Speciation of Pb(II) Sorbed by Burkholderia Cepacia/Goethite Composites

Journal Article · Tue Apr 08 04:00:00 EDT 2003 · Environmental Science and Technology

DOI:https://doi.org/10.1021/es026081b· OSTI ID:15003996

Templeton, Alexis S; Spormann, Alfred M; Brown, Gordon E

Bacterial-mineral composites are important in the retention of heavy metals such as Pb due to their large sorption capacity under a wide range of environmental conditions. However, the partitioning of heavy metals between components in such composites is not probed directly. Using Burkholderia cepacia biofilms coated with goethite (α-FeOOH) particles, the partitioning of Pb(II) between the biological and iron-(oxyhydr)oxide surfaces has been measured using an X-ray spectroscopic approach. EXAFS spectra were fit to quantitatively determine the fraction of Pb(II) associated with each component as a function of pH and [Pb]. At pH <5.5, at least 50% of the total sorbed Pb(II) is associated with the biofilm component, whereas the total uptake within the composite is dominated by goethite (>70% Pb/goethite) above pH 6. Direct comparison can be made between the amount of Pb(II) bound to each component in the composite vs separate binary systems (i.e., Pb/biofilm or Pb/goethite). At high pH, Pb(II) uptake on the biofilm is dramatically decreased due to competition with the goethite surface. In contrast, Pb uptake on goethite is significantly enhanced at low pH (2-fold increase at pH 5) compared to systems with no complexing ligands. The mode of Pb(II)-binding to the goethite component changes from low to high [Pb]. Structural fitting of the EXAFS spectra collected from 10^-5.6 to 10^-3.6 M [Pb]_eq at pH 6 shows that the Pb-goethite surface complexes at low [Pb] are dominated by inner-sphere bidentate, binuclear complexes bridging two adjacent singly coordinated surface oxygens, giving rise to Pb-Fe distances of ~3.9Å. At high [Pb], the dominant Pb(II) inner-sphere complexes on the goethite surface shift to bidentate edge-sharing complexes with Pb-Fe distances of ~3.3Å.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 15003996
• Journal Information: Environmental Science and Technology, Journal Name: Environmental Science and Technology Journal Issue: 10 Vol. 37; ISSN ESTHAG; ISSN 0013-936X
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
BACTERIA
COMPOSITE MATERIALS
Environmental Molecular Sciences Laboratory
GOETHITE
LEAD
PH VALUE
SORPTION
SORPTIVE PROPERTIES
UPTAKE