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As a noteworthy salt hydrate, sodium sulfate decahydrate or Glauber salt can be used as a phase change thermal energy storage material. Kinetic parameters of sodium sulfate decahydrate salt solution are evaluated experimentally. Instead of the traditional polythermal and isothermal methods, a novel constant temperature experimental method (based on the turbidity titration) was adopted to experimentally illustrate the induction time and metastable zone width, in unseeded batch crystallization for sodium sulfate decahydrate salt solution at different temperatures (7, 9, 10, 13, 16, 19, 22 °C) and supersaturation ratio (1.01–1.43). We determined crystallization thermodynamics parameters, solubility, and supersolubility, of sodium sulfate decahydrate salt solution under atmospheric pressure and at different temperatures. The solubility data could be well fitted by the solubility carve of sodium sulfate decahydrate in the phase diagram of sodium sulfate. Statistical analysis shows that there was consistency in the result data of solubility. Two models, classical nucleation theory (primary homogeneous) and secondary nucleation, were employed to analyze the experimental data. The secondary nucleation model helped determine the order of nucleation and nucleation kinetic constants.

In this article, the extraction behavior of halogen-free ionic liquid, 1-butyl-3-methylimidazolium octyl sulfate, was investigated in the separation of lead from the aqueous solution. Experimental parameters include time, impact of pH, feed concentration, amount of ionic liquid, ionic strength, and temperature were optimized for the evaluation of the lead extraction. From the optimum conditions, it was emanated that the maximum extraction efficiency of lead was 97% with the feed concentration of 10 ppm in an equilibrium time of 60 min at the pH of 5 and 2 g of the ionic liquid, respectively. Furthermore, the extraction results revealed that the higher efficiency was achieved without the addition of salt and that the extraction process was spontaneous and endothermic in nature. The metal complexation was formed by the exchange of ionic liquid anion to the aqueous phase, and thereby, the extraction mechanism was proposed. The ionic liquid in the organic phase was stripped using sodium sulfate as a stripping agent. FTIR analysis confirmed the recoverable ionic liquid and effectively reused it five times in the course of extraction. From the analysis, it was authenticated that the ionic liquid, 1-butyl-3-methylimidazolium octyl sulfate, was an effective extractant for the elimination of lead (II) and could be employed for the tertiary treatment of industrial wastes.

An extraction system based on polyethylene glycol 1500 and sodium sulfate for extracting lactic acid from aqueous solutions is proposed. The influence of the extraction time, the initial concentration of lactic acid, the molecular weight of the polymer, and the content of the polymer and sodium sulfate in the system on the extraction of lactic acid is investigated. Based on the experimental data, the possibility of isolating lactic acid from fermentation solutions using the proposed environmentally friendly extraction system is shown.

At present, the crystal size of sodium chloride prepared by a traditional crystallization process (such as stirred crystallization) is inhomogeneous, and it has a great quantity of fine grains in crystallizer. This work presents a novel approach for the growth of sodium chloride from supersaturated solutions by reaction-extractive crystallization in a spray fluidized bed crystallizer (SFBC), in which sodium sulfate solution is transformed into potassium chloride and sulphuric acid based on a reactive extraction-crystallization process using triisooctylamine (TOL) in n-octanol as the extraction system. This paper mainly studies the effect of operating conditions (e.g., circulation flow rate, velocity ratio of oil and aqueous phases, crystallization temperature, hydraulic residence time, and feed velocity) on the crystal size distribution (CSD) during the crystallization process of sodium chloride in a SFBC. Experimental results show that the optimum conditions are 1.0362 m/s as the best circulation flow rate, 9.5 : 8.5 as the best velocity ratio of oil and aqueous phases, 313 K as the best temperature, 4320 s as residence time, and 8 mL.min−1 as the best feed velocity. Meanwhile, the proposed extraction kinetic model about extraction rates is developed and validated against data from the SFBC. And it proves that the reactive extraction system is controlled by diffusion and chemical reaction. Analysis of the extraction kinetic model and comparison with experiments reveal that the extraction kinetic model results are in well agreement with experiments. Furthermore, the uniform and large crystals can be obtained in a spray fluidized bed crystallizer without special concentration since extraction and crystallization are carried out in the same equipment. In addition, all of the sodium chloride products prepared under the optimal conditions in SFBC show a better CSD performance than the stirred crystallization. This research demonstrates that this process enables controlling the crystal size in a rather wide range, thus further underlining the potential of this technique for applications in the crystallization industry.

The complexation of styryl dyes 4-[(E)-2-(3,4-dimethoxyphenyl)]-1-ethylpyridinium perchlorate and trans-4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide with cucurbit[n]urils (CBn) (n = 6, 7) in aqueous solutions in the presence of sodium sulfate with a concentration of 0 to 1 mol/L has been studied by stationary and time-resolved optical spectroscopy, electrochemical, and quantum chemical methods. Adding the electrolyte to the solution decomposes 1 : 1 inclusion complexes with the dyes (D+ · CBn) due to competitive formation of complexes of the cavitand with sodium cations: Na+ · CBn and Na+ · CBn · Na+. Their total formation constants have been determined to be β = 2760 and 168 600 M−2 for CB7 and CB6, respectively, which agrees with the results of quantum chemical calculations. At the same time, no evidence of the presence of Na+ · CBn · D+ type complexes has been found in solutions.

Electrochemical removal of synthesis solution containing 50 mg/L auramine-O through Ti/PbO2 electrodes and carbon felt air-diffusion electrode to in situ generate hydrogen peroxide (H2O2) by the oxygen (O2) reduction. The effects of operating conditions, FeSO4·7H2O concentrations, current density, initial concentration, initial pH value and sodium sulfate (Na2SO4) concentration were investigated. For reaction of 60 min, the auramine-O removal rate reached 99% and total organic carbon (TOC) removal rate was close to 64.27%. This means that the organic macromolecules in the pollutants have been completely destroyed and broken down. The degradation of auramine-O under electro-Fenton (EF) process using Ti/PbO2-carbon felt was analyzed from the dimensions of TOC, mineralization current efficiency, energy consumption, degradation mechanism and kinetics. Comparing EF-Ti/PbO2 with Ti/PbO2 anode, AO (anodic oxidation)-Ti/PbO2 anodic oxidation using Ti/PbO2 anode and EF-Pt EF process with Pt anode, the consequences demonstrated that Ti/PbO2-EF process by hydrogen peroxide produced in situ was the best choice than others.

