Extractive separation of Vanadium(V)

27 International Journal of Analytical and Bioanalytical Chemistry 2013; 3(1): 27-35

ISSN-2231-5012

Original Article

Extractive separation of Vanadium(V) from succinate medium by solvent

extraction using 2-n-octylaminopyridine

Leena E. Noronhaa,b

, Ganesh S. Kamble a,c

, Sanjay S. Kolekara, Mansing A. Anuse*

a Analytical Chemistry Laboratory, Department of Chemistry, Shivaji University, Kolhapur, 416 004, India

b Department of Chemistry, Vivekanand College Kolhapur, India

c Department of Engineering Chemistry, KIT’s College of Engineering, Kolhapur, India

[email protected]

Received 01 February 2013; accepted 14 February 2013

Abstract

A systematic study of liquid liquid extractive separation of Vanadium (V) was carried out from 25ml 0.01M sodium

succinate solution using 10mL 0.087M 2-n-octylaminopyridine as an extractant. Quantitative extraction of Vanadium

(V) was observed at pH 3.0-5.0 in the range of 0.005-0.02M sodium succinate with 0.087M 2-n-OAP in xylene.

Vanadium(V) was back extracted with 6M NH3(3x10mL) and determined spectrophotometrically by 8-quinolinol

method. Various parameters such as effect of acid concentration, stripping agents, equilibration time, loa ding

capacity, aqueous to organic volume ratio, reagent concentration, diluents were studied. From the temperature study

the enthalpy change (∆H) of the extraction was recorded as 34.464KJ mol-1

.The nature of the extracted species in

organic phase was determined by using conventional slope analysis method. The extraction of Vanadium(V) in acidic

range was found to proceed by ion pair mechanism with extracted species being [(RR’NH

+)2 VO(succinate)

2-2 ](org) .The

proposed method was applicable to separate Vanadium(V) from associate metals like Zr(IV), Mo(VI),

W(VI),Re(VII),Co(II),Ni(II),Zn(II), Fe(III) and Pb(II).The method is further extended for the recovery of

Vanadium(V) from various synthetic mixtures, real samples of alloy, pharmaceutical and certain en vironmental

samples.

© 2013 Universal Research Publications. All rights reserved

Keywords: Vanadium (V), liquid liquid extraction, 2-n-octylaminopyridine.

INTRODUCTION Vanadium is widely distributed throughout the earth but

in rather low abundance ranking twenty second among

the elements of the earth’s crust [1,2]. It is always found

in combination with various minerals such as carnotite,

roscoelite, vanadinite, mothramite and patronite, which

are important sources of the metals [3]. Significant

amounts are present in bauxite and carboniferous

materials such as coal, oil shale and tar sand. [1].

Naturally occurring Vanadium consists of two isotopes 50

V (0.24%) and 51

V (99.76%) of which 50

V form is

slightly radioactive and has a half life of more than

3.9x1017

years.[4]. Vanadium is an important trace metal

of bioinorganic importance [5] and is present in most of

the organisms. A substantial amount of vanadium is

released during burning of crude petroleum, coal and

lignite which would then settle on the soil. Some plants

accumulate vanadium up to 80 µg mL-1

, [6] most of

which is accumulated in leaves and roots. Vanadium acts

as a growth –promoting factor and participates in

fixation and accumulation of nitrogen in plants, while

high concentration of vanadium reduces productivity of

the plants [7].Vanadium is an essential element for

normal cell growth [8]. It is beneficial for prevention of

vascular diseases and also has therapeutic potentials for

diabetes with a definite safe dose range because of its

insulin mimic effects. Vanadium complexes can reduce

growth of cancer cells and improves human diabetes

mellitus [9]. The toxicity of Vanadium is dependant on

its oxidation state with Vanadium (V) being more toxic

than Vanadium (IV) [10]). The amount of Vanadium in

blood and urine depends upon intensity and duration of

its exposure. The threshold limit values (TLV) reported

are 0.5mg/cubic meters of air and 0.1mg/cubic meter of

fume. [11]. The amount of Vanadium in excess of TLV

values is reported to cause anemia, cough, emaciation

and irritation of mucous membrane, gastrointestinal

disturbances and bronchopneumonia.[12]. Industrial

exposure to Vanadium has been showed to cause eye and

lung irritation, inhibition of activity to enzyme

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cholinesterase.[13]. Industrial applications of Vanadium

include dyeing, ceramics, ink and catalyst manufacture.

