Phase Equilibria and Thermodynamic Properties in the Zinc Chloride

Article Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Phase Equilibria and Thermodynamic Properties in the Zinc Chloride−Zinc Methanesulfonate−Water System Artem A. Novikov,† Ekaterina V. Belova,† and Irina A. Uspenskaya*,† †

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Chemistry Department, Lomonosov MSU, Moscow, 119991, Russian Federation ABSTRACT: Obtained isothermal sections of the ZnCl2−Zn(CH3SO3)2−H2O phase diagram at −10.8 and 25 °C (262.35 and 298.15 K) showed the Zn(CH3SO3)2·4H2O hydrate to be stable under 25 °C in compositions with high ZnCl2 content. The change of the solubility of the Zn(CH3SO3)2·4H2O is slower with temperature than that of Zn(CH3SO3)2·12H2O both in binary and ternary mixtures. The Laliberte model parameters were obtained for Zn(CH3SO3)2−H2O and were used to predict density in the ternary aqueous solutions. Density and water activity of the aqueous solutions containing both ZnCl2 and Zn(CH3SO3)2 were measured at several temperatures. The measured values were compared with predicted densities; the deviation does not exceed 2% for all compositions.

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INTRODUCTION Solutions of inorganic salts are widely used in the oil and gas industry as heavy workover fluids, which are applied in the operation and drilling of wells under conditions of abnormally high reservoir pressure.1−4 One of the main requirements for such fluids is a high density to create a high hydrostatic pressure.5 Since some oil fields are located in the northern regions, where the temperature can reach −50 °C, the preparation of salt solutions that are resistant to freezing at negative temperatures is a matter of particular interest, since heavy liquids can be transported and stored in such conditions.6 Among heavy workover fluids of high density, compositions based on formate solutions (potassium or cesium) stand out due to their qualities.7−9 However, despite the low eutectic temperature, relative environmental safety, and low corrosivity, such fluids cannot reach very high densities (1.6−2.0 g/cm3) at low freezing temperatures. Therefore, they cannot be used as winter workover fluids in the case of abnormally high reservoir pressure. Zinc salts are often used to increase density of a solution. The zinc salt of methanesulfonic acid can provide a rather high density at 25−30 °C.10 Mixtures containing a methanesulfonate are environmentally safer than halide solutions, since methanesulfonate can be decomposed by living organisms in the natural sulfur cycle.11−13 However, the solubility of zinc methanesulfonate decreases abruptly below 26 °C due to the formation of a hydrate.10 Thus, a methanesulfonate could be used only as an additive in mixtures with a salt with higher solubility, for example, zinc chloride. Information on the density of the solutions and phase equilibria in the ZnCl2−Zn(CH3SO3)2−H2O ternary system is necessary to understand the extent to which the halide can be replaced by the methanesulfonate without loss of the © XXXX American Chemical Society

functional properties of the liquid. However, the system today is not well characterized in the literature. The purpose of this work was to obtain isothermal sections of the phase diagram of a three-component system ZnCl2− Zn(CH3SO3)2−H2O at −10.8 and 25 °C (262.35 and 298.15 K), the activity of water in unsaturated solutions, and the volumetric properties of the liquid phase. This data can be useful in the future to create a thermodynamic model of the liquid, calculate phase equilibria (SLE), and predict volume properties from subzero up to slightly elevated temperatures in heavyweight brines containing Zn2+, Cl−, CH3SO3− ions. It should be noted that aqueous solutions of ZnCl2 have a high viscosity14 and are prone to the formation of supersaturated solutions that undergo a glass transition even at relatively low cooling rates (0.5−2 K/min),15,16 therefore it may be difficult to achieve an equilibrium state in the system under study during cooling. In this regard, in this paper we abandoned the use of dynamic methods and resorted to the Schreinemakers’s method of wet residues,17 which is used in previous works of our laboratory.10,18

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EXPERIMENTAL SECTION Reagents. Commercial reagents used to synthesize Zn(CH3SO3)2·4H2O and Zn(CH3SO3)2·12H2O are listed in Table 1. The purities of the newly synthesized compounds were determined in the same way as in the previous work by Belova et al.10 Distilled water used in the present work for sample preparation has a conductivity of 4.5 μS/cm at 25 °C. Zinc methanesulfonate tetrahydrate was obtained according to the methodology used in the previous work by Belova et Received: April 4, 2019 Accepted: August 22, 2019

A

DOI: 10.1021/acs.jced.9b00292 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Table 1. Purity, CAS Numbers, and Suppliers of the Chemicals chemical name