The sorption isotherms of anionic surfactants (AS) from the aqueous solution on eight polar and nonpolar sorbents were obtained. The equilibrium characteristics of sorption were determined. The SV-50 activated carbon is recommended for the effective recovery of AS based on the values of maximum adsorption and concentration equilibrium constants. It has been established that, when the content of AS is much higher than the maximum permissible concentrations, adsorption proceeds via a monomolecular mechanism, and the onset of multilayer formation corresponds to half of the critical micelle concentration. A sorbent layer consisting of activated carbon SV-50 and ion exchange fiber FIBAN AK-22-1 is proposed for the concentration of AS from aqueous solutions. 0.1 M Solution of sodium sulfate is selected as a solution for elution. The concentration was carried out using sodium dodecyl sulfate as an example. An elution curve was obtained, and the characteristics of the concentration were calculated for AS. The proposed sorption extraction allows to reduce the detection limit of AS for the determination by ion-selective electrodes.

The salting-out ability of sodium sulfate, chloride, and nitrate with respect to mixtures of alkylbenzyldimethylammonium chloride (catamine AB) and ethoxylated nonylphenol (neonol AF 9-12) from aqueous solutions and extraction of metal ions with a 3 : 1 mixture of catamine AB and neonol AF 9-12 in the presence of the sodium nitrate used as salting-out agent were studied. The salting-out and extracting properties of surfactant mixtures are determined by the component that is present in a larger amount.

The output voltage directly determines the energy density of supercapacitors (SCs), and it is closely associated with the type of electrolyte. Here we demonstrate the great feasibility of using a pH-regulation strategy in neutral sodium sulfate electrolyte to widen the voltage window (0–1.3 V) and to achieve an additional redox capacity (234% increase) for sodium-embedded manganese oxide/nitrogen-doped graphene (denoted NMO–NDs@NG) electrode at the same time. The mechanism of the strategy was systematically explored by various in situ and ex situ characterizations, as well as density functional theory calculations. The NMO–NDs@NG showed a surface-controlled pseudocapacitive behavior in the neutral electrolyte, but mainly displayed a battery-like behavior in the alkaline electrolyte. Upon increasing the pH value of the initial neutral electrolyte, the emerging reversible redox reaction effectively inhibited water decomposition occurring on the electrode surface, thereby expanding the voltage window as well as increasing the capacity. Based on this, an aqueous hybrid SC was assembled, which was able to work at 2.7 V and presented a maximum energy density of 68 W h kg−1 and a maximum power density of 27 kW kg−1. The results presented here provide a useful strategy for achieving high-voltage and high-capacity aqueous SCs.

An environmentally friendly aqueous two-phase system based on polyethylene glycol and sodium sulfate has been proposed for the extraction of caffeine and coumarin. The kinetic dependence of distribution coefficients for caffeine and coumarin in the system under investigation has been obtained. The dependences of the quantitative characteristics of caffeine and coumarin extraction on the acidity of the medium, the concentrations of the polymer and phase-forming salt, temperature, and the molecular weight of the polymer have been found. The results of this study can be used in the development of effective chemical processes that meet green chemistry requirements.

In this work, the electrodeposition of lead dioxide on a Pb electrode was realized by a potentiostatic method in 0.5 mol/L sulfuric acid solution at 1.3 V (ECS) during 30 min. The result of XRD showed that the crystal structure of PbO2 in acid solution is pure β-PbO2. The electrodegradation of tris (4-(dimethylamino) phenyl) methylium chloride (methyl violet 10B) dye in an aqueous solution of 0.1 mol/L sodium sulfate has been studied by potentiostatic method using β-PbO2 as anode. The methyl violet 10B was successfully oxidized by hydroxyl radicals electrogenerated from oxidation of water on the Pb/β-PbO2 electrode surface. The anodic oxidation of methyl violet 10B followed the pseudo-first order kinetics. The time and applied potential had significant effect on the electrochemical degradation of methyl violet 10B at the Pb/β-PbO2 electrode with a degradation rate of 10.5 g/(m2 day).

The prospects of the electroflotation method for selective separation of rare-earth metal ions (Ce4+ and La3+) from aqueous solutions in a flow-type plant are described. The separation process proceeds most effectively in sodium sulfate and sodium nitrate solutions at pH value of 5.0. The separation factor of metals is higher than 18. Separation efficiency drops sharply in the presence of cationic surfactant DDAC. The separation does not take place and a mixture of two metals is extracted at pH 10.

An aqueous two-phase system based on polyethylene glycol-1500 and sodium sulfate for the extraction of a number of monocarboxylic acids from aqueous solutions has been studied. The influence of the phase contact time, system composition, the molecular weight of the polymer, and temperature on the quantitative characteristics of the interphase distribution of a number of aliphatic monocarboxylic acids has been investigated. Based on the results, it is concluded that these systems are effective for solving problems of the extraction, separation, and purification of carboxylic acids and they are promising as extraction systems for the extraction of metal salts in the presence of carboxylic acids.

Activated carbon Norit Supra DLS 30 and carbon fabrics L-03 and T-040 were studied as electrode materials for supercapacitors with aqueous sodium sulfate. The use of the T-040 fabric led to higher specific capacity than in the case of carbon tape L-03. The decrease in the capacity when cycling the capacitors with electrode materials of both fabrics was almost the same. The introduction of benzotriazole in the electrolyte or electrode material increased the operating voltage and specific characteristics of the supercapacitor.

An electrode made of loofah sponge derived activated carbon supported on nickel foam (AC/Ni) was successfully fabricated and used to remove ammonium ion (NH4+) from aqueous solution. A multilayer adsorption isotherm was used to describe ammonium electro-sorption on AC/Ni electrodes at different temperature, initial NH4+ concentration, and electrical field. The cyclic voltammetry (CV) results suggested that the electrical capacitance of AC/Ni electrodes, with the AC being prepared without preheating (OAC) or with low temperature heating (i.e., 300 AC), were higher than those prepared at high preheating temperature (i.e., 400 AC and 500 AC). Increasing the electro-sorption temperature from 10 to 50 °C decreased the monolayer NH4+ adsorption capacity from 5 to ca. 2–3 mg-N g−1, respectively. Background electrolyte, namely, sodium sulfate, exhibited significant competitive effect on the adsorption of ammonium ion at sodium ion concentration > 10−2 M. The activation energy and heat of adsorption were 9–23.2 kJ mol−1 and −3.7–−10.7 kJ mol−1, respectively, indicating a physisorption and exothermic adsorption characteristics. Based on the kinetics and thermodynamics analysis, there was slight increase in the activation energy with elevating preheating temperature, which increased the quantity of micro-pores and surface heterogeneity of the AC materials. Overall, results clearly demonstrated that carbon pyrolysis played a role on the capacitive charging behaviors of electrodes and the efficiency of NH4+ electro-sorption on the AC/Ni electrodes.

