Natural Dolomite Research Articles

The Calcium Looping process for energy storage: Insights from in situ XRD analysis

This work reports a novel in situ XRD analysis on the multicycle calcination/carbonation of natural limestone and dolomite at relevant conditions for thermochemical energy storage (TCES) in concentrated solar power (CSP) plants. The experiments allow analysing noninvasively the time evolution of the different phases involved in the Calcium Looping (CaL) process. Our work has revealed new key features to understand the progressive loss of multicyclic carbonation reactivity of the CaO derived from calcination. The CaCO3 structure formed in the first step of dolomite decomposition has smaller unit cell volume than the CaCO3 naturally present in limestone. The CaO that stems from decomposition of the CaCO3 derived from dolomite first decomposition shows a greater carbonation reactivity compared to the CaO derived from limestone. The smaller size of the CaO nascent crystals and their relatively higher reactivity for dolomite compared to limestone is related to the presence of inert MgO crystals, which prevent CaO sintering and crystallite growth. However, the size of the MgO crystals derived from dolomite decomposition increases monotonically with time, which progressively hampers their hindrance effect. Our work also shows a positive correlation between the growth of the CaO crystallite size and the decline of preferred orientation in the CaO (100) plane as the number of cycles is increased and CaO loses reactivity. The observed evolution with the cycles of CaO crystallite size and reactivity can be attributed to the incompletion of carbonation. The unreacted CaO that remains in the calcination step suffers severe sintering which hinders its reactivity. Thus, the fraction of fresh, reactive CaO derived from CaCO3 decomposition that nucleates on the old and less reactive CaO declines progressively with the cycles.

Sintesis Magnesium Oksida (MgO) dari Dolomit Bangkalan dengan Metode Leaching

Magnesium oxide (MgO) is a ceramic material that has potential in the medical and industrial fields, where MgO can be obtained from natural dolomite which has a composition of 21.9% MgO and 54.3% CaCO3. However, MgO from dolomite has not been studied much so that this study was conducted with the aim of analyzing the effect of the holding time of calcination on the synthesized MgO phase. The MgO synthesis method uses the Leaching method, which is dissolving dolomite with HCl and stirring it at 75 ° C for 45 minutes. After that, it is filtered where the results of the filtrate are added with ammonia until the solution reaches pH 12 and a precipitate is formed. Furthermore, the precipitate was filtered and dried at 90 ° C for 6 hours, and calcined at a temperature of 800 ° C with a variation of the holding time of 4, 8, 12, 16, and 20 hours. The calcined powder was characterized by XRD and FTIR. The results showed that the optimum MgO periclase main phase was formed at a holding time of 8 hours at a calcination temperature of 800 ° C and had a nanocrystalline size of 20.12 nm. FTIR results show that the MgO synthesized with a holding time of 8 hours has functional groups Mg-O, Mg-O-Mg, C = O, alkene groups, and H-O-H in the wave number range of 4000 cm-1 - 500 cm-1.

Geopolymers Based on Mechanically Activated Fly Ash Blended with Dolomite

This study reports the effect of natural dolomite addition to fly ash and the mechanical activation of this blend on the geopolymerization process. Dolomite was replaced with fly ash at 1, 3, 5, and 10 wt.%. Geopolymers were synthesized at ambient temperature using NaOH solution as an alkaline agent. The geopolymerization process, reactivity of the raw material, compressive strength, and microstructure were studied using X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetry, and scanning electron microscopy. It was shown that blending fly ash with dolomite and mechanical activation improved the geopolymer strength, especially during the early age of curing. For geopolymers prepared using a 90% fly ash + 10% dolomite blend cured for 7 d, the strengths were 8.2-, 2.3-, and 1.4-fold higher than those for geopolymers prepared using 100% FA for 30 s, 180 s, and 400 s milling times, respectively. A simple method for evaluating the increments of mechanical activation, carbonate additives, and the synergistic effect in the increase in the compressive strength of the composite geopolymer is proposed.

Modified Natural Dolomite and Its Influence on the Production of Glycerol Carbonate: Effects of Structural and Basicity Properties.