CAS number

supplier

purity analysis

purification/purity analysis methods

ZnO ZnCl2 HSO3CH3 Zn(CH3SO3)2·4H2O Zn(CH3SO3)2·12H2O

1314-13-2 7646-85-7 75-75-2

Componet-Reaktiv Reahim Alfa Aesar synthesized in current work synthesized in current work

puriss. p.a.98.8% 98.0% >99.98% >99.93%

as stated by the supplier as stated by the supplier as stated by the supplier recrystallization/TXRF DSC standard purity test recrystallization/TXRF DSC standard purity test

al.10 Complexonometric titration by ethylenediaminetetraacetic acid (EDTA) with Eriochrome Black T was used to determine the quantity of zinc in the synthesized salt. Zinc mass fraction in the analyzed sample was 19.89 ± 0.07 wt % (theoretical value 19.96 wt %). If it was necessary, zinc methanesulfonate dodecahydrate was recrystallized from zinc methanesulfonate tetrahydrate solutions at 0−10 °C. Methods. The study of phase equilibria was performed by the method of isothermal solubility. Taking into account the ratio of components in the compositions under study and possible complications during sampling (e.g., a solid phase finely dispersed in a liquid phase due to close density values of both phases), mixtures for research were prepared by mixing calculated amounts of distilled water, a standardized solution of ZnCl2 and Zn(CH3SO3)2·4H2O (or melt/solution of Zn(CH3SO3) 2·12H2O). For more details of a sample preparation and possible further applications of those side effects during sampling, see Results and Discussion section. The prepared mixture at different temperatures were maintained differently. At 25 °C a liquid thermostat with water as a thermostatic liquid was used. The mixture was kept up to 12 h at temperatures above 50 °C to dissolve some of small particles, and then for 2−3 days at 25 °C to provide crystal growth while reaching equilibria at that temperature. The temperature in the liquid thermostat was recorded using an integrated thermometer with an accuracy of ±0.05 °C, the standard uncertainty was 0.1 °C. The temperature in the bath with a thermostatic mixture was measured using a platinum resistance thermometer (R = 100 Ω) TSPV-1 137 (Izteh, Russia) connected through a precision thermometric DC bridge MIT 8. The accuracy of temperature registered during the experiment in the thermostat was ±0.05 °C. The standard uncertainty of the recorded temperature was 0.1 °C. At −10.8 °C (262.35 K) the mixture was placed in a freezer maintaining the temperature with a standard uncertainty of 0.5 °C. It was possible to decrease the standard uncertainty of temperature maintenance to 0.2 °C due to the use of baths with a water-salt mixture of eutectic composition (KCl−H2O). In the freezer the mixture was kept for 3 to 7 days. The selected duration of the experiments substantially exceeded the time required to reach an equilibrium state, even for samples without mixing. Selected samples of a saturated solution and a wet residue weighing 2−5 g were weighed with an accuracy of 0.001 g, and diluted 5−20 times (up to ∼50 mL), adding distilled water and a dilute solution of nitric acid (puriss.) to prevent hydrolysis. The resulting solution was again weighed with an accuracy of 0.001 g. The concentration of Zn2+ ions in the liquid phase was determined by the complexometric titration method with 0.050 M EDTA and eriochrome Black as an indicator. The concentration of Cl− was determined by the Mohr method with a 10% acidified solution of AgNO3 standardized by 0.01

M NaCl with a 5% solution of K2CrO4 as an indicator. The content of CH3SO3− and water was calculated using an electroneutrality and material balance, respectively. Densities were determined with a VIP-2MP vibrating-tube densimeter. The following expression was used to obtain densities of the solutions: ρ = A + Bτ 2

(1)

where τ is the oscillation period. A and B are coefficients, determined from calibration at the measurement temperatures (298.15, 308.15, 323.15 K) by known densities and oscillation periods of ambient air, ultrapure water, and standard materials (produced and certificated by D.I. Mendeleyev Institute for Metrology, Russia, St. Petersburg, VNIIM). The temperature was maintained by a built-in thermostat, with temperature registration with ±0.005 °C precision; the standard uncertainty of the registered temperature u(T) was 0.02 °C. The determination of water activity coefficients was carried out by the static method. Since one volatile component (water) was present in the system, the determined vapor pressure corresponded to its partial vapor pressure at equilibrium. The measurement of saturated vapor pressure was carried out by the static method at temperatures of 15, 25, and 35 °C (288.15, 298.15, and 308.15 K) at a facility created earlier in the laboratory of Chemical Thermodynamics (the device was described in detail in the work of Kovalenko et al.19).

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RESULTS AND DISCUSSION Volume Properties. Laliberté Model for Density Calculating. To estimate the densities of the ternary solutions, the Laliberté model20 was used. The model specifies density as the reverse sum of two contributions: a pure solvent volume and apparent volume contributions of components: wH2O w v ̅ = 1/ρ = +∑ i ρH O ρapp, i (2) i 2

where ρH2O is water density; wH2O and wi are water and the mass fractions of the dissolved substance, respectively; ρapp,i is an apparent density of the dissolved substance. The last one can be presented as a reciprocal of the specific volume (v̅app,i), which is expressed by the following expression: ij yz (1 − wH2O) + c 2 + c3t jj zz vapp, ̅ i = 1/ρapp, i = 1/jjj z 2 z (c0(1 − wH2O) + c1)·exp(0.000001(t + c4) ) z k {

(3)

where ck (k takes the value from 0 to 4) are parameters for the dissolved substance and t is temperature in °C. To predict the densities of the liquid phase in the Zn(CH3SO3)2−ZnCl2−H2O system, it was necessary to determine the parameters of eq 3 for Zn(CH3SO3)2. Density of Unsaturated Solutions in the Zn(CH3SO3)2− H2O System. The experimentally measured densities of B



