Mechanism Analysis of Carbon Contamination and the Inhibition by an Anode Structure during Soluble K2CrO4 Electrolysis in CaCl2-KCl Molten Salt
Mechanism Analysis of Carbon Contamination and the Inhibition by an Anode Structure during Soluble K2CrO4 Electrolysis in CaCl2-KCl Molten Salt
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DOI：
10.1149/2.1951712jes
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发表时间：
2017
影响因子：
3.9
通讯作者：
W. Weng;Mingyong Wang;X. Gong;Zhi Wang;Dong Wang;Zhancheng Guo
中科院分区：
文献类型：
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作者：
W. Weng;Mingyong Wang;X. Gong;Zhi Wang;Dong Wang;Zhancheng Guo
采用一种新型的阳极结构，在CaCl2-KCl2熔盐中实现了对可溶性K2CrO4的高效电解。使用石墨阳极时，由于碳颗粒的积累和CO32-还原造成的碳污染对电解过程非常不利，特别是在CaCl2-KCl2熔盐中直接将可溶性K2CrO4电解成金属铬的新工艺。本文对K2CrO4电解过程中的碳迁移和CO32-还原进行了分析和讨论。分析了CrO42-和CO32-的阴极电流分布和竞争还原反应。结果表明，电解12h的电流效率仅为45.7%。熔盐上表面有致密的碳析出物，导致阴阳极短路。因此，目前生产铬的效率很低。同时，CO32-和CrO42-之间发生了竞争反应，导致阴极产品中碳含量较高。采用了一种新型的阳极结构，即带多孔氧化镁护罩的石墨阳极，消除了碳析出物，有效地避免了短路。结果表明，电流效率从45.7%提高到88.4%，阴极产品中碳含量从2.47wt%降到0.57wt%。(三)2017年度电化学会。版权所有。
High-efficiency electrolysis of soluble K2CrO4 was realized in the CaCl2-KCl molten salt by adopting a novel anode structure. The carbon contamination due to the accumulation of carbon particles and CO32- reduction was very detrimental to the electrolysis process when a graphite anode was used, especially for the new process that soluble K2CrO4 was directly electrolyzed to metal Cr in the CaCl2-KCl molten salt. In this paper, the carbon migration and CO32- reduction during the K2CrO4 electrolysis were analyzed and discussed. The cathodic current distribution and the competing reduction reactions between CrO42- and CO32- were analyzed. The results indicated that the current efficiency for Cr production was only 45.7% for 12 h electrolysis. Dense carbon precipitations were found on the upper surface of molten salt, which led to the short circuit between anode and cathode. Therefore, the current efficiency is very low for Cr production. Meanwhile, competing reactions between CO32- and CrO42- took place, leading to high carbon contents in the cathode products. By adopting a novel anode structure, i.e. a graphite anode with a porous MgO shroud, the carbon precipitates were eliminated and the short circuit was effectively avoided. Resultantly, the current efficiency for Cr production increased greatly from 45.7% to 88.4% and the carbon content in the cathode products decreased from 2.47 wt% to 0.57 wt%. (C) 2017 The Electrochemical Society. All rights reserved.