Influence Of Na2SO4 Research Articles

The influence of sodium sulphate on sodium aluminosilicate solubility in Bayer liquor aiding the desilication process

The influence of Na2SO4 at chemical equilibrium in the NaOH-Al2O3-SiO2-Na2SO4-H2O system were studied in synthetic Bayer liquors. Sodium aluminosilicate, otherwise referred to as desilication product (DSP) in the alumina industry, was synthesised hydrothermally from kaolin used in a rotating bomb heater. Experiments spanned several days to reach equilibrium at 90 °C, 150 °C and 250 °C and employed Na2SO4 concentration ranging from 0 to 0.4 M. The SO42− incorporation into DSP was best modelled by the mathematical form of Langmuir-type isotherms, and reached maximum occupancy of 85%, primarily displacing OH−, and Al(OH)4− to a lesser degree. The presence of Na2SO4 enhanced desilication (measured by solution SiO2 concentration) by up to 80% compared to sulphate-free tests, with diminishing relative effect with increasing SO42− concentration. Approximate maximum sulphate cage occupancy and effect on desilication were achieved at a Na2SO4 concentration of 0.1 M. Solid residues contained Bayer (alumina)-type cancrinite, sulphate-type cancrinite (vishnevite), hydroxycancrinite, hydroxysodalite and amorphous material as determined by X-ray diffraction. The presence of sulphate led to different transformation pathways for DSP precipitated from kaolin. Sulphate-bearing DSPs exhibited rod-like morphology and presented enhanced thermal stability over their hydroxy counterparts. Valuable new data on the relationship between sulphate ion uptake, and the composition, structure and solubility of DSP are presented, and the results are suitable for the development of kinetic and thermodynamic models describing zeolite equilibria in alumina processing.

Sodium sulfate influence on the electrodeposition of MnO2 films for application in Supercapacitors

Manganese dioxide (MD) was synthesized by cyclic voltammetry using 0.5 mol L−1 MnSO4·6H2O as the precursor solution, with and without the 0.05 mol L−1 of Na2SO4 support electrolyte solution, and effect was studied by several techniques. The AFM analysis allowed the study of the substrate and synthesized films topography; SEM images showed the differences in the morphology and thickness of the films. Through XRD analysis, it was possible to observe the crystallinity of the materials, caused by the influence of Na2SO4 during electrodeposition and electrochemical characterization, which made it possible to obtain results that served as parameters during the studies proposed here. The voltammograms showed the differences in theoretical capacitance of 0.5 mol L−1 manganese dioxide with Na2SO4 (MDNa) and for 0.5 mol L−1 manganese dioxide without the 0.05 mol L−1 of Na2SO4, which were 860.25 and 455 F g−1, respectively, while in the GCD tests, they present 375 and 250 F g−1 of specific capacitance for the 0.5 mol L−1 MDNa and 0.5 mol L−1 MD electrodes; all results measured in 0.5 A g−1. The EIS studies by the Nyquist and Bode plots made it possible to analyze the resistivity regions and the capacitive nature of the materials. It can be concluded that the purpose of this study was successfully achieved, since the results are interrelated and confirm that the MDNa electrode has attractive and more advantageous properties than MD for supercapacitor application.

Salt-induced thermal gelation of xyloglucan in aqueous media

The influence of Na2SO4 as a kosmotropic salt on the thermogelation of xyloglucan (XG) solutions was measured by rheology. The gelation occurred at lower temperatures and shorter times when the salt concentration was increased above 0.5 mol.L−1. For Na2SO4 concentrations equal to 1 mol.L−1, a not thermoreversible elastic hydrogel was obtained. Salts containing various types of anions were used, and it was observed that SO42−, HPO42− and H2PO4− promoted the formation of a gelled network. The gel structure was observed using confocal laser scanning microscopy and scanning electron microscopy. In XG containing SO42 at 1 mol.L−1aggregates and gels were formed by interconnected sub-micrometer XG particles. Increasing the concentration of SO42− led to conformation changes in the XG, from a twisted/helical to an extended/flat conformation, as observed using circular dichroism. The naturally occurring hydrophobic sequences promoted an economically feasible XG gelling that may produce thermo and kosmo-sensitive hydrogels.

