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In this research article, shock wave induced switchable phase transition (β to α and α to β) of potassium sulfate (K2SO4) crystal is demonstrated. The test crystals are subjected to shock waves of ...

In this work, the operation of membrane-assisted seeded batch crystallization is modeled for five substances: potassium nitrate, potassium sulfate, pentaerythritol, succinic acid, and potassium alum. The effect of seed loading, seed size, and water removal rate on product crystal size is investigated. Seed loading and seed size were found to have a significant impact on product crystal size for a given batch time and product yield. Trajectories for the optimal water removal rate versus time were also determined. Overall, the results show that membrane-assisted crystallization behaves similarly to other types of crystallization in terms of product crystal size and size distribution while having the potential to reduce cost and equipment size.

The liquid–liquid equilibriums (LLEs) for 2-propanol + tripotassium phosphate + water at 298.15, 308.15, and 318.15 K and 2-propanol + dipotassium hydrogen phosphate + water at 298.15 K were measured. The binodal curves of 2-propanol + potassium sulfate/potassium sulfite + water at 298.15 K were measured and compared. Accordingly, the experimental binodal data were correlated using Merchuk, Hu, and Pirdashti equations, and the tie-line compositions were correlated using Othmer–Tobias and Bancroft equations. The effect of temperature, anion type, and length of alcohol chain on the binodal curve, tie-line length (TLL), slope of tie-line (STL), and phases’ physical properties were studied. It was found that an increase in salt’s hydrophobicity and alcohol’s carbon number in low temperature led to the expanding biphasic region and approaching the binodal curve to the origin. The phase-forming ability of different anions was studied using effective excluded volume (EEV) model, and the relation between the EEV ...

Thus far, little is known about the use of granitic rubidium ore for the extraction of rubidium. Herein, we examined the extractability of rubidium and potassium from granitic rubidium ore via sulfuric acid baking, reductive decomposition, and alkaline leaching. In addition, the extraction mechanism was studied by using interdisciplinary approaches based on the mineralogy and thermodynamics. Under the optimum conditions, more than 94% and 92% of Rb and K were extracted, respectively. Mineralogical analysis suggests that the Rb is scatted in micas (biotite and muscovite) and potassium feldspar in the form of isomorphism. Micas were transformed into sulfates during the sulfuric acid baking process. Increasing the dosage of coal, the decomposition temperature, and the time was conducive to the decomposition of sulfates. The sulfates were transformed into aluminum oxide and potassium sulfate during the reductive decomposition process. The basic structure of potassium feldspar was unchanged in the stages of ba...

Wet-process phosphoric acid is developed with the lack of a quality mineral. More and more research focuses on the purification of wet-process phosphoric acid with solvent extraction method. Liquid–liquid equilibrium data are of important significance in the industrial reality. In this work, equilibria data have been obtained for the two quaternary systems phosphoric acid–sodium sulfate–water–tri-n-butyl phosphate and phosphoric acid–potassium sulfate–water–tri-n-butyl phosphate, which contain concentrations of components and densities and viscosities of the equilibrium phases, and also the varieties of distribution coefficient of phosphoric acid are analyzed. In different systems (phosphoric acid solution with sodium sulfate or potassium sulfate at 303.2 K), the distribution coefficient of phosphoric acid with sodium was found to be higher than that of potassium ion, which demonstrates that the extraction of phosphoric acid with sodium is greater than that with potassium ion. In addition, NRTL model and ...

Sulfation of condensed alkali chloride significantly affects deposition and corrosion in heat transfer surfaces during biomass combustion. This study investigates the heterogeneous sulfation of condensed potassium chloride (KCl) in a fixed-bed reactor at 523–1023 K with levels of 0.1–2% sulfur oxide (SO2), 2.5–10% oxygen (O2), and 5–15% water vapor. The sulfation rate is determined by measuring the sulfur content in solid residues. No other potassium species are found, and potassium sulfate (K2SO4) is the only sulfation product. The KCl sulfation within the temperature range of 523–1023 K was divided into three stages: (1) slow sulfation rate increase below 723 K, (2) slight decline at 723–773 K, and (3) rapid increase over 823 K. The sulfation mechanism transformation occurs between 723 and 823 K. This change in the reaction mechanism is further proven by investigating the effects of SO2 and O2 reactants and water vapor at 723 and 923 K. The KCl–K2SO4 mixture forms a eutectic to change the reaction mode ...

Alunite is a potential resource for production of alumina and potassium sulfate. Hydrometallurgy is the conventional process employed for this purpose and direct leaching in KOH is suitable as one ...

