Trimetallic layered double hydroxide solid solutions with the compositions Zn/Co-Al, Zn/Cu-Al and Co/Cu-Al (2 M2+:1M3+), intercalated with hydrated sulfate and sodium cations

Trimetallic layered double hydroxides (LDHs) solid solutions with the compositions Zn/Co-Al, Zn/Cu-Al, and Co/Cu-Al, intercalated with hydrated SO42-/Na+ were synthesized by co-precipitation with increasing pH at room temperature, hydrothermally treated at 90 °C for 120 h and dried at 40 °C. The compounds were analyzed by XRD, where all the systems presented basal distances close to 11 Å, typical of the intercalation of sulfate in double-layer arrangements in the presence of hydrated sodium cations. FTIR indicated the presence of typical bands attributed to sulfate, water molecules and metal–oxygen lattice vibrations. SEM and TEM images of the Zn/Co-Al system indicated the presence of micrometric particles, homogeneous aspect and nanometric dimensions along the layer packing (basal directions), in the whole range of replacements. EDS spectra of all samples indicated the presence of the expected elements in all compounds. ICP-OES indicated that all system contained the elements close to the expected concentration, with slightly smaller contents of sulfate and sodium cations. SAED spectra of the Zn/Co-Al system indicated the presence of a√3 × a√3 superstructures in all samples, attributed to the ordering of divalent metals in the layer domains, typical of compounds with 2 M2+:1M3+ molar ratios. Homogeneous solid solutions were obtained for all systems, but a small contamination with carbonate was observed in some samples, producing compounds with the ideal formula [M2+0.666Al0.333(OH)2][(SO4)0.222-x(CO3)xNa0.111] nH2O. This work increases the number of members of trimetallic LDH and opens a new avenue for future applications.