Mechanism Of Lead Oxide On Copper Minerals And Gold Cyanide Leaching

Adding PbO is an effective method to enhance cyanide leaching of copper-bearing gold concentrate.The mechanism of cyanide leaching of copper-bearing gold concentrate strengthened by PbO is still not clear.This paper took gold,chalcopyrite and bornite as research objects.Application of thermodynamic and electrochemical methods,SEM and XPS analyzed the cyanide dissolution reaction of gold,chalcopyrite and bornite in the presence of PbO and the thermodynamic stability zones of various products;studied the electrochemical behavior of gold,chalcopyrite and bornite in cyanide leaching system with PbO;and analyzed the morphology and composition of the surface products of gold,chalcopyrite and bornite with PbO in cyanide leaching system.These studies revealed the mechanism of PbO promoting the cyanide leaching of gold and inhibiting the cyanide leaching of copper sulfide.Thermodynamic,electrochemical and surface analysis of gold showed that adding appropriate amount of PbO could significantly increase the current density of gold cyanide solution and strengthen the anodic dissolution process of gold.Moreover,the leaching effect of PbO first increased and then decreased with the increase of PbO amount.When 0.24g/L PbO was added,the leaching effect was optimal.The mechanism of gold leaching enhanced by PbO was as follows:PbO could be used as an oxidant to promote the dissolution of gold,and the reduction product Pb deposite on the surface of Au.Pb and Au could form corrosion couple due to potential difference,thus promoting the dissolution of gold.Both PbO and Pb?NO₃?₂ could enhance gold leaching,but with the same lead content,lead oxide enhanced effect better than lead nitrate,because lead nitrate used its hydrolysate lead oxide to enhance gold leaching,while lead oxide directly enhanced gold leaching.Thermodynamic,electrochemical and surface analysis of chalcopyrite and bornite showed that lead oxide could effectively inhibit the oxidation and dissolution of chalcopyrite.The potential range of effective inhibition of chalcopyrite was-1.0V⁰.6V.If the potential continued to increase,the oxidation of lead oxide to lead dioxide would promote the cyanide leaching of some chalcopyrite not covered by lead oxide.Bornite could be effectively inhibited in the range of-1.0V¹.0V.The mechanism of lead oxide inhibiting the oxidation and dissolution of chalcopyrite and bornite was as follows:lead oxide could use the hydrolysis Pb?OH?₂ in cyanide leaching system to adsorb with the copper sulfide through electrostatic action and produce a coating effect on copper sulfide.In addition,electrocouple corrosion could be formed by electrostatic potential difference between PbS generated on the surface of copper sulfide and copper sulfide,and PbS could form cathodic protection for copper sulfide and inhibit the dissolution of copper sulfide.Lead nitrate in chalcopyrite surface formation of Pb?OH?₂ was more than lead oxide,bornite surface formation of Pb?OH?₂ and PbS than lead oxide,and lead nitrate on chalcopyrite and bornite inhibition effect was superior to lead oxide.Electrochemical and surface analysis of gold in the presence of chalcopyrite and bornite showed that chalcopyrite and bornite were not conducive to gold cyanide leaching,and the adverse effect of bornite was greater than that of chalcopyrite,which was attributed to the fact that S₂^2-and S_n^2-produced by the dissolution of both of them.The addition of lead oxide could remove S₂^2-and S_n^2-that affect the gold cyanide leaching by forming precipitation PbS.Meanwhile,lead oxide could promote and inhibit effect on the cyanide leaching process of gold and copper sulfide,so the gold cyanide leaching process was effectively strengthened.Lead oxide and lead nitrate could eliminate the adverse effect of chalcopyrite and bornite on gold cyanide leaching,lead oxide was more effective for gold cyanide leaching of chalcopyrite,and lead nitrate was more effective for gold cyanide leaching of bornite.