The application of salicylaldoxime in solvent extraction

Andylica Ckimica Ada Ekvler Publiahlng Company, Amsterdam

9

Printed in TJICNcthcrlondr

THE

AI’I’LICATION

OF SALICYLALDOXIME

Chernicd I?~stilttte A, University o/Oslo. (Rcccivcd

Scptclnbcr

I Ith,

IN

SOLVENT

EXTRACTION

13lidcwt. Oslo 3 (Norway)

19G7)

Salicylaldosimc is recognized as a selective precipitant for copper, although it forms water-insoluble chelates with a number of clemcnts~. The absorption spectra in chloroform of some metal chelates of salicylaldoxime have been discussed”. The solubility of the salicylaldoximatcs in organic solvents has been utilized in the solvent of the extracted extraction of various elenlcnts3-1~. Subsequent determinations . metals have been accomplished either by optical methods, i.e. emission spectroand atomic grapliya, colorirnetryo, absorption”*10 and emissionoeo spectrophotometry, or by radiometric measuremen ts7.8. absorption spectroscopyll, The present paper describes a comparative investigation of the extractability of 9 selected metal ions with solutions of salicylaldoxime in benzene, special attention being given to the effect of PH. E,SPEJIIMISNTAL

All analytical absorbance measurements were made with a Zeiss PMQ II spectrophotometer; absorption curves were obtained with a recording Beckman DB spectrophotometer. A matched set of x.ooo-cm quartz cells with stoppers was used. The PH was measured with a Beckman I
All chemicals were of reagent-grade quality. Salicylaldoxinw solzttions. Exactly weighed amounts of salicylaldoxime (E. Merck A. G., Darmstadt) were dissolved in benzene to give x.00, 0.10, and 0.01 &Z solutions, these being stored in brown bottles. Stock sohctions of metals (ea. sszo- 3 M). These were prepared by dissolving appropriate amounts of the sulphatc, nitrate, or chloride salt in distilled water, adding - where required - a minimum of acid to prevent precipitation, and diluting to a known volume with additional water. The stock solutions were stored in polyAnal. Cl&r.

Acta, 41 (IgG8) g-14

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I.DAHL

cthylenc bottles and standardized by titration with EDTA (disodium salt). Freshly made standard solutions of the metals of lower concentration were prepared by d.ilution. Buffer solutions were made by mixing standard solutions of hydrochloric acid and/or sodium hydroxide with solutions of pot,assium chloride, potassium hydrogen phthalate, potassium dihydrogcn phosphate, boric acid, and disodium hydrogen phosphate, at the concentrations and volumes given in the litcratureia.

Distribution detevnri9zation.s The concentrations of metal in the aqueous and organic phases after extraction were determined respectively by cornpleximctric titration and spectrophotometry. Knowing the total concentration of metal present, generally x.0.10-‘1 M, the percentage extracted was calculated. (Changes in volume were negligible and were ignored.) All experiments were performed at room temperature (20-25"). Procedure To 5 ml each of standard metal and buffer solution IO ml of salicylaldoxime solution were added. The two phases were manually shaken for 5 min and allowed to separate. In all experiments the final PH of the aqueous phase was measured. In most cases, the amount of unextracted metal was then determined by titration with EDTA, applying micro methods. For the spectrophotometric measurements volumes of the organic phase were withdrawn, centrifuged, and transferred to a photometric cell. The absorbance was measured against a reagent blank prepared by extracting 5 ml of distilled water and 5 ml of buffer solution with IO ml of the salicylaldoximc solution. RESULTS

Choice of organic solvent Various organic solvents, viz. chloroforma~7~ **lo, benzene”, n-amyl acetat@, extractions. and methyl isobutyl ketone n~o~ll have been used in salicylaldoxime Preliminary experiments confirmed that the four solvents listed above, as well as carbon tetrachloride, diisopropyl ether and ethyl acetate, could be employed. it was cassumed that a hydrocarbon or its On the basis of earlier investigationsi4, halogen-substituted derivative would be a more selective extracting agent than an oxygen-donor solvent. Accordingly, benzene was selected for the detailed studies of the extractions made at different pH and reagent concentrations. Infhcence of fiH Solutions of the metal ions were extracted with a 0.01 M reagent solution. Plots of the percentage extraction VCYSUSPH for various metals are shown in Fig. I. With increasing PH, copper( nickel(D), lead(H), cobalt(D) and manganese(H) are extracted in the same order as they are precipitated 1; these systems all show extraction curves of the regular pattern. Mercury(I1) is not extracted in the PH region investigated (~-IO), probably because of hydrolysis. Copper is quantitatively extracted in the PH range 3-9.5; this result is in Amal. Chins. Acta, 41 (rgG8) g-11)

SALICYLALDOXIME IN SOLVENT EXTRACTION

11

excellent agreement with that obtained by SIMONSEN AND BURNETT~~ who used a 0.02 M solution of salicylaldoxime in n-amyl acetate. Complete extraction of nickel(H) takes place at ps 6.5-9. It has been found previouslye, that, when a r% solution of the reagent in methyl isobutyl ketone is used, maximum extraction from mannitol-aqueous ammonia solutions occurs at somewhat higher PH values. Lead(H) is completely extracted from boric acid-sodium hydroxide buffered solutions at PI-I 7.5-9. Maximum extraction of cobalt(I1) is reached at pE 7.5-S. More than 70% of manganese(U) is extracted at a PH of about ~0.5. ~a~esium(II) is not extracted in the presence of boric acid/sodium hydroside buffers. From alkaline solutions, however, a maximum extraction of about 90% is achieved. An irregular extraction curve is exhibited by cadmium(II), although more than 90% is extracted at higher pH values. Anomalous extraction behaviour of cadmium(If) with 0.~ M solutions of sali~ylaldoxime in chloroform has also been reported’.

