SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM AND POLYETHYLENEPOLYAMMONIUM CITRATES AQUEOUS SOLUTIONS PRODUCTS COMPOSITION AND THE RELATIVE STABILITY
The paper presents the results of pH, redox, and conductometric studies on the acid-base interaction during sulfur dioxide chemisorption by aqueous solutions containing 0.1 mol/L monoethanolammonium (MEA·1/3CA) and polyethylenepolyammonium (PEPA·1/3CA) citrates, as well as buffer solutions of monoet...
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| Date: | 2025 |
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| Format: | Article |
| Language: | English |
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V.I.Vernadsky Institute of General and Inorganic Chemistry
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Ukrainian Chemistry Journal| _version_ | 1871466115610181632 |
|---|---|
| author | Khoma, Ruslan Vodzinskii, Sergey Bienkovska, Tetyana |
| author_facet | Khoma, Ruslan Vodzinskii, Sergey Bienkovska, Tetyana |
| author_institution_txt_mv | [
{
"author": "Ruslan Khoma",
"institution": "Одесский национальный университет имени И.И. Мечникова"
},
{
"author": "Sergey Vodzinskii",
"institution": "Одесский национальный университет имени И.И. Мечникова"
},
{
"author": "Tetyana Bienkovska",
"institution": "Physico-Chemical Institute of Environment and Human Protection"
}
] |
| author_sort | Khoma, Ruslan |
| baseUrl_str | https://ucj.org.ua/index.php/journal/oai |
| collection | OJS |
| datestamp_date | 2026-07-22T08:23:55Z |
| description | The paper presents the results of pH, redox, and conductometric studies on the acid-base interaction during sulfur dioxide chemisorption by aqueous solutions containing 0.1 mol/L monoethanolammonium (MEA·1/3CA) and polyethylenepolyammonium (PEPA·1/3CA) citrates, as well as buffer solutions of monoethanolamine–monoethanolammonium citrate (MEA·1/6CA) and polyethylenepolyamine–polyethylenepolyammonium citrate (PEPA·1/6CA), in comparison with sodium citrate. The composition of the compounds formed during SO2 absorption by Na3Cit, MEA·1/3CA, PEPA·1/3CA, MEA·1/6CA, and PEPA·1/6CA solutions at 273–313 K was determined.For the same amount of absorbed sulfur dioxide, an increase in specific electrical conductivity (æ) with rising temperature was observed in SO2–Na3Cit–H2O and SO2–MEA×1/3CA–H2O solutions within the 273–313 K range. However, in the SO2–MEA×1/3CA–H2O, SO2–PEPA×1/3CA–H2O, SO2–MEA×1/6CA–H2O, and SO2–PEPA×1/6CA–H2O systems, a decrease in Δæ was noted upon heating to 303 K, which is attributed to their ion-molecular composition.
Based on developed mathematical models, the ion-molecular component composition of SO2–MEA×1/3CA–H2O and SO2–MEA×1/6CA–H2O solutions was determined at 283–313 K. The concentration and thermodynamic constants for the formation of ionic associates were calculated:(NH3CH2CH2OH)2SO3, {H3CH2CH2OH}{HOC3H4(COOH)2(COO-)} (Ia), {H3CH2CH2OH}2{HOC3H4(COOH)(COO-)2} (IIa), {H3CH2CH2OH}2{HOC3H4(COOH)2(COO-)} (IIb), {H3CH2CH2OH}3{HOC3H4(COO-)3} (IIIa), as well as ion-molecular associates:{H3CH2CH2OH}{HOC3H4(COOH)3} (Ib), {NH2CH2CH2OH}3{H3CH2CH2OH}3{HOC3H4(COO-)3} (IVa), {NH2CH2CH2OH}2{H3CH2CH2OH}4{HOC3H4(COO-)3} (IVb).
In SO2–MEA×1/3CA–H2O solutions, as the temperature increases, bond rearrangement occurs in ionic associates IIa and Ib, as indicated by the absence of a clear temperature dependence ofp, along with the strengthening of IIa and Ib. Conversely, in SO2–MEA×1/6CA–H2O solutions, increasing temperature leads to the weakening of the bonds in compounds Ia, IIIa, IVa, and IVb, while in compound Ib, the bonds strengthen. |
| doi_str_mv | 10.33609/2708-129X.91.3.2025.3-24 |
| first_indexed | 2025-09-24T17:44:00Z |
| format | Article |
| fulltext |
3
УДК 546.224-31:547.233:547.477.1 doi: 10.33609/2708-129X.91.3.2025.3-24
SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM
AND POLYETHYLENEPOLYAMMONIUM CITRATES AQUEOUS
SOLUTIONS PRODUCTS COMPOSITION AND THE RELATIVE STABILITY.
R. E. Khoma*, K. V. Tsyganenko, T. S. Bienkovska, Yu. V. Ishkov, S. V. Vodzinskii
Odessa I.I. Mechnikov National University,
2 Dvoryanska str., 65082 Odessa, Ukraine
*e-mail: rek@onu.edu.ua
The paper presents the results of pH, redox, and conductometric studies on the acid-base in-
teraction during sulfur dioxide chemisorption by aqueous solutions containing 0.1 mol/L mono
ethanolammonium (MEA·1/3CA) and polyethylenepolyammonium (PEPA·1/3CA) citrates, as well
as buffer solutions of monoethanolamine – monoethanolammonium citrate (MEA·1/6CA)and poly-
ethylenepolyamine – polyethylenepolyammonium citrate (PEPA·1/6CA), in comparison with sodium
citrate. The composition of the compounds formed during SO2 absorption by Na3Cit, MEA·1/3CA,
PEPA·1/3CA, MEA·1/6CA, and PEPA·1/6CA solutions at 273–313 K was determined. For the same
amount of absorbed sulfur dioxide, an increase in specific electrical conductivity (æ) with rising tem-
perature was observed in SO2–Na3Cit–H2O and SO2–MEA⋅1/3CA–H2O solutions within the 273–313 K
range. However, in the SO2–MEA⋅1/3CA–H2O, SO2–PEPA⋅1/3CA–H2O, SO2–MEA⋅1/6CA–H2O, and
SO2–PEPA⋅1/6CA–H2O systems, a decrease in Δæ was noted upon heating to 303 K, which is attri
buted to their ion-molecular composition.
Based on developed mathematical models, the ion-molecular component composition of
SO2–MEA⋅1/3CA–H2O and SO2–MEA⋅1/6CA–H2O solutions was determined at 283–313 K. The con-
centration and thermodynamic constants for the formation of ionic associates were calculated:
(NH3CH2CH2OH)2SO3, {
+
N H3CH2CH2OH}{HOC3H4(COOH)2(COO−)} (Ia),
{
+
N H3CH2CH2OH}2{HOC3H4(COOH)(COO−)2} (IIa),
{
+
N H3CH2CH2OH}2{HOC3H4(COOH)2(COO−)} (IIb),
{
+
N H3CH2CH2OH}3{HOC3H4(COO−)3} (IIIa),
as well as ion-molecular associates:
{
+
N H3CH2CH2OH}{HOC3H4(COOH)3} (Ib),
{NH2CH2CH2OH}3{
+
N H3CH2CH2OH}3{HOC3H4(COO−)3} (IVa),
{NH2CH2CH2OH}2{
+
N H3CH2CH2OH}4{HOC3H4(COO−)3} (IVb).
In SO2–MEA⋅1/3CA–H2O solutions, as the temperature increases, bond rearrangement occurs in
ionic associates IIa and Ib, as indicated by the absence of a clear temperature dependence of p β
T
IIIа,
along with the strengthening of IIa and Ib. Conversely, in SO2–MEA⋅1/6CA–H2O solutions, increas-
ing temperature leads to the weakening of the bonds in compounds Ia, IIIa, IVa, and IVb, while in
compound Ib, the bonds strengthen.
Keywords: sulfur dioxide, ammonium citrates, acid-base interaction, ion associates, ion-molecular
associates.
4 ISSN 2708-129X. Укр. хім. журн., 2025
SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM AND POLYETHYLENEPOLYAMMONIUM CITRATES
AQUEOUS SOLUTIONS PRODUCTS COMPOSITION AND THE RELATIVE STABILITY.INORGANIC CHEMISTRY
INTRODUCTION. For sanitary air puri-
fication from acidic gases (particularly SO2),
absorption and adsorption methods using
various chemisorbents are widely used [1, 2].
Previously, the authors [3, 4] studied the ac-
id-base interaction of sulfur dioxide with mo
del aqueous solutions of organic N-containing
bases (AM), including monoethanolamine
(MEA) and polyethylenepolyamine (PEPA), to
develop chemisorbents for acidic gas filtration
in respiratory protection [3–5]. To prevent the
evaporation of volatile MEA from the surface
of impregnated fibrous chemisorbents (IFCS)
under the flow of a gas-air mixture, polybasic
acids (particularly citric acid (CA)) were added
to the impregnating aqueous solutions based
on MEA. This modification enhanced the pro-
tective characteristics of IFCS against SO2 ex-
posure [5]. Additionally, aqueous sodium cit
rate solutions (HOC(CH2COONa)2COONa;
Na3Cit) have been identified as effective
chemisorbents for this gas [6–8].
Methods of pH-, redox- and conductomet-
ric titration have been successfully applied to
determine the reactivity of model aqueous AM
solutions towards SO2 and CA, allowing for the
calculation of their ion-molecular composition
and formation constants of weakly dissocia
ted compounds (such as ammonium sulfites,
hydrosulfites, pyrosulfites; and ion-molecular
complexes) [3, 4, 9].
In [9] the acid-base and electrochemical
behavior of Na3Cit – CA – H2O, MEA – CA –
H2O, and PEPA – CA – H2O solutions were
analyzed using pH-metric and conductomet-
ric data. The study determined the influence
of amine type and temperature on the ionic-
molecular composition, ionic strength, and
structural characteristics of these systems. It
also identified key factors (component ratios
and temperature) affecting the formation cons
tants of ionic associates. In [10], the influence
of water content and MEA on the physical and
chemical adsorption of sulfur dioxide by IFCS
samples based on citrate-monoethanolammo-
nium buffer systems was investigated. Com-
petitive adsorption of H2O and SO2 by the sur-
face of the indicated IFCS was noted. However,
no comprehensive data exists in the literature
regarding the interaction of sulfur dioxide with
ammonium citrates.
Given this gap, the present study aims to de-
termine the composition and relative stability
of the products formed during the interaction
of sulfur dioxide with aqueous solutions of so-
dium citrate, monoethanolammonium citrate
(MEA⋅1/3CA), and polyethylenepolyammoni-
um citrate (PEPA⋅1/3CA), as well as with buffer
solutions of monoethanolamine – monoetha
nolammonium citrate (MEA⋅1/6CA) and po
lyethylenepolyamine – polyethylenepolyam-
monium citrate (PEPA⋅1/6CA). To achieve
this goal, a pH, redox, and conductometric
study of the above interactions was carried out.
EXPERIMENT AND DISCUSSION OF
RESULTS. In this study, monoethanolamine
(MEA), sodium citrate (Na3Cit), and citric
acid (CA) of “chemically pure” classification,
as well as polyethylenepolyamine (PEPA)
(CAS 29320-38-5) without preliminary pu-
rification were used. Their characteristics are
given in Table 1. Additionally, gaseous sul-
fur dioxide was supplied from a cylinder. As
chemisorbents, aqueous solutions of Na3Cit,
MEA⋅1/3CA, MEA⋅1/6CA, PEPA⋅1/3CA, and
PEPA⋅1/6CA with a Na+ ion or amine nitrogen
concentration of 0.1 mol/L were used. Aque-
ous solutions of MEA⋅1/3CA and MEA⋅1/6CA
were prepared by adding a CA solution to an
MEA solution at a molar ratio of components
5https://ucj.org.ua
R. E. Khoma, K. V. Tsyganenko, T. S. Bienkovska, Yu. V. Ishkov, S. V. Vodzinskii UCJ № 3 / Vol. 91
of 1.0:3.0 and 1.0:6.0, respectively. Aqueous
solutions of PEPA⋅1/3CA and PEPA⋅1/6CA
were prepared similarly. The procedure for
pH-, redox- and conductometric titration of
aqueous solutions with gaseous sulfur dioxide
is described in detail in [20].