Aqueous two-phase systems (ATPSs) have been recognized as potential alternative techniques for extraction or purification of biomolecules. In this work, partitioning behavior of cefazolin has been investigated in polymer-salt ATPSs. Thus, systems containing polyethylene glycol (PEG) with two different molecular weights (6000 and 8000) and three forms of sodium salts, including sodium citrate, sodium tartrate, and sodium sulfate were examined. Firstly, the binodal curves were determined at 300 K and then correlated with Merchuk equation. Results indicate that the system PEG8000/sulfate owns a wider two-phase area. Then, the tie-lines were plotted for the systems under study, and their validity was evaluated using the Othmer-Tobias and Bancroft equations. Finally, the partition coefficient of cefazolin was investigated in 6 different two-phase systems and 28 tie-lines overall. Effect of salt type, polymer molecular weight and its concentration on partition coefficient were discussed. On the basis of the results it can be declared that as the polymer concentration increases, the partition coefficient increases but the increase of polymer molecular weight leads to partition coefficient reduction. Sodium citrate was better than the other salts used for studying the cefazolin partitioning, that is in good accordance with the excluded volume theory. The maximum amount of partition coefficient equals to 13.4 with a 90.5 recovery percentage in the top phase which belongs to the system combined of PEG6000 (16% w/w) and sodium citrate (14% w/w).

In this study, the formation of particles and evolution of the particle size distribution in the micron range were monitored in situ during acid precipitation of kraft lignin. The objective of this work was to study the influence of anionic specificity and the ion concentration level. The concentrations of ions in the solution were altered both in terms of the concentration of Na+ and the type of anion in the salt added ( SO 4 2 − ${\rm{SO}}_4^{2 - }$ and Cl−). The results indicate that a salting-out phenomenon occurred as NaCl was added (Na+ ≥2 mol kg−1 water) to the kraft lignin solution at high pH, but not when Na2SO4 was added. However, the onset pH of the formation of particles (≥1 μm), triggered by acidification, showed to be virtually non-specific to the anion but strongly dependent on the Na+ concentration. As the pH decreased further to below the onset pH of the formation of particles ≥1 μm, the chord length distributions (particle-size related) indicated that most of the volume of the precipitated kraft lignin (and thus possibly also the mass) may be found among the micron-sized particles, despite the fact that a relatively large number of submicron particles may also be present. The volume-based distributions tended to be wide at relatively low pH and high Na+ concentrations (e.g. pH 9.4 and 2.0 mol kg−1 water).

Water-in-water (w/w) emulsions are particularly advantageous for biomedical-related applications, such as cell encapsulation, bioreactors, biocompatible storage, and processing of biomacromolecules. However, due to ultralow interfacial tension, generation and stabilization of uniform w/w droplets are challenging. In this work, we report a strategy of creating stable and size-controllable w/w droplets that can quickly form polyelectrolyte microcapsules (PEMCs) in a microfluidic device. A three-phase (inner, middle, outer) aqueous system was applied to create a stream of inner phase, which could be broken into droplets via a mechanical perturbation frequency, with size determined by the stream diameter and vibration frequency. The interfacial complexation is formed via electrostatic interaction of polycations of poly(diallyldimethylammoniumchloride) with polyanions of polystyrene sodium sulfate in the inner and outer phases. With addition of negatively charged silica nanoparticles, the stability, permeability, and mechanical strength of the PEMC shell could be well manipulated. Prepared PEMCs were verified by encapsulating fluorescein isothiocyanate-labeled dextran molecules and stimuli-triggered release by varying the pH value or osmotic pressure. A model enzyme, trypsin, was successfully encapsulated into PEMCs and released without impairing their catalytic activity. These results highlight its potential applications for efficient encapsulation, storage, delivery, and release of chemical, biological, pharmaceutical, and therapeutic agents.

Solubilities and physicochemical properties (density and refractive index) for the ternary system (Na+//SO42–, BO2–-H2O) at (288.15 and 308.15) K and 101.325 kPa were studied by the isothermal diss...

A thermodynamic model has been developed for calculating the phase behavior and caloric properties of rare earth elements in multicomponent sulfate solutions over wide ranges of temperature (up to 300 °C) at concentrations extending to solid–liquid saturation. The model has been constructed using the previously developed Mixed-Solvent Electrolyte (MSE) framework, which combines the standard-state thermochemical properties of aqueous and solid species with an ion-interaction formulation for the excess Gibbs energy. The model accurately reproduces the properties of binary aqueous rare earth sulfate solutions and multicomponent systems that include sulfuric acid and/or sodium sulfate. Solid-liquid phase diagrams have been constructed to elucidate the solubility of both stable and metastable solid phases. Regularities in the solubility behavior have been identified as a function of the cation radius for rare earth sulfates and double sodium-rare earth sulfate salts. The solubility of rare earth sulfates at ambient conditions shows an s-shape pattern with a local maximum at Pr, followed by a plateau between Sm and Tb and then an increase starting from Tb. On the other hand, the double salts REE2Na2(SO4)4 show a solubility minimum at Pr, followed by a strong increase in solubility for heavier rare earths. For the double sulfate salts for which no experimental data are available, solubilities have been estimated using an analysis of trends in thermochemical properties across the lanthanide series. The model is part of a systematic effort to develop a comprehensive treatment of the properties of rare earth salt solutions to facilitate the design and optimization of processes for the recovery of rare earth elements.

In this study, we selected the stainless-steel mesh as the electrode material, supplemented with conventional power ultrasound in the electrochemical degradation of the chlorpyrifos effluent. The effect of different operating conditions, such as voltage, initial electrolyte concentration, temperature and ultrasonic power were investigated with synthetic effluent to gain the most efficient degradation rate. The best reaction parameters were: voltage of 20 V, electrolyte concentration of 2 mg L−1, ultrasonic power of 200 W, as well as 20 °C, which led to 93.3% and 72.8% of degradation in US-EC and EC system. Applying higher concentrations of electrolyte (sodium sulfate) and higher voltages, the chlorpyrifos solution can be more efficiently degraded with a high synergy of 37%. The degradation of chlorpyrifos followed pseudo-first-order kinetics.

