Thermodynamic and Kinetic Study of Leaching Magnesia from Natural Magnesites by Carbon Dioxide

2011 ◽  
Vol 309-310 ◽  
pp. 261-264 ◽  
Author(s):  
S. Klochkovskii ◽  
A. Smirnov ◽  
U. Shabalina
Keyword(s):  
Carbon Dioxide ◽  
Particle Size ◽  
Kinetic Study ◽  
Calcination Temperature ◽  
High Purity ◽  
Magnesium Carbonate ◽  
Carbon Dioxide Partial Pressure ◽  
Pressure Leaching ◽  
Translation Process ◽  
Carbon Dioxide Pressure

The applicability of carbon dioxide pressure leaching for the extraction of high purity magnesia from natural magnesites has been investigated. Factors which have influence on the magnesia recovery such as time, temperature, pressure, particle size and calcination temperature have been studied. Optimum values were determined: calcination temperature was in the range 650 – 750 0C, time of the calcination was approximately 5 – 3 hours; carbon dioxide partial pressure leaching for the extraction of magnesia was about 3 bar; particle size was between 0,2 – 0,6 mm. A kinetic study of carbonation of MgO has been investigated at leaching temperature from 00C to 50 0C. Two processes were observed: the formation of a magnesium bicarbonate solution and the precipitation of magnesium carbonate. Our research has determined that the concentration of impurities in magnesium carbonate is virtually no different from their concentration in natural magnesites. Apparently, the formation of magnesium carbonate proceeds without destruction of structure. So the extraction of high purity magnesia from natural magnesites by carbon dioxide is only possible using magnesium bicarbonate. It is necessary to optimize the translation process of magnesium in solution and the technology of extraction of pure MgO from it to generate high purity magnesium on an industrial scale.

Transparent Rubber Compounds. The Effect of Chemical Composition of Magnesium Carbonate Fillers

1941 ◽  
Vol 14 (1) ◽  
pp. 221-226
Author(s):  
Willard F. Bixby ◽  
Howard I. Cramer
Keyword(s):  
Carbon Dioxide ◽  
Particle Size ◽  
Chemical Composition ◽  
Chemical Analysis ◽  
Light Transmission ◽  
Magnesium Carbonate ◽  
High Light ◽  
X Ray ◽  
Rubber Compounds ◽  
Carbonate Sample

Abstract From this investigation the following conclusions may be drawn. 1. The x-ray results of Bixby and Hauser have been substantiated by chemical analysis and by microscopic examination. The magnesium carbonate productive of highest light transmitting properties is of the type: 5MgO.4CO2.xH2O. The normal carbonate, MgCO3, gives very low transmissions. 2. The best Japanese carbonate studied (sample No. 3) is pure 5MgO.4CO2.xH2O. 3. A domestic carbonate (sample No. 20), which is also pure 5MgO.4CO2.xH2O, is commercially available and produces transparency in rubber compounds equal to that obtained with the Japanese product. 4. Domestic carbonates in general contain more carbon dioxide than is required by a 5MgO.4CO2.xH2O carbonate, and are probably mixtures of this material and of the normal carbonate, MgCO3. 5. Light transmitting properties fall rapidly as the proportion of normal carbonate, MgCO3, rises. 6. Carbonates containing less than enough carbon dioxide to provide a 5MgO.4CO2.xH2O carbonate are probably mixtures of this material and hydrated magnesium oxide, MgO.H2O. 7. In preparing basic carbonates for use in producing high light-transmitting rubber, it is better to produce a material with slightly less carbon dioxide than necessary for a 5MgO.4CO2.xH2O carbonate, rather than more. 8. Particle size is an important factor influencing light transmission, especially when the normal carbonate, MgCO3, is present. Generally speaking, especially in the size ranges encountered in these carbonates, a finely divided MgCO3 will offer greater hindrance to the passage of light than will a larger size material.

scholarly journals Carbon dioxide as a line active agent: Its impact on line tension and nucleation rate

2021 ◽  
Vol 118 (33) ◽  
pp. e2102449118
Author(s):  
Romain Bey ◽  
Benoit Coasne ◽  
Cyril Picard
Keyword(s):  
Carbon Dioxide ◽  
Active Agent ◽  
Triple Line ◽  
Line Tension ◽  
Carbon Dioxide Partial Pressure ◽  
Capillary Bridge ◽  
Flat Surfaces ◽  
Order Of Magnitude ◽  
On Line ◽  
Carbon Dioxide Pressure

