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Selective extraction of thallium with N-benzylaniline in chloroform from hydrobromic acid media
.
470
SHORT
:$_::Elscvicr Scicntik
Publishing Company,
rlrltrlj*tictr Chirniccr Acta. 65 ( 1974) 470472 Amsterdam - Printed in The Nethcrlunds
COMMUNICATION
Selective extraction acid media
of thallium
with N-benzylaniline
in chloroform
from hydrobromic
M. M. L. KHOSLA De~errcc Ltrhorcrtory.
J~tlhp;~r
(
Itldirc)
S. I’. RAO
Urliwrsir~ oJ’ Jdhp~r. (Reccivcd
Jodilptrr
( Imlitr)
4th April 1973)
Many solvent extraction methods for thallium have been reported in the literature. Thallium(II1) can be extracted from l-6 M hydrochloric acid’ or from into diethyl ether, but extraction from 1 M hydro0.1-6 hg hydrobromic acidt4 bromic acid containing some free bromine is usually preferred. At this acidity, gold is extracted nearly completely but gallium and iron( III) are not extracted; elements such as copper, cadmium, cobalt and nickel, can be removed from the ether layer by scrubbing with 1 M hydrobromic acid, but arsenic(III), mercury( II) and tin(I1, IV) are co-extracted in appreciable quantities. Thallium(I) can be extracted from ammoniacal citrate-cyanide medium by dithizone’.” into chloroform; indium, bismuth, tin(I1) and lead accompany thallium. Many other rather inselective reagents can also be used for the extraction of thallium, including 8-hydroxyquinoIine’*s, acetylacetone’, thenoy1trifluoroacetone7S’o, Nbenzyl-N-phenylhydroxylamine’ *, tri-n-butylphosphate’ 2, diethyldithiocarbamate’ 3, and high molelcular-weight amines14. It has already been shown l5 that thallium can be separated from indium(II1) by extraction with N-benzylaniline in chloroform froni 2 M hydrobromic acid. The present communication describes a fuller study of this extraction. Thallium(II1) is readily and quantitatively extracted with N-benzylaniline from 0.1-6 M hydrobromic acid media, but the extraction is most selective from 2 M hydrobromic acid, and the phase separation is then rapid. Thallium(II1) is easily stripped from the organic phase with acetate-acetic acid buffer and can be determined by.adding a slight excess of EDTA and back-titration with thorium nitrate solution to xylenol orange indicator. Few cations interfere. Experitnett tal Reagerlts. Analytical-grade reagents were used without purification. All standard solutions were prepared in twice-distilled water. Thalliuttt(IIi) solution. A 0.05 M solution was prepared by dissolving 6.66 g of thallium( I) nitrate (B.D.H. Ltd.) in a minimal quantity of water, followed by threefold evaporation to dryness with 50 ml, 25 ml and 25 ml of aqua regia. Finally the
SHORT
COMMUNICATION
TABLE
I
PERMISSIBLE
Wdll) Pd( II) Pt( IV) Rh(II1) Cu(I1) Cd(H) Bi( III) Pb(I1) Sb( 111) Sn( IV) As( III) As( V) Co(l1) Ni( II) Zn(II) Mn(I1) Fc( III) Al( III) Ga(II1) In( III) Bc( II)
NW) Ta( V)
AMOUNTS
471
OF
50 10 10 30 30 26 30 30 3oh 100 3.5 35 58 5x 30 30 3W 100 100 100 30 14h 14”
u Reduction with sodium sulphite water. h In the prcscncc of tartratc.
