Journal of Radoanalytical and Nuclear Chemistry, Vol. :220, No. 2 (1997) 207-211

Extraction behavior of Tm(IH), Dy(III) and Sm(HI) lanthanide with N-benzoyl-N-phenylhydroxalamine

Munir Ahmed,* Shujaat Ahmed,* M. Mufazzai Saeed, *+ M. Zafar Iqbai** *Nuclear Chemistry Division, Pakistan Institute of Nuclear Science and Technology, P. O. Nilore, lslamabad, Pakistan

**Institute of Chemistry, The University of Punjab, Lahore, Pakistan

(Received October 21, 1996)

The extraction of Sm(lll), Dy(lll) and Tm(III) with N-bonzoyl-N-phenylhydroxalamine (BPHA) in benzene at pH range (I-10) has been studied. Quantitative separation was found in borate media at pH 8. The slope analysis showed that the extracted complex was M(BPHA)3 , where M = Sm(III), Dy(IIl) and Tm(lll). The effect of various masking agents indicated that EDTA, oxalate, fluoride, phosphate and citrate, interfered in this study. Decontamination study showed that Cu(ll), Zn(II), Ni01), Co01), Cr(l/I), Sc(lll) and Fe(Ill) had very poor separation factors, whereas Sn(II), Cd(II), In0II), Ru(ll), Hg(II), AGO), Ta(V) and Hf(IV) had very large separation factor. The effect of different diluents showed that carbontetrachloride, chloroform, benzene, toluene, nitrobenzene dichloromethane, MIBK and cyclohexanone were equally good for extraction except TBP due to ion association.

Introduction Experimental

Some transition metals such as Mn, Ni, Co, Zn, Cd etc. were extracted with N-benzoyl-N-phenylhydroxalamine (BPHA) and its analogue from stable complexes in neutral or basic media) ,2 However, the extraction behavior of rare earth's with BPHA is fairly fragmentary.

SEKIr~, and DYRESSEN 3,4 studied the extraction of Eu(III) and Am(HI) with BPHA in detail from neutral aqueous media. PdEDEL 5 studied the solvent extraction behavior of Ce(III) with BPHA. MURUCAIYAN and SANKAR DAS 6 investigated Ce(III) extraction with BPHA spectrophotometrically. POLUEKTOV et al.7 and THOMASKtrrrY and AGP.AWAL 8 described the extraction and spectrophotometric method for the determination of Dy, Pr, Nd and Sm with BPHA, xylene orange and gallien. ALIMAPa-N et al. 9 elucidated the chemistry of Sm(BPHA)3 complexes after precipitation from neutral media. The extraction behavior of Tm(III) in higher concentration <0.1M BPHA in benzene has been studied and complex composition has been reported to be Tm(BPHA) 3 HBPHA with justification that HBPHA molecules was not directly bonded to central metal atom. 10

In our laboratory the synergic extraction behavior of trivalent lanthanide's with HTTA+ TBA 1~:2 have been extensively studied radiometrically. The extraction behavior of Sm, Tm, and Dy with BPHA is very scanty and not systematic. In our previous work ~3 the extraction of Pr(lIl), Ho(III), and Er(III) with BPHA have been reported) 4 In this paper the results about the exlraction of Tm(HI), SIn(HI) and Dy(HI) with BPHA in alkaline borate media is reported. The stoichiomelric composition of complex selectivity of the extractant and nature of diluent has been evaluated,

N-Benzoyl-N-phenylhydroxalamine (BPHA) was purchased from E-merck and used without further purification. All other chemicals used in this study were of Analar-grade. The buffer solutions were prepared by mixing appropriate quantity of 0.1M of potassium chloride, hydrochloric acid, acetic acid, sodium acetate, boric acid an sodium hydroxide. The stability of the buffer solutions was periodically checked on alternate days using the pH meter at room temperature 23 + 2 ~ Radiotracer 153Sm, 165Dy, and 17~ were prepared by irradiating specpure Sm203, DY20 3 and Tm203 at a thermal neutron flux 2 - I013n �9 cm -2- s -1 in Pakistan Atomic Research Reactor (PARR-I) of this institute.

