CsF in Amino Acid Aqueous Solution

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Thermodynamic study of RbF / CsF in amino acid aqueous solution based on Pitzer, modified Pitzer and extended Debye–Hückel models at 298.15K by a Potentiometric Method Lei Ma, Shuni Li, Quan-Guo Zhai, Yucheng Jiang, and Mancheng Hu Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/ie401411r • Publication Date (Web): 30 Jul 2013 Downloaded from http://pubs.acs.org on August 1, 2013

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Industrial & Engineering Chemistry Research

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Thermodynamic study of RbF / CsF in amino acid aqueous solution

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based on Pitzer, modified Pitzer and extended Debye–Hückel models at

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298.15K by a Potentiometric Method

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Lei Ma, Shuni Li*, Quanguo Zhai, Yucheng Jiang and Mancheng Hu*

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Key Laboratory of Macromolecular Science of Shaanxi Province, School of Chemistry and

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Chemical Engineering, Shaanxi Normal University, Xi’ an, Shaanxi, 710062, P. R. China,

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*Corresponding author, Tel.: +86-29-81530767. Fax: +86-29-81530727

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E-mail: [email protected]; [email protected]

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Abstract:

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This paper reports mean activity coefficients for RbF or CsF in Alanine / Proline / Serine +

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water mixtures by the potentiometric method at 298.15 K. The experimental results were

13

modelled by the Pitzer, the modified Pitzer and the extended Debye–Hückel equations. The

14

result shows that the three models analyze the experimental data well and give satisfactory

15

results. The osmotic coefficients, the excess Gibbs free energy, and the corresponding

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parameters were also obtained.

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Keywords: Mean activity coefficients, RbF, CsF, Alanine, Proline, Serine

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Introduction:

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The thermodynamic behavior of electrolyte in water or mixed solvents systems has been an

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important content of the solution chemical research, due to their important roles in areas such

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as biology, chemistry, desalination, process engineering and atmospheric processes.1 The

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presence of electrolyte solutions has a great effect on the properties and structure of proteins.2

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It is complicated to study the interactions between electrolyte and protein due to many factors,

25

such as pH, surface charge distribution and the complexity of protein structure.3 Amino acids

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ACS Paragon Plus Environment


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are the basic constituent unit of peptides and proteins, the research for amino acids and

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electrolyte system will give an insight on the structures and properties of the protein.4 The

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intermolecular forces have an impact on the properties of substance. Thermodynamic methods

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provide a perspective for the study of the interaction of electrolytes and amino acids molecules.

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There have been a series of studies on the electrolyte + amino acid + water system. Salabat et

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al. reported the osmotic coefficients of MgSO4 in glycine, D-alanine or L-valine + water

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systems using the isopiestic method.5 Zhuo et al. determined the thermodynamic properties for

8

CaCl2 in glycine, alanine, serine or proline + water mixtures at T = 298.15 K.6, 7 The mean

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activity coefficients of KCl in glycine or DL-valine + water mixture, NaCl in glycine or

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L-valine + water systems and NaBr in (glycine or L-valine + water) system have been obtained

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by Modarress and co-worker.8 - 10 Ghalami-Choobar et al. reported the thermodynamic data for

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(KCl + proline + water) and (KCl + KNO3 + proline + water) system.11, 12 However, there are

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very few studies carried out on the interaction between amino acids and the not so common

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ions of alkali metals in water. Our group obtained the mean activity coefficients of RbCl and

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CsCl in Glycine + water mixtures in our previous work.13 As an extension of our series works

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on the thermodynamic properties of unusual salts of alkali metals in the mixed solvent system,

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this paper investigated the thermodynamic behavior of RbF or CsF + Alanine / Proline / Serine

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+ H2O systems. The mean activity coefficients, the osmotic coefficients, the excess Gibbs free

19

energy of the systems were obtained.

