Search Results (9)

Mining waste is generated in vast quantities globally, which can have negative environmental consequences. This study highlights the utilization of iron ore mining waste as feedstock material in the preparatory step of an indirect aqueous mineral carbonation for carbon sequestration. The role of reactive cations (Ca²⁺, Mg²⁺, and Fe²⁺) was investigated in view of their elution behavior to improve carbonation efficiency. An elution experiment was carried out for the divalent cations using different acids (oxalic, HCl, acetic, and formic acid) at different concentration solutions (up to 1.5 M) and times (up to 100 min) at ambient temperature. The initial analysis confirmed the presence of divalent cations in the sample. The elution approach at ambient temperature resulted in the elution efficiency of Fe²⁺ (30.4%), Mg²⁺ (54%) using oxalic acid, and Ca²⁺ (98%) using HCl at a relatively short time between 50 and 100 min. It was found that for the iron ore mining waste, oxalic acid and HCl were best suited as elution agents for the Fe²⁺ and Mg²⁺, and Ca²⁺, respectively. The CO₂ sequestration potential was calculated to be 131.58 g CO₂/kg residue. A further carbonation step using a complexing agent (1,10 phenanthroline) confirmed the formation of siderite and magnesite along with phenanthroline hydrates. Findings have shown that the indirect mineral carbonation of the iron mining waste with complexing agent might improve carbonation efficiency, thus indicating that this material is useful for long-term carbon capture and storage applications. Full article

In the direction of sustainable mining solid waste management and eventually zero-waste production, the MagWasteVal research program aimed to achieve the proper handling of massive quantities of extractive mining waste originating from the magnesite mines after the enrichment process of useful ore. The main objectives of this project were both the investigation of geochemical variables affecting the serpentinization process (degradation) and the respected exploitation and further valorization of stocked-pilled solid (inert) wastes in the mining area. The study of thermal treatment (considering the heating duration and heating temperature) and the addition of various additives (alumina, chromite ore, run of mine, iron oxide, and magnesia) showed that the optimum upgrade for the mining waste samples occurs when a combination of magnesia (according to the optimum defined molar ratio: [MgO] + [FeO])/[SiO₂] = 2) and iron oxide of approximately 2.5% is applied at both 1300 and 1600 °C for 120 min. The final products of the MagWasteVal project may have various potential applications, even on a large scale, for the production of alternative refractory materials/services, substituting other raw materials, and presenting both economic and environmental benefits. Full article

In this study low-grade magnesium oxide (MgO) produced by calcinations of natural magnesite was used in mine water treatment using a laboratory-column device. The treatment of mine water from the abandoned Osor mine (NE Spain) with MgO showed the removal of metals from both mine water and tailing leachates. The PHREEQC numerical code and the Geochemist’s Workbench code (GWB) were used to evaluate the speciation of dissolved constituents and calculate the saturation state of the effluents. The analysis of the treated mine water showed the removal of As (from 1.59 to 0.31 μg/L), Cd (from 1.98 to <0.05 μg/L), Co (from 19.1 to <0.03 μg/L), F (from 2730 to 200 μg/L), Mn (from 841 to 0.6 μg/L), Ni (from 17.9 to <2 μg/L, U (from 9.16 to 0.08 μg/L), and Zn (from 2900 to 68.5 μg/L). Pb was also removed (from 98 to 35.2 μg/L) in the treatment of contaminated leachates from the mine waste. The mixing of MgO and water at room temperature may promote the formation of a stabilizing agent composed of hydroxides, carbonates, and magnesium-silicate-hydrates (MSH), which may remove Cd, Zn, and similar metals by sorption on MSH, substitution on the MSH lattice, and precipitation or co-precipitation with some of the hydrated phases. Full article