Figures 1–8 present the pH, redox, and
conductometric titration curves for 0.1 mol/L
aqueous solutions of Na3Cit, MEA⋅1/3CA,
PEPA⋅1/3CA, MEA⋅1/6CA and PEPA⋅1/6CA
with gaseous sulfur dioxide.
On the integral pH-metric titration curves
(Fig. 1, 2) of aqueous solutions of sodium
citrates, monoethanolammonium, and poly-
ethylenepolyammonium with gaseous sulfur
dioxide, a single jump is observed at the mo-
lar ratios Q(SO2):Q(Na) = (0.86 ÷ 0.97):2.00,
Q(SO2):Q(NMEA) = (0.92 ÷ 0.98):2.00 and
Q(SO2):Q(NPEPA) = (0.63 ÷ 0.81):2.00. These
correspond to the peaks on the differential
curves (see, for example, Fig. 4a) and contrast
with the MEA and PEPA solutions [3], which
exhibit two effects.
3
differential curves (see, for example, Fig. 4a) and contrast with the MEA and PEPA solutions [3],
which exhibit two effects.
Fig. 1. Integral pH-metric titration curves of a 0.1 mol/L Na3Cit aqueous solution with gaseous SO2 at
different temperatures (T, K): 273 – 1; 283 – 2; 293 – 3; 298 – 4; 303 – 5; 313 – 6.
This behavior is due to the weakly alkaline nature of the initial citrate solutions (Fig. 1–2;
pH 7.61 8.82 (Na3Cit), 6.32 6.50 (MEA1/3CA), and 4.80 5.42 (PEPA1/3CA)). The observed
effects on the differential curves occur in an acidic environment (Table 2; pH 3.60 3.94 (Na3Cit),
3.30 3.96 (MEA1/3CA) and 2.81 3.74 (PEPA1/3CA)) and are associated with the formation of
hydrosulfites of the corresponding cations. Deviations of the Q(SO2):Q(Na), Q(SO2):Q(NMEA), and
Q(SO2):Q(NPEPA) ratios from the stoichiometry value (1.00:2.00) are due to additional interactions,
particularly the stepwise protonation of citrate ions in the specified pH range [9, 20].
a b
Fig. 2. Integral pH-metric titration curves of a 0.1 mol/L MEA1/3CA (а) and PEPA1/3CA (b) aqueous solution
with gaseous SO2 at different temperatures (T, K): 273 – 1; 278 – 2; 283 – 3; 288 – 4; 293 – 5; 298 – 6; 303 – 7;
308 – 8; 313 – 9.
Fig. 1. Integral pH-metric titration curves of a 0.1 mol/L Na3Cit aqueous solution with gaseous SO2 at
different temperatures (T, K): 273 – 1; 283 – 2; 293 – 3; 298 – 4; 303 – 5; 313 – 6.
This behavior is due to the weakly alkaline
nature of the initial citrate solutions (Fig. 1–2;
pH 7.61 ÷ 8.82 (Na3Cit), 6.32 ÷ 6.50 (MEA⋅1/
3CA), and 4.80 ÷ 5.42 (PEPA⋅1/3CA)). The
observed effects on the differential curves oc-
cur in an acidic environment (Table 2; pH 3.60
÷ 3.94 (Na3Cit), 3.30 ÷ 3.96 (MEA⋅1/3CA)
and 2.81 ÷ 3.74 (PEPA⋅1/3CA)) and are as-
sociated with the formation of hydrosulfites
of the corresponding cations. Deviations of
the Q(SO2):Q(Na), Q(SO2):Q(NMEA), and
Q(SO2):Q(NPEPA) ratios from the stoichiometry
value (1.00:2.00) are due to additional interac-
tions, particularly the stepwise protonation of
citrate ions in the specified pH range [9, 20].
6 ISSN 2708-129X. Укр. хім. журн., 2025
SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM AND POLYETHYLENEPOLYAMMONIUM CITRATES
AQUEOUS SOLUTIONS PRODUCTS COMPOSITION AND THE RELATIVE STABILITY.INORGANIC CHEMISTRY
a b
Fig. 2. Integral pH-metric titration curves of a 0.1 mol/L MEA⋅1/3CA (а) and PEPA⋅1/3CA (b) aqueous
solution with gaseous SO2 at different temperatures (T, K): 273 – 1; 278 – 2; 283 – 3; 288 – 4; 293 – 5;
298 – 6; 303 – 7; 308 – 8; 313 – 9.
3
differential curves (see, for example, Fig. 4a) and contrast with the MEA and PEPA solutions [3],
which exhibit two effects.
Fig. 1. Integral pH-metric titration curves of a 0.1 mol/L Na3Cit aqueous solution with gaseous SO2 at
different temperatures (T, K): 273 – 1; 283 – 2; 293 – 3; 298 – 4; 303 – 5; 313 – 6.
This behavior is due to the weakly alkaline nature of the initial citrate solutions (Fig. 1–2;
pH 7.61 8.82 (Na3Cit), 6.32 6.50 (MEA1/3CA), and 4.80 5.42 (PEPA1/3CA)). The observed
effects on the differential curves occur in an acidic environment (Table 2; pH 3.60 3.94 (Na3Cit),
3.30 3.96 (MEA1/3CA) and 2.81 3.74 (PEPA1/3CA)) and are associated with the formation of
hydrosulfites of the corresponding cations. Deviations of the Q(SO2):Q(Na), Q(SO2):Q(NMEA), and
Q(SO2):Q(NPEPA) ratios from the stoichiometry value (1.00:2.00) are due to additional interactions,
particularly the stepwise protonation of citrate ions in the specified pH range [9, 20].
a b
Fig. 2. Integral pH-metric titration curves of a 0.1 mol/L MEA1/3CA (а) and PEPA1/3CA (b) aqueous solution
with gaseous SO2 at different temperatures (T, K): 273 – 1; 278 – 2; 283 – 3; 288 – 4; 293 – 5; 298 – 6; 303 – 7;
308 – 8; 313 – 9.
a b
Fig. 3. Integral pH-metric titration curves of MEA⋅1/6CA (а) and PEPA⋅1/6CA (b) aqueous solutions
with gaseous SO2 at different temperatures (T, K): 273 – 1; 278 – 2; 283 – 3; 288 – 4; 293 – 5; 298 – 6; 303 – 7;
308 – 8; 313 – 9.
4
a b
Fig. 3. Integral pH-metric titration curves of MEA1/6CA (а) and PEPA1/6CA (b) buffer solutions with gaseous
SO2 at different temperatures (T, K): 273 – 1; 278 – 2; 283 – 3; 288 – 4; 293 – 5; 298 – 6; 303 – 7; 308 – 8; 313
– 9.
7https://ucj.org.ua
R. E. Khoma, K. V. Tsyganenko, T. S. Bienkovska, Yu. V. Ishkov, S. V. Vodzinskii UCJ № 3 / Vol. 91
Table 1.
Physicochemical characteristics of the starting compounds.
Name Citric acid Sodium citrate Mono
ethanolamine
Polyethylene
polyamine
Designation CA Na3Cit MEA PEPA
Structural
formula
5
Table 1.
Physicochemical characteristics of the starting compounds.
Name Citric acid Sodium citrate Monoethanolamine Polyethylene polyamine
Designation CA Na3Cit MEA PEPA
Structural formula
OH
O
OH
OH
O
OH
O
NH2
OH
N
H
* *
n
General formula HOC3H4(COOH)3 HOC3H4(COONa)3 NH2CH2CH2OH NH2-(CH2CH2NH)k-H
М, g/mol 192.12 258.06 61.08 42.0
pKa 3.13; 4.76; 6.39 [12] 3.13; 4.76; 6.39 [12, 16] 9.20 [1] 9.21 [18]
Melting point., ºС 153 [12, 13] 300 [16] 10.5 [1, 17] -32.0 [18, 19]
Boiling point, ºС 310 [14] – 170.3 [1, 17] Decompos. [18, 19]
P, Pa (20 0С) 2.2110-6 [13] 0 53 [1, 17] <1.33 [18, 19]
lgP -1.64 [15] -1.72 [16] -1.31 [1, 17] -3.67 [18, 19]
O
O
OH
O
O
O
O
Na
+
Na
+
Na
+
5
Table 1.
Physicochemical characteristics of the starting compounds.
Name Citric acid Sodium citrate Monoethanolamine Polyethylene polyamine
Designation CA Na3Cit MEA PEPA
Structural formula
OH
O
OH
OH
O
OH
O
NH2
OH
N
H
* *
n
General formula HOC3H4(COOH)3 HOC3H4(COONa)3 NH2CH2CH2OH NH2-(CH2CH2NH)k-H
М, g/mol 192.12 258.06 61.08 42.0
pKa 3.13; 4.76; 6.39 [12] 3.13; 4.76; 6.39 [12, 16] 9.20 [1] 9.21 [18]
Melting point., ºС 153 [12, 13] 300 [16] 10.5 [1, 17] -32.0 [18, 19]
Boiling point, ºС 310 [14] – 170.3 [1, 17] Decompos. [18, 19]
P, Pa (20 0С) 2.2110-6 [13] 0 53 [1, 17] <1.33 [18, 19]
lgP -1.64 [15] -1.72 [16] -1.31 [1, 17] -3.67 [18, 19]
O
O
OH
O
O
O
O
Na
+
Na
+
Na
+
5
Table 1.
Physicochemical characteristics of the starting compounds.
Name Citric acid Sodium citrate Monoethanolamine Polyethylene polyamine
Designation CA Na3Cit MEA PEPA
Structural formula
OH
O
OH
OH
O
OH
O
NH2
OH
N
H
* *
n
General formula HOC3H4(COOH)3 HOC3H4(COONa)3 NH2CH2CH2OH NH2-(CH2CH2NH)k-H
М, g/mol 192.12 258.06 61.08 42.0
pKa 3.13; 4.76; 6.39 [12] 3.13; 4.76; 6.39 [12, 16] 9.20 [1] 9.21 [18]
Melting point., ºС 153 [12, 13] 300 [16] 10.5 [1, 17] -32.0 [18, 19]
Boiling point, ºС 310 [14] – 170.3 [1, 17] Decompos. [18, 19]
P, Pa (20 0С) 2.2110-6 [13] 0 53 [1, 17] <1.33 [18, 19]
lgP -1.64 [15] -1.72 [16] -1.31 [1, 17] -3.67 [18, 19]
O
O
OH
O
O
O
O
Na
+
Na
+
Na
+
5
Table 1.
Physicochemical characteristics of the starting compounds.
