How to convert anhydrite into dihydrate gypsum

416 Dissolution and Conversions of Gypsum and Anhydrite

Gypsum dissolves by a simple twophase dissociation Anhydrite, when dissolved, forms a solution of calcium sulfate, which at common temperatures and pressures is in equilibrium with The swelling of anhydritic rocks is attributed to the transformation of anhydrite into gypsum crystals This transformation takes place via the solution phase, ie via anhydrite dissolution The Solubilities and Thermodynamic Equilibrium of Anhydrite and 2019年4月30日  In the hightemperature and low water vapor pressure region, gypsum dehydrates to form γCaSO 4 in a singlestep process (CaSO 4 2H 2 O → γCaSO 4 ); with increasing water vapor pressure,(PDF) Dehydration Pathways of Gypsum and the 2019年4月26日  Prasad et al and Carbone et al investigated the dehydration mechanism of gypsum using in situ microRaman and energydispersive XRD, respectively, and concluded that γCaSO 4 was first obtained in the gypsum Dehydration Pathways of Gypsum and the Rehydration

Mechanism and kinetics of gypsum–anhydrite ScienceDirect

2011年6月1日  The transformation of gypsum into anhydrite at low temperatures under atmospheric pressure as well as at elevated temperatures (150 °C and 200 °C) inside an Gypsum and anhydrite are both soluble minerals forming rocks that can dissolve at surface and underground resulting in sulphate karst causing geological hazards, especially subsidence and The dissolution and conversion of gypsum and anhydrite2022年4月28日  Gypsum crystals nucleate on existing gypsum crystals and surfaces of clay minerals The transformation of anhydrite into gypsum proceeds until all the anhydrite present Modeling Solubility of Anhydrite and Gypsum in Aqueous 2020年9月17日  The complete sequence is gypsum → 0625subhydrate → bassanite → hydro γanhydrite → anhydrous γanhydrite → βanhydrite The transformations were also assessed using DSC, TG, DTA and dielectric Evidence of a new phase in gypsum–anhydrite

Anhydrite and gypsum SpringerLink

2013年1月1日  The conversion of gypsum to anhydrite can be penecontemporaneous or it can take place at any stage during burial The depositional environment recorded by bedded 2019年4月30日  The dehydration products of gypsum under different temperature and water vapor pressure were investigated by thermodynamic theory Additionally, the rehydration mechanism of soluble anhydrite was (PDF) Dehydration Pathways of Gypsum and the Introduction Water, the most common chemical on earth, can be found in the atmosphere as water vapor Some chemicals, when exposed to water in the atmosphere, will reversibly either adsorb it onto their surface or include it in 212: Hydrates Chemistry LibreTextsConversion of gypsum to anhydrite and back to gypsum is common due to the thermodynamic instability of these minerals within the physicochemical range of common geologic environments416 Dissolution and Conversions of Gypsum and Anhydrite

Gypsum Properties, Formation, Uses and Deposits Geology

2023年9月9日  Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate (CaSO42H2O) These processes can lead to the conversion of gypsum into anhydrite or other minerals Gypsum deposits can vary in size and purity, and they are often associated with other minerals and rock formations9 Which Gypsum: Anhydrite or Dihydrate? Since calcium sulfate is so broadly useful, it’s natural to ask which form is better for agricultural purposes, anhydrite gypsum or dihydrate gypsum The answer depends on how you define “better” In terms of what they contribute to plants and to the soil, available data suggests that they provide the09 Which Gypsum: Anhydrite or Dihydrate? Best Soil However, laboratory evidence for the synthesis of anhydrite directly from NaClrich waters has shown that gypsum is always the stable phase () Hardie (1967) converted gypsum to anhydrite in solutions containing high concentrations of H 2 SO 4, and Cruft and Chao (1969) showed that under conditions of very high supersaturation, ie, high Ca 2+ or high SO 4 2−, anhydrite Anhydrite and gypsum SpringerLink2021年1月5日  In order to study the physical and mechanical properties of gypsum rock samples in three states (natural, hightemperature dehydration and hydration time), natural gypsum rock was put into hightemperature condition of 220°C for dehydration treatment, and then the hightemperature dehydrated gypsum rock was treated with different hydration time, and the Experimental Study on Physical and Mechanical Properties of Gypsum

Factsheet on: What is Gypsum?

