TY - JOUR
T1 - Towards the establishment of a general rate law for gypsum nucleation
AU - Reznik, Itay J.
AU - Ganor, Jiwchar
AU - Gruber, Chen
AU - Gavrieli, Ittai
N1 - Funding Information:
This research was supported by the Israeli Ministry of National Infrastructure (Grants # ES-38-2005 and # ES-28-2006 to J.G. and I.G.) and by the Israel Science Foundation (grant #902/05 to I.G.). I. J. Reznik expresses his gratitude to the Rieger Foundation – JNF Program for Environmental Studies, Water Authority of Israel and to the Levi Eshkol scholarship fund at the Israeli Ministry of Science for their generous support. We wish to express our gratitude to Y. Tal, G. Antler, Y. Tubul and P. Rendel for their technical assistance.
PY - 2012/5/15
Y1 - 2012/5/15
N2 - Gypsum nucleation kinetics from a wide range of chemical compositions (1.452+/SO42-<115), ionic strengths (I=2.5-10m) and saturation state with respect to gypsum (Ω gyp=1.07-8.4) were examined in batch experiments containing mixtures of Ca 2+-rich Dead Sea brine and SO42--rich seawater with or without addition of extra Na 2SO 4 and CaCl 2·2H 2O. The induction times attained in the present study were compiled together with literature values from experiments carried out under significantly different conditions (synthetic NaCl solutions; I=0.09-6.3 m; Ca 2+/SO42-=1; Ω gyp:1.59-7.76). Despite the variability in the experimental solutions, a single rate law based on classic nucleation theory was formulated to describe the induction times from more than 80 experiments:logTind=log13.17·Cs·exp-7.08ln2Ω+0.072·Cs·exp-1.426ln2Ωwhere T ind is the induction time, C s is the solubility of gypsum and Ω is the saturation state with respect to gypsum.The rate law provides T ind for gypsum precipitation from aqueous solutions at 25°C, containing no synthetic antiscalants or catalysts, within a 95% confidence interval within a factor of 5.Based on this rate law, we show that at present most of the precipitation of gypsum from the Dead Sea brine occurs following significant evaporation in the industrial evaporation ponds and not in the Dead Sea itself. Whereas T ind in Dead Sea brines is very long (on the order of 3years), the evaporation of brine in the industrial ponds leads to increased Ω values, and thus to short T ind in the order of a few days. However, if seawater or reject brine from seawater desalinization will be introduced to the Dead Sea to restore its declining level, T ind will be significantly reduced and gypsum nucleation and precipitation will occur. For evaporated seawater, the proposed rate law predicts that even though saturation is obtained when seawater is evaporated by a factor of 2.8, gypsum will nucleate at reasonable times (few years) only when seawater are evaporated by a factor of ~3.3.
AB - Gypsum nucleation kinetics from a wide range of chemical compositions (1.452+/SO42-<115), ionic strengths (I=2.5-10m) and saturation state with respect to gypsum (Ω gyp=1.07-8.4) were examined in batch experiments containing mixtures of Ca 2+-rich Dead Sea brine and SO42--rich seawater with or without addition of extra Na 2SO 4 and CaCl 2·2H 2O. The induction times attained in the present study were compiled together with literature values from experiments carried out under significantly different conditions (synthetic NaCl solutions; I=0.09-6.3 m; Ca 2+/SO42-=1; Ω gyp:1.59-7.76). Despite the variability in the experimental solutions, a single rate law based on classic nucleation theory was formulated to describe the induction times from more than 80 experiments:logTind=log13.17·Cs·exp-7.08ln2Ω+0.072·Cs·exp-1.426ln2Ωwhere T ind is the induction time, C s is the solubility of gypsum and Ω is the saturation state with respect to gypsum.The rate law provides T ind for gypsum precipitation from aqueous solutions at 25°C, containing no synthetic antiscalants or catalysts, within a 95% confidence interval within a factor of 5.Based on this rate law, we show that at present most of the precipitation of gypsum from the Dead Sea brine occurs following significant evaporation in the industrial evaporation ponds and not in the Dead Sea itself. Whereas T ind in Dead Sea brines is very long (on the order of 3years), the evaporation of brine in the industrial ponds leads to increased Ω values, and thus to short T ind in the order of a few days. However, if seawater or reject brine from seawater desalinization will be introduced to the Dead Sea to restore its declining level, T ind will be significantly reduced and gypsum nucleation and precipitation will occur. For evaporated seawater, the proposed rate law predicts that even though saturation is obtained when seawater is evaporated by a factor of 2.8, gypsum will nucleate at reasonable times (few years) only when seawater are evaporated by a factor of ~3.3.
UR - https://www.scopus.com/pages/publications/84859903961
U2 - 10.1016/j.gca.2012.02.002
DO - 10.1016/j.gca.2012.02.002
M3 - Article
AN - SCOPUS:84859903961
SN - 0016-7037
VL - 85
SP - 75
EP - 87
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
ER -