Discharges from industries contribute to its presence in

the water supply. [14]. In this country the tolerable level

of Vanadium in drinking water is 100 µgL-1

.The most

important use of Vanadium is as an alloying element in

steel industry where it is added to produce grain

refinement and hardenability in steels. Vanadium steels

are used in dies or tapes because of their depth

hardening characteristics and for cutting tools because of

their wear resistance. They are also used as

constructional steel in both light and heavy sections, for

heavy ions and steel castings, forged parts such as shafts

and turbine motors, automobile parts like gears and axles

and for springs and ball bearings. Vanadium is an

important component of ferrous alloys used in jet

aircraft engines and turbine blades where high

temperature creep resistance is a basic requirement. It is

also used as an additive to titanium alloys for aerospace

applications. [15]

Several high molecular weight amines have been used

for solvent extraction of Vanadium. They are N-p-

octyloxybenzoly-N-phenylhyroxyl amine, [16],

trioctylamine[17], diisododecylamine[18], primene 81R

and alamine 336 [19]and tricapryl methyl ammonium

chloride[20]. Extraction of Vanadium by

organophosphorus compounds like, Tri-n-butyl

phosphate(TBP) [21], TBP and tri-n-octyl phosphine

oxide (TOPO)[22,23], di-(2-ethyl hexyl)-phophoric acid

(D2EHPA)[24,25],D2EHPA/TBP[26] and

D2EHPA/TOA[27] was successfully carried out. The

other extractants employed for liquid liquid extraction of

Vanadium were 2-hydroxy-4-methoxy-5-methyl

chalkone oxime, (HMMCO)[28], aliquat-336[29,30,31],

rotaxane hydroxamic acid[32], 8-quinolinol [33] and

LIX.63[34]

The present paper deals with liquid- liquid extraction of

Vanadium (V) with 2-n-octylamino pyridine which gives

an ion pair complex extractable into xylene. The aim of

this work is to develop an efficient extraction process for

the sequential separation of V (V) and Mo (VI).The

method is further applied for the separation of V (V)

from commonly associated metals and for analysis of

several samples with good results.

Experimental Apparatus

An Elico digital pH meter model LT – 120 was used for

pH measurement. Labtronics UV-VIS digital

spectrophotometer model LT-29 with 1 cm quartz cells

was used for absorbance measurements. Tapson’s

analytical single pan balance model 200 T having 0.001

gm accuracy was used for weighing.

Doubly distilled water and analytical reagent – grade

chemicals (BDH or Merck) were used throughout this

study. All apparatus were used during the time period

from January to May 2012.

Reagents

Standard Vanadium (V) solution.

A stock solution of Vanadium (V) was prepared by

dissolving previously ignited Vanadium pentoxide in dil.

NaOH which was acidified with sufficient amount of

conc.H2SO4 and then diluted to 1000ml with doubly

distilled water. The solution was standardized by known

method.

A working solution of 10 µg/mL was made by

appropriate dilution.

2-n-Octylaminopyridine was synthesized by Borshch and

Petrukhin method [35] and its solution was prepared in

xylene (S.D. fine).

0.5 percent 8- quinolinol was prepared in chloroform.

General procedure for the extraction and determination

of vanadium(v))

An aliquot of Vanadium(V) solution containing 50 µg

was mixed with a sufficient quantity of sodium

succinate(0.0675 g) to make its concentration of 0.01 M

in a total volume of 25 mL of the solution.The PH

of the

aqueous solution was adjusted to 3.2 with dilute

hydrochloric acid and sodium hydroxide solution. The

solution was then transferred to a 125 mL separatory

funnel and shaken for 3min. with 10 mL of 0.087M of 2-

n-octylaminopyridine in xylene. The organic phase was

separated and equilibrated with three 10 mL portions of

6M ammonia solution to back extract Vanadium(V). The

back extractants were combined and shaken with 5 mL

of xylene to remove the traces of dissolved amine and

evaporated to moist dryness. Vanadium(V) was

determined spectrophotometrically [40] as follows

The PH

of the aqueous phase was adjusted to 5.0 after

diluting to 25 mL with distilled water. The solution was

then extracted with 2 successive 5ml portions of 0.5%

8quinolinol in chloroform. The black

hydroxyquinolinate complex absorbed at 400 nm. The

amount of Vanadium (V) was computed from a

calibration curve.

