Synthesis of hureaulite by a reflux process at ambient temperature and pressure

Hureaulite was first successfully synthesized by reflux reactions of Mn(H2PO4)2 and MnCl2/H3PO4/NaClO solutions at 40–100 °C under atmospheric pressure. Powder X-ray diffraction (XRD), Rietveld structure refinement, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were utilized to characterize the crystal structures and morphologies of the products. Cell parameters of the as-prepared hureaulites were compared with those formed by hydrothermal reaction. Hureaulites obtained from different reaction systems exhibited various morphologies. Rod-like hureaulite was synthesized from a mixture of 30 mmol H3PO4 and 100 mL of 0.3 mol L−1 Mn(H2PO4)2 solution with or without NaClO solution to the system at 100 °C. However, hureaulite could only be formed from the MnCl2 and H3PO4 solutions by the addition of NaClO solution. The formation mechanism of hureaulite was investigated by refluxing 100 mL of 0.3 mol L−1 Mn(H2PO4)2 solution at 40 °C. A mixture of hureaulite and MnHPO4·3H2O was formed, and the former was approximately 59.24% and 86.11% by mass as the reflux reaction lasted for 12 and 24 h, respectively. Single-phase hureaulite was formed when the reaction was prolonged up to 48 h at 40 °C. Results of Rietveld structure refinement showed that the lattice parameters were compressed in the c direction and β decreased, and the crystal density increased as the reflux temperature was increased. The present work facilitates a thorough knowledge of the natural genesis of hureaulite, and the preparation and applications of hureaulite in the field of materials science and chemistry.

Hureaulite was prepared by refluxing Mn(H2PO4)2 and MnCl2/H3PO4/NaClO solutions at 40–100 °C under atmospheric pressure. MnHPO4·3H2O worked as an intermediate product.Figure optionsDownload as PowerPoint slideHighlights
► A facile method for the preparation of hureaulite by reflux at ambient temperature and pressure.
► Hureaulite crystal density increased with an increase in reaction temperatures.
► A new knowledge on the formation process of hureaulite in the natural environment.