VARIOUS
IONS
Mo( VI) WVI) V(V) Cr( VI) Ti( IV) Cc( IV) U(V1) Th( IV) Zr( IV) Sc( III) Y( III) Sc( IV) Tc( IV) Cn( II) Sr( II) Mg(II) Phosphate Tartrate Citrate Nitrate Chloride Sulphate Arscnutc Borate and
prcfcrentinl
IN THE
EXTRACTION
OF THALLIUM(III)
50 lob 3W 30” 3W 50” 60 35 30 25 30 30 30 100 100 100 2000 1000 1000 1000
1000 500 50 100 oxidation
of thallium(l)
with
snturatcd
bromine
residue was taken up in 120 ml of( 1 + 1) nitric acid and the solution was diluted to 500 ml. The solution was standardized as the chromate. after reduction with sulphur dioxide.More dilute solutions were prepared by accurate dilution. N-Benzylaniline and thorium( IV) solutions were prepared as described previously”. Getzerd procetlwe. To an aliquot of solution containing up to 80 mg of thallium, add sufficient saturated bromide water to oxidize thallium(I) to thallium(II1): a yellow colour should persist. Boil off excess of bromine (colourless solution). Add enough 40”/, hydrobromic acid (E. Merck) and water to give 2 M acid in a volume of 20 ml. Shake the solution for 1 min with 10 ml of.extractant mixture containing 5 ml of N-benzylaniline solution and 5 ml of chloroform. Swirl the separating funnel slightly and separate the chloroform layer. Re-extract the aqueous layer with 10 ml of the extractant mixture. Scrub the combined organic phases with 15 ml of 4.5 M hydrobromic acid to remove any co-extracted elements. Strip the thallium(II1) from the organic phase by shaking for 1 min with two 35-ml portions of the 0.2 M acetate-acetic acid buffer solution, pH 4.5. Transfer the aqueous backextract to a 250-ml conical flask. Add sufficient 0.01 M EDTA, and 7 drops of 0.1x, (w/v) xylenol orange indicator. and back-titrate the excess of
472
SHORT
COMMUNICATION
EDTA with 0.01 M thorium nitrate solution to the colour change from yellow to red-violet. I~~te@~zce of clioe~~e iorzs. Thallium(lII) could be selectively and quantitatively separated from most of the cations tested (Table 1). Bismuth, cadmium, lead and indium were partially extracted, but could be eliminated by scrubbing the organic phase with 4.5 M hydrobromic acid. Mercury( II) was co-extracted with thallium(III), but did not interfere in the recommended titration of thallium(II1). This element could be completely separated from tl~allium(lIl) by twice scrubbing the organic phase with 4.5 M hydrobromic acid, but the recovery of thallium decreased to 95%. Vanadium(V), iron( III), chromium( VI), titanium( IV) and cerium(IV) hindered the extraction of thallium. but did not interfere after reduction with sodium sulphite in diluteacid: the solution was boiled to remove sulphur dioxide, and thallium(l) was then selectively oxidized to thallium(Il1) by gradual addition ‘of saturated bromine water to the hot solution until the precipitate of thallium(I) salt completely dissolved. Palladium(I1) was partially extracted but remained in the organic phase. Antimony(V). niobium(V) and tantalum(V) could be kept in solution with tartaric acid. Common anions such as phosphate, citrate, tartrate, borate, nitrate, chloride, arsenate and sulphate did not interfere.
The concentration of hydrobromic acid was varied from 0.1 M to 6 M while the concentration of thallium(II1) and the extractant were kept constant. The ratio of the aqueous to organic phase was 2.0. Tl~allium(lIl) was quantitatively extracted from 0.1-6 M hydrobromic acid. The. extraction of different amounts of thallium(II1) in the range up to 80 mg with a lixed quantity of the extractant as in the General procedure was quantitative, whereas the extraction of 100 mg of thallium with the same quantity of the extractant was 94%. REFERENCES 1 D. I. Ryabchikov. Ac-ru Chirr~. nctrtl. Sci. Htrrry.. 32 (1962) 193. 2 H. M. N. H. Irving and F. J. C. Rossotti, A~~trlysr. 77 (1952) X01. 3 I. Wadi: and R. Ishi: Bltll. IIISC. P/I~s. Chetr~. Rc.s. ( Tokyo), I3 ( 1934) 262: Sci. Ptrp. III.SI. I’h~s. Rex (Tokyo), 34 ( 1937138) 787. 4 R. Bock, H. Kuschc and E. Bock. Z. ,411crl. C/~c~rjt.. 13X (1953) 167. 5 J. Minczewski. E. Wcitcsku nnd 2. Marczcnko. C/IC~,IL Allo/. ( Wwscw). 6 ( 1961) 5 15. 6 C. W. Sill and H. E. Pctcrson. Ar~c~l. Cltor~.. 21 ( 1949) 1268. 7 V. V. Bngrccv and Yu. A. Zolotov. Z. Arrtrl. Khirn., 17 (1962) 852: I8 ( 1963) 425. 8 R. M. DugnaIl und S. K. Hxsanuddin. Tdcrnrcc. 15 (1968) 1025. 9 J. Stay and E. Hladky, nrlrtl. Clri~rt. nclcc, 28 ( 1963) 227. IO F. Hagcmann. J. Amc~,‘. Clzcrn. Sot.. 72 ( 1950) 768. I 1 S. J. Lyle and A. D. Shcndrikar, Amtl. Cluing. rlcrcc. 32 ( 1965) 575. 12 A. K. De and A. K. Scn. Ttrlonrcc. I4 (1967) 629. I3 H. Bode and F. Ncumun. Z. A&. Clroa, 172 (1960) I. 14 T. Suzuki and T. Satobaynshi. Jap. AIM/.. 14 (1965) 414. 15 M. M. L. Khosla and S. P. Ruo. rltxrl. Chittl. /Ic*ltr. 58 (1972) 3X9.
