Metastable equilibrium for the quaternary system containing with lithium+potassium+magnesium+chloride in aqueous solution at 323K

The metastable equilibrium of the system contained with lithium, potassium, magnesium, and chloride in aqueous system was investigated at 323 K using an isothermal evaporation method. The isothermal experimental data and physicochemical properties, such as density and refractive index of the equilibrated solution, were determined. With the experimental results, the stereo phase diagram, the projected phase diagram, the water content diagram and the physicochemical properties versus composition diagrams were constructed. The projected phase diagram consists of three invariant points, seven univariant curves and five crystallization fields corresponding to single salts potassium chloride (KCl), lithium chloride monohydrate (LiCl·H₂O), bischofite (MgCl₂·6H₂O) and two double salts lithium carnallite (LiCl·MgCl₂·7H₂O) and potassium carnallite (KCl·MgCl₂·6H₂O). Salt KCl has the largest crystallization region; it contains almost 95% of the general crystallization field.     

Solubility measurement and prediction of phase equilibria in the quaternary system LiCl + NaCl + KCl + H_2O and ternary subsystem LiCl+ NaCl + H_2O at 288.15 K

Using isothermal dissolution method, the phase equilibrium relationship in quaternary system LiCl + NaCl + KCl+ H_2O and the ternary subsystem LiCl + NaCl + H_2O at 288.15 K were investigated. Each phase diagram of two systems was drawn. The phase diagram of LiCl + NaCl + H_2O system contains two solid phase regions of crystallization LiCl·2H_2O and NaCl. In the phase diagram of LiCl + NaCl + KCl + H_2O system, there are three crystallization regions: LiCl·2H_2O, NaCl and KCl respectively. In this paper, the solubilities of phase equilibria in two systems were calculated by Pitzer's model at 288.15 K. The predicted phase diagrams generally agree with the experimental phase diagrams.     

Crystallization of zeolite L from Na2O-K2O-Al2O3-SiO2-H2O system

Zeolite L powder was prepared from the substrate mixture of Na₂O-K₂O-Al₂O₃-SiO₂-H₂O system at temperatures of 373-443 K. In order to investigate the factors which influence the synthesis outcome, a reference system which yields zeolite L in a reproducible manner was chosen and subjected to controlled changes in synthesis parameters. The crystalline zeolite L samples obtained were characterized by elemental chemical analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). It was established that phase purity, morphology, and the size of crystals of crystalline product were affected by molar ratios of the substrate, such as SiO₂/Al₂O₃, (K₂O+Na₂O)/SiO₂, Na₂O/(K₂O+Na₂O), and H₂O/(K₂O+Na₂O). Amorphous silica powder (Zeosil) was the preferred silica source, and the crystallization rate was promoted by introducing gel aging, seeding, and rapid heating rate.     

Modification of poly(vinyl alcohol) films by the addition of magnesium chloride hexahydrate

Poly(vinyl alcohol) (PVA) films modified with Magnesium chloride hexahydrate (MgCl₂·6H₂O) were prepared by casting method. The prepared films were characterized by X‐ray diffraction measurements (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and mechanical testing. It was found that the presence of MgCl₂·6H₂O had considerable effects on the crystallinity, thermal, and mechanical properties of PVA films. The crystallization of PVA film was interrupted and the degree of crystallinity of PVA film decreased with the addition of MgCl₂·6H₂O. The glass transition temperature of PVA film decreased with the addition of MgCl₂·6H₂O. After modifying with MgCl₂·6H₂O, PVA film became soft, with lower tensile strength and higher elongation at break. The presence of MgCl₂·6H₂O could significantly increase the moisture content of PVA films and this may be the cause of the plasticizing. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

The system CaO-Al2O3-CaCl2-H2O at 23±2 °C and the mechanisms of chloride binding in concrete

