The interaction between xanthate and sulphur dioxide in the flotation of nickel-copper sulphide ores
Electrochemical methods and small scale flotation tests were used to study the effects of sulphur dioxide and potassium amyl xanthate on the floatabilities of pentlandite, chalcopyrite and nickeliferous pyrrhotite, at pH 5.5. Mixed potentials of all three mineral systems were positive to the dixanthogen/xanthate redox couple, even in the presence of aqueous SO₂. Thus the existence of dixanthogen is thermodynamically favoured in all these systems. The tests also indicated that adsorption of
... adsorption of xanthate by: (i) chalcopyrite is enhanced by SO₂; (ii) pentlandite is impaired by SO₂; (iii) pyrrhotite is unaffected by SO₂; Anodic polarization curves, determined on mineral electrodes, suggested that, in xanthated systems, the collector (probably dixanthogen) forms a film on the electrodes. This film inhibits the continued electron transfer reactions on the surface. The protective character of the film is higher for chalcopyrite (increased by SO₂), than for pentlandite (decreased by SO₂), than for pyrrhotite (unaffected by SO₂). Cathodic polarization curves indicated that the cathodic process, on pentlandite and pyrrhotite electrodes, is controlled by oxygen reduction. The reduction of oxidized species on the surface is suggested as the controlling mechanism on chalcopyrite electrodes. Small scale flotation tests showed that the presence of SO₂ increases an already very high,recovery of chalcopyrite; decreases a high recovery of pentlandite, and decreases further a very low recovery of pyrrhotite.