Chelating resins VI: Chelating resins of formaldehyde condensed phenolic Schiff bases derived from 4,4′-diaminodiphenyl ether with hydroxybenzaldehydes—synthesis, characterization, and metal ion adsorption studies

✍ Scribed by S. Samal; R. R. Das; R. K. Dey; S. Acharya

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 272 KB
• Volume: 77
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/1097-4628(20000801)77:5<967::aid-app3>3.0.co;2-5

✦ Synopsis

Phenolic Schiff bases derived from o-, m-, and p-hydroxybenzaldehydes and 4, 4Ј-diaminodiphenyl ether were subjected to polycondensation reaction with formaldehyde. The resins were found to form polychelates readily with several metal ions. The materials were characterized by elemental analysis, GPC, IR, UV-Vis, 1 H-NMR, XRD, and thermal analyses like TG, DTG, and DSC studies. The 1 H-NMR spectra of the resins provided evidence of polycondensation with well-defined peaks for bridging methylene and terminal methylol functions. The metal-ligand bonds were registered in the IR spectra of the polychelates. The thermal analysis data provided the kinetic parameters like activation energy, frequency factor, and entropy changes associated with the thermal decomposition. These data indicated the resins to be more stable than the polychelates. The DSC and XRD data indicated that the incorporation of metal ions significantly enhanced the crystallinity of the polymers. The resins could adsorb several metal ions from dilute aqueous solutions. Adsorption characteristics of the resins towards Cu(II) and Ni(II) were studied spectrophotometrically both in competitive and noncompetitive conditions. The effects of pH, contact time, quantity of the sorbent, concentration of the metal ions in a suitable buffer medium were studied. The resins were found to be selective for Cu(II) leading to its separation from a mixture of Cu(II) and Ni(II).