The solubilities of the ternary system MgSO4–(NH4)2SO4–H2O and the quaternary system Na2SO4–MgSO4–(NH4)2SO4–H2O at 0 °C were measured, and the phase diagrams of these two systems were plotted. On the basis of the phase diagrams obtained, we analyzed each saturation point and crystalline region. It indicated that ammonium sulfate as the salting-out agent can form double salt MgSO4·(NH4)2SO4·6H2O with magnesium sulfate, realizing better separation of sodium sulfate and magnesium sulfate. On the basis of the Pitzer model of electrolyte solution theory, the ionic strength function was introduced to express the interaction parameters between two kinds of electrolyte at 0 °C. The interaction parameters were regressed from the experimental data of the ternary systems, and the solubilities of Na2SO4–MgSO4–(NH4)2SO4–H2O system at 0 °C were calculated. The results showed that the calculated values were well consistent with experimental results.

Solid–liquid equilibria in the quaternary systems KCl–KBr–K2B4O7–H2O and KCl–KBr–K2SO4–H2O at 373 K were measured by the isothermal solution saturation method. The equilibrium solid phases, solubilities of salts, and densities of saturated solutions in the two systems were determined. The experimental data are used to plot the solubility diagrams, water content diagrams, and solution density diagrams of the two systems. It was found that both systems contain the solid solution of KCl and KBr [K(Cl,Br)], so their solubility diagrams have no invariant point, but each has a univariant curve and two crystallization regions. In the first system, the solids are K(Cl,Br) and potassium borate aquahydrate (K2B4O7·4H2O), and in the second system, the solids are K(Cl,Br) and potassium sulfate (K2SO4).

Lyotropic cholesteric liquid crystalline phases were prepared by doping the quaternary mixture of potassium laurate (KL)/potassium sulfate (K2SO4)/alcohol (n-OH)/water with the chiral agent brucine. Different long-chain alcohols whose alkyl chains (n) vary from 8 (1-octanol) to 16 (1-hexadecanol) were used. The cholesteric uniaxial to cholesteric biaxial phase transitions were investigated by measuring the birefringences via polarizing optical microscopy, and the phase diagram was constructed as a function of the alkyl chain length of the alcohols. Alcohols with 9

Phase equilibria in the ternary systems K2SO4–K2B4O7–H2O and Na2SO4–Na2B4O7–H2O at 348 K were studied by the isothermal solution saturation method. The solubilities and densities of the solution in these ternary systems were determined experimentally. Using the experimental data, the phase diagrams of the two ternary systems were obtained. The ternary systems K2SO4–K2B4O7–H2O and Na2SO4–Na2B4O7–H2O at 348 K are a type of simple common saturation and without complex salt and solid solution. In the phase diagrams and both the two ternary systems at 348 K, all have one invariant point, two univariant curves, and two regions of crystallization. The two crystallization regions of the ternary system K2SO4–K2B4O7–H2O at 348 K correspond to potassium borate tetrahydrate (K2B4O7·4H2O) and potassium sulfate (K2SO4). The two single-salt crystallization regions are sodium borate pentahydrate (Na2B4O7·5H2O) and sodium sulfate (Na2SO4) in the ternary system Na2SO4–Na2B4O7–H2O at 348 K.

The aqueous quaternary system Li2SO4 + Na2SO4 + K2SO4 + H2O is one of the most important subsystems of the sulfate-type salt lake brine located in the Qinghai-Tibet Plateau. The phase equilibria of the aqueous quaternary system Li2SO4 + Na2SO4 + K2SO4 + H2O were investigated at 273.15 K using an isothermal evaporation method. A sodium and lithium sulfate double salt (3Na2SO4·Li2SO4·12H2O) and a potassium and lithium sulfate double salt (KLiSO4) are formed in this quaternary system at 273.15 K. There are three invariant points, seven univariant curves, and five crystallization fields in the phase diagram of this system. The five crystallization fields correspond to sodium sulfate decahydrate (Na2SO4·10H2O), potassium sulfate (K2SO4), lithium sulfate monohydrate (Li2SO4·H2O), and two double salts KLiSO4 and 3Na2SO4·Li2SO4·12H2O. The double-salt glaserite (3K2SO4·Na2SO4) is not formed in this system at research temperature. The three invariant points have different attributes, which invariants E1 and E2 are ...

The solubilties of potassium chloride and potassium sulfate in aqueous glycerol solutions have been measured at temperatures ranging from (289 to 349) K using a dynamic method. The solute-free mass...

