Growth mechanism and process intensification of Ni-Al-layered double hydroxide synthesized via coprecipitation

This work systematically investigated the crystallization process of NiAl-layered double hydroxide (NiAl-LDH) with a Ni(II)/Al(III) ratio of 3 under different crystallization conditions. The results showed that the prepared NiAl-LDH first exhibits sheet-like morphology, which transforms into a hexagonal platelet with further growth. The lateral size and thickness of the prepared NiAl-LDH are ~10–284 nm and ~2–31 nm, respectively. Based on the evolution of morphology, particle size and crystallinity, the growth mechanism of NiAl-LDH was first proposed. The growth of NiAl-LDH in the lateral dimension was governed by Ostwald ripening, while the increase in c direction was dominated by oriented particle attachment before precipitation and dissolution equilibrium. Afterward, the growth of NiAl-LDH was dominated by the oriented particle attachment, leading to further growth of NiAl-LDH. Moreover, a rotating packed bed (RPB) was first adopted to crystallize NiAl-LDH. The results show that RPB can greatly enhance the growth of NiAl-LDH.