Separation of silicon and iron in copper slag by carbothermic reduction-alkaline leaching process
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Separation of silicon and iron in copper slag by carbothermic reduction-alkaline leaching process WANG Hong-yang(王洪阳)1, SONG Shao-xian(宋少先)1, 2 1. School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan 430070, China; 2. Hubei Key Laboratory of Mineral Resources Processing and Environment, Wuhan University of Technology, Wuhan 430070, China © Central South University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract: Approximately 2.0−3.0 t of copper slag (CS) containing 35%−45% iron is generated for every ton of copper produced during the pyrometallurgical process from copper concentrate. Therefore, the recovery of iron from CS utilizes a valuable metal and alleviates the environmental stress caused by stockpile. In this paper, a new method has been developed to realize the enrichment of iron in CS through the selective removal of silica. The thermodynamic analyses and experimental results show that the iron in CS can be fully reduced into metallic iron by carbothermic reduction at 1473 K for 60 min. The silica was converted into free quartz solid solution (QSS) and cristobalite solid solution (CSS). QSS and CSS are readily soluble, whereas metallic iron is insoluble, in NaOH solution. Under optimal leaching conditions, a residue containing 87.32% iron is obtained by decreasing the silica content to 6.02% in the reduction roasted product. The zinc content in the residue is less than 0.05%. This study lays the foundation for the development of a new method to comprehensively extract silicon and iron in CS while avoiding the generation of secondary tailing. Key words: copper slag; quartz solid solution; cristobalite solid solution; carbothermic reduction; alkaline leaching Cite this article as: WANG Hong-yang, SONG Shao-xian. Separation of silicon and iron in copper slag by carbothermic reduction-alkaline leaching process [J]. Journal of Central South University, 2020, 27(8): 2249−2258. DOI: https://doi.org/10.1007/s11771-020-4446-3.
1 Introduction Copper slag (CS) is a byproduct of the pyrometallurgical production of copper. According to statistics, approximately 40−50 million tons of CS are produced annually worldwide [1, 2]. Approximately 35%−45% iron and 25%−35% silica exist in CS, whereas the concentrates of other ingredients of aluminum, calcium, magnesium, zinc and copper are normally less than 10% [3, 4].
Therefore, about 16−20 million tons of iron can be recovered from CS if treated suitably. Unfortunately, only a small amount of CS is used to make building materials and abrasive despite its favourable physico-mechanical characteristics [5, 6]. The majority of CS is disposed by stockpile, which causes land occupation and environmental pollutions [7, 8]. Thus, iron recovery from CS would allow the comprehensive utilization of a valuable metal, decrease the number of dump sites, and alleviate the environmental burden.
Foundation item: Project(WUT: 2019IVA096) supported by the Fundamental Research Funds for the Central Universities, China; Project(2
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