Study on adsorption of heavy metals onto sludge extracellular polymers substances (EPS): A review

Abstract:

Less attention devoting to the disposal of sewage sludge in China in the past decades led to unproper treatment of huge quantity of sewage sludge, which caused serious environmental problems. Since tremendous distribution of the enriched heavy metals in sewage sludge restricted its final land disposal, thus how those heavy metals are adsorbed onto the sludge has been highly concerned. Extracellular polymeric substances (EPS), mainly composed of protein, humic acid, polysaccharides, etc., is the main components of sludge organics. EPS traditionally exhibites a porous polymeric structure, and those polarity heavy metals can be easily adsorbed onto the adsorption sites (such as carboxyl and hydroxyl groups) which existes on the surface of EPS. Overall, the physicochemical structural characteristics of EPS significantly affects the adsorbing processes of heavy metals. In this study, we firstly gave a brief introduction to the current status of sludge treatment and disposal in China. Then, effect of the compositions and structures of sludge EPS on heavy metals adsorption was analyzed and the potential adsorption sites were summarized. Moreover, the analyzing approaches for studying the heavy metals adsorption processes were comparably evaluated. Finally, suggestions on the future research was raised pertinently.