Solubility Of Sodium Salts Research Articles

Study of Sodium Salts Solubility in Eucalyptus Black Liquor to Understand and Prevent Scale Formation in Evaporators

Black liquor is a by-product of wood digestion process in pulp and paper mills and it is composed by organic and inorganic products. After this digestion process, black liquor has a solid content of 15 wt/% and to be used as fuel in the recovery boiler it is necessary to be concentrated above 75 wt/% of solids. This concentration process is performed in an evaporation plant using multiple effect evaporators. Some black liquor physical properties, such as density, solids content, viscosity and sodium salts content, are strongly dependent on the kind of wood processed (hardwood or softwood) and on operating conditions during the digestion process. Knowledge and comprehension of the relationship between these physical properties of black liquor are essential for studies aiming at a greater energetic performance of the black liquor evaporation unit. When black liquor reaches higher solids content (above 50 wt/%), scaling formation is observed on the heat transfer surfaces of evaporators and concentrators, due to the precipitation of sodium salts, reducing the overall efficiency of this equipment. The aim of this work is to investigate and comprehend the mechanism of formation and precipitation of sodium salts in eucalyptus black liquor evaporators, through the study of the relationship between some physical properties (density, viscosity, total solids content) and the solubility of sodium salts, evaluating the influence of these variables. In this study industrial samples of black liquor taken from different process streams of the evaporation plant were used. A greater comprehension of the mechanism which is responsible for the reduction of the solubility of these salts is very important for the development of alternative methods to avoid or reduce scaling formation. Experimental data were used to develop a model based on chemical equilibrium of salts dissociation reactions, considering also temperature and pH of the system, which is capable of estimating sodium sulphate solubility limit and comprehend the process that causes the formation of the first scaling and the behaviour of the salts in the system. This model may be used to establish some operating parameters, trying to avoid or control scaling formation in industrial evaporators.

Solubility of Sodium Salts in Ammonium-Based Deep Eutectic Solvents

The solubility of sodium chloride (NaCl), sodium bromide (NaBr), and sodium carbonate (Na2CO3) was measured in nine ammonium-based deep eutectic solvents (DESs). The aim of the study is to assess the potential use of these DESs as solvents and electrolytes for the separation of sodium metal from its salts. The studied DESs were prepared by combining ammonium salts with various hydrogen-bond donors (HBDs) or metal halides. It was found that the solubility of the sodium salts in DESs increases with temperature in many cases. The maximum solubility of NaCl achieved was 100 w = 80 in N,N-diethylethanolammonium chloride:zinc(II) chloride (molar ratio 1:3) at 90 °C. In addition, the solubility of the sodium salts was modeled successfully using the non-random two liquid (NRTL) model.

