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Indian Journal of Chemistry Vol. 25A, January 1986, pp. 96-98 Reversed Phase Extractive Chromatographic Separation of Titanium(IV) on Malonato Complex Using High Molecular Weight Amines PRAKASH NARAYANAN & s M KHOPKAR* Department of Chemistry, Indian Institute of Technology, Bombay 400076 Received 3 January 1985; revised 18 June 1985; accepted 15 July 1985 Titanium is quantitatively extracted in pH range 2.5 to 6.0 from 0.01 M malonic acid on silica gel column coated with Amberlite LA- I and is separated by stripping with (1-4 M) hydrochloric and nitric acid and (0.05 to 1.0 M) sulphuric acid and is determined spectrophotometrically at 360 nm. Separation of titanium from binary mixtures containing alkali, alkaline earths, chromium (III), manganese, iron(II), cobalt, nickel, lead, aluminium and yttrium is made possible since these elements do not form malonato com- plexes. It is possible to separate it from zirconium, uranium, vanadium, niobium, thorium, molybdenum and iron(III) by exploiting the differences in the stabilities of malonato complexes in the presence of complexing acids. Titanium has been separated from ternary and quaternary mixtures containing chromium, molyb- denum, iron, manganese and nickel, the elements which are nor- mally present in alloys. Tributylphosphate 1.2 and tri-z-octylphosphine oxide v" have earlier been used for the extractive chromatographic separation of titanium from nio- bium, molybdenum and vanadium. Titanium could be separated from iron on haloport-F column by 2- octanone>. Separations with tri-x-octylarnine":" have been reported to be rapid and applicable at microgram concentrations. But systematic investigations on ex- traction chromatography of titanium from organic acids do not appear to have been carried out so far. Titanium forms anionic malona to complex", extract- able with Amberlite LA-I. This fact has been presently utilised for the development of a method for the extractive chromatographic separation of titanium on silica gel column. Apparatus and reagents used were the same as described earlier 901 O. A stock solution containing 2.34 mg/ml of titanium was prepared by dissolving titanium dioxide (2g) in sulphuric acid (10 ml), diluting the solution to 500 ml and standardising gravimetrically with cupferron". An aliquot of solution containing 117jlg of titanium solution was mixed with 5 ml of 0.01 M malonic acid and the pH of the solution adjusted to 2.5 to 6.0. It was 96 passed through a column of silica gel (100-200 mesh) coated with Amberlite LA-I as described earlier I 0. Titanium was stripped with various mineral acids. Ten fractions (5 ml each) were collected and titanium in each fraction was determined spectrophoto- metrically II. In the batch extraction with 0.1 M Amberlite LA-I in xylene titanium was quantitatively extracted in pH range of 3.5 to 6.0 from 0.01 M malonic acid and was stripped with I M hydrochloric acid. Although the extraction was insignificant till pH 2.0 (46.6%), it was quantitative between pH 2.5 and 6.0 and decreased beyond pH 6.5 (86.7%). The optimum concentration of malonic acid for quantitative extraction of titanium at pH 3.5 was 0.01 M. It was observed that 1.0-4.0 M of hydrochloric, nitric acid or sulphuric acid completely stripped titanium from the column. Several elements like alkali, alkaline earths, chromium(III) iron (II), cobalt, nickel, copper, zinc, cadmium, aluminium, thallium and lead do not form anionic malonato complexes at the specified pH and hence do not interfere in the separation of titanium even when present in lO-fold excess in binary com- bination with titanium. The acid used in stripping titanium in the presence of these elements was 0.1 M sulphuric acid. Some elements like uranium, zir- conium, hafnium, molybdenum, thorium and niobium formed relatively stable complexes with malonic acid and were extracted alongwith titanium. Sulphuric acid (0.1 M) was found to be a good stripping agent for titanium but not for all these elements, which were re- extracted as their anionic sulphato complexes on the column and were eluted later with either 2 M hy- drochloric acid or nitric acid. It was possible to strip off titanium at any con- centration of hydrochloric acid, sulphuric acid or nitric acid from a multicomponent mixture containing iron (III), uranium, zirconium, molybdenum and thorium. While uranium and iron(IIl) formed anionic chloro complexes, zirconium, molybdenum, thorium and uranium formed anionic sulphato complexes in dilute sulphuric acid. In a multicomponent mixture these elements were re-extracted while titanium was stripped off. This formed the basis for separation of titanium in multicomponent mixtures (Fig. 1). The mixture of chromiurn(III) or irontlf), vanadium (V) and titanium (IV) was separated by passing it through the column when chromium or iron (II) was not extracted and passed through the column. Va- nadium was stripped with I M malonic acid and titanium was eluted with 0.1 M sulphuric acid.
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Page 1: Reversed Phase Extractive Chromatographic Separation of ...nopr.niscair.res.in/bitstream/123456789/48036/1/IJCA 25A(1) 96-98.… · extractive chromatographic separation of titanium

