137 results on '"Paul L. Brown"'
Search Results
2. Polyethylenimine–Silica–Magnetic Nanoparticle Composites for Efficient Extraction of Dissolved Copper from Aqueous Solutions and Multiphase Mixtures
- Author
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Alexandra Semenova, Mark Louis P. Vidallon, Kiyonori Suzuki, Bart Follink, Paul L. Brown, and Rico F. Tabor
- Subjects
General Materials Science - Published
- 2023
3. Copper-Binding Properties of Polyethylenimine–Silica Nanocomposite Particles
- Author
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Alexandra Semenova, Luke W. Giles, Mark Louis P. Vidallon, Bart Follink, Paul L. Brown, and Rico F. Tabor
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Microgels ,Electrochemistry ,Polyethyleneimine ,General Materials Science ,Surfaces and Interfaces ,Silicon Dioxide ,Condensed Matter Physics ,Copper ,Spectroscopy ,Chelating Agents ,Nanocomposites - Abstract
Increasing demand for copper resources, accompanied by increasing pollution, has resulted in an urgent need for effective materials for copper binding and extraction. Polyethylenimine (PEI) is one of the strongest copper-chelating agents but is not suitable directly (as is) for most applications due to its high solubility in water. PEI-based composite materials show potential as efficient and practical alternatives. In the present work, the interaction of copper ions with PEI-silica nanocomposite particles and precursor PEI microgels (as a reference) is investigated. It is hypothesized that the main driving force of the reaction is chelation of copper ions by amino groups in the PEI network. The presence of silica in the PEI-silica composites was shown to increase the copper-binding capacity in comparison with the parent microgel. The copper-binding behavior of etched (PEI-free "ghost") composite particles in comparison with the original composites and microgel particles shows that silica nanoparticles in the composite structure increase the number of copper-binding sites in the PEI network rather than adsorbing copper themselves. PEI-silica composites can be easily recycled after copper adsorption by simply washing in 1 M nitric acid, which results in complete copper extraction. Employing this recovery method, PEI-silica composite particles can be used for multiple, efficient cycles of copper removal and extraction.
- Published
- 2022
4. The aqueous chemistry of radium
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Paul L. Brown, Artem V. Matyskin, and Christian Ekberg
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Physical and Theoretical Chemistry - Abstract
Available literature data on the aqueous chemistry of radium are compiled. There are limited available experimental data and a significant portion of the data has been estimated using electrostatic techniques, typically based on the corresponding data of barium. The available data are compared with the corresponding data of barium (and strontium) and a methodology for estimating additional radium thermochemical data is described.
- Published
- 2022
5. Synthesis and Characterization of Polyethylenimine–Silica Nanocomposite Microparticles
- Author
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Alexandra Semenova, Mark Louis P. Vidallon, Bart Follink, Paul L. Brown, and Rico F. Tabor
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Electrochemistry ,General Materials Science ,02 engineering and technology ,Surfaces and Interfaces ,010402 general chemistry ,021001 nanoscience & nanotechnology ,0210 nano-technology ,Condensed Matter Physics ,01 natural sciences ,Spectroscopy ,0104 chemical sciences - Abstract
A novel procedure for the synthesis of polyethylenimine (PEI)-silica nanocomposite particles with high adsorption capacities has been developed based on an emulsion templating concept. The exceptional chelating properties of PEI as the parent polymer for the particle core promote the binding abilities of the resulting composite for charged species. Further, the subsequent introduction of silica via the self-catalyzed hydrolysis of tetraethoxysilane facilitates production of robust composite particles with smooth surfaces, enabling potential use in multiphase environments. To enable tailored application in solid/liquid porous environments, the production of particles with reduced sizes was attempted by modulating the shear rates and surfactant concentrations during emulsification. The use of high-speed homogenization resulted in a substantial decrease in average particle size, while increasing surfactant loading only had a limited effect. All types of nanocomposites produced demonstrated excellent binding capacities for copper ions as a test solute. The maximum binding capacities of the PEI-silica nanocomposites of 210-250 mg/g are comparable to or exceed those of other copper binding materials, opening up great application potential in resources, chemical processing, and remediation industries.
- Published
- 2021
6. Hydrolysis of Metal Ions
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Paul L. Brown, Christian Ekberg and Paul L. Brown, Christian Ekberg
- Published
- 2016
7. Thallium toxicity to temperate and tropical marine organisms: Derivation of water quality guidelines to protect marine life
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Scott J. Markich, Jeremy P. Hall, Jude M. Dorsman, and Paul L. Brown
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Aquatic Science ,Oceanography ,Pollution - Published
- 2023
8. Guidelines for thermodynamic sorption modelling in the context of radioactive waste disposal.
- Author
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Tim E. Payne, Vinzenz Brendler, Michael Ochs, Bart Baeyens, Paul L. Brown, Jim A. Davis, Christian Ekberg, Dmitrii A. Kulik, Johannes Lützenkirchen, Tiziana Missana, Yukio Tachi, Luc R. Van Loon, and Scott Altmann
- Published
- 2013
- Full Text
- View/download PDF
9. Analysis of a Large Structure/Biological Activity Data Set Using Recursive Partitioning.
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Andrew Rusinko III, Mark W. Farmen, Christophe G. Lambert, Paul L. Brown, and S. Stanley Young
- Published
- 1999
- Full Text
- View/download PDF
10. Determining Stability Constants Using the AKUFVE Technique
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Christian Ekberg, Mikael Nilsson, and Paul L. Brown
- Subjects
Activity coefficient ,Series (mathematics) ,Chemistry ,General Chemical Engineering ,Extraction (chemistry) ,Analytical chemistry ,02 engineering and technology ,General Chemistry ,010403 inorganic & nuclear chemistry ,01 natural sciences ,Stability (probability) ,0104 chemical sciences ,Physics::Fluid Dynamics ,Condensed Matter::Soft Condensed Matter ,symbols.namesake ,020401 chemical engineering ,Rydberg formula ,symbols ,0204 chemical engineering ,Solvent extraction - Abstract
The AKUFVE techniques were developed by Rydberg and co-workers in the 1960s. The main aim was to be able to perform a series of liquid-liquid extraction data varying one or more parameters ...
- Published
- 2019
11. Weak barium and radium hydrolysis using an ion exchange method and its uncertainty assessment
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Christian Ekberg, Artem V. Matyskin, and Paul L. Brown
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Activity coefficient ,Aqueous solution ,Ion exchange ,Chemistry ,Analytical chemistry ,02 engineering and technology ,Ion-association ,010402 general chemistry ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Ion ,020401 chemical engineering ,Specific ion interaction theory ,Stability constants of complexes ,Ionic strength ,General Materials Science ,0204 chemical engineering ,Physical and Theoretical Chemistry - Abstract
The hydrolysis of Ba2+and Ra2+was studied at 25 °C in aqueous mixtures of NaOH and NaClO4using an ion exchange method and radiotracer and batch techniques. The distribution of133Ba and226Ra between solid (ion exchange resin) and aqueous (mixture of NaOH and NaClO4) phases was measured via gamma spectrometry and liquid scintillation counting. The total ionic strength was kept constant and the concentration of NaOH in the aqueous phase was varied from 0 (pure NaClO4) to pure NaOH from sample to sample. It was shown that an increase of the Ba2+or Ra2+concentration in the aqueous phase with an increase of the NaOH concentration cannot be explained solely by Ba2+or Ra2+activity coefficient differences in the NaOH and NaClO4media (salting out) and that weak BaOH+and RaOH+ion pairing occurs in the systems studied. A model for weak ion association was developed and apparent BaOH+and RaOH+stability constants were derived assuming the formation of weak aqueous NaOH(aq) ion pairs via non-linear curve fitting. It was demonstrated that systematic uncertainties have a much greater contribution to the NaOH(aq), BaOH+and RaOH+stability constant uncertainty budget compared to stochastic uncertainties and a method for estimation of the systematic uncertainties was proposed. The method combines fitting, restricted primitive model computations with surveyed literature data that resulted in a stability constant for NaOH(aq) that ranged from 0 to 1 at ionic strengths below 5 mol·kg−1(i.e. KNaOH= 0.5 ± 0.5, where the uncertainty is a systematic 95% confidence interval). The variation of KNaOHallowed the estimation of the systematic 95% confidence interval in the apparent stability constants of BaOH+and RaOH+. The specific ion interaction theory was used to extrapolate the derived logarithms of the BaOH+and RaOH+apparent stability constants to zero ionic strength (log10K = 0.7 ± 0.2 for both ion pairs) and obtain the relevant ion interaction parameters. It was shown that both the Ba2+and Ra2+ions have similar activity coefficients and undergo similar short-range interactions in aqueous NaOH-NaClO4media.