Fig.1. Extraction of V (V) as a function of 2-n-

octylaminopyridine concentration


Result and discussion Extraction as a function of p

H

The effect of pH

on percentage extraction of Vanadium

(V) was studied with varying pH

range of 1-10 in

presence of weak organic acid such as sodium succinate

(0.01M) with 2-n-OAP in xylene. The extraction of

Vanadium (V) was found to be quantitative in the pH

range 3.0 to 5.0 to form ion pair complex with 0.01M

sodium succinate. An optimum pH 3.2 was used for

efficient extraction of Vanadium (V) for further

recommended procedure.

Extraction of Vanadium as a function of 2-n-

Octylaminopyridine Concentration

In order to optimize for the extraction of Vanadium (V),

xylene solutions of 2-n-octylaminopyridine of varying

concentrations (0.0024-0.49 M) were employed keeping

others parameters like pH, equilibrium time, diluents and

temperature constant. It was found that quantitative

extraction of 50 µg Vanadium (V) from 0.048-0.145 M

2-n-OAP was carried out with 0.01M sodium succinate

at pH 3.2. However increase in the concentration

decreases the extraction. This is due to the formation of

stable ion-pair between 2-n-OAP and succinate.(Fig.1).

Further extraction study of Vanadium (V) was carried

out using 0.087M 2-n-OAP in xylene.

Extraction as a function of weak organic acid

concentration.

The extraction of Vanadium(V) was carried out in

presence of varying concentration of weak acid such as

sodium succinate, sodium malonate, sodium citrate

,sodium tartarate and L-ascorbic acid by keeping all the

parameters constant . The extraction of Vanadium (V)

was found to be quantitative in the range 0.005-0.02M

for sodium succinate, sodium malonate, sodium citrate

and sodium tartarate. There was incomplete extraction of

Vanadium (V) in presence of L-ascorbic acid. However

0.01M sodium succinate was used throughout the

experimental work. [Fig.2]

Fig. 2. Extraction of V (V) as a function of weak

organic acid conc.

Extraction with various diluents

Benzene, xylene, toluene, chloroform, carbon

tetrachloride, amyl alcohol, methyl isobutyl ketone, n-

butanol, kerosene, amyl-acetate and 1, 2 dichoroethane

were examined for use as diluents in the extraction of

Vanadium (V) with 2-n-octylaminopyridine. The most

efficient diluent was found to be xylene.

Effect of stripping agents

Vanadium (V) was stripped with three 10 mL portions of

various stripping agents at different concentrations. The

stripping was found to be incomplete in water(65.31%),

NaOH ( 81.0%), Na2CO3(79.84%),acetic acid(98.45%),

acetate buffer at pH 4.45 (97.25%) and ammonium

chloride-ammonium hydroxide buffer at pH 10.0(7.2%).

But complete stripping was possible using ammonia

(6.0-8.0 M), and KOH (0.5-0.9 M). In the proposed

method 6M ammonia was used as strippant because

it was easier to remove from aqueous phase by

evaporation prior to determining Vanadium (V)

spectrophotometrically. [Table 1].

Effect of equilibration time

When the two immiscible phases were equilibrated for a

period of (0.25 min to 30 min), the extraction was

quantitative over a period of 2-5 min. For the proposed

method, 3 min equilibration time was recommended in

order to ensure complete extraction of Vanadium (V).

Loading capacity of 2-n- OAP

The concentration of Vanadium (V) was varied from 10-

500 µg / 10 mL to determine the loading capacity of 2-n-

octylaminopyridine in xylene. It was found that the

maximum loading capacity of 10 mL 0.087 M 2-n-

octylaminopyridine in xylene was 100µg Vanadium (V).

Effect of aqueous to organic volume ratio

Vanadium (V) was extracted in different aqueous to

organic volume ratios in the range 10-200mL of 0.01m

aqueous sodium succinate medium with 10mL 0.087M

2-n-OAP in xylene. There was sharp increase in the

separation efficiency and distribution ratio of Vanadium

(V) when phase ratio A/O varied from 1:1 to 4:1.

