铜渣碳热还原过程中二氧化硅固溶体的形成机理

Formation mechanism of silica solid solution during carbothermal reduction of copper slag

铜渣是铜火法冶炼过程中产生的主要固体废弃物,碳热还原可实现其主要物相铁橄榄石的分解,有利于后续铁的富集。本文利用XRD、SEM和EDS对铜渣碳热还原过程中的反应行为进行研究,借助碱浸实验考察了焙烧产物中二氧化硅(SiO_(2))固溶体的溶解性,并通过XPS及TEM分析结果探讨SiO_(2)固溶体的形成机理。结果表明:铜渣中的主要物相为铁橄榄石和磁铁矿,锌主要赋存于铁橄榄石相。铁橄榄石经碳热还原分解为金属铁和石英固溶体,温度升高促使石英固溶体转变为方石英固溶体,此时锌被挥发至烟气中。焙烧产物中SiO_(2)因铁的掺杂而表现出石英和方石英的晶体结构,但在微观上仍以非晶态形式存在,致使其易溶于110℃氢氧化钠溶液。

Copper slag is the main solid waste generated during the pyrometallurgical process of copper.Fayalite as the main phase in copper slag can be decomposed into metallic iron and silica through carbothermic reduction,thereby benefiting the enrichment of iron.In this paper,the reaction behavior of copper slag during carbothermic reduction was studied through the analysis methods of XRD,SEM and EDS,meanwhile the alkali leaching experiment was introduced to test the solubility of silica in the reductively roasted copper slag,and ultimately the formation mechanism of silica solid solution was discussed combined with the analysis results of XPS and TEM.The results show that fayalite and magnetite are the predominant phases in copper slag,and zinc mainly exists in fayalite.During carbothermic reduction process,fayalite firstly decomposes into metallic iron and quartz solid solution,then quartz solid solution converts into cristobalite solid solution with increasing temperature.Meanwhile,the zinc in fayalite is removed by vaporization.Due to the doping of iron,the silica from the decomposition of fayalite by carbothermic reduction has the similar crystal structures with quartz and cristobalite,but is still in amorphous state on the micro,resulting in the violent reaction between the silica solid solution and NaOH solution at 110℃.