Journal
JOURNAL OF ENVIRONMENTAL SCIENCES
Volume 25, Issue 5, Pages 916-924Publisher
SCIENCE PRESS
DOI: 10.1016/S1001-0742(12)60210-1
Keywords
extracellular polymeric substances; activated sludge; aluminum ion; three-dimensional excitation emission matrix; fluorescence quenching; Fourier transform infrared spectroscopy
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Funding
- National Natural Science Foundation of China [51138009, 50921064]
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Aluminum flocculant can enhance the flocculating performance of activated sludge. However, the binding mechanism of aluminum ion (Al3+) and extracellular polymeric substances (EPS) in activated sludge is unclear due to the complexity of EPS. In this work, three-dimensional excitation emission matrix fluorescence spectroscopy (3DEEM), fluorescence quenching titration and Fourier transform infrared spectroscopy (FT-IR) were used to explore the binding behavior and mechanism between Al3+ and EPS. The results showed that two fluorescence peaks of tyrosine- and tryptophan-like substances were identified in the loosely bound-extracellular polymeric substances (LB-EPS), and three peaks of tyrosine-, tryptophan- and humic-like substances were identified in the tightly bound-extracellular polymeric substances (TB-EPS). It was found that these fluorescence peaks could be quenched with Al3+ at the dosage of 3.0 mg/L, which demonstrated that strong interactions took place between the EPS and Al3+. The conditional stability constants for Al3+ and EPS were determined by the Stern-Volmer equation. As to the binding mechanism, the -OH, N-H, C=O, C-N groups and the sulfur- and phosphorus-containing groups showed complexation action, although the groups in the LB-EPS and TB-EPS showed different behavior. The TB-EPS have stronger binding ability to Al3+ than the LB-EPS, and TB-EPS play an important role in the interaction with Al3+.
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