Solvent extraction separation of zirconium

Indian Journal of Chemical Technology Vol. 20, July 2013, pp. 252-258

Solvent extraction separation of zirconium (IV) with 2-octylaminopyridine from succinate media—Analysis of real samples Leena E Noronha, Ganesh S Kamble, Sanjay S Kolekar & Mansing A Anuse* Analytical Chemistry Laboratory, Department of Chemistry, Shivaji University, Kolhapur 416 004, India Received 28 May 2012; accepted 22 April 2013 A systematic study on liquid-liquid extraction separation of zirconium (IV) from 25 mL 0.02 M sodium succinate solution using 10 mL 0.087 M 2-Octylaminopyridine (2-OAP) as an extractant has been carried out. Quantitative extraction of Zr (IV) is observed at pH 3.7 – 5.0 using 0.01 – 0.03 M sodium succinate with 0.087 M 2-OAP in xylene. Zirconium (IV) has been back extracted with 0.5 M HNO3 (3×10 mL). The nature of extracted species in organic phase is determined by using conventional slope analysis method. The proposed method is applicable to separate Zr (IV) from associated metals like W(VI), Fe(III), Mo(VI), Y(III), Al(III), V(V), U(VI) and Th(IV) and also in the analysis of Zr (IV) from various synthetic mixtures, real samples of alloy, thin films and nanopowder. Keywords: Liquid-liquid extraction, 2-Octylaminopyridine, Sodium succinate, Zirconium (IV)

Zirconium is widely distributed in nature and has been found to be present in the earth’s crust to the extent of about 0.022%. A wide variety of catalytic effects of zirconium and its compounds have been reported. This is largely a consequence of the Lewis acid properties. Zirconium metal alloyed with niobium is intentionally oxidized to produce an abrasion resistant and high integrity zirconium oxide ceramic surface on total hip or total knee replacement devices. Literature survey shows that several high molecular weight amines have been used for solvent extraction of Zr (IV). These are trioctylamine1-3, tetradentate naphthol derivative Schiff base4, formyl – 4 – hydroxy-N-methyl 2(H)quinoline5, N-n-octylaniline6, amides such as N,N-di-nbutylhexanamide, N, N-di-n-butyl octanamide, N-methyl - N-butyl octanamide7, Alamine 336 S8 and tricapryl methyl ammonium chloride9. A systematic study on the synergistic solvent extraction and separation of Zr (IV) with various organophosphorus compounds such as tri-n-butyl phosphate10,11, di-(2 ethyl hexyl) phosphoric acid (D2EHPA)12,13, diisodecylphosphoric acid14, PC - 88 A15,16 and Cyanex- 27217,18 has already been carried out. The other extractants such as Aliquat 33619, dibenzo–18– crown–620, dicyclohexyl–18–crown–621 and LIX 84 – _________ *Corresponding author. E-mail: [email protected]

IC22 have also been used for solvent extraction of Zr (IV). In the present paper, a simple and selective extraction procedure for Zr (IV) extraction with 2-octylaminopyridine (2-OAP) has been reported. The proposed method is applicable for separation of Zr (IV) from binary and synthetic mixtures, alloys, thin films and nano powder. Experimental Procedure Apparatus

An Elico digital pH meter (model LI – 120) was used for pH measurement. An Elico digital spectrophotometer (model SL-171) with 1 cm quartz cells was used for absorbance measurements. Doubly distilled water and analytical reagent grade chemicals (BDH or Merck) were used throughout this study. Reagents

Standard solution of Zr (IV) was prepared by dissolving 0.6337 g of zirconyl nitrate hydrate in 20 mL hot concentrated HNO3 and diluting it to 250 mL with distilled water. This is 1 mg/mL solution of Zr (IV). The solution was standardized complexometrically23. A working solution of 100 µg/mL was made by diluting the stock solution with distilled water. 2-OAP was synthesized by Borshch and Petrukhin method24 and its solution (0.087 M) was

NORONHA et al.: SOLVENT EXTRACTION SEPARATION OF ZIRCONIUM (IV) WITH 2-OCTYLAMINOPYRIDINE

prepared in xylene. 1% gum arabic and 0.05% Alizarin Red S were prepared in water and used for the spectrophotometric determination of Zr (IV). Extraction and determination procedure of Zr (IV)

