sei-100107031thermochemistry study on the extraction of co(ii) and ni(ii) with cyanex 272 in...

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THERMOCHEMISTRY STUDY ON THE EXTRACTION OF

Co(II) AND Ni(II) WITH CYANEX 272 IN KEROSENE*

X. Yua

, G. Gub

, X. Fuc

, B. Sub

& H. Zhanga

aDept. of Chemistry, Qufu Normal University, Qufu, 273165, China

bQingdao Institute of Chem. Tech., Qingdao, 266042, P. R. China

cQingdao Institute of Chem. Tech., Qingdao, 266042, P. R. China

Version of record first published: 15 Feb 2007.

To cite this article: X. Yu , G. Gu , X. Fu , B. Su & H. Zhang (2001): THERMOCHEMISTRY STUDY ON THE EXTRACTION OF

Co(II) AND Ni(II) WITH CYANEX 272 IN KEROSENE*, Solvent Extraction and Ion Exchange, 19:5, 939-943

To link to this article: http://dx.doi.org/10.1081/SEI-100107031

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RESEARCH NOTE

THERMOCHEMISTRY STUDY ON

THE EXTRACTION OF Co(II) AND Ni(II)WITH CYANEX 272 IN KEROSENE*

X. Yu,1

G. Gu,2

X. Fu,2,{

B. Su,2

and H. Zhang1

1Dept. of Chemistry, Qufu Normal University,

Qufu 273165, China2

Qingdao Institute of Chem. Tech., Qingdao 266042,

P. R. China

ABSTRACT

The extraction of Co(II) and Ni(II) from sulfate solution with

Cyanex 272 in kerosene has been studied by titration microcal-

orimetry. The heats produced in the reaction processes were

determined by the powertime curves and the DrHym values

at 298 K were identified. The extraction equilibrium constants

and thermodynamic functions at different temperatures were

calculated.

Key Words: Microcalorimetry; Extraction; Reaction heat;

Cyanex 272; Co(II); Ni(II).

SOLVENT EXTRACTION AND ION EXCHANGE, 19(5), 939943 (2001)

939

Copyright# 2001 by Marcel Dekker, Inc. www.dekker.com

This study is supported by the National Natural Science Foundation of China (29971020)

and the Natural Science Foundation of Shandong Province (L2000B01).

{Corresponding author.


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INTRODUCTION

The 2277 thermal activity monitor (Sweden) has been widely used in the

measurement of the heat effect in chemical and biochemical systems (1,2).

This instrument is very sensitive. Its detection limit is 0.15mW and the

baseline stability over a period of 24 h is 0.2mW. It can be maintained at a

given temperature in the range of 10$ 80C, for example 298 K, very

accurately.

In a previous paper (3) we studied the extraction of Co(II) and Ni(II) from

sulfate solution with Cyanex 272 in kerosene. The extraction reactions were

determined as

Co2

a 2H

2A

2o CoA

2 2HA

o 2H

a1

Ni2a 3H2A2o NiA2 4HAo 2Ha 2

With the obtained equilibrium constants at different temperatures of 298, 308,

318 and 313 K, respectively, their reaction heats were calculated from the slope of

logK vs. 1/T to be

DrHy

mCo 51:18 kJ=mol 3

and

DrHymNi 9:58 kJ=mol 4

In this paper, the titration microcalorimetry has been used to measure thereaction heats again for above processes under the same experimental

conditions. Using the newly obtained more accurate data of reaction heats

and the reported equilibrium constants at 298 K (logK(Co), 2987.58 and

logK(Ni), 2989.72) from reference (3), we calculated the extraction

equilibrium constants and thermodynamic functions (DrGym and DrS

ym) at

different temperatures.

EXPERIMENTAL

Materials

Solution 1: 0.0100 mol/L CoSO4, 0.2 mol/L Na2SO4, pH 4.35 (at equilibrium);

Solution 2: 0.0100 mol/L NiSO4, 0.2 mol/L Na2SO4, pH 5.50 (at equilibrium);

Solution 3: 0.350 mol/L Cyanex272 in kerosene (based on the monomer).

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Equipment and Method

The 2277 thermal activity monitor contains 23 liters of isothermally

thermostatic water, which can hold up to 4 independent calorimetric units. 4 ml

stainless steel perfusion/titration ampoules are inserted in the thermostats. The

perfusion/titration units come with two stirrer shafts, a hollow one for perfusion

and the other plugged for titration. They are equipped with a stirrer and a stirrer

motor to rotate the shaft at desired speed (usually between 60$ 120rpm). A kalf

turbine is used for a 4 ml system to be filled with 2.5$ 3 ml solution.

In the experiment, two 4 ml ampoule-units were used. One of them

contained the reaction sample and the other the reference solution. The sample

normally occupied position A and the reference occupied position B in the

monitor.

The solutions of the extraction system were: 1.5 ml solution 1 or 2 and

1.5 ml solution 3, the reference contained 1.5 ml solution 1 or 2 and 1.5 ml

kerosene.

All measurements were carried out at 298 K and the amplifier of the

monitor was set at 100mW. Before the monitor began to record the powertime

curve, the stirrer shaft was set at the desired speed of 120 rpm.

