Indian Journal of ChemistryVol. 27 A, November 1988, pp. 983~986

Use of Chelating Ion Exchanger Containing Acetoacetanilide Group in Se-lective Separation of Beryllium

SWAPAN MAJEE & JYOTIRMOY DAS*Department of Chemistry, University of Burdwan, Burdwan 713 104

Received 31 July 1987; revised and accepted 7 December 1987

A macroreticular styrene-divinylbenzene based chelating resin having acetoacetanilide as the functional grouphas been synthesized and characterised. The resin is stable in fairly strong acid or alkaline solution. The sorptionpatterns of Na(I), K(I), Ca(ll), Mg(II), Co(II), Cu(II), Ni(II), Fe(III), Al(III), Ti(IV) and U(VI) have been studied atvarying pH. The selective nature of the absorption of Be(II) at pH 4.0 has been utilized for the separation andconcentration of the metal ion in synthetic mixtures and in beryl. Strong H2S04 (6 N) has been used for the elu-tion of Be(II) from the resin.

In trace analysis preconcentration of metal ion isoften a vital step and various chelating resins hav-ing chelating groups like hydroxylamine and itsderivatives I, iminodiacetate", thioglycolates ', dithi-ozone", hydroxyquinoline>, o-hydroxyaldoxime",I-nitroso- 2-naphthol7, 2-nitroso-1-naphthdI8 havebeen used for the separation of different metalions.

Acetoacetanilide? is a very selective reagent forgravimetric' determination of beryllium. So far on-ly one chelating resin containing l,3-diketo com-pound'" has been synthesized. In this work ace-toacetanilide has been incorporated in styrenedivenylbenzene (DVB) polymer and the resultingion-exchanger has been characterised. The ab-sorption behaviour of several metal ions on thisresin has been studied and a method for the se-paration and preconcentration of Be(II) has beendeveloped.

Materials and MethodsAn atomic absorption spectrophotometer (Shi-

madzu AA-646) and a double beam U'V-visiblespectrophotometer (Beckmann 26) were used formeasurement of concentrations of the metal ions.Infrared spectra were recorded in KBr matrix ona Beckmann Acculab-lO IR spectrophotometer.Gravity flow columns were made of glass with ap-propriate reservoirs.

Fresh solution of benzoyl-m-nitroacetonilidewas prepared by dissolving 0.28 to 0.32 g of thereagent in aqueous ethanol (25 ml). Beryllium so-lution was prepared from beryllium nitrate (E.Merck) in dilute nitric acid. The metal contentwas determined gravimetricallyr-". Aqueous solu-tions of the desired diverse metal ions were pre-

pared from their nitrates, chlorides or sulphatesand a little acid was added to avoid hydrolysis.

For adjusting the pH sodium chloride-hydroch-loric acid buffers were used for the pH range of0.5 to pH less than 4.0 and sodium acetate-aceticacid buffers were used for the range of pH be-tween 4.0 and 6.0. For studying the exchange be-haviour of metal ions above pH 6.0 to 7.5 bufferswere prepared from KH2P04 and Na2HP04•

-Synthesis and ion exchange capacity of resinStyrene-DVB polymer beads (80-100 mesh)

containing 8% DVB (Therrnax Private Ltd.; Poo-na, India) was nitrated using a mixture of concen-trated sulphuric acid and nitric acid. The wet ni-trated product was mixed with tin (20 g), industri-al ethanol (50 ml) and sufficient amount of cone.hydrochloric acid and refluxed for 12 hr to obtainaminopolystyrene. Finally, the aminated productwas condensed with ethyl acetoacetate (4 g forevery 3 g of aminopolystyrene) by refluxing themixture at 110-15° for 24 hr in toluene to get thedesired acetoacetanilide resin.

Ion exchange capacity of the resin for metalions was studied by batch and column operationmethods. In batch operation, air-dried resin (0.5g) was stirred for 24 hr with an excess of the de-sired metal ion solution of known strength ( - 0.1M) and pH controlled by adding suitable buffer;the mixture was filtered and the resin was thor-oughly washed with the same buffer until freefrom the metal ions. The sorbed metal ions werethen completely eluted by H2S04 of appropriatestrength. The whole process was repeated withbuffers of different pH. The eluted metal ionswere determined by standard methods.

