Studies on Adsorptive Removal of Some Heavy Metal Ions by Calix[4]Resorcine

Removal of heavy metal ions (Mn(II), Cu(II), Co(II), Zn(II), and Pb(II)) from aqueous solutions was carried out using C-4-hydroxyphenylcalix[4]resorcinarene as adsorbent surface. The effect of various parameters, such as solution pH, contact time and temperature on the adsorption capacity of C-4-hydroxyphenylcalix[4]resorcinarene for the selected heavy metal ions, was investigated and optimized. The experimental data were investigated using three kinetic models: Santosa first order, Largergen pseudo second order and Ho pseudo second order. Ho pseudo second order model described the adsorption process with high correlation coefficient (R2) compared to the other two models. The selectivity of the adsorbent toward a mixture of heavy metal ions was studied and revealed that the removal percentage of the heavy metal ions in a mixture is ranked differently from the separate heavy metal ions. Three adsorption equilibrium isotherm models - Freundlich, Langmuir and Temkin - were applied on the adsorption experimental data. It was found that the Langmuir model well described the adsorption process much better than the other isotherm models. In addition, the thermodynamic parameters of the adsorption processes for the heavy metal ions were calculated and found to be as follows: negative ΔHº indicating exothermic processes; negative ΔGº indicating spontaneous processes.