Effect of Alkaline Salts on Calcium Sulfoaluminate Cement Hydration

This work analyzes the effect of the presence of 5 wt.% of solid sodium salts (Na₂SO₄, Na₂CO₃, and Na₂SiO₃) on calcium sulfoaluminate cement (CSA) hydration, addresses hydration kinetics; 2-, 28-, and 90-d mechanical strength, and reaction product microstructure (with X-ray diffraction (XRD), and Fourier transform infrared spectroscopy, (FTIR). The findings show that the anions affect primarily the reactions involved. Ettringite and AH₃, are the majority hydration products, while monosulfates are absent in all of the samples. All three salts hasten CSA hydration and raise the amount of ettringite formed. Na₂SO₄ induces cracking in the ≥28-d pastes due to post-hardening gypsum and ettringite formation from the excess SO₄^2– present. Anhydrite dissolves more rapidly in the presence of Na₂CO₃, prompting carbonation. Na₂SiO₃ raises compressive strength and exhibits strätlingite as one of its reaction products.     

Potentiometric determination of free acidity and uranium in uranyl nitrate solutions using sulfate as complexing agent

In this paper free acid and uranium present together in the range of 0.05–3.0 meq and 20–250 mg, respectively, have been determined by potentiometric titration, using Na₂SO₄ and (NH₄)₂SO₄ complexants and NaOH and Na₂CO₃ as titrants. The results are presented as percentage recovery of free acidity and uranium over the range studied. It has been shown that percentage recovery of free acidity suggests a bias which varied from –5% to +74% at different free acidity and uranium concentrations for the Na₂SO₄–NaOH, Na₂SO₄–Na₂CO₃ and (NH₄)₂SO₄–NaOH complexant — titrant combinations. The percentage recovery of uranium always showed a positive bias which could be up to +8% for extreme free acidity — uranium ratios in the case of Na₂SO₄–Na₂CO₃ complexant — titrant combination. For the other Na₂SO₄–NaOH and (NH₄)₂SO₄–NaOH complexant — titrant combinations a positive bias of up to only +4% has been noticed.     

The Solubility of Sodium Sulfate and the Reduction of Aqueous Sulfate by Magnetite under Near-Critical Conditions

The solubility of Na₂SO₄ (s) (thenardite) and the interactions between magnetiteand aqueous Na₂SO₄ near the critical point of water have been determined in azirconium-alloy flow reactor at temperatures 350°C t 375°C and isobaricpressures 190 p 305 bar. The experimental solubility data are describedwell as a function of temperature and solvent density ₁ byln x(Na₂SO₄, aq.) = –10.47 – 27550/T +(4805/T) ln ₁.The interaction between magnetite and Na₂SO₄ (aq.) was examined from 250 to370°C at molalities near the saturation composition of Na₂SO₄ (s). While no solidreaction products were observed, HS^– (aq.) was observed to form above 350°Cby sulfate reduction, as a product of the reaction8 Fe₃O₄(s) + Na₂SO₄ (aq.) + H₂O(l)= 12 Fe₂O₃ (s) + NaHS (aq.) + NaOH (aq.).The reduction reaction appears to be controlled by surface reaction kinetics, ata level well below the equilibrium molality of HS^– (aq.). Metallic iron reactedwith Na₂SO₄ (aq.) in a similar fashion at temperatures above 350°C, to yieldhigher molalities of HS^– (aq.).     

The Cloud Point Behaviors and the Liquid–Liquid Equilibrium of L31—Inorganic Sodium Salt Aqueous Two-Phase Systems

The cloud point (CP) of triblock-copolymer L31 aqueous solution was determined with salting-out salts (Na₂SO₄/Na₂CO₃/NaF/NaCl/NaBr). The results show that all these salts can decrease the CP of L31 aqueous solution and form aqueous two-phase system (ATPS). With increasing concentrations of Na₂SO₄ and Na₂CO₃, an obvious phase inversion could be observed and phase inversion points were found. This was mainly due to the change in density, the salt-rich phase shifted from the top phase to the bottom phase. Meanwhile, the liquid-liquid equilibrium (LLE) data for L31-Na₂SO₄/Na₂CO₃/NaF/NaCl/NaBr ATPSs were measured at 288.15 K. The salt ability to decrease the CP and to induce the phase separation is as follows: Na₂SO₄?>?Na₂CO₃, NaF?>?NaCl?>?NaBr. Finally, the order of anions that reduced the CP and caused phase separation was obtained as follows: SO₄^2? >CO₃^2?, F^??>?Cl^??>?Br^?.     

