The Biosorption of Pb(II) from Solution by Elephant Grass (Pennisetum purpureum): Kinetic, Equilibrium, and Thermodynamic Studies.

The biosorption of Pb(II) from dilute aqueous solution using elephant grass as the biosorbent has been studied. The biosorption study was carried out as a function of pH, contact time, initial metal ion concentration, and temperature. The residual Pb(II) in solution were determined using atomic absorption spectrophotometer (AAS). The FT-IR analysis of elephant grass biomass revealed the presence of bonded OH, -NH stretching, C-H stretching, and C=O stretching of COOH. The study on pH showed that the biosorption was pH dependent as maximum biosorption of Pb(II) was obtained in the range pH 3-5. The biosorption was also time dependent as maximum biosorption was obtained within 30 min of the process. Kinetic studies show that the biosorption of Pb(II) can be described by pseudo- second-order kinetic model. For the metal ions, the biosorption efficiency increased with increase in initial metal ion concentration. The free energy change obtained for the biosorption of Pb(II) at 303K with an initial Pb(II) concentration of 100 mgL -1 was -11.887 kJmol -1 . The entropy change for the biosorption of Pb(II) was 104.84 Jmol -1 K -1