Synthesis, characterization, and metal ion uptake studies of chelating resins derived from formaldehyde/furfuraldehyde condensed phenolic Schiff base of 4,4'-diaminodiphenylmethane and o-hydroxyacetophenone

The synthesis, characterization, and metal ion uptake studies of two chelating resins with multiple functional groups are reported. The chelating resins were synthesized by condensing a phenolic Schiff base derived from 4,4'-diaminodiphenylmethane and o-hydroxyacetophenone with formaldehyde or furfuraldehyde. The resins readily absorbed transition metal ions, such as Cu2+ and Ni2+, from dilute aqueous solutions. The Schiff base, resins, and metal polychelates were characterized by various instrumental techniques, such as elemental-analysis, ultraviolet-visible spectroscopy proton and carbon-13 nuclear magnetic resonance spectroscopy (H-1-NMR and C-13-NMR, respectively), X-ray diffraction (XRD), and thermogravimetric-differential thermogravimetric analyses (TG-DTG). The H-1-NMR and C-13-NMR studies were used to determine the sites for aldehyde condensation with the phenolic moiety. Fourier transform infrared data provided evidence for metal-ligand bonding. Thermogravimetric analysis was employed to compare the relative thermal stabilities of the resins and the polychelates. The TG data were fitted into different models and subjected to computational analysis to calculate the kinetic parameters. The XRD data indicate that the incorporation of metal ion into the resin matrix significantly enhanced the degree of crystallinity of the material. The extent of metal-ion loading into the resins was studied in competitive and noncompetitive conditions, varying the time of contact, metal ion concentrations, and pH of the reaction medium in a suitable buffer medium. The furfuraldehyde-condensed resin was more effective in removing metal ions than the formaldehyde-condensed resins. The resins were selective for Cu2+, resulting in separation of Cu2+ and Ni2+ from the mixture at pH 5.89, (C) 2003 Wiley Periodicals, Inc.