【正文】 cs and mechanism of the reaction on its surface[10?14]. In this study, the electrochemical behavior of the pyrite electrode in a xanthate solution was investigated. Some advanced electrochemical techniques were employed to research the electrodeposit of dixanthogen on the pyrite surface.2 Experimental The pyrite used in this investigation consisted of % (mass fraction) Fe, %S, %SiO2 and was from Mengzi Mine of Yunnan Province, China. Sections cut from the highly mineralized pyrite were fashioned into the form of electrodes for electrochemical measurement. The cut section of mineral was mounted on the tip of a perspex tubule of d 7 mm using epoxy resin and the exposed outer surface was well polished. The exposed surface area of the electrode was about 1 cm2. The reference and auxiliary electrodes were saturated calomel electrode(SCE) and graphite rods, respectively. All potential in this study were quoted in volts, with respect to a standard hydrogen electrode (SHE). The electrochemical measurements were performed with a conventional threeelectrode cell using a electronics potentiostat/galvanostat model EGamp。G corrosion measurement system (Princeton Applied Research Model 352) and Analysis Software (Model 270) were used in the experiment. The studies were carried out using the pyrite as electrode in a mol/L KCl solution in the presence of butyl xanthate.3 Results and discussion Two stages of electrochemical reaction on pyrite surface in butyl xanthate solution While the potentiostat applies a constant current on the pyrite electrode for a specified duration, the overall consumed charge Q can be calculated by the following equation: Q=Qθ+Qc (1) where Qc is the charge consumed by the diffusion of xanthate ion on the pyrite surface, and Qθ is the charge consumed by the electrochemical adsorption of xanthate ion. According to the Sand formula[15]: Q=Q0+(2)where n is the number of transfer electrons in reaction,F is the Farady constant, D is the diffusion coefficient of xanthate, c0 is the initial concentration of butyl xanthate ion, and J is the current density.If the electrochemical adsorption of butyl xanthate ion on the pyrite surface did not occur, the charge consumed by the electrochemical adsorption of xanthate ion (Q θ) would be zero. The value of Q can be verified using galvanostatic technique. Table 1 lists the results of galvanostatic experiments for a pyrite electrode at different currents. The Q value is linearly related with 1/J. Based on the results in Table 1, the plot of the consumed charge Q as a function of the reciprocal of current density (Ja1 ) is drawn in . From this figure, we calculate the charge consumed by the electrochemical adsorption of butyl xanthate ion (Qθ) to be equal to mC/cm , not zero which means that an electrochemical adsorption of buty xanthate ion takes place on the pyrite surface. The electrochemical absorption reaction of butyl xanthate ion on pyrite surface can be written as X→X(ads)+e (3) Relationship between overall charge and current density in galvanostatic experiment ([BX]=104mol/L, pH=, 25℃) shows the voltamograms in pH buffer for a pyrite electrode starting from ? (vs SHE) in the positive direction. There is an anodic peak appeared at V, which indicates that an electrochemical reaction occurs. The possible reaction is the oxidation of butyl xanthate ion on the pyrite surface:2X→X2+2e (4)φ=??[X ], [X ]=104 mol/L, φ=. So we can think that the oxidation of butyl xanthate ion on the pyrite surface is a consecutive charge transfer eaction. The electrochemical reaction can be divided into two stages: the first step is electrochemical adsorption of butyl xanthate ion, and then the adsorbed ion associates with a butyl xanthate ion from the solution and forms a dixanthogen on the sulfide mineral.The oxidation process of xanthate ion is as X(ads)+X1(aq)→X (ads)+e