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Table 2. Parameters for eq 2 for the Laliberté Model ZnCl2 Zn(CH3SO3)2

c0

c1

c2

c3

c4

source

2048.26 2769

367.899 11.84

−0.0069 0

0.00118 0

505.032 −302.8

Laliberté paper20 current work

Table 3. Density of Unsaturated Solutions in the Zn(CH3SO3)2−H2O System at Various Temperatures and 0.1 MPa Pressurea Used To Optimize Parameters density10 ρb, kg/m3 25.0 °C/298.15 K 100waZn(CH3SO3)2

expc

5.12 10.51 15.31 25.37 30.45 37.50

1033.50 1074.50 1113.20 1202.40 1250.50 1327.10

50.0 °C/323.15 K 100Δr(ρ)e

calc

1033.70 0.02 1073.70 −0.07 1112.10 −0.10 1202.00 −0.03 1253.20 0.22 1331.90 0.36 Not Used To Optimize Parameters

25.0 °C/298.15 K

expc

calc

100Δr (ρ)e

1024.10 1064.10 1103.00 1191.10

1024.30 1063.90 1101.80 1190.70

0.02 −0.02 −0.11 −0.04

1314.60

1318.90

0.33

35.0 °C/308.15 K

50.0 °C/323.15 K

density ρ , kg/m (current work) b

3

100waZn(CH3SO3)2

expd

calc

100Δr (ρ)e

expd

calc

100Δr (ρ)e

expd

calc

100Δr (ρ)e

5.26 8.63 14.45 20.95 27.16

1033.90 1058.60 1104.50 1157.60 1210.10

1034.70 1059.40 1105.00 1160.80 1219.60

0.08 0.08 0.05 0.30 0.80

1031.90 1056.80 1101.60 1155.20 1208.00

1031.50 1056.20 1101.60 1157.10 1215.60

−0.04 −0.06 0.00 0.16 0.63

1024.40 1047.90 1091.50 1145.40 1201.40

1025.30 1049.70 1094.80 1149.90 1208.00

0.09 0.18 0.30 0.40 0.60

a

w, mass fraction. bStandard uncertainty of the values of the variables u(T) = 0.02 K, u(P) = 1000 Pa, ur(ρ) = 0.002, ur(w(Zn(CH3SO3)2)) = 0.002. Experimental data published in ref 10. dExperimental data obtained in the current work. eRelative deviation of the values calculated by the Laliberté model from experimental values; ur, relative standard uncertainty. c

unsaturated solutions in the Zn(CH3SO3)2−H2O system at different temperatures are given in Table 2. The parameters of the Laliberté model for the binary Zn(CH3SO3)2−H2O mixture were absent in the literature and were determined by nonlinear optimization in the MATLAB environment using data from our previous work.10 The densities were calculated by eq 2 using the parameters presented in Table 2. The predictive ability of the obtained binary parameters set of the model was tested on the results that were not used in the optimization of parameters (additionally measured in the current work). The results of the comparison of calculated and measured values for both data sets (used and not used in the optimization) are presented in Table 3. Density of Unsaturated Solutions in the ZnCl2 − Zn(CH3SO3)2 − H2O System. The parameters of the Laliberté model for eq 3 for zinc chloride were taken from the paper of Laliberté.20 Using the parameters listed in Table 2, we calculated the densities of the liquid phase in a threecomponent system. The maximum deviation of the experimental results for densities of unsaturated solutions obtained in this work at 298.15 and 323.15 K from calculated values was 1.5 % for both 298.15 and 323.15 K (see Table 4). As in the case of the previous three-component systems, for most solutions the deviation of the calculated densities from the experimental ones is slightly higher than the experimental standard uncertainty (about 1−2%). Such a result is quite expected. The Laliberté model should have a good predictive ability in the qualitative description of the properties of binary solutions. However, like any model

Table 4. Density of Unsaturated Solutions in the ZnCl2− Zn(CH3SO3)2−H2O System at Various Temperatures and a Pressure 0.1 MPaa composition of the solution, 100wa no.

Zn(CH3SO3)2

1 2 3 4 5 6

20.02 14.97 16.36 7.32 7.59 24.48

1 2 3 4 5 6

20.02 14.97 16.36 7.32 7.59 24.48

ZnCl2

density ρ, kg/m3 Exp.

25.0 °C/298.15 K 23.12 1423.1 29.26 1429.3 10.25 1224.9 44.74 1574.6 14.83 1196.8 14.06 1346.2 50.0 °C/323.15 K 23.12 1404.7 29.26 1412.8 10.25 1211.0 44.74 1553.2 14.83 1181.7 14.06 1331.1

Calc.