- Published
- 2019
12. Geochemical and hydrological evolution of mine impacted waters at the Argyle Diamond Mine, Western Australia
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Richard K. Borden, Paul L. Brown, and Samantha Sturgess
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Geochemistry and Petrology ,Environmental Chemistry ,Pollution - Published
- 2022
13. The pH-potential diagram for polonium
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Paul L. Brown and Susan A. Brown
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Physics ,chemistry ,Simple (abstract algebra) ,Diagram ,chemistry.chemical_element ,Thermodynamics ,Polonium - Abstract
The most simple pH-potential diagram for polonium is produced. An outline of the production of pH-potential diagrams is given.
- Published
- 2020
14. Physical and chemical properties
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Susan A. Brown and Paul L. Brown
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Metal ,Chalcogen ,Ion exchange ,Chemistry ,visual_art ,Radiochemistry ,visual_art.visual_art_medium ,chemistry.chemical_element ,Halide ,Solvent extraction ,Isotopes of polonium ,Polonium - Abstract
The physical and chemical properties of polonium are outlined. These include the isotopes of polonium, polonium metal, the oxidation states of polonium, polonium oxides, hydroxides and hydrides, polonium halides, polonides, polonites, and polonium compounds with other chalcogens, polonium nitrates, solvent extraction of polonium, ion exchange of polonium, and other behavior.
- Published
- 2020
15. The use of pH–potential diagrams in practical applications
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Susan A. Brown and Paul L. Brown
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Aqueous solution ,chemistry ,business.industry ,Rare earth ,chemistry.chemical_element ,Seawater ,Tellurium ,Process engineering ,business ,Selenium ,Polonium ,Anode - Abstract
The thermochemical database that has been developed is applied in a relatively wide range of applications. The derivation of pH–potential diagrams is undertaken across a wide range of systems related to polonium, in particular, those of selenium, tellurium, and lead. A number of case studies are then developed to describe the aqueous chemistry of polonium including its behavior in anode slimes, in silver and gold reprocessing, in seawater, in its autodeposition, and in the processing of rare earth minerals.
- Published
- 2020
16. Conclusions
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Susan A. Brown and Paul L. Brown
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- 2020
17. Polonium
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Susan A. Brown and Paul L. Brown
- Published
- 2020
18. Chemical thermodynamics of polonium
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Susan A. Brown and Paul L. Brown
- Subjects
Physics ,symbols.namesake ,Chemical thermodynamics ,chemistry ,symbols ,Thermodynamics ,chemistry.chemical_element ,Polonium ,Gibbs free energy - Abstract
This chapter outlines the general principles associated with development of thermodynamic data for an element and then derives a database of thermodynamic parameters, principally Gibbs energy values, for polonium species. A large number of thermochemical data are derived.
- Published
- 2020
19. The Aqueous Chemistry of Polonium and the Practical Application of Its Thermochemistry
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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
20. Actinide Speciation and Bioavailability in Fresh and Marine Waters
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Scott J. Markich and Paul L. Brown
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geography ,geography.geographical_feature_category ,Chemistry ,Bioaccumulation ,Environmental chemistry ,Genetic algorithm ,chemistry.chemical_element ,Seawater ,Estuary ,Ocean acidification ,Actinide ,Uranium ,Bioavailability - Published
- 2018
21. Barium and Radium Complexation with Ethylenediaminetetraacetic Acid in Aqueous Alkaline Sodium Chloride Media
- Author
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Christian Ekberg, Artem V. Matyskin, Paul L. Brown, and Niklas Hansson
- Subjects
Specific ion interaction theory ,Metal ions in aqueous solution ,Activity coefficient ,Inorganic chemistry ,Biophysics ,Ethylenediaminetetraacetic acid ,010402 general chemistry ,010403 inorganic & nuclear chemistry ,Alkaline-earth metal ,01 natural sciences ,Biochemistry ,Article ,chemistry.chemical_compound ,Physical and Theoretical Chemistry ,Molecular Biology ,Aqueous solution ,Ion exchange ,Ligand ,Chemistry ,Aqueous two-phase system ,EDTA ,Complex formation ,0104 chemical sciences ,Ionic strength ,Infinite dilution - Abstract
The speciation of Ra 2+ and Ba 2+ with EDTA was investigated at 25 °C in aqueous alkaline NaCl media as a function of ionic strength (0.2–2.5 mol·L −1 ) in two pH regions where the EDTA 4− and HEDTA 3− species dominate. The stability constants for the formation of the [BaEDTA] 2− and [RaEDTA] 2− complexes were determined using an ion exchange method. Barium-133 and radium-226 were used as radiotracers and their concentrations in the aqueous phase were measured using liquid scintillation counting and gamma spectrometry, respectively. The specific ion interaction theory (SIT) was used to account for [NaEDTA] 3− and [NaHEDTA] 2− complex formation, and used to extrapolate the logarithms of the apparent stability constants (log 10 K) to zero ionic strength (BaEDTA 2− : 9.86 ± 0.09; RaEDTA 2− : 9.13 ± 0.07) and obtain the Ba 2+ and Ra 2+ ion interaction parameters: [e(Na + , BaEDTA 2− ) = − (0.03 ± 0.11); e(Na + , RaEDTA 2− ) = − (0.10 ± 0.11)]. It was found that in the pH region where HEDTA 3− dominates, the reaction of Ba 2+ or Ra 2+ with the HEDTA 3− ligand also results in the formation of the BaEDTA 2− and RaEDTA 2− complexes (as it does in the region where the EDTA 4− ligand dominates) with the release of a proton. Comparison of the ion interaction parameters of Ba 2+ and Ra 2+ strongly indicates that both metal ions and their EDTA complexes have similar activity coefficients and undergo similar short-range interactions in aqueous NaCl media.
