STRONTIUM CARBONATE PRECIPITATION FROM STRONTIUM SULPHIDE SOLUTION (original) (raw)
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Water leaching of SrS and precipitation of SrCO3 using carbon dioxide as the precipitating agent
Hydrometallurgy, 2000
Strontium sulphide SrS was water-leached at 858C, generating a saturated solution of approximately 50 grL Sr. About 92% of the strontium contained in the SrS was leached within 60-80 min. Almost all of the water-soluble strontium were completely leached out from the sulphide material. The strontium-saturated solution was treated with carbon dioxide to Ž. precipitate strontium carbonate SrCO. Precipitation efficiencies in excess of 99% were attained in both batch and 3 continuous multi-column test programs. Hydrogen sulphide gas was generated as a byproduct in the precipitation process at a slurry pH F 8. Particle size analyses of SrCO precipitates indicate that a longer retention time enhances crystal growth. 3
The production of elemental sulphur and calcium carbonate (CaCO3) from gypsum waste can be achieved by thermally reducing the waste into calcium sulphide (CaS), which is then subjected to a direct aqueous carbonation step for the generation of hydrogen sulphide (H2S) and CaCO3. H2S can subsequently be converted to elemental sulphur via the commercially available chemical catalytic Claus process. This study investigated the carbonation of CaS by examining both the solution chemistry of the process and the properties of the formed carbonated product. CaS was successfully converted into CaCO3; however, the reaction yielded low-grade carbonate products (i.e. <90 mass% as CaCO3) which comprised a mixture of two CaCO3 polymorphs (calcite and vaterite), as well as trace minerals originating from the starting material. These products could replace the Sappi Enstra CaCO3 (69 mass% CaCO3), a by-product from the paper industry which is used in many full-scale AMD neutralisation plants but is becoming insufficient. The insight gained is now also being used to develop and optimize an indirect aqueous CaS carbonation process for the production of high-grade CaCO3 (i.e. >99 mass% as CaCO3) or precipitated calcium carbonate (PCC).
We recently showed that the production of elemental sulphur and calcium carbonate (CaCO3) from gypsum waste by thermally reducing the waste into calcium sulphide (CaS) followed by its direct aqueous carbonation yielded low-grade carbonate products (i.e. <90 mass% as CaCO3). In this study, we used the insight gained from our previous work and developed an indirect aqueous CaS carbonation process for the production of high-grade CaCO3 (i.e. >99 mass% as CaCO3) or precipitated calcium carbonate (PCC). The process used an acid gas (H2S) to improve the aqueous dissolution of CaS, which is otherwise poorly soluble. The carbonate product was primarily calcite (99.5%) with traces of quartz (0.5%). Calcite was the only CaCO3 polymorph obtained; no vaterite or aragonite was detected. The product was made up of micron-size particles, which were further characterised by XRD, TGA, SEM, BET and true density. Results showed that about 0.37 ton of high-grade PCC can be produced from 1.0 ton of gypsum waste, and generates about 0.19 ton of residue, a reduction of 80% from original waste gypsum mass to mass of residue that needs to be discarded off. The use of gypsum waste as primary material in replacement of mined limestone for the production of PPC could alleviate waste disposal problems, along with converting significant volumes of waste materials into marketable commodities.
Hydrometallurgy, 2016
Celestite concentrate (SrSO 4) is one of the most important raw materials used for the industrial production of strontium compounds. In this study, the effects of stirring speed, particle size, CO 3 2ion concentration and temperature on the conversion reaction rate of SrSO 4 to SrCO 3 in solutions obtained by dissolving/hydrolyzing a mixture of equimolar amounts of NH 4 HCO 3 and NH 4 COONH 2 (AC) were investigated. The solution obtained after total dissolution/hydrolysis of AC consisted of NH 4 + , CO 3 2-, HCO 3-, H 2 CO 3 * and NH 3. The conversion reaction proceeds according to dissolution and precipitation mechanism. Sr 2+ ions formed during the dissolution of SrSO 4 precipitates with CO 3 2ions as SrCO 3 pseudomorphically and as a result porous SrCO 3 layer is produced in the form of clusters. The rate determining step is the ion exchange reaction at the interface between dense SrSO 4 and porous SrCO 3 layers. The kinetic parameters for the ion exchange reaction were determined by applying the Shrinking Core Model. While the conversion reaction rate was found to be zero order up to a certain CO 3 2ion concentration, above this CO 3 2ion concentration, it was −0.7th order. The apparent activation energies for the zero and −0.7th order reactions were calculated as 64.84 and 47.79 kJ mol −1 , respectively. The amount of S passed to the solution as SO 4 2− ions was determined quantitatively by ICP-OES. The structural and morphological characterization of the celestite concentrate and solid reaction residues were carried out by XRD and SEM.