Speciation and Structural Properties of Hydrothermal Solutions of Sodium and Potassium Sulfate Studied by Molecular Dynamics Simulations

Aqueous solutions of salts at elevated pressures and temperatures play a key role in geochemical processes and in applications of supercritical water in waste and biomass treatment, for which salt management is crucial for performance. A major question in predicting salt behavior in such processes is how different salts affect the phase equilibria. Herein, molecular dynamics (MD) simulations are used to investigate molecular‐scale structures of solutions of sodium and/or potassium sulfate, which show contrasting macroscopic behavior. Solutions of Na?SO₄ exhibit a tendency towards forming large ionic clusters with increasing temperature, whereas solutions of K?SO₄ show significantly less clustering under equivalent conditions. In mixed systems (Na_xK_2?xSO₄), cluster formation is dramatically reduced with decreasing Na/(K+Na) ratio; this indicates a structure‐breaking role of K. MD results allow these phenomena to be related to the characteristics of electrostatic interactions between K⁺ and SO₄^2?, compared with the analogous Na⁺?SO₄^2? interactions. The results suggest a mechanism underlying the experimentally observed increasing solubility in ternary mixtures of solutions of Na?K?SO₄. Specifically, the propensity of sodium to associate with sulfate, versus that of potassium to break up the sodium–sulfate clusters, may affect the contrasting behavior of these salts. Thus, mutual salting‐in in ternary hydrothermal solutions of Na?K?SO₄ reflects the opposing, but complementary, natures of Na?SO₄ versus K?SO₄ interactions. The results also provide clues towards the reported liquid immiscibility in this ternary system.     

Characterization of Silicate Complexes in Aqueous Sodium Sulfate Solutions by FAB-MS

When the sodium ion (Na⁺) concentration is increased above 0.5 mol-dm⁻³ (M), the concentrations of dissolved silica in aqueous sodium chloride (NaCl) and sodium nitrate (NaNO₃) solutions decrease because of the salting out effect. On the other hand, the concentration of the dissolved silica in aqueous sodium sulfate (Na₂SO₄) solutions increases monotonously as the concentration of Na⁺ is increased above 0.5 M. The purpose of this study is to determine the reasons why the salting-out effect is not observed in Na₂SO₄ solutions. FAB-MS (Fast Atom Bombardment Mass Spectrometry) was used to sample directly the silica species dissolved in aqueous Na₂SO₄, NaCl, and NaNO₃ solutions. In the FAB-MS spectra of these solutions, the peak intensity ratios of the linear tetramer to the cyclic tetramer largely increased for Na⁺ concentrations between (0.1 and 1) M. This shows that some characteristics of the Na₂SO₄ solutions are similar to those of the NaCl and NaNO₃ solutions. In Na₂SO₄ solutions, however, when the concentration of Na⁺ is higher than 1 M, the peak intensity of the dimer is much higher than those of the other silicate complexes. In Na₂SO₄ solutions, the SO₄²⁻ ion undergoes partial hydrolysis to form HSO⁻₄ and OH⁻ is produced. In particular, in the range where the concentration of SO₄²⁻ is high, the pH of the solution increases slightly. This higher pH yields more dimers from the hydrolysis of silicate complexes. This increase in dimer production agrees with the observation that silica dissolves in sodium hydroxide (NaOH) solutions mainly as a dimer when the concentration of NaOH is less than 0.1 M. In Na₂SO₄ solutions at high concentrations, a salting-out effect is not observed for silica. This is due to the increase in the concentration of OH⁻, which accelerates the hydrolysis of silica and results in dimer formation.     

Potentiometric determination of free acidity and uranium in uranyl nitrate solutions

Free acid and uranium in uranyl nitrate solutions have been determined potentiometrically using Na₂SO₄–NaOH, Na₂SO₄–Na₂CO₃ and (NH₄)₂SO₄–NaOH complexant-titrant combinations. The overall recovery of nitric acid varies in the range of 95.25 to 118.5%, depending upon the acid as well as the total uranium present, while that of uranium always a positive bias ranging from 100.2 to 106.4%. The results have been discussed in light of recent available data. It has been concluded that all the complexant-titrant combinations studied provide similar results.     

