物理化学学报(Wuli Huaxue Xuebao)
Acta Phys. ⁃Chim. Sin. 2012, 28 (11), 2567-2573
November
[Article]
2567
www.whxb.pku.edu.cn
doi: 10.3866/PKU.WHXB201208211
CO2 在 Na2Cr2O7 溶液中的平衡溶解度模型
周恩年 1,2,3
余志辉 1,2,*
曲景奎 1,2,*
(1 中国科学院过程工程研究所, 湿法冶金国家重点实验室, 北京 100190;
点实验室, 北京 100190;
摘要:
3
中国科学院研究生院, 北京 100049;
涛 1,2
齐
4
2
韩晓英 1,2,3
张国庆 4
中国科学院过程工程研究所, 绿色过程与工程院重
四川安县银河建化(集团)有限公司, 四川 安县 622656)
为研究重铬酸钠(Na2Cr2O7)对 CO2 溶解的影响, 本文在带有搅拌的气液相高压平衡釜内, 采用静态法测
定了温度在 313.2-333.2 K, 压力在 0.1-1.9 MPa 范围内, 重铬酸钠浓度分别为 0、0.361、0.650、0.901 mol·
kg-1 时, CO2 在 Na2Cr2O7 溶 液 中 的 溶 解 度. 结 果 表 明: (1) Na2Cr2O7 对 CO2 的 溶 解 有 盐 析 效 应; (2) CO2 在
Na2Cr2O7 溶液中的溶解符合亨利定律, 并且 CO2 溶解度是温度和 Na2Cr2O7 浓度的函数, 且用改进的 Setschenow
方程和 Peng-Robinson-Pitzer (PR-Pitzer)方程拟合了在此温度、压力及重铬酸钠浓度范围内的实验数据, 拟合
效果较好, 并且其平均相对误差分别为 4.24%和 3.32%.
关键词:
CO2 溶解度; Na2Cr2O7 溶液; 热力学模型; Setschenow 方程; Peng-Robinson-Pitzer 方程;
亨利常数
中图分类号:
O642
Equilibrium Solubility Modeling of CO2 in Na2Cr2O7 Solutions
ZHOU En-Nian1,2,3
YU Zhi-Hui1,2,*
QU Jing-Kui1,2,*
1,2,3
HAN Xiao-Ying
ZHANG Guo-Qing4
QI Tao1,2
(1National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Institute of Process
Engineering, Chinese Academy of Sciences, Beijing 100190, P. R. China; 2Key Laboratory of Green Process and Engineering,
Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P. R. China; 3Graduate University of
Chinese Academy of Sciences, Beijing 100049, P. R. China; 4Sichuan Anxian YinHe Construction & Chemical Group Co. Ltd.,
Anxian 622656, Sichuan Province, P. R. China)
Abstract: The solubility of CO2 in aqueous Na2Cr2O7 solutions of different concentrations (0, 0.361, 0.650,
and 0.901 mol·kg-1) was measured in a stirred vapor-liquid high-pressure equilibrium cell using the static
method at temperatures and pressures in the ranges of 313.2 to 333.2 K and 0.1 to 1.9 MPa, respectively.
The results indicated that the phenomenon of CO2 dissolved in aqueous Na2Cr2O7 could be interpreted
according to a“salting-out effect”. Furthermore, our solubility data for CO2 in aqueous Na2Cr2O7 was in
agreement with Henryʹs law, and the Henry constant appeared to be a function of temperature, pressure,
and the concentration of Na2Cr2O7. Two thermodynamic models were applied to correlate the experimental
data, including the modified Setschenow and Peng-Robinson-Pitzer equations, and the averaged relative
deviations were found to be 4.24% and 3.32%, respectively.
Key Words: CO2 solubility; Na2Cr2O7 solution; Thermodynamic model;
Peng-Robinson-Pitzer equation;
Setschenow equation;
Henry constant
Received: April 11, 2012; Revised: August 20, 2012; Published on Web: August 21, 2012.
∗
Corresponding authors. QU Jing-Kui, Email: [email protected]. YU Zhi-Hui, Email: [email protected]; Tel: +86-10-82544848;
Fax: +86-10-62631710.
