The limit solubility relationships based on Frenkel’s heterophase fluctuations theory

For a weak one-component solution, in which the solvent and dissolved substances are not chemically bound, a simple analytical approximation was found for temperature dependence of limiting solubility of the dissolve substance. The derivation of the approximation is based on the Frenkel theory of he...

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Veröffentlicht in:Вопросы атомной науки и техники
Datum:2012
Hauptverfasser: Shapovalov, R.V., Osmayev, O.A.
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Sprache:English
Veröffentlicht: Національний науковий центр «Харківський фізико-технічний інститут» НАН України 2012
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Digital Library of Periodicals of National Academy of Sciences of Ukraine
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spelling Shapovalov, R.V.
Osmayev, O.A.
2016-10-14T10:34:40Z
2016-10-14T10:34:40Z
2012
The limit solubility relationships based on Frenkel’s heterophase fluctuations theory / R.V. Shapovalov, O.A. Osmayev // Вопросы атомной науки и техники. — 2012. — № 1. — С. 273-276. — Бібліогр.: 5 назв. — англ.
1562-6016
PACS: 05.10.Gg, 02.60.Ed, 64.60.A–
https://nasplib.isofts.kiev.ua/handle/123456789/107156
For a weak one-component solution, in which the solvent and dissolved substances are not chemically bound, a simple analytical approximation was found for temperature dependence of limiting solubility of the dissolve substance. The derivation of the approximation is based on the Frenkel theory of heterophase fluctuations. It was shown how the parameters of this analytical approximation can be related to experimental data.
Для слабого однокомпонентного раствора, в котором растворитель и примесь не образуют химического соединения, получено аналитическое приближение, позволяющее найти предельное количество растворенного вещества в зависимости от температуры. Вывод приближения основан на теории гетерофазных флуктуаций Френкеля. Показано, как параметры аналитического выражения могут быть связаны с экспериментальными данными.
Для слабкого однокомпонентного розчину, у якому розчинник та домішка не створюють хімічної сполуки, отримано аналітичне наближення, яке дозволяє знайти граничну кількість розчиненої речовини в залежності від температури. Наближення знайдено на базі теорії гетерофазних флуктуацій Френкєля. Показано, як параметри аналітичного співвідношення можуть бути пов’язані з даними експериментів.
en
Національний науковий центр «Харківський фізико-технічний інститут» НАН України
Вопросы атомной науки и техники
Section E. Phase Transitions and Diffusion Processes in Condensed Matter and Gases
The limit solubility relationships based on Frenkel’s heterophase fluctuations theory
Cоотношение для предельной растворимости, полученное на основе теории гетерофазных флуктуаций Френкеля
Співвідношення для граничної розчинністі, отримане на основі теорії гетерофазних флуктуацій Френкеля
Article
published earlier
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
title The limit solubility relationships based on Frenkel’s heterophase fluctuations theory
spellingShingle The limit solubility relationships based on Frenkel’s heterophase fluctuations theory
Shapovalov, R.V.
Osmayev, O.A.
Section E. Phase Transitions and Diffusion Processes in Condensed Matter and Gases
title_short The limit solubility relationships based on Frenkel’s heterophase fluctuations theory
title_full The limit solubility relationships based on Frenkel’s heterophase fluctuations theory
title_fullStr The limit solubility relationships based on Frenkel’s heterophase fluctuations theory
title_full_unstemmed The limit solubility relationships based on Frenkel’s heterophase fluctuations theory
title_sort limit solubility relationships based on frenkel’s heterophase fluctuations theory
author Shapovalov, R.V.
Osmayev, O.A.
author_facet Shapovalov, R.V.