The irradiated metal oxides were dissolved in concenlrated nitric acid and heated near to dryness and de-ionized water was used to make up volume for the desired range of concentration of metals. The radiochemical purity was checked by 25 cm 3 Ge(Li) detector coupled with 4k series 85 Canberra multichannel analyzer.

Extraction procedure

A 2 cm 3 solution of known pH with known concentration of 153Sm, 165Dy and 17~ radiotracer in 16 mm x 25 mm culture tube was mixed with equal volume of organic phase (0.01M BPHA dissolved in benzene). The contents of the tube were equilibrated by shaking mechanically for 5 minutes using wrist action mechanical shaker and after that centrifuged for 3 minutes for phase separation. One cm 3 aliquot of both phases were assayed radiometrically using a well type NaI(TI) crystal connected to a Tennelac counting assembly for gross ~/-measurements. All the results are

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0236-5731/97/USD 17.00 �9 1997 Akad~miai Kiadr, Budapest All r loh te rD~arvDd

Elsevier Science B.V., Amsterdam AkucMmiai Kiadr, Budapest

MUNro Arl~mD et al.: EX'rRACTION BEI-IAVlOR OF TM(III), DV(III) AND SM(III) LANTHANIDE

the average of at least three measurements and estimated errors are about + 3%.

Back extraction

2 cm 3 of the organic phase containing extracted REEs was added to a culture tube along with 2 cm3 of known pH (1-4) solution. The contents were equilibrated by vigorous shaking for 5 minutes. After centrifuging 1 cm 3 of each was assayed radiometrically. The stripping ratio (D) was calculated by the count rate of REEs in the aqueous phase to that in the organic phase.

# ff o

.m

ILl

# t -

.0_

0

#

g

LLI

"1UU - -

8 0 - -

6 0 - -

4 0 - -

2 0 - -

o

100--'

80 - -

60 - -

4 0 - -

20 - -

0

0

100--'

8 0 - -

60

4 0 -

2 0 -

0

0

Dy (111)

I I I I I 2 4 6 8 10

pH

Tm (111)

I I I [ I 2 4 6 8 10

pH

Sm (Ill)

I I I I I 2 4 6 8 10

pH

Fig. 1. Effect ofpH with 0.01M BPHA in benzene

R e s u l t s a n d discussion

Effect of pH

Variation of the distribution ratio (D) of Sm(III), Dy(III) and Tm(IlI) ions with BPHA in benzene was investigated as a function of pH in the range of 1-10. It can be seen from Fig. 1 that as the pH increases, the extraction also increases and quantitative extraction is observed between pH 7-10. At low pH, the main reaction does not take place to any extent because of high concentration of hydrogen ions in the aqueous phase. As pH increases, the concentration of hydrogen ion decreases resulting the hydroxyl ion concentration increase with the complex formation of metal with BPHA due to increase in ionization of BPHA. 14

The effect of shaking time shows that maximum equilibrium was attained within 5 minutes and further shaking has no effect on extraction. At pH 8, the effect of BPHA concentration from 10 -1 to 10-3M, the extraction remains constant. However, on decreasing the concentration of BPHA below 10-3M extraction decreases because ionized BPHA is insufficient to complex metal ions.

Nature of the extracted species

The composition of the extracted species was determined by slope analysis 15 method. The complexes of BPHA with rare earth can be expressed as

M ~§ + (n + m)BPHA ~--~M(BPHA).mHL +nH § (1)

Rearranging Eq. (1) one becomes: 13

log D = log Kex + (m + n) log [BPHA] + n pH (2)

The plot of log D vs. log [BPHA] using Eq. (2) is shown in Fig. 2. The value of (n + m) at constant pH and metal ion concentration is 2.92, 3.17 and 2.93 for Dy(III), Tm(III) and Sm(III), respectively, with a standard deviation of +_0.15. The number of BPHA ligands associated with central metal ion of Sm(III), Dy(III) and Tm(III) was found to be:

