Optimization of dissolution process parameters for uranium ore concentrate powders

Energy Technology Data Exchange (ETDEWEB)

Misra, M.; Reddy, D.M.; Reddy, A.L.V.; Tiwari, S.K.; Venkataswamy, J.; Setty, D.S.; Sheela, S.; Saibaba, N. [Nuclear Fuel Complex, Hyderabad (India)

2013-07-01

Nuclear fuel complex processes Uranium Ore Concentrate (UOC) for producing uranium dioxide powder required for the fabrication of fuel assemblies for Pressurized Heavy Water Reactor (PHWR)s in India. UOC is dissolved in nitric acid and further purified by solvent extraction process for producing nuclear grade UO{sub 2} powder. Dissolution of UOC in nitric acid involves complex nitric oxide based reactions, since it is in the form of Uranium octa oxide (U{sub 3}O{sub 8}) or Uranium Dioxide (UO{sub 2}). The process kinetics of UOC dissolution is largely influenced by parameters like concentration and flow rate of nitric acid, temperature and air flow rate and found to have effect on recovery of nitric oxide as nitric acid. The plant scale dissolution of 2 MT batch in a single reactor is studied and observed excellent recovery of oxides of nitrogen (NO{sub x}) as nitric acid. The dissolution process is automated by PLC based Supervisory Control and Data Acquisition (SCADA) system for accurate control of process parameters and successfully dissolved around 200 Metric Tons of UOC. The paper covers complex chemistry involved in UOC dissolution process and also SCADA system. The solid and liquid reactions were studied along with multiple stoichiometry of nitrous oxide generated. (author)

Dissolution process analysis using model-free Noyes-Whitney integral equation.

Science.gov (United States)

Hattori, Yusuke; Haruna, Yoshimasa; Otsuka, Makoto

2013-02-01

Drug dissolution process of solid dosages is theoretically described by Noyes-Whitney-Nernst equation. However, the analysis of the process is demonstrated assuming some models. Normally, the model-dependent methods are idealized and require some limitations. In this study, Noyes-Whitney integral equation was proposed and applied to represent the drug dissolution profiles of a solid formulation via the non-linear least squares (NLLS) method. The integral equation is a model-free formula involving the dissolution rate constant as a parameter. In the present study, several solid formulations were prepared via changing the blending time of magnesium stearate (MgSt) with theophylline monohydrate, α-lactose monohydrate, and crystalline cellulose. The formula could excellently represent the dissolution profile, and thereby the rate constant and specific surface area could be obtained by NLLS method. Since the long time blending coated the particle surface with MgSt, it was found that the water permeation was disturbed by its layer dissociating into disintegrant particles. In the end, the solid formulations were not disintegrated; however, the specific surface area gradually increased during the process of dissolution. The X-ray CT observation supported this result and demonstrated that the rough surface was dominant as compared to dissolution, and thus, specific surface area of the solid formulation gradually increased. Copyright © 2012 Elsevier B.V. All rights reserved.

Dissolution enhancement of Deflazacort using hollow crystals prepared by antisolvent crystallization process.

Science.gov (United States)

Paulino, A S; Rauber, G; Campos, C E M; Maurício, M H P; de Avillez, R R; Capobianco, G; Cardoso, S G; Cuffini, S L

2013-05-13

Deflazacort (DFZ), a derivate of prednisolone, is a poorly soluble drug which has been proposed to have major advantages over other corticosteroids. Poorly soluble drugs present limited bioavailability due to their low solubility and dissolution rate and several strategies have been developed in order to find ways to improve them. In general, pharmaceutical laboratories use a micronized process to reduce the particle size in order to increase the dissolution of the drugs. However, this process causes changes such as polymorphic transitions, particle agglomeration and a reduction in fluidity and wettability. These solid-state properties affect the dissolution behavior and stability performance of drugs. Crystallization techniques are widely used in the pharmaceutical industry and antisolvent crystallization has been used to obtain ultrafine particles. In this study, DFZ was investigated in terms of its antisolvent crystallization in different solvents and under various preparation conditions (methanol/water ratio, stirring and evaporation rate, etc.), in order to compare the physicochemical properties between crystallized samples and raw materials available on the Brazilian market with and without micronization. Crystalline structure, morphology, and particle size, and their correlation with the Intrinsic Dissolution Rate (IDR) and dissolution profile as relevant biopharmaceutical properties were studied. Crystallization conditions were achieved which provided crystalline samples of hollow-shaped crystals with internal channels, which increased the dissolution rate of DFZ. The antisolvent crystallization process allowed the formation of hollow crystals, which demonstrated a better dissolution profile than the raw material (crystalline and micronized), making this a promising technique as a crystallization strategy for improving the dissolution and thus the bioavailability of poorly soluble drugs. Copyright © 2013 Elsevier B.V. All rights reserved.

Development of dissolution process for metal foil target containing low enriched uranium

International Nuclear Information System (INIS)

Srinivasan, B.; Hutter, J.C.; Johnson, G.K.; Vandegrift, G.F.

1994-01-01

About six times more low enriched uranium (LEU) metal is needed to produce the same quantity of 99 Mo as from a high enriched uranium (HEU) oxide target, under similar conditions of neutron irradiation. In view of this, the post-irradiation processing procedures of the LEU target are likely to be different from the Cintichem process procedures now in use for the HEU target. The authors have begun a systematic study to develop modified procedures for LEU target dissolution and 99 Mo separation. The dissolution studies include determination of the dissolution rate, chemical state of uranium in the solution, and the heat evolved in the dissolution reaction. From these results the authors conclude that a mixture of nitric and sulfuric acid is a suitable dissolver solution, albeit at higher concentration of nitric acid than in use for the HEU targets. Also, the dissolver vessel now in use for HEU targets is inadequate for the LEU target, since higher temperature and higher pressure will be encountered in the dissolution of LEU targets. The desire is to keep the modifications to the Cintichem process to a minimum, so that the switch from HEU to LEU can be achieved easily

Chemistry of proposed calcination/dissolution processing of Hanford Site tank wastes

International Nuclear Information System (INIS)

Delegard, C.H.

1995-01-01

Plans exist to separate radioactive waste stored in underground tanks at the US Department of Energy's Hanford Site in south central Washington State into low-level and high-level fractions, and to immobilize the separate fractions in high-integrity vitrified forms for long-term disposal. Calcination with water dissolution has been proposed as a possible treatment for achieving low/high-level separation. Chemistry development activities conducted since 1992 with simulated and genuine tank waste show that calcination/dissolution destroys organic carbon and converts nitrate and nitrite to hydroxide and benign offgases. The process also dissolves significant quantities of bulk chemicals (aluminum, chromium, and phosphate), allowing their redistribution from the high-level to the low-level fraction. Present studies of the chemistry of calcination/dissolution processing of genuine wastes, conducted in the period October 1993 to September 1994, show the importance of sodium fluoride phosphate double salt in controlling phosphate dissolution. Peptization of waste solids is of concern if extensive washing occurs. Strongly oxidizing conditions imposed by calcination reactions were found to convert transition metals to soluble anions in the order chromate > manganate > > ferrate. In analogy with manganese behavior, plutonium dissolution, presumably by oxidation to more soluble anionic species, also occurs by calcination/dissolution. Methods to remove plutonium from the product low-level solution stream must be developed

Pilot-scale tests of HEME and HEPA dissolution process

Energy Technology Data Exchange (ETDEWEB)

Qureshi, Z.H.; Strege, D.K.

1994-06-01

A series of pilot-scale demonstration tests for the dissolution of High Efficiency Mist Eliminators (HEME`s) and High Efficiency Particulate Airfilters (HEPA) were performed on a 1/5th linear scale. These fiberglass filters are to be used in the Defense Waste Processing Facility (DWPF) to decontaminate the effluents from the off-gases generated during the feed preparation process and vitrification. When removed, these filters will be dissolved in the Decontamination Waste Treatment Tank (DWTT) using 5 wt% NaOH solution. The contaminated fiberglass is converted to an aqueous stream which will be transferred to the waste tanks. The filter metal structure will be rinsed with process water before its disposal as low-level solid waste. The pilot-scale study reported here successfully demonstrated a simple one step process using 5 wt% NaOH solution. The proposed process requires the installation of a new water spray ring with 30 nozzles. In addition to the reduced waste generated, the total process time is reduced to 48 hours only (66% saving in time). The pilot-scale tests clearly demonstrated that the dissolution process of HEMEs has two stages - chemical digestion of the filter and mechanical erosion of the digested filter. The digestion is achieved by a boiling 5 wt% caustic solutions, whereas the mechanical break down of the digested filter is successfully achieved by spraying process water on the digested filter. An alternate method of breaking down the digested filter by increased air sparging of the solution was found to be marginally successful are best. The pilot-scale tests also demonstrated that the products of dissolution are easily pumpable by a centrifugal pump.

Pilot-scale tests of HEME and HEPA dissolution process

International Nuclear Information System (INIS)

Qureshi, Z.H.; Strege, D.K.

1994-06-01

A series of pilot-scale demonstration tests for the dissolution of High Efficiency Mist Eliminators (HEME's) and High Efficiency Particulate Airfilters (HEPA) were performed on a 1/5th linear scale. These fiberglass filters are to be used in the Defense Waste Processing Facility (DWPF) to decontaminate the effluents from the off-gases generated during the feed preparation process and vitrification. When removed, these filters will be dissolved in the Decontamination Waste Treatment Tank (DWTT) using 5 wt% NaOH solution. The contaminated fiberglass is converted to an aqueous stream which will be transferred to the waste tanks. The filter metal structure will be rinsed with process water before its disposal as low-level solid waste. The pilot-scale study reported here successfully demonstrated a simple one step process using 5 wt% NaOH solution. The proposed process requires the installation of a new water spray ring with 30 nozzles. In addition to the reduced waste generated, the total process time is reduced to 48 hours only (66% saving in time). The pilot-scale tests clearly demonstrated that the dissolution process of HEMEs has two stages - chemical digestion of the filter and mechanical erosion of the digested filter. The digestion is achieved by a boiling 5 wt% caustic solutions, whereas the mechanical break down of the digested filter is successfully achieved by spraying process water on the digested filter. An alternate method of breaking down the digested filter by increased air sparging of the solution was found to be marginally successful are best. The pilot-scale tests also demonstrated that the products of dissolution are easily pumpable by a centrifugal pump

Influence of processing-induced phase transformations on the dissolution of theophylline tablets

OpenAIRE

Debnath, Smita; Suryanarayanan, Raj

2004-01-01

The object of this investigation was to evaluate the influence of (1) processing-induced decrease in drug crystallinity and (2) phase transformations during dissolution, on the per-formance of theophylline tablet formulations. Anhydrous theophylline underwent multiple transformations (anhydrate »hydrate»anhydrate) during processing. Although the crystallinity of the anhydrate obtained finally was lower than that of the unprocessed drug, it dissolved at a slower rate. This decrease in dissolut...

Studies on the fission products behavior during dissolution process of BWR spent fuel

International Nuclear Information System (INIS)

Sato, K.; Nakai, E.; Kobayashi, Y.

1987-01-01

In order to obtain basic data on fission products behavior in connection with the head end process of fuel reprocessing, especially to obtain better understanding on undissolved residues, small scale dissolution studies were performed by using BWR spent fuel rods which were irradiated as monitoring fuel rods under the monitoring program for LWR fuel assembly performance entitled PROVING TEST ON RELIABILITY OF FUEL ASSEMBLY . The Zircaloy-2 claddings and the fuel pellets were subjected individually to the following studies on 1) release of fission products during dissolution process, 2) characterization of undissolved residues, and 3) analysis of the claddings. This paper presents comprehensive descriptions of the fission products behavior during dissolution process, based on detailed and through PIE conducted by JNFS under the sponsorship of MITI (Ministry of International Trade and Industry)

Dissolution process of atmospheric aerosol particles into cloud droplets; Processus de dissolution des aerosols atmospheriques au sein des gouttes d'eau nuageuses

Energy Technology Data Exchange (ETDEWEB)

Desboeufs, K

2001-01-15

Clouds affect both climate via the role they play in the Earth's radiation balance and tropospheric chemistry since they are efficient reaction media for chemical transformation of soluble species. Cloud droplets are formed in the atmosphere by condensation of water vapour onto aerosol particles, the cloud condensation nuclei (CCN). The water soluble fraction of these CCN governs the cloud micro-physics, which is the paramount factor playing on the radiative properties of clouds. Moreover, this soluble fraction is the source of species imply in the oxidation/reduction reactions in the aqueous phase. Thus, it is of particular importance to understand the process controlling the solubilization of aerosols in the cloud droplets. The main purpose of this work is to investigate experimentally and theoretically the dissolution of particles incorporated in the aqueous phase. From the studies conducted up to now, we have identify several factors playing on the dissolution reaction of aerosols. However, the quantification of the effects of these factors is difficult since the current means of study are not adapted to the complexity of cloud systems. First, this work consisted to perform a experimental system, compound by an open flow reactor, enabling to follow the kinetic of dissolution in conditions representative of cloud. This experimental device is used to a systematic characterisation of the known factors playing on the dissolution, i.e. pH, aerosol nature, aerosol weathering... and also for the identification and the quantification of the effects of other factors: ionic strength, acid nature, clouds processes. These experiments gave quantitative results, which are used to elaborate a simple model of aerosol dissolution in the aqueous phase. This model considers the main factors playing on the dissolution and results in a general mechanism of aerosol dissolution extrapolated to the cloud droplets. (author)

Double porosity model to describe both permeability change and dissolution processes

International Nuclear Information System (INIS)

Niibori, Yuichi; Usui, Hideo; Chida, Taiji

2015-01-01

Cement is a practical material for constructing the geological disposal system of radioactive wastes. The dynamic behavior of both permeability change and dissolution process caused by a high pH groundwater was explained using a double porosity model assuming that each packed particle consists of the sphere-shaped aggregation of smaller particles. This model assumes two kinds of porosities between the particle clusters and between the particles, where the former porosity change mainly controls the permeability change of the bed, and the latter porosity change controls the diffusion of OH"- ions inducing the dissolution of silica. The fundamental equations consist of a diffusion equation of spherical coordinates of OH"- ions including the first-order reaction term and some equations describing the size changes of both the particles and the particle clusters with time. The change of over-all permeability of the packed bed is evaluated by Kozeny-Carman equation and the calculated radii of particle clusters. The calculated result well describes the experimental result of both permeability change and dissolution processes. (author)

Validation Testing of the Nitric Acid Dissolution Step Within the K Basin Sludge Pretreatment Process

International Nuclear Information System (INIS)

AJ Schmidt; CH Delegard; KL Silvers; PR Bredt; CD Carlson; EW Hoppe; JC Hayes; DE Rinehart; SR Gano; BM Thornton

1999-01-01

The work described in this report involved comprehensive bench-scale testing of nitric acid (HNO 3 ) dissolution of actual sludge materials from the Hanford K East (KE) Basin to confirm the baseline chemical pretreatment process. In addition, process monitoring and material balance information was collected to support the development and refinement of process flow diagrams. The testing was performed by Pacific Northwest National Laboratory (PNNL)for the US Department of Energy's Office of Spent Fuel Stabilization (EM-67) and Numatec Hanford Corporation (NHC) to assist in the development of the K Basin Sludge Pretreatment Process. The baseline chemical pretreatment process for K Basin sludge is nitric acid dissolution of all particulate material passing a 1/4-in. screen. The acid-insoluble fraction (residual solids) will be stabilized (possibly by chemical leaching/rinsing and grouting), packaged, and transferred to the Hanford Environmental Restoration Disposal Facility (ERDF). The liquid fraction is to be diluted with depleted uranium for uranium criticality safety and iron nitrate for plutonium criticality safety, and neutralized with sodium hydroxide. The liquid fraction and associated precipitates are to be stored in the Hanford Tank Waste Remediation Systems (TWRS) pending vitrification. It is expected that most of the polychlorinated biphenyls (PCBs), associated with some K Basin sludges, will remain with the residual solids for ultimate disposal to ERDF. Filtration and precipitation during the neutralization step will further remove trace quantities of PCBs within the liquid fraction. The purpose of the work discussed in this report was to examine the dissolution behavior of actual KE Basin sludge materials at baseline flowsheet conditions and validate the.dissolution process step through bench-scale testing. The progress of the dissolution was evaluated by measuring the solution electrical conductivity and concentrations of key species in the dissolver

Validation Testing of the Nitric Acid Dissolution Step Within the K Basin Sludge Pretreatment Process

Energy Technology Data Exchange (ETDEWEB)

AJ Schmidt; CH Delegard; KL Silvers; PR Bredt; CD Carlson; EW Hoppe; JC Hayes; DE Rinehart; SR Gano; BM Thornton

1999-03-24

The work described in this report involved comprehensive bench-scale testing of nitric acid (HNO{sub 3}) dissolution of actual sludge materials from the Hanford K East (KE) Basin to confirm the baseline chemical pretreatment process. In addition, process monitoring and material balance information was collected to support the development and refinement of process flow diagrams. The testing was performed by Pacific Northwest National Laboratory (PNNL)for the US Department of Energy's Office of Spent Fuel Stabilization (EM-67) and Numatec Hanford Corporation (NHC) to assist in the development of the K Basin Sludge Pretreatment Process. The baseline chemical pretreatment process for K Basin sludge is nitric acid dissolution of all particulate material passing a 1/4-in. screen. The acid-insoluble fraction (residual solids) will be stabilized (possibly by chemical leaching/rinsing and grouting), packaged, and transferred to the Hanford Environmental Restoration Disposal Facility (ERDF). The liquid fraction is to be diluted with depleted uranium for uranium criticality safety and iron nitrate for plutonium criticality safety, and neutralized with sodium hydroxide. The liquid fraction and associated precipitates are to be stored in the Hanford Tank Waste Remediation Systems (TWRS) pending vitrification. It is expected that most of the polychlorinated biphenyls (PCBs), associated with some K Basin sludges, will remain with the residual solids for ultimate disposal to ERDF. Filtration and precipitation during the neutralization step will further remove trace quantities of PCBs within the liquid fraction. The purpose of the work discussed in this report was to examine the dissolution behavior of actual KE Basin sludge materials at baseline flowsheet conditions and validate the.dissolution process step through bench-scale testing. The progress of the dissolution was evaluated by measuring the solution electrical conductivity and concentrations of key species in the

System and process for dissolution of solids

Science.gov (United States)

Liezers, Martin; Farmer, III, Orville T.

2017-10-10

A system and process are disclosed for dissolution of solids and "difficult-to-dissolve" solids. A solid sample may be ablated in an ablation device to generate nanoscale particles. Nanoparticles may then swept into a coupled plasma device operating at atmospheric pressure where the solid nanoparticles are atomized. The plasma exhaust may be delivered directly into an aqueous fluid to form a solution containing the atomized and dissolved solids. The composition of the resulting solution reflects the composition of the original solid sample.

Dissolution process of atmospheric aerosol particles into cloud droplets; Processus de dissolution des aerosols atmospheriques au sein des gouttes d'eau nuageuses

Energy Technology Data Exchange (ETDEWEB)

Desboeufs, K.

2001-01-15

Clouds affect both climate via the role they play in the Earth's radiation balance and tropospheric chemistry since they are efficient reaction media for chemical transformation of soluble species. Cloud droplets are formed in the atmosphere by condensation of water vapour onto aerosol particles, the cloud condensation nuclei (CCN). The water soluble fraction of these CCN governs the cloud micro-physics, which is the paramount factor playing on the radiative properties of clouds. Moreover, this soluble fraction is the source of species imply in the oxidation/reduction reactions in the aqueous phase. Thus, it is of particular importance to understand the process controlling the solubilization of aerosols in the cloud droplets. The main purpose of this work is to investigate experimentally and theoretically the dissolution of particles incorporated in the aqueous phase. From the studies conducted up to now, we have identify several factors playing on the dissolution reaction of aerosols. However, the quantification of the effects of these factors is difficult since the current means of study are not adapted to the complexity of cloud systems. First, this work consisted to perform a experimental system, compound by an open flow reactor, enabling to follow the kinetic of dissolution in conditions representative of cloud. This experimental device is used to a systematic characterisation of the known factors playing on the dissolution, i.e. pH, aerosol nature, aerosol weathering... and also for the identification and the quantification of the effects of other factors: ionic strength, acid nature, clouds processes. These experiments gave quantitative results, which are used to elaborate a simple model of aerosol dissolution in the aqueous phase. This model considers the main factors playing on the dissolution and results in a general mechanism of aerosol dissolution extrapolated to the cloud droplets. (author)

Correlation Study of Magnetite Dissolution in Hybrid Decontamination Process

Energy Technology Data Exchange (ETDEWEB)

Kim, Seon-Byeong; Won, Hui-Jun; Park, Jung-Sun; Park, Sang-Yoon; Moon, Jei-Kwon; Choi, Wang-Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-10-15

In the operating plants, the localized corrosion on SG tubes which are transporters of thermal energy to the secondary side lowers the reduction heat transfer efficiency as well as degrades the lifetime of SG. Magnetite, Fe3O4, is a commonly found corrosion product on the inner surface of reactor coolant system. Simply magnetite can be reduced to hematite, Fe{sub 2}O{sub 3}, and further to iron when oxygen is limited or ample reducing agents are supplied. Along this line, number of decontamination processes has been developed since 1970s and most of them contain organic acid and additive chelating agents. However, many reports have pointed out the negative environmental effect of those chemicals, and currently there are new approaches to overcome the limited decontamination efficiency and large volume of secondary waste from other alternate processes without using such those organic chemicals. In present study, we investigated the magnetite dissolution in HyBRID solution as newly developing decontamination process. As a preliminary study for empirical modeling of decontamination by HyBRID solution, simply correlation study between variable and magnetite dissolution was introduced with studied mechanism and experimental results.

Fracture Dissolution of Carbonate Rock: An Innovative Process for Gas Storage

Energy Technology Data Exchange (ETDEWEB)

James W. Castle; Ronald W. Falta; David Bruce; Larry Murdoch; Scott E. Brame; Donald Brooks

2006-10-31

The goal of the project is to develop and assess the feasibility and economic viability of an innovative concept that may lead to commercialization of new gas-storage capacity near major markets. The investigation involves a new approach to developing underground gas storage in carbonate rock, which is present near major markets in many areas of the United States. Because of the lack of conventional gas storage and the projected growth in demand for storage capacity, many of these areas are likely to experience shortfalls in gas deliverability. Since depleted gas reservoirs and salt formations are nearly non-existent in many areas, alternatives to conventional methods of gas storage are required. The need for improved methods of gas storage, particularly for ways to meet peak demand, is increasing. Gas-market conditions are driving the need for higher deliverability and more flexibility in injection/withdrawal cycling. In order to meet these needs, the project involves an innovative approach to developing underground storage capacity by creating caverns in carbonate rock formations by acid dissolution. The basic concept of the acid-dissolution method is to drill to depth, fracture the carbonate rock layer as needed, and then create a cavern using an aqueous acid to dissolve the carbonate rock. Assessing feasibility of the acid-dissolution method included a regional geologic investigation. Data were compiled and analyzed from carbonate formations in six states: Indiana, Ohio, Kentucky, West Virginia, Pennsylvania, and New York. To analyze the requirements for creating storage volume, the following aspects of the dissolution process were examined: weight and volume of rock to be dissolved; gas storage pressure, temperature, and volume at depth; rock solubility; and acid costs. Hydrochloric acid was determined to be the best acid to use because of low cost, high acid solubility, fast reaction rates with carbonate rock, and highly soluble products (calcium chloride

Plutonium oxide dissolution

International Nuclear Information System (INIS)

Gray, J.H.

1992-01-01

Several processing options for dissolving plutonium oxide (PuO 2 ) from high-fired materials have been studied. The scoping studies performed on these options were focused on PuO 2 typically generated by burning plutonium metal and PuO 2 produced during incineration of alpha contaminated waste. At least two processing options remain applicable for dissolving high-fired PuO 2 in canyon dissolvers. The options involve solid solution formation of PuO 2 With uranium oxide (UO 2 ) and alloying incinerator ash with aluminum. An oxidative dissolution process involving nitric acid solutions containing a strong oxidizing agent, such as cerium (IV), was neither proven nor rejected. This uncertainty was due to difficulty in regenerating cerium (IV) ions during dissolution. However, recent work on silver-catalyzed dissolution of PuO 2 with persulfate has demonstrated that persulfate ions regenerate silver (II). Use of persulfate to regenerate cerium (IV) or bismuth (V) ions during dissolution of PuO 2 materials may warrant further study

Quantification of the resist dissolution process: an in situ analysis using high speed atomic force microscopy

Science.gov (United States)

Santillan, Julius Joseph; Shichiri, Motoharu; Itani, Toshiro

2016-03-01

This work focuses on the application of a high speed atomic force microscope (HS-AFM) for the in situ visualization / quantification of the resist dissolution process. This technique, as reported in the past, has provided useful pointers on the formation of resist patterns during dissolution. This paper discusses about an investigation made on the quantification of what we refer to as "dissolution unit size" or the basic units of patterning material dissolution. This was done through the establishment of an originally developed analysis method which extracts the difference between two succeeding temporal states of the material film surface (images) to indicate the amount of change occurring in the material film at a specific span of time. Preliminary experiments with actual patterning materials were done using a positive-tone EUV model resist composed only of polyhydroxystyrene (PHS)-based polymer with a molecular weight of 2,500 and a polydispersity index of 1.2. In the absence of a protecting group, the material was utilized at a 50nm film thickness with post application bake of 90°C/60s. The resulting film is soluble in the alkali-based developer even without exposure. Results have shown that the dissolution components (dissolution unit size) of the PHS-based material are not of fixed size. Instead, it was found that aside from one constantly dissolving unit size, another, much larger dissolution unit size trend also occurs during material dissolution. The presence of this larger dissolution unit size suggests an occurrence of "polymer clustering". Such polymer clustering was not significantly present during the initial stages of dissolution (near the original film surface) but becomes more persistently obvious after the dissolution process reaches a certain film thickness below the initial surface.

Cognitive Processing in the Aftermath of Relationship Dissolution: Associations with Concurrent and Prospective Distress and Posttraumatic Growth

DEFF Research Database (Denmark)

del Palacio Gonzalez, Adriana; Clark, David; O'Sullivan, Lucia F.

2017-01-01

Non-marital romantic relationship dissolution is amongst the most stressful life events experienced by young adults. Yet, some individuals experience posttraumatic growth following relationship dissolution. Little is known about the specific and differential contribution of trait-like and event...... Distress Scale) following a recent relationship dissolution. Initially, 148 participants completed measures of trait-like and dissolution-specific cognitive processing, growth, and distress (T1). A subsample completed a seven-month follow-up (T2). Higher frequency of relationship-dissolution intrusive...... thoughts predicted concurrent distress after accounting for brooding and relationship characteristics. Further, higher brooding and lower reflection predicted higher distress prospectively. Concurrent growth was predicted by both higher brooding and more deliberate relationship-dissolution thoughts...

Dissolution of metallic uranium and its alloys. Part 1. Review of analytical and process-scale metallic uranium dissolution

International Nuclear Information System (INIS)

Laue, C.A.; Gates-Anderson, D.; Fitch, T.E.

2004-01-01

This review focuses on dissolution/reaction systems capable of treating uranium metal waste to remove its pyrophoric properties. The primary emphasis is the review of literature describing analytical and production-scale dissolution methods applied to either uranium metal or uranium alloys. A brief summary of uranium's corrosion behavior is included since the corrosion resistance of metals and alloys affects their dissolution behavior. Based on this review, dissolution systems were recommended for subsequent screening studies designed to identify the best system to treat depleted uranium metal wastes at Lawrence Livermore National Laboratory (LLNL). (author)

Disintegration and dissolution of spent radioactive cationic exchange resins using Fenton-like oxidation process

International Nuclear Information System (INIS)

Wan, Zhong; Xu, Lejin; Wang, Jianlong

2015-01-01

Highlights: • The spent radioactive resins could be oxidized by Fenton-like process. • The influencing factors on resin oxidation were evaluated. • Chemical oxygen demand (COD) reduction rate was more than 99%. • SEM and Raman spectrum were used to analyze the resins morphological change. - Abstract: The treatment and disposal of the spent radioactive resins is essential for the sustainable development of the nuclear industry. In this paper, the disintegration and dissolution of spent cationic resins were studied by Fenton-like process. The influencing factors on resin dissolution, such as pH, temperature, type and concentration of catalysts were evaluated. The results showed that the spent resins could be effectively dissolved at pH < 1, [Fe 2+ ] = 0.2 M and T = 97 ± 2 °C. Chemical oxygen demand (COD) reduction rate was more than 99%. The scanning electron microscopy and the Raman spectrum were used to observe the morphological changes of the spent resins during the dissolution process. Fenton-like oxidation is an efficient method for the volume reduction and stabilization of the spent resins before further immobilization

Disintegration and dissolution of spent radioactive cationic exchange resins using Fenton-like oxidation process

Energy Technology Data Exchange (ETDEWEB)

Wan, Zhong; Xu, Lejin [Collaborative Innovation Center for Advanced Nuclear Energy Technology, INET, Tsinghua University, Beijing 100084 (China); Wang, Jianlong, E-mail: wangjl@tsinghua.edu.cn [Collaborative Innovation Center for Advanced Nuclear Energy Technology, INET, Tsinghua University, Beijing 100084 (China); Beijing Key Laboratory of Radioactive Wastes Treatment, Tsinghua University, Beijing 100084 (China)

2015-09-15

Highlights: • The spent radioactive resins could be oxidized by Fenton-like process. • The influencing factors on resin oxidation were evaluated. • Chemical oxygen demand (COD) reduction rate was more than 99%. • SEM and Raman spectrum were used to analyze the resins morphological change. - Abstract: The treatment and disposal of the spent radioactive resins is essential for the sustainable development of the nuclear industry. In this paper, the disintegration and dissolution of spent cationic resins were studied by Fenton-like process. The influencing factors on resin dissolution, such as pH, temperature, type and concentration of catalysts were evaluated. The results showed that the spent resins could be effectively dissolved at pH < 1, [Fe{sup 2+}] = 0.2 M and T = 97 ± 2 °C. Chemical oxygen demand (COD) reduction rate was more than 99%. The scanning electron microscopy and the Raman spectrum were used to observe the morphological changes of the spent resins during the dissolution process. Fenton-like oxidation is an efficient method for the volume reduction and stabilization of the spent resins before further immobilization.

Physicochemical Properties and In Vitro Dissolution of Spiramycin Microparticles Using the Homogenate-Antisolvent Precipitation Process

Directory of Open Access Journals (Sweden)

Xiaonan Zhang

2016-12-01

Full Text Available Due to its low bioavailability and slow dissolution rate, the micronized spiramycin powder was thus prepared by the homogenate-antisolvent precipitation (HAP process. The optimum micronization conditions of the HAP process were found to be as follows: precipitation temperature of 4.6 °C, precipitation time of 10 min, spiramycin concentration of 20 mg/mL, dripping speed of the added solvent into the antisolvent of 44 mL/h, antisolvent (water to solvent (dimethyl sulfide (DMSO volume ratio of 7:1, and shear rate of 5000 rpm. With this HAP process, the mean particle size was 228.36 ± 3.99 nm. The micronized spiramycin was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, high-performance liquid chromatography, and gas chromatograph analyses. In comparison with the raw drug, the chemical structure of micronized spiramycin was not changed. The dissolution rate experiments showed that the dissolution rate of the spiramycin was significantly increased after micronization.