Osmayev, O.A.
topic Section E. Phase Transitions and Diffusion Processes in Condensed Matter and Gases
topic_facet Section E. Phase Transitions and Diffusion Processes in Condensed Matter and Gases
publishDate 2012
language English
container_title Вопросы атомной науки и техники
publisher Національний науковий центр «Харківський фізико-технічний інститут» НАН України
format Article
title_alt Cоотношение для предельной растворимости, полученное на основе теории гетерофазных флуктуаций Френкеля
Співвідношення для граничної розчинністі, отримане на основі теорії гетерофазних флуктуацій Френкеля
description For a weak one-component solution, in which the solvent and dissolved substances are not chemically bound, a simple analytical approximation was found for temperature dependence of limiting solubility of the dissolve substance. The derivation of the approximation is based on the Frenkel theory of heterophase fluctuations. It was shown how the parameters of this analytical approximation can be related to experimental data. Для слабого однокомпонентного раствора, в котором растворитель и примесь не образуют химического соединения, получено аналитическое приближение, позволяющее найти предельное количество растворенного вещества в зависимости от температуры. Вывод приближения основан на теории гетерофазных флуктуаций Френкеля. Показано, как параметры аналитического выражения могут быть связаны с экспериментальными данными. Для слабкого однокомпонентного розчину, у якому розчинник та домішка не створюють хімічної сполуки, отримано аналітичне наближення, яке дозволяє знайти граничну кількість розчиненої речовини в залежності від температури. Наближення знайдено на базі теорії гетерофазних флуктуацій Френкєля. Показано, як параметри аналітичного співвідношення можуть бути пов’язані з даними експериментів.
issn 1562-6016
url https://nasplib.isofts.kiev.ua/handle/123456789/107156
citation_txt The limit solubility relationships based on Frenkel’s heterophase fluctuations theory / R.V. Shapovalov, O.A. Osmayev // Вопросы атомной науки и техники. — 2012. — № 1. — С. 273-276. — Бібліогр.: 5 назв. — англ.
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fulltext THE LIMIT SOLUBILITY RELATIONSHIPS BASED ON FRENKEL’S HETEROPHASE FLUCTUATIONS THEORY R.V. Shapovalov 1 ∗and O.A. Osmayev 2,1 1National Science Center “Kharkov Institute of Physics and Technology”, 61108, Kharkov, Ukraine 2Ukrainian State Academy of Railway Transport, 61050, Kharkov, Ukraine (Received October 30, 2011) For a weak one-component solution, in which the solvent and dissolved substances are not chemically bound, a simple analytical approximation was found for temperature dependence of limiting solubility of the dissolve substance. The derivation of the approximation is based on the Frenkel theory of heterophase fluctuations. It was shown how the parameters of this analytical approximation can be related to experimental data. PACS: 05.10.Gg, 02.60.Ed, 64.60.A– 1. INTRODUCTION It is known that generally the quantity of solute which can be dissolved in a solvent under given tempera- ture is limited. As a rule the solvent capability to dissolve grows together with temperature. The sys- tem, where solute fraction is less or equals the cor- responding limit, is in equilibrium state under un- changeable environment. In 1939 it was pointed out by Frenkel [1] that in general case in the equilibrium solution along with monomers there are clusters of two and more solute atoms. Starting from the above mentioned paper these clusters are considered as het- erophase fluctuations. The cluster’s size distribution function was obtained in paper [1] from the principle of thermodynamic potential minimum. In paper [2] much more simple way was proposed for obtaining the distribution function. The method was based on the stationary solution of the system of Becker-Doring equations. In paper [2] it was demonstrated also a causal relationship between heterophase fluctuations and the characteristic times of successive stages of nucleation in a supersaturated solution. The method of study was numerical solution of the Fokker-Plank equation. In the present work the authors attempt to carry the Frenkel’s idea of heterophase fluctuations through to its logical completion. We choose the simplest kind of such systems – a weak perfect single component solution where solute and solvent do not react chem- ically. This simplest system is still a good approach to e.g. inorganic water dissolved salts. 