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Macroscopic and spectroscopic analysis of lanthanide adsorption to bacterial cells

DOI: 10.1016/j.gca.2009.03.018 DOI Help

Authors: Bryne T. Ngwenya (University of Glasgow) , Marisa Magennis (University of Edinburgh) , Janette Tourney (University of Edinburgh) , Valerie Olive (Scottish Universities Environmental Research Centre) , Robert M. Ellam (Scottish Universities Environmental Research Centre) , Kirk Atkinson (Diamond Light Source) , J. Fred W. Mosselmans (Diamond Light Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Geochimica Et Cosmochimica Acta , VOL 73 (11) , PAGES 3134-3147

State: Published (Approved)
Published: January 2009

Abstract: This study was designed to combine surface complexation modelling of macroscopic adsorption data with X-ray Absorption Spectroscopic (XAS) measurements to identify lanthanide sorption sites on the bacterial surface. The adsorption of selected representatives for light (La and Nd), middle (Sm and Gd) and heavy (Er and Yb) lanthanides was measured as a function of pH, and biomass samples exposed to 4 mg/L lanthanide at pH 3.5 and 6 were analysed using XAS. Surface complexation modelling was consistent with the light lanthanides adsorbing to phosphate sites, whereas the adsorption of middle and heavy lanthanides could be modelled equally well by carboxyl and phosphate sites. The existence of such mixed mode coordination was confirmed by Extended X-ray Absorption Fine Structure (EXAFS) analysis, which was also consistent with adsorption to phosphate sites at low pH, with secondary involvement of carboxyl sites at high adsorption density (high pH). Thus, the two approaches yield broadly consistent information with regard to surface site identity and lanthanide coordination environment. Furthermore, spectroscopic analysis suggests that coordination to phosphate sites is monodentate at the metal/biomass ratios used. Based oil the best-fitting pK(a) site, we infer that the phosphate sites are located on N-acetylglucosamine phosphate, the most likely polymer on gram-negative cells with potential phosphate sites that deprotonate around neutral pH.

Subject Areas: Environment

Technical Areas: