Efficient removal of Pb(II) and Hg(II) ions from aqueous solution by amine and thiol modified activated carbon

This study investigates the preparation of a novel chelating adsorbent (AT-MAC), based on the chemical modification of activated carbon (AC) derived from water hyacinth (WH) via functionalization with 2-aminothiazole chelating legend (AT), and then utilizing it for the effective removal of Pb(II) and Hg(II) ions from polluted water. FTIR and XPS spectroscopy confirm the successful incorporation of amine and thiol groups within the porous activated carbon through the amidation reaction between the carboxylic groups of porous activated carbon and 2-aminothiazole legend in presence of DCC as cross coupling agent. The AT-MAC adsorbent exhibited high sorption capacities for the removal of Pb(II) (310.9 mg/g) and Hg(II) (252.5 mg/g) at pH 5.5 and contact time 60 min, which are higher than most previously reported carbon based materials. AT-MAC displayed 100.0% removal for Hg(II) and Pb(II) ions at concentrations up to 50 ppm, thus demonstrating excellent selectivity for Pb(II), and Hg(II) ions. The FTIR before and after adsorption suggested the mechanism of removal based on the complexation between the nitrogen and sulfur atoms on the surface of AT-MAC and Pb(II) forming (C-S-Pb and C-N-Pb). The chemisorption mechanism via the thiol and amine groups grafted onto the surface of AT-MAC was also suggested based on the excellent agreement of the experimental data with a pseudo-second order kinetic model. The AT-MAC also showed high stability over three adsorption–desorption cycles. The results also revealed that AT-MAC is a promising remediation adsorbent for the solid phase extraction of Pb(II) and Hg(II) ions from contaminated water.