Ion Exchange Equilibrium Constants

59 Pages·1975·2.498 MB·English

by  Y. Marcus and D. G. Howery (Auth.)

INTERNATIONAL UNION OF
PURE AND APPLIED CHEMISTRY
ANALYTICAL CHEMISTRY DIVISION
COMMISSION ON EQUILIBRIUM DATA
ION EXCHANGE
EQUILIBRIUM CONSTANTS
Compiled by
Y. MARCUS
Department of Inorganic and Analytical Chemistry, The Institute of
Chemistry, The Hebrew University, Jerusalem, Israel
with the collaboration of
D. G. HOWERY
Department of Chemistry, Brooklyn College, City University of New York,
Brooklyn, NY, USA
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First published 1975
ι International Union of Pure and Applied Chemistry 1975
Suggested UDC No. 541.183.12; 541.123.04
International Union of Pure and Applied Chemistry
1975
ISBN 0 408 70710 0
Printed in England" by Page Bros (Norwich) Ltd, Norwich
INTRODUCTION
The IUPAC Commission V.6 on Equilibrium Data decided at its
meeting in Paris in 1965 to make a test-compilation of equilibrium
constants for ion exchange reactions, in order to consider whether
these could be included in the "Supplement to Stabilty Constants"
then being prepared under its sponsorship. The compilation made
by Y. Marcus in 1967 was discussed at the Commission's meeting in
Prague in 1967, and it was decided to postpone action. At the meet-
ing in Washington in 19 71, it was decided to take up the project
again, and Y. Marcus was asked to bring the compilation up to date,
with the help of G.N. Nancollas.
In a consultation between them, it was decided to keep the
previous format, and prepare an updated compilation. D.G. Howery
volunteered to help, and provided a great deal of material for the
compilation. An early draft has been circulated among the members
of Commission V.6, and has been approved in principle. This draft
has now been completed with further data, and brought up to date
to the end of 1971.
The scope of the compilation
The Table considers ion exchange reactions
AR + B ^ BR + A (1 )
where A- and B- denote one equivalent of the exchanging ions,
and R* denotes one equivalent of th'; exchanger, and the charges
on A (or B) apply to cation and anion exchangers respectively.
Only materials of known and reproducible compositions have been
included, such as monofunctional resins based on a polystyrene
skeleton crosslinked with divinylbenzene, on polyacrylic acid,
or certain synthetic zeolites. Natural zeolites were not includ-
ed, because of their variable compositions, nor were commercial
resins, if polyfunctional or of uncertain compositions.
1
INTRODUCTION
The IUPAC Commission V.6 on Equilibrium Data decided at its
meeting in Paris in 1965 to make a test-compilation of equilibrium
constants for ion exchange reactions, in order to consider whether
these could be included in the "Supplement to Stabilty Constants"
then being prepared under its sponsorship. The compilation made
by Y. Marcus in 1967 was discussed at the Commission's meeting in
Prague in 1967, and it was decided to postpone action. At the meet-
ing in Washington in 19 71, it was decided to take up the project
again, and Y. Marcus was asked to bring the compilation up to date,
with the help of G.N. Nancollas.
In a consultation between them, it was decided to keep the
previous format, and prepare an updated compilation. D.G. Howery
volunteered to help, and provided a great deal of material for the
compilation. An early draft has been circulated among the members
of Commission V.6, and has been approved in principle. This draft
has now been completed with further data, and brought up to date
to the end of 1971.
The scope of the compilation
The Table considers ion exchange reactions
AR + B ^ BR + A (1 )
where A- and B- denote one equivalent of the exchanging ions,
and R* denotes one equivalent of th'; exchanger, and the charges
on A (or B) apply to cation and anion exchangers respectively.
Only materials of known and reproducible compositions have been
included, such as monofunctional resins based on a polystyrene
skeleton crosslinked with divinylbenzene, on polyacrylic acid,
or certain synthetic zeolites. Natural zeolites were not includ-
ed, because of their variable compositions, nor were commercial
resins, if polyfunctional or of uncertain compositions.
