Obtaining Ca(H2PO4)2·H2O, monocalcium phosphate monohydrate, via monetite from brushite by using sonication

Brushite was synthesized by precipitation of calcium chloride (CaCl2) and sodium phosphate monobasic (Na2HPO4) dried in vacuum and monetite was obtained from this brushite by sonication with a frequency of 90 kHz at 500 W for 90 min. Monetite itself was also transformed in Ca(H2PO4)2·H2O, monocalcium phosphate monohydrate (MCPM), by sonication with a frequency of 90 kHz at 500 W for 60 min followed by lyophilization. The MCPM was sonicated and lyophilized by three times more until reach over 240 min, but any other phase transformation was observed. All these phase transformations were analyzed by X-ray diffraction (XRD) and infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated a grain size of about 200 nm in all the samples. The morphology observed was a corn-flake-like grain for brushite, a pseudo-needle-like grains for monetite, and lamellar-like grains for MCPM.

► MCPM was obtained by sonication followed by lyophilization of monetite.
► Monetite was obtained by sonication of brushite.
► Brushite was synthesized by precipitation of calcium chloride and sodium phosphate monobasic.
► Sonication was done at 500 W and a frequency of 90 kHz.
► The phase transformation by sonication implies the unit cell change of the material.