The project was supported by the National Outstanding Youth Scientists Foundation of China (51125018), National Natural Science Foundation of
China (21006119), and High-Tech Research and Development Program of China (863) (2009AA035000, 2011AA060700).
国家杰出青年基金(51125018), 国家自然科学基金(21006119)及国家高新技术研究发展计划项目(863) (2009AA035000, 2011AA060700)资助
Ⓒ Editorial office of Acta Physico⁃Chimica Sinica
2568
1
Acta Phys. ⁃Chim. Sin. 2012
Introduction
With the growing demand for cleaner production processes,
the manufacture of sodium chromate according to the sulfuric
acid method is being gradually phased out and replaced with a
process involving the carbonation of aqueous sodium chromate.1-3 Very little, however, is known about the fundamental
thermodynamic properties of this new processing technology.
The process itself involves the absorption of carbon dioxide into an aqueous sodium chromate solution.4,5 To investigate the
influence of the known by-product NaHCO3 on the absorption
of CO2, Han et al.6 investigated the solubility of CO2 in aqueous NaHCO3 solutions. To the best of our knowledge, prior to
the current study, no research had been conducted to evaluate
the influence of the concentration of Na2Cr2O7 in the aqueous
solution on the solubility of CO2. In the carbonation process
for the manufacture of sodium chromate, however, sodium dichromate is generated in significant quantities and could inhibit the carbonation process by decreasing the solubility of CO2.
The purpose of this work, therefore, was to investigate the
CO2-H2O-Na2Cr2O7 vapor-liquid equilibrium system and collect
fundamental data pertaining to the manufacture of aqueous sodium chromate according to the carbonation process. To acquire an adequate volume of experimental data to describe the
thermodynamic process, the decision was taken to measure the
solubility of CO2 in aqueous solutions of Na2Cr2O7 at several
different concentrations (0, 0.361, 0.650, and 0.901 mol·kg-1)
at temperatures and pressures in the ranges of 313.2 to 333.2 K
and 0.1 to 1.9 MPa, respectively. The temperature and pressure
ranges were chosen to closely reflect the conditions used in the
current industrial manufacturing process.2
There have been a large number of experimental studies focused on the solubility of CO2 in pure water and salt solutions.
Maurer et al.7 evaluated the solubility of CO2 in aqueous
N-methyldiethanolamine and used the Pitzer equation to correlate their data. Feyzi et al.8 investigated the solubility of CO2 in
a 30% (w) aqueous solution of 2-((2-aminoethyl)amino) ethanol and used a thermodynamic model based on the DeshmukhMather method to represent their solubility data. RebolledoMorales et al.9 measured the solubility of CO2 in aqueous
1-amino-2-propanol and applied the Kent-Eisenberg model to
correlate their solubility data. Ferrentino et al.10 measured the
solubility of CO2 in aqueous NaH2PO4 solution using three different thermodynamic models, including the UNIFAC (universal functional activity coefficient) with Peng-Robinson (PR)
equation, the Chen-NRTL (non-random two-liquid) model
with a Redlich-Kwong equation, and the predictive SoaveRedlich-Kwong equation. Kamps et al.11 determined the solubility of CO2 in aqueous KCl and K2CO3 solutions and the vapor-liquid equilibria of the CO2-KCl-H2O and CO2-K2CO3-H2O
systems were described by the Pitzer equation. Gao et al.12 determined the solubility of CO2 in aqueous NaHCO3 and applied
the modified Patel-Teja equation of state to describe the system. Wong et al.13 determined the solubility of CO2 in aqueous
Vol.28
HCl and NaHCO3 solutions and used the Pitzer equation to correlate their solubility data. Han et al.6 measured the solubility
of CO2 in aqueous NaHCO3 solutions and applied the modified
Setschenow and PR-Duan equations to correlate their solubility data. There have also been other reports in the literature
from Han et al.6 providing data for the solubility of CO2 in a variety of other salt solutions. To study the influence of Na2Cr2O7
on the solubility of CO2, the solubility of CO2 in Na2Cr2O7 solutions of different concentrations was measured and two thermodynamic models were applied to correlate the experimental
data.