2. BASIC EQUATIONS It is known that the time evolution of solute clusters size distribution function is described by a system of Becker-Döring kinetic equations ∂f (x, t) ∂t = I (x− 1, t) − I (x, t) , x ≥ 1 (1) I (x, t) = W (x, x+ 1) f (x, t) −W (x+ 1, x) f (x+ 1, t) . (2) Here the value f (x, t) is the number of clusters con- sisting of x monomers normalized to the number of atoms/molecules of solvent in unit volume in the present moment of time t, I (x, t) is the cluster flux in cluster size space, W (x, x+ 1) is the rate of ad- sorption of monomers by solute cluster consisting of x monomers, W (x+ 1, x) is the rate of desorption of monomers off the solute cluster consisting of x + 1 monomers. Equation (1) takes into account the fact of poly- mer cluster immobility in physical space (at any case the cluster mobility has to be much less than the monomer mobility) and their interaction only by ad- sorption or emission of mobile monomers. At the same time the probability of an elementary process with two and more monomers is negligibly small. This is an analogy of the mean field approximation. Analytical form of transient rates is given as a rule by the following expressions W (x, x+ 1) = 3D a2 x1/3c (t) , W (x, x− 1) = 3D a2 cex 1/3 exp ( β1 · x−1/3 T ) . (3) Here D is the diffusion coefficient of monomer in so- lution, a is the lattice parameter of a cluster or, that is the same, of a solute matter in parent phase, c (t) is the monomers concentration, ce is it equilibrium value, β1 = 8πa2γ 3 kB is the cluster surface energy in ∗Corresponding author E-mail address: r v shapo@kipt.kharkov.ua PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY, 2012, N 1. Series: Nuclear Physics Investigations (57), p. 273-276. 273 temperature units, γ is the specific surface energy, kB is Boltzmann constant, and T is the temperature. There is an evident and conventional approach to the study and solution of equation (1). It consists in the transformation of discrete variable into its analog quantity and solving the corresponding Fokker-Plank equation thus obtained from equation (1). The par- abolic differential equation can be solved analytically only approximately for some initial conditions and certain supplementary considerations. The process of its treatment becomes much more complicated if the solute conservation law is taken into account. In that case one can use numerical methods. It is also known that studying relatively small time interval one needs no conservation law and that the asymptotic solution results from arbitrary physical reliable initial condi- tions [3]. 3. EQUILIBRIUM DISTRIBUTION It is evident that the above equations can be ap- plied to the stable state of the system. In this case the initial conditions are at once the solution of equation (1). If one considers a liquid in condition of limiting saturation then there is no need in conservation law. Actually the most evident way to obtain the satu- rated solution is to bring into contact some quantity of solvent with an a priori excess of solute substance. It is evident that some time later the system comes to equilibrium state. Due to excess in advance of sol- vent the equilibrium system will consist of totally sat- urated liquid solution being in thermodynamic bal- ance with the residuum of solute substance. Without loss of generality let us consider a