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Polyurethane foam of the polyether type as a solid polymeric extractant for cobalt and iron from thiocyanate media
Anotytico ~Elsevicr
Chimica Acta. 98 (1978) 133-136 Scientific Publishing Company, Amsterdam
-
Printed
in The Netherlands
Short Communication
POLYURETHANE FOAhl OF THE POLYETI-IER TYPE AS A SOLID POLY&iERIC EXTRACTANT FOR COBALT AND IRON FROM THIOCYANATE MEDIA
T. BRAUN*
and A. B. FARAGB
Institute of Inorganic and Analyticcl I443 Budapest (Hungary) (Received
2nd November
Chemistry,
L. Eiituiis
University.
P.O. Box
Z 23,
1977)
Polyurethane foam immobilizing 1-(2-pyridylazo)-2-naphthol (PAN) has been used for the separation and preconcentration of trace elements [ 11. During that study, it was noticed that unloaded polyurethane foam of the polyether type can estract cobalt from aqueous thiocyanate solutions. Several investigators [2-81 have used untreated polyurethane foam for the absorption and recovery of several inorganic and organic compounds from aqueous solution. However, Gesser et al. [9] were the first to report that openccll polyurethane foam of the polyether type is a convenient solid substitute for liquid ethyl ether in extraction systems; they investigated the separation of gallium and iron from aluminium in acid chloride solutions. The present work gives further proof that open-cell polyethar-type polyurethane foam can act as a solid ether solvent which extracts the thiocyanate complexes of cobalt and iron from aqueous liquid phases. Experimental Reagent and materials. All reagents used were of standard analytical purity except where otherwise mentioned. Polyurethane foam, a polyether of open cell type (Greiner K.G. Schaumstoffwerk-Kremsmiinster, Austria) and an open-cell polyester polyurethane foam (PPI-800 nFR; Eurofoam, Damstraat, 92000 Wetteren) were compared. These foams were cut, washed and dried as previously described [ 11. Stock cobalt(I1) and iron(II1) solutions were prepared from analyticalgrade cobalt(I1) chloride and iron(II1) chloride, respectively. All solutions were standardized by conventional methods [lo]. Solutions containing micrograa amounts of cobalt and iron were prepared daily by diluting the stock solutions. All cobalt and iron solutions were then spiked with cobalt-58 and iron-59, respectively. --__ 5 Permanent address: Chemistry Department, Faculty of Science, Marxoun University. Mansoura,
Egypt.
134
Column preparation. Glass columns of 2%mm diameter and 12-cm were used; 5 g of the dried unloaded foam was packed in the column, previously described [II], to produce a 5-cm bed height. Instrumentation. For activity measurements, a NaI(TI) well crystal ener,gy-selective counting device (type NK-i07/B; Gamma, Budapest) employed.
length as and an were
Results and discussion In acidic media, cobalt(I1)
and iron(II1) form, respectively, blue and red thiocyanati complexes, which are readily extracted with diethyl ether [ 121. In the present investigation, the extraction of these complexes was tested in both batch and column experiments. Fiats of extraction of cobalt and iron from thiocyanate media. Ln separate experiments, 0.1 g of polyurethane foam (polyether type) was mixed with 10 ml of aqueous acidic (0.1 N HCl or H+O,) 0.5 M thiocyanate solution containing 2 Hg of cobalt or iron in a loo-ml stoppered flask. The flasks were shaken mech*anically for l-f30 min. After each shaking period, the radioactivity of 2 ml of the aqueous solution was measured and the concentration of cobalt or iron was determined. The amount of metal ion extracted on the foam was then calculated by difference. As can be seen from Fig. 1, the rate of extraction of cobalt is slightly higher than that of iron, but both extraction rates are quite fast. These results suggested the possibility of using unloaded polyurethane foam of the poiyether type in column operations for the collection of trace amounts of these metal ions from aqueous thiocyanate media at reasonable flow-rates. Cobalt and iron were not extracted at all from acidic thiocyanate solutions on polyurethane foam of the polyester type. This proves that the high
23i I
_ -..
L0
-70
~_.~~~._.~~~ 20
50 Tee.
Fig. 1. Rate of extraction (a) Cobalt. (b) iron.
rC)
5c
60
rn.r.
of cobalt
and iron from
0.3 &I acidic
thiocyanate
solution.
