Polyhydroxamic acids: synthesis, ion exchange separation and atomic absorption spectrophotometric determination of divalent metal ions

Reactive polymers ELSEVIER

Reactive Polymers 25 (1995) 79-87

Polyhydroxamic acids: synthesis, ion exchange separation and atomic absorption spectrophotometric determination of divalent metal ions Y.K. Agrawal, K.V. R a o Chemistry Department, School of Sciences, Gujarat University, Navrangpura, Ahmedabad 380 009, India Received 6 December 1994; accepted in revised form 20 January 1995

Abstract

The preparation and properties of 8 N-phenylsubstituted polyacrylohydroxamic acids as ion exchange resins are described. These were synthesized by the reaction of polyacryloyl chloride with N-aryl hydroxylamines in etherial medium. The chelating properties of the resins were determined and compared with each other. The extraction of divalent metal ions as a function of pH and kinetics of their sorption were studied. The chromatographic separation of metal ions from the mixtures is also described.

Keywords: Polyacrylohydroxamic acid; Resins; Divalent metals

1. Introduction Several hydroxamic acids have been synthesized and extensively used as analytical reagents for the separation and determination of metal ions [1-6]. In recent years, polyhydroxamic acids have been synthesized and reported as chelating ion exchange resins for the separation of metal ions [7-15]. Generally the hydroxamic acids are synthesized by reacting the acid chloride, ester, amide or anhydride with hydroxylamine [1618]. Cornaz et al. have prepared the hydroxamic acid derivatives of Amberlite IRC-50 and other polymethacrylic acid resins, converting first to acid chloride and then reacting with hydroxylamine [19]. Vernon and Eccles have reported the * Corresponding author.

synthesis, properties and applications of poly(hydroxamic acids) [7-9,12]. The synthesis is based on the hydrolysis of acrylonitriledivinylbenzene copolymer to polyacrylamide, followed by the reaction with hydroxylamine of acid to acid chloride and reacting with hydroxylamines [7,8,20,21]. Later Shah and Devi described the synthesis of (polyacrylo) substituted hydroxamic acids based on the reaction of polyacrylic acid with substituted aryl hydroxylamines [22,23]. However, it is not possible to synthesize the hydroxamic acid by this method [22,23] as the carboxylic acids generally do not react with N-arylhydroxylamines [16,17]. The data reported by Shah and Devi [22,23] seem to be of the polyacrylic acids, but not of the polyhydroxamic acids. Several attempts have been made to synthesize the polyhydroxamic acids as described by Shah and Devi [22,23], but the described prod-

0923-1137/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved. SSDI 0 9 2 3 - 1 1 3 7 ( 9 5 ) 0 0 0 2 2 - 4

80

YK. Agrawal, K.F. Rao / Reactive Polymers 25 (1995) 79-87

uct was not obtained. Moreover, no IR data have been mentioned in their communication for characterization. Hence, in the present investigation, the polyhydroxamic acids have been synthesized via acid chloride formation by the modified method of Agrawal and colleagues [24-27].

stand at room temperature with stirring for 2 h. The solid residue thus obtained was washed with water and then methanol and dried over anhydrous phosphorous pentoxide. The dry powder was sized to 600 mesh and the fines rejected.

2.4. Ion-exchange columns 2. Experimental

2.1. Chemicals and apparatus All the chemicals used were of A.R. grade of B.D.H. unless otherwise specified. The solvents were purified by the method of Weissberger et al. [28]. Polyacrylic acid (mol. wt. 2,50,000) Aldrich, was used as such. The metal solutions were prepared as metal perchlorates and standardized with EDTA [29]. The IR spectra were recorded on a Perkin Elmer 1401 ratio recording infrared spectrophotometer as KBr pellets. A Grun SM20 Zeman atomic absorption spectrophotometer (AAS) was used for metal analysis,

2.2. Synthesis 2.2.1. Hydroxylamines The N-phenyl-, N-p-tolyl-, N-m-tolyl-, N-pchlorophenyl-, N-m-chlorophenyl-hydroxylamines were prepared from respective nitrobenzenes and zinc dust as described elsewhere [24-27].

