Solubilities and Modeling of Glycine in Mixed NaClâMgCl2 Solutions

Article pubs.acs.org/jced

Solubilities and Modeling of Glycine in Mixed NaCl−MgCl2 Solutions in a Highly Concentrated Region Ziaul Haque Ansari and Zhibao Li* Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China ABSTRACT: Electrolyte solution has an effect on growth and nonlinear optical properties of glycine crystals at certain conditions. The solubility of glycine in MgCl2−H2O solutions with molality from 0.5 to 3.5 was investigated by a dynamic method from (283.15 to 333.15) K. The solubilities of MgCl2·6H2O in glycine− water solution with molalities from 0.08 to 0.67 were also measured by the same method from (293.15 to 323.15) K. For model validation, the solubility of glycine in mixed NaCl−MgCl2 solutions was also measured. The solubilities of both glycine and MgCl2·6H2O solids were observed to increase with increasing temperature and concentration with respect to one another, acting as solutes. The OLI correlation with an existing model shows large errors in the solubility calculation for the glycine−NaCl−MgCl2−H2O system. A self-consistent model using a unified set of model parameters obtained by regressing the solubility of glycine in single salt systems was developed. The model can accurately predict the solubilities of glycine in mixed NaCl−MgCl2 solutions with average absolute deviations lower than 2.5%.

1. INTRODUCTION Glycine, a biochemical, is an amino acid commonly found in proteins. Glycine broad applications in various types of industries draw attention among researchers to study its properties from many viewpoints. Among them, there is a significant amount of work regarding the thermodynamic properties of glycine, which provide information on processing during industrial synthesis. An aqueous electrolyte solution is used to modify glycine structures in the form of γ-glycine, which crystallizes in the trigonal−hexagonal system with a noncentrosymmetric space group of P31 structure, making it an appropriate substance for optical devices.1,2 The development of γ-glycine in the presence of different electrolytes, such as sodium chloride, sodium hydroxide, sodium fluoride, phosphoric acid, lithium acetate, and lithium bromide from aqueous solutions of glycine, was investigated earlier.3−6 Recently, Dillip et al.7 studied the effect of magnesium chloride on the growth of glycine and found that some of the physical properties of γ-glycine crystals are enhanced by this solute. Furthermore, habit modification occurs when the absorbing layer of both the recipient crystal and the habit-modifying substance corroborates in their atomic arrangement.8 The impact of this view is that habit modification is a two-way phenomenon. Therefore, glycine has been used as an additive to modify the habits of growing salt crystals as well as binding them to withdraw water,9 resulting in improvement of the free flow and anticaking quality of the crystals. Gao and Li’s9 study shows that glycine modified the KCl crystal by changing its morphology from the native cubic to hexagonal prism form. Ballabh et al.,12 in their study, used a concentrated glycine solution to produce rhombicshaped NaCl crystals. A number of investigators8,10,11 studied the morphology of NaCl in the presence of glycine and concluded © XXXX American Chemical Society

that glycine possessed a noteworthy effect on the morphology modification of NaCl. Experimental work for glycine solubilities in electrolyte solution for all possible combinations of conditions is not feasible. Instead, a chemical model better suited for providing reliable estimation of glycine solubilities at different conditions of concentrations and temperatures in electrolyte solutions is favored. Reliable estimation can be useful in understanding and hence controlling industrial processes such as supersaturation in a crystallization process. The idea behind the present work is to generate a comprehensive chemical equilibrium model that can be used to describe the effect of magnesium and sodium chloride salts on glycine solubility. No similar model that used a single set of self-consistent model parameters which is able to predict the effect of glycine solubility in NaCl + MgCl2 solutions exists. Different forms of chemical modeling work has been performed for the solubility and phase equilibria study of the system containing aqueous solutions of glycine and electrolytes. Held et al.13 employed perturbed-chain statistical association theory (PC-SAFT) for calculation of the solubility and activity coefficient of glycine in water. Coutinho et al.14 carried out molecular dynamics simulation for solubility of amino acids, namely, DL-alanine, L-isoleucine, and L-valine, in MgCl2 aqueous solution at 298.15 K. Held et al.15,16 successfully employed ePC-SAFT to predict the solubility of glycine in NaCl aqueous solutions up to 3.0 mol·kg−1 and for the solubility of amino acid,14 namely, DL-alanine and L-valine, in an aqueous solution of Received: May 17, 2016 Accepted: August 30, 2016

A

DOI: 10.1021/acs.jced.6b00403 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Table 1. Specification of Chemicals chemical

CAS no.

glycine

56-40-6

bischofite sodium chloride

7791-18-6 7647-14-5

source Sinopharm Chemical Reagent Co., Ltd. Xilong Chemical Co., Ltd. Beijing Chemical Works

purity (%) 99.5−100 ≥98.0 ≥99.5

Figure 2. Comparison of the literature and calculated data of the NaCl and MgCl2 in pure water at different temperatures. Dots represent literature data, and lines represent calculated data.

Figure 1. Comparison of the literature and calculated data on the solubility of glycine in pure water at different temperatures. Dots represent literature data, and the line represents calculated data.

MgCl2 up to 1 mol·kg−1. Khoshkbarchi and Vera17,18 applied a perturbed-hard-sphere model to calculate the activity coefficients for the system of glycine in aqueous solutions of NaCl and KCl at 298.2 K. Gao and Li9 used the Pitzer model to regress the solubility of glycine in NaCl and KCl solutions in a range of temperatures from 283.2 to 363.2 K. Ferreira et al.19,20 analyzed the effects of KCl and Na2SO4 in the concentration range from 0.0 to 2.0, on the solubility of glycine at 298.2 K and applied the Pitzer−Simonson−Clegg equations for the correlation of activity coefficients of this ternary system. Recently, Zeng et al.21 successfully applied the Bromley−Zemaitis model in the correlation of phase equilibria of the mixed solvent system of glycine− NH4Cl−methanol solution. Besides the measurement of glycine solubility in pure water and various electrolyte solutions,9,17,19−20,22−23 this research field exhibits the potential for improvements. This work is to develop one single model that can correlate glycine solubility in single and mixed salt systems valuable for scientific as well as industrial points of view. Taking consideration of models used by Gao and Li9 and Zeng et al.21 for the successful correlation of solubility in a wide range of concentrations and temperatures, the Bromley−Zemaitis model with the Pitzer formulation was adopted for thermodynamic calculation in this work. For the system glycine−MgCl2−H2O, the solubility of glycine in MgCl2 solution with mole fractions from 0.5 to 3.5 was measured at 283 and 333 K, and the solubility of bischofite (MgCl2·6H2O) in glycine solution with mole fractions from 0.08 to 0.67 at 293−323 K was also determined. For the system glycine−NaCl−MgCl2−H2O, three sets of experiments were performed by fixing the MgCl2 molality at 0.5, 1.0 and 1.5 mol·kg−1, while the NaCl molality was varied from 0.5 to 2.5 mol·kg−1 in the solution. Bromley−Zemaitis ion−ion and Pitzer neutral molecule parameters were employed for the

