THERMOCHEMICAL MEASUREMENTS OF THE SURFACE-REACTIONS OF SODIUM CYCLOHEXYL-DITHIOCARBAMATE, POTASSIUM N-BUTYL XANTHATE AND A THIOL MIXTURE WITH PYRITE

Thermochemical measurements were made of the reactions between sodium cyclohexyl dithiocarbamate, potassium n-butyl xanthate and mixtures th ereof with pyrite at pH = 4, The initial steady state heat of adsorpti on for the potassium n-butyl xanthate and sodium cyclohexyl dithiocarb amate was -67 kJ/mole, When a mixture of these reagents was used this increased to -90 kJ/mole. in all cases the pH increased during the exp eriments, When FeSO4 replaced the pyrite the Delta H for the xanthate decreased to -43.9 kJ/mole, The results indicated that for the xanthat e, the metal thiolate was formed and subsequently oxidised to dixantho gen. The latter reaction did not occur in the case of the dithiocarbam ate, however the extent of the first reaction between the dithiocarbam ate and pyrite was controlled by proton availability, For the mixture of reagents it is proposed that the dithiocarbamate adsorbs preferenti ally due to its faster adsorption kinetics and the more stable nature of the surface complex. The dixanthogen species formed then aggregates around the ''anchors'' and results in enhanced hydrophobicity, This w ill contribute towards the enhanced flotation performance obtained whe n mixtures of collectors are used [1].