1
No generally meaningful equilibrium constants can be derived
for such materials, for inclusion in this compilation. However,
some of the studies with these materials are sufficiently impor-
tant, that they are made available to the interested reader in
Appendix 1. Their selection is based on judgement by the compi-
lers, and is neither complete nor wholly unbiased.
Only such systems were considered, where the exchange
isotherm was obtained over practically the whole composition
range of the exchanger, so that the integrated equilibrium
constant
log K° . £logk d^ (2)
BfA
could be calculated. Here kR . is the equilibrium selectivity
ratio per equivalent of ions A and B (see below), and x is
the equivalent fraction of the incoming ion in the exchanger
phase. In many systems that have been studied, only a small
fraction of the composition range of the exchanger, such as
xD££ 0 for tracer concentrations of B, has been covered. The
selectivity ratio kg ^ often varies considerably with x at the
extreme ends of the composition range, so that the selectivity
at tracer concentrations is not representative of the overall
behavior of the exchange system« On the other hand, tracer
studies may be the only ones that have been made on some impor-
tant systems, and some indication of their behavior is desirable.
Such sytems have been included in Appendix 2. Again, their selec-
tion is based on judgement by the compilers, and is neither com-
plete nor wholly unbiased«
For those systems for which log K° could be calculated
from the published data, the literature search and compilation
has been made to the end of 1971, as complete as the compilers
were able to obtain the literature through the usual abstracting
sources ·
2
The equilibrium constant
The equilibrium selectivity ratio k„ . that enters eq. (2)
^ J B,A
is defined by
- 1/ZB ΓΛ //ZA
7±AC
%A - 1/ZR 1/ZP
(3)
r±BC
Here z and z are the charge numbers of the ions, and the
molar scale (equivalents per liter) is applied to the solution
phase concentrations, [A-J and [B-] . Since only their ratio
enters the equation, other scales, such as the molal (equivalents
per kg. solvent), or the rational can be used instead, in dilute
solutions. The mean molar activity coefficients y.Ar a«">d y1Dr
* A L * Ö C
pertain to the mixed electrolyte solution, and Ct is an equiva-
lent of the counter ion in the solution. (If, eeg. AC is a z :1
electrolyte, then y is the (n ■»· 1 )th root of the activity co-
efficient of the electrolyte). The data are usually obtained at
such dilutions ( <0♦ 1 M) , that Υ,ΑΓ / y.Rr differs insignificantly
from y^Ac/ y^ BC , the ratio of the activity coefficients in sepa-
rate solutions of AC and BC, or from unity. Therefore data were
included if the work was done at an ional concentration [C+] - 0.1,
even if the activity coefficients were not considered.
As mentioned above, kDn ,A. = fix«B ) may be a rather steeply
varying function. The amount of information conveyed by the inte-
o
grated constant, K , is necessarily less than that given by the
complete function, or its representation as, say, a power series
in x . In a general compilation such as the present one, which
a
uses the well known " Stability Constants " by 5illèn and Martell
as a model, it is necessary to condense the information presented,
and the reader is always urged to seek the original publications
for details.
On the other hand, integration over x corrects for the vari-
3
ation of the activity coefficients of the ions in the exchanger,
to at least a first order. Various second order corrections, es-
pecially for the variation of the solvent activity with the compo-
sition of the exchanger, have been proposed, in order to obtain
the true standard Gibbs energy change for reaction (1), for appro-
priately defined standard states. Their evaluation is outside
the scope of this compilation. The quantity -RT In K
may serve for many purposes as the Gibbs energy change. Where
available, the negative of the standard integral enthalpy change
of reaction (1), -ΔΗ , is also given.
4
The symbols used in the Table
Exchanger: the repeating unit of the ion exchanger, i.e. the
functional group together with the portion of the
skeleton to which it is anchored.
Ion A, Ion B : one equivalent of the outgoing and incoming ions
respectively. Ion B is the preferred ion if
log K is positive.
X-link: the nominal crosslinking of the ion exchange re-
sin, in % divinylbenzene.
