Effects of crystal habit modifiers on the morphology of calcium sulfate dihydrate grown in strong CaCl2-HCl solutions

2013 ◽  
Vol 89 (10) ◽  
pp. 1523-1533 ◽  
Author(s):  
Thomas Feldmann ◽  
George P. Demopoulos
Keyword(s):  
Calcium Sulfate ◽  
Crystal Habit ◽  
Calcium Sulfate Dihydrate

Adsorption of Organic Phosphonates on Calcium Sulfate Dihydrate Crystals

CORROSION ◽  
1981 ◽  
Vol 37 (2) ◽  
pp. 120-122 ◽  
Author(s):  
Jasbir S. Gill ◽  
George H. Nancollas
Keyword(s):  
Phosphonic Acid ◽  
Calcium Sulfate ◽  
Crystal Habit ◽  
Active Growth ◽  
Surface Sites ◽  
Calcium Sulfate Dihydrate ◽  
Kinetics Of ◽  
Habit Modification ◽  
Heated Metal ◽  
Kinetics Of Crystal Growth

Abstract 14C labeled ethylenediaminetetra (methylene phosphonic acid) and triethylenediaminetetra (methylene phosphonic acid) have been used to study their adsorption on calcium sulfate dihydrate crystals radiometrically under different conditions. Kinetics of crystal growth of calcium sulfate dihydrate crystals was studied both in solution and on heated metal surface. The growth of gypsum has been shown to follow an equation second order in supersaturation. The heterogeneity of surface sites is responsible for crystal habit modification in the presence of impurities. Blocking of the active growth sites by the inhibitors results in inhibiting the scale formation.

scholarly journals Scaling Risk Assessment in Nanofiltration of Mine Waters

Membranes ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 288
Author(s):  
Krzysztof Mitko ◽  
Ewa Laskowska ◽  
Marian Turek ◽  
Piotr Dydo ◽  
Krzysztof Piotrowski
Keyword(s):  
Calcium Sulfate ◽  
Flow Model ◽  
Membrane Surface ◽  
Mine Waters ◽  
Batch Mode ◽  
Single Pass ◽  
Calcium Sulfate Dihydrate ◽  
Dead End ◽  
In Series ◽  
Stirred Cell

Nanofiltration can be applied for the treatment of mine waters. One of the main problems is the risk of crystallization of sparingly soluble salts on the membrane surface (scaling). In this work, a series of batch-mode nanofiltration experiments of the mine waters was performed in a dead-end Sterlitech® HP 4750X Stirred Cell. Based on the laboratory results, the concentration profiles of individual ions along the membrane length in a single-pass industrial-scale nanofiltration (NF) unit was calculated, assuming the tanks-in-series flow model inside the membrane module. These calculations also propose a method for estimating the maximum achievable recovery before the occurrence of the calcium sulfate dihydrate scaling in a single-pass NF 40″ length spiral wound module, simultaneously allowing metastable supersaturation of calcium sulfate dihydrate. The performance of three membrane types (NF270, NFX, NFDL) has been evaluated for the nanofiltration of mine water.

The Effect of Solvent Polarity on Phase Transformation of Citrogypsum via Hydrothermal Process

2019 ◽  
Vol 803 ◽  
pp. 351-355 ◽  
Author(s):  
Thanakit Sirimahasal ◽  
Yutthana Kalhong ◽  
Lida Simasatitkul ◽  
Siriporn Pranee ◽  
Samitthichai Seeyangnok
Keyword(s):  
Physical Properties ◽  
Calcium Sulfate ◽  
Hydrothermal Process ◽  
Solvent Polarity ◽  
Sem Images ◽  
Crystal Water ◽  
Calcium Sulfate Dihydrate ◽  
Hexagonal Shape ◽  
Ft Ir ◽  
Hexane Solution

