Facile and green hydrothermal synthesis of MgAl/NiAl/ZnAl layered double hydroxide nanosheets: a physiochemical comparison

Abstract Layered double hydroxide (LDH) exhibits a remarkable trait referred to as the ‘memory effect,’ demonstrating its capacity to reconstruct its layered structure from calcined oxides through hydrothermal treatment. Its uniqueness has garnered significant interest from researchers in both industrial and academic domains. Various methods have been utilized to synthesize LDH but most LDH studies still utilize alkali precipitants which might taint the final LDH product. Thus, in this study, layered double hydroxides involving MgAl/NiAl/ZnAl were synthesized via an alkali-free hydrothermal approach in which the formed precipitates of LDH were thermally destroyed via calcination at 450 °C before undergoing a rehydration treatment at 110 °C for 24 h to restore its original structure. Particularly, the physiochemical properties of MgAl/NiAl/ZnAl LDH have been undertaken by multiple techniques such as Powder X-ray Diffraction (PXRD), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), Field Emission Scanning Electron Microscope (FESEM) and Fourier-transform infrared spectroscopy (FTIR). The resultant products exhibited exceptional crystallinity, accompanied by notably larger crystallite sizes and crystallinity index, particularly post-hydrothermal treatment. Among the fresh and calcined products studied, those subjected to HTM (4:1) treatment demonstrated the highest specific surface area and crystallinity surpassing both the fresh and calcined samples. In essence, this research showcased how utilizing the hydrothermal approach resulted in the most substantial increase in crystallite size and specific surface area.