I t

I

I 3

I

I 3

7

9 11 l3 pH of aqueous. phoae

Fig. I. Extraction of 1.0 m-4 M solutions of Cu(If), Niflf), Cd(I1) with 0.01 M salicyIalcloximc in bcnncuc. l

Pb(II), Co(lI), Mn(lI). Mu

au(1

0.2 0.1OpH of oqueous

phase

I

480

I

I

440

I

I

I

I

I

1

360 320 400 Wavelength fnm)

Fig. 2. Extraction of a I .o 10-4 M solution of Zn(fl) with salicyIak_loximc in bcnzcnc: 0.0X M (cutvc I), 0.10 M (curve 2). 1.00 M (curve 3). l

Fig. 3. Absorbance curves of I .o 10-4 M solutions of Cu(II) (curve I), Ni(I1) (curve 2). and Co(lX) (curve 3) cxtractcdinto anequal volume of 0.01 IL? salicylaldoximc in bcnzcnc. Absorbance curve of a reagent blank reckded against benzene (curve 4). l

AsaL Citim. Acfa, 4r (rgG8) 9-14

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Infhience of reagent concc~ttvntion The importance of the rcagent concentration in the organic phase was clearly demonstrated by extracting zinc(I1) with various solutions of salicylalcloxime. The perccntagcs extracted with 0.01, 0.10, and 1.00 M solutions as a func.tion of PH are given in Fig. 2. With 0.01 M salicylaldoxime concentration, only about 5% of zinc (II) is extractccl at pH 8. J3ut when 0.10 and 1.00 M solutions arc used, the percentage extracted is increased to about 50% and So%, respectively. Sfiectrophotonretry Of the salicylaldoxime chelates investigated, only those of copper(1 I), nickel(II), and cobalt (II) absorb strongly at wavelengths above 340 nm. Absorption spectra of the above chelates were recorded against reagent blanks at the PH of maximum extraction. The spectra arc shown in Fig. 3. The absorbance maxima are in good agreement with those obtained in other solvcnts”lfi. Absorbance spectra of the blanks were recorded against benzene. Since the curves were practically identical, only one of them is rcproduccd in Fig. 3. At the wavelength of maximum ahsorption, calibration curves for the metals were plotted. In all cases, Beer’s law was found to be obeyed over the entire range of concentration studied. Data related to the spectrophotometric determination of coppcr( II), nickel (II), and cobalt(I1) with salicylalcloxime are collected in Table I. This Table contains the of the colour reacpercentages estractecl in a single pass, as wel: as the sensitivities tionsin terms of the molar absorptivity and Sandell’s sensitivity index. TABJX

I

Sl’lLCTIZOI’IIO’~Ohl~T~~~C

DETISI1MINA’l’ION

IOll

Codif

lktL’Y~tlilll!d

mc:(IsllYe~nc~Lt

iorrs

of

_--__- .--_-. Cu(L1)

SOME

Linctrr mtrgc of colilwulion cifrve

..--...

p/-t

Olr

(&I.

METAL

IONS WIT11 SALICYLALUO.XIhIB

‘X

Semilivity

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--Molnr

r&J)

(WN)

..--

.._...-

..-.-

..__ -__. _-.-.

_

(f/g

--.

-..-_-----..-

Scusilinity at

.._ ~

8400 2.5-100 >93.!i 4*0 347 Ni(ll) =-99 7.0 387 5 -200 5.300 IO000 z.g-100 Co(L1) w 97 7.9 375 ----~_.----.. - -____ - . ..___ ____ _----.-.-.-._.__--_.--.. lo (0.0008). WhiCh \VLlY CZdCUhtCtl frOlT1 0 Tlw value given by S~N~JI~LL B~~~~~~~~,i~~rongbyoncpo~cr of IO.

ANAJaYTIChJ,

.-.-_

dxiorptivity

IVcrvclcvrgtlr

-. _-..-._.--

-

’

(pg/cr,r

cm)

irrdes

=, A

= o.oor) -_--_----___-_--_-.-_ 0.0070” 0.01 I o.ooG ..-._.___.._.___ -._. .___ .__

thC

thtn

Of

SIMONSEN

ANI)

RPPl,ICATIONS

With a 0.01 M salicylaldoxime solution in benzene, and by selecting the proper PH, it is possible to make analytical separations of the metal ions investigated. For instance, at PH 3-3.5 copper may be quantitatively extracted and separated from all the other elements studied. Separation of nickel and cobalt is obtained at PH 6. Lead is completely separated from manganese at PH S and from zinc at pH g. Separations of cadmium and magnesium from other metals may be performed in strongly alkaline media. And.