135
efficiency of extraction with the polyether-type foam is mainly due to absorption by the polyether, i.e., the thiocyanate complexes dissolve in the polyether instead of being adsorbed on its surface. The relatively high absorption capacity found [9] in the extraction of gallium from aqueous hydrochloric acid solution onto the polyethcr foam also confirms such a mechanism. Similar results have been obtained for the extraction of gold from aqueous cyanide media on unloaded polyurethane foam of polyether type U31. Effect of flow-rate on the extraction efficiency for cobalt and iron. Cobalt or iron (2 pg) in 20 ml of 0.2 M or 0.5 IL1potassium thiocyanate solution, respectively (0.1 N in HCl or HzS04) were allo;ved to pass through the polycther TABLE
1
Effect of Bow-rate on the extraction of 2 pg of cobalt or iron from 0.2 M or 0.5 M thiocyanate solutions, respectively, on unloaded polyethcr foam columns ---.-._ Relative accuracy of the mean (a)
Standard deviation
Flow-rate (ml min-’ )
Average metal ion extracted on foam” (_t-,E) -~
10
99.6b 99.2c
4.4 4.8
0.23 0.36
20
99.Tb 99.5C
- .0.3 -0.5
0.23 0.36
40
99.6b 99.6C
-0.4 -0.4
0.24 0.47
‘LAverage of 5 determinations. TABLE
bCobalt.
Amount of metal ion kg) --
2.0 20.0 200.0
‘Iron.
2
Collection of various concentrations solutions, respectively, on unloaded
0.2
(s)
of cobalt or iron from 0.2 hI or 0.5 M thiocyanate polycther foam columns at flow-rates of 20 ml min-’
Average metal ion extracted on foam” (.?, rb) 99.7b 99.-I= 99 7b 99:5c 99.6h 99:IC 99.5u 99.P
=_4verage of 5 determinations.
Relative accuracy of the mean (a) -0.3 -0.6 -0.3 --0.5 -0.5 4.6 -0.5 +I.7
bCobalt.
Qon.
Standard deviation (s) 0.23 0.30 0.24 0.30 0.22 0.33 0.21 0.38
136 TABLE
3
Premnmntration of 1 ug of cobalt at flow-rates of 30 ml mm-* Metal ion
Average metal ion extracted on foama (5,5)
Cobalt Iron
95.9 96.1
‘Avenge
or iron per litre on
Relative accuracy of the mean (%)
-4.1 -3.9
unloaded polyether foam columns
Standard deviation (s)
Confidence f? isI& t = 0.95
0.85 0.67
95.9 z 0.8 96.1 s 0.6
limit
of five determinations.
polyurethane foam column at various flow-rates (IO-40 ml min-‘). The extraction efficiency was high (Table 1); more or less complete extraction was obtained even at flow-rates of 40 ml min -I. For iron, 0.5 M thiocyanate solution was used, because iron was not completely extracted at lower thiocyanate concentrations. Collection respectiuely.
of cobalt or iron from 0.2 M or 0.5 M thiocyarmte wiutions, Coil ection of various concentrations of cobalt and iron from
acidic thiocyanate solutions on the unloaded polyether foam columns was examined at now-rates of 20 ml min-I. Complete recoveries of cobalt and iron were obtained at concentrations of 0.2-200 pg (Table 2). Again, these results show the high capacity of the foam material for these thiocyanate complexes. The preconcentration of 1 pg of cobalt or iron from 1 1 of aqueous thiocyanate solutions was also tested. Satisfactory results were obtained (Table 3) at flow-rates of 30 ml min-‘. REFERENCES 1 2 3 4 5 6 7 8 9 10 11 12 13
T. Bmun, A. B. Farag and %I. P. Maloney, Anal. Chim. Acb, 93 (1977) 191. H. J. !bI. Bowen, J. Chem. Sot. A, (1970) 1082. H. J. M. Bowcn, Radiochem. Radioanal. Lett., 7 (1971) 71. P. Schiller and G. B. Cook, Anal. Chim. Acta, 54 (1971) 364. H. D. Gcsscr, .2. Chow, F. C. Davis, J. F. Uthc and J. Beinke, Anal. Lett., 4 (1971) 883. T. Braun and A. B. Farag. /ural. Chim. Acta, 66 (1973) 419. H. D. Gesser, A. B. SparIing. A. Chow and C. W. Turner, J. Am. Water Works Assoc., 65 (1973) 220. S. Sukirnan, Radiochem. Radioanal. Lett., 18 (1974) 129. H. D. Gesscr, E. Bock, W. C. Baldwin and A. Chow, Sep. Sci., 11 (1976) 317. A. I. Vogel. Quantitative Inorg*nic Analysis, tingmans, London, 3rd edn., 1961. T. Braun and A. B. Farsg, Anal. Chim. Acta, 61 (1972) 265. A. K. De, S. M. Khopkar and R. A. Chalmers, Solvent Extraction of Metals, Van Nostrand-Reinhold. London. 1970. T. Braun and A. B. Farag. unpublished work.
