Showing papers on "Sodium sulfate published in 2002"
TL;DR: In this article, the thermodynamics of real solutions for sodium sulfate and sodium chloride have been investigated and it was shown that dissolution of its anhydrate produces supersaturations with respect to its decahydrate capable of generating tensile hoop stresses on the order of 10-20 MPa, largely in excess of the tensile strength of almost all stones.
465 citations
TL;DR: In this article, the main parameters studied were evolution of compressive strength, products of degradation, and microstructural changes of AAS concrete in a sulfate environment, and two tests were used to determine resistance to sulfate attack, which involved immersion in 5% magnesium sulfate and 5% sodium sulfate solutions.
339 citations
TL;DR: In this article, the authors investigated the effects of sodium and magnesium sulfate solutions on expansion and microstructure of different types of Portland cement mortars and reported that the expansion of mortars in sodium sulfate solution follows a two-stage process.
318 citations
TL;DR: In this paper, the production of citric acid from sodium citrate was carried out by electrodialysis (ED), using bipolar membranes (BP) prepared from poly(phenylene oxide) (PPO).
Abstract: Production of citric acid from sodium citrate was carried out by electrodialysis (ED), using bipolar membranes (BP) prepared from poly(phenylene oxide) (PPO). The process feasibility was tested using a laboratory ED-cell with an effective area 20 cm 2 . Based on the configuration of BP-cation membranes (C)-BP, the performances of various sodium sulfate concentrations and sodium citrate concentrations are compared and discussed in terms of ionic transport and ion exchange. It is suggested that, in such an operation, the optimum concentration range be 0.5–1.0 M for sodium citrate and 0.25–1.5 M for sodium sulfate from the viewpoint of energy consumption, current efficiency and acid concentration. © 2002 Elsevier Science B.V. All rights reserved.
151 citations
TL;DR: In this article, the influence of sulfate concentration on chloride-induced reinforcement corrosion in Portland cement concretes was reported. But, the results indicated that the presence of sulfates ions in the chloride solution did not influence the time to initiation of chloride induced reinforcement corrosion, but the rate of corrosion increased with increasing sulfate concentrations.
Abstract: This paper reports the influence of sulfate concentration on chloride-induced reinforcement corrosion in Portland cement concretes (with C3A varying from 3.6% to 9.65%). The concrete specimens were exposed to mixed chloride and sulfate solutions for a period of 1200 days. The chloride was fixed at 5% NaCl for all solutions, while the sulfate concentration was varied to represent that noted in the sulfate-bearing soil and ground water. The study included an assessment of the effect of cation type associated with sulfate ions, namely Na+ and Mg2+, on chloride-induced reinforcement corrosion, an important factor that has received little attention. Reinforcement corrosion was evaluated by measuring corrosion potentials and corrosion current density at regular intervals. The results indicate that the presence of sulfate ions in the chloride solution did not influence the time to initiation of chloride-induced reinforcement corrosion, but the rate of corrosion increased with increasing sulfate concentration. Further, the rate of chloride-induced reinforcement corrosion in the concrete specimens exposed to sodium chloride plus magnesium sulfate solutions was more than that in the concrete specimens exposed to sodium chloride plus sodium sulfate solutions.
121 citations
TL;DR: The observed variation of the equivalent capacitance in serum bovine suggests that an adsorption layer of organic molecules develops on the electrode surface and it is responsible for both the decrease in open circuit potential and the higher R(p), because it hinders the oxygen evolution reaction and the charge transfer responsible for the passive film dissolution (or growth).
Abstract: Electrochemical impedance spectroscopy is used to monitor the long-term stability (up to 150 days) of mechanically polished commercial pure titanium, Ti6Al4V, Ti6Al7Nb, and CoCrMo alloys in 0.1M sodium sulfate and fetal bovine serum. A capacitive spectrum in the frequency range from 10(-3) to 10(5) Hz is always found and the impedance spectra can be fitted by a simple parallel RC circuit with a constant phase element. The open circuit potential observed in serum is always more cathodic and the polarization resistance (R(p)) is higher than that recorded in sodium sulfate solutions. The observed variation of the equivalent capacitance in serum bovine suggests that an adsorption layer of organic molecules develops on the electrode surface and it is responsible for both the decrease in open circuit potential and the higher R(p), because it hinders the oxygen evolution reaction and the charge transfer responsible for the passive film dissolution (or growth). Among the alloys studied, Ti6Al4V displayed the highest steady-state values of R(p) both in serum and in sodium sulfate.
