Sulfates Of Mg Research Articles

Innovative application of two-stage sulfuric acid leaching for efficient recovery of Ti from titanium-bearing electric furnace slag

A two-stage sulfuric acid leaching process was developed to efficiently recover Ti from a titanium-bearing electric furnace slag (TEFS) made from V-Ti magnetite, which has a high content of impurities and low Ti content. The efficiency of the recovery mechanism was investigated. Anosovite and gangue minerals in the TEFS reacted with sulfuric acid and generated several solid substances such as TiOSO4, CaSO4, sulfates of Mg and Al, and silicate in the first-stage of the acidolysis, which formed the product layer and hindered the diffusion of sulfuric acid. Moreover, a high content of the impurities caused the gangue minerals to closely wrap around the anosovite, which hindered the acidolysis. By adopting a two-stage acid-leaching process, soluble sulfates, which are the most abundant product of acidolysis, were dissolved in water during the first-stage of the water leaching, which exposed the unreacted anosovite, diopside, and spinel. Accordingly, sulfuric acid completely reacted with the unreacted minerals during the second-stage acidolysis. The Si- and Ca-containing products of the acidolysis mainly existed in the form of silicate and CaSO4 and were later converted to silica gel and gypsum, respectively, after the second-stage water leaching. With this innovative process, the leaching rate of Ti improved significantly, achieving a 99.33% total leaching rate. Moreover, lowering the initial sulfuric acid concentration to 48% still yielded a total leaching rate of 98.04%, with the Ti grade of the final residue dropped to 3.14%.

Kinetics of White Soft Minerals (WSMs) Decomposition under Conditions of Interest for Astrobiology: A Theoretical and Experimental Study

In this paper, the thermal decomposition kinetics of a class of minerals that we call White Soft Minerals (WSMs) is studied by means of theoretical and experimental methods, in connection to the transport of extraterrestrial organic matter to Earth and the possible use of the decomposition reaction in the characterization of these minerals in space. WSMs include, under a single denomination, carbonates and sulphates of Mg, Fe, and Ca. To improve the present knowledge of the properties of such materials, we use the following techniques: kinetic models for chemical decomposition, atmospheric entry models, spectroscopy, and gravimetric analyses. Model results show that the atmospheric entry of WSM grains is strongly affected by their thermal decomposition. The decomposition reaction, being strongly endothermic, tends to significantly lower the grain temperature during the atmospheric entry, especially at high altitudes and for grazing entries. A previously proposed infrared spectroscopic technique to evaluate the degree of advancement of the reaction is found to be in good agreement with gravimetric measurements for calcium carbonate. The numerical model developed for the atmospheric entry scenarios is used to interpret experimental results. These main findings show that an additional contribution to the reaction enthalpy is needed to reproduce the experimental results, suggesting that the present theoretical model needs improvements such as the account of gas diffusion in the materials.

Composition and stability of salts on the surface of Europa and their oceanic origin

We present theoretical models of the composition, the relative abundances, and the stability of hydrated salts on the surface and in the icy shell of Jupiter's satellite Europa and discuss whether those salts have an oceanic origin. The evaluations were done with thermodynamic calculations of (1) salt dehydration equilibria at the conditions of the surface of Europa and its icy shell, (2) chemical equilibria involving solids and water vapor in the Na‐K‐Mg‐Ca‐S‐Cl‐H2O system at surface temperatures and variable partial pressures of water vapor, and (3) changes in aquatic chemistry and sequences of salt precipitation from freezing oceanic water, using cosmochemical, mass balance, and physical‐chemical constraints on the elemental and ionic composition of the ocean. Mass balance calculations of total or partial extraction of elements into an ocean from a carbonaceous chondrite type mantle show that magnesium and sulfate rather than chloride and sodium could be the most abundant solutes in the ocean. Freezing oceanic water of this composition leads to brines that differ in composition from the original water and to deposition of ice and highly hydrated sulfates of Mg, Na, and Ca as well as alkali chlorides. After freezing is complete, highly hydrated salts remain stable in ice‐bearing surface materials and throughout the icy shell. For hypothetical surface salt lag deposits, formed through sublimation/sputtering of ice and dehydration of salts, we predict hydration stratification with depth, approaching the highest hydration states in ice‐bearing materials in the lowest parts of the deposits. We discuss the effects of fast disequilibrium freezing and variable dehydration rates of salts on the predicted mineral assemblages at the surface. All of our models, which are independent of observations, predict the predominance of Mg and Na sulfates in surface salts, in agreement with spectroscopic models for the nonicy surface material in the near infrared spectral region.