The stable quaternary diagram for the system CaO-Al₂O₃-CaCl₂-H₂O at 23±4 °C has been constructed. Among the phases in this system are the calcium oxychlorides Ca(OH)₂.CaCl₂.H₂O and 3Ca(OH)₂.CaCl₂.12H₂O. The formation of Friedel's salt (FS) and calcium oxychlorides provides a mechanism for chloride binding in Portland cement concrete. The compatibility relationships involving these compounds, FS and Ca(OH)₂, were established empirically, and 3Ca(OH)₂.CaCl₂.12H₂O was found not to coexist in equilibrium with FS. The solubility behaviors of these compounds may play a role in affecting temperature-dependent corrosion rates. Additionally, the formation of oxychlorides from solutions containing elevated concentrations of NaCl may provide a mechanism by which ASR is facilitated.     

Efficient degradation of methylene blue dye by catalytic oxidation using the Na8Nb6O19·13H2O/H2O2 system

Na₈Nb₆O₁₉·13H₂O particles were synthesized by a simple hydrothermal method. The catalysts were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and thermogravimetric and differential scanning (TG-DSC). The XRD and TG-DSC analyses indicated that Na₈Nb₆O₁₉·13H₂O was an intermediate hexaniobate during the preparation of NaNbO₃ powders. Methylene blue (MB) dye degradation using Na₈Nb₆O₁₉·13H₂O/H₂O₂, Nb₂O₅/H₂O₂ and NaNbO₃/H₂O₂ systems were investigated, respectively. Among the catalytic oxidation systems, Na₈Nb₆O₁₉· 13H₂O showed the highest activity for degradation of MB in the presence of H₂O₂. The results indicated that the dye degradation efficiency could be 93.5% at 30 °C after 60 min in the presence of the Na₈Nb₆O₁₉·13H₂O/H₂O₂ system. It was also found that the degradation of MB over the catalytic systems followed pseudo-first-order kinetics, and the degradation rate was 0.02376 min⁻¹ in the Na₈Nb₆O₁₉·13H₂O/H₂O₂ system, which was higher than that in the Nb₂O₅/H₂O₂ and NaNbO₃/H₂O₂ systems. A possible mechanism for MB catalytic oxidation degradation using the Na₈Nb₆O₁₉·13H₂O/H₂O₂ system was proposed.     

288 K下Li+,K+//CO2-3,B4O2-7-H2O四元体系的相平衡

Solubilities and properties (density, conductivity and pH value) of solutions in the quaternary system Li⁺,K⁺//CO^2-₃,B₄O^2-₇-H₂O at 288 K were experimentally studied with the isothermal equilibrium method. The phase diagram of the system consisted of two invariant points E and F, five univariant curves, and four crystallization fields that belonged to K₂CO₃·3/2H₂O,Li₂B₄O₇·3H₂O,K₂B₄O₇·4H₂O and Li₂CO₃. The composition of the solution corresponding to E was w（CO^2-₃）=2.27 %,w（B₄O^2-₇）=6.05 %,w（K⁺ ）=4.30%,w(Li⁺)=0.30 % and the equilibrium solids were Li₂B₄O₇· 3H₂O+K ₂B₄O₇·4H₂O+Li₂CO₃;The composition of the solution for F was w(CO^2-₃)=22.45%,w(B₄O^2-₇)=1.88%,w(K⁺ )=29.96%,w(Li⁺ )=0.03% and the equilibrium solids were K₂CO₃·3/2H₂O+K ₂B₄O₇·4H₂O+Li₂CO₃. K₂CO₃ possesses strong salting-out effect on K₂B₄O₇,Li₂CO₃ and Li₂B₄O₇.     