- Published
- 2017
22. Chalcopyrite dissolution: scanning photoelectron microscopy examination of the evolution of sulfur species with and without added iron or pyrite
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Gujie Qian, Yubiao Li, Andrea R. Gerson, Paul L. Brown, Li, Yubiao, Qian, Gujie, Brown, Paul L, and Gerson, Andrea R
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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
23. Chemical speciation of environmentally significant metals with inorganic ligands. Part 5: The Zn2+ + OH–, Cl–, CO3 2–, SO4 2–, and PO4 3– systems (IUPAC Technical Report)
- Author
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Kipton J. Powell, Paul L. Brown, Robert H. Byrne, Tamás Gajda, Glenn Hefter, Ann-Kathrin Leuz, Staffan Sjöberg, and Hans Wanner
- Subjects
TheoryofComputation_ANALYSISOFALGORITHMSANDPROBLEMCOMPLEXITY ,General Chemical Engineering ,General Chemistry - Abstract
The numerical modeling of ZnII speciation amongst the environmental inorganic ligands Cl–, OH–, CO3 2–, SO4 2–, and PO4 3– requires reliable values for the relevant stability (formation) constants. This paper compiles and provides a critical review of these constants and related thermodynamic data. It recommends values of log10 β p,q,r ° valid at I m = 0 mol·kg–1 and 25 °C (298.15 K), and reports the empirical reaction ion interaction coefficients, ∆ε, required to calculate log10 β p,q,r values at higher ionic strengths using the Brønsted–Guggenheim–Scatchard specific ion interaction theory (SIT). Values for the corresponding reaction enthalpies, ∆r H, are reported where available. There is scope for additional high-quality measurements for the Zn2+ + H+ + CO3 2– system and for the Zn2+ + OH– and Zn2+ + SO4 2– systems at I > 0. In acidic and weakly alkaline fresh water systems (pH < 8), in the absence of organic ligands (e.g., humic substances), ZnII speciation is dominated by Zn2+(aq). In this respect, ZnII contrasts with CuII and PbII (the subjects of earlier reviews in this series) for which carbonato- and hydroxido- complex formation become important at pH > 7. The speciation of ZnII is dominated by ZnCO3(aq) only at pH > 8.4. In seawater systems, the speciation at pH = 8.2 is dominated by Zn2+(aq) with ZnCl+, Zn(Cl)2(aq), ZnCO3(aq), and ZnSO4(aq) as minor species. This behaviour contrasts with that for CuII and PbII for which at the pH of seawater in equilibrium with the atmosphere at 25 °C (log10 {[H+]/c°} ≈ 8.2) the MCO3(aq) complex dominates over the MCl n (2–n)+ species. The lower stability of the different complexes of ZnII compared with those of CuII, PbII, and CdII is also illustrated by the percentage of uncomplexed M2+ in seawater, which is ca. 55, 3, 2, and 3.3 % of [MII]T, respectively.
- Published
- 2013
24. Improvement of Quality in Publication of Experimental Thermophysical Property Data: Challenges, Assessment Tools, Global Implementation, and Online Support
- Author
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Lee D. Hansen, Ron D. Weir, Sergey Vyazovkin, Paul M. Mathias, Michael D. Frenkel, Paul L. Brown, Andrei F. Kazakov, William E. Acree, Vicente Rives, John P. O'Connell, Theo W. de Loos, Joan F. Brenneke, Kenneth N. Marsh, Christoph Schick, Daniel G. Friend, Vladimir Diky, Andreas Mandelis, Jiangtao Wu, Chris D. Muzny, Nobuyoshi Koga, Peter T. Cummings, Ilmutdin M. Abdulagatov, Anthony R. H. Goodwin, Robert D. Chirico, Agilio A. H. Padua, Gary R. Hardin, Clare McCabe, Joseph W. Magee, Kenneth Kroenlein, William M. Haynes, and J. P. Martin Trusler
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Property (programming) ,business.industry ,Chemistry ,General Chemical Engineering ,media_common.quotation_subject ,Experimental data ,General Chemistry ,Field (computer science) ,Engineering management ,Software ,NIST ,Fluid phase ,Quality (business) ,business ,Publication process ,media_common - Abstract
This article describes a 10-year cooperative effort between the U.S. National Institute of Standards and Technology (NIST) and five major journals in the field of thermophysical and thermochemical properties to improve the quality of published reports of experimental data. The journals are Journal of Chemical and Engineering Data, The Journal of Chemical Thermodynamics, Fluid Phase Equilibria, Thermochimica Acta, and International Journal of Thermophysics. The history of this unique cooperation is outlined, together with an overview of software tools and procedures that have been developed and implemented to aid authors, editors, and reviewers at all stages of the publication process, including experiment
- Published
- 2013
25. Guidelines for thermodynamic sorption modelling in the context of radioactive waste disposal
- Author
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Timothy E. Payne, James A. Davis, Christian Ekberg, Y. Tachi, Paul L. Brown, Bart Baeyens, L.R. Van Loon, Scott Altmann, Vinzenz Brendler, Tiziana Missana, Michael Ochs, Dmitrii A. Kulik, and Johannes Lützenkirchen
- Subjects
Iterative and incremental development ,Environmental Engineering ,Process (engineering) ,business.industry ,Ecological Modeling ,Environmental engineering ,Radioactive waste ,Context (language use) ,Sorption ,modelling ,repository ,Component (UML) ,radioactive waste ,Range (statistics) ,Environmental science ,Safety case ,distribution coefficient ,Process engineering ,business ,Software - Abstract
Thermodynamic sorption models (TSMs) offer the potential to improve the incorporation of sorption in environmental modelling of contaminant migration. One specific application is safety cases for radioactive waste repositories, in which radionuclide sorption on mineral surfaces is usually described using distribution coefficients (K"d values). TSMs can be utilised to provide a scientific basis for the range of K"d values included in the repository safety case, and for assessing the response of K"d to changes in chemical conditions. The development of a TSM involves a series of decisions on model features such as numbers and types of surface sites, sorption reactions and electrostatic correction factors. There has been a lack of consensus on the best ways to develop such models, and on the methods of determination of associated parameter values. The present paper therefore presents recommendations on a number of aspects of model development, which are applicable both to radioactive waste disposal and broader environmental applications. The TSM should be calibrated using a comprehensive sorption data set for the contaminant of interest, showing the impact of major geochemical parameters including pH, ionic strength, contaminant concentration, the effect of ligands, and major competing ions. Complex natural materials should be thoroughly characterised in terms of mineralogy, surface area, cation exchange capacity, and presence of impurities. During the application of numerical optimisation programs to simulate sorption data, it is often preferable that the TSM should be fitted to the experimentally determined K"d parameter, rather than to the frequently used percentage sorbed. Two different modelling approaches, the component additivity and generalised composite, can be used for modelling sorption data for complex materials such as soils. Both approaches may be coupled to the same critically reviewed aqueous thermodynamic data sets, and may incorporate the same, or similar, surface reactions and surface species. The quality of the final sorption model can be assessed against the following characteristics: an appropriate level of complexity, documented and traceable decisions, internal consistency, limitations on the number of adjustable parameter values, an adequate fit to a comprehensive calibration data set, and capability of simulating independent data sets. Key recommendations for the process of TSM development include: definition of modelling objectives, identification of major decision points, a clear decision-making rationale with reference to experimental or theoretical evidence, utilisation of a suitable consultative and iterative model development process, testing to the maximum practicable extent, and thorough documentation of key decisions. These recommendations are consistent with international benchmarks for environmental modelling.
