CC BY
6
Раздел 02.00.01
Неорганическая химия
УДК 533.583.2 DOI: 10.17122/bcj-2021-3-97-103
С. О. Карабаев (д.х.н., проф.) И. П. Гайнуллина (к.х.н., доц.) И. М. Локшина (к.х.н., доц.) **, А. К. Джунушалиева (ст. преп.) С. В. Луговская (д.н., доц.) 2, Д. Р. Киреева (к.х.н., с.н.с.) 3
ПОВЕРХНОСТНЫЕ И СОЛЬВАТАЦИОННЫЕ ИЗБЫТКИ
ИОНОВ ТЯЖЕЛЫХ МЕТАЛЛОВ ИЗ ВОДНЫХ РАСТВОРОВ НА ДИСПЕРГИРОВАННОЙ ГУМИНОВОЙ КИСЛОТЕ, ВЫДЕЛЕННОЙ ИЗ БУРОГО УГЛЯ
1 Кыргызский национальный университет им. Жусупа Баласагына, кафедра физической и коллоидной химии, *кафедра органической химии и образовательных технологий 720033, Кыргызстан, г. Бишкек, ул. Абдумомунова, 328; e-mail: karabaev_s@mail.ru 2 Ариэльский университет, инженерный факультет 47700, Израиль, г. Ариэль, научный парк, e-mail: svetlanalu@ariel.il 3 Уфимский Институт химии УФИЦ РАН, лаборатория биоорганической химии и катализа 450054, г. Уфа, пр. Октября 71; e-mail: hetcom@anrb.ru
S. O. Karabaev 4, I. P. Gainullina 4, I. M. Lokshina 4, A. K. Dzhunushalieva S. V. Lugovskaya 2, D. R. Kireeva 3
SURFACE AND SOLVATION EXCESSES OF HEAVY METAL IONS FROM AQUEOUS SOLUTIONS ON DISPERSED HUMIC ACID EXTRACTED FROM BROWN COAL
1 Kyrgyz National University named after Jusup Balasagyn 238, Abdymomunova Str., 720000, Bishkek, Kyrgyzstan; e-mail: karabaev_s@mail.ru
2 Ariel University Science Park, Ariel, 47700, Israel; e-mail: svetlanalu@ariel.il 3 Ufa Institute of Chemistry of Ufa Federal Research Centre of the Russian Academy of Sciences 71, Prospekt Oktyabrya Str., 450054, Ufa, Russia; ph. (347)2355677, e-mail: hetcom@anrb.ru
Исследована изотермическая адсорбция ионов тяжелых металлов из водных растворов на дисперсном образце гуминовой кислоты в твердой фазе. Рассмотрено влияние селективной сольватации ионов тяжелых металлов на реакционные центры структурной единицы супрамолекулы дисперсной гуминовой кислоты в водно-электролитных растворах заданного состава. По данным о предельных значениях поверхностных и сольватационных избытков дана размерная оценка комплекса структурной единицы супра-молекулы дисперсной гуминовой кислоты с ионами тяжелых металлов в растворе.
Ключевые слова: адсорбция; диспергированная гуминовая кислота; ионы тяжелых металлов; нулевые коэффициенты активности; поверхностные и сольватационные избытки; размерный эффект; растворимость.
The isothermal adsorption of heavy metal ions from aqueous solutions on a dispersed sample of humic acid in the solid phase has been studied. The effects of selective solvation of heavy metal ions on the reaction centers of the structural unit of the supramolecule of dispersed humic acid in water-electrolyte solutions of a given composition are considered. According to the data on the limiting values of surface and solvation excesses a dimensional estimate of the complex of the structural unit of the supramolecule of dispersed humic acid with heavy metal ions in solution is given.
Key words: adsorption; dispersed humic acid; heavy metal ions; size effect; solubility; surface and solvation excesses; zero activity coefficients.
