Saturated Sodium Sulfate Research Articles

Experimental study on scale inhibition performance and fouling characteristics of spiral insert in heat transfer tube

In order to study the anti-scaling and descaling performance in the process of cooling crystallization, the effects of flow velocity and reciprocating displacement on fouling resistance and overall heat transfer coefficient under two spiral insert schemes are experimentally studied. The system studied in the experiment is a saturated sodium sulfate solution, which forms crystalline fouling during the experiment. The micro structure of the fouling layer is investigated to explain the variation of macroscopic thermal parameters. The average fouling thickness curve is obtained by heat transfer theory analysis. The results show that the maximum decrease of the asymptotic value of the fouling resistance of the fixed spiral insert is 63 % with the increase of the flow velocity. When the reciprocating displacement of the spiral insert increases to one pitch, the asymptotic value of the fouling resistance decreases by 83 %, and the overall heat transfer coefficient decreases by only 3 %. The particle size and porosity of fouling at different observation positions gradually increased, while the shape of fouling crystals changed from small to regular, and the degree of bonding changed from tight to loose. Statistics on the particle size of fouling particles show that the fouling particle size increases from 2-8 μm to more than 30 μm. For the fixed spiral inserts, the porosity of the fouling layer is up to 42 %, but the porosity of the middle layer increases rapidly with the flow velocity. With the change of flow velocity, the flow field characteristics in the tube are the main reason for changing the structure of the fouling layer. With the increase of reciprocating displacement, the collision effect of the spiral on the fouling layer is more comprehensive, and the interlayer bonding of the fouling layer is completely destroyed. In the field of industrial cooling crystallization, it can greatly improve the heat transfer efficiency of the inner wall crystallization process.

Method Improvement for Quantitative Analysis of Chlorophyll Degradation Compounds, Including Pheophorbide, in Chlorella Products

An official analytical method for chlorophyll degradation compounds, including pheophorbide, in chlorella products, is described in notification Kanshoku No. 99 (May 8, 1981). However, this method has several operational issues, such as the formation of emulsion during liquid-liquid partitioning. Additionally, impurities present in the reagents (sodium sulfate decahydrate or anhydrous sodium sulfate) used to prepare saturated sodium sulfate solution can degrade pheophorbide and other related compounds, resulting in a significant decrease in analytical values. In this study, we thoroughly examined each step of the official method to enhance the operability and develop an alternative method that eliminates the need for saturated sodium sulfate solution. The developed method was evaluated for pheophorbide a and pyropheophorbide a at 100 mg%. Satisfactory analytical performance was achieved with trueness of 100% for pheophorbide a and 90% for pyropheophorbide a, and relative standard deviations of intra- and inter-day precision below 5% for both compounds. The proposed method is considered suitable for regulatory analysis of chlorophyll degradation compounds and would be useful for quality control of chlorella products.

Characteristics of rice starches modified by single and dual heat moisture and osmotic pressure treatments

The effect of osmotic pressure treatment (OPT), heat moisture treatment (HMT), and their dual combination as HMT-OPT and OPT-HMT on functional and pasting properties, gel texture, crystallinity, thermal, morphological, and rheological properties, and in vitro digestibility of modified starches were investigated. HMT was done with 29 % moisture at 111 °C for 45 min while OPT was performed at 117 °C for 35 min with saturated sodium sulphate solution. All modifications increased amylose content, improved pasting stability, and reduced swelling power and solubility. Dual modifications caused higher morphological changes than single modified starches. HMT and OPT increased pasting temperature, setback and final viscosity while decreased peak viscosity and breakdown, whereas HMT-OPT and OPT-HMT reduced all pasting parameters except pasting temperature. 1047/1022 and 995/1022 ratios and relative crystallinity decreased. V-type polymorphs were formed, and gelatinization temperature range increased with lower gelatinization enthalpy. Starch gel elasticity, RS and SDS content were enhanced to a greater extent after HMT-OPT and OPT-HMT. HMT as a single and dual form with OPT showed prominent effect on pasting, thermal, crystalline, and rheological properties. Application of HMT, OPT and dual modified starches with improved functionalities may be targeted for suitable food applications such as noodles.