- Published
- 2013
26. Hydrolysis of Metal Ions
- Author
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Christian Ekberg and Paul L. Brown
- Subjects
Hydrolysis ,Chemistry ,Metal ions in aqueous solution ,Inorganic chemistry - Published
- 2016
27. Appendix: Extended Specific Ion Interaction Theory: Ion Interaction Coefficients
- Author
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Christian Ekberg and Paul L. Brown
- Subjects
Specific ion interaction theory ,Chemical physics ,Chemistry ,Computational chemistry ,Ion - Published
- 2016
28. Extension of ThermoML: The IUPAC standard for thermodynamic data communications (IUPAC Recommendations 2011)
- Author
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John E. Ladbury, Erich Königsberger, J. H. Dymond, Paul L. Brown, William A. Wakeham, Heiko Heerklotz, Peter A. Williams, Stephen E. Stein, Vladimir Diky, David P. Remeta, Anthony R. H. Goodwin, Michael D. Frenkel, Robert D. Chirico, Kenneth N. Marsh, and Robert N. Goldberg
- Subjects
Schema (genetic algorithms) ,Information retrieval ,Chemistry ,computer.internet_protocol ,General Chemical Engineering ,Chemical nomenclature ,ComputingMethodologies_DOCUMENTANDTEXTPROCESSING ,General Chemistry ,Extension (predicate logic) ,computer ,XML - Abstract
ThermoML is an XML-based approach for storage and exchange of experimental, predicted, and critically evaluated thermophysical and thermochemical property data. Extensions to the ThermoML schema for the representation of speciation, complex equilibria, and properties of biomaterials are described. The texts of 14 data files illustrating the new extensions are provided as Supplementary Information together with the complete text of the updated ThermoML schema.
- Published
- 2011
29. Chemical speciation of environmentally significant metals with inorganic ligands. Part 4: The Cd2+ + OH–, Cl–, CO32–, SO42–, and PO43– systems (IUPAC Technical Report)
- Author
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Robert H. Byrne, Ann Kathrin Leuz, Tamás Gajda, Staffan Sjöberg, Hans Wanner, Paul L. Brown, Kipton J. Powell, and Glenn Hefter
- Subjects
chemistry.chemical_classification ,Cadmium ,Chemical speciation ,General Chemical Engineering ,Natural water ,Chemical nomenclature ,Complex formation ,Inorganic chemistry ,chemistry.chemical_element ,General Chemistry ,Zinc ,Copper ,chemistry ,TheoryofComputation_ANALYSISOFALGORITHMSANDPROBLEMCOMPLEXITY ,Environmental chemistry ,Organic matter - Abstract
The numerical modeling of CdII speciation amongst the environmental inorganic ligands Cl–, OH–, CO3 2–, SO4 2–, and PO4 3– requires reliable values for the relevant stability (formation) constants. This paper compiles and provides a critical review of these constants and related thermodynamic data. It recommends values of log10 β p,q,r ° valid at I m = 0 mol kg–1 and 25 °C (298.15 K), along with the equations and empirical reaction ion interaction coefficients, ∆ε , required to calculate log10 β p,q,r values at higher ionic strengths using the Brønsted–Guggenheim–Scatchard specific ion interaction theory (SIT). Values for the corresponding reaction enthalpies, ∆r H, are reported where available. Unfortunately, with the exception of the CdII-chlorido system and (at low ionic strengths) the CdII-sulfato system, the equilibrium reactions for the title systems are relatively poorly characterized. In weakly acidic fresh water systems (–log10 {[H+]/c°} < 6), in the absence of organic ligands (e.g., humic substances), CdII speciation is dominated by Cd2+(aq), with CdSO4(aq) as a minor species. In this respect, CdII is similar to CuII [2007PBa] and PbII [2009PBa]. However, in weakly alkaline fresh water solutions, 7.5 < –log10 {[H+]/c°} < 8.6, the speciation of CdII is still dominated by Cd2+(aq), whereas for CuII [2007PBa] and PbII [2009PBa] the carbonato- species MCO3(aq) dominates. In weakly acidic saline systems (–log10 {[H+]/cϒ} < 6; –log10 {[Cl–]/c°} < 2.0) the speciation is dominated by CdCl n (2– n )+ complexes, (n = 1–3), with Cd2+(aq) as a minor species. This is qualitatively similar to the situation for CuII and PbII. However, in weakly alkaline saline solutions, including seawater, the chlorido- complexes still dominate the speciation of CdII because of the relatively low stability of CdCO3(aq). In contrast, the speciation of CuII [2007PBa] and PbII [2009PBa] in seawater is dominated by the respective species MCO3(aq). There is scope for additional high-quality measurements in the Cd2+ + H+ + CO3 2– system as the large uncertainties in the stability constants for the Cd2+-carbonato complexes significantly affect the speciation calculations.
- Published
- 2011
30. 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
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Vladimir Diky, David P. Remeta, Anthony R. H. Goodwin, Kenneth N. Marsh, John E. Ladbury, Robert D. Chirico, Heiko Heerklotz, J. H. Dymond, Erich Königsberger, Stephen E. Stein, Robert N. Goldberg, Michael D. Frenkel, Peter A. Williams, Paul L. Brown, and William A. Wakeham
- Subjects
computer.internet_protocol ,Programming language ,Chemistry ,General Chemical Engineering ,Schema (psychology) ,ComputingMethodologies_DOCUMENTANDTEXTPROCESSING ,General Chemistry ,computer.software_genre ,computer ,XML - Abstract
ThermoML is an XML-based approach for storage and exchange of measured and critically evaluated thermophysical and thermochemical property data. Extensions to the ThermoML schema for the representation of speciation and complex equilibria are described. The text of ThermoML (xml) is provided to illustrate application of the new extensions. These are provided as Supporting Information together with the complete updated ThermoML schema.
- Published
- 2011
31. Complexation of thorium with phosphate
- Author
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Christian Ekberg, Andreas Knutsson, Yngve Albinsson, and Paul L. Brown
- Subjects
chemistry.chemical_compound ,chemistry ,Inorganic chemistry ,Complex formation ,Extraction (chemistry) ,Thorium ,chemistry.chemical_element ,Physical and Theoretical Chemistry ,Solvent extraction ,Phosphate ,Hydrogen phosphate ,Nuclear chemistry - Abstract
Using liquid–liquid extraction and the AKUFVE-technique developed by the Nuclear Chemistry Department at Chalmers University of Technology, Sweden, the complex formation equilibria of hydrogen phosphate (HPO4 2−) with thorium have been studied at different temperatures (15, 25 and 35 °C), varying pH (7, 8 and 8.7) and in 1 M (Na,H)ClO4. Evaluation of the acquired solvent extraction data indicated the formation of the ThHPO4 2+, Th(HPO4)2(aq) and Th(HPO4)3 2− complexes. For Th(HPO4)2(aq) and Th(HPO4)3 2−, the logarithm of the stability constants obtained at 25 °C were 17.0±3.5 and 23.7±0.2, respectively. Only an estimate of the stability of ThHPO4 2+ could be obtained. Enthalpies and entropies of the complex formation reactions have been determined: Th(HPO4)2(aq) (ΔH=698±27 kJ mol−1, ΔS=2669±91 J mol−1 K−1) and Th(HPO4)3 2− (ΔH=499±4 kJ mol−1, ΔS=2137±12 J mol−1 K−1).
- Published
- 2010
32. Dissociation Constants of α-<scp>d</scp>-Isosaccharinic Acid: 'Composite' and 'Intrinsic' Values
- Author
-
Christian Ekberg, Paul L. Brown, and Stefan Allard
- Subjects
Aqueous solution ,General Chemical Engineering ,Inorganic chemistry ,Thermodynamics ,Protonation ,General Chemistry ,Sodium perchlorate ,Dissociation (chemistry) ,Dissociation constant ,chemistry.chemical_compound ,chemistry ,Ionic strength ,Solubility ,Isosaccharinic acid - Abstract
The transformation of alpha-D-isosaccharinic acid into alpha-D-isosaccharino-1,4-lactone proceeds relatively slowly. Consequently, the transformation constant, K-L, has been determined kinetically in 1.0 mol center dot dm(-3) NaClO4 and at 23 degrees C. A previous determination in 0.1 mol center dot dm(-3) NaClO4 and at 23 degrees C has been reinterpreted. The values obtained have been coupled with other data in the literature to demonstrate that the magnitude of the transformation constant is independent of ionic strength, and its value was determined to be log K-L degrees = 0.80 +/- 0.02. Data from the literature for the dissociation of alpha-D-isosaccharinic acid have been re-evaluated to determine both the "intrinsic" and "composite" dissociation constants at zero ionic strength, namely, log K-u degrees = -4.04 +/- 0.06 and log K-c degrees = -4.90 +/- 0.07, respectively. The present data permit a much more thorough understanding of the aqueous chemistry of alpha-D-isosaccharinic acid to be ascertained than has previously been possible.
