scholarly journals The Formation of Pitted Features on the International Simple Glass during Dynamic Experiments at Alkaline pH

MRS Advances ◽  
2019 ◽  
Vol 4 (17-18) ◽  
pp. 993-999
Author(s):  
Adam J. Fisher ◽  
Neil C. Hyatt ◽  
Russell J. Hand ◽  
Claire L. Corkhill
Keyword(s):  
Glass Composition ◽  
Forward Rate ◽  
Alkali Concentration ◽  
Gel Formation ◽  
Forward Rates ◽  
Ph Values ◽  
Rate Of Dissolution ◽  
Dynamic Experiments ◽  
Alkaline Conditions ◽  
Flow Through

ABSTRACTThe forward rate of dissolution of the International Simple Glass (ISG) was determined under alkaline conditions at 40 °C using the Single Pass Flow Through (SPFT) method. Forward rates were consistent with those obtained in the literature for this glass composition. The formation of altered gel layers and surface pits was observed on the surface of glass particles, especially at the very highest pH values, despite the application of high flow rates to prevent the build-up of solubility limiting phases. These features could be attributed to preferential localized dissolution at sites with a higher alkali concentration or from a separate, less durable, vitreous phase. These results may indicate that surface pit and altered gel formation occurs under the forward rate of dissolution as imposed by the SPFT method, particularly for simplified borosilicate glass materials.

Determination of the Forward Rate of Dissolution for SON68 and PAMELA Glasses in Contact With Alkaline Solutions

2008 ◽  
Vol 1107 ◽  
Author(s):  
K. Ferrand ◽  
K. Lemmens
Keyword(s):  
Waste Glass ◽  
Forward Rate ◽  
Alkaline Solutions ◽  
Dynamic Tests ◽  
Forward Rates ◽  
Rate Of Dissolution ◽  
Uv Visible ◽  
Radionuclide Release ◽  
Good Agreement

AbstractIn the new Belgian disposal design, the nuclear waste glass will be surrounded by a 3 cm thick carbon steel overpack and a 70 cm thick concrete buffer. An initially high pH is expected after water intrusion in the concrete buffer and this may have an effect on the radionuclide release from the waste glass. This study was performed in order to determine the forward rate of dissolution for SON68 and PAMELA glasses (SM513 LW11 and SM539 HE 540-12), conducting dynamic tests at 30°C in contact with alkaline solutions. In these experiments, the silicon concentration in solution was determined by UV/Visible spectrophotometry according to the blue â-silicomolybdenum method. The forward rates of dissolution were quite similar for the three glasses except at the highest pH for which a slightly higher value was found for SM539 glass. For SON68 glass, a good agreement with the previously established interpolation law was observed until pH 11.5, but at higher pH, the interpolation law slightly overestimates the dissolution rate [1].

COMMONWEALTH PERSPECTIVE ON PETROLEUM TAXATION

1999 ◽  
Vol 39 (2) ◽  
pp. 126
Author(s):  
B. Layer
Keyword(s):  
Risk Premium ◽  
Petroleum Industry ◽  
Forward Rate ◽  
Gas Transfer ◽  
Development Activity ◽  
Resource Rent ◽  
Forward Rates ◽  
North West ◽  
Percentage Points

In 1997 the petroleum industry sought modifications to the petroleum resource rent tax (PRRT) regime which applies to all Commonwealth offshore areas except the North West Shelf Project area. Industry argued that the PRRT impeded deepwater exploration and development activity and the exploitation of large stranded gas deposits suitable for conversion to liquids such as LNG. Industry suggested that a more appropriate risk/reward balance in the tax structure could be achieved by providing a volume based PRRT exemption for projects located in water depth greater than 400 m and by increasing the uplift rates for unrealised losses. It was proposed that the risk premium for the general (development) expenditure carry forward rate be increased by five percentage points to the long term bond rate (LTRR) plus 10 percentage points. Another industry recommendation was that exploration expenditures incurred more than five years before the issue of a production license (PL), which currently attract the lower GDP factor rate (the five year rule), be uplifted at the long-term bond rate for the period prior to the five year mark and then rolled forward at LTBR plus 15 percentage points. In addition, industry asked that the reference date for the five year rule should be based on the application date for a PL and not the issue date. For integrated gas to liquid projects, industry requested clarification of the basis for valuing feedstock gas for determining gas liability.In response, the Commonwealth decided to adopt a gas transfer price (GTP) methodology based on a combination of established cost plus and net back formulas to be applied to the up and downstream stages of the project respectively. The difference in the price outcome of the two methods, the residual price, is split 50:50 to obtain the GTP. Details of how the residual price method will be applied are currently being finalised with a view to enacting legislation in 1999-2000. The Commonwealth also responded positively to the industry suggestion that the reference date of the five year rule be applied from the date of application for the PL on the proviso that the appropriate authority receives all information pertaining to a successful application. Recommended changes to the PRRT for deepwater areas and proposed increases to the carry forward rates of undeducted losses were rejected mainly on economic efficiency grounds.

