PROTOLYTIC AND COMPLEXING PROPERTIES OF MICROCRYSTALLINE CHITOSAN WITH CO(II), ZN(II), AND CU(II) IONS

It has been evidenced that microcrystalline chitosan (MCCh) with a determined (by the potentiometric method in nonaqueous medium) degree of deacetylation of 0.87 acts as a polymeric chelating agent with cobalt(II) and zinc(II). The predomination of hydrolytic reactions, in the case of copper(II) ions, has been attributed to a change in crystalline character of the ligand. The protolytic reactions have been studied using the Katchalsky-Spitnik equation. The pH profiles have been shown for Co(II)-MCCh and Zn(II)-MCCh systems and the corresponding equilibrium constants have been determined as well. Both the amino and hydroxyl groups are involved in Co2+ complexation, whereas for Zn2+, the complexes are formed only via amino nitrogen. (C) 1995 John Wiley and Sons, Inc.