Pb0 Flue Gas Biosorption in Denitrifying Mbfr: Characteristics and Binding Ability of Extracellular Polymeric Substances

Pb0 in flue gas which is ubiquitous in the environment, poses a certain threat to human and ecology, but the study on EPS-dependent stabilization of lead to remove Pb0 from flue gas remains insufficient. In this investigation, the characteristics and heavy metals-binding ability of four EPS fractions were evaluated. The EPS were extracted from denitrifying membrane biofilm reactor (MBfR) and divided into slime EPS (S-EPS), loosely-bound EPS (LB-EPS), tightly-bound EPS (TB-EPS) and EPS in circulating flow (Y-EPS). The S, LB, TB-EPS related to Pb stabilization on biofilm need more attention. Compared to Pb-S-EPS (0.013 mg g−1) and Pb-LB-EPS (0.13 mg g−1), the Pb-TB-EPS (0.26 mg g−1) was mainly stable form of vapor Pb0, since TB-EPS's higher content (30.67–82.44 mg g−1 VSS), proteins (13.47–36.32 mg g−1 VSS) and polysaccharides (9.37–32.48 mg g−1 VSS) concentration. Particularly, proteins related ligands were more effective in S, LB, TB-EPS dependent adsorption of Pb, complexing with hydrophobic acid ligands further strengthened in TB-EPS adsorption. The Pb-EPS complex formed via binding with functional groups (such as O–H, N–H, C–H and CC) on EPS, also facilitated by loose structure of proteins. This study enlightens the researchers on the bio-treatment and EPS-dependent biosorption of Pb0 in flue gas in denitrifying MBfR.