Kinetic, equilibrium and thermodynamic studies of the biosorption of Pb(II), Cd(II) and Cr(III) by neem leaf

Abstract

The biosorption of Pb(II), Cd(II) and Cr(III) by Neem (Azadirachta indica) 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 at pH 4. The kinetic study shows that the
biosorption of the metal ions followed both pseudo-second-order and Elovich kinetic
models. The sorption was analysed with Freundlich and Langmuir isotherm models and in
each case the Freundlich model appears to have better regression coefficients than the
Langmuir. Thermodynamically, the biosorption of Pb(II) and Cr(III) were found to be
endothermic while that of Cd(II) was exothermic. Similarly positive change in entropy was
observed for each of Pb(II) and Cr(III) while negative change in entropy was observed for
Cd(II).