- Published
- 2010
33. The impact of pyrite variability, dispersive transport and precipitation of secondary phases on the sulphate release due to pyrite weathering
- Author
-
Asaf Pekdeger, Claire M. Linklater, Claus Kohfahl, Kai Mazur, Parviz Irannejad, and Paul L. Brown
- Subjects
Gypsum ,Mineralogy ,Weathering ,engineering.material ,Pollution ,Overburden ,Geochemistry and Petrology ,Vadose zone ,engineering ,Environmental Chemistry ,Spatial variability ,Sedimentary rock ,Pyrite ,Surface water ,Geology - Abstract
The objective of this study was to investigate the impact of flow, transport and geochemical parameters in the unsaturated and saturated zones on the release of SO4 from overburden lignite spoil piles into the adjacent lake. A vertical one-dimensional model was set up using the reactive transport simulator SULFIDOX in order to account for the unsaturated zone. The SULFIDOX model was calibrated for effective diffusion using measured O2 in the gas phase and SO4 concentrations in the liquid phase from the unsaturated zone of the heap. The results show high sensitivity to O2 supply and initially present gypsum, but the inclusion of secondary mineral precipitation in equilibrium is of minor importance for the results. To account for the transport of released SO4 from the saturated zone into the surface water, scenarios were performed by using SULFIDOX results as input concentration for a two-dimensional vertical model set up with PROCESSING MODFLOW and MT3D. These scenarios indicate a rising discharge of SO4 into the adjacent lake due to continued pyrite weathering for 80 a. Results are highly sensitive to dispersivity, whereas the spatial variability of pyrite distribution did not show any influence on the results. The consideration of initially present gypsum shows a major effect on the modelled SO4 release.
- Published
- 2008
34. The kinetics of chlorite dissolution
- Author
-
Geetha Rajaratnam, Richard T. Lowson, M. Josick Comarmond, and Paul L. Brown
- Subjects
chemistry.chemical_compound ,Reaction rate constant ,Aqueous solution ,chemistry ,Geochemistry and Petrology ,Stability constants of complexes ,Inorganic chemistry ,Analytical chemistry ,Rate equation ,Rate-determining step ,Dissolution ,Stoichiometry ,Oxalate - Abstract
A model for the dissolution of chlorite has been developed based on fast ligand assisted proton attack of the alumina tetrahedra within the alumina-silica lattice followed by slower dissolution of the remnant silica lattice. While the rate determining step is within the silica dissolution regime, the rate is a function of the H+ and Al3+ concentrations and the dominant aqueous Al species. Individual rates may be described by a generic rate equation applicable across the spectrum of Al species: r n = k n K n β Al p L q ( 3 p - zq ) a H + 3 p a Al 3 + p 1 + K n β Al p L q ( 3 p - zq ) a H + 3 p a Al 3 + p τ n , where rn is the rate subscripted for the nth Al species, k is the rate constant of the rate controlling step, K is the surface exchange constant, β is the solution stability constant subscripted for the Al species, a is the species activity subscripted for species and raised to the power of the stoichiometry, p and q are stoichiometric coefficients, z is the ligand charge and τ is the fractional coefficient for the precursor of the rate defining step. The observed rate is the sum of the individual rates. When the observed rate is in a domain of dominance for a single aluminium species and in the absence of strong complexing agents such as oxalate, the observed rate is proportional to a H + 3 / a Al 3 + τ n . The model is supported by experimental data for the dissolution of chlorite over a pH range of 3–10 and temperature range 25–95 °C. The results have hydrometallurgical application.
- Published
- 2007
35. Chemical speciation of environmentally significant metals with inorganic ligands Part 2: The Cu2+-OH-, Cl-, CO32-, SO42-, and PO43- systems (IUPAC Technical Report)
- Author
-
Tamás Gajda, Staffan Sjöberg, Glenn Hefter, Paul L. Brown, Kipton J. Powell, Robert H. Byrne, and Hans Wanner
- Subjects
Chemical speciation ,Chemistry ,Environmental chemistry ,General Chemical Engineering ,Chemical nomenclature ,General Medicine ,General Chemistry - Abstract
Complex formation between CuII and the common environmental ligands Cl-, OH-, CO3 2-, SO4 2-, and PO4 3- 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 log10β p,q,r ° valid at I m = 0 mol kg-1 and 25 °C (298.15 K), along with the equations and specific ion interaction coefficients required to calculate log10β p,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)2 2- 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.
- Published
- 2007
36. Chemical Speciation of Environmentally Significant Metals: An IUPAC contribution to reliable and rigorous computer modelling
- Author
-
Hans Wanner, Glenn Hefter, Kipton J. Powell, Ann-Kathrin Leuz, Tamás Gajda, Robert H. Byrne, Staffan Sjöberg, and Paul L. Brown
- Subjects
Chemistry ,Chemical speciation ,Environmental chemistry ,Natural water ,Metal ions in aqueous solution ,Chemical nomenclature ,Computer modelling ,General Medicine ,Bioavailability - Abstract
The mobility and bioavailability of metal ions in natural waters depend on their chemical speciation, which involves a distribution of the metal ions between different complex (metal-ligand) species, colloid-adsorbed species and insoluble phases, each of which may be kinetically labile or inert. For example, in fresh water the metal ions are distributed among organic complexes (e.g., humates), colloids (e.g., as surface-adsorbed species on colloidal phases such as FeOOH), solid phases (e.g., hydroxide, oxide, carbonate mineral phases), and labile complexes with the simple inorganic anionic ligands commonly present in natural waters (e.g., for Zn
- Published
- 2015
37. The kinetics of the dissolution of chlorite as a function of pH and at 25°C
- Author
-
Richard T. Lowson, M. Josick Comarmond, Geetha Rajaratnam, and Paul L. Brown
- Subjects
Single pass ,Aqueous solution ,Kinetics ,Analytical chemistry ,chemistry.chemical_element ,Crystallography ,chemistry.chemical_compound ,chemistry ,Geochemistry and Petrology ,Aluminium ,Sample preparation ,Autocatalytic reaction ,Dissolution ,Chlorite - Abstract
Far from equilibrium, quasi-steady state dissolution rates of an iron rich chlorite (Mg2.76Fe2+1.90Fe3+0.07Al0.97)[Si2.48Al1.52O10](OH)8, have been measured as a function of H+ concentration for the pH range 3 to 10.5 and at 25°C. The rates were determined using a single pass flow through cell and with a time frame for observing the steady state condition of between 10 to 50 days. Rates are independent of the buffers used to control the pH, sample preparation, experimental methodology and chlorite composition. The results were collated with literature values allowing the rate to be expressed as a function of H+ as; log R = − [ 9.79 a H 0.49 + 13.00 + 16.79 / a H 0.43 ] where R stands for the dissolution rate in mol m−2 s−1 and ai refers to the activity of the subscripted aqueous species. When the data for the Al3+ concentration at the outlet was incorporated into the analysis it was found that the rate could also be described by the relationship R = 10 − 10.46 ( a H + 3 a Al 3 + ) 0.27 which suggests the rate controlling complex is formed via a proton attack of the lattice aluminium.