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Experimental Section:

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Analytical reagent RbF and CsF (purity > 0.9950) were purchased from Shanghai China

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Lithium Industrial Co., Ltd., and used without further purification. Alanine (Xi’an Wolsen

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Bio-technology Co., Ltd, A.R. purity > 0.9950), Proline (Sinopharm Chemical Reagent Co., ltd,

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B.R. purity > 0.9900) Serine (Shanghai Season blue Technology Development Co., ltd, B.R.

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purity > 0.9900) dried in vacuum at 393 K for the constant weight before use. Water used in

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experiment was doubly distilled water, the specific conductance was approximately (1.0 to

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1.2) ·10-4 S·m-1. Details of the experimental apparatus and procedure have been described in

28

our previous work.14

29

Rb-ISE and Cs-ISE were a PVC membrane type based on valinomycin, and were filled with

2


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0.10 mol·L-1 RbF or CsF as the internal liquid in K ion-selective electrode. Both the membrane

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electrode and the F-ISE (model 201) were obtained from Jiangsu Electroanalytical Instrument

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Co., the electrodes were calibrated before the experiment, and showed good Nernstian response.

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The cells used in this work are given as follows:

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Rb/Cs-ISE | RbF/CsF (m), Amino acids (mA), water |F-ISE

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Here m is the molalities of RbF or CsF and mA is the amino acid molalities of (0.10, 0.20,

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0.30, 0.40) mol·kg-1. The uncertainties in the electrolyte molalities, amino acid molalities,

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temperature and potential difference are ± 0.0001, ± 0.01, ± 0.1 and ± 0.1, respectively. Each

9

molality of the solutions in experiment was prepared by weighing the materials using an

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analytical balance with a precision of ± 0.1 mg. The potential difference reached a stable value

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with a fluctuation of 0.1 mV after 5-10 minutes at all ionic strengths.

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The calibration of electrode pair of Rb/Cs-ISE and F-ISE:

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Before determining the activity coefficients of RbF or CsF in amino acids + water mixture,

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the cells were measured in water so as to determine the standard potential difference E0 and

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Nernst response slope k. The cell potential E can be expressed by:

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E = E0 + 2k ln (mγ±)

(1)

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E and m represent the cell potential and the molalities of electrolyte, respectively. γ± is the

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mean activity coefficients of RbF or CsF. There k = RT/F represented the theoretical Nernst

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slope. The R, T, and F were the gas constant, Kelvin temperature, and Faraday constant,

20

respectively.

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In Figure S1, when the measured potential difference E was plotted against the lna, a good

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linear correlation is obtained with the values of E0, k, and a correlation coefficient (R2) at

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298.15K. The values of E0, k, R2 and the standard deviation for RbF or CsF systems were listed

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in Table 1, which shows that the experiment data is in close to the theoretical value (theoretical

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Nernst slope: 25.69 mV at 298.15K). The values of E for RbF or CsF in the pure water are

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collected in Table S1. The mean activity coefficients of RbF or CsF in water can be calculated

27

from the Pitzer parameters taken from reference.15 The systems containing Rb-ISE or Cs-ISE

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and F-ISE were satisfactory enough for this work.

29

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Thermodynamic Model

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For electrolyte solutions, it is necessary to have reliable model to fit thermodynamic data at

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different temperatures and concentrations. Many models have been developed to obtain

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thermodynamic properties of electrolyte solutions. 16 This work provided the thermodynamic

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reference data for the interactions of amino acids and inorganic salt by using the pitzer, 15, 17 the

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modified Pitzer18, 19 and the Extended Debye–Hückel models.20, 21

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The Pitzer model:

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For 1–1 type electrolyte, the mean activity coefficients (γ±) can be expressed as: 15 ln γ±= fγ + mBγ + m2Cγ

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fγ = – Aφ [I1/2/(1 + bI1/2) + (2/b)ln (1 + bI1/2)]

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(2) (3)

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Bγ = 2β(0) + 2β(1){[1 – exp( – αI1/2)(1 + αI1/2 – 1/2α2I)]/(α2I)}

(4)

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Cγ = 1.5Cφ

(5)

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I = (1/2) ∑m·Z2

(6)

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the osmotic coefficients (Ф) is given as follows:

