Abstract
The present study focuses on the refractory upgrade and reuse of the mining wastes/by-products of the magnesite mine “Grecian Magnesite SA” (Chalkidiki, N. Greece), by the addition of hematite (α-Fe2O3) nanomaterial. These by-products were also examined after the application of thermal pre-treatment, i.e., treated at 850 °C for 30 min, prior to sintering. Different thermal treatments and times were applied, aiming to induce the formation of forsterite and attempting to examine the respective effects on the refractory properties of up-cycled products. The results indicate that hematite addition of 5 wt.% can improve the major refractory parameters of products, whereas the applied thermal pre-treatment was not found to be particularly beneficial. Nevertheless, the optimum results were realized after thermal treatment at 1300 °C for 120 min heating time, also revealing that the initial mineralogical content of the examined mineral wastes is a key factor for the subsequent upgrade ranking of the final product.
Highlights
Samples, the results show that thereduce final mineralogical content between is similarthe forgrain both applied thermal treatments
For the products obtained from the W5 and W5PT samples, the results show that the final mineralogical content is similar for both applied thermal treatments
(2011), the olivine particles after oxidation decompose along the particle boundary and transform to magnesioferrite crystals and pyroxene/vitreous silica, while at the same time a part of hematite can diffuse into their structure, as this presents rather high solubility in the presence of MgO [25]. At this point it must be underlined that the quantification of mineralogical phases as obtained from the XRD patterns, and the thermal treatment at 1600 ◦ C refers only to the detected crystalline phases and is not representative of the overall content of the product, since there is a high percentage of glassy phase due to the eutectic phases at the heating temperature of 1600 ◦ C, which is not detected by the XRD measurements
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. It is worth noting that several researchers utilized these serpentinized wastes for the re-formation of a (useful) forsterite mineral phase and the subsequent production of forsterite-based refractories (e.g., [4,5]). Different additives, such as chromite [4], zirconia [6], aluminum titanate [3], magnesia [7], magnesium chloride hexahydrate [8], and iron oxides [9], etc., have been examined for this purpose. The by-products/samples were examined after the application of a simple pre-treatment thermal procedure, i.e., the samples were thermally treated at 850 ◦ C for 30 min to achieve the optimum forsterite formation prior to pelletization
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