Removal of Cr(VI) and Pb(II) from aqueous solution using Mg/Al layered double hydroxides-mordenite composite

Mg/Al layered double hydroxides-mordenite nanocomposite (LDH@mordenite) was prepared via the in-situ method to enhance the Cr(VI) and Pb(II) removal efficiency. The results showed that the Cr(VI) and Pb(II) removal efficiency was enhanced by the formation of core-shell structure (mordenite core-LDH shell). The synthesized material with an LDH content of 30% had the highest removal efficiency for both metals at the pH of 5.0. The pseudo-second-order model was the best model for describing the adsorption kinetics of Cr(VI) and Pb(II) on LDH@mordenite. The calculation from the intra-particle diffusion model suggested that the adsorption processes included several steps. Fitting experimental data to the Langmuir, Freundlich, and Temkin models revealed that the Langmuir model was the best model for predicting the isotherms of the adsorption processes. The calculated maximum adsorption capacity at 25 celcius was 54.80 mg/g for Cr(VI) and 67.91 mg/g for Pb(II). Based on the thermodynamic study, the Cr(VI) and Pb(II) adsorption on LDH@mordenite was endothermic and spontaneous. The adsorption mechanisms were studied using the statistical physics model and the calculated parameters indicated that Cr(VI) and Pb(II) ions could interact via one and two adsorption sites of the adsorbent.

Automated summary

The Mg/Al layered double hydroxides-mordenite nanocomposite (LDH@mordenite) was prepared to improve the removal efficiency of Cr(VI) and Pb(II) through in-situ synthesis. The formation of a core-shell structure (mordenite core-LDH shell) enhanced the removal efficiency of Cr(VI) and Pb(II). The highest removal efficiency for both metals was achieved with an LDH content of 30% at pH 5.0. The adsorption kinetics of Cr(VI) and Pb(II) on LDH@mordenite followed the pseudo-second-order model. The Langmuir model provided the best fit for the isotherms of the adsorption process. The maximum adsorption capacity at 25 degrees Celsius was calculated to be 54.80 mg/g for Cr(VI) and 67.91 mg/g for Pb(II). The adsorption of Cr(VI) and Pb(II) onto LDH@mordenite was found to be endothermic and spontaneous based on thermodynamic analysis. The adsorption mechanism involved interactions between the ions and one or two adsorption sites on the adsorbent.