- Published
- 2005
38. Toward a Biotic Ligand Model for Freshwater Green Algae: Surface-Bound and Internal Copper Are Better Predictors of Toxicity than Free Cu2+-Ion Activity When pH Is Varied
- Author
-
Karel De Schamphelaere, Colin Janssen, Karyn L. Wilde, Scott J. Markich, Nicola M. Creighton, Paul L. Brown, Jennifer L. Stauber, and Natasha M. Franklin
- Subjects
Molar concentration ,Chlorophyceae ,chemistry.chemical_element ,Fresh Water ,Chlorophyta ,Ligands ,medicine.disease_cause ,Inhibitory Concentration 50 ,Papua New Guinea ,Botany ,medicine ,Environmental Chemistry ,Edetic Acid ,biology ,Copper toxicity ,Biotic Ligand Model ,General Chemistry ,biology.organism_classification ,medicine.disease ,Copper ,Chlorella ,Models, Chemical ,chemistry ,Zinc toxicity ,Nuclear chemistry - Abstract
The freshwater green microalgae Chlorella sp. and Pseudokirchneriella subcapitata (P. subcapitata) were chronically (48 and 72 h, respectively) exposed to copper at various pH levels, i.e., pH 6-7.5 and pH 5.9-8.5, respectively. Concentrations resulting in 50% inhibition of exponential growth rate (EC50) were determined as dissolved Cu, estimated chemical activity of the free Cu2+ ion (as pCu = - log{Cu2+ activity as molarity}), and as external (surface-bound) Cu and internal Cu in the algal cells. With increasing pH, EC50dissolved decreased from 30 to 1.1 microg of Cu L(-1) for Chlorella sp. and from 46 to 18 microg of Cu L(-1) for P. subcapitata. The pH effect on copper toxicity was even more obvious when expressed as Cu2+ activity. The EC50pCu increased on average 1.4 pCu unit per pH unit for Chlorella sp. and 1.1 pCu unit per pH unit for P. subcapitata, thus indicating a marked increase of Cu2+ toxicity at higher pH (more than 1 order of magnitude per pH unit). In contrast, it was found that EC50 values expressed as surface bound or external copper (EC50external) and as internal copper (EC50internal) did not vary substantially when pH was increased. External Cu was operationally defined as the Cu fraction removable from the algal cell by short-term contact with ethylenediaminetetraacetic acid; internal copper was defined as the nonremovable fraction. For Chlorella sp. the EC50external varied between 5 and 10 fg of Cu/ cell (factor of 2 difference) and the EC50internal between 25 and 40 fg of Cu/cell (factor of 1.6 difference). For P. subcapitata the EC50external varied between 10 and 28 fg of Cu/cell (factor of 2.8 difference) and the EC50internal between 42 and 71 fg of Cu/cell (factor of 1.7 difference). Because the observed variation in EC50external and EC50internal is much less than the variation in EC50Cu2+, it is concluded that both external and internal copper are better predictors of copper toxicity than Cu2+ when pH is varied. From the perspective of toxicity modeling, this observation is the first step toward considering the use of the cell surface as the algal biotic ligand for Cu in a similar way as fish gills fulfill this role in the biotic ligand model for predicting metal toxicity to fish species.
- Published
- 2005
39. Coupled chemistry and transport modelling of sulphidic waste rock dumps at the Aitik mine site, Sweden
- Author
-
D. J. Sinclair, Claire M. Linklater, and Paul L. Brown
- Subjects
Gypsum ,Chemistry ,Water flow ,Mineralogy ,Weathering ,engineering.material ,Pollution ,Infiltration (hydrology) ,chemistry.chemical_compound ,Geochemistry and Petrology ,Jarosite ,engineering ,Environmental Chemistry ,Sulfate ,Dissolution ,Effluent - Abstract
The recently developed geochemical modelling code, SULFIDOX, has been applied to simulate weathering of a waste rock dump at the Aitik mine site, Sweden. SULFIDOX models the key chemical and physical processes in the dump temporally and spatially (in two dimensions). The following processes are represented: gas and heat transport; water infiltration; aqueous speciation; mineral dissolution/oxidation and precipitation. Field observations at the site suggest that sulphide oxidation rates within the dump are variable. Although the major part of the dump is oxidising slowly, there are pockets of more highly oxidising material, particularly toward the dump edges. Using SULFIDOX, several models of the dump were investigated: (i) a dump wholly comprised of slowly oxidising material (representing a case where water flow paths are such that no rapidly oxidising regions are accessed); (ii) a dump wholly comprised of the more rapidly oxidising material (representing the opposite (and probably unlikely) extreme, where water flows only through rapidly oxidising regions in the dump); and (iii) a dump comprising a mixture of both slowly and more rapidly oxidising material, that more closely represents the mix of material in the dump. All the models studied gave O2 depth profiles consistent with those observed in probe holes at the site, and confirmed that only a minimal amount of heat production would be expected in the dump due to the role of exothermic sulphide oxidation reactions. The models suggested that a medium-term steady-state, with respect to effluent chemistry, would be achieved after 3–4 years. Based on sulphide consumption rates during this steady-state period, the time periods required to consume all the sulphide in the dump range from a few hundred to many thousands of years. Using the mixed model, and based on a mixture containing 86% slowly and 14% rapidly oxidising material, the calculated effluent chemistry was in good agreement with the observed effluent chemistry. Improvements with respect to the K concentrations were possible by including precipitation of a K-bearing secondary mineral such a K-jarosite in the model. Results from the more rapidly oxidising model suggested that gypsum precipitation might be expected in those regions of the dump containing this material. In summary, the SULFIDOX modelling code has been used successfully to reproduce observed data for the Aitik waste-rock dump. Using SULFIDOX, valuable insight was gained in relation to the temporal and spatial evolution of the dump.
- Published
- 2005
40. Chemical speciation of environmentally significant heavy metals with inorganic ligands. Part 1: The Hg2+– Cl–, OH–, CO32–, SO42–, and PO43– aqueous systems (IUPAC Technical Report)
- Author
-
Tamás Gajda, Staffan Sjöberg, Hans Wanner, Glenn Hefter, Robert H. Byrne, Kipton J. Powell, and Paul L. Brown
- Subjects
Aqueous solution ,Chemistry ,Chemical speciation ,General Chemical Engineering ,Inorganic chemistry ,Complex formation ,Chemical nomenclature ,Heavy metals ,General Chemistry ,Acid dissociation constant ,chemistry.chemical_compound ,Organic chemistry ,Phosphoric acid ,Equilibrium constant - Abstract
This document presents a critical evaluation of the equilibrium constants and reaction enthalpies for the complex formation reactions between aqueous Hg(II) and the common environmental inorganic ligands Cl–, OH–, CO3 2–, SO4 2–, and PO4 3–. The analysis used data from the IUPAC Stability Constants database, SC-Database, focusing particularly on values for 25 °C and perchlorate media. Specific ion interaction theory (SIT) was applied to reliable data available for the ionic strength range Ic < 3.0 mol dm–3. Recommended values of log10 βp,q,r ° and the associated reaction enthalpies, ∆r H m°, valid at Im = 0 mol kg–1 and 25 °C, were obtained by weighted linear regression using the SIT equations. Also reported are the equations and specific ion interaction coefficients required to calculate log10 βp,q,r ° values at higher ionic strengths and other temperatures. A similar analysis is reported for the reactions of H+ with CO3 2– and PO4 3–. Diagrams are presented to show the calculated distribution of Hg(II) amongst these inorganic ligands in model natural waters. Under typical environmental conditions, Hg(II) speciation is dominated by the formation of HgCl2(aq), Hg(OH)Cl(aq), and Hg(OH)2(aq).