flat interface of a cluster. For weak perfect solutions it yields ψs + T ln ce = ψb . Therefore ce = exp (−Δψ/T ) , (4) where ψs is the specific thermodynamic potential of solute in liquid and ψb is the specific thermodynamic potential of solute in parent phase. The difference Δψ = ψs − ψb is the variation of specific thermody- namic potential under dilution. Equations (1) with fluxes (2) have an evident im- plication for equilibrium state. It is a coupling be- tween distribution function values for different cluster sizes, f (x+ 1) = W (x, x + 1) W (x+ 1, x) f (x) . By means of the explicit form of transient rates (3) some evident conclusions from this equation can be received. First a coupling of distribution functions for two values, x+1 and y respectively can be estab- lished, and after simple transformation one obtains the expression for distribution function of arbitrary size expressed in terms of the stationary monomers concentration c f (x+ 1) = W (x, x+ 1) W (x+ 1, x) f (x) = k=x−y∏ k=0 (x− k)1/3 k=x−y∏ k=0 (x− k + 1)1/3 exp ( β1 T (x− k + 1)−1/3 ) ( c ce )x−y+1 f (y), f (x+ 1) = exp ( −β1 T x+1∑ k=3 k−1/3 ) 21/3 (x+ 1)1/3 ( c ce )x−1 W (1, 2) W (2, 1) f (1). A probability of association of monomers into dimers can have a different form in general case. Let us suppose that W (1, 2) = 3D a2 · B · c (t) , (5) where value B is a coefficient which defines an effi- ciency of monomer collision. The coefficient modifies the rate of monomer association. In paper [2] it was accepted B = 2. In the present paper its numerical value is not considered. W (1, 2) W (2, 1) = 3D a2 ·B · c 3D a2 ce · 21/3 · exp ( β1 T · 2−1/3 ) = c ce 2−1/3 · B · exp ( −β1 T · 2−1/3 ) . Since f (1) ≡ c (t), then f (x) = exp ( −β1 T x∑ k=2 k−1/3 ) Bce x1/3 rx , (6) where r = c/ce is a ratio of monomer concentration to its equilibrium value. Since in the case of limiting saturation c (t) = ce, therefore, cluster distribution function can be written in the form f (x) = exp ( −β1 T x∑ k=2 k−1/3 ) Bce x1/3 . (7) Total value of solute q (T ) is defined either as the number of impurity atoms/molecules relative to the number of solvent atoms/molecules or as volume spe- 274 cific value. It is defined by the next expression q (T ) = ∞∑ x=1 x · f (x) . (8) As it follows from equations (6) and (8) the limit sat- uration is given by qlim (T )= ce [ 1+B ∞∑ x=2 x2/3 exp ( −β1 T x∑ 2 k−1/3 )] . (9) Just the same expression was obtained in papers [1] and [2]. Strictly speaking the main purpose of the present paper is to transform relationship (9) into more convenient form and to show the association of its parameters with experimental data. 4. APPROXIMATION Let us come over to summation of heterophase fluc- tuation. It is necessary to find out a sum of the next series S (β) = ∞∑ x=2 x2/3rx exp ( −β x∑ 2 k−1/3 ) . (10) Here the ratio β = β1/T is a dimensionless coefficient. The method of summation used for calculation of the sum consists in step-by-step application of Euler-MacLoren formula. As it is known [4] for ar- bitrary function, thrice differentiable on a segment M ≤ x ≤ N F (x), the next relationships is valid i=N∑ i=M F (i) = F (M) + F (N) − F (M) 2 + ∫ N M F (x) dx+ F ′ (N) − F ′ (M) 12 +R3 , (11) R3 ≤ 1 120 ∫ N M |F ′′′ (x)|dx , (12) x∑ 2 k−1/3 = a (x) = 3 x2/3 − 22/3 2 + x−1/3 + 2−1/3 2 − x−4/3 − 2−4/3 36 + δ1 (x) , (13) where R3 is the reminder. The obtained relationship (13) shows that the sought-for series (10) is convergent under condition r ≤ 1. The limit saturation corresponds to the case r = 1. Further argumentation is related to this case. By means of formula (13) it is easy to show that the absolute error is δ1 < 3 · 10−3. At the same time one can expect that obtained formula is too compli- cated if it will be repeatedly used in Euler-MacLoren form. It can be shown the penultimate item in ex- pression (13) is not negative and its absolute value could not exceed 1/90. Taking this fact into