五元体系KCl-KBr-K2SO4-K2B4O7-H2O 323 K和348 K的相平衡

用等温溶解平衡法研究了五元体系KCl-KBr-K₂SO₄-K₂B₄O₇-H₂O在323 K和348 K时的相平衡关系,测定了该五元体系在相应温度条件下平衡溶液的溶解度和密度,根据相平衡实验数据绘制相应的相图(K₂SO₄饱和)。研究结果表明:该五元体系在323 K和348 K条件下均属于固溶体型,相图中均有2个平衡固相结晶区,其平衡固相分别为固溶体K(Cl,Br)和K₂B₄O₇·4H₂O,1条单变量曲线。该五元体系323 K和348 K的相图相比,348 K时K₂ B₄O₇·4H₂O结晶区变小,而固溶体K(Cl,Br)结晶区变大。     

Influence of ionic equilibrium in the CuSO4-H2SO4-H2O system on the formation of irregular electrodeposits of copper

The relative concentration of hydrogen ion (H⁺) as a function of sulfuric acid (H₂SO₄) concentration (calculated using Pitzer's model) and the electrochemical processes by which irregular copper deposits are formed were correlated. Irregular deposits are formed by potentiostatic electrodeposition at a high overpotential where the hydrogen evolution reaction occurs parallel to copper electrodeposition. Two sets of acid sulfate solutions were analyzed. In one set of experiments, the concentration of CuSO₄ was constant while the concentration of H₂SO₄ was varied. The other set of experiments was performed with a constant concentration of H₂SO₄ and different concentrations of CuSO₄. Then, the volumes of the evolved hydrogen (calculated as the average current efficiencies of hydrogen evolution) and the morphologies of copper deposits, characterized by the SEM technique, obtained for the same ratio of CuSO₄/H₂SO₄ were mutually compared and discussed in terms of the relative concentrations of hydrogen ions (H⁺) as a function of the H₂SO₄ concentration. Good agreement between the ionic equilibrium in the CuSO₄-H₂SO₄-H₂O system and the results of the electrochemical processes was obtained. In this way, it was shown how this ionic equilibrium can be applied to predict and analyze the solution composition in electrolytic copper deposition processes.     

Thermodynamics of supersaturated solutions: From ternary electrolyte+solute+H2O to binary solute+H2O systems

In our previous paper, a new experimental technique based on the potentiometric method was developed to obtain thermodynamic activity data (in form of activity ratio) particularly for ternary electrolyte+nonelectrolyte+H₂O solutions supersaturated with the nonelectrolyte. In this paper, a rigorous thermodynamic approach is proposed to derive activity data for binary nonelectrolyte+H₂O solutions in the supersaturated region, via cell potentials of an electrolyte tracer and solubility data of the nonelectrolyte. An analysis of thermodynamic consistency is presented to evaluate the reliability and accuracy of the measured data. A systematic experimental investigation of three ternary electrolyte+nonelectrolyte+H₂O and two binary nonelectrolyte+H₂O systems is reported in both under-saturated and supersaturated regions (up to a supersaturation level of approximately 27%). Interesting thermodynamic behaviors are observed and their significance is discussed, with the role of thermodynamics in exploration of crystallization phenomena highlighted.     

Modeling solid–liquid equilibrium of NH4Cl‐MgCl2‐H2O system and its application to recovery of NH4Cl in MgO production

A new method to recover NH₄Cl from NH₄Cl‐rich aqueous solutions generated in the magnesia (MgO) production is developed on the basis of modeling the solid–liquid equilibrium (SLE) for the NH₄Cl‐MgCl₂‐H₂O system with the Pitzer model embedded in Aspen Plus? platform. The SLE values for the ternary system were determined from 278.15 to 348.15 K. The new standard‐state chemical potentials of NH₄Cl and MgCl₂·6H₂O were judicially obtained. The resulting equilibrium constants were used to determine new interaction parameters for the NH₄Cl‐H₂O and MgCl₂‐H₂O systems. These new parameters, together with the mixing parameters determined from correlating the experimental values, were used to correlate the equilibrium constant for NH₄MgCl₃·6H₂O, which plays a key role in NH₄Cl recovery. The results could extend SLE calculation for the NH₄Cl‐MgCl₂‐H₂O system from 278.15 to 388.15 K, satisfying the process identification and simulation requirement involved in the recovery process. The phase‐equilibrium diagram generated by modeling was illustrated to identify the process alternatives for recovering NH₄Cl. The resulting course to recover NH₄Cl by three fractional crystallization operations was finally proved feasible. © 2010 American Institute of Chemical Engineers AIChE J, 2011.     

