Low-grade Magnesite Research Articles

Sintering behavior and thermal shock resistance of MgO-Mg2SiO4 refractories by co-doped silica fume and quicklime

To solve the serious environmental pollution of low-grade magnesite tailings, MgO-Mg2SiO4 refractories were prepared by low-grade magnesite tailings, materials and silica fume and quicklime as raw materials. The effects of calcium-silicate ratio (mol ratio) on the phase composition, microstructure, sintering behavior and thermal shock resistance of MgO-Mg2SiO4 refractories were investigated. When calcium-silicate ratio was 5/5, the samples showed the optimum bulk density and apparent porosity of 2.81 g/cm3 and 16.37 %, respectively. Controlled the calcium-silicate ratio of samples to 5/5 significantly improved the thermal shock resistance of samples, the residual compressive strength rate of 69.78 % and the residual flexural strength rate of 19.86 %, while the thermal parameter R was 34.45. The improvement in the thermal shock resistance can be attributed to the bonding phase transformation from monticellite phase to forsterite phase, thereby enhancing the bond strength between aggregate and matrix.

Mechanism of action of the novel reagent dodecyl trimethyl ammonium chloride on magnesite and quartz surfaces

Silica impurities are one of the key factors that reduce the quality of magnesite. In this experiment, dodecyl trimethylammonium chloride (KDMP) was used as a quartz collector for silica-magnesium separation, and mineral flotation tests demonstrated that KDMP can effectively desiliconize and purify magnesite under the conditions of 20 mg/L and pH 5.0. Contact angle and Zeta potential measurements show that KDMP alters quartz’s characteristics more than magnesite. X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FTIR) tests show that KDMP works on quartz and adsorbs solely on its surface, not on magnesite. Field Emission Scanning Electron Microscopy (FESEM) and Atomic Force Microscopy (AFM) images revealed that the KDMP collector adsorbed exclusively on the quartz surface, forming a layer of adsorption structure, but was weak on the magnesite surface. As a result, the KDMP collector is a highly intriguing flotation collector that can efficiently separate magnesite from quartz while also introducing a new form of collector for the separation and purification of low-grade magnesite.

An environmentally friendly depressant for magnesite and calcite flotation separation: Selective depression and adsorption mechanism

The similar crystal structures and chemical properties of magnesite and calcite make their effective separation through flotation challenging. This study explores the use of Glutamic acid diacetic acid tetrasodium salt (GLDA), a novel environmentally friendly chelating reagent, to enhance the flotation separation of magnesite and calcite. Flotation test results indicate that in a sodium oleate (NaOL) system, GLDA selectively inhibits the flotation of calcite. Under optimal conditions (slurry pH=9.20, GLDA 15 mg/L, and NaOL 140 mg/L), a flotation concentrate with an MgO grade of 46.21 %, CaO grade of 1.39 %, and an MgO recovery rate of 73.17 % was achieved. GLDA minimally affects the hydrophobicity of magnesite but significantly reduces the hydrophobicity of calcite. The selective inhibition mechanism of GLDA was investigated using zeta potential measurements, FTIR, and XPS analyses. Results show that GLDA selectively reacts with Ca sites on the calcite surface, adsorbing and covering it, thereby preventing NaOL from adsorbing on the calcite. Conversely, GLDA has a minor impact on the Mg sites on the magnesite surface, resulting in a negligible effect on NaOL adsorption by magnesite. Consequently, GLDA enhances the flotation separation efficiency of magnesite and calcite. The research results have potential for application in the purification of low-grade magnesite ore.

Triboelectric characteristics and separation of magnesite and quartz

Tribo-electrostatic separation is a promising method for effectively utiliing low-grade magnesite resources by removing quartz and improving the grade of magnesite. To determine the charge-to-mass ratios of pure magnesite and quartz, a triboelectric measurement system was employed, and a laboratory tribo-electrostatic separation system was used to separate low-grade magnesite. The results showed that the maximum difference in charge-to-mass ratio between pure magnesite and quartz particles was observed after friction with polyvinyl chloride. The grade and recovery of magnesite increased with temperature and initially increased with increasing voltage, feed rate, and air flowrate before gradually decreasing. The optimal conditions resulted in a concentrate with 46.91% MgO content and 77.36% recovery, while the quartz content decreased from 7.02% to 1.95%. These experimental results demonstrate the effectiveness and potential of tribo-electrostatic separation in removing quartz and upgrading magnesite.