Study on the Characteristics of Pore Change in Tuff under the Frost and Salt Action Using High-Precision CT Scanning Equipment

Using high-precision CT scanning equipment, two series of tests on frost and salt weathering were conducted to investigate the characteristics of pore change in tuff. Experiments on frost and salt aging were performed with pieces of tuff from the same area of southeast China. One set of tuff samples was soaked in saturated sodium sulfate or magnesium sulfate solutions for 60 days. Another set of tuff samples were subjected to 60 freeze–thaw cycles after being submerged in saturated sodium sulfate or magnesium sulfate solutions for 48 h. Our study demonstrates that processes such as salt erosion and freeze–thaw affect the pore evolution of tuffs significantly. Tuff lost 1.56% of its mass after being submerged in magnesium sulfate solutions for 60 days, while tuff submerged in sodium sulfate solutions gained a negative 0.33% of its mass. After 60 freeze–thaw cycles, the mass loss of tuff samples immersed in sodium sulfate, magnesium sulfate, and distilled water solutions was 3.52%, 3.58%, and 3.82%, respectively. The average porosity of the magnesium sulfate and sodium sulfate test groups increased by 6.59% and 4.14%, respectively, when the number of days of salt erosion was extended from 10 to 60 days. The average porosity of tuff samples immersed in magnesium persulfate and sodium sulfate solutions increased by 2.25% and 2.18%, respectively, as the number of freeze–thaw cycles went from 10 to 60.

Saturated brine dissolution and liquid-liquid extraction combined with UPLC-MS/MS for the detection of typical Alternaria toxins in pear paste.

Alternaria can infest pears to produce metabolites, which can contaminate pears and their processed products. Pear paste, one of the most important pear-based products, is popular among Chinese consumers especially for its cough relieving and phlegm removal properties. Although people are concerned about the risk of Alternaria toxins in many agro-foods and their products, little is known about the toxins in pear paste. A method was developed for the determination of tenuazonic acid, alternariol, alternariol menomethyl ether, altenuene and tentoxin in pear paste by ultra-performance liquid chromatography tandem mass spectrometry with saturated sodium sulphate dissolution and acidified acetonitrile extraction. The mean recoveries of the five toxins were 75.3-113.8% with relative standard deviations of 2.8-12.2% at spiked levels of 1.0-100 μg kg-1 . Alternaria toxins were detected in 53 out of 76 samples, with a detection rate of 71.4%. Tenuazonic acid (67.1%), alternariol (35.5%), tentoxin (23.7%) and alternariol monomethyl ether (7.9%) were detected in all samples at concentrations of < limit of quantification (LOQ)-105.0 μg kg-1 , < LOQ-32.1 μg kg-1 , < LOQ-74.2 μg kg-1 and < LOQ-15.1 μg kg-1 , respectively. Altenuene was never found in pear paste samples. Tenuazonic acid, alternariol, tentoxin and alternariol menomethyl ether should be focused on due to their toxicity and detection rates. To the best of our knowledge, this is the first report on the detection method and residue levels of Alternaria toxins in pear paste. The proposed method and research data can provide technical support for the Chinese government to continuously monitor and control Alternaria toxins in pear paste, especially tenuazonic acid. It can also provide a useful reference for related researchers. © 2023 Society of Chemical Industry.

Soluble Salts Transport in Building Materials

The most widely used materials in building construction are porous materials and the combined effect of rising dampness with soluble salts is one major problem. This phenomenon is caused by the migration of the salt ions dissolved in water into the porous network of the construction materials in the building walls, which causes fractures in the materials after several cycles of crystallization/dissolution. This work presents an extensive experimental campaign with different cycles of water absorption (capillarity absorption tests) and drying (drying tests). The samples of building material used are red brick, and the samples were, previously, submitted to capillarity absorption tests with two different saturated solutions (sodium sulphate and potassium chloride). The results showed that the two salts studied influence the porous materials and their capillary coefficient in clearly different ways and the samples immersed in sodium chloride present higher drying rates than those immersed in a saturated sodium sulphate solution.

Green Analysis: Rapid-Throughput Analysis of Volatile Contaminants in Plants by Freeze-Thaw-Equilibration Sample Preparation and SPME-GC-MS Analysis.