Aqueous two-phase partitioning system (ATPS) was used to extract and purify catalase from Bacillus pumilus. The system parameters for effective purification of catalase were optimized. The best catalase recovery (123%) with a 4.6-fold purification was obtained in the bottom phase of ATPS including the mixture of 15% (w/w) PEG4000, 10% (w/w) Na

Novel two-component gel systems based on aliphatic acid–hydroxy/base interaction were developed as smart materials for environmental remediation. The G1-A16 gelator could be used directly as a powder form to selectively gel aromatic solvents (nitrobenzene and o-dichlorobenzene) from their mixtures with wastewater (containing 0.5 M sodium nitrate and 0.5 M sodium sulfate) via a simple shaking strategy at room temperature without employing co-solvents and a heating–cooling process. Meanwhile, the two-component gel system can efficiently remove the toxic dyes from the aqueous solution. The dominant factors that drive gelation in the case of the gelator and nitrobenzene or water have been studied using FT-IR, 1H NMR, and XRD. Overall, our research provides an efficient two-component approach for facilely tuning the properties of one-component gel for the realization of high-performance functionalities of gels. At the same time, our study demonstrates potential industrial application prospect in removing pollutants efficiently (such as aromatic solvents and toxic dye removal). Electronic supplementary material The online version of this article (10.1186/s11671-019-2865-6) contains supplementary material, which is available to authorized users.

Recently, the development of safe, stable, and long-life supercapacitors has attracted considerable interest driven by the fast-growth of flexible wearable devices. Herein, we report an MnO2-based symmetric all-solid-state supercapacitor, using a neutral gum electrolyte that was prepared by embedding aqueous sodium sulfate solution in a biopolymer xanthan gum. Resulting from the high ion conductivity 1.12 S m−1, good water retention, and high structure adaption of such gum electrolyte, the presently described supercapacitor showed high electrochemical performance with a specific capacitance of 347 F g−1 at 1 A g−1 and an energy density of 24 μW h cm−2 The flexible supercapacitor possesses excellent reliability and achieves a retaining capacitance of 82% after 5000 cycles. In addition, the as-prepared supercapacitor demonstrated outstanding electrochemical stability at temperatures between −15 °C to 100 °C.

Supplementary material related to this article can be found, inthe online version, at doi:https://doi.org/10.1016/j.chroma.2018.11.015., Effects of two salt additives, NaCl and NaClO4, at the fixed concentrations of 0.215?M on the properties of aqueous two-phase systems (ATPSs) formed by dextran (Dex) and polyethylene glycol (PEG), and the effects of NaClO4 at the same concentration on the properties of ATPS formed by PEG and Na2SO4 were examined. The effects of these salt additives on partitioning of 12 small organic compounds and five proteins in the above ATPSs were studied. In each system with a given salt additive, 0.5?M sorbitol, 0.5?M sucrose, and 0.5?M and 1.5?M trimethylamine N-oxide (TMAO) were also used as additives. The results obtained were compared with those reported previously for the Dex-PEG ATPS without salt additives and PEG-Na2SO4 ATPS without salt additives and in the presence of 0.215?M NaCl. It is shown that the differences between the solvent properties of the phases in the systems formed by polymer and salt exceed those observed in the systems formed by two polymers. The three most significant solvent features of the systems are hydrophobic and electrostatic properties and hydrogen bonding donor acidity of the solvent media. Osmolyte additives were found to have a significant effect on the differences between the electrostatic properties of the phases. Analysis of the partition coefficients of 12 organic compounds and five proteins showed that the osmolyte additives may affect the partition behavior of compounds in a compound-specific manner. The relative contributions of different types of interactions of a given compound with aqueous media change in the presence of salt and osmolyte additives. Analysis of the variability ranges of partition coefficient, K, in the systems studied showed that for small organic compounds, the ranges of K-values observed in the PEG-Na2SO4 ATPSs exceed those determined in the Dex-PEG ATPSs quite significantly, whereas for proteins, the range of K-values in Dex-PEG ATPSs exceeded those in PEG-Na2SO4 ATPSs for three proteins, and were very similar for two proteins. This observation supported the notion that the ATPSs formed by two polymers are more suitable for protein analysis than those formed by a single polymer and a salt. The single polymer-salt ATPSs have an advantage for protein isolation/separation., Nuno R. da Silva acknowledges the financial support byFundac¸ ão para a Ciência e Tecnologia (FCT) of the Portuguese’s Min-istry for Science, Technology and Higher Education (MCTES), in theframework of the POCH – Programa Operacional Capital Humano,co-funded by the European Social Fund (SFRH/BD/111825/2015).This work was also supported by FCT under the scope ofthe strategic funding of UID/BIO/04469 unit and COMPETE2020 (POCI-01-0145-FEDER-006684) and BioTecNorte opera-tion (NORTE-01-0145-FEDER-000004) funded by the EuropeanRegional Development Fund under the scope of Norte2020 – Pro-grama Operacional Regional do Norte., info:eu-repo/semantics/publishedVersion

The self-organization processes in aqueous solution of polyvinyl alcohol (PVA), L-cysteine, and silver nitrate treated with sodium sulfate were studied by a complex of methods (viscometry, UV and IR spectroscopy, pH measurements, and dynamic light scattering). It was shown that PVA macromolecules interact with [—Ag−S(R)—Ag−S(R)—]n supramolecular chains based on cysteine and silver (where R is the cysteine residue) by the formation of hydrogen bonds. The increase in PVA concentration leads to the increase in viscosity of the obtained hydrogels; the thixotropic properties become more pronounced; the intensity of the main absorption bands of the UV spectrum corresponding to the formation of supramolecular structures becomes higher; the pH increases; the average hydrodynamic sizes of particles increase; the electrical conductivity of the system decreases. Scanning electron microscopy showed the formation of a regular macroporous structure of dried hydrogels. It was established that both the density of the spatial network and the porosity of dried hydrogel can be controlled by changing the PVA concentration in solution. A superporous structure of dried hydrogel was observed at high PVA concentration (2%) in solution.

The article investigates kinetics of electrocatalytic oxidation of phenol in the solution of sodium sulfate on a platinum electrode in the presence of dispersed oxides of metals of varied valence. It is shown that the degree of phenol oxidation in the presence of oxides increase by 10–15%. The most active catalysts include oxides of cobalt, chromium, copper and titanium, whose catalytic activity diminishes in the series Co3O4 > Cr2O3 > Cr2O3 > TiO2 > CuO; the rate of electrooxidation of phenol increases at a decrease of anolyte. It was shown that a limiting stage of electrochemical oxidation of phenol in aqueous solutions with the concentration 50 mg/dm3 is a diffusion of the substance to the electrode.