In the context of a circular economy/zero-waste, the conversion of extractive wastes into new products is of particular importance. At the Grecian Magnesite SA mine (Chalkidiki, N. Greece), millions of tons of waste accumulate in the operation field. To achieve these goals, the effect of caustic calcined magnesia (MgO) at 10, 15, and 20 wt.% was investigated in combination with 0.5, 1, 2.5, and 5 wt.% Fe₂O₃ at 1300 °C and 1600 °C for 120 min. The main refractory properties were determined along with the mineralogical content. The morphological examination has been performed by SEM-EDS analysis. The addition of MgO increases the desired olivine and eliminates the unwanted pyroxenes, causing the formation of magnesium-ferrite and periclase. MgO wt.% addition resulted in the decrease of firing shrinkage at 1300 °C but increased with Fe₂O₃. At 1600 °C, firing shrinkage had a minimum value at the optimum MgO dose. Mechanical strength at 1600 °C achieved a maximum value at the optimum MgO dose plus 5 wt.% MgO and 2.5 wt.% Fe₂O₃ due to sintering process/magnesioferrite formation. These results indicate that MgO and Fe₂O₃ upgrade the refractoriness of magnesite mining wastes due to the diffusion of Fe₂O₃ in MgO excess. Full article

Serpentinized peridotite samples—considered nowadays as deposited waste at the magnesite mine of Gerakini (Chalkidiki, N. Greece)—were collected, and their chemical and mineralogical characterization analyzed with Energy-Dispersive X-ray Fluorescence (ED-XRF) and X-ray Diffractometry (XRD). Dry magnetic separation was used as a convenient enrichment method; however, no significant effect was shown in the chemical composition of separated (magnetic and non-magnetic) fractions, except for small increases in the olivine, antigorite and enstatite contents, which were observed in the non-magnetic fraction. Finally, the calcination of ground peridotites at 1520 °C, with the addition of CaO, Al₂O₃ and SiO₂, presented a negative effect on the structure of the products with regard to their main refractory properties. In contrast, the addition of Cr₂O₃ and ΜgO mineral oxides showed improved refractory properties when compared with the initial material. Full article

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. Full article

Lightweight aggregates are extensively used in construction and other industrial applications due to their technological characteristics. The extraction of natural aggregates results in serious environmental effects. Thus, within the circular economy concept, the valorization of waste through the optimization of materials and product design is encouraged. In this work, glass lightweight aggregates were prepared from mixtures of white glass cullet and carbonate wastes from mining (wastes originating from the extraction, manufacture and marketing of magnesite and its derivatives) and the food industry (eggshell and mussel shell). The effects of different processing parameters, such as the particle size of the base glass, percentage of the blowing additive, shaping method, heating rate, temperature and processing time, were evaluated. The results indicate that the mineralogical composition of the blowing agent and the particle size of the base glass are the two processing parameters with the greatest impact on expansion efficiency. Thus, glass artificial aggregates were obtained with characteristics similar to those of commercial products (density values ranged between 0.3 and 0.8 g/cm³ and mechanical strength between 0.7 and 1.5 MPa) from thermal shock expansion treatments in the temperature range 800–900 °C and with dwell times no longer than 15 min. Full article

Grecian Magnesite S.A., located in Gerakini, Chalkidiki, N. Greece, is a magnesite mining company, which produces and commercializes several Mg-based products. For production purposes, water is applied in large quantities for several uses. As a result, 5 × 10⁶–7 × 10⁶ m³ of wastewater, consisting mainly of muddy water, is produced from the magnesite ore washing facilities each year. In this study, the environmental impact of mining and industrial activities is examined, and the water management issues are addressed through its recovery. Water recovery reaches up to 96% (v/v), whereas the remaining sludge waste is safely deposited in tailings ponds. Full article

This paper investigates an alternative use of sterile aggregate materials which may arise from various construction applications in conjunction with other low-cost mineral raw materials to remediate the acid mine drainage phenomenon. This study is based on the combination of unprocessed mineral raw materials, as well as on the basic concept of the cyclic economy where the conversion of a waste into a raw material for another application can be achieved. In this study, in order to examine the remediation, in lab scale, of the drainage waste water of Agios Philippos mine, an experimental electrically continuous flow-driven forced device was constructed, enriching the research gap relative to this type of remediation approach. Through this experimental device, the use of certain mixes of mineral raw materials (serpentinite, andesite, magnesite, peat, and biochar) was studied. Our results focus on the impact of the studied mineral raw materials and especially on their synergy on the water purification potential under continuous water flow operation. Using the new 7-day experimental electrically continuous flow-driven forced device with certain mixes of mineral raw materials, the increase of pH values from 3.00 to 6.82 was achieved. Moreover, with use of the experimental device, the removal of toxic load was achieved, and more specifically the concentration of Fe was decreased from 6149 to 1300 ppb, Cu from 8847 to 35 ppb, and Zn from 285,458 to 50,000 ppb. Full article