Adsorption of Methylene Blue by Sludges and the Roles of Extracellular Polymeric Substances

Abstract:

A comparative study is made of the adsorption of a dye,Methylene Blue,by activated sludge and anaerobic sludge.The roles of extracellular polymeric substances (EPS) including the soluble EPS (SEPS) and bound EPS (BEPS) for the biosorption of activated sludge and anaerobic sludge were further determined.Results show that Longmuir model for the Methylene Blue adsorption is fitter to EPS,SEPS and BEPS from activated sludge as well as EPS and BEPS from anaerobic sludge.Freundlich model is fitter to SEPS from anaerobic sludge.The amount of the adsorbed Methylene Blue by unit mass SEPS is more than the corresponding values of BEPS,with an average of 14.1 times for activated sludge and 5.8 times for anaerobic sludge.However,the amount of the adsorbed Methylene Blue by EPS is mostly contributed by BEPS due to much greater amount of BEPS than corresponding amount of SEPS for both sludges.