The present study aims at the generation of a triblock copolymer vs sodium sulfate aqueous biphasic system (ABS), its application toward extraction of molybdenum species, and finally purification and regeneration of the block copolymer. The ABS was characterized for its biphasic region by constructing the phase diagram using turbidometric titration methods. Extractions were monitored using the spectrophotometric method directly in the block copolymer medium. Complete extraction of molybdenum species was observed in this method. Interference from other closely related metal ions in the extraction process was found to be negligible excepting oxo and polyoxometallates of vanadium and tungsten. Regeneration of the polymer was done using a thermoseparation technique followed by successive treatment with ion exchange resins. ∼87% of the pure triblock copolymer could be regenerated as a result of such treatment.

This work presents a study about synthesis of polypyrrole films electrochemically doped with iodine by luminescent discharge plasma in aqueous sodium sulfate solution, and its structural, morphological and electrical characterization. The synthesis is carried out at atmospheric pressure with square pulse from -1.06 to 1.16 V for 120 minutes. Doping times of the films are 10, 30 and 50 minutes. The films have thicknesses of 6, 12.7, 20.32 and 25.4 μm, and linear growth trend according to the time exposure of their synthesis. The main chemical groups exhibited in the films are C-H, N-H and CH2I, which are characteristics of film doped with Iodine. The electrical conductivity calculated of polypyrrole films is in the range 10-5-10-3 S/cm, and its activation energy is between 0.052 and 1.77 eV.

Polyaniline/TiO2 nanotube arrays composite electrodes were achieved by depositing polyaniline onto TiO2 nanotube arrays through cyclic voltammetry method. Neutral sodium sulfate aqueous solution was used as a testing electrolyte and the effects of monomer solvent on the electrode performance were studied. Results show that the sample prepared in ethanol solution has much better capacitance performance than that in acetone or aqueous solutions. The potential window of the electrode could be enlarged to 2 V (−0.2–1.8 V) and the highest energy density of the active material reached 727.3 J/g. The composite electrode also has excellent rate and cycling performance.

A novel hydrate form of sodium dodecyl sulfate (SDS) was firstly discovered through a hydrate screening with the use of organic solvents, while SDS is generally prepared solely in aqueous media. Surprisingly, a novel SDS hydrate form with needle-shaped crystals produced by adding acetonitrile to a 20 wt % SDS aqueous solution at a ratio of 3:1 (v/v) and further cooling to around 5 °C could be found with a trace amount in one of the two purchased SDS products that we examined. After comprehensive solid-state characterizations by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), Raman spectroscopy, dynamic vapor sorption (DVS), and elemental analysis (EA), it is also successfully made directly from the synthesis of SDS through esterification and saponification. Four times the equal proportion of acetone was added into the reaction solution at an interval of 5 min to separate the side product, sodium sulfate, from the mother liquor. The desired novel hydrate form of SDS was then obtained by cooling the filtered mother liquor to 5 °C and aged for 8 h for a preferential growth.

Made available in DSpace on 2021-06-25T10:15:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-02-15 The green fluorescent protein (GFP) is a biomolecule used in many biological applications such as biomarkers and biosensors, which require high purity levels. It is usually obtained from recombinant Escherichia coli strains, which also produces other endogenous proteins, demanding multiple purification steps, and consequently, increasing the overall costs to obtain pure GFP. Simpler and cheaper purification methods like Aqueous Biphasic Systems (ABS) were already successfully applied to purify GFP at lab scale. Therefore, the development of automatized industrially compatible purification platforms, such as countercurrent chromatography using ABS, can potentially improve the GFP production. This work studied the continuous purification of the variant enhanced GFP (EGFP) by applying ABS composed of polyethylene glycol (PEG 8000), sodium polyacrylate (NaPA 8000) and sodium sulfate (Na2SO4) as electrolyte. An initial screening was carried by changing the electrolyte content in the ABS. The increase of this condition has demonstrated an increase on the EGFP partition for the PEG-rich phase. The most efficient ABS and, at the same time, with the most appropriate conditions, namely the system composed of 15 wt% PEG 8000 + 4.5 wt% NaPA 8000 + 2.5 wt% Na2SO4 was chosen and applied on the fast centrifugal partition chromatography (FCPC). After optimization, the best operational conditions were identified, i.e. a flow rate of 2.5 mL.min−1 and rotation speed of 2000 rpm at ascending mode, and the best results obtained, meaning a purification of 89.93% and a recovery yield of 82.3%, confirming the potential of FCPC to the continuous purification of EGFP. CICECO – Aveiro Institute of Materials Department of Chemistry University of Aveiro Department of Biochemical and Pharmaceutical Technology University of São Paulo Department of Bioprocesses and Biotechnology School of Pharmaceutical Sciences São Paulo State University (UNESP) Univ Coimbra CIEPQPF Department of Chemical Engineering, Rua Sílvio Lima, Pólo II – Pinhal de Marrocos Department of Bioprocesses and Biotechnology School of Pharmaceutical Sciences São Paulo State University (UNESP)