account one obtains an approximate reduced formula provid- ing a good accuracy. a (x) ≈ 3 x2/3 − 22/3 2 + x−1/3 + 2−1/3 2 . In that way expression (10) can be written with a good accuracy in the next form S (β) ≈ S̃ (β) exp ( β · 5 · 2−4/3 ) , (14) S̃ (β) = ∞∑ x=2 x2/3 exp ( −β 3x2/3 + x−1/3 2 − λx ) . Here value λ = − ln r = ln ce/c is nonnegative one. In the received expression slowly increasing power func- tion is multiplied by fast decreasing exponent. Let us transform formula (14) in the same way as (10) but with some simplifications. In expression (11) one keeps only two first terms and retains first term in (14) with unchangeable form to compensate inaccu- racy. In that way one gets S̃ (β) ≈ 22/3 exp (−β · 7 · 2−4/3 − λ · 2)+ + 32/3 2 exp ( −β · 5 · 3−1/3 − λ · 3 ) + + ∫ ∞ 3 x2/3 exp ( −β · 3x2/3 + x−1/3 2 − λ · x ) dx. The integral in the obtained relationship plays the main role in the region of small values β. For region β ≤ 10 one can use a good approximation for involved integral in the next form I (β) ≈ 3 exp ( −3−1/3β 2 ) (15) × ∫ ∞ 31/3 z4 exp ( −3z2β 2 − λ · z3 ) dz. As the purpose of the work is an investigation of the case of the limit saturated solution it is sufficient to find out the value of expression (14) subject to con- ditions that r = 1 → λ = 0. With that the right side of (15) could be calculated in accordance with the exact formula. This calculation allows us to obtain the unknown sum S (β).∫ ∞ zmin z4 exp (−b · z2 ) dz = zmin ( 3 + 2bz2 min ) 4b2 e(−bz2 min)+ 3 √ π 8b5/2 erfc ( b1/2zmin ) , S (β) ≈ 22/3 exp ( −2−1/3β ) (16) + 2 · 31/3+ 6β+ 32/3β2 2β2 exp ( −5β ( 3−1/3 − 2−4/3 )) + π1/2 61/2β5/2 exp ( 5β 24/3 − 3−1/35β 2 ) erfc ( 35/6β1/2 21/2 ) . It is rather difficult to get an analytical estimate of the error of this expression, but numerical calcula- tion has shown that in a segment 10−2 ≤ β ≤ 102 the given formula provides an accuracy not less than 96%, minimal one has place at β ≈ 0.49. The calcu- lations assumed that the upper limit of the sum 10 275 is 108. It can be shown that in this range of β this value of upper limit provides sufficient accuracy. The above calculations allow to write down the maximum concentration of the equilibrium solution at given temperature in the following simple form qlim (T ) = ce [1 +B · S (β)] . (17) For example, consider a water solution of nickel nitrate Ni (NO3)2, it has a molecular mass 182. The limit concentration of Ni (NO3)2 in aqueous ammonia [5] T, K 273 293 298 303 313 q·10−2 7.84 9.326 9.9 10.425 11.76 T, K 323 333 358.5 373 q·10−2 13.78 15.61 20.295 22.275 The fitting curve for data in the table Using data from the table one can construct the fitting curve by means of Levenberg-Marquardt algo- rithm. The figure illustrates the fact that the equation (17) quite satisfactory describes the dependence of limit solubility on temperature. 5. CONCLUSIONS 1. In the framework of a simple thermodynamic model an analytical expression is obtained which allows to determine the maximal quan- tity of solute that can be dissolved in a solvent as a function of temperature. 2. By an example of a water solution of nickel ni- trate it is shown a good agreement of the found approximation with experimental data. References 1. J.I. Frenkel. A general theory of heterophase fluctuations and pretransition phenomena // J. Chem. Phys. 1939, v. 7, p. 538-547. 2. A.A. Turkin, A.S. Bakai. Modeling the precipita- tion kinetics in systems with strong heterophase fluctuations // Problems of Atomic Science and Technology. 2007, iss. 3(2), p. 394-398. 3. I.M. Lifshitz, V.V. Slyozov. The kinetics of pre- cipitation from supersaturated solid solutions // J. Phys. Chem. Solids. 1961, v. 19, N 1-2, p. 35- 50. 4. Frank W.J. Olver. Asymptotic and Special Func- tions. New York: “Academic Press”, 1974. p. 279-289. 5. V.A. Rabinovich, Z.Y. Havin. An Abriged Chemi- cal Reference Book. 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