A systematic study over different treatment conditions, including hydrothermal and acid-thermal, was successfully carried out to determine the most suitable conditions to enhance the textural properties and surface chemical composition of natural dolomite. The reconstruction of dolomite after various treatments enhanced the surface area by 4–5 times and diminished the pore diameter between 70% and 81% compared to the untreated parent dolomite. The Rietveld analysis of the X-ray diffraction (XRD) patterns revealed changes in the crystalline compositions after each treatment. When the treated dolomite was used as a catalyst to produce glycerol carbonate via a transesterification reaction of glycerol and dimethyl carbonate, the crystalline Ca(OH)2 concentration of the modified dolomite and the apparent glycerol carbonate formation rate (rgc) are well-correlated. The results suggest that an increase of the crystalline Ca(OH)2 concentration could be related with surface basicity at the weak and moderate strength sites that may lead to an increase in catalytic activity. The hydrothermal treated dolomite showed a selectivity of glycerol carbonate greater than 99% and rgc value 3.42 mmol/min·gcat, which was higher than that achieved on other samples. This study could aid to the proper selection of dolomite treatment for the desired crystalline composition, depending on the applications of this highly available mineral.

Phosphate removal from aqueous solutions using natural and thermic treated dolomites: equilibrium, kinetic, and thermodynamic

This study aims to evaluate the effect of natural and calcined dolomites on phosphate removal in aqueous solution. The solids were characterized and the effects of pH, contact time, and solid concentration on the removal process were analyzed. Dolomite showed an enhanced surface property induced by the thermal treatment at 800 °C, which increased the surface area from 2.350 to 6.229 m2 g−1, calcium and magnesium carbonates were converted to their respective oxides, and the material showed better sorption proprieties for phosphate removal. The adsorption process showed 70–90% of phosphate removal using natural and calcined dolomites, respectively, under the experimental conditions of pH 11, 60 min contact time, and 10 mg L−1 initial phosphate concentration. Pseudo-second-order and Langmuir/Redlich–Peterson were the mathematical models that best described the kinetic and equilibrium mechanisms for phosphate removal. The thermodynamic parameters suggest a spontaneous, endothermic, and random process at the solid/solution interface, confirming a favorable adsorption system. The removal process was controlled by chemisorption phenomena. In that context, natural dolomite can be modified to enhance the surface property induced by the thermal treatment making it a more promising material for use in immobilization of anion pollutants such as phosphate.

Tools for uranium characterization in carbonate samples: case studies of natural U–Pb geochronology reference materials

Abstract. Laser ablation U–Pb analyses of carbonate (LAcarb) samples has greatly expanded the potential for U–Pb dating to a variety of carbonate-producing settings. Carbonates that were previously considered impossible to date using isotope dilution methods may preserve radiogenic domains that can be dated using spatially resolved laser ablation geochronology techniques. Work is ongoing to identify reference materials and to consider best practices for LAcarb. In this study we apply standard and emerging characterization tool sets on three natural samples with the dual goal of enhancing the study of carbonates and establishing a new set of well-characterized natural reference materials for LAcarb studies. We start with the existing carbonate reference material WC-1 from the Permian Reef Complex of Texas, building on the published description to offer a deeper look at U and associated trace elements. We consider a tufa sample from the Miocene Barstow Formation of the Mojave Block, California, as a possible secondary calcite reference material due to its well-behaved U–Pb systematics. There are currently no natural dolomite standards. We present an unusual dolomite sample with very well-behaved U–Pb systematics from the Miocene of the Turkana Basin of Kenya as a possible dolomite reference material for LAcarb dating. In addition to using X-ray fluorescence (XRF) mapping and spectroscopy to better understand U in these natural samples, we have analyzed multiple aliquots of each of them for 87Sr/86Sr by thermal ionization mass spectrometry (TIMS). The Sr isotope compositions are analytically homogeneous within petrographically homogeneous regions of all three samples, and thus these materials could be used as Sr isotope standards as well. While not part of the current contribution, this combination could streamline simultaneous LA analyses of 87Sr/86Sr and U–Pb geochronology.

Effects of Lizardite Addition on Technological Properties of Forsterite-monticellite Rich Ceramics Prepared from Natural Magnesite and Dolomite

Lizardite rich peridotite has never been used to prepare ceramic specimens, especially in Morocco. For this raison, potential use of naturally abundant lazirditic material from the Rif domain, as a supply for ceramic industry, has been evaluated. The effects of lizardite addition to magnesite and dolomite mixtures on the thermomechanical properties of the calcined ceramics were also detailed. To achieve this target, natural lizardite, magnesite and dolomite samples were collected in ultrabasic Beni Bousra massif. Those raw samples were used for the synthesis of a forsterite-monticellite rich ceramics. Both raw and sintered samples were characterized by x-ray diffraction, scanning electron microscope and fourier transform infrared. The obtained results showed that both magnesite and dolomite were mainly composed of MgCO3 and CaCO3. In contrast, lizardite sample showed high amounts of SiO2, MgO and Fe2O3. An increased amount of lizardite in the initial mixtures enhanced mechanical and dimensional properties of the prepared ceramic specimens, and subsequently, the production of ceramics with the required technological properties. Thus, the preparation of Moroccan lizardite-based ceramics is technically feasible, economically justifiable and socially desirable due to the contribution to the economic growth of the raw materials sector, especially ceramic industry.

