Removal of Cu(II) Ions from Aqueous Solutions by Adsorption onto Natural Bentonites

The removal of Cu (II) ions from aqueous solutions using the adsorption process onto natural Slovak bentonites from deposits Jelsovy potok, Hlinik nad Hronom and Lieskovec has been investigated in this study. The adsorption experiments were carried out under batch process with initial concentration Cu (II) ions, time and temperature as the variables. A flame atomic absorption spectrometer was used for measuring the copper concentration before and after adsorption. Adsorption was very fast at low coverage and equilibrium was approached within 30 min. The results best fitted the pseudo-second order kinetic model. Langmuir and Freundlich isotherms were applied and isotherm coefficients were computed. The Langmuir isotherm was found to fit better the experimental data measured for used bentonites. The Langmuir maximum adsorption capacity of the adsorbents was from 13.4 to 43.1 mg g−1. The effect of temperature on the equilibrium adsorption of copper from aqueous solution using natural bentonites was investigated at three different temperatures (293, 303 and 313 K). Thermodynamic parameters, such as standard free energy changes (ΔGo), standard enthalpy change (ΔHo) and standard entropy change (ΔSo), were calculated using adsorption equilibrium constant obtained from the Langmuir isotherm. The copper adsorption on bentonite was a spontaneous and endothermic process. The results suggested that natural bentonites are suitable as a adsorbent material for recovery and adsorption of Cu (II) ions from aqueous solutions. Comparing the measured results for used bentonites is evident that for the removal of Cu (II) ions from aqueous solutions is more suitable the bentonite from Jelsovy potok.