A combined method for investigating solubility and determining the composition of equilibrium solid phases saturating eutonic solutions in a NaCl-Na2SO4-Na2CO3-H2O system at 50°C

The composition of equilibrium solid phases NaCl, Na₂SO₄, Na₂CO₃ · 2Na₂SO₄ (berkeyite) and NaCl, Na₂CO₃ · H₂O, Na₂CO₃ · 2Na₂SO₄ (without preparative determination), saturating E₁ and E₂ eutonic solutions respectively, was established via nonvariant area boundary determination in a NaCl-N₂SO₄- Na₂CO₃-H₂O system at 50°C with the use of a combined method.     

Synthesis and Sorption Behaviour of Some Radioactive Nuclides on Sodium Titanate as Cation Exchanger

Crystalline (Na₄TiO₄·0.32H₂O) and amorphous (Na₂TiO₃·1.45H₂O) forms of sodium titanate were prepared by fusion reaction of TiO₂ and Na₂CO₃ at 1100°C in molar ratios of 2:1 and 1:2, respectively. The prepared products were characterized using IR, DTA-TG, X-ray and elemental analyses. Kinetic studies of the order of reaction (n) and activation energy (E _a) for crystallization transformation step (for crystalline sodium titanate only) have been determined from DTA thermogram and their values were found to be 0.87 (univalent order) and 3.97 kJ mol^–1, respectively. Ion exchange capacities and some distribution studies were carried out at different conditions in the presence of some complexing agents (EDTA, boric and citric acids) and the results showed that the capacities of the crystalline form are always less than the amorphous one.     

Li＋, Na＋//SO42－, CO32－-H2O交互四元体系288 K介稳相平衡研究

采用等温蒸发法研究了四元体系Li^＋, Na^＋// SO₄^2－, CO₃^2－-H₂O 288 K介稳相平衡及平衡液相的密度、电导率、折光率、粘度和pH值, 测定了该四元体系288 K条件下介稳平衡溶液溶解度及物化性质. 根据实验数据绘制了相应的介稳相图. 研究发现: 该体系介稳平衡中有复盐Na₃Li(SO₄)₂•6H₂O形成. 其介稳相图中有3个共饱点, 7条单变量曲线, 平衡固相为: Li₂SO₄•H₂O, Na₂SO₄, Na₃Li(SO₄)₂•6H₂O, Li₂CO₃, Na₂CO₃•10H₂O. 复盐Na₃Li(SO₄)₂•6H₂O和一水硫酸锂(Li₂SO₄•H₂O)的结晶区较小, 而Li₂CO₃的结晶区最大; 该四元体系介稳平衡条件下未发现Na₂SO₄•10H₂O的结晶区.     

Zur polarographischen Bestimmung von Selen als Selenosulfat in Kupferkonzentraten

Zusammenfassung Selenosulfatanion liefert in alkalischen Lösungen mit 0,2 Mol/l Na₂CO₃ und 0,2 Mol/l Na₂SO₃ eine gut ausgebildete polarographische Stufe, die die Bestimmung von vierwertigem Selen im Konzentrationsbereich von 10–5 bis 10–3 Mol erlaubt. Da für die Bildung des Selenosulfats die Abtrennung von elementarem Selen notwendig ist, sind Fremdionen ohne Einflu\.

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Summary Selenosulphate anion yields in alkaline solutions of 0.2 Mol Na₂CO₃ and 0.2 Mol Na₂SO₃ a well-shaped polarographic wave, which makes possible the determination of tetravalent selenium within the concentration range of 10^–5 to 10^–3 Mole. As the formation of selenosulphate requires the separation of elementary selenium, various metals are not interfering.

     

Experimental and Mathematical Modelling of Factors Influencing Carbon Dioxide Absorption into the Aqueous Solution of Monoethanolamine and 1-Butyl-3-methylimidazolium Dibutylphosphate Using Response Surface Methodology (RSM)

This paper investigated the solubility of carbon dioxide (CO₂) in an aqueous solution of monoethanolamine (MEA) and 1-butyl-3-methylimidazolium dibutylphosphate ((BMIM)(DBP)) ionic liquid (IL) hybrid solvents. Aqueous solutions of MEA-(BMIM)(DBP) hybrid solvents containing different concentrations of (BMIM)(DBP) were prepared to exploit the amine’s reactive nature, combined with the IL’s non-volatile nature for CO₂ absorption. Response surface methodology (RSM) based on central composite design (CCD) was used to design the CO₂ solubility experiments and to investigate the effects of three independent factors on the solubility of CO₂ in the aqueous MEA-(BMIM)(DBP) hybrid solvent. The three independent factors were the concentration of (BMIM)(DBP) (0–20 wt.%), temperature (30 °C–60 °C) and pressure of CO₂ (2–30 bar). The experimental data were fitted to a quadratic model with a coefficient of determination (R²) value of 0.9791. The accuracy of the developed model was confirmed through additional experiments where the experimental values were found to be within the 95% confidence interval. From the RSM-generated model, the optimum conditions for CO₂ absorption in aqueous 30 wt% MEA-(BMIM)(DBP) were 20 wt% of (BMIM)(DBP), a temperature of 41.1 °C and a pressure of 30 bar.     

