Effect of pH and succinic acid on the morphology of α-calcium sulfate hemihydrate synthesized by a salt solution method

Fan, Li; Liu, Jianli; Yang, Guangtao; Pan, Zongyou; Ni, Xiao; Xu, Huazi; Huang, Qing

doi:10.1016/j.jcrysgro.2013.03.042

Cited by 72 publications

(46 citation statements)

References 20 publications

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“…These results, combined with the XRD patterns in Figure 2, showed three characteristic peaks at 11.62 • , 20.72 • , and 29.11 • for FGD gypsum, indicating that the main component of the raw material is calcium sulfate dihydrate (CSD). Many literature studies have revealed that CSD can easily dehydrate into products with improved performance under specific conditions [37,38]. In this paper, the major product in CSHW is pure α calcium sulfate hemihydrate (α-CSH), which has been verified by the XRD pattern in Figure 2 and TG/DTA curve in Figure 3.…”

Section: Basic Characteristics Of Cshwsupporting

confidence: 61%

Calcium Sulfate Hemihydrate Whiskers Obtained from Flue Gas Desulfurization Gypsum and Used for the Adsorption Removal of Lead

Wang

et al. 2017

Crystals

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As a recycled material, flue gas desulfurization gypsum has been used to prepare calcium sulfate hemihydrate whisker (CSHW) through hydrothermal synthesis for several decades. However, the subsequent utilization of this resultant material has not yet received considerable attention. In the present research, CSHW was successfully synthesized at a certain region, and was used for the adsorption of lead ions from aqueous solutions, thereby broadening the research field for the practical application of CSHW. Its adsorption capacity was significantly influenced by various parameters, particularly, the pH level and initial lead concentration. The pH value highly affected the hydrolysis degree of lead ions and dominated the adsorption of lead. The equilibrium isotherms under two different temperatures were simulated using Langmuir, Freundlich, and Temkin models. Both Langmuir and Temkin models showed a good fit to the data. Combined with the well-fitted pseudo-second-order model, the adsorption mechanism was thought to be a chemisorption process that was enforced by the ion exchange reaction. In addition, the specific crystal structure of CSHW revealed that ion exchange reaction occurred on the (010) and (100) facets due to their preferential growth and negatively charged property. The residual solid phase after adsorption was collected and detected using X-ray diffraction and scanning electron microscopy with energy dispersive X-ray spectroscopy. Results revealed that PbSO 4 was formed on the surface of CSHW. The alkaline condition introduced the tribasic lead sulfate, and thus reduced the stability of the adsorption system.

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Section: Basic Characteristics Of Cshwsupporting

confidence: 61%

Calcium Sulfate Hemihydrate Whiskers Obtained from Flue Gas Desulfurization Gypsum and Used for the Adsorption Removal of Lead

Wang

et al. 2017

Crystals

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“…During the hydrothermal process, the impurity molecules tend to absorb on the polar crystal faces rather than on the prismatic faces, which would inhibit the crystal growth along the plane. [15][16][17][18] According to the above results, the influence of the supernatant on the HH crystal growth was greater than the organics. In these impurities, PO 4 3and Fcan react with Ca 2+ to form difficult-to-dissolve compounds (Ca 3 (PO 4 ) 2 , CaF 2 ), which can firmly adsorb on the HH crystal surfaces and hinder the crystal growth.…”

Section: ) Effects Of Pg Impurities On the Crystal Growthmentioning

confidence: 74%

“…Firstly, the homogeneous nucleation of calcium sulfate hemihydrate took place; secondly, self-assembly of calcium sulfate hemihydrate aggregated co-oriented along their c axes; finally, the crystalline grain grown occurred and the whiskers formed. 17 Calcium sulfate hemihydrate normally crystallizes in the whiskers (1D shape) because the crystal lattice of calcium sulfate hemihydrate consists of -SO 4 -Ca-SO 4 -Cachains, with each S atom and four O atoms forming a tetrahedron. These chains are hexagonally arranged and form a framework parallel to the c axis, where one water molecule is attached to every two calcium sulfate molecules.…”

Section: ) Effects Of Pg Impurities On the Crystal Growthmentioning

confidence: 99%

Effects of impurities from phosphogypsum on the crystal growth of calcium sulfate hemihydrates

Tan¹,

Dong²,

Liu³

et al. 2018

Mater. Tehnol.