Name Citric acid Sodium citrate Monoethanolamine Polyethylene polyamine
Designation CA Na3Cit MEA PEPA
Structural formula
OH
O
OH
OH
O
OH
O
NH2
OH
N
H
* *
n
General formula HOC3H4(COOH)3 HOC3H4(COONa)3 NH2CH2CH2OH NH2-(CH2CH2NH)k-H
М, g/mol 192.12 258.06 61.08 42.0
pKa 3.13; 4.76; 6.39 [12] 3.13; 4.76; 6.39 [12, 16] 9.20 [1] 9.21 [18]
Melting point., ºС 153 [12, 13] 300 [16] 10.5 [1, 17] -32.0 [18, 19]
Boiling point, ºС 310 [14] – 170.3 [1, 17] Decompos. [18, 19]
P, Pa (20 0С) 2.2110-6 [13] 0 53 [1, 17] <1.33 [18, 19]
lgP -1.64 [15] -1.72 [16] -1.31 [1, 17] -3.67 [18, 19]
O
O
OH
O
O
O
O
Na
+
Na
+
Na
+
General
formula HOC3H4(COOH)3 HOC3H4(COONa)3 NH2CH2CH2OH NH2-(CH2CH2NH)k-H
М, g/mol 192.12 258.06 61.08 42.0
pKa 3.13; 4.76; 6.39 [12] 3.13; 4.76; 6.39 [12, 16] 9.20 [1] 9.21 [18]
Melting
point., ºС
153 [12, 13] 300 [16] 10.5 [1, 17] -32.0 [18, 19]
Boiling
point, ºС 310 [14] – 170.3 [1, 17] Decompos. [18, 19]
P, Pa (20 0С) 2.21⋅10-6 [13] 0 53 [1, 17] <1.33 [18, 19]
lgP -1.64 [15] -1.72 [16] -1.31 [1, 17] -3.67 [18, 19]
In the case of MEA⋅1/6CA solutions, two
jumps are observed on the integral pH-met-
ric curves (Fig. 3a; Table 2) and two maxima
on the differential pH-metric curves (e.g.,
Fig. 4b) at the ratios Q(SO2):Q(NMEA) = (0.34
÷ 0.52):2.00 and (0.49 ÷ 0.63):1.00. In contrast,
PEPA⋅1/6CA solutions (Fig. 3b; Table 2) exhi
bit only one effect on the corresponding curves
at Q(SO2):Q(NPEPA) = (0.68 ÷ 0.86):2.00. This
difference arises from the more alkaline nature
of the initial MEA⋅1/6CA solutions (pH 9.53 ÷
9.74) compared to PEPA⋅1/6CA solutions (pH
7.76 ÷ 8.67).
Analyzing the data shown in Fig. 1-3, the
pH values of chemisorption systems at 293 K
can be arranged in the following sequence:
– for Q(SO2) < 0.02 mol/L MEA⋅1/6CA
> PEPA⋅1/6CA > MEA⋅1/3CA > Na3Cit >
PEPA⋅1/3CA;
– for 0.02 < Q(SO2) < 0.05 mol/L MEA⋅1/
6CA > MEA⋅1/3CA > Na3Cit > PEPA⋅1/6CA >
PEPA⋅1/3CA;
– for 0.05 < Q(SO2) < 0.10 mol/L MEA⋅1/
3CA > MEA⋅1/6CA ≥ Na3Cit > PEPA⋅1/6CA ≥
PEPA⋅1/3CA.
These results indicate that at SO2 concent
rations above 0.05 mol/L, solutions based on
monoethanolammonium citrate exhibit the
highest efficiency in binding this toxicant.
8 ISSN 2708-129X. Укр. хім. журн., 2025
SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM AND POLYETHYLENEPOLYAMMONIUM CITRATES
AQUEOUS SOLUTIONS PRODUCTS COMPOSITION AND THE RELATIVE STABILITY.INORGANIC CHEMISTRY
a b
Fig. 4. Differential pH-metric titration curves of 0.1 M Na3Cit (1а), MEA⋅1/3CA (2а), PEPA⋅1/3CA
(3а), MEA⋅1/6CA (1b) and PEPA⋅1/6CA (2b) aqueous solutions with gaseous SO2 at 298 K.
6
In the case of MEA1/6CA solutions, two jumps are observed on the integral pH-metric
curves (Fig. 3a; Table 2) and two maxima on the differential pH-metric curves (e.g., Fig. 4b) at the
ratios Q(SO2):Q(NMEA) = (0.34 0.52):2.00 and (0.49 0.63):1.00. In contrast, PEPA1/6CA
solutions (Fig. 3b; Table 2) exhibit only one effect on the corresponding curves at Q(SO2):Q(NPEPA)
= (0.68 0.86):2.00. This difference arises from the more alkaline nature of the initial MEA1/6CA
solutions (pH 9.53 9.74) compared to PEPA1/6CA solutions (pH 7.76 8.67).
a b
Fig. 4. Differential pH-metric titration curves of 0.1 M Na3Cit (1а), MEA1/3CA (2а), PEPA1/3CA (3а),
MEA1/6CA (1b) and PEPA1/6CA (2b) aqueous solutions with gaseous SO2 at 298 K.
a b
Fig. 5. Redox-metric titration curves of 0.1 mol/L Na3Cit (а) and MEA1/3CA (b) aqueous solutions with
gaseous SO2 at different temperatures (T, K): 273 – 1; 283 – 2; 293 – 3; 298 – 4; 303 – 5; 313 – 6.
6
In the case of MEA1/6CA solutions, two jumps are observed on the integral pH-metric
curves (Fig. 3a; Table 2) and two maxima on the differential pH-metric curves (e.g., Fig. 4b) at the
ratios Q(SO2):Q(NMEA) = (0.34 0.52):2.00 and (0.49 0.63):1.00. In contrast, PEPA1/6CA
solutions (Fig. 3b; Table 2) exhibit only one effect on the corresponding curves at Q(SO2):Q(NPEPA)
= (0.68 0.86):2.00. This difference arises from the more alkaline nature of the initial MEA1/6CA
solutions (pH 9.53 9.74) compared to PEPA1/6CA solutions (pH 7.76 8.67).
a b
Fig. 4. Differential pH-metric titration curves of 0.1 M Na3Cit (1а), MEA1/3CA (2а), PEPA1/3CA (3а),
MEA1/6CA (1b) and PEPA1/6CA (2b) aqueous solutions with gaseous SO2 at 298 K.
a b
Fig. 5. Redox-metric titration curves of 0.1 mol/L Na3Cit (а) and MEA1/3CA (b) aqueous solutions with
gaseous SO2 at different temperatures (T, K): 273 – 1; 283 – 2; 293 – 3; 298 – 4; 303 – 5; 313 – 6.
a b
Fig. 5. Redox-metric titration curves of 0.1 mol/L Na3Cit (а) and MEA⋅1/3CA (b) aqueous solutions
with gaseous SO2 at different temperatures (T, K): 273 – 1; 283 – 2; 293 – 3; 298 – 4; 303 – 5; 313 – 6.
9https://ucj.org.ua
R. E. Khoma, K. V. Tsyganenko, T. S. Bienkovska, Yu. V. Ishkov, S. V. Vodzinskii UCJ № 3 / Vol. 91
a b
Fig. 6. Differential Redox-metric titration curves of 0.1 mol/L Na3Cit (a) and MEA⋅1/3CA (b) aqueous
solutions with gaseous SO2 at 288 K (b), and 293 K (а).
7
a b
Fig. 6. Differential Redox-metric titration curves of 0.1 mol/L Na3Cit (a) and MEA1/3CA (b) aqueous
solutions with gaseous SO2 at 288 K (b), and 293 K (а).
Analyzing the data shown in Fig. 1-3, the pH values of chemisorption systems at 293 K can
be arranged in the following sequence:
– for Q(SO2) < 0.02 mol/L MEA1/6CA > PEPA1/6CA > MEA1/3CA > Na3Cit >
PEPA1/3CA;
– for 0.02 < Q(SO2) < 0.05 mol/L MEA1/6CA > MEA1/3CA > Na3Cit > PEPA1/6CA >
PEPA1/3CA;
– for 0.05 < Q(SO2) < 0.10 mol/L MEA1/3CA > MEA1/6CA Na3Cit > PEPA1/6CA
PEPA1/3CA.
These results indicate that at SO2 concentrations above 0.05 mol/L, solutions based on
monoethanolammonium citrate exhibit the highest efficiency in binding this toxicant.
Negative æ values suggest the formation of weakly dissociated compounds in the SO2 –
Na3Cit – H2O, SO2 – MEA1/3CA – H2O, and SO2 – MEA1/6CA – H2O systems (Fig. 7 – 9; Table
3). In PEPA-containing solutions, positive æ values (Q(SO2) > 0.05 mol/L; T = 273 – 283 K)
indicate an increase in the degree of dissociation of existing species (H2O, SO2H2O, HSO
3 ), the
formation of new strongly dissociated compounds, and an increase in the mobility of newly formed
ions [3, 11, 20], as discussed below.
Negative ƾ values suggest the formation
of weakly dissociated compounds in the SO2 –
Na3Cit – H2O, SO2 – MEA⋅1/3CA – H2O, and
SO2 – MEA⋅1/6CA – H2O systems (Fig. 7 – 9;
Table 3). In PEPA-containing solutions, posi-
tive ∆æ values (Q(SO2) > 0.05 mol/L; T = 273 –
283 K) indicate an increase in the degree of
dissociation of existing species (H2O, SO2⋅H2O,
HSO3
–), the formation of new strongly dissocia
ted compounds, and an increase in the mobili-
ty of newly formed ions [3, 11, 20], as discussed
below.
Fig. 7. Conductometric titration curves of 0.1 M
Na3Cit aqueous solutions with gaseous SO2 at dif-
ferent temperatures (T, K): 273 – 1; 283 – 2; 293 – 3;
303 – 4; 313 – 5.
8
Fig. 7. Conductometric titration curves of 0.1 M Na3Cit aqueous solutions with gaseous SO2 at different
temperatures (T, K): 273 – 1; 283 – 2; 293 – 3; 303 – 4; 313 – 5.
In the SO2 – MEA1/3CA – H2O system (Fig. 8a; Table 3), the relative decrease in æ with
increasing sulfur dioxide content up to 0.040 mol/L (at 303, 283 K) and 0.050 mol/L (at 273, 278,
293, and 313) is attributed to the formation of monoethanolammonium sulfite, similar to findings in
[3, 20]. Further increases in Q(SO2) are accompanied by a relative increase in the specific electrical
conductivity, driven by the formation of monoethanolammonium hydrosulfite and pyrosulfite. As
the temperature increases within the 283–303 K range, a relative decrease in æ is observed at the
same Q(SO2) values in the 0.01 0.05 mol/L region.
a b
Fig. 8. Conductometric titration curves of 0.1 M MEA1/3CA (a), and PEPA1/3CA (b) aqueous solutions
with gaseous SO2 at different temperatures (T, K): 273 – 1; 278 – 2; 283 – 3; 293 – 4; 298 – 5; 303 – 6; 313
– 7.
10 ISSN 2708-129X. Укр. хім. журн., 2025
SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM AND POLYETHYLENEPOLYAMMONIUM CITRATES
AQUEOUS SOLUTIONS PRODUCTS COMPOSITION AND THE RELATIVE STABILITY.INORGANIC CHEMISTRY
In the SO2 – MEA⋅1/3CA – H2O system
(Fig. 8a; Table 3), the relative decrease in ƾ
with increasing sulfur dioxide content up to
0.040 mol/L (at 303, 283 K) and 0.050 mol/L
(at 273, 278, 293, and 313 K) is attributed to
the formation of monoethanolammonium
sulfite, similar to findings in [3, 20]. Further
increases in Q(SO2) are accompanied by a rel-
ative increase in the specific electrical conduc-
tivity, driven by the formation of monoetha-
nolammonium hydrosulfite and pyrosulfite.