Figure 3. Comparison of the literature and calculated data of the NaCl− MgCl2−water system at 323 and 348 K. Dots represent literature data, and lines represent calculated data.

regression of the solubility data to develop a model. The parameters obtained by regression were embedded in the OLI Stream Analyzer 9.1.25 At last, via regression, new parameters that are able to correlate the solubility’s data for this system were obtained.

2. EXPERIMENTAL SECTION 2.1. Chemicals. Glycine, 99.8% purity, from the Sinopharm Chemical Reagent Co., Ltd., magnesium chloride hexahydrate, 99.8% purity, from Xilong Chemical Co., Ltd., and sodium chloride, 99.8% purity, from Beijing Chemical Works were used without further purification. Deionized water, specific conductivity < 0.1 μS·cm−1, was used in the experiments. The detailed specifications of used chemicals are listed in Table 1. 2.2. Experimental Procedure. Measurements of solubilities for the glycine−MgCl2−H2O and glycine−NaCl−MgCl2−H2O systems were conducted by the dynamic method.9 The experiments B



Article

Table 2. Experimental Solubilities of Glycine(s) in the MgCl2−H2O System in the Temperature Range of 283.15−333.15 K at Pressure p = 0.1 MPaa m(glycine), mol·kg−1 T = 283.15 K 2.3330 2.7026 3.3000 3.7838 4.1453 4.8344 5.4461 6.3359 T = 313.15 K 4.4200 4.6789 5.3112 5.8252 5.9306 6.7009 7.6685 8.0932 a

m(MgCl2), mol·kg−1 0.0000 0.4980 0.9999 1.5001 2.0008 2.4988 2.9980 3.4993 0.0000 0.4980 0.9999 1.5001 2.0008 2.4988 2.9980 3.4993

m(glycine), mol·kg−1

m(MgCl2), mol·kg−1

T = 293.15 K 2.9865 3.5202 4.0173 4.5310 4.8282 5.4899 6.2278 6.8816 T = 323.15 K 5.2100 5.4685 6.2609 6.7488 6.8037 7.7246 8.6465 9.0397

0.0000 0.4980 0.9999 1.5001 2.0008 2.4988 2.9980 3.4993 0.0000 0.4980 0.9999 1.5001 2.0008 2.4988 2.9980 3.4993



T = 303.15 K 3.5200 4.6055 5.1392 5.9677 6.9210 7.3754

0.0000 0.9999 1.5001 2.4988 2.9980 3.4993

T = 333.15 K 6.0300 6.3156 7.1413 7.7084 7.6600 8.6493 9.7464 9.9501

0.0000 0.4980 0.9999 1.5001 2.0008 2.4988 2.9980 3.4993

Water is used as the solvent for molality calculation. Standard uncertainties u are u(T) = 0.10 K, ur(m) = 0.03, and u(p) = 1 kPa.

3. THERMODYNAMIC MODEL 3.1. Chemical Equilibria. Glycine in solution behaves as a zwitterion (+NH3CH2COO−), cation (+NH3CH2COOH), and anion (NH2CH2COO−). For the glycine−MgCl2−H2O and glycine−NaCl−MgCl2−H2O systems, dissolution reactions that include glycine, bischofite, and sodium chloride stated in eqs 1−5 are taken into account to create the model. NH 2CH 2COOH(s) ↔ + NH3CH 2COO−

(1)

+

NH3CH 2COO− ↔ NH 2CH 2COO− + H+

(2)

+

NH3CH 2COOH ↔ + NH 3CH 2COO− + H+

(3)

MgCl2· 6H 2O(s) ↔ Mg 2 + + 2Cl− + 6H 2O

(4)

NaCl ↔ Na + + Cl−

(5)

The respective equilibrium constants, assigned as K1 to K5 for eqs 1−5 are

Figure 4. Comparison of the experimental and calculated data of glycine in the MgCl2−water system: ■ 283, ● 293, ▲ 303, ◆ 313, ▼ 323, and + 333 K. Dots represent experimental data, and lines represent calculated data.

K1 = αG± = mG±γG±

were carried out in a tightly sealed 250 mL jacketed quartz vessel equipped with a magnetic stirrer. A well-controlled circulating water bath supplied thermostatic water through the jacket of the vessel. The investigated temperature range was from 283 to 343 K. A brief description about the solubility measurement is described here, taking examples for the solubility of glycine in a single electrolyte and in mixed electrolytes solutions. In the case of a single electrolyte system, a known composition of MgCl2−water solution was prepared in the vessel, whereas in the case of a mixed electrolytes system, first, a known composition of MgCl2−water solution was prepared in the vessel, and later NaCl was added to it at a required concentration. Glycine was then added to the solutions in fractions until the last trace of solid remained undissolved. The total mass of the glycine added ahead of the last addition is the solubility at a given condition.

