Removal and Recycling of Antimony from Liquid Copper by Using CuCl-CaO Fluxes at 1423 K
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copper scrap has become increasingly important from the viewpoints of efficient use of resources, environmental protection, and energy saving.[1,2] Copper scrap inevitably contains some impurity elements, especially heavy metals such as antimony and lead. These heavy metal impurities, which affect not only the properties of copper such as YANG CUI, Graduate Student, TASUKU HAMANO, Research Associate, and FUMITAKA TSUKIHASHI, Professor, are with the Department of Advanced Materials Science, Graduate School of Frontier Sciences, The University of Tokyo, Chiba 277-8561, Japan. Contact e-mail: [email protected] HIROYUKI MATSUURA, Research Associate, Formerly Graduate Student, Department of Advanced Materials Science, Graduate School of Frontier Sciences, The University of Tokyo, is with the Center for Iron and Steelmaking Research (CISR), Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA. Manuscript submitted August 19, 2006. Article published online May 4, 2007. METALLURGICAL AND MATERIALS TRANSACTIONS B
the electric conductivity but also the environment, must be removed from copper scrap. On the other hand, some removed impurities such as antimony used as the semiconductor and electrode materials should be recycled as resource. In the recycling process of copper scrap, it is effective to remove impurities from copper scrap by oxidation refining with flux, because almost all impurities have a stronger affinity with oxygen than copper. Therefore, from the viewpoints of the improvement of operating condition and decrease of copper loss, the Cu2O-based fluxes are significant for the removal of impurities, and some correlative research[3–6] has been done. Nakamura[1] and Fujisawa et al.[3] systematically summarized the effect of Cu2O-based flux on the removal of impurities from liquid copper and presented that the impurities such as Sb, Pb, and Ni were difficultly removed. Moreover, some problems such as the reuse of used fluxes besides the low removal efficiency for some impurities should be solved. Therefore, the development of the new refining method and effective flux for the recycling of copper scrap is expected. Moreover, the recycling of removed impurities as resources and the low-temperature operation for the saving of energy are also necessary. The chlorination refining by chlorination reaction is effective for the recycling of aluminum scrap[7] and refining of crude lead. Moreover, the chlorination reaction with chlorine gas or chloride is also used for the treatment of waste such as the dust from metal industry.[8] However, there are few researches related to the chlorination refining in the recycling process of copper scrap. Based on the thermodynamic viewpoint, it is possible to remove some impurities from liquid copper by the chlorination reaction and recycle their chlorides via gas phase because of their high vapor pressures. Hatta and Tsukihashi[9] reported that the partition ratios of Fe and Pb between CuCl-based flux and liquid copper at 1473 K increased with the additi
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