Facile synthesis of pyroaurite-type Co-Fe layered double hydroxides for anionic dye adsorbents

Layered double hydroxides (LDHs) are characterised by the two-dimensional lamellar-stacking structure through weak interactions and have attracted great interest because of their extensive applications as ion-exchanging carriers, adsorbents, precursors of metal oxide catalysts etc. In this work, a facile hydrothermal route has been developed to synthesise novel pyroaurite-type Co-Fe LDHs, with a formula of Co^II_5.84Fe^III_2.16(OH)₁₆(CO₃)_1.08 · 0.32H₂O, using lysine (Lys) molecules as the directing reagent. Co-Fe LDH nanostructures obtained were characterised by means of a scanning electron microscope, transmission electron microscopy, X-ray diffraction, fourier transform infrared and thermogravimetric analysis. Furthermore, the adsorption performance of Co-Fe LDH nanostructures, both the flower-like and octahedral structure, was assessed using different dyes as the model. The results demonstrate that pyroaurite-type Co-Fe LDHs exhibit excellent adsorption performance on anionic dyes (such as Methyl orange, Congo red and Acid blue 80) in aqueous solution, indicating great potential for the removal of anionic organic contaminants from the industrial effluents.