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The influences of organic compounds, supernatant, calcium phosphate and calcium fluoride on the morphology of calcium sulfate hemihydrate were investigated in hydrothermal conditions by using calcium sulphate dihydrate of analytical grade as the raw material, while the organic compounds and supernatant were obtained from phosphogypsum (PG). The influence of the supernatant on the crystal growth was greater than the organic compounds. The crystal diameter increased and the aspect ratio decreased, while the added amounts of calcium fluoride and calcium phosphate increased. The influence of calcium phosphate on the crystal growth was more obvious than with calcium fluoride. Extremely non-uniform whiskers were observed when the amount of calcium fluoride and calcium phosphate were 5 % and 3 % (w/%), respectively. Key words: phosphogypsum; calcium sulfate hemihydrate; crystal morphology; impurities Avtorji so v pri~ujo~em prispevku raziskovali vplive organskih spojin, plavajo~ih ostankov, kalcijevega sulfata in kalcijevega fluorida na morfologijo kalcijevega sulfat polhidrida v hidrotermalnih pogojih. Kot surovino so uporabili sulfat dihidrat anali-ti~ne~istosti. S to sintezo so dobili organske spojine in plavajo~e ostanke iz fosfatnega gipsa (PG). Vpliv plavajo~ih ostankov na rast kristalov je bil ve~ji kot vpliv organskih spojin. Premer kristalov je nara{~al, medtem ko je razmerje med dol`ino in premerom kristalov padalo z nara{~anjem dodatka kalcijevega fluorida oz. kalcijevega fosfata. Vpliv kalcijevega fosfata na rast kristalov je bil o~itnej{i kot vpliv jedavca (kalcijevega fluorida). Vlakna skrajno nepravilnih oblik so nastajala, ko je bila vsebnost kalcijevega fluorida in kalcijevega fosfata 5 % oz. 3 %.

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“…[36] This inhibits crystal growth along c-axis and alters crystal habit of α-CSH. [29,31] Therefore, when the appropriate concentration of the crystal modifier, i.e. 0.10 wt.% maleic acid, is used, the growth rate in all directions is balanced.…”

Section: Effect Of Modifier On the Morphology Of α-Cshmentioning

confidence: 99%

“…In addition, pH is also one of the important factors that affect crystal morphology of α-CSH. [31] However, little attention has been paid on the effects of pH on the crystal morphology in such a semi-dry method.…”

Section: Introductionmentioning

confidence: 99%

Morphology‐Controlled Preparation of α‐Calcium Sulfate Hemihydrate from Phosphogypsum by Semi‐Liquid Method

Chen

et al. 2017

Crystal Research and Technology

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Phosphogypsum (PG), a by-product of phosphoric acid industry, causes environmental issues. In this paper, PG was effectively transformed into alpha-calcium sulfate hemihydrate (ɑ-CSH) via a semi-liquid method. The phase evolution and the effects of different organic acids and pH values on crystal morphology of the α-CSH were investigated by SEM, XRD and EDS. The properties of the prepared α-CSH with different aspect ratio were also compared. The results indicate that PG can be successfully transformed into α-CSH by the semi-liquid method at 140°C for 3.0 h. The morphology of the produced α-CSH is significantly influenced by the concentrations of organic acid and pH value. α-CSH crystal with well-morphology is obtained under the condition of 0.1 wt.% maleic acid and pH = 7.0. The obtained α-CSH with uniform particle size has the aspect ratio of 1.2. The 2 h and 3 d bending/compressive strengths of the hardened paste prepared from the α-CSH reach 6.4/20.6 MPa and 10.5/43.7 MPa respectively, which are comparable to those of the commercial α-CSH. Moreover, the lower aspect ratio of ɑ-CSH results in more compact microstructure and higher mechanical strengths of the hardened paste.

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Effect of pH and succinic acid on the morphology of α-calcium sulfate hemihydrate synthesized by a salt solution method

Cited by 72 publications

References 20 publications

Calcium Sulfate Hemihydrate Whiskers Obtained from Flue Gas Desulfurization Gypsum and Used for the Adsorption Removal of Lead

Calcium Sulfate Hemihydrate Whiskers Obtained from Flue Gas Desulfurization Gypsum and Used for the Adsorption Removal of Lead

Effects of impurities from phosphogypsum on the crystal growth of calcium sulfate hemihydrates

Morphology‐Controlled Preparation of α‐Calcium Sulfate Hemihydrate from Phosphogypsum by Semi‐Liquid Method

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