2
Experimental
2.1 Materials
All materials are listed in Table 1.
2.2 Apparatus
The solubility was measured according to the static approach that has been reported previously in the literature.9,10,14,15
The apparatus used to determine the solubility of CO2 is shown
in Fig.1.
The experimental setup (model GCF2, Dalianzikong Co.,
China) consisted of a 1000-mL stainless steel cylindrical tank
equipped with a magnetically coupled stirrer attached to its
top. The tank could tolerate a maximum pressure of 30 MPa
and was attached to a 2XZ-4 vacuum pump, which had a pressure limit of 6×10-2 Pa. An electronic balance (Mettler Toledo
AL104) with an accuracy of 0.0001 g was used together with a
Table 1 Experiment materials
Name
Specification
Factory
CO2
analytical pure≥99.9%
Beijng Qianxi Jingcheng Gas
Sales Center
Na2Cr2O·
7 2H2O
analytical pure≥99.5%
Fe(NH4)2(SO4)·
analytical pure≥99%
2 6H2O
C13H11NO2
Tianjin Guangfu Sciences and
Technology Development Co., Ltd.
analytical pure≥99.5%
Sinopharm Chemical Reagent
Co., Ltd.
Sinopharm Chemical Reagent
Co., Ltd.
pure water
Fig.1
electrical conductivity
≤0.079 μS·cm-1
Jiangchuan Water Treatment
Plant
Schematic representation of the experimental equipment
1: magnetic stir; 2: equilibrium caldron; 3: water bath; 4: heating jacket;
5: vacuum pump; 6: gas mass-flow controller; 7: computer;
V1, V2, V3: valves; P: pressure transducer
No.11
2569
ZHOU En-Nian et al.: Equilibrium Solubility Modeling of CO2 in Na2Cr2O7 Solutions
CH2015 thermostatic bath, which had an accuracy of ±0.05 K.
A gas mass-flow controller (SevenStar CS200) with an uncertainty of ± 1 mL·min-1 was also used as well as a pressure
transducer (Rosemount 3051T) with an accuracy of ± 0.075%
of scale (0 to 2.1 MPa).
2.3 Procedure
The aqueous Na2Cr2O7 solutions were prepared and their concentrations were determined using a conventional titration
method.
All of the air was removed from the equilibrium cell (the
whole volume of the equilibrium cell is Vt) using a vacuum
pump. Aqueous Na2Cr2O7 solutions of known volume (Vsol (the
volume of the aqueous Na2Cr2O7 solution), 500 mL) and concentration were injected into the equilibrium cell. The aqueous
Na2Cr2O7 solutions were all degassed prior to use. The temperature of the vapor-liquid equilibrium cell was controlled by the
thermostatic water bath to within ±0.1 K of the desired temperature. The gas volume (V0) was controlled using a gas flow meter that was operated and read from a computer. The gas-liquid
equilibrium pressure (peq) was obtained from a pressure transducer when the equilibrium was reached.
The solubility (unit in mol) of CO2 in the aqueous Na2Cr2O7
solutions was determined from the difference between the
amount of CO2 (n0), where n0 represented the molarity (unit in
mol) of CO2 initially injected into the equilibrium cell, and the
amount of CO2 (neq), where neq represented the molarity (unit in
mol) of CO2 remaining in the gas phase when the equilibrium
was achieved. The n0 value was calculated using equation (1).
V0 ⋅ ρ(CO 2)
n0=
(1)
M (CO 2)
where, ρ(CO2) and M(CO2) are the density and molar mass of
CO2, respectively.
The neq values were determined using the PR equation16,17 in
concordance with equations (2) to (6), where the pCO2, pH2O, and
T represented the CO2 partial pressure, water partial pressure,
and temperature, respectively, when the equilibrium was
achieved, and the symbols Vg and Vm represented the volume of
gas phase in the equilibrium cell and the molar volume of CO2,
respectively. The pCO2 value in this instance was computed using Daltonʹs law, and the partial pressure of water (pH2O) in the
vapor mixture was the same as the saturation pressure of pure
water.18 Thus, pH2O values were 0.00737, 0.01228, and 0.01988
MPa at 313.2, 323.2, and 333.2 K, respectively.
