Synthesis of MnPO4·H2O by refluxing process at atmospheric pressure

Serrabrancaite (MnPO4·H2O) was synthesized by oxidizing Mn(H2PO4)2 with NaClO solution using a refluxing process at atmospheric pressure, and a mixed solution of MnCl2 and H3PO4 could substitute for Mn(H2PO4)2 in the process. The products were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. Hureaulite was formed when single solution of Mn(H2PO4)2 was refluxed for 12 h at 60 °C. Rodlike hureaulite was fabricated by refluxing reaction of 30 mmol Mn(H2PO4)2 and 60 mmol NaClO solution with adding hydrochloric acid within 40 mmol. Granular hureaulite was formed by refluxing of 30 mmol MnCl2 and 60 mmol NaClO solution with adding phosphoric acid within 30 mmol. For the two above-mentioned reaction systems, MnPO4·H2O was prepared by adding hydrochloric acid no less than 80 mmol and phosphoric acid no less than 60 mmol respectively. MnPO4·H2O yield increased with elevating reflux temperature, and increased firstly and then decreased with increasing additional amount of acid. The highest recovery yield of MnPO4·H2O reached 84.1% when Mn(H2PO4)2 was performed as bivalent manganese source, and approached 74.0% when MnCl2 and H3PO4 were used instead.

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