Self-assembly of a tris(urea) anion receptor with Na2SO4 or K2SO4 yields crystalline capsules held together by coordinating Na+ or K+ cations and hydrogen-bonding water bridges, with the sulfate anions encapsulated inside urea-lined cavities. The sodium-based capsules can be selectively crystallized in excellent yield from highly competitive aqueous alkaline solutions (∼6 M Na+, pH 14), thereby providing for the first time a viable approach to sulfate separation from nuclear wastes.

The solubilities and densities of the solution in the quaternary system Na2B4O7−Na2SO4−K2B4O7−K2SO4−H2O at 288 K were investigated using the method of isothermal dissolution equilibrium. The solid−liquid stable equilibria in the quaternary system Na2B4O7−Na2SO4−K2B4O7−K2SO4−H2O at 288 K were studied experimentally. On the basis of experimental data, the stable phase diagram of the quaternary system was plotted. In the solubility diagram of the quaternary system Na2B4O7−Na2SO4−K2B4O7−K2SO4−H2O at 288 K, there are three invariant points, seven solubility isotherm curves, and five crystallization regions, which correspond to borax (Na2B4O7·10H2O), potassium tetraborate (K2B4O7·4H2O), mirabilite (Na2SO4·10H2O), arcanite (K2SO4), and glaserite (Na2SO4·3K2SO4). It can be found from the experimental results that sulfates have bigger solubilities than borates in the quaternary system Na2B4O7−Na2SO4−K2B4O7−K2SO4−H2O at 288 K.

The solubilities of (sodium and copper(II)) sulfate + ethanol + water mixtures have been determined at (278.15, 288.15, and 298.15) K and for the potassium sulfate + ethanol + water system at the same temperatures and also at (308.15 and 318.15) K. The equilibrium composition for different points has been calculated by means of refraction index and density measurements. An empirical correlation for the solubilities of the ternary mixtures has been used to correlate experimental values as a function of the solvent composition. Data fitting shows a good agreement with experimental values.

The solubilities and the physicochemical properties including the density, viscosity, refractive index, conductivity, and pH value of the aqueous quaternary system LiCl + KCl + Li2SO4 + K2SO4 + H2O at 308.15 K were determined with the isothermal evaporation method. On the basis of the Janecke indices, the dry-salt phase diagram, the water-phase diagram, and the diagrams of physicochemical properties were plotted. The dry-salt phase diagram of the system includes three three-salt cosaturation invariant points, seven univariant solubility curves, and five crystallization zones corresponding to potassium sulfate, potassium chloride, the double salt lithium potassium sulfate, lithium sulfate monohydrate, and lithium chloride monohydrate. Single-salt parameters β(0), β(1), and C(φ) for lithium sulfate, potassium sulfate, and potassium chloride, mixed electrolyte parameters θCl,SO4 and ΨK,Cl,SO4, and the Debye−Hukel limiting slope AΦ at 308.15 K were calculated according to the temperature-dependent equations p...

In an attempt to understand the problem of severe slagging in biomass-fired boilers, slags formed on the fourth-, second-, and first-stage superheaters in a 12 MW biomass-fired grate furnace have been collected, sampled, and analyzed using X-ray fluorescence (XRF) and X-ray diffraction (XRD) techniques. The slag collected on each superheater has a unique morphology and structure. The slag on the fourth-stage superheater is loose and porous, while on the secondary and the primary superheaters, the slag shows a clear layered structure of different colors and levels of hardness. Aluminosilicate is the major component in the slag on the fourth-stage superheater, which is formed by Si, Al, and alkali species. On both the secondary and primary superheaters, the sticky sylvine, potassium calcium sulfate, and aphthitalite in the bottom layer trap coarse, large particles, resulting in further slagging. In the alternating layers, the particles containing high concentrations of K, Na, and Cl form the initial deposit...

The refractive indices (sodium line) of sodium, potassium, and ammonium sulfate in water and ethanol + water solutions have been determined experimentally over the temperature range (288.15 to 318.15) K and at atmospheric pressure. Parameters of polynomial equations which represent the composition dependence are gathered. The predicted results show good agreement with the experimental data.

