EFFECTS OF Cu, Cr AND Pb ADSORPTION ON THE NANOSTRUCTURE OF CHITOSAN FILMS

C. MACCHI; A. SOMOZA; P.S. ANBINDER

Simposio; XII SIMPOSIO ARGENTINO DE POLÍMEROS; 2017

Biosorption is an emerging area in which heavy metals are adsorbed and retained in biomaterials. The main advantages linked to biosorption include biocompatibility, biodegradability, price affordability with high effectiveness, minimum usage of chemicals, restoration of biosorbent and possible usage of recovered metal [1]. Among biomaterials, biopolymers are especially used as heavy metal removals due to their proved ability to bind transition metals. One of the most studied biopolymers for this kind of application is the chitosan, which is the partially deacetylated form of the chitin, a natural polysaccharide extracted from crabs, shrimps and other crustacean skeleton. Despite there are a lot of works reported in the literature dealing with the heavy metals removal capacity of chitosan (see for example Refs. [1,2]), only in few of them [3,4] detailed information on what morphological changes results in the chitosan nanostructure due to that adsorption has been reported.An interesting approach to the mentioned issue could be given through the use of positron annihilation lifetime spectroscopy (PALS), a unique non-destructive technique capable of directly measuring subnanometer sized free volume holes and their distributions in polymers, even in biological systems. To this aim, chitosan films were immersed for 24 h at room temperature in solutions with different metallic ions of environmental interest (Cu+2, Pb+2 and Cr+6). Then, the chitosan-based sorbent films were analyzed using different techniques including PALS; specifically, DSC, SEM, FTIR and DRX. Results are discussed in terms of the interaction of the metal ions with the biopolymer matrix taking under consideration the initial concentration of the metal solutions, the metal ion size and valence number, among others.