Cheo~.
470
SHORT
:$_::Elscvicr Scicntik
Publishing Company,
rlrltrlj*tictr Chirniccr Acta. 65 ( 1974) 470472 Amsterdam - Printed in The Nethcrlunds
COMMUNICATION
Selective extraction acid media
of thallium
with N-benzylaniline
in chloroform
from hydrobromic
M. M. L. KHOSLA De~errcc Ltrhorcrtory.
J~tlhp;~r
(
Itldirc)
S. I’. RAO
Urliwrsir~ oJ’ Jdhp~r. (Reccivcd
Jodilptrr
( Imlitr)
4th April 1973)
Many solvent extraction methods for thallium have been reported in the literature. Thallium(II1) can be extracted from l-6 M hydrochloric acid’ or from into diethyl ether, but extraction from 1 M hydro0.1-6 hg hydrobromic acidt4 bromic acid containing some free bromine is usually preferred. At this acidity, gold is extracted nearly completely but gallium and iron( III) are not extracted; elements such as copper, cadmium, cobalt and nickel, can be removed from the ether layer by scrubbing with 1 M hydrobromic acid, but arsenic(III), mercury( II) and tin(I1, IV) are co-extracted in appreciable quantities. Thallium(I) can be extracted from ammoniacal citrate-cyanide medium by dithizone’.” into chloroform; indium, bismuth, tin(I1) and lead accompany thallium. Many other rather inselective reagents can also be used for the extraction of thallium, including 8-hydroxyquinoIine’*s, acetylacetone’, thenoy1trifluoroacetone7S’o, Nbenzyl-N-phenylhydroxylamine’ *, tri-n-butylphosphate’ 2, diethyldithiocarbamate’ 3, and high molelcular-weight amines14. It has already been shown l5 that thallium can be separated from indium(II1) by extraction with N-benzylaniline in chloroform froni 2 M hydrobromic acid. The present communication describes a fuller study of this extraction. Thallium(II1) is readily and quantitatively extracted with N-benzylaniline from 0.1-6 M hydrobromic acid media, but the extraction is most selective from 2 M hydrobromic acid, and the phase separation is then rapid. Thallium(II1) is easily stripped from the organic phase with acetate-acetic acid buffer and can be determined by.adding a slight excess of EDTA and back-titration with thorium nitrate solution to xylenol orange indicator. Few cations interfere. Experitnett tal Reagerlts. Analytical-grade reagents were used without purification. All standard solutions were prepared in twice-distilled water. Thalliuttt(IIi) solution. A 0.05 M solution was prepared by dissolving 6.66 g of thallium( I) nitrate (B.D.H. Ltd.) in a minimal quantity of water, followed by threefold evaporation to dryness with 50 ml, 25 ml and 25 ml of aqua regia. Finally the
SHORT
COMMUNICATION
TABLE
I
PERMISSIBLE
Wdll) Pd( II) Pt( IV) Rh(II1) Cu(I1) Cd(H) Bi( III) Pb(I1) Sb( 111) Sn( IV) As( III) As( V) Co(l1) Ni( II) Zn(II) Mn(I1) Fc( III) Al( III) Ga(II1) In( III) Bc( II)
NW) Ta( V)
AMOUNTS
471
OF
50 10 10 30 30 26 30 30 3oh 100 3.5 35 58 5x 30 30 3W 100 100 100 30 14h 14”
u Reduction with sodium sulphite water. h In the prcscncc of tartratc.
