Preparation, characterization and sorption properties of crosslinked starch-based exchangers

Starch-based polymers were prepared by a crosslinking reaction of starch-enriched flour using epichlorohydrin as a crosslinking agent in the presence of NH4OH. Yield, mobility and structural properties of crosslinked starch materials with various compositions were investigated by elemental analysis, electrophoretic mobility and NMR spectroscopy. In particular cross-polarization magic angle spinning (CPMAS) and magic angle spinning (MAS) techniques were used, as well as relaxation time measurements. The homogeneity and the molecular mobility of these polymers were analyzed in terms of cross-relaxation time between protons and carbons (T-CH), H-1 spin-lattice relaxation in the rotating frame ((T1 rho H)-H-1) and H-1 longitudinal spin-lattice relaxation time ((T1H)-H-1). A correlation was found between the structure, mobility and degree of crosslinking of these sorbents. This correlation was discussed. Finally, these crosslinked starch-based materials, containing tertiary amine groups have been used for the recovery of various dyes from aqueous solutions. Sorption studies are presented, focusing on the polymer and dye structures. The results showed that these polymers exhibited interesting sorption properties and that the sorption mechanism was correlated to the structure of the polymer. (c) 2004 Elsevier Ltd. All rights reserved.