Indian Journal of ChemistryVol. 25A, January 1986, pp. 96-98

Reversed Phase Extractive ChromatographicSeparation of Titanium(IV) on

Malonato Complex Using High MolecularWeight Amines

PRAKASH NARAYANAN & s M KHOPKAR*Department of Chemistry, Indian Institute of Technology, Bombay

400076

Received 3 January 1985; revised 18 June 1985;accepted 15 July 1985

Titanium is quantitatively extracted in pH range 2.5 to 6.0 from0.01 M malonic acid on silica gel column coated with Amberlite LA-I and is separated by stripping with (1-4 M) hydrochloric and nitricacid and (0.05 to 1.0 M) sulphuric acid and is determinedspectrophotometrically at 360 nm. Separation of titanium frombinary mixtures containing alkali, alkaline earths, chromium (III),manganese, iron(II), cobalt, nickel, lead, aluminium and yttrium ismade possible since these elements do not form malonato com-plexes. It is possible to separate it from zirconium, uranium,vanadium, niobium, thorium, molybdenum and iron(III) byexploiting the differences in the stabilities of malonato complexes inthe presence of complexing acids. Titanium has been separated fromternary and quaternary mixtures containing chromium, molyb-denum, iron, manganese and nickel, the elements which are nor-mally present in alloys.

Tributylphosphate 1.2 and tri-z-octylphosphineoxide v" have earlier been used for the extractivechromatographic separation of titanium from nio-bium, molybdenum and vanadium. Titanium could beseparated from iron on haloport-F column by 2-octanone>. Separations with tri-x-octylarnine":" havebeen reported to be rapid and applicable at microgramconcentrations. But systematic investigations on ex-traction chromatography of titanium from organicacids do not appear to have been carried out so far.Titanium forms anionic malona to complex", extract-able with Amberlite LA-I. This fact has been presentlyutilised for the development of a method for theextractive chromatographic separation of titanium onsilica gel column.

Apparatus and reagents used were the same asdescribed earlier 901 O.

A stock solution containing 2.34 mg/ml of titaniumwas prepared by dissolving titanium dioxide (2g) insulphuric acid (10 ml), diluting the solution to 500 mland standardising gravimetrically with cupferron".

An aliquot of solution containing 117jlg of titaniumsolution was mixed with 5 ml of 0.01 M malonic acidand the pH of the solution adjusted to 2.5 to 6.0. It was

96

passed through a column of silica gel (100-200 mesh)coated with Amberlite LA-I as described earlier I 0.

Titanium was stripped with various mineral acids. Tenfractions (5 ml each) were collected and titanium ineach fraction was determined spectrophoto-metrically II.

In the batch extraction with 0.1 M Amberlite LA-Iin xylene titanium was quantitatively extracted in pHrange of 3.5 to 6.0 from 0.01 M malonic acid and wasstripped with I M hydrochloric acid. Although theextraction was insignificant till pH 2.0 (46.6%), it wasquantitative between pH 2.5 and 6.0 and decreasedbeyond pH 6.5 (86.7%). The optimum concentration ofmalonic acid for quantitative extraction of titanium atpH 3.5 was 0.01 M. It was observed that 1.0-4.0 M ofhydrochloric, nitric acid or sulphuric acid completelystripped titanium from the column.

Several elements like alkali, alkaline earths,chromium(III) iron (II), cobalt, nickel, copper, zinc,cadmium, aluminium, thallium and lead do not formanionic malonato complexes at the specified pH andhence do not interfere in the separation of titaniumeven when present in lO-fold excess in binary com-bination with titanium. The acid used in strippingtitanium in the presence of these elements was 0.1 Msulphuric acid. Some elements like uranium, zir-conium, hafnium, molybdenum, thorium and niobiumformed relatively stable complexes with malonic acidand were extracted alongwith titanium. Sulphuric acid(0.1 M) was found to be a good stripping agent fortitanium but not for all these elements, which were re-extracted as their anionic sulphato complexes on thecolumn and were eluted later with either 2 M hy-drochloric acid or nitric acid.

It was possible to strip off titanium at any con-centration of hydrochloric acid, sulphuric acid or nitricacid from a multicomponent mixture containing iron(III), uranium, zirconium, molybdenum and thorium.While uranium and iron(IIl) formed anionic chlorocomplexes, zirconium, molybdenum, thorium anduranium formed anionic sulphato complexes in dilutesulphuric acid. In a multicomponent mixture theseelements were re-extracted while titanium was strippedoff. This formed the basis for separation of titanium inmulticomponent mixtures (Fig. 1).