Dissolution kinetics of meta-torbernite under circum-neutral to alkaline conditions

2009 ◽  
Vol 6 (6) ◽  
pp. 551 ◽  
Author(s):  
Dawn M. Wellman ◽  
Bruce K. McNamara ◽  
Diana H. Bacon ◽  
Elsa A. Cordova ◽  
Ruby M. Ermi ◽  
...  
Keyword(s):  
Dissolution Kinetics ◽  
Coupled Processes ◽  
Effect Of Temperature ◽  
Subsurface Environments ◽  
Alkaline Conditions ◽  
Flow Through ◽  
Uranium Phosphate ◽  
The Stability ◽  
Kinetics Of

Environmental context. Uranium-phosphate minerals have been identified as a long-term controlling phase that limit the mobility of uranium to groundwater in many contaminated subsurface environments. Complex, coupled processes confound the ability to isolate the rates attributed to individual processes. Results of this investigation provide the necessary information to refine current prediction on the release and long-term fate of uranium in subsurface environments. Abstract. The purpose of this investigation was to conduct a series of single-pass flow-through (SPFT) tests to (1) quantify the effect of temperature (23–90°C) and pH (6–10) on meta-torbernite dissolution; (2) compare the dissolution of meta-torbernite to other autunite-group minerals; and (3) evaluate the effect of aqueous phosphate on the dissolution kinetics of meta-torbernite. Results presented here illustrate meta-torbernite dissolution rates increase by ~100× over the pH interval of 6 to 10, irrespective of temperature. The power law coefficient for meta-torbernite, η = 0.59 ± 0.07, is greater than that quantified for Ca-meta-autunite, η = 0.42 ± 0.12. This suggests the stability of meta-torbernite is greater than that of meta-autunite, which is reflected in the predicted stability constants. The rate equation for the dissolution of meta-torbernite as a function of aqueous phosphate concentration is log rdissol (mol m–2 s–1) = –4.7 × 10–13 + 4.1 × 10–10[PO43–].

Determination of Radial Dispersion Coefficient in Beds of Sand from Measurements of the Rate of Dissolution of Buried Cylinders Aligned with the Flow

2015 ◽  
Vol 3 ◽  
pp. 21-37
Author(s):  
J.M.P.Q. Delgado
Keyword(s):  
Molecular Diffusion ◽  
Flow Direction ◽  
Silica Sand ◽  
Average Particle ◽  
Transverse Dispersion ◽  
Rate Of Dissolution ◽  
Dispersion Data ◽  
Data Points ◽  
Radial Dispersion ◽  
Flow Through

A method is presented for determining the coefficient of transverse dispersion in flow through packed beds, which is based on the measurement of the rate of dissolution of planar or cylindrical surfaces, buried in the bed and aligned with the flow direction. The underlying theory is initially explained and experiments are then described in which more than three hundred new data points were obtained. These data are for the flow of water, at interstitial velocities between 0.1 and 1.5 mm/s, through beds of silica sand with average particle sizes between 0.219 and 0.496 mm. The experiments were performed at a range of temperatures, between 20oC and 35oC, and this yielded dispersion data for values of the Schmidt number (Sc=μ/ρDm) between 1170 and 570. For all the data reported, the ratio between the coefficient of transverse dispersion and the coefficient of molecular diffusion was shown to correlate well with the Reynolds number (Re=udρ/μ), both for beds with narrow and with wide particle size distributions.

scholarly journals CDO TERM STRUCTURE MODELLING WITH LÉVY PROCESSES AND THE RELATION TO MARKET MODELS

2012 ◽  
Vol 15 (01) ◽  
pp. 1250008 ◽  
Author(s):  
THORSTEN SCHMIDT ◽  
JERZY ZABCZYK
Keyword(s):  
Term Structure ◽  
Forward Rate ◽  
Collateralized Debt Obligations ◽  
Top Down ◽  
Market Models ◽  
Forward Rates ◽  
Finite Dimensional ◽  
Generalized Framework ◽  
Collateralized Debt ◽  
Absence Of Arbitrage

This paper considers the modelling of collateralized debt obligations (CDOs). We propose a top-down model via forward rates generalizing Filipović, Overbeck and Schmidt (2009) to the case where the forward rates are driven by a finite dimensional Lévy process. The contribution of this work is twofold: we provide conditions for absence of arbitrage in this generalized framework. Furthermore, we study the relation to market models by embedding them in the forward rate framework in spirit of Brace, Gatarek and Musiela (1997).

Production of Nanocrystalline Sulfated Zirconia Catalysts via a Flow-Through Hydrothermal Process

1998 ◽  
Vol 520 ◽  
Author(s):  
D.W. Matson ◽  
J.G. Darab ◽  
T.D. Brewer ◽  
P.D. Kaviratna
Keyword(s):  
Catalytic Activity ◽  
Sulfated Zirconia ◽  
Hydrothermal Process ◽  
Gel Formation ◽  
Hydrothermal Conditions ◽  
Sulfate Content ◽  
Powder Formation ◽  
Flow Through ◽  
Sulfated Zirconia Catalysts ◽  
Zirconia Powders

ABSTRACTNanocrystalline sulfated zirconia catalysts were prepared using the rapid thermal decomposition of precursors in solution (RTDS) powder formation process. Zirconia gel formation, initial crystallization, and sulfate incorporation occurred during a brief exposure to hydrothermal conditions in the RTDS reactor. The partially crystalline zirconia solid was collected as a suspension, separated by centrifugation, and subjected to calcination to achieve full catalytic activity. Crystallinity, sulfate content, and catalytic activity of the calcined powders toward butane isomerization varied according to the hydrothermal conditions at which the zirconia powders were originally precipitated. The powders were characterized using powder XRD, FTIR, and XAS.

