Моделювання взаємодії поверхні кремнезему з кислотами та лугами у водному середовищі
A quantum chemical analysis has been carried out of the equilibrium structure of hydrated HCl and HBr acid complexes and alkaline metal hydroxides on silica surface by means of density functional theory method with extended basis set 6-31++G(d,p) and exchange-correlation functional B3LYP. Deprotonat...
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Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine
2015
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| author | Kravchenko, A. A. Demianenko, E. M. Tsendra, O. M. Lobanov, V. V. Grebenyuk, A. G. Terets, M. I. |
| author_facet | Kravchenko, A. A. Demianenko, E. M. Tsendra, O. M. Lobanov, V. V. Grebenyuk, A. G. Terets, M. I. |
| author_institution_txt_mv | [
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"author": "A. A. Kravchenko",
"institution": "Інститут хімії поверхні ім. О.О. Чуйка Національної академії наук України"
},
{
"author": "E. M. Demianenko",
"institution": "Інститут хімії поверхні ім. О.О. Чуйка Національної академії наук України"
},
{
"author": "O. M. Tsendra",
"institution": "Інститут хімії поверхні ім. О.О. Чуйка Національної академії наук України"
},
{
"author": "V. V. Lobanov",
"institution": "Інститут хімії поверхні ім. О.О. Чуйка Національної академії наук України"
},
{
"author": "A. G. Grebenyuk",
"institution": "Інститут хімії поверхні ім. О.О. Чуйка Національної академії наук України"
},
{
"author": "M. I. Terets",
"institution": "Інститут хімії поверхні ім. О.О. Чуйка Національної академії наук України"
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| author_sort | Kravchenko, A. A. |
| baseUrl_str | |
| collection | OJS |
| datestamp_date | 2018-11-27T09:34:56Z |
| description | A quantum chemical analysis has been carried out of the equilibrium structure of hydrated HCl and HBr acid complexes and alkaline metal hydroxides on silica surface by means of density functional theory method with extended basis set 6-31++G(d,p) and exchange-correlation functional B3LYP. Deprotonation constants of silica surface hydroxyl group and of its cationic form have been calculated. |
| first_indexed | 2025-07-22T19:34:08Z |
| format | Article |
| fulltext |
Поверхность. 2015. Вып. 7(22). С. 36–41 36
UDC 544.723: 544.183
SIMULATION OF THE INTERACTION BETWEEN
SILICA SURFACE AND ACID OR ALKALINE AQUEOUS
MEDIA
A.A. Kravchenko, E.M. Demianenko, O.M. Tsendra, V.V. Lobanov,
A.G. Grebenyuk , M.I. Terets
Chuiko Institute of Surface Chemistry, National Academy of Sciences of Ukraine,
17 General Naumov Str., Kyiv 03164, Ukraine
A quantum chemical analysis has been carried out of the equilibrium structure of hydrated
HCl and HBr acid complexes and alkaline metal hydroxides on silica surface by means of density
functional theory method with extended basis set 6-31++G(d,p) and exchange-correlation functional
B3LYP. Deprotonation constants of silica surface hydroxyl group and of its cationic form have been
calculated.
Introduction
Highly dispersed silica due to its exceptional physical and chemical properties,
including the well-developed surface, chemical inertness, good adsorption capacity, is used as
a sorbent and a carrier of drugs and pharmaceutical compositions in various fields of
medicine, pharmacy, veterinary, biotechnology etc. [1]. Silica surface properties at the
adsorption from aqueous solutions depend on many factors such as energy of interaction
between surface functional groups and some segments of adsorbate molecule, surface charge,
ionic strength and acidity of the solution. Knowledge about the mechanism of acid-base
balance at silica surface–solution interface at atomic level is necessary for creation of new
silica-based sorbents and for their effective use.
Information about the structural parameters and thermodynamic values such as the
change ΔG in Gibbs free energy of dissociation of neutral and protonated surface silanol
groups, dissociation constant of the both hydroxyl group (рKа) and surface silanol group in a
cationic form (рKb), as well as the point of zero charge (pzc) can be provided by methods of
quantum chemistry.
