Abstract
Conventional methods of heavy metal removal from water such as chemical precipitation and filtration, oxidation and reduction, electrochemical treatment, reverse osmosis, ion exchange or distillation are economically non-viable, because they involve the use of sophisticated equipment and high cost of plant maintenance. This necessitated the search for cheap and promising methods of water treatment. Moringa oleifera seeds have been reported to have biosorption properties, however, the efficiency and mechanism of biosorption has not been fully established. In this study, Fourier transform infrared (FT-IR) spectroscopy, batch adsorption and batch kinetics studies were conducted, to determine the functional groups, biosorption performance and probable biosorption mechanism of M. oleifera seeds powder. FT-IR analysis revealed the complex nature of the seed with carbonyl group (C=O), amine group (C-NH), hydroxyl group (OH) and stretching of C-H bond of CH2 groups present. Regression analysis revealed that Pb(II) and Cd(II) adsorption fits better to Freundlich isotherm model than Langmuir model. The theoretical maximum adsorption capacity () and adsorption intensity (b) were higher for Cd(II) when compared to Pb(II). The adsorption of Cd(II) fits the intraparticle diffusion model. The constant depicting boundary layer effect (C), indicated that Cd(II) and Pb(II) adsorption occur via a multilayer adsorption mechanism and mass transfer was not the only rate limiting step in the biosorption process. This finding suggest that M. oleifera seeds has higher biosorption activity for Cd(II) than Pb(II), and that the adsorption occurs via physical process rather than chemical process.
