Thermodynamics and technology of extracting gold from low-grade gold ore in system of NH4Cl-NH3-H2O

• Published in: Transactions of Nonferrous Metals Society of China Vol. 16; no. 1; pp. 203 - 208
• Main Author: 巨少华 唐谟堂 杨声海
• Format: Journal Article
• Language: English
• Published: School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China 01.02.2006
• Subjects: MATLAB; NH4Cl-NH3-H2O; 提金技术; 氯化铵; 湿法冶金; 热力学; gold; gold extraction; thermodynamics; ammonium chloride; NH4Cl-NH3-H2O; hydrometallurgy
• ISSN: 1003-6326
• DOI: 10.1016/S1003-6326(06)60036-8

According to the principles of simultaneous chemical equilibrium and electronic charge neutrality, the thermodynamics of Au-NH4Cl-NH3-H2O system was studied by using the exponential computation method and through MATLAB programming, and the solid figure of potential-c（NH4Cl）-c（NH4OH） was drawn. The results show that when the sum concentration of Au^＋ and Au^3＋ is equal to 5× 10^-5 mol/L,ψ（Au^＋/Au） is about -0.2 V; when the sum comes up to 0.5 mol/L, the value of ψ（Au^＋/Au） increases to 0.2 V. In this case, ψ（O2/OH^-） is as high as 0.7 V. This means that it is feasible to extract gold in this system. In addition, to predict the feasibility of reducing gold from the Au（I）-NI-NH4Cl-NH3-H2O system with copper or zinc powder, the solid figures of potential-c（NH4Cl）-c（NH4OH） for both systems of Cu-NH4Cl-NH3-H2O and Zn-NH4Cl-NH3-H2O were also drawn. The results indicate that both copper and zinc powders can reduce Au^＋ into metal gold, and zinc powder can also reduce H2O into H2, while copper powder can not. The leaching results of a cuprous gold ore show that the extraction of gold can reach 80% in this system. The preliminary results of reduction with copper and zinc powders show that with deoxygenizing, the reduction effects are relatively good.