Solvent extraction and separation of Bi(III) and Sb(III) from HCl and HBr media using tri-n-octyl phosphine oxide (TOPO)

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1 Indian Journal of Chemical Technology Vol. 8, July 21, pp Solvent extraction and separation of Bi(III) and Sb(III) from HCl and HBr media using tri-n-octyl phosphine oxide (TOPO) Kamaruddin Abdar Ali & Ajay K Vanjara* Applied Chemistry Division, Department of Chemical Technology, University of Mumbai, Matunga, Mumbai 4 19, India Received 9 November 2; accepted 24 March 21 The solvent extraction and separation of Bi(III) and Sb(III) from aqueous acidic media was investigated using Tri-noctyl phosphine oxide (TOPO) in toluene. Quantitative extraction of Bi(III) was observed in acid range of.1-.1m of HCI and. 1-.1M of HBr and that for Sb(III) extraction was incomplete in HCI media over the entire concentration range studied. The extraction of Sb(III) was quantitative in range. 1-.1M of HBr media. Effect of various other parameters such as reagent concentration, type of diluents, stripping agents, effect of diverse ions were studied to ascertain optimum conditions for the quantitative extraction and separation of Bi(III) and Sb(III). After equilibration Bi(III) from organic phase was stripped with 3M HN 3 and determined spectrophotometrically by thiourea method at 47 nm, while Sb(III) was stripped with 9M H 2 S 4 and determined spectrophotometrically by iodide method at 425 nm. The effect of temperature on the extraction of Bi(III) and Sb(III) from HCI and HBr media has also been studied. The method is applicable to the analysis of pharmaceutical samples and alloys. Organophosphorous compounds have been recognized as efficient extractants for various metals in the solvent extraction processes. The neutral organosphosphorous compound like tributylphosphate 1 ' 2 and bis(2-ethylhexyl)phosphate 3 have been used earlier for solvent exraction studies of Bi(III) and Sb(III). Bi(III) has also been extracted with mesityl oxide from bromide media 4, hexaaceto calix(6)arene was used for extraction of Bi(Ill) from HCl media 5. The separation and determination of Bi(III) and Cu(II) with dimethyl dithiocarbamate for HBr media is reported by Karadakov and Sakharieva 6. On the other hand, ethyl acetate 7, di-isobutyl carbinol 8 were used for extraction of Sb(V) whereas tertiary amine 9 and MIBK-cyclohexanone system 1 is used for extraction of Sb(III) from acidic media. In this paper Tri-n-octyl phosphine oxide is used for extraction of Bi(III) and Sb(III) from halide media. The proposed method in this paper is simple, rapid and selective. It permits separation and determination of Bi(III) and Sb(III) within few minutes and also has applications in determination of Bi(III) and Sb(III) in real samples. Experimental Procedure A GBC 911A spectrophotometer with 1 mm quartz cuvettes was used for experimental absorbance *For correspondence: sslele@foodbio.udct.emet.in; Fax : measurements and digital ph meter [Elico Pvt. Ltd.; India Model LI-2] was used to measure the ph of the solutions. The stock solutions containing 1 ).!g/ml of Bi(III) and Sb(III) were prepared by dissolving.58 g of bismuth nitrate and.1 g of antimony metal in concentrated HN 3 and H 2 S4 acid respectively and standardised by literature methods 11 The working solutions containing 1 J-tg/mL of Bi(III) or Sb(III) were prepared by ten-fold dilution of stock solution with distilled water. The extractant Tri-n-octyl phosphine oxide (Cyanex 921) also known as TOPO was supplied by American Cyanamide Company and used without further purification. All other chemicals used were of AR grade. An aliquot of solution containing Bi(III) [1 ).!g] or Sb(III) [1 ).!g] was taken and its acid concentration is adjusted to required morality by HCl or HBr and diluted to 1 ml. This solution was transferred to a separating funnel and equilibrated with 1 ml of 1x1-2 mol dm- 3 of TOPO for 1 min. After phase separation Bi(III) was stripped with 3 M HN 3 and determined spectrophotometrically by Thiourea method 12 whereas Sb(III) was stripped with 9 M H 2 S4 and determined by Iodide method 13. The temperature study was done in glass reactor ( 1 ml capacity) with stirrer in water bath. The temperature was controlled with accuracy ± 1 C with 2 rpm stirring speed. Bi(III) and Sb(III) were extracted from 1. M HBr and.1 M HCl with 1x1-2 M TOPO in toluene at different temperatures.

