Pyrite is the principal mineral in copper--zinc ores of the Urals. The electrochemical processes on the surface of pyrite largely determine its flotation activity.Little work has been done on these processes on mineral surfaces.Insufficient attention has been paid to the mechanism of attachment of xanthate to the surfaces of sulfide minerals. This is due to the fact that when the mineral is immersed in aqueous solutions of flotation reagents, simultaneouslywlth adsorption of xanthate on the mineral surface there occurs solution of the mineral itself.The xanthate ions may react with the solution products after attachment on the surface.The data on the electrochemical behavior of minerals in solutions of flotation reagents are rather contradictory [i, 2]. It is therefore of interest to investigate the kinetics of solution of pyrite and adsorption of xanthate on a mineral surface under conditions of artificial polarization in alkaline media.Whereas the procedure for investigating the electrochemical behavior of metals has been developed, for minerals it is greatly complicated by the high resistivity of the mineral and by the unusual behavior of sulfides in nonintrinsic ions. The semiconductive character of minerals accounts for many new characteristics on the kinetics of electrode processes.The investigations were performed on p-type pyrite in alkaline media obtained by adding lime and caustic potash.In some experiments potassium xanthate was used. The procedures used to prepare the electrodes and electrolytes were described in [3]. The polarization curves were recorded on a potentiostat under potentiodynamic conditions [4]. The advantage of this method is the accuracy of maintenance of the potential and current during polarization of the mineral; in this respect it differs in advantage from measurement of sulfide electrode potentials by means of a compensation circuit, which enables one to make only a qualitative assessment of the degree of change in the mineral surface.The results of the investigations showed that the rate of establishment of the steady electrode potential of pyrite is governed by the character and composition of the solution. In solutions of lime and caustic potash with added potassium xanthate, on increase in the collector concentration, at a specific pH, E (V) shifts toward the more negative side; this may be due to adsorption of the surfactant, xanthate, on the mineral surface. Figure 1 is a plot of the steady-state potential of pyrite in a KOH solution (i) with added potassium ethyl xanthate (2) vs the pH.Curves 1 and 2 can be divided into two sectors:the first at pH = 7.0-9.0, in which a monotonic change in the potential is observed, and the second sector at pH = 9.0-11.0, with a steep slope.The difference in the potentials induced by addition of xanthate to the KOH solution, characterizing the degree of reaction of flotation reagent with the mineral, decreases on increase in the solution pH. This shows that adsorption of xanthate on pyrite decreases on increase in the solution pH. The absol...
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