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2. The Aqueous Chemistry of Polonium and the Practical Application of Its Thermochemistry

Author

Susan A. Brown, Paul L. Brown, Susan A. Brown, and Paul L. Brown

Subjects
Polonium, Thermochemistry
Abstract

The Aqueous Chemistry of Polonium and the Practical Application of its Thermochemistry provides a thermochemical database and derived pH-potential diagrams to give readers a better understanding of polonium behavior. The book provides an introduction to polonium and its physical and chemical properties, as well as a detailed overview of polonium's chemical thermodynamics. Drawing on the knowledge of expert authors, the book provides key insights for those working with polonium across a range of different fields, from mining industry professionals and analytical chemists, to environmental remediation scientists. - Provides a unique and detailed review of polonium chemistry - Presents pH-potential diagrams for polonium and case studies showing their use in practice - Reviews the practical use of polonium in a range of different applications

Published
2019

3. Chalcopyrite dissolution: scanning photoelectron microscopy examination of the evolution of sulfur species with and without added iron or pyrite

Author

Gujie Qian, Yubiao Li, Andrea R. Gerson, Paul L. Brown, Li, Yubiao, Qian, Gujie, Brown, Paul L, and Gerson, Andrea R

Subjects
Supergene (geology), sulfur species, Sulfide, surface oxidation, Inorganic chemistry, chemistry.chemical_element, dissolution, 02 engineering and technology, 010501 environmental sciences, engineering.material, 01 natural sciences, Redox, 020501 mining & metallurgy, Geochemistry and Petrology, XPS, Dissolution, 0105 earth and related environmental sciences, chemistry.chemical_classification, Chemistry, Chalcopyrite, Sulfur, Sulfide minerals, chalcopyrite, 0205 materials engineering, visual_art, SPEM, engineering, visual_art.visual_art_medium, Pyrite
Abstract

Dissolution and oxidation of sulfide minerals play key roles in both acid and metalliferous rock drainage and supergene enrichment. Surface speciation heterogeneity, critical to understanding mechanisms of mineral sulfide dissolution, has to date largely not been considered. To this end synchrotron scanning photoelectron microscopy (SPEM) was employed to examine freshly fractured and partially dissolved chalcopyrite (CuFeS 2 ) surfaces (pH 1.0 HClO 4 solution, redox potential 650 mV relative to a standard hydrogen electrode, 75 °C). S 2− (bulk), S 2 2− and S n 2− were found to be present on all samples at varying concentrations. Oxidation was observed to take place heterogeneously at the sub-micron scale. As compared to chalcopyrite partially dissolved for 5 days, extended dissolution to 10 days did not show appreciably enhanced oxidation of surface species; however surface roughness increased markedly due to the growth/overlap of oxidised sulfur species. On addition of 4 mM iron both S 0 and SO 4 2− were observed but not SO 3 2− , indicating that the greater Fe 3+ activity/concentration promotes heterogeneous sulfur oxidation. On contact of pyrite (FeS 2 ) with chalcopyrite, significantly greater chalcopyrite surface oxidation was observed than for the other systems examined, with S 0 , SO 3 2− and SO 4 2− being identified heterogeneously across the surface. It is proposed that chalcopyrite oxidative dissolution is enhanced by increasing its cathodic area, e.g . contacting with pyrite, while increased Fe 3+ activity/concentration also contributes to increased dissolution rates. The high degree of surface heterogeneity of these surface products indicates that these surfaces are not passivated by their formation. These results suggest that chalcopyrite dissolution will be accelerated when in contact with pyrite at solution redox potential intermediate between the rest potentials of chalcopyrite and pyrite (560 mV and 660 mV, respectively) and/or iron rich acidic waters with resulting enhanced formation of secondary sulfur containing species and release of copper and iron. This in turn suggests accelerated supergene formation and enhanced metalliferous drainage under these conditions.

Published
2017

4. ThermoML: an XML-Based Approach for Storage and Exchange of Experimental and Critically Evaluated Thermophysical and Thermochemical Property Data. 5. Speciation and Complex Equilibria.

Author

Michael Frenkel, Vladimir Diky, Robert D. Chirico, Robert N. Goldberg, Heiko Heerklotz, John E. Ladbury, David P. Remeta, John H. Dymond, Anthony R. H. Goodwin, Kenneth N. Marsh, William A. Wakeham, Stephen E. Stein, Paul L. Brown, Erich Königsberger, and Peter A. Williams

Published
2011
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5. Chemical speciation of environmentally significant metals with inorganic ligands Part 2: The Cu2+-OH-, Cl-, CO32-, SO42-, and PO43- systems (IUPAC Technical Report).

Author

Kipton J. Powell, Paul L. Brown, Robert H. Byrne, Tamas Gajda, Glenn Hefter, Staffan Sjöberg, and Hans Wanner

Subjects
*CHEMICAL speciation, *METALS, *LIGANDS (Chemistry), *ANALYTICAL chemistry
Abstract

Analytical Chemistry DivisionComplex formation between CuII and the common environmental ligands Cl-, OH-, CO32-, SO42-, and PO43- can have a significant effect on CuII speciation in natural waters with low concentrations of organic matter. Copper(II) complexes are labile, so the CuII distribution amongst these inorganic ligands can be estimated by numerical modeling if reliable values for the relevant stability (formation) constants are available. This paper provides a critical review of such constants and related thermodynamic data. It recommends values of log10βp,q,r° valid at Im = 0 mol kg-1 and 25 °C (298.15 K), along with the equations and specific ion interaction coefficients required to calculate log10βp,q,r values at higher ionic strengths. Some values for reaction enthalpies, ΔrHm, are also reported where available. In weakly acidic fresh water systems, in the absence of organic ligands, CuII speciation is dominated by the species Cu2+(aq), with CuSO4(aq) as a minor species. In seawater, it is dominated by CuCO3(aq), with Cu(OH)+, Cu2+(aq), CuCl+, Cu(CO3)OH-, Cu(OH)2(aq), and Cu(CO3)22- as minor species. In weakly acidic saline systems, it is dominated by Cu2+(aq) and CuCl+, with CuSO4(aq) and CuCl2(aq) as minor species. [ABSTRACT FROM AUTHOR]

Published
2007
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6. Studies on the Hydrolytic Behavior of Zirconium(IV).

Author

Christian Ekberg, Göran Källvenius, Yngve Albinsson, and Paul L. Brown

Subjects
HYDROLYSIS, ZIRCONIUM, SOLVENT extraction, ELECTROCHEMICAL analysis
Abstract

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)22+, Zr(OH)3+, and Zr(OH)40(aq) as well as the polymeric species Zr4(OH)88+ and Zr2(OH)62+. 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 Δ Ho and Δ So 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)40(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 *Ks10) 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. [ABSTRACT FROM AUTHOR]

Published
2004

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