An aliquot of solution containing 400 µg/mL of Zr (IV) was mixed with 0.02 M sodium succinate (0.135 g) adjusted to pH 4.0 with (1:1) ammonia and dilute HCl and finally the volume was made to 25 mL with distilled water. The solution was then transferred into a 125 mL separatory funnel and shaken with 10 mL 0.087 M 2-OAP in xylene for 3 min. The aqueous phase was discarded. The organic phase was shaken with 0.5 M nitric acid (3×10 mL) to strip Zr (IV). The acid layer was withdrawn and shaken with xylene (2×5 mL) in order to remove the traces of dissolved amine. The aqueous phase containing Zr (IV) was evaporated to moist dryness. The dark residue obtained was given perchloric acid treatment. The excess acid was removed by washing the phase 2-3 times with water and evaporating to moist dryness. The aqueous phase containing Zr (IV) was determined by Alizarin Red S. The absorbance was measured at 525 nm using a reagent blank as reference and the amount of Zr (IV) was computed from a calibration curve. Results and Discussion Extraction as a function of pH

Zr (IV) was extracted in the pH range 1.0 – 10.0 in the presence of (0.02 M) sodium succinate. Quantitative extraction of Zr (IV) was observed in the pH range 3.8 – 4.2 (Fig. 1). Upto pH 4.2 there are more H+ ions in the solution for protonation of the amine (RR’NH) which favours the formation of RR’NH2+ species. However, when pH further increases there is no availability of H+ ions in the basic condition and so formation of RR’NH2+ stops. Hence, the extraction decreases with increase in the pH. In the proposed method pH 4.0 is recommended for further studies.

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organic species [(RR’NH2+)2 succinate2-] and there is adverse effect on the extraction of Zr (IV). It is found that 10 mL of 0.084 M 2-OAP is sufficient for the quantitative extraction of 400 µg Zr (IV) from 0.02 M sodium succinate at pH 4. However, in the recommended procedure, 0.087 M 2-OAP in xylene is used to ensure the complete extraction of Zr (IV) metal ion. Extraction as a function of weak organic acid concentration

The extraction of Zr (IV) was also carried out at pH 4.0 with 0.087 M 2-OAP in xylene in presence of different concentrations of sodium succinate, sodium malonate, sodium citrate, sodium tartarate and L–ascorbic acid as weak acid media. The extraction of Zr (IV) is found to be quantitative at pH 4.0 using 0.01-0.03 M sodium succinate and 0.009-0.01 M sodium malonate. The decrease in the extraction at high acid concentration is presumably due to preferential formation of succinate or malonate of 2-OAP. Sodium succinate (0.02 M) was used throughout the work as it is cheaper than sodium malonate and also has wide range of concentration than malonate. However, there is incomplete extraction of Zr (IV) from sodium citrate (36.3%), sodium tartarate (71%) and L-ascorbic acid (70%) media. Extraction with various diluents

Keeping all the other variables constant, Zr (IV) was extracted with 0.087 M 2-OAP in various diluents. The extraction is found to be quantitative

Extraction as a function of 2-OAP concentration

Increase in 2-OAP concentration favours the formation of RR’NH2+ and increases the percentage extraction of Zr (IV) which becomes quantitative in the concentration range 0.002430.3883 M. Further increase in the 2-OAP concentration of results in the formation of stable

Fig. 1—Extraction behaviour of Zr (IV) as a function of p H from 0.02 M sodium succinate with 0.087 M 2-OAP

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using xylene and toluene as the diluents because the distribution ratio of the ion-pair complex is high in these solvents whereas, kerosene (95%), chloroform (99%), carbon tetrachloride (99%), benzene (98%), 1, 2-dichloroethane (98%), n-butanol (52%), amyl alcohol (51.83%) and methyl isobutyl ketone (42.20%) are found to be poor solvents. In xylene phase separation is obtained quickly, and hence it is advantageous over other solvents. Effect of time of equilibrium

An aliquot of Zr (IV) having 0.02 M sodium succinate concentration and 4.0 pH in 25 mL volume was equilibrated with 10 mL 2-OAP in xylene for a period of 15 s to 30 min. The extraction of Zr (IV) is found to be quantitative over a period of 3-5 min. Further increase in the equilibration period decreases the percentage extraction of Zr (IV) due to the dissociation of the ion pair complex with more agitation. In the present work, a 3 min equilibration time is recommended to ensure complete extraction of Zr (IV). Effect of stripping agents

Zirconium (IV) was stripped with three 10 mL portions of various stripping agents at different concentrations. The stripping is found to be complete with 0.49 – 0.52 M nitric acid, while it is found to be incomplete with 0.4 M hydrochloric acid (97.1%), 0.5 M acetic acid (98%), 0.4 M sulphuric acid (71.9%), ammonia (0.2%), water (10.2%) and acetate buffer of pH 4.05 (54.1%) and 4.27 (55.9%). In the proposed method 0.5 M nitric acid was used as a strippant for complete recovery of Zr (IV).