The glass columns, length 20 cm, internal diameter 1 cm were packed with 5 g of poly(hydroxamic acids) (H + form). After conditioning the resin in the appropriate buffer for 2 h, the metal solution after adjusting the pH was passed through the column at the rate of 0.25 ml/min. The effluent fractions were collected in 10-ml volumetric flasks and analyzed for the metal ions by atomic absorption spectrophotometry.

2.5. Total cation exchange capacity Each resin (1 g) was transferred to a 150ml stoppered conical flask and the appropriate amount of 1 M HCI was added to convert to H + form. The flask was kept for 24 h. The resin was filtered, washed with distilled water and dried. A sample of resin (0.5 g) was taken in a dry 250-ml stoppered conical flask and 200 ml of 0.1 M NaOH in 5% NaCl was added. The contents were kept for 24 h. An aliquot of 25 ml of the supernatant solution was titrated with 0.1 M HCI. The total cation exchange capacity (CEC) was calculated as (200 x M NaOH) x (8 ml of M HCI)

2.2.2. Poly(acryloyl chloride)

Polyacrylic acid (3 g) was refluxed with thionyl chloride (6 ml) for 20 h. The excess of thionyl chloride was removed under reduced pressure,

CEC =

2.3. Substitutedpolyhydroxamic acids

g of dry resin (H+ form) (g) where % solid = wt of dried sample x 100/wt of the sample before drying.

Into a 500-ml three-necked flask equipped with stirrer, thermometer and dropping funnel diethyl ether (100 ml) freshly crystallized Narylhydroxylamine (0.1 mol) and a fine suspension of sodium bicarbonate (126 g, 40.15 mol) in water (20 ml) were added. Then poly(acryloyl chloride) (12 g) was added dropwise over a pcriod of 20 min. The mixture was allowed to

wt of the. sample (% solid/100) mg equivalent of cation exchange (mmol)

2.6. Rate of sodium absorption A resin sample (0.2 g) was transferred into a series of 250-ml stoppered conical flasks placed on the magnetic stirrer. Then 100 ml of 0.1 M NaOH (prepared in 0.1 M NaC1) was added to

YK. Agrawal, K.V. Rao / Reactive Potymers 25 (1995) 79-87

the flasks. After an appropriate time interval, the sodium ion concentration was determined by titrating the contents of flask with 0.1 M HC1.

81

in Table 1. A broad band in the region of 33403190 cm -1 is assigned for ( O - - H ) stretching vibrations while the ( C = O ) stretching vibrations are assigned in the region of 1670-1645 cm -1. The physicochemical properties of the polyacrylohydroxamic acids are shown in Table 1. The moisture content, true density (wet and dry) and apparent density were determined by the method described elsewhere [30]. The moisture (%) content in the Nsubstituted polyacrylohydroxamic acids varies between 23.0 and 16.8. The unsubstituted (Nphenyl polyacrylohydroxamic acid, I) has the lowest moisture content (16.8%) while the pchloro-substituted (N-p-chlorophenyl polyacrylohydroxamic acid, V) has the maximum moisture content (23%). This may be because of the less rigid structure. Thus, the resins under the present study have an intermediate range of moisture content compared to those of commercially available resins in H-form [31,32]. The dry and wet densities of the polymers are in the

2. 7. Metal sorption studies

A glass column (20 x 1 cm) was packed with the resin after conditioning the resin in the appropriate buffer for 2 h. The metal ion solutions (copper, lead, nickel), after adjusting the pH, were passed through the column at a flow rate of 0.5 ml/min. The effluent fractions were collected in 10-ml portions and analyzed for metal ion by AAS. 3. Results and discussion The polyacrylohydroxamic acids, synthesized by the present acid chloride method, are pure and give 80-95% yield. The characteristic vibrations of hydroxamate functional group of infrared data of polyacrylohydroxamic acids are given Table 1 Physical properties of the resins Properties (1) (2) (3) (4)