pCO2=peq-pH2O
(2)
Vg=Vt-Vsol
(3)
RT
a
pCO2 =
(4)
V m -b V m (V m + b) + b(V m -b)
Vg
neq =
(5)
Vm
The solubility of CO2 in the aqueous Na2Cr2O7 solutions was
given by mCO2 (mol CO2 per kg H2O) according to equation (6)
as follows:
n0 -neq
mCO2 =
(6)
m sol
Table 2 Comparison of the data for the solubility of CO2 in pure
water from this work and literature at 303.2 K
pCO2/MPa
experiment
0.105
1.542
literature20
mCO2/(mol·kg-1)
0.0310
0.4631
0.1
0.0300
1.5
0.4597
where, msol is the mass of the water (kg) present in the fresh
aqueous Na2Cr2O7 sample.
The mex value was estimated with an uncertainty of 4%. This
uncertainty value was determined from the uncertainty values
in temperature, pressure, and volume, which were ±0.1%,
±0.075%, and ±1%, respectively.
2.4 Experimental method validation
To establish the accuracy of the experimental equipment and
method used in the current study, we measured the solubility
data for CO2 in pure water at a temperature of 303.2 K and
pressures of 0.1 and 1.5 MPa, and compared the data obtained
to those reported by Lide et al.19 for the solubility of CO2 in
pure water. A comparison of these data sets is shown in Table
2. From these data, it was clear that the experiment values differed from the literature values20 by 1.6% and -2.0% at 0.1 and
1.5 MPa, respectively, indicating that this equipment was capable of producing accurate solubility results that were in good
agreement with the experimental values previously reported in
the literature.
3
Experimental results
The solubility of CO2 in aqueous Na2Cr2O7 solutions was
measured at different concentrations (0, 0.361, 0.650, and
0.901 mol·kg-1) as well as temperatures and pressures in the
ranges of 313.2 to 333.2 K and 0.1 to 1.9 MPa, respectively.
The experimental results are shown in Table 3. It is clear from
these data that the solubility of CO2 in aqueous Na2Cr2O7 decreased as the concentration of the Na2Cr2O7 solution increased
at a given temperature and pressure.
4
Thermodynamic models
4.1 Modified Setschenow equation
It is well known that a linear relationship is obeyed between
the dissolved CO2 concentration and the equilibrium CO2 partial pressure in the gas phase of the low pressure region, which
can be described as follows according to Henryʹs law.
pCO2=H·mCO2
(7)
where H represents the Henry constant.
The modified Setschenow equation20 was derived using the
concentration of the salt solutions (ms) and T, according to
equation (8).
lnH=k·
(8)
s ms+k0
where, ks and k0 represent the salting-out effect constants. In
this instance, the non-idealities of both the gas and liquid phases were neglected. A combination of equations (7) and (8) pro-
Acta Phys. ⁃Chim. Sin. 2012
2570
Table 3
mNa Cr O /(mol·kg )
pCO /MPa
0.000
0.102
2 7
0.361
0.650
0.901
T=323.2 K
mCO /(mol·kg-1)
pCO /MPa
0.0235
0.117
0.485
0.1082
0.902
T=333.2 K
mCO /(mol·kg-1)
pCO /MPa
0.0229
0.128
0.478
0.0845
0.349
0.0538
0.2000
0.904
0.1654
0.957
0.1467
1.353
0.3103
1.299
0.2359
1.487
0.2286
1.655
0.4015
1.582
0.2860
1.758
0.2708
0.123
0.0249
0.110
0.0193
0.115
0.0156
0.561
0.1056
0.498
0.0842
0.486
0.0651
1.019
0.1945
0.903
0.1477
0.893
0.1173
1.421
0.2714
1.303
0.2141
1.323
0.1818
1.611
0.3061
1.711
0.2819
1.711
0.2359
0.112
0.0212
0.137
0.0197
0.126
0.0142
0.499
0.0867
0.532
0.0779
0.520
0.0604
0.915
0.1583
1.021
0.1466
0.941
0.1092
1.348
0.2291
1.400
0.2029
1.356
0.1580
1.761
0.3055
1.781
0.2610
1.720
0.1992
0.108
0.0167
0.158
0.0205
0.113
0.0180
0.488
0.0751
0.530
0.0608
0.551
0.0578
0.897
0.1269
0.960
0.1111
1.060
0.1113
1.304
0.1897
1.180
0.1374
1.505
0.1535
1.553
0.2241
1.570
0.1836
1.860
0.2036
2
2
vides equation (9).
