN AQUEOUS-SOLUTION

The reaction between galena powder and ethylxanthate ions has been studied in aqueous solution. Qualitative analysis of the compounds present on the galena surfaces before and after treatment with potassium ethylxanthate has been performed by means of diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Atomic absorption spectrophotometry has been used to determine the total lead concentration in the aqueous phase of galena slurries. Calorimetric techniques have been used to study the heats of reaction. Galena surfaces are easily oxidized to lead(II) sulfate and thiosulfate, and lead(II) carbonate is found on the galena surfaces as well. DRIFT measurements have shown that solid lead(II) ethylxanthate is formed on the surfaces of oxidized galena after treatment with a dilute, 0.2 mM, aqueous solution of potassium ethylxanthate. The amount of lead(II) ethylxanthate on the surfaces increases with increasing concentration of potassium ethylxanthate solution. A previously proposed monolayer complex has been questioned. The mechanism for the hydrophobation of oxidized galena surfaces involves: (1) fairly soluble lead(II) salts, present or formed on the galena surface, which are dissolved from the surface during slurrying in water, and a concentration gradient of lead(II) species formed around the galena particles; (2) small islands of solid lead(II) ethylxanthate which are formed on the galena surface in the presence of alkylxanthate ions in the aqueous phase during slurrying. The degree of hydrophobicity of a galena particle depends on the amount and the degree of coverage of hydrophobic compounds on its surface. The degree of coverage of hydrophobic compounds on the galena surface necessary for a successful flotation increases with increasing particle size and weight. A redesigned titration calorimeter is described in this paper.