However in the recommended procedure the phase ratio

used was 2.5:1.

Fig. 3.Log-log plot of log D V (V) Vs log C [2-OAP] at

fixed succinate conc


Fig. 4. Log-log plot of log D V(V) Vs log C [succinate]

at fixed 2-n-octylaminopyridine conc .

Fig. 5. Effect of temperature on extraction of V (V)

Nature of the extracted species

The probable composition of the extracted species were

ascertained by plotting a graph of log D V (V) against log

C (2-n-OAP) at fixed sodium succinate concentrations (0.01

M) (fig 3). The plots were linear having slopes of 1.8.

and 2.0 at pH 5.0 and 5.5. This indicates that the metal :

extractant ratio was 1:2 Also plots of log D V (V) against

log C (succinate) at fixed 2-n-OAP concentration (0.087 M)

were linear and with slopes of 2.0 and 1.9 (fig. 4). This

indicates two succinate ions participate in the formation

of anionic species. Thus the probable composition of

extracted species is calculated to be 1:2:1(metal:

acid:extractant). A mechanism of the extractant species:

Reaction

RR’NH(org) + H

+(aq) RR

’NH

+2(org) (1)

VO2+

(aq) +2 succinate 2-

VO(succinate)22-

(aq) (2)

2RR’NH

+2(org)+VO(succinate)2

2-(aq)[(RR

’NH2)2

VO(succinate2-

)2 ](org) (3 )

Effect of temperature

The extraction of Vanadium (V) from the aqueous

solution in presence of 0.01 M with 0.087 M of 2-n-

octylaminopyridine in xylene was studied at varying

temperature between 299 and 307 K. The change of

extraction equilibrium constant (kex) with temperature is

expressed by Vant Hoff equation:-

𝑑(𝑙𝑜𝑔 𝑘𝑒𝑥 )

d (

1

T) =

−Δ𝐻

2.303R

The plot of log (kex) Vs 1000/T is linear with slope (-

1.8) and enthalpy change of the extraction reaction was

evaluated as ∆H = 34.464 KJ mol-1

which suggest that

the reaction is endothermic.

The free energy (∆G) and entropy (∆S) were calculated

from eqns (1) and (2). The values of ∆G are negative

while the value of enthalpy is positive. [Table 2]

∆G = 2.303 RT. log kex ………. (1)

ΔS =ΔH−ΔG

T ………. (2)

The negative value of ∆G indicates the reaction is

spontaneous. The positive enthalpy value indicates that

the extraction of Vanadium (V) with 2-n-

octylaminopyridine is favourable with rise in

temperature (Fig. 5).

Effect of diverse ions

The effect of various cations and anions on the recovery

of Vanadium (V) was investigated. The tolerance limit

was set as the amount of foreign ions causing a change

±2% error in the recovery of Vanadium(V). Initially the

foreign ions were added to Vanadium (V) solution in

large excess, 100 mg for anions and 25 mg for cations.

The result shows that most common ions do not interfere

with the determination, suggesting high selectivity of

proposed method. Only some cations such as Al(III),

Ga(III), Fe(III), Nb(V), Ni(II), Tl(I) and Sb(III) can be

eliminated by masking with 10mg F,- 50mg SCN

- and

10mg citrate. The selectivity of this method is

increasesed by using suitable masking agents (Table 2).

The anions such as EDTA and Ascorbate interfered in

the extraction of Vanadium (V) by the proposed method.

Applications

Separation and determination of Vanadium (V) from

binary mixture:

The suitability of above developed method

was examined by applying it to the separation and


Table 1: Extraction behaviour of V(V) as a function of stripping agents

% RECOVERY

Molarity NH3 NaOH KOH Na2CO3 CH3COOH

0.1 25.23 49.22 72.20 22.43 50.56

0.2 38.29 52.41 79.87 35.39 55.24

0.3 49.26 61.39 86.90 46.27 60.32

0.4 58.42 72.44 96.42 52.46 69.48

0.5 67.28 75.06 100 55.25 75.74

0.6 70.11 77.24 100 63.29 80.91

0.7 72.24 79.51 100 69.80 85.48

0.9 73.91 81.22 100 74.52 89.92

1.0 74.52 76.24 98.00 76.19 94.28

2.0 87.26 73.59 92.05 79.84 95.08

3.0 90.41 65.04 88.15 66.79 96.14

4.0 93.20 61.16 84.00 61.25 97.21

5.0 96.43 54.12 76.28 59.46 98.45

6.0 100 45.27 65.45 55.24 95.21

7.0 100 - - 50.55 91.16

8.0 100 - - 42.91 88.46

9.0 99.42 - - 37.62 84.23

10.0 95.52 - - 29.28 80.14

Water-recovery 65.31%); Ammonia Buffer (pH=10.0) (7.2%) recovery; Acetate buffer (pH=4.45): recovery 97.25%

