Optimisation of the synthesis parameters of mechanochemically prepared CaAl-layered double hydroxide

•Synthesis of CaAl-LDH by manual grinding and two-step milling•Identifying the optimum synthesis parameters•Characterisation of the sample prepared under optimal conditions

In this work, not so commonly used methods, manual grinding and milling, were applied in an attempt of preparing phase-pure CaAl-LDH (CaAl-layered double hydroxide). For manual grinding a mortar and a pestle and the components with some added water or NaOH solution were used. Milling was a two-step procedure: dry milling was followed by milling in the presence of minute (and controlled) amount of water. The thus prepared samples were characterised by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). It was proven that even though manual grinding did produce LDH, only mechanochemical energy provided by the two-step milling procedure was able to transform the precursors nearly completely to CaAl-LDH. Optimisation of the milling parameters could reproducibly lead to close-to-phase-pure CaAl-LDH.