COPPER

Author: FUENTES CÁCERES GERARDO.
Year: 2005.
University: BARCELONA [www.ub.es].
Place of defense: FACULTAD DE QUÍMICA.
Place of preparation: FACULTAD DE QUÍMICA.

Summary: The transformation has been studied hydrothermal sphalerite (ZnS), bornite (Cu5FeS4), collection (guinea pig) and pyrite (FeS2) with solutions of Cu2 + to 100-240Â ° C and 1-35 atm. The reaction of sphalerite with a pH between 1,1-1,3 produces digenita (Cu1, 8S) between 180-212Â ° C and calcocita (Cu2S) 225Â ° C. The reaction can be observed through a compact layer of copper sulfide, which surrounds a core without reacting. The reaction follows a parabolic law, with constant speed inversely proportional to the square of the initial radius of the particle. The reaction rate is independent of the concentration of copper. The activation energy is about 147 kJ / mol and control is kinetic ion diffusion in the solid state. The reaction of the beautiful, like pH, produces digenita larger 160Â ° C. At higher temperatures there training djurleíta (Cu1, 94S). The speed of reaction kinetics law continues diffusion layer products. No effect of the concentration of copper. The activation energy is about 100kJ/mol and control is also kinetic ion diffusion in the solid state. The reaction of covellita at the same pH, produces digenita larger 200Â ° C. At higher temperatures and times there transformation calcocita (QyM) occurring at the expense of digenita. No forms a continuous layer and that the reaction occurs by nucleation of digenita and erratic growth area. The reaction rate is still an act of chemical kinetics. The reaction rate is sensitive to the concentration of Cu2 +, in order experimental 0.6. The activation energy of the process is about 110kJ/mol and control is a kinetic Electrochemical. The reactions of pyrite, in the interval 180-200Â ° C produces mixtures digenita and calcocita Q. At temperatures of 240Â ° C and cupric fungicide for concentrations of 10 gpL detected a process of oxidation of ferrous to ferric, by hydrolysis to produce hematite. The main reaction is caused by irregular nucleation to digenita and growth of porous layer, resulting in breakage in areas of high tension as a result of the high value of the relationship Pilling-Bedworth (1.56-1.61). The speed of reaction kinetics continues chemical control law. The reaction rate is sensitive to the concentration of Cu2 + orderly 0.6. The activation energy of the process is 110kJ/mol and electrochemical control. The reaction of copper concentrates is similar to that of the pure species. The order of reactivity is of the type: bornita-calcopirita-vovellita-esfalerita-pirita. A 225Â ° C there is an almost complete transformation of the bornite, chalcopyrite, covelita and sphalerite. The elements are eliminated by hydrothermal reaction, how are greater Zn, Cd, IT and Bi. The PB and you have intermediate extractions while the Mo, Sb and As reactions are moderate. THE temperature is the variable that is most influential in removing impurities. A concentrate containing 33% Cu, 33% for S, 22% Fe and 2% Zn can be converted to a superconcnetrado of 70% Cu, 19% S, 3% Fe. The advantages of a concentrate of this type would be: Raise more than twice the capacity of melting due to the high wealth in copper slag generation minimum losses and minimum trapping copper reduction and nearly 50% of the emission of sulfur and finally have the option of a chemical or biochemical treatment.

Author: CÓRDOBA TUTA ELCY MARÍA.
Year: 2005.
University: COMPLUTENSE DE MADRID [www.ucm.es].
Place of defense: FACULTAD DE CIENCIAS QUÍMICAS.
Place of preparation: FACULTAD DE CIENCIAS QUÍMICAS.

Summary: We 3 studies related to biological and chemical leaching of chalcopyrite. The first, called the preliminary studies, evaluated the leachability of the chalcopyrite and consisted of leachate tests with ground ore and bulk samples, which were then analyzed by different surface analysis techniques such as XRD, SEM - EDS AND XPS. The second looked at potential controlled, assessed the effect on the redox potential of leaching chemical and biological dela chalcopyrite and its interaction with other variables such as temperature, concentration of iron, pH, addition of silver, pulp density, type of bacterial culture and the presence of oxygen. With this study delved into the mechanisms of the leaching of calopiritia. Finally, we performed a study of electrochemical dissolution of chalcopyrite, which consisted of the electrode electrochemical characterization previously attacked in a manner and under conditions potenciostáticas electrochemical, chemical form of previously attacked, with solutions Fe3 + / Fe2 + at different redox potential and biologically attacked with thermophilic microorganisms mesóflios and mixed oxidants and sulfur. It is concluded that chalcopyrite dissolves through training intermediate covelina which is subsequently oxidised by the ferric ion, the jarosite that is the leading cause of the passivation of the calopirita during its dissolution, while the elemental sulfur is not formed a barrier difusional .