As the temperature increases within the 283–
303 K range, a relative decrease in ƾ is ob-
served at the same Q(SO2) values in the 0.01 ÷
0.05 mol/L region.
a b
Fig. 8. Conductometric titration curves of 0.1 M MEA⋅1/3CA (a), and PEPA⋅1/3CA (b) aqueous
solutions with gaseous SO2 at different temperatures (T, K): 273 – 1; 278 – 2; 283 – 3; 293 – 4; 298 – 5;
303 – 6; 313 – 7.
Table 2.
Characteristics of pH-metric titration curves of Na3Cit, MEA⋅1/3CA, PEPA⋅1/3CA,
MEA⋅1/6CA, and PEPA⋅1/6CA aqueous solutions with gaseous SO2.
Т, K 1st maximum 2nd maximum
Q(SO2) : Q(Na/N) pH dpH/dpQ(SO2) Q(SO2) : Q(Na/N) pH dpH/dpQ(SO2)
Na3Cit
273 0.429 3.88 8.21 − − −
283 0.429 3.60 7.32 − − −
293 0.476 3.90 8.56 − − −
298 0.404 3.62 7.15 − − −
303 0.486 3.81 7.60 − − −
313 0.476 3.94 7.49 − − −
8
Fig. 7. Conductometric titration curves of 0.1 M Na3Cit aqueous solutions with gaseous SO2 at different
temperatures (T, K): 273 – 1; 283 – 2; 293 – 3; 303 – 4; 313 – 5.
In the SO2 – MEA1/3CA – H2O system (Fig. 8a; Table 3), the relative decrease in æ with
increasing sulfur dioxide content up to 0.040 mol/L (at 303, 283 K) and 0.050 mol/L (at 273, 278,
293, and 313) is attributed to the formation of monoethanolammonium sulfite, similar to findings in
[3, 20]. Further increases in Q(SO2) are accompanied by a relative increase in the specific electrical
conductivity, driven by the formation of monoethanolammonium hydrosulfite and pyrosulfite. As
the temperature increases within the 283–303 K range, a relative decrease in æ is observed at the
same Q(SO2) values in the 0.01 0.05 mol/L region.
a b
Fig. 8. Conductometric titration curves of 0.1 M MEA1/3CA (a), and PEPA1/3CA (b) aqueous solutions
with gaseous SO2 at different temperatures (T, K): 273 – 1; 278 – 2; 283 – 3; 293 – 4; 298 – 5; 303 – 6; 313
– 7.
11https://ucj.org.ua
R. E. Khoma, K. V. Tsyganenko, T. S. Bienkovska, Yu. V. Ishkov, S. V. Vodzinskii UCJ № 3 / Vol. 91
Т, K 1st maximum 2nd maximum
Q(SO2) : Q(Na/N) pH dpH/dpQ(SO2) Q(SO2) : Q(Na/N) pH dpH/dpQ(SO2)
MEA⋅1/3CA
273 0.472 3.78 13.47 − − −
278 0.472 3.78 18.71 − − −
283 0.458 3.96 14.51 − − −
288 0.472 3.55 14.97 − − −
293 0.486 3.30 18.51 − − −
298 0.458 3.61 13.33 − − −
303 0.472 3.47 10.48 − − −
308 0.486 3.30 15.43 − − −
313 0.458 3.65 10.15 − − −
PEPA⋅1/3CA
273 0.404 3.30 3.73 0.543 2.79 4.26
278 0.315 3.66 3.62 0.515 2.94 4.43
283 0.315 3.74 3.62 0.515 2.97 4.03
288 0.572 3.04 4.48 − − −
293 0.458 3.07 3.57 − − −
298 0.572 2.82 4.49 − − −
303 0.543 2.81 3.41 − − −
308 0.515 2.92 4.03 − − −
313 0.343 3.16 2.90 − − −
MEA⋅1/6CA
273 0.172 7.75 16.92 0.572 3.64 16.61
278 0.200 8.67 8.96 0.601 3.9 14.16
283 0.172 7.75 10.74 0.572 3.5 21.10
288 0.258 7.63 15.05 0.629 4.32 19.80
293 0.200 8.26 18.97 0.543 3.94 15.33
298 0.200 7.77 14.79 0.486 4.58 13.67
303 0.200 7.91 10.91 0.572 3.94 13.02
308 0.129 8.02 8.41 0.486 3.92 12.91
313 0.229 7.61 10.0 0.601 4.15 14.16
313 0.343 3.16 2.90 − − −
PEPA⋅1/6CA
273 0.372 3.42 7.48 − − −
278 0.486 3.51 8.36 − − −
283 0.372 3.68 8.34 − − −
288 0.315 4.18 7.25 − − −
293 0.372 3.98 7.48 − − −
298 0.372 3.61 7.19 − − −
303 0.429 3.28 6.01 − − −
308 0.404 3.66 6.84 − − −
313 0.3432 3.75 6.35 − − −
12 ISSN 2708-129X. Укр. хім. журн., 2025
SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM AND POLYETHYLENEPOLYAMMONIUM CITRATES
AQUEOUS SOLUTIONS PRODUCTS COMPOSITION AND THE RELATIVE STABILITY.INORGANIC CHEMISTRY
Table 3.
Characteristics of conductometric titration curves of MEA⋅1/3CA, PEPA⋅1/3CA,
MEA⋅1/6CA, and PEPA⋅1/6CA aqueous solutions.
Т, К
І-th effect ІІ-th effect ІІІ-th effect IV-th effectт
Q(SO2) : Q(N)
(curve shape)
ƾ,
Сm/m
Q(SO2) : Q(N)
(curve shape)
ƾ,
Сm/m-1
Q(SO2) : Q(N)
(curve shape)
ƾ,
Сm/m-1
Q(SO2) : Q(N)
(curve shape)
ƾ,
Сm/m-1
MEA⋅1/3CA
273 0.200 (bend) -0.35 0.510 (bend) -0.608 0.740 (bend) -0.276 − −
278 0.480 (bend) -1.06 0.540 (bend) -1.060 0.710 (bend) -0.760 − −
283 0.071 (bend) -0.06 0.400 (min) -0.510 0.710 (bend) 0.020 − −
293 0.043 (bend) -0.114 0.457 (min) -0.640 0.570 (bend) -0.565 − −
298 0.428 (min) -0.833 0.570 (bend) -0.729 0.714 (bend) -0.503 − −
303 0.400 (bend) -0.895 0.510 (bend) -0.885 0.740 (bend) -0.510 − −
313 0.171 (bend) -0.156 0.457 (min) -0.415 0.686 (bend) -0.130 − −
PEPA⋅1/3CA
273 0.143 (bend) -0.192 0.404 (min) -0.258 0.715 (bend) 0.332 − −
278 0.072 (max) 0.002 0.429 (min) -0.259 0.715 (bend) 0.221 − −
283 0.057 (bend) -0.017 0.143 (bend) -0.078 0.400 (bend) -0.096 0.744 (bend) 0.734
293 0.572 (bend) -0.717 − − − − − −
298 0.572 (bend) -0.222 0.429 (min) -0.520 0.486 (bend) -0.498 0.629 (bend) -0.506
303 0.400 (min) -0.729 0.486 (bend) -0.699 0.686 (bend) -0.700 − −
313 0.086 (min) -0.090 0.129 (max) -0.070 0.286 (bend) -0.110 0.400 (bend) -0.12
MEA⋅1/6CA
273 0.110 (max) 0.026 0.486 (min) -0.38 0.714 (bend) 0.134 − −
278 0.110 (min) 0.086 0.466 (bend) -0.38 0.514 (min) -0.520 0.714 (bend) -0.030
283 0.100 (max) 0.220 0.486 (min) -0.21 0.714 (bend) 0.160 − −
293 0.170 (max) 0.040 0.514 (min) -0.29 0.714 (bend) 0.140 − −
298 0.428 (min) -0.215 0.200 (max) -0.074 0.486 (min) -0.480 0.714 (bend) -0.043
303 0.043 (min) -0.270 0.710 (max) -0.24 0.151 (bend) -0.280 0.540 (bend) -0.780
313 0.071 (min) -0.070 0.020 (max) 0.04 0.543 (min) -0.200 0.628 (bend) -0.20
PEPA⋅1/6CA
273 0.143 (bend) -0.248 0.468 (min) -0.432 0.743 (bend) -0.182 − −
278 0.071 (bend) -0.013 0.310 (bend) -0.236 0.400 (bend) -0.236 0.743 (bend) 0.434
283 0.100 (bend) -0.068 0.143 (bend) -0.015 0.400 (min) -0.231 0.710 (bend) 0.258
293 0.200 (bend) -0.313 0.314 (bend) -0.326 0.428 (min) -0.381 0.743 (bend) -0.159
298 0.143 (bend) -0.364 0.428 (min) -0.540 0.629 (max) -0.396 − −
303 0.400 (bend) -0.701 0.714 (max) -0.661 − − − −
313 0.017 (min) -0.123 0.129 (bend) -0.129 0.429 (bend) -0.148 0.571 (bend) -0.038
13https://ucj.org.ua
R. E. Khoma, K. V. Tsyganenko, T. S. Bienkovska, Yu. V. Ishkov, S. V. Vodzinskii UCJ № 3 / Vol. 91
a b
Fig. 9. Conductometric titration curves of 0.1 mol/L MEA⋅1/6CA (a) and PEPA⋅1/6CA (b) aqueous
solutions with gaseous SO2 at different temperatures (T, K): Т (К): 273 – 1; 278 – 2; 283 – 3; 293 – 4;
298 – 5; 303 – 6; 313 – 7.
11
At the same Q(SO2) values, an increase in σ with rising temperature (273–313 K) is
observed for SO2 – Na3Cit – H2O and SO2 – MEA1/3CA – H2O solutions. In contrast, in SO2 –
MEA1/3CA – H2O, SO2 – PEPA1/3CA – H2O, SO2 – MEA1/6CA – H2O and SO2 – PEPA1/6CA
– H2O systems (Figs. 8, 9), æ values decrease upon heating within the 283–303 K range. his
behavior is attributed to the ionic-molecular composition of the studied systems, which is discussed
below.
When sulfur dioxide is absorbed by an MEA1/6CA solution, æ acquires positive values
(Fig. 9a) only in specific sections of the æ = f(Q(SO2)) curves at: 273 K (0.005 < Q(SO2) < 0.020
mol/L), 278 K (0.002 < Q(SO2) < 0.020 mol/L), 283 K (0.002 < Q(SO2) < 0.030 mol/L), 293 K
(0.012 < Q(SO2) < 0.025 mol/L) and 313 K (0.013 < Q(SO2) < 0.025 mol/L). Under other
experimental conditions, æ 0 Cmm-1. For PEPA1/6CA solutions, æ values remain negative
(Fig. 9b) during SO2 chemisorption, except at T = 278 and 283 K (curves 2 and 3) when
Q(SO2):Q(N) 0.55.
Unlike pH-metric curves (Fig. 3), conductometric curves (Fig. 9; Table 3) exhibit three or
four effects. When sulfur dioxide is introduced into the MEA1/6CA solution, a decrease in æ is
observed within 0.020 < Q(SO2) < 0.050 mol/L across the studied temperature range (Fig. 9a).
Further addition of SO₂ leads to a æ increase up to Q(SO2) 0,070 mol/L (except at T = 293 K),
after which the æ = f(Q(SO2)) dependencies reach stationary regions.
The addition of SO2 to the PEPA1/6CA solution leads to a decrease in æ within 0.010 <
Q(SO2) < 0.040 mol/L across the studied temperature range (Fig. 9b). When Q(SO2) exceeds (0.040
0.045 mol/L), æ values begin to increase.
Each æ = f(Q(SO2)) curve for SO2 chemisorption in the studied solutions at a given
temperature exhibits distinct effects (Fig. 9; Table 3).