Calcium sulfate dihydrate (CaSO4•2H2O, CSD), gypsum is a by-product in the production of citric acid (citryogypsum). This by-product could neither be exploited nor distributed as a reactant because of its physical properties including those that are not equivalent to natural gypsum. Moreover, the mentioned citrogypsum has been continually increasing environmental problems. Therefore, this research aims at how to recycle gypsum that is synthesized by hydrothermal method at 95oC for 7 hrs under the atmospheric pressure via different solutions (MeOH, EtOH, PrOH, BuOH and Hexane). In order to produce alpha-calcium sulfate hemihydrate (α-CaSO4•0.5H2O, α-CSH) with improved physical properties that will be used for different industries. FT-IR reveals the chemical composition of crystal and the adsorption of methyl group on the surface. Besides, TGA thermogram shows the theoretical crystal water content of CSD and α-CSH 20.9 wt% and 6.2 wt% respectively. The DSC thermogram, shows that endothermic peaks at 151.2 oC and 168.5 oC. There were two steps of loss at 1.5 and 0.5 water molecule respectively. With SEM images of crystal shows the plate-like shape of citrogypsum, while α-CSH shows the hexagonal shape excluding hexane solution. Of all the results, the polarity of solution has an impact on the transition of CSD to α-CSH under this condition.

scholarly journals A technological study on the 17th century raised gilded substrates in three royal palaces of Isfahan, Iran

2013 ◽  
Vol 1 (1) ◽  
pp. 21 ◽  
Author(s):  
Parviz Holakooei ◽  
Abbas Abed-Esfahani ◽  
Samad Samanian ◽  
Hesam Aslani
Keyword(s):  
Seventeenth Century ◽  
Iron Oxides ◽  
Calcium Sulfate ◽  
Analytical Data ◽  
Animal Glue ◽  
X Ray ◽  
Calcium Sulfate Dihydrate ◽  
Proteinaceous Binder ◽  
Technological Study ◽  
Layer Chromatography

The raised substrates of gilding decorations, called lāyachīnīī in Persian, were widely used throughout the Safavid period (1501-1736 AD) in Iran. This paper presents the first analytical data obtained from the lāyachīnīs of three seventeenth century royal Safavid buildings (ʿAlī- Qāpū, Chihil-Sutūn, and Hasht-Bihisht) in Isfahan, Iran, using energy dispersive X-ray spectroscopy, scanning electron microscope, Xray powder diffraction, and thin layer chromatography. According to the analytical data, different forms of calcium sulfate (dihydrate, β-hemihydrate, and anhydrite), the red iron oxides, and a proteinaceous binder (probably animal glue) are the main constituents of the raised lāyachīnī substrates. The results show that a dry mixture of the plaster of Paris and the red iron oxides are mixed with diluted animal glue to obtain a slurry to be applied in several layers, one top of the another, to achieve the raised substrates. This technique is similar to those European raised pastiglia substrates although the method of the preparation in the Persian technique is different from the European one.

Hyperpressed Calcium Sulfate Dihydrate Structure

2014 ◽  
Vol 1025-1026 ◽  
pp. 820-823 ◽  
Author(s):  
Victoria Petropavlovskaya ◽  
Аleksandr Buryanov ◽  
Тatyana Novichenkova
Keyword(s):  
Calcium Sulfate ◽  
Raw Materials ◽  
Disperse Systems ◽  
Calcium Sulfate Dihydrate ◽  
Ceramic Manufacture ◽  
The Way

In article the method of formation of structure of disperse systems on a basis of calcium sulfate dihydrate is described. It is based on various concentration of a solution at a surface of particles of the various size. As raw materials it was used calcium sulfate dihydrate − a withdrawal of ceramic manufacture. The picked up structure of particles in the sizes was applied. For acknowledgement of the offered method following researches have been carried out on: solubilities of powders, to deformations of a raw mix, durability of structure. The way of reception of gypsum products allows to simplify technology. Energy expenses decrease. Burning is excluded and the grinding is reduced.

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