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Ф – 1 = fφ + mBφ + m2Cφ

(7)

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fφ = – Aφ(I1/2/(1 + bI1/2))

(8)

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Bφ = β(0) + β(1)exp( – αI1/2)

(9)

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the excess Gibbs free energy(GE) can be calculated from the activity and osmotic

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coefficients:

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GE = 2RTI (1− Ф + lnγ±)

(10)

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Here m is the molalities of electrolyte (mol·kg−1), I represents the ionic strength, α and b are

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empirical parameters with values of 2.0 and 1.2 kg1/2·mol-1/2, respectively. Z represents the ion

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charge number. β(0)( kg·mol−1), β(1)(kg·mol−1) and Cφ (kg·mol−1)2 are the Pitzer parameters of

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solute, β(0)( kg·mol−1) represents the total binary ionic interactions and β(1)(kg·mol−1) represents

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the interactions between unlike-charged ions. Aφ is the Debye–Hückel constant for the osmotic

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coefficient defined by eq. 11:

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Aφ = (1/3)[(2πNAρ)/1000]1/2·[e2/(εkT)]3/2

(11)

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where the constants NA, ρ, ε, and k represent the Avogadro constant, density of the solvent,

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vacuum permittivity and Boltzmann constant, respectively. The values of Aφ in pure water is

4


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0.3921 kg1/2·mol-1/2 at 298.15 K.

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Modified Pitzer model:

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Pérez-Villaseñor et al. proposed a modified Pitzer model considering the closest approach

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parameter in the Debye–Hückel term as an adjusting parameter and determined various

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interaction terms.18 This modification which contains only three adjusting parameters improves

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the correlative capacity of the equation, is convenient to use.19 The modified Pitzer model has

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been shown in eq. 12 to 13:

8 9 10 11 12

ln γ± = – Aφ [I1/2/(1 + bMXI1/2) + (2/bMX) ln (1 + bMXI1/2)] + 2mBMX + 3m2CMX

φ − 1 = − Aϕ I 1 / 2 /(1 + bMX I 1 2 ) + mBMX + 2m 2 C MX

(12) (13)

Extended Debye–Hückel equation: The Extended Debye–Hückel equation20, 21 for mean activity coefficients has the following form in eq. 14:

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log γ± = – Am1/2 / (1 + Bam1/2) + cm + dm2 – log(1 + 0.002mM) + Ext

(14)

14

M = MA · XB + Mw (1 – XB)

(15)

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where a is the ion size parameter, c and d indicate the ion-interaction parameters, M represents

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the average molecular mass of mixed solvent, MA and Mw indicate molecular mass of amino

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acid and pure water, respectively, XB represents the mole fraction. Ext is the contribution of the

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extended terms. The Debye– Hückel constants A and B are given by eq. 16 and 17:

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A = 1.8247·106 ρ1/2/(εT)3/2 kg1/2·mol−1/2

(16)

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B = 50.2901ρ1/2/(εT)1/2 kg1/2·mol−1/2·Å−1

(17)

21

The values of Debye–Hückel osmotic coefficient parameter (Aφ), dielectric constant and

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density(ρ and ε) of pure water and amino acids aqueous solution are get from the literature 6, 7

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and are listed in Table S2 together with the values for M, A, B.

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Results and discussion:

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Calculation of thermodynamic properties:

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By combining eqs.1 and 2, 1 and 12 or 1 and 14, the values of E0 can be optimized, as well

27

as the characteristic interaction parameters of each model. Given that the maximum

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concentration studied is 0.6-0.7 mol·kg-1, is it appropriate to omit the parameters Cφ in the

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equations of Pitzer and the parameter d in the extended Debye-Hückel equation. In Table 2 to 4, 5



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these values are presented along with the corresponding standard deviation of the fit.

