scholarly journals Dissolution, Stability and Solubility of Tooeleite [Fe6(AsO3)4(SO4)(OH)4·4H2O] at 25–45 °C and pH 2–12

Minerals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 921 ◽  
Author(s):  
Zongqiang Zhu ◽  
Jun Zhang ◽  
Yinian Zhu ◽  
Jie Liu ◽  
Shen Tang ◽  
...  
Keyword(s):  
Aqueous Medium ◽  
Solubility Product ◽  
Arsenic Concentration ◽  
Dissolved Iron ◽  
Activity Product ◽  
Free Energy Of Formation ◽  
Ion Activity ◽  
Initial Ph ◽  
Energy Of Formation

Tooeleite [Fe6(AsO3)4(SO4)(OH)4·4H2O] was synthesized and characterized to investigate its possible immobilization for arsenic in acidic and alkali environments by a long-term dissolution of 330 d. The synthetic tooeleite was platy crystallites of ~1μm across, giving the lattice parameters of a = 6.4758 Å, b = 19.3737 Å and c = 8.9170 Å. For the tooeleite dissolution, the dissolved arsenic concentration showed the lowest value of 427.3~435.8 mg/L As at initial pH 12 (final pH 5.54). The constituents were dissolved preferentially in the sequence of SO42− > AsO33− > Fe3+ in the aqueous medium at initial pH 2–12. The dissolved iron, arsenite and sulfate existed mainly as FeSO4+/Fe3+, H3AsO30 and SO42− at initial pH 2, and in the form of Fe(OH)30/Fe(OH)2+, H3AsO30 and SO42− at initial pH 12, respectively. The tooeleite dissolution was characterized by the preferential releases of SO42− anions from solid surface into aqueous medium, which was fundamentally controlled by the Fe-O/OH bond breakages and the outer OH− group layers. From the data of the dissolution at 25 °C and initial pH 2 for 270–330 d, the ion-activity product [logˍIAP], which equaled the solubility product [Ksp] at the dissolution equilibrium, and the Gibbs free energy of formation [ΔGfo] were estimated as −200.28 ± 0.01 and −5180.54 ± 0.07 kJ/mol for the synthetic tooeleite, respectively.

scholarly journals Dissolution and Solubility Product of Cd-Fluorapatite [Cd5(PO4)3F] at pH of 2–9 and 25–45°C

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Ju Lin ◽  
Zongqiang Zhu ◽  
Yinian Zhu ◽  
Huili Liu ◽  
Lihao Zhang ◽  
...  
Keyword(s):  
Solubility Product ◽  
Pure Water ◽  
Solution Ph ◽  
Cadmium Ions ◽  
Molar Ratios ◽  
Free Energy Of Formation ◽  
Initial Ph ◽  
Naoh Solution ◽  
Total Dissolution ◽  
Energy Of Formation

Dissolution of the synthetic cadmium fluorapatite [Cd5(PO4)3F] at 25°C, 35°C, and 45°C was experimentally examined in HNO3 solution, pure water, and NaOH solution. The characterization results confirmed that the cadmium fluorapatite nanorods used in the experiments showed no obvious variation after dissolution. During the dissolution of Cd5(PO4)3F in HNO3 solution (pH = 2) at 25°C, the fluoride, phosphate, and cadmium ions were rapidly released from solid to solution, and their aqueous concentrations had reached the highest values after dissolution for <1 h, 1440 h, and 2880 h, respectively. After that, the total dissolution rates declined slowly though the solution Cd/P molar ratios increased incessantly from 1.55∼1.67 to 3.18∼3.22. The solubility product for Cd5(PO4)3F (Ksp) was determined to be 10−60.03 (10−59.74∼10−60.46) at 25°C, 10−60.38 (10−60.32∼10−60.48) at 35°C, and 10−60.45 (10−60.33∼10−60.63) at 45°C. Based on the log Ksp values obtained at an initial pH of 2 and 25°C, the Gibbs free energy of formation for Cd5(PO4)3F (ΔGf0) was calculated to be −4065.76 kJ/mol (−4064.11∼−4068.23 kJ/mol). The thermodynamic parameters for the dissolution process were computed to be 342515.78 J/K·mol, −85088.80 J/mol, −1434.91 J/K·mol, and 2339.50 J/K·mol for ΔG0, ΔH0, ΔS0, and ΔCp0, correspondingly.

