"Trace impurities are always present in industrial electrolytes used in zinc electrowinning. The most deleterious impurities such as Ge, Sb, As, and Ni cause excessive hydrogen evolution and localized zinc corrosion, thus decreasing the current efficiency and quality of the zinc cathode. In this research, attempts have been made to characterize the electrochemical behavior of these impurities and learn more about the fundamental mechanisms involved in the zinc deposition process.
Electrochemical impedance spectroscopy (EIS) showed that the charge resistance decreased in the presence of antimony while it increased with gelatin and thallium. According to the EIS results, antimony and germanium behaved similarly, interacting in the cathode interfacial region, possibly disrupting the zinc hydroxide film. Gelatin and thallium modified the intermediate reactions, possibly including adsorption of the Had and Zn+ad species.
Chronoamperometry (CA) test results were also sensitive to the presence of antimony, gelatin, or a balanced mixture of the two additives. The different additives could be easily differentiated using the current-time relationships and results were in agreement with those from polarization measurements.
Thallium was found to be effective in counteracting the effects of a variety of harmful impurities, but was detrimental in some cases when nickel was the active impurity. EIS measurements showed that thallium substantially increased the charge transfer resistance, showing characteristics of modifying the intermediate reactions during zinc electrowinning"--Abstract, page iv.
O'Keefe, T. J. (Thomas J.)
Askeland, Donald R.
Johnson, James W., 1930-2002
Kohser, Ronald A.
Materials Science and Engineering
Ph. D. in Metallurgical Engineering
University of Missouri--Rolla
Journal article titles appearing in thesis/dissertation
- Effects of organic additives on current efficiency and deposition morphology in zinc sulfate electrolytes
- Synergism of Tl3+ with certain impurities in zinc electrowinning
- Characterization of Sb3+-gelatin additives in zinc sulphate electrolytes using impedance analysis electrowinning
- Influence of Ge4+ and Tl3+ on zinc polarization
- Correlation between cyclic boltammetry and chronoamperometry evaluation for zinc deposition in the presence of Sb3+ and gelatin
xxxi, 161 pages
© 1996 Xuewen Tang, All rights reserved.
Dissertation - Restricted Access
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Electronic access to the full-text of this document is restricted to Missouri S&T users. Otherwise, request this publication directly from Missouri S&T Library or contact your local library.http://laurel.lso.missouri.edu/record=b3075929~S5
Tang, Xuewen, "Electrochemical characterization of impurities and additives in zinc electrowinning" (1996). Doctoral Dissertations. 1123.
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