Natural template derived porous carbon nanoplate architectures with tunable pore configuration for a full-carbon sodium-ion capacitor

Porous carbon nanoplates with tailored morphology were fabricated as electrodes of SIC by using natural dolomite as a template and coal tar as a carbon precursor. The full-carbon SIC exhibits high energy and power densities as well as a long cycling lifespan.

Combined first-principles calculations and experimental study on the photocatalytic mechanism of natural dolomite.

Mineral-based photocatalysts have received great attention due to their low cost. In this study, the photocatalytic activity of natural dolomite and its mechanism were investigated based on designed experiments and first-principles calculations. The kinetic study showed that natural dolomite showed notable photocatalytic activity for the degradation of target compounds including methylene blue, diphenhydramine, and tetracycline. The EPR analysis demonstrated that O2−˙, ˙OH, and 1O2 were produced in the dolomite system under simulated sunlight irradiation. The first-principles calculations indicated that the isomorphous substitution of Fe2+ for Mg2+ in the dolomite lattice led to the impurity levels appearing in the forbidden band, which caused a significant decrease of the band gap from 5.02 to 1.63 eV. As a result, natural dolomite could act as a semiconductor photocatalyst in photochemical reactions due to the substitution of Mg2+ by Fe2+. Under simulated sunlight irradiation, photogenerated electron–hole pairs in the natural dolomite were separated and transferred to the surface, and then formed reactive radicals through further reactions, thereby enhancing the degradation of target compounds. This research may contribute to the understanding of the photocatalytic activity of natural minerals.

Precipitation of low-temperature disordered dolomite induced by extracellular polymeric substances of methanogenic ArchaeaMethanosarcina barkeri: Implications for sedimentary dolomite formation

AbstractA correlation between methanogenesis and dolomite formation has been reported; however, the mechanism underlying this association is not fully understood. In this study, we conducted forced carbonate precipitation experiments at room temperature in calcite-seeded Ca/Mg carbonate solutions containing either purified non-living biomass or bound extracellular polymeric substances (EPS) of the methanogen Methanosarcina barkeri. Purified non-living biomass and bound EPS was used so as to avoid the possible influence of the complex components of the growing microbial culture on carbonate crystallization. Our results demonstrated that non-living biomass of M. Barkeri can enhance the Mg incorporation into calcitic structure and induce the crystallization of disordered dolomite. In the presence of ~113 mg L–1 of non-living biomass, disordered dolomite with ~41 and 45 mol% of MgCO3 was precipitated in solutions with initial Mg:Ca ratios of 5:1 and 8:1, respectively. A systematic increase in the MgCO3 contents of the precipitated Ca-Mg carbonates was also observed with the increased non-living biomass concentration. Bound EPS was shown to be the component of non-living biomass that catalyzed the precipitation of disordered dolomite. At only ~25 mg L–1 of bound EPS, disordered dolomite with ~47 and 48 mol% of MgCO3 was precipitated in solutions with initial Mg:Ca ratios of 5:1 and 8:1, respectively. We propose that adsorption of bound EPS to growing carbonate surfaces through hydrogen bonding is the key to catalyzing disordered dolomite crystallization, and that this mechanism is also applicable to natural EPS-induced dolomite formation. This study provides significant insight into the formation mechanism of microbial-induced dolomite with high δ13C values.

Study of Chemical and Physical Characterization of the Natural Dolomite of Ain Mlila-Algeria

Dolomite is one of the commonest minerals that abound in the formation of a number of geological conditions. And it is found in abundance in eastern Algeria, especially Ain Mlila-Wilaya of Oum El Bouaghi-Algeria. The analyzed sample of raw dolomite has been by various physical-chemical techniques. The constituents of these carbonates are Ca, Mg, C, O, Al, Si, Fe, Ba, F, and Sr, analysis by XRD, and Raman, show that in addition to CaMg(CO3)2, we may have calcium carbonate. The Photoluminescence analysis characterizes the intrinsic and extrinsic defects of this carbonate. Differential thermal analysis reveals the different transformations of this mineral during heating. Indeed several stages including the elimination of water, the departure of CO2, the formation of MgO, and finally the formation of CaO.