Chimica Acta. 98 (1978) 133-136 Scientific Publishing Company, Amsterdam
-
Printed
in The Netherlands
Short Communication
POLYURETHANE FOAhl OF THE POLYETI-IER TYPE AS A SOLID POLY&iERIC EXTRACTANT FOR COBALT AND IRON FROM THIOCYANATE MEDIA
T. BRAUN*
and A. B. FARAGB
Institute of Inorganic and Analyticcl I443 Budapest (Hungary) (Received
2nd November
Chemistry,
L. Eiituiis
University.
P.O. Box
Z 23,
1977)
Polyurethane foam immobilizing 1-(2-pyridylazo)-2-naphthol (PAN) has been used for the separation and preconcentration of trace elements [ 11. During that study, it was noticed that unloaded polyurethane foam of the polyether type can estract cobalt from aqueous thiocyanate solutions. Several investigators [2-81 have used untreated polyurethane foam for the absorption and recovery of several inorganic and organic compounds from aqueous solution. However, Gesser et al. [9] were the first to report that openccll polyurethane foam of the polyether type is a convenient solid substitute for liquid ethyl ether in extraction systems; they investigated the separation of gallium and iron from aluminium in acid chloride solutions. The present work gives further proof that open-cell polyethar-type polyurethane foam can act as a solid ether solvent which extracts the thiocyanate complexes of cobalt and iron from aqueous liquid phases. Experimental Reagent and materials. All reagents used were of standard analytical purity except where otherwise mentioned. Polyurethane foam, a polyether of open cell type (Greiner K.G. Schaumstoffwerk-Kremsmiinster, Austria) and an open-cell polyester polyurethane foam (PPI-800 nFR; Eurofoam, Damstraat, 92000 Wetteren) were compared. These foams were cut, washed and dried as previously described [ 11. Stock cobalt(I1) and iron(II1) solutions were prepared from analyticalgrade cobalt(I1) chloride and iron(II1) chloride, respectively. All solutions were standardized by conventional methods [lo]. Solutions containing micrograa amounts of cobalt and iron were prepared daily by diluting the stock solutions. All cobalt and iron solutions were then spiked with cobalt-58 and iron-59, respectively. --__ 5 Permanent address: Chemistry Department, Faculty of Science, Marxoun University. Mansoura,
Egypt.
134
Column preparation. Glass columns of 2%mm diameter and 12-cm were used; 5 g of the dried unloaded foam was packed in the column, previously described [II], to produce a 5-cm bed height. Instrumentation. For activity measurements, a NaI(TI) well crystal ener,gy-selective counting device (type NK-i07/B; Gamma, Budapest) employed.
length as and an were
Results and discussion In acidic media, cobalt(I1)
and iron(II1) form, respectively, blue and red thiocyanati complexes, which are readily extracted with diethyl ether [ 121. In the present investigation, the extraction of these complexes was tested in both batch and column experiments. Fiats of extraction of cobalt and iron from thiocyanate media. Ln separate experiments, 0.1 g of polyurethane foam (polyether type) was mixed with 10 ml of aqueous acidic (0.1 N HCl or H+O,) 0.5 M thiocyanate solution containing 2 Hg of cobalt or iron in a loo-ml stoppered flask. The flasks were shaken mech*anically for l-f30 min. After each shaking period, the radioactivity of 2 ml of the aqueous solution was measured and the concentration of cobalt or iron was determined. The amount of metal ion extracted on the foam was then calculated by difference. As can be seen from Fig. 1, the rate of extraction of cobalt is slightly higher than that of iron, but both extraction rates are quite fast. These results suggested the possibility of using unloaded polyurethane foam of the poiyether type in column operations for the collection of trace amounts of these metal ions from aqueous thiocyanate media at reasonable flow-rates. Cobalt and iron were not extracted at all from acidic thiocyanate solutions on polyurethane foam of the polyester type. This proves that the high
23i I
_ -..
L0
-70
~_.~~~._.~~~ 20
50 Tee.
Fig. 1. Rate of extraction (a) Cobalt. (b) iron.
rC)
5c
60
rn.r.
of cobalt
and iron from
0.3 &I acidic
thiocyanate
solution.