Sodium salt effect on aqueous solutions containing Tween 20 and Triton X-102

The effect of six different high charge density sodium inorganic salts, such as Na₂CO₃, Na₂SO₄, Na₂S₂O₃, Na₂SO₃, Na₂HPO₄ and NaCH₃COO, in aqueous solutions of two anionic surfactants Tween 20 and Triton X-102 was investigated at T = 298.15 K and atmospheric pressure. The results were qualitatively analyzed in the light of the Hofmeister series. Also, a quantitative thermodynamic analysis in terms of molar Gibbs free energy of hydration (Δ_hydG) was carried out. The Merchuck equation was used to correlate the solubility curves and the tie line data were modelled by applying the Othmer–Tobias and Bancroft equations.     

Reactivity,Syntheses, and Crystal Structures of Na5[MO2][X] with M = Co+, Ni+, Cu+; X = CO32—, SO42—, SO32—, S2—, and Na25[CuO2]5[SO4]4[S]

Na₅[CuO₂][CO₃], Na₅[CuO₂][SO₃], Na₅[CuO₂][S], and Na₅[CuO₂][SO₄] were obtained as single crystals and powders from reactions of Na₂O, Cu₂O, and Na₂X with X = CO₃^2—, SO₃^2—, S^2—, and SO₄^2—, respectively. A redox reaction between CdO and Co metal occurs in the presence of Na₂O and Na₂X, yielding Na₅[CoO₂][X] with X = CO₃^2— and S^2—. From a mixture of Na₂SO₄, CdO and Na₂O in Ni‐containers we observed the formation of Na₅[NiO₂][S] single crystals. Single crystals of Na₂₅[CuO₂]₅[SO₄]₄[S] can be grown by annealing Na₅[CuO₂][SO₃] at 600 °C, leading to the decomposition of SO₃^2—, yielding SO₄^2— and S^2— at 550 °C. The structures have been determined from single crystal data and powder data. All structures contain the isolated complex [MO₂]^3— in a dumb‐bell like arrangement. The main feature of these compounds is that the anions SO₄^2—, SO₃^2—, CO₃^2— and S^2— are not connected to the transition metal. The formation of Na₅[CuO₂][X] (X = S^2—, SO₄^2—, SO₃^2—, CO₃^2—) has been studied by thermal analysis and in situ X‐ray diffraction techniques. Infrared spectra confirm the presence of SO₄^2—, SO₃^2—, and CO₃^2—, respectively, in the structures.     

Thermodynamics of electrolytes. Binary mixtures formed from aqueous NaCl,Na2SO4, CuCl2, and CuSO4, at 25°C

Osmotic coefficients to high ionic strengths are reported for five of the binary mixtures formed from NaCl, Na₂SO₄, CuCl₂, and CuSO₄; the sixth system studied, NaCl–Na₂SO₄, is one studied by Wu, Rush, and Scatchard. The equations recently developed by Pitzer are used successfully in the interpretation of the experimental results. Revised values are given for the activity and osmotic coefficients for pure CuSO₄ and CuCl₂ solutions.     

准东煤灰渣烧结熔融过程中钠基化合物作用机理研究

将Na₂CO₃添加剂按折算为Na₂O以20%的比例掺入煤灰中制成混合灰样,对混合灰样在不同温度下烧结.对不同温度下的烧结灰进行EDS元素分析和XRD物相分析,探究钠基化合物在准东煤灰烧结过程中的转变机理.并以EDS分析结果为基础用Fact sage 5.2计算软件中的Equilib模块进行化学热力学平衡反应计算.结果表明,随着烧结温度的升高,硫会发生富集,而钠主要和硫反应生成Na₂SO₄.同时会有NaCl的产生,NaCl会与含钾化合物反应置换出KCl.NaCl、KCl和Na₂SO₄与其他物质产生低温共熔物.     

