Abstract
As anionic alloy or layered compounds, layered double hydroxides (LDH) have recently attracted much attention due to their excellent adsorption and catalytic properties. In this work, NiFe layered double hydroxide (NiFeLDH) was utilized as a precursor to synthesize NiFeLDH/Au nanocomposites via a simple urea-hydrolyzed hydrothermal process under UV–vis light irradiation. The as-prepared nanomaterials were characterized using XRD, FT-IR, XPS, BET, UV–vis, TEM, and FESEM analysis. The performance of NiFeLDH and NiFeLDH/Au nanocomposites was evaluated in the adsorptive removal of congo red (CR) dye from aqueous media using two methods of adsorption, i.e. liquid phase sorption (MS) and sono-sorption (US). The sono-sorption technique exhibited higher removal efficiency due to the generation of small bubbles, strong shock waves, high-velocity microjets, and diminished thickness of diffusion layers. Furthermore, the NiFeLDH/Au nanocomposite offered much higher performance in CR removal, exhibiting a dye removal efficiency of 95% in 7 minutes of sono-sorption time. The superior performance of the NiFeLDH/Au composite can be assigned to the high specific surface area of the sorbent, better dispersion of Au nanoparticles onto the surface of NiFeLDH materials, and synergistic effects between Au and NiFeLDH. Also, the isothermal evaluation showed that the data of CR adsorption onto fabricated nanohybrids could be well-matched with the Langmuir model indicating uniform surface energies. Moreover, kinetics studies revealed that the best data fitting for CR adsorption can be provided by Ho’s pseudo-second-order kinetics. The thermodynamic study revealed that the adsorption of CR dye onto NiFeLDH/Au was an endothermic and spontaneous process at the investigated temperatures and CR concentrations. Finally, this research suggests a simple method for the synthesis of an LDH-based nano-sorbent capable of almost completely removing organic dyes from aqueous media