983

INDIAN J. CHEM., VOL. 27A, NOVEMBER 1988

It was found that 50 ml 4 N sulphuric acidwere sufficient for eluting cobalt(ll), copper(Il), ir-on(IlI), calcium{II), magnesium{II) and nickel{II)while 50 ml 6 N sulphuric acid were required fortitanium{IV), uranium{VI) and beryllium{II).

In column operation, a glass column (30 emlength and 1 em i.d.) was packed with - 25 g ofair-dried resin (initially swollen with 2 N hydroch-loric acid for 24 hr). The bed was thoroughlywashed with deionised water at a flow rate of 0.5-1.0 ml/min till free from acid. This rate of flowwas maintained in all subsequent steps. Knownvolumes of the desired metal ion (50 mI, - 2 M),adjusted to the desired pH by adding appropriatebuffer, was passed through the column, washedwith sufficient amount of deionised water and fi-nally the sorbed metal ions were eluted with sul-phuric acid of appropriate strength and deter-mined by appropriate method.

Concentrations of the metal ions before and af-ter elution from the resins were determined bystandard procedures. Titanium{IV), uranium{VI),beryllium(ll) and copper(II) were determinedspectrophotometrically, titanium{IV} was deter-mined with hydrogen peroxide in acid medium!",beryllium{II) with benzoyl- m-nitroacetanilide 13

and copper(II) with sodium diethyl dithiocarbam-ate". Aluminium(III), iron{III), cobalt{II), sodi-um(I) and potassium(I) were determined by atom-ic absorption spectrophotometry. Nickel(II} wasdetermined gravimetrically with dimethylglyox-ime!". Calcium{II) and magnesium(II} were deter-mined by titration with EDTA using Eriochromeblack-T as indicator'".

Separation procedureFor the separation of Be(II) from its binary mix-

ture with Cu{II), Co{II}, Ca{U), Mg(II), Ni(U),A1{IlI), Fe(III}, Ti{IV) or U(VI), the resin columnwas equilibrated with the buffer solution of pH4.0. The pH of the solution containing the mix-ture of metal ions was adjusted to 4.0 in the pres-ence of EDTA. The solution was then percolatedthrough the resin column, washed thoroughly withthe same buffer and eluted with 150 ml 6 NH2S04.

It was observed that over 99% beryllium couldbe recovered using 150 ml of 6 N H2S04 as elu-ant.

Results and Discussion

Characterisation of the resinThe resin was characterised by its water regain

value, infrared spectrum, its stability towards acid

984

and alkali, elemental analysis and metal ion ex-change capacity.

A sample of dry resin was immersed in deio-nised water for 48 hr, centrifuged, air-dried andweighed. It was then dried at 100°C for 48 hr andweighed again. Water regain, calculated from thedifference in weight, was found to be 0.21 gigresin.

Infrared spectrum exhibited two bands at 1500and 1330 em - I assignable to - CONH - andCH3CO - groups respectively. The resin wasfound to be stable in 6 N H2S04 and 4 N NaOHsince no appreciable change in its nitrogen con-tent and sorption capacity for titanium was found.

Estimation of nitrogen and amino groupSmall amounts of the air-dried resin of the ni-

trated polystyrene, aminopolystyrene and the che-lating resin containing diketo group {all belongingto the same batch} were thoroughly dried by heat-ing at 80°C for 48 hr and then keeping in a desic-cator over phosphorus pentoxide . Nitrogen ineach case was determined by micro Duma's meth-od. The amino group content of the aminopolys-tyrene was determined by titration in nonaqueousmedium 15.

The nitrogen content and the capacity forTi(IV) remained unchanged after treatment with6 N H2S04 or less or with 2N NaOH or less. Thesmall value of water regain of the resin indicatedthat its sorption capacity may not be very high,but experiments showed that the resin had a mod-erate capacity for beryllium.