A framework for shear driven dissolution of thermally stable particles during friction stir welding and processing

Energy Technology Data Exchange (ETDEWEB)

Palanivel, S. [Advanced Materials and Manufacturing Processes Institute, Center for Friction Stir Processing, Department of Materials Science and Engineering, University of North Texas, Denton, TX 76203 (United States); Arora, A. [Materials Science and Engineering, Indian Institute of Technology Gandhinagar, Palaj, Gandhinagar 382355, Gujarat (India); Doherty, K.J. [U.S. Army Research Laboratory, Materials and Manufacturing Science Division, Aberdeen Proving Ground, MD 21005 (United States); Mishra, R.S., E-mail: Rajiv.Mishra@unt.edu [Advanced Materials and Manufacturing Processes Institute, Center for Friction Stir Processing, Department of Materials Science and Engineering, University of North Texas, Denton, TX 76203 (United States)

2016-12-15

A framework is proposed to explain the dissolution and fragmentation of particles during friction stir welding and processing. Two major mechanisms dissolve the particle during the process: (i) thermally activated diffusion, and (ii) dislocation and grain boundary sweeping of atoms. We use a three-dimensional coupled viscoplastic flow and heat transfer model to quantify these mechanisms. For illustration purposes, calculations were done on a thermally stable Mg{sub 2}Y intermetallic that dissolved during processing. The framework is universal and applies to any second phase dissolution and fragmentation during friction stir welding and processing, thus enabling a science-based approach to tailor microstructures.

Mathematical modeling of drug dissolution.

Science.gov (United States)

Siepmann, J; Siepmann, F

2013-08-30

The dissolution of a drug administered in the solid state is a pre-requisite for efficient subsequent transport within the human body. This is because only dissolved drug molecules/ions/atoms are able to diffuse, e.g. through living tissue. Thus, generally major barriers, including the mucosa of the gastro intestinal tract, can only be crossed after dissolution. Consequently, the process of dissolution is of fundamental importance for the bioavailability and, hence, therapeutic efficacy of various pharmaco-treatments. Poor aqueous solubility and/or very low dissolution rates potentially lead to insufficient availability at the site of action and, hence, failure of the treatment in vivo, despite a potentially ideal chemical structure of the drug to interact with its target site. Different physical phenomena are involved in the process of drug dissolution in an aqueous body fluid, namely the wetting of the particle's surface, breakdown of solid state bonds, solvation, diffusion through the liquid unstirred boundary layer surrounding the particle as well as convection in the surrounding bulk fluid. Appropriate mathematical equations can be used to quantify these mass transport steps, and more or less complex theories can be developed to describe the resulting drug dissolution kinetics. This article gives an overview on the current state of the art of modeling drug dissolution and points out the assumptions the different theories are based on. Various practical examples are given in order to illustrate the benefits of such models. This review is not restricted to mathematical theories considering drugs exhibiting poor aqueous solubility and/or low dissolution rates, but also addresses models quantifying drug release from controlled release dosage forms, in which the process of drug dissolution plays a major role. Copyright © 2013 Elsevier B.V. All rights reserved.

The dissolution phenomenon of lysozyme crystals

Energy Technology Data Exchange (ETDEWEB)

Mueller, C.; Ulrich, J. [Martin Luther University Halle-Wittenberg, Department of Thermal Separation Processes, Centre of Engineering Science, Halle/Saale (Germany)

2012-02-15

Dissolution studies on lysozyme crystals were carried out since the observed dissolution pattern look different from non-protein dissolved crystals. The Tetragonal, High Temperature and Low Temperature Orthorhombic morphologies, crystallized using sodium chloride, were chosen and the influence of different pH, salt and protein concentration on their dissolution was investigated. An increase in pH and/or salt concentration can modify the dissolution behaviour. The pattern of the crystals during the dissolution process will, therefore, develop differently. Frequently a skeleton like crystal pattern followed by a falling apart of the crystals is observed. The multi-component character of the lysozyme crystal (protein, water, buffer, salt) as well as ''solvatomorphism'' gives first insights in the phenomena happening in the dissolution process. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Dissolution Dominating Calcification Process in Polar Pteropods Close to the Point of Aragonite Undersaturation

Science.gov (United States)

Bednaršek, Nina; Tarling, Geraint A.; Bakker, Dorothee C. E.; Fielding, Sophie; Feely, Richard A.

2014-01-01

Thecosome pteropods are abundant upper-ocean zooplankton that build aragonite shells. Ocean acidification results in the lowering of aragonite saturation levels in the surface layers, and several incubation studies have shown that rates of calcification in these organisms decrease as a result. This study provides a weight-specific net calcification rate function for thecosome pteropods that includes both rates of dissolution and calcification over a range of plausible future aragonite saturation states (Ωar). We measured gross dissolution in the pteropod Limacina helicina antarctica in the Scotia Sea (Southern Ocean) by incubating living specimens across a range of aragonite saturation states for a maximum of 14 days. Specimens started dissolving almost immediately upon exposure to undersaturated conditions (Ωar∼0.8), losing 1.4% of shell mass per day. The observed rate of gross dissolution was different from that predicted by rate law kinetics of aragonite dissolution, in being higher at Ωar levels slightly above 1 and lower at Ωar levels of between 1 and 0.8. This indicates that shell mass is affected by even transitional levels of saturation, but there is, nevertheless, some partial means of protection for shells when in undersaturated conditions. A function for gross dissolution against Ωar derived from the present observations was compared to a function for gross calcification derived by a different study, and showed that dissolution became the dominating process even at Ωar levels close to 1, with net shell growth ceasing at an Ωar of 1.03. Gross dissolution increasingly dominated net change in shell mass as saturation levels decreased below 1. As well as influencing their viability, such dissolution of pteropod shells in the surface layers will result in slower sinking velocities and decreased carbon and carbonate fluxes to the deep ocean. PMID:25285916

Formation, transformation and dissolution of phases formed on surfaces

International Nuclear Information System (INIS)

Shoesmith, D.W.

1983-03-01

The basic mechanisms of film growth, transformation, and dissolution of phases formed on surfaces are discussed. Film growth can occur via solid-state processes or via substrate (usally metal or alloy) dissolution, followed by local supersaturation and precipitation of an insoluble phase. The phase(s) formed may be metastable and transform to a more stable phase, via either solid-state or dissolution-reprecipitation processes. Film dissolution reactions can also occur via a variety of mechanisms, including: (i) direct chemical dissolution when no oxidation state change occurs; (ii) redox dissolution when the film dissolves via a redox reaction involving a reducing or oxidizing agent in solution; and (iii) autoreduction, where film dissolution is coupled to metal dissolution. Such film-growth and dissolution processes, which often produce complex multilayer films, are common in the nuclear industry. A number of examples are discussed

Insights into the Surface Transformation and Electrochemical Dissolution Process of Bornite in Bioleaching

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Hongbo Zhao

2018-04-01

Full Text Available In this work, density functional theory (DFT calculations, X-ray photoelectron spectroscopy (XPS and electrochemistry analysis were combined to analyze the electrochemical dissolution process of bornite during bioleaching. DFT calculations showed that bornite was a conductor with metallic conductivity. The formula of bornite may be (Cu+5Fe3+(S2−4 and the surface reconstruction of (111-S surface was discussed. Electrochemistry and XPS analysis showed that bornite tended to be directly oxidized with high conductivity when the potential was higher than 0.3 V vs. Ag/AgCl. Elemental sulfur (S0, FeOOH and CuS were the main intermediate species on the bornite surface during the oxidation process. The production of S0 and FeOOH on bornite surface can be significantly accelerated with increased redox potential, but no insoluble sulfate (SO42− formed on bornite surface in 0.3–0.65 V vs. Ag/AgCl. The oxidative dissolution of bornite was significantly accelerated with increasing redox potential, which was one important reason why mixed culture was more effective than single strains of A. caldus and L. ferriphilum in bornite bioleaching. The insoluble SO42− was formed mainly through the chemical reactions in solution and then covered the bornite surface in bioleaching. Based on the obtained results, a model for interpreting the dissolution process of bornite in bioleaching was proposed.

Interactions between magnetite and humic substances: redox reactions and dissolution processes.

Science.gov (United States)

Sundman, Anneli; Byrne, James M; Bauer, Iris; Menguy, Nicolas; Kappler, Andreas

2017-10-19

Humic substances (HS) are redox-active compounds that are ubiquitous in the environment and can serve as electron shuttles during microbial Fe(III) reduction thus reducing a variety of Fe(III) minerals. However, not much is known about redox reactions between HS and the mixed-valent mineral magnetite (Fe 3 O 4 ) that can potentially lead to changes in Fe(II)/Fe(III) stoichiometry and even dissolve the magnetite. To address this knowledge gap, we incubated non-reduced (native) and reduced HS with four types of magnetite that varied in particle size and solid-phase Fe(II)/Fe(III) stoichiometry. We followed dissolved and solid-phase Fe(II) and Fe(III) concentrations over time to quantify redox reactions between HS and magnetite. Magnetite redox reactions and dissolution processes with HS varied depending on the initial magnetite and HS properties. The interaction between biogenic magnetite and reduced HS resulted in dissolution of the solid magnetite mineral, as well as an overall reduction of the magnetite. In contrast, a slight oxidation and no dissolution was observed when native and reduced HS interacted with 500 nm magnetite. This variability in the solubility and electron accepting and donating capacity of the different types of magnetite is likely an effect of differences in their reduction potential that is correlated to the magnetite Fe(II)/Fe(III) stoichiometry, particle size, and crystallinity. Our study suggests that redox-active HS play an important role for Fe redox speciation within minerals such as magnetite and thereby influence the reactivity of these Fe minerals and their role in biogeochemical Fe cycling. Furthermore, such processes are also likely to have an effect on the fate of other elements bound to the surface of Fe minerals.

Dissolution mechanisms of CO2 hydrate droplets in deep seawaters

International Nuclear Information System (INIS)

Gabitto, Jorge; Tsouris, Costas

2006-01-01

Carbon dioxide dissolution at intermediate ocean depths was studied using physical and mass transfer models. Particle density and hydrate layer thickness were determined using existing field data. Pseudo-homogeneous and heterogeneous mass transfer models were proposed to study the dissolution process. Pseudo-homogeneous models do not seem to represent the dissolution process well. Although heterogeneous models interpret the physical behavior better, unresolved issues related to hydrate dissolution still remain. For example, solid hydrate forms on one side of the hydrate film while it dissolves on the other. Dissolution is a complex process that comprises at least two sequential steps. The global process is controlled by mass transfer inside the hydrate layer or by a dissolution reaction at the hydrate-water interface

DISSOLUTION OF IRRADIATED MURR FUEL ASSEMBLIES

Energy Technology Data Exchange (ETDEWEB)

Kyser, E.

2010-06-17

A literature survey on the dissolution of spent nuclear fuel from the University of Missouri Research Reactor (MURR) has been performed. This survey encompassed both internal and external literature sources for the dissolution of aluminum-clad uranium alloy fuels. The most limiting aspect of dissolution in the current facility configuration involves issues related to the control of the flammability of the off-gas from this process. The primary conclusion of this work is that based on past dissolution of this fuel in H-Canyon, four bundles of this fuel (initial charge) may be safely dissolved in a nitric acid flowsheet catalyzed with 0.002 M mercuric nitrate using a 40 scfm purge to control off-gas flammability. The initial charge may be followed by a second charge of up to five bundles to the same dissolver batch depending on volume and concentration constraints. The safety of this flowsheet relies on composite lower flammability limits (LFL) estimated from prior literature, pilot-scale work on the dissolution of site fuels, and the proposed processing flowsheet. Equipment modifications or improved LFL data offer the potential for improved processing rates. The fuel charging sequence, as well as the acid and catalyst concentrations, will control the dissolution rate during the initial portion of the cycle. These parameters directly impact the hydrogen and off-gas generation and, along with the purge flowrate determine the number of bundles that may be charged. The calculation approach within provides Engineering a means to determine optimal charging patterns. Downstream processing of this material should be similar to that of recent processing of site fuels requiring only minor adjustments of the existing flowsheet parameters.

Factors governing dissolution process of lignocellulosic biomass in ionic liquid: current status, overview and challenges.

Science.gov (United States)

Badgujar, Kirtikumar C; Bhanage, Bhalchandra M

2015-02-01

The utilisation of non-feed lignocellulosic biomass as a source of renewable bio-energy and synthesis of fine chemical products is necessary for the sustainable development. The methods for the dissolution of lignocellulosic biomass in conventional solvents are complex and tedious due to the complex chemical ultra-structure of biomass. In view of this, recent developments for the use of ionic liquid solvent (IL) has received great attention, as ILs can solubilise such complex biomass and thus provides industrial scale-up potential. In this review, we have discussed the state-of-art for the dissolution of lignocellulosic material in representative ILs. Furthermore, various process parameters and their influence for biomass dissolution were reviewed. In addition to this, overview of challenges and opportunities related to this interesting area is presented. Copyright © 2014 Elsevier Ltd. All rights reserved.

Development of a continuous dissolution process for the new reprocessing plants at La Hague

International Nuclear Information System (INIS)

Auchapt, P.; Patarin, L.; Tarnero, M.

1984-01-01

The French Commissariat a l'Energie Atomique has designed a continuous rotary dissolver for LWR fuel reprocessing. An industrial prototype has been tested since 1979 at the Service des Prototypes Industriels, at Marcoule. This type of dissolver will be installed at the COGEMA's Reprocessing Plants at La Hague. The advantages of a continuous process are listed, compared to batch dissolutions (chemistry, operation, capacity). The industrial prototype, featuring safe geometry, is described. The R and D program is indicated, and the main results of inactive tests already performed on the industrial prototype are given, including heating, mechanical, and chemical tests (UO 2 dissolutions at 4tU per day)

Development of a continuous dissolution process for the new reprocessing plants at La Hague

International Nuclear Information System (INIS)

Auchapt, P.; Patarin, L.; Tarnero, M.

1984-08-01

The French Commissariat a l'Energie Atomique has designed a continuous rotary dissolver for LWR fuel reprocessing. An industrial prototype has been tested since 1979 at the Service des Prototypes Industriels, at Marcoule. This type of dissolver will be installed at the COGEMA's Reprocessing Plants at La Hague. The advantages of a continuous process are listed, compared to batch dissolutions (chemistry, operation, capacity). The industrial prototype, featuring safe geometry, is described. The R and D program is indicated, and the main results of inactive tests already performed on the industrial prototype are given, including heating, mechanical, and chemical tests (UO 2 dissolutions at 4tU per day)

Study of dissolution process and its modelling

Directory of Open Access Journals (Sweden)

Juan Carlos Beltran-Prieto

2017-01-01

Full Text Available The use of mathematical concepts and language aiming to describe and represent the interactions and dynamics of a system is known as a mathematical model. Mathematical modelling finds a huge number of successful applications in a vast amount of science, social and engineering fields, including biology, chemistry, physics, computer sciences, artificial intelligence, bioengineering, finance, economy and others. In this research, we aim to propose a mathematical model that predicts the dissolution of a solid material immersed in a fluid. The developed model can be used to evaluate the rate of mass transfer and the mass transfer coefficient. Further research is expected to be carried out to use the model as a base to develop useful models for the pharmaceutical industry to gain information about the dissolution of medicaments in the body stream and this could play a key role in formulation of medicaments.

Optimization of LiCoO2 powder extraction process from cathodes of lithium-ion batteries by chemical dissolution

Directory of Open Access Journals (Sweden)

Lucas Evangelista Sita

2015-05-01

Full Text Available A chemical process has been applied to extract LiCoO2 powder from cathodes of spent lithium-ion batteries by dissolution of the binder that agglutinate the powder particle each other as well to the Al collector surface. As solvents dimethylformamide (DMF and N-methyilpirrolidone (NMP were employed and the variables, cathode area, solution temperature, ultrasound bath power and solution stirring were chosen to optimize the extraction process. NMP solutions presented best results for powder extraction than DMF solutions. At 100 oC and under mechanical stirring or low power ultrasound bath NMP solution optimizes the binder dissolution. Powder extractions under DMF solutions are slow and an increase in the powder extraction efficiency was observed for crushed cathodes on solutions under ultrasound bath, at medium power. Filtration processes can separate the decanted LiCoO2 powder extracted upon DMF dissolution while the powder in suspension in the NMP solutions is separated by centrifugation techniques.

In-line ATR-UV and Raman Spectroscopy for Monitoring API Dissolution Process During Liquid-Filled Soft-Gelatin Capsule Manufacturing.

Science.gov (United States)

Wan, Boyong; Zordan, Christopher A; Lu, Xujin; McGeorge, Gary

2016-10-01

Complete dissolution of the active pharmaceutical ingredient (API) is critical in the manufacturing of liquid-filled soft-gelatin capsules (SGC). Attenuated total reflectance UV spectroscopy (ATR-UV) and Raman spectroscopy have been investigated for in-line monitoring of API dissolution during manufacturing of an SGC product. Calibration models have been developed with both techniques for in-line determination of API potency. Performance of both techniques was evaluated and compared. The ATR-UV methodology was found to be able to monitor the dissolution process and determine the endpoint, but was sensitive to temperature variations. The Raman technique was also capable of effectively monitoring the process and was more robust to the temperature variation and process perturbations by using an excipient peak for internal correction. Different data preprocessing methodologies were explored in an attempt to improve method performance.

Process control plan for Single Shell Tank (SST) Saltcake Dissolution Proof of Concept

International Nuclear Information System (INIS)

ESTEY, S.D.

2001-01-01

This document describes the process controls for the tank 241-U-107 (U-107) saltcake dissolution proof-of-concept operations. Saltcake dissolution is defined as a method by which water-soluble salts will be retrieved from the Hanford Site radioactive waste tanks utilizing dissolution as the mobilizing mechanism. The proof-of-concept operations will monitor the retrieval process and transfer at least 100 kgal of fluid from tank U-107 to the double-shell tank (DST) system during the performance period. Tank U-107 has been identified as posing the highest long-term risk to the Columbia River of all single shell tanks (SSTs). This is because of the high content of mobile, long-lived radionuclides mostly in the saltcake waste in the tank. To meet current contractual and consent decree commitments, tank U-107 is being prepared for interim stabilization in August 2001. It is currently scheduled for saltcake retrieval in 2023, near the end of the SST retrieval campaign because of a lack of infrastructure in U-Farm. The proof-of-concept test will install a system to dissolve and retrieve a portion of the saltcake as part of, and operating in parallel with, the standard interim stabilization system to be installed on tank U-107. This proof-of-concept should provide key information on spray nozzle selection and effective spray patterns, leak detection, monitoring, and mitigation (LDMM) and in-tank saltcake solubility data that will help in the design of a full-tank retrieval demonstration system

Modelling of the UO2 dissolution mechanisms in synthetic groundwater solutions. Dissolution experiments carried out under oxic conditions

International Nuclear Information System (INIS)

Cera, E.; Grive, M.; Bruno, J.; Ollila, K.

2001-02-01

The analytical data generated during the last three years within the 4th framework program of the European Community at VTT Chemical Technology concerning UO 2 dissolution under oxidising conditions have been modelled in the present work. The modelling work has been addressed to perform a kinetic study of the dissolution data generated by Ollila (1999) under oxidising conditions by using unirradiated uranium dioxide as solid sample. The average of the normalised UO 2 dissolution rates determined by using the initial dissolution data generated in all the experimental tests is (6.06 ± 3.64)* 10 -7 mol m -2 d -1 . This dissolution rate agrees with most of the dissolution rates reported in the literature under similar experimental conditions. The results obtained in this modelling exercise show that the same bicarbonate promoted oxidative dissolution processes operate for uranium dioxide, as a chemical analogue of the spent fuel matrix, independently of the composition of the aqueous solution used. (orig.)

A copper-catalyzed bioleaching process for enhancement of cobalt dissolution from spent lithium-ion batteries

International Nuclear Information System (INIS)

Zeng, Guisheng; Deng, Xiaorong; Luo, Shenglian; Luo, Xubiao; Zou, Jianping

2012-01-01

Highlights: ► Catalytic ion was first applied to the bioleaching process of spent lithium-ion batteries. ► The bioleaching efficiency was great improved from 43.1% to 99.9% in the presence of copper ion. ► A new reaction model was proposed to explain the catalytic mechanism. - Abstract: A copper-catalyzed bioleaching process was developed to recycle cobalt from spent lithium-ion batteries (mainly LiCoO 2 ) in this paper. The influence of copper ions on bioleaching of LiCoO 2 by Acidithiobacillus ferrooxidans (A.f) was investigated. It was shown that almost all cobalt (99.9%) went into solution after being bioleached for 6 days in the presence of 0.75 g/L copper ions, while only 43.1% of cobalt dissolution was obtained after 10 days without copper ions. EDX, XRD and SEM analyses additionally confirmed that the cobalt dissolution from spent lithium-ion batteries could be improved in the presence of copper ions. The catalytic mechanism was investigated to explain the enhancement of cobalt dissolution by copper ions, in which LiCoO 2 underwent a cationic interchange reaction with copper ions to form CuCo 2 O 4 on the surface of the sample, which could be easily dissolved by Fe 3+ .

Dissolution rate of BTEX contaminants in water

International Nuclear Information System (INIS)

Njobuenwu, D.O.; Amadi, S.A.; Ukpaka, P.C.

2005-01-01

Benzene, toluene, ethylbenzene and xylenes (BTEX) and substituted benzenes are the most common aromatic compounds in petroleum. BTEX components are the most soluble and mobile fraction of crude oil and many petroleum products, and frequently enter soil, sediments and aquatic environments because of accidental spills, leaks and improper oil waste disposal practices. The mass transfer process of hydrocarbons in aquatic mediums has received considerable attention in the literature. This paper focused on the molecular mass transfer rate of BTEX in water, with the aim of understanding and predicting contaminant fate and transport. A comprehensive model was developed to simulate the molecular dissolution rate of BTEX in a natural water stream. The model considered the physicochemical properties of the BTEX compounds and physical processes relevant to the spreading of contaminants in the sea. The dissolution rate was a function of oil slick area, dissolution mass transferability and oil solubility in water. The total dissolution rate N was calculated and the dissolution mass transfer coefficient K was given as the point value of mass transfer coefficient. Results for the dissolution rate based on the solubility of the components in the water were compared with analytical solutions from previous studies and showed good agreement. The model showed that benzene had the largest dissolution rate, while o-xylene had the lowest rate because of its lower fraction. Benzene dissolution rate was approximately 2.6, which was 20.6 times that of toluene and ethylbenzene. It was concluded that the model is useful in predicting and monitoring the dissolution rate of BTEX contaminants in soil and water systems. 22 refs., 2 tabs., 3 figs

Dissolution of covalent adaptable network polymers in organic solvent

Science.gov (United States)

Yu, Kai; Yang, Hua; Dao, Binh H.; Shi, Qian; Yakacki, Christopher M.

2017-12-01

It was recently reported that thermosetting polymers can be fully dissolved in a proper organic solvent utilizing a bond-exchange reaction (BER), where small molecules diffuse into the polymer, break the long polymer chains into short segments, and eventually dissolve the network when sufficient solvent is provided. The solvent-assisted dissolution approach was applied to fully recycle thermosets and their fiber composites. This paper presents the first multi-scale modeling framework to predict the dissolution kinetics and mechanics of thermosets in organic solvent. The model connects the micro-scale network dynamics with macro-scale material properties: in the micro-scale, a model is developed based on the kinetics of BERs to describe the cleavage rate of polymer chains and evolution of chain segment length during the dissolution. The micro-scale model is then fed into a continuum-level model with considerations of the transportation of solvent molecules and chain segments in the system. The model shows good prediction on conversion rate of functional groups, degradation of network mechanical properties, and dissolution rate of thermosets during the dissolution. It identifies the underlying kinetic factors governing the dissolution process, and reveals the influence of different material and processing variables on the dissolution process, such as time, temperature, catalyst concentration, and chain length between cross-links.

Kinetics of oxidic phase dissolution in acids

International Nuclear Information System (INIS)

Gorichev, I.G.; Kipriyanov, N.A.

1981-01-01

The critical analysis of the experimental data on dissolution kinetics of metal oxides (BeO, V 2 O 5 , UO 2 , Nb 2 O 5 , Ta 2 O 5 etc.) in acid media is carried out. Kinetic peculiarities of oxide dissolution are explained on the basis of the notions of electron- proton theory. It is established that the surface nonstoichiometric ccomposition of oxide phase and potential jump, appearing on the interface of the oxide-electrolyte phase are the important factors, determining the dissolution rate of a solid phase. The dissolution rate of metal oxides is limited by the transition of protons into the solid oxide phase. Morphological models of heterogeneous kinetics are used when explaining kinetic regularities of oxide dissolution process [ru

Dissolution of metallic uranium in alkalis

International Nuclear Information System (INIS)

Mondino, Angel V.; Wilkinson, Maria V.; Manzini, Alberto C.

1999-01-01

The dissolution of U metallic foils has been studied in the framework of the development of an improved 99 Mo-production process. The best conditions for the dissolution of uranium foils of approximately 150 μm are the following: a) NaClO concentrations of 0.20 and 0.23 M with NaOH of 0.27 and 0.31 M respectively; b) temperature of the solution, 70 C degrees; c) volume of the solution, 15 ml / cm 2 of uranium foil; d) dissolution time, 30 minutes. (author)

A copper-catalyzed bioleaching process for enhancement of cobalt dissolution from spent lithium-ion batteries

Energy Technology Data Exchange (ETDEWEB)

Zeng, Guisheng, E-mail: zengguisheng@hotmail.com [Key Laboratory of Jiangxi Province for Ecological Diagnosis-Remediation and Pollution Control, Nanchang Hangkong University, Nanchang 330063 (China); College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082 (China); Deng, Xiaorong [Key Laboratory of Jiangxi Province for Ecological Diagnosis-Remediation and Pollution Control, Nanchang Hangkong University, Nanchang 330063 (China); School of Environment and Chemical Engineering, Nanchang Hangkong University, Nanchang 330063 (China); Luo, Shenglian, E-mail: sllou@hnu.edu.cn [Key Laboratory of Jiangxi Province for Ecological Diagnosis-Remediation and Pollution Control, Nanchang Hangkong University, Nanchang 330063 (China); College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082 (China); School of Environment and Chemical Engineering, Nanchang Hangkong University, Nanchang 330063 (China); Luo, Xubiao; Zou, Jianping [Key Laboratory of Jiangxi Province for Ecological Diagnosis-Remediation and Pollution Control, Nanchang Hangkong University, Nanchang 330063 (China); School of Environment and Chemical Engineering, Nanchang Hangkong University, Nanchang 330063 (China)

2012-01-15

Highlights: Black-Right-Pointing-Pointer Catalytic ion was first applied to the bioleaching process of spent lithium-ion batteries. Black-Right-Pointing-Pointer The bioleaching efficiency was great improved from 43.1% to 99.9% in the presence of copper ion. Black-Right-Pointing-Pointer A new reaction model was proposed to explain the catalytic mechanism. - Abstract: A copper-catalyzed bioleaching process was developed to recycle cobalt from spent lithium-ion batteries (mainly LiCoO{sub 2}) in this paper. The influence of copper ions on bioleaching of LiCoO{sub 2} by Acidithiobacillus ferrooxidans (A.f) was investigated. It was shown that almost all cobalt (99.9%) went into solution after being bioleached for 6 days in the presence of 0.75 g/L copper ions, while only 43.1% of cobalt dissolution was obtained after 10 days without copper ions. EDX, XRD and SEM analyses additionally confirmed that the cobalt dissolution from spent lithium-ion batteries could be improved in the presence of copper ions. The catalytic mechanism was investigated to explain the enhancement of cobalt dissolution by copper ions, in which LiCoO{sub 2} underwent a cationic interchange reaction with copper ions to form CuCo{sub 2}O{sub 4} on the surface of the sample, which could be easily dissolved by Fe{sup 3+}.

Toward a consistent model for glass dissolution

International Nuclear Information System (INIS)

Strachan, D.M.; McGrail, B.P.; Bourcier, W.L.

1994-01-01

Understanding the process of glass dissolution in aqueous media has advanced significantly over the last 10 years through the efforts of many scientists around the world. Mathematical models describing the glass dissolution process have also advanced from simple empirical functions to structured models based on fundamental principles of physics, chemistry, and thermodynamics. Although borosilicate glass has been selected as the waste form for disposal of high-level wastes in at least 5 countries, there is no international consensus on the fundamental methodology for modeling glass dissolution that could be used in assessing the long term performance of waste glasses in a geologic repository setting. Each repository program is developing their own model and supporting experimental data. In this paper, we critically evaluate a selected set of these structured models and show that a consistent methodology for modeling glass dissolution processes is available. We also propose a strategy for a future coordinated effort to obtain the model input parameters that are needed for long-term performance assessments of glass in a geologic repository. (author) 4 figs., tabs., 75 refs

Monitoring the hydrolyzation of aspirin during the dissolution testing for aspirin delayed-release tablets with a fiber-optic dissolution system

Directory of Open Access Journals (Sweden)

Yan Wang

2012-10-01

Full Text Available The purpose of this study was to investigate the hydrolyzation of aspirin during the process of dissolution testing for aspirin delayed-release tablets. Hydrolysis product of salicylic acid can result in adverse effects and affect the determination of dissolution rate assaying. In this study, the technique of differential spectra was employed, which made it possible to monitor the dissolution testing in situ. The results showed that the hydrolyzation of aspirin made the percentage of salicylic acid exceed the limit of free salicylic acid (4.0, and the hydrolyzation may affect the quality detection of aspirin delayed-release tablets. Keywords: Aspirin delayed-release tablets, Drug dissolution test, Fiber-optic dissolution system, UV–vis spectrum

Dissolution rates of DWPF glasses from long-term PCT

International Nuclear Information System (INIS)

Ebert, W.L.; Tam, S.W.

1996-01-01

We have characterized the corrosion behavior of several Defense Waste Processing Facility (DWPF) reference waste glasses by conducting static dissolution tests with crushed glasses. Glass dissolution rates were calculated from measured B concentrations in tests conducted for up to five years. The dissolution rates of all glasses increased significantly after certain alteration phases precipitated. Calculation of the dissolution rates was complicated by the decrease in the available surface area as the glass dissolves. We took the loss of surface area into account by modeling the particles to be spheres, then extracting from the short-term test results the dissolution rate corresponding to a linear decrease in the radius of spherical particles. The measured extent of dissolution in tests conducted for longer times was less than predicted with this linear dissolution model. This indicates that advanced stages of corrosion are affected by another process besides dissolution, which we believe to be associated with a decrease in the precipitation rate of the alteration phases. These results show that the dissolution rate measured soon after the formation of certain alteration phases provides an upper limit for the long-term dissolution rate, and can be used to determine a bounding value for the source term for radionuclide release from waste glasses. The long-term dissolution rates measured in tests at 20,000 per m at 90 degrees C in tuff groundwater at pH values near 12 for the Environmental Assessment glass and glasses made with SRL 131 and SRL 202 frits, respectively

Chemical dissolution of spent fuel and cladding using complexed fluoride species

International Nuclear Information System (INIS)

Rance, P.J.W.; Freeman, G.A.; Mishin, V.; Issoupov, V.

2001-01-01

The dissolution of LWR fuel cladding using two fluoride ion donors, HBF 4 and K 2 ZrF 6 , in combination with nitric acid has been investigated as a potential reprocessing head-end process suitable for chemical decladding and fuel dissolution in a single process step. Maximum zirconium concentrations in the order of 0,75 to 1 molar have been achieved and dissolution found to continue to low F:Zr ratios albeit at ever decreasing rates. Dissolution rates of un-oxidised zirconium based fuel claddings are fast, whereas oxidised materials exhibit an induction period prior to dissolution. Data is presented relating to the rates of dissolution of cladding and UO 2 fuels under various conditions. (author)

8 Dissolution Kinetics

African Journals Online (AJOL)

user

Experiments measuring the dissolution rates of stilbite (NaCa [Al Si O ].14H O) in pH-buffered ... The rate law was established as R = k (a ) , where k is ... crystalline hydrated aluminosilicate minerals ..... from the crushing process, thin edges or.

