Facile Synthesis of Sodium Dodecyl Sulfate Intercalated Mg-Al LDH and its Excellent Adsorption Performances for Cu²⁺ from Aqueous Solution

In this study, the magnesium aluminum layered double hydroxide intercalated with sodium dodecyl sulfate (Mg-Al S-LDH) was synthesized by using a roasting-restoration method based on the Mg-Al LDH precursor, and their effectiveness in removing Cu2+ from aqueous solutions was investigated. Detailed microstructural characterization of these adsorption materials involved employing X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption/desorption isotherms (N-2 ad/desorption), and thermogravimetric-differential thermal gravimetric analysis (TG-DTG). The experimental results revealed that Mg-Al S-LDH displayed a plate-like layered structure with a larger surface area and enhanced adsorption ability. Specifically, the maximum adsorption capacity, reaching 96.15 mg & sdot; g(-1), was achieved at a temperature of 298 K, accompanied by a rapid adsorption rate. The adsorption kinetics adhered to the pseudo-second-order model, suggesting that chemisorption controlled the adsorption behavior. Furthermore, the adsorption of Cu2+ followed the Freundlich model, signifying a multi-site adsorption mechanism onto the surface and layers of Mg-Al S-LDH. Thermodynamic investigations indicated that higher temperatures facilitated Cu2+ dissolution and strengthened the affinity with Mg-Al S-LDH, with a positive Delta H-Theta value suggesting that the Cu2+ adsorption process was endothermic and temperature-enhancing. Ion selectivity experiments demonstrated that Cd2+ and Pb2+ ions had a significant impact on Cu2+ adsorption, while the effects of Zn2+ and Fe2+ ions were less pronounced. The primary adsorption mechanisms of Cu2+ onto Mg-Al S-LDH encompassed precipitation, complexation on the surface and layers, and isomorphous substitution. This study sheds light on the promising potential of Mg-Al S-LDH as an effective adsorbent for heavy metal removal and provides valuable insights into its adsorption mechanisms and performance in different environmental conditions.