Now when the interest is increasing to reach a sustainable infrastructure, one possibility SCA is experimenting with is the possibility to produce renewable hydrocarbons from black liquor which can be extracted from a Kraft process. However, when extracting the black liquor, a lot of sodium-based compounds are removed from the recovery process and when hydrocarbons are produced in SCA’s biorefinery, these compounds are caught in an aqueous solution. The aqueous solution is received at 50°C, and the sodium-based compounds are mainly sodium sulfate and sodium carbonate, where the solution do also contain organic compounds and a solvent that is used in the biorefinery. This thesis focused on building a concept to extract sodium sulfate from the aqueous solution. The thesis did also include if any additional preparatory work needs to be done to the solution before extracting sodium sulfate. Finally, a flow chart that maps the energy needed for the process was created. The method that was used was crystallisation by cooling the solution. By cooling the solution, sodium sulfates solubility decreases which will result in that sodium sulfate falls out of the solution as crystals. It was determined that the solvent that the solution contains should be extracted if the solvents boiling temperature is below 100°C. Further, by cooling the solution under stirring to 15°C with a residence time of 3 hours, unwanted compounds can be extracted. By later cooling the solution under stirring to 5°C with a residence time of 1 hour, it gave sodium sulfate decahydrate (Na2SO4·10H2O) with small amounts of organic compounds. By removing the water, the dry product reached a purity of 94wt% sodium sulfate with a yield of 12% (mass of dry product/mass of aqueous solution). This result reached the specific objectives that were set at the start of this thesis, which was to reach a purity of 90wt% sodium sulfate with a yield of 5%. The energy intensity for evaporating the solvent is expected to be high. It highly depends on which solvent is used. However, this process can use the lowest quality of steam that is available from the pulp mill. It is expected that the cooling will require high amounts of cooling water and a high investment cost for the heat exchanger. Yet, this is a vital part of the process to reduce the need for coolers which is powered by electricity. Nu när intresset ökar, för att nå en hållbar infrastruktur, så experimenterat SCA med möjligheten att producera förnybara kolväten från svartlut som kan extraheras från en sulfatprocess. Vid extrahering av svartluten tas dock mycket natriumbaserade föreningar bort från återvinningsprocessen och när kolväten produceras i SCA:s bioraffinaderi fastnar dessa föreningar i en vattenlösning. Den lösningen tas emot vid 50°C och de natriumbaserade föreningarna är huvudsakligen natriumsulfat och natriumkarbonat, där lösningen också innehåller organiska föreningar och ett lösningsmedel som används i bioraffinaderiet. Denna avhandling fokuserade på att bygga ett koncept för att extrahera natriumsulfat från vattenlösningen. Avhandlingen omfattade också om ytterligare förberedande arbete måste göras av lösningen innan man extraherar natriumsulfat. Slutligen skapades ett flödesschema som kartlägger den energi som behövs för processen. Metoden som bestämde sig för att användas var kristallisering genom kylning av lösningen. Genom att kyla lösningen minskar lösligheten av natriumsulfater vilket leder till att natriumsulfat faller ut ur lösningen som kristaller. Det bestämdes att lösningsmedlet som lösningen innehåller skulle extraheras om lösningsmedlets koktemperatur är under 100°C. Vidare, genom att kyla lösningen under omrörning till 15°C med en uppehållstid på 3 timmar, kan oönskade ämnen extraheras. Genom att senare kyla lösningen under omrörning till 5°C med en uppehållstid på 1 timme gav natriumsulfatdekahydrat (Na2SO4·10H2O) med små mängder organiska föreningar. Genom att avlägsna vattnet nådde den torra produkten en renhet av 94 vikt% natriumsulfat med ett utbyte av 12% (massa torr produkt/massa vattenlösning). Detta resultat nådde de specifika mål som sattes i början av denna avhandling, vilket var att nå en renhet av 90 vikt% natriumsulfat med ett utbyte på 5%. Energiintensiteten för att förånga lösningsmedlet förväntas vara hög. Det beror mycket på vilket lösningsmedel som används. Denna process kan dock använda den lägsta ångkvaliteten som finns tillgänglig från massafabriken. Det förväntas att kylningen kommer att kräva stora mängder kylvatten och höga investeringskostnader för värmeväxlaren. Ändå är detta en viktig del av processen för att minska behovet av kylare som drivs av elektricitet.

Made available in DSpace on 2021-06-25T11:05:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-12-01 Thin films of the metal-organic framework (MOF) Cu(BDC) were electrochemically grown by anodic deposition of the ligand 1,4-benzenedicarboxylate (1,4-BDC) on metallic copper to form Cu/Cu2O-Cu(BDC) electrode. The construction of the electrode was optimized by investigating parameters such as current density, time of anodization, and temperature that directly affect its stability and photoactivity. The best performing electrode was prepared when a current density of 2.5mA cm-2 was applied for 6.5min at 110°C. A methanol concentration of 234μmolL-1 was produced from the photoelectron reduction of CO2 under UV-vis irradiation for 3h, an applied potential of +0.10V, and 0.1mol L-1 aqueous sodium sulfate solution saturated with CO2 as supporting electrolyte. The rate of CO2 reduction to methanol was found to be ∼20 times that obtained using Cu/Cu2O electrode alone presumably due to preconcentration of dissolved CO2 in the MOF. The capture of CO2 in the MOF surface and/or cavities was confirmed by ATR and DRIFT spectroscopy. São Paulo State University (UNESP) Institute of Chemistry, 55 Prof. Francisco Degni St National Institute for Alternative Technologies of Detection Toxicological Evaluation and Removal of Micropollutants and Radioactivies (INCT-DATREM) São Paulo State University (UNESP) Institute of Chemistry Department of Chemistry Wake Forest University São Paulo State University (UNESP) Institute of Chemistry, 55 Prof. Francisco Degni St National Institute for Alternative Technologies of Detection Toxicological Evaluation and Removal of Micropollutants and Radioactivies (INCT-DATREM) São Paulo State University (UNESP) Institute of Chemistry

Reactor plugging induced by salt precipitation in supercritical water (SCW) is a major problem during the hydrothermal treatment of hypersaline waste. Considering that current investigations have focused strictly on pure water systems, a continuous tube reactor was designed herein to study the precipitation of Na2SO4 and Na2CO3 in a complex SCW environment, which was generated using C2H5OH and H2O2 in order to reproduce real SCW conditions. Results indicate that salt precipitation was accelerated in the presence of C2H5OH and H2O2. The passage rate was only 87% for Na2SO4 and 43% for Na2CO3 in an aqueous solution of 0.1 wt% C2H5OH and 0.5 times of H2O2, compared to the solubility of these salts in pure water at 385 °C and 25 MPa. Organics and gases reduce the fluid density and further aggravate salt precipitation. Salt precipitation occurred mainly in the area around gas inlet and mixer in a real SCW process.

