Pseudo-second-order kinetic equations for modeling adsorption systems for removal of lead ions using multi-walled carbon nanotube

This study investigated the lead ion removal of the multi-walled carbon nanotubes (MWCNTs) and oxidized multi-walled carbon nanotubes (MWCNT-COOH). The main purpose of this work is to study the possibilities on the removal of Pb(II) ions from aqueous solutions using MWCNTs and MWCNT-COOH surfaces as adsorbents. Removal of Pb(II) ions was investigated using solutions with different concentrations in the range 10 to 100 mg/L. In this study, removal of Pb(II) ions on surfaces has been investigated by atomic absorption spectrophotometry. The microstructure of carbon nanotubes were characterized using scanning electron microscopy. Three different kinetic theories were applied to experimental data. The kinetic rates were modeled using the pseudo-first-order, four-type linear pseudo-second-order, and intraparticle diffusion. The pseudo-second-order model was found to explain the adsorption kinetics most effectively. The results indicated a significant potential of the multi-walled carbon nanotube as an adsorbent for Pb(II) ion removal.