Fig. 2—Log-log plot (a) log D[Zr(IV)] - log C[(2-OAP)] at 0.02 M sodium succinate with pH 6.0 and 6.5 and (b) log D[Zr(IV)] - log C[Succinate] at 0.087 M 2-OAP with pH 6.0 and 6.5

combines with Zr (IV) to form anionic species such Nature of extracted species

Attempts were also made to ascertain the nature of the extracted complex species using log D – log C plots. The graphs of log D[Zr(IV)] against log C[2-OAP] at fixed sodium succinate concentration (0.02 M) are found to be linear having slopes of 2.0 and 2.0 at pH 6.0 and 6.5 respectively (Fig. 2a). Also plots of log D[Zr(IV)] against log C[succinate] at fixed 2-OAP concentration (0.087 M) are found to be linear with slopes of 2.4 and 2.4 at pH 6.0 and 6.5 respectively (Fig. 2b). The probable composition of the extracted species is calculated as 1:2:2 (metal:acid:extractant). The possible mechanism of the extracted species appears to be protonated 2-OAP which forms cationic species as RR’ NH2+ while succinate

as  ZrO(succinate)2 

2 −8,25,26

. Both of them associate to

, form ion pairs of the type (RR'NH2+ ) ZrO (Succinate)22 −    which being neutral constitutes extractable species. The mechanism of the formation of ion – pair complex may be represented as:

RR’NH(org) + H+(aq)
RR’NH2+ (org)

…(1)

ZrO2+(aq) + 2 succinate 2-(aq)
[ZrO(succinate)2]2-(aq)

…(2)

2RR’NH2+(org) + [ZrO(succinate)2]2-(aq)
[(RR’NH2+)2ZrO(succinate)22-](org)

…(3)

where R = -C5H4N; R’ = - CH2(CH2)6CH3

NORONHA et al.: SOLVENT EXTRACTION SEPARATION OF ZIRCONIUM (IV) WITH 2-OCTYLAMINOPYRIDINE

Loading capacity of 2-n-OAP

The loading capacity of 2-OAP is determined by using fixed concentration of the extractant, 10 mL of 0.087 M 2-OAP (0.180 g) and varying amount of Zr (IV) from 50 µg to 1000 µg. It is found that 10 mL of 0.087 M 2-OAP (0.180 g) extracts maximum of 500 µg of Zr (IV). Effect of aqueous to organic volume ratio on Zr (IV) extraction

The effect of contacting different volume ratios of organic to aqueous phase was studied. The results indicate that the preferred aqueous/organic (A/O) phase ratio in this study is 4:1 or less. This is evident from the sharp increase in the separation efficiency as well as distribution ratio of Zr (IV) when the phase ratio (A/O) is changed from 20:1 to 5:1. This may be due to the unavailability of reagent for metal extraction and a crowding effect occurs at a low phase ratio. However, in the recommended procedure, the phase ratio is 2.5:1. Effect of temperature

The extraction of Zr (IV) from 2-OAP was carried out in the temperature range 299-307 K. The plot of log kex against 1000/T is linear. Thus, the extraction of Zr (IV) with 2-OAP in xylene is favorable with the rise in temperature. The enthalpy change, (∆H in kJ mol-1) is evaluated from this plot by using the following equation: ∆H = - {slope} × 2.303 × R

…(4)

where R is gas constant = 8.314 kJ mol-1, Slope = -2.66 The free energy change (∆G in kJ mol-1) and entropy change, kJ mol-1 (∆S in kJ mol-1) were calculated using the following equations: ∆G = 2.303 RT log Kex

…(5)

where Kex = D / [RR’NH] [H+] RR’NH = 2-OAP ∆S = ∆H - ∆G / T

…(6)

The values of ∆G are negative, while that of enthalpy is positive. The activation parameters obtained for the solvent extraction of Zr (IV) are ∆G = -26.58 kJ mol-1; ∆H = 50.93 kJ mol-1 ∆S = 0.2557 kJ mol-1

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The negative value of ∆G indicates that the reaction is spontaneous. The positive value of enthalpy indicates that the reaction is endothermic. Effect of diverse ions