(6)

K2 =

mG−γG−m H+γH+ αG−αH+ = mG±γG± αG±

(7)

K3 =

mG±γG±m H+γH+ αG±αH+ = mG+γG+ αG+

(8)

K4 = α Mg 2+αCl−2αH2O6 = m Mg 2+γMg 2+mCl−2γCl−2αH2O6 K5 = α Na+αCl− = m Na+γNa+mCl−γCl− ±

+

(9) (10)

−

where G , G , and G are the zwitterion, cation, and anion species of glycine, respectively, α is the activity, γ is the activity coefficient, and m is the concentration in terms of molality. In most modeling cases, only the zwitterionic form is taken into account for being the prominent species in isoelectric solutions,26−28 though all three forms are considered in chemical modeling for this research. C



Article

Table 3. Experimental Solubilities of Bischofite(s) in the Glycine−H2O System in the Temperature Range of 293.15−323.15 K at Pressure p = 0.1 MPaa m(MgCl2), mol·kg−1


T = 293.15 K 5.7499 5.8650 5.9500 6.0200 6.0600

0.0000 0.1773 0.3481 0.5149 0.6789

T = 323.15 K 6.2424 6.2807 6.3227 6.3978 6.4230 6.4741

0.0000 0.0799 0.1575 0.3072 0.4566 0.5976

a



T = 303.15 K 5.8795 5.9500 6.0010 6.0830 6.1459 6.1717



T = 313.15 K 6.0583 6.1183 6.1688 6.2333 6.2754 6.3106

0.0000 0.0871 0.1726 0.3397 0.5016 0.6630

0.0000 0.0843 0.1659 0.3251 0.4805 0.6330


properties of aqueous species and the solution. The standard partial molal Gibbs free energy of formation of an aqueous species was calculated by eq 13 Δ Gf°P , T = Δ Gf°Pr , Tr − S P°r , Tr(T − Tr) ⎤ ⎡ ⎛T ⎞ − c1⎢T ln⎜ ⎟ − T + Tr ⎥ ⎥⎦ ⎢⎣ ⎝ Tr ⎠ ⎧⎡ ⎪ ⎛ 1 ⎞⎟ ⎛ 1 ⎞⎤⎜⎛ Θ − T ⎞⎟ ⎨⎢⎜ − c 2⎪ −⎜ ⎟⎥ ⎩⎢⎣⎝ T − Θ ⎠ ⎝ Tr − Θ ⎠⎥⎦⎝ Θ ⎠ −

T ⎡ Tr(T − Θ) ⎤⎫ ln⎢ ⎥⎬ + a1(P − Pr) Θ2 ⎣ T (Tr − Θ) ⎦⎭ ⎪

⎪

⎛Ψ + P⎞ ⎛ P − Pr ⎞ ⎟ + a 2 ln⎜ ⎟ + a3⎜ ⎝T − Θ⎠ ⎝ Ψ + Pr ⎠ ⎛ Ψ + P ⎞⎛ 1 ⎞ ⎛1 ⎞ ⎟ + ω⎜ + a4 ln⎜ − 1⎟ ⎟⎜ ⎝ ⎠ ⎝ ⎠ ε ⎝ Ψ + Pr ⎠ T − Θ

Figure 5. Comparison of the literature and calculated data of the glycine−NaCl−water system: ■ ★ 298, ● 303, ▲ 313, ◆ 323, ▼ 333, and + 343 K. Dots represent experimental data, and lines represent calculated data.

⎛ 1 ⎞ − ω Pr , Tr⎜⎜ − 1⎟⎟ + ω Pr , TrYPr , Tr(T − Tr) ⎝ εPr , Tr ⎠ (13)

3.2. Equilibrium Constants. The equilibrium constants, that is, K1−K5 in eqs 6−10, were calculated by the standard-state chemical potential of their respective species included in the dissociation reaction The equilibrium constant K was calculated from ln K = −

ΔR G° RT

where Δ Gf°Pr , Tr stands for the standard-state partial molal Gibbs free energy of formation at the reference state (298.15 K, 1 bar), S P°r , Tr is the standard-state partial molal entropy for the sum at the reference state (298.15 K, 1 bar), T and Tr denote the temperature and reference temperature of 298.15 K, respectively, P and Pr are the pressure and reference pressure of 1 bar, respectively, α1−α4 represent pressure-dependent parameters for aqueous species, c1 and c2 are temperature-dependent parameters for aqueous species, Y refers to the Born function, ω is a speciesdependent equation of state parameter at temperature T, Ψ and Θ are solvent-dependent parameters equal to 2600 bar and 228 K, respectively, for water, and ε designates the dielectric constant of water at temperature T. The equilibrium constants K2 and K3 stated in eqs 7 and 8 were calculated by the HKF equation of state. In case of inavailability of accurate thermodyanic data, an empirical equation can be used to calculate the equilibrium constant

(11)

where ΔR G° is the standard-state partial molal Gibbs free energy of reaction, which is ΔR G° =

∑ νiΔ Gf° i

(12)

where νi denotes the stoichiometric coefficient and Δ Gf° represents the standard-state partial molal Gibbs free energy of formation for species i. The Helgeson−Kirkham−Flowers (HKF) equation of state29−31 is used to calculate the standard-state partial thermodynamic D



Article

Table 4. Experimental Solubilities of Glycine(s) in the NaCl−MgCl2−H2O System at Molality m(MgCl2) = 0.5 mol·kg−1 in the Temperature Range of 283.15−343.15 K at Pressure p = 0.1 MPaa m(glycine), mol·kg−1 T = 283.15 K 3.1478 3.2048 3.2123 3.2474 3.3370 3.3778

T = 293.15 K 3.5913 3.7238 3.7687 3.8781 3.9434 3.9479 T = 323.15 K 5.6164 5.7118 5.7194 5.6881 5.8720 5.7191 5.7978 5.9170 5.8863 6.1639 5.9848 6.1427 a

m(NaCl), mol·kg−1 1.5023 1.8032 2.0040 2.3053 2.4058 2.4776


m(NaCl), mol·kg−1

T = 303.15 K 4.2325 4.3269 4.2632 4.2618 4.4265 4.4092 4.3017 4.3771 4.5029 4.6056 4.4843 4.6282

0.1500 0.5001 0.7506 1.0010 1.1513 1.2516 1.5023 1.8032 2.0040 2.3053 2.4058 2.4776

m(glycine), mol·kg−1 T = 313.15 K 4.8420 4.9316 4.7848 4.8345 5.0354 4.9252 4.9966 5.0742 5.1469 5.3053 5.2497 5.3318

m(NaCl), mol·kg−1 0.1500 0.5001 0.7506 1.0010 1.1513 1.2516 1.5023 1.8032 2.0040 2.3053 2.4058 2.4776