119 citations
TL;DR: In this paper, a theoretical analysis of the detrimental influence of weak sodium sulfate solutions (Na2SO4) on the durability of concrete is presented using a numerical model that takes into account the coupled transport of ions and liquid and the chemical equilibrium of solid phases within the (partially) saturated system.
Abstract: A theoretical analysis of the detrimental influence of weak sodium sulfate solutions (Na2SO4) on the durability of concrete is presented. It was conducted using a numerical model that takes into account the coupled transport of ions and liquid and the chemical equilibrium of solid phases within the (partially) saturated system. Numerous simulations were performed to investigate the influence of various parameters such as water/cement (w/c) ratio (0.45, 0.65 and 0.75), type of cement (CSA Type 10 and Type 50), sulfate concentration (0–30 mmol/l of SO4) and the gradient in relative humidity across the material. All input data related to the properties of concrete were obtained by testing well-cured laboratory mixtures. Numerical results indicate that exposure to weak sulfate solutions can result in a significant reorganization of the microstructure of concrete. The penetration of sulfate ions into the material is not only at the origin of the precipitation of sulfate-bearing phases (such as ettringite and eventually gypsum) but also results in calcium hydroxide dissolution and C–S–H decalcification. Data also clearly emphasize the fact that w/c ratio remains the key parameter that controls the durability of concrete to sulfate attack.
105 citations
TL;DR: In this article, the effect of ammonium sulfate on the microstructure, crystallography, mechanical, and corrosion resistance properties of manganese deposits are investigated, and it is found that ammonium sulfurate enhances the reduction reaction of the manganous ion and provides a buffering effect.
Abstract: Manganese coatings of high quality are electrodeposited on steel substrates from simple sulfate solutions with addition of ammonium sulfate. Potentiodynamic scans and galvanostatic experiments are used to study manganese electrodeposition in a wide range of pH and current density. The effect of these variables on the microstructure, crystallography, mechanical, and corrosion resistance properties of manganese deposits are investigated, It is found that ammonium sulfate enhances the reduction reaction of the manganese ion and provides a buffering effect. Two types of manganese deposits can be obtained depending on current density: crystalline films (type I, body-centered tetragonal γ-Mn) at low current density and amorphous films (type II) at high current density, Bright manganese films with (002) preferential orientation are electrodeposited at low pH. Type I structures show recrystallization at room temperature with phase transformation; the rate of phase transformation from γ-Mn to α-Mn (body-centered cubic) follows a Johnson-Mehl-Avrami kinetics, Crystalline films obtained at relatively high current density and low pH tend to have higher phase transformation rates. Amorphous films show good corrosion resistance both in acidic sodium sulfate/ borate and sodium chloride electrolytes.
100 citations
TL;DR: In this paper, the effect of reactant concentrations and barium or sulfate excess on crystal-size distribution and morphology is investigated in a tubular reactor in a wide range of operating conditions.
Abstract: In this work barium sulfate precipitation is studied in a tubular reactor in a wide range of operating conditions. The effect of reactant concentrations and barium or sulfate excess on crystal-size distribution and morphology is investigated. Experimental results show that ion excess has a strong influence and that at high concentration aggregation takes place. Computational fluid dynamics is coupled with the finite-mode probability density function approach for taking into account both macro- and micromixing, whereas the population balance is treated by using the standard moment method. Comparison with experimental data suggests that when micromixing and agglomeration are properly taken into account, the agreement is improved. However, this statement is partially affected by the lack of knowledge in barium sulfate kinetics.
96 citations
TL;DR: In this article, the effect of cell configurations on the energy consumption and the electroacidification parameters in the production of citric acid using a bipolar membrane electrodialysis (BPED) was evaluated and compared.
93 citations
TL;DR: In this article, asymmetric poly(vinyl alcohol) (PVA) membranes crosslinked with glutaraldehyde (GA) were prepared by phase inversion technique for pervaporation dehydration of isopropanol (IPA).
Abstract: Asymmetric poly(vinyl alcohol) (PVA) membranes crosslinked with glutaraldehyde (GA) were prepared by phase inversion technique for pervaporation dehydration of isopropanol (IPA). The crosslinking solutions contain sodium sulfate, sulfuric acid and different contents of GA, wherein sulfuric acid serves as a catalyst. The effects of three variables involved in the membrane preparation, including PVA molecular weight, PVA concentration and GA concentration on pervaporation characteristics were investigated. The results showed that the permeation flux decreases with the increase of these three factors, whereas the selectivity has an opposite trend. The influence of feed IPA concentration and temperature on pervaporation performances was also studied to find optimum operating conditions.
