Removal of Toxic Metals from Water using Cabbage, Carrots and Lettuce as Biofilters

The existing technologies for removing toxic metals from the environment are very expensive and impractical for use in developing countries. In the present study we investigated the use of Lettuce (Lactuca sativa), Cabbage (Brassica oleracea var. capitata) and Carrots (Daucus carota subsp. Sativus) as biosorbents for removing Copper (Cu), Lead (Pb), and Zinc metal ions from polluted water via biofiltration. The filtrates were analysed via Atomic Absorption Spectroscopy (AAS) in order to quantitate any remaining, unremoved metals. All three biosorbents showed considerable abilities to remove the above metals, with about 95% removal efficiency in the case of zinc (Zn2+). In order to understand the chemistry of the adsorption processes, the biosorbent materials, after biofiltration, were analysed via FT-IR spectroscopy, which revealed that all three biosorbents contained compounds with phenol, ether, alkanol, carbonyl and alkanoic acid groups that were involved in the formation of surface complexes during the adsorption of the metal ions. To investigate the effect of this biofiltration process on the overall quality of water, the physicochemical parameters (pH, conductivity, colour, turbidity, TDS and TSS) were also measured on river water samples that have been pre-treated with the biosorbents. There was general improvement in the water quality although the biofilters appeared to have introduced some mineral ions, which increased the conductivity and TDS of the water.