- Published
- 2005
41. Studies on the Hydrolytic Behavior of Zirconium(IV)
- Author
-
Göran Källvenius, Paul L. Brown, Christian Ekberg, and Yngve Albinsson
- Subjects
Zirconium ,Aqueous solution ,Acetylacetone ,Extraction (chemistry) ,Inorganic chemistry ,Biophysics ,chemistry.chemical_element ,Solubility equilibrium ,Biochemistry ,Zirconate ,chemistry.chemical_compound ,chemistry ,Stability constants of complexes ,Physical and Theoretical Chemistry ,Solubility ,Molecular Biology - 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)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 Δ H o and Δ 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.
- Published
- 2004
42. The hydrolysis of uranium(VI)
- Author
-
Paul L. Brown
- Subjects
Potentiometric titration ,Inorganic chemistry ,chemistry.chemical_element ,Uranium ,Chloride ,chemistry.chemical_compound ,Perchlorate ,Hydrolysis ,Nitrate ,chemistry ,medicine ,Physical and Theoretical Chemistry ,Sulfate ,Nuclear chemistry ,medicine.drug - Abstract
SummaryThe hydrolysis of uranium(VI) has been investigated in 0.10 mol dm−3NaClO4and KCl and 1.0 mol dm−3KNO3using the potentiometric technique. The results of the data analysis have been combined with data previously obtained from this laboratory and the literature to provide a more definitive description of the hydrolysis behaviour of uranium(VI). The species UO2OH+, (UO2)2(OH)22+, (UO2)3(OH)42+, (UO2)3(OH)5+and (UO2)4(OH)7+have been identified in nitrate media and all but the last of these species in chloride and perchlorate media. The differences in the complexation behaviour in the media may be due to oxoanion binding by the nitrate, a process which has also been observed for sulfate.
- Published
- 2002
43. Solubility of Radium and Strontium Sulfate across the Temperature Range of 0 to 300°C
- Author
-
Paul L. Brown, Christian Ekberg, Henrik Ramebäck, Hanna Hedström, and Artem V. Matyskin
- Subjects
Standard enthalpy of reaction ,chemistry.chemical_compound ,Strontium ,Alkaline earth metal ,Chemistry ,Inorganic chemistry ,Analytical chemistry ,chemistry.chemical_element ,Strontium sulfate ,Solubility equilibrium ,Solubility ,Atmospheric temperature range ,Molar solubility - Abstract
Solubility constant data for radium and strontium (celestite) sulfate has been determined across the temperature range of 0 to 300°C based on the available literature data for these two phases as well as similar data for calcium (anhydrite) and barium (barite) sulfate for which solubility constant data is available across the same temperature range. The thermodynamic data for the phases have been determined by assuming that the solubility constants are a function of the inverse of absolute temperature with a constant, but non-zero, heat capacity change. The sol-ubility for all phases shows a peak with respect to temperature, with the temperature at which the peak occurs increasing as the alkaline earth metals become heavier. The heat capacity change is a function of the ionic radius of the alkaline earth metal ion whereas the enthalpy of reaction at 25°C is related to the peak at which the maximum solubility occurs. The entropy of reaction at 25°C is related to the solubility constant and the derived enthalpy of reaction at that temperature.
- Published
- 2014
44. Divalent metal accumulation in freshwater bivalves: an inverse relationship with metal phosphate solubility
- Author
-
Scott J. Markich, Paul L. Brown, and Ross A. Jeffree
- Subjects
Environmental Engineering ,Mineralogy ,Fresh Water ,Phosphates ,Metal ,chemistry.chemical_compound ,Dry weight ,Nickel ,Animals ,Environmental Chemistry ,Tissue Distribution ,Solubility ,Waste Management and Disposal ,Mollusca ,Manganese ,biology ,Granule (cell biology) ,Australia ,Cobalt ,Phosphate ,Bivalvia ,biology.organism_classification ,Pollution ,Trace Elements ,Zinc ,Lead ,chemistry ,visual_art ,Bioaccumulation ,Environmental chemistry ,Models, Animal ,visual_art.visual_art_medium ,Uranium ,Calcium ,Environmental Pollution ,Environmental Sciences ,Copper ,Water Pollutants, Chemical ,Cadmium ,Environmental Monitoring - Abstract
Whole soft tissue concentrations of Mn, Co, Ni, Cu, Zn, Pb, Cd and U were measured in two species of freshwater (unionid) bivalves (Hyridella depressa and Velesunio ambiguus) from a minimally polluted site in the Hawkesbury-Nepean River, south-eastern Australia. Although the mean concentrations of metals in the tissue were similar for each bivalve species, their patterns of accumulation were dissimilar. For each metal, positive linear relationships between tissue concentration and shell length (r2 = 0.37-0.77; P < or = 0.001) and tissue dry weight (r2 = 0.29-0.51; P < or = 0.01) were found in H. depressa, but not in V. ambiguus. However, for both species, positive linear relationships were found between the tissue concentration of each divalent metal and Ca tissue concentration (r2 = 0.59-0.97; P < or = 0.001). For both bivalve species, the normalised rates of accumulation of the metals relative to increasing Ca concentration and/or size, were U approximately = Cd > or = Pb > or = Mn > Co > or = Zn > Cu > Ni. The differential rates of accumulation of divalent metals are interpreted as being predominantly governed by their varying loss rates, which are controlled by the differing solubilities (log Ksp values) of the metals in the phosphatic extracellular granules, the demonstrated major sites of metal deposition in the tissue of H. depressa and V. ambiguus. The rates of accumulation of Mn, Co, Zn, Cu and Ni were linearly and inversely related (r2 = 0.91-0.97; P < or = 0.001) to their solubilities as hydrogen phosphates, a finding consistent with the bioaccumulation model previously developed for the alkaline-earth metals. However, for U, Cd and Pb, this linear inverse relationship did not continue to hold, i.e. their rates of accumulation did not increase with decreasing solubility. However, these results are still consistent with the model if U, Cd and Pb are so insoluble in the granules of H. depressa and V. ambiguus over their lifetime (up to approx. 50 years) that there is effectively no loss of these metals, and hence, no differential between their rates of accumulation. The present results reaffirm the use of Ca tissue concentration to predict the tissue concentrations of other divalent metals by explaining up to 94 and 97% of the variability between individual bivalves of H. depressa and V. ambiguus, respectively. The use of Ca tissue concentration to effectively minimise the inherent variability between individuals in their metal tissue improves the ability of an investigator to discern smaller spatial and/or temporal differences in the metal tissue concentrations of these bivalves, and thus to detect metal pollution.
- Published
- 2001
45. Communicating the Benefits of the Behavioral Approach to the Business Community
- Author
-
Paul L. Brown
- Subjects
Organizational behavior management ,Metaphor ,business.industry ,Strategy and Management ,Business community ,media_common.quotation_subject ,Public relations ,Management of Technology and Innovation ,SAFER ,Tribe ,business ,Psychology ,Social psychology ,Applied Psychology ,media_common - Abstract
For those who have charted a course as consultants to the business community, the stated mission is to enter those cultures with the express purpose of influencing and hopefully improving their cultural practices. When behaviorally oriented professionals are attempting to influence another culture, indeed another “tribe,” there are protocols, rules, procedures and practices which make the journey safer and more successful. Language is important. Measurements are important. Tools and technology are important. In this paper, recommendations for communicating the benefits of a behavioral approach are provided for each of these three areas. In addition, this paper encourages behavior analysts who seek to enter other cultures and bring about change to adopt the metaphor of coach: By using behavioral principles and techniques to teach behavioral principles and techniques, behavior analysts model the very behaviors that will help people in positions of leadership and influence.