The uniformity of acid-base and electrochemical behavior in solutions containing sodium,
monoethanolammonium, and polyethylenepolyammonium citrates is confirmed by the overlapping
initial sections of the dpH/dpQ(SO2) – Q(SO2) and æ – Q(SO2) curves (Fig. 4, 10).
a b
Fig. 9. Conductometric titration curves of 0.1 mol/L MEA1/6CA (a) and PEPA1/6CA (b) aqueous solutions
with gaseous SO2 at different temperatures (T, K): Т (К): 273 – 1; 278 – 2; 283 – 3; 293 – 4; 298 – 5; 303 –
6; 313 – 7.
At the same Q(SO2) values, an increase
in σ with rising temperature (273–313 K) is
observed for SO2 – Na3Cit – H2O and SO2 –
MEA⋅1/3CA – H2O solutions. In contrast, in
SO2 – MEA⋅1/3CA – H2O, SO2 – PEPA⋅1/3CA –
H2O, SO2 – MEA⋅1/6CA – H2O and SO2 –
PEPA⋅1/6CA – H2O systems (Figs. 8, 9), ∆æ
values decrease upon heating within the 283–
303 K range. his behavior is attributed to the
ionic-molecular composition of the studied
systems, which is discussed below.
When sulfur dioxide is absorbed by an
MEA⋅1/6CA solution, ∆æ acquires positive
values (Fig. 9a) only in specific sections of
the ƾ = f(Q(SO2)) curves at: 273 K (0.005 <
Q(SO2) < 0.020 mol/L), 278 K (0.002 < Q(SO2) <
0.020 mol/L), 283 K (0.002 < Q(SO2) <
0.030 mol/L), 293 K (0.012 < Q(SO2) <
0.025 mol/L) and 313 K (0.013 < Q(SO2) <
0.025 mol/L). Under other experimental con-
ditions, ∆æ ≤ 0 Cm⋅m-1. For PEPA⋅1/6CA
solutions, ƾ values remain negative (Fig. 9b)
during SO2 chemisorption, except at T = 278
and 283 K (curves 2 and 3) when Q(SO2):Q(N)
≥ 0.55.
Unlike pH-metric curves (Fig. 3), conducto-
metric curves (Fig. 9; Table 3) exhibit three or
four effects. When sulfur dioxide is introduced
into the MEA⋅1/6CA solution, a decrease in ∆æ
is observed within 0.020 < Q(SO2) < 0.050 mol/L
across the studied temperature range (Fig. 9a).
Further addition of SO₂ leads to a ∆æ in-
crease up to Q(SO2) ≈ 0,070 mol/L (except at
T = 293 K), after which the ƾ = f(Q(SO2))
dependencies reach stationary regions.
The addition of SO2 to the PEPA⋅1/6CA solu-
tion leads to a decrease in ƾ within 0.010 <
Q(SO2) < 0.040 mol/L across the studied
14 ISSN 2708-129X. Укр. хім. журн., 2025
SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM AND POLYETHYLENEPOLYAMMONIUM CITRATES
AQUEOUS SOLUTIONS PRODUCTS COMPOSITION AND THE RELATIVE STABILITY.INORGANIC CHEMISTRY
temperature range (Fig. 9b). When Q(SO2) ex-
ceeds (0.040 ÷ 0.045 mol/L), ∆æ values begin
to increase.
Each ƾ = f(Q(SO2)) curve for SO2 che
misorption in the studied solutions at a given
temperature exhibits distinct effects (Fig. 9; Ta-
ble 3).
The uniformity of acid-base and electro-
chemical behavior in solutions containing
sodium, monoethanolammonium, and poly-
ethylenepolyammonium citrates is confirmed
by the overlapping initial sections of the
dpH/dpQ(SO2) РQ(SO2) and ƾ РQ(SO2)
curves (Fig. 4, 10). 12
Fig. 10. Conductometric titration curves of
0.1 mol/l Na3Cit (1), MEA1/3CA (2) and
PEPA1/3CA (2) MEA1/6CA (4), and
PEPA1/6CA (5) aqueous solutions with
gaseous SO2 at 293 K.
Physicochemical models of SO2 interaction with MEA – CA – H2O and PEPA – CA – H2O
solutions.
According to [9], in aqueous MEA1/3CA solutions, the following processes take place:
water autoprotolysis (reaction 1), MEA protonation (reaction 2), and stepwise dissociation of CA
(reactions 3–5). Additionally, the formation of ionic associates occurs:
{
N H3CH2CH2OH}{HOC3H4(COOH)2(COO)} (Ia),
{
N H3CH2CH2OH}2{HOC3H4(COOH)(COO)2} (IIa),
{
N H3CH2CH2OH}2{HOC3H4(COOH)2(COO)} (IIb), {
N H3CH2CH2OH}3{HOC3H4(COO)3}
(IIIa), as well as the ionic-molecular associate {
N H3CH2CH2OH}{HOC3H4(COOH)3} (Ib)
(reactions 6–10).
2H2O H3O+ + OH (1)
NH2CH2CH2OH + H3O+
a/1 K
N H3CH2CH2OH + H2O (2)
HOC3H4(COOH)3 + H2O HOC3H4(COOH)2COO + H3O+ (3)
HOC3H4(COOH)2COO + H2O HOC3H4(COOH)(COO)2 + H3O+ (4)
HOC3H4(COOH)(COO)2 + H2O HOC3H4(COO)3 + H3O+ (5)
N H3CH2CH2OH + HOC3H4(COOH)2(COO)
Ιa
{
N H3CH2CH2OH}{HOC3H4(COOH)2(COO)}
(6)
N H3CH2CH2OH + HOC3H4(COOH)3
Ib
{
N H3CH2CH2OH}{HOC3H4(COOH)3}
(7)
2
N H3CH2CH2OH + HOC3H4(COOH)(COO)2
ΙIa
{
N H3CH2CH2OH}2{HOC3H4(COOH)(COO)2}
(8)
2
N H3CH2CH2OH + HOC3H4(COOH)2(COO)
ΙIb
{
N H3CH2CH2OH}2{HOC3H4(COOH)2(COO)}
(9)
Fig. 10. Conductometric titration curves of 0.1 mol/l Na3Cit (1), MEA⋅1/3CA (2) and PEPA⋅1/3CA (3)
MEA⋅1/6CA (4), and PEPA⋅1/6CA (5) aqueous solutions with gaseous SO2 at 293 K.
Physicochemical models of SO2 interaction with
MEA – CA – H2O and PEPA – CA – H2O solutions.
According to [9], in aqueous MEA⋅1/3CA
solutions, the following processes take place:
water autoprotolysis (reaction 1), MEA proto-
nation (reaction 2), and stepwise dissociation
of CA (reactions 3–5). Additionally, the forma-
tion of ionic associates occurs:
{ +
N H3CH2CH2OH}{HOC3H4(COOH)2(COO−)} (Ia),
{ +
N H3CH2CH2OH}2{HOC3H4(COOH)(COO−)2} (IIa),
{ +
N H3CH2CH2OH}2{HOC3H4(COOH)2(COO−)} (IIb),
{ +
N H3CH2CH2OH}3{HOC3H4(COO−)3} (IIIa), as well as the ionic-molecular associate
{ +
N H3CH2CH2OH}{HOC3H4(COOH)3} (Ib) (reactions 6–10).
15https://ucj.org.ua
R. E. Khoma, K. V. Tsyganenko, T. S. Bienkovska, Yu. V. Ishkov, S. V. Vodzinskii UCJ № 3 / Vol. 91
2H2O H3O
+ + OH− (1)
NH2CH2CH2OH + H3O
+
1/Ka
+
N H3CH2CH2OH + H2O
(2)
HOC3H4(COOH)3 + H2O HOC3H4(COOH)2COO− + H3O
+ (3)
HOC3H4(COOH)2COO− + H2O HOC3H4(COOH)(COO−)2 + H3O
+ (4)
HOC3H4(COOH)(COO−)2 + H2O HOC3H4(COO−)3 + H3O
+ (5)
+
N H3CH2CH2OH + HOC3H4(COOH)2(COO−)
βIa
{
+
N H3CH2CH2OH}{HOC3H4(COOH)2(COO−)}
(6)
+
N H3CH2CH2OH + HOC3H4(COOH)3
βIb
{
+
N H3CH2CH2OH}{HOC3H4(COOH)3}
(7)
2
+
N H3CH2CH2OH + HOC3H4(COOH)(COO−)2
βIIa
{
+
N H3CH2CH2OH}2{HOC3H4(COOH)(COO−)2}
(8)
2
+
N H3CH2CH2OH + HOC3H4(COOH)2(COO−)
βIIb
{
+
N H3CH2CH2OH}2{HOC3H4(COOH)2(COO−)}
(9)
3
+
N H3CH2CH2OH + HOC3H4(COO−)3
βIIIa
{
+
N H3CH2CH2OH}3{HOC3H4(COO−)3}
(10)
When SO2 interacts with MEA⋅1/3CA –
H2O solutions, reactions 11–18 occur, lead-
ing to the formation of sulfur dioxide hydrate,
sulfite, hydrosulfite, and pyrosulfite anions,
as well as monoethanolammonium sulfite
(IS), hydrosulfite (IIS), and pyrosulfite (IIIS)
[3, 20].
SO2
г
SO2
р (11)
SO2
р + Н2О SO2⋅Н2О (12)
SO2⋅Н2О + Н2О
K1
H3O
+ + НSО3
– (13)
2НSО3
–
K*
S2О5
2– + H2O (14)
НSО3
–+ Н2О
K2
H3O
+ + SО3
2–, (15)
when SO2
г, SO2
р – sulfur dioxide in the gas
phase and dissolved in water, respectively.
2NH2CH2CH2OH + SO2⋅H2O
βIS
(NH3CH2CH2OH)2SO3
(16)
NH2CH2CH2OH + SO2⋅H2O
βIIS
(NH3CH2CH2OH)НSO3
(17)
2NH2CH2CH2OH + 2(SO2⋅H2O)
βIIIS
(NH3CH2CH2OH)2S2O5 + H2O
(18)
SO2 – Na3Cit – H2O solutions
Based on [3, 4, 11, 20], the interaction of
citrate ions with SO2 hydrate results in the for-
mation of sulfite and hydrocitrate anions (re-
action 19). Additionally, the reaction of sulfite
ions with SO2 in water leads to the formation
of hydrosulfite ions (reaction 20). These pro-
cesses are responsible for the initial jumps ob-
served on the pH-metric titration curves of so-
dium citrate aqueous solutions (Fig. 1).
16 ISSN 2708-129X. Укр. хім. журн., 2025
SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM AND POLYETHYLENEPOLYAMMONIUM CITRATES
AQUEOUS SOLUTIONS PRODUCTS COMPOSITION AND THE RELATIVE STABILITY.INORGANIC CHEMISTRY
HOC3H4(COO−)3 + SO2⋅Н2О + OH− → SО3
2– + HOC3H4(COOH)(COO−)2 + H2O (19)
SО3
2– + SO2⋅Н2О → 2HSО3
– (20)
When HOC3H4(COOH)(COO−)2 ions in-
teract with SO2, hydrosulfite and dideprotona
ted citrate anions are formed (reaction 21). Hyd
rosulfite ions are also generated through the
dissociation of «sulfuric» acid (reaction 13).
Reactions 13 and 21 are responsible for the se
cond jumps on the pH-metric titration curves
and the minima on the conductometric curves.
Additionally, at pH 4.5–6.0, hydrosulfite ion
dimerization (reaction 14) leads to the forma-
tion of pyrosulfite ions, causing the first jumps
on the redox-metric curves (Fig. 5a).