The effect of various foreign ions on the extraction of 400 µg Zr (IV) with 10 mL of 0.087 M 2-OAP in xylene at pH 4.0 from 0.02 M sodium succinate media was investigated following the recommended procedure. The tolerance limit of foreign ions was set not to cause more than ±2% error in the extraction of Zr (IV). The results show that 50 mg thiourea or nitrate, 25 mg fluoride or sulphate, 10 mg nitrite, iodide or thiocyanate, 5 mg bromide, thiosulphate, Tl(III), Zn(II) or Mo(VI), 3 mg In(III), Mg(II) or U(VI), 2 mg Cu(II) or Bi(III), 1 mg ascorbate, Al(III), Ba(II), V(V), Cr(VI), Y(III), Se(IV), Th(IV), Sn(II), Sn(IV), Ca(II) or Ni(II), 0.5 mg Ga(III), La(III), Fe(III), W(VI), tartarate, oxalate or phosphate do not interfere. The tolerance limit of Fe(II), Hg(II), Ce(IV), Pb(II) and Cd(II) was increased by masking with 10 mg SCN-, 10 mg I-, 25 mg F-, 25 mg SO4-and 10 mg I- respectively and prior extraction of cations Fe(II), Hg(II), Ce(IV), Pb(II) and Cd(II) was performed with the same reagent. Application

The suitability of the above developed method was examined by applying it to the separation and determination of Zr (IV) in a variety of binary mixtures which are commonly associated with it. Extraction from binary mixture

Binary mixtures of metals such as Mo(VI), Y(III), Cr(VI), La(III) and U(VI) remained unextracted under optimum conditions with Zr (IV) using 0.02 M sodium succinate and 10 mL of 0.087 M 2-OAP because they do not form a succinate complex at pH 4.0. Hence, the organic phase was stripped with 0.5 M nitric acid (3×10 mL) and determined spectrophotometrically as recommended in the procedure. Metal ions from the aqueous phase were determined by standard methods27,28. Separation of Zr (IV) from V(V) was made possible by selective stripping. Zr (IV) from the organic phase was stripped first with 0.5 M nitric acid (3×10 mL) followed by the stripping of V(V) with 1:1 NH3 (3×10 mL). V(V) was determined by hydrogen peroxide method29 and Zr (IV) by recommended procedure.

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The proposed method was extended for separation of Zr (IV) from Fe(III), Th(IV) and Al(III) by masking with 25 mg F- and W(VI) by masking with 10 mg SCN-. The masked metal ion remained in the aqueous phase while Zr (IV) was extracted selectively in to the organic phase with 2-OAP in xylene. It was stripped from organic phase with nitric acid (0.5 M) and estimated as per the given procedure. After demasking Fe(III), Al(III) and W(VI) with 5 mL HCl acid and Th(IV) with 5 mL perchloric

acid, the volume of the aqueous phase was reduced and added metal ions were determined by standard procedure (Table 1). Extraction from synthetic mixtures

The applicability of the method for the isolation and determination of Zr (IV) in ternary mixtures was also studied (Table 2). A solution containing 400 µg Zr (IV) was taken and known amount of other metals were added. Amount of Zr (IV) was extracted under the optimum extraction conditions. The results obtained are found to be in good agreement with the amount added.

Table 1—Separation of Zr (IV) from binary mixtures Metal ion

Amount µg

Average % recovery*

Zr(IV) Mo(VI) Zr(IV) Y(III) Zr(IV) Cr(VI) Zr(IV) La(III) Zr(IV) W(VI)a Zr(IV) Fe(III)b Zr(IV) U(VI) Zr(IV) Th(IV)b Zr(IV) Al(III)b Zr(IV) V(V)

400 400 400 200 400 400 400 200 400 400 400 150 400 300 400 100 400 200 400 800

99 99 99 98 100 99 99 98 99 99 98 99 99 99 98 97.4 99 97.2 98 97.7

Chromogenic ligand

Alizarin Red S Thiocyanate Alizarin Red S Diphenyl carbazide Arsenazo I Thiocyanate Thiocyanate Arsenazo I Arsenazo III Eriochrome cyaninR Hydrogen peroxide

*Average of five determination. a Masked by 10 mg SCN-. bMasked by 25 mg F- .

The method was further extended to determine Zr (IV) in real samples of alloy. Since we could not procure alloy samples containing Zr (IV), synthetic samples of alloy were created. An aliquot from each alloy solution was then analysed for Zr (IV) by the proposed method (Table 3). Extraction from nanopowder composite

The proposed method was also successfully applied for the determination of Zr (IV) from nanopowder composites. These samples were boiled with 10 mL aqua regia and then evaporated to moist dryness. The solution was boiled with hot water and filtered through Whatmann filter paper No.1. The residue was evaporated to moist dryness by the addition of 2×5 mL HCl. The filtrate was diluted to required volume with water. An aliquot of Zr (IV) solution was analyzed by recommended procedure. The results are found to be in good agreement with those obtained by atomic absorption spectrophotometer (Table 4).

