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1.
The solubility of calcium sulfate dihydrate (CaSO4·2H2O) and calcium hydroxide (Ca(OH)2) in alkali solutions is essential to understand their desilication behavior from Bayer liquor. In this work, solubilities of calcium sulfate dihydrate and calcium hydroxide for the ternary systems of CaSO4·2H2O–NaOH–H2O, CaSO4·2H2O–KOH–H2O, and Ca(OH)2–NaOH–H2O were measured by using the classic isothermal dissolution method over the temperature range of 25–75 °C. The Pitzer model embedded in Aspen Plus platform was used to model the experimental solubility data for these systems. The experimental solubility data was employed to obtain the new binary interaction parameters for Ca(OH)+–OH−, Ca(OH)+–Ca2+ and Ca(OH)+–K+, suggesting that the species Ca(OH)+ is a dominant species in simulated solubility for alkali systems. Validation of the parameters was performed by predicting the solubility for the ternary systems of Ca(OH)2–NaOH–H2O, CaSO4·2H2O–NaOH–H2O and CaSO4·2H2O–KOH–H2O with the overall average relatively deviation (ARD) of 2.12%, 0.75% and 1.63%, respectively. 相似文献
2.
Photooxidation of polylactide/calcium sulphate composites 总被引:1,自引:0,他引:1
Mélanie Gardette Sandrine Thérias Jean-Luc Gardette Marius MurariuPhilippe Dubois 《Polymer Degradation and Stability》2011,96(4):616-623
Stable CaSO4 β-anhydrite II (AII), a specific type of dehydrated gypsum and a by-product of the lactic acid (LA) production process, was melt-blended with bio-sourced polylactide (PLA) to produce highly filled composites. Samples containing different amounts of filler (10-40 wt.%) with various granulometries were used for preparation of films by compression moulding. The influence of adding filler (calcium sulphate) on the photochemical behaviour of PLA-AII composites was studied by irradiation under photo-oxidative conditions (λ > 300 nm, temperature of 60 °C and in the presence of oxygen). Several analytical methods were used to characterise the polymer degradation. Oxidation of the polymer matrix was evaluated by infrared and UV-visible spectroscopies, differential scanning calorimetry (DSC) and size exclusion chromatography (SEC). The main photoproducts formed upon UV-light irradiation of the PLA were identified along with the influence of filler content and its particle size on the rate of oxidation. It was shown that oxidation of PLA and PLA-AII composites occurred without any induction time and that the presence of the CaSO4 filler (AII) increased the oxidation rate of the polymer. Moreover, a faster degradation rate of PLA was observed in composites containing natural anhydrite of lower particle size (4 μm). 相似文献
3.
选择水杨基荧光酮-乳化剂OP-盐酸为显色体系,应用双波长分光光度法扣除硫酸锌的基体干扰,不分离直接测定了湿法炼锌过程中硫酸锌净化液中的痕量锗。测定范围在0-40mg/L。本法应用于株洲冶炼厂锌净化液中锗的测定,结果与该厂长期的萃取-比色法结果相吻合,而测定速度较萃取-比色法至少提高了一倍。 相似文献
4.
《The Chemical Engineering Journal》1986,32(3):145-150
A thermodynamic model for the system CaCO3-CaSO4·2H2O-NaCl-CO2-H2O has been developed for calculating calcium carbonate solubilities as a function of the carbon dioxide pressure under vapour-liquid-solid equilibrium conditions.The model has been tested against available data and its predictive capability compares favourably with that of other proposed models. Numerical values for model parameters are also given.The main feature of the model used in the present work is that the excess Gibbs energy is the sum of three terms: a Debye-Huckel contribution, a Born term as a correction for the change in dielectric constant and a short range interactions contribution calculated according to the non-random two-liquid (NRTL) equation.Our results may be useful in describing and interpreting the general characteristics of hydrothermal solutions with a view to their utilization for energy production. 相似文献
5.