Cross link (%) Solid (%) Moisture (%) True density (g/cm 3) Dry

Wet (5) Apparent density (6) Swelling (7) Vol. capacity (mmol/cm 3) (8) Concentration of ionogenic

Polyacrylohydroxamic acids a I

II

III

IV

V

VI

VII

VIII

5 74.3 16.8

5 75.4 20.0

5 77.6 19.0

5 78.8 20.0

5 77.9 23.0

5 76.7 20.2

5 79.3 19.5

5 78.8 21.0

1.41 1.21 0.30 1.90 7.0 1.56

1.37 1.19 0.29 2.00 5.9 1.20

1.40 1.22 0.26 2.70 6.5 1.45

1.26 1.17 0.22 1.98 5.6 1.78

1.33 1.26 0.25 1.85 4.9 1.38

1.41 1.30 0.27 2.50 7.2 1.90

1.48 1.35 0.20 2.60 7.5 1.95

1.55 1.37 0.29 2.80 7.6 2.00

0.80 3.30

0.79 3.25

0.75 3.42

0.73 3.45

0.71 3.45

0.68 3.30

0.66 3.22

0.67 3.25

7.90

7.82

6.90

6.95

7.85

6.30

5.8

5.3

4.28 8.40

4.23 8.80

4.17 8.60

4.20 8.50

4.22 8.70

4.27 8.55

4.18 8.50

4.17 8.61

3250 1665

3290 1660

3190 1670

3300 1660

3200 1665

3280 1650

3340 1645

1645 1650

group (mmol/cm3) (9) Void volume (10) Sodium hydrogen

capacity (mmol/g) (11) Cation exchange capacity (mEq/g) (12) pKa (13) Infrared frequency (cm -1)

VOH vc = O

Compounds: 1, N-phenyl-, II, N-p-tolyl-, III, N-m-tolyl-, IV, N-o-tolyl-, V, N-p-chlorophenyl-, VI, N-m-chlorophenyl- VII, N-pbromophenyl-, and VIII, N-p-iodophenyl-polyacrylohydroxamic acid.

82

Y.K. Agrawal, K.V. Rao / Reactive Polymers 25 (1995) 79-87

range of 1.48-1.26 and 1.35-1.17 g/cm 3, respectively. The swelling in organic solvent is less and hence the structure remains rigid. The values for column density lie between 0.22 and 0.30 g/ml for compounds I-VIII. The void volume was evaluated from density data [30]. It is shown in Table 1 that void volume fraction varies in the range of 0.66 to 0.80. Since the polymers have a large void volume fraction, the diffusion of the ions and hence the rate of the ion exchange may be facilitated. The concentration of fixed ionogenic groups refers to the state of resin in particular process conditions and hence it is variable. The concentration of fixed ionogenic group (Cr) for the resin is calculated as:

Cr

dres ( 1 0 0 - % moisture) =

100

x EC

where dres is the density of the resin and EC is the exchange capacity (weight) of the resin. The volume capacity ( Q ) of the resin can also be calculated as Q = (1 - void volume fraction) Cr. The values are shown in Table 1. The hydrogen ion capacity is the measure of carboxylic acid units remaining in final product [11]. The values obtained are 2.98 4- 0.13 mmol/ g results that around 20% remained as acrylic acid in polyacrylohydroxamic acids (Compounds I-VIII). The pKa values have been determined by the method of Agrawal [5] and values are given in Table 1. The pKa values around 4.30 4- 0.50 and 8.60 4- 0.20 are due to acrylic acid and hydroxamic acids, respectively. The order of pKa obtained is II > I > V > IV > Ill > VI-IV > VIII > VII. The p-substituted acids have the higher pK~ values compared to ortho- and metasubstituted acids. Moreover CH3 > C1 as the methyl has positive inductive effect while the CI group has an electron-withdrawing effect which lowers the pK~ values. Fig. 1 shows the sodium ion uptake of the polyacrylohydroxamic acids (compounds I VIII). The t0.5 (the time required for an average half of the sodium ion to be taken up by the resin out of the maximum sodium ion uptake) is around 13 4- 2 min for compounds I, II, III and

