Cd(II) and Pb(II) sorption by extracellular polymeric substances (EPS) extracted from anaerobic granular biofilms: Evidence of a pH sorption-edge

This work investigates the ability of EPS extracted by cationic exchange resin (CER) from 3 different anaerobic granular sludges to bind Pb or Cd as a function of pH. EPS display a better binding ability for Pb than Cd as it has been often shown in literature. The experimental sorption data show the presence of a pH sorption edge. The experimental data are well fitted by the Kurbatov model. Nevertheless, the molar ratio of proton exchanged with metal ions underlines that other mechanisms are also involved in metal ion sorption by EPS from anaerobic granular sludges. Moreover, the mineral fraction present in extracted EPS and trapped by the organic fraction or under particle form seems to be involved in the metal ions sorption process.

► EPS from anaerobic granular sludges display, a better ability to bind Pb than Cd.
► The ability of EPS to bind Cd or Pb increases with the increase of the pH.
► The experimental sorption data show the presence of a pH sorption edge.
► Other mechanisms that proton exchange are involved in Cd or Pb sorption by EPS.
► The role of mineral fraction of the EPS in Cd or Pb sorption is assumed.