Hydrothermal synthesis of nanocrystalline hydroxyapatite from phosphogypsum waste

Hydroxyapatite (HAp) nanorods are synthesized from phosphogypsum waste (PG) and potassium dihydrogen phosphate (KH2PO4) under hydrothermal conditions. The influence of several synthesis parameters such as temperature (100-200 degrees C), synthesis time (1-15 h), and solution pH (5-11) on product structure and purity is addressed by X-ray diffraction and Fourier Transformed-Infrared Spectroscopy. Phase-pure HAp nanorods with diameter and length of 18 and 63 nm, respectively, are obtained after 10 h at 200 degrees C and pH similar to 11. The influence of Brij-93 surfactant on the morphology of prepared HAp is investigated by transmission and scanning electron microscopy. The aspect ratio and the mean size of HAp crystals increase to 1013 and 205 x 20 nm, respectively, with increasing the concentration of Brij-93 surfactant to 0.01 mol. Hence, the PG recycling could be accomplished using an easy synthesis route with relatively cheap reactants for the production of nanocrytalline HAp.