Synthesis, spectral, thermal, and chelation potentials of polymeric hydrazone based on 2,4-dihydroxy benzophenone

摘要

A chelating polymer, poly(2,4-dihydroxy benzophenone hydrazone- formaldehyde) [poly(DHBpH-F)], was synthesized by the polycondensation of 2,4-dihydroxy benzophenone hydrazone with formaldehyde in the presence of oxalic acid as a catalyst. Poly(DHBPH-F) was characterized by Fourier transform infrared and 1H-NMR spectral data. The molecular weight of the polymer was determined by gel permeation chromatography. Polyche- lates were obtained when the dimethylformamide solution of the polymer containing a few drops of ammonia was treated with an aqueous solution of metal ions. Elemental analysis of the polychelates indicated that the metal-ligand ratio was 1:2. The IR spectra of the polymer-metal complexes suggested that the metals were coordinated through the oxygen of the phenolic-OH group and the nitrogen of the azomethine group. The electron paramagnetic resonance and magnetic moment data indicated a square planar configuration for Cu(II) chelate and an octahedral structure for Ni(II) chelate. The ther- mogravimetric analysis, differential scanning calorimetry, and X-ray diffraction data indicated that the incorporation of the metal ions significantly enhanced the degree of crystallinity. The polymerization initiation, electrical conductivity, and catalytic activity of the polychelates are discussed. Heavy-metal ions [viz., Cu(II) and Ni(II)] were removed with this formaldehyde resin, and the metal-ion uptake efficiency at different pH's, the nature and concentration of the electrolyte, and the reusability of the resin were also studied.