A Study On Processes And Fundamentals Of Electrogenerative Leaching Of Sulfide Minerals

The environmental constraints that are being imposed on smelters have created much interest in the extraction of metals from their sulfide ores with hydrometallurgy. As a result, a large number of new hydrometallurgical processes is emerging, however, which consume too much energy. In order to exploit the chemical energy during the processes of sulfide ores reasonably and simplify the purifying, in this study the principle of electro-generative has been applied to the process of oxidative leaching of minerals based on the summarization on the FeCl3 leaching of sulfide minerals, electrochemical aspect of oxidative leaching and simultaneous leaching. The technology and relative theory of the processes and affecting factor of FeCl3 electro-generative leaching and simultaneous leaching of MnO2 and sulfide minerals are investigated emphasitically. The subjects of the present dissertation are as follows:A dual cell technique was used to study the influence of electrode structure in the electro-generative leaching for the first time. The output current and power increase with the addition of acetylene black to the sulfide mineral electrode. The electrode mixed with acetylene black is better than that mixed with graphite. Filter net electrode was also applied to electro-generative process of sulfide minerals to overcome the problems in the compacted electrode and slurry electrode, which made the electro-generative leaching process significant in practice in obtaining both metal ions and electric energy.An ion-elective membrane was used to separate the anolyte and catholyte compartments, which could decrease the electric resistance of loop and improve purifying process.The influence of temperature on the electro-generative leaching process of sulfide minerals with FeCl3 has been explored in detail. The activation energy of each system under the present conditions was determined, respectively, as: Ea(PbS) =18.26kJ mol-1, Ea(Galena)= 14.96 KJ mol-1, Ea(ZnS)=21.22KJ mol-1, Ea(Sphalerite)=25.66KJ mol-1,Ea(Nickel concentrates)= 34.63 KJ mol-1, Ea(Chalcopyrite concentrates)= 17.28~27.72KJ mol-1. From these values it can be concluded that electrogenerative-leaching rate of sulfide minerals with FeCl3 is controlled by diffusion and electrochemistry at the same time. The affecting factor of temperature is smaller.Chlorine ions are involved in the electro-generative leaching process of sulfide minerals directly. The output power increases as NaCl concentration increases. There has little influence on the leaching efficiency when the NaCl concentration reaches a certain value. The mechanism of anodic reaction has been deduced under reasonable hypothesis, and kinetic equations with respect to chlorine ions for each sulfide mineral are obtained as follows:The above conclusions are in agreement with experimental results.The influence of ferric ions on the electro-generative leaching of sulfide minerals and synthetic sulfides is similar. Ferric ions play an important role in limiting the electro-generative leaching rate at a relatively low concentration (<0.1-0.2 mol-L-1 FeCl3). The mechanism of cathodic reaction is proposed, and kinetic equations with respect to ferric ions for each sulfide mineral are as follows:The proposal mechanism agrees well with experimental results.The electro-generative leaching of sulfide minerals with acidic MnO2 is superior to that with FeCl3. The former systems possess the larger output current, output potential and leaching efficiency.The electrochemical behaviors of sulfide mineral electrode or corresponding carbon paste electrodes have been studied by the cyclic voltammetry. The electro-catalytic property of carbon in electrode is shown in experiments.The anodic processes of sulfide minerals have been investigated by a.c. impedance method. An equivalent circuit of electro-generative leaching process is built, and electrochemical impedance spectroscopy of the process is deduced theoretically, which agrees with experimental results. The results show that anodic po...