Emerging and fugitive contaminants (EFCs) can be introduced into the food chain through plants, particularly crop plants, and have threatened food safety and human health. The method for determination of volatile EFCs in plant tissues remains challenging. A new rapid, simple, precise, and accurate freeze-thaw-equilibration followed by head space (HS)-solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) analytical method was developed in this study for high-throughput analysis of 1,4-dioxane and 1,2,3-trichloropropane (TCP) in tissues of three representative crop plants, corn, wheat, and tomato. The samples were treated by a freeze-thaw procedure, then equilibrated in a saturated sodium sulfate solution, and analyzed by HS-SPME-GC-MS method. Method detection limits ranged from 0.6 to 16 ng/g. The calibration showed good linearity (R2 > 0.9). Recoveries of spiked analytes in the three plant species ranged from 82.69 to 106.3%. The ability of plant uptake of the compounds from soil has been investigated. As demonstrated in this study, this method is used to measure the concentrations of volatile contaminants in the stems of crop plants. This method should also be applicable for other plant tissues and therefore will contribute significantly to the sight of EFC transport in plants and to assess the potential risks EFCs pose to food safety and human health.

The Equilibrium Time and Salt Expansion Characteristic of Sulfate Saline Soil upon Cooling

The salt expansion disease is severe for the soil containing sodium sulfate in cold regions. This paper carried out one‐dimensional salt expansion tests of saline soil, the crystallization test of saturated sodium sulfate solution, and the numerical cooling tests to explore the stability time of the salt expansion test and determine the standard procedure of salt expansion tests. The test results demonstrate that (i) the temperature equilibrium and the crystallization process are almost simultaneously completed in both sulfate saline soil and sulfate solution upon cooling; (ii) referring to the deformation equilibrium standard used in soil consolidation test, an expansion rate of less than 0.02 mm/h is suggested in the saline expansion test; and (iii) the equilibrium time is found to have a quadratic polynomial relationship to sample size and is much shorter under liquid bath conditions than under gas bath conditions. Based on these findings, a standard procedure of the one‐dimensional salt expansion test is proposed, in which the test equipment, the test process, the deformation stabilization time of salt expansion, and the data processing method are provided. As the deformation and the temperature are synchronized, the deformation stabilization time of samples with different sizes in different cooling media is recommended.

Solid-Liquid Phase Equilibria in the Quinary System NaCl + NaOH + Na2CO3 + Na2SO4 + H2O at 363.15 K.

Solid–liquid equilibria in the quinary system NaCl + NaOH + Na2CO3 + Na2SO4 + H2O at 363.15 K were measured by the wet residue method, and the equilibrium solid phases and solubilities of saturated solutions were determined experimentally. Using the experimental results, dry-salt phase diagrams and water diagrams versus composition diagrams were plotted (saturated with saturated sodium chloride, sodium hydroxide, sodium carbonate, and sodium sulfate). The experimental results show that there are a solid solution (γ-salt, mNa2SO4·nNa2CO3) and co-saturation complex salts (S3, Na2SO4·NaCl·NaOH and S1, NaOH·Na2SO4) formed in this quinary system. Based on Xu’s activity coefficient model, the solubilities of the quinary system NaCl + NaOH + Na2CO3 + Na2SO4 + H2O at 363.15 K were calculated with corresponding parameters. Comparing the experimental and calculated results, it was shown that the calculated values had a good agreement with the experimental ones.

Verification and Improvement of an Official Method for Determining Chlorophyll Decomposition Products Including Pheophorbide

The official method described in Direction Notification Kanshoku No. 99 （May 8, 1981） for the determination of chlorophyll decomposition products including pheophorbide was verified and improved in order to overcome several problems. Firstly, extraction with a mortar required improvement because of the difficulty of maintaining equal power for a long time. Secondly, the saturated sodium sulfate reagent caused a red-shift of the absorption maximum wavelength from the measured wavelength given in the official method; consequently, the absorption was decreased and a new absorption peak was detected around 729 nm. As a result, chlorophyll decomposition products including pheophorbide were underestimated. Lastly, it was impossible to make up the volume of the diethyl ether layer accurately to 20 mL before measuring the absorption. These points were improved in the modified method, and a validation test was performed. The mean recovery was 82.7％ and the within-laboratory reproducibility was 5.8％.

