Precipitation of Strontium Sulphate

Sühnel, Otakar; Handlířová, Marie

doi:10.1002/crat.2170190407

Cited by 9 publications

(2 citation statements)

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“…Furthermore, published values for celestite surface area vary between 0.44 and 72.7 m 2 g −1 (e.g. [ 34 , 35 ]). In addition, two commercially available powders were measured with N 2 -BET and were found to have surface areas of 0.525 and 0.998 m 2 g −1 , respectively.…”

Section: Resultsmentioning

confidence: 99%

Mineral precipitation-induced porosity reduction and its effect on transport parameters in diffusion-controlled porous media

et al. 2015

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BackgroundIn geochemically perturbed systems where porewater and mineral assemblages are unequilibrated the processes of mineral precipitation and dissolution may change important transport properties such as porosity and pore diffusion coefficients. These reactions might alter the sealing capabilities of the rock by complete pore-scale precipitation (cementation) of the system or by opening new migration pathways through mineral dissolution. In actual 1D continuum reactive transport codes the coupling of transport and porosity is generally accomplished through the empirical Archie’s law. There is very little reported data on systems with changing porosity under well controlled conditions to constrain model input parameters. In this study celestite (SrSO4) was precipitated in the pore space of a compacted sand column under diffusion controlled conditions and the effect on the fluid migration properties was investigated by means of three complementary experimental approaches: (1) tritiated water (HTO) tracer through diffusion, (2) computed micro-tomography (µ-CT) imaging and (3) post-mortem analysis of the precipitate (selective dissolution, SEM/EDX).ResultsThe through-diffusion experiments reached steady state after 15 days, at which point celestite precipitation ceased and the non-reactive HTO flux became constant. The pore space in the precipitation zone remained fully connected using a 6 µm µ-CT spatial resolution with 25 % porosity reduction in the approx. 0.35 mm thick dense precipitation zone. The porosity and transport parameters prior to pore-scale precipitation were in good agreement with a porosity of 0.42 ± 0.09 (HTO) and 0.40 ± 0.03 (µ-CT), as was the mass of SrSO4 precipitate estimated by µ-CT at 25 ± 5 mg and selective dissolution 21.7 ± 0.4 mg, respectively. However, using this data as input parameters the 1D single continuum reactive transport model was not able to accurately reproduce both the celestite precipitation front and the remaining connected porosity. The model assumed there was a direct linkage of porosity to the effective diffusivity using only one cementation value over the whole porosity range of the system investigated.ConclusionsThe 1D single continuous model either underestimated the remaining connected porosity in the precipitation zone, or overestimated the amount of precipitate. These findings support the need to implement a modified, extended Archie’s law to the reactive transport model and show that pore-scale precipitation transforms a system (following Archie’s simple power law with only micropores present) towards a system similar to clays with micro- and nanoporosity.Graphical abstract:Electronic supplementary materialThe online version of this article (doi:10.1186/s12932-015-0027-z) contains supplementary material, which is available to authorized users.

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Section: Resultsmentioning

confidence: 99%

Mineral precipitation-induced porosity reduction and its effect on transport parameters in diffusion-controlled porous media

et al. 2015

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“…Despite the fact that the system has been intensively investigated over the past three decades many aspects await reliable answers. A considerable amount of the published literature is concerned with batch, seeded growth studies, − investigations in various hydrodynamic conditions, − and spontaneous precipitation experiments. − The solution chemistry of the aqueous media in which the various calcium sulfate hydrates form is very important and needs to be carefully considered in order to quantify the mechanisms of the formation of the various calcium sulfate forms. Calcium sulfate may crystallize as gypsum (CaSO 4 ·2H 2 O, CSD), calcium sulfate hemihydrate (CaSO 4 · 1 / 2 H 2 O, CSH) and anhydrite (CaSO 4 , CSA).…”

Section: Introductionmentioning

confidence: 99%

Role of Temperature in the Spontaneous Precipitation of Calcium Sulfate Dihydrate

1999

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The spontaneous precipitation of calcium sulfate in supersaturated solutions over the temperature range between 25.0 and 80.0°C was investigated by monitoring the solution specific conductivity during desupersaturation. From measurements of the induction times preceding the onset of precipitation the surface energy of the forming solid, identifield as gypsum, was found between ca. 12 and 25 mJ m -2 for the temperature range between 80.0 and 25.0°C, respectively. Kinetics analysis showed that over 50°C it is possible that anhydrous calcium sulfate is forming as a transient phase converting into the more stable calcium sulfate dihydrate. The linear dependence of the rates of precipitation on the relative solution supersaturation suggested a mechanism according to which the growth units are integrated into the active sites of the supercritical nuclei by surface diffusion. According to the morphological examination of the crystals it is possible that crystal growth occurs by the advancement of steps.

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Experimental investigation of precipitation reactions under homogeneous mixing conditions

Manth

Mignon

Offermann

1996

Chemical Engineering Science

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Precipitation of Strontium Sulphate

Cited by 9 publications

References 30 publications

Mineral precipitation-induced porosity reduction and its effect on transport parameters in diffusion-controlled porous media

Mineral precipitation-induced porosity reduction and its effect on transport parameters in diffusion-controlled porous media

Role of Temperature in the Spontaneous Precipitation of Calcium Sulfate Dihydrate

Experimental investigation of precipitation reactions under homogeneous mixing conditions

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