Biosorption of Few Heavy Metal Ions Using Agricultural Wastes

Since a few years a lot of interest has been shown in monitoring environmental pollution caused by heavy metals. Many methods such as precipitation, electroplating, evaporation, ion exchange etc. have been employed in the treatment of waste water, but have not proven to be much advantageous due to greater sludge production, higher reagent requirement etc. Biosorption which can be defined as the selective sequestering of metal soluble species, resulting in the immobilization of the metals is a striking technology for retaining heavy metals from dilute solutions with high efficiency. Several prior studies and research in environmental biotechnology have shown that many biosorbents occurring in the environment have the capacity to remove heavy metals from solutions. This paper presents the potential and result of studies carried out on economically cheaper natural materials like agricultural wastes such as peanut shells and banana peels as biological adsorbent for the removal of toxic heavy metal ions from waste water. The different metal ions studied were lead, copper, zinc and cadmium. The biosorption of the above metals was studied by various techniques such as Atomic Absorption Spectrophotometry, X-ray Difftaction and Scanning Electron Microscopy. Using peanut shells, adsorption of metal ions shown was in the order of lead > zinc > copper > cadmium, whereas using banana peels adsorption was in the order of cadmium > copper > lead > zinc. X-ray Difftaction results showed the presence of zinc, copper, mercury whereas the images obtained from Scanning Electron Microscope showed metal adsorption on the surface clearly at a magnification power of 500 µm and 200 µm.