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Effect of Mg2+ ions on the nucleation kinetics of calcium sulfate in concentrated calcium chloride solutions / Baohong Guan in Industrial & engineering chemistry research, Vol. 49 N° 12 (Juin 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 12 (Juin 2010) . - pp. 5569–5574 Titre : Effect of Mg2+ ions on the nucleation kinetics of calcium sulfate in concentrated calcium chloride solutions Type de document : texte imprimé Auteurs : Baohong Guan, Auteur ; Liuchun Yang, Auteur ; Zhongbiao Wu, Auteur Année de publication : 2010 Article en page(s) : pp. 5569–5574 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Metastable  calcium  sulfate  hemihydrate  Nucleation  kinetics Résumé : The precipitation kinetics of the metastable calcium sulfate hemihydrate (HH) from aqueous solutions has seldom been addressed. For the first time, the nucleation kinetics of calcium sulfate (probably in α-HH form) in concentrated CaCl2 solutions at 90 °C and the effect of Mg2+ ions were investigated by spontaneous precipitation experiments and a turbidity monitoring method. The results indicate that, at a moderate supersaturation with respect to calcium sulfate, Mg2+ ions retard the nucleation with 0.01 M Mg2+ ions showing the strongest effect; at a higher supersaturation, the inhibition effect decreases when the concentration of Mg2+ ions increases from 0.001 to 0.10 M, and 0.20 M Mg2+ ions show a promoting effect on the precipitation. The interfacial tension values increase with the concentration of Mg2+ ions, resulting in a decrease in nucleation rate in Mg2+ ion-containing solutions compared to Mg2+ ion-free solutions. This may indicate an involvement of Mg2+ ions in the surface reaction during calcium sulfate precipitation. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie902022b [article] Effect of Mg2+ ions on the nucleation kinetics of calcium sulfate in concentrated calcium chloride solutions [texte imprimé] / Baohong Guan, Auteur ; Liuchun Yang, Auteur ; Zhongbiao Wu, Auteur . - 2010 . - pp. 5569–5574. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 12 (Juin 2010) . - pp. 5569–5574 Mots-clés : Metastable  calcium  sulfate  hemihydrate  Nucleation  kinetics Résumé : The precipitation kinetics of the metastable calcium sulfate hemihydrate (HH) from aqueous solutions has seldom been addressed. For the first time, the nucleation kinetics of calcium sulfate (probably in α-HH form) in concentrated CaCl2 solutions at 90 °C and the effect of Mg2+ ions were investigated by spontaneous precipitation experiments and a turbidity monitoring method. The results indicate that, at a moderate supersaturation with respect to calcium sulfate, Mg2+ ions retard the nucleation with 0.01 M Mg2+ ions showing the strongest effect; at a higher supersaturation, the inhibition effect decreases when the concentration of Mg2+ ions increases from 0.001 to 0.10 M, and 0.20 M Mg2+ ions show a promoting effect on the precipitation. The interfacial tension values increase with the concentration of Mg2+ ions, resulting in a decrease in nucleation rate in Mg2+ ion-containing solutions compared to Mg2+ ion-free solutions. This may indicate an involvement of Mg2+ ions in the surface reaction during calcium sulfate precipitation. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie902022b

Solubility and phase transitions of calcium sulfate in KCl solutions between 85 and 100 °C / Liuchun Yang in Industrial & engineering chemistry research, Vol. 48 N° 16 (Août 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 16 (Août 2009) . - pp. 7773–7779 Titre : Solubility and phase transitions of calcium sulfate in KCl solutions between 85 and 100 °C Type de document : texte imprimé Auteurs : Liuchun Yang, Auteur ; Baohong Guan, Auteur ; Zhongbiao Wu, Auteur Année de publication : 2009 Article en page(s) : pp. 7773–7779 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Calcium  sulfate  KCl  solution Résumé : The solubility(s) of the three phases of CaSO4, namely, CaSO4·2H2O (DH), CaSO4·0.5H2O (α-HH), and CaSO4 (AH II), in 0.0−18.0 wt % KCl solutions were systemically investigated at temperatures ranging from 85 to 100 °C. At fixed temperature, the solubility(s) of the three phases all change with KCl concentration and possess a maximum value. The relative magnitudes of the variance of solubility for AH and α-HH are larger than that for DH. This was considered to be correlated to the combined effects of the temperature and concentration of KCl solution on the activity coefficients and water activity. The phase transition behaviors of α-HH and DH are presented with possible intermediate phases, which can be well-explained by the solubility difference of the three forms of CaSO4 and the tendency of forming görgeyite (K2Ca5(SO4)6·H2O). En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900372j [article] Solubility and phase transitions of calcium sulfate in KCl solutions between 85 and 100 °C [texte imprimé] / Liuchun Yang, Auteur ; Baohong Guan, Auteur ; Zhongbiao Wu, Auteur . - 2009 . - pp. 7773–7779. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 16 (Août 2009) . - pp. 7773–7779 Mots-clés : Calcium  sulfate  KCl  solution Résumé : The solubility(s) of the three phases of CaSO4, namely, CaSO4·2H2O (DH), CaSO4·0.5H2O (α-HH), and CaSO4 (AH II), in 0.0−18.0 wt % KCl solutions were systemically investigated at temperatures ranging from 85 to 100 °C. At fixed temperature, the solubility(s) of the three phases all change with KCl concentration and possess a maximum value. The relative magnitudes of the variance of solubility for AH and α-HH are larger than that for DH. This was considered to be correlated to the combined effects of the temperature and concentration of KCl solution on the activity coefficients and water activity. The phase transition behaviors of α-HH and DH are presented with possible intermediate phases, which can be well-explained by the solubility difference of the three forms of CaSO4 and the tendency of forming görgeyite (K2Ca5(SO4)6·H2O). En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900372j