Дата поступления 19.05.21
The establishment of a heterogeneous equilibrium at the humic acid — aqueous solution of an asymmetric electrolyte interface is accompanied by two coupled processes. Adsorption of heavy metal ions from aqueous solutions on a macro-molecule in the solid phase and selective solva-tion of charged particles on the reaction centers of the structural unit of a supermolecule of dispersed humic acid dissolved in the liquid phase. The quantitative characteristics of these processes, under equilibrium conditions, are surface and solvation excesses. The theory and practice of ion-exchange adsorption from solutions on solid adsorbents is described in 1. It is shown that to calculate the relative surface excess (adsorption) of ions, the following relation can be used (1):
JO, -Q)■¥
•1000,
(l)
where a — adsorption value, mmol/g;
C0 and Ce — initial and final (equilibrium) concentrations of adsorbate, mol/l;
V — solution volume, l;
m — mass of adsorbent, g;
1000 — the conversion factor used to get the data to be expressed in mmol/g.
For non-electrolyte solutions, in which the admissible chemical reactions are homo- and hetero-association reactions, the value of the solvation excess is determined by the reference relation (2) 2:
d lga
Gk
(2)
J T ,P,a
where
Gi(j) — solvation excess of a particle of type
GJ _ N •I (Pki-Pj) • w dr,
V
(3)
where rC — molecular correlation radius;
Ni — number of particles of type i in volume V; Pki pp) — radial distribution function.
If the central particle k is a macromolecule, then equation (2) is also applicable due to the ther-modynamic definition of the concepts of chemical potential and activity coefficient of supramole-cules 3. For example, for aqueous solutions of urea, saturated with the structural unit of a supermolecule of dispersed humic acid 2, the reference relation (2) was written in the form of equation (4):
dlg УС
GKd
dlgam
_ _GGKd , m(w) '
(4)
'Traed
where G,
CKd m( w)
solvation excess of urea over water
on a structural unit of a supermolecule of dispersed humic acid in solution;
yGfdd — zero activity coefficient of a structural unit over a molecule of dispersed humic acid; am — activity of urea in aqueous solution.
Relation (2), taking into account identity (3), establishes a connection between thermodynamic quantities (left side) and radial distribution functions (right side) used in statistical thermodynamics. Moreover, from the standpoint of statistical thermodynamics, the correctness of the problem of calculating the quantity is not associated with whether the particles i, j, k have a charge or not 4.In this regard, for water-electrolyte solutions of a given stoichiometric composition , saturated with the structural unit of the supermolecule of dispersed humic acid 5, it is easy to obtain the expression:
1 f tigfcKd } 1 ~GKd 1
V I dlga±
• C
CKd _
Mz+ (w) _
• G
GKd
А2- (w) '
, (5)
i over a particle of type j in the solvation environment of particles of type k;
yk — rational coefficient of activity of a particle of sort k;
ai — activity of a particle of type i; T — temperature; P — pressure; l = i, l = j.
The physical meaning of the solvation excess of an i-particle over j in the environment of a mole of particles of type k is determined by the relation (3):
TpaGKd
where ggk:, . (GGKd ,) — solvation excess of ion
M (w) Az (w)
over water on the reaction centers of the structural unit over the dispersed humic acid molecule;
Y^Kd — zero activity coefficient of the structural unit of the supramolecule of dispersed humic acid; a± — average electrolyte activity Mz+Az-; v= (v+ V-) — stoichiometric coefficients.
For aqueous solutions of heavy metal ions (M2+= Cu2+, Ni2+, Cd2+), saturated with a structural unit of a supermolecule of dispersed humic acid(GZCrf), equation (5) takes the form:
_ I f dlg /g a 3
G
CKd M 2+
'CKd
dlg a±
(б)
ST,P,an
In equation (6), the value of the solvation excess of ion over water on the structural unit of
the supramolecule of dispersed humic acid is an analogue of the binding parameter of small ions on the macromolecule in the liquid phase, which is widely used in biothermodynamics to describe complex equilibria 6.
This work is devoted to the characterization of the adsorption and solvation properties of a dispersed sample of humic acid in aqueous solutions of heavy metal ions and estimation of the size effect of the complex of the structural unit of the supramolecule of dispersed humic acid with heavy metal ions in an aqueous solution.
