Spectroscopic Comparison of Eu(III) Binding to Various Biosorbents

Abstract

Biosorption of Eu(III) to various biogenic materials was investigated using luminescence spectroscopy involving excitation of non-degenerate ⁷F₀ → ⁵D₀ transition of bound metal ions. Materials included cultured anther cell fragments from Datura innoxia, pecan shells (Protandrous spp.), dried bean sprouts (vigna spp.), and dried tissues from the roots, stems, and leaves of mature tumbleweeds (Salsola spp.), non-viable algae cells of Chlorella vulgaris immobilized within a polysilicate matrix, sphagnum peat, dried peat, and a commercially available organic peat material. Analysis of resulting excitation spectra indicated only minimal variation in binding environments for the different tumbleweed tissues when respective spectra were visually compared. Observed red-shifts in excitation spectral envelopes suggest an increased stabilization of surface ligand-metal associations for all materials compared to D. innoixia. Application of principal component analysis to these spectra resulted in segregation of materials using a model accounting for 89.48% of the variance using three principal components. This analysis revealed similarities among the spectra from the roots and stems of the tumbleweeds along with that from the bean sprout sample. The model confirmed differences in metal binding to the D. innoxia materials. It also indicated significant differences in metal ion binding to the organic peat and Chlorella-based biosorbents.

Keywords:

• biosorbents
• biosorption
• Europium III luminescence
• principal component analysis

ACKNOWLEDGEMENTS

The authors gratefully acknowledge the financial support of the National Institutes of Health RISE program for the support of DDS as a pre-doctoral fellow. Similarly, the support of the National Science Foundation Alliance for Graduate Education and the Professorate program is acknowledged.