Dissolution of uranium oxide TBP-HNO3 complex

International Nuclear Information System (INIS)

Mizuno, Mineo; Kosaka, Yuji; Mori, Yukihide; Shimada, Takashi

2002-12-01

As a head end process for the pulverization of the spent fuel, the mechanical method (the shredder method) and the pyro-chemical method (oxidisation heat-treatment) have been examined. UO 2 is a main ingredient of Uranium oxide powder by the mechanical method, and U 3 O 8 is that by the pyro-chemical method. Moreover, the particle size of the pulverized powder depend on the conditions of the pulverizing process. As it was considered that the difference of dissolution rates of samples was caused by the difference of sample chemical forms and dissolution temperature, parametric surveys on chemical form and particle size of powder and dissolution temperature were carried out, and the following results were obtained. 1) The remarkable difference of dissolution rate between U 3 O 8 powder (average particle size 3.7 μm) and UO 2 powder (average particle size 2.4 μm) which have comparatively similar particle size was not observed. 2) It was confirmed that the dissolution rate became lower according to the particle size increase (average particle size 2.4 μm-1 mm). And it was considered that dissolution rate had strong dependency on particle size, according to the results that the powder with 1 mm particle size did not dissolute completely after 5 hours test. 3) The temperature dependency of the dissolution rate was confirmed by dissolution test with UO 2 powder (average particle size 2.4 μm-1 mm). The higher dissolution rate was obtained in the higher dissolution temperature, and 11 kcal/mol was obtained as activation energy of dissolution. 4) In the dissolution test of UO 2 powder, the nitric acid concentration started to change earlier than that of U 3 O 8 powder and concentration change range became larger compared with that in the dissolution test of U 3 O 8 powder. It was considered that those differences were caused by difference in mole ratio of Uranium and nitric acid which are consumed in the dissolution reaction (3:7 for U 3 O 8 , 3:8 for UO 2 ). 5) In case

Dissolution studies of spent nuclear fuels

International Nuclear Information System (INIS)

1991-02-01

To obtain quantitative data on the dissolution of high burnup spent nuclear fuel, dissolution study have been carried out at the Department of Chemistry, JAERI, from 1984 under the contract with STA entitled 'Reprocessing Test Study of High Burnup Fuel'. In this study PWR spent fuels of 8,400 to 36,100 MWd/t in averaged burnup were dissolved and the chemical composition and distribution of radioactive nuclides were measured for insoluble residue, cladding material (hull), off-gas and dissolved solution. With these analyses basic data concerning the dissolution and clarification process in the reprocessing plant were accumulated. (author)

Dissolution of aluminium

International Nuclear Information System (INIS)

Uriarte Hueda, A.; Berberana Eizmendi, M.; Pereira Sanchez, G.

1968-01-01

The dissolution of aluminum with acid solutions ( nitric acid-mercuric nitrate) and alkaline solutions (sodium hydroxide-sodium nitrate) has been studied. The instantaneous dissolution rate (IDR) has been studied in function of the concentration of the used reagents and the dissolution temperature. The complete dissolution has been included in the second part of this report, to know the total dissolution time, the consume of reagents and the stability of the resultant solutions. (Author)

Dissolution Processes at Step Edges of Calcite in Water Investigated by High-Speed Frequency Modulation Atomic Force Microscopy and Simulation.

Science.gov (United States)

Miyata, Kazuki; Tracey, John; Miyazawa, Keisuke; Haapasilta, Ville; Spijker, Peter; Kawagoe, Yuta; Foster, Adam S; Tsukamoto, Katsuo; Fukuma, Takeshi

2017-07-12

The microscopic understanding of the crystal growth and dissolution processes have been greatly advanced by the direct imaging of nanoscale step flows by atomic force microscopy (AFM), optical interferometry, and X-ray microscopy. However, one of the most fundamental events that govern their kinetics, namely, atomistic events at the step edges, have not been well understood. In this study, we have developed high-speed frequency modulation AFM (FM-AFM) and enabled true atomic-resolution imaging in liquid at ∼1 s/frame, which is ∼50 times faster than the conventional FM-AFM. With the developed AFM, we have directly imaged subnanometer-scale surface structures around the moving step edges of calcite during its dissolution in water. The obtained images reveal that the transition region with typical width of a few nanometers is formed along the step edges. Building upon insight in previous studies, our simulations suggest that the transition region is most likely to be a Ca(OH) 2 monolayer formed as an intermediate state in the dissolution process. On the basis of this finding, we improve our understanding of the atomistic dissolution model of calcite in water. These results open up a wide range of future applications of the high-speed FM-AFM to the studies on various dynamic processes at solid-liquid interfaces with true atomic resolution.

Efavirenz Dissolution Enhancement I: Co-Micronization

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Helvécio Vinícius Antunes Rocha

2012-12-01

Full Text Available AIDS constitutes one of the most serious infectious diseases, representing a major public health priority. Efavirenz (EFV, one of the most widely used drugs for this pathology, belongs to the Class II of the Biopharmaceutics Classification System for drugs with very poor water solubility. To improve EFV’s dissolution profile, changes can be made to the physical properties of the drug that do not lead to any accompanying molecular modifications. Therefore, the study objective was to develop and characterize systems with efavirenz able to improve its dissolution, which were co-processed with sodium lauryl sulfate (SLS and polyvinylpyrrolidone (PVP. The technique used was co-micronization. Three different drug:excipient ratios were tested for each of the two carriers. The drug dispersion dissolution results showed significant improvement for all the co-processed samples in comparison to non-processed material and corresponding physical mixtures. The dissolution profiles obtained for dispersion with co-micronized SLS samples proved superior to those of co-micronized PVP, with the proportion (1:0.25 proving the optimal mixture. The improvements may be explained by the hypothesis that formation of a hydrophilic layer on the surface of the micronized drug increases the wettability of the system formed, corroborated by characterization results indicating no loss of crystallinity and an absence of interaction at the molecular level.

Study on the dissolution of uranium dibutyl phosphate deposits

International Nuclear Information System (INIS)

Rufus, A.L.; Sathyaseelan, V.S.; Velmurugan, S.; Narasimhan

2008-01-01

An insoluble sticky complex of uranium dibutyl phosphate (U-DBP) formed on the inner surfaces of a reprocessing facility can host radioactive nuclides resulting in radiation exposure hazard. Removal of this layer will greatly result in the reduction of radiation field. Hence, dissolution studies with synthetically prepared U-DBP were carried out. A two-step dissolution process consisting of an initial oxidation with acid permanganate followed by reduction with NAC (NTA, Ascorbic acid and Citric acid) was used. Oxidation kinetics of DBP by permanganate, dissolution of synthetic U-DBP complex as a powder and also as a film over SS surface was studied. XRF and SEM techniques were used to monitor the process of dissolution. Material compatibility of welded SS-304 specimens was also studied. It was found that the two-step process was more efficient when compared to either permanganate or NAC treatment alone. (author)

Study on the dissolution of uranium dibutyl phosphate deposits

Energy Technology Data Exchange (ETDEWEB)

Rufus, A.L.; Sathyaseelan, V.S.; Velmurugan, S.; Narasimhan [Bhabha Atomic Research Centre Facilities, Water and Steam Chemistry Div., Kalpakkam (India)], E-mail: svn@igcar.gov.in

2008-07-01

An insoluble sticky complex of uranium dibutyl phosphate (U-DBP) formed on the inner surfaces of a reprocessing facility can host radioactive nuclides resulting in radiation exposure hazard. Removal of this layer will greatly result in the reduction of radiation field. Hence, dissolution studies with synthetically prepared U-DBP were carried out. A two-step dissolution process consisting of an initial oxidation with acid permanganate followed by reduction with NAC (NTA, Ascorbic acid and Citric acid) was used. Oxidation kinetics of DBP by permanganate, dissolution of synthetic U-DBP complex as a powder and also as a film over SS surface was studied. XRF and SEM techniques were used to monitor the process of dissolution. Material compatibility of welded SS-304 specimens was also studied. It was found that the two-step process was more efficient when compared to either permanganate or NAC treatment alone. (author)

[Process monitoring of dissolution of valsartan and hydrochlorothiazide tablets by fiber-chemical sensor assisted by mathematical separation model of linear equations].

Science.gov (United States)

Ding, Hai-Yan; Li, Gai-Ru; Yu, Ying-Ge; Guo, Wei; Zhi, Ling; Li, Xin-Xia

2014-04-01

A method for on-line monitoring the dissolution of Valsartan and hydrochlorothiazide tablets assisted by mathematical separation model of linear equations was established. UV spectrums of valsartan and hydrochlorothiazide were overlapping completely at the maximum absorption wavelength respectively. According to the Beer-Lambert principle of absorbance additivity, the absorptivity of Valsartan and hydrochlorothiazide was determined at the maximum absorption wavelength, and the dissolubility of Valsartan and hydrochlorothiazide tablets was detected by fiber-optic dissolution test (FODT) assisted by the mathematical separation model of linear equations and compared with the HPLC method. Results show that two ingredients were real-time determined simultaneously in given medium. There was no significant difference for FODT compared with HPLC (p > 0.05). Due to the dissolution behavior consistency, the preparation process of different batches was stable and with good uniformity. The dissolution curves of valsartan were faster and higher than hydrochlorothiazide. The dissolutions at 30 min of Valsartan and hydrochlorothiazide were concordant with US Pharmacopoeia. It was concluded that fiber-optic dissolution test system assisted by the mathematical separation model of linear equations that can detect the dissolubility of Valsartan and hydrochlorothiazide simultaneously, and get dissolution profiles and overall data, which can directly reflect the dissolution speed at each time. It can provide the basis for establishing standards of the drug. Compared to HPLC method with one-point data, there are obvious advantages to evaluate and analyze quality of sampling drug by FODT.

Calcite Dissolution Kinetics

Science.gov (United States)

Berelson, W.; Subhas, A.; Dong, S.; Naviaux, J.; Adkins, J. F.

2016-12-01

A geological buffer for high atmospheric CO2 concentrations is neutralization via reaction with CaCO3. We have been studying the dissolution kinetics of carbonate minerals using labeled 13C calcite and Picarro-based measurements of 13C enrichments in solution DIC. This methodology has greatly facilitated our investigation of dissolution kinetics as a function of water carbonate chemistry, temperature and pressure. One can adjust the saturation state Omega by changing the ion activity product (e.g. adjusting carbonate ion concentration), or by changing the solubility product (e.g. adjusting temperature or pressure). The canonical formulation of dissolution rate vs. omega has been refined (Subhas et al. 2015) and shows distinct non-linear behavior near equilibrium and rates in sea water of 1-3 e-6 g/cm2day at omega = 0.8. Carbonic anhydrase (CA), an enzyme that catalyzes the hydration of dissolved CO2 to carbonic acid, was shown (in concentrations 500x. This result points to the importance of carbonic acid in enhancing dissolution at low degrees of undersaturation. CA activity and abundance in nature must be considered regarding the role it plays in catalyzing dissolution. We also have been investigating the role of temperature on dissolution kinetics. An increase of 16C yields an order of magnitude increase in dissolution rate. Temperature (and P) also change Omega critical, the saturation state where dissolution rates change substantially. Increasing pressure (achieved in a pressure reaction chamber we built) also shifts Omega critical closer to equilibrium and small pressure increases have large impact on dissolution kinetics. Dissolution rates are enhanced by an order of magnitude for a change in pressure of 1500 psi relative to the dissolution rate achieved by water chemistry effects alone for an omega of 0.8. We've shown that the thermodynamic determination of saturation state does not adequately describe the kinetics of dissolution. The interplay of mineral

Accelerated dissolution of iron oxides in ice

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D. Jeong

2012-11-01

Full Text Available Iron dissolution from mineral dusts and soil particles is vital as a source of bioavailable iron in various environmental media. In this work, the dissolution of iron oxide particles trapped in ice was investigated as a new pathway of iron supply. The dissolution experiments were carried out in the absence and presence of various organic complexing ligands under dark condition. In acidic pH conditions (pH 2, 3, and 4, the dissolution of iron oxides was greatly enhanced in the ice phase compared to that in water. The dissolved iron was mainly in the ferric form, which indicates that the dissolution is not a reductive process. The extent of dissolved iron was greatly affected by the kind of organic complexing ligands and the surface area of iron oxides. The iron dissolution was most pronounced with high surface area iron oxides and in the presence of strong iron binding ligands. The enhanced dissolution of iron oxides in ice is mainly ascribed to the "freeze concentration effect", which concentrates iron oxide particles, organic ligands, and protons in the liquid like ice grain boundary region and accelerates the dissolution of iron oxides. The ice-enhanced dissolution effect gradually decreased when decreasing the freezing temperature from −10 to −196 °C, which implies that the presence and formation of the liquid-like ice grain boundary region play a critical role. The proposed phenomenon of enhanced dissolution of iron oxides in ice may provide a new pathway of bioavailable iron production. The frozen atmospheric ice with iron-containing dust particles in the upper atmosphere thaws upon descending and may provide bioavailable iron upon deposition onto the ocean surface.

Etching of semiconductor cubic crystals: Determination of the dissolution slowness surfaces

Science.gov (United States)

Tellier, C. R.

1990-03-01

Equations of the representative surface of dissolution slowness for cubic crystals are determined in the framework of a tensorial approach of the orientation-dependent etching process. The independent dissolution constants are deduced from symmetry considerations. Using previous data on the chemical etching of germanium and gallium arsenide crystals, some possible polar diagrams of the dissolution slowness are proposed. A numerical and graphical simulation method is used to obtain the derived dissolution shapes. The influence of extrema in the dissolution slowness on the successive dissolution shapes is also examined. A graphical construction of limiting shapes of etched crystals appears possible using the tensorial representation of the dissolution slowness.

Aqueous dissolution rates of uranium oxides

International Nuclear Information System (INIS)

Steward, S.A.; Mones, E.T.

1994-10-01

An understanding of the long-term dissolution of waste forms in groundwater is required for the safe disposal of high level nuclear waste in an underground repository. The main routes by which radionuclides could be released from a geological repository are the dissolution and transport processes in groundwater flow. Because uranium dioxide is the primary constituent of spent nuclear fuel, the dissolution of its matrix in spent fuel is considered the rate-limiting step for release of radioactive fission products. The purpose of our work has been to measure the intrinsic dissolution rates of uranium oxides under a variety of well-controlled conditions that are relevant to a repository and allow for modeling. The intermediate oxide phase U 3 O 8 , triuranium octaoxide, is quite stable and known to be present in oxidized spent fuel. The trioxide, UO 3 , has been shown to exist in drip tests on spent fuel. Here we compare the results of essentially identical dissolution experiments performed on depleted U 3 O 8 and dehyrated schoepite or uranium trioxide monohydrate (UO 3 ·H 2 O). These are compared with earlier work on spent fuel and UO 2 under similar conditions

Collective dissolution of microbubbles

Science.gov (United States)

Michelin, Sébastien; Guérin, Etienne; Lauga, Eric

2018-04-01

A microscopic bubble of soluble gas always dissolves in finite time in an undersaturated fluid. This diffusive process is driven by the difference between the gas concentration near the bubble, whose value is governed by the internal pressure through Henry's law, and the concentration in the far field. The presence of neighboring bubbles can significantly slow down this process by increasing the effective background concentration and reducing the diffusing flux of dissolved gas experienced by each bubble. We develop theoretical modeling of such diffusive shielding process in the case of small microbubbles whose internal pressure is dominated by Laplace pressure. We first use an exact semianalytical solution to capture the case of two bubbles and analyze in detail the shielding effect as a function of the distance between the bubbles and their size ratio. While we also solve exactly for the Stokes flow around the bubble, we show that hydrodynamic effects are mostly negligible except in the case of almost-touching bubbles. In order to tackle the case of multiple bubbles, we then derive and validate two analytical approximate yet generic frameworks, first using the method of reflections and then by proposing a self-consistent continuum description. Using both modeling frameworks, we examine the dissolution of regular one-, two-, and three-dimensional bubble lattices. Bubbles located at the edge of the lattices dissolve first, while innermost bubbles benefit from the diffusive shielding effect, leading to the inward propagation of a dissolution front within the lattice. We show that diffusive shielding leads to severalfold increases in the dissolution time, which grows logarithmically with the number of bubbles in one-dimensional lattices and algebraically in two and three dimensions, scaling respectively as its square root and 2 /3 power. We further illustrate the sensitivity of the dissolution patterns to initial fluctuations in bubble size or arrangement in the case

Dissolution of minerals with rough surfaces

Science.gov (United States)

de Assis, Thiago A.; Aarão Reis, Fábio D. A.

2018-05-01

We study dissolution of minerals with initial rough surfaces using kinetic Monte Carlo simulations and a scaling approach. We consider a simple cubic lattice structure, a thermally activated rate of detachment of a molecule (site), and rough surface configurations produced by fractional Brownian motion algorithm. First we revisit the problem of dissolution of initial flat surfaces, in which the dissolution rate rF reaches an approximately constant value at short times and is controlled by detachment of step edge sites. For initial rough surfaces, the dissolution rate r at short times is much larger than rF ; after dissolution of some hundreds of molecular layers, r decreases by some orders of magnitude across several time decades. Meanwhile, the surface evolves through configurations of decreasing energy, beginning with dissolution of isolated sites, then formation of terraces with disordered boundaries, their growth, and final smoothing. A crossover time to a smooth configuration is defined when r = 1.5rF ; the surface retreat at the crossover is approximately 3 times the initial roughness and is temperature-independent, while the crossover time is proportional to the initial roughness and is controlled by step-edge site detachment. The initial dissolution process is described by the so-called rough rates, which are measured for fixed ratios between the surface retreat and the initial roughness. The temperature dependence of the rough rates indicates control by kink site detachment; in general, it suggests that rough rates are controlled by the weakest microscopic bonds during the nucleation and formation of the lowest energy configurations of the crystalline surface. Our results are related to recent laboratory studies which show enhanced dissolution in polished calcite surfaces. In the application to calcite dissolution in alkaline environment, the minimal values of recently measured dissolution rate spectra give rF ∼10-9 mol/(m2 s), and the calculated rate

Plutonium dissolution from Rocky Flats Plant incinerator ash

International Nuclear Information System (INIS)

Delegard, C.H.

1985-06-01

Rockwell Hanford Operations (Rockwell) soon will commence recovery of plutonium from Rocky Flats Plant incinerator ash. In preparation for this processing, Rockwell undertook literature and laboratory studies to identify, select and optimize plutonium dissolution methods for treating the ash. Ash reburning, followed by dissolution in nitric acid containing calcium fluoride, was selected as the processing method for the ash. Recommended values of process parameters were identified. Using the selected process, 99.5% plutonium recovery was achieved, leaving about 12.7 wt % heel residue for an equal weight composite of the three ashes tested. 15 refs., 26 figs

Criticality safety in high explosives dissolution

International Nuclear Information System (INIS)

Troyer, S.D.

1997-01-01

In 1992, an incident occurred at the Pantex Plant in which the cladding around a fissile material component (pit) cracked during dismantlement of the high explosives portion of a nuclear weapon. Although the event did not result in any significant contamination or personnel exposures, concerns about the incident led to the conclusion that the current dismantlement process was unacceptable. Options considered for redesign, dissolution tooling design considerations, dissolution tooling design features, and the analysis of the new dissolution tooling are summarized. The final tooling design developed incorporated a number of safety features and provides a simple, self-contained, low-maintenance method of high explosives removal for nuclear explosive dismantlement. Analyses demonstrate that the tooling design will remain subcritical under normal, abnormal, and credible accident scenarios. 1 fig

Dissolution of Fe(III) (hydr) oxides by metal-EDTA complexes

Science.gov (United States)

Ngwack, Bernd; Sigg, Laura

1997-03-01

The dissolution of Fe(III)(hydr)oxides (goethite and hydrous ferric oxide) by metal-EDTA complexes occurs by ligand-promoted dissolution. The process is initiated by the adsorption of metal-EDTA complexes to the surface and is followed by the dissociation of the complex at the surface and the release of Fe(III)EDTA into solution. The dissolution rate is decreased to a great extent if EDTA is complexed by metals in comparison to the uncomplexed EDTA. The rate decreases in the order EDTA CaEDTA ≫ PbEDTA > ZnEDTA > CuEDTA > Co(II)EDTA > NiEDTA. Two different rate-limiting steps determine the dissolution process: (1) detachment of Fe(III) from the oxide-structure and (2) dissociation of the metal-EDTA complexes. In the case of goethite, step 1 is slower than step 2 and the dissolution rates by various metals are similar. In the case of hydrous ferric oxide, step 2 is rate-limiting and the effect of the complexed metal is very pronounced.

Dissolution of ion exchange resin by hydrogen peroxide

International Nuclear Information System (INIS)

Lee, S.C.

1981-08-01

The resin dissolution process was conducted successfully in full-scale equipment at the SRL Semiworks. A solution containing 0.001M Fe 2+ , or Fe 3+ , and 3 vol % H 2 O 2 in 0.1M HNO 3 is sufficient to dissolve up to 40 vol % resin slurry (Dowex 50W-X8). Foaming and pressurization can be eliminated by maintaining the dissolution temperature below 99 0 C. The recommended dissolution temperature range is 85 to 90 0 C. Premixing hydrogen peroxide with all reactants will not create a safety hazard, but operating with a continual feed of hydrogen peroxide is recommended to control the dissolution rate. An air sparging rate of 1.0 to 1.5 scfm will provide sufficient mixing. Spent resin from chemical separation contains DTPA (diethylenetriaminepentaacetic acid) residue, and the resin must be washed with 0.1M NH 4 OH to remove excess DTPA before dissolution. Gamma irradiation of resin up to 4 kW-hr/L did not change the dissolution rate significantly

Dissolution of mixed oxide spent fuel from FBR

International Nuclear Information System (INIS)

Sanyoshi, H.; Nishina, H.; Toyota, O.; Yamamoto, R.; Nemoto, S.; Okamoto, F.; Togashi, A.; Kawata, T.; Hayashi, S.

1991-01-01

At the Tokai Works of the Power Reactor and Nuclear Fuel Development Corporation (PNC), the Chemical Processing Facility (CPF) has been continuing operation since 1982 for laboratory scale hot experiments on reprocessing of FBR mixed oxide fuel. As a part of these experiments, dissolution experiments have been performed to define the key parameters affecting dissolution rates such as concentration of nitric acid, temperature and burnup and also to confirm the amount of insoluble residue. The dissolution rate of the irradiated fuel was determined to be in proportion to the 1.7 power of the nitric acid concentration. The activation energy determined from the experiments varied from 6 to 11 kcal/mol depending on the method of dissolution. The dissolution rate decreased as the fuel burnup increased in low nitric acid media below 5 mol/l. However, it was found that the effect of the burnup became negligible in a high concentration of nitric acid media. The amount of insoluble residue and its constituents were evaluated by changing the dissolution condition. (author)

The Influence of Milling on the Dissolution Performance of Simvastatin

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Thomas Rades

2010-12-01

Full Text Available Particle size reduction is a simple means to enhance the dissolution rate of poorly water soluble BCS-class II and IV drugs. However, the major drawback of this process is the possible introduction of process induced disorder. Drugs with different molecular arrangements may exhibit altered properties such as solubility and dissolution rate and, therefore, process induced solid state modifications need to be monitored. The aim of this study was two-fold: firstly, to investigate the dissolution rates of milled and unmilled simvastatin; and secondly, to screen for the main milling factors, as well as factor interactions in a dry ball milling process using simvastatin as model drug, and to optimize the milling procedure with regard to the opposing responses particle size and process induced disorder by application of a central composite face centered design. Particle size was assessed by scanning electron microscopy (SEM and image analysis. Process induced disorder was determined by partial least squares (PLS regression modeling of respective X-ray powder diffractograms (XRPD and Raman spectra. Valid and significant quadratic models were built. The investigated milling factors were milling frequency, milling time and ball quantity at a set drug load, out of which milling frequency was found to be the most important factor for particle size as well as process induced disorder. Milling frequency and milling time exhibited an interaction effect on the responses. The optimum milling settings using the maximum number of milling balls (60 balls with 4 mm diameter was determined to be at a milling frequency of 21 Hz and a milling time of 36 min with a resulting primary particle size of 1.4 μm and a process induced disorder of 6.1% (assessed by Raman spectroscopy and 8.4% (assessed by XRPD, at a set optimization limit of < 2 μm for particle size and < 10% for process induced disorder. This optimum was tested experimentally and the process induced disorder

Influence of the Efavirenz Micronization on Tableting and Dissolution

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Lucio Mendes Cabral

2012-09-01

Full Text Available The purpose of this study was to propose an analytical procedure that provides the effects of particle size and surface area on dissolution of efavirenz. Five different batches obtained by different micronization processes and with different particle size distribution and surface area were studied. The preformulation studies and dissolution curves were used to confirm the particle size distribution effect on drug solubility. No polymorphic variety or amorphization was observed in the tested batches and the particle size distribution was determined as directly responsible for the improvement of drug dissolution. The influence of the preparation process on the tablets derived from efavirenz was observed in the final dissolution result in which agglomeration, usually seen in non-lipophilic micronized material, was avoided through the use of an appropriate wet granulation method. For these reasons, micronization may represent one viable alternative for the formulation of brick dust drugs.

Effect drug loading process on dissolution mechanism of encapsulated amoxicillin trihydrate in hydrogel semi-IPN chitosan methyl cellulose with pore forming agent KHCO3 as a floating drug delivery system

Science.gov (United States)

Fithawati, Garnis; Budianto, Emil

2018-04-01

Common treatment for Helicobacter pylori by repeated oral consumption of amoxicillin trihydrate is not effective. Amoxicillin trihydrate has a very short residence time in stomach which leads into its ineffectiveness. Residence time of amoxicillin trihydrate can be improved by encapsulating amoxicillin trihydrate into a floating drug delivery system. In this study, amoxicillin trihydrate is encapsulated into hydrogel semi-IPN chitosan methyl cellulose matrix as a floating drug delivery system and then treated with 20% KHCO3 as pore forming agent. Drug loading process used are in-situ loading and post loading. In-situ loading process has higher efficiency percentage and dissolution percentage than post loading process. In-situ loading process resulted 100% efficiency with 92,70% dissolution percentage. Post loading process resulted 98,7% efficiency with 90,42% dissolution percentage. Mechanism of drug dissolution study by kinetics approach showed both in-situ loading process and post loading process are diffusion and degradation process (n=0,4913) and (n=0,4602) respectively. These results are supported by characterization data from optical microscope and scanning electron microscopy (SEM). Data from optical microscope showed both loading process resulted in coarser hydrogel surface. Characterization using SEM showed elongated pores in both loading process after dissolution test.

The Dissolution of Double Holliday Junctions

DEFF Research Database (Denmark)

Bizard, Anna H; Hickson, Ian D

2014-01-01

as "double Holliday junction dissolution." This reaction requires the cooperative action of a so-called "dissolvasome" comprising a Holliday junction branch migration enzyme (Sgs1/BLM RecQ helicase) and a type IA topoisomerase (Top3/TopoIIIα) in complex with its OB (oligonucleotide/oligosaccharide binding......Double Holliday junctions (dHJS) are important intermediates of homologous recombination. The separate junctions can each be cleaved by DNA structure-selective endonucleases known as Holliday junction resolvases. Alternatively, double Holliday junctions can be processed by a reaction known......) fold containing accessory factor (Rmi1). This review details our current knowledge of the dissolution process and the players involved in catalyzing this mechanistically complex means of completing homologous recombination reactions....

TECHNOLOGY DEMONSTRATION OF SLUDGE MASS REDUCTION VIA ALUMINUM DISSOLUTION: GLASS FORMULATION PROCESSING WINDOW PREDICTIONS FOR SB5

International Nuclear Information System (INIS)

Fox, K.; Tommy Edwards, T.; David Peeler, D.

2007-01-01

Composition projections for Sludge Batch 5 (SB5) were developed, based on a modeling approach at the Savannah River National Laboratory (SRNL), to evaluate possible impacts of the Al-dissolution process on the availability of viable frit compositions for vitrification at the Defense Waste Processing Facility (DWPF). The study included two projected SB5 compositions that bound potential outcomes (or degrees of effectiveness) of the Al-dissolution process, as well as a nominal SB5 composition projection based on the results of the recent Al-dissolution demonstration at SRNL. The three SB5 projections were the focus of a two-stage paper study assessment. A Nominal Stage assessment combined each of the SB5 composition projections with an array of 19,305 frit compositions over a wide range of waste loading (WL) values and evaluated them against the DWPF process control models. The Nominal Stage results allowed for the down-selection of a small number of frits that provided reasonable projected operating windows (typically 27 to 42 wt% WL). The frit/sludge systems were mostly limited by process related constraints, with only one system being limited by predictions of nepheline crystallization, a waste form affecting constraint. The criteria applied in selecting the frit compositions somewhat restricted the compositional flexibility of the candidate frits for each individual SB5 composition projection, which may limit the ability to further tailor the frit for improved melt rate. Variation Stage assessments were then performed using the down-selected frits and the three SB5 composition projections with variation applied to each sludge component. The Variation Stage results showed that the operating windows were reduced in width, as expected when variation in the sludge composition is applied. However, several of the down-selected frits exhibited a relatively high degree of robustness to the applied sludge variation, providing WL windows of approximately 30 to 39 wt%. The

Influence of oxalic acid on the dissolution kinetics of manganese oxide

Science.gov (United States)

Godunov, E. B.; Artamonova, I. V.; Gorichev, I. G.; Lainer, Yu. A.

2012-11-01

The kinetics and electrochemical processes of the dissolution of manganese oxides with various oxidation states in sulfuric acid solutions containing oxalate ion additives is studied under variable conditions (concentration, pH, temperature). The parameters favoring a higher degree of the dissolution of manganese oxides in acidic media are determined. The optimal conditions are found for the dissolution of manganese oxides in acidic media in the presence of oxalate ions. The mechanism proposed for the dissolution of manganese oxides in sulfuric acid solutions containing oxalic acid is based on the results of kinetic and electrochemical studies. The steps of the dissolution mechanism are discussed.

Testing of the Defense Waste Processing Facility Cold Chemical Dissolution Method in Sludge Batch 9 Qualification

Energy Technology Data Exchange (ETDEWEB)

Edwards, T. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Pareizs, J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Coleman, C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Young, J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Brown, L. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2016-05-10

For each sludge batch that is processed in the Defense Waste Processing Facility (DWPF), the Savannah River National Laboratory (SRNL) tests the applicability of the digestion methods used by the DWPF Laboratory for elemental analysis of Sludge Receipt and Adjustment Tank (SRAT) Receipt samples and SRAT Product process control samples. DWPF SRAT samples are typically dissolved using a method referred to as the DWPF Cold Chemical or Cold Chem Method (CC), (see DWPF Procedure SW4- 15.201). Testing indicates that the CC method produced mixed results. The CC method did not result in complete dissolution of either the SRAT Receipt or SRAT Product with some fine, dark solids remaining. However, elemental analyses did not reveal extreme biases for the major elements in the sludge when compared with analyses obtained following dissolution by hot aqua regia (AR) or sodium peroxide fusion (PF) methods. The CC elemental analyses agreed with the AR and PF methods well enough that it should be adequate for routine process control analyses in the DWPF after much more extensive side-by-side tests of the CC method and the PF method are performed on the first 10 SRAT cycles of the Sludge Batch 9 (SB9) campaign. The DWPF Laboratory should continue with their plans for further tests of the CC method during these 10 SRAT cycles.

Dissolution studies with pilot plant and actual INTEC calcines

International Nuclear Information System (INIS)

Herbst, R.S.; Garn, T.G.