Development Status of Low-Grade Magnesite Beneficiation Technology

Development Status of Low-Grade Magnesite Beneficiation Technology

Study on Selective Adsorption Behavior and Mechanism of Quartz and Magnesite with a New Biodegradable Collector

Research on the efficient flotation desilication of low-grade magnesite is of great significance for the sustainable development of magnesium resources. Traditional collectors usually have some disadvantages, such as poor selectivity, severe environmental pollution, and weak water solubility. To strengthen the desilication flotation process of magnesite ore, the biodegradable surfactant, cocamidopropyl amine oxide (CPAO), was first utilized as the collector for the separation of the magnesite and quartz. The selective adsorption behavior and mechanism of the quartz and magnesite with the CPAO as the collector were studied through the micro-flotation experiments of the single mineral and the artificially mixed mineral, contact angle and atomic force microscopy (AFM) measurements, fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses. The flotation results indicated that the CPAO showed good selectivity and could effectively separate magnesite and quartz. When the concentration of the CPAO was 10.0 mg/L in the natural pulp pH (about 7.2), the concentrates with 97.67% MgO recovery and 45.62% MgO grade were obtained. The contact angle and AFM measurements indicated that the CPAO could selectively adsorb on the quartz surface rather than the magnesite surface to improve the interface difference between them, especially its surface hydrophobicity. The results of the FTIR and XPS analyses indicated that the CPAO is selectively adsorbed on the surface of the quartz, mainly through electrostatic interaction and hydrogen bonding. In conclusion, the CPAO had good selectivity and great potential as an effective collector in the reverse flotation desilication progress of magnesite.

Preparation of magnesium oxysulfate cement with semidry carbonation high calcium content light-burned magnesium (Ca-LBM)

With the large amount of high-quality magnesite mining, low-grade magnesite is discarded, which not only pollutes the environment but also wastes resources. Therefore, to utilize high-calcium magnesite tailings, carbonated light-burned magnesium with a high calcium content was used to prepare magnesium oxysulfate (MOS) cement. Characterization was performed by FT-IR, SEM, TEM, TG-DTG, TG-MS, MIP, XRD, and zeta potential measurements. The following conclusions are drawn: a porous shell layer was formed on the surface of the carbonated powder particles; thus, the hydration reactivity was reduced, but a better dispersibility was obtained. The setting time of the samples increased with increasing carbonation treatment time, and the early strength was lower than that of the control, but it increased significantly with the curing period. The 28 d compressive strength of the samples treated with carbonation for 2 min was 12.1 % higher than that of the control, and the volume density was 3.7 % lower than that of the control. In addition, a carbon-containing 517 phase (C- 517) structure was found. This C-517 phase exhibited better stability and resistance to sodium chloride erosion. After immersion in sodium chloride solution for 28 d, the softening coefficient was 0.84, which was 385 % of the control, so the carbonated samples had better durability than the ordinary MOS cement. The semidry method is used to carbonate light-burned magnesium with high calcium content, which avoids the negative effect of calcium oxide on the hydration process of MOS cement and provides a method to solve the discarding of high-calcium magnesite tailings.

Engineering properties and sustainability evaluation of crushed low grade magnesite mortars

China is the country in the world with the most abundant magnesite resources. The ever-increasing deposit of low grade magnesite ore derived from the process of magnesium products has occupied a substantial space and caused environmental damages. In this study, crushed low grade magnesite (CLGM) was prepared and then applied in mortar as fine aggregate to partially or entirely replace natural river sand (30%, 60%, and 100%), while 100% limestone sand (LSS) was applied as the reference group. The findings of this study demonstrated a positive correlation between the ratio of CLGM substitution and the improvement of both engineering properties and sustainable potential in the mortar. Compared with the control group at 28 d, the 100% CLGM mortar exhibited improvements of up to 6% in splitting strength, 25.86% in compressive strength, 16% in porosity reduction, 22.22% in impermeability enhancement, 27.52% in resistance to chloride ion penetration, 21.66% in frost resistance (after 150 cycles), and a remarkable 54.8% in anti-abrasion property. Furthermore, the sustainability evaluation assessed its potential societal value, and highlighted its reduced production costs (down 52.28%) and impressive environmental benefits (notable decreases of 28.3% in ozone depletion potential, 33.2% in land use potential, 38.7% in marine ecotoxicity, and 33.9% in fossil resource scarcity). These findings well demonstrated the feasibility of adopting magnesite tailings as a substitute of conventional aggregate within the construction sector along with substantial economic savings and positive environmental ramifications. The successful application of CLGM mortar in cleaner production can further facilitate the sustainable advancement of environment and construction industry.