Cirinr. Acts,

41 (rgG8)

9-14

SALICYLALDOXIME

IN

SOLVENT

I3

EXTRACTION

The influence of reagent concentration may also be utilized for separation purposes. Thus, by consecutive extractions with 0.01 and x.00 M salicylaldoxime solutions, cadmium and zinc, respectively, are separated from mercury. Copper(I1) may be determined spectrophotometrically with a 0.01 ICI1solution of salicylaldoxime in benzene after its selective extraction at pi 3-4, The sensitivity of this method is of the same magnitude as that of the well-known copper(I) reagent, neocuproine*G. The determ’nation is rapid and the stability of the colour system very good. Salicylaldoxime has already been applied for the determination of copper in aluminium and zinc-base alloysb. The method is probably also applicable to the determination of copper in a matrix of other metals, e.g. nickel and cobalt. As apparent from Table I, nickcl(I1) and cobalt(I1) may be determined spectrophotometrically with salicylaldoxime. It should be stressed, however, that these systems are less stable, hence absorbance measurements should be maclc as soon as possible after the extraction. SUMMARY

The extraction of divalent magnesium, manganese, cobalt, nickel, copper, zinc, cadmium, mercury, and lead with solutions of snlicylaldosime in benzene was investigated. The effect of the reagent concentration :md particularly the pH of the aqueous phase on the extractability was studied. The application of salicylaldoxime extractions in the separation and determination of various elements is discussed.

On a examin l’extraction des cations divalents des bldments: Mg, Mn, Co, Ni, Cu, Zn, Cd, Hg et I’b & l’aidc de solutions de salicylaldoxime dans lc benz&nc. On a &udi& l’influencc de la concentration du rdactif et particulic\rement du 1)~ de la phase aqueuse sur I’extractibilitG. Une discussion est l&sent&e sur l’applicntion des extractions “salicylaldoxime” pour la separation et lc dosage de divers 616ments. ZUSAMMENFASSUNC;

Die Extraktion von zweiwertigem Magnesium, Mangan, Kobalt, Nickel, Kupfer, Zink, Cadmium, Quecksilber und Blei mit Liisungen von Salicylaldoxim in Benz01 wurde untersucht. Der Einfluss der Reagenzkonzentration und besonders des pa-Werts der wtissrigen Phase auf die Extmllierbarkeit wurde geprtift. Die Anwendung dieser Extraktionen zur Trennung und Uestimmung zahlreicher Elemente wird cliskutiert.

AND N. I-I.I:unnsAN, Id. JZvtg.C/rem., Amd. La?.. I 2 (xg1)0)‘52g. J. Am. Ckon. Sot., 75 (1953) 5207. 3 G. GORUACH AND I;. POIIL, Mikrockmr. vey. &‘Iikvod&u. flctn, 38 (1951) 258. 4 V. M. PESHKOVA, V. I. SHLISNSKAYA AND A. 1. I
2

Ii. SONE,

Atad.

Clrinr.

Ada,

Ultiv.. SCY. Fiz.

41 (xgG8)

g-14

I.

I4

DAHI.

I-I.C. ISSIIIZLBIAN AND J. A. DISAN, Awrl. Cllem., 33 (rgW) 1339. 7 G.l<. %ll\VlWt'ZL5l~ ANI) 11. I<. ~~ANl~OLl'iI,~?tU~.~/~ittl. nCff8. 26 (Igh) 567. 8 G.Ic. sC?I\VEITZI'_I~ AND 1i.D. ~OI~TON,~7tU~.C~ti?n.~C~U, 30 (fg64) IIg. g H. C. I~SIIISLICIAN, J. DYIZR AND J, AwuewroH, And. Ckint. Ada, 32 (rgG5) 41 I. IO J. 13. ~IAICTIN, JR., ‘Thesis, L’nivcrnity of Texas. 1gG5; Disscvlulion Ah&., 26 (1905) 1890. I I T. TAKDUCIII, M. SUZUKI AND IU. YANAGISAWA, AN&. C/rim. A&a, 3G (xgGG) 258. 12 It. G. 131\TI’_s, -1. Nes. Null. fjrrr. Std., A Ob (rgG2) x79. 13 V. E. Bowwz ANI) 1C. G. Y~ATI!S, ,/. Itas. Nali. Urcv. Std., 55 (1955) 197; I<. G. BATES AND V. E. Bowers, Anul. Clrcnt., 28 (1g5G) I 322. I. 1'. 1~LIMARIN. S'~Otm31 KcmiS14 f.. P. ~LIMARIN AND YIJ. A. %OLOTOV, 'I'&lllU, g (lgh) 8gI; tilchfi, A 39 (rgGG) 103. 15 1.C. 13. SANDELL, Colovimdric Delermiwdiorr of ‘I’rc~.ccs of Melds, 3rd Etln., Intcrscicncc, New York 1959, P 443. G

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