New acetate-intercalated CoNiFe, ZnNiFe and CoZnFe layered double hydroxides: Synthesis by hydrolysis in polyol medium and characterization

Nawal A Drici Setti,Noureddine Jouini,Zoubir Derriche

doi:10.24297/jac.v10i9.875

Abstract

New layered double hydroxides (LDHs) CoNiFe, ZnNiFe and CoZnFe with MII/MIII molar ratio of 3, with acetate ions in the interlayer region have been prepared by forced hydrolysis in polyol medium.The physico-chemical properties of all products were characterized by the methods of powder X-ray Diffraction, Infrared Spectroscopy, UV-Spectroscopy, Elemental analysis, Thermal analysis, Transmission Electron Microscopy and Scanning Electron Microscopy.It was found that all compounds present the typical features of hydrotalcite-like structure and exhibit a turbostratic character.The insertion of acetate anions into LDHs was confirmed and the interlayer spacing values were respectively 12.47, 13.64 and 14.69 Å for CoNiFe, ZnNiFe and CoZnFe.We notice that there is a difference between the interlayer spacing for all synthesized phases with and without zinc. This can be explained by a structural modification on the level of the layers and/ or different arrangement from the inserted species (anions + water) in the interlayer space for zinc materials.57Fe Mössbauer spectrometry allows concluding the presence of Fe3+ cations which occupy octahedral sites and confirming the absence of Fe2+ in the as-prepared compounds.

Highlights

Hydrotalcite-like compounds, called anionic clays or layered double hydroxides (LDHs) are very attractive materials for a broad range of applications [1, 2].They can be presented by the general formula [MII1-x MIIIx (OH)2]+x/n (A-n) x/n.mH2O
The samples were synthesized with a molar ratio (M/Fe) of 3 by forced hydrolysis in polyol medium according to the method described by Poul et al for elaboration of layered hydroxysalts [8]
The patterns were indexed in a hexagonal lattice with rhombohedral symmetry (R-3m), commonly used as a description of the layered double hydroxide structure [14]

Summary

Introduction

Hydrotalcite-like compounds, called anionic clays or layered double hydroxides (LDHs) are very attractive materials for a broad range of applications [1, 2].They can be presented by the general formula [MII1-x MIIIx (OH)2]+x/n (A-n) x/n.mH2O. LDHs are elaborated by several synthesis methods: coprecipitation at fixed pH and exchange reactions [4], reconstruction [5], mechanochemical process [6] and reverse microemulsion method [7]. The coprecipitation is the most commonly used method with carbonate as the intercalated anion in the most cases. It needs a precise control of several parameters mainly the pH. The carbonate anion has a great affinity toward the inorganic layer charged positively. This limits exchange reactions and the obtention of LDHs with desired intercalated anions

Methods

Results

Conclusion