重金属湿法冶金过程中钙镁结晶的工业现状及相关相图研究进展 总被引:1,自引:0,他引:1
首先介绍湿法冶金和材料制备过程中钙镁结晶危害的工业现状及其对溶液化学和结晶相化学基础研究的要求,然后系统地评述相关体系溶液化学和相化学基础研究的进展.接着在作者的系统工作及文献结果分析基础上指出:钙在重金属硫酸盐体系高温溶解度的实验研究、能描述硫酸盐离子缔合的合理热力学预测模型、硫酸盐水溶液结构的光谱和量子化学研究、以及硫酸盐水溶液高温下水的活度测定等是未来研究工作的重点.这些研究工作将加深对重金属湿法冶金过程中钙镁结晶危害行为及规律的认识,为廉价、环保地避免钙镁结晶危害的新工艺开发奠定了重要基础. 相似文献
6.
Abolghasem Jouyban Fleming Martinez William E. Acree Jr 《Physics and Chemistry of Liquids》2018,56(6):816-820
The recently reported solubility data of dipyrone in binary solvent mixtures of {ethanol + water}, {methanol + ethanol} and {methanol + 1-propanol} at various temperatures have been used to report further numerical results based on the Jouyban–Acree model. 相似文献
7.
Measurement and correlation of the solubility of MnSO4·H2O in ethanol + water + MgSO4·7H2O solutions
P. Safaeefar H.M. Ang H. Kuramochi Y. Asakuma K. Maeda M.O. Tade K. Fukui 《Fluid Phase Equilibria》2006,250(1-2):64-69
Data on the solubility of manganese sulphate monohydrate in water, and in aqueous alcohols is essential for salting-out crystallisation studies. The solubilities of the quaternary system MnSO4·H2O + MgSO4·7H2O + H2O + EtOH were determined in the temperature range 293.2–323.2 K over the ethanol mole fraction range of 0.00–0.12. The solubility data were used for modelling with the modified extended electrolyte non-random two-liquid (NRTL) equation. The present extension uses ion-specific parameters instead of the electrolyte-specific NRTL binary interaction parameters. This approach has feasibility for many electrolytes and mixed aqueous solution systems in principle. The model was found to correlate the solubility data satisfactorily. 相似文献
8.
Measured values of the pressure of H2O over saturated solutions in equilibrium with the dihydrate, tetrahydrate or hexahydrate of CaCl2 are converted to osmotic coefficients and compared with literature values for solutions of smaller molality. It is found that the osmotic coefficient is constant, within the uncertainty, from about 7 mol-kg–1 to soturation at all temperatures from 25 to 100°C. From this simple approximation, the activity coefficient is calculated for high molalities and at saturation. By combination of these results with other established data, entropies and Gibbs energies of formation are calculated for the crystalline hydrates of CaCl2. 相似文献
9.
In this study, the dissolution kinetics of celestite in solutions of sodium hydroxide was investigated by batch process. The results showed that the parameters which had the greatest effect on the dissolution of celestite in sodium hydroxide solutions were reaction temperature, the concentration of sodium hydroxide and stirring speed. It was determined that the dissolution rate increased with increased stirring speed, sodium hydroxide concentration, reaction time and temperature and decreased with increasing particle size and solid-liquid ratio. The leaching process fitted the shrinking core model with diffusion through the product layer model as the rate-determining step. The activation energy of the dissolution of celestite was calculated as 62.24?kJ/mol. A semi-empirical kinetic model was obtained for dissolution of celestite in sodium hydroxide solution. 相似文献
10.
A new apparatus to measure solubility data of aromatics in aqueous solutions has been designed. It is based on a static-analytic method with Rolsi™ pneumatic samplers for on line gas chromatograph analysis. Operating pressures and temperatures are between 0.3 and 10 MPa and between 293 and 393 K.
Solubility measurement results are reported for several aromatic compounds (benzene, toluene, ethylbenzene and xylene) in different amine aqueous solutions (monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA), diglycolamine (DGA)). Several influent parameters are studied (temperature, total pressure, etc.). 相似文献
11.
