C-dots/Fe3O4 magnetic nanocomposite as nanoadsorbent for removal of heavy metal cations

In this work, C-dots/Fe3O4 magnetic nanocomposite as nanoadsorbent was implemented for adsorption of Cu(II), Cr(III) and Pb(II) cations from aqueous solutions. The effect of various parameters on adsorption process of all three mentioned cations such as nanoadsorbent dosage, initial cation concentration, contact time and pH were explored to find the mechanism of adsorption. Different kinetic models including pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion kinetic models were used to fit experimental data. In this way, pseudo-second-order model described the kinetic data of all three cations well. Also, equilibrium isotherm studies were examined by application of different conventional isotherms such as Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich models to explain the experimental data. The Freundlich isotherm fitted equilibrium data of all three cations, whereas other models were not fitted well. Results indicate that the adsorption of all three cations is followed by chemisorption mechanism via electrostatic attraction at heterogeneous surface of nanoadsorbent.