Precipitation of magnesium carbonate (original) (raw)
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Chinese Journal of Chemical Engineering, 2009
Homogeneous (unseeded) precipitation of magnesium carbonate hydrates by the reaction of MgCl 2 with Na 2 CO 3 in supersaturated solutions between 273 and 363 K was investigated. The compositions, morphologies and filtration characteristics of the precipitates were studied in detail. The magnesium carbonate hydrates obtained at 313 K and in the range of 343 363 K showed good morphologies and filtration characteristics. Magnesium oxides (MgO) with high purity (97.6% 99.4%) were obtained by calcining magnesium carbonate hydrates at 1073 K.
Precipitation in the Mg-carbonate system—effects of temperature and CO2 pressure
Chemical Engineering Science, 2008
The precipitation of different forms of magnesium carbonate has been studied at temperatures between 25 and 120 • C and at a partial pressure of CO 2 between 1 and 100 bar. These conditions are relevant for mineral carbonation applications. Precipitation was triggered by the supersaturation created by mixing Na 2 CO 3 solutions in equilibrium with a CO 2 atmosphere with MgCl 2 solutions. Experiments were monitored using attenuated total reflection Fourier transform infrared (ATR-FTIR) and Raman spectroscopy as well as a focused beam reflectance measurement (FBRM) probe and a turbidimeter. Solubility and supersaturation were calculated using the software package EQ3/6. Solids were identified using X-ray diffraction (XRD) analysis and scanning electron microscope (SEM) images. At 25 • C and P CO 2 = 1 bar, only the hydrated carbonate nesquehonite (MgCO 3 · 3H 2 O) precipitates, as it has previously been observed. Solutions undersaturated with respect to nesquehonite did not form any precipitates in experiments lasting 16 h. Induction times increased with decreasing supersaturation with respect to nesquehonite. At 120 • C and P CO 2 = 3 bar, hydromagnesite ((MgCO 3 ) 4 · Mg(OH) 2 · 4H 2 O) was formed which transformed within 5-15 h into magnesite (MgCO 3 ). Solutions undersaturated with respect to brucite (Mg(OH) 2 ) did not form any precipitates in experiments lasting 19 h. At 120 • C and P CO 2 = 100 bar, direct formation of magnesite and, at elevated levels of supersaturation, the co-precipitation of magnesite and hydromagnesite has been observed. In the latter case, hydromagnesite transformed within a few hours into magnesite. Solutions undersaturated with respect to hydromagnesite did not form any precipitates in experiments lasting 20 h. ᭧
Kinetics of Magnesium Extraction from Activated Serpentine by Carbonic Acid
2015
The dissolution characteristic of thermally activated serpentine under the additive-free carbonic acid system plays a significant role in the success of the serpentine-based mineral carbonation process. It is believed that magnesium (as MgO in activated rock) is liberated by the protons associated with the MgO-CO 2-H 2 O equilibria. The availability of protons is inhibited by the accumulation of magnesium in the aqueous phase as the extraction proceeds. Parallel with leaching, the precipitation of MgCO 3 under hydrothermal conditions further contributes to the complexity of this system. The OLI-MSE thermodynamic simulations provided predictions for the reaction pathways in the MgO-CO 2-H 2 O system. Under the reaction conditions applicable for the ex situ mineral carbonation process, e.g., T = 423 K and P CO2 = 100 bar, the equilibrium solubility of magnesite is predicted as ~0.0197 mol kg −1 at the corresponding pH of 5.3. Experiments were carried out over a wide range of conditions, covering different reaction temperatures (from 303 to 473 K), pressures (from 10 to 160 bar), mass loading factors (from 0.03 to 1 min), and particle sizes (20 to 180 μm) by using a continuous fluidised bed reactor under the saturated CO 2-H 2 O system. The increase in concentrations of magnesium in the effluent corresponds to higher rates of extraction in the reactor; however, at sufficiently high rates, concentrations were found to be limited by the equilibrium solubility of MgCO 3. No evidence for MgCO 3 particles in the effluent or/in the reactor was found. It was concluded that the corresponding formation of solid magnesium carbonate species must be associated with the porous substrate. The experimental data for which magnesium concentrations were below the saturation value were correlated as, ⁄ The form of the rate function at ~0.25 showed a minimum standard deviation with ≅ 1 and also implied that 0, suggesting that First and foremost, I would like to express my sincere appreciation to my supervisor Professor Brian S. Haynes for his continuous support, guidance and patient during my Ph.D. project. This thesis would not have been possible without his valuable academic insight, and I am very thankful for his precise and thoughtful feedback on my thesis. I am grateful to have had Brain as my supervisor. I would like to thank Dr. Jason Mann for his help and guidance at initial stages of my project, and I acknowledge him for our collaboration opportunities. Also, I would like to thank my co-supervisor Dr. Alejandro Montoya. My thanks go to all members of the combustion group, past and present,
Powder Technology, 2015
The preparation of basic magnesium carbonate (BMC) by the simultaneous absorption of NH 3 and CO 2 into MgCl 2 solution in a rotating packed bed (RPB) was studied. The influences of the operating conditions including the rotation speed, liquid volumetric flow rate, gas volumetric flow rate, reaction temperature and initial concentration of MgCl 2 solution on the crystal structure and morphology of BMC were investigated. The scanning electron microscope image of the as-prepared BMC showed that the BMC particles had a unique rose-like structure with a mean size of 5.3 μm, a petal thickness of 20 nm and a particle size distribution mainly in the range of 2.8-7 μm.
Synthesis of Magnesium Carbonate via Carbonation under High Pressure in an Autoclave
Metals
Magnesium carbonate powders are essential in the manufacture of basic refractories capable of withstanding extremely high temperatures and for special types of cement and powders used in the paper, rubber, and pharmaceutical industries. A novel synthesis route is based on CO2 absorption/sequestration by minerals. This combines the global challenge of climate change with materials development. Carbon dioxide has the fourth highest composition in earth’s atmosphere next to nitrogen, oxygen and argon and plays a big role in global warming due to the greenhouse effect. Because of the significant increase of CO2 emissions, mineral carbonation is a promising process in which carbon oxide reacts with materials with high metal oxide composition to form chemically stable and insoluble metal carbonate. The formed carbonate has long-term stability and does not influence the earth’s atmosphere. Therefore, it is a feasible and safe method to bind carbon dioxide in carbonate compounds such as mag...
SYNTHESIS OF MgO IN MAGNESIUM HYDROXIDE CARBONATISATION PROCESS
Fizykochemiczne Problemy Mineralurgii - Physicochemical Problems of Mineral Processing
A method for synthesis of magnesium oxide by calcination of magnesium carbonate, obtained by carbonisation of magnesium hydroxide with carbon dioxide, is presented and the products obtained are characterised. The influence of the following experimental conditions on the final product properties was established: pH of the reaction medium, mode and rate of reagents supply. The final products were characterised by determination of their dispersion properties, wettability profiles (with water), specific surface area (BET), size and volume of pores. The products were identified by the X-ray diffraction method. The results proved a significant influence of the reaction conditions on the physicochemical parameters of the final magnesium oxide.