The Characteristic Dissolution and Physical Chemistry Parameter of Synthetic Pyromorphite

2014 ◽  
Vol 887-888 ◽  
pp. 975-978
Author(s):  
Xin Zhao ◽  
Wei Zou ◽  
Zong Lan Zhang ◽  
Zong Qiang Zhu ◽  
Yi Nian Zhu
Keyword(s):  
Free Energy ◽  
Solubility Product ◽  
Apatite Structure ◽  
Batch Experiments ◽  
Batch Dissolution ◽  
Free Energy Of Formation ◽  
The Mean ◽  
The Fourier Transform ◽  
Chemistry Parameter ◽  
Energy Of Formation

The Dissolution of Synthetic Pyromorphite was Studied at 25°C in a Series of Batch Experiments. in Addition, the Aqueous Concentrations from the Batch Dissolution were Used to Calculate the Solubility Product and Free Energy of Formation of Pyromorphite. the Results of the Fourier Transform Infrared Spectroscopy Analyses Indicated that the Synthetic, Microcrystalline Pyromorphite with Apatite Structure Used in the Experiments has Not Changed after Dissolution. the Mean KspValue was Calculated for Pb5(PO4)3Cl of 10-78.31 at 25°C; the Free Energy of Formation ΔGf0[Pb5(PO4)3Cl] was-3756.82kJ/mol.

scholarly journals Synthesis and solubility of brompyromorphite Pb5(PO4)3Br

Mineralogia ◽  
2012 ◽  
Vol 43 (1-2) ◽  
pp. 129-135 ◽  
Author(s):  
Urszula Janicka ◽  
Tomasz Bajda ◽  
Maciej Manecki
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Solubility Product ◽  
X Ray Diffraction ◽  
Ph Measurements ◽  
X Ray ◽  
Ph Values ◽  
Free Energy Of Formation ◽  
Scanning Electron ◽  
Energy Of Formation

AbstractThe bromide analogue of pyromorphite Pb5(PO4)3Br was synthesized and characterized by X-ray diffraction, infrared spectroscopy and scanning electron microscopy. The solubility of the brompyromorphite was measured at 25°C and pH values of 2.0, 2.6 and 3.2. For the 3 pH measurements, the average solubility product, log KSP, for the reaction Pb5(PO4)3Br ⇔ 5Pb2+ + 3PO- 3- + Br- at 25ºC is -77.38 ± 0.70. The free energy of formation, ΔG°f,298, calculated from this measured solubility product is -3724.7 ± 4.3 kJ mol−1. These results confirm that brompyromorphite is more soluble than pyromorphite.

Solubility of mimetite Pb5(AsO4)3Cl at 5 - 55°C

2010 ◽  
Vol 7 (3) ◽  
pp. 268 ◽  
Author(s):  
Tomasz Bajda
Keyword(s):  
Solubility Product ◽  
Contaminated Sites ◽  
Background Solution ◽  
Alkaline Ph ◽  
Arsenic Compounds ◽  
Weakly Alkaline ◽  
Hydrochemical Modelling ◽  
Ph Values ◽  
Free Energy Of Formation ◽  
Energy Of Formation

Environmetal context.The mobility of toxic arsenic compounds in the environment can be controlled by the solubility of certain minerals. To predict and model the fate and behaviour of these contaminants, the solubility and related thermodynamic properties of the lead and arsenic mineral mimetite were determined. The data obtained in this study will be used to optimise and increase the effectiveness of remediation procedures that are already applied to contaminated sites. Abstract.The solubility of the synthesised mimetite was measured in a series of dissolution experiments at 5–55°C and at pH values between 2.00 and 2.75. The solubility product logKSP for the reaction Pb5(AsO4)3Cl ↔ 5Pb2+ + 3AsO43– + Cl– at 25°C is –76.35 ± 1.01. The free energy of formation ΔGf,2980 calculated from this measured solubility product equals –2634.3 ± 5.9 kJ mol–1. The temperature dependence of the logKSP is non-linear, indicating that the enthalpy of the reaction depends on the temperature. The enthalpy of the formation of mimetite ΔHf0, is –2965.9 ± 4.7 kJ mol–1, the entropy, ΔS0, is 39.5 J mol–1 K–1, and the heat capacity, ΔCp,f0 is –6172 ± 105 J mol–1 K–1. Hydrochemical modelling indicates that regardless of the composition of the background solution, Pb5(AsO4)3Cl is most stable at neutral to weakly alkaline pH.