Röntgenkristallographische Ausdehnungsmessungen an einigen Alkalisulfaten

Zusammenfassung Zellkonstantenmessungen an den hexagonalen Hochtemperaturmodifikationen der Sulfate einwertiger Kationen zeigen, daß dem Sulfation bei der Umwandlungstemperatur in allen Fällen der gleiche Raum zur Verfügung steht. Dieser Raum ist zu klein für die postulierte, freie Rotation der Sulfationen, reicht aber aus zur ausbildung einer Orientierungsfehlordnung nachFrenkel. Die in Frage kommenden Fehlordnungslagen können aus Platz-und Symmetriebetrachtungen hergeleitet werden. —Das so erhaltene Bild von der (mittleren) Symmetrie der Sulfatpunktlagen in der fehlgeordneten Struktur steht in Einklang mit der Art, in der sich ein teilweiser austausch von SO₄ ⁼ gegen CO₃ ⁼ auf die Gitterkonstanten von Na₂SO₄ I auswirkt.Die experimentellen Resultate umfassen in erster Linie vollständige Ausdehnungsmessungen an den Modifikationen V, III und I von Na₂SO₄ sowie an K₂SO₄ in den Modifikationen II und I. Für Rb₂SO₄, Cs₂SO₄ und Tl₂SO₄ wurden die Zellkonstanten der Hochform am Umwandlungspunkt bestimmt. Der Gang der Gitterkonstanten im System Na₂SO₄–Na₂CO₃ (Modifikation I) wurde an unterkühlten Präparaten bei Zimmertemp. ermittelt.Mit 8 AbbildungenHerrn Prof. Dr.O. Kratky zum 60. Geburtstag gewidmet.     

手性纳米磷酸锌钠的热化学研究

Chirai sodium zincophosphate nanocrystalline has been prepared and characterized. The standard molar enthaipy of the following reaction 12Na3PO4·12H2O（s）＋ 12ZnSO4·7H2O（s）= Na12（Zn12P12O48）·12H2O（s）＋ 12Na2SO4（s）＋216H2O（1） was determined by solution reaction calorimetric at 298.15 K, and calculated to be 33.666±0.195 kl/mol. From the results and other auxiliary quantities, the standard enthalpy of formation for sodium zincophosphate nanocrystalline was derived to be △fHm^⊙ [Na12（Zn12P12O48）·12H2O（s）, 298.15 K] =- 24268.494 ± 0.815 kJ/mol.     

Transference numbers of aqueous NaCl and Na2SO4 at 25°C from EMF measurements with sodium-selective glass electrodes

Transference numbers in aqueous solutions of NaCl and Na ₂ SO ₄ were obtained by measuring the emf of cells with liquid junction using sodium-selective glass electrodes. Transference numbers in the NaCl–H₂O system from about 0.1 to 4 mol-kg ^–1 (m) are in good agreement with literature data obtained by various experimental techniques, but are markedly lower than recent data obtained from emf measurements with Ag,AgCl-electrodes. Transference numbers in the Na ₂ SO ₄ –H ₂ O system from about 0.03 to 1.9 m show a small decrease with increasing salt concentration, which is near the limit of experimental uncertainty. Sodium-selective electrodes are well suited to perform determinations of transference numbers and may provide an alternative to amalgam electrodes.     

Production of high-purity carbon dioxide and sodium bicarbonate by lime cellar gas cleaning and chemical recycling: Process simulation and techno-economic analysis

The cement industry is responsible for 8% of total global CO₂ emissions, which mainly originate from limestone calcination and fuel combustion. In view of the application potential of using CO₂ to produce chemicals, this paper developed a novel process based on the Aspen Plus process simulation for the co-production of 99.99% CO₂ by means of Methyldiethanolamine (MDEA) absorption/desorption and NaHCO₃ by carbonization of CO₂, NH₃ and Na₂SO₄. The effects of absorption temperature, NH₃ and Na₂SO₄ feeding amount, crystallizer temperature and pressure on CO₂ capture rate and utilization rate were explored. The results showed that the best CO₂ capture rate was achieved when the cellar gas inlet temperature of the absorber tower was 37 °C; Saturated Na₂SO₄ solution was favorable for CO₂ absorption, and the CO₂ utilization rate increased with the increase of Na₂SO₄ dosage; NaHCO₃ yield decreased with the increase of crystallizing temperature, and the best NaHCO₃ yield was achieved when the crystallizer temperature was 35.5 °C; Crystallizing pressure had little impact on the reaction. Economic analysis showed that the project will start to be profitable in 6.48 years with a Net Return Rate (NRR) value of 13.51%. It indicates that the project has economic benefits and provides a new way to reduce CO₂ emissions from lime cellar gas.