Table 2—Determination of Zr (IV) from ternary mixtures Composition, µ g Zr(IV), 400; W(VI)a, 400; Mo(VI), 500 Zr(IV), 400; Pb(II), 400; Al(III)b, 300 Zr(IV), 400; Fe(III)b, 500; Cr(VI), 400 Zr(IV), 400; La(III), 600; Mg(II), 400 Zr(IV), 400; Ni(II), 400; Co(II), 400 Zr(IV), 400; Re(VII), 500; Mn(II), 500 Zr(IV), 400; Ir(III), 500; Os(VIII), 500 Zr(IV), 400; Ce(IV), 500; Nd(III), 500 *Average of five determination. a Masked with 10 mg SCN- bmasked with 25 mg F- .

Average % recovery*

Relative error

99. 9 99.9 99.9 99.9 99.9 99.9 99.9 99.9

0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1

NORONHA et al.: SOLVENT EXTRACTION SEPARATION OF ZIRCONIUM (IV) WITH 2-OCTYLAMINOPYRIDINE

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Table 3─Determination of Zr (IV) from synthetic mixtures corresponding to real samples of alloy Alloy

Composition of alloy, %

Zircaloy 1

Zr (IV) taken %

Zr (IV) found %

Average % recovery*

Zr, 97.5; W, 2.5

97.5

97.4

99.9

Zircaloy 2

Zr, 97.5; Al, 1.0; Sn, 1.0; Mo, 1.0

97.5

97.4

99.9

Zircaloy 3

Zr, 98.65; W, 1.2-1.70; Fe, 0.07-0.20; Cr, 0.05-0.15; Ni, 0.03-0.08

98.6

98.6

99.9

Cu-Cr-Zr alloy

Zr, 14; Cu,70; Cr, 16

14.0

13.9

99.3

Zr-Mg-Zn alloy (MA-14)

Zr, 93.8; Zn, 0.7; Mg, 5.5

93.8

93.7

99.9

Steel alloy

Si, 0.52; Mn,1.37; P, 0.33; S, 0.006; Nb, 0.87; Mo, 0.54; Ti, 0.095; V, 0.097; Re, 0.025; Zr, 0.098

0.098

0.097

99.0

Steel alloy

C, 0.14; Si, 0.54; S, 0.009; Ti, 0.14; Mn, 0.87; V, 0.36; Nb, 0.34; Zr ,0.21

0.21

0. 209

99.5

Steel alloy

Ti, 0.06; Ta,0.02; Nb, 0.02; V, 0.05; Co, 0.01; Ni, 0.01; Ce, 0.02; Zr, 0.05

0.05

0.049

98.0

Steel alloy

Th, 0.05; Mo, 0.1; Sn,0.1; Zr, 0.05

0.05

0.049

98.0

Al alloy

Cu, 0.0073; Mg, 8.57; Mn,0.26; Si,0.17; Fe, 0.092; Ni, 0.093; Sb, 0.025; Re, 0.1; Zr, 0.12

0.12

0.119

99.2

*Average of five determination. Table 4─Determination of Zr (IV) from Zirconium deposited thin films and nanopowder composites Zirconium nanomaterials Sample No. 1 a Sample No. 2 a Sample No. 3 a Zr-Ce-nano composite powderb Zr-Mo-nano composite powderb

Certified value µg/mL 300.0 450.0 600.0 108 216

Amount of Zr (IV) found µg/mL Proposed method AAS method 300.0 450.0 600 107 215

299 449 599 107 215

Average % recovery* 99.7 99.8 99.8 99.07 99.53

RSD % 0.3 0.2 0.2 0.93 0.46

a

Zirconium deposited thin film, Department of Physics, Shivaji University, Kolhapur, India. Department of Physics, Shivaji University, Kolhapur, India. *Average of five determination. b

Conclusion The developed method is found to be very simple, selective, reproducible, accurate and rapid. Low reagent concentration of 2-OAP is required for quantitative recovery of Zr (IV) as compared to other high molecular weight amines. The method is free from interference of large number of foreign ions which are associated with Zr (IV) in its natural occurrence. The method permits selective separation of Zr (IV) from other metals such as Mo(VI), La(III), U(VI), W(VI), Y(III), Fe(III), Al(III) and Cr(VI). The method can also be employed for the analysis of Zr (IV) present in synthetic mixtures, real samples of alloy, thin films, and nanopowder composites.

Acknowledgement The authors are grateful to UGC–SAP and DST– FIST for providing financial assistance. One of the authors (Leena E Noronha) expresses her gratitude to Mrs. Shubhangi Gavade, the Secretary of Swami Vivekanand Shikshan Sanstha for her kind encouragement. References 1 2 3 4

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