SO2⋅Н2О + HOC3H4(COOH)(COO−)2 → HSО3
– + HOC3H4(COOH)2(COO−) (21)
SO2 – MEA⋅1/3CA – H2O solutions
The replacement of sodium citrate with mo-
noethanolammonium citrate in chemisorption
solutions introduces additional reactions 22–23.
Alongside the reactions occurring in the SO2 –
Na3Cit – H2O system, this system also allows
for the interaction of the ionic associate (mono
ethanolammonium citrate) with SO2, which is
responsible for the first jumps on the pH-met-
ric curves (Fig. 2a). At pH 4,0–6,0, the reaction
between SO2 and monoethanolammonium ca
tions in water produces an ionic associate – am-
monium sulfite (reaction 23), leading to mini-
ma on the conductometric curves (Fig. 8 a).
{ +
N H3CH2CH2OH}3{HOC3H4(COO−)3} + SO2⋅Н2О → { +
N H3CH2CH2OH}2(SО3
2–) +
+ +
N H3CH2CH2OH + HOC3H4(COOH)2(COO−)
(22)
2 +
N H3CH2CH2OH + SO2⋅Н2О + 2H2O → {
+
N H3CH2CH2OH}2(SО3
2–) + 2H3O
+ (23)
The multicomponent nature of SO2 –
MEA⋅1/3CA – H2O solutions, resulting from
the formation of H-bonded ionic associates,
leads to variations in redox-metric curve
shapes at different temperatures.
SO2 – PEPA⋅1/3CA – H2O solutions.
The interaction of SO2 with polyethylene
polyammonium citrate (reaction 24) leads to
the formation of polyethylenepolyammoni-
um sulfite, polyethylenepolyamine, and di-
hydrocitrate ions. This process causes jumps
in the pH-metric curves (Fig. 2 b) and breaks
or minima in the conductometric curves
(Fig. 8 b).
{ +
N H3(CH2CH2
+
N H2)kH}3{HOC3H4(COO−)3}k+1 + (k+1)SO2⋅Н2О + Н2О →
→ { +
N H3(CH2CH2
+
N H2)kH}2(SО3
2–)k+1 + NH2(CH2CH2NH)kH +
+ (k+1)HOC3H4(COOH)2(COO−) + Н3О
+
(24)
The component composition of SO2 – MEA⋅1/
3CA – H2O solutions.
Considering the law of mass action (equa-
tions 1 – 18), along with the material balance
equations for nitrogen (25), citrates (26), and
sulfur (27), and the electroneutrality condition
(28), a system of mathematical equations (1–
18, 25–28) is established.
17https://ucj.org.ua
R. E. Khoma, K. V. Tsyganenko, T. S. Bienkovska, Yu. V. Ishkov, S. V. Vodzinskii UCJ № 3 / Vol. 91
QN = [NH2CH2CH2OH] + [ +
N H3CH2CH2OH] + CIa + CIb + 2CIIa + 2CIIb +
+ 3CIIIa+ 2CIS + CIIS + 2CIIIS
(25)
QCit = [HOC3H4(COOH)3] + [HOC3H4(COOH)2COO−] + [HOC3H4(COOH)(COO−)2] +
[HOC3H4(COO−)3] + CIa + CIb + CIIa + CIIb + CIIIa
(26)
Q(SO2) = [SO2⋅H2O] + [НSО3
–] + 2[S2О5
2–] + [SО3
2–] + CIS + CIIS + 2CIIIS (27)
[H+] + [ +
N H3CH2CH2OH] + CIb + CIIb = [ОH−] + [НSО3
–] + 2[S2О5
2–] + 2·[SО3
2–] (28)
where CIS = [(NH3CH2CH2OH)2SO3], CIIS = [(NH3CH2CH2OH)НSO3],
CIIIS = [(NH3CH2CH2OH)2S2O5], CIa = [{ +
N H3CH2CH2OH}{HOC3H4(COOH)2(COO−)}],
CIb = [{ +
N H3CH2CH2OH}{HOC3H4(COOH)3}],
CIIa = [{ +
N H3CH2CH2OH}2{HOC3H4(COOH)(COO−)2}],
CIIb = [{ +
N H3CH2CH2OH}2{HOC3H4(COOH)2(COO−)}],
CIIIa = [{ +
N H3CH2CH2OH}3{HOC3H4(COO−)3}].
Solving this system using pH-metric data
(Fig. 2 a) and incorporating the pKa values of
CA and MEA (Table 1) enabled the calcula-
tion of the component composition of SO2 –
MEA⋅1/3CA – H2O solutions (Fig. 11).
According to the obtained data, as Q(SO2)
increases from 1.4·10-3 to 1.4·10-2 mol/L, a rise in
the relative content of monoethanolammonium
cation (curve 6) is observed due to the dissocia-
tion of ionic associate IIIa (Fig. 11, curves 4, 7).
In the region where ionic associate IIIa and
ionic-molecular associate IIb form (Table 2),
the total SO2 content increases the cation’s par-
tial binding into ammonium sulfite IS (curve 8).
When ionic associate IIb transitions into com-
pound IIa Q(SO2) > 0.26 mol/L, the relative con-
tent of IS decreases (curve 8), while the binding
of monoethanolamine and citrate in IIa increa
ses sharply (curves 4 and 7). Across the calcula
ted section of the pH = f(Q(SO2)) curve, a rise in
the molar fraction of hydrosulfite ions (curve 9;
Q(SO2) > 0.01 mol/L) is observed, along with a
decrease in ammonium sulfite content (curve
10) relative to the total SO2 concentration. The
relative content of SO2 hydrate, sulfite, and py-
rosulfite ions, as well as free MEA, does not ex-
ceed 0.7%.
Fig. 11. Partial distribution diagrams of dif-
ferent forms of interaction in the SO2 – MEA⋅1/
3CA – H2O system depending on QSO2
at 293 K.
Ni – molar fraction of Cit3− (1), HCit2− (2), H2Cit−
(3), CIIa + CIIb + CIIIa . (4, 7), NH2CH2CH2OH (5),
+
N H3CH2CH2OH (6), CIS (8, 10), НSО3
–(9) relative
to the total content of citrates (1–4), nitrogen (5–8)
and sulfur (9, 10).
15
Fig. 11. Partial distribution diagrams of different forms of interaction in the SO2 – MEA1/3CA – H2O
system depending on QSO2 at 293 K. Ni – molar fraction of Cit3 (1), HCit2 (2), H2Cit (3), CIIa + CIIb + CIIIa .
(4, 7), NH2CH2CH2OH (5),
N H3CH2CH2OH (6), CIS (8, 10),
3HSO (9) relative to the total content of
citrates (1–4), nitrogen (5–8) and sulfur (9, 10).
The concentration constants for the formation of ionic associates (IIIS, Ia – IIIa, Ib, and
IIb) have been calculated. Under the experimental conditions, these formation constants exceed 10.
The concentration and thermodynamic constants (IIIS) for ammonium sulfite formation in
SO2–MEA1/3CA–H2O solutions are nearly identical to those in SO2 – MEA solutions [3, 20]. The
dependences of рi (for compounds Ib, IIa, and IIIa) on ionic strength (, М) follow a linear
relationship (equation 29), whereas the dependence of рIIb = f() is more complex (equation 30).
The parameters of these equations are provided in Table 4.
pi = Ai + Bi (29)
pIIb = Ai + Bi0,5 + Ci (30)
By definition [21], the coefficients Aі in equations 29 and 30 represent the negative decimal
logarithms of the conditional thermodynamic constants (Ia – IIIa). As temperature increases, bond
rearrangements occur in ionic associates IIa, IIIa, and compound Ib, as indicated by the lack of a
clear dependence of p T
IIIa = f(T). Additionally, compounds IIa and Ib exhibit increased stability,
as reflected in the Ai values of equation 29 (Table 4).
Table 4.
The values of the coefficients Аi, Вi in equation (29) for compounds Ib, IIa, and IIIa, and Аi, Вi, Ci in
equation (30) for associate IIb in SO2 MEA1/3CA H2O solutions *
T, K Ai
Bi R2 Q(SO2):QN
IIIa
288 -12.53 28.5 0.9142 0.07150.172
293 -16.16 41.93 0.9384 0.07150.129
303 -9.078 16.76 0.9735 0.05720.257
313 -15.10 38.30 0.9492 0.05720.486
IIa
283 -5.55 9.18 0.9868 0.0720.143
293 -8.10 21.6 0.9690 0.2860.515
Ib
283 -17.44 69.80 0.9839 0.4000.515
288 -20.24 87.86 0.9653 0.3430.458
18 ISSN 2708-129X. Укр. хім. журн., 2025
SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM AND POLYETHYLENEPOLYAMMONIUM CITRATES
AQUEOUS SOLUTIONS PRODUCTS COMPOSITION AND THE RELATIVE STABILITY.INORGANIC CHEMISTRY
The concentration constants for the forma-
tion of ionic associates (βIIIS, βIa – βIIIa, βIb, and
βIIb) have been calculated. Under the experi-
mental conditions, these formation constants
exceed 10.
The concentration and thermodynamic con-
stants (βIIIS) for ammonium sulfite formation
in SO2–MEA⋅1/3CA–H2O solutions are nearly
identical to those in SO2 – MEA solutions [3,
20]. The dependences of рβi (for compounds
Ib, IIa, and IIIa) on ionic strength (µ, М)
follow a linear relationship (equation 29),
whereas the dependence of рβIIb = f(µ) is
more complex (equation 30). The parameters
of these equations are provided in Table 4.
pβi = Ai + Bi⋅µ (29)
pβIIb = Ai + Bi⋅µ0,5 + Ci⋅µ (30)
By definition [21], the coefficients Aі in
equations 29 and 30 represent the negative
decimal logarithms of the conditional ther-
modynamic constants (βIa – βIIIa). As tempera-
ture increases, bond rearrangements occur in
ionic associates IIa, IIIa, and compound Ib,
as indicated by the lack of a clear dependence
of pβT
IIIa= f(T). Additionally, compounds IIa
and Ib exhibit increased stability, as reflected
in the Ai values of equation 29 (Table 4).
Table 4.
The values of the coefficients Аi, Вi in equation (29) for compounds Ib, IIa, and IIIa,
and Аi, Вi, Ci in equation (30) for associate IIb in SO2 − MEA⋅1/3CA − H2O solutions *
T, K Ai Bi R2 Q(SO2):QN
IIIa
288 -12.53 28.5 0.9142 0.0715÷0.172
293 -16.16 41.93 0.9384 0.0715÷0.129
303 -9.078 16.76 0.9735 0.0572÷0.257
313 -15.10 38.30 0.9492 0.0572÷0.486
IIa
283 -5.55 9.18 0.9868 0.072÷0.143
293 -8.10 21.6 0.9690 0.286÷0.515
Ib
283 -17.44 69.80 0.9839 0.400÷0.515
288 -20.24 87.86 0.9653 0.343÷0.458
303 0.05 0 − 0.315
IIb
Ai Bi Ci R2 Q(SO2):QN
283 -21.11 115.72 -191.1 0.9900 0.172÷0.372
288 -13.28 63.59 -88.61 0.9993 0.200÷0.315
293 -9.083 0 23.97 0.7959 0.172÷0.257
303 -1.730 0 0 − 0.286
*R2 is the value of the approximation reliability.
19https://ucj.org.ua
R. E. Khoma, K. V. Tsyganenko, T. S. Bienkovska, Yu. V. Ishkov, S. V. Vodzinskii UCJ № 3 / Vol. 91
With rising temperature, the absolute pβT
IIb
values decrease, following a relationship de-
scribed by equation 31 within the 283–303 K
range.
pβT
IIb = 264,15 - 88312/T, (31)
where T is the absolute temperature, K.