1.5023 1.8032 2.0040 2.3053 2.4058 2.4776 0.1500 0.5001 0.7506 1.0010 1.1513 1.2516 1.5023 1.8032 2.0040 2.3053 2.4058 2.4776

T = 333.15 K 6.5457 6.6171 6.6032 6.6127 6.8328 6.6925 6.6620 6.8635 6.8669 7.0511 6.9771 7.0837

0.1500 0.5001 0.7506 1.0010 1.1513 1.2516 1.5023 1.8032 2.0040 2.3053 2.4058 2.4776

T = 343.15 K 7.5712 7.6857 7.6829 7.7370 7.9432 7.7406 7.5481 7.8994 7.8344 8.1341 8.0906 8.1877

0.1500 0.5001 0.7506 1.0010 1.1513 1.2516 1.5023 1.8032 2.0040 2.3053 2.4058 2.4776

Water is used as the solvent for molality calculations. Standard uncertainties u are u(T) = 0.10 K, ur(m) = 0.03, and u(p) = 1 kPa.

Table 5. Experimental Solubilities of Glycine(s) in the NaCl−MgCl2−H2O System at Molality m(MgCl2) = 1.0 mol·kg−1 in the Temperature Range of 283.15−343.15 K at Pressure p = 0.1 MPaa m(glycine), mol·kg−1 T = 283.15 K 3.1533 3.3044 3.4583 3.5677 3.4977 3.6715 3.7153 3.7252 3.7103 3.5432 T = 313.15 K 5.5385 5.4556 5.3836 5.5589 5.6391 5.7274 5.9406 5.7922 5.9779

m(NaCl), mol·kg−1 0.1500 0.5002 0.7504 1.0008 1.2012 1.5020 1.8029 2.0037 2.3049 2.5058 0.1500 0.5002 0.7504 1.0008 1.2012 1.5020 1.8029 2.0037 2.3049



T = 293.15 K 4.0229 4.0171 4.0328 4.1629 4.1643 4.3207 4.3717 4.3644 4.3793 4.3020 T = 323.15 K 6.3815 6.3667 6.1742 6.3952 6.4145 6.5408 6.8094 6.5603 6.7977

0.1500 0.5002 0.7504 1.0008 1.2012 1.5020 1.8029 2.0037 2.3049 2.5058 0.1500 0.5002 0.7504 1.0008 1.2012 1.5020 1.8029 2.0037 2.3049 E

m(glycine), mol·kg−1 T = 303.15 K 4.7875 4.7391 4.7132 4.8310 4.9587 5.0264 5.1634 5.0529 5.1766 5.1588 T = 333.15 K 7.0861 7.0564 6.9788 7.1418 7.1701 7.3865 7.6332 7.3926 7.7495

m(NaCl), mol·kg−1 0.1500 0.5002 0.7504 1.0008 1.2012 1.5020 1.8029 2.0037 2.3049 2.5058 0.1500 0.5002 0.7504 1.0008 1.2012 1.5020 1.8029 2.0037 2.3049



Article

Table 5. continued m(glycine), mol·kg−1 T = 313.15 K 6.0074 T = 343.15 K 7.6924 8.0546 7.9335 8.1771 a

m(NaCl), mol·kg−1 2.5058 0.1500 0.5002 0.7504 1.0008



T = 323.15 K 6.8123 T = 343.15 K 8.1219 8.3719 8.5702 8.3934

2.5058 1.2012 1.5020 1.8029 2.0037

m(glycine), mol·kg−1 T = 333.15 K 7.7775 T = 343.15 K 8.7679 8.7565

m(NaCl), mol·kg−1 2.5058 2.3049 2.5058


Table 6. Experimental Solubilities of Glycine(s) in the NaCl−MgCl2−H2O System at Molality m(MgCl2) = 1.5 mol·kg−1 in the Temperature Range of 283.15−343.15 K at Pressure p = 0.1 MPaa m(glycine), mol·kg−1 T = 283.15 K 3.8134 3.9266 3.9260 3.9242 4.0782 4.1933 4.2852 4.3345 4.3929 4.4550 T = 313.15 K 5.7982 6.1443 6.2739 6.2815 6.2502 6.3491 6.4638 6.5704 6.6967 6.7335 T = 343.15 K 8.4590 8.9767 9.0391 9.1928 a

m(NaCl), mol·kg−1 0.1500 0.5001 0.7504 1.0007 1.2011 1.5020 1.8029 2.0037 2.3049 2.5058 0.1500 0.5001 0.7504 1.0007 1.2011 1.5020 1.8029 2.0037 2.3049 2.5058 0.1500 0.5001 0.7504 1.0007



T = 293.15 K 4.4876 4.6276 4.7006 4.7095 4.7630 4.8711 4.9432 4.9706 5.0315 5.0272 T = 323.15 K 6.5762 6.9880 7.1191 7.1934 7.1061 7.2360 7.3538 7.4923 7.5985 7.6564 T = 343.15 K 9.0954 9.1441 9.3845 9.6913

0.15 0.5001 0.7504 1.0007 1.2011 1.5020 1.8029 2.0037 2.3049 2.5058 0.1500 0.5001 0.7504 1.0007 1.2011 1.5020 1.8029 2.0037 2.3049 2.5058 1.2011 1.5020 1.8029 2.0037

m(glycine), mol·kg−1 T = 303.15 K 5.1331 5.3486 5.4716 5.5395 5.4673 5.4558 5.7401 5.7891 5.8932 5.9044 T = 333.15 K 7.5203 7.9050 8.0563 8.1047 7.9157 8.2045 8.2977 8.4574 8.5268 8.5835 T = 343.15 K 9.7595 9.7172

m(NaCl), mol·kg−1 0.15 0.5001 0.7504 1.0007 1.2011 1.5020 1.8029 2.0037 2.3049 2.5058 0.1500 0.5001 0.7504 1.0007 1.2011 1.5020 1.8029 2.0037 2.3049 2.5058 2.3049 2.5058


log K = A +

B + CT + DT 2 T

where β0(m−m) and β1(m−s) are the adjustable parameters as a function of temperature for molecule−molecule interactions and molecule−ion interactions, respectively, and mm and ms are the concentrations of neutral species and ions, respectively. β0(m−m) and β1(m−s) are functions of temperature and are expressed as