Since pzc is an arithmetic mean of the рKа and рKb values, firstly the рKа value
(deprotonation constant of the Si-OH groups) was calculated according to the equation:
Si–OH Si–O– + H+. (1)
The constant of deprotonation (рKb) of cationic form of silanol groups was found from
the equation:
Si–OН2
+ Si–OH + Н+. (2)
It is known [2], that the surface of SiO2 particles may acquire negative charge when
the pH of solution increases. The value of the negative charge is determined by the degree of
ionization of surface hydroxyl groups which can also interact with alkali metal cations
according to the equation:
SiOH + Ме+ + OH– SiO–Ме+ + Н2O. (3)
It has been shown [3] that adsorption of lithium, sodium and potassium cations on
silica surface decreases in a series Li+>Na+>K+ at pH> 9.5, in contrast to the average values
of pH (6-8). Nevertheless some parameters of elementary stages of the interaction between
silica surface and alkaline aqueous solution cannot be determined by experimental methods.
37
Therefore it is necessary to study the interaction of hydrated HCl and HBr acid complexes
and alkaline metal hydroxides with silica surface by means of quantum chemical methods.
Simulation of acid-base properties of the silica surface, according to the equations (1) and (2),
as well as its sorption properties in relation to the alkaline metal cations (according to the
equation (3)) is the subject of this study.
Objects and methods
Calculations have been performed by density functional theory method [4] using
exchange-correlation functional B3LYP [5,6] and 6-31++G(d,p) valence-split basis set. The
effect of the aqueous medium was taken into account using polarizable continuum solvent
model (CPCM) [7, 8]. A cubic-like structure (Si8O12(OH)8) was chosen as the model of silica
surface. The deprotonation constants for cationic forms of silanol group рKа and рKb were
found after the formula:
рK= ΔG/2.303RT (4)
where R – universal gas constant, T – temperature, ΔG – change in Gibbs free energy of
deprotonation reaction. The pzc value (point of zero charge) was calculated according to the
formula:
pzc = (рKа + рKb)/2. (5)
All the calculations were performed using the software package US GAMESS [9].
Results and discussion
To study the reaction of silanol group deprotonation, we have obtained equilibrium
geometrical parameters of molecules Si8O12(OH)8, which interacts with four water molecules
in both molecular state and charge separation state which contains dissociated silanol group
and hydronium cation (Figure 1).
a b
Fig. 1. The equilibrium structure of the complexes with (a) undissociated silanol group and
wa-ter molecules; (b) dissociated silanol group, water molecules and a hydronium
cation
The calculated results show that рKа of dissociation of silanol groups is a positive
value of 7.2, which is consistent with experimental values for silica acidity (close to 8) [10]. It
proves this model for silica surface to be appropriate for modeling further acid-base
processes.
The reaction of deprotonation for cationic form silanol groups according to equation
(2) in the presence of Cl– and Br– anions is the proton transfer reaction from a positively
charged group Si–OH2
+ (Fig. 2, a, b) to corresponding halogen anion (Fig. 2, b, d). As can
be seen from the Table 1, for complexes containing Cl– or Br– anions, the change in total
energy of deprotonation reaction of positively charged silanol groups (Ereact.) is almost the
38
same; the change in Gibbs free energy of deprotonation reactions (Greact.) differs for
6.4 kJ/mol. Dissociation constants (рKb), for cationic form of silanol groups in complexes
containing Cl– and Br– are calculated according to the equation (4); they are -0.3 and 0.9
respectively.
a b
c d
Fig. 2. Equilibrium structures for complexes consisting of a cluster Si8O12(OH)8, two anions
Cl– (а, b) or Br– (c, d) and hydronium ion: cationic forms of silanol groups (a, c);
ordinary forms of silanol group (b, d)
The values of dissociation constant (рKb) for cationic forms of silanol groups along
with deprotonation constant of neutral form of silanol groups (рKа) make it possible to
calculate the value of pzc, this is about 3 and agree well with experimental data [10].
Table 1. The total energy changes value for deprotonation reaction (Ereact.), the value of
Gibbs free energy change in deprotonation reactions (Greact.), and the
deprotonation constant (рKb) of cationic form of silanol groups
Complex Ereact, kJ/mol
G react,
kJ/mol
рKb
2Cl– Н2О +H2OSi8O12(OH)7 3.7 -1.5 -0.3
2Br– Н2О +H2OSi8O12(OH)7 10.1 4.9 0.9
When modeling the interaction between an alkaline aqueous solution and silica
surface, it is assumed (equation 3), that protons of silanol groups are neutralized by hydroxide
anions to form water molecules. In this regard, considered electroneutral complexes
(innerspheric complexes), consisting of the cations Li+, Na+ and K+ (hydrated nine water
molecules) and the molecules Si8O12(OH)8 with deprotonated silanol groups (Fig. 3).
