I. V. Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials of the Russian Academy of Sciences Kola Science Center (IHTREMS KNC RAN)

V. A. Matveev, Senior Researcher

V. I. Zakharov, Head of Laboratory

D. V. Mayorov, Senior Researcher, e-mail: mayorov@chemy.kolasc.net.ru

Published data have been analyzed to consider the mechanism of pseudoboehmite production from aluminium salt acidic solutions attacked by basic reagent. It has been shown that producing hydrated aluminium oxides as pseudoboehmite should involve limiting of the mobility of aluminium aquaions during hydrolysis in order to prevent, or reduce to minimum, their polymerization. Analysis of the structure of aluminium crystal hydrate salts has revealed that each aluminium cation in them, the same as in solution, is surrounded by six water molecules. This suggests that hydrolysis can proceed by the mechanism of aluminium aquacomplex deprotonation in the presence of gaseous ammonia. The results of solid-phase hydrolysis of potassium alums have allowed to develop a principally new method for the production of aluminium hydroxide with the structure of pseudoboehmite incorporating treating of potassium alums with gaseous ammonia, leaching of the ammonization product with washing circulating solutions, separating of the hydrated aluminium oxide precipitate followed by its ageing in ammonia solutions at pH of no less than 10. The resulting pseudoboehmite has a specific surface of 260–360 m²/g at impurity contents in the range of, mass %: Fe₂O₃ — 0.015–0.025; K₂O — 0.03–0.05; SiO₂ — 0.02–0.035; SO₃ — 0.6–1.1, l.o.i. — 32–40%. These characteristics are high enough for using the material in the production of catalysts, adsorbents and dehumidifiers. The possibility of side production of an NK product containing 14–14.5 nitrogen and 15–15.5 K₂O applicable as a component of complex fertilizers is outlined.

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