By considering a water capillary bridge confined between two flat surfaces, we investigate the thermodynamics of the triple line delimiting this solid–liquid–vapor system when supplemented in carbon dioxide. In more detail, by means of atom-scale simulations, we show that carbon dioxide accumulates at the solid walls and, preferably, at the triple lines where it plays the role of a line active agent. The line tension of the triple line, which is quantitatively assessed using an original mechanical route, is shown to be driven by the line excess concentrations of the solute (carbon dioxide) and solvent (water). Solute accumulation at the lines decreases the negative line tension (i.e., more negative) while solvent depletion from the lines has the opposite effect. Such an unprecedented quantitative assessment of gas-induced line tension modifications shows that the absolute value of the negative line tension increases upon increasing the carbon dioxide partial pressure. As a striking example, for hydrophilic surfaces, the line tension is found to increase by more than an order of magnitude when the carbon dioxide pressure exceeds 3 MPa. By considering the coupling between line and surface effects induced by gaseous adsorption, we hypothesize from the observed gas concentration-dependent line tension a nontrivial impact on heterogeneous nucleation of nanometric critical nuclei.

scholarly journals Influencing Factors of the Mineral Carbonation Process of Iron Ore Mining Waste in Sequestering Atmospheric Carbon Dioxide

2021 ◽  
Vol 13 (4) ◽  
pp. 1866
Author(s):  
Noor Allesya Alis Ramli ◽  
Faradiella Mohd Kusin ◽  
Verma Loretta M. Molahid
Keyword(s):  
Carbon Dioxide ◽  
Particle Size ◽  
Chemical Composition ◽  
Iron Ore ◽  
Divalent Cations ◽  
Mining Industry ◽  
Mining Waste ◽  
Aluminum Silicate ◽  
Mineral Carbonation ◽  
Carbonation Process

Mining waste may contain potential minerals that can act as essential feedstock for long-term carbon sequestration through a mineral carbonation process. This study attempts to identify the mineralogical and chemical composition of iron ore mining waste alongside the effects of particle size, temperature, and pH on carbonation efficiency. The samples were found to be alkaline in nature (pH of 6.9–7.5) and contained small-sized particles of clay and silt, thus indicating their suitability for mineral carbonation reactions. Samples were composed of important silicate minerals needed for the formation of carbonates such as wollastonite, anorthite, diopside, perovskite, johannsenite, and magnesium aluminum silicate, and the Fe-bearing mineral magnetite. The presence of Fe2O3 (39.6–62.9%) and CaO (7.2–15.2%) indicated the potential of the waste to sequester carbon dioxide because these oxides are important divalent cations for mineral carbonation. The use of small-sized mine-waste particles enables the enhancement of carbonation efficiency, i.e., particles of <38 µm showed a greater extent of Fe and Ca carbonation efficiency (between 1.6–6.7%) compared to particles of <63 µm (0.9–5.7%) and 75 µm (0.7–6.0%). Increasing the reaction temperature from 80 °C to 150–200 °C resulted in a higher Fe and Ca carbonation efficiency of some samples between 0.9–5.8% and 0.8–4.0%, respectively. The effect of increasing the pH from 8–12 was notably observed in Fe carbonation efficiency of between 0.7–5.9% (pH 12) compared to 0.6–3.3% (pH 8). Ca carbonation efficiency was moderately observed (0.7–5.5%) as with the increasing pH between 8–10. Therefore, it has been evidenced that mineralogical and chemical composition were of great importance for the mineral carbonation process, and that the effects of particle size, pH, and temperature of iron mining waste were influential in determining carbonation efficiency. Findings would be beneficial for sustaining the mining industry while taking into account the issue of waste production in tackling the global carbon emission concerns.

scholarly journals Synthesis of magnesium carbonate hydrate from natural talc

2020 ◽  
Vol 18 (1) ◽  
pp. 951-961
Author(s):  
Qiuju Chen ◽  
Tao Hui ◽  
Hongjuan Sun ◽  
Tongjiang Peng ◽  
Wenjin Ding
Keyword(s):  
Crystal Structure ◽  
Particle Size ◽  
Crystal Growth ◽  
Crystal Morphology ◽  
Magnesium Carbonate ◽  
Organic Additives ◽  
X Ray Diffraction ◽  
Morphological Transformation ◽  
X Ray ◽  
Carbonation Process

AbstractVarious morphologies of magnesium carbonate hydrate had been synthesized without using any organic additives by carefully adjusting the reaction temperature and time during the talc carbonation process. At lower temperatures, magnesium carbonate hydrate was prone to display needle-like morphology. With the further increase of the carbonation temperature, the sheet-like crystallites became the preferred morphology, and at higher aging temperatures, these crystallites tended to assemble into layer-like structures with diverse morphologies, such as rose-like particles and nest-like structure. The reaction time had no effect on the crystal morphology, but it affected the particle size and situation of the crystal growth. X-Ray diffraction results showed that these various morphologies were closely related to their crystal structure and compositions. The needle-like magnesium carbonate hydrate had a formula of MgCO3·3H2O, whereas with the morphological transformation from needle-like to sheet-like, rose-like, and nest-like structure, their corresponding compositions also changed from MgCO3·3H2O to 4MgCO3·Mg(OH)2·8H2O, 4MgCO3·Mg(OH)2·5H2O, and 4MgCO3·Mg(OH)2·4H2O.

