New attempts to synthesize trimetallic layered double hydroxides with the composition [Ma 6-xMb 2+x Al3(OH)18][(SO4)2Na].yH2O (Ma 2+2+,Mb 2+= Zn, Mn, Mg)

Trimetallic layered double hydroxides with the composition [Ma 6-xMb 2+ x Al3(OH)18][(SO4)2Na].yH2O (Ma 2+ 2+,Mb 2+= Zn, Mn, Mg; x from 0 to 6 by step of one unit) were investigated for the first time. The XRD analyses of all compounds, independent of the composition, presented basal spacing close to 11 A, typical of LDH intercalated with sulfate in double layer arrangement with hydrated alkali metal cations. The FTIR spectra indicated that all compositions contained intercalated sulfate, typical bands attributed to LDH lattice along with water molecules. ICP-OES analyses confirmed the obtainment of homogeneous solid solutions in the Zn/Mn-Al system in the whole range of replacements. In the Zn/Mg-Al system, homogeneous solid solutions were obtained only for 5Zn/1Mg/ 3Al while in the Mg/Mn-Al system, the successful synthesis occurred for the phases 2 Mg/4Mn/3Al and 1 Mg/ 5Mn/3Al. SEM images of Zn/Mn-Al system indicated micrometric-sized particles and nanometric particles in the Zn/Mg-Al and Mg/Mn-Al systems, as also attested by XRD.This study's results suggest that new trimetallic LDH intercalated with sulfate and alkali metal cations can be synthesized, and that new minerals can be identified with the suggested formulations, particularly in the Zn/Mn-Al system and with alkali metal cations other than sodium, like lithium and potassium. This study also broadens the range of potential applications of layered double hydroxides.