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

Abstract

a b s t r a c tIn 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.

Exploring the Wet Mechanochemical Synthesis of Mg-Al, Ca-Al, Zn-Al and Cu-Al Layered Double Hydroxides from Oxides, Hydroxides and Basic Carbonates

“…Ca-Al LDH synthesised in the presence of a carbonate source formed more readily when compared to that synthesised with no CaCO 3 . Previous studies have shown that Ca-Al LDH and katoite (tricalcium aluminate) can result when reacting Ca(OH) 2 and Al(OH) 3 in the absence of an additional phase or carbonate source, with little to no LDH formation occurring at times [11,21,29]. Studies have also shown that, upon the addition of a third phase such as CaCO 3 or CaCl 2 •2H 2 O LDH, formation occurs more readily with little to no katoite formation.…”

“…The most common types of mechanochemical synthesis techniques include single-step or one-pot grinding [5,6], mechano-hydrothermal synthesis [7][8][9][10] and two step grinding. Two-step grinding can consist of an initial grinding step followed by an additional treatment step or a second grinding step [11][12][13]. Grinding of raw materials can be conducted wet, dry or as a paste.…”

“…Various techniques and combinations involving the wet or dry milling of raw materials have been attempted and found to be successful [2]. Studies have shown that the type of grinding technique can largely affect the success of LDH synthesis, with some techniques not producing sufficient mechanical energy for the synthesis to occur readily [11]. Research has indicated that a large amount of mechanochemical methods explored typically involve the use of ball mills, mixer mills or a mortar and pestle as the primary grinding technique [2].…”

Synthesis and formulation of functional bionanomaterials with superoxide dismutase activity

“…26 Although LDHs are less frequent than the cationic clays in nature, their synthesis is simple even in large amount and various methods are available. [27][28][29][30][31][32] The structure of the LDHs is based on Mg(OH) 2 (brucite) of octahedral coordination around the metal ions. The Mg 2+ can be substituted with trivalent cations (e.g., Al 3+ and Fe 3+ ) of similar coordination properties.…”

Applications of Mechanochemically Prepared Layered Double Hydroxides as Adsorbents and Catalysts: A Mini-Review

“…Ferencz et al [37] attempted to manufacture Ca-Al LDH by manual grinding and ball milling of Al(OH) 3 and Ca(OH) 2 . The manual milling operation failed to produce Ca-Al LDH, but the two-step milling process gave a pure phase of Ca-Al LDH.…”