Experimental determination and modeling of gypsum and insoluble anhydrite solubility in the system CaSO4–H2SO4–H2O

Wang, Wenlei; Zeng, Dewen; Chen, Qiyuan; Yin, Xiang

doi:10.1016/j.ces.2013.06.023

Cited by 54 publications

(59 citation statements)

References 21 publications

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“…Anhydrite binders can be obtained by high-temperature firing of gypsum stone as well as by fine grinding of anhydrite stone with the addition of hardening activators. At the same time, the properties of anhydrite, both artificial and natural, are significantly different from that of gypsum binder Wang et al, 2013) due to greater reactivity and surface activity.…”

Section: Introductionmentioning

confidence: 98%

A Study on Mechanical Properties and Structure of Anhydrite Binder Modified by Ultra-Dispersed Siltstone

Tokarev

Yakovlev

Saidova

et al. 2020

Engineering Structures and Technologies

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This research is devoted to modification of physical and mechanical properties and structure of a binder based on natural anhydrite. A sedimentary rock siltstone was added into the composition as a mineral ultrafine additive. The presence of aluminosilicate minerals proves that finely ground siltstone can be used as a mineral additive in the composition of the anhydrite binder, accelerating crystallization of gypsum new formations and densifying the structure of gypsum stone. For the first time, the effectiveness of using sodium and ammonium phosphates as hardening activators of an anhydrite binder was shown. Siltstone, added to the composition in the amount from 0 to 5%, lead to up to 40% increase in strength, which is due to the action of siltstone particles as “crystallization centers” and formation of crystalline hydrates of calcium sulfate dihydrate on their surface. Combined action of calcined siltstone and lime leads to a 45% increase in strength due to the additional compaction by new hydration products formed in the course of metakaolin and lime interaction. Microstructural analysis showed that samples with calcined siltstone and lime have a more dense and uniform structure with a lower porosity, compared to those with only natural siltstone.

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Section: Introductionmentioning

confidence: 98%

A Study on Mechanical Properties and Structure of Anhydrite Binder Modified by Ultra-Dispersed Siltstone

Tokarev

Yakovlev

Saidova

et al. 2020

Engineering Structures and Technologies

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“…-4.38 ). The solubility of CaSO4 decreases with increasing temperature [43,44], which further explains this trend reversal.…”

Section: In Hcl Solutionsmentioning

confidence: 81%

Thermodynamics of Tungsten Ores Decomposition Process Options

Shen

Taskinen

2018

The Minerals, Metals &Amp; Materials Series

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The thermodynamics of tungsten ore decomposition in mineral acid and alkaline solutions were studied. The published thermodynamic data of tungsten minerals were collected and assessed. The Gibbs energies of CaWO4 (-1538.43 kJ/mol), FeWO4 (-1053.91 kJ/mol), MnWO4 (-1206.08 kJ/mol), H2WO4 (-1003.92 kJ/mol), and Na2WO4 (-1455.58 kJ/mol, aq) at 25 o C were adopted in the calculation using HSC software. The results show that CaWO4 is decomposed more readily in Na2CO3 solution than in NaOH, while FeWO4 and MnWO4 are more reactive in NaOH solutions. From a thermodynamic point of view, tungsten ore decomposes easily in acid solutions despite most ∆ increasing slightly with temperature. Oxidizing Fe 2+ to Fe 3+ in acidic solutions facilitates decomposition of FeWO4, and the reaction of CaWO4 in H2SO4 solution occurs more easily than in other mineral acids, due to the formation of sparsely soluble CaSO4. The results fit well with the experimental data and industrial experience previously reported in the literature.

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“…The SEM micrographs of the samples obtained in 20 mass% H 2 SO 4 solution at different reaction time and with 24) . At high H 2 SO 4 concentration, the saturated solution is easily obtained and the crystal growth ratio of AH is high.…”

Section: Resultsmentioning

confidence: 99%

Preparation of Anhydrous Calcium Sulfate Whiskers from Phosphogypsum in H2O-H2SO4 Autoclave-Free Hydrothermal System

et al. 2017

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The anhydrous calcium sulfate (AH) whiskers were prepared in H 2 O-H 2 SO 4 autoclave-free hydrothermal system by using phosphogypsum (PG) as raw materials. The in uences of solid/solution ratio, reaction time, H 2 SO 4 concentration and maleic acid on crystal growth were detected.The whiskers with smooth surface and high aspect ratio were obtained in a 20 mass% H 2 SO 4 solution for hydrothermal 1 h with 1:60 ratio of solid/solution. The aspect ratio decreased but the amount of whiskers increased in sample by increasing the addition amount of maleic acid.The whiskers were not obtained in 30 mass% H 2 SO 4 solution for hydrothermal 1, 2 and 3 h, respectively, with 1:60 ratio of solid/solution, and the whiskers were also not obtained by adding maleic acid in the solution.

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Experimental determination and modeling of gypsum and insoluble anhydrite solubility in the system CaSO4–H2SO4–H2O

Cited by 54 publications

References 21 publications

A Study on Mechanical Properties and Structure of Anhydrite Binder Modified by Ultra-Dispersed Siltstone

A Study on Mechanical Properties and Structure of Anhydrite Binder Modified by Ultra-Dispersed Siltstone

Thermodynamics of Tungsten Ores Decomposition Process Options

Preparation of Anhydrous Calcium Sulfate Whiskers from Phosphogypsum in H<sub>2</sub>O-H<sub>2</sub>SO<sub>4</sub> Autoclave-Free Hydrothermal System

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