Solubility is a fundamental physicochemical property of proteins because of its importance over other protein properties in foods. Water solubility characteristics determine appropriate protein extraction and fractionation conditions in foods. In this study protein solubility of jackfruit seed flour (Artocarpus integrifolia L.) was determined, combined with the effect of pH and sulfate, chloride and trisodium citrate salt concentration variations. Protein solubility was higher in more acidic (pH =2.0) and alkaline (8.0≤ pH ≥10.0) mediums, in the absence of salts. It was also verified that the best solubility conditions under pH 2.0 using trisodium citrate was at 0.25 mol/L; and for pH 6.0, it was 1.0 mol/L. For sodium chloride, the best conditions occurred at 0.25 mol/L for pH 2.0, 6.0 and 10.0; and the best solubility values using sodium sulfate under pH 4.0 and 8.0 was 0.25 mol/L; and 0.50 mol/L under pH 6.0 and 10.0. Jackfruit seeds flour can be used as an alternative source of edible protein and as a substitute for products already available in the market. La solubilidad es una propiedad físico-química fundamental de las proteínas debido a su importancia sobre otras propiedades proteicas en los alimentos. Las características de solubilidad en agua determinan las condiciones adecuadas para la extracción y el fraccionamiento de proteínas en los alimentos. En este estudio, se determinó la solubilidad proteica de la harina de yaca (Artocarpus integrifolia L.) combinando el efecto de las variaciones de pH y las concentraciones de sulfato, cloruro y citrato trisódico. La solubilidad de la proteína fue mayor en medios más ácidos (pH = 2.0) y alcalinos (8.0≤ pH ≥10.0), en ausencia de sales. También se encontró que las mejores condiciones de solubilidad a pH 2.0 con citrato trisódico fueron 0.25 mol/L; y a pH 6.0 fue de 1.0 mol/L. Para el cloruro de sodio, las mejores condiciones ocurrieron a 0.25 mol/L para pH 2.0, 6.0 y 10.0; y los mejores valores de solubilidad usando sulfato de sodio a pH 4.0 y 8.0 fueron 0.25 mol/L; y 0,50 mol/L a pH 6,0 y 10,0. La harina de yaca puede utilizarse como fuente alternativa de proteína comestible y como sustituto de productos ya disponibles en el mercado. A solubilidade é uma propriedade físico-química fundamental das proteínas devido à sua importância sobre outras propriedades proteicas nos alimentos. As características de solubilidade em água determinam as condições adequadas de extração e fracionamento de proteínas nos alimentos. Neste estudo, a solubilidade proteica da farinha do caroço de jaca (Artocarpus integrifolia L.) foi determinada combinando-se o efeito das variações de pH e concentrações de sulfato, cloreto e citrato trissódico. A solubilidade das proteínas foi maior em meios mais ácidos (pH = 2,0) e alcalinos (8,0≤ pH ≥10,0), na ausência de sais. Verificou-se também que as melhores condições de solubilidade em pH 2,0 com citrato trissódico foi 0,25 mol/L; e em pH 6,0 foi 1,0 mol/L. Para o cloreto de sódio, as melhores condições ocorreram em 0,25 mol/L para pH 2,0, 6,0 e 10,0; e os melhores valores de solubilidade usando sulfato de sódio sob pH 4,0 e 8,0 foram 0,25 mol/L; e 0,50 mol/L sob pH 6,0 e 10,0. A farinha do caroço de jaca pode ser utilizada como fonte alternativa de proteína comestível e como substituta de produtos já disponíveis no mercado.

Oxacillin antibiotic was removed from aqueous effluents using the biodegradable nonionic surfactant Triton X-114 (TX-114) and the ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate ([C4C1im]PF6). The experimental results of oxacillin extraction from aqueous solution according to the surfactant (Xt) or ionic liquid (XIL) concentration and temperature (T) were expressed by the following parameters: antibiotic extraction extent (E%), remaining antibiotic concentration (Xs,w), residual surfactant (Xt,w) or ionic liquid (XIL,w) concentration in aqueous phase after extraction, and volume fraction of coacervate at equilibrium (ϕc). High extraction yields were reached under optimal conditions: 99% for TX-114 and 89% using [C4C1im]PF6. The concentration of antibiotic in effluent was reduced by about 7-fold and 6-fold using TX-114 and [C4C1im]PF6, respectively. Sodium sulfate addition (3 wt%) increased E% from 20% to 88% at only 2 wt% of TX-114. Finally, solute stripping from the micellar phase using Winsor II microemulsion extraction was investigated. Thereby, 90% of the TX-114 in the micelle-rich phase was separated into the organic phase (Om).

Binary (Chitosan-Cu(II), CCu) and Ternary (Chitosan-Alginate-Cu(II), CACu) composite materials were synthesized at variable composition: CCu (1:1), CACu1 (1:1:1), CACu2 (1:2:1) and CACu3 (2:1:1). Characterization was carried out via spectroscopic (FTIR, solids C-13 NMR, XPS and Raman), thermal (differential scanning calorimetry (DSC) and TGA), XRD, point of zero charge and solvent swelling techniques. The materials&rsquo, characterization confirmed the successful preparation of the polymer-based composites, along with their variable physico-chemical and adsorption properties. Sulfate anion (sodium sulfate) adsorption from aqueous solution was demonstrated using C and CACu1 at pH 6.8 and 295 K, where the monolayer adsorption capacity (Qm) values were 288.1 and 371.4 mg/g, respectively, where the Sips isotherm model provided the &ldquo, best-fit&rdquo, for the adsorption data. Single-point sorption study on three types of groundwater samples (wells 1, 2 and 3) with variable sulfate concentration and matrix composition in the presence of composite materials reveal that CACu3 exhibited greater uptake of sulfate (Qe = 81.5 mg/g, 11.5% removal) from Well-1 and CACu2 showed the lowest sulfate uptake (Qe of 15.7 mg/g, 0.865% removal) from Well-3. Generally, for all groundwater samples, the binary composite material (CCu) exhibited attenuated sorption and removal efficiency relative to the ternary composite materials (CACu).

The Taylor dispersion technique has been used for measuring the tracer diffusion coefficients, D0Tracer, for poly (vinyl alcohol) (PVA) in aqueous systems containing two specific electrolytes (i.e., NaCl and Na2SO4) at three different concentrations (0.020, 0.050 and 0.10 mol dm−3), and at 25 °C. The selection of these salts has been based on the Hofmeister series of cations and anions, which order the ions with respect to the behavior of some macroscopic properties (such as, surface tension) and that can be interpreted as an effect salting-out or salting-in, depending if the target ions are strongly (kosmotropic) or a weakly hydrated (chaotropic). In this work, we have been used the combination of two kosmotropic ions (Na2SO4) and another one with a kosmotropic cation and a chaotropic anion (NaCl). These data, complemented by NMR measurements, permit us to have a better understanding about the effect of these sodium salts on transport and thermodynamic behaviour of PVA.