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The mean activity coefficients γ± is one of the important parameters for the electrolyte

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solution thermodynamics, which reflects the interaction between the electrolyte ions as well as

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the ion and the solvent. The mean activity coefficients γ± and osmotic coefficients Φ describe

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the non-ideality of the actual solution and solvent, respectively. The excess Gibbs free energy

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GE represents the non-ideality in the behavior of the studied systems and informs us about

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fundamental interactions between solute and solvent. 22, 23 It can be observed from Table 2 to 4

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that the E0 values obtained from the Pitzer equation, the modified Pitzer equation and the

9

extended Debye–Hückel equation are in satisfactory agreement with each other and the

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standard deviations of the adjustments are comparable, so the mean activity coefficients, the

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osmotic coefficients and the excess Gibbs free energy for RbF/CsF + amino acids + water

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systems obtained from the Pitzer equation are given only in Table S3 to S5.

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By the RbF + Serine systems as an example, in Figure 1, the mean activity coefficients and

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the excess Gibbs free energy increase as the molalities of amino acids increase and the total

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ionic strength decrease. This trend may be explained by the electrostatic interactions and the

16

increase in density and dielectric constant of the mixed solvents. On the one hand, the

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increasing electrolyte molalities enhanced the electrostatic attraction between electrolyte ions,

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the values of γ± and GE decreased. On the other hand, the polar groups in amino acids had an

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influence on the interaction between the anion and cation (electrostatic interaction between

20

amino acids and ions reduces the interaction between the electrolyte anion and cation, the

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salvation free ions concentration increases). The bigger molality of amino acids in mixed

22

solvents, the larger the mean activity coefficients and the excess Gibbs free energy.

23

In Figure 2, the mean activity coefficients γ± and the excess Gibbs free energy GE of CsF in

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different Amino acids + water mixed solvent systems were compared at 298.15 K, the data of

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Glycine system are get from the literature.

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γ±(Proline) > γ±(Glycine) > γ±(Serine), GE/RT(Alanine) > GE/RT(Proline) > GE/RT(Glycine) >

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GE/RT(Serine), this trends can be explained with the properties of mixed solvents(such as

28

dielectric constant and density), ε(Alanine) > ε(Serine) > ε(Proline) > ε(Glycine). Serine has an

29

OH linked to the alkyl group, the strong interactions between OH and cation decrease the mean

30

activity coefficients and the excess Gibbs free energy.7

24

It can be seen from Figure 2: γ± (Alanine) >

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The standard Gibbs energy of transfer is used to measure the change in the total energy of

2

the solute when it is transferred from one solvent to another. It can be defined as the difference

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between the standard Gibbs free energy per electrolyte mol in a pure solvent, usually water,

4

and another pure solvent or mixed solvents. 25 The expression is written as: 26, 27

5

∆Gt0= F (Em0–Ew0) + 2RTln (dw / dm)

(18)

6

Where Ew0 and Em0 indicate the standard of potential difference of RbF or CsF in pure water

7

and in mixed solvents, dw and dm represent the relative density of water and mixture of solvents,

8

respectively. The values of ∆Gt0 at 298.15 K are given in Table S6. The ∆Gt0 are all negative

9

obviously, indicating that the interactions are mainly controlled by zwitterion and ion

10

attractions 7 and the transference of RbF or CsF from water to the Amino acids + water mixed

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solvent is spontaneous. ∆Gt0 becomes more negative with the increasing concentration of

12

Amino acids due to the stronger interaction between the electrolyte and zwitterion in amino

13

acid solution.

14

Conclusion:

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This work determined the potential difference of RbF / CsF + Alanine / Proline / Serine +

16

Water systems at 298.15 K. The experimental results were modelled with the Pitzer, the

17

modified Pitzer and the extended Debye–Hückel models, three models could correlate the

18

experimental data satisfactorily. The mean activity coefficients, osmotic coefficients, and

19

excess Gibbs free energy were obtained along with the corresponding parameters for three

20

models. The value of the mean activity coefficients γ± and excess Gibbs free energy GE

21

decrease as the total ionic strength increase and the molalities of Amino acids decrease. This

22

phenomenon may be explained by the electrostatic interactions model and the properties of

23

mixed solvent. The ∆Gt0 are all negative obviously, indicating that the interactions are mainly

24

controlled by zwitterion and ion attractions and the transference of RbF or CsF from water to

25

the Amino acids + water mixed solvent is spontaneous. To sum up, this work provided the

26

thermodynamic reference data for the interactions of Amino acids and inorganic salt by using

27

the experiment, model fitting, data analysis and other means.

