Mechanism of the High Removal Rate of Cobalt in Conventional Cementation by Zinc Dust with Arsenic Oxide in the Presence of Cupturic Ions.
Mechanism of the High Removal Rate of Cobalt in Conventional Cementation by Zinc Dust with Arsenic Oxide in the Presence of Cupturic Ions.
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DOI：
10.2473/shigentosozai.116.779
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
T. Ohgai;H. Fukushima;T. Akiyama;S. Heguri
中科院分区：
文献类型：
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作者：
T. Ohgai;H. Fukushima;T. Akiyama;S. Heguri
通过极化测量、扫描微电极技术、ESCA 和 EPMA 分析，研究了合成锌浸出溶液中 As2O3 和 Cu2+ 在锌粉胶结 Co 中的作用。证实了Co具有在其平衡电位时不开始沉积的固有性质，并且Co开始沉积的电位在硫酸锌溶液中被极化，几乎达到Zn的平衡电位。 Co 特有的这些特性直接导致了单独使用 Zn 粉尘的胶结中 Co 去除率极低。在硫酸锌溶液中，当存在 As2O3 和 Cu2+ 时，Co 的部分极化曲线显着向更高的方向移动，表明这些添加剂充当催化剂，在大量 Zn2+ 存在下促进动力学抑制的 Co 沉积速率。考虑到在平衡电位下开始电沉积的 Cu 立即被 Zn 粉尘还原为金属态，初始 Zn 粉尘表面上沉积的 Cu 将提供活性阴极区域，Co 可以轻松沉积在其上。另一方面，As2O3 也优先于 Co 被 Zn 粉尘还原，并以金属和氧化物的形式沉积。金属As起到了沉积Co上析氢的抑制剂的作用，而As氧化物则起到了催化剂的作用，降低了Co固有的沉积过电势，促进了Co的置换速率。
The roles of As2O3 and Cu2+ in the cementation of Co by Zn dust were studied in synthetic Zn leach solutions by polarization measurements, scanning micro-electrode technique, ESCA and EPMA analyses. It was confirmed that Co had an inherent property of not beginning to deposit at its equilibrium potential and that the potential at which Co began to deposit was polarized in Zn sulfate solution almost to reach the equilibrium potential of Zn. These properties peculiar to Co were directly responsible for the extremely small removal rate of Co in the cementation using Zn dust alone. The partial polarization curves of Co were significantly shifted to more noble direction in the presence of As2O3 and Cu2+ in Zn sulfate solution, indicating that these additives acted as a catalyst which promoted the kinetically suppressed deposition rate of Co in the presence of large amounts of Zn2+. Considering the fact that Cu, which began to electrodeposit at its equilibrium potential, was reduced to metallic state by Zn dust immediately, the deposited Cu on the initial Zn dust surface would offer active cathode area on which Co can deposit easily. On the other hand, As2O3 was also reduced by Zn dust in preference to Co and deposited in the forms of metal and oxide. The metallic As acted as an inhibitor for hydrogen evolution on the deposited Co, while As oxide worked as a catalyst to reduce the inherent deposition overpotential of Co and promoted the cementation rate of Co.