From a chemical point of view it is Calcium Sulphate Dihydrate ( CaSO 42H 2O) deposited in sedimentary layers on the sea bed Under high pressure and temperature Gypsum turns into Anhydrite ( CaSO 4) In nature, Gypsum and Anyhdrite occur as beds or nodular masses up to a few metres thick Gypsum is formed by the hydration of Anhydrite2011年6月1日  Theoretically, gypsum is the stable solid phase in water up to 45–50 °C, and above that it transforms into anhydrite (Dutrizac, 2002, Farrah et al, 2004, Freyer and Voigt, 2003; Nývlt, 1997)During sulphuric acid neutralization with calciumcontaining bases which occurs below 100 °C, first gypsum forms as a metastable phase because of its higher Mechanism and kinetics of gypsum–anhydrite ScienceDirect2023年9月21日  Anhydrite and gypsum are omnipresent in sedimentary rocks of all types They occur as massive layers or are distributed within other geological formations as in clays(PDF) Solubility of anhydrite and gypsum at temperatures below 2013年1月1日  Anhydrite (CaSO 4) and gypsum (CaSO 4 2H 2 O) are the two most abundant minerals of ancient marine evaporite deposits and are also common in nonmarine evaporite deposits Sedimentary gypsum forms by direct precipitation out of evaporating seawater under arid climatic conditions in hydrologically restricted marine and marginal marine environments Anhydrite and gypsum SpringerLink

New insight into the phase changes of gypsum

2024年6月15日  A possible transition from gypsum (CaSO 4 2H 2 O) directly to anhydrite II (between 42 ± 1 °C) is also discussed in the literature [] (especially in relation to the solubility diagram)The research of this transition has a long history, which is well described by Freyer and Wolfgang in []—the conclusions are that this transition is estimated between 42 and 60 °C; the 2023年10月27日  Gypsum is a soft mineral composed of calcium sulfate dihydrate Anhydrite is also a calcium sulfate mineral, anhydrite can absorb water and convert back to gypsum 13 In nature, gypsum often forms through the evaporation of seawater Can gypsum transform into anhydrite? Yes, by heating and removing its water content 9Gypsum vs Anhydrite — What’s the Difference?A similar dehydration mechanism was observed when solid gypsum was added to saturated calcium sulfate salt solution and dehydrated to natural anhydrite These data are shown in Table 3 Since the formation of the hemihydrate is an intermediate in the conversion of gypsum to anhydrite, gypsum will not convert to anhydrite unless conditions Table 5Conversion of gypsum to anhydrite in aqueous salt solutionsGypsum in contact with aqueous salt solutions was converted to natural anhydrite at 905°C The mechanism of the reaction is the conversion of gypsum first to the hemihydrate then to natural anhydrite Thermodynamic calculations and experimental evidence substantiate the Conversion of gypsum to anhydrite in aqueous salt solutions