pCO2
lg
= k s∙m s + k0
mCO2
2
2
mCO2/(mol·kg-1)
2
0.0194
l
μCO
(T, m)=μl(0)
CO (T)+RTlnαCO2(T, m)
2
=μl(0)
(12)
CO (T)+RTlnmCO2+RTlnγCO2(T, m)
Furthermore, the chemical potential of CO2 in the gas phase
(μgCO2(T, p)) can be related to the temperature (T) and the CO2
partial pressure (p) as follows:22
μgCO2(T, p)=μg(0)
CO (T)+RTlnfCO2(T, p, y)
=μg(0)
(13)
CO (T)+RTlnpCO2+RTlnφCO2(T, p, y)
From the equality of the chemical potentials of CO2 in the
liquid and the vapor phases, we obtain equation (14).
2
(9)
In accordance with the work of Li and Mather,21 the ks and k0
parameters, which were dependent upon T, were selected as in
equation (10).
f(T)=alnT+ b +c
(10)
T
The objective function for regression was defined according
to equation (11).
| m -m |
Fobj= ∑| ca ex |
(11)
| mex |
where, mca represents the correlated solubility of CO2 derived
from equation (9).
The fitted parameters have been presented in Table 4, whereas the correlation results are shown in Figs.2-4. The average
relative deviation in the solubility of CO2 in pure water was
3.61%, whereas the value was 4.24% for all of the experimental data.
4.2 PR-Pitzer equation
According to a report in the literature,22 the chemical potenl
tial of CO2 in the liquid phase (μCO
(T, m)) can be related to the
2
temperature (T) and the concentration (m) of physically dissolved CO2 as follows:
Table 4 Fitted values for the Henry constants of
the CO2-Na2Cr2O7-H2O system derived from the modified
Setschenow equation
a
b/K
-1
c
-191.22
-61088
1294.4
k0
92.157
27574
-616.18
2
2
pCO2 μCO2 (T ) -μCO2 (T)
=
mCO2
RT
l(0)
ln
g(0)
ln φCO2 (T, p, y ) + ln γCO2 (T, m)
(14)
where, αCO2, fCO2, and φCO2 are the activity coefficient, fugacity,
Fig.2
Solubility of CO2 in the aqueous Na2Cr2O7 solutions as a
function of pCO2 at 313.2 K
The points represent the experimental data. The dotted lines represent the
correlated values derived from the modified Setschenow equation.
mNa2Cr2O7/(mol·kg-1): n 0;
0.361;
n
ks
2
▼
2
Solubility of CO2 in aqueous Na2Cr2O7 solutions
T=313.2 K
-1
Vol.28
0.650; ▼ 0.901
No.11
2571
ZHOU En-Nian et al.: Equilibrium Solubility Modeling of CO2 in Na2Cr2O7 Solutions
ln γCO2 = 2 ∑ λCO2 - c mc + 2 ∑ λCO2 - a ma +
c
a
3∑ ∑ ζCO2 - a - c mc ma
c
(17)
a
where mc and ma represent the concentrations of cations and anions in the liquid phase, respectively, and the parameters λ and
ζ are the second- and third-order interaction parameters, respectively. By substituting equation (17) into (14), equation (18) is
obtained:
0
pCO2 ΔG m,CO
2
ln
=
-ln φCO2 + 2 ∑ λCO2 - c mc +
mCO2
RT
c
Fig.3
2 ∑ λCO2 - a ma + 3∑ ∑ ζCO2 - a - c mc ma
a
Solubility of CO2 in aqueous Na2Cr2O7 solutions as a
function of pCO at 323.2 K
(18)
a
When λCO2-Cr2O27- is set to zero in equation (18), one of the λ parameters can be deleted because measurements can only be
made in electronically neutral solutions (mc=2ma). To calculate
the solubility of CO2 in aqueous Na2Cr2O7 solutions, only three
parameters need to be determined, including λCO -Na + , ζCO -Na +-Cr O27and ΔG0m,CO /RT, which are all only dependent upon T. The following equation was selected for these parameters.
