Electrochemical investigation of contact angle and of flotation in the presence of alkylxanthates. II. Galena and pyrite surfaces

Abstract

The contact angle between a nitrogen bubble and galena and pyrite surfaces immersed in methyl-, ethyl- or butyl-xanthates has been determined as a function of the electrode potential and of the quantity of xanthate species formed by interaction with the mineral surface. For galena, the initial chemisorbed xanthate layer was found to be hydrophobic when ethyl- or butyl-xanthates were employed, but hydrophilic for the methyl homologue. The presence of dixanthogen enhanced the contact angle but the metal xanthate diminished it. This conclusion was supported by contact angle studies at a lead electrode. For pyrite the surface was hydrophilic except when dixanthogen was formed, but a significant quantity was required on the mineral surface before a finite contact angle was observed. This behaviour is interpreted in terms of the presence of hydrated iron oxide on the pyrite surface.     The potentials at which particulate bed electrodes of galena and pyrite begin to float were determined for ethyl- and butyl- xanthates. The potentials correspond to the regions where chemisorption of xanthate takes place on galena and where significant quantities of dixanthogen are formed on pyrite.     With butylxanthate, flotation was inhibited when excessive quantities of xanthate species were present on galena or pyrite. The inhibition arose from flocculation of the mineral particles.