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Thomas J. O'keefe - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of Lead Anode Reactions in Acid Sulfate Electrolytes. I. Lead Alloys with Cobalt Additives
Journal of The Electrochemical Society, 1999Co-Authors: Pu Yu, Thomas J. O'keefeAbstract:Lead Alloys, such as Lead-calcium-tin and Lead-silver, are the primary insoluble anodes used in the electrowinning of metals. While some difficulties are encountered in their use, there is no obvious replacement that is economically and technically competitive. Two of the specific problems with Lead include decreased cathode purity due to incorporation from corrosion products and the relatively high overpotential which increases cell voltage. To gain an improved understanding of the fundamental behavior of Lead anodes, the polarization behavior of six different Alloys in sulfuric acid was evaluated. Some tests were also made with Co(II) in the acid sulfate electrolyte. Notable differences were found in the multiple activation-passivation cycles, stability, and relative activity for oxygen evolution for the Alloys, and the relative trends in behavior were established. Electrochemical impedance spectroscopy studies were also conducted at selected potentials. Overall, the data show that the electrochemical response, particularly the degree of polarization for the oxygen evolution reaction, of the Lead alloy anodes are dependent on the surface phases and structures present. The ability to depolarize the anode reaction using Co(II) was particularly sensitive to the Lead composition.
S Zarev - One of the best experts on this subject based on the ideXlab platform.
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investigation of the processes of obtaining plastic treatment and electrochemical behaviour of Lead Alloys in their capacity as anodes during the electroextraction of zinc ii electrochemical formation of phase layers on binary pbag and pbca and terna
Hydrometallurgy, 1996Co-Authors: St Rashkov, Y Stefanov, Ts Dobrev, Z Noncheva, M Petrova, N Kunchev, D Petrov, St Vlaev, V Mihnev, S ZarevAbstract:Abstract The electrochemical oxidation processes and phase formation on binary PbAg and PbCa, and ternary PbAgCa Alloys during anodic treatment of the electrodes for conditions in a sulphuric acid electrolyte were investigated. The electrochemical behaviour of Lead and its Alloys was studied by the cyclic voltammetry method (CVA). X-ray and SEM were used for the phase composition and surface structure analysis. It was established that only the ternary plastically treated PbAg 0.5%-Ca 0.11% Alloys reveal similarities to the industrially applied PbAg 1 % anodes. It may be assumed in the case of ternary Alloys that the catalytic layer is composed of a dense non-conductive MnO2 layer of crystals serving as basic sites for oxygen evolution.
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investigation of the processes of obtaining plastic treatment and electrochemical behaviour of Lead Alloys in their capacity as anodes during the electroextraction of zinc i behaviour of pbag pbca and pbagca Alloys
Hydrometallurgy, 1996Co-Authors: M Petrova, Ts Dobrev, St Rashkov, Z Noncheva, D Petrov, St Vlaev, V Mihnev, S Zarev, N Kounchev, L GeorgievaAbstract:Abstract The influence of the mode of obtaining and plastic treatment of binary PbAg and PbCa, and ternary PbAgCa Alloys (used as anodes in Zn electro-extraction from sulphate electrolytes) on their electrochemical behaviour and corrosion resistance is studied. It has been established that the rolled PbAg Alloys possess a higher corrosion resistance and lower anodic polarization compared to the cast Lead-silver ones due to the structural fineness and homogeneity of the plastic deformed anodes. The plastic deformation of the ternary Alloys with calcium content of 0.06% causes Pb3Ca precipitation in the solid solution. The hot-rolled Alloys form an solid solution of Pb3Ca with fine-grained structure, deformed through the rolling direction. The cold-rolled Alloys possess clearly expressed oriented structures also through the rolling direction. Cast and plastically deformed PbCa anodes possess better electrochemical and corrosion characteristics than pure Pb but a considerably higher anodic polarization and lower corrosion resistance than PbAg Alloys. Both PbCa systems, with a calcium content of 0.08 and 0.11 % are very appropriate for the preparation of ternary PbAgCa Alloys. These Alloys (PbAg 0.5 %-Ca 0.11 %) possess better electrochemical and corrosion characteristics than binary PbCa ones. Only ternary rolled Alloys have equal corrosion and electrochemical properties to those of the alloy PbAg (0.75%–1.0%) used in practice.