Composition of SO2 – MEA⋅1/6CA – H2O
solutions
For MEA⋅1/6CA solutions, in addition to
reactions 1–24, there is also the potential for-
mation of ion-molecular associates IVa and
IVb, as described by equations 32 and 33.
3NH2CH2CH2OH + 3 +
N H3CH2CH2OH + HOC3H4(COO−)3
βIVa
{NH2CH2CH2OH}3{
+
N H3CH2CH2OH}3{HOC3H4(COO−)3},
(32)
2NH2CH2CH2OH + 4 +
N H3CH2CH2OH + HOC3H4(COO−)3
βIVb
{NH2CH2CH2OH}2{
+
N H3CH2CH2OH}4{HOC3H4(COO−)3}.
(33)
Based on experimental data (Fig. 3a) and
a mathematical model that incorporates the
law of mass action (equations 1–18, 32, 33),
along with the material balance equations for
nitrogen (34), citrates (35), and sulfur (27), as
well as the electroneutrality condition (36), the
ionic-molecular composition of SO2−MEA⋅1/
6CA−H2O solutions was determined (for
example, Fig. 12).
QN = [NH2CH2CH2OH] + [ +
N H3CH2CH2OH] + CIa + CIb + 2CIIa + 2CIIb +
+ 3CIIIa + 2CIS + CIIS + 2CIIIS + 6CIVa + 6CIVb
(34)
QCit = [HOC3H4(COOH)3] + [HOC3H4(COOH)2COO−] + [HOC3H4(COOH)(COO−)2] +
+ [HOC3H4(COO−)3] + CIa + CIb + CIIa + CIIb + CIIIa + CIVa + CIVb
(35)
[H+] + [ +
N H3CH2CH2OH] + CIb + CIIb + CIVb = [ОH−] + [НSО3
–] + 2[S2О5
2–] + 2·[SО3
2–] (36)
де CIVa = {NH2CH2CH2OH}3{
+
N H3CH2CH2OH}3{HOC3H4(COO−)3},
CIVb = {NH2CH2CH2OH}2{
+
N H3CH2CH2OH}4{HOC3H4(COO−)3}.
17
Fig. 12. Partial distribution diagrams of different forms of interaction in the SO2–1/6CA–H2O
system depending on QSO2 at 293 K. Ni – molar fraction of Cit3 (1), HCit2 (2), H2Cit (3), CIVa–
(4, 7), NH2CH2CH2OH (5),
N H3CH2CH2OH (6), CIS (8, 10),
3HSO (9) relative to the total content
of citrates (1–4), nitrogen (5–8) and sulfur (9, 10).
According to the calculations (Fig. 12), the chemisorption of sulfur dioxide by an
MEA1/6CA aqueous solution occurs due to its binding to monoethanolammonium sulfite IS (curve
10) at Q(SO2) < 0.0572 mol/L, following reaction 37. This process is accompanied by:
An increase in the molar fraction of citrate anions (curve 1) and monoethanolammonium
cations (curve 6).
A decrease in the relative content of compound IVa (curves 4, 7).
2{NH2CH2CH2OH}3{
N H3CH2CH2OH}3{HOC3H4(COO)3} + 3SO2H2O
3(NH3CH2CH2OH)2SO3 + 2HOC3H4(COO)3 + 6
N H3CH2CH2OH
(37)
With further SO2 addition, the relative content of hydrosulfite anions (curve 9) and
monoethanolammonium cations (curve 6) increases due to reaction 38.
(NH3CH2CH2OH)2SO3 + SO2H2O 2
N H3CH2CH2OH + 2
3HSO (38)
In this case:
The mole fraction of the IS compound relative to total nitogen (curve 8) reaches a maximum at
Q(SO2):QN = 1.0:4.0;
The mole fraction of citrate anions (curve 1) reaches a maximum at Q(SO2):QN = 1.0:10.0,
accompanied by partial protonation of citrate anions with the formation of
HOC3H4(COOH)(COO)2 (curve 2) and dihydrocitrate anions (curve 3).
The relative content of HOC3H4(COOH)(COO)2 (curve 2) reaches a maximum at Q(SO2) = 0.0286
mol/L, while HOC3H4(COOH)2COO (curve 3) increases throughout the studied range.
The content of unbound MEA (as a free base), undissociated CA, sulfite and pyrosulfite
anions, and SO2Н2О does not exceed 0.02 relative units. Notably, ionic associates IIa and IIb are
not formed during the chemisorption of SO2 in the studied concentration (Q(SO2)) and temperature
ranges, unlike in the MEA1/3CA solution.
The concentration dependences = f(Q(SO2)) exhibit complex behavior due to the
multicomponent nature of the chemisorption system during SO2 absorption (at 283–288 and 298–
313 K). However, at 293 K, only the ion-molecular complex IVa is formed between MEA and CA,
leading to a linear dependence:
= 0,0177 + 1,0261Q(SO2); n = 14; R2 = 0,9940. (39)
Fig. 12. Partial distribution diagrams of
different forms of interaction in the SO2–
MEA⋅1/6CA–H2O system depending on
QSO2
at 293 K. Ni – molar fraction of Cit3−
(1), HCit2− (2), H2Cit− (3), CIVa– (4, 7),
NH2CH2CH2OH (5),
+
N H3CH2CH2OH (6),
CIS (8, 10), НSО3
– (9) relative to the total
content of citrates (1–4), nitrogen (5–8) and
sulfur (9, 10).
20 ISSN 2708-129X. Укр. хім. журн., 2025
SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM AND POLYETHYLENEPOLYAMMONIUM CITRATES
AQUEOUS SOLUTIONS PRODUCTS COMPOSITION AND THE RELATIVE STABILITY.INORGANIC CHEMISTRY
According to the calculations (Fig. 12), the
chemisorption of sulfur dioxide by an MEA⋅1/
6CA aqueous solution occurs due to its binding
to monoethanolammonium sulfite IS (curve
10) at Q(SO2) < 0.0572 mol/L, following reac-
tion 37. This process is accompanied by:
An increase in the molar fraction of citrate
anions (curve 1) and monoethanolammonium
cations (curve 6).
A decrease in the relative content of com-
pound IVa (curves 4, 7).
2{NH2CH2CH2OH}3{
+
N H3CH2CH2OH}3{HOC3H4(COO−)3} + 3SO2⋅H2O →
3(NH3CH2CH2OH)2SO3 + 2HOC3H4(COO−)3 + 6 +
N H3CH2CH2OH
(37)
With further SO2 addition, the relative
content of hydrosulfite anions (curve 9) and
monoethanolammonium cations (curve 6) in-
creases due to reaction 38.
(NH3CH2CH2OH)2SO3 + SO2⋅H2O → 2 +
N H3CH2CH2OH + 2НSО3
– (38)
In this case:
The mole fraction of the IS compound re
lative to total nitogen (curve 8) reaches a maxi
mum at Q(SO2):QN = 1.0:4.0;
The mole fraction of citrate anions (curve 1)
reaches a maximum at Q(SO2):QN = 1.0:10.0,
accompanied by partial protonation of citrate
anions with the formation of HOC3H4(COOH)
(COO−)2 (curve 2) and dihydrocitrate anions
(curve 3).
The relative content of HOC3H4(COOH)
(COO−)2 (curve 2) reaches a maxi-
mum at Q(SO2) = 0.0286 mol/L, while
HOC3H4(COOH)2COO− (curve 3) increases
throughout the studied range.
The content of unbound MEA (as a free
base), undissociated CA, sulfite and pyrosulfite
anions, and SO2⋅Н2О does not exceed 0.02 re
lative units. Notably, ionic associates IIa and
IIb are not formed during the chemisorption
of SO2 in the studied concentration (Q(SO2))
and temperature ranges, unlike in the MEA⋅1/
3CA solution.
The concentration dependences µ =
f(Q(SO2)) exhibit complex behavior due to
the multicomponent nature of the chemisorp-
tion system during SO2 absorption (at 283–
288 and 298–313 K). However, at 293 K, only
the ion-molecular complex IVa is formed be-
tween MEA and CA, leading to a linear de-
pendence:
µ = 0,0177 + 1,0261⋅Q(SO2);
n = 14; R2 = 0,9940. (39)
Using the obtained component composition
data for SO2–MEA⋅1/6CA – H2O solutions,
the concentration constants for the formation
of compounds IIIS, Ia, Ib, IIIa, Iva, and IVb
were calculated. The dependence рβIIb = f(µ)
is described by equation 29, with parameters
provided in Table 5.
With increasing temperature, bond weake
ning is observed in compounds Ia, IIIa, IVa
and IVb, as indicated by an increase in pβi
values, which are numerically equal to the
Ai coefficients in equation 29 (Table 5). Con-
versely, the stability of complex Ib increas-
es. The concentration and thermodynamic
constants βIIIS for SO2–MEA⋅1/6CA–H2O
and SO2–MEA⋅1/3CA–H2O solutions show
no significant difference compared to SO2 –
MEA solutions [3, 20].
21https://ucj.org.ua
R. E. Khoma, K. V. Tsyganenko, T. S. Bienkovska, Yu. V. Ishkov, S. V. Vodzinskii UCJ № 3 / Vol. 91
Table 5.
The values of the Аi, Вi coefficients in equation (29) for compounds Ia, Ib, IIIa, IVa,
and IVb in SO2−MEA⋅1/6CA−H2O in solutions*.
T, K Ai Bi R2 Q(SO2):QN
Ia
303 -5,44 79,27 0,9954 0,315÷0,458
313 19,11 -274,7 0,9890 0,286÷0,400
Ib
283 -3,94 6,63 0,9895 0,315÷0,949
288 -5,08 -9,78 0,9741 0,257÷0,486
IIIa
288 -17,33 -102,56 0,9978 0,0715÷0,200
313 -6,873 41,14 0,9995 0,0286÷0,143
IVa
293 -12,16 -45,31 0,9885 0,014÷0,529
313 22,835 -382 0,8303 0,172÷0,257
IVb
283 -18,14 15,30 0,9920 0,072÷0,286
303 18,23 -377,0 0,9935 0,175÷0,263
*R2 – the value of the approximation confidence.
CONCLUSIONS.
This study, based on pH, redox, and con-
ductometric analyses, evaluates the acid-base
interaction during the chemisorption of sulfur
dioxide by aqueous solutions of monoethanol-
ammonium and polyethylenepolyammonium
citrates in comparison with sodium citrate.
The composition and relative stability of the
reaction products formed during SO2 interac-
tion with aqueous solutions of Na3Cit, MEA⋅1/
3CA, PEPA⋅1/3CA, MEA⋅1/6CA, and PEPA⋅1/
6CA were determined. It was shown that in
the presence of ammonium citrates (MEA and
PEPA), the following species are formed: ionic
associates Ia, IIa, IIb, IIIa; ion-molecular as-
sociates Ib, IVa, IVb; and ammonium sulfites,
hydrosulfites, and pyrosulfites. The component
composition, as well as the concentration and
thermodynamic constants of these associates,
were calculated. In SO2–MEA⋅1/3CA–H2O
solutions, increasing temperature enhances the
relative stability of compounds IIa and Ib. In
SO2−MEA⋅1/6CA−H2O solutions, the stability
of compounds Ia, IIIa, IVa and IVb decrea
ses, while Ib increases with rising temperature.
Adding CA to the SO2−MEA−H2O system in
MEA:CA ratios of 3:1 and 6:1 has no significant
effect on the concentration and thermodyna
mic constants of ammonium sulfites formation.
