Kinetic and equilibrium studies on the biosorption of Cd (II), Pb (II) and Zn (II) from aqueous solutions using banana (Musa acuminate) leaf

The biosorption of Cd(II), Pb(II)and Zn(II) by banana (Musa acuminata) leaf is reported in this work. The effects of solution pH, contact time, initial metal ion concentration and temperature on the biosorption of the metal ions were investigated. Optimum pH for each metal ion was obtained as the biosorption of each of the metal ions was found to be pH-dependent. Kinetic study shows that the pseudo-second-order kinetic model best represents the biosorption of the metal ions. The sorption of each metal ion was analysed with Freundlich and Langmuir isotherm models, in each case, the Freundlich model appears to have better regression coefficients than the Langmuir model. The study on the effect of dosage shows that the dosage of the biomass significantly affects the uptake of the metal ions from solution. Thermodynamically, the biosorption of each of the metal ions is endothermic and the order of spontaneity of the biosorption process being Cd(II)>Pb(II)>Zn(II). Similarly, positive change in entropy was observed for each and the order of disorder is Cd(II)>Pb(II)>Zn(II).