Abstract
In the current work, the possibility of introducing simultaneously two different functions onto the surface of mesoporous material SBA-15 was achieved. In fact, the thiol and amino organic functions, respectively, were incorporated according to post and successive grafting. The rate of grafting of these ligands was discussed using the following characterization methods: XRD, N(2) adsorption-desorption, and FT-IR. A dramatic decrease was found in the textural characteristics due to the success grafting also evidenced by FT-IR spectroscopy and XRD analyses. After that, the adsorption study of Pb(2+) and Cd(2+) from aqueous solution using the resulting bifunctional adsorbents at ambient temperature shows significant exaltation for lead adsorbed quantities against reduction of cadmium adsorbed ones; this behavior is due to the synergic effect coming from the simultaneous existence of -SH and -NH(2) fragments. Thus, the adsorption of Pb(2+) on both adsorbents is more efficient (medium adsorption rate = 84%) compared to Cd(2+) (adsorption rate does not exceed 10%). The maximum adsorption capacities are found between 164 and 168 mg/g for lead ions and between 19 and 16 mg/g for cadmium ions. The kinetic study demonstrates that the process is moderately fast; the equilibrium is achieved within 50 min, whereas the kinetics analysis revealed that the overall Pb(2+) and Cd(2+) adsorption process by two adsorbents was more consistent with the pseudo-second-order model. Besides, the adsorption isotherms fit well the Freundlich model. Additionally, high adsorption efficiencies were attained at the pH of each metal solution, around 5.3 for lead and 6.1 for cadmium. Moreover, the reuse performance shows the possibility of efficiently reusing these adsorbents even after three cycles, which means that the synergic effect is also maintained.