Kinetics and mechanisms of the adsorption of Pb(II), Cu(II) and Cd(II) onto ETS-10

Highly crystalline ETS-10 zeolite was prepared with a surface area of 250 m 2 /g and an average pore size of 1.67 nm. • Adsorption was highly pH-dependent, reaching peak efficiency at pH 5.0 for Pb(II) and pH 6.0 for both Cu(II) and Cd(II). • The Sips model best described the adsorption without being limited by concentration. • The adsorption kinetic of Pb(II) follows the PSO model, whereas the ID model controls the removal of Cd(II) and Cu(II). • The removal of Pb, Cu, Cd occurred via stoichiometric Na+/K+ ion exchange within 12-membered rings and surface complexation. Understanding adsorption kinetics and mechanisms play an instrumental role to determine the speed, efficiency, and pathways by which adsorbents remove pollutants. In this study, kinetics and mechanisms of the adsorption of Pb(II), Cu(II) and Cd(II) onto ETS-10 are investigated based on the combination of experimental, theoretical models (Langmuir, Freundlich, Sips, Pseudo-First-Order (PFO), Pseudo-Second-Order (PSO), Intraparticle diffusion (ID)), and modern analytical techniques (XRD, SEM-EDX, FT-IR and BET-BJH). Obtained results show that Sips models give the best fit with experimental data for three ions, while kinetic of Pb(II) adsorption follows PSO and kinetics of Cu(II) and Cd(II) uptakes follow ID models. The adsorption rates of Pb(II) > Cd(II) > Cu(II) during the diffusion process on the surface, whereas the ones of Pb(II) > Cu(II) > Cd(II) in the intraparticle diffusion process. The mechanisms of intraparticle diffusion, ion-exchange and complexion play mainly roles in the removal of Pb(II), Cd(II) and Cu(II). Download: Download high-res image (302KB) Download: Download full-size image