The system CaOAl2O3Fe2O3 with added fluoride flux

Effects of fluoride fluxes, especially CaSiF₆·2H₂O upon phase equilibria in the system CaOAl₂O₃Fe₂O₃ are described, presenting liquidus data, new phase field boundaries and invariant points and solid solution areas. The primary phase field for C_12?xA₇·CaF₂ is increased substantially in size, and liquidus or invariant temperatures are depressed by amounts ranging from 20 to 80°C.     

The solubility of selenate-AFt (3CaO·Al2O3·3CaSeO4·37.5H2O) and selenate-AFm (3CaO·Al2O3·CaSeO4·xH2O)

The Se(VI)-analogues of ettringite and monosulfate, selenate-AFt (3CaO·Al₂O₃·3CaSeO₄·37.5H₂O), and selenate-AFm (3CaO·Al₂O₃·CaSeO₄·xH₂O) were synthesised and characterised by bulk chemical analysis and X-ray diffraction. Their solubility products were determined from a series of batch and resuspension experiments conducted at 25 °C. For selenate-AFt suspensions, the pH varied between 11.37 and 11.61, and a solubility product, log K_so=61.29±0.60 (I=0 M), was determined for the reaction 3CaO·Al₂O₃·3CaSeO₄·37.5H₂O+12 H⁺⇔6Ca²⁺+2Al³⁺+3SeO₄²⁻+43.5H₂O. Selenate-AFm synthesis resulted in the uptake of Na, which was leached during equilibration and resuspension. For the pH range of 11.75 to 11.90, a solubility product, log K_so=73.40±0.22 (I=0 M), was determined for the reaction 3CaO·Al₂O₃·CaSeO₄·xH₂O+12 H⁺⇔4Ca²⁺+2Al³⁺+SeO₄²⁻+(x+6)H₂O. Thermodynamic modelling suggested that both selenate-AFt and selenate-AFm are stable in the cementitious matrix; and that in a cement limited in sulfate, selenate concentration may be limited by selenate-AFm to below the millimolar range above pH 12.     

Electrokinetic Properties of Vermiculite and Expanded Vermiculite: Effects of pH,Clay Concentration and Mono- and Multivalent Electrolytes

Abstract

In this study, the zeta potential values of vermiculite and expanded vermiculite were measured to determine the effect of pH, clay concentration, and various mono- and multivalent electrolytes including NaCl, KCl, NH₄Cl, NaNO₃, NaClO₄, Na₂SO₄, Na₂CO₃, Na₃PO₄·12H₂O, MgCl₂·6H₂O, CaCl₂·2H₂O, BaCl₂, SrCl₂·6H₂O, CuCl₂·2H₂O, CoCl₂·6H₂O, NiCl₂, AlCl₃, and CrCl₃·6H₂O on the electrokinetic properties of vermiculite samples. It was found that generally the measured zeta potential values of expanded vermiculite for the studied systems were slightly more negative than that of vermiculite. The pH profiles of vermiculite and expanded vermiculite at acidic, natural, and basic pH values were obtained to determine the effect of time on the pH values of clay suspensions. The zeta potential measurements showed that the surface charge of clay particles was negative in water. The isoelectric point of vermiculite and expanded vermiculite were determined as pH 2.30 and 2.57, respectively. Divalent cations (Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺), heavy metal ions (Cu²⁺, Ni²⁺, and Co²⁺) and trivalent cations (Al³⁺ and Cr³⁺) were potential determining ions for vermiculite and expanded vermiculite particles. Moreover, divalent and trivalent cations caused the change of surface charge from negative to positive. On the other hand, monovalent cations (Na⁺, K⁺ and NH₄ ⁺), monovalent anions (Cl^?, NO₃ ^?, and ClO₄ ^?) and multivalent anions (SO₄ ^2?, CO₃ ^2?, and PO₄ ^3?) acted as indifferent ions for these clay particles.     