Concentrates of polyunsaturated fatty acids from Lappula squarosa seed oil

Polyunsaturated fatty acids (PUFA), gamma-linolenic (GLA), alpha-linolenic (ALA), and stearidonic (SA), exhibit high biological activity [1]. Various attempts have been made to prepare PUFA fractions enriched in one PUFA or another for use in drugs and dietary products. A method based on the different solubilities of sodium salts of FA in EtOH that was used for this enabled PUFA concentrates to be obtained from seed oil of Echium fastuosum, Borago officinalis, and Anchusa azurea (Boraginaceae) [2]. We obtained good results for the isolation of FA fractions enriched in ALA and GLA from linseed oil and seed oil of B. officinalis by using low-temperature crystallization at –80°C from CH3CN:Me2CO (7:3) [3]. The resulting fraction (mother liquor) from linseed oil, which contains 55% ALA, consisted of 88.5% ALA; from total FA of B. officinalis with 23.4% GLA, 88.3% of this FA. Crystallization of FA from hexane solution (10%) at –70°C enabled GLA and SA concentrates to be obtained from E. fastuosum seed oil. This method could be used on an industrial scale [4]. Fractions with high GLA and SA contents could be obtained by chromatographic methods such as HPLC, CC over silica gel and over silica gel impregnated with AgNO3, and centrifugal preparative chromatography (CPC). However, they are suitable only for laboratory studies [5]. Extraction by supercritical CO2 in order to isolate and enrich oils in GLA and SA did not give the desired result [6–8]. Fractionation of urea complexes of FA was used to isolate epoxytetraenoic acid from total FA of fish and microalgae [9]; a mixture of GLA with ALA, from FA of Ribes nigrum seed oil [10] and from FA of seed oil of A. azurea, E. fastuosum, and S. scophila [11]. As a rule, a urea:FA ratio of 4:1 (by mass) is used [9]. Production of FA fractions enriched with PUFA using urea complexes (clathrates) depends primarily on the initial set of PUFA and their content in the oil. The main difficulty in producing FA fractions with a high SA content is the presence in oils of SA and its precursor ALA. Until now, plants with oil that contains only SA have not been found [1]. Studies of seed lipids from several species of the family Boraginaceae indigenous to the Republic of Bashkortostan found that Lappula squarosa seed lipids contained >70% PUFA including >16% SA [12]. Separation of the FA from Lappula seed oil as the urea clathrates afforded fractions enriched with PUFA. For this, mild alkaline hydrolysis (10% KOH solution in MeOH, 70–80°C, 30 min) isolated from the oil the total FA. EtOH was used as the solvent to prepare the urea complexes because it was shown earlier that enrichment of PUFA in it occurred better by using FA from B. officinalis seed oil as an example [13]. FA were separated in two steps [13]. In the first step, a mixture of FA (0.8 g) was treated with a saturated solution of urea in EtOH (FA:urea ratio 1:3 by mass), stirred on a magnetic stirrer with heating (60°C) until totally dissolved, and left at room temperature for 3 h and then at 10°C for 24 h. The resulting clathrate crystals were separated on a Schott filter and washed with cold saturated urea solution in EtOH to produce mother liquor 1 and a precipitate of crystalline FA urea complexes, clathrates 1. The yield of FA fractions (mass% of starting FA) was 36.25 and 57.5, respectively (Table 1). Next, the FA compositions of the mother liquor and clathrates were analyzed. The mother liquor was evaporated to half the volume in a rotary evaporator, diluted with H2O, and extracted with Et2O in order to isolate the FA from it. The Et2O extracts were washed with H2O and dried over anhydrous Na2SO4. The solvent was evaporated. The resulting FA (0.29 g, mother liquor 1) were methylated by diazomethane and studied by GC (Table 1).

Conductivities and thermal studies of polymeric electrolytes based on poly(epichlorohydrin)/sodium salts

The halogenated polyether named Hydrin-T® is a terpolymer constituted of epichlorohydrin-ethylene oxide-allyl glycidyl ether. It was studied as a polymeric electrolyte in polymer/NaX systems (X = Br - , I-, SCN - , ClO 4 - and B(C 6 H 5 ) 4 - ). In this work we present an investigation of the ionic conductivity (measured by impedance spectroscopy) and thermal properties (measured by differential scanning calorimetry-DSC, modulated DSC and thermogravimetry) of the polymeric electrolyte as a function of the composition in the range of 5 to 40 m/m (%) of the sodium salt. The solubility of sodium salts in the elastomer terpolymer matrix is comparable to the solubility in the best known matrix of linear semicrystalline PEO. The conductivities of the terpolymer/Nal electrolytes are higher than those of membranes prepared with other salts studied (10 -5 S/cm for the former versus 10 -7 to 10 -6 S/cm for the latter). This system also is the most homogeneous up to 40 m/m (%) and showed the smallest increase of T g values as a function of salt concentration [between -53°C for the pure polymer and -35°C for the 40 m/m (%) of NaI]. Modulated DSC confirmed the homogeneity of the terpolymer/NaI system showing T g transition in a range of only 5°C. A decrease of variation of heat capacity during glass transition with the increase of salt concentration was observed.