Effects of competing cations on cadmium biosorption by chitin

In natural aqueous systems several metallic ions will be present, and a selective uptake of these ions by chitin surface groups can be expected. In order to investigate this phenomenon, the effect of co-ions Cu2+ and Zn2+ on the cadmium biosorption kinetic and equilibrium on chitin was examined, at free solution pH and 25 degreesC, in static conditions. All experimental cadmium biosorption rate curves exhibited common characteristics. The apparent equilibrium biosorption was reached within the 6 h of contact. All determined biosorption isotherms exhibited a similar shape resembling that of Langmuir type isotherm of gas adsorption. The biosorption of individual metals followed the sequence Cu > Cd > Zn. While, Zn2+ ions had any appreciate effect on the cadmium uptake capacity of chitin under the conditions examined, the presence of Cu2+ ions alter the affinity of chitin for cadmium: the uptake of Cd decreased. (C) 2002 Elsevier Science B.V. All rights reserved.