Improved hydration resistance of MgO–2CaO·SiO2–3CaO·SiO2 composite refractory using low-grade minerals

Three low-grade mineral raw materials, i.e., natural dolomite, high-silicon magnesite, and forsterite tailings were used to prepare a MgO–2CaO·SiO2–3CaO·SiO2 composite refractory, and its hydration resistance was essentially improved. Free CaO was converted into more stable calcium silicate which protected MgO from hydration, and low melting phases formed by impurities promoted densification. The composite refractory, predominantly composed of MgO, β-2CaO·SiO2, and 3CaO·SiO2 with a bulk density of 3.13 g cm−3 and apparent porosity of 4.6%, was obtained after being calcined at 1600 °C for 3 h. The prepared composite exhibited excellent hydration resistance with a weight increase of only 0.03% at 1600 °C. Microstructural analysis revealed that a dense matrix consisting of intergranular calcium–silicate phases, was dispersed by rounded MgO aggregates.

Valorisation of vegetable market wastes to gas fuel via catalytic hydrothermal processing

Residues of leek, cabbage and cauliflower from the market places as representatives of lignocellulosic biomass were processed via hydrothermal gasification to produce energy fuel. The experiments were carried out in a batch reactor at temperatures 300, 400, 500 and 600 °C and corresponding pressures varying in the range of 7.5–43 MPa. Natural mineral additives trona, dolomite and borax were used as homogenous catalysts to determine their effects on the gasification. More than 70 wt% of carbon in vegetable residue samples were detected in the gas phase after the hydrothermal gasification process at 600 °C. The addition of trona mineral further promoted the gasification reactions and as a result, less than 5 wt% carbon remained in the solid residue at the same temperature, degrading the biomass samples into gas and liquid products. The fuel gas with the highest calorific value was recorded to be 25.6 MJ/Nm3, from the hydrothermal gasification of cabbage at 600 °C, when dolomite was used as the homogeneous catalyst. The liquid products obtained in the aqueous phase were detected as organic acids, aldehydes, ketones, furfurals and phenols. The gas products were consisted of hydrogen, carbon dioxide, methane, and as minors; carbon monoxide and low molecular weight hydrocarbons (ethane, propane, etc.). Above 500 °C, all biomass samples yielded 50–55 vol% of CH4 and H2 while the CO2 composition was around 40 vol% as the gas product.

Study of the Influence of Temperature on the Optical and Structural Properties of Dolomite.

The present work reports the results of structural and optical investigations in samples of natural dolomite, subjected to thermal treatment at different temperatures (500 ℃ to 700 ℃) and times (one up to three hours). The motivation is the evaluation of the changes that may occur in carbonaceous asteroids and meteorites, respectively, subjected to the action of the solar radiation and heated during the fall in the atmosphere. We carried out scanning electron microscopy, electron dispersive spectroscopy, X-ray diffraction, optical reflectance and photoluminescence measurements.

Adsorptive extraction of uranium(VI) from aqueous phase by dolomite

Natural dolomite rock collected from Chhitapandariya, Jaijaipur, Janjgir Champa region of Chhattisgarh, India, was tested for its uranium(VI) removal efficiency from aqueous phase. Adsorption characteristics relating to powdered dolomite rock were examined by conducting batch experiments under various adsorption parameters like pH, concentration, contact time, adsorbent dose, along with temperature. At 303 K when the optimum experimental conditions were employed, the removal of 78.8% of uranium(VI) was attained. The impact of temperature upon uranium(VI) extraction by dolomite adsorbent was studied at 303, 313, and 323 K and thermodynamic quantities (the change in Gibbs free energy, enthalpy and entropy of adsorption) were evaluated. The adsorption mechanism was specified by Langmuir adsorption isotherm and pseudo-first-order kinetics. The results suggested that natural dolomite rock has remarkable capability of treatment of uranium(VI) contaminated water.

Application of Natural Dolomite for Soil Upgrading

Soil degradation is the conditions with low-soil quality. It can result in low fertility, in soil. To overcome this problem, soil-quality upgrading should be applied. For this study, the acidic soil from Nan, Thailand is used to upgrade the soil conditions to fit well with the agricultural activities by using natural dolomite as a waste from the industries. It is blended with the acidic soil in various ratios from 5-30 % by weight. The optimal conditions for various soil properties such as pH, electrical conductivity (EC), bulk density and soil texture are investigated. From the results, the higher amount of dolomite can improve the soil properties. Acidity is lowered from 4.832 to 6.047. Bulk density is decreased at 1.1114 g/cm3. Particle size distribution is sharply increased with the amount of dolomite. EC values are raised up to 4.25 dS/m. The natural dolomite can increase the soil quality from Nan province.