Microstructure of renovation plasters and their resistance to salt

One of the most important factors which decide about the durability of the renovation plasters is the resistance to crystallization of salt which dissolves under the influence of moisture. This paper demonstrates the results of the research on the influence of the microstructure of pores in cement-lime mortars and their resistance to various cyclical salts. Six plasters differing in porosity and microstructure were selected for the study. The purpose of the study was to alternatively soak samples with three solutions of salts: NaCl at a concentration of 25.9%, Na2SO4 at 18.3% and NaNO3 at 45%, and then crystallize the salts. It was found that salts solutions have a various intensity of destructive effect on renovation plasters. It was demonstrated that the durability of plasters depends to a greater extent on the pore size distribution than on the total porosity Pc. Salts solutions do not have a destructive effect on plasters with a large variety of pores, whereas plasters with low porosity and monomodal pore size distribution were destroyed under the influence of Na2SO4 and NaNO3 solutions. Porosimetry and electron microscopy were used in the studies.

Migration and distribution of sodium ions and organic matters during electro-dewatering of waste activated sludge at different dosages of sodium sulfate

In this study, the influence of Na2SO4 on electro-dewatering (EDW) of waste activated sludge (WAS) was investigated. The highest water removal efficiency of 42.5% was achieved at the optimum Na2SO4 dosage of 12.5 g kg−1 DS during EDW process at a constant voltage of 20 V. The migration and distribution of water, organic matters and Na+ at different Na2SO4 dosages were investigated through layered experiments. The results indicated the entire EDW process followed the S curve model, and it can be divided into three stages: (1) initial desalination stage: at the initial few min of EDW process, the rate of electroosmosis was extremely slow while electromigration of ions like Na+ was intense, and the electromigration was more obvious with increased Na2SO4 dosage; (2) dewatering stage: the dewatering efficiency increased dramatically via electroosmosis; (3) the dewaterability limit stage: the maximum value of dewatering efficiency has been achieved, while the water removal efficiency and dry solids content remained constant. During the EDW process, the possible electrolysis resulted in a pH gradient in the sludge cake. With the addition of Na2SO4 in the EDW, the pH gradient was intensified, and the migration rate of organic matters moving from cathode to anode increased while compared with the raw WAS. This study provided insights into the mechanism of EDW process at different dosages of Na2SO4.

Thermal properties of 60P2O5–20Fe2O3–20Al2O3 glass for salt waste immobilization

Vitrification is the most effective method of hazardous waste immobilization. Toxic elements are incorporated into a glass structure. Iron alumino-phosphate glasses are presently being considered as a matrix for storage of a radioactive waste which cannot be vitrified using conventional borosilicate waste glasses. Influence of Na2SO4 as a one of components such the waste on thermal properties and crystallization ability of 60P2O5–20Fe2O3–20Al2O3 glass was studied. It was observed that Na2SO4 decreases transformation temperature and increases ΔCp. The glass characteristic temperatures, glass crystallization ability and crystallizing phases were determined. Na2SO4 increases the glass crystallization ability which could be related with ΔCp heat capacity accompanying glass transition changes. The glass internal structure rebuilding accompanying the sodium content increase is considered. The obtained results were compared with structural model previously developed for 60P2O5–40Fe2O3 glass and showed the structural similarity between these glasses.