Studies on solution crystallization of Na2SO4·10H2O embedded in porous polyurethane foam for thermal energy storage application

Inorganic salt hydrates as a phase change material have the advantage of high latent heat values, high thermal conductivity and are not flammable. Phase segregation is the key downside feature that restricts its application in thermal energy storage application. A PU-PCM composite was prepared by incorporating aqueous saturated sodium sulphate solution, inorganic phase change material (PCM), within open pores of polyurethane (PU) foam. Experimental study on the thermal insulation performance of this composite, aqueous sodium sulphate solution embedded in open cell polyurethane foam, was discussed. This paper presents the computational solving approach for the thermal analysis of this composite having crystallization of sodium sulphate decahydrate, from its aqueous solution, within open pores of PU foam. Thermal study of salt solution in a porous material that undergoes phase change was done using COMSOL Multiphysics software and results were compared with experimental result.

Application of osmotic pressure in modification of Amaranthus viridis starch

The modification of Amaranthus viridis starch by osmotic pressure using central composite design (CCD) and artificial neural network (ANN) was studied. The amount of starch, saturated sodium sulphate (Na2SO4) solution and reaction time were established as significant (p < 0.05) factors. The extent of involvement of process variables were identified as 37.89%, 35.67% and 26.45% for saturated Na2SO4 solution, reaction time and starch solids, respectively. Optimal condition of starch (150 g), saturated Na2SO4 solution (250 mL) and time of 20 min with corresponding total amylose (36.77%), free amylose (27.31%) and lipid-complexed amylose (9.46%) were established for CCD. The ANN gave optimal condition of 149.04 g (starch), 248.40 mL (saturated Na2SO4 solution) and time (19.41 min) with corresponding total amylose, free amylose and lipid-complexed amylose of 36.38%, 28.01% and 8.37%, respectively. The high amylose content of the starch indicated that it has high degree of flakiness. The presence of lipid-complexed amylose showed its potential in improving colonic health microflora and lower glycemic index. Pareto charts showed that the most significant (p < 0.05) term was starch solids x reaction time for total amylose. The results itemized basic information on development of thrifty and efficient process for derivation of osmotic pressured starch from A. viridis grain.

ELECTROLYTIC DISSOCIATION OF SODIUM SULFATE IN AQUEOUS ETHANOL SOLUTIONS

The reducing the degree of electrolytic dissociation of sodium sulphate with the increasing a proportion of ethanol in the hydroalcoholic solution was shown with the conductometric method. It was established that the dissociation constant of sodium sulfate decreases with the increasing a concentration of alcohol in the solution. Physico-chemical properties of sodium sulfate in water-alcohol solutions on salt solubility and dissociation were not studied. In this regard, in the present study we examined an electrolytic dissociation of sodium sulfate in water-ethanol solutions. Firstly, a saturated aqueous solution of sodium sulfate, sodium sulfate solubility process was observed with the aid of crystal optic method. For this purpose, a saturated aqueous sodium sulfate was added, and the calculated amount of alcohol measured on mass of precipitated sodium sulfate decahydrate after drying to constant weight. By weight difference between the original and the precipitate salt (calculated as sodium sulphate) dissolved salt mass was measured. It is generally recognized that the degree of dissociation of the electrolyte in the electrolytic solution depends on the dielectric constant of the solvent. Water (e= 78.53) and ethanol (e = 24.3) has vary large permittivity. Therefore, by varying the alcohol content in the mixture with water it may receive different solvents with a dielectric constant, affecting the equilibrium state in the salt solution. To find the degree of electrolytic dissociation used Na2SO4 conductometric method based on measuring the electrical conductivity of solutions with variable molar concentration of salt and alcohol was applied. The dependence of the molar conductivity of aqueous solutions of sodium sulphate is transformed to direct line in coordinate of Kohlrausch equation. It is known that the degree of electrolytic dissociation of the electrolyte depends not only on its nature, but on the dielectric constant of the medium. Therefore, in water-ethanol solutions sodium sulfate shows the properties of weak electrolyte. In this case, the dependence of conductivity on the molar concentration of sodium sulphate in water-ethanol solutions will have a different appearance.Forcitation:Borisov I.M., Nabiev A.A., Mukhamedyanova A.A., Soliev L., Toshov A.F., Musodzhonova Dzh.M. Electrolytic dissociation of sodium sulfate in aqueous ethanol solutions. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 6. P. 59-64.