Functional imaging techniques play a major role in the study of brain activation by monitoring the changes in blood flow and energy metabolism. In order to interpret functional neuroimaging data better, the existing mathematical models describing the links that may exist between electrical activity, energy metabolism and hemodynamics in literature are thoroughly analyzed for their advantages and disadvantages in terms of their prediction of available experimental data. Then, these models are combined within a single model that includes membrane ionic currents, glycolysis, mitochondrial activity, exchanges through the blood-brain barrier, as well as brain hemodynamics. Particular attention is paid to the transport and storage of calcium ions in neurons since calcium is not only an important molecule for signalling in neurons, but it is also essential for memory storage. Multiple efforts have underlined the importance of calcium dependent cellular processes in the biochemical characterization of Alzheimer's disease (AD), suggesting that abnormalities in calcium homeostasis might be involved in the pathophysiology of the disease. The ultimate goal of this study is to investigate the hypotheses about the physiological or biochemical changes in health and disease and to correlate them to measurable physiological parameters obtained from functional neuroimaging data as in the time course of blood oxygenation level dependent (BOLD) signal. When calcium dynamics are included in the model, both BOLD signal and metabolite concentration profiles are shown to exhibit temporal behaviour consistent with the experimental data found in literature. In the case of Alzheimer's disease, the effect of halved cerebral blood flow increase results in a negative BOLD signal implying suppressed neural activity. 相似文献
12.
M. Bojinov 《Journal of Solid State Electrochemistry》1997,1(2):161-171
Two model approaches to the formation of passive films as adsorbed layers during the active anodic dissolution of a metal
in acid and their subsequent growth are presented. The first depicts passivation as proceeding in parallel to active dissolution.
Adsorption of water on active surface sites leads to passivation, whereas adsorption of acid leads to active dissolution of
the metal. The model is consistent with the impedance response during passivation of Fe and an Fe-20%Mo alloy in concentrated
H3PO4. The second model is an updated version of the so-called surface charge approach to the mechanism of conduction of anodic
passive films. It is based on the assumptions that oxygen vacancies are the main ionic charge carriers and the field strength
in the barrier layer is constant. A negative surface charge built up at the film/solution interface via accumulation of metal
vacancies accelerates oxygen vacancy transport, thus explaining the pseudoinductive behaviour of the metal/film/electrolyte
system under small amplitude a.c. perturbation. The model describes the growth of thin anodic films on Fe, Mo and an Fe-20%Mo
alloy in concentrated H3PO4.
Received: 24 January 1997 / Accepted: 18 April 1997 相似文献
13.
Determination of calcium, magnesium and zinc in unused lubricating oils by atomic absorption spectroscopy 总被引:1,自引:0,他引:1
Varying concentrations of lanthanum and strontium were added to solutions of ashed unused lubricating oils for the determination of calcium, magnesium and zinc content using flame atomic absorption spectrophotometry. At least 3000 μg g−1 of lanthanum or strontium was required to completely overcome the interference of the phosphate ion, PO3−4, and give peak values for calcium. The presence of lanthanum or strontium did not cause an appreciable increase in the amount of magnesium and zinc obtained from the analyses. The method is fast and reproducible, and the coefficients of variation calculated for the elements using one of the samples were 1.6% for calcium, 3.5% for magnesium and 0.2% for zinc. Results obtained by this method were better than those obtained by other methods for the same samples. 相似文献
14.
Jørgen M. Mollerup Martin P. BreilChristina Vogelpohl Gabriele Sadowski 《Fluid Phase Equilibria》2011,301(2):163-170
The chromatographic retention in hydrophobic and reversed phase chromatography and the solubility of proteins display some common features. The chromatographic retention, as well as the solubility, is modulated by the thermodynamic properties of the solute in the fluid phase. The retention measurements at linear conditions provide information of the solution properties of the protein at infinite dilution, and the solubility measurements produce the supplementary information about the solution properties at the saturation limit. This provides a useful approach to simultaneous correlation of the chromatographic retention and the solubility.The experimental data, used for the correlation, comprise retention measurements of lysozyme on different HIC adsorbents using an aqueous ammonium sulphate eluant, an aqueous ammonium sulphate eluant with an admixture of ethanol, as well as published solubility data.The chromatographic retention data and the corresponding solubility data have been correlated using a chemical potential model derived from Kirkwood's theory of solutions of charged macro-ions and zwitterions in electrolyte solutions. The model correlated the chromatographic retention factor and the solubility data within the precision of the measurements. The model was applied in a pH range from 4 to 11. It was demonstrated experimentally, as well as theoretically, that an admixture of ethanol to the aqueous eluant changes the thermodynamic retention factor on various adsorbents identically when compared to the thermodynamic retention factor in an ethanol free eluant. 相似文献
15.