39
a b
Fig. 3. The equilibrium structures of the
complex containing molecule
Si8O12(OH)8, nine water molecules
and lithium cation (a), those of
sodium (b) and potassium (c) in a
state of separated charges and in a
state that meets the direct contact
between the deprotonated cation and
silanol groups.
c
The calculated results have shown that the greatest impact on the energy of siloxane
bond relates to the smallest radius of cations. As it is well known [11], potassium cations in
solution can have a hydration number up to eight. That is why to model the hydration of alkali
metal cations we used nine water molecules – enough to saturate the first hydration shell of a
cation, some of them being included into the second hydration shell.
Hydrated lithium cation has no direct contact with oxygen atoms of deprotonated
silanol groups (Fig. 3, a), what can be explained by its small radius and large polarization
capability with respect to water molecules of its own hydration shell. The latters in turn form
strong hydrogen bonds with oxygen atoms of deprotonated silanol groups and therefore
sterically hinder direct contact with its Li+ cation. It should be noted that the distance between
the oxygen atom of undissociated silanol group and alkali metal cations increases
proportionally to the radius of the hydrated cation. Thus, the hydration shell of lithium cation
contains five water molecules (Fig. 3, a), and those of sodium and potassium contain six
water molecules (Fig. 3, b, c).
The energy of interaction of alkali metal cations (E) (see Table 2) with silica acid
oligomer is calculated as the total energy difference between the values for outerspheric and
of inner-spheric systems, the transformations occurring due to following scheme:
Si O– ··· (Н2О)9···Ме+ SiO–Ме+ ··· (Н2О)9.
The Gibbs free energy of interaction (see Table 2) increases with growth of radii of
hydrated alkali metal cations in the series Li <Na <K, what correlates with the experimental
adsorption values (A) found in [6] at pH > 9.5. The calculated G values indicate a relatively
negligible adsorption capability of silica surface concerning alkali metal cations. The total
energy changes due to transition from outerspheric complex to inner-spheric ones indicate
greater probability of formation of the formers relative to the latters. This conclusion is
40
consistent with the data from [12], where the dependences were examined of the surface
charge value pH within solutions of LiCl, NaCl, KCl, RbCl, CaCl2, SrCl2 and BaCl2
electrolytes in order to evaluate their effect on the rate of silica dissolution. The authors
presented models based on the idea that the alkali metal ions affect the proton donor
properties of the surface via formation of outerspheric complexes resulting in moving off
charged surface active centers. The authors believe the surface charge density to depend on
the radii and charge of counter- ions. Within this model, the rate of silica dissolution depends
on the electrolyte nature and content, due to its effect on the surface electrostatic properties.
Thus, the greater charge should be accumulated on silica surface containing weak-hydrated
ions of large size, as compared with strong hydrated ions.
Table 2. Changes in the total energy (E) and Gibbs free energy (G) for interaction between
hydrated alkali metal cations and negatively charged silica surface, and experimental
values of their adsorption (A).
Reaction scheme E, kJ/mol
G,
kJ/mol
АA, mg-eq/g,
[6]
SiO– ···(Н2О)9 ··· Li+ SiO– Li+ ···(Н2О)9 -16.9 -36.8 -6.5
Si O– ···(Н2О)9 ··· Na+ SiO– Na+···(Н2О)9 26.4 13.5 2.4
Si O– ···(Н2О)9 ··· K+ SiO– K+ ···(Н2О)9 19.1 2.2 0.4
Conclusions
A proton transfer is probable from hydronium ion to the oxygen atoms of silanol groups
with formation of their cationic form due to interaction of hydrated ion pairs of HCl and HBr
with silica surface in aqueous solutions. Deprotonation constant of cationic form of silanol
group depends on the nature of an anion and increases in magnitude with increasing anion
radius.