135
efficiency of extraction with the polyether-type foam is mainly due to absorption by the polyether, i.e., the thiocyanate complexes dissolve in the polyether instead of being adsorbed on its surface. The relatively high absorption capacity found [9] in the extraction of gallium from aqueous hydrochloric acid solution onto the polyethcr foam also confirms such a mechanism. Similar results have been obtained for the extraction of gold from aqueous cyanide media on unloaded polyurethane foam of polyether type U31. Effect of flow-rate on the extraction efficiency for cobalt and iron. Cobalt or iron (2 pg) in 20 ml of 0.2 M or 0.5 IL1potassium thiocyanate solution, respectively (0.1 N in HCl or HzS04) were allo;ved to pass through the polycther TABLE
1
Effect of Bow-rate on the extraction of 2 pg of cobalt or iron from 0.2 M or 0.5 M thiocyanate solutions, respectively, on unloaded polyethcr foam columns ---.-._ Relative accuracy of the mean (a)
Standard deviation
Flow-rate (ml min-’ )
Average metal ion extracted on foam” (_t-,E) -~
10
99.6b 99.2c
4.4 4.8
0.23 0.36
20
99.Tb 99.5C
- .0.3 -0.5
0.23 0.36
40
99.6b 99.6C
-0.4 -0.4
0.24 0.47
‘LAverage of 5 determinations. TABLE
bCobalt.
Amount of metal ion kg) --
2.0 20.0 200.0
‘Iron.
2
Collection of various concentrations solutions, respectively, on unloaded
0.2
(s)
of cobalt or iron from 0.2 hI or 0.5 M thiocyanate polycther foam columns at flow-rates of 20 ml min-’
Average metal ion extracted on foam” (.?, rb) 99.7b 99.-I= 99 7b 99:5c 99.6h 99:IC 99.5u 99.P
=_4verage of 5 determinations.
Relative accuracy of the mean (a) -0.3 -0.6 -0.3 --0.5 -0.5 4.6 -0.5 +I.7
bCobalt.
Qon.
Standard deviation (s) 0.23 0.30 0.24 0.30 0.22 0.33 0.21 0.38
136 TABLE
3
Premnmntration of 1 ug of cobalt at flow-rates of 30 ml mm-* Metal ion
Average metal ion extracted on foama (5,5)
Cobalt Iron
95.9 96.1
‘Avenge
or iron per litre on
Relative accuracy of the mean (%)
-4.1 -3.9
unloaded polyether foam columns
Standard deviation (s)
Confidence f? isI& t = 0.95
0.85 0.67
95.9 z 0.8 96.1 s 0.6
limit
of five determinations.
polyurethane foam column at various flow-rates (IO-40 ml min-‘). The extraction efficiency was high (Table 1); more or less complete extraction was obtained even at flow-rates of 40 ml min -I. For iron, 0.5 M thiocyanate solution was used, because iron was not completely extracted at lower thiocyanate concentrations. Collection respectiuely.
of cobalt or iron from 0.2 M or 0.5 M thiocyarmte wiutions, Coil ection of various concentrations of cobalt and iron from
acidic thiocyanate solutions on the unloaded polyether foam columns was examined at now-rates of 20 ml min-I. Complete recoveries of cobalt and iron were obtained at concentrations of 0.2-200 pg (Table 2). Again, these results show the high capacity of the foam material for these thiocyanate complexes. The preconcentration of 1 pg of cobalt or iron from 1 1 of aqueous thiocyanate solutions was also tested. Satisfactory results were obtained (Table 3) at flow-rates of 30 ml min-‘. REFERENCES 1 2 3 4 5 6 7 8 9 10 11 12 13
T. Bmun, A. B. Farag and %I. P. Maloney, Anal. Chim. Acb, 93 (1977) 191. H. J. !bI. Bowen, J. Chem. Sot. A, (1970) 1082. H. J. M. Bowcn, Radiochem. Radioanal. Lett., 7 (1971) 71. P. Schiller and G. B. Cook, Anal. Chim. Acta, 54 (1971) 364. H. D. Gcsscr, .2. Chow, F. C. Davis, J. F. Uthc and J. Beinke, Anal. Lett., 4 (1971) 883. T. Braun and A. B. Farag. /ural. Chim. Acta, 66 (1973) 419. H. D. Gesser, A. B. SparIing. A. Chow and C. W. Turner, J. Am. Water Works Assoc., 65 (1973) 220. S. Sukirnan, Radiochem. Radioanal. Lett., 18 (1974) 129. H. D. Gesscr, E. Bock, W. C. Baldwin and A. Chow, Sep. Sci., 11 (1976) 317. A. I. Vogel. Quantitative Inorg*nic Analysis, tingmans, London, 3rd edn., 1961. T. Braun and A. B. Farsg, Anal. Chim. Acta, 61 (1972) 265. A. K. De, S. M. Khopkar and R. A. Chalmers, Solvent Extraction of Metals, Van Nostrand-Reinhold. London. 1970. T. Braun and A. B. Farag. unpublished work.