Carnallite decomposition into magnesia,hydrochloric acid and potassium chloride: A thermal analysis study; formation of pure periclase

A thermal analysis study of the one-stage decomposition of small (mg) quantities of carnallite, KCl. MgCl₂, 6H₂O → KCl + MgO + 5H₂O ↑ + 2HCl ↓, showed that dehydration and hydrolysis require temperatures above 300 °C. Decomposition of greater amounts, and analysis of the products, showed that at 450 °C, 88 to 90% of the magnesium occurs as chloride-free high-purity periclase. At higher temperatures increasing amounts of chlorides remain in the periclase and are difficult to separate. Unglazed porcelain is a suitable material for the decomposition vessel.     

Structural-microstructural characterization and optical properties of Eu3+,Tb3+-codoped LaPO4·nH2O and LaPO4 nanorods hydrothermally synthesized with microwaves

Rhabdophane-type Eu³⁺,Tb³⁺-codoped LaPO₄·nH₂O single-crystal nanorods with the compositions La_0.99999-xEu_xTb_0.00001PO₄·nH₂O (x?=?0–0.03), La_0.99999-yTb_yEu_0.00001PO₄·n′H₂O (y?=?0–0.010), and La_0.99999-zTb_zEu_0.000007PO₄·n′′H₂O (z?=?0–0.012) were hydrothermally synthesized with microwaves. It is shown that the Eu³⁺,Tb³⁺ codoping does not affect the thermal stability of these nanorods, which is due to the formation of substitutional solid solutions with both Eu³⁺ and Tb³⁺ replacing La³⁺ in the crystal lattice. Moreover, it is also shown that monazite-type Eu³⁺,Tb³⁺-codoped LaPO₄ single-crystal nanorods can be obtained by calcining their rhabdophane-type Eu³⁺,Tb³⁺-codoped LaPO₄·(n,n′ or n′′)H₂O counterparts at moderate temperature in air, and that they are thermally stable. It is also observed that, for the same Eu³⁺,Tb³⁺-codoping content, the monazite-type Eu³⁺,Tb³⁺-codoped LaPO₄ nanorods exhibit higher photoluminescent efficiency than the rhabdophane-type Eu³⁺,Tb³⁺-codoped LaPO₄· (n,n′ or n′′)H₂O nanorods. Moreover, it is found that the highest photoluminescence emission corresponds to the monazite-type La_0.96999Eu_0.02Tb_0.00001PO₄ nanorods for the La_0.99999-xEu_xTb_0.00001PO₄ system. However, for those compositions energy transfer from Tb³⁺ to Eu³⁺ does not occur. In addition, for an efficient energy transfer to occur, a content of at least 1?mol% Tb³⁺ is needed in all the studied materials.     

Atom transfer radical polymerizations of methyl methacrylate catalyzed by EBiB/SnCl2·2H2O(FeCl2·4H2O)/FeCl3·6H2O/MA5-DETA systems

The ATRP of methyl methacrylate (MMA) with the system of FeCl₂·4H₂O, N,N,N′,N″,N″-penta(methyl acylate)diethylenetriamine (MA₅-DETA) and ethyl 2-bromoisobutyrate (EBiB) showed high activity and is not well-controlled. The addition of a certain amount of FeCl₃·6H₂O as the additive into the above system results in the decrease of the polymerization rate and the improvement of the controllability. When SnCl₂·2H₂O was added instead of FeCl₂·4H₂O, a novel catalyst system SnCl₂·2H₂O/FeCl₃·6H₂O/EBiB/MA₅-DETA formed shows better controllability, higher catalytic activity and higher initiating efficiencies (more than 90%) in comparison with the system FeCl₂·2H₂O/FeCl₃·6H₂O/EBiB/MA₅-DETA. The polydispersities of the polymers kept range from M_w/M_n=1.18-1.26. The real active species in the new system is Fe (II) formed from the reaction of FeCl₃·6H₂O with the active radical species produced from the reaction of SnCl₂·2H₂O with EBiB.     

