New insights into the nucleation of magnesium hydroxide and the influence of poly(acrylic acid) during the early stages of Mg(OH)2 crystallisation. Issue 44 (14th October 2022) - Scheck, J.
Abstract : Potentiometric titrations and transmission electron microscopy reveal the complex mechanisms of magnesium hydroxide formation from solution and show how polycarboxylates may interfere with the process and alter the properties of the final product. Abstract : Nucleation is a unique process with broad relevance across a wide range of scientific disciplines and applications. While considerable progress in the understanding of the mechanisms underlying the nucleation of minerals from solution has been made for popular model systems such as calcium carbonate, corresponding detailed insights are still missing for other, less prominent minerals. Here, we present a potentiometric titration-based method that allows the early stages of the crystallisation of brucite, Mg(OH)2, to be monitored and quantified. Together with complementary characterisation provided by (cryogenic) transmission electron microscopy, the collected data shed novel light on the species occurring prior to, during, and after nucleation of brucite. In the second part of the work, the newly developed approach was applied to investigate the effects of added poly(acrylic acid) on the different stages of the crystallisation process. The polymer is found to stabilise brucite nanoplatelets and co-precipitate with the inorganic phase, yielding a composite material. The methodology established in this study can readily be used to screen other chemistries for their ability to prevent magnesium hydroxide scaling and/or afford brucite nanomaterials with tailored properties.