Thermochimica Acta, 2019
Strontium cobaltite was produced by heating the mixture containing equimolar amounts of Sr(NO 3) 2 and Co (NO 3) 2 •6H 2 O under dynamic air atmosphere. The reactions occurred during heating were determined and the intermediate and final products obtained at each reaction step were characterized using TG/DTA-MS, ICP-OES, XRD and FT-IR techniques. The oxygen stoichiometry of strontium cobaltite was determined using iodometric titration method and carbonation process. It was determined by thermal analysis results that Co(NO 3) 2 •6H 2 O was decomposed to CoO by forming the intermediate products Co(NO 3) 2 •4H 2 O, Co(NO 3) 2 •2H 2 O, Co(NO 3) 2 •H 2 O, Co(NO 3) 2 , CoOOH, Co 2 O 3 and Co 3 O 4. Sr (NO 3) 2 was decomposed to SrO. Sr 6 Co 5 O 15 was formed by solid state reaction of SrO, Co 3 O 4 and O 2. Sr 2 Co 2 O 5 was produced at elevated temperatures from Sr 6 Co 5 O 15 and Co 3 O 4. Analyses carried out for the characterization of compounds obtained at different isothermal conditions showed that final product Sr 2 Co 2 O 5 was obtained via Sr 14 Co 11 O 33 and Sr 6 Co 5 O 15. Sr 2 Co 2 O 5 was decomposed to a mixture of Sr 6 Co 5 O 15 and Co 3 O 4 with a mole ratio of 1 : 0.333 during slow cooling to the room temperature.
Materials, 2021
Co-processing of radioactive effluents with coal fly ash-derived materials is recognized as a resource-saving approach for efficient stabilization/solidification of radioactive components of wastewater. In this context, the paper is focused on the hydrothermal synthesis of Sr2+-bearing aluminosilicate/silicate phases as analogs of a mineral-like 90Sr waste form using hollow glass-crystalline aluminosilicate microspheres from coal fly ash (cenospheres) as a glassy source of Si and Al (SiO2-Al2O3)glass) and Sr(NO3)2 solutions as 90Sr simulant wastewater. The direct conversion of cenosphere glass in the Sr(NO3)2-NaOH-H2O-(SiO2-Al2O3)glass system as well as Sr2+ sorption on cenosphere-derived analcime (ANA) in the Sr(NO3)2-H2O-ANA system were studied at 150–200 °C and autogenous pressure. The solid and liquid reaction products were characterized by SEM-EDS, PXRD, AAS and STA. In the Sr(NO3)2-NaOH-H2O-(SiO2-Al2O3)glass system, the hydrothermal processing at 150–200 °C removes 99.99% of t...
Synthesis and Stability of the Strontium Cobaltite Thermally Treated in Air
Revista de Chimie, 2019
This paper reports, the studies on chemical transformations at thermal treatment of a mixture of SrCO3 and Co3O4 corresponding to stoichiometric ratio of SrCoO3 compound. The mixture of raw materials was prepared by mechanical activation. Thermal analysis, X-ray diffraction and scanning electron microscopy were used for these studies. It was found that SrCoO3 forms at 930oC but is not stable and turn immediately into Sr2Co2O5 by eliminating of oxygen. This compound, Sr2Co2O5, is unstable and by increasing of the temperature decomposes in Sr3Co2O6 and cobalt oxide. At temperatures above the 1250oC, the samples melt and Sr3Co2O6 crystallizes from vitreous phase by cooling.
Materials Letters, 2008
This work reports the results of laboratory experiments conduced to follow the kinetics of strontium recovery into the Al-Mg alloy by metallothermic reduction of SrO. The reagent was incorporated to molten alloy by the use of submerged powders injection technique. The variables analyzed were the injection time, the melt temperature and the initial magnesium content. Magnesium is added to the melt to increase the reactivity and reduce the surface tension of the molten aluminum. It was possible to increase the strontium content from 0 to 5 wt.% after 60 min of treatment. The results were fitted to a general kinetic equation, which allowed it to obtain the kinetic parameters, i.e. order of reaction and activation energy of the process. As the main mechanism of the strontium recovery process is of diffusive type, the global process rate increases as the temperature and initial amount of the magnesium increased.