VARIOUS
IONS
Mo( VI) WVI) V(V) Cr( VI) Ti( IV) Cc( IV) U(V1) Th( IV) Zr( IV) Sc( III) Y( III) Sc( IV) Tc( IV) Cn( II) Sr( II) Mg(II) Phosphate Tartrate Citrate Nitrate Chloride Sulphate Arscnutc Borate and
prcfcrentinl
IN THE
EXTRACTION
OF THALLIUM(III)
50 lob 3W 30” 3W 50” 60 35 30 25 30 30 30 100 100 100 2000 1000 1000 1000
1000 500 50 100 oxidation
of thallium(l)
with
snturatcd
bromine
residue was taken up in 120 ml of( 1 + 1) nitric acid and the solution was diluted to 500 ml. The solution was standardized as the chromate. after reduction with sulphur dioxide.More dilute solutions were prepared by accurate dilution. N-Benzylaniline and thorium( IV) solutions were prepared as described previously”. Getzerd procetlwe. To an aliquot of solution containing up to 80 mg of thallium, add sufficient saturated bromide water to oxidize thallium(I) to thallium(II1): a yellow colour should persist. Boil off excess of bromine (colourless solution). Add enough 40”/, hydrobromic acid (E. Merck) and water to give 2 M acid in a volume of 20 ml. Shake the solution for 1 min with 10 ml of.extractant mixture containing 5 ml of N-benzylaniline solution and 5 ml of chloroform. Swirl the separating funnel slightly and separate the chloroform layer. Re-extract the aqueous layer with 10 ml of the extractant mixture. Scrub the combined organic phases with 15 ml of 4.5 M hydrobromic acid to remove any co-extracted elements. Strip the thallium(II1) from the organic phase by shaking for 1 min with two 35-ml portions of the 0.2 M acetate-acetic acid buffer solution, pH 4.5. Transfer the aqueous backextract to a 250-ml conical flask. Add sufficient 0.01 M EDTA, and 7 drops of 0.1x, (w/v) xylenol orange indicator. and back-titrate the excess of
472
SHORT
COMMUNICATION
EDTA with 0.01 M thorium nitrate solution to the colour change from yellow to red-violet. I~~te@~zce of clioe~~e iorzs. Thallium(lII) could be selectively and quantitatively separated from most of the cations tested (Table 1). Bismuth, cadmium, lead and indium were partially extracted, but could be eliminated by scrubbing the organic phase with 4.5 M hydrobromic acid. Mercury( II) was co-extracted with thallium(III), but did not interfere in the recommended titration of thallium(II1). This element could be completely separated from tl~allium(lIl) by twice scrubbing the organic phase with 4.5 M hydrobromic acid, but the recovery of thallium decreased to 95%. Vanadium(V), iron( III), chromium( VI), titanium( IV) and cerium(IV) hindered the extraction of thallium. but did not interfere after reduction with sodium sulphite in diluteacid: the solution was boiled to remove sulphur dioxide, and thallium(l) was then selectively oxidized to thallium(Il1) by gradual addition ‘of saturated bromine water to the hot solution until the precipitate of thallium(I) salt completely dissolved. Palladium(I1) was partially extracted but remained in the organic phase. Antimony(V). niobium(V) and tantalum(V) could be kept in solution with tartaric acid. Common anions such as phosphate, citrate, tartrate, borate, nitrate, chloride, arsenate and sulphate did not interfere.
The concentration of hydrobromic acid was varied from 0.1 M to 6 M while the concentration of thallium(II1) and the extractant were kept constant. The ratio of the aqueous to organic phase was 2.0. Tl~allium(lIl) was quantitatively extracted from 0.1-6 M hydrobromic acid. The. extraction of different amounts of thallium(II1) in the range up to 80 mg with a lixed quantity of the extractant as in the General procedure was quantitative, whereas the extraction of 100 mg of thallium with the same quantity of the extractant was 94%. REFERENCES 1 D. I. Ryabchikov. Ac-ru Chirr~. nctrtl. Sci. Htrrry.. 32 (1962) 193. 2 H. M. N. H. Irving and F. J. C. Rossotti, A~~trlysr. 77 (1952) X01. 3 I. Wadi: and R. Ishi: Bltll. IIISC. P/I~s. Chetr~. Rc.s. ( Tokyo), I3 ( 1934) 262: Sci. Ptrp. III.SI. I’h~s. Rex (Tokyo), 34 ( 1937138) 787. 4 R. Bock, H. Kuschc and E. Bock. Z. ,411crl. C/~c~rjt.. 13X (1953) 167. 5 J. Minczewski. E. Wcitcsku nnd 2. Marczcnko. C/IC~,IL Allo/. ( Wwscw). 6 ( 1961) 5 15. 6 C. W. Sill and H. E. Pctcrson. Ar~c~l. Cltor~.. 21 ( 1949) 1268. 7 V. V. Bngrccv and Yu. A. Zolotov. Z. Arrtrl. Khirn., 17 (1962) 852: I8 ( 1963) 425. 8 R. M. DugnaIl und S. K. Hxsanuddin. Tdcrnrcc. 15 (1968) 1025. 9 J. Stay and E. Hladky, nrlrtl. Clri~rt. nclcc, 28 ( 1963) 227. IO F. Hagcmann. J. Amc~,‘. Clzcrn. Sot.. 72 ( 1950) 768. I 1 S. J. Lyle and A. D. Shcndrikar, Amtl. Cluing. rlcrcc. 32 ( 1965) 575. 12 A. K. De and A. K. Scn. Ttrlonrcc. I4 (1967) 629. I3 H. Bode and F. Ncumun. Z. A&. Clroa, 172 (1960) I. 14 T. Suzuki and T. Satobaynshi. Jap. AIM/.. 14 (1965) 414. 15 M. M. L. Khosla and S. P. Ruo. rltxrl. Chittl. /Ic*ltr. 58 (1972) 3X9.
Cheo~.