1999-01-01

The dissolution of Idaho Nuclear Technology and Engineering Center (INTEC) pilot plant calcines was examined to determine solubility of calcine matrix components in acidic media. Two representatives pilot plant calcine types were studied: Zirconia calcine and Zirconia/Sodium calcine. Dissolution of these calcines was evaluated using lower initial concentrations of nitric acid than used in previous tests to decrease the [H+] concentration in the final solutions. Lower [H+] concentrations contribute to more favorable TRUEX/SREX solvent extraction flowsheet performance. Dissolution and analytical results were also obtained for radioactive calcines produced using high sodium feeds blended with non-radioactive Al(NO 3 ) 3 solutions to dilute the sodium concentration and prevent bed agglomeration during the calcination process. Dissolution tests indicated >95 wt.% of the initial calcine mass can be dissolved using the baseline dissolution procedure, with the exception that higher initial nitric acid concentrations are required. The higher initial acid concentration is required for stoichiometric dissolution of the oxides, primarily aluminum oxide. Statistically designed experiments using pilot plant calcine were performed to determine the effect of mixing rate on dissolution efficiency. Mixing rate was determined to provide minimal effects on wt.% dissolution. The acid/calcine ratio and temperature were the predominate variables affecting the wt.% dissolution, a result consistent with previous studies using other similar types of pilot plant calcines

Jarosite dissolution rates in perchlorate brine

Science.gov (United States)

Legett, Carey; Pritchett, Brittany N.; Elwood Madden, Andrew S.; Phillips-Lander, Charity M.; Elwood Madden, Megan E.

2018-02-01

Perchlorate salts and the ferric sulfate mineral jarosite have been detected at multiple locations on Mars by both landed instruments and orbiting spectrometers. Many perchlorate brines have eutectic temperatures bearing rocks and sediments may have been altered by perchlorate brines. Here we measured jarosite dissolution rates in 2 M sodium perchlorate brine as well as dilute water at 298 K to determine the effects of perchlorate anions on jarosite dissolution rates and potential reaction products. We developed a simple method for determining aqueous iron concentrations in high salinity perchlorate solutions using ultraviolet-visible spectrophotometry that eliminates the risk of rapid oxidation reactions during analyses. Jarosite dissolution rates in 2 M perchlorate brine determined by iron release rate (2.87 × 10-12 ±0.85 × 10-12 mol m-2 s-1) were slightly slower than the jarosite dissolution rate measured in ultrapure (18.2 MΩ cm-1) water (5.06 × 10-12 mol m-2 s-1) using identical methods. No additional secondary phases were observed in XRD analyses of the reaction products. The observed decrease in dissolution rate may be due to lower activity of water (ɑH2O = 0.9) in the 2 M NaClO4 brine compared with ultrapure water (ɑH2O = 1). This suggests that the perchlorate anion does not facilitate iron release, unlike chloride anions which accelerated Fe release rates in previously reported jarosite and hematite dissolution experiments. Since dissolution rates are slower in perchlorate-rich solutions, jarosite is expected to persist longer in perchlorate brines than in dilute waters or chloride-rich brines. Therefore, if perchlorate brines dominate aqueous fluids on the surface of Mars, jarosite may remain preserved over extended periods of time, despite active aqueous processes.

Solubility limits on radionuclide dissolution

Energy Technology Data Exchange (ETDEWEB)

Kerrisk, J.F.

1984-12-31

This paper examines the effects of solubility in limiting dissolution rates of a number of important radionuclides from spent fuel and high-level waste. Two simple dissolution models were used for calculations that would be characteristics of a Yucca Mountain repository. A saturation-limited dissolution model, in which the water flowing through the repository is assumed to be saturated with each waste element, is very conservative in that it overestimates dissolution rates. A diffusion-limited dissolution model, in which element-dissolution rates are limited by diffusion of waste elements into water flowing past the waste, is more realistic, but it is subject to some uncertainty at this time. Dissolution rates of some elements (Pu, Am, Sn, Th, Zr, Sm) are always limited by solubility. Dissolution rates of other elements (Cs, Tc, Np, Sr, C, I) are never solubility limited; their release would be limited by dissolution of the bulk waste form. Still other elements (U, Cm, Ni, Ra) show solubility-limited dissolution under some conditions. 9 references, 3 tables.

The velocity dependent dissolution of spent nuclear fuel in a geologic repository

International Nuclear Information System (INIS)

Nutt, W.M.

1990-02-01

A model describing the dissolution of fission products and transuranic isotopes from spent nuclear fuel into flowing ground water has been developed. This model is divided into two parts. The first part of the model calculates the temperature within a consolidated spent fuel waste form at a given time and ground water velocity. This model was used to investigate whether water flowing at rates representative of a geological repository located at Yucca Mountain, Nevada, will cool a wasteform consisting of consolidated spent nuclear fuel pins. Time and velocity dependent temperature profiles were generated. These profiles were input into the second model, which calculates the dissolution rate of waste isotopes from a spent fuel pin. Two dissolution limiting processes were modeled; the processes are dissolution limited by the solubility limit of an isotopes in the ground water, and dissolution limited by the diffusion of waste isotopes from the interior of a spent fuel pin to the surface where dissolution can occur

Accelerated dissolution testing for controlled release microspheres using the flow-through dissolution apparatus.

Science.gov (United States)

Collier, Jarrod W; Thakare, Mohan; Garner, Solomon T; Israel, Bridg'ette; Ahmed, Hisham; Granade, Saundra; Strong, Deborah L; Price, James C; Capomacchia, A C

2009-01-01

Theophylline controlled release capsules (THEO-24 CR) were used as a model system to evaluate accelerated dissolution tests for process and quality control and formulation development of controlled release formulations. Dissolution test acceleration was provided by increasing temperature, pH, flow rate, or adding surfactant. Electron microscope studies on the theophylline microspheres subsequent to each experiment showed that at pH values of 6.6 and 7.6 the microspheres remained intact, but at pH 8.6 they showed deterioration. As temperature was increased from 37-57 degrees C, no change in microsphere integrity was noted. Increased flow rate also showed no detrimental effect on integrity. The effect of increased temperature was determined to be the statistically significant variable.

Dissolution Flowsheet for High Flux Isotope Reactor Fuel

Energy Technology Data Exchange (ETDEWEB)

Daniel, W. E. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Rudisill, T. S. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); O' Rourke, P. E. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Karay, N. S [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2016-09-27

As part of the Spent Nuclear Fuel (SNF) processing campaign, H-Canyon is planning to begin dissolving High Flux Isotope Reactor (HFIR) fuel in late FY17 or early FY18. Each HFIR fuel core contains inner and outer fuel elements which were fabricated from uranium oxide (U₃O₈) dispersed in a continuous Al phase using traditional powder metallurgy techniques. Fuels fabricated in this manner, like other SNF’s processed in H-Canyon, dissolve by the same general mechanisms with similar gas generation rates and the production of H₂. The HFIR fuel cores will be dissolved and the recovered U will be down-blended into low-enriched U. HFIR fuel was previously processed in H-Canyon using a unique insert in both the 6.1D and 6.4D dissolvers. Multiple cores will be charged to the same dissolver solution maximizing the concentration of dissolved Al. The objective of this study was to identify flowsheet conditions through literature review and laboratory experimentation to safely and efficiently dissolve the HFIR fuel in H-Canyon. Laboratory-scale experiments were performed to evaluate the dissolution of HFIR fuel using both Al 1100 and Al 6061 T6 alloy coupons. The Al 1100 alloy was considered a representative surrogate which provided an upper bound on the generation of flammable (i.e., H₂) gas during the dissolution process. The dissolution of the Al 6061 T6 alloy proceeded at a slower rate than the Al 1100 alloy, and was used to verify that the target Al concentration in solution could be achieved for the selected Hg concentration. Mass spectrometry and Raman spectroscopy were used to provide continuous monitoring of the concentration of H₂ and other permanent gases in the dissolution offgas, allowing the development of H₂ generation rate profiles. The H₂ generation rates were subsequently used to evaluate if a full HFIR core could be dissolved in an H-Canyon dissolver without exceeding 60% of the

Magnetic resonance imaging of tablet dissolution.

Science.gov (United States)

Nott, Kevin P

2010-01-01

Magnetic resonance imaging (MRI) is the technique of choice for measuring hydration, and its effects, during dissolution of tablets since it non-invasively maps (1)H nuclei associated with 'mobile' water. Although most studies have used MRI systems with high-field superconducting magnets, low-field laboratory-based instruments based on permanent magnet technology are being developed that provide key data for the formulation scientist. Incorporation of dissolution hardware, in particular the United States Pharmacopeia (USP) apparatus 4 flow-through cell, allows measurements under controlled conditions for comparison against other dissolution methods. Furthermore, simultaneous image acquisition and measurement of drug concentration allow direct comparison of the drug release throughout the hydration process. The combination of low-field MRI with USP-4 apparatus provides another tool to aid tablet formulation. Copyright 2009 Elsevier B.V. All rights reserved.

A new method for alkaline dissolution of uranium metal foil

International Nuclear Information System (INIS)

Mondino, A.V.; Wilkinson, M.V.; Manzini, A.C.

2001-01-01

In order to develop a production process of 99 Mo by fission of low-enriched uranium, the first purification step, which consists of dissolution of a uranium metal foil target, was studied. It was found that alkaline NaClO gave good results, reaching the dissolution of up to 300 μm of uranium foil. The different conditions for the dissolution were studied and the optimum ones were found. The influence of NaClO and NaOH concentration, temperature, dissolving solution volume per unit of surface and dissolution time were investigated. During this step, a gas identified as H 2 , was generated, and a precipitate characterized as Na 2 U 2 O 7 was observed. A stoichiometric reaction for this uranium dissolution is proposed. (author)

Effect of Bulk and Interfacial Rheological Properties on Bubble Dissolution

NARCIS (Netherlands)

Kloek, W.; Vliet, van T.; Meinders, M.

2001-01-01

This paper describes theoretical calculations of the combined effect of bulk and interracial rheological properties on dissolution behavior of a bubble in an infinite medium at saturated conditions. Either bulk or interracial elasticity can stop the bubble dissolution process, and stability criteria

Dissolution, agglomerate morphology, and stability limits of protein-coated silver nanoparticles.

Science.gov (United States)

Martin, Matthew N; Allen, Andrew J; MacCuspie, Robert I; Hackley, Vincent A

2014-09-30

Little is understood regarding the impact that molecular coatings have on nanoparticle dissolution kinetics and agglomerate formation in a dilute nanoparticle dispersion. Dissolution and agglomeration processes compete in removing isolated nanoparticles from the dispersion, making quantitative time-dependent measurements of the mechanisms of nanoparticle loss particularly challenging. In this article, we present in situ ultra-small-angle X-ray scattering (USAXS) results, simultaneously quantifying dissolution, agglomeration, and stability limits of silver nanoparticles (AgNPs) coated with bovine serum albumin (BSA) protein. When the BSA corona is disrupted, we find that the loss of silver from the nanoparticle core is well matched by a second-order kinetic rate reaction, arising from the oxidative dissolution of silver. Dissolution and agglomeration are quantified, and morphological transitions throughout the process are qualified. By probing the BSA-AgNP suspension around its stability limits, we provide insight into the destabilization mechanism by which individual particles rapidly dissolve as a whole rather than undergo slow dissolution from the aqueous interface inward, once the BSA layer is breached. Because USAXS rapidly measures over the entire nanometer to micrometer size range during the dissolution process, many insights are also gained into the stabilization of NPs by protein and its ability to protect the labile metal core from the solution environment by prohibiting the diffusion of reactive species. This approach can be extended to a wide variety of coating molecules and reactive metal nanoparticle systems to carefully survey their stability limits, revealing the likely mechanisms of coating breakdown and ensuing reactions.

A method for phenomenological and chemical kinetics study of autocatalytic reactive dissolution by optical microscopy. The case of uranium dioxide dissolution in nitric acid media

Science.gov (United States)

Marc, Philippe; Magnaldo, Alastair; Godard, Jérémy; Schaer, Éric

2018-03-01

Dissolution is a milestone of the head-end of hydrometallurgical processes, as the stabilization rates of the chemical elements determine the process performance and hold-up. This study aims at better understanding the chemical and physico-chemical phenomena of uranium dioxide dissolution reactions in nitric acid media in the Purex process, which separates the reusable materials and the final wastes of the spent nuclear fuels. It has been documented that the attack of sintering-manufactured uranium dioxide solids occurs through preferential attack sites, which leads to the development of cracks in the solids. Optical microscopy observations show that in some cases, the development of these cracks leads to the solid cleavage. It is shown here that the dissolution of the detached fragments is much slower than the process of the complete cleavage of the solid, and occurs with no disturbing phenomena, like gas bubbling. This fact has motivated the measurement of dissolution kinetics using optical microscopy and image processing. By further discriminating between external resistance and chemical reaction, the "true" chemical kinetics of the reaction have been measured, and the highly autocatalytic nature of the reaction confirmed. Based on these results, the constants of the chemical reactions kinetic laws have also been evaluated.

A method for phenomenological and chemical kinetics study of autocatalytic reactive dissolution by optical microscopy. The case of uranium dioxide dissolution in nitric acid media

Directory of Open Access Journals (Sweden)

Marc Philippe

2018-01-01

Full Text Available Dissolution is a milestone of the head-end of hydrometallurgical processes, as the stabilization rates of the chemical elements determine the process performance and hold-up. This study aims at better understanding the chemical and physico-chemical phenomena of uranium dioxide dissolution reactions in nitric acid media in the Purex process, which separates the reusable materials and the final wastes of the spent nuclear fuels. It has been documented that the attack of sintering-manufactured uranium dioxide solids occurs through preferential attack sites, which leads to the development of cracks in the solids. Optical microscopy observations show that in some cases, the development of these cracks leads to the solid cleavage. It is shown here that the dissolution of the detached fragments is much slower than the process of the complete cleavage of the solid, and occurs with no disturbing phenomena, like gas bubbling. This fact has motivated the measurement of dissolution kinetics using optical microscopy and image processing. By further discriminating between external resistance and chemical reaction, the “true” chemical kinetics of the reaction have been measured, and the highly autocatalytic nature of the reaction confirmed. Based on these results, the constants of the chemical reactions kinetic laws have also been evaluated.

Dissolution of mixed oxide fuel as a function of fabrication variables

International Nuclear Information System (INIS)

Lerch, R.E.

1979-08-01

Dissolution properties of mechanically blended mixed oxide fuel were very dependent on the six fuel fabrication variables studied. Fuel sintering temperature, source of PuO 2 and PuO 2 content of the fuel had major effects: (1) as the sintering temperature was increased from 1400 to 1700 0 C, pellet dissolution was more complete; (2) pellets made from burned metal derived PuO 2 were more completely dissolved than pellets made from calcined nitrate derived PuO 2 which in turn were more completely dissolved than pellets made from calcined nitrate derived PuO 2 ; (3) as the PuO 2 content decreased from 25 to 15 wt % PuO 2 , pellet dissolution was more complete. Preferential dissolution of uranium occurred in all the mechanically blended mixed oxide. Unirradiated mixed oxide fuel pellets made by the Sol Gel process were generally quite soluble in nitric acid. Unirradiated mixed oxide fuel pellets made by the coprecipitation process dissolved completely and rapidly in nitric acid. Fuel made by the coprecipitation process was more completely dissolved than fuel made by the Sol Gel process which, in turn, was more completely dissolved than fuel made by mechanically blending UO 2 and PuO 2 as shown below. Addition of uncomplexed fluoride to nitric acid during fuel dissolution generally rendered all fuel samples completely dissolvable. In boiling 12M nitric acid, 95 to 99% of the plutonium which was going to dissolve did so in the first hour. Irradiated mechanically blended mixed oxide fuel with known fuel fabrication conditions was also subjected to fuel dissolution tests. While irradiation was shown to increase completeness of plutonium dissolution, poor dissolubility due to adverse fabrication conditions (e.g., low sintering temperature) remained after irradiation

Dissolution studies on Nickel ferrite in dilute chemical decontamination formulations

Energy Technology Data Exchange (ETDEWEB)

Ranganathan, S. [New Brunswick Univ., Fredericton, NB (Canada). Dept. of Chemical Engineering; Srinivasan, M.P. [Bhabha Atomic Research Centre (BARC) (India). Water and Steam Chemistry Laboratory; Raghavan, P.S. [Madras Christian College, Chennai (India); Narasimhan, S.V. [Bhabha Atomic Research Centre, Bombay (India); Gopalan, R. [Madras Christian College, Chennai (India). Department of Chemistry

2004-09-01

Nickel ferrite is one of the important corrosion products in the pipeline surfaces of water-cooled nuclear reactors. The dissolution of the nickel ferrite by chelating agents is very sensitive to the nature of the chelant, the nature of the reductant used in the formulation and the temperature at which the dissolution studies are performed. The dissolution is mainly controlled by the reductive dissolution of the ferrite particles, but complexing agents also play a significant role in the dissolution process. This study deals with the leaching of iron and nickel from nickel ferrite prepared by the solid-state method. The dissolution studies are performed in pyridine-2,6-dicarboxylic acid (PDCA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA) formulations containing organic reductants like ascorbic acid and low oxidation state transition metal ion reductants like Fe(II)-L (where L = PDCA, NTA, EDTA) at 85 C. The dissolution of nickel ferrite in PDCA, NTA and EDTA formulations is influenced by the presence of reductants in the formulations. The addition of Fe(II)-L in the formulation greatly enhances the dissolution of nickel ferrite. The preferential leaching of nickel over iron during the dissolution of nickel ferrite was observed in all the formulations. (orig.)

Dissolution studies on Nickel ferrite in dilute chemical decontamination formulations

International Nuclear Information System (INIS)

Ranganathan, S.; Narasimhan, S.V.; Gopalan, R.

2004-01-01

Nickel ferrite is one of the important corrosion products in the pipeline surfaces of water-cooled nuclear reactors. The dissolution of the nickel ferrite by chelating agents is very sensitive to the nature of the chelant, the nature of the reductant used in the formulation and the temperature at which the dissolution studies are performed. The dissolution is mainly controlled by the reductive dissolution of the ferrite particles, but complexing agents also play a significant role in the dissolution process. This study deals with the leaching of iron and nickel from nickel ferrite prepared by the solid-state method. The dissolution studies are performed in pyridine-2,6-dicarboxylic acid (PDCA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA) formulations containing organic reductants like ascorbic acid and low oxidation state transition metal ion reductants like Fe(II)-L (where L = PDCA, NTA, EDTA) at 85 C. The dissolution of nickel ferrite in PDCA, NTA and EDTA formulations is influenced by the presence of reductants in the formulations. The addition of Fe(II)-L in the formulation greatly enhances the dissolution of nickel ferrite. The preferential leaching of nickel over iron during the dissolution of nickel ferrite was observed in all the formulations. (orig.)

Iron oxides photochemical dissolution

International Nuclear Information System (INIS)

Blesa, M.A.; Litter, M.I.

1987-01-01

This work was intended to study the light irradiation influence of diverse wave-lengths on iron oxides dissolution in aqueous solutions. The objectives of this work were: the exploration of photochemical processes with the aim of its eventual application in: a) decontamination and chemical cleaning under special conditions; b) materials for solar energy conversion. (Author)

Laboratory simulation of salt dissolution during waste removal

International Nuclear Information System (INIS)

Wiersma, B.J.; Parish, W.R.

1997-01-01

Laboratory experiments were performed to support the field demonstration of improved techniques for salt dissolution in waste tanks at the Savannah River Site. The tests were designed to investigate three density driven techniques for salt dissolution: (1) Drain-Add-Sit-Remove, (2) Modified Density Gradient, and (3) Continuous Salt Mining. Salt dissolution was observed to be a very rapid process as salt solutions with densities between 1.38-1.4 were frequently removed. Slower addition and removal rates and locating the outlet line at deeper levels below the top of the saltcake provided the best contact between the dissolution water and the saltcake. It was observed that dissolution with 1 M sodium hydroxide solution resulted in salt solutions that were within the current inhibitor requirements for the prevention of stress corrosion cracking. This result was independent of the density driven technique. However, if inhibited water (0.01 M sodium hydroxide and 0.011 M sodium nitrite) was utilized, the salt solutions were frequently outside the inhibitor requirements. Corrosion testing at conditions similar to the environments expected during waste removal was recommended

Downstream processing of a ternary amorphous solid dispersion: The impacts of spray drying and hot melt extrusion on powder flow, compression and dissolution.

Science.gov (United States)

Davis, Mark T; Potter, Catherine B; Walker, Gavin M

2018-06-10

Downstream processing aspects of a stable form of amorphous itraconazole exhibiting enhanced dissolution properties were studied. Preparation of this ternary amorphous solid dispersion by either spray drying or hot melt extrusion led to significantly different powder processing properties. Particle size and morphology was analysed using scanning electron microscopy. Flow, compression, blending and dissolution were studied using rheometry, compaction simulation and a dissolution kit. The spray dried material exhibited poorer flow and reduced sensitivity to aeration relative to the milled extrudate. Good agreement was observed between differing forms of flow measurement, such as Flow Function, Relative flow function, Flow rate index, Aeration rate, the Hausner ratio and the Carr index. The stability index indicated that both powders were stable with respect to agglomeration, de-agglomeration and attrition. Tablet ability and compressibility studies showed that spray dried material could be compressed into stronger compacts than extruded material. Blending of the powders with low moisture, freely-flowing excipients was shown to influence both flow and compression. Porosity studies revealed that blending could influence the mechanism of densification in extrudate and blended extrudate formulations. Following blending, the powders were compressed into four 500 mg tablets, each containing a 100 mg dose of amorphous itraconazole. Dissolution studies revealed that the spray dried material released drug faster and more completely and that blending excipients could further influence the dissolution rate. Copyright © 2018 Elsevier B.V. All rights reserved.

CHARACTERIZATION AND ALUMINUM DISSOLUTION DEMONSTRATION WITH A 3 LITER TANK 51H SAMPLE

International Nuclear Information System (INIS)

Hay, M; John Pareizs, J; Cj Bannochie, C; Michael Stone, M; Damon Click, D; Daniel McCabe, D

2008-01-01

A 3-liter sludge slurry sample was sent to SRNL for demonstration of a low temperature aluminum dissolution process. The sludge was characterized before and after the aluminum dissolution. Post aluminum dissolution sludge settling and the stability of the decanted supernate were also observed. The characterization of the as-received 3-liter sample of Tank 51H sludge slurry shows a typical high aluminum HM sludge. The XRD analysis of the dried solids indicates Boehmite is the predominant crystalline form of aluminum in the sludge solids. However, amorphous phases of aluminum present in the sludge would not be identified using this analytical technique. The low temperature (55 C) aluminum dissolution process was effective at dissolving aluminum from the sludge. Over the three week test, ∼42% of the aluminum was dissolved out of the sludge solids. The process appears to be selective for aluminum with no other metals dissolving to any appreciable extent. At the termination of the three week test, the aluminum concentration in the supernate had not leveled off indicating more aluminum could be dissolved from the sludge with longer contact times or higher temperatures. The slow aluminum dissolution rate in the test may indicate the dissolution of the Boehmite form of aluminum however; insufficient kinetic data exists to confirm this hypothesis. The aluminum dissolution process appears to have minimal impact on the settling rate of the post aluminum dissolution sludge. However, limited settling data were generated during the test to quantify the effects. The sludge settling was complete after approximately twelve days. The supernate decanted from the settled sludge after aluminum dissolution appears stable and did not precipitate aluminum over the course of several months. A mixture of the decanted supernate with Tank 11 simulated supernate was also stable with respect to precipitation

DEVELOPMENT OF A KINETIC MODEL OF BOEHMITE DISSOLUTION IN CAUSTIC SOLUTIONS APPLIED TO OPTIMIZE HANFORD WASTE PROCESSING

International Nuclear Information System (INIS)

Disselkamp, R.S.

2011-01-01

Boehmite (e.g., aluminum oxyhydroxide) is a major non-radioactive component in Hanford and Savannah River nuclear tank waste sludge. Boehmite dissolution from sludge using caustic at elevated temperatures is being planned at Hanford to minimize the mass of material disposed of as high-level waste (HLW) during operation of the Waste Treatment Plant (WTP). To more thoroughly understand the chemistry of this dissolution process, we have developed an empirical kinetic model for aluminate production due to boehmite dissolution. Application of this model to Hanford tank wastes would allow predictability and optimization of the caustic leaching of aluminum solids, potentially yielding significant improvements to overall processing time, disposal cost, and schedule. This report presents an empirical kinetic model that can be used to estimate the aluminate production from the leaching of boehmite in Hanford waste as a function of the following parameters: (1) hydroxide concentration; (2) temperature; (3) specific surface area of boehmite; (4) initial soluble aluminate plus gibbsite present in waste; (5) concentration of boehmite in the waste; and (6) (pre-fit) Arrhenius kinetic parameters. The model was fit to laboratory, non-radioactive (e.g. 'simulant boehmite') leaching results, providing best-fit values of the Arrhenius A-factor, A, and apparent activation energy, E A , of A = 5.0 x 10 12 hour -1 and E A = 90 kJ/mole. These parameters were then used to predict boehmite leaching behavior observed in previously reported actual waste leaching studies. Acceptable aluminate versus leaching time profiles were predicted for waste leaching data from both Hanford and Savannah River site studies.

Fundamental study on dissolution behavior of poly(methyl methacrylate) by quartz crystal microbalance

Science.gov (United States)

Konda, Akihiro; Yamamoto, Hiroki; Yoshitake, Shusuke; Kozawa, Takahiro

2016-03-01

Ionizing radiations such as extreme ultraviolet (EUV) and electron beam (EB) are the most promising exposure source for next-generation lithographic technology. In the realization of high resolution lithography, it is necessary for resist materials to improve the trade-off relationship among sensitivity, resolution, and line width roughness (LWR). In order to overcome them, it is essential to understand basic chemistry of resist matrices in resist processes. In particular, the dissolution process of resist materials is a key process. Therefore, it is essential for next-generation resist design for ionizing radiation to clarify the dissolution behavior of the resist film into developer. However, the details in dissolution process of EUV and EB resist films have not been investigated thus far. In this study, main chain scission and dissolution behavior of poly(methyl methacrylate) (PMMA) as main chain scission type resist was investigated using quartz crystal microbalance (QCM) method and gel permeation chromatography (GPC) in order to understand the relationship between the degree of PMMA degradation and dissolution behavior. The relationship between the molecular weight after irradiation and the swelling behavior was clarified.

Calcination/dissolution residue treatment

International Nuclear Information System (INIS)

Knight, R.C.; Creed, R.F.; Patello, G.K.; Hollenberg, G.W.; Buehler, M.F.; O'Rourke, S.M.; Visnapuu, A.; McLaughlin, D.F.

1994-09-01

Currently, high-level wastes are stored underground in steel-lined tanks at the Hanford site. Current plans call for the chemical pretreatment of these wastes before their immobilization in stable glass waste forms. One candidate pretreatment approach, calcination/dissolution, performs an alkaline fusion of the waste and creates a high-level/low-level partition based on the aqueous solubilities of the components of the product calcine. Literature and laboratory studies were conducted with the goal of finding a residue treatment technology that would decrease the quantity of high-level waste glass required following calcination/dissolution waste processing. Four elements, Fe, Ni, Bi, and U, postulated to be present in the high-level residue fraction were identified as being key to the quantity of high-level glass formed. Laboratory tests of the candidate technologies with simulant high-level residues showed reductive roasting followed by carbonyl volatilization to be successful in removing Fe, Ni, and Bi. Subsequent bench-scale tests on residues from calcination/dissolution processing of genuine Hanford Site tank waste showed Fe was separated with radioelement decontamination factors of 70 to 1,000 times with respect to total alpha activity. Thermodynamic analyses of the calcination of five typical Hanford Site tank waste compositions also were performed. The analyses showed sodium hydroxide to be the sole molten component in the waste calcine and emphasized the requirement for waste blending if fluid calcines are to be achieved. Other calcine phases identified in the thermodynamic analysis indicate the significant thermal reconstitution accomplished in calcination

Chemistry of application of calcination/dissolution to the Hanford tank waste inventory

International Nuclear Information System (INIS)

Delegard, C.H.; Elcan, T.D.; Hey, B.E.

1994-05-01

Approximately 330,000 metric tons of sodium-rich radioactive waste originating from separation of plutonium from irradiated uranium fuel are stored in underground tanks at the Hanford Site in Washington State. Fractionation of the waste into low-level waste (LLW) and high-level waste (HLW) streams is envisioned via partial water dissolution and limited radionuclide extraction operations. Under optimum conditions, LLW would contain most of the chemical bulk while HLW would contain virtually all of the transuranic and fission product activity. Calcination at around 850 C, followed by water dissolution, has been proposed as an alternative initial treatment of Hanford Site waste to improve waste dissolution and the envisioned LLW/HLW split. Results of literature and laboratory studies are reported on the application of calcination/dissolution (C/D) to the fractionation of the Hanford Site tank waste inventory. Both simulated and genuine Hanford Site waste materials were used in the lab tests. To evaluation confirmed that C/D processing reduced the amount of several components from the waste. The C/D dissolutions of aluminum and chromium allow redistribution of these waste components from the HLW to the LLW fraction. Comparisons of simple water-washing with C/D processing of genuine Hanford Site waste are also reported based on material (radionuclide and chemical) distributions to solution and solid residue phases. The lab results show that C/D processing yielded superior dissolution of aluminum and chromium sludges compared to simple water dissolution. 57 refs., 26 figs., 18 tabs

Mechanism and Kinetics for the Dissolution of Apatitic Materials in Acid Solutions

Directory of Open Access Journals (Sweden)

Calmanovici C.E.

1997-01-01

Full Text Available Abstract - This work concerns the study of the digestion step in the production process of phosphoric acid. Some qualitative experiments indicate that the difference between the pH at the surface of the phosphate and that in the bulk of the solution is negligible and that the dissolution is controlled by diffusion of products away from the phosphate particle. In further experiments, to isolate the dissolution phenomenon from the formation of calcium sulfate, the sulfuric acid normally used industrially is replaced by hydrochloric acid. The phosphate material used in our experiments is a model apatitic material: synthetic hydroxyapatite (HAP. The dissolution of calcium hydroxyapatite was studied with increasing amounts of calcium and phosphate at different temperatures. A simple method was developed for this observation based on the time required for complete dissolution of the HAP powder. The results confirm that the dissolution is controlled by a diffusional process through an interface of calcium and phosphate ions released from the solid surface. A kinetic model for the dissolution of apatitic materials is proposed which assumes a shrinking particle behaviour controlled by diffusion of calcium ions. The experimental results are fitted to this model to determine the mass transfer constant for HAP dissolution in acid solutions. The activation energy of the reaction is about 14kJ/mol. This study was carried on in conditions similar to the industrial ones for the production of phosphoric acid by the dihydrate-process

Chemistry of application of calcination/dissolution to the Hanford tank waste inventory

Energy Technology Data Exchange (ETDEWEB)

Delegard, C.H.; Elcan, T.D.; Hey, B.E.

1994-05-01

Approximately 330,000 metric tons of sodium-rich radioactive waste originating from separation of plutonium from irradiated uranium fuel are stored in underground tanks at the Hanford Site in Washington State. Fractionation of the waste into low-level waste (LLW) and high-level waste (HLW) streams is envisioned via partial water dissolution and limited radionuclide extraction operations. Under optimum conditions, LLW would contain most of the chemical bulk while HLW would contain virtually all of the transuranic and fission product activity. Calcination at around 850 C, followed by water dissolution, has been proposed as an alternative initial treatment of Hanford Site waste to improve waste dissolution and the envisioned LLW/HLW split. Results of literature and laboratory studies are reported on the application of calcination/dissolution (C/D) to the fractionation of the Hanford Site tank waste inventory. Both simulated and genuine Hanford Site waste materials were used in the lab tests. To evaluation confirmed that C/D processing reduced the amount of several components from the waste. The C/D dissolutions of aluminum and chromium allow redistribution of these waste components from the HLW to the LLW fraction. Comparisons of simple water-washing with C/D processing of genuine Hanford Site waste are also reported based on material (radionuclide and chemical) distributions to solution and solid residue phases. The lab results show that C/D processing yielded superior dissolution of aluminum and chromium sludges compared to simple water dissolution. 57 refs., 26 figs., 18 tabs.