2 24 INDIAN J. CHEM. TECHNOL., JULY w ~ log [Acid] [M] a> L L._--t ~ _j..: log [TOPO] [M) Fig. 1-Effect of acid concentration on extraction of Bi(III) (-HBr, -HCI) Fig. 3-Effect of reagent concentration on extraction of Bi(III). (-.LM HBr, Slope= 1.64, -O.OLM HCI, Slope= 1.72) ~ ~ ~--~ Log [Acid) [M) Fig. 2-Effect of acid concentration on extraction of Sb(III) (-HBr, -HCI) Results and Discussion Effect of acidity and TOPO concentration The extraction of Bi(III) was found to be quantitative in the acidic range concentration.1-.1 Min HCl and.1-.1 M HBr for Bi(III). The extraction of Sb(III) was not quantitative (88% at 3M HCI) from HCl media while extraction is quantitative in.1-.1 M HBr as shown in Figs 1 & 2 respectively. Bi(III) and Sb(III) were extracted using varying concentrations of the reagent TOPO ranging from.1-.1 M dissolved in toluene. The minimum concentration of TOPO required for quantitative extraction was found to be.1 M. A log-log plot of the distribution ratio versus concentration of TOPO [Figs 3 & 4] for Bi(III) at.1 M HCl and.1 M HBr show slope of 1.72 and 1.64 respectively and that for Sb(III) at 3 M HCl and.1 M HBr show slope of 1.67 and 1.61 respectively. The value of slope indicates that metal to reagent ratio '' "'> i log [TOPO) [M) Fig. 4-Effect of reagent concentration on extraction of Sb(Ill) (-3M HCI, Slope= 1.67, -.1M HBr, Slope= 1.61) in the extractant species is 1 :2. Hence the probable species is MX 3.2TOPO where X is Cl or Br. Effect of equilibration time Variation of the shaking period from 1 to 2 min showed that 5 min of equilibration time is adequate for quantitative extraction of Bi(III) and Sb(III) from both hydrochloric and hydrobromic acid media. As a general procedure 1 min of equilibration time is recommended in order to ensure the complete extraction of metal ions from hydrochloric and hydrobromic acid media. However a prolonged shaking up to 2 min has no adverse effect on the extraction of Bi(III) and Sb(III). Effect of various diluent on extraction of Sb(III) and Bi(Ill) Bi(III) and Sb(III) were extracted with 1 x 1-2 mol dm- 3 TOPO in various diluents. The effect of diluent on extraction of Bi(III) and Sb(III) is shown in Table 1. It is observed that extraction of Bi(III) was

3 ALI & VANJARA: SOLVENT EXTRACTION AND SEPARATION OF Bi(III) AND Sb(III) FROM HCL AND HBr 241 Table 1-Effect of diluent on extraction of Bi(III) and Sb(III) Diluent Extraction of Bi(III) Extraction of Sb(III) % Extraction % Extraction % Extraction % Extraction.1M HBr.1M HCI.1 M HBr 3.MHCI Benzene Xylene Cyclohexane Carbon tetrachloride Chloroform 68.8 n-hexane 81.6 Dichloroethane Toluene Table 2-Effect of temperature on distribution ratio of Bi(III) and Sb(III) Bi(III) Sb(III) Temperature Distribution ratio Distribution ratio K 1M HBr.1M HCI 1M HBr O.IM HCI Cl _ _ /Tx 14(K-1) Fig. 5-Effect of temperature on extraction of Bi(III). <P-1M HBr, Slope=-2.71, -.1M HCI, Slope=-2.5) quantitative with toluene, cyclohexane, benzene in.1 M HBr media, while in.1 M HCl media n-hexane also gives quantitative extraction. The extraction of Sb(III) was quantitative with toluene,. xylene, cyclohexane, carbon tetrachloride, n-hexane in.1 M HBr media. Toluene was preferred as a suitable diluent for both metals because it gives better phase separation and is less toxic as compared to other diluents. Effect of temperature on th'e extraction procedure The effect of temperature on solvent extraction of metal ions is studied in temperature. range between Table 3-Effect of diverse ions on extraction of Sb(III) and Bi(III) at O.IM HBr Ions Ratio Bi(III) 1 Jlg Sb(III) 1 Jlg 1:2 1:15 Cu(II), Zn(II), Hg(II), Co(ll), Pb(II) Au(JII), Fe(III), Mg(II), Phosphate Cu(II), Mg(II), Pb(II) Cd(II), Zn(II), Fe(III), Pl)osphate, Chloride, Nitrate 1:1 Mn(II), Ni(II), Chloride, Ni(II), Mn(II) Nitrate 1:5 Ions severely interfering Sn(II), Sb(III), In(III) EDTA Bi(III), Hg(II), Au(III) Te(IV), Sn(II) 3 C and 75 C (Table 2). Applying Vant Hoffs equation and writing it in terms of distribution coefficient, the following expression is obtained t1j[o log D =- +C 2.33RT where D is the distribution coefficient, C is a constant and!1r is enthalpy change for the extraction process. The value of tl.h is equal to -2.33xRxslope. The plots of log D versus lit for Bi(III) are linear as shown in Fig. 5. The enthalpy change (Kcallmol) is estimated to be in 1 M HBr and in.1 M HCl"showing that the extraction of Bi(III) by TOPO-toluene solution is an endothermic process. Also the plot of log D versus lit for Sb(III) are linear as shown in Fig. 6 and the enthalpy change (Kcal/mol) is estimated to be in 1 M HBr and in.1 M HCI showing that the extraction of Sb(III) by TOPO-toluene solution is an endothermic process.