Modeling Solubility of Anhydrite and Gypsum in Aqueous

2022年4月28日  Gypsum crystals nucleate on existing gypsum crystals and surfaces of clay minerals The transformation of anhydrite into gypsum proceeds until all the anhydrite present in the rock is converted to gypsum This process (gypsification of anhydrite) is accompanied by about 61% increase in volume (Butscher et al 2011, 2017; Jarzyna et al 2021)2007年12月1日  Gypsum (calcium sulfate dihydrate) Les plâtres β forment une anhydrite II bien cristallisée, (010), then the solid is divided into [101] polycrystalline needles (5–10 x 30–300 μm) The dihydrate‐hemihydrate transformation in gypsumThe development of karst is a complex system driven by the dissolution of a host rock and the subsequent removal of dissolved matter by moving water It is the process that, at various stages, initiates or triggers associated processes including erosion, collapse and subsidence The dissolution of sulphate rocks proceeds by different mechanisms and at different rates to those The dissolution and conversion of gypsum and anhydriteanhydrite into gypsum crystals This transformation takes place via the solution phase, ie via anhydrite dissolution and gypsum precipitation The chemical dissolution and precipitation reactions of gypsum and anhydrite are CaSO 4 2H 2O $ Ca2þ þ SO2 4 þ 2H 2O ð1Þ and CaSO 4 $ Ca2þ þ SO2 4; ð2Þ respectivelyThe Solubilities and Thermodynamic Equilibrium of Anhydrite and Gypsum

Dehydration Pathways of Gypsum and the Rehydration Mechanism

2019年4月26日  The dehydration products of gypsum under different temperature and water vapor pressure were investigated by thermodynamic theory Additionally, the rehydration mechanism of soluble anhydrite was also studied by Monte Carlo (MC) simulations The thermodynamic calculation results reveal that the dehy 2023年9月20日  222 Transition temperature gypsumanhydrite in water The purely statistically fitted curves of the data by Krumgalz (Eqs 6, 9) yield a crossing point of the gypsumanhydrite solubility curve at 456°C This value looks like Frontiers Solubility of anhydrite and gypsum at 2020年9月17日  It is a wellknown fact that the water molecule is a dipolar molecule with water dimer resonances in the microwave frequency band 59 which is easily polarized by the electric field and transforms the electromagnetic Evidence of a new phase in gypsum–anhydrite Main Differences Between Gypsum and Anhydrite Gypsum is a mineral that is aqueous and contains 2 water molecules, while anhydrite, as it is known, is an anhydrous mineral and does not contain water molecules The chemical Gypsum vs Anhydrite: Difference and Comparison

Dissolution and conversions of gypsum and anhydrite

Solubility of gypsum and anhydrite: (A) = Curves for gypsum and anhydrite based on the experimental data of Blount and Dickson (1973) The upper curve shows the mass loss of gypsum 161 is lower than that of gypsum under these pressure conditions and 2024年1月10日  Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, whereas anhydrite is its anhydrous form Home; New; Gypsum vs Anhydrite: Know the Difference The gypsum rock was easily carved into a sculpture 8 Shumaila Saeed Dec 25, 2023 ADVERTISEMENT AnhydriteGypsum vs Anhydrite: Know the Difference2022年12月8日  Gypsum (calcium sulfate dihydrate) is one of the most used inorganic binding materials in the world During calcination, calcium sulfate subhydrates are formed and, for technical reasons, are mixed with water to form dihydrate again Therefore, the dehydration process of gypsum and the rehydration of hemihydrate were investigated This dehydration Formation of alpha;Hemihydrate Inside of a Gypsum Crystal2020年9月3日  Of the precipitates, calcium sulfate – crystallizing mainly in the form of gypsum, calcium sulfate dihydrate (CaSO 4 2H 2 O) – is one of the most common representatives, which is present (or may form) in a large variety of natural and industrial processes, such as acidic wastewater treatment , phosphonic acid production , wet flue gas desulfurization , reverse The kinetics of the precipitation of gypsum, CaSO42H2O

