P22

UPTAKE OF TOXIC HEAVY METAL IONS BY INACTIVATED CELLS OF LARREA TRIDENTATA (CREOSOTE BUSH)

Experiments were performed to determine the ability of creosote biomass (grown in heavy metal-uncontaminated soils) to adsorb Pb(II), Cd(II), and Ni(II) ions from aqueous solutions. Batch pH profile experiments for the indicated metal ions showed that the metal ion binding was different for every metal tested but increased as the pH was raised as high as 6.0. The metal binding as a function of pH also varied for the creosote's roots, stems, and leaves.

Experiments designed to determine how fast the metal ion adsorption process occurs, showed that the metal uptake is quite rapid. This suggests a metal surface binding mechanism. Binding capacity experiments showed the following amounts of metal ions bound per gram of creosote biomass: roots, 53.5 Pb(II), 20.1 Cd(II), 11.0 Ni(II); stems, 52.2 Pb(II),18.0 Cd(II), 9.1 Ni(II); and leaves, 58.2 Pb(II), 20.8 Cd(II), 11.4 Ni(II). A more significant binding capacity for lead ions was observed.

A great portion of the adsorbed lead, cadmium, and nickel by the creosote's roots, stems, and leaves was desorbed by treatment with 0.1 M HCl (up to 99% in some cases). Results of Cr(III), Zn(II), and Cr(VI) binding to creosote biomass will also be presented. Biomass of creosote bush may prove to be useful to remove and recover metal ions from contaminated waters by using a creosote phyto-filtration system.

Key words: Larrea tridentata, metal binding, phyto-filtration