A kinetic, equilibrium, and thermodynamic study on the biosorption of Tl+ and Cd2+ by Eichhornia crassipes roots using carbon paste electrode

Abstract

In this work, Eichhornia crassipes roots were used as a modifier for carbon paste electrode in a biosorption study of thallium (Tl+) and cadmium (Cd2+) ions. The ions were accumulated on modified electrode surfaces at open circuit potential and analyzed by square wave anodic stripping voltammetry. Before the biosorption study, the effect of ratio of biomass and binder in uptake metal was evaluated. The biosorption study shows that adsorption of ions was dependent on pH. The kinetic study showed that, for both ions, experimental data were well described by the pseudo-second order model (R2 > 0.99) and the equilibrium was better described by the Langmuir model. The value of dimensionless equilibrium parameter (RL) obtained in the equilibrium study showed that Eichhornia crassipes can be considered an effective biomaterial for Tl+ and Cd2+ removal from an aqueous solution. The thermodynamic parameters calculated, enthalpy (ΔH°), entropy (ΔS°) and Gibbs energy (ΔG°), indicated that the biosorption process was spontaneous and endothermic.