亜鉛電解採取における電析亜鉛の再溶解挙動に及ぼす不純物の相乗作用 [in Japanese] Synergistic Effect of Impurities on the Dissolution Behavior of Zn Electrodeposited from Electrowinning Solutions [in Japanese]
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The synergistic effect of impurities on the dissolution behavior of Zn electrodeposited from the electrowinning solutions containing a different combination of impurities has been investigated by measuring the time-dependence of cathode potential during electrolysis and the polarization curves in the solutions. The impurities are classified into four groups ; group I (Ag, Cu, Cd) which changes inherent hydrogen overpotential <I>η</I><SUP>0</SUP><SUB>H</SUB> by depositing at limiting current density; group II (Ni, Co, Fe) which reduces <I>η</I><SUP>0</SUP><SUB>H</SUB> by partially depositing at lower current densities than limiting one ; group III (As, Sb, Ge) which catalytically reduces <I>η</I><SUP>0</SUP><SUB>H</SUB> ; and group IV (Al, Pb) which causes no change in <I>η</I><SUP>0</SUP><SUB>H</SUB>. In the solution containing both iron-group metal of group II and Cu of group I or Sb of group III as impurity, the dissolution of deposited Zn was more likely to occur than in the solution containing each impurity alone. Cu and Sb increase the kinetically suppressed deposition rate of iron-group metals, resulting in the increase in the critical current density for Zn deposition. The occurrence of dissolution of deposited Zn was closely related to the increase in critical current density for Zn deposition. Although the cycle of deposition and dissolution of Zn was repeated in the solution containing iron-group metal alone, no Zn deposited again after the dissolution occurred in the solution containing iron-group metal and Cu or Sb. This is ascribed to cathode surface replaced by Cu and iron-group metal during dissolution of Zn.
Shigen-to-Sozai 124(3), 179-183, 2008-03-25
The Mining and Materials Processing Institute of Japan