Lead Complexation of Soluble and Bound Extracellular Polymeric Substances from Activated Sludge: Characterized with Fluorescence Spectroscopy and Ftir Spectroscopy

ABSTRACT

Extracellular polymeric substances (EPS) are important components of activated sludge and play an important role in removing heavy metals. The interaction of soluble EPS (SEPS)/bound EPS (BEPS) with Pb(II) was investigated using excitation—emission matrix (EEM) fluorescence spectroscopy and infra-red spectrometry. One protein-like fluorescence peak (peak A) was identified from the EEM spectra of SEPS and BEPS, and one aromatic protein peak (peak B) was observed in the EEM spectra of SEPS. the interaction of Pb(II) with SEPS was governed by collision sorption, while the binding of Pb(II) to BEPS was due to complexation. Functional groups of proteins, polysaccharides, lipids, and uronic acid were involved in Pb(II) adsorption to SEPS/BEPS. The organic acids in SEPS are also responsible for binding Pb(II) to SEPS. Other groups such as the phosphate group in the fingerprint zone also participated in binding of Pb(II) to EPS. There were no significant differences in the values of binding constants and conditional stability constants between SEPS and BEPS.

Keywords:

• biosorption
• binding
• fluorescence quenching
• binding constant
• conditional stability constant