Preparation of α-hemihydrate gypsum from phosphogypsum in recycling CaCl2 solution

Lu, Wenda; Ma, Baoguo; Su, Ying; He, Xingyang; Jin, Zihao; Qi, Huahui

doi:10.1016/j.conbuildmat.2019.04.148

Cited by 55 publications

(19 citation statements)

References 33 publications

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“…To obtain α-hemihydrate from gypsum-bearing wastes, the salt solution method is often considered [19][20][21][22][23][24][25]. In this case, dehydration is carried out in a solution of salts (Na 2 SO 4 [19], CaCl 2 , MgCl 2 , KCl [20][21][22][23][24][25], etc.) at elevated temperatures up to 97 °C in the presence of various modifiers (maleic acid, L-aspartic acid, sodium succinate, potassium sodium tartrate, sodium citrate, etc.…”

Section: Plaster Bindersmentioning

confidence: 99%

“…At the final stage of the process, filtration is carried out, the filtrate is washed with water and pure ethanol and dried at a temperature of 60-80 °С. Moreover, it is possible to synthesize a binder in salt solutions both at atmospheric [19][20][21][22][23][24] and at elevated pressure [25]. Additionally, the quality of binders can be improved by preliminary purification of phosphogypsum from impurities [22].…”

Section: Plaster Bindersmentioning

confidence: 99%

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Utilization of Gypsum-Bearing Wastes in Materials of the Construction Industry and Other Areas

Alfimova

Pirieva

Titenko

2021

Construction Materials and Products

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rational environmental management is one of the priorities of the technological development of the Russian Federation and most countries of the world. Particularly important in this area is the work undertaken with previously generated and accumulated waste, a whole group of which is gypsum-bearing wastes (GBW), which includes by-products of various industries: phosphogypsum, borogypsum, chlorogypsum, ferrogypsum, citrogypsum, vitamin gypsum, etc. GBW features are similar compositions, prevalence, perennial volumes of stored reserves with stable dynamics of annual growth. This determines the relevance of research on the development of a unified methodology for converting GBW of various types into target products particularly for construction purposes, providing maximum energy efficiency and minimal generation of secondary waste. The starting point of the research is the monitoring of approaches developed by the scientific community which are presented in the article. It is shown that researchers are exploring several main areas of GBW conversion: components of Portland cement and clinker; single and multicomponent binders; direct raw materials for the production of building materials; and road construction. The latter two directions have the greatest potential capacity for the consumption of GBW. The general level of research on the issue is not exhaustive, but has the potential to improve on existing methods of processing and application and promote the search for new and more efficient methods

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Section: Plaster Bindersmentioning

confidence: 99%

Section: Plaster Bindersmentioning

confidence: 99%

Utilization of Gypsum-Bearing Wastes in Materials of the Construction Industry and Other Areas

Alfimova

Pirieva

Titenko

2021

Construction Materials and Products

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“…Up to now, researchers have investigated the transformation process from PG to α-HH in CaCl2 (Li et al, 2019;Lu et al, 2019;Ma et al, 2012;Ma et al, 2018), NaCl (Ru et al, 2012), Na2SO4 (Li et al, 2018), and Ca-Na-Cl mixed solutions (Ma et al, 2013b) under atmosphere pressure. Ma and Li et al studied in deep the phase transition from PG to α-HH in CaCl2 solutions, and found that the reaction time was significantly shortened by higher reaction temperature and CaCl2 content.…”

Section: The Salt Solution Processmentioning

confidence: 99%

“…Additionally, chloride-free Na2SO4 solution was suggested to prepare α-HH from PG by Li et al for eliminating the influence of chloride ions. In order to avoid the secondary pollution caused by the used electrolyte solution containing complicated impurities, Lu et al (Lu et al, 2019) explored the feasibility of recycling electrolyte solution in α-HH preparation from PG in laboratory and pilot scale tests. And the tests demonstrated that CaCl2 solution could be recycled for 6 times without affecting the α-HH quality.…”

Section: The Salt Solution Processmentioning

confidence: 99%

Preparation of α-calcium sulfate hemihydrate from industrial by-product gypsum: A review

Guan¹,

Sui²,

Zhang³

et al. 2020

Physicochem. Probl. Miner. Process.

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In recent years, the massive accumulation of industrial by-product gypsum, especially flue gas desulfurization (FGD) gypsum and phosphogypsum (PG), not only encroaches on lands but also causes serious environmental pollution. The preparation of α-calcium sulfate hemihydrate (α-HH) from industrial by-product gypsum is an important way to solve the massive accumulation. α-HH possessing larger, dense and well-grown crystals with fewer cracks and pores has high added value and a wide range of application. Hitherto the preparation methods of α-HH from industrial by-product gypsum mainly include the autoclave process, salt/acid solution process, or alcohol-water solution process. Thereinto, the autoclave process is the only method to realize industrialization. In order to solve the high energy consumption and unfavorable continuous operation of the autoclave process, researchers suggested alternative approaches, such as salt/acid solution process and alcohol-water solution process. However, these methods are basically in the laboratory stage or pilot scale test at present. Compared with FGD gypsum, the utilization rate of PG with a larger emission is very low owing to the high impurity content. And combining the preparation of α-HH with the recovery of valuable impurities from PG seems a promising way to solve the bulk deposition of PG.

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“…In the field of crystallization, XRD data is often used to determine the degree of crystallinity. The reaction process can be determined from Raman data [24], thermogravimetric analysis (TGA) [25][26][27], pH value [28], X-ray diffraction (XRD) [29], and atomic absorption spectroscopy (AAS) [28]. Then the empirical data can be used to fit the known dynamic model to understand and predict the appropriate parameters of the control mechanism.…”

Section: Introductionmentioning

confidence: 99%

Crystallization Kinetics of α-Hemihydrate Gypsum Prepared by Hydrothermal Method in Atmospheric Salt Solution Medium

Wei

Zhang

2021

Crystals

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α-Calcium sulfate hemihydrate (α-HH) is an important cementitious material, which can be prepared by hydrothermal method from calcium sulfate dihydrate (DH) in an electrolyte solution. Study of the conversion kinetics of DH to α-HH in NaCl solution is helpful for understanding the control process. In this paper, X-ray diffraction (XRD) patterns were applied to study the effect of temperature on the crystallization kinetics of α-HH to determine the kinetic parameters. The research results show that the sigmoidal shape of the α-HH crystallization curve follows the Avrami-Erofeev model, which describes the crystallization kinetics of α-HH formation. Applying Arrhenius law in experimental data and model calculations, an apparent activation energy of 124 kJ/mol for nucleation and an apparent activation energy of 810 kJ/mol for growth were obtained. By adjusting the temperature of the solution, the number of α-HH nucleation and growth steps increases, which can effectively increase the DH-α-HH conversion rate in the NaCI solution.

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Preparation of α-hemihydrate gypsum from phosphogypsum in recycling CaCl2 solution

Cited by 55 publications

References 33 publications

Utilization of Gypsum-Bearing Wastes in Materials of the Construction Industry and Other Areas

Utilization of Gypsum-Bearing Wastes in Materials of the Construction Industry and Other Areas

Preparation of α-calcium sulfate hemihydrate from industrial by-product gypsum: A review

Crystallization Kinetics of α-Hemihydrate Gypsum Prepared by Hydrothermal Method in Atmospheric Salt Solution Medium

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