Crystallization kinetics of gypsum from dense suspension of hemihydrate in water

Amathieu, L.; Boistelle, R.

doi:10.1016/0022-0248(88)90275-8

Cited by 74 publications

(65 citation statements)

References 21 publications

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“…Amathieu and Boistelle [10] studied crystallization kinetics of calcium sulfate dihydrate both in homogeneous and in heterogeneous conditions. The authors showed that t ind strongly depends on the supersaturation (σ), decreasing from 1,200 to 60 s when σ increases from 4 to 7.…”

Section: Introductionmentioning

confidence: 99%

Crystallization of calcium sulfate dihydrate at different supersaturation ratios and different free sulfate concentrations

Abdel-Aal

Rashad

El‐Shall

2004

Cryst. Res. Technol.

104

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Free Sulfate is a major parameter affecting gypsum crystallization during phosphoric acid production. Gypsum crystal size, shape and filtration rate are significantly affected by the concentration of free sulfate. It is, therefore, important to evaluate the effectiveness of different sulfate levels from 1.5% to 3.5% on induction time and gypsum morphology. The crystallization of gypsum was carried out under simulated conditions of phosphoric acid production by the dihydrate process. Calcium hydrogen phosphate and sulfuric acid were mixed with dilute phosphoric acid at 80 o C, and the turbidity of the reaction mixture was measured at different time periods to calculate the induction time of gypsum crystals formation. With increasing free sulfate concentration, the induction time was significantly decreased. Chemical processing of Central and South Florida phosphate concentrates under different concentrations of free sulfate from 1.5% to 5.5% was carried out. The change on crystal size distribution and filtration rate were traced with free sulfate concentrations. The results show that, filtration rate of phosphogypsum was correlated to the mean diameter of crystals. In addition, induction time and co-crystallized (lattice) P 2 O 5 % in gypsum are decreased with increasing free sulfate content from 1.5% to 3.5%. Morphology of formed gypsum crystals at different sulfate contents and different supersaturation ratios are investigated.

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Section: Introductionmentioning

confidence: 99%

Crystallization of calcium sulfate dihydrate at different supersaturation ratios and different free sulfate concentrations

Abdel-Aal

Rashad

El‐Shall

2004

Cryst. Res. Technol.

104

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“…Amathieu and Boistelle 19) investigated the amounts of dissolving bassanite as a function of time. They reported that about 42 g/L of bassanite was immediately dissolved.…”

Section: Dissolution Of Bassanitementioning

confidence: 99%

“…In our experiment, the amount of bassanite in the waste calcite could be estimated to be 0. mol/L). 19) The dissolution of the bassanite could proceed according to eq. (4).…”

Section: Dissolution Of Bassanitementioning

confidence: 99%

Enhanced Cd(II) Uptake by the Bassanite Phase Contained in Waste Calcite Produced via the Carbonation of Flue Gas Desulfurization (FGD) Gypsum

et al. 2011

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The uptake of Cd(II) by waste calcite, a by-product of the carbonation of flue gas desulfurization (FGD) gypsum, was investigated in a batch experiment. The uptake of Cd(II) by and the dissolution of Ca(II) from the waste calcite particles were monitored simultaneously as a function of exposure time to 0.89 mM Cd(II) solution. The reagent-grade calcite particles were also examined for a comparative study. The waste calcite contained bassanite, dolomite, and muscovite as the major impurity phases. X-ray diffraction study revealed that the bassanite phase dissolved almost completely during the 1st hour of the exposure to the solution while other phases were intact for two days. The amount of removed Cd(II) was found to be proportionally related to dissolved Ca(II) reflecting the exchange nature of the adsorption. The use of waste calcite instead of reagent-grade calcite enhanced Ca(II) dissolution and thereby Cd(II) uptake significantly. The waste calcite removed about 90% of initial Cd(II) while reagent calcite removed only 6% during the exposure for 2 days to 0.89 mM Cd(II) solution. The enhanced Ca(II) dissolution and Cd(II) uptake by the waste calcite were attributed to the fast-dissolving bassanite phase which provides the substantial quantity of Ca(II) and sulfate ions to the calcite/solution interface.

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“…The growth kinetics of gypsum (calcium sulfate dihydrate, CSD) has been investigated at equivalent calcium sulfate concentration by a number of workers (Liu and Nancollas 1970, Smith and Sweett 1971, Nancollas 1973, Liu and Nancollas 1973, Christoffersen and Christoffersen 1982, Amathieu and Boistelle 1988, Witkamp et al 1990). However, in most practical applications, such as scale formation , gypsum wallboard manufacture (Ridge 1960), and phosphoric acid production (Stevens 1961), gypsum crystallization proceeds in a nonstoichiometric medium.…”

Section: Rate Determinationmentioning

confidence: 99%

Precipitation and Dissolution of Alkaline Earth Sulfates: Kinetics and Surface Energy

Hina

Nancollas

2000

Reviews in Mineralogy and Geochemistry

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Crystallization kinetics of gypsum from dense suspension of hemihydrate in water

Cited by 74 publications

References 21 publications

Crystallization of calcium sulfate dihydrate at different supersaturation ratios and different free sulfate concentrations

Crystallization of calcium sulfate dihydrate at different supersaturation ratios and different free sulfate concentrations

Enhanced Cd(II) Uptake by the Bassanite Phase Contained in Waste Calcite Produced via the Carbonation of Flue Gas Desulfurization (FGD) Gypsum

Precipitation and Dissolution of Alkaline Earth Sulfates: Kinetics and Surface Energy

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