Synthesis of crosslinked chitosan-crown ethers and evaluation of these products as adsorbents for metal ions

Two new crosslinked-crown ethers (CCTS-N=CH-B-15-C-5 and CCTS-N=CH-B-18-C-6) were synthesized by the reaction of crosslinked chitosan (CCTS-NH 2 ) with 4'-formyl benzo-15-crown-5 and 4'-formyl benzo-18-crown-6. Their structures were confirmed with elemental analysis, infrared spectra analysis, solid-state 13 C NMR analysis, X-ray diffraction analysis, and differential scanning calorimetry thermogram analysis. In the infrared spectra of CCTS-N=CH-B-15-C-5 and CCTS-N=CH-B-18-C-6, the characteristic peak of C=N stretch vibration appeared at 1650 cm 1 . The X-ray diffraction analysis showed that the peak at 2θ = 20° decreased greatly in CCTS-N=CH-B-15-C-5 and CCTS-N=CH-B-18-C-6. In the 13 C NMR spectra of CCTS-N=CH-B-15-C-5 and CCTS-N=CH-B-18-C-6, the characteristic peak of aromatic carbon appeared at 128-ppm, the characteristic peak of carbon in the C=N group appeared at 151 ppm. The adsorption and selectivity properties of CCTS-N=CH-B-15-C-5 and CCTS-N=CH-B-18-C-6 for Ag', Pd 2+ , Pb 2+ , Cd 2+ , and Cr 3- were studied. The experimental results showed that the two crosslinked chitosan-crown ethers have not only good adsorption capacities for Ag' and Pd 2+ , but also high selectivity for the adsorption of Ag + or Pd 2+ with the coexistence of Pb 2+ and Cr The selectivity coefficients of CCTS-N=CH-B-15-C-5 and CCTS-N=CH-B-18-C-6 were K Pd 2+/ Pb 2+ = 9.9, K Ag/Pb 2+ = 9.8, K Pd 2+ /Cr 3 = ∞, K Pd 2+ /Pb 2+ 11.5, K Ag + /Pb 2+ = 7.1, K Pd 2+ /Cr 3+ = ∞ respectively.