The isothermal evaporation method was employed to investigate the phase equilibria in the quinary system Li2B4O7 + Na2B4O7 + K2B4O7 + Li2SO4 + Na2SO4 + K2SO4 + H2O at 273.15 K. The solubilities and densities of the equilibrated solution were measured. The crystalloid forms of the solid phase were determined using chemical analysis and an X-ray diffraction method. On the basis of the experimental data, the stereophase diagram, the projected phase diagram saturated with Li2B4O7, the projected phase diagram saturated with Na2B4O7, and the lithium content diagram of the quinary system were plotted. The stereophase diagram consists of six invariant points, eighteen univariant curves, and eight crystallization fields corresponding to sodium sulfate decahydrate (Na2SO4·10H2O), potassium sulfate, lithium sulfate monohydrate, sodium tetraborate decahydrate (borax, Na2B4O7·10H2O), potassium tetraborate tetrahydrate (K2B4O7·4H2O), lithium metaborate octahydrate (LiBO2·8H2O), a potassium and lithium sulfate double sa...

Vapor pressures of water over saturated solutions with regard to two salts, in the NaCl + KCl + H2O, NaCl + NaNO3 + H2O, KCl + KBr + H2O, KCl + KI + H2O, KCl + KNO3 + H2O, and KCl + K2SO4 + H2O systems, are reported in the (278 to 323) K temperature range. The determined vapor pressures served to obtain the water activities, the osmotic coefficients, and the molar enthalpies of vaporization.

The phase equilibria in the quaternary system Na 2 SO 4 + K 2 SO 4 + Na 2 CO 3 + K 2 CO 3 + H 2 O were studied at 273.15 K using an isothermal evaporation method. The solubilities and densities of the equilibrated solution were determined experimentally. The crystalloid forms of the solid phase were determined using chemical analysis and an X-ray diffraction method. On the basis of the experimental data, the isothermal equilibrium phase diagram, water content diagram, and density composition diagram of the quaternary system were plotted. The phase diagram consists of four invariant points, nine univariant curves, and six crystallization fields corresponding to sodium sulfate decahydrate (Na 2 SO 4 ·10H 2 O), potassium sulfate, sodium carbonate decahydrate (Na 2 CO 3 ·10H 2 O), potassium carbonate hydrate (K 2 CO 3 ·3/ 2 H 2 O), potassium and sodium carbonate double salt (K 2 CO 3 ·Na 2 CO 3 12H 2 O), and sulfate and carbonate double salt of sodium (2Na 2 SO 4 ·Na 2 CO 3 ). This quaternary system is of a complex type. Two kinds of double salts are formed. Na 2 CO 3 ·10H 2 O is the only crystalloid form of sodium carbonate in the given system at 273.15 K. Na 2 CO 3 ·7H 2 O and Na 2 CO 3 ·H 2 O are not formed.

The metastable solubilities and the physicochemical properties (density, viscosity, refractive index, conductivity, and pH) of the aqueous quaternary system (Li2SO4 + K2SO4 + MgSO4 + H2O) at 288.15 K were determined with the isothermal evaporation method. According to the experimental data, the dry-salt phase diagram, water-phase diagram, and the physicochemical properties vs composition diagram were plotted. It was found that there are three invariant points, seven univariant curves, and five metastable crystallization regions corresponding to lithium sulfate monohydrate (Li2SO4·H2O), arcanite (K2SO4), epsomite (MgSO4·7H2O), double salt 1 (LiKSO4), and picromerite (K2SO4·MgSO4·6H2O) formed in the metastable quaternary system. A comparison of the diagrams between the metastable equilibrium at 288.15 K and the stable equilibrium at 298.15 K shows that the metastable behavior of magnesium sulfate is obvious and the crystallizing regions of epsomite and arcanite are much larger than those in the stable phase...

Viscosities of ammonium sulfate, potassium sulfate, and aluminum sulfate in water and water + (5 %, 10 %, 15 %, and 20 %) N,N-dimethylformamide mixed solvent have been measured at T = (298.15 and 308.15) K and at atmospheric pressure. A molality range has been studied between (0.0081 and 0.1000) mol·kg−1. The viscosity data have been analyzed with the Jones−Dole equation, and B coefficients have been calculated. The results have been interpreted in terms of structure making/breaking behavior of these salts in water and water + DMF mixed solvents.

Experimental studies on the metastable solubilities and the physicochemical properties including density, viscosity, refractive index, conductivity, and pH of the aqueous quaternary system (KCl + K2SO4 + K2B4O7 + H2O) at 308.15 K were determined with the method of isothermal evaporation. According to the experimental results, the dry-salt phase diagram, the water diagram, and the physicochemical properties via composition diagrams were plotted. It was found that there is one three-salt cosaturation point of KCl + K2SO4 + K2B4O7·4H2O, three univariant curves, and three metastable crystallization fields corresponding to potassium chloride, potassium sulfate, and potassium borate tetrahydrate formed in the metastable quaternary system. Neither solid solution nor double salts were found.