Experiment
In the work, we used humic acid (GK), extracted from brown coal from the Kara-Keche deposit (Kyrgyzstan) according to the Orlov method 7. The ash content of the preparation was 10.70% and the moisture content was 3.63%. According to the data on elemental composition, atomic ratios, using Van Krevelen diagrams, it was concluded that the initial GK sample corresponds to the averaged complex of characteristic features for humic acids extracted from brown coals 8. Dispersed humic acid (GKd), which is the main object of this study, was obtained by mechanochemical treatment of the initial GK sample in a ball mill. Note that in order to avoid contamination of the final object with metals, grinding balls and an agate beaker were chosen. Milling was carried out at 300 rpm for 3 minutes. The local macroelement composition (C, O, N) at different points on the surface of dispersed humic acid, in contrast to the initial sample, is practically the same, which indicates the homogeneity of the studied sorbent powder. The surface of the particles of dispersed humic acid is flat, not permeated with pores and capillaries, and there are no roughnesses of any kind. The sample is characterized by the presence of condensed aromatic systems, aliphatic and alicyclic hydrocarbon groups, and oxygen-containing functional groups. As a result of the mechanochemical destruction of the aromatic
Concentrations of heavy metal ions, pH of w adsorption on a dispersed sample of
framework of the carbon matrix of humic acid, the relative amount of all functional groups in relation to the relative amount of aromatic polyconjugated systems increased markedly for the dispersed sample 9.
Heterogeneous equilibrium in an aqueous solution of an asymmetric electrolyte system (CuCl2, NiCl2, CdCl2) — the dispersed humic acid in the solid phase was set in a dry — air thermostat at 298 0K for 24 hours.The mass of the adsorbent in all cases was 0.1 g, and the volume of the solution was 50 ml. In this case, the first 2 hours of the phase were mixed every 10 minutes. After the establishment of heterogeneous equilibrium, the water-electrolyte solution, saturated with the structural unit of the supermolecule of dispersed humic acid, was separated from the sorbent in the solid phase using a syringe filter with pore sizes of 1—5 ¡um. The resulting liquid phase (filtrate) was analyzed for changes in the concentration of heavy metal ions, pH after adsorption on a solid adsorbent. The concentration of heavy metal ions in solutions was determined by trilono-metric titration. The acidity of water-electrolyte solutions saturated with the structural unit of the supermolecule of dispersed humic acid was measured by the EMF method using a galvanic pair, a glass electrode with a hydrogen function and a saturated silver chloride electrode. At this pH-metric electrodes previously calibrated by standard buffer solutions 10. Experimental data on equilibrium concentrations of heavy metal ions, pH of water-electrolyte solutions before and after adsorption on dispersed humic acid in the solid phase are given in Tab. 1.
From Tab. 1, you can see a significant decrease in the pH of water-electrolyte solutions after the adsorption of charged particles on a solid adsorbent. The obtained result indicates the ion-exchange adsorption of heavy metal ions from aqueous solutions on the acidic functional groups of dispersed humic acid in the solid phase. Obviously, these are, first of all, the carboxyl groups of the polyelectrolyte 9.
Table 1
vater-electrolyte solutions before and after
humic acid in a solid phase at 298 °K
CM2+ C0 (mol/l) H2O-CuCl2 H2O-NiCl2 H2O-CdCl2
PH0 РН e CCu2+ -102, mol/l e pHo pHe CN?* 402, mol/l PH 0 pHe Cci" . 102, mol/l
0.0010 5.5 3.1 0.06± 0.01 6.4 3.5 0.08 ±0.01 6.4 3.4 0.08±0.01
0.0050 5.0 2.9 0.44± 0.04 6.0 3.2 0.48 ±0.05 6.4 3.2 0.44 ±0.04
0.0100 4.8 2.8 0.93± 0.09 6.1 3.1 0.96 ±0.10 6.4 3.1 0.92 ±0.09
0.0200 4.6 2.7 1.92± 0.19 6.0 3.1 1.94 ±0.19 6.3 3.1 1.92±0.19
0.0300 4.4 2.7 2.91 ± 0.29 6.0 3.0 2.92 ±0.29 6.1 3.0 2.92 ±0.29
0.0400 4.3 2.7 3.90± 0.39 6.1 3.0 3.91 ±0.39 6.2 3.0 3.92 ±0.39
The solubility of the structural unit of the su-pramolecule of dispersed humic acid in an aqueous electrolyte solution of a given composition was determined spectrophotometrically at a wavelength of 340 nm. The data obtained were used to calculate the zero activity coefficients of the structural unit of the supramolecule of dispersed humic acid in the investigated water-electrolyte solutions according to the equation 11:
CGKJw)
!g y°GKd = !g-
CsoaL(w-el)'
(7)
where CG^t w) — solubility of a structural unit of
a supramolecule of dispersed humic acid in water, g/l;
CçKdd(w-el) — solubility of a structural unit
of a supramolecule of dispersed humic acid in a water-electrolyte solution of a given composition, g/l;
by the normalization condition = 1 at aw = 1 (in pure water).