(14)

where T denotes the temperature (K) and A−D are empirical parameters. Equilibrium constants K1, K4, and K5 stated in in eqs 6, 9, and 10 were calculated by empirical equations. 3.3. Activity Coefficient Model. Equations 6−10 show that the determination of the solubility product is affiliated with the activity coefficients of relevant ions and neutral aqueous species. Among various activity coefficient models integrated in the OLI system, the Pitzer formulation and the Bromley− Zemaitis model were chosen for the regression of solubility in the glycine−MgCl2−H2O and glycine−NaCl−MgCl2−H2O systems. For neutral aqueous species, the Pitzer formulation32 was implemented to calculate the activity coefficients ln γaqPitzer = 2β0(m−m)mm + 2β1(m−s)ms

β0(m−m) = B01ij + B02ij t + B03ij t 2

(16)

β1(m−s) = B11ij + B12ij t + B13ij t 2

(17)

where t is the temperature in degrees Centigrade and B01ij, B02ij, B03ij, and so on are adjustable parameters for species i and j that can be obtained by the regression of experimental data. The Bromley−Zemaitis activity coefficient model33 was used to calculate activity coefficients for the ionic species. This model produces better results for electrolytes with higher concentrations and temperatures, that is, up to 30 mol·kg−1 and 473.15 K, respectively. The Bromley−Zemaitis activity coefficient is expressed as

(15) F



log γi B−Z =

−AZi2 1+

Article

⎡ ⎢ (0.06 + 0.6B )|Z Z | I ij i j + ∑⎢ + Bij 2 ⎢ I ⎛ 1.5I ⎞ j ⎜ ⎟ 1 + |Z Z | ⎢ ⎝ i j ⎠ ⎣

⎤ ⎥⎛ | Z | + | Z | ⎞ 2 i j 2⎥ + CijI + DijI ⎜ ⎟ mj ⎥⎝ 2 ⎠ ⎥ ⎦

of MgCl2. Bischofite is acidic because of chloride ions; therefore, its addition in water lowers the pH of the solution, which leads to an increment change in the solubility of glycine. The solubility of bischofite (MgCl2·6H2O) in the glycine−H2O mixtures with 0.08−0.67 mole fractions was also determined at 293−323 K. The solubility data are compiled in Table 3, which indicate that the temperature and glycine concentration have somewhat increasing effects on the solubility of bischofite all through the inquired temperature and concentration range. For the solubility of glycine in an aqueous solution of NaCl, solubility data provided by Gao and Li9 and Held et al.15 as shown in Figure 5 are used. For the system glycine−NaCl−MgCl2−H2O, three sets of experiments were performed by fixing the MgCl2 molality at 0.5, 1.0 and 1.5 mol·kg−1 while the molality of NaCl was varied in the solution. The solubility data are compiled in Tables 4−6 and depicted in Figures 6−8. The solubilities of

(18)

where j indicates anions in solution, A denotes the Debye−Hückel parameter, I is the ionic strength of the solution, Bij, Cij, and Dij are temperature-dependent coefficients, and Zi and Zj are the charge numbers of the cation and anion, respectively. Bij is given by Bij = B1ij + B2ij t + B3ij t 2

(19)

where t is the temperature in degrees Centigrade and B1ij, B2ij, and B3ij are adjustable parameters for species i and j. Other adjustable parameters in eq 18, that is, Cij and Dij, have similar forms of temperature state.

4. RESULTS AND DISCUSSION 4.1. Solubility Measurements in the Glycine−MgCl2− H2O and Glycine−NaCl−MgCl2−H2O Systems. Figures 1−3 represents the literature solubility of the systems glycine− H2O9,17,19−21 NaCl−H2O,9 MgCl2−H2O,24 and NaCl−MgCl2− H2O.34 It can be seen from these figures that the solubility of glycine and MgCl2 is higher than that of NaCl in pure water. The reason for higher solubility is that glycine has a very small side chain of only one hydrogen atom23 and bischofite contains six molecules of water and is acidic in nature. The solubility measurements in this work were performed by the dynamic method mentioned above. The solubility of glycine in aqueous magnesium chloride solutions with 0.5−3.5 mole fractions were obtained at 283−333 K. The results are provided in Table 2 and depicted as can be seen in Figure 4. The solubility of glycine increases with an increase in the temperature and concentration

Figure 7. Comparison of the experimental and calculated data of glycine in the 1.0m MgCl2−NaCl−water system: ■ 283, ● 293, ▲ 303, ◆ 313, ▼ 323, + 333, and × 343 K. Dots represent experimental data, and lines represent calculated data.

Figure 6. Comparison of the experimental and calculated data of glycine in the 0.5m MgCl2−NaCl−water system: ■ 283, ● 293, ▲ 303, ◆ 313, ▼ 323, + 333, and × 343 K. Dots represent experimental data, and lines represent calculated data.

Figure 8. Comparison of the experimental and calculated data of glycine in the 1.5m MgCl2−NaCl−water system: ■ 283, ● 293, ▲ 303, ◆ 313, ▼ 323, + 333, and × 343 K Dots represent experimental data, and lines represent calculated data. G



Article

Table 7. Newly Regressed Pitzer Parameters for Glycine in the NaCl−MgCl2−H2O System Pitzer Interaction Parameters species

