Porous magnesium oxide was synthesized by a combustion method, with Mg(NO 3) 2 , ethylene glycol and deionized water as reactants, and characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and nitrogen sorption/desorption. The results showed that the as-prepared porous magnesium oxide has the multi-scale porous size with a large BET surface area of 203.8 m 2 g −1. Magnesium oxides synthesized with other reactants have rod-shaped and granular morphologies, and their BET surface areas are 17.6 and 3.4 m 2 g −1 , respectively. Compared to the magnesium oxide with the low specific surface area, porous magnesium oxide exhibited higher adsorption efficiency with a maximum adsorption capacity of approximately 1088 mg g −1 in removing Congo red. The as-synthesized porous magnesium oxide could be used as an efficient adsorption material in Congo red removal from the wastewater.
In this paper, flower-like layered double hydroxides were synthesized with eggshell membrane assistant. The as-prepared samples were characterized by a series of techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Thermal gravity-differential thermal analysis and Nitrogen sorption/desorption. The resulting layered double hydroxides were composed of nanoplates with edge-to-face particle interactions. The specific surface area and total pore volume of the as-prepared flower-like layered double hydroxides were 160[Formula: see text]m2/g and 0.65[Formula: see text]m3/g, respectively. The adsorption capacity of flower-like layered double hydroxides to Congo Red was 258[Formula: see text]mg/g, which was higher than that of layered double hydroxides synthesized by the traditional method.
Different from alumina, magnesium oxide is seldom used in the synthesis of layered double hydroxide. In this work, Mg Al layered double hydroxide with hierarchical structure was synthesized by using porous MgO as precursor via a facile in situ reaction at room temperature. And no chemical reagents are needed to provide an alkaline environment that allows precipitation to form during the synthesis process.Crystal structure, morphology, functional group, and surface features of the porous MgO precursor, the synthesized layered double hydroxide and its calcined product were characterized by X-ray diffraction, Fourier transform infrared techniques. The results demonstrate that the synthesized layered double hydroxide is a pure phase and composed of nanosheets. Moreover, the synthesized layered double hydroxide inherits the morphology of the porous MgO precursor and forms a hierarchical structure. This structure has a large specific surface area (249 m 2 g À1 ) to increase the adsorption properties. Adsorption experimental results show that the maximum adsorption capacities of Congo red and Cr(VI) ions over the synthesized layered double hydroxide were 847.5 and 103.7 mg g À1 , respectively. The adsorption process follows the Langmuir and pseudo-second equation. Both adsorption processes were found to be spontaneous and endothermic.
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