Abstract
Synthesis of sodium magnesium phosphates by an oxidative decomposition method of EDTA-metal chelate with hydrogen peroxide were investigated. Three new compounds and trimagnesium phosphate pentahydrate (TMP5) were obtained. These compounds are NaMg7 (PO4) 5·12H2O (described as NNa-1), NaMg2 (PO4) (HPO4) ·3H2O (described as NNa-2) and NaMg4 (PO4) 3·6H2O (described as NNa-3), and these structures are orthorhombic, monoclinic and orthorhombic (or monoclinic), respectively.
These compounds are obtained by controlling the concentrations of Na+, Mg2+ and oxo-phosphate ions as mono phase of each compound. NNa-1 was successfully obtained by allowing to react the solution with the conditions of high pH, R value (Mg2+ /PO43- molar ratio) =1.0 and lower concentration of sodium ion, NNa-2 was obtained under the condition of R value = 0.1, and NNa-3 was obtained under the conditions of R value=1.0 and higher concentration of sodium ion.