Continuous, transcutaneous carbon-dioxide monitoring to avoid hypercapnia in complex catheter ablations under conscious sedation

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
K Weinmann ◽  
A Lenz ◽  
R Heudorfer ◽  
D Aktolga ◽  
M Rattka ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Conscious Sedation ◽  
Venous Blood ◽  
Patient Comfort ◽  
Carbon Dioxide Partial Pressure ◽  
Close Monitoring ◽  
Blood Gas ◽  
Transcutaneous Carbon Dioxide ◽  
The Difference ◽  
Venous Blood Gas

Abstract Background Ablation of complex cardiac arrhythmias requires an immobilized patient. For a successful and safe intervention and for patient comfort, this can be achieved by conscious sedation. Administered sedatives and analgesics have respiratory depressant side effects and require close monitoring. Purpose We investigated the feasibility and accuracy of an additional, continuous transcutaneous carbon-dioxide partial pressure (tpCO2) measurement during conscious sedation in complex electrophysiological catheter ablation procedures. Methods We evaluated the accuracy and additional value of tpCO2 detection by application of a Severinghaus electrode in comparison to arterial and venous blood gas analyses. Results We included 110 patients in this prospective observational study. Arterial pCO2 (paCO2) and tpCO2 showed good correlation throughout the procedures (r=0.60–0.87, p&lt;0.005). Venous pCO2 (pvCO2) were also well correlated to transcutaneous values (r=0.65–0.85, p&lt;0.0001). Analyses of the difference of pvCO2 and tpCO2 measurements showed a tolerance within &lt;10mmHg in up to 96–98% of patients. Hypercapnia (pCO2&lt;70mmHg) was detected more likely and earlier by continuous tpCO2 monitoring compared to half-hourly pvCO2 measurements. Conclusion Continuous tpCO2 monitoring is feasible and precise with good correlation to arterial and venous blood gas carbon-dioxide analysis during complex catheter ablations under conscious sedation and may contribute to additional safety. Funding Acknowledgement Type of funding source: None

Exercise end-tidal carbon dioxide pressure: a new prognostic marker after acute myocardial infarction?

2021 ◽  
Vol 28 (Supplement_1) ◽  
Author(s):  
J Ferreira ◽  
P Rio ◽  
A Castelo ◽  
I Cardoso ◽  
S Silva ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Carbon Dioxide ◽  
Acute Myocardial Infarction ◽  
Prognostic Marker ◽  
Systolic Function ◽  
Prognostic Role ◽  
End Tidal Carbon Dioxide ◽  
Carbon Dioxide Pressure ◽  
End Tidal ◽  
Maximal Effort

Abstract Funding Acknowledgements Type of funding sources: None. Background Although several cardiopulmonary exercise testing (CPET) parameters have already proved to predict prognosis, there is increasing interest in finding variables that do not require maximal effort. End-tidal carbon dioxide pressure (PETCO2), an indirect indicator of cardiac output, is one of such variables. Studies in heart failure populations already suggest its role as a prognostic factor. However, data concerning other populations are still scarce. Purpose To assess the association between exercise PETCO2, cardiac biomarkers and systolic function following acute myocardial infarction (AMI) and to evaluate its potential prognostic role in this population. Methods A retrospective single-centre analysis was conducted including patients who underwent symptom-limited CPET early after AMI. We assessed PETCO2 at baseline (PETCO2-B), at anaerobic threshold (PETCO2-AT) and at peak exercise and calculated the difference between PETCO2-AT and PETCO2-B (PETCO2-difference). We analysed their association with B-natriuretic peptide (BNP), maximal troponin after AMI as well as with left ventricular ejection fraction (LVEF) 1 year after. Results We included 40 patients with a mean age of 56 years (87.5% male), assessed with CPET a median of 3 months after AMI (80% of which were ST-elevation myocardial infarctions). Average respiratory exchange ratio was 1,1 with 48% of patients not reaching maximal effort. Mean PETCO2-AT was 37mmHg, with a mean increase from baseline of 6mmHg (PETCO2-difference). There was a significant positive correlation between all the PETCO2 variables measured and BNP values at time of AMI and on follow-up (best correlation for PETCO2-AT with BNP at AMI hospitalization, r = 0.608, p &lt; 0.001). Maximal troponin was not correlated with PETCO2. Both PETCO2-AT and PETCO2-difference were significantly and positively correlated with LVEF 1-year post-AMI (r = 0.421, p = 0.040 and r = 0.511, p = 0.011, respectively). Conclusion PETCO2-AT and PETCO2-difference are both correlated with BNP, an established prognostic marker, and with medium-term systolic function after AMI, suggesting their potential prognostic role in this population. Further studies with larger samples are required to confirm the results of this pilot study and assess PETCO2 as a definite predictor of prognosis after AMI.

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