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Synthesis of α-hemihydrate gypsum from cleaner phosphogypsum

Ma, Baoguo, Lu, Wenda, Su, Ying, Li, Yubo, Gao, Chao, He, Xingyang
Journal of cleaner production 2018 v.195 pp. 396-405
atmospheric pressure, byproducts, calcium chloride, phosphogypsum, strength (mechanics), wastes
Phosphogypsum (PG), as a waste by-product with high content and complicated impurities, is difficult to be utilised effectively. Herein, cleaner PG is prepared with “HClH2SO4 method”, and thus is used to synthesise α-hemihydrate gypsum (α-HH) in CaCl2 solution under atmospheric pressure. Morphology and mechanical strength are controlled by introducing varying dosages of modifier (0–0.06 wt% of the PG). Results show that reaction time extends from 120 min to 390 min and average length/diameter (L/D) ratio of α-HH crystal is decreased from 10.3 to 0.6 with the increase in the modifier dosage from 0 to 0.045 wt%. When the modifier dosage is 0.04 wt%, the converted product shows the best mechanical performance and fine commercial application prospect. The impurity content of α-HH synthesised from cleaner PG significantly decreases to approximately 5% of that from traditional PG. The mechanical strength of α-HH prepared from cleaner PG is better than that from traditional PG. The work presents a new and practical method to utilise PG efficiently.