RATE OFSODIUMION UPTAKE ~oo ~ , / 8o 60 40 20 . . . . . . . . . . . . . . . o 2 5 to ~5 zo 2~ 30 40 50 6o 2 4 a 12 ~6 24 R A T E OF SODIUM ION UPTAKE~Time min/hr) -e.- COMPD.

I

-÷-

COMPD. II

-')$- COMPO.Ul

"{3" COMPD. IV

* coaPD v -o- coeP0v, -~- couP~v,, * coMPov,, Fig. 1. Rate of sodium ion uptake for N-pbenyl-substituted polyacrylohydroxamic acid. V while 10 min for compound IV and 22 4- 2 rain for compounds VI, VII and VIII, respectively. These results indicate that the polymers require much less time for equilibration.

3.1. Metal ion capacity The p H for maximum sorption of the metal ions (copper, lead and nickel) and the corresponding capacities are given in Table 2.

Kd =

amount of solute / on resin /

weight of resin, g

amount of solute in solution

volume of solution, ml

The distribution coefficient is determined by batch experiments in which a known quantity of the resin is shaken with solution containing a known concentration of the solute (at the desired pH), followed by analysis of two phases after equilibrium has been attained. The effect of p H on the distribution coefficient Kd of the polyacrylohydroxamic acids resin for copper, lead and nickel is shown in Fig. 2. All the resins show high affinity to form the chelate with copper, lead and nickel at the pH between 2.5 and 5.0. The Kd values varies between 5 and 2900 for copper, lead and nickel for compounds I-VIII at different pH. The order of Kd values is Cu > Ni > Pb in all the cases. The exchange capacity for these metals at different p H is given in Fig. 3. The complete exchange takes place within 24 h for all the resins for copper, lead and nickel. The

YK. Agrawal, K. V. Rao / Reactive Polymers 25 (1995) 79-87

83

Table 2 Metal sorption properties of the polyacryiohydroxamic acids Polyacrylohydroxamic acids

Copper

Nickel

pH a

Capacity (mmol/g/l)

Time b (min)

pH a (mmol/g/l)

Capacity (min)

Time b

pH a (mmol/g/l)

Capacity (min)

Time a

I

4

II III IV V VI VII VIII

4 4 4 4 4 4 4

1.50 1.31 0.98 0.90 1.30 1.15 0.70 0.68

2.5 2.5 2.5 3.0 2.2 2.5 3.0 3.0

4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5

1.03 1.00 0.70 0.65 1.02 0.95 0.85 0.80

3.0 3.2 3.5 3.0 3.0 3.5 4.0 4.0

4 4 4 4 4 4 4 4

1.40 1.20 0.90 0.80 1.20 1.05 0.60 0.58

2.5 2.5 2.5 2.5 3.0 3.0 3.0 3.0

Lead

a pH for maximum sorption. b Approximate time for maximum sorption.

3000

~

3000

3000,

2500

~ / " ~

2500

2500

u) u.J ._.1

2000

o3 u.J 2 0 0 0 D .._1

-o

1500

*o

I

(z) uJ D ._.1

1500

"~

1500

1000

1000

500

500

500

,

,

b

I'0 2"0 3"0 4"0 5-0 6 0

pH

'

2000

1000

1-0 2'0 3"0 4"0 5"0

I

pH

2

3

4

5

6

pH

Fig. 2. Variation of Kd with pH for N-phenyl-substituted polyacrylohydroxamic acid (Compounds I-VIII). (a) copper, (b) lead, (c) nickel ion.

time required for the sorption to reach 50% of its maximum value, which is a measure of the uptake of various metal ions is given in Table 2. The values are less than 5 min showing that the sorption of the copper, lead and nickel is rapid,

ities. The breakthrough curves for copper, lead and nickel at the pH of maximum sorption at the flow rate of 0.5 ml/min are given in Fig. 4. All the curves are steep at the breakthrough point of different times, indicating the possibility of separating these metal ions from their mixtures.

