Journal of Sustainable Metallurgy ( IF 2.5 ) Pub Date : 2022-01-10 , DOI: 10.1007/s40831-021-00482-9 Levent Kartal 1
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In this study, electrochemical cobalt (Co) production from cobalt sulfide (CoS), which was obtained by leaching and sulfide precipitation from waste cemented carbide scraps, was investigated under galvanostatic and potentiostatic conditions at a constant temperature of 973 K in NaCl–KCl electrolyte. To determine the reduction conditions before the electrochemical reductions experiments, the electrochemical behavior of CoS was investigated with cyclic voltammetry (CV). According to the CV results, it was observed that CoS was reduced at − 0.25 V, well below the electrolyte breakdown voltage against the graphite electrode. Pelletized CoS was used in electrochemical reduction experiments. First, the reduction of pelletized CoS was carried out galvanostatically at 250 and 500 mA/cm2 current densities for different times. A rapid increase in cell voltages overtime was shown at both current densities. As a result of galvanostatic experiments, it was observed that all of the sulfur in the structure was removed at a current density of 500 mA/cm2, and around 0.5% sulfur remained in the structure at a current density of 250 mA/cm2. After the galvanostatic reductions, potentiostatic reductions of pelletized CoS were carried out at 3.0 V constant cell voltage at 973 K for 900 s and 1800 s electrolysis durations condition. As a result of potentiostatic experiments, it was determined that all of the sulfur could be removed from the structure by prolonging the electrolysis time. In the light of obtained results from galvanostatic and potentiostatic experiments, it was determined that the cathode products obtained were in dendritic structures and were oxidized in a small amount during the cleaning steps from the electrolyte.
Graphical Abstract
中文翻译：
硫化钴在熔融 NaCl–KCl 中的电化学还原
在这项研究中，研究了在 973 K 恒温恒电流和恒电位条件下，在 NaCl-KCl 电解质中，通过从废硬质合金废料中浸出和硫化物沉淀获得的硫化钴 (CoS) 电化学生产钴 (Co)。 . 为了在电化学还原实验之前确定还原条件，用循环伏安法 (CV) 研究了 CoS 的电化学行为。根据 CV 结果，观察到 CoS 在 - 0.25 V 时降低，远低于针对石墨电极的电解质击穿电压。粒状 CoS 用于电化学还原实验。首先，颗粒化 CoS 的还原在 250 和 500 mA/cm 2 下恒电流进行不同时期的电流密度。在两种电流密度下都显示了电池电压随时间的快速增加。作为恒电流实验的结果，观察到在 500 mA/cm 2的电流密度下，结构中的所有硫都被去除，在250 mA/cm 2的电流密度下，大约 0.5% 的硫保留在结构中. 在恒电流还原后，在 3.0 V 恒定电池电压和 973 K 条件下，在 900 秒和 1800 秒电解持续时间的条件下进行颗粒化 CoS 的恒电位还原。作为恒电位实验的结果，确定可以通过延长电解时间从结构中去除所有硫。根据从恒电流和恒电位实验中获得的结果，确定所获得的阴极产物呈树枝状结构，并且在电解液的清洁步骤中被少量氧化。
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