Effect of nickel and magnesium on zinc electrowinning using sulfate solutions

Abstract

-Zinc electrowinning is performed with the application of a current through insoluble electrodes (Pb-Ag), causing the electrolysis of zinc sulfate, with or without impurities, and zinc deposition on the cathode of aluminum. The impurities can reduce the current efficiency and increase the energy consumption in zinc electrolysis. In this work, the effect of nickel and magnesium on zinc electrodeposition was studied using the electrochemical techniques of galvanostatic deposition and cyclic voltammetry. Additions of nickel, magnesium or both cations in zinc sulfate electrolyte resulted in a marginal increase in current efficiency. Addition of nickel or magnesium polarizes the cathode; however, the extent of polarization in the presence of magnesium is more than that of nickel. Addition of magnesium to the zinc electrolyte caused zinc reduction at a more negative potential. The addition of nickel to the zinc electrolyte increased the current density of the anodic peaks, thus increasing the dissolution of zinc and hydrogenated phases. The addition of nickel to the zinc and magnesium solutions decreased the nucleation loop, facilitating zinc deposition.

Cyclic Voltammetric Study of High Speed Silver Electrodeposition and Dissolution in Low Cyanide Solutions

“…In contrast to the onset potential of silver electrodeposition at the 1st scan cycle, the reduction of silver ions starts at a more positive potential from the 2nd scan cycle onwards, which is at ∼−280 mV. As platinum working electrode (which is different from the deposited metal) is employed, the initiation of nucleation normally consumes more energy to produce the first nucleus [20]. Besides that, the presence of nondissolved silver film on the electrode may also facilitate the nucleation and growth processes during the 2nd scan cycle.…”

Highly reflective metallic thin films for high brightness LEDs

“…High purity (99.999%) silver single crystals with specific orientations of the (100), (110) and (111) were purchased from Goodfellow Cambridge Ltd, UK. These one-sided polished single crystals have diameter of 10 mm and thicknesses of 2 mm for the (100) and (111) samples and 1 mm for the (110) sample. The orientation tolerance of these single crystals was ± 3º.…”

“…2D (Ra) and 3D (Sdr) roughness parameters were used to characterize the surface texture of single crystal silver. It is found that surface roughness plays a more critical role in determining the reflectance while the crystal (100), (110) and (111) orientations have negligible effect on the silver reflectance. Moreover, correlations in predicting the silver reflectance by employing either 2D or 3D roughness parameters as the input variables have also been proposed.…”

“…Table Captions xii electrons and x-ray (redrawn from [80]). 100, Ag (110) and Ag (111) with different specular reflectance (a) -(c) R450nm…”

“…is employed, the initiation of nucleation normally consumes more energy to produce the first nucleus [111]. Besides that, the presence of non-dissolved silver film on the electrode may also facilitate the nucleation and growth processes during the 2 nd scan cycle.…”