The MgO nanoparticles were synthesized by the precipita- tion of magnesium hydroxide gels in aqueous solution using Mg(NO3)2•6H2O as salt and ammonia solution as the precipi- tating agent. First, 0.1 mol/L magnesium nitrate solution was prepared by dissolving Mg(NO3)2•6H2O (Merck) in deionized water.
The pH of 200 ml deionized water was adjusted to 10.5 by the addition of ammonia solution (25%), and to this solu- tion, 0.1 mol/L magnesium nitrate solution was added dropwise with vigorous stirring.
During the addition, the pH of the mixture decreased due to the hydrolysis of the salt.
The pH was maintained at 10.5 by the controlled addition of ammonia solution. After completion of the precipitation procedure, the Mg(OH)2 gel was transferred into the Milestone microwave oven (MicroSYNTH) operated at 350 W for 15 min. During the microwave irradiation, the temperature of the solution reached 80 °C.
The resulting precipitate was then cooled to room tem- prature, filtered, and washed with deionized water more than five times.
The solid obtained was dried at 120 °C for 1 h and calcined at 500 °C for 2 h to give the final product.