Approximately 55,000 tonnes of cobalt are produced annually worldwide, which represents an estimated $1–3 billion in annual sales depending on cobalt price changes. Cobalt is a common impurity in ...both non-ferrous mineral sulfide and oxide processing. In this paper some business and technical considerations are presented to facilitate the decision-making process required to produce either an intermediate or a finished cobalt product via a hydrometallurgical route. Methods currently available and practiced for the recovery of cobalt are considered, and process requirements up- and down-stream associated with each chosen method are discussed. In particular, some environmental, energy, or other sustainable development implications of each process are mentioned. An outlook on the future of the cobalt industry and anticipated future trends is included.
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CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The effect of applying sandblasting during pretreatment while preparing titanium based IrO2−Ta2O5 anodes by the conventional method was investigated. It was observed that sandblasting influences the ...surface morphology both before and after coating as deeper and smaller etching pits are obtained on the substrate before coating process and rougher surface is obtained after coating. As a result larger outer electrochemical active surface area (ECSA) is obtained on the anodes with sandblasting, which was determined based on cyclic voltammetry, whereas the inner ECSA is independent of the pretreatment. The polarization measurements in a quasi-steady state reveal that sandblasting has slight influence on the catalytic activity. Accelerated lifetime tests were carried out in acidic 0.9 mol L−1 Na2SO4 solution (pH = 2) at a current density of 5 × 107 A cm−2 under galvanostatic conditions. It shows that sandblasting would shorten the lifetime of the anode due to oxidation of the titanium substrate. This is suggested to be due to the shorter distance between the lowest spot of the outer coating surface and the highest spot of the outer substrate of the anode after applying sandblasting in titanium substrate pretreatment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The deactivation was due to coating loss or combined with passivation of the titanium substrate.•The coating loss was occurring as coating dissolution, coating spalling and coating peeling off.•No ...critical value of the amount of the residual iridium was found in this work to predict the eventual deactivation before forming the passive oxide film.•Deactivation of the anodes was found to be more dependent on the calcination temperature than other manufacturing parameters.
In this work, series of IrO2-Ta2O5 anodes were investigated. The catalytic activity towards oxygen evolution reaction (OER) of these anodes are determined by calcination temperature, coating loading (coating thickness), pretreatment of titanium substrate and coating method. The difference in OER performance among the anodes are ascribed to the crystallinity of the IrO2 phase and the phase composition of the coatings. The durability of the anodes were also studied by conducting an accelerated lifetime test (ALT) in acidic 0.9 mol L−1 Na2SO4 solution at a current density of 5 kA m−2. An anode prepared at a moderate temperature exhibits an excellent lifetime of almost one year although its catalytic activity is not the best. Nevertheless, using the electrostatic spraying method to replace the hand-brush method in the coating preparation can prolong the service life even further and with less amount of coating loading. Moreover, it reveals that the coating loss or combined with titanium substrate passivation results in the eventual deactivation of the anodes during ALT. No critical value of the amount of the residual iridium was found in this work to predict the eventual deactivation before forming the passive oxide film. In addition, the deactivation of the anodes strongly depends on the calcination temperature.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The effect of applying sandblasting during pretreatment while preparing titanium based IrO2−Ta2O5 anodes by the conventional method was investigated. It was observed that sandblasting influences the ...surface morphology both before and after coating as deeper and smaller etching pits are obtained on the substrate before coating process and rougher surface is obtained after coating. As a result larger outer electrochemical active surface area (ECSA) is obtained on the anodes with sandblasting, which was determined based on cyclic voltammetry, whereas the inner ECSA is independent of the pretreatment. The polarization measurements in a quasi-steady state reveal that sandblasting has slight influence on the catalytic activity. Accelerated lifetime tests were carried out in acidic 0.9 mol L−1 Na2SO4 solution (pH = 2) at a current density of 5 × 107 A cm−2 under galvanostatic conditions. It shows that sandblasting would shorten the lifetime of the anode due to oxidation of the titanium substrate. This is suggested to be due to the shorter distance between the lowest spot of the outer coating surface and the highest spot of the outer substrate of the anode after applying sandblasting in titanium substrate pretreatment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this work, industrial IrO2-Ta2O5 anodes calcined at different temperatures were investigated. The results show that the calcination temperature has significant influence on the surface ...microstructure including the crystallinity and the preferred orientation of IrO2 crystallite of the formed IrO2-Ta2O5 binary oxide. The IrO2 phase is partially amorphous at low calcination temperature in the present study. The (101) IrO2 planes dominates at low or moderate calcination temperatures, whereas the (110) IrO2 orientation was preferred at the highest calcination temperature. Surface morphology of the anodes was revealed as mud-cracks surrounded by a flat area with plenty of scattered nano-IrO2 crystallites. The size of the nano-IrO2 crystallites is calcination temperature dependent, which in turn determines the electrochemical active surface area (ECSA). In this IrO2-Ta2O5 binary oxides coating, (101) IrO2 was found to have higher catalytic activity than (110) IrO2 with respect to the oxygen evolution reaction (OER). The moderate temperature is suggested as the best calcination temperature for this certain anode regarding the ECSA, electrocatalytic activity for OER and stability potential.
Nickel may be produced by electrolysis in acidic chloride based electrolytes. Nickel is initially deposited on stainless steel or titanium starting sheets while chlorine gas is evolved on DSA anodes. ...Stress in the nickel deposit may cause bending of the cathode sheet. Also irregular growth such as dendrite formation may occur. In extreme cases short circuiting of electrodes will happen. Fundamental electrochemical studies of the initial stages of the electrodeposition process may give valuable information for obtaining smooth nickel deposits.
Initial experiments were carried out by using cyclic voltammetry on cathodes of titanium. Ongoing studies are performed by potential step chronoamperometry to study the nucleation and growth of nickel on titanium cathode substrates. Experiments to study the effect of electrolyte composition, pH and temperature on the nickel deposition process are under way. Electrolysis to deposit macroscopic amounts of nickel will be carried out to characterize the deposits by optical methods.
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