The increase in adsorption of alkali metal cations with decreasing cation radius
(observed in the experiment at high pH) is due to the formation of inside-sphere complexes
and is defined by polarization capability of cations. Smaller values of the Gibbs free energy
changes in complexes containing lithium cation, compared with those in complexes with
sodium and potassium cations, can be explained by the presence of lithium cations resulting
in to decreasing the electron density on the oxygen atom of deprotonated silanol group and so
in reducing the ionicity of the Si O–···Ме+ bond (between the oxygen atom of silanol group
and corresponding alkali metal atom).
References
1. Medical chemistry and clinical application of silicon dioxide / A.A. Chuiko, Ed. – Kyiv:
Nauk. Dumka, 2003. – 415 p. (in Russian).
2. Zuyi T., Hongxia Z. Acidity and Alkali Metal Adsorption on the SiO2–Aqueous
Solution Interface // J. Colloid Interface Sci. – 2002. – V. 252, N 1. – P. 15-20.
3. Silica gel based sorbents in radiochemistry / B.N. Laskorin, Ed. – Moskow: Atomiydat,
1977. – 304 p. (in Russian).
4. Baerends E.J., Gritsenco O.V. A quantum chemical view of density functional theory //
J. Phys. Chem. A. – 1997. – V. 101, N 30. – P. 5383-5403.
5. Becke A.D. Density functional thermochemistry. III. The role of exact exchange //
J. Chem. Phys. – 1993. – V. 98, N 7. – P. 5648-5653.
6. Lee C., Yang W., Parr R.G. Development of the Colle-Salvetti correlation-energy
formula into a functional of the electron density // Phys. Rev. B. – 1988. – V. 37, N 2. –
P. 785-789.
7. Cossi M., Barone V., Cammi R., Tomasi J. Ab initio study of solvated molecules: a new
implementation of the polarizable continuum model // Chem. Phys. Lett. – 1996. – V.
255, N 4-6. – P. 327-335.
41
8. Fortunelli A., Tomasi J. The implementation of density functional theory within the
polarizable continuum model for salvation // Chem. Phys. Lett. – 1994. – V. 231, N 1. –
P. 34-39.
9. Schmidt M.W., Baldridge K.K., Boatz J.A., Elbert S.T., Gordon M.S., Jensen J.H.,
Koseki S., Matsunaga N., Nguen K.A., Su S.J., Windus T.L., Dupuis M.,
Montgomery J.A.. General atomic and molecular electronic-structure system: Review //
J. Comput. Chem. – 1993. – V. 14, N 11. – P. 1347-1363.
10. R.K. Iler The Chemistry of Silica: Solubility, Polymerization, Colloid and Surface
Properties and Biochemistry of Silica. - Published by John Wiley Sons Inc, United
States (1979).
11. Enderby J.E. Ion Solvation via Neutron Scattering // Chem. Soc. Rev. – 1995. – V. 23,
N 3. – P. 159-168.
12. Karlsson M., Craven C., Dove P M., Casey W.H. Surface Charge Concentrations on
Silica in Different 1.0 M Metal-Chloride Background Electrolytes and Implications for
Dissolution Rates // Aquatic Geochemistry. – 2001. – V. 7, N1. – P. 13-32.
МОДЕЛИРОВАННЯ ВЗАИМОДЕЙСТВИЯ ПОВЕРХНОСТИ
КРЕМНЕЗЕМА С КИСЛОТАМИ И ОСНОВАНИЯМИ В ВОДНОЙ СРЕДЕ
А.А. Кравченко, Е.Н. Демяненко, О.М. Цендра, В.В. Лобанов,
А.Г. Гребенюк, М.И. Терец
Институт химии поверхности им. А.А. Чуйко Национальной академии наук Украины
ул. Генерала Наумова, 17, Киев, 03164, Украина
Методом функционала плотности с использованием расширенного базисного
набора 6-31++G(d,p) и обменно-корреляцийного функционала B3LYP проведен
квантовохимический анализ строения гидратированных комплексов кислот HCl и HBr
и гидроксидов щелочных металлов на поверхности кремнезема. Рассчитаны
константы депротонирования гидроксильной группы поверхности кремнезема и её
катионной формы.
