Sorption of heavy metal ions by the nonliving biomass of freshwater macrophytes

The removal of heavy metal ions by the nonliving biomass of aquatic macrophytes was investigated. The work involved studies of physical and biochemical properties of the materials, batch sorption experiments carried out in agitation flasks, and continuous runs in a packed bed column at laboratory scale. Results showed that the dried biomass of Potamogeton lucens, Salvinia herzogii, and Eichhornia crassipes were excellent biosorbents for Cr(III), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(II). The sorption mechanism by these biomaterials was found to proceed mainly by ion exchange reactions between the metal ions and the cationic weak exchanger groups present on the plant surface. Sorption followed the Langmuir isotherm, and maximum metal uptakes values (independently of the metal ion species) were attained at about 1.5 mequiv g(-1) for P. lucens, 0.9 mequiv g(-1) for S. herzogii, and 0.7 mequiv g(-1) for E. crassipes. Advantages and disadvantages found in the use of these natural adsorbents for heavy metals ions present in industrial wastewaters are envisaged.