| Summary: | A typical lignocellulosic agricultural residue, namely tobaccodust, was investigated for its heavymetal binding efficiency. The tobaccodust exhibited a strong capacity for heavymetals, such as Pb(II), Cu(II), Cd(II), Zn(II) and Ni(II), with respective equilibrium loadings of 39.6, 36.0, 29.6, 25.1 and 24.5 mg of metal per g of sorbent. Moreover, the heavymetals loaded onto the biosorbent could be released easily with a dilute HCl solution. Zeta potential and surface acidity measurements showed that the tobaccodust was negatively charged over a wide pH range (pH > 2), with a strong surface acidity and a high OH- adsorption capacity. Changes in the surface morphology of the tobaccodust as visualized by atomic force microscopy suggested that the sorption of heavymetal ions on the tobacco could be associated with changes in the surface properties of the dust particles. These surface changes appeared to have resulted from a loss of some of the structures on the surface of the particles, owing to leaching in the acid metal ion solution. However, Fourier transform infrared spectroscopy (FTIR) showed no substantial change in the chemical structure of the tobaccodust subjected to biosorption. The heavymetal uptake by the tobaccodust may be interpreted as metal–H ion exchange or metal ion surface complexation adsorption or both.
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