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 degrees C. The advantage of the magnesium powder as the starting material is it slowly generated Mg2+. Thus, the low centration of Mg2+ 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. (C) 2017 Elsevier Inc. All rights reserved.