Solubility of Ca6[Al(OH)6]2(CrO4)3·26H2O, the chromate analog of ettringite; 5–75°C

Perkins, Robert B.; Palmer, Carl D.

doi:10.1016/s0883-2927(99)00109-2

Cited by 87 publications

(45 citation statements)

References 17 publications

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“…For instance, the solid solution between barite (BaSO 4 ) and BaCrO 4 is assumed to be ideal [31], which means that both phases are end-members of a complete solid solution [32]. Other sulfate minerals like ettringite [17,33] or jarosite [34] can also incorporate small amounts of CrO 4 2´s ubstituting SO 4 2´.…”

Section: Discussionmentioning

confidence: 99%

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The Growth of Gypsum in the Presence of Hexavalent Chromium: A Multiscale Study

et al. 2016

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Abstract:The sorption of dissolved inorganic pollutants into the structure of minerals is an important process that controls the mobility and fate of these pollutants in the Earth's crust. It also modifies the surface structure and composition of the host mineral, affecting its crystallization kinetics. Here, we investigate the effect of hexavalent chromium, Cr(VI), on the nucleation and growth of gypsum by conducting two types of experiments: (i) in situ atomic force microscopy (AFM) observations of the growth of gypsum {010} surfaces in the presence of Cr(VI) and (ii) gypsum precipitation experiments by mixing aqueous solutions containing variable amounts of Cr(VI). Gypsum precipitation is progressively delayed when occurring from solutions bearing increasing Cr(VI) concentrations. Chemical analyses of gypsum precipitates show that gypsum incorporates small Cr(VI) amounts that correlate with the content of this ion in the aqueous solution. Gypsum cell parameters variation reflects this incorporation. At the molecular scale, Cr(VI) induces a slowdown of step advance rates on gypsum {010} surfaces accompanied by the roughening of nanostep edges and the so-called "template effect". This effect involves the reproduction of the original nanotopography after the completion of individual advancing monolayers and appears as a general nanoscale phenomenon occurring during growth of solid solutions from aqueous solutions even in the case of compositionally-restricted solid solutions.

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Section: Discussionmentioning

confidence: 99%

“…Other possible solid phases, such as chromatite (CaCrO 4 ) or calcium chromate dihydrate (CaCrO 4¨2 H 2 O), were not taken into consideration due to the very high solubilities of these phases [17]. All the experiments were conducted at 25˝C and atmospheric pressure.…”

Section: Methodsmentioning

confidence: 99%

The Growth of Gypsum in the Presence of Hexavalent Chromium: A Multiscale Study

et al. 2016

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“…Chrysochoou et al (2010) indicated that the presence of organic matter (as in forest soil) or sulfides (as in pyritic material) facilitates Cr(VI) reduction to Cr(III), which can precipitate at pH > 5. Avundainayagam et al (2001) found that Ca 2+ can favor Cr(VI) retention in calcareous soils, acting as a cationic bridge on negatively charged surfaces, or by means of CaCrO 4 formation (Perkins and Palmer, 2000). Although without statistical significance, the mussel shell amendment increased Cr(VI) desorption from the granitic material (Fig.…”

Section: Sorptionmentioning

confidence: 92%

Cr(VI) sorption/desorption on untreated and mussel-shell-treated soil materials: fractionation and effects of pH and chromium concentration

et al. 2015

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Abstract. We used batch-type experiments to study Cr(VI) sorption/desorption on granitic material, forest soil, pyritic material, mussel shell, and on forest soil and granitic material amended with 12 t ha −1 (1.2 kg m −2 ) shell, considering the effects of varying Cr(VI) concentration and pH. Sequential extractions were carried out to fractionate adsorbed Cr(VI) and to determine the stability of Cr(VI) retention. The pyritic material had the highest Cr(VI) retention capacity, whereas the granitic material showed the lowest retention potential. When high Cr concentrations were added, some saturation of the adsorbent surfaces became apparent, but Cr release remained low. The highest Cr retention was achieved at a very acid pH value, with release progressively increasing as a function of increasing pH. The amendment with 12 t ha −1 mussel shell did not cause marked changes in Cr(VI) retention. Sorption data were satisfactory adjusted to the Freundlich model. Regarding Cr(VI) fractionation, the soluble fraction (weakly bound) was dominant in mussel shell and in the unamended and amended granitic material, whereas more stable fractions dominated in the pyritic material (residual fraction) and in the forest soil (oxidizable fraction). In conclusion, the pyritic material presented the highest Cr(VI) retention capacity, while the retention was low and weak on the granitic material; mussel shell was not characterized by a marked Cr(VI) retention potential, and it did not cause remarkable increase in Cr(VI) retention when used to amend the granitic material or the forest soil.

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“…This was performed for both the ash waters and the resulting mixing solutions. To the database was added the following solid phases: schwertmannite (Yu et al 1999), ettringite (Myneni et al 1998), chromate hydrocalumite (Perkins and Palmer 2001), chromate ettringite (Perkins and Palmer 2000), barium sulfochromate 1 (Ba(S 0.77 Cr 0.23 )O 4 ) and barium sulfochromate 2 (Ba(S 0.96 Cr 0.04 )O 4 ) (Fällman 1997). Saturation index (SI) is defined as the logarithmic representation of the ratio between the ion activity product and the solubility constant (K so ).…”

Section: Geochemical Calculationsmentioning

confidence: 99%

Mixing of Acid Rock Drainage with Alkaline Ash Leachates—Fate and Immobilisation of Trace Elements

Bäckström

Sartz

2011

Water Air Soil Pollut

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Acid rock drainage (ARD) often contains ferrous iron, sulphate and high concentrations of trace elements detrimental to the environment. Future costs will be enormous if the problem is not treated today. Simple and cost-effective methods for remediation of historical mine sites are therefore desired. In this study, three mine waters were mixed with alkaline ash leachates, and the fate of trace elements from both the mine waters (Cd, Cu, Pb, Zn, Ni and Co) and the ash leachates (Cr and Mo) was studied. Addition of ash water precipitates hydrous ferric oxides (HFO) and hydrous aluminium oxides (HAO) induced trace element sorption and coprecipitation. Composition of the formed HFO/HAO mix determines efficiency of the sorption and the relative order of sorption for different trace elements. Sorption occurred much earlier (often one pH unit or more) in a system with high iron concentrations compared to systems with lower iron concentrations. Removal of cadmium and zinc was low, below pH 8, if the amount of precipitates was low. Using ash for generation of alkaline water may be a problem with regard to chromium and molybdenum. This study shows that it is possible to avoid problems with molybdenum by keeping the final pH around 7, and chromium(VI) from the ash water will be reduced into chromium(III) and precipitated as the hydroxide in the presence of iron(II). Results imply that it is possible to also use fly ashes in alkaline leach beds in order to neutralize ARD followed by precipitation and sorption of trace elements.

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Solubility of Ca6[Al(OH)6]2(CrO4)3·26H2O, the chromate analog of ettringite; 5–75°C

Cited by 87 publications

References 17 publications

The Growth of Gypsum in the Presence of Hexavalent Chromium: A Multiscale Study

The Growth of Gypsum in the Presence of Hexavalent Chromium: A Multiscale Study

Cr(VI) sorption/desorption on untreated and mussel-shell-treated soil materials: fractionation and effects of pH and chromium concentration

Mixing of Acid Rock Drainage with Alkaline Ash Leachates—Fate and Immobilisation of Trace Elements

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