Industrial & Engineering Chemistry Research, Vol.57, No.45, 15243-15253, 2018
Efficient Uptake of Cd(II) and Pb(II) Ions by Aromatic Polyamidoximes
Polyamidoximes were synthesized by condensing presynthesized monomers, 2,6-bis(4-chloroformylphenoxy) benzonitrile or 2,6-bis(4-aminophenoxy) benzonitrile, with diamines and diacid chlorides at low temperature. These polyamidoximes were exploited as potential metal-chelating adsorbents owing to the presence of amidoxime as pendant groups on the polyamide backbone. The synthesis of monomers was verified by Fourier transform infrared spectroscopy and nuclear magnetic resonance analyses. The molar masses of the polymers were measured using gel permeation chromatography, and thermal decomposition temperatures were found to be in the range of 426-489 degrees C with high char yields. Metal-ion uptake was investigated through atomic absorption spectroscopy with more than 99% adsorption capacity at optimized parameters, i.e., a contact time of 3 h at pH 6. The mechanism of adsorption was further analyzed by Freundlich and Langmuir adsorption isotherms. The data indicated that metal ions uptake followed monolayer adsorption and that the adsorbent possessed homogeneous active sites. The relative uptake of divalent metal ions was monitored as Fe2+ > Pb2+ > Cd2+ > Cu2+.