Preparation of Calcium Sulfate Whisker Using Waste Residue of Phosphogypsum by Hydrothermal Method

Using waster residue phosphogypsum as raw materials, calcium sulfate whiskers were prepared by the hydrothermal method. The products were characterized by XRD, SEM and FT-IR, etc. The effects of reaction temperature and time, initial solid-to-liquid ratio of slurry, and different additives on the morphology and content of the samples´ soluble-phosphates were studied. The results showed that the optimal reaction conditions were at the temperature of 140°C, time of 2h , initial solid-to-liquid ratio of 1:10, the best additive of glycerin with dosage of Vglycerin/Vsolution=50%. The product was hexagonal CaSO₄·0.5H₂O whisker with diameter of 1~3μm and aspect ratio of 45. The synthesis rate was about 95%, and the soluble phosphate was decreased from in raw materials 0.41% to 0.21% in the products.