Synthesis of a novel layered double hydroxides [MgAl4(OH)12](Cl)2•2.4H2O and its anion-exchange properties

A novel layered double hydroxide of Mg and Al with composition [Mg0.96Al4.00(OH)(12)]Cl-1.86(CO3)(0.03)center dot 2.4H(2)O, designated as MgAl4-Cl, was synthesized by mixing crystalline gibbsite (gamma-Al(OH)(3)) and solid MgCl2 center dot 6H(2)O with subsequent hydrothermal treatment at 160 degrees C for 72 h. The MgAl4-Cl exhibited a crystalline material of a layered structure, as evidenced from X-ray diffraction. Anion uptake experiments with the MgAl4-Cl showed that Cl- in the interlayer space can be exchanged with anions such as Br-, H2PO4-, CO32- or dodecyl sulfate (DS-) from aqueous solutions with preservation of the layered structure. Uptake of NO3-, BrO3- or SO42- on the MgAl4-Cl showed different behavior; these anions can be exchanged within 1 h maintaining the layered structure, but a release of Mg2+ cations from the sample was observed with increased reaction time, resulting in collapse of the layered structure and formation of the gibbsite phase, as determined from chemical analyses and X-ray diffraction. (C) 2010 Elsevier B.V. All rights reserved.