The organization of multiple subcellular compartments is controlled by liquid-liquid phase separation. Phase separation of this type occurs with the emergence of interfacial tension. Aqueous two-phase systems formed by two non-ionic polymers can be used to separate and analyze biological macromolecules, cells and viruses. Phase separation in these systems may serve as the simple model of phase separation in cells also occurring in aqueous media. To better understand liquid-liquid phase separation mechanisms, interfacial tension was measured in aqueous two-phase systems formed by dextran and polyethylene glycol and by polyethylene glycol and sodium sulfate in the presence of different additives. Interfacial tension values depend on differences between the solvent properties of the coexisting phases, estimated experimentally by parameters representing dipole-dipole, ion-dipole, ion-ion, and hydrogen bonding interactions. Based on both current and literature data, we propose a mechanism for phase separation in aqueous two-phase systems. This mechanism is based on the fundamental role of intermolecular forces. Although it remains to be confirmed, it is possible that these may underlie all liquid-liquid phase separation processes in biology.

The selective extraction of the hydrophilic sulfate ion from water is highly challenging because the high free energy of hydration of this ion makes it more difficult to extract than less hydrophilic ions such as chloride and nitrate. Lipophilic macrocyclic squaramide receptors 1 and 2 were synthesized. Receptor 2 efficiently extracted sulfate from aqueous sodium sulfate solutions into a chloroform phase, via exchange with nitrate ions, overcoming the Hofmeister bias. The resulting 2$SO4 2� complex was readily recycled through precipitation of BaSO4. Transport of sulfate across a bulk chloroform membrane by 2 was demonstrated across a wide pH range (pH 3.2–9.4) and in the presence of high concentrations of competing anions (chloride, nitrate and dihydrogenphosphate), opening the door to the use of 2 for the selective removal of sulfate from water across a range of applications.

The partial molar volume of lysozyme and bovine serum albumin in aqueous solutions at different pH values and in aqueous solutions containing sodium chloride, ammonium chloride, sodium sulfate, or ammonium sulfate at different concentrations at pH 7.0 was investigated experimentally at 298.15 K and 1 bar. It was found that the influence of the pH value and the salts on the partial molar volume of the proteins is small, but trends were measurable. Furthermore, the partial molar volume of lysozyme in pure water at different pH values and in aqueous solutions with different sodium chloride concentrations at pH 7.0 was predicted by molecular simulations. The predictions are in good agreement with the experimental data.

The valorization of phosphogypsum (PG) is an efficient way to minimize its negative environmental impacts. This work is built on the use of PG as an environmental-friendly source for the production of sodium sulfate and calcium silicate. The reaction of PG transformation is carried out at room temperature using sodium silicate prepared from Tunisian silica sand. The results show that the highest reaction yield (98%) is obtained when the sodium silicate solution ([SiO32−] = 1.7 mol L−1) is dropwise added during 30 min to the aqueous slurry of PG (mwater/mPG = 12) under stirring for 60 min. The liquid product leads to a sodium sulfate salt with high purity by simple evaporation. The solid product retains the majority of impurities and their concentrations are two times lower compared to raw PG, as confirmed by inductively coupled plasma and X-ray fluorescence spectroscopies.

Poly(3,4-ethylenedioxypyrrole) films on gold substrate were prepared by electropolymerization of ethylenedioxypyrrole monomer (EDOP) under potentiodynamic conditions in aqueous sodium sulfate solutions. The aim of the work was to characterize the gold | poly(3,4-ethylenedioxypyrrole) electrodes in aqueous sulfuric acid solutions and to compare the results with those of other studies that investigated similar systems. However, the experimental results obtained for the PEDOP modified electrodes significantly deviated from the expectations based on studies with similar systems. According to the results, two distinct types of polymer films were formed depending on the storage history of the monomer solutions. By using “fresh” monomer solutions polymer films with nearly ideal capacitive behavior were obtained and almost rectangular-shaped cyclic voltammograms could be observed in a rather broad potential range. Impedance spectra revealed that the charge transfer resistance between the substrate and the film was low. According to the SEM images the polymer layer on the gold substrate was relatively smooth with some small and short cracks. In contrast, working with “old” monomer solution that was not properly stored, the shapes of the cyclic voltammograms recorded at the Au | PEDOP | 0.1 M sulfuric acid (aq) electrode exhibited two peaks, a reduction peak at about −0.2 V vs. SSCE and an oxidation peak close to 0.2 V vs. SSCE, and the charge transfer resistances were considerably higher than those estimated for the electrode prepared using “fresh” monomer solutions. SEM images showed that the surface of the polymer film was extremely rough, with several wrinkles, creases and large cracks. This behavior was quite unexpected, because the two types of samples were prepared in the same way and only the storage histories of the two commercial monomer solutions were different.

This study is concerned on the influence of sodium chloride, sodium sulfate and magnesium sulfate salts on the liquid–liquid equilibrium (LLE) of water + phenol + 1-hexyl-3-methylimidazolium bus(trifluoromethanesulfonyl)imide, [Hmim][NTf2], ionic liquid (IL) system under conditions of T = 298.2 K and ambient pressure of 81.5 kPa. The results showed that salting-out effect was significant and their effectiveness appeared in the order of MgSO4 > Na2SO4 > NaCl, as predicted by the Hofmeister series. Between the used 0.005 and 0.020 salt mass fractions in aqueous phase, the higher concentration was more effective especially at low phenol concentrations. In comparison with salt-free system, enhancements in the separation factor, within (20.55–96.56)% with NaCl, (51.94–154.58)% with Na2SO4 and (73.91–242.57)% with MgSO4 were achieved. The consistency of experimental data was examined with the improved version of Eisen-Joffe equation. Further, the NRTL and UNIQUAC thermodynamic models were satisfactorily used to correlate the phase equilibrium data and the appropriate interaction parameters were determined. Prediction of mass fraction tie-lines gives the maximum root-mean square deviations of only 0.0083 and 0.0367 for NRTL and UNIQUAC models, respectively.

The aqueous solubility of the least soluble salts in mixtures of sodium hydrogen succinate, sodium succinate, sodium hydrogen glutarate, and sodium glutarate with and without ammonium sulfate present has been studied. Solubility temperatures were determined in solutions of known concentration using Differential Scanning Calorimetry. The identity of the least soluble solid was determined by a combination of X-ray crystallography and infrared spectroscopy. The identified solids included ammonium sulfate, sodium sulfate, sodium ammonium sulfate dihydrate (lecontite), sodium hydrogen succinate, sodium succinate hexahydrate, sodium hydrogen glutarate dihydrate, and ammonium hydrogen glutarate. Of the 16 series of solutions studied, lecontite was most frequently the least soluble solid.