TL;DR: Nuclear magnetic resonance spectroscopy was used to study the composition of the phases resulting from salting out and to compare the effectiveness of sodium sulfate and magnesium sulfate as drying agents, showing that considerable amounts of water remained in the organic phase after phase separation.
Abstract: Water-miscible solvents, such as acetone and acetonitrile, effectively extract both polar and nonpolar pesticide residues from nonfatty foods. The addition of sodium chloride to the resulting acetonitrile-water or acetone-water extract (salting out) results in the separation of the water from the organic solvent. However, the organic solvent layer (pesticide extract) still contains some residual water, which can adversely affect separation procedures that follow, such as solid-phase extraction and/or gas chromatography. Drying agents, such as sodium sulfate or magnesium sulfate, are used to remove the water from the organic extracts. In the present study, we used nuclear magnetic resonance spectroscopy to study the composition of the phases resulting from salting out and to compare the effectiveness of sodium sulfate and magnesium sulfate as drying agents. The study showed that considerable amounts of water remained in the organic phase after phase separation. Sodium sulfate was a relatively ineffective drying agent, removing little or no residual water from the organic solvent. Magnesium sulfate proved to be a much more effective drying agent.
TL;DR: In this article, simple chemistry-based empirical models have been developed to assess the role of temperature and concentration of the sulfate solution in the process of expansion of cement mortars that are subjected to external sulfate attack.
TL;DR: In this article, the authors found that the addition of 0.10-1.00% of K 4 Fe(CN) 6 to sodium chloride in Monks Park limestone experiments increased the flow rate of solutions through the stone, resulting in efflorescence in place of subflorescence, and yielded a massive formation of extended dendritic filaments without damaging the stone.
TL;DR: In this paper, the effect of particle size on Raman intensity has been measured for a number of crystalline solids with a fiber-optic-based Raman spectrometer.
Abstract: The effect of particle size on Raman intensity has been measured for a number of crystalline solids with a fiber-optic-based Raman spectrometer. Particle sizes ranged from 76 to 605 μm. Materials examined were sodium nitrate, sodium chlorate, sodium bromate, potassium ferrocyanide, potassium ferricyanide, and copper(II) sulfate. Raman intensity was found to decrease with increasing particle size. The factors responsible for this trend are discussed. We conclude that the major factor is diffuse reflectance that enhances the overlap between the excitation and collection beams. The depth of sample contributing to the Raman signal has been examined for both powders and tablets as a function of powder particle size. Materials examined in this study were sodium nitrate, sodium sulfate, sodium chlorate, sodium bromate, potassium ferrocyanide, potassium ferricyanide, and copper(II) sulfate. For nonabsorbing powders, the depth of sample contributing to the signal exceeded 15 mm. The effect of the pressure used in forming tablets on the Raman signal strength and reproducibility has been examined for sodium nitrate. The Raman intensity was found to decrease with increasing pressure until a tablet of constant density was formed. The effect of particle size and particle size mismatch on the sodium nitrate Raman signal in binary mixtures with potassium chloride, potassium bromide, and potassium iodide has been examined. Good reproducibility was found to require matching of component particle sizes.
TL;DR: In this paper, the results showed that 95% zinc was achieved from the concentrate of particle size −150 μm at a temperature of 333 K for 5 h in the presence of 20% ammonium persulphate (APS) with 5% (v/v) sulphuric acid concentration.
TL;DR: In this paper, the solubilities of amino acids (glycine, β-alanine, γ-amino butyric acid, dl-aline, Dl-valine) were measured in water and aqueous solutions of 0.5, 1.0, and 1.5 M sodium sulfate at (288.15, 298.15 and 308.15) K.
Abstract: The solubilities of amino acids (glycine, β-alanine γ-amino butyric acid, dl-alanine, dl-amino butyric acid, and dl-valine) have been measured in water and aqueous solutions of 0.5, 1.0, and 1.5 M sodium sulfate at (288.15, 298.15, and 308.15) K. Related transfer parameters are also calculated. A model, with a maximum standard deviation of 1 g per l00 g of solvent, based on the experimental data, is given to predict solubilities of these amino acids under other conditions. The results have been interpreted in terms of interactions of the amino acids with the solvent, and a qualitative comparison has been done with other cosolvents.
TL;DR: In this article, the heat capacities of aqueous solutions of Na2SO4 and Na2CO3 up to near saturation (1.9 and 2.5 mol·kg-1, respectively) with a Picker flow calorimeter were measured at 25 °C.
