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Mesoporous MgO nanosheets with a high adsorption rate and excellent adsorption capacity for removing Ni (II) were successfully synthesized by a hydrothermal and annealing method. The Mg(OH) 2 was first synthesized by a hydrothermal process using magnesium powder as the starting material. MgO was then obtained by annealing the as-prepared Mg(OH) 2 at 450 °C. The advantage of the magnesium powder as the starting material is it slowly generated Mg 2+ . Thus, the low centration of Mg 2+ guaranteed a slow rate of forming Mg(OH) 2 , which benefited with a mesoporous structure. The effect of the hydrothermal time on the structure and adsorption performance was studied. The results showed that the MgO synthesized for 4 h had the highest adsorption performance of 2217 mg/g and the highest adsorption rate, which resulted in an efficient adsorption of 96% in 5 min for Ni (II) with the concentration of 500 mg/L. [ABSTRACT FROM AUTHOR]

The mesoporous MgO nanosheets were obtained using Mg(NO 3 ) 2 ·6H 2 O and urea as the raw materials without any surfactant via hydrothermal and calcination method. The effect of annealing temperature on the nanostructures and the adsorption performance were reported. The MgO annealed at 600 °C were mesoporous nanosheets with surface area of 45 m 2 /g. More interestingly, it exhibited high-rate adsorption property of Ni (Ⅱ) with a removal efficiency up to 99.99% in 15 min and a maximum adsorption capacity of 885 mg/g. [ABSTRACT FROM AUTHOR]

Hexagonal mesoporous MgO nanosheets with a side length of 250 nm and specific surface area of 181.692 m 2 /g were fabricated by a three-step process. Firstly, MgO powders were obtained by sintered Mg 5 (OH) 2 (CO 3 ) 4 ⋅4H 2 O, which was synthesized by a wet precipitation process using ammonium hydrogen carbonate as precipitants. Secondly, the above-MgO were distilled 2 h in a three-necked bottle with condenser device. Lastly, we annealed the distilled-MgO at 500–800 °C to form mesoporous MgO nanosheets. We found the pore size distribution and the thicknesses of nanosheets were determined by the distillation process in step 2 and annealed temperature in step 3. By optimizing the experimental parameters, the mesoporous dis-MgO annealed at 600 °C displayed uniform hexagonal structure with the largest pore volume (0.875 cm 3 /g) and highest BET surface area (181.692 m 2 /g), as well as the maximum adsorption capability of 1684.25 mg/g for Ni(II). [ABSTRACT FROM AUTHOR]