Papers by Keyword: Chalcocite

Abstract: The dissolution of metal sulfides is controlled by their solubility product and valence bond theory, pyrite and chalcocite have different electronic nature of the valence energy band, with which the electrolyte may exchange electrons during dissolution reaction, so they have different principals of dissolution. Pyrite which has a higher rest potential is galvanically protected, while chalcopyrite which has a lower rest potential is preferentially leached. Pyrite is intentionally added to the leaching of chalcocite concentrates, we investigated the influence of pyrite to chalcocite weight ratio, solution pH , Eh and the presence of bacteria on assisted leaching of chalcocite concentrates. The leaching solution redox potential, pH, iron, copper and bacteria were monitored, leached residue was collected and analysed to understand leaching mechanism. We found that chalcocite leaching efficiency is enhanced with pyrite:chalcocite weight ratio increased.

Abstract: Electrochemical behaviors of chalcopyrite, covellite, chalcocite and bornite in 9K medium at 65 °C were compared in this paper to verify they whether or not the intermediate products of chalcopyrite. The results confirmed that bornite, chalcocite and covellite are the intermediate products of chalcopyrite. Chalcocite and bornite can both oxidize to covellite.

Abstract: The importance of comprehensive laboratory evaluation for development of an ore body to commercial processing using biohydrometallurgy cannot be understated. Laboratory evaluation for a biohydrometallurgical process must include the microbiological component and definition of operating parameters for the engineers to design the commercial plant. Failure to meet commercial production at a mine site can be a consequence of incomplete understanding of biohydrometallurgical technologies for processing a specific ore. One example is the inability of a copper bioleach process to meet the design criteria in part because of lack of sufficient testing to demonstrate the ramifications of fluoride toxicity to the microbial component of the bioleach process. Laboratory research has demonstrated toxicity of low levels of fluoride to Acidithiobacillus species. However, laboratory determined toxicity values are not always relevant to field conditions at commercial bioleach operations. This is the case with fluoride toxicity where complexing reactions increase the amount of fluoride required for toxicity. Consequently, the toxic fluoride concentrations at field sites can be significantly higher than toxic levels reported in the laboratory, but still achieve concentration inhibitory for the microorganisms.

Abstract: During Zijinshan copper heap bioleaching, pyrite was leached in plenty resulting in high ferric concentration in solution. This affected bioleaching and extraction processing greatly. The paper studied the factors influencing in the course of leaching of pyrite and a mixture of chalcocite and pyrite respectively. It focuses on the effect of the redox potential for copper bioleaching so as to find key factors affecting the dissolution difference between chalcocite and pyrite. The experiment results showed that redox potential is an important influencing factor in bioleaching. Copper and pyrite extents of the leaching process were 95% and 11% respectively and there is great dissolution difference between them at redox potential 700 mV (SHE). It is indicated that copper can be selectively bioleached by controlling redox potential of bioleaching. The conclusion will provide theoretic foundation on balance of acid and iron during bioleaching for copper of higher S/Cu ratio. A simple sulfide, pyrite and chalcocite, were selected as test minerals. The samples were obtained from rich mineral in Zijin Mine. The concentrated samples were milled to obtain the size fraction of 320 mesh percent of 90. Bacterium culture: 9K culture medium contained the following composition in kg/m3 distilled water: (NH4)2SO4, 3.0; K2HPO4·3H2O, 0.5; KCl, 0.1; MgSO4·7H2O, 0.5; Ca(NO3)2·2H2O, 0.01. The initial ferrous concentration was 9.0g/L, the initial pH was adjusted to 1.6, and the temperature set at 30°C. The rotation speed of shaking bed was 150r/min. A three-day-old inoculum previously grown in medium was used in bioleaching process. A 5% inoculum was added to give an initial bacteria concentration in the medium was (3-6)×107 cells/m3. The experiments investigated factors influencing bioleaching including ferrous concentration and redox potential during bioleaching. The extent Cu leached was over 90%. Cu leached velocity increased as redox potential turned higher. Cu leached velocity rapid increased at redox potential 700mV. During chalcocite and pyrite bioleaching, redox potential is important factor to influence of bioleaching rate and the results showed that pyrite and chalcocite bioleaching rate was correlated with redox potential. It is indicated that copper can be selectively bioleached during copper bioleaching by controlling redox potential of bioleaching. It can be concluded that: (1) Pyrite and chalcocite bioleaching rate was correlated with redox potential. Redox potential was shown to be the key factor affecting the dissolution difference between chalcocite and pyrite. (2) Chalcocite and pyrite leaching efficiency were 95% and 11% respectively and there is great dissolution difference between them at redox potential 700 mV (SHE). (3) It is indicated that copper can be selectively bioleached during copper bioleaching by controlling redox potential of bioleaching.

Abstract: Los Bronces has two ROM dump leach operations called Leach I and Leach II. Leach I was commissioned in 1998 and currently produces 12,700 ton per year. The copper mineralization in these dumps is largely sulfides, namely 60% chalcocite/covellite, 30% chalcopyrite and the balance is oxides. The Leach II plant, commissioned in early 2002, was built to treat around 700 million ton of marginal ore having 0.45% total copper. The copper mineralogy of this material is estimated to be 70% chalcopyrite, 20% chalcocite/covellite and the balance oxides. Current copper production is 33,700 ton per year. Early in 2004 it was decided to conduct a complete column test work program, aimed at reducing power, acid and lime consumption at the Leach II plant. The results of this work, partially reported at IBS 2005, have been successfully applied to the commercial operation since the end of 2005. As a consequence, the projected reduction in operating costs for 2006 of US$ 5.5 million was accomplished. The main results of the column test work program, the modifications implemented together with the results obtained at the operation, including a molecular characterization of the microbial population, are discussed in this paper.