The Optimal Conditions of Preparation of Phosphogypsum-Based Calcium Sulfate Hemihydrate Whiskers by Hydrothermal Method Using Phosphogypsum

Calcium sulfate hemihydrate whisker was prepared successfully by hydrothermal method with phosphogypsum; the morphology and synthesis rate of calcium sulfate hemihydrate whisker were very sensitive to reaction temperature, reaction time, and additives. Therefore, L25(5(6)) orthogonal experiments were carried out to obtain the optimal conditions. Composition, morphology, and structure of calcium sulfate hemihydrate whisker were characterized by SEM, XRD, and FT-IR. The results showed that the optimal conditions were ball-milling time 1.5 h, reaction temperature 160 degrees C, reaction time 2 h, solid liquid mass ratio 1:20, V (glycerol)/V (solution) = 10 %, and drying temperature 140 degrees C. Calcium sulfate hemihydrate whisker synthesis rate was 95 %; its aspect ratio was up to 45.