Table 2: Effect of diverse ions

Foreign ion Tolerance limit(mg) Masking agent Foreign ion Tolerance limit(mg) Masking agent

Without

masking

agent

With

masking

agent

Without

masking

agent

With

masking

agent

Sr(II) 5 25 10mg citrate Ni(II) 0.5 3 50mg SCN-

Zn(II) 4 20 10mg citrate Al(III) 0.5 2 10mgF-

Ca(II) 4 20 10mg citrate Ga(III) 0.5 5 10mgF-

Mg(II) 4 20 10mg citrate In(III) 0.5 5 10mgF-

Fe(III) 3 25 10mgF- Nb(V) 0.1 1 10mgF

-

Co(II) 2 20 50mg SCN- Tl(I) 0.4 2 10mg citrate

Cd(II) 1.0 15 50mg SCN- W(VI) 0.5 3 10mgF

-

Cr(VI) 1.0 10 10mg citrate Sb(III) 0.5 3 10mg citrate

Au (III) 1.0 10 100mg Br- Acetate 100

Bi(III) 1.0 10 10mg citrate Iodide 100

Pb(II) 1.0 20 100mg I- Bromide 100

Ge(IV) 1.0 10 10mgF- Thiourea 100

Hg(II) 1.0 20 100mg I- Tartarate 100

Cu(II) 1.0 25 100mg I- Thiocyanate 50

Se(IV) 1.0 15 10mg citrate Nitrate 50

Ce(IV) 1.0 15 10mgF- Nitrite 50

La(III) 1.0 10 10mgF- Salicylate 50

U(VI) 1.0 10 10mgF- Citrate 10

Th(IV) 1.0 10 10mgF- Fluoride 10

Re(VII) 1.0 10 50mg SCN- Thiosulphat

e 5

Ba(II) 1.0 10 10mg citrate Sulphate 1

Zr(IV) 1.0 5.0 10mgF- Phosphate 1

Mo(VI) 1.0 5.0 50mg SCN- Oxalate 1

determination of Vanadium (V) in varieties of binary

mixtures which are commonly associated with it by

taking the advantages of the difference in extraction

condition of the metal, such as PH of the aqueous phase,

reagent concentration and use of masking agent.

Sequential separation of Vanadium (V) and Molybdenum

(VI): To an aliquot containing 50 µg Vanadium(V) and

400 µg Molybdenum (VI) in a 25 ml volumetric flask

enough sodium succinate and water were added to give a

final concentration of 0.01M. The pH of the solution was


Table 3: Separation of V(V) from binary mixtures

Metal ion Amount (µg) Average (%)Recovery Chromogenic ligand Reference No.