РАЗРАБОТКА МЕТОДИКИ ИЗОЛИРОВАНИЯ ТОФИЗОПАМА В МОДЕЛЬНОЙ СМЕСИ МОЧИ

Forensic chemical examination is carried out in order to isolate, identify and quantify toxic, narcotic, psychotropic and potent substances in the organs and fluids of the human body. The present study we researched the process of extraction of 2,3-benzodiazepine - tofisopam. There have been cases of tofisopam poisoning. And there are no descriptions of tofisopam isolation from biological fluids in the literature. Liquid extraction, an effective and commonly used method of isolation in the chemical-toxicological analysis, is used when extracting substances from blood, lymph, saliva, urine and stomach washings. The process of isolation may be influenced by the nature of the organic solvent, pH, the presence of an electrolyte, time and frequency of extraction. We have studied the effect of each factor on tofisopam isolation from aqueous solutions. It has been found that the optimal organic solvent for the extraction of the solutions is dichloroethane, which extracts maximum amount of the analyte at pH = 5.0. Saturated sodium sulphate has a salting-in effect for tofisopam. The optimum conditions for tofisopam isolating are 7 minutes with double extraction. Based on the research method of tofisopam isolating the model mixture of urine was developed. We found that this model urine mixture isolates 66.51-67.9l % of tofisopam. We performed validation assessment of the developed method for evaluation of precision and accuracy. The assessment showed the suitability of techniques for the analysis.

Facile Preparation of Soy Protein/Poly(vinyl alcohol) Blend Fibers with High Mechanical Performance by Wet-Spinning

Using formic acid as a cosolvent and saturated sodium sulfate as a coagulation bath, soy protein/poly(vinyl alcohol) (PVA) blend fibers were prepared using wet-spinning approaches. The structure and mechanical, thermal, and water- uptake properties of the spun fibers were investigated. Morphological analysis with polarized optical microscopy (POM) and scanning electron microscopy (SEM) showed that spun PVA or blend fibers were composed of nanoparticles and exhibited a porous morphology. Blend fibers exhibited only one glass transition temperature in differential scanning calorimetry (DSC) thermograms due to high compatibility between the two components. The best mechanical strength and thermal stability were achieved when 70% PVA was composited with soy protein. This was thought to be due to the effects of cross-linking and hydrogen bonding between functional groups of soy protein and PVA hydroxyl groups.

The effects of temperature and hydrodynamics on the crystallization fouling under cross flow conditions

Crystallization fouling experiments were performed in a channel for a cross flow of hot saturated sodium sulphate (Na2SO4) solution over a pipe containing cold water. The heat transfer coefficient and fouling thermal resistance were determined from measurements of local surface temperature and the thickness of the crystalline fouling layer. A systematic assessment of the asymptotic variation of these parameters with time was obtained for a range of hot salt solution Reynolds number based on pipe diameter (RehD) of 165–485, salt solution bulk temperature of 30 °C–50 °C, and cold water (at 5 °C) Reynolds number in the pipe (Rec) of 7500–25000. It was found that the temperature of the salt solution has a large effect on the fouling rate. Increasing the pipe surface temperature decreases the crystallization fouling rate. Increasing the hot solution Reynolds number, via the velocity, decreases the fouling thermal resistance, while increasing the cold water Reynolds number, via the velocity, decreases the fouling thermal resistance, but at the same time it increases the fouling layer thickness. The crystallization process that applies here was found to be under activation control (i.e. chemical kinetic control) so that the mass transport of salt plays only a minor role.