Dissolution Methods Database

Data.gov (United States)

U.S. Department of Health & Human Services — For a drug product that does not have a dissolution test method in the United States Pharmacopeia (USP), the FDA Dissolution Methods Database provides information on...

Development of dissolution test method for a telmisartan/amlodipine besylate combination using synchronous derivative spectrofluorimetry

Directory of Open Access Journals (Sweden)

Panikumar Durga Anumolu

2014-04-01

Full Text Available The dissolution process is considered an important in vitro tool to evaluate product quality and drug release behavior. Single dissolution methods for the analysis of combined dosage forms are preferred to simplify quality control testing. The objective of the present work was to develop and validate a single dissolution test for a telmisartan (TEL and amlodipine besylate (AML combined tablet dosage form. The sink conditions, stability and specificity of both drugs in different dissolution media were tested to choose a discriminatory dissolution method, which uses an USP type-II apparatus with a paddle rotating at 75 rpm, with 900 mL of simulated gastric fluid (SGF without enzymes as the dissolution medium. This dissolution methodology provided good dissolution profiles for both TEL and AML and was able to discriminate changes in the composition and manufacturing process. To quantify both drugs simultaneously, a synchronous first derivative spectrofluorimetric method was developed and validated. Drug release was analyzed by a fluorimetric method at 458 nm and 675 nm for AML and TEL, respectively. The dissolution method was validated as per ICH guidance.

Experimental results: Pilot plant calcine dissolution and liquid feed stability

International Nuclear Information System (INIS)

Herbst, R.S.; Fryer, D.S.; Brewer, K.N.; Johnson, C.K.; Todd, T.A.

1995-02-01

The dissolution of simulated Idaho Chemical Processing Plant pilot plant calcines, containing none of the radioactive actinides, lanthanides or fission products, was examined to evaluate the solubility of calcine matrix materials in acidic media. This study was a necessary precursor to dissolution and optimization experiments with actual radionuclide-containing calcines. The importance of temperature, nitric acid concentration, ratio of acid volume to calcine mass, and time on the amount, as a weight percentage of calcine dissolved, was evaluated. These parameters were studied for several representative pilot plant calcine types: (1) Run No. 74 Zirconia calcine; (2) Run No. 17 Zirconia/Sodium calcine; (3) Run No. 64 Zirconia/Sodium calcine; (3) Run No. 1027 Alumina calcine; and (4) Run No. 20 Alumina/Zirconia/Sodium calcine. Statistically designed experiments with the different pilot plant calcines indicated the effect of the studied process variables on the amount of calcine dissolved decreases in the order: Acid/Calcine Ratio > Temperature > HNO 3 Concentration > Dissolution Time. The following conditions are suitable to achieve greater than 90 wt. % dissolution of most Zr, Al, or Na blend calcines: (1) Maximum nitric acid concentration of 5M; (2) Minimum acid/calcine ratio of 10 mL acid/1 gram calcine; (3) Minimum dissolution temperature of 90 degrees C; and (4) Minimum dissolution time of 30 minutes. The formation of calcium sulphate (CaSO 4 ) precipitates was observed in certain dissolved calcine solutions during the dissolution experiments. Consequently, a study was initiated to evaluate if and under what conditions the resulting dissolved calcine solutions would be unstable with regards to precipitate formation. The results indicate that precipitate formation in the calcine solutions prepared under the above proposed dissolution conditions are not anticipated

A kinetic model for borosilicate glass dissolution based on the dissolution affinity of a surface alteration layer

International Nuclear Information System (INIS)

Bourcier, W.L.; Peiffer, D.W.; Knauss, K.G.; McKeegan, K.D.; Smith, D.K.

1989-11-01

A kinetic model for the dissolution of borosilicate glass is used to predict the dissolution rate of a nuclear waste glass. In the model, the glass dissolution rate is controlled by the rate of dissolution of an alkali-depleted amorphous surface (gel) layer. Our model predicts that all components concentrated in the surface layer, affect glass dissolution rates. The good agreement between predicted and observed elemental dissolution rates suggests that the dissolution rate of the gel layer limits the overall rate of glass dissolution. The model predicts that the long-term rate of glass dissolution will depend mainly on ion concentrations in solution, and therefore on the secondary phases which precipitate and control ion concentrations. 10 refs., 5 figs., 1 tab

Hydro-chemo-mechanical coupling in sediments: Localized mineral dissolution

KAUST Repository

Cha, Minsu; Santamarina, Carlos

2016-01-01

Mineral dissolution is inherently a chemo-hydro-mechanical coupled process. Field evidence and laboratory results show that dissolution may localize and form open conduits in cohesive media such as carbonate rocks. This study focuses on the evolution of localized dissolution in soils (i.e., frictional and non-cohesive granular materials) under effective confining stresses. Experimental results show the development of localized dissolution (“pipe”) when a carbonate-quartz sand is subjected to reactive fluid flow: only loosely packed quartz grains remain within pipes, and the number of pipes decreases away from the inlet port. Concurrent shear wave velocity measurements show a decrease in stiffness during dissolution due to stress and fabric changes, and more complex signal codas anticipate the development of internal heterogeneity. The discrete element method is used to simulate localized vertical dissolution features in granular materials, under constant vertical stress and zero lateral strain far-field boundaries. As porosity increases along dissolution pipes, vertical load is transferred to the surrounding soils and marked force chains develop. In terms of equivalent stress, principal stress rotation takes place within pipes and the sediment reaches the Coulomb failure condition inside pipes and in the surrounding medium. Dissolution pipes alter the geo-plumbing of the subsurface, enhance fluid transport but limit the long term performance of storage systems, alter the fluid pressure and effective stress fields, soften the sediment and may trigger shear failures.

Hydro-chemo-mechanical coupling in sediments: Localized mineral dissolution

KAUST Repository

Cha, Minsu

2016-06-11

Mineral dissolution is inherently a chemo-hydro-mechanical coupled process. Field evidence and laboratory results show that dissolution may localize and form open conduits in cohesive media such as carbonate rocks. This study focuses on the evolution of localized dissolution in soils (i.e., frictional and non-cohesive granular materials) under effective confining stresses. Experimental results show the development of localized dissolution (“pipe”) when a carbonate-quartz sand is subjected to reactive fluid flow: only loosely packed quartz grains remain within pipes, and the number of pipes decreases away from the inlet port. Concurrent shear wave velocity measurements show a decrease in stiffness during dissolution due to stress and fabric changes, and more complex signal codas anticipate the development of internal heterogeneity. The discrete element method is used to simulate localized vertical dissolution features in granular materials, under constant vertical stress and zero lateral strain far-field boundaries. As porosity increases along dissolution pipes, vertical load is transferred to the surrounding soils and marked force chains develop. In terms of equivalent stress, principal stress rotation takes place within pipes and the sediment reaches the Coulomb failure condition inside pipes and in the surrounding medium. Dissolution pipes alter the geo-plumbing of the subsurface, enhance fluid transport but limit the long term performance of storage systems, alter the fluid pressure and effective stress fields, soften the sediment and may trigger shear failures.

Studies of the thermal dissolution process of the Suzuki phase of the Eu2+ ion in KBr single crystals by analysis of photoacoustic signals

International Nuclear Information System (INIS)

MejIa-Uriarte, E V; Castaneda-Guzman, R; Villagran-Muniz, M; Camarillo, E; A, J Hernandez; S, H Murrieta; Navarrete, M

2003-01-01

An experimental investigation of the thermal behaviour of the dissolution process of the Suzuki phase (SP) by continuous heating (1 deg. C min -1 ) of KBr:Eu 2+ crystals is reported in this work. The thermal profiles were determined by the correlation functions between subsequent photoacoustic (PA) signals registered during the dissolution process. The behaviour of the thermal profile is directly related to the absorption coefficient of the Eu 2+ ion in precipitated states that are present in the crystal. The PA signal is detected as a consequence of the non-radiative processes that take place after the excitation of the low-energy band of the Eu 2+ ion by means of a focused laser pulse at 355 nm. The results obtained by this method are compared with those simultaneously obtained by the photoluminescence (PL) technique. The samples were heated from room temperature to 205 deg. C. The PA signal and PL spectrum were obtained every 6 deg. C. The temperature range of the SP dissolution process was from 77 to 115 deg. C. These results are in agreement with those obtained by the PL technique and with the data reported in the literature

Optimization of Dissolution Compartments in a Biorelevant Dissolution Apparatus Golem v2, Supported by Multivariate Analysis

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Ivan Stupák

2017-11-01

Full Text Available Biorelevant dissolution instruments represent an important tool for pharmaceutical research and development. These instruments are designed to simulate the dissolution of drug formulations in conditions most closely mimicking the gastrointestinal tract. In this work, we focused on the optimization of dissolution compartments/vessels for an updated version of the biorelevant dissolution apparatus—Golem v2. We designed eight compartments of uniform size but different inner geometry. The dissolution performance of the compartments was tested using immediate release caffeine tablets and evaluated by standard statistical methods and principal component analysis. Based on two phases of dissolution testing (using 250 and 100 mL of dissolution medium, we selected two compartment types yielding the highest measurement reproducibility. We also confirmed a statistically ssignificant effect of agitation rate and dissolution volume on the extent of drug dissolved and measurement reproducibility.

The dissolution kinetics of magnetite under regenerative conditions

International Nuclear Information System (INIS)

Ranganathan, S.

2004-01-01

Dissolution studies of magnetite were carried out under regenerative conditions in dilute chemical decontamination formulations. During regeneration of the formulation, the H + from the strong acid cation exchange resin gets released and the metal is absorbed on the resin. The efficiency of the regenerative process depends on the stability constants of the complexes involved and the selectivity on the ion exchange column. The regenerative condition helps to maintain a constant chelating agent concentration and pH during the dissolution experiment. Such a condition is ideal for obtaining data on the dissolution behaviour of the corrosion products with special application to actual reactor decontamination. The ethylenediaminetetraacetic acid (EDTA) based formulation used was found to be ineffective due to the high stability constant of Fe(III)-EDTA complex, which is not easily cleaved by the cation exchange resin. Hence, knowledge of the kinetics of magnetite dissolution under regenerative condition is of primary importance. The 2,6-pyridinedicarboxylic acid formulation is found to be better for the dissolution of Fe 3 O 4 in both static and regenerative modes in the presence of reductants than nitrilotriacetic acid and EDTA. (orig.)

The dissolution kinetics of magnetite under regenerative conditions

Energy Technology Data Exchange (ETDEWEB)

Ranganathan, S. [New Brunswick Univ., Frederiction (Canada). Dept. of Chemical Engineering; Raghavan, P.S.; Gopalan, R.; Srinivasan, M.P.; Narasimhan, S.V. [Water and Steam Chemistry Lab. of Bhabha Atomic Research Centre (BARC) (India)

2004-07-01

Dissolution studies of magnetite were carried out under regenerative conditions in dilute chemical decontamination formulations. During regeneration of the formulation, the H{sup +} from the strong acid cation exchange resin gets released and the metal is absorbed on the resin. The efficiency of the regenerative process depends on the stability constants of the complexes involved and the selectivity on the ion exchange column. The regenerative condition helps to maintain a constant chelating agent concentration and pH during the dissolution experiment. Such a condition is ideal for obtaining data on the dissolution behaviour of the corrosion products with special application to actual reactor decontamination. The ethylenediaminetetraacetic acid (EDTA) based formulation used was found to be ineffective due to the high stability constant of Fe(III)-EDTA complex, which is not easily cleaved by the cation exchange resin. Hence, knowledge of the kinetics of magnetite dissolution under regenerative condition is of primary importance. The 2,6-pyridinedicarboxylic acid formulation is found to be better for the dissolution of Fe{sub 3}O{sub 4} in both static and regenerative modes in the presence of reductants than nitrilotriacetic acid and EDTA. (orig.)

Development of In Vitro-In Vivo Correlation for Amorphous Solid Dispersion Immediate-Release Suvorexant Tablets and Application to Clinically Relevant Dissolution Specifications and In-Process Controls.

Science.gov (United States)

Kesisoglou, Filippos; Hermans, Andre; Neu, Colleen; Yee, Ka Lai; Palcza, John; Miller, Jessica

2015-09-01

Although in vitro-in vivo correlations (IVIVCs) are commonly pursued for modified-release products, there are limited reports of successful IVIVCs for immediate-release (IR) formulations. This manuscript details the development of a Multiple Level C IVIVC for the amorphous solid dispersion formulation of suvorexant, a BCS class II compound, and its application to establishing dissolution specifications and in-process controls. Four different 40 mg batches were manufactured at different tablet hardnesses to produce distinct dissolution profiles. These batches were evaluated in a relative bioavailability clinical study in healthy volunteers. Although no differences were observed for the total exposure (AUC) of the different batches, a clear relationship between dissolution and Cmax was observed. A validated Multiple Level C IVIVC against Cmax was developed for the 10, 15, 20, 30, and 45 min dissolution time points and the tablet disintegration time. The relationship established between tablet tensile strength and dissolution was subsequently used to inform suitable tablet hardness ranges within acceptable Cmax limits. This is the first published report for a validated Multiple Level C IVIVC for an IR solid dispersion formulation demonstrating how this approach can facilitate Quality by Design in formulation development and help toward clinically relevant specifications and in-process controls. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

Universal Linear Scaling of Permeability and Time for Heterogeneous Fracture Dissolution

Science.gov (United States)

Wang, L.; Cardenas, M. B.

2017-12-01

Fractures are dynamically changing over geological time scale due to mechanical deformation and chemical reactions. However, the latter mechanism remains poorly understood with respect to the expanding fracture, which leads to a positively coupled flow and reactive transport processes, i.e., as a fracture expands, so does its permeability (k) and thus flow and reactive transport processes. To unravel this coupling, we consider a self-enhancing process that leads to fracture expansion caused by acidic fluid, i.e., CO2-saturated brine dissolving calcite fracture. We rigorously derive a theory, for the first time, showing that fracture permeability increases linearly with time [Wang and Cardenas, 2017]. To validate this theory, we resort to the direct simulation that solves the Navier-Stokes and Advection-Diffusion equations with a moving mesh according to the dynamic dissolution process in two-dimensional (2D) fractures. We find that k slowly increases first until the dissolution front breakthrough the outbound when we observe a rapid k increase, i.e., the linear time-dependence of k occurs. The theory agrees well with numerical observations across a broad range of Peclet and Damkohler numbers through homogeneous and heterogeneous 2D fractures. Moreover, the theory of linear scaling relationship between k and time matches well with experimental observations of three-dimensional (3D) fractures' dissolution. To further attest to our theory's universality for 3D heterogeneous fractures across a broad range of roughness and correlation length of aperture field, we develop a depth-averaged model that simulates the process-based reactive transport. The simulation results show that, regardless of a wide variety of dissolution patterns such as the presence of dissolution fingers and preferential dissolution paths, the linear scaling relationship between k and time holds. Our theory sheds light on predicting permeability evolution in many geological settings when the self

Study of the solubility and stability of polystyrene wastes in a dissolution recycling process

International Nuclear Information System (INIS)

Garcia, Maria Teresa; Gracia, Ignacio; Duque, Gema; Lucas, Antonio de; Rodriguez, Juan Francisco

2009-01-01

Dissolution with suitable solvents is one of the cheapest and more efficient processes for polystyrene waste management. In this work the solubility of polystyrene foams in several solvents benzene, toluene, xylene, tetrahydrofuran, chloroform, 1,3-butanediol, 2-butanol, linalool, geraniol, d-limonene, p-cymene, terpinene, phellandrene, terpineol, menthol, eucalyptol, cinnamaldheyde, nitrobenzene, N,N-dimethylformamide and water has been determined. Experimental results have shown that to develop a 'green process' the constituents of essential oils, d-limonene, p-cymene, terpinene, phellandrene, are the most appropriate solvents. The action of these solvent does not produce any degradation of polymer chains. The solubility of the polymer in the mentioned solvents at different temperatures has been investigated. The solvent can be easily recycled by distillation.

Aluminum Target Dissolution in Support of the Pu-238 Program

Energy Technology Data Exchange (ETDEWEB)

McFarlane, Joanna [ORNL; Benker, Dennis [ORNL; DePaoli, David W [ORNL; Felker, Leslie Kevin [ORNL; Mattus, Catherine H [ORNL

2014-09-01

Selection of an aluminum alloy for target cladding affects post-irradiation target dissolution and separations. Recent tests with aluminum alloy 6061 yielded greater than expected precipitation in the caustic dissolution step, forming up to 10 wt.% solids of aluminum hydroxides and aluminosilicates. We present a study to maximize dissolution of aluminum metal alloy, along with silicon, magnesium, and copper impurities, through control of temperature, the rate of reagent addition, and incubation time. Aluminum phase transformations have been identified as a function of time and temperature, using X-ray diffraction. Solutions have been analyzed using wet chemical methods and X-ray fluorescence. These data have been compared with published calculations of aluminum phase diagrams. Temperature logging during the transients has been investigated as a means to generate kinetic and mass transport data on the dissolution process. Approaches are given to enhance the dissolution of aluminum and aluminosilicate phases in caustic solution.

Dissolution of nuclear fuels

International Nuclear Information System (INIS)

Uriarte Hueda, A.; Berberana Eizmendi, M.; Rainey, R.

1968-01-01

A laboratory study was made of the instantaneous dissolution rate (IDR) for unirradiated uranium metal rods and UO 2 , PuO 2 and PuO 2 -UO 2 pellets in boiling nitric acid alone and with additives. The uranium metal and UO 2 dissolved readily in nitric acid alone; PuO 2 dissolved slowly even with the addition of fluoride; PuO 2 -UO 2 pellets containing as much as 35% PuO 2 in UO 2 gave values of the instantaneous dissolution rate to indicate can be dissolved with nitric acid alone. An equation to calculate the time for complete dissolution has been determinate in function of the instantaneous dissolution rates. The calculated values agree with the experimental. Uranium dioxide pellets from various sources but all having a same density varied in instantaneous dissolution rate. All the pellets, however, have dissolved ved in the same time. The time for complete dissolution of PuO 2 -UO 2 pellets, having the same composition, and the concentration of the used reagents are function of the used reagents are function of the fabrication method. (Author) 8 refs

Optimization of LiCoO2 powder extraction process from cathodes of lithium-ion batteries by chemical dissolution

OpenAIRE

Lucas Evangelista Sita; Stephany Pires da Silva; Paulo Rogério Catarini da Silva; Alexandre Urbano; Jair Scarminio

2015-01-01

A chemical process has been applied to extract LiCoO2 powder from cathodes of spent lithium-ion batteries by dissolution of the binder that agglutinate the powder particle each other as well to the Al collector surface. As solvents dimethylformamide (DMF) and N-methyilpirrolidone (NMP) were employed and the variables, cathode area, solution temperature, ultrasound bath power and solution stirring were chosen to optimize the extraction process. NMP solutions presented best results for powder e...

Evaluation of a three compartment in vitro gastrointestinal simulator dissolution apparatus to predict in vivo dissolution.

Science.gov (United States)

Takeuchi, Susumu; Tsume, Yasuhiro; Amidon, Gregory E; Amidon, Gordon L

2014-11-01

In vitro dissolution tests are performed for new formulations to evaluate in vivo performance, which is affected by the change of gastrointestinal (GI) physiology, in the GI tract. Thus, those environmental changes should be introduced to an in vitro dissolution test. Many studies have successfully shown the improvement of in vitro-in vivo correlations (IVIVC) by introducing those physiological changes into dissolution tests. The gastrointestinal simulator (GIS), a multicompartment in vitro dissolution apparatus, was developed to evaluate in vivo drug dissolution. A gastric-emptying rate along with transit rate are key factors to evaluate in vivo drug dissolution and, hence, drug absorption. Dissolution tests with the GIS were performed with Biopharmaceutical Classification System class I drugs at five different gastric-emptying rates in the fasted state. Computational models were used to determine in vivo gastric-emptying time for propranolol and metoprolol based on the GIS dissolution results. Those were compared with published clinical data to determine the gastric half-emptying time. In conclusion, the GIS is a practical tool to assess dissolution properties and can improve IVIVC. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

Anomalous dissolution of metals and chemical corrosion

Directory of Open Access Journals (Sweden)

DRAGUTIN M. DRAZIC

2005-03-01

Full Text Available An overview is given of the anomalous behavior of some metals, in particular Fe and Cr, in acidic aqueous solutions during anodic dissolution. The anomaly is recognizable by the fact that during anodic dissolutionmore material dissolves than would be expected from the Faraday law with the use of the expected valence of the formed ions. Mechanical disintegration, gas bubble blocking, hydrogen embrittlement, passive layer cracking and other possible reasons for such behavior have been discussed. It was shown, as suggested by Kolotyrkin and coworkers, that the reason can be, also, the chemical reaction in which H2O molecules with the metal form metal ions and gaseous H2 in a potential independent process. It occurs simultaneously with the electrochemical corrosion process, but the electrochemical process controls the corrosion potential. On the example of Cr in acid solution itwas shown that the reason for the anomalous behavior is dominantly chemical dissolution, which is considerably faster than the electrochemical corrosion, and that the increasing temperature favors chemical reaction, while the other possible reasons for the anomalous behavior are of negligible effect. This effect is much smaller in the case of Fe, but exists. The possible role of the chemical dissolution reacton and hydrogen evolution during pitting of steels and Al and stress corrosion cracking or corrosion fatigue are discussed.

Spent fuel dissolution mechanisms

International Nuclear Information System (INIS)

Ollila, K.

1993-11-01

This study is a literature survey on the dissolution mechanisms of spent fuel under disposal conditions. First, the effects of radiolysis products on the oxidative dissolution mechanisms and rates of UO 2 are discussed. These effects have mainly been investigated by using electrochemical methods. Then the release mechanisms of soluble radionuclides and the dissolution of the UO 2 matrix including the actinides, are treated. Experimental methods have been developed for measuring the grain-boundary inventories of radionuclides. The behaviour of cesium, strontium and technetium in leaching tests shows different trends. Comparison of spent fuel leaching data strongly suggests that the release of 90 Sr into the leachant can be used as a measure of the oxidation/dissolution of the fuel matrix. Approaches to the modelling UO 2 , dissolution are briefly discussed in the next chapter. Lastly, the use of natural material, uraninite, in the evaluation of the long-term performance of spent fuel is discussed. (orig.). (81 ref., 37 figs., 8 tabs.)

Disintegration of highly soluble immediate release tablets: a surrogate for dissolution.

Science.gov (United States)

Gupta, Abhay; Hunt, Robert L; Shah, Rakhi B; Sayeed, Vilayat A; Khan, Mansoor A

2009-01-01

The purpose of the work was to investigate correlation between disintegration and dissolution for immediate release tablets containing a high solubility drug and to identify formulations where disintegration test, instead of the dissolution test, may be used as the acceptance criteria based on International Conference on Harmonization Q6A guidelines. A statistical design of experiments was used to study the effect of filler, binder, disintegrating agent, and tablet hardness on the disintegration and dissolution of verapamil hydrochloride tablets. All formulation variables, i.e., filler, binder, and disintegrating agent, were found to influence tablet dissolution and disintegration, with the filler and disintegrating agent exerting the most significant influence. Slower dissolution was observed with increasing disintegration time when either the filler or the disintegrating agent was kept constant. However, no direct corelationship was observed between the disintegration and dissolution across all formulations due to the interactions between different formulation components. Although all tablets containing sodium carboxymethyl cellulose as the disintegrating agent, disintegrated in less than 3 min, half of them failed to meet the US Pharmacopeia 30 dissolution criteria for the verapamil hydrochloride tablets highlighting the dependence of dissolution process on the formulation components other than the disintegrating agent. The results identified only one formulation as suitable for using the disintegration test, instead of the dissolution test, as drug product acceptance criteria and highlight the need for systematic studies before using the disintegration test, instead of the dissolution test as the drug acceptance criteria.

Role of nitrous acid during the dissolution of UO2 in nitric acid

International Nuclear Information System (INIS)

Deigan, N.; Pandey, N.K.; Kamachi Mudali, U.; Joshi, J.B.

2016-01-01

Understanding the dissolution behaviour of sintered UO 2 pellet in nitric acid is very important in designing an industrial scale dissolution system for the plutonium rich fast reactor MOX fuel. In the current article we have established the role of nitrous acid on the dissolution kinetics of UO 2 pellets in nitric acid. Under the chemical conditions that prevail in a typical Purex process, NO and NO 2 gases gets generated in the process streams. These gases produce nitrous acid in nitric acid medium. In addition, during the dissolution of UO 2 in nitric acid medium, nitrous acid is further produced in-situ at the pellet solution interface. As uranium dissolves oxidatively in nitric acid medium wherein it goes from U(IV) in solid to U(VI) in liquid, presence of nitrous acid (a good oxidizing agent) accelerates the reaction rate. Hence for determining the reaction mechanism of UO 2 dissolution in nitric acid medium, knowing the nitrous acid concentration profile during the course of dissolution is important. The current work involves the measurement of nitrous acid concentration during the course of dissolution of sintered UO 2 pellets in 8M starting nitric acid concentration as a function of mixing intensity from unstirred condition to 1500 RPM

TANK 12 SLUDGE CHARACTERIZATION AND ALUMINUM DISSOLUTION DEMONSTRATION

International Nuclear Information System (INIS)

Reboul, S.; Hay, Michael; Zeigler, Kristine; Stone, Michael

2009-01-01

A 3-L sludge slurry sample from Tank 12 was characterized and then processed through an aluminum dissolution demonstration. The dominant constituent of the sludge was found to be aluminum in the form of boehmite. The iron content was minor, about one-tenth that of the aluminum. The salt content of the supernatant was relatively high, with a sodium concentration of ∼7 M. Due to these characteristics, the yield stress and plastic viscosity of the unprocessed slurry were relatively high (19 Pa and 27 cP), and the settling rate of the sludge was relatively low (∼20% settling over a two and a half week period). Prior to performing aluminum dissolution, plutonium and gadolinium were added to the slurry to simulate receipt of plutonium waste from H-Canyon. Aluminum dissolution was performed over a 26 day period at a temperature of 65 C. Approximately 60% of the insoluble aluminum dissolved during the demonstration, with the rate of dissolution slowing significantly by the end of the demonstration period. In contrast, approximately 20% of the plutonium and less than 1% of the gadolinium partitioned to the liquid phase. However, about a third of the liquid phase plutonium became solubilized prior to the dissolution period, when the H-Canyon plutonium/gadolinium simulant was added to the Tank 12 slurry. Quantification of iron dissolution was less clear, but appeared to be on the order of 1% based on the majority of data (a minor portion of the data suggested iron dissolution could be as high as 10%). The yield stress of the post-dissolution slurry (2.5 Pa) was an order of magnitude lower than the initial slurry, due most likely to the reduced insoluble solids content caused by aluminum dissolution. In contrast, the plastic viscosity remained unchanged (27 cP). The settling rate of the post-dissolution slurry was higher than the initial slurry, but still relatively low compared to settling of typical high iron content/low salt content sludges. Approximately 40% of the

Revisiting classical silicate dissolution rate laws under hydrothermal conditions

Science.gov (United States)

Pollet-Villard, Marion; Daval, Damien; Saldi, Giuseppe; Knauss, Kevin; Wild, Bastien; Fritz, Bertrand

2015-04-01

In the context of geothermal energy, the relative intensities of primary mineral leaching and secondary mineral precipitation can affect porosity and permeability of the reservoir, thereby influencing its hydraulic performance and the efficiency of the geothermal power station. That is why the prediction of reaction kinetics of fluid/rock interactions represents a critical issue in this context. Moreover, in several geothermal systems such as the one of Soultz-sous-Forêts (Alsace, France), the circulation of aqueous fluids induces only modest modifications of their chemical composition. Therefore, fluid-rock interactions take place at close-to-equilibrium conditions, where the rate-affinity relations are poorly known and intensively debated [1]. To describe more precisely the dissolution processes, our strategy consists in investigating the dissolution of the main cleavages of K-spar minerals (one of the prevalent primary minerals in the reservoir of Soultz-sous-Forêts geothermal system) over a wide range of Gibbs free energy (ΔG) conditions. The aims are to decipher the impact of crystallographic orientation and microstructural surface modifications on the dissolution kinetics and to propose a relation between K-spar dissolution rate and ΔG. Our experimental work relies on a coupled approach which combines classical experiments of K-spar dissolution monitored by aqueous chemical analyses (ICP-AES) and innovative techniques of nm- to μm-scale characterization of solid surface (SEM, AFM, VSI) [2]. Our results confirm that K-spar dissolution is an anisotropic process: we measure a tenfold factor between the slowest and the fastest-dissolving surfaces. Moreover, the formation of etch pits on surfaces during their alteration has been evidenced on all of the different faces that have been studied. This complex evolution of the surface topography casts doubt of the relevance of a surface model based on shrinking particles and represents a possible cause of an

Dissolution of aluminium; Disolucion de aluminio

Energy Technology Data Exchange (ETDEWEB)

Uriarte Hueda, A; Berberana Eizmendi, M; Pereira Sanchez, G

1968-07-01

The dissolution of aluminum with acid solutions ( nitric acid-mercuric nitrate) and alkaline solutions (sodium hydroxide-sodium nitrate) has been studied. The instantaneous dissolution rate (IDR) has been studied in function of the concentration of the used reagents and the dissolution temperature. The complete dissolution has been included in the second part of this report, to know the total dissolution time, the consume of reagents and the stability of the resultant solutions. (Author)

Dissolution Coupled Biodegradation of Pce by Inducing In-Situ Biosurfactant Production Under Anaerobic Conditions

Science.gov (United States)

Dominic, J.; Nambi, I. M.

2013-12-01

Biosurfactants have proven to enhance the bioavailability and thereby elevate the rate of degradation of Light Non Aqueous Phase Liquids (LNAPLs) such as crude oil and petroleum derivatives. In spite of their superior characteristics, use of these biomolecules for remediation of Dense Non Aqueous Phase Liquids (DNAPLs) such as chlorinated solvents is still not clearly understood. In this present study, we have investigated the fate of tetrachloroethylene (PCE) by inducing in-situ biosurfactants production, a sustainable option which hypothesizes increase in bioavailability of LNAPLs. In order to understand the effect of biosurfactants on dissolution and biodegradation under the inducement of in-situ biosurfactant production, batch experiments were conducted in pure liquid media. The individual influence of each process such as biosurfactant production, dissolution of PCE and biodegradation of PCE were studied separately for getting insights on the synergistic effect of each process on the fate of PCE. Finally the dissolution coupled biodegradation of non aqueous phase PCE was studied in conditions where biosurfactant production was induced by nitrate limitation. The effect of biosurfactants was differentiated by repeating the same experiments were the biosurfactant production was retarded. The overall effect of in-situ biosurfactant production process was evaluated by use of a mathematical model. The process of microbial growth, biosurfactant production, dissolution and biodegradation of PCE were translated as ordinary differential equations. The modelling exercise was mainly performed to get insight on the combined effects of various processes that determine the concentration of PCE in its aqueous and non-aqueous phases. Model simulated profiles of PCE with the kinetic coefficients evaluated earlier from individual experiments were compared with parameters fitted for observations in experiments with dissolution coupled biodegradation process using optimization

Principles of calcite dissolution in human and artificial otoconia.

