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Heavy metal pollution has become one of the most serious environmental problems today. The preparation of magnesium hydroxy carbonate from low-grade magnesite, and the chemical precipitation of heavy metal wastewater with magnesium hydroxy carbonate as precipitating agent were undertaken. The removal efficiencies of heavy metals were improved by increasing the dose of magnesium hydroxy carbonate, and the applicable dose of magnesium hydroxy carbonate was 0.30 g for 50 mL of the wastewater (6,000 mg/L). The precipitation reactions proceeded thoroughly within 20 min. At this time, the removal efficiencies of heavy metals were above 99.9%. The final pH value was 7.1, the residual VO2+, Cr3+ and Fe3+ concentrations were 0.01, 0.05 and 1.12 mg/L, respectively, which conformed to the limit of discharge set by China (0.5–2.0 mg/L, GB 8978–1996). The precipitate was mainly composed of Fe2O3, V2O5 and Cr2O3, which can be recycled as secondary raw material for metallurgical industry. The treatment of the heavy metal wastewater with magnesium hydroxy carbonate was successful in decreasing the concentrations of VO2+, Cr3+ and Fe3+ in wastewater.

The article deals with composite materials based on caustic magnesite binder and wood fillers used in the fabrication of various types of objects in mechanical engineering, construction engineering, and oil and gas industries. Under operational conditions, caustic magnesite composites can be exposed to aggressive actions of microorganisms. This study looked into resistance of wood-filled composites upon exposure to byproducts of filamentous fungi (micromycetes). This research substantiated the choice of model medium for testing – byproducts of metabolism of micromycetes. Designed experiments were carried out. The samples were held in model solutions with different concentrations of aggressive medium agents. Lines of equal values of materials’ resistance were plotted. It was found from experiments that composites without fillers had a lower biocorrosive resistance compared to those filled with pine sawdust.

During their usage, caustic magnesite composites are susceptible to aggressive microbial action. This paper investigated the resistance of wood-filled caustic magnesite composites in a standard filamentous fungi medium. Caustic magnesite composites based on caustic magnesite, filled with wood sawdust from lime, ash, pine, and aspen trees were studied. The compositions were cured using magnesium chloride. The findings showed that composites filled with fine-fraction wood powders exhibited improved strength and resistance properties of caustic magnesite. If this requirement is met, then optimal conditions are created for the formation of an improved matrix in composites with filler and film phase. Tests in the standard medium showed that wood-filled caustic magnesite composites were fungistatic, but not fungicidal. This means that in case of external contamination, wood-filled caustic magnesite composites are susceptible to biodegradation. Tests demonstrated that exposure to the standard fungal medium resulted in an increased mass content and decreased strength of the samples.

During the sintering process in the shaft kiln of refractory factories, a considerable quantity of materials is separated and dumped as Waste Magnesite (WM). The other superior grades, Lightly-Calcined Magnesite (LCM) and Dead-Burned Magnesite (DBM), are separated at different temperatures from the shaft kiln. The WM materials still have 8% of magnesium with some sand and dust particles in huge ranges. These materials are primarily used in the applications of medicine and fertilizers and animal feed processing and additives. This work investigates the potential of WM particles as reinforcement materials in the Al 6061 alloy matrix. In order to compare the characteristics of WM-based composite, LCM and DBM powders were also considered as reinforcement particles. The WM, LCM, and DBM particles were mixed with a 15% weight ratio to Al 6061 alloy, and composites were fabricated using the Stir Casting method. The surface morphology investigations through Scanning Electron Microscopy (SEM) revealed that these particles were well distributed and dispersed within the alloy matrix and with good interfacial adhesion. It is noted that Al 6061/15% wt. LCM composite possesses a better tensile strength than Al 6061/15% wt. WM and Al 6061/15% wt.DBM composites. The impact value produced by the WM-based composite is better than the LCM and DBM composites. The Wear Rate and Coefficient of Friction (COF) were examined through a Pin-on-Disc apparatus. Al 6061/15% wt. WM composite tested a low wear rate (9.74 × 10 −6 mm 3 m) −1 . The results show that Al 6061/15% wt. LCM composite achieved the least COF value of 0.681 at an applied load of 0.5 Kg and a sliding distance of 2826 m. The results prove that the wastage magnesite is good enough and the most robust reinforcement material for Aluminum 6061 alloy-based composite.

Flash calcination of magnesite in a transport bed offers notable advantages. However, the backwardness of testing technology seriously affects the stability of the quality of its product, light-burned magnesia (LBM). This paper addresses the problem of predicting the loss on ignition (LOI) of LBM by proposing a prediction method based on feature importance ranking and LSTM networks. First, the XGBoost model is employed to rank the importance of input features, and a split node is set to filter out key features. Subsequently, an LSTM model is constructed based on the selected features to predict the LOI. To further enhance model performance, a Bayesian optimization approach is adopted to optimize the structural parameters of the LSTM model as well as the feature split node. Experimental results demonstrate that the proposed method significantly improves the accuracy of LOI prediction, providing robust support for optimizing the flash calcination process of magnesite in a transport bed.