f(T)=c1+c2/T+c3lnT
(19)
The ΔG0m,CO /RT term was fitted using the CO2 solubility data
in pure water with an average relative deviation of 3.05%. The
λCO -Na + and ζCO -Na +-Cr O27- terms were then evaluated by fitting equation (18) using the CO2 solubility data in aqueous Na2Cr2O7 solutions with a total average relative deviation of 3.32%. The resulting parameters are presented in Table 5, and the correlation
results are shown in Figs.5-7.
2
The points represent the experimental data. The dotted lines represent the
correlated values derived from the modified Setschenow equation.
n
mNa2Cr2O7/(mol·kg-1): n 0;  0.361;
c
0.650; ▼ 0.901
2
2
2
2
2
2
Fig.4
Solubility of CO2 in aqueous Na2Cr2O7 solutions as
a function of pCO at 333.2 K
5
2
2
2
Discussion
From the data presented in Tables 2-5 and Figs.2-7, it is
The points represent the experimental data. The dotted lines represent the
correlated values derived from the modified Setschenow equation.
n
mNa2Cr2O7/(mol·kg-1): n 0;  0.361;
0.650; ▼ 0.901
l(0)
g(0)
and fugacity coefficient of CO2, respectively. μ CO
(T) and μ CO
(T, p) represent the standard chemical potentials of CO2 in the
ideal liquid phase (mCO2=1 mol·kg-1) and in the ideal gas phase
l(0)
(pCO =1 MPa), respectively. The difference between μ CO
(T, m)
l(0)
0
and μCO (T, p) can be defined as ΔGm,CO .
The fugacity coefficient of CO2 (φCO2) can be expressed as
follows:
∞
∂p
ln φ = 1 ∫ [( )T,V,ni -( RT )]dVi -ln Z
(15)
RT V ∂n
Vi
2
2
2
2
2
2
Table 5 Temperature dependence of several parameters for the
PR-Pitzer equation
0
ΔGm,CO
/RT
2
λCO -Na+/kg-1
2
ζCO -Na+-Cr O /kg-2
2
22 7
c1
2.6899×10
2
-3.1022×10
3
c2
-1.4588×10
4
1.4752×10
5
2.6394×103
-1.2532×105
c3
-3.8626×10
1
4.5788×10
2
-3.8964×102
m
Fig.5
Solubility of CO2 in aqueous Na2Cr2O7 solutions as
a function of pCO2 at 313.2 K
The points represent the experimental data. The dotted lines represent the
correlated values derived from the PR-Pitzer equation.
mNa2Cr2O7/(mol·kg-1): n 0;  0.361;
n
In the current work, the fugacity coefficient of CO2 in the
pure CO2 phase was used as opposed to that of the coefficient
from the gas phase of CO2-H2O. In accordance with the work
reported by Peng and Robison,23 lnφCO2 was derived from the
following equation.
éZ + (1 + 2)Bù
úú
ln φCO2 = Z -1 -ln(Z -B) - A ln êê
(16)
2 2B ë Z + (1 - 2)B û
where A, B, Z are defined as follows:
ap
bp
pV m
A=
,
B=
, Z=
RT
RT
(RT)2
lnγCO2 was derived from equation (17), which was obtained
from Pitzer et al.24-26
0.650; ▼ 0.901
Acta Phys. ⁃Chim. Sin. 2012
2572
Vol.28
Table 6 Reduction amplitude (ηCO ) at Na2Cr2O7 concentrations of
0.1, 0.5, and 1.0 mol·kg-1 and temperatures in the range from
313.2 to 333.2 K
2
T/K
ηCO2
0.1 mol·kg-1
0.5 mol·kg-1
1.0 mol·kg-1
323.2
0.045855
0.20919
0.37462
333.2
0.031109
0.14616
0.27096
313.2
0.043387
0.19891
0.35826
exp(k0)
(21)
exp(k s m s + k0)
It was clear that at certain temperatures the reduction amplitude was only a function of the concentration of Na2Cr2O7. The
reduction amplitude at concentrations of 0.1, 0.5, and 1.0 mol·
kg-1 was calculated at temperatures in the range of 313.2 to
333.2 K. The results are shown in Table 6.
It is clear from Table 6 that the solubility of CO2 in the aqueous Na2Cr2O7 solutions decreased significantly with increasing
Na2Cr2O7 concentration. With this in mind, it is therefore necessary to consider the influence of Na2Cr2O7 on the absorption of
CO2 in the carbonization process.