Abstract: Heat capacities of aqueous solutions of Na2SO4 and Na2CO3 up to near saturation (1.9 and 2.5 mol·kg-1, respectively) and of NaOH (to 7 mol·kg-1) have been measured at 25 °C with a Picker flow calorimeter. The calorimeter performance was checked using concentrated NaCl(aq) solutions. On the basis of these measurements, an experimental protocol suitable for the reliable determination of the heat capacities of concentrated electrolyte solutions by Picker calorimetry was established. The heat capacities for Na2SO4(aq), Na2CO3(aq), and NaOH(aq) and literature data for the apparent molar volumes of NaOH(aq) at 25 °C were correlated using the Pitzer formalism. A number of inadequacies in previous models at high concentrations and for extrapolation to infinite dilution are discussed. In particular, it has been confirmed that the heat capacity data for Na2CO3(aq) at low concentrations must be corrected for the hydrolysis of the carbonate ion. Standard partial molar heat capacities for the three salts and the stand...
TL;DR: In this paper, the two most frequently mentioned mechanisms used to explain the severe damage that occurs when a porous material, containing the anhydride phase of sodium sulfate, is exposed to either water or rising humidity are critically reviewed.
Abstract: The two most frequently mentioned mechanisms used to explain the severe damage that occurs when a porous material, containing the anhydride phase of sodium sulfate, is exposed to either water or rising humidity are critically reviewed. Both derivations are presented along with their underlying hypotheses. Critical differences are discussed and it is concluded that crystallization pressure is the relevant mechanism. In effect however, it is shown that the expressions obtained both for crystallization pressure and hydration pressure are quite similar.
TL;DR: Sodium and potassium salt deposition has been studied in a series of propane and hydrogen flames free of sulfur or halogen impurities as discussed by the authors, with the collection probe in the 400 to 800 K range.
TL;DR: Tin electrodeposition in its initial stages in acid sulfate/gluconate baths was studied with varying tin and gluconate concentrations using potential-controlled electrochemical techniques as discussed by the authors.
Abstract: Tin electrodeposition in its initial stages in acid sulfate/gluconate baths was studied with varying tin and gluconate concentrations using potential-controlled electrochemical techniques. The deposit morphology was observed by scanning electron microscopy (SEM). A comparison with tin electrodeposition from acid sulfate baths in the absence of gluconate was also carried out. Use of a highly acidic bath leads to nonuniform deposits, even in the presence of gluconate; at pH 4 deposits are uniform, brilliant and suitable for finishing applications. Tin crystallites have a well defined morphology which depends on bath agitation conditions. In the absence of agitation, the crystallites have the same tetragonal shape as in a sulfate bath without gluconate.
TL;DR: In this article, the electrodeposition of copper onto steel using an alkaline electrolyte based on glycerol has been investigated by voltammetric techniques and SEM analysis indicated that the reduction process occurs through two different copper(II) species.
Abstract: The electrodeposition of copper onto AISI 1010 steel using an alkaline electrolyte based on glycerol has been studied. The influence of NaOH concentration and the addition of sulfate as supporting electrolyte were investigated by voltammetric techniques. For a NaOH concentration ≥ 0.6 M the plating bath was stable and immersion deposition onto steel was avoided. Voltammetric studies and SEM analysis indicated that the reduction process occurs through two different copper(II) species. The copper films were golden in colour, even in the high hydrogen evolution region, indicating that glycerinate anions prevent the copper deposits becoming darker. The presence of the sulfate anions affected the morphology of the copper films, acting as brighteners.
TL;DR: The electrochemical behavior of a coating of cobalt oxide on cold-rolled steel in alkaline sodium sulfate was studied using the electrochemical techniques of open-circuit potential measurements and electrochemical impedance spectroscopy as mentioned in this paper.
TL;DR: In this article, the zinc electrodeposition onto glassy-carbon electrode from the sulfate, chloride and acetate solutions was examined using cyclic voltammetry and chronoamperometry.
Abstract: The zinc electrodeposition onto glassy-carbon electrode from the sulfate, chloride and acetate solutions is examined using cyclic voltammetry and chronoamperometry. The surface morphology of zinc deposited films is observed by scanning electron microscopy. The results show that all mechanisms of the zinc electrocrystallization on glassy-carbon electrode in the three solutions follow the same three-dimensional instantaneous nucleation and growth. The anions mainly affect the nucleation densities during zinc deposition, which results in different surface morphology. In the presence of acetate and chloride ions, the deposited zinc film tends to grow in a multi-layered pattern, while in sulfate solution the zinc deposition forms irregular grains.
