Precipitation Of Calcium Sulfate Dihydrate Research Articles

Effects of additives on morphology of precipitated calcium sulfate and calcium sulfite — implications on slurry properties

The presence of active compunds, such as nitrilotri (methylene phosphonic acid), during precipitation of calcium sulfate dihydrate and calcium sulfite hemihydrate can cause modifications of particle morphology. Generally, the altered particles are larger with a reduced aspect ratio. Aqueous suspensions of such particles exhibit enhanced rates of filtration and sedimentation. This technique to facilitate dewatering may prove to be an attractive alternative to conventional methods of addressing sludge management.

Study on the Process of Precipitation of Calcium Sulfate Dihydrate from Aqueous Solution by Calcium Ion Electrode

Study on the Process of Precipitation of Calcium Sulfate Dihydrate from Aqueous Solution by Calcium Ion Electrode

The precipitation of calcium sulphate dihydrate from aqueous solution: Induction periods, crystal numbers and final size

The precipitation of calcium sulphate dihydrate was studied from solutions of concentration ( C) from 0.02 to 0.24 M, supersaturation ( S) from 1.5 to 16, by optical microscopy and chemical analysis; induction periods, final crystal lengths and numbers were measured. The induction periods ( t̄) decreased from 12000 to 3 sec over this range; t̄ varied with C according to the relation t ̄ = K t/▿C 4 . The crystal numbers ( N) varied with C according to the relation N = K N C 7. The final crystal lengths decreased from 3 to 0.15 cm over this range. The precipitations occured through a heterogeneous nucleation process. Heterogeneous nuclei were formed immediately after mixing and then grew, by a slow growth process, to small crystallites during the induction periods: these latter then grew by a more rapid growth process to the large crystals. The “reaction order” for the nucleation was 9–10; the “order” of the slow growth process was 4.

Observations on calcium sulphate dihydrate formed in media rich in phosphoric acid. I. Precipitation of calcium sulphate dihydrate

AbstractA study has been made of the properties of the products of digesting calcium sulphate hemihydrate in media containing finally 29·4% P2O5. Hydration to the dihydrate occurred at temperatures between 35° and 65°. The product was almost phosphate‐free when the reaction was carried out between 52·5° and 57·5°.