ηCO2= 1 -
Fig.6
Solubility of CO2 in aqueous Na2Cr2O7 solutions as a
function of pCO at 323.2 K
2
The points represent the experimental data. The dotted lines represent the
correlated values derived from the PR-Pitzer equation.
n
mNa2Cr2O7/(mol·kg-1): n 0;  0.361;
0.650; ▼ 0.901
6
Fig.7
Solubility of CO2 in aqueous Na2Cr2O7 solutions as a
function of pCO at 333.2 K
2
The points represent the experimental data. The dotted lines represent the
correlated values derived from the PR-Pitzer equation.
n
mNa2Cr2O7/(mol·kg-1): n 0;  0.361;
0.650; ▼ 0.901
clear that the amount of CO2 dissolved in the aqueous solutions
studied was proportional to the partial CO2 pressure and decreased with the increase in the salt concentration. The
CO2-H2O-Na2Cr2O7 system therefore obeyed Henryʹs law, and
the phenomenon can be interpreted according to the “salting-out effect”. The deviations of the two thermodynamics
models, including the modified Setschenow and PR-Pitzer
equations, were 4.24% and 3.32%, respectively.
To allow for a quantitative study of the influence of
Na2Cr2O7 on the solubility of CO2, the modified Setschenow
equation was applied to calculate the reduction amplitude of
the CO2 solubility in pure water relative to that of the solubility
in an aqueous Na2Cr2O7 solution at different concentrations and
temperatures. The reduction amplitude (ηCO2) can be defined as
follows:
mCO2 - pure -mCO2 - sol
ηCO2=
(20)
mCO2 - pure
where, mCO -pure and mCO -sol represent the CO2 solubility in pure
water and in aqueous Na2Cr2O7 solutions, respectively.
According to the modified Setschenow equation (9), equation (20) can now be calculated as follows:
2
Conclusions
The solubility of CO2 in aqueous Na2Cr2O7 solutions was
measured in a stirred vapor-liquid equilibrium cell at temperatures and pressures in the ranges from 313.2 to 333.2 K and 0.1
to 1.9 MPa, respectively. Based on the results, three conclusions were made as follows.
(1) The solubility of CO2 in aqueous Na2Cr2O7 solutions
obeys Henryʹs law and the phenomenon can be interpreted according to the“salting-out effect”.
(2) The modified Setschenow and PR-Pitzer equations provided data that were in good agreement with the experimental
data with deviations of 4.24% and 3.32%, respectively.
(3) The Na2Cr2O7 concentration had a significant influence
on the absorption of CO2 and should be taken into consideration during the carbonization process for the manufacture of
sodium chromate.
References
(1)
Shreve, R. N. The Chemical Process Industries; McGraw-Hill:
New York, 1956.
(2)
Cheng, S. W.; Ding, Y.; Yang, C. R. Production Engineering of
Chromium Salts; Chemical Industry Press: Beijing, 1988; p 127.
[成思危, 丁 翼, 杨春荣. 铬盐生产工艺. 北京: 化学工业出版
社, 1988:127.]
(3)
Li, Z. Y. Inorg. Chem. Ind. 2006, 38, 1.
[李兆业. 无机盐工
业, 2006, 38, 1.]
(4)
Li, Z. Y. Inorg. Chem. Ind. 2005, 37, 1. [李兆业. 无机盐工业,
2005, 37, 1.]
2
(5)
Ding, Y. Chem. Ind. Eng. Prog. 2003, 23, 345.
[丁
翼. 化工
进展, 2003, 23, 345.]
