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1.
A platinum-lined, flowing autoclave facility is used to investigate the solubility behavior of copper(II) oxide (CuO) in aqueous sodium phosphate solutions at temperatures between 19 and 262°C. Copper solubilities are observed to increase continuously with temperature and phosphate concentration. The measured solubility behavior is examined via a Cu(II) ion hydrolysis/complexing model and thermodynamic functions for the hydrolysis/complexing reactions are obtained from a leastsquares analysis of the data. Altogether, thermochemical properties are established for five anionic complexes: Cu(OH)
3
–
, Cu(OH)
4
2–
, Cu(OH)
2
(HPO
4
)
2–
, Cu(OH)
3
(H
2
PO
4
)
2–
, and Cu(OH)
2
(PO
4
)
3–
. Precise thermochemical parameters are also derived for the Cu(OH)+ hydroxocomplex based on CuO solubility behavior previously observed (Ref. 3) for pure water at elevated temperatures. The relative ease of Cu(II) ion hydrolysis is such that Cu(OH)
3
–
species become the preferred hydroxocomplex for pH9.4.Prepared for presentation at the Fourth International Symposium on solubility Phenomena, Rensselaer Polytechnic Institute, August 1990. 相似文献
2.
A platinum-lined, flowing autoclave facility is used to investigate the solubility behavior of Cr2O3 and FeCr2O4 in alkaline sodium phosphate, sodium hydroxide, and ammonium hydroxide solutions between 21 and 288°C. Baseline Cr(III) ion solubilities were found to be on the order of 0.1 nmolal, which were enhanced by the formation of anionic hydroxo and phosphato complexes. At temperatures below 51°C, the activity of Cr(III) ions in aqueous solution is controlled by a Cr(OH)3·3H2O solid phase rather than Cr2O3; above 51°C the saturating solid phase is -CrOOH. Measured chromium solubilities were interpreted via a Cr(III) ion hydrolysis/complexing model and thermodynamic functions for the hydrolysis/complexing reaction equilibria were obtained from least-squares analyses of the data. The existence of four new Cr(III) ion complexes is reported: Cr(OH)3(H2PO4)–, Cr(OH)3(HPO4)2–, Cr(OH)3(PO4)3–, and Cr(OH)4(HPO4)-(H2PO4)4–. The last species is the dominant Cr(III) ion complex in concentrated, alkaline phosphate solutions at elevated temperatures. 相似文献
3.
A platinum-lined, flowing autoclave facility was used to investigate the solubility behavior of titanium dioxide (TiO2) in aqueous sodium phosphate, sodium hydroxide and ammonium hydroxide solutions between 17 and 288°. Baseline Ti(IV) solubilities were found to be on the order of one nanomolal, which were enhanced by the formation of anionic hydroxo- and phosphato-complexes. The measured solubility behavior was examined via a titanium(IV) ion hydrolysis/complexing reaction equilibria were obtained from a least squares analysis of the data. The existence of three new Ti(IV) ion complexes is reported for the first time: Ti(OH)4(HPO4)2–, Ti(OH)5(H2PO4)2– and Ti(OH)5(HPO4)3–. The triply-charged anionic complex was the dominant Ti(IV) species in concentrated, alkaline phosphate solutions at elevated temperatures. This complex is expected to exhibit C.N.=4 (i.e., Ti(OH)2OPO
4
3–
). A summary of thermochemical properties for species in the systems TiO2-H2O and TiO2-P2O5-H2O is also provided. 相似文献
4.
