Synthesis of Na-A zeolite loaded bentonite and its application for removal of Cu(II) from aqueous solutions

Abstract

Zeolites are highly valued as adsorbent materials for the removal of heavy metals due to their exceptional adsorption properties, ease of synthesis, stability, and high adsorption capacity. Bentonite is an abundant and cheap adsorption material, and its aluminosilicate layers have large spacing to accommodate massive hydrated ions or macromolecular organics. In this study, bentonite is designed as the carrier material and Na-A zeolite is synthesized between its aluminosilicate layers, in order to obtain a low-cost modified bentonite with high heavy metal adsorption capacity. Results demonstrate that Na-A zeolite could be satisfactorily synthesized between bentonite aluminosilicate layers at a low synthesis temperature (80 °C) and short time (10 h). The pseudo-second-order kinetic model is more appropriate for characterizing the Cu(II) adsorption process on Na-A zeolite loaded bentonite, and the Freundlich isotherm is favorable for fitting the experimental data of Cu(II) adsorption. The Cu(II) adsorption mechanism by this composite material involves both ion exchange and chemical bonding, associated with its lamellar and cubic combined microstructure.