Abstract
The transformation of struvite MgNH4PO4 · 6H2O into newberyite MgHPO4 · 3H2O is studied in aqueous solutions at 25° C and 37° C by following the evolution of solutions, supersaturated with respect to both phases in the concentration range 0.025–0.50 M. The precipitation of struvite as the first phase is accompanied by a sharp decrease of pH, which subsequently remains constant. During this period, newberyite crystals can nucleate whereas struvite is dissolving. Another decrease of pH, due to the newberyite growth, is observed when almost all struvite has disappeared. Finally pH tends asymptotically to a constant value, corresponding to a stable equilibrium. The whole process may take several months. At neither stage were epitaxial relationships observed between struvite and newberyite. The shape of the newberyite crystals is an indicator of their origin in mineralogical and biological systems.
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Boistelle, R., Abbona, F. & Lundager Madsen, H.E. On the transformation of struvite into newberyite in aqueous systems. Phys Chem Minerals 9, 216–222 (1983). https://doi.org/10.1007/BF00311958
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DOI: https://doi.org/10.1007/BF00311958