Affinity distributions of lead ion binding to an immobilized biomaterial derived from cultured cells of Datura innoxia

Datura innoxia biomass has been targeted as a potential sorbent for heavy metal remediation. Of interest in our laboratory are the binding mechanisms responsible for metal uptake. In this study, the binding behavior of Pb(II) to immobilized Datura innoxia biomaterial was investigated under different chemical conditions, such as ionic strength, the presence of calcium, and pH. Regularized regression analysis was employed to derive the corresponding affinity distributions. Two classes of binding sites were determined, having mean affinity of approximately 200 and 10(5) M-1, depending on solution conditions. Variations in apparent affinity distributions with ionic strength and pH suggest the low-affinity sites involve sulfonates and carboxylates in an ion exchange process. The high-affinity sites are proposed to result from the coordination of carboxylates to Pb2+ ions. (C) 2002 Elsevier Science Ltd. All rights reserved.