Synthesis of Crosslinked Chitosan Possessing Schiff Base and Its Use in Metal Removal

A chitosan resin derivatized with Schiff bases was synthesized by using a crosslinked chitosan (CCTS) as base material. We first synthesized N-benzylidene chitosan (CTB) by the reaction of benzaldehyde with chitosan. After this reaction crosslinking was carried out in the usage of epichlorohydrine (ECH) as a crosslinking agent. The Schiff base was removed by reacting diluted ethyl alcohol hydrochloride solution to give crosslinked chitosan (CCTS). The CCTS was suspended in a mixture of ethyl alcohol/deionized water followed by the addition of epichlorohydrine and by this way crosslinked chitosan-epichlorhydrine (CCTS-ECH) resin was synthesized. After the reaction was completed, the product was filtered, washed with ethyl alcohol and deionized water and dried in vacuum. The two novel polymeric ligands (CCTS-ECH-DHSalophen and CCTS-ECH-DHDPE) were synthesized by the reaction of CCTS-ECH with N,N'-bis(2,5 dihydroxybenzylidene)-1,2-diaminobenzene (DHSalophen), and N,N'-bis(2,5 dihydroxybenzylidene)-4,4'-diaminodiphenylether (DHDPE). The structures of the ligands were characterized by elemental analysis, infrared spectroscopy(FT-IR), scanning electron microscopy(SEM) and thermogravimetric analysis (TGA/DTA). Adsorption experiments (pH dependency, kinetics, and equilibrium) of compounds toward Cr(VI) from waste water were carried out at 25 degrees C.