Pb flue gas biosorption in denitrifying MBfR: Characteristics and binding ability of extracellular polymeric substances.

Pb 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 Pb 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) and Pb-LB-EPS (0.13 mg g), the Pb-TB-EPS (0.26 mg g) was mainly stable form of vapor Pb, since TB-EPS's higher content (30.67-82.44 mg g VSS), proteins (13.47-36.32 mg g VSS) and polysaccharides (9.37-32.48 mg g 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 Pb in flue gas in denitrifying MBfR.