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George P. Demopoulos - One of the best experts on this subject based on the ideXlab platform.
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effects of crystal habit modifiers on the morphology of Calcium Sulfate Dihydrate grown in strong cacl2 hcl solutions
Journal of Chemical Technology & Biotechnology, 2014Co-Authors: Thomas Feldmann, George P. DemopoulosAbstract:BACKGROUND This work deals with the effect of several additives on the morphology of Calcium Sulfate Dihydrate (DH) crystals, produced by reactive crystallization involving strong CaCl2–HCl solutions. Experiments were conducted at 40 °C under various conditions, namely homogeneous and seeded (heterogeneous) crystallization in CaCl2/HCl solutions ranging from very dilute (0.42 mol L−1/0.04 mol L−1) to very concentrated (1.8 mol L−1/6.3 mol L−1). RESULTS In the absence of additives a distinct difference in crystal morphology was observed depending on solution composition. Homogeneously formed DH crystals from dilute solution were in the form of needles. DH crystals formed in concentrated acid solution were thick elongated plates. The most influential additives in concentrated solutions were CTAB (cetyltrimethylammoniumbromide), PAA (polyacrylic acid) and PVS (polyvinyl sulfonic acid). CTAB favoured formation of industrially interesting thick slab crystals. In contrast PAA favoured the formation of elongated and thinner crystals as a result of preferential crystal plane adsorption. PVS had a detrimental effect on DH crystal nucleation and growth explained by its polymeric structure. CONCLUSION Apart from PVS, CTAB and PAA no influence was seen for the majority of additives tested. This was attributed to lack of ionization caused by the highly acidic solutions. © 2013 Society of Chemical Industry
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Effects of crystal habit modifiers on the morphology of Calcium Sulfate Dihydrate grown in strong CaCl2‐HCl solutions
Journal of Chemical Technology & Biotechnology, 2013Co-Authors: Thomas Feldmann, George P. DemopoulosAbstract:BACKGROUND This work deals with the effect of several additives on the morphology of Calcium Sulfate Dihydrate (DH) crystals, produced by reactive crystallization involving strong CaCl2–HCl solutions. Experiments were conducted at 40 °C under various conditions, namely homogeneous and seeded (heterogeneous) crystallization in CaCl2/HCl solutions ranging from very dilute (0.42 mol L−1/0.04 mol L−1) to very concentrated (1.8 mol L−1/6.3 mol L−1). RESULTS In the absence of additives a distinct difference in crystal morphology was observed depending on solution composition. Homogeneously formed DH crystals from dilute solution were in the form of needles. DH crystals formed in concentrated acid solution were thick elongated plates. The most influential additives in concentrated solutions were CTAB (cetyltrimethylammoniumbromide), PAA (polyacrylic acid) and PVS (polyvinyl sulfonic acid). CTAB favoured formation of industrially interesting thick slab crystals. In contrast PAA favoured the formation of elongated and thinner crystals as a result of preferential crystal plane adsorption. PVS had a detrimental effect on DH crystal nucleation and growth explained by its polymeric structure. CONCLUSION Apart from PVS, CTAB and PAA no influence was seen for the majority of additives tested. This was attributed to lack of ionization caused by the highly acidic solutions. © 2013 Society of Chemical Industry
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Influence of Impurities on Crystallization Kinetics of Calcium Sulfate Dihydrate and Hemihydrate in Strong HCl-CaCl2 Solutions
Industrial & Engineering Chemistry Research, 2013Co-Authors: Thomas Feldmann, George P. DemopoulosAbstract:The effects of inorganic impurities on the crystallization of Calcium Sulfates in strong HCl (6.3 mol L–1)-CaCl2 (1.8 mol L–1) solutions were investigated. The impurities considered relate to hydrochloric acid leaching of apatite-type ores for the extraction of rare earth elements. The impurities investigated were K+, Mg2+, Sr2+, Ba2+, Al3+, Fe2+, Fe3+, La3+, Y3+, F– (fluoride), and PO43– (phosphate). The investigation was done in the context of a continuous steady-state crystallization process. Therefore, temperature-controlled, semibatch crystal growth experiments with regulated reagent addition, to ensure nearly constant supersaturation, were performed. The experiments were conducted at 40 and 80 °C corresponding, respectively, to crystallization of Calcium Sulfate Dihydrate (DH) and Calcium Sulfate hemihydrate (HH). Among all impurities investigated, phosphate and strontium were found to have the most significant effects, with La3+ and Y3+ having some modest effects. Phosphate (added as phosphoric aci...
