Characterization and sorption study of Zn2[FeAl]-CO3 layered double hydroxide for Cu(II) and Pb(II) removal

This study reports the synthesis of a ternary layered double hydroxide (LDH) from ZnII, FeIII, and AlIII (Zn2[FeAl]-CO3) for the efficient removal Cu(II) and Pb(II) from water samples. Herein, Zn2[FeAl]-CO3 was prepared by a co-precipitation method and characterized using X-ray powder diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy, N2 adsorption-desorption isotherms and differential scanning calorimetry analysis. The characterization results ensured the formation of a mesoporous LDH with carbonate as the interlayer anion and the presence of Zn, Fe and Al on the surface with a MII/MIII molar ratio of about 1.82. The Cu(II) and Pb(II) sorption process has been thoroughly studied for different parameters. The kinetic data showed that the process is very fast and follows a pseudo-first-order model. In addition, both surface sorption and intraparticle diffusion contributed to the rate-limiting steps in the sorption system. The sorption isotherms were evaluated quantitatively with four different isotherm models. It was found that the Redlich-Peterson and Freundlich models showed better correlation with the experimental data. The thermodynamics study indicates the endothermic, disorder-increasing and spontaneous nature of the sorption process. In conclusion, these results suggest that the synthesized Zn2[FeAl]-CO3 is favorable and useful for the removal of the studied metal ions and the high sorption capacity makes it a promising candidate material for the removal of heavy metals from water.