Effect of pH on cadmium and lead binding by extracellular polymeric substances (EPS) extracted from environmental bacterial strains

Cd and Pb binding by extracellular polymeric substances (EPS) extracted from seven environmental bacterial strains were investigated as a function of pH. The study was carried out by using a polarographic method in the stripping mercury dropping electrode (SMDE) mode which is able to determine labil...

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Bibliographic Details
Published in:Colloids and surfaces, B, Biointerfaces B, Biointerfaces, 2008-05, Vol.63 (1), p.48-54
Main Authors: Guibaud, Gilles, Bordas, François, Saaid, Asmaa, D’abzac, Paul, Van Hullebusch, Eric
Format: Article
Language:English
Subjects:
Algorithms
Analytical chemistry
Bacteria
Bacteria - chemistry
Cadmium - chemistry
Catalase - chemistry
Chemical and Process Engineering
Chemical Sciences
Engineering Sciences
Environmental Pollutants - chemistry
Environmental Sciences
Extracellular polymeric substances
Hydrogen-Ion Concentration
Inorganic chemistry
Lead - chemistry
Linear Models
Oxidoreductases - chemistry
Polymers - chemistry
Sewage - microbiology
Sorption
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Summary:Cd and Pb binding by extracellular polymeric substances (EPS) extracted from seven environmental bacterial strains were investigated as a function of pH. The study was carried out by using a polarographic method in the stripping mercury dropping electrode (SMDE) mode which is able to determine labile metal in solution containing soluble ligands such as EPS. The results obtained provide evidence for the presence of a pH-sorption/desorption edge for Cd and Pb by EPS. Kurbatov's model gives information on the mechanisms involved through the determination of “relative complexation constants” (operationally defined) and the number of exchanged protons. This model shows that proton exchange with metals is not the only mechanism involved in metal biosorption by bacterial EPS. The position of the pH-sorption edge curves and the “relative complexation constants” show that Pb displays a greater affinity for EPS than Cd. For a given metal, the seven EPS investigated did not display differences regarding the binding strength. This work suggests that a wide range of products of bacterial species isolated from activated sludge exhibit similar binding behaviours for Cd or Pb, which may potentially simplify the modelling of the distribution and the speciation of metals in bacteria-bearing natural systems.
ISSN:0927-7765
1873-4367
DOI:10.1016/j.colsurfb.2007.11.002