Cellulose aluminium oxide coated with organofunctional groups containing nitrogen donor atoms

A composite of cellulose and aluminium oxide, cel/Al2O3, was prepared and further modified with organofunctional groups by reacting with the coupling reagent (C2H5O)(3)SiL, where L represents -(CH2)(3)NH2, -(CH2)(3)NH(CH2)(2)NH2, -(CH2)(3)NH(CH2)(2)NH(CH2)(2)NH2 or -(CH2)(3)N(C3H3)N [-N(C3H3)N = imidazolyl radical], abbreviated to ap, enp, dienp and imp, respectively. The experimental preparation procedures were very reproducible and resulted in the following values for the amount of organofunctional groups grafted on cel/Al2O3 (average values in mmol g(-1)): cel/Al2O3/Si(ap) = 0.35; cel/Al2O3/Si(enp) = 0.30; cel/Al2O3/Si(dienp) = 0.25 and cel/Al2O3/Si(imp) = 1.0. The Al-27 MAS NMR spectra, which show an intensification of the area under the peak at 62 ppm due to Al in a tetrahedral environment, and the increase of the Al/C atomic ratios (determined from X-ray photoelectron spectra) after reaction with the coupling reagents indicate that Al atoms have migrated to the surface. This indicates that (C2H5O)(3)SiL is adsorbed on the matrix surface and reacts with the AlOH groups forming Al-O-Si bonds. The adsorption isotherms from ethanol solutions of FeCl3, CuCl2 and ZnCl2 were obtained at 298 K. The average stability constants were determined for each metal halide and the results indicated that the constants for the bi- and tridentate ligands, enp and dienp, are slightly higher than those for ap and imp, both monodentate ligands.