28 29

7



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Acknowledgment

2

This project was supported by the National Natural Science Foundation of China (No.

3

21171111) and the Fundamental Research Funds for the Central Universities (Program No.

4

GK200902011).

5 6

Supporting Information Available: Data for experimental values for potential difference E,

7

mean activity coefficients γ±, osmotic coefficients Φ and excess Gibbs free energy GE at

8

different RbF/CsF Molalities in the sytems, Values of Average Molecular Mass M, Dielectric

9

Constant ε, Density ρ, Debye–Hückel Constants A, B and Pitzer Constants Aφ for Alanine /

10

Proline / Serine + Water Mixtures, and Standard Gibbs Energy of Transfer ∆Gt0. Plots of mean

11

activity coefficients and excess Gibbs free energy with the total ionic strength of RbF/CsF in

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amino acid + water mixed solvent systems at 298.15 K. This information is available free of

13

charge via the Internet at http://pubs.acs.org/.

8


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1

Structure of the Alcohol on Vapor Pressures and Osmotic Coefficients of Binary Mixtures

2

Alcohol + 1-hexyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide at T =323.15 K.

3

Fluid Phase Equilib. 2012, 313, 38-45.

4

(23) Domańska, U.; Królikowski, M.; Acree Jr., W. E. Thermodynamics and Activity

5

Coefficients at Infinite Dilution Measurements for Organic Solutes and Water in the Ionic

6

Liquid 1-butyl-1-methylpyrrolidinium Tetracyanoborate. J. Chem. Thermodyn. 2011, 43,

7

1810-1817.

8

(24) Ma, L.; Li, S.;, Zhai,Q.; Jiang, Y.; Hu, M. Pitzer, Modified Pitzer and Extended

9

Debye–Hückel Modeling Approaches: Ternary RbF or CsF + Glycine + Water Electrolyte

10

Systems at 298.15 K. J. Chem. Eng. Data 2012, 57, 3737-3743.

11

(25) Hernández-Luis, F.; Rodríguez-Raposo, R.; Galleguillos, H. R.; Morales, J. W. Activity

12

Coefficients of KCl in PEG 4000 + Water Mixtures at 288.15, 298.15 and 308.15 K. Fluid

13

Phase Equilib. 2010, 295, 163-171.

14

(26) Feakins, D.; Voice, P. J. Studies in Ion Solvation in Non-aqueous Solvents and Their

15

Aqueous Mixtures: Part 14. Free Energies of Transfer of the Alkali-metal Chlorides from

16

Water to 10-99 % (w/w) Methanol + Water Mixtures at 25℃. J. Chem. Soc. Faraday Trans.

17

1972, 168, 1390-1405.

18

(27) Kalidas, C.; Hefter, G.; Marcus, Y. Gibbs Energies of Transfer of Cations from Water to

19

Mixed Aqueous Organic Solvents. Chem. Rev. 2000, 100, 820-852.

20 21 22 23 24 25 26 27 28 29 30 11



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1

Caption for Tables and Figures

2

Table 1 The result of calibration of Rb/Cs-ISE electrodes and F-ISE electrode pair for different

3

systems

4

Table 2 Standard Potential Difference E0 and the Parameters of RbF/CsF Obtained from the

5

Pitzer Equation, for Different Amino acids + H2O Mixtures at 298.15 K.

