Synthesis, characterization, and ion exchange properties of hydrotalcite Mg6Al2(OH)16(A)x(A′)2-x•4H2O (A, A′ = Cl-, Br, I-, and NO3-, 2≥x≥0) derivatives

A series of monovalent anion-containing hydrotalcites (HTCs) with the general formula Mg6Al2(OH)(16)(A)(x)(A')(2-x).4H(2)O (A, A' = Cl-, Br-, I-, and NO3-, 2 greater than or equal to x greater than or equal to 0) have been studied. Samples were synthesized by three different methods: ion exchange (IE), hydrothermal (HT), and recrystallization based on "memory effect" (ME). The physical, structural, and chemical characteristics and properties of the HTCs have been studied as a function of the synthetic methods and anions used. All three synthetic methods produced HTCs of good crystallinity and uniform particle size. When a second (A') or all four (Cl-, Br-, I-, NO3-) anions were present together with an A-HTC in an aqueous medium, the order of ion exchange preference was Br- > Cl- > NO3- > I-. When using one-pot synthetic methods (HT, ME), the same order of anion incorporation preference, Br- > Cl- > NO3- > I-, was observed.