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Department of Civil Engineering & Geological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
* E-mail address of corresponding author: pmaurice{at}nd.edu
Siderophores are low molecular weight organic ligands synthesized by aerobic microorganisms to acquire Fe. In addition to Fe(III), siderophores may complex other metals such as Pb and Cd. This study compared the effects of the trihydroxamate siderophores desferrioxamine-B (DFO-B), desferrioxamine-D1 (DFO-D1), desferrioxamine-E (DFO-E), and the monohydroxamate siderophore-like ligand acetohydroxamic acid (aHA) on Pb and Cd (except for DFO-E) adsorption to kaolinite (KGa-1b) at pH 4.5 to 9, in 0.1 M NaClO4, at 22°C, in the dark. At pH >6, all of the studied ligands decreased Pb adsorption to kaolinite: aHA by 540% and DFO-B, DFO-D1 and DFO-E by 3075%; the greater effects were at higher pH. The studied ligands decreased Cd adsorption to kaolinite at pH >8: aHA by 520% and the trihydroxamates by as much as 80%. We also observed enhancement of Pb adsorption in the presence of DFO-B at pH ~56.0, probably due to adsorption of the doubly positively charged H3Pb (DFO-B)2+complex, although spectroscopic evidence is needed.
Key Words: Adsorption Cadmium Kaolinite Lead Ligand Siderophore
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