V(V)) 40 99.9 8- quinolinol 40

Zr(IV) 100 99.7 Alizarin red S 38

V(V) 40 99.8

Mo(VI) 400 99.6 Thiocyanate 37

V(V) 40 99.8

WVI) a 200 99.8 Thiocyanate 37

V(V) 40 99.9

Ni(II) b

200 99.9 DMG 38

V(V) 40 99.9

Re(VII) 200 99.7 Thiocyanate 37

V(V) 40 99.8

Pb(II) 400 99.5 EBT 39

V(V) 40 99.8

Co(II) 400 99.6 Thiocyanate 38

V(V) 40 99.9

Fe(III) 500 99.8 Thiocyanate 38

V(V) 40 99.9

Zn(II) 500 99.8 EBT 36

V(V) 40 99.9

Cr(VI) 200 99.7 Diphenyl carbazide 38

a masked by 10 mg F-

b masked by 50 mg SCN-

Table 4: Separation of V(V) from synthetic mixtures

Composition (g) Average

Recovery* %

Relative

error

V(V),50;Zr(IV),400; Pb(II), 500 99.9 0.1

V(V),50; Mo(VI), 300; Fe(III),

300 99.8 0.2

V(V),50; Cu(II), 400; Mo(VI),

300 99.9 0.1

V(V),50 ; Bi(III), 400; Au

(III),500 99.8 0.2

V(V),50 ; Hg(II), 500; Sr(II),

500 99.8 0.2

V(V),50; Zn(II), 500; W(VI) a,

300 99.8 0.2

V(V),50 ; Cr(VI), 300; Ni(II) b,

200 99.8 0.2

V(V), 50 ; Re(VII), 300; Th(IV),

400 99.9 0.1

V(V), 50 ;Sb(III)400 c ; Co(II),

300 99.8 0.2

* Average of five determinations; a Masked by 10 mg F-; b

Masked by50 mg SCN-; c Masked by 10 mg citrate

adjusted to 3.2 and this solution was equilibrated with

10mL of 0.087M 2-n-OAP in xylene. Under this

condition Vanadium (V) was quantitatively extracted

into organic phase leaving behind Mo (VI) in the

aqueous phase. The organic phase was back stripped

with (3x10mL) portion of 6M NH3 and Vanadium (V)

was determined spectrophotometrically as recommended

in the procedure. The aqueous phase was reduced and

then mixed with HCL and LiCl to give final

concentration of 2M and 5M respectively in total volume

of 10mL. The solution was than transferred to a 125

separating funnel and shaken for 1 minute with10 mL of

0.233M of 2-n-OAP in xylene. The organic phase was

separated and equilibrated with (3x10mL) of 1M NH3 to

back extracted Mo (VI) which was later determined

spectrophotomerically by thiocyanate method [37]

Vanadium is present with cations such as Fe(III),

Ni(II), Cu(II), Co(II) , Pb(II), Zn(II) and Cr(VI) in

various minerals such as bravite, davidite, roscoelite and

magnetite. Hence it is essential to separate Vanadium

from such cations. Vanadium(V) was separated from

Fe(III), Pb(II) , Zn(II),Re(VII),Cr(VI)andCo(II) by

extraction with 10mL of 0.087M of 2-n-OAP in xylene

from 0.01M sodium succinate adjusting the pH to3.2.

Under these conditions, the added metal ions remained

quantitatively in the aqueous phase. The aqueous phase

was washed with 5mL xylene to remove the traces of the

reagent. Metal ions Pb(II)and Zn(II), from the aqueous

phase were determined complexometrically [36] while

other cations Fe(III), Re(VII), Cr(VI) and Co(II)were

determined spectrophotometrically by standard

methods[Table 3]. Vanadium (V) was determined by the

proposed method after back stripping the organic phase.

Separation of W (VI) and Ni(II) from Vanadium(V) was

carried out by masking them with 10 mg F- and 50mg

SCN- respectively. The masked cations W (VI) and Ni

(II) remained in the aqueous phase under an optimum

condition of Vanadium (V). From the organic phase

Vanadium (V) was stripped with 6M NH3 (3x10 mL) and

determined spectrophotometrically as per general

procedure. After demasking W (VI) and Ni (II) with

5mL HCL acid, the aqueous phase was evaporated to

moist dryness. W (VI) and Ni(II) were determined

spectrophotometrically by Thiocyanate and DMG

respectively

There is co-extraction of Zirconium(IV) under an

optimum condition of Vanadium(V). This was made

possible by selective stripping. Vanadium (V) from the

organic phase was stripped first with 6M NH3 (3x10 mL)

followed by stripping of Zirconium (IV) with 0.5M

HNO3 (3x10 mL). Vanadium (V) was determined by


Table 5: Determination of V(V) in alloys

Alloy Sample Composition % Amount

Recovery % V taken % V found %

NBS steel 72

0.301C, 0.54 Mn, 0.014 P, 0.024 S, 0.256 Si,

0.062 Cu

0.05 Ni, 0.89 Cr, 0.005 V, 0.009 N, 0.184 Mo

0.005 0.005 100

NBS STD

sample153a steel

0.90C, 0.192Mn, 1.76W a, 0.023P, 0.007S,

0.27Si, 0.094 Cu, 2.06 V,8.47 Co, 0.024 N,

8.85 Mo

2.06 2.06 100

Tool steel

SRM 134

0.81C, 0.218 Mn, 0.18 P, 0.007 S, 0.323 Si,

0.101 Cu, 0.088 Ni, 3.67 Cr, 1.25 V, 2.0 W a,

8.35Mo

1.25 1.24 99.9

BCS-401

(Low alloy steel)

1.06 C, 0.59 Si, 0.02 Ni, 0.009 S, 0.042 P,

1.0 Mn, 0.1Cu, 0.52 V, 0.52 Mo. 0.52 0.52 100

BCS – 320

Carbon Steel

0.25 C, 0.172 Ni b, 0.37 Si, 0.008 V, 0.024

Sn, 0.02 P, 0.018 Ti, 0.22 Cr, 0.29 Mn, 0.058

As, 0.004 Sb, 0.009 S, 0.25 W, 0.1 Mo

0.008 0.008 100

* Average of five determinations; a Masked by10mg F- ; b Masked by 50 mg SCN-;

Table 6 : Recovery of V (V) from synthetic leach solutions of spent catalyst

Spent catalyst mixtures Composition % Mo(VI) found % Recovery* R.S.D. %

Sample 1 a

10Ala, 3.0Mo, 0.5 V, 0.5Ni

, 1.0

Co, 0.2 Fe 0.5 0.5 100

Sample 2

0.28 Mo, 0.997 Al,

0.091V,0.047Ni,0.095

Co,0.024Fe

0.091 0.091 100

Sample 3a

2.05 Mo, 0.42 V, 5.6 Al, 10.7

SiO2 0.42 0.42 100

* Average of three determinations, a masked by 10 mg F-;

Table 7 : Analysis of V(V) in pharmaceutical drugs

Allopathic

Sample Composition (mg)

Certified

value of

V(V))

mg/tablet

Amount of V(V) found

mg/tablet Recovery* % R.S.D.%

Proposed

method

AAS

method

Maxi Prenatal

support

multivitamin

800mgCa,18mgFe,404mgP, 0.225mg

I,400mg Mg, 15mg Zn, 0.025mg Se,

1mg Cu, 7mg Mn, 0.12 mg Cr, 99

mgK, 1 mgV

1.0 1.0 1.0 100 0.0

Green Pro96

multivitamin)

50 mg Ca, 19 mg P, 225mcg I, 50

Mg,2.0 mg Zn, 0.025mg Se, 0.2 mg

Cu,2mg Mn,

0.05mgCr,0.025mgMo,0.025 mg V

.

0.025 0.025 0.025 100 0.0

Supractiv Abbott

(Piramal

Healthcare Pvt.

Ltd. Chembur,

Munmbai)

10 mg K, 9.07 mg Zn, 5.0 mg Mg, 5.0

mg P, 5.0 mg Ca, 3.86 mg Cu, 2.2

mgMn, 2.0 mg Si, 1.0 mg B0.080 mg

Cr, 0.070 mg Se, 0.050 mg Ni,

0.005mg V, 0.002 mgSn, 0.5 mg Mo

0.005 0.005 0.005 100 0.0

*Average of five determinations.

recommended procedure while Zirconium (IV) was

determined by Alizarin Red S spectrophotometrically.

Determination of Vanadium (V) in synthetic mixture

The applicability of the developed method for the

separation and determination of Vanadium (V) in

synthetic mixtures was studied [Table 4]. In the

synthetic mixtures, Vanadium was extracted under the

optimum extraction conditions and quantitatively

recovered in all the mixtures.

Determination of Vanadium (V) from alloys

(NBS steel 72, NBS STD 153a steel, Tool steel SRM

134a, BCS-401and BCS-320)

About 0.05 g of each sample of alloy was dissolved in

10 mL of aqua regia and heated to moist dryness.

Further 5 mL conc. hydrochloric acid was added to the

mixture and heated to expel the nitrate. The residue

obtained was filtered through Whatmann filter paper

No.1 to remove silica and metastannic acid if present.