(6)
Han, X. Y.; Yu, Z. H.; Qu, J. K.; Qi, T.; Guo, W.; Zhang, G. Q.
No.11
ZHOU En-Nian et al.: Equilibrium Solubility Modeling of CO2 in Na2Cr2O7 Solutions
J. Chem. Eng. Data 2011, 56, 1213. doi: 10.1021/je1011168
(7)
(8)
Ermatchkov, V.; Kamps, A. P. S.; Maurer, G. J. Solut. Chem.
田宜灵. 化工学报, 2006, 57, 2270.]
(17)
Chem. Ind. Eng. 2008, 59, 287. [黄群武, 王一平, 张国建, 韩
Zoghi, A. T.; Feyzi, F.; Zarrinpashneh, S. J. Chem.
立君, 梁 瑛. 化工学报, 2008, 59, 287.]
(18)
Gubkov, N. A.; Fermor, N. A.; Smirnov, N. I. Zh. Prikl. Khim.
(19)
Lide, D. R.; Frederikse, H. P. R. CRC Handbook of Chemistry
(20)
Li, Y. G. Thermodynamics of Metal Solvent Extraction;
Rebolledo-Morales, M. A.; Rebolledo-Libreros, M. E.; Trejo, A.
J. Chem. Thermodynamics 2011, 43, 690. doi: 10.1016/j.jct.
1964, 37, 2204.
and Physics, 76th ed.; CRC Press Inc.: Boca Raton, FL, 1995.
2010.12.008
(10)
Ferrentino, G.; Barletta, D.; Balaban, M. O.; Ferrari, G.; Poletto,
M. J. Supercrit. Fluids 2009, 1, 1.
(11)
Tsinghua University Press: Beijing, 1988. [李以圭. 电解质溶
Kamps, P. S.; Meyer, E.; Rumpf, B.; Maurer, G. J. Chem. Eng.
Data 2007, 52, 817. doi: 10.1021/je060430q
(12)
液理论. 北京: 清华大学出版社, 1988.]
(21)
Gao, J.; Zheng, D. Q.; Guo, T. M. J. Chem. Eng. Data 1997, 42,
69. doi: 10.1021/je960275n
Li, Y. G.; Mather, A. E. Ind. Eng. Chem. Res. 1996, 35, 4804.
doi: 10.1021/ie960244l
(22) Wang, Z. L.; Zhou, Y. P. Physical Chemistry; Higher Education
(13) Wong, C. S.; Tishchenko, P. Y.; Johnson, W. K. J. Chem. Eng.
Press: Beijing, 2003. [王正烈, 周亚平. 物理化学. 北京: 高等
教育出版社, 2003.]
Data 2005, 50, 817. doi: 10.1021/je049716q
(14)
Huang, Q. W.; Wang, Y. P.; Zhang, G. J.; Han, L. J.; Liang, Y. J.
2006, 45, 6081.
Thermodynamics 2012, 44, 66. doi: 10.1016/j.jct.2011.08.011
(9)
2573
Derks, P. W. J. D.; Dijkstra, H. B. S. D.; Hogendoorn, J. A.;
(23)
Peng, D. Y.; Robinson, D. B. Ind. Eng. Chem. 1976, 15, 59.
Versteeg, G. F. Am. Inst. Chem. Eng. J. 2005, 51, 2311. doi:
(24)
Pitzer, K. S. J. Phys. Chem. 1973, 77, 268. doi: 10.1021/
(25)
Pitzer, K. S.; Mayorga, G. J. Phys. Chem. 1973, 77, 2300. doi:
(26)
Pitzer, K. S.; Janice, J. K. J. Am. Chem. Soc. 1974, 96, 5701.
10.1002/(ISSN)1547-5905
j100621a026
(15)
Dong, L. H.; Chen, J.; Gao, G. H. J. Chem. Eng. Data 2010, 55,
(16)
Zhu, R. J.; Yu, J. L.; Xu, W.; Liu, Z. H.; Tian, Y. L. J. Chem.
1030. doi: 10.1021/je900492a
Ind. Eng. 2006, 57, 2270. [朱荣娇, 于景琳, 徐
10.1021/j100638a009
伟, 刘志华,
doi: 10.1021/ja00825a004