Effect of preparation method on particle properties of carbonate-type magnesium–aluminum layered double hydroxides

Abstract

Abstract Carbonate ion-intercalated Mg–Al layered double hydroxides (CO 3 -type Mg–Al LDHs) were prepared by using various methods to mix a solution of Mg(NO 3 ) 2 and Al(NO 3 ) 3 with an alkaline solution, and the particle properties of the obtained samples were compared. By mixing stoichiometric quantities of Mg 2+ , Al 3+ , and OH − according to the coprecipitation reaction for preparing CO 3 -type Mg–Al LDHs, Mg 2+ and Al 3+ in solution were quantitatively precipitated, and the Mg/Al molar ratios of the obtained Mg–Al LDHs were equal to those of the solution, irrespective of the preparation method. However, the different preparation methods resulted in different particle properties, namely, different particle size distributions, particle morphologies, and sedimentation properties were observed. These differences were attributed to different formation processes for Mg–Al LDH. The ideal preparation method was determined to involve the addition of Mg(NO 3 ) 2 and Al(NO 3 ) 3 solution to Na 2 CO 3 solution at a constant pH, which was achieved by adjusting with NaOH solution. This preparation method resulted in the formation of CO 3 -type Mg–Al LDH particles with uniform primary particles, good sedimentation properties, and a narrow distribution of secondary particle aggregates. Such characteristics make these Mg–Al LDHs excellent candidates for wastewater treatment.