Sm 3§ + 3BPHA -~Sm(BPHA)3 + 3H § (3)

Dy 3§ + 3BPHA -~Dy(BPHA)3 + 3H § (4)

Tm 3§ + 3BPHA ~---~Tm(BPHA)3 + 3H § (5)

This indicates that 3 hydrogen ions are released during the formation of each chelating species. Hence, the stoichiometric composition of extracted complex is MfBPHA) 3 where M = Dy, Tm and Sm. The probability of

208

0.0 ~ I ) / ( l i t ) Tm (Il l) 2 . 0

-2.0

-4.0

-1.0 - -

I I = -3.5 -3.0

IOg [BPHA]

2.0 '

:2 _r 1 . 0 -

M t ~ B AItMEO ct al.: EXTRACtiON BmlIAVlOR OF TM(III), Du , ~ o SM~III) IAN'rsAr~IVE

Sm (Oil)

.~ 1 . 0 -

0.0 I I D 0.0 - , I I D

-4.0 -3.5 -3.0 -3.0 -2.5 -2.0

log [ BPHA ] log [ BPHA ]

Fig, 2. Effect of metal ions concentration at pH 8 with 0.01M BPHA in benzene

Table 1. Extraction constants of REEs, at pH 8, ionic strength 0.01M fH +, s o 3)

Element Slope Intercept Kex

Dy(llI) 2.92 7.99 -15.40 Tin(I/l) 3.17 11.82 -13.54 Sm(III) 2.93 8.08 -15.36

Interferences

The influence of the most common anions (10 mg/cm 3) was studied and the results are given in Table 2. The extraction of Sm(Ill), Dy(Ill) and Tm(III) is masked by the EDTA, oxalate, ascarbate, fluoride and phosphate. However, citrate masks the exlraction up to 50%, whereas thiourea, thiosulphate, tarlrate, acetate, chloride, bromide,

the formation of aqua complexes of the type M(BPHA)3 �9 �9 n .I-LzO is also ruled out because these complexes are hydrophilic and fairly soluble in polar solvents. The low dielectric constant (2.28 e), inertness and non-polar nature of benzene as diluent inhabits the formation of aqua complexes. The reaction of Sm(III), Dy0II) and Tm(III) with BPHA is shown in Eqs (3)-(5).

BPHA act as a bidentate ligand and form chelates with metal ions. The metal ligand ratio in the complexes is 1 : 3 showing the coordination number of 6 for all three rare earth metal ions. The titration data 16 also show that the maximum complexation involved in (BPHA) is 6 coordination species and no hepta or octa coordination species is formed. The stability constants, Kex of the adducts are given in Table 1, which reflect the stability of the complex.

The effect of rare earth metal ion concenlration on the exlraction is given in Fig. 3. This figure shows that up to 0.6 g/l of Tm(III), 0.8 g/l of Dy(III) and 0.8 g/l of SmOlI) can be extracted quantitatively in a single extraction.

Table 2. Effect of varions anions (10 rag/era 3) on the extraction of REE with 0.01M BPHA in benzene

Anion Extraction, %

Sin(Ill) Dy(IIl) Tmfm)

Thiourea 98 83 99 Citrate 44 71 55 Ascarbate < 1 < I < 1 EDTA < 1 < 1 < 1 Thiosulphate 94 84 99 Oxalate <1 <1 <1 Taarate 97 82 99 Acetate 93 92 99 Fluoride < 1 < 1 < 1 Chloride 97 98 99 Bromide 98 92 99 Iodide 97 94 99 Thiocyanate 98 95 99 Cyanide 97 93 98 Sulphate 98 93 99 Nitrate 98 95 99 Phosphate < 1 < 1 < 1

209

Mt~m AHM~ et al.: Ex'r~cnoN Br.nAVmR OF TM(III), DY01I) ~ v SM(III) LANTHANmE

Table 3. Extraction of other metal ions and their separation factor with respect to each rare earth with 0.01M BPHA in benzene