Transformation enthalpy of the alkali-earths sulfates (SrSO 4, CaSO 4, MgSO 4, BaSO 4)

During the heating of SrSO 4 a structural change occurs at 1413 K. This structural change has effect on the thermodynamic and kinetic properties of the reduction process of SrSO 4 to SrSO 3. The structural change of the SrSO 4 has not been reported in the literature, hence, it was decided to determine the heat of transformation of this phenomena, using the differential thermal analysis technique. It was found that this structural change also occurs in the sulfates of the alkali-earth metals. In the case of the sulfates of Mg, Ca and Ba, there are not reports of transformation heat data; the literature only reports the temperature at which the transformation takes place. In this work, the heats of transformation of MgSO 4, CaSO 4 and BaSO 4 were also determined.

Composite dextran gels as size exclusion chromatography stationary phases

AbstractComposite dextran gels have been prepared using epichlorohydrin as the covalent cross‐linker and a modifying agent, typically a polyvalent metal compound creating complexes with the residual OH groups of the polymer matrix. Two series of gels were prepared and investigated by a comparison of their swellabilities in water as well as the separation characteristics when used as size exclusion chromatography (SEC) stationary phases. The gels were in situ modified with sulfates of Mg(II), Zn(II), Co(II), Ni(II), Cu(II), Mn(II), Al(III), Fe(III) and tetraethylorthotitanate or with the oxides: MgO, ZnO, Al2O3, TiO2 and SiO2. Large differences in the swellabilities and SEC calibration dependences for poly(ethylene glycol) standards in an aqueous eluent have been found and discussed.

TLC of Phenylthiohydantotn Amino Acids on Silica Gel Layers Impregnated With Metal Salts

Abstract The determination of primary structure of proteins is still an important and challenging task. The Edman reaction, using phenyl isothiocyanate as the N-terminal labelling agent and making available the N-terminal amino acids as PTH-derivative, lies at the core of all modern sequencing strategies. TLC, however, can be considered to have several advantages over other methods of chromatography because it is sensitive, simpler, and inexpensive, and allows the elution of compounds for subsequent use. The present paper reports the TLC separation and identification of PTH-amino acids in a fifteen component mixture. TLC plates (20×20cm × 0.5mm) were prepared by spreading slurries of silica, gel impregnated with sulphate, acetate, phosphate and chloride of zinc; and sulphates of Mg, Mn, Fe and Co. The chromatograms were developed in pre-equilibrated, rectangular glass chambers using several binary and ternary solvent systems. The spots were located by exposing the chromatograms to iodine vapour. The PTH-a...

Thin-layer chromatography of phenyl thiohydantoin derivatives of amino acids on silica gel thin layers impregnated with zinc salts and some metal sulphates.

Thin-layer chromatography of fifteen-component mixtures of phenyl thiohydantoin derivatives of amino acids was carried out on silica gel plates impregnated with various Zn salts (chloride, sulphate, phosphate and acetate) and sulphates of Mg, Mn, Fe and Co, and three solvent systems were developed. The effect of various anions and cations on the chromatographic behaviour is discussed.

Ionic association in aqueous solutions of bivalent sulphates

Osmotic coefficient data for the sulphates of Mg, Ca, Zn, Ni and Cu in aqueous solution have been analysed to obtain the dissociation constants (d.c.) of ion pairs, triplets and quadruplets, as well as information on their state of hydration. The d.c.’s of the sulphate ion pairs, though of similar magnitude, show distinct individualities, and the trend is similar to that of the d.c.’s calculated for the nitrates of di-valent ions, though the d.c.’s of the latter are about 200 times larger. The d.c.’s of the ion triplets show no correlations, but their absolute values are similar to those calculated from the theory of Fuoss & Kraus (1933, 1935) based on electrostatic considerations. The hydration parameters of the associated sulphates (both pairs and triplets), as characterized in the linear (statistical) terms of the osmotic coefficients, are only slightly smaller than those of the fully dissociated electrolytes, indicating that there is only little loss of hydration water in the process of association, in spite of the heavy hydration of the divalent cations and the relatively close approach of the sulphate ion. The complete analysis of the osmotic coefficient curves makes it possible to calculate the absolute values of the activity coefficients of the divalent sulphates (previously not known to any accuracy).