The effect of electrolyte composition on the cathodic reduction of CuFeS2

Electrochemical characterization of chemical species formed during the electrochemical treatment of chalcopyrite in sulfuric acid

“…The CPE-chalcocite was generated from the application of a constant potential pulse (E cat = −0.285 V) to CPE-CP for 180 s to induce a higher concentration of chalcocite formed at the electrode surface, in according to the previous studies [20].…”

Surface characterization by X-ray photoelectron spectroscopy and cyclic voltammetry of products formed during the potentiostatic reduction of chalcopyrite

“…At present, hydrometallurgical treatments with different reducing agents have been shown to produce copper sulfides with low iron content. Actually, one of the greatest challenges is to determine the optimum reducing agent, medium and temperature which allow the efficient removal of the iron [7][8][9][10][11]. However, this requires a better understanding of the chalcopyrite reduction mechanism with other characterization techniques, which permit the identification of intermediates and the final products of the reaction.…”

“…Despite the fact that several authors [4,7,10,12,13] have carried out reduction studies on chalcopyrite at different experimental conditions, these continue to detect the coexistence of two copper sulfides, bornite (Cu 5 FeS 4 ) and chalcocite (Cu 2 S), which decreases the efficiency of the chalcopyrite to chalcocite conversion and indicates that the energetic conditions for complete conversion to chalcocite are still unknown. Electrochemical studies on chalcopyrite reduction have established mechanistic models that describe the inhibition phenomenon which occurs at the beginning of the process [3][4][5][6]9,12]; however, the overpotential value, required for a complete transformation to Cu 2 S, is uncertain. On the other hand, characterization of the reduction products is impractical, even when different methods are used to complement the information on the nature of the species formed (scanning Auger, atomic absorption spectroscopy, atomic force microscopy, optical micrographs, electron microprobe analysis) since they do not allow the detection of transient products [6,9].…”

“…Electrochemical studies on chalcopyrite reduction have established mechanistic models that describe the inhibition phenomenon which occurs at the beginning of the process [3][4][5][6]9,12]; however, the overpotential value, required for a complete transformation to Cu 2 S, is uncertain. On the other hand, characterization of the reduction products is impractical, even when different methods are used to complement the information on the nature of the species formed (scanning Auger, atomic absorption spectroscopy, atomic force microscopy, optical micrographs, electron microprobe analysis) since they do not allow the detection of transient products [6,9]. Additionally, there are few methods that distinguish each product formed, such as cyclic voltammetry (CV), only acknowledge the existence of Cu 2 S [9]; however, there is still an uncertainty regarding the composition of Cu 2 S electrochemically generated.…”

A Guerra do Chaco

“…Afigurou-se-lhe então que o Brasil perdera prestígio e influência, e a mudança nos papéis que ele e a Argentina até então desempenharam seria "vantajoso" para o Paraguai, cujo novo Governo se mostrava imbuído de "idéias modernas de civilização e de progresso" 38 . Conforme o historiador norte-americano Harris Gaylord Warren, posteriormente, observou, enquanto o Brasil nada fez para perpetuar sua influência, a Argentina patrocinou a revolução e o Paraguai, arrastado de volta para sua órbita, nela, como um "satélite", permaneceria por muitas décadas 39 .…”