100Δr(ρ)b

1429.2 1450.9 1227.8 1581.5 1195.4 1361.0

−0.4 −1.5 −0.2 −0.4 0.1 −1.1

1412.7 1433.7 1214.2 1562.9 1180.8 1346.0

0.6 1.5 0.3 0.6 0.1 1.1

a

w, mass fraction. Standard uncertainty of the values of the variables u(T) = 0.02 K, u(P) = 1000 Pa, ur(ρ) = 0.004, ur(w(Zn(CH3SO3)2)) = 0.002, ur(w(ZnCl2)) = 0.002. bRelative deviation of the values calculated by the Laliberté model from experimental values (in %); ur, relative standard uncertainty.

based on the rules for mixing binary parameters, it inherits a number of drawbacks of this type of model. First of all, these descriptions include multicomponent systems with strong interactions between components (formation of associates, C



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studied by several authors,27−31 a phase diagram in a wide range of compositions and temperatures was first presented in the work of Belova et al.10 Features of the Samples Preparation at Different Conditions. Making compositions with a high content of zinc chloride was fraught with difficulties. Because of the high density and viscosity of the solutions, the diffusion processes were slowed down. As a result, crystal growth was hampered, which caused the formation of a finely dispersed solid phase, the density of which was often close to the density of the liquid. For this reason, the sedimentation of the solid phase was slow and incomplete. We managed to separate the liquid phase well from the precipitate; however, it was not possible to isolate the precipitate in areas of high density of the solution (see Isothermal Section at 25 °C). To obtain as large crystals as possible, a number of methods for preparing compositions from various starting compounds were developed. The choice of zinc methanesulfonate precursor for the preparation of the studied mixtures depended on the results of the preliminary thermostatting of test compounds:

etc.), which include the majority of solutions of zinc salts. The addition of zinc chloride with another zinc salt affects a zinc speciation in a solution. Strong zinc chloride solutions are eager to form network structures,21 and zinc chloride trihydrate melt is an ionic liquid formed by [Zn(H2O)6]2+ and [ZnCl4]2−.22 In a less concentrated solution, both these forms exist, too.22 It seems that the [Zn(H2O)6]2+ form prevails in methanesulfonate solutions, and it should act as a network modifier for ZnCl2. This seems to be the reason why the predicted density values turn out to be slightly higher compared to the measured ones in solutions with high total zinc content. Empiric property models do not take into account structure: it seems that parameters fitted from the binary ZnCl2−H2O system were achieved for a more condensed network than ternary ones with the same water content. Lines of equal density, estimated using the Laliberté model with parameters for ZnCl2 and Zn(CH3SO3)2 from Table 2, are shown in Figure 1. They are combined with the isothermal

1. Wet large crystals of Zn(CH3SO3)2·4H2O were isolated from saturated hot solution for the preparation of compositions in which the corresponding hydrate was the equilibrium solid phase. 2. Melted Zn(CH3SO3)2·12H2O/saturated hot solution of Zn(CH3SO3)2·4H2O was used to prepare the initial compositions of a given concentration in the case when the equilibrium solid phase was supposedly one or another zinc chloride hydrate, or when in equilibrium with a solution there should be two solid phases. 3. The dry Zn(CH3SO3)2·4H2O with proved water stoichiometry was used in the preparation of most of the initial compositions maintained at −10.8 °C. Isothermal Section at 25 °C (298.15 K). As mentioned above, the study of the region of ZnCl2 high concentrations at room temperature was greatly hampered by the fact that the density of saturated solutions was close to the density of the solid phase, because of which the solid formed a suspension or floated (Table 5, compositions 1−2). For this reason, the separation of the solid phase from the solution was difficult in practice and wet residue concentrations were the same as the liquid composition within the standard uncertainty of the chemical analysis. In such a situation, conduction of the Schreinemakers’s rays does not allow obtaining statistically significant estimates. On the basis of the literature data on the ZnCl2−H2O system, it can be assumed that the equilibrium solid phase at 25 °C/298.15 K in this concentration range will be ZnCl2·4/3H2O (Figure 2, built on the values given in Table 5); the area of hydrate stability is in the range from 80.5 wt % ZnCl2, 0 wt % Zn(CH3SO3)2 to 65.72 wt % ZnCl2, 10.29 wt % Zn(CH3SO3)2. The obtained concentrations of the liquid phase were used to construct the crystallization field of this compound. The curvature of the resulting surface agrees well with the solubility of this phase in binary solutions. Since the determination of the composition of wet residues was difficult, the cosaturation point of ZnCl2·4/3H2O and Zn(CH3SO3)2·4H2O was obtained by extrapolating the corresponding fields; its approximate coordinates are 66 wt % ZnCl 2 , 13 wt % Zn(CH 3 SO 3 ) 2 . Although the Zn(CH3SO3)2·12H2O hydrate becomes stable at this temper-

Figure 1. Lines of equal density (in kg/m3) calculated by the Laliberté model, combined with isothermal section at −10.8 °C/ 262.35 K. (A) pure solid of ZnCl2·3H2O; (B) pure solid of Zn(CH3SO3)2·4H2O; (C) pure solid of Zn(CH3SO3)2·12H2O; (D) water.

section at −10.8 °C/262.35 K (obtained from the data presented in Table 6). According to the figure, the chloride can be replaced by biodegradable methanesulfonate to 10−20 wt % of the total content of both zinc salts without loss of density and stability of the solution to freezing to −10 °C. This is an interesting result, since the replacement of halide with another anion may reduce the rate of corrosion. Phase Equilibria in the ZnCl2−Zn(CH3SO3)2−H2O System. In the study of phase equilibria in the ternary system, data on two-component systems of zinc chloride− water and zinc methanesulfonate−water were taken into account. The phase equilibria and thermodynamic properties of the phases in the ZnCl2−H2O system were studied in sufficient detail in the works.23−26 A large number of original works are cited, in particular, in the work of Iliuta et al.27 The Zn(CH3SO3)2−H2O system has not been studied until recently. Although the stability and structure of transition metals methanesulfonates and their hydrates were previously D



Article

Table 5. Solubility of Salts in the Zn(CH3SO3)2−ZnCl2−H2O System at 25.0 °C/298.15 K Temperature and 0.1 MPa Pressurea composition of the liquid phase, 100wb no.