A platinum-lined, flowing autoclave facility was used to investigate the solubility/phase behavior of nickel oxide (NiO) in aqueous sodium phosphate solutions between 290 and 560 K. A layer of hydrous nickel oxide was concluded to exist on the nickel oxide surface below 468 K; only at higher temperatures did the anhydrous nickel oxide phase control the nickel ion solubility behavior. The measured solubility behavior was examined via a nickel(II) ion hydrolysis/complexing model and thermodynamic functions for the hydrolysis/complexing reaction equilibria were obtained from a least-squares analysis of the data. The existence of two new nickel ion complexes are reported for the first time: Ni(OH)2(HPO4)= and Ni(OH)3(H2PO4)=. The positive entropy change associated with the formation of Ni(OH)3(H2PO4)= leads to its dominance in alkaline phosphate solutions at elevated temperatures. 相似文献
5.
A platinum-lined flowing autocláve facility was used to investigate the solubility behavior of magnetite (Fe3O4) in alkaline sodium phosphate and ammonium hydroxide solutions between 21 and 288°C. Measured iron solubilities were interpreted via a Fe(II)/Fe(III) ion hydroxo-, phosphato-, and ammino-complexing model and thermodynamic functions for these equilibria were obtained from a least-squares analysis of the data. A total of 14 iron ion species were fitted. Complexing equilibria are reported for 8 new species: Fe(OH)(HPO4)–, Fe(OH)2(HPO4)2–, Fe(OH)3(HPO4)2–, Fe(OH)(NH3)+, Fe(OH)2(PO4)3–, Fe(OH)4(HPO4)3–, Fe(OH)2(H2PO4)–, and Fe(OH)3(H2PO4)3–. At elevated temperatures, hydrolysis and phosphato complexing tended to stabilize Fe(III) relative to Fe(II), as evidenced by free energy changes fitted to the oxidation reactions.
相似文献
6.
Wolfram W. Rudolph Murray H. Brooker Peter R. Tremaine 《Journal of solution chemistry》1999,28(5):621-630
Raman spectra have been measured for aqueous ZnSO4 solutions under hydrothermal conditions at steam saturation to 244°C; solubility has been recorded as a function of temperature from 25 to 256°C. The high-temperature Raman spectra contained two polarized bands, which suggest that a second sulfato complex, possibly bidentate, is formed in solution, in addition to the 1:1 zinc(II) sulfato complex, which is the only ion pair identified at lower temperatures. Under hydrothermal conditions, it was possible to observe the hydrolysis of the zinc(II) aquo ion by measuring the relative intensity of bands due to SO
4
2–
and HSO
4
–
according to the equilibrium reaction Zn(OH2)6]2+ + SO
4
2–
[Zn(OH2)5OH]+ + HSO
4
–
The precipitate in equilibrium with the solution at 210°C could be characterized as ZnSO4 · H2O (gunningite) by x-ray diffraction (XRD) and Raman and infrared spectroscopy. At 244°C the equilibrium precipitate could be identified as ZnSO4 (zincosite). 相似文献
7.
An aqueous thermodynamic model is developed which accurately describes the effects of high base concentration on the complexation of Ni2+ by ethylenedinitrilotetraacetic acid (EDTA). The model is primarily developed from an extensive dataset on the solubility of Ni(OH)2(cr) in the presence of EDTA and in the presence and absence of Ca2 + as the competing metal ion. The solubility data for Ni(OH)2(cr) were obtained in solutions ranging in NaOH concentration from 0.01 to 11.6 mol-kg–1, and in Ca2 + concentrations extending to saturation with respect to portlandite, Ca(OH)2. Owing to the inert nature of the Ni-EDTA complexation reactions, solubility experiments were approached from both the oversaturation and undersaturation direction and over time frames extending to 413 days. The final aqueous thermodynamic model is based upon the equations of Pitzer, accurately predicts the observed solubilities to concentrations as high as 11.6 mol-kg–1 NaOH, and is consistent with UV–Vis spectroscopic studies of the complexes in solution. 相似文献
8.