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Solubility and scale prevention of gypsum in transportation pipes of well brine with salinities up to 5 M at temperature range of 278-298 K
Desalination and Water Treatment, 2010Co-Authors: Hongqing Wang, Daoguang Wang, George P. DemopoulosAbstract:The results of work performed on reducing gypsum scale formation in transportation pipes of well salt brine are described. Two methods: seeding with Calcium Sulfate Dihydrate and dilution of brine were proposed. With the first method, various mass and size distributions of seeds were introduced into an perspex reactor with well salt brine (NaCl: 300 g/L, Na(2)SO(4): 20 g/L) to investigate the factors that influence crystallization of Calcium Sulfate Dihydrate, such as temperature, mass of seed crystals, and size distribution of seed crystals. The kinetics of Calcium Sulfate Dihydrate growth at temperatures ranging between 5 and 25 degrees C were obtained. Results showed that the elimination of supersaturation was enhanced with increasing temperature and the dosage of seed crystal. It was also found that the more efficient in scale prevention was obtained when smaller seed crystals were employed. It was seen that the crystal growth of Calcium Sulfate Dihydrate in brine was proportional to the square of supersaturation at the investigated temperatures. With the second method, results showed that a complete elimination of supersaturation was achieved when 4.3% water was added into the brine with the help of solubility determination of Calcium Sulfate Dihydrate.
Yonggang Yan - One of the best experts on this subject based on the ideXlab platform.
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developing a biodegradable triCalcium silicate glucono delta lactone Calcium Sulfate Dihydrate composite cement with high preliminary mechanical property for bone filling
Materials Science and Engineering: C, 2020Co-Authors: Zhengwen Ding, Hong Chen, Qiyi Zhang, Yonggang YanAbstract:Abstract Bone cements with the feature of easily shaping could ideally match the defect site and prevent the ingrowth of fibrous tissue. In this manuscript, a biodegradable triCalcium silicate (C3S)/glucono-delta-lactone (GDL)/Calcium Sulfate Dihydrate (CSD) organic-inorganic composite cement was fabricated with shorter setting time (less than 15 min) and high preliminary mechanical property (5.27 MPa in the first hour). Many methods were applied to study the physicochemical and biological properties of the cement in vitro. The weight loss in PBS can reach 58% after 12 weeks soaking indicating the better biodegradability. The excellent bioactivity in vitro was emerging after the cement was soaked in the simulated body fluid. The cell experiments showed that suitable concentration of the extract liquid of cement was conducive to the proliferation, differentiation and extracellular matrix calcification of the mouse bone marrow stromal cells. Briefly, the C3S/GDL/CSD composite cement would have the bright capacity for bone filling.
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Developing a biodegradable triCalcium silicate/glucono-delta-lactone/Calcium Sulfate Dihydrate composite cement with high preliminary mechanical property for bone filling
Materials Science and Engineering: C, 1Co-Authors: Zhengwen Ding, Hong Chen, Qiyi Zhang, Yonggang YanAbstract:Abstract Bone cements with the feature of easily shaping could ideally match the defect site and prevent the ingrowth of fibrous tissue. In this manuscript, a biodegradable triCalcium silicate (C3S)/glucono-delta-lactone (GDL)/Calcium Sulfate Dihydrate (CSD) organic-inorganic composite cement was fabricated with shorter setting time (less than 15 min) and high preliminary mechanical property (5.27 MPa in the first hour). Many methods were applied to study the physicochemical and biological properties of the cement in vitro. The weight loss in PBS can reach 58% after 12 weeks soaking indicating the better biodegradability. The excellent bioactivity in vitro was emerging after the cement was soaked in the simulated body fluid. The cell experiments showed that suitable concentration of the extract liquid of cement was conducive to the proliferation, differentiation and extracellular matrix calcification of the mouse bone marrow stromal cells. Briefly, the C3S/GDL/CSD composite cement would have the bright capacity for bone filling.