Zn(CH3SO3)2

ZnCl2

1 2 3 4 5 6 7 8 9 10 11 12

1.26 5.35 10.29 14.18 23.71 24.13 27.47 36.74 36.90 41.55 46.60 50.80

75.83 70.73 65.72 63.05 43.70 43.30 36.05 18.77 18.68 14.62 7.31 2.40

composition of wet residues, 100wb Zn(CH3SO3)2

ZnCl2

17.31 26.78 31.24 33.66 40.79

61.31 11.00 33.20 33.97 17.30

44.10 47.48

13.41 7.20

equilibrium solid phase ZnCl2·4/3H2Oc ZnCl2·4/3H2Oc ZnCl2·4/3H2Oc Zn(CH3SO3)2·4H2O Zn(CH3SO3)2·4H2O Zn(CH3SO3)2·4H2O Zn(CH3SO3)2·4H2O Zn(CH3SO3)2·4H2O Zn(CH3SO3)2·4H2O Zn(CH3SO3)2·4H2O Zn(CH3SO3)2·4H2O Zn(CH3SO3)2·4H2O

a

Standard uncertainty of the values of the variables u(T) = 0.1 K, u(P) = 1000 Pa, ur(w(ZnCl2)) = 0.012, ur(w(Zn(CH3SO3)2)) = 0.018. bw, mass fraction; ur, relative standard uncertainty. cAssumed solid phase. Fine precipitates are not uncommon unless very pure, doubly sublimed ZnCl2 is utilized.

Figure 2. Isothermal section of ZnCl2−Zn(CH3SO3)2−H2O system at 25 °C/298.15 K. (A) Pure solid of ZnCl2·4/3H2O; (B) pure solid of Zn(CH3SO3)2·4H2O. (●) Composition of coexisting phases according to analysis data; (⧫) initial (raw) composition; (▲) individual substances according to binary system data.

Figure 3. Isothermal section of ZnCl2−Zn(CH3SO3)2−H2O system at −10.8 °C/262.35 K. A, pure solid of ZnCl2·3H2O; (B) pure solid of Zn(CH3SO3)2·4H2O; (C) pure solid of Zn(CH3SO3)2·12H2O; (D) water; (●) composition of coexisting phases according to analysis data; (⧫) initial (raw) composition; (▲) the individual substances according to binary system data.

ature, its relative stability is very small, and the crystallization field Zn(CH3SO3)2·12H2O turns out to be degenerate due to the proximity of the selected temperature to hydrate’s melting point (26 °C) and due to lowering the melting temperature of the mixture by adding the third component. The boundary of the crystallization field of Zn(CH3SO3)2·4H2O is in good agreement with the solubility of Zn(CH3SO3)2 at 25 °C/ 298.15 K.10 Isothermal Section at −10.8 C (262.35 K). The crystallization field of Zn(CH3SO3)2·12H2O increases with a temperature decrease. Our additional experiment on solubility at 15 °C/288.15 K for the choice of compositions studied by the vapor pressure method (see section on water activities) showed that this compound was stable up to ∼25 wt % ZnCl2. However, Zn(CH3SO3)2·4H2O tetrahydrate becomes stable with an increase of zinc chloride concentration. At a temperature of −10.8 °C/262.3 K, ice, ZnCl2·3H2O, Zn(CH3SO3)2·4H2O, and Zn(CH3SO3)2·12H2O become stable (Figure 3, constructed according to the values given in

Table 6). The crystallization field of ZnCl2·3H2O (like ZnCl2·4/3H2O at 25 °C/298.15 K) is rather narrow compared to the crystallization fields of zinc methanesulfonate crystalline hydrates. The extrapolated cosaturation point of ZnCl2·3H2O and Zn(CH3SO3)2·4H2O falls on 15 wt % Zn(CH3SO3)2, 59 wt % ZnCl2. Although the corresponding temperature is subsolidus for the Zn(CH3SO3)2−H2O system, ice and Zn(CH3SO3)2·12H2O are in equilibrium in the binary system. The crystallization field of Zn(CH3SO3)2·4H2O in the threecomponent system decreases as the temperature decreases from 25 °C/298.15 K to −10.8 °C/262.35 K. The cosaturation point of Zn(CH3SO3)2·12H2O and Zn(CH3SO3)2·4H2O at −10.8 °C/262.35 K lies at 13.5 wt % Zn(CH3SO3)2 and 42.5 wt % ZnCl2. At some point due to temperature reduction and the composition of the solution shear in the region of higher concentrations, the density of the solution reaches a value intermediate between the calculated crystallographic densities of both solid phases (see Table 7). Because of this, there is a E



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Table 6. Solubility of Salts in the Zn(CH3SO3)2−ZnCl2−H2O System at −10.8 °C/262.35 K Temperature and 0.1 MPa Pressurea composition of the liquid phase, 100wb

composition of wet residues 100wb

no.