Directory of Open Access Journals (Sweden)

Leif Erik Walther

Full Text Available Human otoconia provide mechanical stimuli to deflect hair cells of the vestibular sensory epithelium for purposes of detecting linear acceleration and head tilts. During lifetime, the volume and number of otoconia are gradually reduced. In a process of degeneration morphological changes occur. Structural changes in human otoconia are assumed to cause vertigo and balance disorders such as benign paroxysmal positional vertigo (BPPV. The aim of this study was to investigate the main principles of morphological changes in human otoconia in dissolution experiments by exposure to hydrochloric acid, EDTA, demineralized water and completely purified water respectively. For comparison reasons artificial (biomimetic otoconia (calcite gelatin nanocomposits and natural calcite were used. Morphological changes were detected in time steps by the use of environmental scanning electron microscopy (ESEM. Under in vitro conditions three main dissolution mechanisms were identified as causing characteristic morphological changes of the specimen under consideration: pH drops in the acidic range, complex formation with calcium ions and changes of ion concentrations in the vicinity of otoconia. Shifts in pH cause a more uniform reduction of otoconia size (isotropic dissolution whereas complexation reactions and changes of the ionic concentrations within the surrounding medium bring about preferred attacks at specific areas (anisotropic dissolution of human and artificial otoconia. Owing to successive reduction of material, all the dissolution mechanisms finally produce fragments and remnants of otoconia. It can be assumed that the organic component of otoconia is not significantly attacked under the given conditions. Artificial otoconia serve as a suitable model system mimicking chemical attacks on biogenic specimens. The underlying principles of calcite dissolution under in vitro conditions may play a role in otoconia degeneration processes such as BPPV.

Dissolution kinetics of B clusters in crystalline Si

International Nuclear Information System (INIS)

De Salvador, D.; Napolitani, E.; Bisognin, G.; Carnera, A.; Bruno, E.; Mirabella, S.; Impellizzeri, G.; Priolo, F.

2005-01-01

Boron (B) clustering in crystalline Si induced by interaction with Si self-interstitials is a widely studied phenomenon of fundamental importance for Si micro- and nano-electronic technology. The requested B activation increase brings the B concentration to a very high level and a detailed understanding of B clustering at high concentration is demanded. In the present work we present some recent results regarding the B clustering process starting from B concentration both below and above the B solubility limit. We show that B clusters, produced by self-interstitial interaction with substitutional B in crystalline Si, dissolve under annealing according to two distinct paths with very different characteristic times. The two regimes generally coexist, but while the faster dissolution path is predominant for clusters formed at low B concentration (1 x 10 19 B/cm 3 ), the slower one is characteristic of clusters formed above the solubility limit and dominates the dissolution process at high B concentration (2 x 10 2 B/cm 3 ). The activation energies of both processes are characterized and discussed. It is shown that the faster path can be connected to a direct emission of mobile B from small clusters, while the slower path is demonstrated not to be self-interstitial limited and it is probably related to a more complex cluster dissolution process

Effect of sodium lauryl sulfate in dissolution media on dissolution of hard gelatin capsule shells.

Science.gov (United States)

Zhao, Fang; Malayev, Vyacheslav; Rao, Venkatramana; Hussain, Munir

2004-01-01

Sodium lauryl sulfate (SLS) is a commonly used surfactant in dissolution media for poorly water soluble drugs. However, it has occasionally been observed that SLS negatively impacts the dissolution of drug products formulated in gelatin capsules. This study investigated the effect of SLS on the dissolution of hard gelatin capsule shells. The USP paddle method was used with online UV monitoring at 214 nm (peptide bond). Empty size #0 capsule shells were held to the bottom of the dissolution vessel by magnetic three-prong sinkers. SLS significantly slowed down the dissolution of gelatin shells at pH < 5. Visually, the gelatin shells transformed into some less-soluble precipitate under these conditions. This precipitate was found to contain a higher sulfur content than the gelatin control sample by elemental analysis, indicating that SLS is part of the precipitate. Additionally, the slowdown of capsule shell dissolution was shown to be dependent on the SLS concentration and the ionic strength of the media. SLS interacts with gelatin to form a less-soluble precipitate at pH < 5. The use of SLS in dissolution media at acidic pH should be carefully evaluated for gelatin capsule products.

Investigating Dissolution and Precipitation Phenomena with a Smartphone Microscope

Energy Technology Data Exchange (ETDEWEB)

Lumetta, Gregg J.; Arcia, Edgar

2016-10-11

A novel smartphone microscope can be used to observe the dissolution and crystallization of sodium chloride at a microscopic level. Observation of these seemingly simple phenomena through the microscope at 100× magnification can actually reveal some surprising behavior. These experiments offer the opportunity to discuss some basic concepts such as how the morphological features of the crystals dictates how the dissolution process proceeds, and how materials can be purified by re-crystallization techniques.

Dissolution of targets for the production of Mo-99: Part 1. Influence of NaOH concentration and the addition of NaNO3 and NaNO2 on the dissolution time

International Nuclear Information System (INIS)

Camilo, Ruth L.; Araujo, Izilda da C.; Mindrisz, Ana C.; Forbicini, Christina A.L.G. de O.

2011-01-01

Faced with global crisis in the production of radioisotope 99 Mo, which product of decay, 99 mTc, is the tracer element most often used in nuclear medicine and accounts for about 80% of all diagnostic procedures in vivo, since September 2008 Brazil is developing the project called Brazilian Multipurpose Reactor (RMB). Within the Brazilian Nuclear Program (PNB) the construction of the RMB, is seen as a long term solution to meet all domestic demand relative to the supply of radioisotopes and radiopharmaceuticals. In the process to be studied to obtain 99 Mo from irradiated UA1 x -A1 LEU targets employing alkaline dissolution, processing time should be minimized, considering the short half life of 99 Mo and 99 mTc, about 66 h and 6 h, respectively. That makes dissolution time a significant factor in the development of the process. This paper presents the results of alkaline dissolution of scraps of Al, used to simulate the dissolution process of UA1 x -A1 targets. Al corresponds to about 79% of the total weight of the UA1 x -A1 target. The effect of NaOH concentration on dissolution time for the interval of 1 to 3.5 mol.L-1 was studied, keeping the molar ratio in 1Al:2.16NaOH and the initial temperature of 88 degree C. The influence of reagent composition over dissolution time was studied using three different solutions: a) 3 mol.L -1 NaOH, b) 3 mol.L -1 NaOH/NaNO 3 and c) 3 mol.L -1 NaOH/NaNO 2 , keeping the same molar ratio and temperature. The results showed that the dissolution time decreases with increasing NaOH concentration and the addition of NaNO 3 or NaNO 2 in the NaOH solution reduces both dissolution time and volume of gases released. (author)

A multiphase interfacial model for the dissolution of spent nuclear fuel

Energy Technology Data Exchange (ETDEWEB)

Jerden, James L., E-mail: jerden@anl.gov [Argonne National Laboratory, 9700 South Cass Ave., Argonne, IL 60439 (United States); Frey, Kurt [University of Notre Dame, Notre Dame, IN 46556 (United States); Ebert, William [Argonne National Laboratory, 9700 South Cass Ave., Argonne, IL 60439 (United States)

2015-07-15

Highlights: • This model accounts for chemistry, temperature, radiolysis, U(VI) minerals, and hydrogen effect. • The hydrogen effect dominates processes determining spent fuel dissolution rate. • The hydrogen effect protects uranium oxide spent fuel from oxidative dissolution. - Abstract: The Fuel Matrix Dissolution Model (FMDM) is an electrochemical reaction/diffusion model for the dissolution of spent uranium oxide fuel. The model was developed to provide radionuclide source terms for use in performance assessment calculations for various types of geologic repositories. It is based on mixed potential theory and consists of a two-phase fuel surface made up of UO{sub 2} and a noble metal bearing fission product phase in contact with groundwater. The corrosion potential at the surface of the dissolving fuel is calculated by balancing cathodic and anodic reactions occurring at the solution interfaces with UO{sub 2} and NMP surfaces. Dissolved oxygen and hydrogen peroxide generated by radiolysis of the groundwater are the major oxidizing agents that promote fuel dissolution. Several reactions occurring on noble metal alloy surfaces are electrically coupled to the UO{sub 2} and can catalyze or inhibit oxidative dissolution of the fuel. The most important of these is the oxidation of hydrogen, which counteracts the effects of oxidants (primarily H{sub 2}O{sub 2} and O{sub 2}). Inclusion of this reaction greatly decreases the oxidation of U(IV) and slows fuel dissolution significantly. In addition to radiolytic hydrogen, large quantities of hydrogen can be produced by the anoxic corrosion of steel structures within and near the fuel waste package. The model accurately predicts key experimental trends seen in literature data, the most important being the dramatic depression of the fuel dissolution rate by the presence of dissolved hydrogen at even relatively low concentrations (e.g., less than 1 mM). This hydrogen effect counteracts oxidation reactions and can limit

Understanding dissolution behavior of 193nm photoresists in organic solvent developers

Science.gov (United States)

Lee, Seung-Hyun; Park, Jong Keun; Cardolaccia, Thomas; Sun, Jibin; Andes, Cecily; O'Connell, Kathleen; Barclay, George G.

2012-03-01

Herein, we investigate the dissolution behavior of 193-nm chemically amplified resist in different organic solvents at a mechanistic level. We previously reported the effect of solvent developers on the negative tone development (NTD) process in both dry and immersion lithography, and demonstrated various resist performance parameters such as photospeed, critical dimension uniformity, and dissolution rate contrast are strongly affected by chemical nature of the organic developer. We further pursued the investigation by examining the dependence of resist dissolution behavior on their solubility properties using Hansen Solubility Parameter (HSP). The effects of monomer structure, and resist composition, and the effects of different developer chemistry on dissolution behaviors were evaluated by using laser interferometry and quartz crystal microbalance. We have found that dissolution behaviors of methacrylate based resists are significantly different in different organic solvent developers such as OSDTM-1000 Developer* and n-butyl acetate (nBA), affecting their resist performance. This study reveals that understanding the resist dissolution behavior helps to design robust NTD materials for higher resolution imaging.

The Use of Artificial Neural Network for Prediction of Dissolution Kinetics

Directory of Open Access Journals (Sweden)

H. Elçiçek

2014-01-01

Full Text Available Colemanite is a preferred boron mineral in industry, such as boric acid production, fabrication of heat resistant glass, and cleaning agents. Dissolution of the mineral is one of the most important processes for these industries. In this study, dissolution of colemanite was examined in water saturated with carbon dioxide solutions. Also, prediction of dissolution rate was determined using artificial neural networks (ANNs which are based on the multilayered perceptron. Reaction temperature, total pressure, stirring speed, solid/liquid ratio, particle size, and reaction time were selected as input parameters to predict the dissolution rate. Experimental dataset was used to train multilayer perceptron (MLP networks to allow for prediction of dissolution kinetics. Developing ANNs has provided highly accurate predictions in comparison with an obtained mathematical model used through regression method. We conclude that ANNs may be a preferred alternative approach instead of conventional statistical methods for prediction of boron minerals.

UV imaging for in vitro dissolution and release studies: Initial experiences

DEFF Research Database (Denmark)

Østergaard, Jesper; Lenke, James; Jensen, Sabrine Smedegaard

2014-01-01

UV imaging has recently been introduced as a method in drug dissolution and release testing. Spatially and temporally resolved mapping of drug oncentrations in a 7 × 9 mm imaging area provides new opportunities for visualization and study of drug dissolution and release. This review describes...... in hydrogels with relevance for characterization of parenteral depots. UV imaging may be of particular use when the amounts of material are sparse and detailed insights into dissolution and release processes are required, that is in solid form screening, preformulation, and early drug development....

Preparation of chromous complexes and their effect on the dissolution of ferrites and chromites

International Nuclear Information System (INIS)

Sathyaseelan, V.S.; Rufus, A.L.; Velmurugan, S.; Pavithra, E.

2012-09-01

Decontamination of reactor coolant circuits is inevitable in minimising radiation exposure hazard especially during maintenance. Dilute chemical decontamination processes involving organic complexing agents viz., EDTA or NTA along with reducing agents such as ascorbic acid or oxalic acid are quite effective in dissolving magnetite, the predominant corrosion product oxide in carbon steel systems viz., PHWRs. However, dissolution of hematite, mixed ferrites and chromites found in stainless steel systems of BWRs and PWRs are not that easy to dissolve. A two-step process involving oxidation and reduction processes is required to dissolve these oxides. Studies were carried out to develop a single step process. Our earlier studies on high temperature decontamination at 160 deg. C have showed improved dissolution of magnetite, nickel ferrite and other oxides. In the present study, attempt has been made to carry out the oxide dissolution in formulations containing strong reducing agents such as chromous complexes. Dissolution of hematite is very effective under reducing conditions. Addition of ascorbic acid to the formulation containing EDTA and citric acid (EC) enhanced the kinetics 20 folds, while the addition of Cr (II)-EDTA to EC formulation increased the rate 100 folds. In the case of formulation containing NTA and citric acid (NC), the addition of chromous-NTA increased the rate 14 folds. NiFe 2 O 4 showed hardly any dissolution in EC formulation. However, in EAC (formulation containing EDTA, citric acid and ascorbic acid), the rate constant for the dissolution was 1.2x10 -3 min -1 , while it was 8.5x10 -3 min -1 in the case of ECCr (EDTA, citric acid containing chromous ions) formulation. In NTA based formulations also, dissolution rate was found to be enhanced in the presence of chromous ions. Further, there was no preferential dissolution of either Fe or Ni by both EDTA and NTA based formulations and also the rate of dissolution was found to depend linearly on the

Advances in heterogeneous autocatalytic reactions applied to uranium dissolution - 5317

International Nuclear Information System (INIS)

Marc, P.; Magnaldo, A.; Godard, J.; Schaer, E.

2015-01-01

Dissolution and the solubilization of the chemical elements is a milestone of the head-end of hydrometallurgical processes. When dissolving spent nuclear fuels, additional constraints are added due to the permanent need to strictly control and limit the hold-up. Thus the need for kinetic modeling concerning the dissolution of spent nuclear fuels in nitric acid. This study aims at better understanding the chemical and physical-chemical phenomena of uranium dioxide dissolution reactions in nitric medium. It has been documented that the nitric acid attack of sintering-manufactured uranium dioxide solids occurs through preferential attack sites. This non uniform attack leads to the development of cracks in the solids. Optical microscopy observations show that in some cases, the development of these cracks can lead to the solid cleavage. In this case, we show that the dissolution of the detached fragments is much slower than the time required for the complete cleavage of the solid. These points motivated the measurements of dissolution kinetics using optical microscopy and image processing. A comparison of the measured kinetics with the diffusion kinetics by the mean of the external resistance fraction allows discriminating between measured kinetics corresponding to the chemical reaction or mass-transport limitation. This capability to measure, for the very first time, the 'true' chemical kinetics of the reaction has enabled the confirmation of the highly autocatalytic nature of the reaction, and first evaluation of the constants of the chemical reactions kinetic laws. These data are fundamental to set the kinetic parameters of the chemical reactions in a future model of the dissolution of uranium dioxide sintered pellets. (authors)

High temperature dissolution of ferrites, chromites and bonaccordite in chelating media

Energy Technology Data Exchange (ETDEWEB)

Sathyaseelan, V.S.; Subramanian, H.; Anupkumar, B.; Rufus, A.L.; Velmurugan, S.; Narasimhan, S.V., E-mail: snv@igcar.gov.in [BARC Facilities, Water and Steam Chemistry Div., Tamilnadu (India)

2010-07-01

Different methods have been employed world wide for the decontamination of reactor coolant system surfaces. The success of a decontamination process mainly depends on the oxide dissolution efficiency of the decontamination formulation. Among the oxides, Fe{sub 3}O{sub 4} undergoes easy dissolution in organic acid media at normal temperatures. However, dissolution of chromites and mixed ferrites is not that easy in organic chelant media at normal temperatures even in the presence of redox reagents. Hence, a high temperature process was attempted for the dissolution of ferrites and chromites. A re-circulation system consisting of an autoclave, pump, heat exchanger etc. all lined with teflon was used for carrying out high temperature dissolution experiments. This study describes the high temperature dissolution kinetics of Fe{sub 3}O{sub 4}, NiFe{sub 2}O{sub 4}, and Cr{sub 2}O{sub 3}. Nitrilotriacetic acid (NTA), a well known solvent for metal oxides, was applied at temperatures ranging from 80 to 180{sup o}C. About six fold increase in dissolution rate was observed for Fe{sub 3}O{sub 4} in this temperature range. Effect of N{sub 2}H{sub 4} on oxide dissolution was studied. Lower dissolution rates were observed for Fe{sub 3}O{sub 4} and NiFe{sub 2}O{sub 4} in the presence of hydrazine. Oxide dissolution efficiency of other chelating agents like EDTA, PDCA etc. and the effect of reducing agents like oxalic acid and ascorbic acid on high temperature dissolution also has been studied. The effect of incorporation of boron and zinc in the iron and chromium oxides has also been studied. Bonaccordite (Ni{sub 2}FeBO{sub 5}) has been observed in the fuel deposits of pressurized Water Reactors especially in the AOA affected plants. Zinc ferrite/chromite are formed in reactors adopting zinc injection passivation technique to control radiation field. Bonaccordite and zinc ferrite/chromite formed over the reactor coolant system structural materials are also difficult to dissolve

HB-Line Dissolution of Glovebox Floor Sweepings

International Nuclear Information System (INIS)

Gray, J.H.

1998-02-01

Two candidate flowsheets for dissolving glovebox floor sweepings in the HB-Line Phase I geometrically favorable dissolver have been developed.Dissolving conditions tested and modified during the laboratory program were based on the current processing scheme for dissolving high-fired Pu-238 oxide in HB-Line. Subsequent adjustments made to the HB-Line flowsheet reflected differences in the dissolution behavior between high-fired Pu-238 oxide and the MgO sand/PuF 4 /PuO 2 mixture in glovebox floor sweepings. Although both candidate flowsheets involved two separate dissolving steps and resulted incomplete dissolution of all solids, the one selected for use in HB-Line will require fewer processing operations and resembles the initial flowsheet proposed for dissolving sand, slag, and crucible material in F-Canyon dissolvers. Complete dissolution of glovebox floor sweepings was accomplished in the laboratory by initially dissolving between 55 and 65 degree in a 14 molar nitric acid solution. Under these conditions, partial dissolution of PuF 4 and complete dissolution of PuO 2 and MgO sand were achieved in less than one hour. The presence of free fluoride in solution,uncomplexed by aluminum, was necessary for complete dissolution of the PuO 2 .The remaining PuF 4 dissolved following addition of aluminum nitrate nonahydrate (ANN) to complex the fluoride and heating between 75 and 85 degree C for an additional hour. Precipitation of magnesium and/or aluminum nitrates could occur before, during, and after transfer of product solutions. Both dilution and/or product solution temperature controls may be necessary to prevent precipitation of these salts. Corrosion of the dissolver should not be an issue during these dissolving operations. Corrosion is minimized when dissolving at 55-65 degree C for one to three hours at a maximum uncomplexed free fluoride concentration of 0.07 molar and by dissolving at 75-85 degree C at a one to one aluminum to fluoride mole ratio for another

Studies on the dissolution of mixed oxide spent fuel from FBR

International Nuclear Information System (INIS)

Nemoto, Shin-ichi; Shibata, Atsuhiro; Shioura, Takao; Okamoto, Fumitoshi; Tanaka, Yasumasa

1995-01-01

At the Chemical Processing Facility(CPF) in the Tokai Works of the Power Reactor and Nuclear Fuel Development Corporation(PNC), since 1982 Laboratory scale hot experiments have been carried out on the development of reprocessing technology for FBR mixed oxide fuel. The spent fuel pins which have been used in out experiments were irradiated in Experimental Fast Reactor 'Joyo' Phenix (France) and DFR(UK). Burn-up of the fuel pins were 4,400-100,000 MWd/t. This paper Summarizes a dissolution study that have been performed to define the Key parameters affecting dissolution rate such as concentration of nitric acid, burn-up, and temperature. And this paper also discusses about the character of releasing 85 Kr in chopping and dissolution process, and about the amount of insoluble residue. (author)

UO2 dissolution rates: A review

International Nuclear Information System (INIS)

McKenzie, W.F.

1992-09-01

This report reviews literature data on UO 2 dissolution kinetics and provides a framework for guiding future experimental studies as well as theoretical modeling studies. Under oxidizing conditions, UO 2 dissolution involves formation of an oxidized surface layer which is then dissolved by formation of aqueous complexes. Higher oxygen pressures or other oxidants are required at higher temperatures to have dissolution rates independent of oxygen pressure. At high oxygen pressures (1-5 atm, 25-70 C), the dissolution rate has a one-half order dependence on oxygen pressure, whereas at oxygen pressures below 0.2 atm, Grandstaff (1976), but nobody else, observed a first-order dependence on dissolution rate. Most people found a first-order dependence on carbonate concentration; Posey-Dowty (1987) found independence of carbonate at pH 7 to 8.2. Dissolution rates increase with temperature except in experiments involving granitic groundwater. Dissolution rates were generally greater under acid or basic conditions than near neutral pH

Mockup testing of remote systems for zirconium fuel dissolution process at the Idaho Chemical Processing Plant

International Nuclear Information System (INIS)

Paige, D.M.

1979-01-01

A facility is being constructed at the Idaho National Engineering Laboratory for storage and dissolution of spent zirconium reactor fuels. The dissolution is carried out in chemical type equipment contained in a large shielded cell. The design provides for remote operations and maintenance as required. Equipment predicted to fail within 5 years is designed for remote maintenance. Each system was fabricated for mockup testing using readily available materials. The mockups were tested, redesigned, and retested until satisfactory remote designs were achieved. Records were made of all the work. All design changes were then incorporated into the ongoing detailed design for the actual equipment. Several of these systems are discussed and they include valve replacement, pump replacement, waste solids handling, mechanism operations and others. The mockup program has saved time and money by eliminating many future problems. In addition, the mockup program will continue through construction, cold startup, and hot operations

Dissolution of Used Nuclear Fuel Using a TBP/N-Paraffin Solvent

Energy Technology Data Exchange (ETDEWEB)

Rudisill, T. S. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Shehee, T. C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Jones, D. H. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); DelCul, G. D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2017-10-02

The dissolution of unirradiated used nuclear fuel (UNF) pellets pretreated for tritium removal was demonstrated using a tributly phosphate (TBP) solvent. Dissolution of pretreated fuel in TBP could potentially combine dissolution with two cycle of solvent extraction required for separating the actinides and lanthanides from other fission products. Dissolutions were performed using UNF surrogates prepared from both uranyl nitrate and uranium trioxide produced from the pretreatment process by adding selected actinide and stable fission product elements. In laboratory-scale experiments, the U dissolution efficiency ranged from 80-99+% for both the nitrate and oxide surrogate fuels. On average, 80% of the Pu and 50% of the Np and Am in the nitrate surrogate dissolved; however, little of the transuranic elements dissolved in the oxide form. The majority of the 3+ lanthanide elements dissolved. Only small amounts of Sr (0-1.6%) and Mo (0.1-1.7%) and essentially no Cs, Ru, Zr, or Pd dissolved.

Dissolution kinetics of magnesium hydroxide for CO{sub 2} separation from coal-fired power plants

Energy Technology Data Exchange (ETDEWEB)

Bharadwaj, Hari Krishna [Chemical Engineering Program, School of Energy, Environmental, Biological, and Medical Engineering, University of Cincinnati, Cincinnati, OH 45221-0012 (United States); Lee, Joo-Youp, E-mail: joo.lee@uc.edu [Chemical Engineering Program, School of Energy, Environmental, Biological, and Medical Engineering, University of Cincinnati, Cincinnati, OH 45221-0012 (United States); Li, Xin; Liu, Zhouyang [Chemical Engineering Program, School of Energy, Environmental, Biological, and Medical Engineering, University of Cincinnati, Cincinnati, OH 45221-0012 (United States); Keener, Tim C. [Environmental Engineering Program, School of Energy, Environmental, Biological, and Medical Engineering, University of Cincinnati, Cincinnati, OH 45221-0012 (United States)

2013-04-15

Highlights: ► Magnesium hydroxide dissolution was found to be controlled by chemical reaction. ► The intrinsic kinetics has a fractional order between 0.20 and 0.31. ► The true activation energy value was found to have 76 ± 11 kJ/gmol. ► A shrinking-core model predicted experimental data with good accuracy. -- Abstract: The dissolution of magnesium hydroxide in water for the release of magnesium and hydroxyl ions into the solution to maintain suitable alkalinity is a crucial step in the Mg(OH){sub 2}-based CO{sub 2} absorption process. In this study, the rate of dissolution of Mg(OH){sub 2} was investigated under different operating conditions using a pH stat apparatus. The dissolution process was modeled using a shrinking core model and the overall Mg(OH){sub 2} dissolution process was found to be controlled by the surface chemical reaction of Mg(OH){sub 2} with H{sup +} ions. Under the chemical reaction control regime, the dissolution of Mg(OH){sub 2} in alkaline conditions was found not to follow a first-order reaction, and the fractional order of reaction was estimated to lie between 0.20 and 0.31. This suggests that the dissolution reaction is a non-elementary reaction, consisting of a sequence of elementary reactions, via most likely forming a surface magnesium complex. The true activation energy value of 76 ± 11 kJ/gmol was found to be almost twice as much as the observed activation energy value of 42 ± 6 kJ/gmol determined at pH 8.6, and was comparable with the previously reported values. The particle sizes predicted from the intrinsic kinetics determined from the model were in good agreement with the experimentally measured particle sizes during the dissolution process.

Influence of dissolution processing of PVA blends on the characteristics of their hydrogels synthesized by radiation—Part I: Gel fraction, swelling, and mechanical properties

International Nuclear Information System (INIS)

Alcântara, M.T.S.; Brant, A.J.C.; Giannini, D.R.; Pessoa, J.O.C.P.; Andrade, A.B.; Riella, H.G.; Lugão, A.B.

2012-01-01

In this work several hydrogels were obtained with two different poly(vinyl alcohol)s/PVAs as the main polymer in aqueous solutions containing 10% of PVA, 0.6% of agar, and 0.6% of κ-carrageenan (KC), cross-linked by gamma-rays from a 60 Co irradiation source. The PVAs tested have different degrees of hydrolysis and viscosities at 4% with values closed to 30 mPa s. The aqueous polymeric solutions were prepared using two distinct processes: the simple process of heating–stirring and that of making use of an autoclave. The purpose of this study was to evaluate the influence of the dissolution process by means of both methods on the hydrogels’ properties obtained. These were investigated by means of degree of cross-linking/gel fraction, degree of swelling in water, and some mechanical properties. The results that are obtained for hydrogels synthesized from solutions of PVA, agar, KC, and blends thereof prepared by both dissolution processes showed higher degrees of swelling for hydrogels from the autoclaved polymer solutions than those from the solutions prepared by simple heating–stirring process. Furthermore, their hydrogels containing totally hydrolyzed PVA displayed higher tensile strength and lower elongation properties. - Highlights: ► Hydrogels from γ-irradiated PVA and PVA-polysaccharide blends were obtained. ► PVA molar mass and degree of hydrolysis play an important role in their hydrogels. ► Dissolution processes of PVAs have influenced on their hydrogel characteristics. ► Degrees of swelling of hydrogels were lower when prepared from autoclaved solutions.

Study of dissolution factors of U, Th and Ta

International Nuclear Information System (INIS)

Santos, Maristela; Medeiros, Geiza; Zouain, Felipe; Cunha, Kenya Dias da; Pitassi, Gabriel; Lima, Cintia; Leite, Carlos Vieira Barros; Nascimento, Jose Eduardo; Dalia, Kely Cristina

2009-01-01

Air pollution can be a problem in industrial processes, but monitoring and controlling the aerosols in the work place is not enough to estimate the occupational risk due to dust particle inhalation. The solubility in lung fluid is considered to estimate this risk. The aim of this study is to determine in vitro specific dissolution parameters for thorium (Th), uranium (U) and tantalum (Ta) associated to crystal lattice of a niobium mineral (pyrochlore). Th, U and Ta dissolution factors in vitro were obtained using the Gamble solution (Simulant Lung Fluid, SLF), PIXE (Particle Induced X ray Emission) and alpha spectrometry as analytical techniques. Ta, Th and U are present in the pyrochlore crystal lattice as oxide; however they have shown different dissolution parameters. The rapid dissolution fraction (fr), rapid dissolution rate (λr); slow dissolution rate (fs) and slow dissolution fraction ((λs) measured for tantalum oxide were equal to 0.1, 0.45 d -1 and 0.00007 d -1 , respectively; for uranium oxide fr was equal to 0.05, (λr equal to 1.1 d -1 ; (λs equal to 0.000068 d -1 ; for thorium oxide fr was 0.025, (λr was 1.5 d -1 and (λs: 0.000065 d -1 . These results show that chemical behavior of these 3 compounds in the SLF could not be represented by the same parameter. The ratio of uranium concentration in urine and feces samples from workers exposed to pyrochlore dust particle was determined. These values agree with the theoretical values of estimated uranium concentration using specific parameters for uranium oxide present in pyrochlore. (author)

Plant-scale anodic dissolution of unirradiated IFR fuel pins

International Nuclear Information System (INIS)

Gay, E.C.; Tomczuk, Z.; Miller, W.E.

1993-01-01

This report discusses anodic dissolution which is a major operation in the pyrometallurgical process for recycling spent metal fuels from the Integral Fast Reactor (IFR), an advanced reactor design developed at Argonne National Laboratory. This process involves electrorefining the heavy metals (uranium and plutonium) from chopped, steel-clad fuel segments. The heavy metals are electrotransported from anodic dissolution baskets to solid and liquid cathodes in a molten salt electrolyte (LiCl-KCI) at 500 degrees C. Uranium is recovered on a solid cathode mandrel, while a uranium-plutonium mixture is recovered in a liquid cadmium cathode. The anode configuration consists of four baskets mounted on an anode shaft. These baskets provide parallel circuits in the electrolyte and salt flow through the chopped fuelbed as the baskets are rotated. The baskets for the engineering-scale tests were sized to contain up to 2.5 kg of heavy metal. Anodic dissolution of 10 kg batches of chopped, steel-clad simulated tuel (U-10% Zr and U-Zr-Fs alloy) was demonstrated

Dissolution of coccolithophorid calcite by microzooplankton and copepod grazing

Science.gov (United States)

Antia, A. N.; Suffrian, K.; Holste, L.; Müller, M. N.; Nejstgaard, J. C.; Simonelli, P.; Carotenuto, Y.; Putzeys, S.

2008-01-01

Independent of the ongoing acidification of surface seawater, the majority of the calcium carbonate produced in the pelagial is dissolved by natural processes above the lysocline. We investigate to what extent grazing and passage of coccolithophorids through the guts of copepods and the food vacuoles of microzooplankton contribute to calcite dissolution. In laboratory experiments where the coccolithophorid Emiliania huxleyi was fed to the rotifer Brachionus plicatilis, the heterotrophic flagellate Oxyrrhis marina and the copepod Acartia tonsa, calcite dissolution rates of 45-55%, 37-53% and 5-22% of ingested calcite were found. We ascribe higher loss rates in microzooplankton food vacuoles as compared to copepod guts to the strongly acidic digestion and the individual packaging of algal cells. In further experiments, specific rates of calcification and calcite dissolution were also measured in natural populations during the PeECE III mesocosm study under differing ambient pCO2 concentrations. Microzooplankton grazing accounted for between 27 and 70% of the dynamic calcite stock being lost per day, with no measurable effect of CO2 treatment. These measured calcite dissolution rates indicate that dissolution of calcite in the guts of microzooplankton and copepods can account for the calcite losses calculated for the global ocean using budget and model estimates.

Improving the dissolution properties of curcumin using dense gas antisolvent technology.

Science.gov (United States)

Kurniawansyah, Firman; Quachie, Lisa; Mammucari, Raffaella; Foster, Neil R

2017-04-15

The dissolution properties of curcumin are notoriously poor and hinder its bioavailability. To improve its dissolution properties, curcumin has been formulated with methyl-β-cyclodextrin and polyvinylpyrrolidone by the atomized rapid injection solvent extraction (ARISE) system. The compounds were co-precipitated from organic solutions using carbon dioxide at 30°C and 95bar as the antisolvent. Curcumin formulations were also produced by physical mixing and freeze drying for comparative purposes. The morphology, crystallinity, solid state molecular interactions, apparent solubility and dissolution profiles of samples were observed. The results indicate that the ARISE process is effective in the preparation of curcumin micro-composites with enhanced dissolution profiles compared to unprocessed material and products from physical mixing and freeze drying. Copyright © 2017 Elsevier B.V. All rights reserved.