RESULTS AND DISCUSSION

The powertime curves reflect the solvent extraction process and the area

under the curve represents the reaction heat. The powertime curves of the

extraction of cobalt and nickel with Cyanex 272 in kerosene have been

determined at 298 K, see Figures 1 and 2 respectively. Based on the data of pt and

t in the curves, the reaction heats Q were obtained from three experiments. Then

the reaction enthalpy changes were calculated by DrHymQ/n, where n

represented the reacted amounts of metal ions at equilibrium. The values of n

were calculated from logKex reported in reference (3). Both the reactions are

exothermic reaction as

for reaction (1), DrHymCo 53:60:43 kJ=mol;

for reaction (2), DrHymNi 10:00:13 kJ=mol;

Comparing them with the data of the reaction enthalpy changes at the same

experimental conditions reported in reference (3), we can see that the data

obtained by the two methods are very near. The relative errors of the results in

reference (3) are 4.51% and 4.20% for cobalt and nickel respectively, if thenew data are considered to be more accurate.

Based on the determined enthalpy changes here and the extraction

equilibrium constants reported in reference (3) at 298 K, we can calculate the

CYANEX 272 941
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thermodynamic functions (DrGym, DrSym) and the equilibrium constants at

different temperatures with GibbsHelmholtz equation, DrGymRTlnK

y and

DrGymDrH

ym7TDrS

ym, when DCp% 0 over the range of studied temperatures

was regularly assumed. The obtained data are listed on the left side of Table 1 (for

extraction of cobalt) and Table 2 (for extraction of nickel) respectively. The right

side of both the tables shows the data reported in reference (3) for comparison.

Table 1. Equilibrium Constants and Thermodynamic Functions at Different Tempera-

tures for the Extraction of Cobalt, Reaction (1)

Data of This Paper

(Microcalorimetric Method)

Data from Reference (3)

(Equilibrium Method)

T/K

DrHym

kJ/mol

DrSy

m

J/K.mol

DrGy

m

kJ/mol logKyDrH

ym

kJ/mol

DrSy

m

J/K.mol

DrGy

m

kJ/mol logKy

293 43.5 7.75

298 53.6 34.6 43.3 7.58* 51.18 26.6 43.3 7.58

303 43.1 7.43

308 42.9 7.28 27.2 42.8 7.26

313 42.8 7.16

318 42.6 7.00 26.7 42.7 7.01

333 42.1 6.60 26.5 42.3 6.63

* Taken from (3).

Table 2. Equilibrium Constants and Thermodynamics Functions at Different Tempera-

tures for the Extraction of Nickel, Reaction (2)

Data of This Paper

(Microcalorimetric Method)

Data from Reference [3]

(Equilibrium Method)

T/K

DrHy

m

kJ/mol

DrSy

m

J/Kmol

DrGy

m

kJ/mol logKyDrH

y

m

kJ/mol

DrSy

m

J/Kmol

DrGy

m

kJ/mol logKy

293 54.8 9.77

298 10.0 153 55.5 9.72 9.58 154 55.5 9.72

303 56.4 9.72

308 57.1 9.68 153 56.7 9.61

313 57.9 9.66318 58.7 9.64 154 58.4 9.60

333 60.9 9.55 154 60.8 9.53

* Taken from (3).

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The uncertainty of enthalpies determined by calorimetry comes mainly

from the data of log Kex but not from the heat measurement. The heats measured

here are accurate to within 1.3%. The error propagations ofDrGym andDrS

ym are

also from the uncertainty of log Kex taken from reference (3) where the original

distribution data are not available. The comparison indicates that the two series

data are very similar and that the results obtained by the two methods can be

confirmed. The higher value of DrGym and the negative entropy make the

extraction of nickel more difficult.

CONCLUSION

The microcalorimetric method can also be used in the measurement of

reaction heat for two-phase extraction systems. Combining the equilibrium

constant, one can get much information about the thermodynamic functions.

These data are very useful in studies of the thermokinetic properties of solvent

extraction (4).

REFERENCES

1. Lu, C.; Yu, X.; Zhang, H. Determination of the reaction heat and studies of

thermodynamic functions Hydrolytic polymerization of chromium(III) at

relatively high concentrations by microcalorimetry. J. of Thermal Analysis

1997, 48, 327.

2. Zhang, H.; Sun, H.; Liu, Y.; Nan, Z.; Xu, L.; Shan, Q.; Su, X.; Zhang, G.Determination of power-time curves of bacterial growth and study of

optimum allowable concentration of a synthetic medicine. J. of Thermal

Analysis 1995, 45, 87.

3. Fu, X.; Golding, J.A. Solvent extraction of cobalt and nickel in bis(2,4,4-

trimethylpentyl) phosphinic acid, Cyanex 272. Solvent Extraction and Ion

Exchange 1987, 5 (2), 205.

4. Zhang, H.; Sun, S. Determination of reaction heat and thermokinetic study

on the extraction of Co(II) with HEH[EHP] in kerosene from sulfate

solution. Chinese J. of Appl. Chem. 2000, 17 (6), 666.

Received January 5, 2001

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