Application of Non-Destructive Technology in Evaluating Concrete to Sulfate Attack

The deterioration on sulfate attack was investigated both in physical crystallization and the chemical erosion. Specimens that suffered long-term immersion and dry-wet cycles in saturated sodium sulfate solution are compared to trace the physical attack. And the chemical erosion was conducted by comparing specimens which have been suffered long-term immersion in saturated sodium sulfate solution and saturated limestone solution. In the investigation, the non-destructive detecting indexes, such as the ultrasonic velocity, and the dynamic modulus of elasticity were measured. The permeability, the porosity and mechanical strength at 28-day age were measured. The flexural/compressive strength was measured after 90 wet-dry cycles. And then all the specimens were cut into cubes to take the measure of compressive strength. Based on the experiments, feasibility of various parameters, such permeability, relative dynamic modulus of elasticity, ultrasonic velocity and relative flexural/compressive strength, were investigated to evaluate the concrete deterioration. The results indicate that there is a close relationship between the deterioration by sulfate attack and concrete permeability, so the reduction of permeability is effective in promoting the resistance. The index of the resistance expressed by the dynamic modulus of elasticity ratio is comparable to that expressed by the relative flexural strength. A novel method was suggested in evaluating concrete by sulfate attack, namely, combined with some mechanical tests, the parameter of relative dynamic modulus of elasticity can be used to evaluate the deterioration; the permeability denoted as the amount of transporting charges within 6 hours can be used to evaluate the properties to sulfate attack.

Sodium sulfate heptahydrate: a synchrotron energy-dispersive diffraction study of an elusive metastable hydrated salt

We describe an unusual application of synchrotron energy-dispersive diffraction with hard X-rays to obtain structural information on metastable sodium sulfate heptahydrate. This hydrate was often mentioned in nineteenth and early twentieth century scientific literature but rarely in modern publications, and it had not been characterised structurally. Using a unique three-detector fixed-angle X-ray geometry, a good quality powder diffraction pattern was obtained directly from a stirred suspension of hydrate crystals in saturated aqueous sodium sulfate solution at about 14 °C. The suspension of crystals was contained in the 22 mm dia sealed cylindrical bottle in which crystallization occurred. Indexing showed that the heptahydrate has a tetragonal unit cell with a = 7.1668 A and c = 22.2120 A with a few weak unindexed reflections arising from the 2a supercell. New gravimetric data and the cell dimensions confirm the heptahydrate composition originally proposed by Loewel (Ann. Chim. Phys., 1850, 29, 62–127).

Structural Transformation of Sago Starch by Heat‐Moisture and Osmotic‐Pressure Treatment

AbstractSago starch was modified by osmotic‐pressure treatment (OPT) and heat‐moisture treatment (HMT) and physicochemical characteristics were compared. In OPT, sago starch was suspended in saturated sodium sulfate solution and heated for 1 h at 100, 110 and 120°C, corresponding to a calculated osmotic pressure of 32,728, 33,640 and 34,552 kPa (assuming sodium sulfate dissociates completely), respectively, and in HMT, sago starch with 20% moisture content was used. Change of X‐ray diffraction pattern from C‐type to A‐type was obtained for OPT and HMT starch at 110°C and 120 °C, respectively. RVA viscograms of both OPT and HMT starch exhibited a decrease of peak and breakdown viscosity but increase of final viscosity and pasting temperature. Onset (To), peak (Tp), and conclusion temperature (Tc) of gelatinization of both OPT and HMT starch increased significantly with increase of treatment temperature. Biphasic broadening of Tp was observed for HMT starch indicating an inhomogeneous heat transfer during HMT. The observed narrow peaks of DSC curves indicated better homogeneity of OPT. These properties suggest that OPT starch is more suitable for large‐scale production.

Nonuniform Reaction Rates during CO and CO/H2 Oxidation on Coupled Pt Electrodes

The electro-catalytic oxidation of CO and CO/H2 mixtures on polycrystalline Pt has been investigated on two electrodes with controllable degrees of coupling strength by means of experiments and numerical simulations. With strong positive coupling, large differences between the currents of the two almost-identical electrodes arise in a range of potential. Experiments on CO oxidation were carried out in three different electrolytes; all three electrolytes support pattern formation to an extent in the following order: 0.05 mol/L sulfuric acid with saturated sodium sulfate > 0.05 mol/L sulfuric acid > 0.1 mol/L perchloric acid. Experiments with 2% CO/H2 mixtures also exhibit nonuniform states with coupling. Numerical simulations on CO electro-oxidation confirmed the experimental findings: the current differences occur due to a symmetry breaking both with identical electrodes (through a pitchfork bifurcation) and with electrodes with inherent heterogeneities (due to a formation of an isola). The nonuniform r...