The mixture of chromiurn(III) or irontlf), vanadium(V) and titanium (IV) was separated by passing itthrough the column when chromium or iron (II) wasnot extracted and passed through the column. Va-nadium was stripped with I M malonic acid andtitanium was eluted with 0.1 M sulphuric acid.

Page 2: Reversed Phase Extractive Chromatographic Separation of ...nopr.niscair.res.in/bitstream/123456789/48036/1/IJCA 25A(1) 96-98.… · extractive chromatographic separation of titanium

80604020

a8060402ll0

80604020

0>- 80ocui 60>0u 40wIX

0

~

604020O~~~~~~~~~~~~

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Fig. I-Separation of titanium from multicomponent mixtures

A mixture containing chromium (III), titanium (IV)and iron (III) could be separated into individualcomponents by passing it through the column, whenchromium (III) was washed with water, titanium with4 M hydrochloric acid and iron with 0.1 M hy-drochloric acid.

Yttrium or lanthanum, titanium (IV) and zirconiumor hafnium were separated by passing the mixturethrough the column when yttrium or lanthanum wasnot extracted. The extracted titanium was strippedwith 0.1 M sulphuric acid and during the processzirconium or hafnium was re-extracted as sulphatocomplex on the column. Zirconium or hafnium wasfinally stripped with 2 M hydrochloric acid.

NOTES

A ternary mixture containing nickel or manganese,titanium (IV) and molybdenum (VI) could be sepa-rated by passing it through the column, when nickel ormanganese was not extracted and passed through thecolumn. The extracted titanium was stripped with 0.1M sulphuric acid and molybdenum with 1 M am-monium hydroxide.

The separation of tantalum, titanium (IV) andniobium was carried out by passing the mixturethrough the column. Tantalum was washed with 0.01M malonic acid buffered at pH 3.5 and titanium wasstripped with 0.1 M malonic acid and hydrochloricacid containing 1.5% hydrogen peroxide. Niobiumwas finally stripped with 2 M hydrochloric acid.

Lanthanum, titanium (VI), zirconium and uranium(VI) were separated by passing the mixture through thecolumn. Lanthanum passed through the column withwater, while titanium was stripped with 0.1 M sul-phuric acid, zirconium with 6.0 M hydrochloric acidand uranium with 2.0 M nitric acid.

Titanium from steel sample AISI No. 321 wasseparated by first passing an aliquot of solutionthrough the column when chromium, manganese,nickel were not extracted. The extracted titanium wasstripped with 4 M hydrochloric acid and iron with 0.1M hydrochloric acid. Titanium found was 0.42%against a certified value of 0.45%.

In all the separations from binary and multicom-ponent mixtures, the pH of the mixture was firstadjusted to 2.5 to 6.0 in the presence of 0.01 M malonicacid and then passed through the column at a flow rateof 1 ml/min. The elements after stripping from theorganic phase were determined spectrophoto-metrically with suitable chromogenic ligands 12.

The proposed method is useful as it permits sepa-ration of titanium from commonly associated elementslike chromium, nickel, manganese and molybdenum.The separation of titanium from niobium, uranium,zirconium, thorium, lanthanum and yttrium is impor-tant as they are found together in fission products. Themethod is rapid, simple and reasonably selective. Themethod is applicable at microgram concentrations ofthe metals.

We are thankful to the CSIR, New Delhi, forsponsoring this project and for the award of a seniorresearch fellowship to one of us (P N).

ReferencesI Alimarin I P, Gibalo I M & Lapenko LA, Chem Abstr, 78 (1973)

11124.2 Minczewski & Rozycki C, Chem Anal, 10 (1965) %5.3 Cerrai E & Testa C, J Chromatog, 9 (1%2) 216.4 Cerrai E & Testa C, Energia Nucleare, 8 (1%1) 510.5 Fritz J S & Hedrick C E, Anal Chem, 34 (1962) 1411.6 Cerrai E & Testa C, J Chromatog, 6 (1%1) 443.

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INDIAN J. CHEM., VOL. 25A, JANUARY 1986

7 A1imarin I P, Gibalo 1M&; Mymrik N A, ClremAbstr, 76 (1972)28147.

8 Sawant M A &;KhopkaC S M, Talonta.21 (1983) 482-9 Narayanan P &; Khopkar S M, J radioanol cI nucl Cbem, 84

(1984) 33.

98

10 Narayanan P &;Khopkar S M, Anal Leu, 16 (1983) 443.

11 Easton A J, AMI Chim Acta. 78 (1975) 224.

12 Snell F D, Photometric and fluorometric methods of analysis(Wiley, New York) 1978.