Sorption and desorption studies on chitin gels

The aim of this work was to study various transport phenomena in chitin gel s obtained by N-acetylation of chitosan in a water-alcohol mixture. Three k inds of transport were investigated: the sorption of solutes interacting wi th chitin, the desorption of solutes without significant interaction with t he polymer, and osmosis phenomena. In the case of interactive sorption dyes having different chemical structures such as C.I. Acid Blue 74, C.I. React ive Violet 5 or C.I. Direct Red 28 were tested. Sorptions of C.I. Acid Blue 74 and C.I. Reactive Violet 5 depend on the charge density of the polymer network and. as a consequence, on DA, pH and the dielectric constant of the media. This result reveals the importance of electrostatic interactions. O n the other hand, the sorption of C.I. Direct Red 28 is mainly due to hydro phobic interactions and H-bonding, it is limited to the extreme surface of the gel. Concerning the non-interactive desorption, solutes of different st eric hindrance such as PP vitamin, B1 vitamin and caffeine exhibit similar diffusion coefficients located within 3.7-5.6 x 10(-6) cm(2) s(-1). Finally , the osmotic behaviour of the gel immersed in a concentrated solution of g elatine allows us to multiply by 25 the concentration of chitin in the gel without any penetration of gelatine. (C) 2001 Elsevier Science B.V. All rig hts reserved.