Zn(CH3SO3)2

ZnCl2

Zn(CH3SO3)2

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

4.89 9.52 16.18 17.29 17.67 17.40 14.92 13.52 12.95 12.04 10.68 11.03 13.38 12.77 11.55 8.57 7.09 5.20

17.54 13.44 7.34 7.18 7.45 9.60 12.67 14.90 14.33 22.87 30.30 32.06 42.62 43.00 46.76 60.68 63.28 62.50

2.60 6.65 10.07 16.29 22.48 33.81 54.17

10.43 9.99 5.30 2.49 2.00 4.99 0.58

ZnCl2

equilibrium solid phase

33.91 33.65 26.85 22.27c 51.59d 27.73c, 43.86d 17.51 14.69 6.01 3.24

9.97 15.02 20.23 32.69c, 17.03d 27.84c, 23.07d 42.93 57.21 64.85 67.28

ice ice ice ice + Zn(CH3SO3)2·12H2O ice + Zn(CH3SO3)2·12H2O Zn(CH3SO3)2·12H2O Zn(CH3SO3)2·12H2O Zn(CH3SO3)2·12H2O Zn(CH3SO3)2·12H2O Zn(CH3SO3)2·12H2O Zn(CH3SO3)2·12H2O Zn(CH3SO3)2·12H2O Zn(CH3SO3)2·4H2O + Zn(CH3SO3)2·12H2O Zn(CH3SO3)2·4H2O + Zn(CH3SO3)2·12H2O Zn(CH3SO3)2·4H2O Zn(CH3SO3)2·4H2O ZnCl2·3H2O ZnCl2·3H2O

a Standard uncertainty of the values of the variables u(T) = 0.1 K, u(P) = 1000 Pa, ur(w(ZnCl2)) = 0.012, ur(w(Zn(CH3SO3)2)) = 0.018. bw, mass fraction; ur, relative standard uncertainty. At the point of saturation, a spatial separation of sediment was observed. cUpper fraction. dLower fraction.

Table 7. Phase Densities at 25 °C/298.15 K

Table 8. Composition of the Studied Solutions in the ZnCl2−Zn(CH3SO3)2−H2O System after Degassing and Measuring the Saturated Vapor Pressure

composition of the liquid phase, 100wa Zn(CH3SO3)2 5.00 10.00 13.00

ZnCl2

70.00 65.00 42.00 solid phase

ρ, kg/m3 2080 2070 1640

Zn(CH3SO3)2·12H2O ZnCl2·3H2O Zn(CH3SO3)2·4H2O

calculation by weight loss, 100wa

source current work: evaluation by Laliberté model ρ, kg/m3

source

1501 1970 1910

10 22 32

result of chemical analysis, 100wa

no.

Zn(CH3SO3)2

ZnCl2

Zn(CH3SO3)2

ZnCl2

1 2 3 4 5 6

22.11 14.97 16.67 8.11 7.62 24.73

23.86 29.26 10.25 44.77 14.90 13.98

22.36 15.12 16.80 8.56 7.18 24.94

23.67 29.35 10.27 44.54 14.99 13.89

a

a

spatial separation of solid phases: the Zn(CH3SO3)2·12H2O phase, which is less dense than the solution, emerges, and the heavy phase −Zn(CH3SO3)2·4H2O− appears at the bottom of the vessel (wet residues of both sediments are presented for this point in Table 6). This phenomenon was observed at −10.8 °C/262.35 K. The crystallization field of Zn(CH3SO3)2·12H2O, the solubility of which strongly decreases with temperature in both the binary and in the ternary system at −10.8 °C/262.35 K, intersects the field of ice crystallization at the saturation point with 17.3 wt % Zn(CH3SO3)2 and 7.18 wt % ZnCl2. This value is in good agreement with the eutectic coordinate of the boundary binary Zn(CH3SO3)2−H2O system: 23.2 ± 2.1 wt % Zn(CH3SO3)2 at −9.6 °C/263.55 K.10 Water Activities in the ZnCl2−Zn(CH3SO3)2−H2O System. The composition of the studied solutions are presented in Table 8. After degassing and saturated vapor pressure measurements, an additional chemical analysis was performed to clarify the content of Zn2+ and Cl−. It was necessary to correctly relate the results of measuring P(H2O)

to certain compositions of the liquid phase. The chemical analysis did not show a significant change in the Zn to Cl ratio, whereas a sample mass lowered by 3−5% during degassing. As one can see from Table 8, differences in solution concentrations after degassing (calculated from initial concentrations after degassing assuming water the only volatile component) and the ones obtained by direct chemical analysis of the resulting solutions does not exceed the standard uncertainty. Thus, we can assume that water is indeed the only volatile component. The measured vapor pressure and the water activities calculated from them in unsaturated solutions of the ZnCl2− Zn(CH3SO3)2−H2O system are listed in Table 9. In Zn(CH3SO3)2 concentrated solutions, a bulk sediment of Zn(CH3SO3)2·2H2O is likely to precipitate during degassing. Therefore, the studied solutions contained no more than 30 wt % of Zn(CH3SO3)2. Figure 4 presents the compositions of the solutions under investigation after degassing and the solubility of Zn(CH 3 SO 3 ) 2 ·12H 2 O, Zn(CH 3 SO 3 ) 2 ·4H 2 O, and

w, mass fraction.