Thomas Feldmann - One of the best experts on this subject based on the ideXlab platform.
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effects of crystal habit modifiers on the morphology of Calcium Sulfate Dihydrate grown in strong cacl2 hcl solutions
Journal of Chemical Technology & Biotechnology, 2014Co-Authors: Thomas Feldmann, George P. DemopoulosAbstract:BACKGROUND This work deals with the effect of several additives on the morphology of Calcium Sulfate Dihydrate (DH) crystals, produced by reactive crystallization involving strong CaCl2–HCl solutions. Experiments were conducted at 40 °C under various conditions, namely homogeneous and seeded (heterogeneous) crystallization in CaCl2/HCl solutions ranging from very dilute (0.42 mol L−1/0.04 mol L−1) to very concentrated (1.8 mol L−1/6.3 mol L−1). RESULTS In the absence of additives a distinct difference in crystal morphology was observed depending on solution composition. Homogeneously formed DH crystals from dilute solution were in the form of needles. DH crystals formed in concentrated acid solution were thick elongated plates. The most influential additives in concentrated solutions were CTAB (cetyltrimethylammoniumbromide), PAA (polyacrylic acid) and PVS (polyvinyl sulfonic acid). CTAB favoured formation of industrially interesting thick slab crystals. In contrast PAA favoured the formation of elongated and thinner crystals as a result of preferential crystal plane adsorption. PVS had a detrimental effect on DH crystal nucleation and growth explained by its polymeric structure. CONCLUSION Apart from PVS, CTAB and PAA no influence was seen for the majority of additives tested. This was attributed to lack of ionization caused by the highly acidic solutions. © 2013 Society of Chemical Industry
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Effects of crystal habit modifiers on the morphology of Calcium Sulfate Dihydrate grown in strong CaCl2‐HCl solutions
Journal of Chemical Technology & Biotechnology, 2013Co-Authors: Thomas Feldmann, George P. DemopoulosAbstract:BACKGROUND This work deals with the effect of several additives on the morphology of Calcium Sulfate Dihydrate (DH) crystals, produced by reactive crystallization involving strong CaCl2–HCl solutions. Experiments were conducted at 40 °C under various conditions, namely homogeneous and seeded (heterogeneous) crystallization in CaCl2/HCl solutions ranging from very dilute (0.42 mol L−1/0.04 mol L−1) to very concentrated (1.8 mol L−1/6.3 mol L−1). RESULTS In the absence of additives a distinct difference in crystal morphology was observed depending on solution composition. Homogeneously formed DH crystals from dilute solution were in the form of needles. DH crystals formed in concentrated acid solution were thick elongated plates. The most influential additives in concentrated solutions were CTAB (cetyltrimethylammoniumbromide), PAA (polyacrylic acid) and PVS (polyvinyl sulfonic acid). CTAB favoured formation of industrially interesting thick slab crystals. In contrast PAA favoured the formation of elongated and thinner crystals as a result of preferential crystal plane adsorption. PVS had a detrimental effect on DH crystal nucleation and growth explained by its polymeric structure. CONCLUSION Apart from PVS, CTAB and PAA no influence was seen for the majority of additives tested. This was attributed to lack of ionization caused by the highly acidic solutions. © 2013 Society of Chemical Industry
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Influence of Impurities on Crystallization Kinetics of Calcium Sulfate Dihydrate and Hemihydrate in Strong HCl-CaCl2 Solutions
Industrial & Engineering Chemistry Research, 2013Co-Authors: Thomas Feldmann, George P. DemopoulosAbstract:The effects of inorganic impurities on the crystallization of Calcium Sulfates in strong HCl (6.3 mol L–1)-CaCl2 (1.8 mol L–1) solutions were investigated. The impurities considered relate to hydrochloric acid leaching of apatite-type ores for the extraction of rare earth elements. The impurities investigated were K+, Mg2+, Sr2+, Ba2+, Al3+, Fe2+, Fe3+, La3+, Y3+, F– (fluoride), and PO43– (phosphate). The investigation was done in the context of a continuous steady-state crystallization process. Therefore, temperature-controlled, semibatch crystal growth experiments with regulated reagent addition, to ensure nearly constant supersaturation, were performed. The experiments were conducted at 40 and 80 °C corresponding, respectively, to crystallization of Calcium Sulfate Dihydrate (DH) and Calcium Sulfate hemihydrate (HH). Among all impurities investigated, phosphate and strontium were found to have the most significant effects, with La3+ and Y3+ having some modest effects. Phosphate (added as phosphoric aci...