Element K d Separation factor = Ka~EE]/Kd[M]

SmOll) Dy(lll) Tm(IlI)

Nil 5.03.103 7.54-102 2.91- 102 Sn01) 2.0-10 -3 2.51.105 3.77.105 1.45.105 CdflI) 1.1.10 -4 5.03.107 7.54.106 2.91.106 In(Ill) 5.1.10-1 1.0- 104 1.50.103 5.82. 102 Sb(III) 2.6- 10 -2 1.93. 105 2.90. 104 1.11.104 Ru(III) 2.9.10-3 1.73.106 2.60. 105 1.0.105 Hg(II) 9.6.10-1 5.24.10 3 7.85.10 2 3.03.10 2 Sc(III) 8.38.101 6.0.101 8.99.100 3.47- 10 ~ Fe(III) 1.86.101 2.70. 102 4.04- 101 1.56.101 Cr(HI) 2.5- 10-4 2.01- 107 3.01- 106 1.16.106 Ta(V) 5,5,10 -3 9.15- 105 1.37. 105 5.29.104 Zr(IV) 1.52.10 ~ 3.31.103 4.97.102 1.91- 102 Hf0W) 2.8.10 -1 8.01.102 1.20.102 4.63.101 MnflI) 2.1.101 2.39. 102 3.59.101 1.38.101 Co01) 1.13- 10-1 4.44.102 6.65.101 2.56.101 AgO) 1.3.10 -2 3.87. 105 5,80~ 104 2.23- 104 Ni(II) 5.4.101 9.32.101 13.96.100 5.38.100 La0II) 4.33.10 ~ 1.16.103 1.74. 102 6.72.101 Zn(II) 1.06. 102 4.47.101 7.11.100 2.74.100 Cu(lI) 9.69. 102 5.19- 100 7.78.10-1 3.0- 10-1

Table 4. Back extraction of Dy0ll), TmfllI) and Sm(llI) at different pHs

Dy(Ill) Tm(II1) Sm(lll) pH

log K d E, % logK d E, % log K d E, %

1 1.95 99 2.55 99 2.80 99 2 1.90 99 2.41 99 2.94 99 3 1.87 99 2.45 99 2.70 99 4 1.80 99 2.28 99 2.75 99

Table 5. Distribution constant and solubility parameter, extraction with 0.01M BPHA at pH 8 (H3BO 3 + NaOH) for different solvents

Dielec. log K d Extraction, % Diluents constant

Sm(III) Dy(IIl) Tm(III) S m 0 1 1 ) Dy(Ill) Tm(III)

Carbontetrachloride 2:23 2.87 2.35 2.48 99 99 99 Clorofonn 4.80 2.57 2.70 2.62 99 99 99 Tributylphosphate -1.02 -1.31 -1.13 -1.20 4.8 4.6 6.7 Nitrobenzene 35.74 2.13 2.79 2,94 99 99 99 Benzene 2.28 2.15 2.65 2.51 c:9 99 99 Dichloromethane 9.08 3.10 3.2 3.17 99 99 99 MIBK 13.1 0.87 1.6 1.51 88 98 97 Cyclohexanone 18.3 1.09 0.9 0.87 93 90 88 Cydohexanol 13.9 1.22 1.51 1.18 93 97 93 Diethylether 4.15 1.04 1.19 1.33 91 95 95 Toluene 2.43 2.52 2.39 2.43 99 99 99 O-Xylene 2.56 2.45 2.40 2.42 99 99 99 p-Xylene 2.27 2.46 2.58 2.60 99 99 99 Cydohexane 2.02 1.17 1.04 1.50 93 91 96 n-Hexane 1.89 0.11 0.27 0.18 56 65 60

210

MVNm AHMED et al.: EXTRACnON SEnAWOR or TM(III), Du ANn SM(III) LANTHANg)E

"6

tu

100.--I

80- -

60 - -

40- -

20- -

0

0

Oy (,,t)

I I I I I 200 400 600 800 1000

d ._o "6

ill

ppm

loo-',.-..---.-._._ 80-- Tm (Ill) \ 60-

40-

20--

0 I I I I I 0 200 400 600 800 1000

# =- .0

E ILl

1 0 0 -

8 0 -

60 - -

40 - -

20 - -

0

0

ppm

I I I I I 200 400 6OO 8O0 1000

ppm

Fig. 3. Variation in distribution ratio of metal as a function of BPHA at pH 8, ionic strength 0.01M (H +, BO3)

iodide, cyanide, sulphate, nitrate has no effect on extraction.

