Zn(Ⅱ) Ion Biosorption onto Surface of Eucalyptus Leaf Biomass: Isotherm, Kinetic, and Mechanistic Modeling

摘要

Bioremediation of Zn(Ⅱ) by biosorption across aqueous phase on to surface of eucalyptus leaf powder has been investigated in present research work. The adsorptive potential of eucalyptus leaf powder was evaluated as function of pH, temperature, contact time, agitation rate and particle size. Maximum metal ion uptake and percentage removal capacity of eucalyptus leaf powder were 23.5 mg g~(-1) and 94%, respectively, at optimized pH 5, 20 ± 1℃, contact time 6 h, particle size 0.5 mm and agitation rate 200 rpm. The biomass surface analysis revealed the fact that the biomass surface was heterogeneous and porous in nature. The functional groups like amine, amide, carboxyl, hydroxyl, and methyl groups, significantly important for metal ion binding were present on biomass surface in tremendous amount. Additionally, the Fourier transformation IR spectrum analysis of acid and base activated eucalyptus leaf biomass ruled out all the possibilities of the presence of surface functional groups mentioned above. The reaction rate was studied by applying two rate limiting models pseudo first and pseudo second order. Pseudo second order model was found to be more suitable (R~2 = 0.998) in comparison to pseudo first order (R~2 = 0.724). Adsorption equilibrium of batch stirred reaction data fitting shows the dominance of Langmuir isotherm (R~2 = 0.99) against Freundlich isotherm (R~2 = 0.887) model with equipartitional involvement of both film and intra particle diffusion as rate limiting steps at differential status of contact time.