6


7

Modified Pitzer Equation, for Different Amino acids + H2O Mixtures at 298.15 K

8


9

Debye–Hückel Equation, for Different Amino acids + H2O Mixtures at 298.15 K

10 11

Figure 1 The mean activity coefficients (a) and excess Gibbs free energy (b) for RbF versus

12

total ionic strength of electrolyte in Serine + water mixed solvent systems containing 0.00, 0.10,

13

0.20, 0.30 and 0.40 mol·kg-1 molalities of amino acids at 298.2 K

14

Figure 2 Variation of mean activity coefficients (a) and excess Gibbs free energy (b) with total

15

ionic strength of electrolyte in CsF + amino acids aqueous solution (m = 0.40 mol·kg-1) at

16

298.15 K

17 18 19 20 21 22 23 24 25 26

12


Page 12 of 18

Page 13 of 18

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1


Table 1 MF

E0/mV

RbF CsF

429.55 421.46

RbF CsF

171.15 144.99

RbF CsF

149.79 160.78

k Alanine+ water 25.47 25.13 Proline+ water 25.13 25.15 Serine+ water 25.40 25.26

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

13


SD

R2

0.13 0.02

1 1

0.16 0.10

1 1

0.27 0.10

1 1


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1

Page 14 of 18

Table 2 mAlanine/ mol·kg-1

β(0)/ β(1) / C φ/ kg· mol-1 kg· mol-1 kg2· mol-2

E0 / mV

SD

β(1) / β(0) / C φ/ kg· mol-1 kg· mol-1 kg2· mol-2

RbF + Alanine + H2O system

E0 / mV

SD

CsF + Alanine + H2O system

0.10

0.0691

0.3516

0.0000

423.9 0.16

0.0578

0.5063

0.0000

415.1

0.06

0.20

0.0657

0.3468

0.0000

422.2 0.08

0.0715

0.4945

0.0000

410.3

0.05

0.30

0.0622

0.3509

0.0000

420.5 0.08

0.0586

0.5399

0.0000

406.3

0.03

0.40

0.0693

0.3150

0.0000

417.9 0.12

0.0008

0.7686

0.0000

403.1

0.04

RbF + Proline + H2O system

CsF + Proline + H2O system

0.10

0.0046

0.5536

0.0000

167.5 0.14

0.0134

0.6213

0.0000

135.2

0.19

0.20

0.0111

0.5192

0.0000

166.7 0.10

0.0174

0.6191

0.0000

142.7

0.09

0.30

0.0524

0.3890

0.0000

166.2 0.12

0.0672

0.5034

0.0000

141.1

0.08

0.40

0.0434

0.4656

0.0000

163.4 0.17

0.0087

0.6723

0.0000

140.5

0.24

RbF + Serine + H2O system

CsF + Serine + H2O system

0.10

0.0527

0.4179

0.0000

143.2 0.07

0.0563

0.4263

0.0000

154.0

0.05

0.20

0.0513

0.3909

0.0000

141.3 0.08

0.0666

0.3925

0.0000

151.7

0.06

0.30

0.0552

0.3734

0.0000

139.7 0.07

0.0654

0.4254

0.0000

147.6

0.07

0.40

0.0673

0.3182

0.0000

139.1 0.05

0.0881

0.3529

0.0000

146.7

0.05

2 3 4 5 6 7 8 9 10 11 12 13 14 15

14


Page 15 of 18

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1


Table 3 E0 / mV

mAlanine bMX/ BMX/ CMX/ -1 1/2 -1/2 -1 /mol·kg kg ·mol kg· mol kg2· mol-2

SD

bMX/ BMX/ CMX/ 1/2 -1/2 -1 kg · mol kg· mol kg2· mol-2

RbF + Alanine + H2O

E0 / mV

SD

CsF + Alanine + H2O

0.10

3.3080

-0.0074

0.0289

423.5 0.10

2.8252

0.0978

-0.0259

415.0

0.06

0.20

2.3078

0.0798

-0.0103

422.2 0.09

2.7978

0.1172

-0.0290

410.3

0.05

0.30

3.1815

0.0128

0.0183

420.2 0.03

3.0724

0.1111

-0.0307

406.3

0.04

0.40

