Chemical modification and X-ray absorption studies for lead(II) binding by Medicago sativa (alfalfa) biomass

Abstract

Traditional methods currently employed to remediate heavy metal contaminated waters prove to be cost prohibitive. Therefore, more cost-effective methods of remediating heavy metals from contaminated waters need to be developed. The use of plant materials as metal adsorbents may be a possible solution. Previously performed experiments have shown that alfalfa shoot biomass can bind an appreciable amount of heavy metal ions, even from multi-contaminate containing solutions. Although the alfalfa biomass has shown to be very effective at removing heavy metal ions from aqueous solution, more research is needed to understand the metal binding mechanism. Carboxyl groups were chemically modified in order to determine their contribution to the metal binding process. Batch experiments were performed with the modified biomass and suggest that carboxyl groups play a significant role in the binding of lead(II). In addition, X-ray absorption spectroscopic analysis (XANES and EXAFS) corroborate these results. These studies are important for determining the ligands that may be involved in the binding of lead ions to alfalfa biomass, thus aiding in our understanding of the mechanisms involved in the removal and recovery of metal ions from contaminated waters through phytofiltration.