Dhanpat Rai Dean A. Moore Nancy J. Hess Linfeng Rao Sue B. Clark 《Journal of solution chemistry》2004,33(10):1213-1242
Chromium(III)-phosphate reactions are expected to be important in managing high-level radioactive wastes stored in tanks at many DOE sites. Extensive studies on the solubility of amorphous Cr(III) solids in a wide range of pH (2.8–14) and phosphate concentrations (10–4 to 1.0 m) at room temperature (22±2)°C were carried out to obtain reliable thermodynamic data for important Cr(III)-phosphate reactions. A combination of techniques (XRD, XANES, EXAFS, Raman spectroscopy, total chemical composition, and thermodynamic analyses of solubility data) was used to characterize solid and aqueous species. Contrary to the data recently reported in the literature,(1) only a limited number of aqueous species [Cr(OH)3H2PO–4, Cr(OH)3(H2PO4)2–2), and Cr(OH)3HPO2–4] with up to about four orders of magnitude lower values for the formation constants of these species are required to explain Cr(III)-phosphate reactions in a wide range of pH and phosphate concentrations. The log Ko values of reactions involving these species [Cr(OH)3(aq)+H2PO–4⇌Cr(OH)3H2PO–4; Cr(OH)3(aq)+2H2PO–4⇌Cr(OH)3(H2PO4)2–2; Cr(OH)3(aq)+HPO2–4⇌Cr(OH)3HPO2–4] were found to be 2.78±0.3, 3.48±0.3, and 1.97±0.3, respectively. 相似文献
9.
Christian Ekberg Göran Källvenius Yngve Albinsson Paul L. Brown 《Journal of solution chemistry》2004,33(1):47-79
The stability constants of zirconium(IV) hydrolysis species have been measured at 15, 25, and 35 °C [in 1.0 mol-dm–3 (H,Na)ClO4] using both potentiometry and solvent extraction. In addition, the solubility of [Zr(OH)4(am)] has been investigated in a 1 mol-dm–3 (Na,H)(ClO4,OH) medium at 25 °C over a wide range of –log [H+] (0-15). The results indicate the presence of the monomeric species Zr(OH)3+, Zr(OH)2
2+, Zr(OH)3
+, and Zr(OH)4
0(aq) as well as the polymeric species Zr4(OH)8
8+ and Zr2(OH)6
2+. The solvent extraction measurements required the use of acetylacetone. As such, the stability constants of zirconium(IV) with acetylacetone were also measured using solvent extraction. All stability constants were found to be linear functions of the reciprocal of temperature (in kelvin) indicating that H
o
and S
o
are both independent of temperature (over the temperature range examined in the study). The results of the solubility experiments have shown four distinctly different solubility regions. In strongly acidic solutions, the solubility is controlled by the formation of polynuclear hydrolysis species in solution whereas in less acidic solution the formation of mononuclear hydrolysis species becomes dominant. The largest portion of the solubility curve is controlled by equilibrium with aqueous Zr(OH)4
0(aq) where the solubility is independent of the proton concentration. In alkaline solutions, the solubility increases due to formation of the zirconate ion. The middle region was used to determine the solubility constant (log *K
s10) of Zr(OH)4(s). From the data in the alkaline region, a value of the stability of the zirconate ion has been determined. This is the first time that the possible evidence for the zirconate ion has been identified in aqueous solution that has previously been found only in the solid phase. 相似文献
10.
The solubility of Cd(OH)2(c) was studied in 0.01M NaClO4 solutions, from both the over- and the undersaturation directions, with OH– ion concentration ranging from 10–6 to 1.0 mol-L–1, and the equilibration period ranging from 2 to 28 days. Equilibrium Cd concentrations were reached in less than 2 days. The Cd(OH)2(c) solubility showed an amphoteric behavior. In the entire range of OH–/H+ investigated, the only dominant aqueous Cd(II) species required to explain the solubility of Cd(OH)2(c) are Cd2+, Cd(OH)
2
0
, and Cd(OH)
4
2–
. The logarithms of the thermodynamic equilibrium constants of the Cd(OH)2(c) solubility reactions involving these species, that is, the reactions
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