Removal of pb(Ii) ion from aqueous solution using dithizone-immobilized natural bentonite

Removal of Pb(II) ion using activated and dithizone-immobilized natural bentonites has been carried out. Natural bentonite was activated by immersing and stirring the bentonite in 6M HCl solution. The dithizone-immobilized natural bentonite was prepared by mixing the bentonite and dithizone in toluene at 50o C for 6 h and the immobilized adsorbents was characterized by FTIR and XRD. The dithizone immobilization is aimed to increase the capacity and selectivity of the adsorbent towards Pb(II) ions. Characterization results suggest that dithizone has been successfully immobilized on the surface of bentonites indicated by the emerge of new peaks of dithizone in the FTIR and XRD spectra. The optimum conditions for the adsorption of Pb(II) ion are at pH 5, 0.1 gram of adsorbent mass, initial concentration of 70 ppm and contact time of 60 minutes. Experimental results show that the adsorption of Pb(II) on both adsorbents follows pseudo second order kinetic models and best described by the Langmuir isotherm models with the adsorption capacities of 0.452 and 0.506 mg/g for activated and dithizone-immobilized natural bentonites, respectively. It also reveals that the adsorption energies of Pb(II) ion on activated and dithizone-immobilized natural bentonites are 27,17 and 29,59 kJ/mol, respectively, suggesting that the adsorption of Pb(II) ion on both adsorbent is chemisorption. © 2021 Trans Tech Publications Ltd, Switzerland.