The stability, free energy and heat of formation of imogolite

Clay Minerals ◽  
1979 ◽  
Vol 14 (2) ◽  
pp. 103-107 ◽  
Author(s):  
V. C. Farmer ◽  
B. F. L. Smith ◽  
J. M. Tait
Keyword(s):  
Free Energy ◽  
Heat Of Formation ◽  
Free Energy Of Formation ◽  
The Stability ◽  
Energy Of Formation

AbstractFrom equilibrium silica concentrations over imogolite and boehmite at 100–155°C, the heat and free energy of the reaction (HO)3Al2O3SiOH + H2O ⇌ 2AlOOH + Si(OH)4 have been obtained: ΔH°r (298·15 K)=38·6 ± 4·1, ΔG°r (298·15 K) = 26.8 ± 1·1 kJ mol−1, and hence the heat and free energy of formation of imogolite: ΔH°f (298·15 K) = −3189·6 ± 4·1, ΔG°f (298·15 K) = − 2926·7 ± 1·1 kJ mol−1 These results are consistent with observations indicating that imogolite, halloysite and gibbsite can co-exist in soils, but that imogolite is metastable relative to either halloysite or gibbsite in the long term. At temperatures above 25°C there is a widening range of silica concentrations in which imogolite is more stable than halloysite, although both are metastable relative to kaolinite.

scholarly journals Solubility Product of Vanadinite Pb5(VO4)3Cl at 25 °C—A Comprehensive Approach to Incongruent Dissolution Modeling

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 135
Author(s):  
Justyna Topolska ◽  
Bartosz Puzio ◽  
Olaf Borkiewicz ◽  
Julia Sordyl ◽  
Maciej Manecki
Keyword(s):  
Nuclear Waste ◽  
Solubility Product ◽  
Geochemical Modeling ◽  
Incongruent Dissolution ◽  
Mineral Solubility ◽  
Actual Application ◽  
Universal Approach ◽  
Solubility Constant ◽  
First Time

Although vanadinite (Pb5(VO4)3Cl) occurs in abundance in various terrestrial geochemical systems of natural and anthropogenic origin and is seriously considered as a potential nuclear waste sequestering agent, its actual application is severely limited by a lack of understanding of its basic thermodynamic parameters. In this regard, the greatest challenge is posed by its incongruent dissolution, which is a pivotal hurdle for effective geochemical modeling. Our paper presents an universal approach for geochemical computing of systems undergoing incongruent dissolution which, along with unique, long-term experiments on vanadinites’ stability, allowed us to determine the mineral solubility constant. The dissolution experiments were carried out at pH = 3.5 for 12 years. Vanadinite has dissolved incongruently, continuously re-precipitating into chervetite (Pb2V2O7) with the two minerals remaining in mutual equilibrium until termination of the experiments. The empirically derived solubility constant Ksp,V,298 = 10–91.89 ± 0.05 of vanadinite was determined for the first time. The proposed modeling method is versatile and can be adopted to other mineral systems undergoing incongruent dissolution.

Standard Gibbs free energy of formation of ZrOS

1990 ◽  
Vol 163 (1) ◽  
pp. 109-113 ◽  
Author(s):  
Zhi-Tong Sui ◽  
Xing-Yi Xiao ◽  
Ke-Qin Huang ◽  
Chang-Zhen Wang
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Standard Gibbs Free Energy ◽  
Free Energy Of Formation ◽  
Energy Of Formation
Sign in / Sign up

Export Citation Format

Share Document