Kinetics, equilibrium and isotherms of Pb2+ adsorption from aqueous solutions on carbon nanotubes functionalized with 3-amino-5a,10a-dihydroxybenzo[b] indeno [2,l-d]furan-10-one

Abstract

Multi-wall carbon nanotubes functionalized with 3-Amino-5a, 10a-dihydroxybenzo [b] indeno [2,ld]furan-10-one (ADIF), (MWCNT-ADIF), were used as the adsorbent to remove lead ions (Pb2+) from aqueous solutions. The samples were characterized by FT-IR, SEM, TGA and DTG. Effects of pH, initial Pb2+ concentration, adsorbent dosage and contact time on adsorption kinetics and equilibrium were investigated in a batch mode. Adsorption isotherms of Pb2+ ions were investigated using four two-parameter models (Langmuir, Freundlich, Tempkin, Dubinin-Radushkevich) and six three-parameter models (Redlich-Peterson, Khan, Sips, Radke-Prausnitz, Toth, Hill). Adsorption kinetics were investigated by the pseudo first-order kinetic model, the pseudo second-order kinetic model and the intra particle diffusion model. Three error analysis methods, correlation coefficient, chi-square test and average relative errors, were used to determine the best fitted isother. Results indicated that adsorption kinetics was best described by the pseudo second-order kinetic model. Error analysis indicated that three-parameter models described the Pb2+ sorption data better than the two-parameter models . The isotherm data were best fitted by the Langmuir, Hill and Sips models. Pb2+ ions could be desorbed from MWCNT-ADIF up to 92% at pH=3 and the recycled MWCNT-ADIF could be reused for 5 regeneration cycles.