The parameters of Mg/Fe(Al) layered double hydroxides/mixed oxides related to the synthesis

Abstract

The Mg-Fe layered double hydroxides (LDH) are becoming to be a group of promising materials with a lot of applications depending on their properties. These are influenced by the methods of synthesis, where it is not clearly presented which synthesis is suitable for materials with desired parameters. The aim of this work was to synthesize MgFe LDH according to standard recipes used for common MgAl LDH, when showing similarities and differences in-between the samples of Mg-Al and Mg-Fe LDH and derived mixed oxides (MO). Extensive experimental characterization of material structure and surface has been performed. Originally, statistical analysis of the characterization data revealed that LDH from particular synthesis were grouped together, showing statistical similarities. The structure properties of samples from particular synthesis were similar to both series of Mg/Al and Mg/Fe and also for the molar metal ratios 3/1 and 4/1. Oxides were completely rehydrated to the LDH form only for the co-precipitation method. The cell parameters in LDH and rehydrated forms mutually strongly correlated indicating the same layer properties of parent LDH and their rehydrated forms. The oxides that originated from the hydrothermal method had significantly higher densities of basic centres and population of strong O2− basic structures due to the abundance of surface defects and other phases. Oxides prepared by the sol-gel method showed somewhat higher density of the acid centres.