The kinetics of anodic dissolution of rhenium in aqueous electrolyte solutions

International Nuclear Information System (INIS)

Atanasyants, A.G.; Kornienko, V.A.

1986-01-01

The kinetics of anodic rhenium dissolution was investigated by means of potentiodynamic and potentiostatic polarization curves recorded at temperature from 293 to 333 K in different media (NaOH, KOH, NaCl, NaBr, HCl, H 2 SO 4 ) using the rotating disc technique. It is shown that the kinetics of anodic rhenium dissolution and effective activation energy depend not only on the composition and pH value of the solutions but also on the structure of the dissolving rhenium surface. The investigation of the anodic behaviour of the rhenium monocrystal revealed the existence of anisotropy of the monocrystal electrochemical properties. The experimental results point to an important role of adsorption processes in anodic rhenium dissolution. Rhenium dissolution proceeds with formation of intermediate surface adsorption complexes between the metal and the components of the solution

Correlation of dissolution and disintegration results for an immediate-release tablet.

Science.gov (United States)

Nickerson, Beverly; Kong, Angela; Gerst, Paul; Kao, Shangming

2018-02-20

The drug release rate of a rapidly dissolving immediate-release tablet formulation with a highly soluble drug is proposed to be controlled by the disintegration rate of the tablet. Disintegration and dissolution test methods used to evaluate the tablets were shown to discriminate manufacturing process differences and compositionally variant tablets. In addition, a correlation was established between disintegration and dissolution. In accordance with ICH Q6A, this work demonstrates that disintegration in lieu of dissolution is suitable as the drug product quality control method for evaluating this drug product. Copyright © 2017 Elsevier B.V. All rights reserved.

Hydrothermal alteration of deep fractured granite: Effects of dissolution and precipitation

Science.gov (United States)

Nishimoto, Shoji; Yoshida, Hidekazu

2010-03-01

This paper investigates the mineralogical effects of hydrothermal alteration at depth in fractures in granite. A fracture accompanied by an alteration halo and filled with clay was found at a depth of 200 m in a drill core through Toki granite, Gifu, central Japan. Microscopic observation, XRD, XRF, EPMA and SXAM investigations revealed that the microcrystalline clays consist of illite, quartz and pyrite and that the halo round the fracture can be subdivided into a phyllic zone adjacent to the fracture, surrounded by a propylitic zone in which Fe-phyllosilicates are present, and a distinctive outer alteration front characterized by plagioclase breakdown. The processes that result in these changes took place in three successive stages: 1) partial dissolution of plagioclase with partial chloritization of biotite; 2) biotite dissolution and precipitation of Fe-phyllosilicate in the dissolution pores; 3) dissolution of K-feldspar and Fe-phyllosilicate, and illite precipitation associated with development of microcracks. These hydrothermal alterations of the granite proceed mainly by a dissolution-precipitation process resulting from the infiltration of hydrothermal fluid along microcracks. Such infiltration causes locally high mobility of Al and increases the ratio of fluid to rock in the alteration halo. These results contribute to an understanding of how granitic rock becomes altered in orogenic fields such as the Japanese island arc.

Dissolution of targets for the production of Mo-99: Part 1. Influence of NaOH concentration and the addition of NaNO{sub 3} and NaNO{sub 2} on the dissolution time

Energy Technology Data Exchange (ETDEWEB)

Camilo, Ruth L.; Araujo, Izilda da C.; Mindrisz, Ana C.; Forbicini, Christina A.L.G. de O., E-mail: rcamilo@ipen.br, E-mail: icaraujo@ipen.br, E-mail: acmindri@ipen.br, E-mail: cforbici@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN/SP), Sao Paulo, SP (Brazil)

2011-07-01

Faced with global crisis in the production of radioisotope {sup 99}Mo, which product of decay, {sup 99}mTc, is the tracer element most often used in nuclear medicine and accounts for about 80% of all diagnostic procedures in vivo, since September 2008 Brazil is developing the project called Brazilian Multipurpose Reactor (RMB). Within the Brazilian Nuclear Program (PNB) the construction of the RMB, is seen as a long term solution to meet all domestic demand relative to the supply of radioisotopes and radiopharmaceuticals. In the process to be studied to obtain {sup 99}Mo from irradiated UA1{sub x}-A1 LEU targets employing alkaline dissolution, processing time should be minimized, considering the short half life of {sup 99}Mo and {sup 99}mTc, about 66 h and 6 h, respectively. That makes dissolution time a significant factor in the development of the process. This paper presents the results of alkaline dissolution of scraps of Al, used to simulate the dissolution process of UA1{sub x}-A1 targets. Al corresponds to about 79% of the total weight of the UA1{sub x}-A1 target. The effect of NaOH concentration on dissolution time for the interval of 1 to 3.5 mol.L-1 was studied, keeping the molar ratio in 1Al:2.16NaOH and the initial temperature of 88 degree C. The influence of reagent composition over dissolution time was studied using three different solutions: a) 3 mol.L{sup -1} NaOH, b) 3 mol.L{sup -1} NaOH/NaNO{sub 3} and c) 3 mol.L{sup -1} NaOH/NaNO{sub 2}, keeping the same molar ratio and temperature. The results showed that the dissolution time decreases with increasing NaOH concentration and the addition of NaNO{sub 3} or NaNO{sub 2} in the NaOH solution reduces both dissolution time and volume of gases released. (author)

Nonmarital romantic relationship commitment and leave behavior: the mediating role of dissolution consideration.

Science.gov (United States)

Vanderdrift, Laura E; Agnew, Christopher R; Wilson, Juan E

2009-09-01

Two studies investigated the process by which individuals in nonmarital romantic relationships characterized by low commitment move toward enacting leave behaviors. Predictions based on the behavioral, goal, and implementation intention literatures were tested using a measure of dissolution consideration developed for this research. Dissolution consideration assesses how salient relationship termination is for an individual while one's relationship is intact. Study 1 developed and validated a measure of dissolution consideration and Study 2 was a longitudinal test of the utility of dissolution consideration in predicting the enactment of leave behaviors. Results indicated that dissolution consideration mediates the association between commitment and enacting leave behaviors, is associated with taking more immediate action, and provides unique explanatory power in leave behavior beyond the effect of commitment alone. Collectively, the findings suggest that dissolution consideration is an intermediate step between commitment and stay/leave behavior in close relationships.

Use of micro-reactors to obtain new insights into the factors influencing tricalcium silicate dissolution

International Nuclear Information System (INIS)

Suraneni, Prannoy; Flatt, Robert J.

2015-01-01

A micro-reactor approach, developed previously, is used to study the early dissolution of tricalcium silicate. This approach uses micron-sized gaps mimicking particles in close contact to understand dissolution, nucleation, and growth processes. The main factors influencing the dissolution kinetics of tricalcium silicate are presented. We show that the presence of defects caused by polishing does not affect the extent of dissolution. A strong effect of aluminum in solution reducing the extent of dissolution is however identified. This effect is highly dependent on the pH, and is much lower above pH 13. We show also that superplasticizers reduce the extent of dissolution; however, the exact reason for this effect is not clear.

Dissolution studies of natural analogues spent fuel and U(VI)-Silicon phases of and oxidative alteration process

International Nuclear Information System (INIS)

Perez Morales, I.

2000-01-01

In order to understand the long-term behavior of the nuclear spent fuel in geological repository conditions, we have performed dissolution studies with natural analogues to UO 2 as well as with solid phases representatives of the oxidative alteration pathway of uranium dioxide, as observed in both natural environment and laboratory studies. In all cases, we have studied the influence of the bicarbonate concentration in the dissolution process, as a first approximation to the groundwater composition of a granitic environment, where carbonate is one of the most important complexing agents. As a natural analogue to the nuclear spent fuel some uraninite samples from the Oklo are deposit in Gabon, where chain fission reactions took place 2000 millions years ago, as well as a pitchblende sample from the mine Fe ore deposit, in Salamanca (spain) have been studied. The studies have been performed at 25 and 60 deg C and 60 deg C, and they have focussed on the determination of both the thermodynamic and the kinetic properties of the different samples studied, using batch and continuous experimental methodologies, respectively. (Author)

Long-term kinetic effects and colloid formations in dissolution of LWR spent fuels

Energy Technology Data Exchange (ETDEWEB)

Ahn, T.M.

1996-11-01

This report evaluates continuous dissolution and colloid formation during spent-fuel performance under repository conditions in high-level waste disposal. Various observations suggest that reprecipitated layers formed on spent-fuel surfaces may not be protective. This situation may lead to continuous dissolution of highly soluble radionuclides such as C-14, Cl-36, Tc-99, I-129, and Cs-135. However, the diffusion limits of various species involved may retard dissolution significantly. For low-solubility actinides such as Pu-(239+240) or Am-(241+243), various processes regarding colloid formation have been analyzed. The processes analyzed are condensation, dispersion, and sorption. Colloid formation may lead to significant releases of low-solubility actinides. However, because there are only limited data available on matrix dissolution, colloid formation, and solubility limits, many uncertainties still exist. These uncertainties must be addressed before the significance of radionuclide releases can be determined. 118 refs.

Long-term kinetic effects and colloid formations in dissolution of LWR spent fuels

International Nuclear Information System (INIS)

Ahn, T.M.

1996-11-01

This report evaluates continuous dissolution and colloid formation during spent-fuel performance under repository conditions in high-level waste disposal. Various observations suggest that reprecipitated layers formed on spent-fuel surfaces may not be protective. This situation may lead to continuous dissolution of highly soluble radionuclides such as C-14, Cl-36, Tc-99, I-129, and Cs-135. However, the diffusion limits of various species involved may retard dissolution significantly. For low-solubility actinides such as Pu-(239+240) or Am-(241+243), various processes regarding colloid formation have been analyzed. The processes analyzed are condensation, dispersion, and sorption. Colloid formation may lead to significant releases of low-solubility actinides. However, because there are only limited data available on matrix dissolution, colloid formation, and solubility limits, many uncertainties still exist. These uncertainties must be addressed before the significance of radionuclide releases can be determined. 118 refs

Thoria/thoria-urania dissolution studies for reprocessing application

International Nuclear Information System (INIS)

Srinivas, C.; Yalmali, Vrunda; Pente, A.S.; Wattal, P.K.; Misra, S.D.

2012-06-01

Thoria dissolution is normally conducted in 13M nitric acid in the presence of 0.03M sodium fluoride or HF as catalyst and 0.1M aluminium nitrate for mitigation of fluoride related corrosion of SS 304L dissolver vessel. Addition of aluminium nitrate in such high concentrations has undesirable consequences in the downstream high level radioactive liquid waste vitrification process at 900-1000 degC. Besides, because of the highly corrosive nature of fluoride ion, lowering its concentration in the dissolution reaction is advantageous in reducing the corrosion of dissolver and other downstream equipments. The present work was done with twin objectives of avoiding aluminium nitrate addition and lowering the fluoride ion concentration during dissolution reaction. High temperature sintered thoria and thoria-4 weight% urania dissolution reactions were investigated in the absence of aluminium nitrate and at reduced fluoride concentrations. Corrosion rates of SS 304L zircaloy in various dissolvent mixtures were studied by weight loss method. These studies clearly showed that aluminium nitrate addition for control of fluoride related corrosion of SS 304L can be avoided when zircaloy-clad thoria/thoria-urania pellets are dissolved. Dissolved zirconium ion was observed to be as effective as aluminium ion. Moreover, dissolution could be achieved with reasonable reaction rates at reduced fluoride concentration of 0.005-0.01M instead of 0.03M by changing the method of addition of the fluoride catalyst. (author)

A mathematical analysis of drug dissolution in the USP flow through apparatus

Science.gov (United States)

McDonnell, David; D'Arcy, D. M.; Crane, L. J.; Redmond, Brendan

2018-03-01

This paper applies boundary layer theory to the process of drug dissolution in the USP (United States Pharmacopeia) Flow Through Apparatus. The mass transfer rate from the vertical planar surface of a compact within the device is examined. The theoretical results obtained are then compared with those of experiment. The paper also examines the effect on the dissolution process caused by the interaction between natural and forced convection within the apparatus and the introduction of additional boundaries.

Chemical alteration of cement hydrates by dissolution

International Nuclear Information System (INIS)

Sugiyama, Daisuke; Fujita, Tomonari; Nakanishi, Kiyoshi

2000-01-01

Cementitious material is a potential waste packaging and backfilling material for the radioactive waste disposal, and is expected to provide both physical and chemical containment. In particular, the sorption of radionuclides onto cementitious material and the ability to provide a high pH condition are very important parameters when considering the release of radionuclides from radioactive wastes. For the long term, in the geological disposal environment, cement hydrates will be altered by, for example, dissolution, chemical reaction with ions in the groundwater, and hydrothermal reaction. Once the composition or crystallinity of the constituent minerals of a cement hydrate is changed by these processes, the pH of the repository buffered by cementitious material and its sorption ability might be affected. However, the mechanism of cement alteration is not yet fully understood. In this study, leaching experiments of some candidate cements for radioactive waste disposal were carried out. Hydrated Ordinary Portland Cement (OPC), Blast Furnace Slag blended cement (OPC/BFS) and Highly containing Flyash and Silicafume Cement (HFSC) samples were contacted with distilled water at liquid:solid ratios of 10:1, 100:1 and 1000:1 at room temperature for 200 days. In the case of OPC, Ca(OH) 2 dissolved at high liquid:solid ratios. The specific surface area of all cement samples increased by leaching process. This might be caused by further hydration and change of composition of constituent minerals. A model is presented which predicts the leaching of cement hydrates and the mineral composition in the hydrated cement solid phase, including the incongruent dissolution of CSH gel phases and congruent dissolution of Ca(OH) 2 , Ettringite and Hydrotalcite. Experimental results of dissolution of Ca-O-H and Ca-Si-O-H phases were well predicted by this model. (author)

Assessing the effect of dissolved organic ligands on mineral dissolution rates: An example from calcite dissolution

International Nuclear Information System (INIS)

DeMaio, T.; Grandstaff, D.E.

1997-01-01

Experiments suggest that dissolved organic ligands may primarily modify mineral dissolution rates by three mechanisms: (1) metal-ligand (M-L) complex formation in solution, which increases the degree of undersaturation, (2) formation of surface M-L complexes that attack the surface, and (3) formation of surface complexes which passivate or protect the surface. Mechanisms (1) and (2) increase the dissolution rate and the third decreases it compared with organic-free solutions. The types and importance of these mechanisms may be assessed from plots of dissolution rate versus degree of undersaturation. To illustrate this technique, calcite, a common repository cementing and vein-filling mineral, was dissolved at pH 7.8 and 22 C in Na-Ca-HCO 3 -Cl solutions with low concentrations of three organic ligands. Low citrate concentrations (50 microM) increased the dissolution rate consistent with mechanism (1). Oxalate decreased the rate, consistent with mechanism (3). Low phthalate concentration (<50 microM) decreased calcite dissolution rates; however, higher concentrations increased the dissolution rates, which became faster than in inorganic solutions. Thus, phthalate exhibits both mechanisms (2) and (3) at different concentrations. In such cases linear extrapolations of dissolution rates from high organic ligand concentrations may not be valid

The influence of milling on the dissolution performance of simvastatin

DEFF Research Database (Denmark)

Zimper, Ulrike; Aaltonen, Jaakko; Krauel-Goellner, Karen

2012-01-01

properties such as solubility and dissolution rate and, therefore, process induced solid state modifications need to be monitored. The aim of this study was two-fold: firstly, to investigate the dissolution rates of milled and unmilled simvastatin; and secondly, to screen for the main milling factors......, as well as factor interactions in a dry ball milling process using simvastatin as model drug, and to optimize the milling procedure with regard to the opposing responses particle size and process induced disorder by application of a central composite face centered design. Particle size was assessed...... by scanning electron microscopy (SEM) and image analysis. Process induced disorder was determined by partial least squares (PLS) regression modeling of respective X-ray powder diffractograms (XRPD) and Raman spectra. Valid and significant quadratic models were built. The investigated milling factors were...

Dissolution of metal and metal oxide nanoparticles in aqueous media

International Nuclear Information System (INIS)

Odzak, Niksa; Kistler, David; Behra, Renata; Sigg, Laura

2014-01-01

The dissolution of Ag (citrate, gelatin, polyvinylpyrrolidone and chitosan coated), ZnO, CuO and carbon coated Cu nanoparticles (with two nominal sizes each) has been studied in artificial aqueous media, similar in chemistry to environmental waters, for up to 19 days. The dissolved fraction was determined using DGT (Diffusion Gradients in Thin films), dialysis membrane (DM) and ultrafiltration (UF). Relatively small fractions of Ag nanoparticles dissolved, whereas ZnO dissolved nearly completely within few hours. Cu and CuO dissolved as a function of pH. Using DGT, less dissolved Ag was measured compared to UF and DM, likely due to differences in diffusion of organic complexes. Similar dissolved metal concentrations of ZnO, Cu and CuO nanoparticles were determined using DGT and UF, but lower using DM. The results indicate that there is a need to apply complementary techniques to precisely determine dissolution of nanoparticles in aqueous media. - Highlights: • Three different techniques used simultaneously to measure NPs dissolution. • ZnO-NPs are the most soluble, followed by CuO-NPs, carbon coated Cu-NPs and Ag-NPs. • Dissolution is an important process affecting the fate of nanoparticles. • Complementary techniques are needed to precisely determine dissolution of NPs. - Dissolution of several types of nanoparticles was examined in aqueous media using three complementary techniques

A Study of Analytical Solution for the Special Dissolution Rate Model of Rock Salt

Directory of Open Access Journals (Sweden)

Xin Yang

2017-01-01

Full Text Available By calculating the concentration distributions of rock salt solutions at the boundary layer, an ordinary differential equation for describing a special dissolution rate model of rock salt under the assumption of an instantaneous diffusion process was established to investigate the dissolution mechanism of rock salt under transient but stable conditions. The ordinary differential equation was then solved mathematically to give an analytical solution and related expressions for the dissolved radius and solution concentration. Thereafter, the analytical solution was fitted with transient dissolution test data of rock salt to provide the dissolution parameters at different flow rates, and the physical meaning of the analytical formula was also discussed. Finally, the influential factors of the analytical formula were investigated. There was approximately a linear relationship between the dissolution parameters and the flow rate. The effects of the dissolution area and initial volume of the solution on the dissolution rate equation of rock salt were computationally investigated. The results showed that the present analytical solution gives a good description of the dissolution mechanism of rock salt under some special conditions, which may provide a primary theoretical basis and an analytical way to investigate the dissolution characteristics of rock salt.

Effects of gastric pH on oral drug absorption: In vitro assessment using a dissolution/permeation system reflecting the gastric dissolution process.

Science.gov (United States)

Kataoka, Makoto; Fukahori, Miho; Ikemura, Atsumi; Kubota, Ayaka; Higashino, Haruki; Sakuma, Shinji; Yamashita, Shinji

2016-04-01

The aim of the present study was to evaluate the effects of gastric pH on the oral absorption of poorly water-soluble drugs using an in vitro system. A dissolution/permeation system (D/P system) equipped with a Caco-2 cell monolayer was used as the in vitro system to evaluate oral drug absorption, while a small vessel filled with simulated gastric fluid (SGF) was used to reflect the gastric dissolution phase. After applying drugs in their solid forms to SGF, SGF solution containing a 1/100 clinical dose of each drug was mixed with the apical solution of the D/P system, which was changed to fasted state-simulated intestinal fluid. Dissolved and permeated amounts on applied amount of drugs were then monitored for 2h. Similar experiments were performed using the same drugs, but without the gastric phase. Oral absorption with or without the gastric phase was predicted in humans based on the amount of the drug that permeated in the D/P system, assuming that the system without the gastric phase reflected human absorption with an elevated gastric pH. The dissolved amounts of basic drugs with poor water solubility, namely albendazole, dipyridamole, and ketoconazole, in the apical solution and their permeation across a Caco-2 cell monolayer were significantly enhanced when the gastric dissolution process was reflected due to the physicochemical properties of basic drugs. These amounts resulted in the prediction of higher oral absorption with normal gastric pH than with high gastric pH. On the other hand, when diclofenac sodium, the salt form of an acidic drug, was applied to the D/P system with the gastric phase, its dissolved and permeated amounts were significantly lower than those without the gastric phase. However, the oral absorption of diclofenac was predicted to be complete (96-98%) irrespective of gastric pH because the permeated amounts of diclofenac under both conditions were sufficiently high to achieve complete absorption. These estimations of the effects of

Rapid Automated Dissolution and Analysis Techniques for Radionuclides in Recycle Process Streams

International Nuclear Information System (INIS)

Sudowe, Ralf; Roman, Audrey; Dailey, Ashlee; Go, Elaine

2013-01-01

The analysis of process samples for radionuclide content is an important part of current procedures for material balance and accountancy in the different process streams of a recycling plant. The destructive sample analysis techniques currently available necessitate a significant amount of time. It is therefore desirable to develop new sample analysis procedures that allow for a quick turnaround time and increased sample throughput with a minimum of deviation between samples. In particular, new capabilities for rapid sample dissolution and radiochemical separation are required. Most of the radioanalytical techniques currently employed for sample analysis are based on manual laboratory procedures. Such procedures are time- and labor-intensive, and not well suited for situations in which a rapid sample analysis is required and/or large number of samples need to be analyzed. To address this issue we are currently investigating radiochemical separation methods based on extraction chromatography that have been specifically optimized for the analysis of process stream samples. The influence of potential interferences present in the process samples as well as mass loading, flow rate and resin performance is being studied. In addition, the potential to automate these procedures utilizing a robotic platform is evaluated. Initial studies have been carried out using the commercially available DGA resin. This resin shows an affinity for Am, Pu, U, and Th and is also exhibiting signs of a possible synergistic effects in the presence of iron.

Surface controlled dissolution rates of gypsum in aqueous solutions exhibit nonlinear dissolution kinetics

Science.gov (United States)

Jeschke, Alexander A.; Vosbeck, Katrin; Dreybrodt, Wolfgang

2001-01-01

The effective dissolution rates of gypsum are determined by mixed kinetics, where the rate constants of dissolution at the surface and the transport constant of molecular diffusion of dissolved material are similar. To obtain the surface reaction rate law it is necessary to know the transport constant. We have determined the surface rate law for monocrystalline selenite by using a rotating disc set-up, where the transport coefficients are well known. As a result, up to a calcium concentration of 0.6 · ceq, we find a nearly linear rate law Rs = ksl (1- cs/ ceq) n1, where cs is the total calcium concentration at the surface and ceq the equilibrium concentration with respect to gypsum, n1 = 1.2 ± 0.2, and ksl = 1.1 · 10 -4 mmol cm -2 s -1 ± 15%. We also employed batch-experiments for selenite, alabaster and gypsum rock samples. The result of these experiments were interpreted by using a transport constant determined by NaCl dissolution experiments under similar physical conditions. The batch experiments reveal a dissolution rate law Rs = ksl (1- cs/ ceq) n1, ksl = 1.3 · 10 -4 mmol · cm -2 s -1, n1 = 1.2 ± 0.2 for c ≤ 0.94 · ceq. Close to equilibrium a nonlinear rate law, Rs = ks2 (1- cs/ ceq) n2, is observed, where ks2 is in the order of 10 mmol · cm -2 s -1 and n2 ≈ 4.5. The experimentally observed gypsum dissolution rates from the batch experiments could be accurately fitted, with only minor variations of the surface reaction constant obtained from the rotating disk experiment and the transport coefficient from the NaCl dissolution batch experiment. Batch experiments on pure synthetic gypsum, reveal a linear rate law up to equilibrium. This indicates inhibition of dissolution in natural samples close to equilibrium, as is known also for calcite minerals.

An electrochemical investigation on the dissolution of bilayered porous anodic alumina

International Nuclear Information System (INIS)

Liao, Jinfu; Ling, Zhiyuan; Li, Yi; Hu, Xing

2015-01-01

Highlights: • Pulse polarization was introduced to investigate the dissolution of PAA. • Electric field within the bilayers was estimated. • The formation of the barrier layer involves mainly solid-state processes. • The structure should be the determining factor in the dissolution of the bilayers. - Abstract: Anodic alumina attracts much research interest in many disciplines for its versatility. Meanwhile, some aspects regarding its growth are still not well-understood, such as the formation and properties of its bilayer structure. In this paper, along with capacitance measurement, pulse polarization is introduced to study the dissolution of bilayered porous anodic alumina (PAA). Combined with electron microscope observation, the electric field in the outer layer is estimated to be slightly higher than that in the inner layer. By comparing with (oxy-)hydroxide layers, the electric field distribution within barrier layer of PAA confirms that the bilayers are compact and are formed mainly by solid-state ionic migration. The changes of dissolution rates after annealing and application of electric pulses suggest that structure may be a determining factor for the dissolution behaviors of the bilayers.

Developing a quality by design approach to model tablet dissolution testing: an industrial case study.

Science.gov (United States)

Yekpe, Ketsia; Abatzoglou, Nicolas; Bataille, Bernard; Gosselin, Ryan; Sharkawi, Tahmer; Simard, Jean-Sébastien; Cournoyer, Antoine

2017-11-02

This study applied the concept of Quality by Design (QbD) to tablet dissolution. Its goal was to propose a quality control strategy to model dissolution testing of solid oral dose products according to International Conference on Harmonization guidelines. The methodology involved the following three steps: (1) a risk analysis to identify the material- and process-related parameters impacting the critical quality attributes of dissolution testing, (2) an experimental design to evaluate the influence of design factors (attributes and parameters selected by risk analysis) on dissolution testing, and (3) an investigation of the relationship between design factors and dissolution profiles. Results show that (a) in the case studied, the two parameters impacting dissolution kinetics are active pharmaceutical ingredient particle size distributions and tablet hardness and (b) these two parameters could be monitored with PAT tools to predict dissolution profiles. Moreover, based on the results obtained, modeling dissolution is possible. The practicality and effectiveness of the QbD approach were demonstrated through this industrial case study. Implementing such an approach systematically in industrial pharmaceutical production would reduce the need for tablet dissolution testing.

Microbially mediated barite dissolution in anoxic brines

International Nuclear Information System (INIS)

Ouyang, Bingjie; Akob, Denise M.; Dunlap, Darren; Renock, Devon

2017-01-01

Fluids injected into shale formations during hydraulic fracturing of black shale return with extraordinarily high total-dissolved-solids (TDS) and high concentrations of barium (Ba) and radium (Ra). Barite, BaSO_4, has been implicated as a possible source of Ba as well as a problematic mineral scale that forms on internal well surfaces, often in close association with radiobarite, (Ba,Ra)SO_4. The dissolution of barite by abiotic processes is well quantified. However, the identification of microbial communities in flowback and produced water necessitates the need to understand barite dissolution in the presence of bacteria. Therefore, we evaluated the rates and mechanisms of abiotic and microbially-mediated barite dissolution under anoxic and hypersaline conditions in the laboratory. Barite dissolution experiments were conducted with bacterial enrichment cultures established from produced water from Marcellus Shale wells located in northcentral Pennsylvania. These cultures were dominated by anaerobic halophilic bacteria from the genus Halanaerobium. Dissolved Ba was determined by ICP-OES and barite surfaces were investigated by SEM and AFM. Our results reveal that: 1) higher amounts of barium (up to ∼5 × ) are released from barite in the presence of Halanaerobium cultures compared to brine controls after 30 days of reaction, 2) etch pits that develop on the barite (001) surface in the presence of Halanaerobium exhibit a morphology that is distinct from those that form during control experiments without bacteria, 3) etch pits that develop in the presence of Halanaerobium exhibit a morphology that is similar to the morphology of etch pits formed in the presence of strong organic chelators, EDTA and DTPA, and 4) experiments using dialysis membranes to separate barite from bacteria suggest that direct contact between the two is not required in order to promote dissolution. These results suggest that Halanaerobium increase the rate of barite dissolution in anoxic

Polymorphic Transformation of Indomethacin during Hot Melt Extrusion Granulation: Process and Dissolution Control.

Science.gov (United States)

Xu, Ting; Nahar, Kajalajit; Dave, Rutesh; Bates, Simon; Morris, Kenneth

2018-05-10

To study and elucidate the effect of the intensity and duration of processing stresses on the possible solid-state changes during a hot melt extrusion granulation process. Blends of α-indomethacin and PEG 3350 (w/w 4:1) were granulated using various screw sizes/designs on the melt extruder under different temperature regimes. Differential Scanning Calorimetry and X-ray Powder Diffraction were employed for characterization. The dissolution behavior of the pure polymorphs and the resulting granules was determined using in-situ fiber optic UV testing system. An XRPD quantitation method using Excel full pattern fitting was developed to determine the concentration of each constituent (amorphous, α and γ indomethacin and PEG) in samples collected from each functioning zone and in granules. Analysis of in-process samples and granules revealed that higher temperature (≥130°C) and shear stress accelerated the process induced phase transitions from amorphous and/or the α form to γ indomethacin during heating stage. However, rapid cooling resulted in an increased percentage of the α form allowing isolation of the meta-stable form. By determining the conditions that either prevent or facilitate process induced transformations of IMC polymorphs during melt granulation, a design space was developed to control the polymorph present in the resulting granules. This represents the conditions necessary to balance the thermodynamic relationships between the polymorphs of the IMC system and the kinetics of the possible transformations as a function of the processing stresses.

Affinity functions for modeling glass dissolution rates

Energy Technology Data Exchange (ETDEWEB)

Bourcier, W.L. [Lawrence Livermore National Lab., CA (United States)

1997-07-01

Glass dissolution rates decrease dramatically as glass approach ''saturation'' with respect to the leachate solution. Most repository sites are chosen where water fluxes are minimal, and therefore the waste glass is most likely to dissolve under conditions close to ''saturation''. The key term in the rate expression used to predict glass dissolution rates close to ''saturation'' is the affinity term, which accounts for saturation effects on dissolution rates. Interpretations of recent experimental data on the dissolution behaviour of silicate glasses and silicate minerals indicate the following: 1) simple affinity control does not explain the observed dissolution rate for silicate minerals or glasses; 2) dissolution rates can be significantly modified by dissolved cations even under conditions far from saturation where the affinity term is near unity; 3) the effects of dissolved species such as Al and Si on the dissolution rate vary with pH, temperature, and saturation state; and 4) as temperature is increased, the effect of both pH and temperature on glass and mineral dissolution rates decrease, which strongly suggests a switch in rate control from surface reaction-based to diffusion control. Borosilicate glass dissolution models need to be upgraded to account for these recent experimental observations. (A.C.)

Dissolution of Si in Molten Al with Gas Injection

Science.gov (United States)

Seyed Ahmadi, Mehran

Silicon is an essential component of many aluminum alloys, as it imparts a range of desirable characteristics. However, there are considerable practical difficulties in dissolving solid Si in molten Al, because the dissolution process is slow, resulting in material and energy losses. It is thus essential to examine Si dissolution in molten Al, to identify means of accelerating the process. This thesis presents an experimental study of the effect of Si purity, bath temperature, fluid flow conditions, and gas stirring on the dissolution of Si in molten Al, plus the results of physical and numerical modeling of the flow to corroborate the experimental results. The dissolution experiments were conducted in a revolving liquid metal tank to generate a bulk velocity, and gas was introduced into the melt using top lance injection. Cylindrical Si specimens were immersed into molten Al for fixed durations, and upon removal the dissolved Si was measured. The shape and trajectory of injected bubbles were examined by means of auxiliary water experiments and video recordings of the molten Al free surface. The gas-agitated liquid was simulated using the commercial software FLOW-3D. The simulation results provide insights into bubble dynamics and offer estimates of the fluctuating velocities within the Al bath. The experimental results indicate that the dissolution rate of Si increases in tandem with the melt temperature and bulk velocity. A higher bath temperature increases the solubility of Si at the solid/liquid interface, resulting in a greater driving force for mass transfer, and a higher liquid velocity decreases the resistance to mass transfer via a thinner mass boundary layer. Impurities (with lower diffusion coefficients) in the form of inclusions obstruct the dissolution of the Si main matrix. Finally, dissolution rate enhancement was observed by gas agitation. It is postulated that the bubble-induced fluctuating velocities disturb the mass boundary layer, which

Solid-state, triboelectrostatic and dissolution characteristics of spray-dried piroxicam-glucosamine solid dispersions.