TL;DR: In this paper, the NRTL (nonrandom, two-liquid) model was used to correlate liquid-liquid equilibria for aqueous two-phase polymer-salt solutions, with different molecular masses for PEG and the salts potassium phosphate, sodium sulfate, sodium carbonate and magnesium sulfate.
Abstract: The NRTL (nonrandom, two-liquid) model, expressed in mass fraction instead of mole fraction, was used to correlate liquid-liquid equilibria for aqueous two-phase polymer-salt solutions. New interaction energy parameters for this model were determined using reported data on the water + poly(ethylene glycol) + salt systems, with different molecular masses for PEG and the salts potassium phosphate, sodium sulfate, sodium carbonate and magnesium sulfate. The correlation of liquid-liquid equilibrium is quite satisfactory.
TL;DR: In this article, the vapour pressure of saturated aqueous solutions of Na2SO4, CaBr2,FeCl3, Zn(NO3)2, Ca(NO 3)2 and LiNO3 were determined in the temperature range from 278 k to 323 k using an electronic hygrometer with an electrolyte sensor and compared with literature data.
TL;DR: The solubility of hydrogen sulfide in aqueous solutions of N-methyldiethanolamine (MDEA) and MDEA sulfate (2 and 1 m, respectively) was investigated in this article.
Abstract: The solubility of hydrogen sulfide in aqueous solutions of N-methyldiethanolamine (MDEA) and MDEA sulfate (2 and 1 m, respectively) and in aqueous solutions of MDEA and sodium sulfate (2 and 1 m, r...
Patent•
10 Jul 2002
TL;DR: The paper soap component of the paper soap include carboxymethyl cellulose sodium, fatty alcohol polyioxymethyl ethyleneethere sodium sulfate, sodium dodecyl benzene sulfonate, lauryl sodium sulfates, cocinin diethanolamide, nonly phenol polyoxyethyleneether, glycerine, quaternary ammonium salt and citric acid as discussed by the authors.
Abstract: The component of the paper soap include carboxymethyl cellulose sodium, fatty alcohol polyioxymethyl ethyleneethere sodium sulfate, sodium dodecyl benzene sulfonate, lauryl sodium sulfate, cocinin diethanolamide, nonly phenol polyoxyethyleneether, glycerine, quaternary ammonium salt and citric acid. Its preparation includes preparing carboxymethyl cellulose sodium mother liquor, adding the mixed solution of other components to prepare solution through stirring, spraying the prepared solution of PVC plate and drying in a sealed room and moisture extract at 35-40 deg.c to form film.
TL;DR: The effect of alcohol and electrolytes on simple coacervation in the phospholipid−water−alcohol system is described in detail in this paper, where three different alcohols, methanol, ethanol and 1-propanol, were used as a lipid solvent.
Abstract: The effect of alcohol and electrolytes on simple coacervation in the phospholipid−water−alcohol system is described in detail. The optimal coacervation conditions for formation of lipid vesicles in the phospholipid−water−alcohol system were examined by the triangular phase diagram. Three different alcohols, methanol, ethanol, and 1-propanol, were used as a lipid solvent. Water and various electrolyte solutions such as sodium chloride, ammonium chloride, magnesium chloride, calcium chloride, and sodium sulfate were used as a poor solvent for the lipids. When methanol and 1-propanol were used as lipid solvents, the entire phase resulted in a transparent, highly viscous gel phase. On the other hand, the profile of the coacervate precipitation of the phospholipid was observed when ethanol was used as a lipid solvent. Moreover, when 1-propanol was used as a lipid solvent, a large volume of water phase was required to induce the coacervation in the systems in comparison with methanol or ethanol. The coacervatio...
TL;DR: In this article, the solubilities of three sulfate salts (Na2SO4, K2SO 4, MgSO4) and two chloride (NaCl, KCl) with a second salt in water were measured at 313 K, and the data were used to obtain the eutectic concentrations of ternary systems.
Abstract: The solubilities of three sulfate salts (Na2SO4, K2SO4, MgSO4) and two chloride salts (NaCl, KCl) with a second salt in water were measured at 313 K. The ternary systems studied were water + NaCl + KCl, water + NaCl + Na2SO4, water + KCl + K2SO4, water + Na2SO4 + K2SO4, water + K2SO4 + MgSO4, and water + Na2SO4 + MgSO4. The solubilities of two salts in the ternary systems were obtained, and the data were used to obtain the eutectic concentrations of the ternary systems. The solubility data were also predicted by the electrolyte−NRTL model, in which parameters were obtained from the binary data. The qualitative effect of the second salt on the solubility of the first salt in water is discussed.