Thomas J Okeefe - One of the best experts on this subject based on the ideXlab platform.
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evaluation of Lead anode reactions in acid sulfate electrolytes ii manganese reactions
Journal of The Electrochemical Society, 2002Co-Authors: Thomas J OkeefeAbstract:Lead Alloys containing calcium-tin, silver, or similar combinations are the primary insoluble anodes used for copper and zinc electrowinning. One potential concern with these anodes is the detrimental effect on cathode purity from incorporation of Lead corrosion products. Other factors which are important to process economics are the reaction potential and overpotential required for oxygen evolution. In addition to the inherent overpotential, impurities in the electrolyte can have a significant polarization impact, such as the films that may form when manganese is present. In order to gain a better understanding of the fundamental behavior of various concentrations of manganese ions at Lead anodes, the polarization behavior of Lead calcium-tin and Lead-silver Alloys in sulfuric acid was evaluated. A common depolarizing agent, Co(II), was also used in some cases to determine possible interactions with manganese. The data show that manganese ions are active on the Lead anodes and may precipitate manganese oxide in addition to electrochemical deposition. One possible precipitation mechanism seems to occur by the disproportionation of Mn(III). Co(II) lowers the electrode potential at given current densities which decreases Pb corrosion but favors MnO 2 formation.
Pu Yu - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of Lead Anode Reactions in Acid Sulfate Electrolytes. I. Lead Alloys with Cobalt Additives
Journal of The Electrochemical Society, 1999Co-Authors: Pu Yu, Thomas J. O'keefeAbstract:Lead Alloys, such as Lead-calcium-tin and Lead-silver, are the primary insoluble anodes used in the electrowinning of metals. While some difficulties are encountered in their use, there is no obvious replacement that is economically and technically competitive. Two of the specific problems with Lead include decreased cathode purity due to incorporation from corrosion products and the relatively high overpotential which increases cell voltage. To gain an improved understanding of the fundamental behavior of Lead anodes, the polarization behavior of six different Alloys in sulfuric acid was evaluated. Some tests were also made with Co(II) in the acid sulfate electrolyte. Notable differences were found in the multiple activation-passivation cycles, stability, and relative activity for oxygen evolution for the Alloys, and the relative trends in behavior were established. Electrochemical impedance spectroscopy studies were also conducted at selected potentials. Overall, the data show that the electrochemical response, particularly the degree of polarization for the oxygen evolution reaction, of the Lead alloy anodes are dependent on the surface phases and structures present. The ability to depolarize the anode reaction using Co(II) was particularly sensitive to the Lead composition.
Alexander Aerts - One of the best experts on this subject based on the ideXlab platform.
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active oxygen control by a pbo mass exchanger in the liquid Lead bismuth eutectic loop mexico
Journal of Nuclear Science and Technology, 2017Co-Authors: J Lim, A Marino, Alexander AertsAbstract:ABSTRACTAccurate control of dissolved oxygen concentration is crucial in order to use liquid Lead Alloys as a coolant of advanced nuclear systems. An oxygen control system based on PbO mass exchanger (PbO MX) technology was implemented in order to control the dissolved oxygen concentration in the liquid Lead--bismuth eutectic (LBE) loop MEXICO. The oxygen control system consisted of a packed bed of PbO spheres, an oxygen sensor and a pneumatic control valve. The concentration of dissolved oxygen in the loop was controlled by regulating the LBE flow through the PbO MX using a proportional–integral–derivative (PID) controller with feedback from the oxygen sensor. Highly accurate control of the dissolved oxygen concentration in the loop was achieved by this system.