Complex Formation Between Pd(II) and Immobilized Imidazol-Azo-Chromotropic Acid

Jasmina Savić and Vesna Vasić

Vinča Institute of Nuclear Sciences, POB 522, 11001 Belgrade, Serbia and Montenegro. E-mail: jasnas@vin.bg.ac.yu

Abstract
1,8-Dihydroxy-2-(imidazol-2-ylazo)-naphthalene-3,6-disulphonic acid (imidazol-azo-chromotropic acid - IACA) was immobilized onto the anion exchange resin Dowex 1-X8, 50-100 mesh. The aim of this work was to investigate the mechanism of the complex formation between Pd(II) and immobilized IACA by following the absorption spectra of the solid phase. The reaction between Pd(II) and immobilized azo-dye was followed in the acidity range from pH 1 to pH 7. Pd(II) and IACA form 1:1 complex with the absorption maximum at 650 nm. The kinetics of complex formation was followed in pH range from 1 to 6, as the function of Pd(II) in excess. The effective forward (k_f) and reverse (k_b) pH dependent rate constants for complex formation were obtained from the linear dependence of k_obs vs. Pd(II) concentration. Bell shaped pH profile (k_f vs. pH) indicated that both ligand and metal ion, were included in acidic - basic equilibrium with H⁺ ion.

Key words: azo dye, immobilization, ion-exchange resin, Pd(II), determination