Zhengwen Ding - One of the best experts on this subject based on the ideXlab platform.
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developing a biodegradable triCalcium silicate glucono delta lactone Calcium Sulfate Dihydrate composite cement with high preliminary mechanical property for bone filling
Materials Science and Engineering: C, 2020Co-Authors: Zhengwen Ding, Hong Chen, Qiyi Zhang, Yonggang YanAbstract:Abstract Bone cements with the feature of easily shaping could ideally match the defect site and prevent the ingrowth of fibrous tissue. In this manuscript, a biodegradable triCalcium silicate (C3S)/glucono-delta-lactone (GDL)/Calcium Sulfate Dihydrate (CSD) organic-inorganic composite cement was fabricated with shorter setting time (less than 15 min) and high preliminary mechanical property (5.27 MPa in the first hour). Many methods were applied to study the physicochemical and biological properties of the cement in vitro. The weight loss in PBS can reach 58% after 12 weeks soaking indicating the better biodegradability. The excellent bioactivity in vitro was emerging after the cement was soaked in the simulated body fluid. The cell experiments showed that suitable concentration of the extract liquid of cement was conducive to the proliferation, differentiation and extracellular matrix calcification of the mouse bone marrow stromal cells. Briefly, the C3S/GDL/CSD composite cement would have the bright capacity for bone filling.
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Developing a biodegradable triCalcium silicate/glucono-delta-lactone/Calcium Sulfate Dihydrate composite cement with high preliminary mechanical property for bone filling
Materials Science and Engineering: C, 1Co-Authors: Zhengwen Ding, Hong Chen, Qiyi Zhang, Yonggang YanAbstract:Abstract Bone cements with the feature of easily shaping could ideally match the defect site and prevent the ingrowth of fibrous tissue. In this manuscript, a biodegradable triCalcium silicate (C3S)/glucono-delta-lactone (GDL)/Calcium Sulfate Dihydrate (CSD) organic-inorganic composite cement was fabricated with shorter setting time (less than 15 min) and high preliminary mechanical property (5.27 MPa in the first hour). Many methods were applied to study the physicochemical and biological properties of the cement in vitro. The weight loss in PBS can reach 58% after 12 weeks soaking indicating the better biodegradability. The excellent bioactivity in vitro was emerging after the cement was soaked in the simulated body fluid. The cell experiments showed that suitable concentration of the extract liquid of cement was conducive to the proliferation, differentiation and extracellular matrix calcification of the mouse bone marrow stromal cells. Briefly, the C3S/GDL/CSD composite cement would have the bright capacity for bone filling.
Mason B. Tomson - One of the best experts on this subject based on the ideXlab platform.
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the seeded growth of Calcium Sulfate Dihydrate crystals in nacl solutions up to 6 m and 90 c
Journal of Colloid and Interface Science, 1994Co-Authors: John E. Oddo, Mason B. TomsonAbstract:The kinetics of Calcium Sulfate crystal growth is of importance in various fields, such as geochemistry, desalination technology, petroleum industry, and water and wastewater treatment. The seeded crystal growth rate of Calcium Sulfate Dihydrate was measured as a function of supersaturation in NaCl electrolyte solutions from 0 to 6 m at temperatures of 25, 50, 70, and 90 C. The growth followed a second-order parabolic rate law with activation energies greater than 53 kJ/mol which suggested the surface reaction as the rate-limiting step. It was observed that the rate constant and the activation energy are solution composition dependent. The rate constant increases with NaCl concentration up to 3 molal and then begins to fall slightly. The activation energy dropped from 61 kJ/mol in the pure Ca-SO[sub 4]H[sub 2]O system to 53 kJ/mol in 3.0 m NaCl solutions. The electrolyte effect was similar to the crystal solubility behavior in aqueous electrolyte solutions resulting from the variation of the mean activity coefficient of the crystal with ionic strength. The rate constant is proportional to the crystal solubility and inversely proportional to the edge work or the interfacial tension as expected in the classic BCF model.
