Prediction of the kinetics, equilibrium and thermodynamic parameters of adsorption of copper(II) ions onto 8-hydroxy quinoline immobilized bentonite

In this study, the chelating agent of 8-hydroxy quinoline (HQ) was firstly used for the immobilization of bentonite and then it was used for the adsorption of copper(II) ions from aqueous solutions. The parameters of pH, contact time, adsorbent and initial copper(II) ions concentrations and temperature were investigated in the adsorption experiments. The surface characterization of both natural- and HQ-immobilized bentonite was undertaken using FTIR spectroscopic technique. The XRD, elemental and thermal analyses were also carried out to observe the intercalation of HQ between bentonite layers. The kinetic parameters were calculated from the experimental data and it was shown that they could be fitted well to the pseudo-second-order kinetic model. The adsorption data obtained were well described by the Langmuir adsorption isotherm model. The maximum adsorption capacity was found to be 56.55 mg g−1 from the Langmuir isotherm model at 50 °C. The thermodynamic parameters such as ΔG°, which are all negative, indicated that the adsorption of copper(II) ions onto HQ-bentonite is spontaneous and the positive value of ΔH° (+17.18 kJ mol−1) shows that the adsorption is physical in nature. The results show that HQ-immobilized bentonite is the effective adsorbent for the removal of heavy metal contaminants.