Enhancement of adsorption ability of calcium alginate gel beads towards Pd(II) ion. A kinetic and equilibrium study on hybrid Laponite and Montmorillonite-alginate gel beads

The adsorption ability of hybrid Montmorillonite and Laponite-calciumalginate gel beads towards Pd2+ ion was studied in the pH range 2-4, in pure water and in aqueous NaCl solution at I=0.01 mol L-1 and T=25 °C. The pseudo second order kinetic equation and the Langmuir and Freundlich isotherms were used to fit the kinetic and thermodynamic experimental data. A comparison of the results already published on the adsorption capacity of calcium alginate gel beads at the same experimental conditions was made. Enhancement of palladium(II) adsorption by alginate beads with the addition of the two clay minerals was obtained, with increments higher than 50% of Pd(II) ion recovered/removed. The physico-chemical characterization of gel beads was also made. SEMmicrographs, EDX and FT-IR spectra as well as the values of the physical parameters calculated for each adsorbent material were analysed in order to find correlations between their chemical and physical properties and their behaviour in terms of palladium adsorption.