Oil refinery is one of the fast growing industries across the globe and it is expected to progress in the near future. The worldwide increase in the generation of refinery wastewater along with strict environmental regulations in the discharge of industrial effluent, persistent efforts have been devoted to recycle and reuse the treated water. The wastewater from the refining operation leads to serious environmental threat to the ecosystem. Therefore, this study aimed to synthesize silica (SiO2) and calcium carbonate nanoparticles (CaCO3) in the reduction of organics from refinery wastewater. The synthesized nanoparticles were employed in the reduction of chemical oxygen demand (COD) from refinery wastewater by studying the influence of solution pH, contact time, dosage of nanoparticles and stirring speed on adsorption performance. From the batch experimental studies, the optimized processing conditions for the reduction of COD using SiO2 nanoparticles are pH 4.0, dosage 0.5 g, stirring speed 125 rpm and 90 min stirring time, and the corresponding values for CaCO3 nanoparticles are pH 8.0, dosage 0.4 g, stirring speed 100 rpm and 90 min stirring time. The study demonstrates that SiO2 and CaCO3 nanoparticles have a promising future in the reduction organics from refinery wastewater in different pH regimes. 相似文献
16.
Lilibeth dlC. Coo Terence J. Cardwell Robert W. Cattrall Spas D. Kolev 《Analytica chimica acta》1998,360(1-3):153-159
The solubility and the protolytic constants of 1-(2-pyridylazo)-2-naphthol (PAN) have been accurately determined at temperatures between 20.0 and 30.0°C in ethanol–water solutions with ethanol concentrations ranging from 10.0% to 95.0% (v/v). The measurement of the protolytic constants is based on the spectrophotometric determination of the concentrations of the corresponding conjugate acid–base pairs in ethanol–water solutions containing PAN and hydrochloric acid or sodium hydroxide. The traditionally used pH measurements in such studies in non-aqueous solutions are thus avoided. The solubility and the protolytic constants of PAN in pure water have been calculated by extrapolating the ethanol–water results to pure water where PAN is practically insoluble. The determination of the thermodynamic data mentioned above is necessary for elucidating the interactions of PAN with various metal ions in solutions and in cation-exchange membranes (e.g., Nafion®) used as PAN-based optodes. 相似文献
17.
Lubricating oils are used to decrease wear and friction of movable parts of engines and turbines, being in that way essential for the performance and the increase of that equipment lifespan. The presence of some metals shows the addition of specific additives such as detergents, dispersals and antioxidants that improve the performance of these lubricants. In this work, a method for determination of calcium, magnesium and zinc in lubricating oil by flame atomic absorption spectrometry (F AAS) was developed. The samples were diluted with a small quantity of aviation kerosene (AVK), n-propanol and water to form a three-component solution before its introduction in the F AAS. Aqueous inorganic standards diluted in the same way have been used for calibration. To assess the accuracy of the new method, it was compared with ABNT NBR 14066 standard method, which consists in diluting the sample with AVK and in quantification by F AAS. Two other validating methods have also been used: the acid digestion and the certified reference material NIST (SRM 1084a). The proposed method provides the following advantages in relation to the standard method: significant reduction of the use of AVK, higher stability of the analytes in the medium and application of aqueous inorganic standards for calibration. The limits of detection for calcium, magnesium and zinc were 1.3 μg g−1, 0.052 μg g−1 and 0.41 μg g−1, respectively. Concentrations of calcium, magnesium and zinc in six different samples obtained by the developed method did not differ significantly from the results obtained by the reference methods at the 95% confidence level (Student's t-test and ANOVA). Therefore, the proposed method becomes an efficient alternative for determination of metals in lubricating oil. 相似文献
18.