Potassium sulfate crystals orient and overgrow 2-aminobenzenesulfonate (OSA), and many other sulfonated aromatic compounds, on particular facets during growth from solution. The energetics associated with adsorption of OSA and benzenesulfonate (BS) were calculated using both molecular mechanical and density functional methods, in order to assess the surface binding effectiveness of these compounds on various faces of potassium sulfate. It was found that both theoretical techniques predicted that OSA and BS bind to potassium sulfate to a similar extent. The surface binding capacities were also assessed experimentally by studying the growth rates of individual faces of K2SO4, with results showing similar findings to those from the computational studies.

An experimental study on phase equilibria at 288 K in the quinary system Li+ + Na+ + K+ + SO42- + B4O72- + H2O was performed using the isothermal evaporation method. Equilibrium solubility and density of the solution were measured. The equilibrium phase diagram for the solution saturated with the salt Li2B2O4·16H2O was constructed. The phase diagram of this system consists of 7 invariant points, 14 univariant curves, and 8 crystallization fields corresponding to potassium tetraborate pentahydrate (K2B4O7·5H2O), borax (Na2B4O7·10H2O), potassium sulfate, lithium sulfate monohydrate (Li2SO4·H2O), sodium sulfate, lithium−potassium sulfate double salt (Li2SO4·K2SO4), lithium−sodium sulfate double salt (Li2SO4·Na2SO4), and potassium−sodium sulfate double salt (3K2SO4·Na2SO4). There are three kinds of double salts formed in the system. The crystallization forms of lithium and potassium borate were K2B4O7·5H2O and Li2B2O4·16H2O, respectively, which are different from the usual forms of K2B4O7·4H2O and Li2B4O7·3H2...

The effect of the addition of chlorine and/or sulfur to the fuel on fly ash composition, deposit formation, and superheater corrosion has been studied during biomass combustion in a circulating fluidized-bed boiler. The chlorine (HCl (aq)) and sulfur (SO2 (g)) were added in proportions of relevance for the potassium chemistry. The composition of the bottom and the fly ashes was analyzed. Gas and particle measurements were performed downstream of the cyclone before the convection pass and the flue gas composition was recorded in the stack with a series of standard instruments and an FTIR analyzer. At the position downstream of the cyclone, a deposit probe was situated, simulating a superheater tube. Deposits on the probe and initial corrosion were examined. It is concluded that addition of sulfur and chlorine increases the formation of submicron particles leading to deposition of potassium sulfate and chloride. The results compare well with earlier work based on laboratory-scale experiments concerning effects of chlorine and sulfur on potassium chemistry.

In this work, the effect of temperature on the crystal growth rate of potassium sulfate in aqueous K2SO4 and KCl−K2SO4 solutions is analyzed. The crystal growth rate equation of K2SO4 is developed on the basis of the difference of chemical potentials of K2SO4 at the solid−liquid interface. The Lu−Maurer model is used to predict the activity coefficient of K2SO4. The crystal growth rate of K2SO4 in aqueous K2SO4 solution decreases, then increases with increasing temperature, and reaches its lowest value around 303.15 K, which is in accordance with previous experimental results. Meanwhile, the optimal crystallization temperature of K2SO4 in aqueous KCl−K2SO4 solution is discussed. An effective method is found to increase the yield of K2SO4 by increasing the crystallization temperature to 333.15 K.

Although bittern of oceanic origin can be utilized for the production of K2SO4 via kainite (KCl·MgSO4·2.75H2O) and schoenite (K2SO4·MgSO4·6H2O) double salts, certain limitations are encountered in practice. These include (i) difficulties in obtaining pure schoenite from crude kainite and (ii) the requirement of KCl in the K2SO4 forming process. When schoenite is prepared from kainite through a simple reaction-cum-leaching process and the liquid effluent is desulfated with CaCl2 as part of a scheme to coproduce magnesia (Ghosh et al. U.S. Patent Publication No. 2005/0220698 A1, 2005 (Notice of Allowance); International Patent Publication No. WO 2005/063626 A1, July 14, 2005), the composition of the resultant effluent is found to be ideally positioned in the phase diagram for direct recovery of sylvinite (NaCl/KCl). The intermediate steps of carnallite crystallization and decomposition, encountered during sylvinite preparation from Dead Sea brine and desulfated oceanic bittern, are avoided as a result. In t...

