Isotherm, kinetic and thermodynamic analysis of some heavy metal ion's adsorption on natural and modified clay minerals (Siirt/Kurtalan)

In this study, raw and modified clay are being used for removal of Pb(II) and Cu(II) from aqueous environment. The parameters affecting the adsorption, such as temperature, concentration, pH, contact time were examined. The data were applied to the Freundlich, Langmuir, Temkin and Dubinin-Radushkevich adsorption isotherms and Langmuir adsorption isotherm model was evaluated as the best fit in accordance with the data. Adsorption capacities of 298, 303, 313 K were found to be 11.06, 18.86 and 37.17mgCu/g raw clay and 169.49, 185.18 and 196.08 mg Pb/g raw clay, respectively. As a result of the activation of the clay, the same processes were repeated and the adsorption capacity was found to be 30.30, 26.18 and 47.17 mg Cu/g activated clay and 13.67, 21.28 and 46.73 mg Pb/g activated clay, respectively. When the kinetic data were applied to the Lagergren, Ho-McKay, weber- Morris and Elovich models, it was seen that the data mostly complies with the Ho-McKay second order rate equation. Also, thermodynamic data such as free energy, enthalpy and entropy were calculated and as a result Pb (II) for activated clay ΔHo=13.37 k j/mol, ΔSo=0.094 k j/mol ve ΔG298= - 14.64 kj/mol, ΔG308= -15.58 kj/mol, ΔG318= - 16.52 kj/mol, Pb (II) for raw clay, ΔHo= 18.31 k j/mol, ΔSo=0.117 k j/mol ve ΔG298= - 16.55 kj/mol, ΔG308= -17.73 kj/mol, ΔG318= - 19.90 kj/mol, Cu (II) for activated clay ΔHo= 107.07 k j/mol, ΔSo=0.378 k j/mol ve ΔG298= - 5.75 kj/mol, ΔG308= -9.54 kj/mol, ΔG318= - 13.32 kj/mol, Cu (II) for raw clay, ΔHo= 60.69 k j/mol, ΔSo=0.236 k j/mol ve ΔG298= - 8.46 kj/mol, ΔG308= -12.00 kj/mol, ΔG318= - 14. kj/mol were determined.