The extraction of other metal ions was studied under the selected optimal conditions and separation factor were calculated with respect to each rare earth ion and are recorded in Table 3. The separation factors for Sn([l),

Cd(H), Sb(IH), Ru(II), Hg(II), Cr(III), TAW), Zr(IV), Hf(IV) and AgO) are very high, whereas Cu(II), Zn(II), La(III), Co(H) and M_n0D are low.

The back extraction of Sm(III), Dy(llI) and Tm(III) complexes studied from pH 1 to 4 buffer solutions is shown in Table 4, It is observed that these complexes are highly unstable towards the acidic aqueous pliase and slriping of Sm(III), Dy(III) and Tm(III) is quantitative.

Effect of various solvents

The effect of various organic diluents on the extraction of Sm(Ill), Dy(III) and Tm(l/I) are recorded in Table 5. The solvents of high dielectric constants show that proton in these molecules are more likely to form hydrogen bonds with the carbonyl oxygen of BPHA. The chlorinated aliphatic solvents are compatible with aromatic solvents. The solubility of BPHA is greater in chloroform than in benzene, but we have selected the benzene in our study, because, cryoscopic measurements show that BPHA is a monomeric in benzene solution. 17 TBP decreases the extraction due to the association of T B P with BPHA.

R e f e r e n c e s

1. A. K. MAmMOER, N-Benzoylphenylhydroxalamine and Its Analogues, Pergamon Press, Oxford, 1972.

2. S. P. BAG, S. l.,Amm, J. haorg. Nud. Chem., 38 (1976) 1611. 3. D. DYRESSE~, Acta China. Scand., 10 (1956) 353. 4. T. SEKIr~, D. DY~SSEN, Talanta, 11 (1964) 867. 5. A. REn~EL, J. Radioanal. Chem., 6 (1970) 75. 6. P. MURUGAPtAN, M. SArO~R DAS, Anal. China. Acta, 48 (1969) 155. 7. N. S. POLUFXTOV, L. A. OVO-[AR, R. S. LAVER, S. F. POTAPVA,

Zh. Analit. Khim., 29 (1974) 1715. 8. P. T. THOMASKUTIT, Y. K. AGRAWAL, J. Radiotmal. Nuct Chem., 116

(1987) 365. 9. I. P. ALIMAmN, F. P. SODAKOV, B. G. GOLOWaN, Usp. Khim., 31

(1962) 989. 10. K. F. Foucym, H. J. LE Rotrx, Intern. Conf. csa Solvettt Extraction

Chemistry, The Hague, Netherlands, 1971, p. 499. 11. M. M. SAEED, MUNIR ArtMED, AKBAR ALI, M. N. ~ J.

Radioanal. Nucl. Chem., 164 (1992) 1. 12. M. MUFAZZAL SAEED, MUNro AHMED, AKBAR Ata, M. N. CHEEMA,

Radiochim. Acta, 57 (1992) 125. 13. MUNro AHMED, S. AHMED, M. M. SAEE~, M. ZAFAR IQBAL, J.

Radioanal. Nucl. Chem., 212 (1996) 269. 14. B. DAS, S. C. SHOME, Anal. Chim. Acta, 32 (1965) 52. 15. J. H. YoE, A. E. HARVEY, J. Am. Chem. Soc., 70 (1948) 64& 16. Y. IL AGgAWAL, J. Inorg. Nucl. Chem., 39 (1977) 479. 17. J. HAl.A, J. Inorg. Nucl. Chem., 29 (1967) 1777.

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