The calculation results are shown in Tab. 2. There are also presented the values of both the average activities and the average activity coefficients of the studied asymmetric electrolytes, obtained by the second approximation of the Debye-Huckel theory in the form of the Guntelberg equation 12.
Tab. 2 shows that with an increase in the concentration of heavy metal chlorides in aqueous solutions, the structural unit of the su-pramolecule of dispersed humic acid in the liquid phase stabilizes, since the logarithms of the zero activity coefficients of the polyelec-trolyte decrease. However, the dependence of (MCl2) on the composition of the water-electrolyte solution indicates the manifestation of the effects of selective solvation in the systems under study 11.
The data in Tab. 1 and 2 were the basis for further calculations of the surface and solvation excess of heavy metal ions at the reaction centers of dispersed humic acid in the solid phase, a structural unit of a supermolecule in solution.
Results and discussion
Using the data in Tab. 1, according to equation (1), the surface excesses (adsorption) of heavy metal ions from aqueous solutions on dispersed humic acid in the solid phase were calculated. The calculation results are shown in Fig. 1.
Table 2
Zero activity coefficients of the structural unit of the supramolecule of dispersed humic acid in water-electrolyte solutions at 298 °K
CMa2 , mol/l igy± lga± lgy^ (CUCI2) lg yGKd (NiC|2) lg yG*d (CdC|2)
0.0010 -0.053 -2.852 0.071±0.007 0.097±0.010 0.084±0.008
0.0050 -0.132 -2.211 0.071±0.007 0.097±0.010 0.115±0.012
0.0100 -0.177 -1.949 -0.051±0.005 -0.028±0.003 0.097±0.010
0.0200 -0.199 -1.698 -0.146±0.015 -0.061±0.006 0.084±0.008
0.0300 -0.234 -1.556 -0.237±0.024 -0.176±0.018 0.050±0.005
0.0400 -0.261 -1.458 -0.296±0.030 -0.235±0.024 0.066±0.007
а„г+ (mmol/g]
Cf (mol/l)
Fig. 1. Isotherms of adsorption of heavy metal ions from water solutions on dispersed humic acid in solid phase at 298 îK
It is easy to see that Langmuir-type adsorption isotherms are observed. In this case, the values of adsorption of heavy ions from aqueous solutions on a dispersed sample of humic acid in all considered cases are arranged in a row, similar to the row for the stability constants of acetate complexes of copper (II), nickel (II), cadmium (II) ions 13.Thus, the adsorption of heavy metal ions from aqueous solutions on dispersed humic acid in the solid phase is provided mainly by the surface carboxyl groups of the sorbent.
To calculate the solvation excesses, the logarithms of the zero activity coefficients of the structural unit of the supramolecule of dispersed humic acid (Tab. 2) were described by the method of nonlinear regression by quadratic functions of the average activity of the electrolyte in solution. By analytical differentiation of the obtained polynomials, according to equation (6), we calculated the solvation excess of heavy metal ions over water on the structural unit of the su-permolecule of dispersed humic acid in solution. The results of calculations of solvation excesses are shown in Fig. 2 depending on the equilibrium concentrations of heavy metal ions in solution.
