Isotherm, Thermodynamic and Kinetic Studies on the Adsorption of Cu(II), Cd(II) and Ni(II) Ions from Aqueous Solution onto Coconut Shell Activated Carbon

This study throws light on the use of coconut shell in the removal of heavy metal ions Cu (II), Cd (II) and Ni (II) from the aqueous solution. The adsorption parameters were determined using both Langmuir and Freundlich isotherm models. The adsorption kinetics followed the pseudo-second-order model. This model gives the best-fit to experimental data for heavy metal ions. The second order kinetics give highest correlation coefficient values 0.989, 0.993, 0.995 for Cu2+, Cd2+, Ni2+respectively. Thermodynamic parameters such as change in Gibbs free energy (G0), enthalpy change (H0), and entropy change (S0) were also evaluated. The values showed that the adsorption process for Cu (II), Cd (II) and Ni (II) ions was endothermic. The negative value of G0 suggests the spontaneity of the reaction. The final result of the study suggests that the coconut shell carbon (CNS) has a good efficiency to remove Cu (II), Cd (II) and Ni (II) ions from aqueous solution and it is a cost effective adsorbent too.