Quantification of the interactions between Ca,Hg and extracellular polymeric substances (EPS) of sludge |
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Authors: | Guo-Ping Sheng Juan XuWei-Hua Li Han-Qing Yu |
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Affiliation: | Department of Chemistry, University of Science and Technology of China, Hefei 230026, China |
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Abstract: | The interactions between metals (Ca2+ and Hg2+) and extracellular polymeric substances (EPS) extracted from the aerobic and anaerobic sludge in wastewater treatment reactors were investigated using a combination of zeta potential measurement and 3-dimensional excitation–emission matrix (EEM) fluorescence spectroscopy with parallel factor (PARAFAC) analysis. Results show that Ca2+ had no substantial effects on the EEM fluorescence spectra of the EPS, but their zeta potentials increased with the increasing Ca2+ dosage. However, Hg2+ had a significant effect on the EEM fluorescence spectra of the EPS, while their zeta potentials seemed not to be affected by the dose of Hg2+. The interactions between Hg2+ and EPS were elucidated using the fluorescence quenching with PARAFAC analysis, while the interactions between Ca2+ and EPS were evaluated by the zeta potential technique. The binding constants for Hg2+ and EPS were two orders of magnitude higher than those for Ca2+ and EPS, suggesting that the binding mechanisms between Ca2+ and EPS were different from those between Hg2+ and EPS. The results might be useful for understanding the roles of EPS in bacterial self-protection against heavy metals and the aggregate formation mechanisms through ionic bridging interactions. |
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Keywords: | Excitation&ndash emission matrix (EEM) Extracellular polymeric substances (EPS) Metal binding Parallel factor analysis (PARAFAC) Sludge Zeta potential |
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