4 242 INDIAN J. CHEM. TECHNOL., JULY 21 Table 4-Analysis of alloys and pharmaceutical samples Sample Composition Amount present Amount founda Recovery R.S.D. (%) (%) (%) Leaded brass Cu, 58.7; Pb, 2.24; Fe,.15; Zn, 38.5; Sn,.7; 2.5 mgbi 2.49 mg (BCS85) Ni,.13; AI,.5 Tin base white metal Sn, 82.2; Zn,.4; Cu, 4.58; Pb, 3.18; As,.1; 9.45 mg Sb 9.35 mg (BCS178-2) Bi,.11; Cd,O.l4; Fe.264; Ni,.17 Denol (Elder Pharmaceutical Ltd., India) Colloidal Bi-subcitate as Bi 2 3 (12 mg) mg of Bi 16.9mg "Average of triplicated analysis , ~.7 -" ~ je :::::: / T X 1 4 (K - 1 ) Fig. 6-Effect of temperature on extraction of Sb(III). (-.1M HCI, Slope=-5.67, e-im HBr, Slope=-5.27) Effect of various stripping agents Bi(III) and Sb(III) were stripped with different strength of mineral acids such as HCl, HBr, H 2 S4 and HN 3, after extraction. The stripping of Bi(III) was quantitative with 3M HN 3 whereas that of Sb(III) was quantitative with 9M H 2 S4. Effect of diverse ions on extraction of Bi(III) and Sb(III) An interference study is carried out by adding varying amount of foreign ions to a fixed amount of Bi(III) or Sb(III) at.1 M HBr. The tolerance limit was set at the amount required to cause a ± 2% error in metal recovery (Table 3). Mutual separation of Bi(IIl) and Sb(III) The separation of Sb(III) [1 J,lg] and Bi(III) [ loo J,lg] from one another was studied in.1 M HBr by extracting Bi(III) and Sb(III) by 1x l- 2 mol dm- 3 TOPO in toluene with an equilibration of 1 min. From the organic phase containing Bi(III) and Sb(III), Bi(III) was first stripped with 3. M HN 3 and determined spectrophotometrically by thiourea method. The organic phase containing Sb(III) was further stripped with 9. M H 2 S 4 and determined spectrophotometrically by potassium iodide method. Analysis of Bi(III) and Sb(III) from alloys Leaded brass (BCS385) (1 mg) was dissolved in 3. ml of concentrated nitric acid, filtered, 2.5 mg of bismuth was added, and diluted to 5 ml. Tin base white metal was dissolved in concentrated nitric acid and evaporated to dryness. The residue was leached with water and analysed by the proposed method. Analysis of pharmaceutical sample A Denol tablet was dissolved m 1 ml of hydrochloric acid. The solution was evaporated to almost dryness, taken-up in water, filtered and the filtrate was diluted to 5 ml. An aliquot of solution was taken from which bismuth(iii) was extracted and analysed as per general procedure and compared with the certified value of bismuth. The experimental results were found in good agreement with the certified value as shown in Table 4. References l Yadav A A & Khopker S M, Bull Chern Soc Jpn, 44 (1971) Tomioka H & Terashima K, Japan Analyst, 16 ( 1967) Levin I S, Mukhin Yu M & Vorsina I A, /zv sib Otdel Akad Nauk SSSR (2), Ser Khim Nauk, l (197) Desai G S & Shinde V M, Bull Chern Soc Jpn, 64 (199 1) Malkhede D D, Dhadke P M & Khopker S M, Indian J Chern Technol, 7 (2) 7. 6 Karadakov B & Sakharieva M, Anal Chern Acta, 125 (198 1) White C E & Ross H J, Anal Chern, 25 ( 1953) 351.

5 ALI & VANJARA: SOLVENT EXTRACTION AND SEPARATION OF Bi (III) AND Sb(III) FROM HCL AND HBr Lowe R W, Prestwood S M, Rickard R R & Wyatt E I, Anal Chern, 33 (1961) Alian A & Sanad W, Talanta, 14 (1967) Navratil, Meindl J & Kos J, Collect Czech Chern Commun, 46 (1981) Vogel A I, A Textbook of Quantitative Inorganic Analysis, 3rd Edn (Longmans, London), 1961, 385, Sandell E B, Colorimetric Determination of Trace Metal (lnterscience, New York), 1944, Sandell E B, Colorimetric Determination of Trace Metal (lnterscience, New York), 1944, 131, 139.