Synthesis of hierarchical flower-like Mg₂Al-Cl layered double hydroxide in a surfactant-free reverse microemulsion

Hierarchical flower-like Mg₂Al-Cl LDH microspheres were synthesized using a reverse surfactant-free microemulsion (SFME) route at a low temperature (∼25°C), and characterized by XRD, TEM, SEM, FT-IR, TG, N₂ adsorption/desorption, and elemental analyses. The SFME used consists of n-hexane, isopropanol, and water. The so-obtained flower-like microspheres are constructed with LDH nanosheets with ∼10nm thickness. After destroyed by calcination, their crystal structure and flower-like morphology can be reconstructed by rehydration. The flower-like LDH and its calcined product (CLDH) have large specific surface areas being ∼84.3 and 163.9m²g^-1, respectively. The sorption of methyl orange (MO) on the LDH and CLDH were determined, showing high MO sorption capacities of ∼559 and 1112gg^-1, respectively, which are obviously higher than those reported for conventional LDHs and CLDHs. Possible mechanisms for the flower-like microsphere formation and the MO sorption are discussed. Our results demonstrate that, like traditional surfactant-based microemulsions, SFMEs as microreactors or templates can be used to synthesize nanomaterials. The hierarchical flower-like LDH microspheres and their calcined product have potential applications such as in the treatment of organic waste water.