To avoid dangerous climate change, new technologies must remove billions of tonnes of CO 2 from the atmosphere every year by mid-century. Here we detail a land-based enhanced weathering cycle utilizing magnesite (MgCO 3 ) feedstock to repeatedly capture CO 2 from the atmosphere. In this process, MgCO 3 is calcined, producing caustic magnesia (MgO) and high-purity CO 2 . This MgO is spread over land to carbonate for a year by reacting with atmospheric CO 2 . The carbonate minerals are then recollected and re-calcined. The reproduced MgO is spread over land to carbonate again. We show this process could cost approximately $46–159 tCO 2 −1 net removed from the atmosphere, considering grid and solar electricity without post-processing costs. This technology may achieve lower costs than projections for more extensively engineered Direct Air Capture methods. It has the scalable potential to remove at least 2–3 GtCO 2 year −1 , and may make a meaningful contribution to mitigating climate change. To remove CO 2 from the atmosphere every year by mid-century will need new technologies. Here the authors proposed the use of magnesia (MgO) in ambient looping processes to remove CO 2 from the air and they found that the proposed approach will cost $46–195 tCO 2 −1 net removed from the atmosphere considering both grid and solar electricity resources without including post-processing costs.

Major changes in atmospheric and ocean chemistry occurred in the Paleoproterozoic era (2.5 to 1.6 billion years ago). Increasing oxidation dramatically changed Earth’s surface, but few quantitative constraints exist on this important transition. This study describes the sedimentology, mineralogy, and geochemistry of a 2-billion-year-old, ~800-meter-thick evaporite succession from the Onega Basin in Russian Karelia. The deposit consists of a basal unit dominated by halite (~100 meters) followed by units dominated by anhydrite-magnesite (~500 meters) and dolomite-magnesite (~200 meters). The evaporite minerals robustly constrain marine sulfate concentrations to at least 10 millimoles per kilogram of water, representing an oxidant reservoir equivalent to more than 20% of the modern ocean-atmosphere oxidizing capacity. These results show that substantial amounts of surface oxidant accumulated during this critical transition in Earth’s oxygenation.

A high content of heavy metals in the soil and plants of a magnesite mining area might cause serious damage to the environment and can be a threat to the health of the surrounding population. This paper presents the results of research that focused on analyzing the heavy metal content in soil and plants in the dumping grounds of the magnesite mining factory Jelšava-Lubeník (Slovakia). The analysis focused on the content of heavy metals in soil (X-ray fluorescence spectrometry, atomic absorption spectrometry), in plants (inductively coupled plasma mass spectrometry, inductively coupled plasma atomic emission spectrometry), and pH (1M KCl solution). The results showed that the soil in the study area was slightly acidic to strongly alkaline and the content of Cr, As, Mn, and Mg exceeded by several times the limit values for the Slovak Republic. The results of the hierarchical cluster analysis and the correlation analysis show that the grouped metals come from the same sources of pollution. The content of heavy metals in plants was high and the highest concentration was found in the roots of Elytrigia repens > Agrostis stolonifera > Phragmites australis and flowers of Phragmites australis. The findings confirmed the suitability of the used plants in the process of phytoextraction and phytostabilization. The acquired knowledge can help in planning and realization remediation measures and improve the state of the environment in areas exposed to magnesite mining.

Earth’s deep carbon cycle affects atmospheric CO 2 , climate, and habitability. Owing to the extreme solubility of CaCO 3 , aqueous fluids released from the subducting slab could extract all carbon from the slab. However, recycling efficiency is estimated at only around 40%. Data from carbonate inclusions, petrology, and Mg isotope systematics indicate Ca 2+ in carbonates is replaced by Mg 2+ and other cations during subduction. Here we determined the solubility of dolomite [CaMg(CO 3 ) 2 ] and rhodochrosite (MnCO 3 ), and put an upper limit on that of magnesite (MgCO 3 ) under subduction zone conditions. Solubility decreases at least two orders of magnitude as carbonates become Mg-rich. This decreased solubility, coupled with heterogeneity of carbon and water subduction, may explain discrepancies in carbon recycling estimates. Over a range of slab settings, we find aqueous dissolution responsible for mobilizing 10 to 92% of slab carbon. Globally, aqueous fluids mobilise 35 − 17 + 20 % ( 27 − 13 + 16 Mt/yr) of subducted carbon from subducting slabs. Carbonate mineral aqueous solubility decreases as carbonates become more Mg-rich during subduction. Coupled with regional variations in amounts of carbon and water subducted, this explains discrepancies in estimates of carbon recycling, suggesting that only around a third returns to the surface.

Magnesite Mine Tailings (MMT) is a kind of waste produced during the mining of magnesite ore. Due to open cast mining process, huge amount of tailings are generated and dumped as open landfill that leads to numerous environmental hazards in the vicinity. MMT from Salem mine dump site, India, is collected, and a series of laboratory tests related to physical, chemical, mineralogical, mechanical, electrical and thermal properties have been conducted to characterise the MMT as construction material. Further, the results are compared with river sand and conventional coarse aggregates. The results indicate that the MMT can be used as aggregates in concrete for non-wearing surfaces, manufacturing of bricks, low thermal insulation panels, embankment and thermal insulation fills.