B01

B02

B03

B11

B12

B13

βglycine−Cl− βglycine−glycine35 βglycine−Na+

−2.131 × 10−1 −0.00369203 8.696 × 10−2

1.281 × 10−3 0.000293458

−1.31 × 10−5 −1.36664 × 10−6

−2.113 × 10−1 −0.04276616

−1.271 × 10−2 0.000214054

1.22 × 10−4 −2.38567 × 10−7

Bromley−Zemaitis Interaction Parameters36,37 B1

B2

B3

C1

C2

C3

0.15371 0.065937

−0.000049429 −0.00008384

1.45720 × 10−6 7.83390 × 10−7

−0.00141 −0.000884

−6.30550 × 10−6 −2.61300 × 10−6

−7.09600 × 10−8 −3.80000 × 10−8

species Cl− Cl−

Mg2+ Na+

Table 8. Parameters of the HKF Equation of State (Equation 13) for Species31,38 species

a1 (×10) cal·bar−1·mol−1

a2 (×10−2) cal·mol−1

a3 cal·K·bar−1·mol−1

a4 (×10−4) cal·K·mol−1

c1 cal·K−1·mol−1

c2 (×10−4) cal·K·mol−1

ω (×10−5) cal·mol−1

H+ Mg2+ + NH3CH2COOH OH− Cl− NH2CH2COO− + NH3CH2COO− Na+

0 −0.8217 7.6046 1.2527 4.0320 7.6046 7.6046 1.839

0 −8.599 7.0825 0.0738 4.8010 7.0825 7.0825 −2.285

0 8.39 10.9119 1.8423 5.5630 10.9119 10.9119 3.256

0 −2.3900 −3.0717 −2.7821 −2.8470 −3.0717 −3.0717 −2.7260

0 20.8 42.9011 4.15 −4.4 14.1998 14.1998 18.18

0 −5.8920 −3.4185 −10.346 −5.7140 −3.4185 −3.4185 −2.9810

0 1.53720 −0.2330 1.7246 1.4560 −0.2330 −0.2330 0.33060

Table 9. Thermodynamic Data for the Main Species in Glycine in the NaCl−MgCl2−H2O System38−40,a species

ΔG°f,298.15K KJ mol−1

ΔH°f,298.15K KJ mol−1

S°298.15K J·mol−1·K−1

C°p,298.15K J·mol−1·K−1

V°298.15K L·mol−1

Mg + NH3CH2COOH OH− Cl− NH2CH2COO− H2O + NH3CH2COO− MgCl2·6H2O(s) NH2CH2COOH(s) NaCl(s)

−453.960 −384.133 −157.298 −131.290 −315.045 −237.190 −370.704 −2114.890 −368.933 −384.237

−465.970 −519.624 −229.987 −167.080 −471.600 −285.830 −515.377 −2498.850 −528.500 −411.260

−138.1 184.256 −10.711 56.735 113.602 69.95 153.458 366.1 103.5 72.1494

−22.34

−0.02155

−137.193 −123.177 0 75.3 39.33 315.725 99.2 50.5009

−0.00418 0.01779 0.04377 0.01806 0.04319 0.1296 0.06788 0.02701

2+

a ΔGf,298.15K ° , ΔHf,298.15K ° , Sf,298.15K ° , Cp,298.15K ° , and Vf,298.15K ° denote the Gibbs free energy of formation, enthalpy of formation, entropy, heat capacity, and volume at 298.15 K.38−40

model in this work. Via regression of the experimental solubility data conducted in this work, new Pitzer neutral−ion interaction parameters, specifically βglycine−Na+ and βglycine−Cl−, were identified. The subscript glycine referred to in the parameters represents the neutral form, that is, +NH3CH2COO−. The results are plotted in Figures 4, 6, 7, and 8. These figures show excellent agreement between the experimental and correlated values. It can be understood that molecule−ion interactions between glycine− Na+ and glycine−Cl− are predominant in modeling. The Pitzer parameters determined via regression are listed in Table 7. The default parameters for Bromley−Zemaitis interactions,36,37 the HKF equation of state,31,38 thermodynamic data,38−40 and empirical parameters41 are shown in Tables 7−10, respectively. The relative deviation (RD) and the average absolute deviation (AAD) were obtained by the eqs 20 and 21, respectively

glycine were found to increase with increasing temperature and concentration of NaCl in all three sets of experiments having different concentrations of MgCl2. Similarly, the addition of MgCl2 made the solubility of glycine in NaCl solutions gradually increase, as seen from Figures 6−8. The standard uncertainties (u) in determining experimental results are 0.10 K, 0.03g, and 1 kPa for temperature, weight, and pressure, respectively. 4.2. Model Parameterization. The predicted results using OLI’s Stream Analyzer software package (9.1)25 with existing model show a large error for the solubility of glycine−MgCl2−water and glycine−NaCl−MgCl2−water systems. Thus, new modeling is required for improvement by modifying model parameters. Prior to the experimental work, literature data for the solubility of glycine and electrolytes in pure water were regressed to obtain the interaction parameters of Bromley−Zemaitis for ion−ion and Pitzer for molecule−molecule interactions. Upon observing the results plotted in Figures 1−3, it is clear that the used model is successful in correlating the solubilties of glycine and the two electrolytes NaCl and MgCl2 in aqueous media. Also, work9 published for the system glycine−NaCl−H2O was regressed, and the results are shown in Figure 5. Good agreement between the literature data and the regressed results validates the use of the

RDi =

Xi ,calc − Xi ,exp Xi ,exp n

∑i = 1 AAD = H

(20)

X i ,calc − X i ,exp X i ,exp

n

(21) DOI: 10.1021/acs.jced.6b00403 J. Chem. Eng. Data XXXX, XXX, XXX−XXX


Article

Table 10. Empirical Parameters of Equation 14 for Species41 species

A

B

C

D

NH3CH2COO− MgCl2·6H2O NaCl

0.826096 −31.6216 −2.2852

−345.0285 4055.7 532.06

0.00179425 0.10741 0.009082

2.44634 × 10−6 −0.00010585 −7.03270 × 10−6

+

A = Debye−Hückel parameter, empirical parameter of log K a1, a2, a3, a4 = pressure-dependent terms of the HKF equation of state B = empirical parameter of log K, parameter of the Pitzer equation, parameter of the Bromley−Zemaitis equation c1, c2 = temperature-dependent terms of the HKF equation of state C = empirical parameter of log K, parameter of the Bromley− Zamaitis equation D = empirical parameter of log K, parameter of the Bromley− Zamaitis equation Δ Gf° = standard-state partial molal Gibbs free energy of formation, J·mol−1 Δ GP°, T = standard-state partial molal Gibbs free energy of formation, J·mol−1 Δ G P°r , Tr = standard-state partial molal Gibbs free energy of formation at the reference state (298.15 K, 1 bar), J·mol−1 I = ionic strength K = dissociation or dissolution equilibrium constant m = molality of a species, mol·kg−1 M = molarity of a species, mol·L−1 P = pressure, Pa S P°r , Tr = standard-state partial molal entropy for the sum at the reference state (298.15 K, 1 bar), J·mol·K−1 t = absolute temperature, °C T = absolute temperature, K Y = Born function Z = cation or anion charge β = parameter of the Pitzer equation γ = compound activity coefficient ε = dielectric constant of water at temperature T Θ = solvent-dependent parameter equal to 228 K for water ν = stoichiometric coefficient Ψ = solvent-dependent parameter equal to 2600 bar for water ω = species-dependent equation of state parameter at temperature T

where Xi,calc and Xi,exp stand for the calculated and experimental values, respectively, for individual point i and n referring to the number of data points. The results for RDs and AADs are listed in Table 11. The RD for the solubility of glycine in aqueous Table 11. Relative Deviation (RD) and Average Absolute Deviation (AAD) RD systems

min. (%)

max (%)

