Theoretical and Experimental Study of M+2 adsorption on biopolymers III Comparative Kinetic PAttern of Pb, Hg and Cd

A. L. DEBAUUDT; M. L. FERREIRA; M. E. GSCHAIDER

CARBOHYDRATE POLYMERS

Año: 2004 vol. 56 p. 321 - 332

0144-8617

Chitosan, pectin and chitosan-pectin pellets were studied as adsorbents for Cd+2 from acidic aqueous solutions at selected conditions. Several adsorption sites were considered and adsorption mechanisms for the biopolymers-metal interactions are proposed taking into account theoretical and experimental results. Langmuir adsorption isotherms for Hg, Pb and Cd on pellets gave KL values of 796, 1551 and 7265 LmEq-1; their Me max (mEq/g) being 0.027 (2.71 mg/g), 0.1075 (11.2 mg/g) and 0.022 (1.23 mg/g) respectively. Chitosan adsorption of Hg achieved 85-100 % and 70-75 % for Pb and Cd. Ci (initial concentration) was 47045.4 m g /g chitosan for Pb, 6863.6 m g/g chitosan for Hg and 5.4436 m g /g chitosan for Cd. When pectin was the adsorbent 15 % of Hg and not more than 4 % Pb and Cd were adsorbed, Ci Pb being 9409.1 m g /g pectin Ci Hg=1372.7 m g /gpectin and CiCd=1064.5 m g/g pectin. In the case of pellets 100 % initial Hg, Cd and Pb present initially in solution were adsorbed, Ci Pb being =103.5 mg/g, Ci Hg=15 mg/g and CiCd=12 mg/g. Molecular Mechanics (MM2) and PM3 calculations were done, trying to identify evidence of the proposed kinetic model and an explanation of the equilibrium uptake of the metal adsorption on chitosan-pectin pellets.