The results obtained will be applied in the
development of chemosorbents for respiratory
protection.
22 ISSN 2708-129X. Укр. хім. журн., 2025
SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM AND POLYETHYLENEPOLYAMMONIUM CITRATES
AQUEOUS SOLUTIONS PRODUCTS COMPOSITION AND THE RELATIVE STABILITY.INORGANIC CHEMISTRY
ACKNOWLEDGEMENT. The work
was carried out within the framework
of the state budget theme “Scientific
principles of creating hybrid fibrous
filter materials for personal and col
lective protection equipment”, state
registration number: 0124U000930.
СКЛАД ТА ВІДНОСНА СТІЙКІСТЬ ПРОДУКТІВ
ВЗАЄМОДІЇ ДІОКСИДУ СІРКИ З ВОДНИМИ
РОЗЧИНАМИ ЦИТРАТІВ МОНОЕТАНОЛ
АМОНІЮ ТА ПОЛІЕТИЛЕНПОЛІАМОНІЮ
Р. Є. Хома , К. В. Циганенко,
Т. С. Бєньковська, Ю. В. Ішков,
С. В. Водзінський
Одеський національний університет імені
І. І. Мечникова,
вул. Дворянська, 2, Одеса 65082, Україна
email: rek@onu.edu.ua
В роботі наведено результати pH-, ре-
докс- та кондуктометричного досліджен-
ня кислотно-основної взаємодії при хемо
сорбції діоксиду сірки водними розчинами
на основі 0,1 моль/л цитратів моноетано-
ламонію (MEA⋅1/3CA) та поліетиленполі-
амонію (PEPA⋅1/3CA), а також буферни-
ми розчинами моноетаноламін – цитрат
моноетаноламонію (MEA⋅1/6CA) та полі
етиленполіамін – цитрат поліетиленполі-
амонію (PEPA⋅1/6CA) у порівнянні із цит
ратом натрію. Встановлено склад сполук,
що утворюються при поглинанні SO2 роз-
чинами Na3Cit, MEA⋅1/3CA, PEPA⋅1/3CA,
MEA⋅1/6CA, PEPA⋅1/6CA при 273 – 313 К.
За одних і тих самих значень кількості по-
глинутого діоксиду сірки) для розчинів
SO2–Na3Cit–H2O та SO2–MEA⋅1/3CA–H2O
відмічено збільшення значень питомої
електропровідності (æ) з ростом темпе-
ратури при 273–313 К; значення ∆æ змен-
шуються в системах SO2–MEA⋅1/3CA–H2O,
SO2–PEPA⋅1/3CA–H2O, SO2–MEA⋅1/6CA–
H2O та SO2–PEPA⋅1/6CA–H2O під час на-
грівання при 283–303 К, що спричинено
їхнім йон-молекулярним складом. На осно-
ві розроблених математичних моделей роз-
раховано йон-молекулярний компонент-
ний склад розчинів SO2– MEA⋅1/3CA–H2O
та SO2–MEA⋅1/6CA–H2O при 283–313 К та
концентраційні і термодинамічні констан-
ти утворення іонних асоціатів:
(NH3CH2CH2OH)2SO3, {
+
N H3CH2CH2OH}
{HOC3H4(COOH)2(COO−)} (Ia),
{ +
N H3CH2CH2OH}2
{HOC3H4(COOH)(COO−)2} (IIa),
{ +
N H3CH2CH2OH}2
{HOC3H4(COOH)2(COO−)} (IIb),
{ +
N H3CH2CH2OH}3{HOC3H4(COO−)3} (IIIa),
а також іон-молекулярних асоціатів
{ +
N H3CH2CH2OH}{HOC3H4(COOH)3} (Ib),
{NH2CH2CH2OH}3{
+
NH3CH2CH2OH}3
{HOC3H4(COO−)3} (IVa), {NH2CH2CH2OH}2
{ +
N H3CH2CH2OH}4{HOC3H4(COO−)3} (IVb).
У розчинах SO2–MEA⋅1/3CA–H2O з ро-
стом температури відбувається перегрупу-
вання зв’язків у іонних асоціатах IIa та Ib, на
що вказує відсутність чіткої температурної
залежності pβT
IIIa, а також зміцнення сполук
IIa та Ib. В розчинах SO2–MEA⋅1/6CA–H2O
з підвищенням температури відбувається
послаблення зв’язків у сполуках Ia, IIIa, IVa
та IVb, а у сполуці Ib, навпаки, посилення.
Ключові слова: діоксид сірки, амоніє-
ві цитрати, кислотно-основна взаємодія,
іонні асоціати, іон-молекулярні асоціати.
23https://ucj.org.ua
R. E. Khoma, K. V. Tsyganenko, T. S. Bienkovska, Yu. V. Ishkov, S. V. Vodzinskii UCJ № 3 / Vol. 91
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SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM AND POLYETHYLENEPOLYAMMONIUM CITRATES
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Стаття надійшла 05.01.2025.
|
| id | oai:ojs2.1444248.nisspano.web.hosting-test.net:article-712 |
| institution | Ukrainian Chemistry Journal |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2026-07-23T01:12:48Z |
| publishDate | 2025 |
| publisher | V.I.Vernadsky Institute of General and Inorganic Chemistry |
| record_format | ojs |
| resource_txt_mv | ucjorgua/98/8c3a872fea5acfaa22331d2c69492698.pdf |
| spelling | oai:ojs2.1444248.nisspano.web.hosting-test.net:article-7122026-07-22T08:23:55Z SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM AND POLYETHYLENEPOLYAMMONIUM CITRATES AQUEOUS SOLUTIONS PRODUCTS COMPOSITION AND THE RELATIVE STABILITY Khoma, Ruslan Vodzinskii, Sergey Bienkovska, Tetyana sulfur dioxide, ammonium citrates, acid-base interaction, ion associates, ion-molecular associates. The paper presents the results of pH, redox, and conductometric studies on the acid-base interaction during sulfur dioxide chemisorption by aqueous solutions containing 0.1 mol/L monoethanolammonium (MEA·1/3CA) and polyethylenepolyammonium (PEPA·1/3CA) citrates, as well as buffer solutions of monoethanolamine–monoethanolammonium citrate (MEA·1/6CA) and polyethylenepolyamine–polyethylenepolyammonium citrate (PEPA·1/6CA), in comparison with sodium citrate. The composition of the compounds formed during SO2 absorption by Na3Cit, MEA·1/3CA, PEPA·1/3CA, MEA·1/6CA, and PEPA·1/6CA solutions at 273–313 K was determined.For the same amount of absorbed sulfur dioxide, an increase in specific electrical conductivity (æ) with rising temperature was observed in SO2–Na3Cit–H2O and SO2–MEA×1/3CA–H2O solutions within the 273–313 K range. However, in the SO2–MEA×1/3CA–H2O, SO2–PEPA×1/3CA–H2O, SO2–MEA×1/6CA–H2O, and SO2–PEPA×1/6CA–H2O systems, a decrease in Δæ was noted upon heating to 303 K, which is attributed to their ion-molecular composition. Based on developed mathematical models, the ion-molecular component composition of SO2–MEA×1/3CA–H2O and SO2–MEA×1/6CA–H2O solutions was determined at 283–313 K. The concentration and thermodynamic constants for the formation of ionic associates were calculated:(NH3CH2CH2OH)2SO3, {H3CH2CH2OH}{HOC3H4(COOH)2(COO-)} (Ia), {H3CH2CH2OH}2{HOC3H4(COOH)(COO-)2} (IIa), {H3CH2CH2OH}2{HOC3H4(COOH)2(COO-)} (IIb), {H3CH2CH2OH}3{HOC3H4(COO-)3} (IIIa), as well as ion-molecular associates:{H3CH2CH2OH}{HOC3H4(COOH)3} (Ib), {NH2CH2CH2OH}3{H3CH2CH2OH}3{HOC3H4(COO-)3} (IVa), {NH2CH2CH2OH}2{H3CH2CH2OH}4{HOC3H4(COO-)3} (IVb). In SO2–MEA×1/3CA–H2O solutions, as the temperature increases, bond rearrangement occurs in ionic associates IIa and Ib, as indicated by the absence of a clear temperature dependence ofp, along with the strengthening of IIa and Ib. Conversely, in SO2–MEA×1/6CA–H2O solutions, increasing temperature leads to the weakening of the bonds in compounds Ia, IIIa, IVa, and IVb, while in compound Ib, the bonds strengthen. V.I.Vernadsky Institute of General and Inorganic Chemistry 2025-04-25 Article Article Inorganic Chemistry Неорганическая химия Неорганічна хімія application/pdf https://ucj.org.ua/index.php/journal/article/view/712 10.33609/2708-129X.91.3.2025.3-24 Ukrainian Chemistry Journal; Vol. 91 No. 3 (2025): Ukrainian Chemistry Journal; 3-24 Украинский химический журнал; ##issue.vol## 91 ##issue.no## 3 (2025): Ukrainian Chemistry Journal; 3-24 Український хімічний журнал; Том 91 № 3 (2025): Ukrainian Chemistry Journal; 3-24 2708-129X 2708-1281 en https://ucj.org.ua/index.php/journal/article/view/712/360 Copyright (c) 2025 Ruslan Khoma, Sergey Vodzinskii, Tetyana Bienkovska https://creativecommons.org/licenses/by-nc/4.0 |
| spellingShingle | Khoma, Ruslan Vodzinskii, Sergey Bienkovska, Tetyana SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM AND POLYETHYLENEPOLYAMMONIUM CITRATES AQUEOUS SOLUTIONS PRODUCTS COMPOSITION AND THE RELATIVE STABILITY |
| title | SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM AND POLYETHYLENEPOLYAMMONIUM CITRATES AQUEOUS SOLUTIONS PRODUCTS COMPOSITION AND THE RELATIVE STABILITY |
| title_full | SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM AND POLYETHYLENEPOLYAMMONIUM CITRATES AQUEOUS SOLUTIONS PRODUCTS COMPOSITION AND THE RELATIVE STABILITY |
| title_fullStr | SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM AND POLYETHYLENEPOLYAMMONIUM CITRATES AQUEOUS SOLUTIONS PRODUCTS COMPOSITION AND THE RELATIVE STABILITY |
| title_full_unstemmed | SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM AND POLYETHYLENEPOLYAMMONIUM CITRATES AQUEOUS SOLUTIONS PRODUCTS COMPOSITION AND THE RELATIVE STABILITY |
| title_short | SULFUR DIOXIDE INTERACTION WITH MONOETHANOLAMMONIUM AND POLYETHYLENEPOLYAMMONIUM CITRATES AQUEOUS SOLUTIONS PRODUCTS COMPOSITION AND THE RELATIVE STABILITY |
| title_sort | sulfur dioxide interaction with monoethanolammonium and polyethylenepolyammonium citrates aqueous solutions products composition and the relative stability |
| topic_facet | sulfur dioxide ammonium citrates acid-base interaction ion associates ion-molecular associates. |
| url | https://ucj.org.ua/index.php/journal/article/view/712 |
| work_keys_str_mv | AT khomaruslan sulfurdioxideinteractionwithmonoethanolammoniumandpolyethylenepolyammoniumcitratesaqueoussolutionsproductscompositionandtherelativestability AT vodzinskiisergey sulfurdioxideinteractionwithmonoethanolammoniumandpolyethylenepolyammoniumcitratesaqueoussolutionsproductscompositionandtherelativestability AT bienkovskatetyana sulfurdioxideinteractionwithmonoethanolammoniumandpolyethylenepolyammoniumcitratesaqueoussolutionsproductscompositionandtherelativestability |