Table 8: Determination of vanadium content in environmental samples

Samples Vanadium added

(g)/mL

Vanadium

found(g)/mL Recovery %

SOIL

A

B

25.0

35.0

25.0

35.0

100

100

NATURAL WATER

C

D

10.0

15.0

10.0

15.0

100

100

SEA WATER

E

F

5.8

9.5

5.8

9.5

100

100

PLANT MATERIAL

Tobacco

Carrots

Almonds

Tea leaves

Rice

16.5

15.3

30

6.5

5.4

16.2

15.0

30

6.5

5.4

100

98.03

100

100

100

The filtrate obtained was diluted to 50 mL with distilled

water. An aliquot from each alloy solution was then

analysed by the proposed method to determine

Vanadium (V) [Table 5].

Determination of Vanadium (V)) from environmental

samples A] SOIL:

An air dried homogenized soil sample (1g) was weighed

accurately and placed in a 100 mL kjeldahl flask. The

sample was digested in presence of 50mL concentrated

HCL and 10mL of concentrated HNO3 for 1 hr. on a

sand bath. The solution was then evaporated to dryness.

The residue was boiled with 50mL of 0.1M HCL acid

and filtered. The filtrate and washings were evaporated

to dryness and the residue was taken up and the solution

diluted accurately to 100mL with 0.1M HCL acid. An

appropriate aliquot was used for the analysis of

Vanadium (V) by the proposed method.

B] WATER:

The required amount of water samples were filtered and

analyzed for vanadium. They tested negative. To these

samples, known amount of vanadium (V) were added

and analyzed by the proposed procedure for vanadium.

C] PLANT MATERIAL

To 10g food samples 25mL concentrated HCL was

added, followed by digestion on a sand bath for 1 hour

and evaporation to dryness. The residue was dissolved in

10-15mL concentration HCL along with 0.5g ammonium

persulphate and digested for 20 min on a sand bath.

Later the contents were boiled with 20mL of 0.1m HCL

and finally the filtrate and washings were diluted to 100

mL with doubly distilled water.

An appropriate aliquot was used for the analysis by the

proposed method. Whenever the measured signal

exceeded that of a linear working range the sample was

further diluted.

Recovery of Vanadium (V) from synthetic leach solutions

of spent catalyst

The synthetic leach solutions of spent catalyst were

masked by 50 mg thiocyanate and extracted with 10 mL

of 0.087 M 2-n-octylaminopyridine in xylene in

presence of 0.01M sodium succinate. The aqueous phase

was first separated for removal of Al, Mo, Ni, Co, Fe

and SiO2.The organic phase containing Vanadium (V)

was then stripped with 6M ammonia (3x10mL) and then

washed with 5 mL xylene to remove the traces of amine

and used to determine Vanadium (V) by the proposed

method [Table.9].

Analysis of Vanadium (V) in pharmaceutical drugs

Pharmaceutical allopathic tablets such as Supractive,

MaxiPrenatal Support and Green Pro 96 multivitamins

were selected for the analysis of Vanadium(V).A known

weight of the sample was dissolved in 5.0 mL of aqua

regia solution and evaporated to moist dryness by

heating gently on a hot plate. Addition of perchloric acid

was avoided to stop spurting. The residue obtained was

dissolved in 1:1 HCL and filtered through Whatmann

filter paper No.1. The filtrate was diluted to 100 mL in a

standard volumetric flask with distilled water. An

aliquot of each solution was then taken for the extraction

of Vanadium (V) by the proposed method. The results

obtained were confirmed by AAS (Table.10).

Conclusions The important features of the method described here are:

Quantitative extraction of Vanadium (V) was achieved

in 3 min. with 0.087 M of 2-n-octylaminopyridine in

xylene. Very low reagent concentration is required for

the extraction. The extraction mechanism corresponds to

form an ion pair complex of [(RR’NH2)2 VO (succinate

2-)2

](org) in the organic phase. The method is free from the

interferences of large number of foreign ions. The

proposed method is simple, rapid, selective, reproducible

and suitable for separation and determination of

Vanadium (V) from associated metal ions, synthetic

mixtures, alloys, pharmaceutical samples, synthetic

leach solutions of catalyst and various environmental

samples.


Acknowledgements

The authors are grateful to UGC – SAP and DST – FIST

for providing financial assistance. The author expresses

her gratitude to Secretary, Vivekanand Shiksan

Sanstha’s, Mrs. Shubhangi Gavade for her kind

encouragement.

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Source of support: UGC – SAP and DST – FIST; Conflict of interest: None declared

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Extractive separation of Vanadium(V)