Table of Contents
Journal of Geochemistry
Volume 2014, Article ID 168938, 10 pages
Research Article

Lead Immobilization and Hydroxamate Ligand Promoted Chloropyromorphite Dissolution

1Department of Environmental Engineering and Geological Sciences, Fitzpatrick, University of Notre Dame, South Bend, IN 27695-7619, USA
2Department of Geology & Geophysics, University of Wyoming, Laramie, WY 82071, USA
3Biomineral Systems LLC, South Bend, IN 27695, USA

Received 2 February 2014; Revised 29 May 2014; Accepted 29 May 2014; Published 20 July 2014

Academic Editor: Andrew Hursthouse

Copyright © 2014 Nadia K. Adam. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The immobilization of lead, a major environmental contaminant, through phosphate amendments to form the sparingly soluble lead phosphate mineral chloropyromorphite [Pb5(PO4)3] (CPY) is an effective in situ strategy for soil remediation. An important question is the effect of microbial processes on this remediation. Here, we investigate the role of the microbial siderophore ligand desferrioxamine-D1 (DFO-D1) and its analog acetohydroxamic acid (aHA) in CPY lability using pH-dependent batch dissolution kinetics and model calculations. Both (0.01) M aHA and (0.00024) M DFO-D1 are similarly effective and enhance lead release from CPY by more than two orders of magnitude at pH > 6 compared to in the absence of ligands. This is consistent with model calculations of pH-dependent (aqueous) complexation of lead with hydroxamate ligands. More importantly, pH-dependent ligand sorption is predictive of its ligand promoted dissolution behavior. Our results suggest that organic ligands can significantly increase CPY lability at alkaline pHs in soils and sediments and that addition of P amendments to immobilize Pb as CPY may only be successful at acid pHs.