The use of fuels other than natural gas in gas turbine generators still is fraught with blade corrosion problems that result from the formation of sodium sulfate or potassium sulfate, in the presence of chlorine. The present work illustrates that the addition of molybdenum salts to synthetic fuels (synfuels) modifies this deposition process and benign protective coatings of alkali polymolybdates are produced instead. This study is a follow-up to research published earlier in this journal that showed closely similar behavior with tungsten salt additives. In the case of molybdenum, a new preferential ranking of product formation on the surface is established that is closely related to the thermodynamic stabilities, namely, Na2Mo2O7 > Na2SO4 > Na2MoO4 > NaCl and K2Mo4O13 > K2Mo3O10 > K2Mo2O7 > K2SO4 > K2MoO4 > KCl. This chemistry exists under fuel-lean conditions and is otherwise not sensitive to the fuel, combustion conditions, surface temperature, or material. The required additive trace levels of molybden...

An experimental study on phase equilibria at 288 K in the quaternary system Na2SO4 + K2SO4 + Na2B4O7 + K2B4O7 + H2O was done by the isothermal evaporation method. Equilibrium solubilities and properties such as density, electrical conductivity, and pH of the solution were measured, and the equilibrium phase diagram was constructed in which there were two invariant points, six univariant curves, and four crystallization fields corresponding to borax (Na2B4O7·10H2O), sodium sulfate, potassium sulfate, and potassium borate quahydrate (K2B4O7·4H2O). No solid solutions or double salts were found.

The Zdanovskii rule, in simple and modified form, was used for the estimation of supersaturated K2SO4-(aq) osmotic coefficients at T = 298.15 K by treatment of the isopiestic data of the mixed electrolyte solutions. The results were compared with the predictions of the Akerlof-Thomas rule and of weighted averages. Estimated values by the Zdanovskii rule together with the K2SO4(aq) osmotic coefficient experimental data in unsaturated solution were used in fitting the data to the extended Pitzer equation. The reliability of the Zdanovskii rule estimation was tested on the prediction of the osmotic coefficients in several mixed electrolyte solutions containing K2SO4 and having an ionic strength much greater than the ionic strength of saturated K2SO4(aq) and on the osmotic coefficient estimation for supersaturated Na2SO4(aq) at T = 298.15 K.

An approach to simulate the operation of batch crystallization of brittle materials by means of a semiempirical model is proposed. The model is derived from an experimental plan specifically designed to reduce the correlation among the values of the unknown parameters to be determined. The experimentation was carried out by using a pilot-scale DT crystallizer, 13.5 L in capacity, with and without seeding. The examined system was the crystallization of potassium sulfate from aqueous solutions. The developed model, accounting for the first nucleation point, crystal attrition, and growth rate dispersion, gave satisfactory results. The work, thus, indicates an overall procedure to provide a prediction model for an existing batch crystallizer.

The thermodynamic behavior of the aqueous KCl + K2SO4 electrolyte has been studied on the basis of potential difference measurements on the reversible cell K-amalgam|KCl (mKCl) + K2SO4 (mK2SO4) |AgCl|Ag|Pt. The mean molal activity coefficients γKCl of KCl at molalities mKCl and γK2SO4 of K2SO4 at mK2SO4 in (KCl + K2SO4) mixtures have been determined at various constant values of total ionic strengths I of the mixed electrolyte studied. It has been found that log(γKCl) is a linear function of mKCl at each constant ionic strength studied, thus obeying Harned's rule. The corresponding trace activity coefficients, γ(0)KCl, vary linearly with log I. Using Pitzer's scheme of equations has allowed fair reproduction of the experimental activity coefficients γKCl for I values ≥ 0.5 mol·kg-1 and the evaluation of γK2SO4 in the same range.

Isopiestic vapor-pressure measurements were made for K2SO4(aq) from (0.228 to 0.740) mol·kg-1 at 298.15 K and from (0.200 to 0.957) mol·kg-1 at 323.15 K, using NaCl(aq) as the isopiestic reference standard. These isopiestic measurements extend to saturation at 323.15 K and to slightly above saturation at 298.15 K. There are no previous isopiestic studies for K2SO4(aq) at 323.15 K. Thermodynamic properties from the literature for the potassium sulfate + water system and the present measurements were used to generate equations that represent the thermodynamic properties of this system from the freezing point of the aqueous solution to 500 K. The measured values included for least-squares estimation of the model parameters spanned the temperature range approximately 271 K to 530 K for K2SO4(aq).

