Phragmites australis: A novel biosorbent for the removal of heavy metals from aqueous solution

Reed (Phragmites australis), a commonly used macrophyte in the wetlands constructed for water purification, was investigated as a new biosorbent for the removal of Cu2+, Cd2+, Ni2+, Pb2+ and Zn2+ from aqueous solution. The metal adsorption capacity of reed biomass was improved significantly by water-wash, base- and acid-treatment. The maximum sorption of NaOH-pretreated reed biomass was observed near neutral pH for Cu2+, Cd2+, Ni2+ and Zn2+, while that for Pb2+ was from an acidic range of pH 4.0 or higher. The maximum metal adsorption capacity on a molar basis assumed by Langmuir model was in the order of Cu2+>Ni2+>Cd2+>Zn2+>Pb2+. Reed biosorbent showed a very high adsorption affinity value, which helps predict its high ability to adsorb heavy metals at low concentration. Desorption of heavy metals and regeneration of the biosorbent was attained simultaneously by acid elution. Even after three cycles of adsorption-elution, the adsorption capacity was regained completely and the desorption efficiency of metal was maintained at around 90%.