The nitrogen content of the nitrated polymerwas found to be 5.53%. After reduction, the per-centage of nitrogen of the amino resin was foundto be 7.1% as total nitrogen and 5.23% as aminonitrogen (from the estimation of amino group)with 1.87% nitrogen as unconverted nitro group.The nitrogen content of the final resin was foundto be 5.47%.

In order to study the cation retention capacityof the residual nitro and amino groups of the res-in, the capacities of both polynitrostyrene-divinyl-benzene and polyaminostyrene-divinylbenzenehave been studied and found to be negligible.

Metal absorption capacity and separationThe absorption capacity of beryllium on resin

column was slightly lower than that in batch oper-ation (Fig. 1). The total capacity versus pH curvesfor the metals studied, shown in Fig. 1, indicatethat the resin exhibits high selectivity for Be(Il},which starts getting absorbed by the resin around

MAJEE & DAS : CHELATING ION EXCHANGER CONTAINING ACETOACETANIUDE GROUP

0.45

0.40

0.35

0..10 Be

-'ll'>•.•• 0.25o .l:E~ 0.20·ueIt.~ 0.1'0

0.10

0.05Hi

0/ Co/V

7 •

pH

Fig. 1 - Exchange capacity of acetoacetanilide resin for differ-ent metal ions as a function of pH [---, total exchange ca-

pacity; , exchange capacity in the resin column].

Table 1 - Separation of Beryllium from Diverse Ions[Beryllium taken = 45 mg]

Diverse ions(mg)

Al(lJI)Na(I)K(I)

Ca(lI)Mg(lI)Fe(III)Ni(IJ)Co(Il)Co(lI)Ni(IJ)Cu(lI)Al(lJI)Fe(lIJ)Ni(IJ)

Beryllium recovered(%)

10050505050

5010010010010010010050

100

99.77

99.66

99.85

99.56

Table 2 - Determination of Beryllium in Beryl OreWt Be found Be found BeO found BeO found

(rng) (rng) (0;',) (%) (%)Beryl ore by given by given by given by standard

taken method" method" method" method"

211.732.260.421,

4.5 10K

4.4964

12.5312.49

12.5812.58

• Mean of three determinations.

pH 1.5, followed by a maximum with a peak atpH 4.0.

Among the other metal ions studied, Fe(II1),Co(ll), CU(Il) and Ni(ll) are only negligibly ab-sorbed by the resin, while Na(I), K(I), Ca(ll),Mg(ll) and Al(II1) are not absorbed at all. So aclear separation of Be(U) from Al(III), Na(I), K(I)Ca(ll) and Mg(II) is possible. Separation of Be(ll)from Fe(III), Ni(II) and Co(II), separation of BetIl)from Cotll), Ni(ll) and separation of Be(II) fromAl(III), Fe(III) and Ni(II) are also possible. Addi-tion of 10-20 rnl of Na2EDTA (0.1%) and boilingthe mixture for 2 min prevent precipitation ofbase metals due to hydrolysis at pH 4.0. Some ex-amples of separation of Be(II) in synthetic mixtureare shown in Table 1.

Separation and determination of beryllium inberyl

Finely powdered beryl (- 0.2 g) was decom-posed " by fusion with NaF, cooled and taken upin conc. H2S04, The mixture was heated to fumesto drive out all the fluoride and transferred into abeaker containing water ( - 100 ml), A clear solu-tion was obtained by boiling and the volume wasmade upto 250 rnl.

Aliquots of this solution was adjusted to pH 4.0by acetate buffer and passed through resin co-lumn (initially adjusted to pH 4.0 by the samebuffer), when only beryllium was absorbed on thecolumn. The resin column was washed with thesame buffer and finally Be(II) was eluted with 50ml6 N H2S04 and collected in a 100 rnl volumet-ric flask. Beryllium was determined spectropho-tometrically using benzoyl-m-nitroacetanilide. Theresults are given in Table 2.

AcknowledgementWe are thankful to Mis. Thermax Private Ltd.,

Poona for supplying the polystyrene DVB resinbeads as gift sample and to Geological Survey ofIndia, Calcutta for supplying the sample of Beryl.One of us (SM) is grateful to the University ofBurdwan for the award of a fellowship.

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INDIAN J.CHEM., VOL. 27A,NOVEMBER 1988

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t,.