Fig. 2 shows that the isotherms of solvation excess of heavy metal ions over water on the structural unit of the supramolecule of dispersed humic acid are positive and increase with increasing equilibrium concentrations of charged particles in solution. The obtained result suggests that the formation of solvation excess is provided by the predominant filling of the reaction centers of the structural unit of the su-pramolecule of dispersed humic acid with heavy metal ions in a water-electrolyte solution of a given composition. In this case, the values of
solvation excesses are arranged in a row similar to the row for the stability constants of acetate complexes of copper (II), nickel (II), cadmium (II) ions 13.
According to the theory 2'5, the radius of the structural unit of the supramolecule of dispersed humic acid, the reaction centers of which are maximally filled with heavy metal ions in the solution, can be written as the ratio:
GKd M2+ =
S GKd ' GGKd H M2+ v '
4nNA ~GKd ( \ ■ aMK+ H
(8)
where r'
GKd
the radius of the structural unit of the
supermolecule of dispersed humic acid in solution with the maximum filling of its reaction centers with heavy metal ions;
G^ (œ) — limiting solvation excess of a
heavy metal ion over water on the structural unit of the supramolecule of dispersed humic acid in solution;
aMK^ (œ) — limiting adsorption of a heavy
metal ion from a solution on dispersed humic acid in the solid phase;
Sgkcî — the limiting value of the specific surface
area of the dispersed humic acid in the solid phase; Na — Avogadro's number.
In equation (8), the limiting value of the solvation excess G^ (œ) is provided by the
maximum saturation of the reaction centers of the structural unit above the dispersed humic acid molecule with heavy metal ions in solution. For this value ( G^d (œ) ), by analogy with the
Scatchard equation 6, we can write the expression:
GKd
'M2 +
Cf+ (mol/l)
Fig. 2. Isotherms of the solvation excess of heavy metal ions over water on the structural unit of the supramolecule of dispersed humic acid in solution at 298 °K
GGKd
-£-= GMKK M ■ k - k■ GK, (9)
Ce
where K — the constant of binding of a doubly charged ion at the reaction center by a structural unit of a su-permolecule of dispersed humic acid in a solution;
CM — equilibrium concentration of a heavy
metal ion in solution;
G
GKd
M 2+
solvation excess of an ion on a struc-
tural unit per molecule of dispersed humic acid in a water-electrolyte solution of a given composition.
Limit value of adsorption a^fd , obviously, it is also due to the maximum filling of the sorbent surface in the solid phase with metal ions from the solution. To calculate this value
( a^K (~) ) the Langmuir equation 14 was used in the form of the ratio:
a
C
GKd
M2+ _ aGKd M 2 e
GKd
_ aMKdH■ K' - K'-a
M 4 '
M2
(10)
where K' — constant of adsorption equilibrium;
CM — equilibrium concentration of a heavy metal ion in solution;
adsorption of a heavy metal ion from
a
GKd
M 2+
is associated with the use of the law of mass action. This explains the uniformity of equations (9), (10).
Tab. 4 shows the values of all limiting values that are on the right side of equation (9). The size of the limiting area ( S^Kd ), occupied by
the supramolecule of dispersed humic acid, was obtained by the adsorption method, using a fer-rication cation as a probe particle 18. To calculate the limiting values of surface and solvation excesses, the experimental data in Fig. 1 and 2 are considered in the coordinates of equations (9) and (10). The corresponding linear regression equations (kcorr i 0.98) are shown in Tab. 4.
There are also given the radii ( f^) complex
particles of the structural unit of the su-pramolecule of dispersed humic acid with heavy metal ions in aqueous solutions, calculated according to equation (8).
Tab. 4 shows that in all cases the sizes of the complexes of the structural unit of the su-pramolecule of dispersed humic acid with heavy
metal ions in solution ( r^ff ) are less than
m 2
one
a water-electrolyte solution of a given composition on dispersed humic acid in a solid phase.