Determination of ionized calcium in serum that has been exposed to air.

1976 ◽  
Vol 22 (7) ◽  
pp. 1009-1011 ◽  
Author(s):  
D R Wybenga ◽  
F A Ibbott ◽  
D C Cannon
Keyword(s):  
Total Protein ◽  
Protein Concentration ◽  
Calcium Concentration ◽  
Electrode System ◽  
Ionized Calcium ◽  
Ph Change ◽  
Air Samples ◽  
Ph Values ◽  
Flow Through

Abstract We examined changes in ionized calcium concentration in serum after its exposure to air. Samples with total protein concentrations ranging from 50 to 90 g/liter were equilibrated with CO2 in nitrogen (5/95, by vol) or CO2 alone, to produce pH values of 7.0 to 8.0. Ionized calcium was then measured with an Orion flow-through electrode system. Curves relating pH and ionized calcium concentration had statistically identical slopes regardless of protein concentration. A factor was derived, based on pH change, for correcting values for ionized calcium in serum exposed to air, and its validity was confirmed by comparing corrected values for samples allowed to stand at ambient temperature (23 degrees C) without anaerobic precautions with values initially obtained on anaerobic aliquots of the same samples.

scholarly journals Investigation of PO43- Removal in Aerated and Unaerated High Fe EAF-Slag Filter System

2018 ◽  
Vol 7 (4.30) ◽  
pp. 557
Author(s):  
Hamdan R ◽  
Siti Zu Nurain Ahmad ◽  
Nur ‘Ain Nazirah Mohd Arshad ◽  
Wan Afnizan Wan Mohamed ◽  
Syahrul Nizam Maarup
Keyword(s):  
Removal Efficiency ◽  
Phosphorus Removal ◽  
Steel Slag ◽  
Synthetic Wastewater ◽  
Weekly Basis ◽  
Ph Values ◽  
Main Culprit ◽  
Alkaline Conditions ◽  
Eaf Slag ◽  
Slag Column

Phosphorus in wastewater is one the main culprit which accelerates eutrophication in waterbody if it is not being treated properly. Steel slag filter emerged as one alternative treatment for wastewater. However, the variousness of metal oxides including Fe in steel slag will affect the phosphorus removal efficiency. Thus, this study was conducted to investigate the ability of a series of lab-scale high Fe electric arc furnace (EAF- slag) column filters in removing PO43- from synthetic wastewater. The systems were operated under aerated and unaerated within acidic and alkaline conditions. Synthetic wastewater contained 25 mg/L was prepared as the feed and monitored weekly basis for the PO43- removal efficiency and the total metals (Ca, Fe, and Mg) concentrations in the effluents. The results show that both aerated and unaerated high Fe EAF-slag filter systems have high PO43- removal efficiency under acidic condition, which unaerated system performed slightly better. It can be observed that unaerated systems performed better in removing PO43- at acidic and neutral pH values but not at extremely high pH. As for the PO43- removal mechanism was achieved by adsorption and precipitation at acidic pH and the concentration of Ca, Mg and Fe in effluents was related to the PO43- removal efficiency at different pH values.  

Modelling the Behaviour of Organic Degradation Products

1988 ◽  
Vol 127 ◽  
Author(s):  
J. E. Cross ◽  
F. T. Ewart ◽  
B. F. Greenfield
Keyword(s):  
Organic Waste ◽  
Degradation Products ◽  
Organic Ligand ◽  
Solubility Enhancement ◽  
Major Objective ◽  
Experimental Conditions ◽  
Organic Species ◽  
Ph Values ◽  
Alkaline Conditions ◽  
Significant Factors

ABSTRACTResults are presented from recent studies at Harwell which show that the degradation products which are formed when certain organic waste materials are exposed to the alkaline conditions typical of a cementitious environment, can enhance the solubility of plutonium, even at pH values as high as 12, by significant factors. Characterisation of the degradation products has been undertaken but the solubility enhancement does not appear to be related to the concentration of any of the major organic species that have been identified in the solutions. While it has not been possible to identify by analysis the organic ligand responsible for the increased solubility of plutonium, the behaviour of D-Saccharic acid does approach the behaviour of the degradation products. The PHREEQE code has been used to simulate the solubility of plutonium in the presence of D-Saccharic acid and other model degradation products, in order to explain the solubility enhancement. The extrapolation of the experimental conditions to the repository is the major objective, but in this work the ability of a model to predict the behaviour of plutonium over a range of experimental conditions has been tested.

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