w, mass fraction. Relative standard uncertainty ur(w(ZnCl2)) = 0.012, ur(w(Zn(CH3SO3)2)) = 0.018.

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Table 9. Results of Saturated Vapor Pressure Measurements in the ZnCl2−Zn(CH3SO3)2−H2O System ZnCl2−Zn(CH3SO3)2−H2O Ta/K

P/kPa

308.15 298.15 288.15

3.978 2.205 1.175

308.15 298.15 288.15

5.036 2.830 1.516

308.15 298.15 288.15

5.156 2.893 1.550

u(P)/kPa Sample 1 0.012 0.005 0.003 Sample 3 0.011 0.007 0.004 Sample 5 0.015 0.007 0.004

a(H2O)

Ta/K

u(a)

P/kPa

0.707 0.6963 0.6896

0.002 0.0016 0.0018

308.15 298.15 288.15

4.150 2.314 1.243

0.895 0.894 0.890

0.002 0.002 0.002

308.15 298.15 288.15

3.135 1.723 0.912

0.917 0.914 0.910

0.003 0.002 0.002

308.15 298.15 288.15

4.498 2.517 1.347

u(P)/kPa Sample 2 0.009 0.005 0.003 Sample 4 0.009 0.004 0.003 Sample 6 0.012 0.007 0.004

a(H2O)

u(a)

0.7379 0.7307 0.7295

0.0016 0.0016 0.0018

0.5575 0.5441 0.5352

0.0016 0.0013 0.0018

0.800 0.795 0.791

0.002 0.002 0.002

a

Standard uncertainty u(T) = 0.02 K.

ZnCl2·4/3H2O at 15 and 25 °C. It can be seen that the obtained values of vapor pressure can be attributed to unsaturated solutions for all compositions in the entire temperature range studied. As shown by the results of measuring the vapor pressure (Figure 5) for six solutions of the ZnCl2−Zn(CH3SO3)2−H2O system, for concentrated mixtures containing >10 wt % of ZnCl2, the change in water activity from temperature significantly exceeds the experimental standard uncertainty even in such a narrow temperature range (15−35 °C), and the maximum change is observed for the most concentrated zinc chloride solution (sample no. 4). For sample no. 3 with a ZnCl2 content of less than 10% by weight, the change in water activity with temperature is insignificant. The results obtained are in good agreement with the observation that the change in water activity with temperature in such a narrow temperature range (15−35 °C) does not exceed the measurement standard uncertainty in a binary Zn(CH3SO3)2−H2O system,33 while in the ZnCl2− H2O system, the activity of the components significantly depends on the temperature.34

Figure 4. Composition of the solutions selected for measuring the saturated vapor pressure, after degassing, depicted by red circles; solubility of Zn(CH3SO3)2·12H2O, Zn(CH3SO3)2·4H2O, and ZnCl2·4/3H2O at 15 and 25 °C, depicted by blue circles and black circles, respectively.

