Synthesis, Characterization, and Anion Exchange Reactions of Zn2Cr Layered Double Hydroxides Intercalated with Acetate and Chloride

Layered double hydroxides (LDH) with the composition Zn2Cr, intercalated with acetate and chloride ions were synthesized by co-precipitation with increasing pH and characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and inductively coupled plasma-optical emission spectrometry (ICP-OES). The samples synthesized at optimized pH showed XRD patterns with basal diffraction peaks typical of layered structures, with basal distances of 7.88 and 12.69 Å for intercalated chloride (Zn2Cr/Cl) and acetate (Zn2Cr/Ac), respectively. After optimization experiments, exchange reactions were performed with different anions, using an excess of five times the anions to be intercalated. Zn2Cr/Cl was exchanged with CH3COO−, F−, Br−, I−, SO4 2− and NO3−, and Zn2Cr/Ac was exchanged with F−, Cl−, Br−, I−, SO42− and NO3−. Not all reactions were effective, indicating that among the evaluated anions, CH3COO− was preferred for exchange, mainly attributed to the pre-expansion with bigger anions, facilitating the exchange with smaller anions.