Separation of silicon and iron in copper slag by carbothermic reduction-alkaline leaching process

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.

摘要

以铜精矿为原料,采用火法冶炼工艺每生产1.0 t 金属铜将产生2.0~3.0 t 含铁35%~45%的铜渣。 因此,从铜渣中回收铁不仅能实现有价金属的提取,还能减少其因堆存而带来的环境问题。本文提出 了一种通过选择性脱硅而实现铜渣中铁富集的新方法。热力学计算及实验结果表明,铜渣中的铁在 1473 K 碳热还原60 min 可被完全还原为金属铁,此时氧化硅转变为游离的石英固溶体和方石英固溶 体。石英固溶体和方石英固溶体均易溶于碱溶液而金属铁不溶于碱溶液。在最佳浸出条件下,铜渣还 原焙烧产物中的氧化硅可降低至6.02%,同时获得含铁87.32%的浸出渣。浸出渣中锌含量低于0.05%。 本研究为铜渣中硅和铁综合提取新技术的开发奠定基础,并避免二次尾矿的产生。