The effect of pre-reduced Pt and Ir modifiers towards simultaneous determination of As, Se and In in a sodium sulphate matrix was investigated. In spite of application of very isothermal THGA atomizer, negative influence of the matrix is pronounced. The efficiency of iridium modifier is somewhat higher than that of platinum modifier. However compared to palladium modifier both are significantly less effective in sulphate media. Taking into account our previous data, effectiveness of platinum group metal (PGM) modifiers in the determination of As, Se and In in the presence of sodium sulphate increases in the order Ru<Rh≈Pt<Ir<Pd. This order is opposite to the data on enthalpy of formation of PGM sulphides. This supports our hypothesis that effectiveness of PGM modifiers in the presence of sulphate matrix is determined mainly by stability of the corresponding sulphides. Efforts to enhance the effectiveness of Pt modifier mixing it with small (10-20%) amounts of Pd, Rh or Ir were not successful. Although mixture containing equal amounts of Pd, Pt, Rh and Ru is relatively effective, pure pre-reduced Pd is the best modifier for the simultaneous determination of As, Se and In in a sulphate media. 相似文献
19.
The influence of Cu(II) impurity on chemical equilibria in unsaturated and saturated ammonium oxalate (AO) aqueous solutions was investigated as a function of concentration ci of impurity. Using the computer programme “Hyss” the species present in the solutions were analysed. It was found that in the aqueous solutions of ammonium oxalate containing Cu(II) ions the following species are formed: Cu2+, Cu(OH)+, Cu(OH)2, CuC2O40 and Cu(C2O4)22− in addition to C2O42−, HC2O4−, H2C2O4 and (NH4)2C2O40 species, and their concentration depends on concentrations ci of Cu(II) impurity and c of ammonium oxalate. The dependences of solution pH and of absorbance A and the corresponding wavelength λ for unsaturated aqueous solutions on ammonium oxalate concentration c containing different concentrations ci of Cu(II) ions showed three well-defined regions characterised by transition values of solution pH or solute concentration c. Speciation analysis revealed that Cu2+ and CuC2O40, CuC2O40 and Cu(C2O4)22−, and Cu(C2O4)22− complexes are predominantly present in the solute concentration intervals c≤0.01 mol/dm3, 0.01 mol/dm3 <c<0.03 mol/dm3 and c≥0.03 mol/dm3, respectively. The concentration interval range 0.01 mol/dm3 <c<0.03 mol/dm3 corresponds to the pH interval where Cu(OH)2 is precipitated. It was found that the solubility of ammonium oxalate at 30 °C increases practically linearly with an increase in the concentration of Cu(II) impurity. Speciation analysis of saturated aqueous solutions of ammonium oxalate revealed that Cu(II) ions contained in AO saturated solutions exist mainly as Cu(C2O4)22−-type complexes, and the increase in the solubility of AO in the presence of Cu(II) impurity is essentially due to an increase in the ratio of the concentrations of CuC2O40 and Cu(C2O4)22− species. 相似文献
20.
Ca(II) ions are added in the spinning dope to adjust the solidification rate of regenerated silk fibroin (RSF) solution during the wet-spinning process since Ca(II) ions are proved to be favorable to maintain the stable silk fibroin network in our previous work. The results show that when Ca(II)/RSF ratios are 1/50 and 1/20, the resulted RSF fibers exhibit good performance with the breaking energy more than 70 kJ/kg. However, higher Ca(II)/RSF ratio (for example, 1/10) hinders the solidification of spinning dope and results in poor RSF fibers. These observations together with earlier papers from this laboratory confirm that to produce tough silk fibers the spinning conditions must allow sufficient time for the adjustment of silk fibroin molecular chains. 相似文献