Hydrothermal synthesis of ZnO whiskers from ɛ-Zn(OH)2 in NaOH/Na2SO4 solution

The influence of Na2SO4 on the formation of ZnO whiskers was investigated in this paper. ZnO whiskers with aspect ratios of up to 50 were synthesized by dissolving ɛ-Zn(OH)2 precursor in NaOH/Na2SO4 solution at room temperature, followed by aging of the resulting solution at 140°C for 6h. Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy analyses revealed that SO42− ions were primarily adsorbed on the (100) plane of the ZnO whiskers via an outer-sphere complex configuration (OH···O), thereby promoting the one-dimensional growth of ZnO whiskers along the c-axis.

Thermal properties of phosphate glasses for salt waste immobilization

Vitrification is the most effective method of the hazardous waste immobilization. Toxic elements are incorporated into glass structure. Iron phosphate glasses are presently being considered as a matrix for storage of the radioactive waste which cannot be vitrified using a conventional borosilicate glass. Influence of Na2SO4 as one of the components such the waste on thermal properties and crystallization ability of iron phosphate waste glass was studied. It was observed that Na2SO4 decreases transformation temperature and increases ΔC p. The glass characteristic temperatures, glass crystallization ability, and crystallizing phases were determined. Na2SO4 increases the glass crystallization ability which could be related with ΔC p heat capacity accompanying glass transition changes. The glass internal structure rebuilding, accompanying the sodium content increase, is considered. It is shown that ΔC p is a suitable, structure-sensitive glass crystallization ability, parameter.

A Study on the Influence of Na2SO4 on the Solubility of CO2 in Aqueous Solutions of (N,N-dimethylmethanamide)

Abstract The influence of sodium sulphate on the solubility of carbon dioxide in aqueous solutions of N,N-dimethylmethanamide {= N,N-dimethylformamide, (CH3)2N-C(H)O, DMF} was investigated experimentally at three temperatures (314 K, 354 K, and 395 K). The solvent was an aqueous solution of DMF (mole fraction of DMF in the salt-free solution ≈ 0.05) and sodium sulphate (molality ≈ 0.6 mol·(kgH2O)−1). The maximum pressure of the new experimental gas solubility data reaches nearly 10 MPa. A thermodynamic model that combines two models for the solubility of CO2 (in aqueous solutions of Na2SO4 on one side and in aqueous solutions of DMF on the other side) is used to predict the influence of Na2SO4 on the solubility of CO2 in aqueous solutions of DMF. The new experimental data are compared with such predictions and with calculations from an extension of that model where a single ternary parameter for interactions between the three solutes (i.e., CO2, Na2SO4, and DMF) is adjusted to improve the representation of the experimental data.

The effect of the Hofmeister series on the deswelling isotherms of poly(N-isopropylacrylamide) and poly(N,N-diethylacrylamide)

The influence of Na2SO4, NaCl, NaBr, and NaI was studied on the deswelling isotherms of thin films of photo-crosslinked poly(N-isopropylacrylamide) and poly(N,N-diethylacrylamide) to help elucidate the mechanisms by which ions of the Hofmeister series affect the solubility of neutral, amide-based polymers. The films were characterized with both ellipsometry and FTIR to determine both water content and the frequency of the CO, N–H, and CH3 vibrations associated with the polymers. When compared at the same water content, the frequency of the N–H bend in poly(NIPAAm) red-shifts in the order I− > Cl− > Br− > SO42−. The red-shift is consistent with disrupted hydrogen bonding of the N–H moiety due to an ion–dipole attraction. The CO stretch on the other hand is insensitive to the ion, suggesting that the ion pairs primarily with the partially positive end of the HN–CO dipole. For poly(DEAAm), which lacks an N–H moiety, the CO stretch is now sensitive to the ion, with the trend following the order of the ion in the Hofmeister series. Both of these findings signify that I− > Cl− > Br− > SO42− with respect to the strength of the ion–dipole interaction. Moreover, the ion–dipole interaction is stronger in poly(NIPAAm) than poly(DEAAm), suggesting that the specificity of the Hofmeister ions arises from the effect of vicinal groups on the amide dipole.