- Published
- 2001
46. Valve movement responses of Velesunio angasi (Bivalvia: Hyriidae) to manganese and uranium: An exception to the free ion activity model
- Author
-
Scott J. Markich, Paul L. Brown, Ross A. Jeffree, and Richard P. Lim
- Subjects
Chemical Phenomena ,Metal hydroxide ,Movement ,Health, Toxicology and Mutagenesis ,media_common.quotation_subject ,chemistry.chemical_element ,Mineralogy ,Manganese ,Aquatic Science ,Models, Biological ,Ion ,Metal ,Dissolved organic carbon ,Animals ,Benzopyrans ,media_common ,Ions ,biology ,Chemistry, Physical ,Manganese Poisoning ,Hydrogen-Ion Concentration ,Uranium ,Bivalvia ,biology.organism_classification ,Speciation ,chemistry ,Mollusca ,Environmental chemistry ,visual_art ,visual_art.visual_art_medium ,Algorithms - Abstract
The veracity of the free ion activity model (FIAM) was tested by examining the acute (48 h) valve movement responses (VMR) (measured in terms of the duration of valve opening) of the Australian tropical freshwater unionid bivalve, Velesunio angasi to increasing concentrations of total Mn or U, in a standard synthetic water under conditions of varying pH (5.0-6.0) and/or dissolved organic carbon (model fulvic acid, FA) concentrations (0-8.9 mg l(-1)). Valve movement behaviour, measured using an automated data acquisition system, was shown to be a quantifiable and rapid, real-time endpoint for assessing the toxic effects of Mn and U exposures. For Mn, the VMR of V. angasi were independent (P>0.05) of pH and/or model FA concentration. In contrast, VMR to U exposures were highly dependent (P< or =0.05) on pH and/or model FA concentration; individuals were more sensitive to U at low pH and model FA concentrations. Valve movement responses to Mn were directly proportional to the activity of the free metal ion (Mn(2+)), which is consistent with the FIAM. In contrast, VMR to U were regarded as an 'exception' to the FIAM, since they were a weighted function of the activities of the free metal ion and the 1:1 metal hydroxide species (i.e. 1.86 x UO2(2+) + UO2OH(+)). Additionally, the effect of U on V. angasi demonstrates the importance of examining VMR at more than one pH. At a fixed pH, the results for U were consistent with the FIAM (i.e. response was directly proportional to UO2(2+)); only when pH was altered, were the results inconsistent with the FIAM. The inconsistency in the VMR of V. angasi to U exposures in this study, together with similar examples from other studies using different metals (e.g. Al or Zn), raises questions regarding the veracity of the FIAM. A detailed examination of the conceptual development of the FIAM is required to probe its apparent failure to describe several metal-organism interactions.
- Published
- 2000
47. Learning front top-performing managers
- Author
-
Paul L. Brown
- Subjects
Knowledge management ,Total quality management ,Performance management ,Organization development ,business.industry ,Evaluation methods ,General Medicine ,Business ,Administration (government) ,Front (military) - Published
- 2000
48. [Untitled]
- Author
-
Christian Ekberg, Yngve Albinsson, M. Josick Comarmond, and Paul L. Brown
- Subjects
Standard enthalpy of reaction ,Acetylacetone ,Enthalpy ,Inorganic chemistry ,Biophysics ,Thorium ,chemistry.chemical_element ,Actinide ,Sodium perchlorate ,Biochemistry ,chemistry.chemical_compound ,Hydrolysis ,chemistry ,Stability constants of complexes ,Physical and Theoretical Chemistry ,Molecular Biology - Abstract
The stability constants of thorium(IV) hydrolysis species have been measured at15, 25, and 35°C (in 1.0 mol dm−3 NaClO4) using both potentiometry and solventextraction. The results indicate the presence of the monomeric speciesTh(OH)3+, Th(OH)2+2, Th(OH)+3, and Th(OH)4, in addition to the polymericspecies Th4(OH)8+8 and Th6(OH)9+15. The polymeric species were found to beimportant, although the total thorium concentration was limited to 0.01–0.1mmol-dm−3. The solvent extraction measurements required the use of acetylacetone.As such, the stability constants of thorium(IV) with acetylacetone were alsomeasured using both potentiometry and solvent extraction. All logarithms of thestability constants were found to be linear functions of the reciprocal absolutetemperature indicating that ΔHo and ΔSo of reaction are both independent oftemperature (over the temperature range examined in the study).
- Published
- 2000
49. Analysis of a Large Structure/Biological Activity Data Set Using Recursive Partitioning
- Author
-
Mark W. Farmen, S. Stanley Young, Christophe G. Lambert, Andrew Rusinko, and Paul L. Brown
- Subjects
Structure (mathematical logic) ,Biological data ,Drug Industry ,Computer program ,Computer science ,Process (computing) ,Recursive partitioning ,General Chemistry ,computer.software_genre ,Computer Science Applications ,Data set ,Structure-Activity Relationship ,Computational Theory and Mathematics ,Drug Design ,Combinatorial Chemistry Techniques ,Data mining ,computer ,Drug industry ,Information Systems - Abstract
Combinatorial chemistry and high-throughput screening are revolutionizing the process of lead discovery in the pharmaceutical industry. Large numbers of structures and vast quantities of biological assay data are quickly being accumulated, overwhelming traditional structure/activity relationship (SAR) analysis technologies. Recursive partitioning is a method for statistically determining rules that classify objects into similar categories or, in this case, structures into groups of molecules with similar potencies. SCAM is a computer program implemented to make extremely efficient use of this methodology. Depending on the size of the data set, rules explaining biological data can be determined interactively. An example data set of 1650 monoamine oxidase inhibitors exemplifies the method, yielding substructural rules and leading to general classifications of these inhibitors. The method scales linearly with the number of descriptors, so hundreds of thousands of structures can be analyzed utilizing thousands to millions of molecular descriptors. There are currently no methods to deal with statistical analysis problems of this size. An important aspect of this analysis is the ability to deal with mixtures, i.e., identify SAR rules for classes of compounds in the same data set that might be binding in different ways. Most current quantitative structure/activity relationship methods require that the compounds follow a single mechanism. Advantages and limitations of this methodology are presented.
- Published
- 1999
50. Uranium and other contaminant migration in groundwater at a tropical Australian Uranium Mine
- Author
-
Richard T. Lowson, Marianne Guerin, Stuart Hankin, and Paul L. Brown
- Subjects
Pollution ,Hydrology ,Irrigation ,Groundwater flow ,media_common.quotation_subject ,MODFLOW ,Environmental engineering ,chemistry.chemical_element ,Uranium ,chemistry ,Soil water ,Cation-exchange capacity ,Environmental Chemistry ,Environmental science ,Groundwater ,Water Science and Technology ,media_common - Abstract
Hydrogeochemical modelling (utilising the modelling tools MODFLOW, MT3D and HARPHRQ) has been used in conjunction with laboratory-based experiments and a field monitoring program to investigate the fate of uranium and other contaminants in excess water sprayed on a 33 ha region of the Ranger Uranium Mine (RUM), northern Australia. The results indicate that uranium is retained in the surficial layer of the lateritic soils of the area. Conservative contaminants are not retained by the soils and are transported into the groundwater. Subsequently, they migrate relative to the groundwater flow rate towards the river system down hydraulic gradient of the irrigation area.
- Published
- 1998
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