The effects of temperature, nickel concentration and current density on the current efficiency and the electrolyzer voltage were investigated in the process of electrowinning nickel. The results show that the current ...The effects of temperature, nickel concentration and current density on the current efficiency and the electrolyzer voltage were investigated in the process of electrowinning nickel. The results show that the current efficiency is above 90% under the various experimental conditions, and the electrolyzer voltage is less than that of traditional electrolyzer system. Therefore, the optimized parameters, i.e. temperature of 50 ℃, current density of 400 A/m 2, are determined. It is also elucidated that anodic product is high valent nickel compound in the process of electrodeposition in terms of X-ray diffraction and chemical analysis. The amount of solid product formed on the electrode surface decreases with an increase in ammonium chloride concentration by cyclic voltammetry analysis. It is also indicated that the anodic gas species are mainly composed of nitrogen by vapor phase chromatograph.展开更多
The black nickel formation process in leaching solution containing ammonia and chloride was investigated in terms of cyclic voltammetric and galvanostatic reduction techniques. The structure of black nickel was examin...The black nickel formation process in leaching solution containing ammonia and chloride was investigated in terms of cyclic voltammetric and galvanostatic reduction techniques. The structure of black nickel was examined by means of X-ray diffraction technique. The results show that in the scanning region, two oxidization current peaks are observed during the positive sweep, one of which is attributed to a valence state transformation of Ni（OH）2 to high valence nickel compound（black nickel）, and the other is caused by nitrogen evolution. During the formation process of black nickel, γ-NiOOH probably tends to self-discharge with water to form α-Ni（OH）2. As a result, it is observed that Ipa/Ipc(Ipa—anodic peak current; Ipc—cathodic peak current) maintains at a constant with the scanning rate increasing. Two reduction current peaks in cyclic voltammogram and two potential plateaus in galvanostatic reduction curve for black nickel are ascribed to the reduction of various oxidization states of nickel oxide. The potential plateaus at about 0.75 V reach the maximum in galvanostatic reduction curves. Black nickel presents amorphous structure.展开更多
文摘The effects of temperature, nickel concentration and current density on the current efficiency and the electrolyzer voltage were investigated in the process of electrowinning nickel. The results show that the current efficiency is above 90% under the various experimental conditions, and the electrolyzer voltage is less than that of traditional electrolyzer system. Therefore, the optimized parameters, i.e. temperature of 50 ℃, current density of 400 A/m 2, are determined. It is also elucidated that anodic product is high valent nickel compound in the process of electrodeposition in terms of X-ray diffraction and chemical analysis. The amount of solid product formed on the electrode surface decreases with an increase in ammonium chloride concentration by cyclic voltammetry analysis. It is also indicated that the anodic gas species are mainly composed of nitrogen by vapor phase chromatograph.
基金Project(50004005) supported by the National Natural Science Foundation of China
文摘The black nickel formation process in leaching solution containing ammonia and chloride was investigated in terms of cyclic voltammetric and galvanostatic reduction techniques. The structure of black nickel was examined by means of X-ray diffraction technique. The results show that in the scanning region, two oxidization current peaks are observed during the positive sweep, one of which is attributed to a valence state transformation of Ni（OH）2 to high valence nickel compound（black nickel）, and the other is caused by nitrogen evolution. During the formation process of black nickel, γ-NiOOH probably tends to self-discharge with water to form α-Ni（OH）2. As a result, it is observed that Ipa/Ipc(Ipa—anodic peak current; Ipc—cathodic peak current) maintains at a constant with the scanning rate increasing. Two reduction current peaks in cyclic voltammogram and two potential plateaus in galvanostatic reduction curve for black nickel are ascribed to the reduction of various oxidization states of nickel oxide. The potential plateaus at about 0.75 V reach the maximum in galvanostatic reduction curves. Black nickel presents amorphous structure.