AAD (%)

glycine−MgCl2−H2O glycine−NaCl−0.5MgCl2−H2O glycine−NaCl−1.0MgCl2−H2O glycine− NaCl−1.5MgCl2− H2O

−2.0 −5.0 −4.0 −5.0

9.0 4.0 7.0 3.0

2.53 1.65 1.61 2.39

MgCl2 is within the range from −2.0 to 9.0%, while in the system glycine−NaCl−MgCl2−H2O, the RDs for the solubility of glycine are −5.0 to 4.0%, −4.0 to 7.0%, and −5.0 to 3.0% for 0.5, 1.0, and 1.5 mol·kg−1 MgCl2, respectively in NaCl + MgCl2 solutions. Furthermore, for the system glycine−MgCl2−H2O, the AAD is 2.53%, while for the system glycine−NaCl−MgCl2− H2O, it is 1.65, 1.61, and 2.39%, respectively, for the 0.5, 1.0, and 1.5 mol·kg−1 MgCl2 in NaCl + MgCl2 solutions. These small values signify that parameters obtained via regression are able to predict the experimental data precisely.

5. CONCLUSIONS The preliminary estimation of solubilities in glycine−MgCl2− H2O and glycine−NaCl−MgCl2−H2O systems with the OLI System’s Stream Analyzer (9.1) yielded poor results. Thus, solubility measurements were carried for the above-mentioned systems in a temperature range from 283 to 343 K. The solubility of glycine was found to increase with an increase in temperature and concentration of solutes in both of the systems. Via regression of the solubility data obtained in this work and published elsewhere, a new set of Pitzer parameters for molecule−ion interactions were determined. With the aid of newly improved model parameters, a model was developed that was found capable of correlating the solubility of glycine in mixed NaCl + MgCl2 solutions in the experimental range.

■

■

REFERENCES

(1) Power, L. F.; Turner, K. E.; Moore, F. H. The crystal and molecular structure of α-glycine by neutron diffraction − a comparison. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1976, 32, 11−16. (2) Iitaka, Y. The crystal structure of γ-glycine. Acta Crystallogr. 1958, 11, 225−226. (3) Bhat, M. N.; Dharmaprakash, S. M. Effect of solvents on the growth morphology and physical characteristics of nonlinear optical γ-glycine crystals. J. Cryst. Growth 2002, 242, 245−252. (4) Balakrishnan, T.; Babu, R. R.; Ramamurthi, K. Growth, structural, optical and thermal properties of γ-glycine crystals. Spectrochim. Acta, Part A 2008, 69, 1114−1118. (5) Dhanaraj, P. V.; Rajesh, N. P. Growth and characterization of nonlinear optical γ-glycine single crystal from lithium acetate as solvent. Mater. Chem. Phys. 2009, 115, 413−417. (6) Parimaladevi, R.; Sekar, C. Crystal growth and spectral studies of nonlinear optical γ-glycine single crystal grown from phosphoric acid. Spectrochim. Acta, Part A 2010, 76, 490−495.

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel./Fax: + 86 10 62551557. Funding

The authors gratefully thank the National Natural Science Foundation of China (Grants 21476235 and U1407112) and the National Basic Research Development Program of China (973 Program with Grant 2013CB632605) for financial support of this work. Notes

The authors declare no competing financial interest.

