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

Abstract

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 (N2 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 ⋅ 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 ΔHΘ 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.