Effect of Organic Diacid Carbon Chain Length on Crystal Morphology of α-Calcium Sulfate Hemihydrate in Preparation from Flue Gas Desulphurization Gypsum

Liu, Xian Feng; Peng, Jia Hui; Zhang, Jian Xin; Qu, Jin Dong; Li, Mei

doi:10.4028/www.scientific.net/amm.253-255.542

Cited by 3 publications

(3 citation statements)

References 10 publications

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“…Therefore, the OA and PD cannot regulate the crystal habit of α-CaSO4•0.5H2O, and we can infer that the separation between the two COOH in the crystal modifier molecule cannot be lower than two methylene groups. The results agree with previously studies, for example, Liu et al [29] also found that OA did not modify the crystal morphology of α-CaSO4•0.5H2O, which was still acerose or linear clavate, and the crystal morphology of α-CaSO4•0.5H2O had no significant changes with the addition of PD. However, when the The effect of dicarboxylic acids on the crystal habit of α-CaSO 4 •0.5H 2 O is presented in Figure 10, and the corresponding length, width, and aspect ratio are shown in Table 3.…”

Section: Effect Of Straight-chain Dicarboxylic Acid On the Crystal Hasupporting

confidence: 92%

Effect of Molecular Structure of Organic Acids on the Crystal Habit of α-CaSO4·0.5H2O from Phosphogypsum

Zhang

2020

Crystals

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The organic acid crystal modifiers play an important role in the control of the crystal habit of α-hemihydrate gypsum (α-CaSO4·0.5H2O) from phosphogypsum, but the molecular structure characteristics of crystal modifiers have not been clarified, which makes it difficult to judge whether an organic acid has the ability to regulate the crystal habit of α-CaSO4·0.5H2O directly. In this work, the effect of organic acids with different molecular structures on the crystal habit of α-CaSO4·0.5H2O and its adsorption differences onto the α-CaSO4·0.5H2O surface were explored. The results show that the molecular structure characteristics of crystal modifiers contain two or more carboxylic groups (COOH) that are separated by two methylene or methine groups. Furthermore, organic acids with the regulation ability can adsorb on the surface of α-CaSO4·0.5H2O and change its growth habit. With the increase in the crystal modifier concentration, the α-CaSO4·0.5H2O crystals are shortened in length and enlarged in width, resulting in the decrease in aspect ratio and the increase in compressive strength. Conversely, when the adsorption of ineffective organic acids on the surface of α-CaSO4·0.5H2O was not detected, the α-CaSO4·0.5H2O crystals remained long hexagonal prisms. These results have guiding significance for the screening of novel organic acid crystal modifiers.

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Section: Effect Of Straight-chain Dicarboxylic Acid On the Crystal Hasupporting

confidence: 92%

Effect of Molecular Structure of Organic Acids on the Crystal Habit of α-CaSO4·0.5H2O from Phosphogypsum

Zhang

2020

Crystals

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“…The crystal growth period is controlled by two processes: mass transfer and surface integration [15]. During the autoclave processes, salts [16], inorganic [10] and organic acids [17] often support the process. They help accelerating the process or affect shape or size of the crystals [13].…”

Section: Introductionmentioning

confidence: 99%

“…They help accelerating the process or affect shape or size of the crystals [13]. Salts can lower the transformation temperature from gypsum to hemihydrate [13] and tend to increase the growth rate of α-HH [17]. Most crystallization aids inhibit the formation of α-HH seeds [13].…”

Section: Introductionmentioning

confidence: 99%

α‐calcium sulfate hemihydrate formation using natural anhydrite as raw material

Eicheler,

Heisig,

Hilbig

et al. 2023

ce papers

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This study investigates the potential of α‐HH formation from gypsum originating from activated and hydrated natural anhydrite. For this, gypsum was prepared from natural anhydrite and treated in an autoclave process under hydrothermal conditions (150 mbar and 130 °C). For comparison, fgd‐gypsum was treated accordingly. Succinic acid, maleic acid and additional α‐HH seeds were used as crystallization aids. QXRD results show the transformation of gypsum into hemihydrate after a residence time of 8 h and 4 h. SEM images distinguish the α‐HH and β‐HH modifications. For fgd‐gypsum pellets, the β‐HH modification predominates. Gypsum from natural anhydrite shows α‐HH crystals with succinic acid and without crystallization aid. When maleic acid is present, crystals appear as intermediates between α‐HH and β‐HH. To isolate the effect of the crystallization aids, α‐HH and succinic acid were used separately and simultaneously. SEM images indicate the formation of α‐HH from β‐HH. The shapes of the original β‐HH conglomerates are still visible, yet acicular crystals with smooth surfaces (α‐HH) are visible at a high magnification. Longest crystals appear when α‐HH and succinic acid are used simultaneously indicating a synergetic effect of both crystallization aids.

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Effect of sulfuric acid concentration on morphology of calcium sulfate hemihydrate crystals

Wang

Mao

Chen

et al. 2020

Mater. Res. Express

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Calcium sulfate hemihydrate whiskers were prepared in sulfuric acid-distilled water system by hydrothermal method using calcium sulfate dihydrate as raw materials. The influence mechanism of sulfuric acid concentration on morphology of calcium sulfate hemihydrate crystals was investigated. The results show that the morphology of hydrothermal products is fibrous when the suitable sulfuric acid concentration is from 5.0 × 10−6 mol l−1 to 5.0 × 10−4 mol l−1. The promoting effect of sulfuric acid on the dissolution of calcium sulfate dihydrate increases the amount of Ca2+ in the solution, which is beneficial to the crystallization of calcium sulfate hemihydrate crystals. Meanwhile, the selective adsorption of H+ produced by sulfuric acid ionization on the (310) crystal plane of calcium sulfate hemihydrate crystals can hinder the aggregation of Ca2+ on the crystal plane, which results in preferential growth of the calcium sulfate hemihydrate crystal along the (001) crystal plane. However, when the sulfuric acid concentration is up to 5.0 × 10−3 mol l−1, the HSO 4 − produced by the interaction of H+ with SO 4 2 − can reduce the electronegativity of SO 4 2 − and inhibit SO 4 2 − adsorption on the crystal surface. So the growth of calcium sulfate hemihydrate crystals along (001) crystal plane is hindered, which leads to the decrease of the fibrous products.

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Effect of Organic Diacid Carbon Chain Length on Crystal Morphology of α-Calcium Sulfate Hemihydrate in Preparation from Flue Gas Desulphurization Gypsum

Cited by 3 publications

References 10 publications

Effect of Molecular Structure of Organic Acids on the Crystal Habit of α-CaSO4·0.5H2O from Phosphogypsum

Effect of Molecular Structure of Organic Acids on the Crystal Habit of α-CaSO4·0.5H2O from Phosphogypsum

α‐calcium sulfate hemihydrate formation using natural anhydrite as raw material

Effect of sulfuric acid concentration on morphology of calcium sulfate hemihydrate crystals

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