| Arsenopyrite is a common refractory auriferous sulfide.With the decline of the easily processed gold deposit,refractory gold has gradually become the main source of gold industry.Pressurized acid leaching and oxidation is a conventional method for pretreatment of refractory gold ores.However,there are few studies on the mechanism of pressurized oxidation and leaching of arsenopyrite at elevated temperatures,so it is of great significance to study the mechanism of pressurized oxidation and leaching of arsenopyrite.In this paper,the FeAsS-H2O potential-pH diagram was firstly drawn through thermodynamic calculation under elevated temperature conditions,and the rule of the FeAsS-H2O potential-pH diagram changing with temperature was analyzed,which was verified by X-ray diffraction(XRD),scanning electron microscope(SEM)and other means.Secondly,the kinetics of pressure acid leaching and oxidation of arsenopyrite was studied to study the influence of single factors such as temperature,oxygen partial pressure,initial acidity and mineral particle size on the pressure acid leaching of arsenopyrite and establish the kinetic model of As.Finally,the kinetics of the oxidation leaching mechanism of arsenopyrite in sulfuric acid solution was investigated by means of an internal reference electrode(IRE)and electrochemical tests such as open circuit potential(OCP)and polarization curve.Thermodynamic calculation results showed that the stable region of Ferric Arsenate at FeAsS-H2O potential-pH diagram expanded with the increase of temperature,and the results of verification test showed that the leaching rate of arsenic and iron increased with the increase of temperature,while the leaching rate of arsenic and iron decreased at 180?,which was consistent with the variation rule of FeAsS-H2O potential-pH diagram.The kinetics of pressure acid leaching and oxidation of arsenopyrite shows that the leaching process of arsenic element in arsenopyrite under 170? is controlled by surface chemical reaction,while that above 180? is controlled by chemical reaction and diffusion.And the leaching process of iron was controlled by chemical reaction and diffusion within the range of test temperature.Both elements followed the law of shrinking core model.The kinetic model of As leaching by pressure oxidation leaching of arsenopyrite was established as following:1-(1-x)1/3=1.90×108×CH2SO40.37×PO21.33×(1/(?1.07))×exp((-70060)/(RT))tElectrochemical study results show that the result of Fe,As,S element migration rate and dissolution is different,the metal-deficient sulfide was formed under arsenopyrite surfaces,therefore the phenomenon of passivation appears,and the passivation layer hinders further leaching arsenic pyrite,improving the system of oxidation reduction potential or enhancing the system temperature can promote the dissolution of arsenopyrite.When the temperature increases,the passivation of arsenopyrite gradually decreases in H2SO4 solution,and the corrosion current density icorr and corrosion potential Ecorr increase. |
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