Chlorine Dioxide Dip Gold System,

Methods of leaching gold in the last few years were reviewed and discussed. A new method of leaching gold was reported,which is leaching gold from gold ore in the ClO₂-Cl^--H₂O system. On the basis of studying theory about the new gold leaching process, the E-pHdiagram for Au-ClO₂-Cl^--H₂O system was drawn. This paper discussed thethermodynamic feasibility of gold leaching process and made analysis on effect of theother elements in the leaching process. Using the rotating disk technique, the effects ofrotation speed, concentration of chlorine dioxide and chlorine,as well as temperaturewere measured.First order reaction rate was found with respect to ClO₂ and half orderreaction rate with respect to Cl^-. The experimental activation energy showed that a rate-controlling process other than simple diffusion may controll the dissolution of gold in ClO₂ solution.The experiments of leaching gold were carried out for the refractory gold ore andoxidizing type of gold ore. The feasibility of leaching gold for the refractory gold orewas analysed. The optimum leaching conditions for oxidizing type of gold oreachieved were listed as follows: a leaching duration of 10h,a pH of 3.0, a temperatureof 40℃,sodium chlorine concentration of 0.50mol·L^-1 and a ratio of liquid to solid is3.0:1.0. The experimental results,under the optimum conditions, showed that theextraction percentage of gold can be over 95.5%. Leaching gold in chlorine dioxide system is a no-toxic and efficient method of greenleaching gold.