scholarly journals Geometrical Isomers of Anionic Complexes Favorable to Chiral Discriminatory Ion-Pairing withΛ-[Co(en)3]3+Ion and the Diastereomeric Ion-Pair Formation Constants in Solution

1988 ◽  
Vol 61 (9) ◽  
pp. 3145-3151 ◽  
Author(s):  
Akira Tatehata ◽  
Yasuyuki Asaba
Keyword(s):  
Ion Pairing ◽  
Formation Constants ◽  
Ion Pair ◽  
Pair Formation ◽  
Geometrical Isomers ◽  
Ion Pair Formation ◽  
Anionic Complexes

scholarly journals Pb Mineral Precipitation in Solutions of Sulfate, Carbonate and Phosphate: Measured and Modeled Pb Solubility and Pb2+ Activity

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 620
Author(s):  
Xinxin Li ◽  
Behrooz Azimzadeh ◽  
Carmen Enid Martinez ◽  
Murray B. McBride
Keyword(s):  
Contaminated Soils ◽  
Formation Constants ◽  
Ion Pair ◽  
Pair Formation ◽  
X Ray Diffraction ◽  
Ion Pair Formation ◽  
Thermodynamic Constants ◽  
Ion Activity ◽  
Ion Activities ◽  
Ph Range

Lead (Pb) solubility is commonly limited by dissolution–precipitation reactions of secondary mineral phases in contaminated soils and water. In the research described here, Pb solubility and free Pb2+ ion activities were measured following the precipitation of Pb minerals from aqueous solutions containing sulfate or carbonate in a 1:5 mole ratio in the absence and presence of phosphate over the pH range 4.0–9.0. Using X-ray diffraction and Fourier-transform infrared spectroscopic analysis, we identified anglesite formed in sulfate-containing solutions at low pH. At higher pH, Pb carbonate and carbonate-sulfate minerals, hydrocerussite and leadhillite, were formed in preference to anglesite. Precipitates formed in the Pb-carbonate systems over the pH range of 6 to 9 were composed of cerussite and hydrocerussite, with the latter favored only at the highest pH investigated. The addition of phosphate into the Pb-sulfate and Pb-carbonate systems resulted in the precipitation of Pb3(PO4)2 and structurally related pyromorphite minerals and prevented Pb sulfate and carbonate mineral formation. Phosphate increased the efficiency of Pb removal from solution and decreased free Pb2+ ion activity, causing over 99.9% of Pb to be precipitated. Free Pb2+ ion activities measured using the ion-selective electrode revealed lower values than predicted from thermodynamic constants, indicating that the precipitated minerals may have lower KSP values than generally reported in thermodynamic databases. Conversely, dissolved Pb was frequently greater than predicted based on a speciation model using accepted thermodynamic constants for Pb ion-pair formation in solution. The tendency of the thermodynamic models to underestimate Pb solubility while overestimating free Pb2+ activity in these systems, at least in the higher pH range, indicates that soluble Pb ion-pair formation constants and KSP values need correction in the models.

Acid dependence and ion pairing in the anation reactions yielding iron(III) monosulfate

1970 ◽  
Vol 48 (19) ◽  
pp. 3100-3103 ◽  
Author(s):  
F. L. Baker ◽  
W. MacF. Smith
Keyword(s):  
Rate Constant ◽  
Ion Pairing ◽  
Ion Pair ◽  
Pair Formation ◽  
Association Constants ◽  
Stopped Flow ◽  
Ion Pair Formation ◽  
Significant Dependence ◽  
Kinetics Of ◽  
Acid Dependence

Stopped-flow studies of the kinetics of the a nation reaction yielding iron(III) monosulfate indicate a significant dependence of rate constant on acidity and also a dependence on iron concentrations. This is consistent with association constants for outer ion pair formation between the reactants which have about three times the Fuoss values.

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