Medium: the solution (aqueous, unless otherwise stated)
medium used, with the concentration of C when
known. For mixed or nonaqueous solvents, the
mole- or volume-fraction is stated. The tempera-
ture is given if not 25 C. I denotes the ionic
strength.
Log K : the dimensionless equilibrium constant for reac-
tion (1), calculated according to eq, (2) and (3).
- Δ H : the negative of the standard integral enthalpy
change of reaction (1), in kcal per equivalent
(convert to kJ/ equiv. by multiplying with 4.184)
Ref: references are given according to the format in
"Stability Constants". 70R/52H means calculated
in réf. 70R from data in réf. 52H,
Other abbreviations used are: MeOH - methanol, EtOH - ethanol,
Me2C0 - acetone, PrOH - piopanol, DMSO - dimethyl sulfoxide,
liq. NHq - liquid ammonia.
Arrangement of the Table
The ions are ordered according to the scheme of "Stability
4 *
Constants", and for each pair A~ and B~ , according to chronolo-
gical order of the publieations
5
The symbols used in the Table
Exchanger: the repeating unit of the ion exchanger, i.e. the
functional group together with the portion of the
skeleton to which it is anchored.
Ion A, Ion B : one equivalent of the outgoing and incoming ions
respectively. Ion B is the preferred ion if
log K is positive.
X-link: the nominal crosslinking of the ion exchange re-
sin, in % divinylbenzene.
Medium: the solution (aqueous, unless otherwise stated)
medium used, with the concentration of C when
known. For mixed or nonaqueous solvents, the
mole- or volume-fraction is stated. The tempera-
ture is given if not 25 C. I denotes the ionic
strength.
Log K : the dimensionless equilibrium constant for reac-
tion (1), calculated according to eq, (2) and (3).
- Δ H : the negative of the standard integral enthalpy
change of reaction (1), in kcal per equivalent
(convert to kJ/ equiv. by multiplying with 4.184)
Ref: references are given according to the format in
"Stability Constants". 70R/52H means calculated
in réf. 70R from data in réf. 52H,
Other abbreviations used are: MeOH - methanol, EtOH - ethanol,
Me2C0 - acetone, PrOH - piopanol, DMSO - dimethyl sulfoxide,
liq. NHq - liquid ammonia.
Arrangement of the Table
The ions are ordered according to the scheme of "Stability
4 *
Constants", and for each pair A~ and B~ , according to chronolo-
gical order of the publieations
5
Ion A Ion B X-link Medium Log K° -AH° Ref,
I. Exchanger: Γ-CHCH(C _H . SO.")- ]
L d. 6 4 J n
H"" Li* 8 -0.10 54B
10 -0.09 55R
10 -0.06 56M
4 0.1MC1" -0.12 57B/54Ba
θ -0.10
16 -0.17
10 -0.09 -0,. 39 57C
4 -0.11 -0,. 24 61B
θ -0.10 -0,. 53
16 -0.17 -0,. 52
θ -0.06 61Ba
8 0.1MCl"Me0H -0.46 63F
8 0. 1Μ -0.05 63S
4 -0.19 65G
50%v/vMe0H 0.06
10 -0.18
50%v/vMeOH 0.06
10 1 = 0 -0.33 66G
0.1MC1" -0.19 67Ga
1.OMCl" 0.15
4 0.1MC1" -0.19
50%v/vMeOH -0.21
50%v/vEtOH 0.18
50%v/vMe2C0 0.19
10 0.1MC1~ -0.18
50%v/vMeOH -0.20
50#v/vEtOH 0.23
H* Li" 10 50%v/vMe2C0 0.26 67Ga
~ 10.7 -0.13 67Sc
10 -0.19 -0,. 99 68Ga
25%v/vMeOH 0.05 -2, .74
60%v/vMeOH 0.23 -1 .,5 8
80%v/vMeOH 0.38 -1 .,2 4
6 0,- 1MCJ-"XMM e CP0n -o.i 0.00 68Sc
XMe2C0=02.5 0.60
6.5 -0, .33 725
10.5 -o<,4 2
25 -0, ,67
6