Novel Bimetallic and Trimetallic Layered Double Hydroxides with the Compositions Ni 6-x Zn x Al 3 (OH) 18 A(H 2 O) 6 (SO 4 ) 2 ·6H 2 O ( x from 0 to 6; A= Na + o K + )

Bimetallic and trimetallic layered double hydroxides with the composition Ni6-xZnxAl3(OH)18A(H2O)6(SO4)2·6H2O (x from 0 to 6; A = Na+ or K+) were synthesized by coprecipitation with increased pH and characterized by several instrumental techniques. X-ray diffraction (XRD) indicated the prevalence of basal diffraction peaks with basal distances close to 11 Å, typical of LDHs intercalated with sulfate in double-layer arrangement in the presence of potassium cations, in both cases hydrated. Fourier-transform infrared spectroscopy (FTIR) revealed a typical series of bands, attributed to S–O (from sulfate), M–OH (M = metal of the layers), and O–H (from water molecules and hydroxide layers). Scanning electron microscopy (SEM) images indicated the typical platelet-like morphology of LDH, with micrometric particles having nanometric thicknesses, while energy-dispersive X-ray spectroscopy (EDS) indicated the expected distribution of metals in the series. Inductively coupled plasma optical emission spectroscopy (ICP-OES) confirmed the compositions of the materials, which were close to ideal according to the chemical used in the syntheses, suggesting the absence of simultaneous precipitation of other materials (especially hydroxides). Thermogravimetric analyses (TGA) and the respective derivative curves (DTG) also confirmed the decomposition in several steps, attributed to the removal of physiosorbed water molecules, dehydration of cations/anions, dehydroxylation of the layers, and decomposition of the metal sulfates to oxides/spinels.