Removal of Cu(II) from aqueous solutions by zinc oxide‐montmorillonite composite

Abstract Background Cu(II) is considered to be a heavy metal ion that is quite hazardous to water. Aims Zinc oxide‐montmorillonite composite (ZnO‐Mt) for the removal of Cu(II) from aqueous solutions. Materials & Methods ZnO‐Mt was prepared through ion exchange followed by heat treatment to form a highly effective adsorbent. Results The structure and morphology of the composite were investigated by X‐ray diffraction, scanning electron microscope, and fourier transform infrared spectroscopy and it was found that Zinc oxide was successfully coated on montmorillonite. The composite has a superior removal effect on Cu(II) in an aqueous solution with an adsorption capacity of 192.89 mg·g −1 . The adsorption kinetic model and the adsorption isotherm model are described by the pseudo‐second‐order kinetic equation and the Langmuir equation, respectively. The activation energy (E a ) was 84.18 kJ·mol −1 , indicating that the adsorption was dominated by chemisorption. In addition, ZnO‐Mt can be applied in a wide pH range (3 ~ 8) and exhibits satisfactory selectivity for the adsorption of Cu(II) in the presence of coexisting cations. The removal efficiency of ZnO‐Mt for Cu(II) remains at 72% of the fresh adsorbent after five cycles. Discussion A combination of experiment, characterization, and density functional theory analysis showed that the mechanism of Cu(II) removal was mainly surface complexation, ion exchange, and electrostatic attraction. Conclusion Therefore, the ZnO‐Mt composite is a promising and efficient adsorbent for the removal of Cu(II) from aqueous solutions.