Figure 5. Water activity vs temperature for samples 1−6. G



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(9) Caenn, R.; Darley, H. C.; Gray, G. Composition and Properties of Drilling and Completion Fluids; Gulf Professional Publishing, 2011. (10) Belova, E. V.; Krasnov, V. S.; Ilyukhin, A. B.; Uspenskaya, I. A. Solid-Liquid Phase Equilibrium in the Water−Zn(II) Methanesulfonate and Water−Cu(II) Methanesulfonate Systems. Thermochim. Acta 2018, 668, 46−57. (11) Bentley, R.; Chasteen, T. G. Environmental VOSCs–Formation and Degradation of Dimethyl Sulfide, Methanethiol and Related Materials. Chemosphere 2004, 55, 291−317. (12) Schafer, H.; Myronova, N.; Boden, R. Microbial Degradation of Dimethylsulphide and Related C1-Sulphur Compounds: Organisms and Pathways Controlling Fluxes of Sulphur in the Biosphere. J. Exp. Bot. 2010, 61, 315−334. (13) Boden, R.; Murrell, J. C.; Schäfer, H. Dimethylsulfide Is an Energy Source for the Heterotrophic Marine Bacterium Sagittula Stellata. FEMS Microbiol. Lett. 2011, 322, 188−193. (14) Weingaertner, H.; Mueller, K. J.; Hertz, H. G.; Edge, A. V. J.; Mills, R. Unusual Behavior of Transport Coefficients in Aqueous Solutions of Zinc Chloride at 25. Degree. C. J. Phys. Chem. 1984, 88, 2173−2178. (15) Kanno, H.; Shirotani, I.; Minomura, S. Isotope Effect of the Glass Transition Temperature of Aqueous Solution. LiCl and ZnCl 2 Solutions in Water and D 2 O. Bull. Chem. Soc. Jpn. 1980, 53, 2079− 2080. (16) Kanno, H.; Hiraishi, J. Raman Spectroscopic Study of Glassy Aqueous Zinc Halide Solutions. J. Raman Spectrosc. 1980, 9, 85−89. (17) Schott, H. A Mathematical Extrapolation for The Method of Wet Residues. J. Chem. Eng. Data 1961, 6, 324−324. (18) Belova, E. V.; Mamontov, M. N.; Uspenskaya, I. A. A Sodium Chloride−Zinc Chloride−Water System: Solubility of Solids and Density of Liquid in Wide Range of Temperatures. J. Chem. Eng. Data 2016, 61, 2426−2432. (19) Kovalenko, N. A.; Pustovgar, E. A.; Uspenskaya, I. A. The Water-18-Crown-6 System: Experimental Investigation and Thermodynamic Modeling. J. Chem. Eng. Data 2013, 58, 159−166. (20) Laliberté, M.; Cooper, W. E. Model for Calculating the Density of Aqueous Electrolyte Solutions. J. Chem. Eng. Data 2004, 49, 1141− 1151. (21) Follner, V. H.; Brehler, B. Die Kristallstruktur des ZnCl2. 4/ 3H2O. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1970, 26, 1679−1682. (22) Wilcox, R. J.; Losey, B. P.; Folmer, J. C.; Martin, J. D.; Zeller, M.; Sommer, R. Crystalline and liquid structure of zinc chloride trihydrate: a unique ionic liquid. Inorg. Chem. 2015, 54, 1109−1119. (23) Goldberg, R. N. Evaluated Activity and Osmotic Coefficients for Aqueous Solutions: Bi-univalent Compounds of Zinc, Cadmium, and Ethylene Bis(Trimethylammonium) Chloride and Iodide. J. Phys. Chem. Ref. Data 1981, 10, 1−56. (24) Anstiss, R. G.; Pitzer, K. S. Thermodynamics of Very Concentrated Aqueous Electrolytes: LiCl, ZnCl2, and ZnCl2-NaCl at 25°C. J. Solution Chem. 1991, 20, 849−858. (25) Kirgincev, A. N.; Trushnikova, L. N., Lavrenteva, V. G. Rastvorimost Neorganicheskih Veshchestv v Vode (Solubility of Inorganic Substances in Water); Khimiya: Leningrad, 1972. (26) Zdanovsky, A. B.; Solov’eva, E. F.; Ezrokhi, L. L.; Lyakhovskaya, E. I. Spravochnik Ehksperimentalnyh Dannyh Po Rastvorimosti Solevyh Sistem (Handbook of Experimental Data on the Solubility of Salt Systems). 4. Binary Systems. Group II Elements and Their Compounds; Lengoskhimizdat: Leningrad, 1963. (27) Iliuta, M. C.; Thomsen, K.; Rasmussen, P. Modeling of Heavy Metal Salt Solubility Using the Extended UNIQUAC Model. AIChE J. 2002, 48, 2664−2689. (28) Charbonner, F. Thermal Behavior of Some Compounds of Methanesulfonic Acid with Transition Metals. Thermochim. Acta 1979, 33, 31−39. (29) Ramírez, A.; Gómez, M. L.; Guerrero, A.; Jerez, A. Thermal Decomposition of Co(II), Cu(II) AND Zn(II) Methanesulfonates. Thermochim. Acta 1988, 124, 9−16.

CONCLUSIONS As a result of the present studies a set of new experimental data within the properties of binary and ternary systems with Zn(CH3SO3)2 as a component was obtained: 1. The phase equilibria in the ZnCl2−Zn(CH3SO3)2−H2O system have been studied in the temperature range of 262.35−298.15 K. 2. The activity values of the solvent in ZnCl2−Zn(CH3SO3)2−H2O systems at 15, 25, 35 °C/288.15, 298.15, 308.15 K were determined for the first time. 3. The densities of solutions in Zn(CH3SO3)2−H2O and ZnCl2−Zn(CH3SO3)2−H2O systems were obtained in the temperature range of 298.15−323.15 K. The analysis of these data allows concluding that (1) zinc chloride can be replaced by biodegradable methanesulfonate to 10−20 wt % of the total content of both zinc salts without loss of density and stability of the liquid phase to −10 °C, and (2) the parameters of the Laliberté model for estimating the density of solutions containing a CH3SO3−-ion can be recommended for further calculations.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected], [email protected]. ORCID

Irina A. Uspenskaya: 0000-0001-6271-1316 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The present study was performed in the framework of Program “Chemical Thermodynamics” (AAAA-A16-116061750195-2) and by partial financial support of RFBR No.16-33-00958. The authors acknowledge partial support from M.V. Lomonosov Moscow State University Program of Development.

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REFERENCES

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Phase Equilibria and Thermodynamic Properties in the Zinc Chloride

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