3.0758

0.0161

0.0190

417.7 0.06

3.8725

0.1256

-0.0658

403.0

0.06

RbF + Proline + H2O

CsF + Proline + H2O

0.10

4.2156

-0.0487

0.0364

167.1 0.07

5.2755

-0.0527

0.0376

134.5

0.07

0.20

4.1851

-0.0439

0.0351

166.3 0.02

3.8631

0.0363

-0.0092

142.7

0.05

0.30

2.4161

0.0873

-0.0256

166.2

0.11

3.1406

0.0906

-0.0149

141.0

0.08

0.40

4.0009

-0.0112

0.0336

163.0 0.12

6.4636

-0.0510

0.0447

139.9

0.05

RbF + Serine + H2O

CsF + Serine + H2O

0.10

2.9735

0.0300

0.0080

143.0 0.04

2.8694

0.0474

0.0008

153.8

0.03

0.20

2.8802

0.0322

0.0064

141.2 0.06

2.7788

0.0575

-0.0002

151.6

0.03

0.30

2.8203

0.0370

0.0082

139.6 0.05

3.1601

0.0470

0.0061

147.4

0.04

0.40

2.6546

0.0440

0.0078

139.0 0.03

2.7031

0.0797

-0.0010

146.6

0.04

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



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1

Page 16 of 18

Table 4 mAlanine/ mol·kg-1

a/ Å

E0 / mV

c/ d/ -1 2 kg· mol kg · mol-2

SD

a/ Å

RbF + Alanine + H2O

c/ d/ -1 2 kg· mol kg · mol-2

E0 / mV

SD

415.0

0.06

410.3

0.06

CsF + Alanine + H2O

0.10

5.04

0.0398

0.0000

423.8 0.15

6.21

0.0386

0.20

5.19

0.0386

422.1 0.07

6.32

0.0537

0.30

5.39

0.0375

0.0000 0.0000

0.0000 0.0000

420.4 0.07

7.08

0.0461

0.0000

406.2

0.06

0.40

5.22

0.0444

0.0000

417.9 0.10

9.91

0.0241

0.0000

402.8

0.11

RbF + Proline + H2O 0.10

6.67

-0.0054

0.20

6.59

0.30 0.40

CsF + Proline + H2O 167.3 0.11

7.56

0.0022

0.0000

134.9

0.14

-0.0002

0.0000 0.0000

166.5 0.07

7.54

0.0120

0.0000

142.8

0.05

5.50

0.0335

0.0000

166.2 0.12

6.58

0.0514

0.0000

141.0

0.07

6.50

0.0282

0.0000

163.2 0.15

9.10

0.0098

0.0000

140.2

0.16

153.9

0.04

151.6

0.04

RbF + Serine + H2O 0.10

5.48

0.0295

0.20

5.43

0.30 0.40

CsF + Serine + H2O 143.1 0.05

5.52

0.0337

0.0294

0.0000 0.0000

141.3 0.07

5.43

0.0427

0.0000 0.0000

5.40

0.0348

0.0000

139.7 0.06

5.92

0.0439

0.0000

147.5

0.05

5.10

0.0441

0.0000

139.1 0.04

5.41

0.0627

0.0000

146.6

0.05

2 3 4 5 6 7 8 9 10 11 12 13 16


Page 17 of 18

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1

2 3 4

(a)

(b)

(a)

(b)

Figure 1

5 6

7 8 9

Figure 2

10 11

17



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1

TOC

2

3

Thermodynamic study of RbF / CsF in amino acid aqueous solution

4

based on Pitzer, modified Pitzer and extended Debye–Hückel models at

5

298.15K by a Potentiometric Method

6

Lei Ma, Shuni Li*, Quanguo Zhai, Yucheng Jiang and Mancheng Hu*

7

Key Laboratory of Macromolecular Science of Shaanxi Province, School of Chemistry and

8

Chemical Engineering, Shaanxi Normal University, Xi’ an, Shaanxi, 710062, P. R. China,

9

*Corresponding author, Tel.: +86-29-81530767. Fax: +86-29-81530727

10

E-mail: [email protected]; [email protected]

11

12 13 14

18


Page 18 of 18

CsF in Amino Acid Aqueous Solution

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