Note that surface and solvation excesses by their nature are excess thermodynamic quantities 15, the use of which to describe equilibria in homo geneous and heterogeneous systems MM7
Table 4
Radii of complexes of the structural unit of the supramolecule of dispersed humic acid with heavy metal ions in aqueous solutions at 298 °K
nanometer. Thus, when a heterogeneous equilibrium is established between the investigated sample of dispersed humic acid in the solid phase and an aqueous solution of an asymmetric electrolyte, as a result of the effects of solvation selectivity, true weakly acid solutions of complex compounds of small-sized structural units of the polyelectrolyte supramolecule with heavy metal ions are formed.
Ion Linear regression equations SGKd ■ m2/g aMK H) , mmol/g GGf И M ^ ' jGKd ГM2+ , nm
Cu2+ GGKd C"Z _ 208 - 728 ■ GGKd çCu с?* 315.9 0.54±0.05 0.32±0.03 0.16±0.02
aGKd cui _ 1373 - 2543 ■ aGKd+ C^Cu Ci*
Ni2+ GGKd M2++ _ 328 - 1491- GGK ç-Ni'* Ni2+ 315.9 0.49±0.05 0.30±0.03 0.16±0.02
aGKd Nil _ 145.7 - 2973 ■ aGKd CjNi2* Ni2+
Cd2+ GGKd GCdl _ 13,7 - 151,8 ■ G™ CjCd2* ' Cd2+ 315.9 0.44±0.04 0.11±0.01 0.10±0.01
aGKd Cgr _ 1517 - 344.7 ■ aGKd
Литература
1. Parfitt G.D., Rochester C.H. Adsorption from Solution at the Solid/Liquid Interface.— London, New York: Academic Press, 1983.— 416 p.
2. Karabaev S., Gainullina I., Harchenko A., Satarova M., Lugovskoy S., Pendin A. Solvation Excess of Urea over Water in Humic Acid in Three-Component Solutions Saturated with the Biopolymer // Journal of Solution Chemistry.-2012.- V.41, №6.- Pp.1013-1019.
3. Русанов А. И. Лекции по термодинамике поверхностей.- СПб.: Издательство «Лань», 2013.— 237 с.
4. Hill T. L. Thermodynamics of small systems. P.1.- New York: Benjamin, 1963.- 171 p.
5. Пендин А. А., Леонтьевская П. К. Поверхностные свойства водных растворов сильных электролитов и их высаливающее (всаливающее) действие // Журнал физической химии.- 2000.-Т.74, №10.- С.1792-1797
6. Edsall, J.T., Gutfreund H. Biothermodynamics: The Study of Biochemical Processes at Equilibrium. New York: Wiley, 1983.- 262 с.
7. Орлов Д.С.Химия почв.- М.: Изд-во МГУ, 1992.- 400 с.
8. Перминова И. В. Анализ, классификация и прогноз свойств гумусовых кислот: дис. ... докт. хим. наук.- М.: МГУ им. М. В. Ломоносова, 2000.- 360 с.
9. Karabaev S., Kharchenko A., Lokshina I., Gainullina I., Dzhunushalieva A., Lugovskoy S., Pendin A. Physical And Chemical Characterization Of Raw And Mechanochemically Treated Humine And Humic Acid From Brown Coals // Diffusion And Defect Data. Pt A Defect And Diffusion Forum.- 2015.- V.364.- Pp.18-26.
10. Bates R.G. Solute-Solvent Interactions.-NewYork: Marcel Dekker, 1969.- P. 45.
11. Gordon J.E. The Organic Chemistry of Electrolyte Solutions.- New York: Wiley&Sons, 1975.- 712 p.
12. Harned H.S., Owen B.B. The Physical Chemistry of Electrolytic Solutions.- New York, 1950.756 p.
13. Химическая энциклопедия в 5-ти томах / Под ред. И. Л. Кнунянц.- М.: Издательство «Советская энциклопедия», 1988-1998.
14. Adamson A.W. Physical chemistry of surfaces.-Chichester: John Wiley & Sons, 1990.- 698 p.
15. Prigogine I., Defay R. Chemical Thermodynamics.- London-New, York-Toronto: Longman Green and Co., 1954.- 533 p.
16. Evans D.F., Mitchell D.J., Ninham B.W. Ion Binding and Dressed Micelles // The Journal of Physical Chemistry.- 1984.- V.88, №25.-Pp.6344-6348.
