Investigation of heavy metal removal by using modifier organic compounds immobilized bentonite

In this study, 4-aminobenzhydrazide (M1), 3-aminobenzhydrazide (M2), 2-aminobenzhydrazide (M3), 4,5-diamino-6-hydroxy-2-mercapto pyrimidine (MM) were separately immobilized onto natural bentonite. The FTIR and thermal analyses were performed to observe the immobilization of samples. After that the adsorption of lead(II) and cadmium(II) ions was investigated on natural and immobilized forms. According to the obtained results, 4,5-diamino-6-hydroxy-2-mercapto pyrimidine (MM) immobilized-bentonite can be used as a respective adsorbent for the removal of the heavy metal pollutants. In adsorption; parameters e.g. pH, concentration and temperature were examined. Maximum adsorption values for lead(II) and cadmium(II) ions are obtained at pH=5.50. Lagergren-first-order, pseudo-second-order, Elovich kinetics and intraparticle diffusion models were applied to the experimental data and the rate constants are extracted. The experimental kinetic data indicate that the adsorption of lead(II) and cadmium(II) ions fits well with the pseudo-second-order kinetic model (very high r2 values). The adsorption capacity was increased by an increase on the concentration for lead(II) and cadmium(II) ions. The isotherm graphs were plotted for the adsorption of lead(II) and cadmium(II) ions onto MM-B. The reusability of MM-B was also investigated. Beside, the competitive adsorption experiments of heavy metals onto MM-B were carried out. The results indicate that MM-B is more selective adsorbent for the removal of lead(II) ions.