Calcium Sulfate Hemihydrate an overview ScienceDirect Topics

Naturally occurring crystals are calcium sulfate dihydrate, CaSO 4 2H 2 O, known as gypsum, and anhydrous calcium sulfate, IICaSO 4 When gypsum is heated, dehydration occurs to form hemihydrates, CaSO 4 1/2H 2 O, followed by anhydrite, IIICaSO 4 The hemihydrates and the anhydrite have two modifications, α and β, respectivelyThe process as disclosed herein continuously converts dihydrate gypsum into alpha gypsum hemihydrate in the order of minutes, rather than hours Upon further loss of water, gypsum anhydrite is produced according to the following chemical equation: CaSO 405H 2 O+heat→CaSO 4 +05H 2 OProcess for producing alphahemihydrate gypsum Google 2009年10月1日  Gypsum (calcium sulfate dihydrate, CaSO 4 2H 2 O) is the most aqueous phase in the system CaSO 4 –H 2 O and, besides anhydrite II, the stable phase under ambient atmospheric conditions With increasing temperature gypsum starts to dehydrate and form calcium sulfates with lower H 2 O contentQuantitative determination of anhydrite III from dehydrated gypsum 2019年4月30日  The dehydration products of gypsum under different temperature and water vapor pressure were investigated by thermodynamic theory Additionally, the rehydration mechanism of soluble anhydrite was (PDF) Dehydration Pathways of Gypsum and the

212: Hydrates Chemistry LibreTexts

Introduction Water, the most common chemical on earth, can be found in the atmosphere as water vapor Some chemicals, when exposed to water in the atmosphere, will reversibly either adsorb it onto their surface or include it in Conversion of gypsum to anhydrite and back to gypsum is common due to the thermodynamic instability of these minerals within the physicochemical range of common geologic environments416 Dissolution and Conversions of Gypsum and Anhydrite2023年9月9日  Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate (CaSO42H2O) These processes can lead to the conversion of gypsum into anhydrite or other minerals Gypsum deposits can vary in size and purity, and they are often associated with other minerals and rock formationsGypsum Properties, Formation, Uses and Deposits Geology 9 Which Gypsum: Anhydrite or Dihydrate? Since calcium sulfate is so broadly useful, it’s natural to ask which form is better for agricultural purposes, anhydrite gypsum or dihydrate gypsum The answer depends on how you define “better” In terms of what they contribute to plants and to the soil, available data suggests that they provide the09 Which Gypsum: Anhydrite or Dihydrate? Best Soil

Anhydrite and gypsum SpringerLink

However, laboratory evidence for the synthesis of anhydrite directly from NaClrich waters has shown that gypsum is always the stable phase () Hardie (1967) converted gypsum to anhydrite in solutions containing high concentrations of H 2 SO 4, and Cruft and Chao (1969) showed that under conditions of very high supersaturation, ie, high Ca 2+ or high SO 4 2−, anhydrite 2021年1月5日  In order to study the physical and mechanical properties of gypsum rock samples in three states (natural, hightemperature dehydration and hydration time), natural gypsum rock was put into hightemperature condition of 220°C for dehydration treatment, and then the hightemperature dehydrated gypsum rock was treated with different hydration time, and the Experimental Study on Physical and Mechanical Properties of Gypsum From a chemical point of view it is Calcium Sulphate Dihydrate ( CaSO 42H 2O) deposited in sedimentary layers on the sea bed Under high pressure and temperature Gypsum turns into Anhydrite ( CaSO 4) In nature, Gypsum and Anyhdrite occur as beds or nodular masses up to a few metres thick Gypsum is formed by the hydration of AnhydriteFactsheet on: What is Gypsum?2011年6月1日  Theoretically, gypsum is the stable solid phase in water up to 45–50 °C, and above that it transforms into anhydrite (Dutrizac, 2002, Farrah et al, 2004, Freyer and Voigt, 2003; Nývlt, 1997)During sulphuric acid neutralization with calciumcontaining bases which occurs below 100 °C, first gypsum forms as a metastable phase because of its higher Mechanism and kinetics of gypsum–anhydrite ScienceDirect

(PDF) Solubility of anhydrite and gypsum at temperatures below

2023年9月21日  Anhydrite and gypsum are omnipresent in sedimentary rocks of all types They occur as massive layers or are distributed within other geological formations as in clays

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