Adsorption of Pb(II), Cu(II), Cd(II), Ni(II), and Co(II) ions by newly synthesized 2-(2′-Hydroxyphenyl)Benzothiazole-functionalized silica

This study employed chemically functionalized silica to adsorptively remove Pb(II), Cu(II), Cd(II), Ni(II), and Co(II) ions from water samples. The adsorbent was prepared by chemically immobilizing newly synthesized 5-chloro-2-(2 '-hydroxyphenyl)benzothiazole (Cl-HPBT) on the silica surface using 3-aminopropyl-trimethoxysilane (APTMES), and the final structure was named SiO2-NH-HPBT. The novel Cl-HPBT ligand was characterized by FT-IR and H-1 NMR spectroscopy and elemental analysis. FT-IR spectroscopy, elemental analysis, SEM, and EDX determined the structures of the silica particles before and after modification. The initial concentrations of the metal ions, the contact time, and the pH of the solution were optimized. Single- and multi-component adsorption experiments investigated the selective removal of target metal ions from aqueous solutions. The adsorption mechanism was ascertained by fitting the Langmuir, Freundlich, and Dubinin-Radushkevich isotherms to the adsorption data. The adsorption isotherm conformed to the Langmuir model with a correlation coefficient of 0.99. The adsorption kinetics indicated that the Lagergren pseudo 2nd-order kinetic model was more appropriate. The maximum adsorption capacities of SiO2-NH-HPBT were found to be 68.6 +/- 0.55, 20.5 +/- 0.50, 24.7 +/- 0.35, 23.0 +/- 0.60, and 13.8 +/- 0.50 mg/g for Pb(II), Cu(II), Cd(II), Ni(II), and Co(II), respectively. Single- and multi-component adsorption experiments evaluated the adsorption performance of SiO2-NH-HPBT in synthetic wastewater. Multi-component adsorption results demonstrated that Cu(II) and Pb(II) could be removed from synthetic wastewater by SiO2-NH-HPBT. (C) 2021 Published by Elsevier B.V.