The solubilities of three sulfate salts (Na2SO4, K2SO4, MgSO4) and two chloride salts (NaCl, KCl) with a second salt in water were measured at 313 K. The ternary systems studied were water + NaCl + KCl, water + NaCl + Na2SO4, water + KCl + K2SO4, water + Na2SO4 + K2SO4, water + K2SO4 + MgSO4, and water + Na2SO4 + MgSO4. The solubilities of two salts in the ternary systems were obtained, and the data were used to obtain the eutectic concentrations of the ternary systems. The solubility data were also predicted by the electrolyte−NRTL model, in which parameters were obtained from the binary data. The qualitative effect of the second salt on the solubility of the first salt in water is discussed.

The width of metastable zone of unseeded potassium alum solutions was determined for different conditions and in the presence of additives. The measurements were taken at three different cooling rates and for three different saturation temperatures at a cooling rate of 10 K/h by means of an ultrasonic measuring technique. The influence of Cr3+, Cu2+, and Mg2+ ions on the width of metastable zone of a potassium alum solution was investigated at a cooling rate of 5 K/h. The influence of Mg2+ ions on the width of metastable zone of potassium chloride solutions was also investigated at a cooling rate of 10 K/h. Cr3+, Cu2+, and Mg2+ ions show both enlargement and suppression effects on the width of metastable zone of potassium alum and potassium chloride solutions depending on their concentrations. Cr3+, Cu2+, and Mg2+ ions also change the saturation temperature of potassium alum solutions depending on their concentrations.

The solubilities, densities, refractive indices, electrical conductivities, and viscosities were determined for saturated solutions of potassium sulfate in aqueous solutions of 1-propanol over the temperature range of 298.15−318.15 K. Different mass fractions of propanol/solution were studied in a range from 0 to 0.6. Equations are given for these properties as a function of temperature and mass fraction of propanol. Knowledge of the properties evaluated and solubility data are useful in the study of the crystallization of potassium sulfate from aqueous solutions by means of the addition of 1-propanol.

This study focuses on the adaptive mesh method for simulation of crystallization processes. Because the models of the processes are very complex, giving partial and ordinary differential, algebraic...

An adiabatic calorimeter was used to measure enthalpies of solution into water of sodium chloride (∼0.13 mol·kg-1) at nominal temperatures of 298.15 K, 303.15 K, and 308.15 K and of potassium sulfate (∼0.039 mol·kg-1) at nominal temperatures of 298.15 K and 303.15 K. The results for sodium chloride were compared to a previous equation of state so as to validate the use of values from that equation of state for calibration of, or checks on the accuracy of, solution calorimeters. Thermodynamic properties from the literature for the potassium sulfate + water system and the present measurements were used to generate equations that represented the thermodynamic properties of this system from the freezing point of the aqueous solution to 500 K. The measured values included in the fitted equations spanned the range of temperature of approximately 271 K to 530 K for K2SO4(aq) and 13 K to 854 K for K2SO4(cr). New equations and/or values for the following properties are given in the present work: (1) thermal prope...

4-Chloro-3-methylphenol (c = 2.0 mM), representing a model pollutant, was oxidized in pressurized hot water and in supercritical water in a continuous flow system. Potassium persulfate was used as oxidant in concentrations of 8.0 and 40.0 mM. Contact times (reaction times) were 3-59 s, temperatures 110-390 degrees C, and pressures 235-310 bar. A wide temperature range was tested to determine the range over which potassium persulfate can be used effectively. Good oxidation efficiencies for 4-chloro-3-methylphenol were obtained at both oxidant concentrations and with short contact times at temperatures clearly underthe critical temperature of water; total organic carbon content of the effluent was low under optimized conditions. Corrosion, measured as nickel and chromium concentrations of the effluent, was more severe at oxidant concentration of 40.0 mM. Sulfate was present in the effluent in high concentrations. Sulfate is the limiting factor in the use of potassium persulfate in wastewater treatment and requires further water treatment.

The growth kinetics of a potassium sulfate crystal was investigated in the presence of traces of chromium(III) impurity (0.5 and 2 ppm) in a flow cell at different rates of change of supercooling (± 0.1 and ± 0.2 °C/min). Hysteresis in crystal growth rates with chromium(III) impurity was induced by decreasing and increasing the supercooling. The rate of supercooling change affected this hysteresis behavior. The cause of hysteresis was hypothesized to occur due to a slow adsorption of impurity at high supercooling.

Liquid−liquid equilibrium data for the quaternary system (water + ethanol + alcohol + salt) were measured at 25 °C and 40 °C. The alcohols were 1-butanol, 1-pentanol, and 3-methyl-1-butanol. The salts were sodium chloride, sodium acetate, calcium chloride, potassium chloride, potassium sulfate, and potassium bromide. The results were compared with experimental liquid−liquid equilibrium data for the ternary, salt-free systems, both from the literature and determined in this work. In this way, the salt effect could be evaluated.

