ISSN print edition: 0366-6352
ISSN electronic edition: 1336-9075
Registr. No.: MK SR 9/7
Preparation of magnesium hydroxide from nitrate aqueous solution
Pavel Fellner, Ján Híveš, Vladimír Khandl, Milan Králik, Jana Jurišová, Tibor Liptaj, and Ladislav Pach
Institute of Inorganic Chemistry, Technology, and Materials, Slovak University of Technology in Bratislava, Radlinského 9, Bratislava, SK-812 37 Slovakia
Abstract: Nucleation of Mg(OH)2 was investigated by measuring the electrical conductivity and pH of the Mg(NO3)2 reaction solution to which ammonia containing different amounts of NH4NO3 was added. NH4NO3 increases solubility and slows down precipitation of Mg(OH)2 in the system. Data are presented on the influence of NH4NO3 on the solubility of Mg(OH)2 at 25°C. The phenomena observed can be explained by the solvation effect of nitrate ions brought to the system with the addition
of ammonium nitrate, which was proved by NMR spectroscopy. When the mass fraction of NH4NO3 exceeds 15 %, homogeneous nucleation does not proceed. It was found that seeding of the system with Mg(OH)2 crystals only influenced the rate of Mg(OH)2 crystallisation, not the size and shape of the crystals. Primary crystals are smaller than 0.1 μm. The large difference in
the surface energy of individual crystal planes leads to oriented agglomeration. This process is accelerated in a pressure
reactor at 130°C. The resulting polycrystals are hexagonal plates 0.2 μm thin with a diameter of 1–2 μm. Under variable reaction
conditions, agglomerates as big as 30 μm can be prepared.
Keywords: Mg(OH)2 – precipitation – nitrate – electrical conductivity – NMR
Full paper is available at www.springerlink.com.
Chemical Papers 65 (4) 454–459 (2011)