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the nucleation kinetics of Calcium Sulfate Dihydrate in nacl solutions up to 6 m and 90 c
Journal of Colloid and Interface Science, 1994Co-Authors: John E. Oddo, Mason B. TomsonAbstract:Abstract Induction periods for the nucleation of Calcium Sulfate Dihydrate were experimentally determined as a function of supersaturation in NaCl solutions from 0 to 6 m at 25°C and in 3.0 m NaCl solutions at temperatures from 25 to 90°C. Using classic nucleation theory, the interfacial tension between gypsum and 3.0-m NaCl solution was estimated to be about 39 mJ/m2 at 25°C and increases with increasing temperature (to 63 mJ/m2 at 90°C). It was observed that the induction period decreases with increasing NaCl concentrations up to 3 m and then starts to increase slightly at a given temperature and saturation state. The electrolyte effect on nucleation was proportional to the enhanced solubility of Calcium Sulfate Dihydrate in NaCl solutions. This phenomenon may result from decreased crystal-solution interfacial tensions caused by increased gypsum solubility in electrolyte solutions. Although anhydrite is the thermodynamically stable phase at elevated temperatures and in concentrated solutions, only gypsum was nucleated.
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The Nucleation Kinetics of Calcium Sulfate Dihydrate in NaCl Solutions up to 6 m and 90°C
Journal of Colloid and Interface Science, 1994Co-Authors: John E. Oddo, Mason B. TomsonAbstract:Abstract Induction periods for the nucleation of Calcium Sulfate Dihydrate were experimentally determined as a function of supersaturation in NaCl solutions from 0 to 6 m at 25°C and in 3.0 m NaCl solutions at temperatures from 25 to 90°C. Using classic nucleation theory, the interfacial tension between gypsum and 3.0-m NaCl solution was estimated to be about 39 mJ/m2 at 25°C and increases with increasing temperature (to 63 mJ/m2 at 90°C). It was observed that the induction period decreases with increasing NaCl concentrations up to 3 m and then starts to increase slightly at a given temperature and saturation state. The electrolyte effect on nucleation was proportional to the enhanced solubility of Calcium Sulfate Dihydrate in NaCl solutions. This phenomenon may result from decreased crystal-solution interfacial tensions caused by increased gypsum solubility in electrolyte solutions. Although anhydrite is the thermodynamically stable phase at elevated temperatures and in concentrated solutions, only gypsum was nucleated.
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The Seeded Growth of Calcium Sulfate Dihydrate Crystals in NaCl Solutions up to 6 m and 90°C
Journal of Colloid and Interface Science, 1994Co-Authors: John E. Oddo, Mason B. TomsonAbstract:The kinetics of Calcium Sulfate crystal growth is of importance in various fields, such as geochemistry, desalination technology, petroleum industry, and water and wastewater treatment. The seeded crystal growth rate of Calcium Sulfate Dihydrate was measured as a function of supersaturation in NaCl electrolyte solutions from 0 to 6 m at temperatures of 25, 50, 70, and 90 C. The growth followed a second-order parabolic rate law with activation energies greater than 53 kJ/mol which suggested the surface reaction as the rate-limiting step. It was observed that the rate constant and the activation energy are solution composition dependent. The rate constant increases with NaCl concentration up to 3 molal and then begins to fall slightly. The activation energy dropped from 61 kJ/mol in the pure Ca-SO[sub 4]H[sub 2]O system to 53 kJ/mol in 3.0 m NaCl solutions. The electrolyte effect was similar to the crystal solubility behavior in aqueous electrolyte solutions resulting from the variation of the mean activity coefficient of the crystal with ionic strength. The rate constant is proportional to the crystal solubility and inversely proportional to the edge work or the interfacial tension as expected in the classic BCF model.