3.2. Breakthrough studies 3.3. Effects of eluents The breakthrough capacities are more significant for chromatographic applications of the resins (compounds I-VIII) than the batch capac-

The elution of copper, lead and nickel from the loaded resins in columns was studied with

98.5 40.0

86.9 99.9 78.0

87.0 99.0 37.0

1.0 2.0

H2SO4 0.2 0.5 1.0

HNO3 0.2 1.0 2.0

CH3COOH 4.0 0.80 5.0 13.0

80.5

HCI 0.2

30.5 10.0

90.0 98.7 18.9

-

40.0 50.0

30.0

-

87.5 99.9 45.0

84.0 99.5 70.5

97.5 33.0

70.5

Cu

Cu

Pb

II

I

18.0 8.0

88.0 98.5 60.0

-

40.2 45.0

29.0

Pb

20.0 16.0

83.5 98.5 60.0

86.5 99.3 68.0

95.0 36.0

82.5

Cu

Ill

6.5 4.5

90.5 99.5 50.0

-

42.0 48.0

25.0

Pb

16.5 16.0

79.0 97.5 39.0

80.5 99.8 66.5

96.5 33.0

70.5

Cu

IV

7.8 5.0

70.0 98.0 60.0

-

25.0 35.0

20.0

Pb

8.5 10.5

82.0 99.0 32.0

87.0 99.9 69.0

93.0 29.0

80.0

Cu

V

10.5 9.8

90.0 97.3 50.0

-

45.0 53.0

30.0

Pb

Table 3 Effect of various eluents of different concentrations on the copper- and lead-loaded resins (compounds I-VIII)

7.9 10.0

79.0 98.0 23.0

82.0 99.0 70.0

94.0 40.0

76.0

Cu

VI

0.5 0.6

79.0 95.0 60.0

-

25.0 48.0

28.0

Pb

6.5 8.5

78.0 99.9 25.0

80.0 98.5 68.0

96.0 30.0

68.9

Cu

VII

-

60.9 90.0 40.0

-

25.0 36.0

20.0

Pb

10.0 18.0

76.0 99.0 26.0

80.0 98.6 68.0

93.0 32.0

28.0

Cu

VIII

0.6 1.0

61.0 82.0 50.0

-

28.0 42.0

18.0

Pb

oo "~

"~

,~

P~ ~-

~-.

.~ -~

o~

Oo

YK. Agrawal, K.V. Rao / Reactive Polymers 25 (1995) 79-87 1.6

a

i

1.4

Tm"

E

1-6

.ff

7t3n

1"4

1.2

~

1.2

10

E

1"0

0.8

F

b

~.6 I

85

c

1"4i

1.2 NI K

~_"

08

1-0

08

; g

o2

o-z 0

2.0

4.0

2-0

4.0

6.0

2,.0

4.0

6.0

pH pH

pH

Fig. 3. The exchange capacity for (a) copper, (b) lead and (c) nickel with N-phenyl-substituted polyacrylohydroxamic acids (Compounds I-VIII).

~oo T_~ E

nickel could not be eluted from any acid. However, it can be quantitatively eluted from 1.0 M tartrate solution. In the present investigation, the resin bed length was kept at 4-5 cm for the compounds by which it was found that the maximum flow rate of 5 ml/min can be maintained. The increase in the column length results in a resistance to flow. The low flow rate may increase the degree of column utilization. The optimum flow rate of 0.5-1.0 ml/min was kept throughout the present studies.

?

80

~ ~

~_ 60 "6

4O

b

N~ ~ :u

zo ,~

°

J ,oo

i 2o0

/

i ~oo

400

Effluent Volume, ml.

Fig. 4. Breakthrough curves for copper, lead and nickel ions on N-phenylpolyacrylohydroxamic acid.

various eluents. The study was restricted to acids (HCI, HNO3, H2SO4, C H 3 C O O H and tartrate) only as the resins were found to swell in electrolyte to a large extent. These data are given in Table 3. It is evident that copper can easily be eluted quantitatively from H2SO4, HNO3, HC1; however, from acetic acid the elution is only 9.518% for all the resins. The lead is quantitatively eluted from HNO3. The amount of lead eluted from HC1 is 40-60% from H2SO4 1.5-3.0% and 0.6-10% from CH3COOH. The copper and lead could not be eluted with tartrate. Similarly, the

3.4. Separation of copper, lead and nickel The batch capacities, breakthrough curves and p H of the sorption reveal that the resins have the selectivity for metal ions (copper, lead and nickel). The kinetic studies make the resins useful for separation of these ions on a column. The ion exchange column is loaded with copper, lead and nickel and elution curves are obtained for each ion by preferential elution with 0.5 M H2SO4, 0.5 M HMO3 and 1 M tartrate, respectively (Fig. 5). It is observed that copper can be separated from lead and nickel in mixture without crosscontamination with 100% recovery after eluting it with 0.5 M H2SO4. The elution of lead can be carried out by 0.5 M HNO3 and, finally, nickel can be eluted with 1 M tartrate. The results of the analysis of synthetic mixtures are given in Table 4.

Y.K. Agrawal, K. V. Rao / Reactive Polymers 25 (1995) 79-87

86

Table 4 Quantitative separation of copper, lead and nickel with polyacrylohydroxamic resins Sample

Metal ions

no.

separated

1

Cu(II) Pb(II) Ni(II)

2

3

Effluent

Metal (rag)

Standard deviation

Loaded

Recovered

(mg) a

0.5 M H2SO4 0.5 M HNO3 1 M Tartrate

100 100 100

99.9 99.9 I00.1

0.20 0.22 0.16

Cu(II) Pb(II) Ni(II)

0.5 M H2SO4 0.5 M HNO3 1 M Tartrate

200 150 100

200.1 149.8 99.8

0.12 0.23 0.25

Cu(II) Pb(II) Ni(II)

0.5 M H2504 0.5 M HNO3 1 M Tartrate

50 25 100

49.8 25.0 100.2

0.20 0.10 0.21

a Mean of 7 determinations.

Ioo

~-0'SMHzS04 =;~0SMHN% 4=

g 75

1MTot

=.,

/"

"~ _~ 50 ~, 25I//

, ' , ~ / 10

20

........

3~r

. . . . .

11"

~',' 30

~

4o

5o

ions is rapid and to a larger extent with high Kd values and exchange capacities. The elation of the metals is rapid (to.5 = 10 min). The copper, lead and nickel have been separated quantita-

tively. All attempts failed to elate nickel from 6o

H C 1 a n d H N O 3 ; however, it c a n b e elated quantitatively from I M tartrate solution.

H2SO4,

V o l u m e , ml

I

5. Acknowledgement 1"*-O.SM H2SO4

,lJ

loo r

0-SM HNO 3

~=

IM Tor--~

'-"

;~;c,

The authors are thankful to the C.S.I.R., New Delhi for providing the financial support.

75

®

50

",

" =P:

,'

"

,

lO ..... ........

~rr ra

2o 8, " ~ Z ~

3o

4o

5o

6o

V o l u m e , ml

Fig. 5. Separation of copper, lead and nickel in a concentration ratio of 1 : 1 : 1, using cation exchangers, Compounds 1-VIII (N-phenyl substituted polyacrylohydroxamic adds. Tar, tartrate.

4. Conclusion The present method f o r t h e synthesis of polyacrylohydroxamic acids gives 80-95% yield and pure product with less amount of unreacted polyacrylic acid. The sorption of the divalent metal

6. References [1] Y.K. Agrawal, Rev. Anal. Chem., 5 (1980) 3. [2] Y.K. Agrawal and S.A. Patel, Rev. Anal. Chem., 4 (1980) 237. [3] Y.K. Agrawal and R.D. Roshania, Bull. Soc. Chem. Belg., 89 (1980) 159. [4] Y.K. Agrawal, Anal. Chem., 47 (1975) 940. [5] Y.K. Agrawal, Russ. Chem. Rev., 48 (1979) 1773. [6] A.K. Majumdar, N-Benzoylphenylhydroxylamine and its Analogues, Pergamon, London, 1971. [7] E Vernon and H. Eccles, Anal. Chem. Acta, 83 (1976) 187. [8] E Vernon and H. Eccles, Anal. Chem. Acta, 82 (1976) 369. [9] E Vernon, Pure Appi. Chem., 54 (1982) 2131. [10] R.J. Phillips and J.S. Fritz, Anal. Chem. Acta, 121 (1980) 225. [11] R.J. Phillips and J.S. Fritz, Anal. Chem. Acta, 139 (1982) 237. [12] E Vernon and J.H. Khorassani, Talanta, 25 (1978) 410.

YK. Agrawal, K. V. Rao / Reactive Polymers 25 (1995) 79-87

[13] A. Dyer, M.J. Hudson and EA. Williams (Eds.), Ion Exchange Processes: Advances and Applications, Roy. Soc. Chem., London, 1993. [14] C.E. Harland, Ion Exchange: Introduction to Theory and Practice, Roy. Soc. Chem., London, 1994. [15] M. Marhol, Ion Exchangers in Analytical Chemistry. Their Properties and Use in Inorganic Chemistry Cornprehensive Analytical Chemistry, Vol. XIV, Elsevier, Amsterdam, 1982. [16] H.L. Yale, Chem. Rev., 33 (1943) 209. [17] S.R. Sandler and W. Karo, Organic Functional Group Preparation, Vol. III, Academic Press, New York, 1972. [18] Y.K. Agrawal, D.Sc. Thesis, A.ES., Univ. Rewa, 1979. [19] J.P. Cornaz, K. Hutschneker and H. Deuel, Helv. Chem. Acta, 40 (1957) 2015. [20] E Vernon and H. Eccles, Anal. Chem. Acta, 77 (1975) 145. [21] E Vernon and H. Eccles, Anal. Chem. Acta, 79 (1975) 229. [22] A. Shah and S. Devi, Analyst, 110 (1985) 1501.

87

[23] A. Shah and S. Devi, Analyst, 112 (1987) 325. [24] Y.K. Agrawal and S.G. Tandon, J. Chem. Eng. Data, 16 (1971) 371,495. [25] Y.K. Agrawal and R.D. Roshania, J. Chem. Eng. Data, 23 (1978) 259. [26] A. Mudaliar and Y.K. Agrawal, J. Chem. Eng. Data, 24 (1979) 246. [27] R.K. Jain and Y.K. Agrawal, J. Chem. Eng. Data, 24 (1979) 250. [28] A. Weissberger, E.S. Proskauer, J.A. Riddick and E.E. Toops Jr., Techniques of Organic Chemistry, Vol. VII, lnterscience, New York, 1955. [29] EJ. Welcher, Analytical Uses of Ethylenediaminetetraacetic Acid, Van Nostrand, Princeton, NJ, 1965. [30] G.P. Simon, Ion Exchange Training Manual, Van Nostrand Reinhold, New York, 1991. [31] E Helfferich, Ion Exchange, McGraw-Hill, New York, 1962. [32] R. Kunin, Ion Exchange Resins, 2nd edn., John Wiley, New York, 1958.