Experimental data of density, absolute viscosity, and electric conductivity for the K2SO4 + H2O + 1-propanol system have been determined at (303.15, 308.15, 313.15, and 318.15) K. Different mass fractions of alcohol/water (free salt) were studied in the range from 0 to 0.55. For these mass fractions of 1-propanol/water, the range of variation of potassium sulfate was from (0.0168 to 0.698) mol·kg−1. The Williams, Landel, and Ferry equation was used to fit the absolute viscosity and equivalent conductance (determined from electric conductivity) data, and mean absolute deviations of 0.017 mPa·s and 0.19 (cm2·equiv Ω−1) were obtained, respectively. The glass-transition temperature was estimated with the experimental data of viscosity and equivalent conductance. Because the values obtained are relatively similar, we conclude that both transport properties are governed by the same molecular movement. Knowledge of the evaluated properties is useful in the study of the drowning-out crystallization process.

The process of condensation of KH2PO4 and NH4H2PO4 with a K2SO4 mixture at a temperature of 400 °C, as the product of conversion of potassium chloride with ammonium dihydrogen phosphates and ammonium sulfate, was investigated. At the same time, the ammonium ion was replaced with sodium ion (as Na2CO3) or calcium ion (as CaCO3 or CaO). The effect of potassium sulfate addition on the phase composition of produced polyphosphates as well as their water solubility and the fraction of ortho-, pyro-, and tripolyphosphates and higher condensed phosphates was determined. It was found that potassium sulfate reacts partially with ingredients of the initial mixture, forming potassium, potassium−sodium, and potassium−calcium phosphates or probably compounds of type P−O−S.

Catalytic activities of potassium sulfate and chloride were studied for the combustion of activated carbon grains at 673−773 K by supporting the salts on the carbon or a perovskite type oxide (La0.8Sr0.2Cr0.5Mn0.45Pt0.05O3, LSCMP). Both K2SO4 and KCl supported on LSCMP exhibited much higher activities than those supported on the carbon. Such salts supported on LSCMP liberated SO2 or Cl2 during the carbon combustion reaction, and the temperatures for their decomposition were almost the same as the temperatures where carbon combustion started. In contrast, the salts supported on carbon hardly disintegrated under the present conditions. A part of the salts supported on LSCMP was found to be converted into K2CO3 after reaction as indicated by an IRνC-O band assigned to K2CO3. Being observed in IR spectra, O2 and LSCMP appear to promote disintegration of K2SO4 and KCl in contact with carbon to active species of either potassium metal or oxide in an early stage of the carbon combustion. The active species can s...

This paper reports the results of studying ion-exchange synthesis of chlorine-free potassium sulfate from KCl and Na2SO4 on strong acid cation-exchange and strong base anion-exchange resins using an ion-exchange isothermal supersaturation (IXISS) effect. This effect is observed for a number of ion-exchange systems, where the ion-exchange process is accompanied by the formation of a stable supersaturated solution of slightly or sparingly soluble substances in the interstitial space of ion-exchange columns. The formation of stable K2SO4 solutions in the columns has been observed by the displacement of either K+ or SO42- ions from a cation or anion exchanger with concentrated Na2SO4 or KCl solutions, respectively. After leaving the column, a supersaturated solution crystallizes spontaneously, which allows for the design of a practically ideal ion-exchange process where a crystalline chlorine-free potassium sulfate is obtained right after the ion-exchange conversion cycle. The process is practically wasteless...

We report the kinematic viscosities and densities (at 298.1 K) of solutions of K2SO4, Na2SO4, KCl, NaCl, KNO3, or NaNO3 in (0.5 + 0.5) mol·dm-3 (K2CO3 + KHCO3) and (0.5 + 0.5) mol·dm-3 (Na2CO3 + NaHCO3) buffer at temperatures ranging from 293.1 to 323.1 K at 5 K intervals. Total ionic strength ranged from 2.0 to 5.0 mol·dm-3. The experimental viscosity data were satisfactorily correlated with the temperature and/or solute concentration by means of empirical equations.

The solubility of lithium potassium sulfate double salt in water and in aqueous ethanol has been determined at a temperature of 298.15 K, in the ethanol mass concentration range of 0-0.4 kg of ethanol/kg of water. An equation is given for the solubility as a function of the composition of potassium sulfate in solution. The densities and viscosities of the saturated solutions are also reported. Equations are given for both properties as a function of the solubility.