Biosorption of Cadmium, Chromium, Lead, and Zinc by Biomass of Medicago sativa

that the African shoots population had an excellent ability to bind copper(II) and nickel(II) ions from aqueous solution. Batch laboratory pH profile, time dependency, and capacity experiments were performed to determine the binding ability of the African shoots to cadmium(II), chromium(III), chromium(VI), lead(II), and zinc(II). Batch pH profile experiments for the mentioned ions indicated that the optimum pH for metal binding is approximately 5.0. Time dependency experiments for the metal ions showed that for all the metals studied, binding to the African alfalfa shoots occurred within five minutes. Binding capacity experiments revealed the following amounts of metal ions bound per gram of biomass: 7.1 mg Cd, 7.7 mg Cr(III), 43 mg Pb(II), and 4.9 mg Zn(II). However, no binding occurred for chromium(VI). Nearly all of the metals studied were recovered by treatment with 0.1M HCl, with the exception of chromium(III). Column experiments were performed to stud