Dehydration Series in the System CaSiO3— SiO2— H2O

Hydrothermal studies show a dehydration series involving CSH(I), tobermorite, xonotlite gyrolite, truscottite (reyerite), silica, and wollastonite. The synthetic equivalents of gyrolite and Qruscottite (reyerite) have ideal compositions very close to 2CaO.3SiO₂.2H₂O and 3CaO.5SiO₂.1SH₂O respectively. With rising temperature the following reactions take place: (1) CSH(1) or tobermorite + silica = gyrolite (+H₂O); (2) gyrolite + silica = truscottite + H₂O; (3) gyrolite = tobermorite + truscottite + H₂O (high pressure); (4) gyrolite = xonotlite + truscottite + H₂0 (low pressure); (5) tobermorite = xonotlite + H₂0; (6) truscottite = xonotlite + quartz + H₂O; (7) xonotlite = wollastonite + H₂O. Data on reactions (l), (5), and (7) confirm results of previous workers. The water pressure-temperature curves or bands, except the one involving the breakdown of tobermorite, are steep. This curve crosses the curve representing the breakdown of gyrolite at a quintuple point. None of the reactions was reversed, and the temperatures indicated are approximate and are based on runs of about 4-weeks duration. For much shorter times somewhat higher temperatures are needed to cause the reactions, and conversely in much longer runs slightly lower temperatures might suffice. The silica was usually amorphous, cristobalite, or quartz with a mineralizer and therefore of higher activity than quartz alone. Up to 2 % alkali fluorides facilitated the formation of gyrolite; this is probably related to the fact that apophyllite in many cases accompanies gyrolite in amygdules. Truscottite (reyerite) forms very easily, and the rarity of reported occurrences, compared with those of xonotlite, gyrolite, and opaline silica, suggests that some workers may have overlooked it.     

四元水盐体系KCl-NaCl-CaCl2-H2O蒸气压测定

钢铁企业富钾烧结电除尘灰水浸液经脱除重金属杂质后可看作四元水盐体系KCl-NaCl-CaCl2-H2O,从该体系分离出氯化钾,需要首先通过蒸发浓缩及蒸发结晶。为了合理有效的控制蒸发操作过程,今采用静态法实验测定了四元水盐体系KCl-NaCl-CaCl2-H2O在KCl浓度为0～3 mol L 1,NaCl浓度为0～2 mol L 1,CaCl2浓度为0～1 mol L 1,温度为303.15～373.15 K的蒸气压,并通过数学线性回归得出了该体系的蒸气压与温度和体系组成的关系式,该关系式的获得有望为实际蒸发操作过程控制提供理论依据。     

Melt processing of poly(vinyl alcohol) through adding magnesium chloride hexahydrate and ethylene glycol as a complex plasticizer

The melt processing of poly(vinyl alcohol) (PVA) was achieved using magnesium chloride hexahydrate (MgCl₂·6H₂O) and ethylene glycol as a complex plasticizer. The interaction between the complex plasticizer and PVA was studied by Fourier transform infrared spectroscopy (FT‐IR). The PVA films were characterized using X‐ray diffraction (XRD), differential scanning calorimetry, thermogravimetric analysis (TGA), scanning electron microscope, and dynamic thermomechanical analysis (DMA) techniques. The band shift of the observed peak around 3335 cm^?1 in the FT‐IR spectra indicates that the complex plasticizer MgCl₂·6H₂O and ethylene glycol could form strong interactions with PVA and thus interrupt the intermolecular and intramolecular hydrogen bonding in PVA. The XRD results show that the addition of the complex plasticizer would significantly destroy the crystallites of PVA and result to the decrease of the degree of crystallinity of PVA. The melting point was reduced from 229°C of pure PVA to around 170°C after the plasticization. The TGA studies show that with the complex plasticizer, the thermal stability of PVA is improved. PVA plasticized by 30 wt% MgCl₂·6H₂O and 10 wt% ethylene glycol shows the tensile strength of 33 MPa and the elongation at break of 362%. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers