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Ligand Exchange Chromatography and Recovery of some Meta l Ions on P A N Sorbed Tin(IV) Sil icate Columns Dhruv Kumar Singh and Rishi Raj Bhatnagar

Department of Chemistry, Harcourt Butler Technological Institute, Kanpur-208 002, India

Liganden-Austausch-Chromatographie: Trennung yon Metallionen an mit PAN getr/inkten Zinn(IV)-silicat-S/iulen

In the ligand exchange column-chromatographic separations of metal ions developed, an inorganic ion-exchanger [tin(IV) silicate] sorbed with PAN [1-(2-pyridyl-azo)-2-naphthol] is utilized. Tin(IV) silicate was prepared [1] by mixing 0.04 tool/1 stannic chloride and 0.15 tool/1 sodium silicate in the volume ratio 4:1 at pH 8.5. The exchanger (60-100 mesh) was sorbed with PAN (0.1% for 24 h). Rate of sorption studies for Cu 2+ and Fe 3 + reveal that equilibrium is attained within 5 min only due to the chelating agent (PAN). The results of distribution studies of 12 metal ions in different pH-systems are presented in Table 1. The exchanger has been found to be selective for Ni 2 +. The reason for selective sorption and desorption of certain metal ions can be attributed to large differences in stability constants of metal-PAN complexes at certain pH values. The elution is based on the stability constant of the metal eluting ligand complex. The quantitative separations possible (Table 2) include Co z + -Ni 2 +, Cu z +-Ni 2 +, Pt 4 +-Ni z +, Pt 4 +-Fe 3 +, Ag +- Cu 2 +, Mn 2 +-Zn 2 + and P b 2 + - C d 2 +. The recovery of Pt 4 + and Au 3 + (1 - 5 mg) from dilute solutions in the presence of Co 2 +,

Table 1. Kda-values of metal ions

Metal ions pH 2 pH 4 pH 6 pH 8 pH 10

C o 2+ 27.5 100.2 150.0 208.7 46.2 Ni 2+ 1,375 T.A. T.A. T.A. 150.0 Cu 2+ 18.6 132.0 350.0 81.3 3.4 Fe 3+ 78.2 130.2 250.0 - - M n 2+ 0.0 33.6 87.5 98.2 -- Pb 2+ 10.2 66.5 75.0 90.5 2.8 Zn 2+ 42.6 83.2 128.7 73.2 0.0 Cd / + 20.8 51.3 200.0 203.3 125.0 H g 2 + 3.0 41.2 80.0 -- -- Au 3+ 23.0 160.2 196.2 148.2 0.2 Pt 4+ 0.0 0.5 0.8 0.8 0.8 Ag + 90.8 296.8 375.0 - 0.0

a Kd Amount of metal ion in exchanger phase �9 g- 1

Amount of metal ion in solution phase �9 cm- 3

N i 2+, C a 2 + and Fe 2 + (5 mg each) has also been studied at pH 2.

Acknowledgement. The authors are thankful to Professor A. K. Vasishtha, Director and Professor R. S. Tewari, Head, Depart- ment of Chemistry, Harcourt Butler Technological Institute, Kanpur-208002, India, for providing research facilities.

Reference 1. Desai G-T, Baxi D-R (1978) J Technol 16:201

Received August 29, 1985; revised October 7, 1985

Table 2 Separations on PAN-sorbed tin(IV) silicate columns

Offprint requests to." Dhruv Kumar Singh

Sample Mixture Eluent Eluate Amount Amount (ml) loaded recovered

(gg) (gg)

Percentage error

1 C o 2+ A 50 250.6 253.1 0.99 Ni z+ B 90 248.4 243.0 2.18

2 Cu 2 + C 40 460.5 468.0 1.63 N i 2+ B 90 248.4 243.6 1.93

3 Pt 4+ D 50 256.7 252.0 1.83 Ni 2+ B 110 352.6 361.1 2.41

4 Pt 4+ D 60 375.0 365.9 2.42 Fe 3 + C 70 406.6 414.2 1.87

5 Ag + E 60 304.0 300.0 1.31 Cu 2+ C 50 460.5 467.4 1.50

6 M n 2+ A 40 373.2 368.5 1.26 Z n 2+ C 70 240.8 244.6 1.58

7 Pb 2+ C 60 414.3 406.7 1.83 Cd z+ A 80 402.9 413.8 2.70

Abbreviations used: A 0.01 tool/1 HC1; B 0.05 mol/1 EDTA in 0.01 mol/1 HC1; C 4 mol/1 NH3; D Demineralized water; E 0.1 mol/1 NH3

Fresenius Z Anal Chem (1986) 325:195 �9 Springer-Verlag 1986

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