Abstract
Steel slag is considered a by-product of the steel industry and its reuse is a strategy for environmental protection, since it consists of potential polluting materials. Its main applications involve the use of large quantities of the raw material, but the extraction of ores in smaller proportions can be attractive. For example, magnetite (Fe3O4) may be of great interest for its magnetic properties in the production of composites with different applications. On the other hand, rare earth elements (REE) production is vital for new technologies and since traces of the different REE are found in most iron ores, their extraction can be conducted together. However, previous characterization of the slag is necessary; since they vary in mineralogical composition conform to steelmaking operations. Classical characterization techniques of ores such as X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) may be limited to characterize small fractions of materials. Therefore, in this study, neutron activation analysis was used as the characterization technique to confirm the presence of iron and REE in the slag. The steel slag composite sample of the Linz-Donawitz (LD) process was collected in a steelwork localized in the Iron Quadrangle, Minas Gerais, Brazil. The steel slag sample was characterized by instrumental neutron activation analysis (INAA), using the nuclear research reactor TRIGA MARK I IPR-R1. The results are compared with the characterizations made with XRD and SEM-EDS. Although XRD and EDS results indicated the presence of magnetite in a small proportion, INAA was decisive confirming the presence of REE in the mineralogical composition of the composite sample collected.
Highlights
The extraction of iron ore and its transformation into steel is an economically important activity for Brazil and, especially for Minas Gerais state [1, 2]
X-Ray Diffraction (XRD) and Energy Dispersive X-ray Spectrometry (EDS) results indicated the presence of magnetite in a small proportion, Instrumental Neutron Activation Analysis (INAA) was decisive confirming the presence of rare earth elements (REE) in the mineralogical composition of the composite sample collected
The slag texture can be an important parameter for studying the presence of REE, since they appear frequently associated with clay minerals [23]
Summary
The extraction of iron ore and its transformation into steel is an economically important activity for Brazil and, especially for Minas Gerais state [1, 2]. Considering the amount of slag produced daily, other forms of economic use of these wastes are objects of study. In this work it is considered the possibility of extracting Fe3O4 and rare earth elements (REE) from steel slag. Magnetite has interesting magnetic properties and several biotechnological applications involving the use of a small fraction of the material, justifying the extraction in steelmaking residues [5]. Small fractions of this mineral may already be of interest for extraction taking into account the expressive amount of slag generated in a steel industry and the ease of separation by magnetic extraction
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