МОДЕЛЮВАННЯ ВЗАЄМОДІЇ ПОВЕРХНІ КРЕМНЕЗЕМУ З КИСЛОТАМИ ТА
ЛУГАМИ У ВОДНОМУ СЕРЕДОВИЩІ
А.А. Кравченко, Є.М. Дем’яненко, О.М. Цендра, В.В. Лобанов,
А.Г. Гребенюк, М.І. Терець
Інститут хімії поверхні ім. О.О. Чуйка Національної академії наук України
вул. Генерала Наумова, 17, Київ, 03164, Україна
Методом функціоналу густини з використанням розширеного базисного набору
6-31++G(d,p) та обмінно-корреляційного функціоналу B3LYP проведено
квантовохімічний аналіз будови гідратованих комплексів кислот HCl і HBr та
гідроксидів лужних металів на поверхні кремнезему. Розраховані константи
депротонування гідроксильної групи групи поверхні кремнезему і її катіонної форми.
|
| id | oai:ojs.pkp.sfu.ca:article-566 |
| institution | Surface |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2025-07-22T19:34:08Z |
| publishDate | 2015 |
| publisher | Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine |
| record_format | ojs |
| resource_txt_mv | surfacezbircomua/06/a9e3f4854a921ccff0b8ccafab0a6d06.pdf |
| spelling | oai:ojs.pkp.sfu.ca:article-5662018-11-27T09:34:56Z Simulation of the interaction between silica surface and acid or alkaline aqueous media Моделировання взаимодействия поверхности кремнезема с кислотами и основаниями в водной среде Моделювання взаємодії поверхні кремнезему з кислотами та лугами у водному середовищі Kravchenko, A. A. Demianenko, E. M. Tsendra, O. M. Lobanov, V. V. Grebenyuk, A. G. Terets, M. I. A quantum chemical analysis has been carried out of the equilibrium structure of hydrated HCl and HBr acid complexes and alkaline metal hydroxides on silica surface by means of density functional theory method with extended basis set 6-31++G(d,p) and exchange-correlation functional B3LYP. Deprotonation constants of silica surface hydroxyl group and of its cationic form have been calculated. Методом функционала плотности с использованием расширенного базисного набора 6‑31++G(d,p) и обменно-корреляцийного функционала B3LYP проведен квантовохимический анализ строения гидратированных комплексов кислот HCl и HBr и гидроксидов щелочных металлов на поверхности кремнезема. Рассчитаны константы депротонирования гидроксильной группы поверхности кремнезема и её катионной формы. Методом функціоналу густини з використанням розширеного базисного набору 6‑31++G(d,p) та обмінно-корреляційного функціоналу B3LYP проведено квантовохімічний аналіз будови гідратованих комплексів кислот HCl і HBr та гідроксидів лужних металів на поверхні кремнезему. Розраховані константи депротонування гідроксильної групи групи поверхні кремнезему і її катіонної форми. Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine 2015-09-09 Article Article application/pdf https://surfacezbir.com.ua/index.php/surface/article/view/566 Surface; No. 7(22) (2015): Surface; 36-41 Поверхность; № 7(22) (2015): Поверхность; 36-41 Поверхня; № 7(22) (2015): Поверхня; 36-41 3154-8091 3154-8083 en https://surfacezbir.com.ua/index.php/surface/article/view/566/566 Авторське право (c) 2015 A.A. Kravchenko, E.M. Demianenko, O.M. Tsendra, V.V. Lobanov, A.G. Grebenyuk , M.I. Terets |
| spellingShingle | Kravchenko, A. A. Demianenko, E. M. Tsendra, O. M. Lobanov, V. V. Grebenyuk, A. G. Terets, M. I. Моделювання взаємодії поверхні кремнезему з кислотами та лугами у водному середовищі |
| title | Моделювання взаємодії поверхні кремнезему з кислотами та лугами у водному середовищі |
| title_alt | Simulation of the interaction between silica surface and acid or alkaline aqueous media Моделировання взаимодействия поверхности кремнезема с кислотами и основаниями в водной среде |
| title_full | Моделювання взаємодії поверхні кремнезему з кислотами та лугами у водному середовищі |
| title_fullStr | Моделювання взаємодії поверхні кремнезему з кислотами та лугами у водному середовищі |
| title_full_unstemmed | Моделювання взаємодії поверхні кремнезему з кислотами та лугами у водному середовищі |
| title_short | Моделювання взаємодії поверхні кремнезему з кислотами та лугами у водному середовищі |
| title_sort | моделювання взаємодії поверхні кремнезему з кислотами та лугами у водному середовищі |
| url | https://surfacezbir.com.ua/index.php/surface/article/view/566 |
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