Biosorption properties of hexavalent chromium on to biomass of tobacco-leaf residues
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Equilibrium isotherms of Cr(VI) uptake by tobacco-leaf residues, under controlled solution pH and temperature, were obtained with batch uptake experiments. Batch uptake kinetics under different initial Cr(VI) concentrations was also obtained. The results showed that Cr(VI) uptake capacities of the tobacco-leaf residues were up to 113.2 mg g -1(dry wt). The uptake capacity was found to be dependent on solution pH and the maximum values were obtained at a pH of around 1.0. On the other hand, the effect of temperature the uptake capacity was found to be small. All equilibrium isotherms were well correlated with the standard Langmuir equation. Kinetics profiles showed that the uptake process was fast, and equilibrium was reached within 30 minutes of mixing contact. The role of polyphenols in Cr(VI) biosorption was studied and the results indicated that complex formation with Cr(VI) may be an important mechanism for Cr(VI) removal. The study indicated that abundantly available tobacco-leaf residues can be used as efficient biosorbent materials for Cr(VI) removal from wastewater.