Synthesis of Struvite in Aqueous-Salt Systems in which Competing Phases of Magnesium Phosphate Crystal Hydrates of Different Compositions Can Be Formed

• Published in: Russian journal of applied chemistry 2021-11, Vol.94 (11), p.1469-1482
• Main Authors: Kuznetsova, Yu. V., Vol’khin, V. V., Permyakova, I. A.
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Composition; Crystal structure; Hydrates; Industrial Chemistry/Chemical Engineering; Inorganic Synthesis and Industrial Inorganic Chemistry; Ion exchange; Magnesium phosphate; Solid phases; Supersaturation; Thermodynamic equilibrium
• ISSN: 1070-4272; 1608-3296
• DOI: 10.1134/S1070427221110021

Thermodynamic, kinetic, and structural approaches were combined to reveal the major factors determining the phase formation in aqueous-salt systems in which crystal hydrates of different compositions can be formed. The solution supersaturation indices with respect to magnesium phosphate crystal hydrates of different compositions were calculated by modeling of chemical equilibria, and the thermodynamic probability of the formation of their solid phases in aqueous-salt systems of different compositions was refined using these data. Primary precipitation of metastable struvite under the conditions of its possible competition with other, more stable phases was substantiated. A decrease in the content of ammonium ions in struvite was accounted for by isomorphic substitution of NH 4 + ions in the solid phase by the x Н + – x ʹН 2 O group without changes in the struvite structure, and the possibility of reverse saturation of struvite with ammonium ions by ion exchange was demonstrated.