Catalytic Pyrolysis of Palm Empty Fruit Bunch over Activated Natural Dolomite Catalyst: Product Distribution and Product Analysis

In this study, an activated natural dolomite catalyst is used as catalyst for the palm empty fruit bunches (PEFB) pyrolysis to produce bio-oil. The research was conducted in fixed bed reactors operating in batches by varying several parameters, which are temperature (400-600°C) and nitrogen gas flow rate (100-300 mL.min-1). The results show that the catalytic pyrolysis process using an activated natural dolomite catalyst obtains a maximum liquid yield of 35.87% when using a 500°C catalytic pyrolysis temperature and the rate of nitrogen gas is 100 cm3/minute, while the yield of gas and solids is 53.12% and 11.76%, respectively. The use of the dolomite activation catalyst influences the product distribution of pyrolysis and the bio-oil chemical compounds.

USE OF NATURAL DOLOMITE AS A CHEAP FOAMING AGENT FOR PRODUCING GLASS FOAMS FROM GLASS WASTE IN THE MICROWAVE FIELD

The paper presents experimental results obtained in the process of making glass foam from glass waste using a cheap foaming agent (natural dolomite). The originality of the work is the application of the microwave energy, unlike the conventional techniques commonly used in the world. The main advantage highlighted by the experiments is the very low specific energy consumption (below 1.5 kWh/kg), due to the peculiarities of the microwave heating technique. The foamed product has physical, mechanical and morphological characteristics (density between 0.30-0.32 g/cm3, thermal conductivity between 0.064-0.067 W/m·K, compressive strength in the range 2.2-2.6 MPa), which are similar to those of foams made by conventional methods and are suitable for its use as insulating material in construction.

Plasma Diagnostic by Optical Emission Spectroscopy on Dolomite and Cross-Validation Using Scanning Electron Microscopy Coupled with Energy Dispersive X-ray Spectroscopy and Electron Probe Micro-Analysis

Dolomite [CaMg(CO3)2] is an important carbonate mineral mainly composed of calcium magnesium carbonate. The correct determination of magnesium content in carbonate rocks is important for accessing its suitability for different applications; however, presence of different phases with varying magnesium contents makes their analysis difficult. In the present work, a natural carbonate mineral dolomite is analyzed qualitatively and quantitatively using laser-induced breakdown spectroscopy along with X-ray diffraction, scanning electron microscopy coupled with energy dispersive spectroscopy and electron-probe microanalysis. The optical emission spectra recorded in 200–720 nm wavelength region revealed presence of emission lines for Ca, Mg, Al, Sr, and Na with varying intensities. We used two different techniques, that is, Boltzmann plot and Saha–Boltzmann plot methods to calculate the plasma temperature, and an average value of 4500 ± 450 K was deduced.The Stark broadening line profile method was exploited to calculate the electron number density using calcium and magnesium lines which resulted in 2.39 × 1017 cm–3. The quantitative compositional analysis was carried out using calibration-free laser-induced breakdown spectroscopy method for which the local thermodynamic equilibrium and optically thin plasma conditions were satisfied.The composition for dolomite major constituents calcium and magnesium were estimated as 68.58 and 31.41%, respectively.The results demonstrated the LIBS, EDS, and EPMA ability as an effective, powerful and complementary analytical techniques for the elemental composition analysis of carbonate minerals.

USE OF NATURAL DOLOMITE AS A CHEAP FOAMING AGENT FOR PRODUCING GLASS FOAMS FROM GLASS WASTE IN THE MICROWAVE FIELD

<p>The paper presents experimental results obtained in the process of making glass foam from glass waste using a cheap foaming agent (natural dolomite). The originality of the work is the application of the microwave energy, unlike the conventional techniques commonly used in the world. The main advantage highlighted by the experiments is the very low specific energy consumption (below 1.5 kWh/kg), due to the peculiarities of the microwave heating technique. The foamed product has physical, mechanical and morphological characteristics (density between 0.30-0.32 g/cm<sup>3</sup>, thermal conductivity between 0.064-0.067 W/m·K, compressive strength in the range 2.2-2.6 MPa), which are similar to those of foams made by conventional methods and are suitable for its use as insulating material in construction.</p>