Process Optimization and Kinetics of Leaching Magnesium from Low-Grade Magnesite with Ammonium Bisulfate

Process Optimization and Kinetics of Leaching Magnesium from Low-Grade Magnesite with Ammonium Bisulfate

Mechanism of CaO in Light-Burned Magnesia on the Formation Process, Mechanical Properties, and Water and Chloride Resistance of the 517 Phase

With the continuous exploitation of high-quality magnesite ores, a large number of low-grade magnesite ores with high calcium contents were abandoned, thereby occupying the land, polluting the environment, and causing substantial resource waste. Therefore, resource utilization of low-grade magnesite ores is urgently needed. These low-grade magnesite ores can be used by calcination to prepare raw materials of magnesium oxysulfate (MOS) cement, but CaO could be produced during calcination because dolomite is a dominant mineral. Therefore, this paper mainly studied how CaO affects the formation process, mechanical properties, and water and chloride resistance of the pure 517 phase. Light-burned dolomite (LBD) was used to offer CaO, replacing a certain amount of light-burned magnesia (LBM) in this work. It was found that CaO will react with Mg2+ and SO42− to form an amorphous phase that remains stable when curing in air but unstable when immersing in water. When immersed in water, Ca2+ would continue to react with SO42− to precipitate gypsum, thus destroying the original structure and reducing the stability of the pure 517 phase. Therefore, in the preparation of MOS cement, attention should be given to the content of CaO, and modifiers should be added to obtain a low solubility calcium compound to reduce the negative effects of CaO on MOS cement.

Study on the properties of periclase-forsterite lightweight heat-insulating refractories for ladle permanent layer

The heat dissipation of the ladle permanent layer is urgent to be tackled. Periclase has good compressive strength, high fire resistance, and high chemical stability. The thermal conductivity of forsterite is only 1/3–1/4 of periclase, which is low. Thus, the periclase-forsterite lightweight heat-insulating refractories for a permanent layer of steel ladle prepared from low-grade talc powder and light burned magnesia powder made by low-grade magnesite can well satisfy the requirements of the permanent layer. In this study, the effect of raw material ratio on as-prepared refractories was systematically investigated. The results demonstrated that with the increase in talc, the bulk densities of the samples decreased from 1.73 g/cm3 to 1.46 g/cm3, the porosities increased from 42% to 58%, and the compressive strengths decreased from 49 MPa to 28 MPa; besides, the thermal conductivities decreased from 1.062 to 1.22 W m−1 K−1 to 0.496–0.61 W m−1 K−1 with the increase in forsterite. Additionally, talc promoted the formation of intercrystalline pores, and the synthesis of forsterite in the experiment was dominated by the “Template growth” mechanism.

Process Optimization and Kinetics of Leaching Magnesium from Low-Grade Magnesite with Ammonium Bisulfate

Process Optimization and Kinetics of Leaching Magnesium from Low-Grade Magnesite with Ammonium Bisulfate

The effect of calcium fluoride on extracting magnesium from magnesite and calcium carbonate by silicothermal reduction in flowing argon

At present, the production of magnesium is mainly carried out semi-continuously with ferrosilicon as reducing agent under high temperature and high vacuum. In order to continuously produce magnesium, a new method of extracting magnesium from low-grade magnesite and calcium carbonate by silicothermal method in flowing inert gas was proposed. The effects of calcium fluoride (CaF2) on decomposition rate, decomposition kinetics, reduction rate of magnesia, and crystal type of dicalcium silicate in reduction slag were investigated in the paper. The experimental results showed that calcium fluoride could accelerate the decomposition of carbonate, and had no side effect on the calcined products. In addition, the analysis results of DTA curves showed that calcium fluoride could reduce the decomposition reaction activation energy and the reaction temperature of carbonate in the prefabricated pellets. The results of reduction experiments showed that proper calcium fluoride could promote the reduction rate of magnesia, and in the temperature range of 1250? ~ 1350?, with the same timeframe, the corresponding calcium fluoride contents were 5%, 3%, and 1% respectively when the reduction rate reached the maximum. Excessive calcium fluoride reduced the reduction rate of magnesia, but it promoted the transformation of dicalcium silicate to ? phase in the reduction slag.

Effect of La2O3 addition on the microstructural evolution and thermomechanical property of sintered low-grade magnesite

The rich mineral resources of magnesite have been decreasing rapidly, while the low-grade magnesite is abandoned, and the requirement on utilization of low-grade magnesite is causing much attention. La2O3 has been introduced as an additive in this study, considering its positive role in the modification of the magnesia matrix. Low-grade magnesite containing 0–3 wt% La2O3 was fired at 1550 °C for 3 h. The effect of La2O3 on the microstructural evolution and thermomechanical property of sintered low-grade magnesite was investigated. The results showed that La2O3 markedly improve the microstructure of sintered low-grade magnesite. The distribution state of the low melting monticellite phases among the periclase grains evolved from distribute continuously to concentrate in isolation at the triple-point junction of the periclase grains, and the generated CaO·3SiO2·2La2O3 based dendrites phases interlaced in the magnesia matrix. The hot modulus of rupture (HMOR) was significantly enhanced with increasing addition of La2O3 due to the low-melting monticellite phases were transformed to CaO·3SiO2·2La2O3 phases based dendrites with large aspect ratio, effectively reducing the availability of monticellite. Besides, the bridging phenomenon resulting due to the dendritic phase exhibited an optimal toughening effect, attributing to the increase in crack deflection and resistance to crack propagation.