17. Русанов А.И., Куни Ф.М., Ш^кин А.К. Точечные избытки в теории обычных и мицеллярных растворов // Журнал физической химии.-2009.- Т.83, №2.- С.290-298.
18. Никольский Б. П., Пальчевский В. В., Пендин А. А., Якубов X. М. Оксредметрия.- Л.: Химия, 1975.- 304 с.
References
1. Parfitt G.D., Rochester C.H. [Adsorption from Solution at the Solid/Liquid Interface]. London, New York, Academic Press, 1983, 416 p.
2. Karabaev S., Gainullina I., Harchenko A., Satarova M., Lugovskoy S., Pendin A. [Solvation Excess of Urea over Water in Humic Acid in Three-Component Solutions Saturated with the Biopolymer]. Journal of Solution Chemistry, 2012, vol.41, no.6, pp.1013-1019.
3. Rusanov A.I. Lektsii po termodinamike poverkh-nostey [Lectures on surface thermodynamics]. St. Petersburg, Lan Publ., 2013, 237 p.
4. Hill T. L. [Thermodynamics of small systems. Part 1]. New York, Benjamin, 1963, 171 p.
5. Pendin A.A., Leont'evskaya P.K. [The Surface Properties Of Aqueous Solutions Of Strong Electrolytes And Their Salting Out (Salting In) Action]. Russian Journal of Physical Chemistry A, 2000, vol.74, no. 10, pp.1626-1631
6. Edsall, J.T., Gutfreund H. [Biothermodynamics: The Study of Biochemical Processes at Equilibrium]. New York, Wiley, 1983, 262 p.
7. Orlov D.C. Khimiya pochv [Chemistry of Soils]. Moscow, Lomonosov Moscow State University Publ., 1992, 400 p.
8. Perminova I.V. Analiz, klassifikatsiya i prognoz svoystv gumusovykh kislot. Diss. dokt. khim. nauk [Analysis, classification and prognosis of humic acid properties. Dr. Chem. Sci. Diss.]. Moscow, Lomonosov Moscow State University, 2000, 360 p.
9. Karabaev S., Kharchenko A., Lokshina I., Gainullina I., Dzhunushalieva A., Lugovskoy S., Pendin A. [Physical And Chemical Characterization Of Raw And Mechanochemically Treated Humine And Humic Acid From Brown Coals]. Diffusion And Defect Data. Pt A Defect And Diffusion Forum, 2015, vol.364, pp.18-26.
10. Bates R.G. [Solute-Solvent Interactions]. New York, Marcel Dekker, 1969, p.45.
11. Gordon J.E. [The Organic Chemistry of Electrolyte Solutions]. New York, Wiley&Sons, 1975, 712 p.
12. Harned H.S., Owen B.B. [The Physical Chemistry of Electrolytic Solutions]. New York, 1950, 756 p.
13. Knunyants I.L. [Chemical encyclopedia in 5 volumes]. Moscow, Soviet Encyclopedia, 1988.
14. Adamson A.W. [Physical chemistry of surfaces]. Chichester, John Wiley & Sons, 1990, 698 p.
15. Prigogine I., Defay R. [Chemical Thermodynamics]. London, Longman Green and Co., 1954, 533 p.
16. Evans D.F., Mitchell D.J., Ninham B.W. [Ion Binding and Dressed Micelles]. The Journal of Physical Chemistry, 1984, vol.88, no.25, pp.6344-6348.
17. Rusanov A.I., Kuni F.M., Shchekin A.K. [Point Excesses In The Theory Of Ordinary And Micellar Solutions]. Russian Journal of Physical Chemistry A, 2009, vol.83, no.2, pp.223-230.
18. Nikol'skiy B. P., Pal'chevskiy V. V., Pendin A. A., Yakubov X. M. Oksredmetriya [Oxredmetry]. Leningrad, Khimiya Publ., 1975, 304 p.
