Competitive adsorption of heavy metal by extracellular polymeric substances (EPS) extracted from sulfate reducing bacteria

Competitive adsorption of heavy metals by extracellular polymeric substances (EPS) extracted from Desulfovibrio desulfuricans was investigated. Chemical analysis showed that different EPS compositions had different capacities for the adsorption of heavy metals which was investigated using Cu2+ and Zn2+. Batch adsorption tests indicated that EPS had a higher combined ability with Zn2+ than Cu2+. This was confirmed and explained by Fourier transform infrared (FTIR) and excitation–emission matrix (EEM) spectroscopy analysis. FTIR analysis showed that both polysaccharides and protein combined with Zn2+ while only protein combined with Cu2+. EEM spectra further revealed that tryptophan-like substances were the main compositions reacted with the heavy metals. Moreover, Zn2+ had a higher fluorescence quenching ability than Cu2+.