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

Abstract

Phenolic Schiff bases derived from o‐, m‐, and p‐hydroxybenzaldehydes and 4, 4′‐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, 1H‐NMR, XRD, and thermal analyses like TG, DTG, and DSC studies. The 1H‐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). © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 967–981, 2000

A silicon-containing polyazomethine and derived metal complexes: synthesis, characterization, and evaluation of the properties

“…The metal ions in the polychelates were stated to be responsible in catalyzing the thermal decomposition resulting in the molecular framework to undergo fragmentation. [41][42][43] Based on the similar structures studied in literature, [44] one may assume that, due to the high temperature, the azomethine linkage (-HC=N-) is the first breaking unit, in all cases. This process is attributed to the second thermal decomposition stages of PAZ, PAZ-Cu, and PAZ-Co samples and to the third stage in the case of PAZ-Zn sample.…”

Rapid removal of heavy metal cations and anions from aqueous solutions by an amino-functionalized magnetic nano-adsorbent

“…The chelating resins with nitrogen-containing complex ligands have excellent adsorption capability for polyvalent metal cations owing to the strong affinity between the nitrogen atom and metal cations [18,19,[23][24][25]. In addition, they are also capable of adsorbing anionic species after protonation.…”

Synthesis and Characterization of the Polymeric Phenolic Schiff Bases Containing Aminothiazole Moiety

“…The Schiff bases having multiple coordination sites are known to form complexes with transition metal ion readily [19][20][21] present in a polymeric matrix they are expected to show affinity selectivity towards the metal ions at an appropriate pH. This simple idea inspired our research group to synthesize a number of chelating resins containing Schiff base moiety and study their metal ion uptake behavior [22][23][24][25][26][27][28] . Literature studies reveal that metal ion uptake behavior of resins containing Schiff bases of heterocyclic compounds especially aminothiazole Schiff bases are yet to be studied and also there is no report of antibacterial activity of thiazole compounds present in a resin matrix.…”