■

NOMENCLATURE a = activity I



Article

(7) Dillip, G. R.; Bhagavannarayana, G.; Raghavaiah, P.; Deva Prasad Raju, B. Effect of magnesium chloride on growth, crystalline perfection, structural, optical, thermal and NLO behavior of γ-glycine crystals. Mater. Chem. Phys. 2012, 134, 371−376. (8) Fenimore, C. P.; Thrailkill, A. The mutual habit modification of sodium chloride and dipolar ions. J. Am. Chem. Soc. 1949, 71, 2714− 2717. (9) Gao, W.; Li, Z. Determination and chemical modeling of phase equilibria for the glycine−KCl−NaCl−H2O system and its application to produce crystals with anticaking characteristics. Ind. Eng. Chem. Res. 2012, 51, 8315−8325. (10) Boistelle, R.; Gindt, R.; Kern, R.; Weiss, R.; Charruit, P. Influence of ferri and ferrocyanide ions on the external form of crystals of sodium chloride-Industrial applications. Bull. Soc. Lorraine Sci. 1962, 2, 62−69. (11) Cooke, E. G. The influence of added impurities on the growth and nucleation of sodium chloride. Krist. Tech. 1966, 1, 119−126. (12) Ballabh, A.; Trivedi, D. R.; Dastidar, P.; Ghosh, P. K.; Pramanik, A.; Kumar, V. G. A practical approach to produce near-spherical common salt crystals with better characteristics. Cryst. Growth Des. 2006, 6, 1591−1594. (13) Held, C.; Cameretti, L. F.; Sadowski, G. Measuring and modeling activity coefficients in aqueous amino-acid solutions. Ind. Eng. Chem. Res. 2011, 50, 131−141. (14) Tome, L. I. N.; Pinho, S. P.; Jorge, M.; Gomes, J. R. B.; Coutinho, J. A. P. Salting-in with a Salting-out Agent: Explaining the Cation Specific Effects on the Aqueous Solubility of Amino Acids. J. Phys. Chem. B 2013, 117, 6116−6128. (15) Held, C.; Reschke, T.; Müller, R.; Kunz, W.; Sadowski, G. Measuring and modeling aqueous electrolyte/amino-acid solutions. with ePC-SAFT. J. Chem. Thermodyn. 2014, 68, 1−12. (16) Held, C.; Reschke, T.; Mohammad, S.; Luza, A.; Sadowski, G. ePC-SAFT revised. Chem. Eng. Res. Des. 2014, 92, 2884−2897. (17) Khoshkbarchi, M. K.; Vera, J. H. Effect of NaCl and KCl on the solubility of amino acids in aqueous solutions at 298.2 K: Measurements and modeling. Ind. Eng. Chem. Res. 1997, 36, 2445−2451. (18) Khoshkbarchi, M. K.; Vera, J. H. Measurement of activity coefficients of amino acids in aqueous electrolyte solutions: Experimental data for the systems H2O + NaCl + glycine and H2O + NaCl + DL-Alanine at 25 °C. Ind. Eng. Chem. Res. 1996, 35, 2735−2742. (19) Ferreira, L. A.; Macedo, E. A.; Pinho, S. P. Effect of KCl and Na2SO4 on the solubility of glycine and DL-alanine in water at 298.15 K. Ind. Eng. Chem. Res. 2005, 44, 8892−8898. (20) Ferreira, L. A.; Macedo, E. A.; Pinho, S. P. KCl effect on the solubility of five different amino acids in water. Fluid Phase Equilib. 2007, 255, 131−137. (21) Zeng, Y.; Li, Z.; Demopoulos, G. P. Phase equilibria for the glycine-methanol-NH4Cl-H2O system. Ind. Eng. Chem. Res. 2014, 53, 16864−16872. (22) Ferreira, L. A.; Macedo, E. A.; Pinho, S. P. The effect of ammonium sulfate on the solubility of amino acids in water at (298.15 and 323.15) K. J. Chem. Thermodyn. 2009, 41, 193−196. (23) Dalton, J. B.; Schmidt, C. L. A. The solubilities of certain amino acids in water, the densities of their solutions at twenty-five degrees, and the calculated heats of solution and partial molal volumes. J. Biol. Chem. 1933, 103, 549−578. (24) Wang, D.; Li, Z. Modeling solid-liquid equilibrium of NH4ClMgCl2-H2O system and its application to recovery of NH4Cl in MgO production. AIChE J. 2011, 57, 1595−1606. (25) OLI Analyzer Studio: Stream Analyzer, version 9.1.2014; OLI Systems, Inc.: Cedar Knolls, NJ, 2014; available at http://www. olisystems.com/new-streamanalyzer.shtml (accessed Oct 15, 2014). (26) Gude, M. T.; Meuwissen, H. H. J.; van der Wielen, L. A. M.; Luyben, K. Ch. A. M. Partition coefficients and solubilities of α-amino acids in aqueous 1-butanol solutions. Ind. Eng. Chem. Res. 1996, 35, 4700−4712. (27) Khoshkbarchi, M. K.; Vera, J. H. Measurement and modeling of activities of amino acids in aqueous salt systems. AIChE J. 1996, 42, 2354−2364.

(28) Chen, C. C.; Zhu, Y.; Evans, L. B. Phase partitioning of biomolecules: Solubilities of amino acids. Biotechnol. Prog. 1989, 5, 111− 118. (29) Helgeson, H. C.; Kirkham, D. H.; Flowers, G. C. Theoretical prediction of the thermodynamic behavior of aqueous electrolytes at high pressures and temperatures. IV. Calculation of activity coefficients, osmotic coefficients, and apparent molar and standard and relative partial molar properties to 600 °C and 5 kb. Am. J. Sci. 1981, 281, 1249− 1516. (30) Tanger, J. C.; Helgeson, H. C. Calculation of thermodynamic and transport properties of aqueous species at high pressures and temperatures; Revised equations of state for the standard partial molal properties of ions and electrolytes. Am. J. Sci. 1988, 288, 19−98. (31) Shock, E. L.; Helgeson, H. C. Calculation of the thermodynamic and transport properties of aqueous species at high pressures and temperatures: Correlation algorithms for ionic species and equation of state predictions to 5 kb and 1000 °C. Geochim. Cosmochim. Acta 1988, 52, 2009−2036. (32) Aqueous System Modeling Course and Workshop, OLI’s Manual; OLI Systems, Inc.: Cedar Knolls, NJ, 2002. (33) Zemaitis, J. F.; Clark, D. M.; Rafal, M.; Scrivner, N. C. Handbook of Aqueous Electrolyte Thermodynamics: Theory & Application; AIChE: New York, 1986. (34) Yang, J.-m.; Zhang, R.-z.; Liu, H.; Ma, S. H. Solid-Liquid Phase Equilibria at 50 and 75°C in the NaCl + MgCl2 + H2O System and the Pitzer Model Representations. Russ. J. Phys. Chem. A 2013, 87, 2195− 2199. (35) Stephen, H.; Stephen, T. Solubilities of Inorganic and Organic Compounds; Pergamon Press, 1963; Vol. 1, p 1933. (36) Lobo, V. M. M. Handbook of Electrolyte Solutions; Elsevier Science Publish. Co: Amsterdam, Oxford, New York, Tokyo, 1989; Parts A and B. (37) Hamer, W. J.; Wu, Y. C. Osmotic Coefficients and Mean Activity Coefficients of Uni-univalent Electrolytes in Water at 25 deg. C. J. Phys. Chem. Ref. Data 1972, 1, 1047−1099. (38) Shock, E. L.; Helgeson, H. C. Calculation of the Thermodynamic and Transport Properties of Aqueous Species at High Pressure and Temperatures: Standard Partial Molal Properties of Organic Species. Geochim. Cosmochim. Acta 1990, 54, 915−945. (39) OLI technique for evaluation of thermodynamic properties of organic, inorganic, and metal organic complexes in aqueous solution, 1993. (40) Shock, E. L.; Koretsky, C. M. Geochim. Cosmochim. Acta 1995, 59, 1497. (41) Linke, F. Solubilities of Inorganic and Metal-Organic Compounds, 4th ed.; American Chemical Society: Washington, D.C., 1965.

J


Solubilities and Modeling of Glycine in Mixed NaClâMgCl2 Solutions

Recommend Documents

Solubilities and Modeling of Glycine in Mixed NaClâMgCl2 Solutions