Research on new beneficiation process of low-grade magnesite using vertical roller mill

Research on new beneficiation process of low-grade magnesite using vertical roller mill

Chemical precipitation of heavy metals from wastewater by using the synthetical magnesium hydroxy carbonate.

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.

Utilizing mixed-mineralogy ferroan magnesite tailings as the source of magnesium oxide in magnesium potassium phosphate cement

A mixed-mineralogy talc mine tailing (MT) fraction consisting of 80% ferroan magnesite (MgCO3) was studied for utilization as the source of magnesium oxide (MgO) in magnesium potassium phosphate cement (MKPC). The effects of calcination temperature of this low-grade magnesite on the composition, BET surface area and phosphate reactivity of the resulting magnesia powder were studied. The 4-point flexural strength of resulting MKPC was measured for all calcined raw material fractions that produced a solid. Based on the strength measurement results, the optimal range for calcination resided between 700 °C and 1150 °C, which is drastically lower than commonly recommended for finer magnesia sources in MKPCs. Accelerated reactivity assessment showed that phosphate reactivity behavior could not be entirely predicted by BET surface area. The presence of impurity silicates and high iron content in all the constituent minerals was posed as the reason for densification and loss of reactivity at higher calcination temperatures.

Experimental study on mix proportion and the strength of law-grade magnesite hollow block

In this paper, the properties of test block and hollow block made of low-grade magnesite is analysed and studied. First, in order to get the results, the X-ray diffraction analysis was carried out on the phases composition of low-grade magnesite. Then, the influence is researched successively by orthogonal experimental design of water consumption, water-cement ratio, sand ratio and building gypsum on the compressive intensity of test block which can get the best Mix. Finally, the optimum mix ratio of magnesite hollow block is obtained by using the vibration extrusion method to prepare the traditional size distribution concrete hollow block, and the strength relationship between magnesite hollow block and traditional block is solved by linear regression equation. The conclusions shows: compressive strength of hollow block presents a tendency that decreased first and then increased, and strength ranks of all first group hollow blocks exceed MU10.

Soil fertility analysis in and around magnesite mines, Salem, India

ABSTRACT The opencast mining operations have periodical effects in surrounding landscape and it is important to monitor the quality of the soil. The pre- and post-mining activities influence the soil quality due to removal of vegetation and topsoil cover. The low-grade magnesite ores and dumping of waste materials are the root causes of contamination of soil. The samples collected from the depth of 15 cm on the surface of soil with different physical (soil texture and soil moisture) and chemical (pH, organic carbon, and nitrogen) parameters are analyzed to study the effect of opencast mining on the surrounding soil. Nine soil samples collected from three magnesite mine sites include agriculture land in close proximity. The result of this analysis predicts the sample soils deficiency of nutrients contents like nitrogen, phosphorus, potassium, and calcium. The soil analysis comprises chemical parameters such as pH, lime status, texture, electrical conductivity, available macronutrients nitrogen (N), phosphorous (P), potassium (K), and micronutrients such as Fe, Mn, Zn, and Cu percentages which are used to determine the condition and quality of the soil. The STATISTICA software (ver.8) was used for analysis of Pearson’s correlation with linear relationship of soil samples and rows and columns of data matrix on cluster analysis.

Novel insights into the adsorption mechanism of the isopropanol amine collector on magnesite ore: A combined experimental and theoretical computational study

This paper focuses on the adsorption behavior and mechanism of the isopropanol amine collector as a novel collector on magnesite ore to expand the application of hydroxyl amine collectors and improve the efficiency of low-grade magnesite ore resource usage. Novel insights into the adsorption mechanism of the isopropanol amine collector on magnesite ore were proposed through a combined experimental and theoretical computational study. Flotation tests showed that the collector exhibited different flotation behaviors to three minerals (quartz > dolomite > magnesite). Adsorption was achieved due to the electrostatic and hydrogen bond affinities by Fourier Transform infrared spectroscopy (FTIR), and zeta potential measurements, and the exposed O on the surface was involved in the adsorption interaction. Molecular dynamics simulations confirmed the same rules of the flotation behaviors and illustrated that a compact inner layer of N-dodecyl-isopropanolamine (DIPA) formed on the quartz surface. The hydrogen bonds played a significant role in the different flotation behaviors of DIPA to quartz (OS··HOR and OS··HNR), magnesite (only little OS··HOR), and dolomite (OS··HOR). Additionally, the results indicated that the flotation behaviors of DIPA were closely related to the O sites density and charge of the surfaces of three minerals. Furthermore, the results reveal some straightforward mechanisms of introducing isopropanol groups at the molecular scale, which is vital for screening the functional groups and guiding the design of the novel collectors for minerals.