Science.gov (United States)

Adebisi, Adeola O; Kaialy, Waseem; Hussain, Tariq; Al-Hamidi, Hiba; Nokhodchi, Ali; Conway, Barbara R; Asare-Addo, Kofi

2016-10-01

This work explores the use of both spray drying and d-glucosamine HCl (GLU) as a hydrophilic carrier to improve the dissolution rate of piroxicam (PXM) whilst investigating the electrostatic charges associated with the spray drying process. Spray dried PXM:GLU solid dispersions were prepared and characterised (XRPD, DSC, SEM). Dissolution and triboelectric charging were also conducted. The results showed that the spray dried PXM alone, without GLU produced some PXM form II (DSC results) with no enhancement in solubility relative to that of the parent PXM. XRPD results also showed the spray drying process to decrease the crystallinity of GLU and solid dispersions produced. The presence of GLU improved the dissolution rate of PXM. Spray dried PXM: GLU at a ratio of 2:1 had the most improved dissolution. The spray drying process generally yielded PXM-GLU spherical particles of around 2.5μm which may have contributed to the improved dissolution. PXM showed a higher tendency for charging in comparison to the carrier GLU (-3.8 versus 0.5nC/g for untreated material and -7.5 versus 3.1nC/g for spray dried materials). Spray dried PXM and spray dried GLU demonstrated higher charge densities than untreated PXM and untreated GLU, respectively. Regardless of PXM:GLU ratio, all spray dried PXM:GLU solid dispersions showed a negligible charge density (net-CMR: 0.1-0.3nC/g). Spray drying of PXM:GLU solid dispersions can be used to produce formulation powders with practically no charge and thereby improving handling as well as dissolution behaviour of PXM. Copyright © 2016 Elsevier B.V. All rights reserved.

Impact of dissolution on the sedimentary record of the Paleocene-Eocene thermal maximum

Science.gov (United States)

Bralower, Timothy J.; Kelly, D. Clay; Gibbs, Samantha; Farley, Kenneth; Eccles, Laurie; Lindemann, T. Logan; Smith, Gregory J.

2014-09-01

The input of massive amounts of carbon to the atmosphere and ocean at the Paleocene-Eocene Thermal Maximum (PETM; ˜55.53 Ma) resulted in pervasive carbonate dissolution at the seafloor. At many sites this dissolution also penetrated into the underlying sediment column. The magnitude of dissolution at and below the seafloor, a process known as chemical erosion, and its effect on the stratigraphy of the PETM, are notoriously difficult to constrain. Here, we illuminate the impact of dissolution by analyzing the complete spectrum of sedimentological grain sizes across the PETM at three deep-sea sites characterized by a range of bottom water dissolution intensity. We show that the grain size spectrum provides a measure of the sediment fraction lost during dissolution. We compare these data with dissolution and other proxy records, electron micrograph observations of samples and lithology. The complete data set indicates that the two sites with slower carbonate accumulation, and less active bioturbation, are characterized by significant chemical erosion. At the third site, higher carbonate accumulation rates, more active bioturbation, and possibly winnowing have limited the impacts of dissolution. However, grain size data suggest that bioturbation and winnowing were not sufficiently intense to diminish the fidelity of isotopic and microfossil assemblage records.

The dissolution of chalcopyrite in chloride media

International Nuclear Information System (INIS)

Ibanez, T.; Velasquez, L.

2013-01-01

The aim of this investigation is to determinate the effects of parameters and additives on the kinetics of dissolution of chalcopyrite on moderated conditions by means of dissolutions test with chalcopyrite concentrate and pure chalcopyrite in shake flasks and instrumented stirred reactors. A study of the dissolution of chalcopyrite in chloride solutions has demonstrated that the rate of dissolution of chalcopyrite is strongly dependent on the potential of the solution within a range of 540 to 630 mV (versus SHE). Leaching at pH around 2.5 results in increased rates of copper dissolution suggesting the possibility to keep the solution potential within the range. Both pyrite and silver ions enhance the dissolution of chalcopyrite and this effect increases when both species are present. The MnO 2 has a negative effect on the dissolution increasing the solution potential to values where the rate decreases considerably. (Author)

Dissolution of copper and iron from malachite ore and precipitation of copper sulfate pentahydrate by chemical process

OpenAIRE

H. Kokes; M.H. Morcali; E. Acma

2014-01-01

The present work describes an investigation of a chemical process for the recovery of copper and iron from malachite ore. For the dissolution of copper and iron, H2SO4 was employed as well as H2O2 as an oxidizing agent. The effects of reaction temperature and time, acid concentration, liquid-to-solid ratio and agitation rate on the copper and iron percentage were investigated. Following the steps of dissolving the copper and iron sulfate and filtering, iron (III) hydroxide was precipitated by...

Dissolution glow curve in LLD

International Nuclear Information System (INIS)

Haverkamp, U.; Wiezorek, C.; Poetter, R.

1990-01-01

Lyoluminescence dosimetry is based upon light emission during dissolution of previously irradiated dosimetric materials. The lyoluminescence signal is expressed in the dissolution glow curve. These curves begin, depending on the dissolution system, with a high peak followed by an exponentially decreasing intensity. System parameters that influence the graph of the dissolution glow curve, are, for example, injection speed, temperature and pH value of the solution and the design of the dissolution cell. The initial peak does not significantly correlate with the absorbed dose, it is mainly an effect of the injection. The decay of the curve consists of two exponential components: one fast and one slow. The components depend on the absorbed dose and the dosimetric materials used. In particular, the slow component correlates with the absorbed dose. In contrast to the fast component the argument of the exponential function of the slow component is independent of the dosimetric materials investigated: trehalose, glucose and mannitol. The maximum value, following the peak of the curve, and the integral light output are a measure of the absorbed dose. The reason for the different light outputs of various dosimetric materials after irradiation with the same dose is the differing solubility. The character of the dissolution glow curves is the same following irradiation with photons, electrons or neutrons. (author)

Critical and subcritical parameters of the system simulating plutonium metal dissolution

International Nuclear Information System (INIS)

Vasilev, Yury Yu.; Ryazanov, Boris G.; Sviridov, Victor I.; Mozhayeva, Lubov I.

2003-01-01

Dissolution of plutonium metal was simulated using the Monte Carlo computer code to calculate criticality safety limits for the process. Calculations were made for the constant masses of plutonium charged to the dissolving vessel considering distribution of plutonium in metal and solution phases. Critical parameters and limits were calculated as a function of dissolving vessel volume and plutonium metal mass. 240 Pu content was assumed to be from 0% to 10% (mass). Critical parameters were evaluated for the system with a water reflector. Results of this paper may be used in the designing process equipment for plutonium metal dissolution. (author)

Effect of organic solvents on dissolution process of mechano-chemically activated molybdenum by inorganic acid solutions

International Nuclear Information System (INIS)

Shevtsova, I.Ya.; Chernyak, A.S.; Khal'zov, A.A.

1992-01-01

The process of chemical dissolution of mechanochemically activated and nonactivated molybdenite by inorganic acid solutions in certain organic solvents of different nature was considered. It is shown that the highest extraction of molybdenum in solution is achieved in the presence of nitric acid. The dissociation constant of the acid used in the given organic solvent does not affect molybdenite solubility. When dissolving molybdenite by solutions of nitric acid in carbonic acids, alcohols and esters, the solubility of the concentrate depends on the length of hydrocarbon chain of the organic solvent and dispersion degree of mineral source material

Numerical Simulation of Tuff Dissolution and Precipitation Experiments: Validation of Thermal-Hydrologic-Chemical (THC) Coupled-Process Modeling

Science.gov (United States)

Dobson, P. F.; Kneafsey, T. J.

2001-12-01

As part of an ongoing effort to evaluate THC effects on flow in fractured media, we performed a laboratory experiment and numerical simulations to investigate mineral dissolution and precipitation. To replicate mineral dissolution by condensate in fractured tuff, deionized water equilibrated with carbon dioxide was flowed for 1,500 hours through crushed Yucca Mountain tuff at 94° C. The reacted water was collected and sampled for major dissolved species, total alkalinity, electrical conductivity, and pH. The resulting steady-state fluid composition had a total dissolved solids content of about 140 mg/L; silica was the dominant dissolved constituent. A portion of the steady-state reacted water was flowed at 10.8 mL/hr into a 31.7-cm tall, 16.2-cm wide vertically oriented planar fracture with a hydraulic aperture of 31 microns in a block of welded Topopah Spring tuff that was maintained at 80° C at the top and 130° C at the bottom. The fracture began to seal within five days. A 1-D plug-flow model using the TOUGHREACT code developed at Berkeley Lab was used to simulate mineral dissolution, and a 2-D model was developed to simulate the flow of mineralized water through a planar fracture, where boiling conditions led to mineral precipitation. Predicted concentrations of the major dissolved constituents for the tuff dissolution were within a factor of 2 of the measured average steady-state compositions. The fracture-plugging simulations result in the precipitation of amorphous silica at the base of the boiling front, leading to a hundred-fold decrease in fracture permeability in less than 6 days, consistent with the laboratory experiment. These results help validate the use of the TOUGHREACT code for THC modeling of the Yucca Mountain system. The experiment and simulations indicate that boiling and concomitant precipitation of amorphous silica could cause significant reductions in fracture porosity and permeability on a local scale. The TOUGHREACT code will be used

Study of the dissolution of (U,P)O2 mixed oxides with a high plutonium content

International Nuclear Information System (INIS)

Fournier, S.

2001-01-01

Plutonium from nuclear reactors is partially integrated in the fuel cycle as Mixed OXide (U,Pu)O 2 (MOX). Their dissolution in nitric acid is needed to reprocess them in present reprocessing plants. The main difficulty of this study is that dissolution is a phenomenon depending on solution characteristics as well as the structural properties of the pellets, which depend themselves on the material fabrication process. After showing kinetic and thermodynamic dissolution data of mixed oxides in nitric media, an inventory of the parameters which affect the dissolution process has been made. A separable variable concept was introduced in order to describe the process by studying separately the role of chemical parameters of the solution and geometric parameters of the material. The first part of the study estimates the effect of nitric solution chemical parameters (concentrations, acidity, temperature) on the dissolution and underlines the role of the oxide surface protonation step. The second part of this work deals with the study of surface area evolution for materials with controlled plutonium rich heterogeneities. Experimental results show that the pellet surface undergoes erosion and is progressively weakened by the formation of fault lines in the bulk of the material followed by the dispersion of sub-millimeter fragments in the solution. An heterogeneous kinetic model derived from study of solid-gas interface systems has been applied to fuel pellets dissolution, allowing a mechanism to be proposed, based on surface dissolution of the oxide as well as fault creation in the volume. The dissolution kinetics are therefore dependant on the microstructure and mechanical strength and cohesion of the pellets. (author)

The use of commercial microwave dissolution equipment for the fast and reliable dissolution of high-fired POX and MOX samples

International Nuclear Information System (INIS)

Tushingham, J.; McInnes, C.; Firkin, S.

1998-09-01

The use of commercially available microwave dissolution equipment for the fast and reliable dissolution of high-fired plutonium dioxide (POX) and mixed oxide (MOX) samples has been evaluated for application to Safeguards Analysis. Under the auspices of the UK R and D Support Programme to the IAEA, equipment has been purchased and tested for the high-pressure microwave dissolution of POX samples fired to 1250 deg. C and MOX samples fired to 1600 deg. C, in concentrated nitric acid and hydrofluoric acid mixture. Considerable problems were encountered during development of procedures for microwave dissolution, resulting largely from sudden changes in pressure within dissolution vessels, which resulted in actuation of safety interlocks designed to prevent overpressurisation. These difficulties were alleviated by controlling the microwave power to reduce the reaction temperature and pressure, and also by introducing additional safety valves into the digestion vessels. Using microwave digestion, dissolution times for high fired POX and MOX samples were substantially reduced. Samples which required ca. 10 hours to dissolve by conventional means could be dissolved in ca. 80 minutes by microwave digestion. Whilst a similar performance in terms of plutonium recovery was achieved for some materials by microwave and conventional dissolution, for other materials microwave dissolution gave higher plutonium recoveries but with poorer precision. This suggests the possible presence of some plutonium oxide within high-fired materials which is more difficult to dissolve than the bulk, and which is perhaps dissolved to an additional but variable degree by the current microwave dissolution procedure. Microwave dissolution has been demonstrated to increase the speed of dissolution of high-fired POX and MOX materials, compared with conventional dissolution. However, the technique has not yet proved satisfactory for the complete dissolution of all high-fired materials tested because of

Dissolution of anodic zirconium dioxide films in aqueous media

International Nuclear Information System (INIS)

Merati, A.; Cox, B.

1999-01-01

Zirconium with a low thermal neutron cross section, good corrosion resistance in high-temperature water, and high thermal conductivity is an ideal material for nuclear reactors. Its good resistance to water and steam at reactor temperatures is of the greatest interest to nuclear fuel designers. Dissolution of zirconium dioxide (ZrO 2 ) films in aggressive media was investigated. The extent of uniform and localized dissolution was measured by ultraviolet-visible (UV-VIS) spectrometry and an alternating current (AC) impedance test, respectively. Scanning electron microscopy (SEM) showed the extent of dissolution of ZrO 2 was a function only of the fluoride ion content and pH of the medium. Cathodic polarization was used to identify the preferred sites for localized dissolution of the oxide film. In 0.1 M potassium bifluoride (KHF 2 ), both uniform thinning and local breakdown of the oxide were observed. Within the limits of the investigating techniques, no evidence of dissolution was observed in the other solutions tested: 0.5 M sulfuric acid (H 2 SO 4 ). 1.0 M nitric acid (HNO 3 ), 5 M hydrochloric acid (HCl), or 0.1 M potassium fluoride (KF). In areas around iron-containing particles, fine cracks in the anodic oxide at prior metal grain boundaries and arrays of cracks in the oxide associated with residual scratches from the initial specimen preparation were the preferred spots for localized dissolution of the oxide film. Iron precipitates immediately below the surface of the oxide layer increased the local electrical conductivity. Enrichment of iron in the oxide matrix around these precipitates during the anodization process appeared to cause prospective spots, acting as anodic sites for pH formation

Unravelling the relationship between degree of disorder and the dissolution behavior of milled glibenclamide

DEFF Research Database (Denmark)

Mah, Pei T; Laaksonen, Timo; Rades, Thomas

2014-01-01

Milling is an attractive method to prepare amorphous formulations as it does not require the use of solvents and is suitable for thermolabile drugs. One of the key critical quality attributes of milled amorphous formulations is their dissolution behavior. However, there are limited studies...... that have investigated the relationship between degree of disorder induced by milling and dissolution behavior. The main aim of this study was to identify the analytical technique used to characterize degree of disorder that correlates best with the recrystallization behavior during dissolution of milled...... glibenclamide samples. Solid state and surface changes during dissolution of milled glibenclamide samples were monitored in order to elucidate the processes that influence the dissolution behavior of milled glibenclamide samples. Glibenclamide was ball milled for different durations and analyzed using X...

Development of Dissolution Test Method for Drotaverine ...

African Journals Online (AJOL)

Development of Dissolution Test Method for Drotaverine ... Methods: Sink conditions, drug stability and specificity in different dissolution media were tested to optimize a dissolution test .... test by Prism 4.0 software, and differences between ...

Mechanistic Basis of Cocrystal Dissolution Advantage.

Science.gov (United States)

Cao, Fengjuan; Amidon, Gordon L; Rodríguez-Hornedo, Naír; Amidon, Gregory E

2018-01-01

Current interest in cocrystal development resides in the advantages that the cocrystal may have in solubility and dissolution compared with the parent drug. This work provides a mechanistic analysis and comparison of the dissolution behavior of carbamazepine (CBZ) and its 2 cocrystals, carbamazepine-saccharin (CBZ-SAC) and carbamazepine-salicylic acid (CBZ-SLC) under the influence of pH and micellar solubilization. A simple mathematical equation is derived based on the mass transport analyses to describe the dissolution advantage of cocrystals. The dissolution advantage is the ratio of the cocrystal flux to drug flux and is defined as the solubility advantage (cocrystal to drug solubility ratio) times the diffusivity advantage (cocrystal to drug diffusivity ratio). In this work, the effective diffusivity of CBZ in the presence of surfactant was determined to be different and less than those of the cocrystals. The higher effective diffusivity of drug from the dissolved cocrystals, the diffusivity advantage, can impart a dissolution advantage to cocrystals with lower solubility than the parent drug while still maintaining thermodynamic stability. Dissolution conditions where cocrystals can display both thermodynamic stability and a dissolution advantage can be obtained from the mass transport models, and this information is useful for both cocrystal selection and formulation development. Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Dissolution flowsheet for high flux isotope reactor fuel

Energy Technology Data Exchange (ETDEWEB)

Foster, T. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2016-09-27

As part of the Spent Nuclear Fuel (SNF) processing campaign, H-Canyon is planning to begin dissolving High Flux Isotope Reactor (HFIR) fuel in late FY17 or early FY18. Each HFIR fuel core contains inner and outer fuel elements which were fabricated from uranium oxide (U₃O₈) dispersed in a continuous Al phase using traditional powder metallurgy techniques. Fuels fabricated in this manner, like other SNF’s processed in H-Canyon, dissolve by the same general mechanisms with similar gas generation rates and the production of H₂. The HFIR fuel cores will be dissolved and the recovered U will be down-blended into low-enriched U. HFIR fuel was previously processed in H-Canyon using a unique insert in both the 6.1D and 6.4D dissolvers. Multiple cores will be charged to the same dissolver solution maximizing the concentration of dissolved Al. The objective of this study was to identify flowsheet conditions through literature review and laboratory experimentation to safely and efficiently dissolve the HFIR fuel in H-Canyon. Laboratory-scale experiments were performed to evaluate the dissolution of HFIR fuel using both Al 1100 and Al 6061 T6 alloy coupons. The Al 1100 alloy was considered a representative surrogate which provided an upper bound on the generation of flammable (i.e., H₂) gas during the dissolution process. The dissolution of the Al 6061 T6 alloy proceeded at a slower rate than the Al 1100 alloy and was used to verify that the target Al concentration in solution could be achieved for the selected Hg concentration. Mass spectrometry and Raman spectroscopy were used to provide continuous monitoring of the concentration of H₂ and other permanent gases in the dissolution offgas allowing the development of H₂ generation rate profiles. The H₂ generation rates were subsequently used to evaluate if a full HFIR core could be dissolved in an H-Canyon dissolver without exceeding 60% of the

Preparation of iron metal nano solution by anodic dissolution with high voltage

International Nuclear Information System (INIS)

Nguyen Duc Hung; Do Thanh Tuan

2012-01-01

Iron nano metal solution is prepared from anodic dissolution process with ultra- high Dc voltage. The size and shape of iron nanoparticles determined by Tem images and particle size distribution on the device LA-950 Laser Scattering Particle Distribution Analyzer V2. The concentration of nano-iron solution was determined by the analytical methods AAS atomic absorption spectrometry and Faraday's law. The difference in concentration of both methods demonstrated outside the anodic dissolution process has created the water electrolysis to form H 2 and O 2 gases and heating the solution. (author)

In Vitro-In Vivo Predictive Dissolution-Permeation-Absorption Dynamics of Highly Permeable Drug Extended-Release Tablets via Drug Dissolution/Absorption Simulating System and pH Alteration.

Science.gov (United States)

Li, Zi-Qiang; Tian, Shuang; Gu, Hui; Wu, Zeng-Guang; Nyagblordzro, Makafui; Feng, Guo; He, Xin

2018-05-01

Each of dissolution and permeation may be a rate-limiting factor in the absorption of oral drug delivery. But the current dissolution test rarely took into consideration of the permeation property. Drug dissolution/absorption simulating system (DDASS) valuably gave an insight into the combination of drug dissolution and permeation processes happening in human gastrointestinal tract. The simulated gastric/intestinal fluid of DDASS was improved in this study to realize the influence of dynamic pH change on the complete oral dosage form. To assess the effectiveness of DDASS, six high-permeability drugs were chosen as model drugs, including theophylline (pK a1  = 3.50, pK a2  = 8.60), diclofenac (pK a  = 4.15), isosorbide 5-mononitrate (pK a  = 7.00), sinomenine (pK a  = 7.98), alfuzosin (pK a  = 8.13), and metoprolol (pK a  = 9.70). A general elution and permeation relationship of their commercially available extended-release tablets was assessed as well as the relationship between the cumulative permeation and the apparent permeability. The correlations between DDASS elution and USP apparatus 2 (USP2) dissolution and also between DDASS permeation and beagle dog absorption were developed to estimate the predictability of DDASS. As a result, the common elution-dissolution relationship was established regardless of some variance in the characteristic behavior between DDASS and USP2 for drugs dependent on the pH for dissolution. Level A in vitro-in vivo correlation between DDASS permeation and dog absorption was developed for drugs with different pKa. The improved DDASS will be a promising tool to provide a screening method on the predictive dissolution-permeation-absorption dynamics of solid drug dosage forms in the early-phase formulation development.

Chemoinformetrical evaluation of dissolution property of indomethacin tablets by near-infrared spectroscopy.

Science.gov (United States)

Otsuka, Makoto; Tanabe, Hideaki; Osaki, Kazuo; Otsuka, Kuniko; Ozaki, Yukihiro

2007-04-01

The purpose of this study was to use near-infrared spectrometry (NIR) with chemoinformetrics to predict the change of dissolution properties in indomethacin (IMC) tablets during the manufacturing process. A comparative evaluation of the dissolution properties of the tablets was performed by the diffused reflectance (DRNIR) and transmittance (TNIR) NIR spectroscopic methods. Various kinds of IMC tablets (200 mg) were obtained from a powder (20 mg of IMC, 18 mg of microcrystalline cellulose, 160 mg of lactose, and 2 mg of magnesium stearate) under various compression pressures (60-398 MPa). Dissolution tests were performed in phosphate buffer, and the time required for 75% dissolution (T75) and mean dissolution time (MDT) were calculated. DRNIR and TNIR spectra were recorded, and the both NIR spectra used to establish a calibration model for predicting the dissolution properties by principal component regression analysis (PCR). The T75 and MDT increased as the compression pressure increased, since tablet porosity decreased with increasing pressure. Intensity of the DRNIR spectra of the compressed tablets decreased as the compression pressure increased. However, the intensity of TNIR spectra increased along with the pressure. The calibration models used to evaluate the dissolution properties of tablets were established by using PCR based on both DRNIR and TNIR spectra of the tablets. The multiple correlation coefficients of the relationship between the actual and predictive T75 by the DRNIR and TNIR methods were 0.831 and 0.962, respectively. It is possible to predict the dissolution properties of pharmaceutical preparations using both DRNIR and TNIR chemoinformetric methods. The TNIR method was more accurate for predictions of the dissolution behavior of tablets than the DRNIR method. (c) 2007 Wiley-Liss, Inc.

FY 2000 Saltcake Dissolution and Feed Stability Workshop

International Nuclear Information System (INIS)

Hunt, R.D.; McGinnis, C.P.; Weber, C.F.; Welch, T.D.; Jewett, J.R.

2000-01-01

The Tanks Focus Area (TFA) continues to work closely with the Office of River Protection (ORP) to better understand the chemistry involved with the retrieval, transport, and pretreatment of nuclear wastes at Hanford. Since a private contractor is currently responsible for the pretreatment and immobilization activities in this remediation effort, the TFA has concentrated on saltcake dissolution and waste transport at the request of the ORP. Researchers at Hanford have performed a series of dissolution experiments on actual saltcake samples. Staff members at Mississippi State University (MSU) continue to model the dissolution results with the Environmental Simulation Program (ESP), which is used extensively by ORP personnel. Several ways to improve the predictive capabilities of the ESP were identified. Since several transfer lines at Hanford have become plugged, TFA tasks at AEA Technologies, Florida International University (FIU), MSU, and Oak Ridge National Laboratory (ORNL) are investigating the behavior of the supernatants and slurries during transport. A combination of experimental and theoretical techniques is used to study the transport chemistry. This effort is expected to develop process control tools for waste transfer. The results from these TFA tasks were presented to ORP personnel during the FY 2000 Saltcake Dissolution and Feed Stability Workshop, which was held on May 16-17 in Richland, Washington. The minutes from this workshop are provided in this report

In vitro dissolution methodology, mini-Gastrointestinal Simulator (mGIS), predicts better in vivo dissolution of a weak base drug, dasatinib.

Science.gov (United States)

Tsume, Yasuhiro; Takeuchi, Susumu; Matsui, Kazuki; Amidon, Gregory E; Amidon, Gordon L

2015-08-30

USP apparatus I and II are gold standard methodologies for determining the in vitro dissolution profiles of test drugs. However, it is difficult to use in vitro dissolution results to predict in vivo dissolution, particularly the pH-dependent solubility of weak acid and base drugs, because the USP apparatus contains one vessel with a fixed pH for the test drug, limiting insight into in vivo drug dissolution of weak acid and weak base drugs. This discrepancy underscores the need to develop new in vitro dissolution methodology that better predicts in vivo response to assure the therapeutic efficacy and safety of oral drug products. Thus, the development of the in vivo predictive dissolution (IPD) methodology is necessitated. The major goals of in vitro dissolution are to ensure the performance of oral drug products and the support of drug formulation design, including bioequivalence (BE). Orally administered anticancer drugs, such as dasatinib and erlotinib (tyrosine kinase inhibitors), are used to treat various types of cancer. These drugs are weak bases that exhibit pH-dependent and high solubility in the acidic stomach and low solubility in the small intestine (>pH 6.0). Therefore, these drugs supersaturate and/or precipitate when they move from the stomach to the small intestine. Also of importance, gastric acidity for cancer patients may be altered with aging (reduction of gastric fluid secretion) and/or co-administration of acid-reducing agents. These may result in changes to the dissolution profiles of weak base and the reduction of drug absorption and efficacy. In vitro dissolution methodologies that assess the impact of these physiological changes in the GI condition are expected to better predict in vivo dissolution of oral medications for patients and, hence, better assess efficacy, toxicity and safety concerns. The objective of this present study is to determine the initial conditions for a mini-Gastrointestinal Simulator (mGIS) to assess in vivo

Friendship Dissolution Within Social Networks Modeled Through Multilevel Event History Analysis

Science.gov (United States)

Dean, Danielle O.; Bauer, Daniel J.; Prinstein, Mitchell J.

2018-01-01

A social network perspective can bring important insight into the processes that shape human behavior. Longitudinal social network data, measuring relations between individuals over time, has become increasingly common—as have the methods available to analyze such data. A friendship duration model utilizing discrete-time multilevel survival analysis with a multiple membership random effect structure is developed and applied here to study the processes leading to undirected friendship dissolution within a larger social network. While the modeling framework is introduced in terms of understanding friendship dissolution, it can be used to understand microlevel dynamics of a social network more generally. These models can be fit with standard generalized linear mixed-model software, after transforming the data to a pair-period data set. An empirical example highlights how the model can be applied to understand the processes leading to friendship dissolution between high school students, and a simulation study is used to test the use of the modeling framework under representative conditions that would be found in social network data. Advantages of the modeling framework are highlighted, and potential limitations and future directions are discussed. PMID:28463022

Evaporite dissolution relevant to the WIPP site, northern Delaware Basin, southeastern New Mexico

International Nuclear Information System (INIS)

Lambert, S.J.

1982-01-01

Evaluation of the threat of natural dissolution of host evaporites to the integrity of the Waste Isolation Pilot Plant (WIPP) in southeastern New Mexico has taken into consideration (1) the volume of missing rock salt, (2) the occurrence (or not) of characteristic dissolution brines, (3) geomorphic features, some of which are unrelated to dissolution, and (4) the time intervals over which dissolution may have been active. Even under the assumption that all missing halite was originally present and has been removed by dissolution, there is no evidence of active preferential removal of the lower Salado Formation halite by any geologically reasonable process. The geologic record contains evidence of dissolution in the Triassic and Jurassic; to constrain all removal of basinal halite to the late Cenozoic yields an unrealistically high rate of removal. Application to the lower Salado of a stratabound mechanism known to be active in Nash Draw, a near-surface feature within the Basin, allows a minimum survival time of 2,500,000 years to be predicted for the subsurface facility for storage of radioactive waste at WIPP. This calculation is based on an analysis of all known dissolution features in the Delaware Basin, and takes into account the wetter (pluvial) climate during the past 600,000 years. 2 figures, 1 table

Enhanced dissolution of TCE in NAPL by TCE-degrading bacteria in wetland soils

International Nuclear Information System (INIS)

Lee, Sangjin

2007-01-01

The influence of trichloroethene (TCE) dechlorinating mixed cultures in dissolution of TCE in nonaqueous phase liquid (NAPL) via biodegradation was observed. Experiments were conducted in batch reactor system with and without marsh soils under 10 and 20 deg. C for 2 months. The dissolution phenomenon in biotic reactors containing mixed cultures was showed temporal increases compared to abiotic reactors treated with biocide. Effective NAPL-water transfer rate (K m ) calculated in this study showed more than four times higher in biotic reactors than that in abiotic reactors. The results might be attributed to the biologically enhanced dissolution process via dechlorination in reactors. Temperature would be a factor to determine the dissolution rate by controlling bacterial activity. The TCE dechlorination occurred even in an interface of TCE-NAPL that demonstrated no previous TCE biodegradation, suggesting that microbes may be useful in developing source-zone bioremediation system. In conclusion, dechlorinating mixed culture could enhance dissolution in NAPL that may be useful in the application of source zone bioremediation

Description of the Material Balance Model and Spreadsheet for Salt Dissolution

International Nuclear Information System (INIS)

Wiersma, B.J.

1994-01-01

The model employed to estimate the amount of inhibitors necessary for bearing water and dissolution water during the salt dissolution process is described. This model was inputed on a spreadsheet which allowed many different case studies to be performed. This memo describes the assumptions and equations which are used in the model, and documents the input and output cells of the spreadsheet. Two case studies are shown as examples of how the model may be employed

Dissolution-recrystallization method for high efficiency perovskite solar cells

Energy Technology Data Exchange (ETDEWEB)

Han, Fei; Luo, Junsheng; Wan, Zhongquan; Liu, Xingzhao; Jia, Chunyang, E-mail: cyjia@uestc.edu.cn

2017-06-30

Highlights: • Dissolution-recrystallization method can improve perovskite crystallization. • Dissolution-recrystallization method can improve TiO{sub 2}/perovskite interface. • The optimal perovskite solar cell obtains the champion PCE of 16.76%. • The optimal devices are of high reproducibility. - Abstract: In this work, a dissolution-recrystallization method (DRM) with chlorobenzene and dimethylsulfoxide treating the perovskite films during the spin-coating process is reported. This is the first time that DRM is used to control perovskite crystallization and improve the device performance. Furthermore, the DRM is good for reducing defects and grain boundaries, improving perovskite crystallization and even improving TiO{sub 2}/perovskite interface. By optimizing, the DRM2-treated perovskite solar cell (PSC) obtains the best photoelectric conversion efficiency (PCE) of 16.76% under AM 1.5 G illumination (100 mW cm{sup −2}) with enhanced J{sub sc} and V{sub oc} compared to CB-treated PSC.

Dissolution rate enhancement of piroxicam by ordered mixing.

Science.gov (United States)

Saharan, Vikas Anand; Choudhury, Pratim Kumar

2012-07-01

Micronized piroxicam was mixed with lactose, mannitol, sorbitol, maltitol and sodium chloride to produce ordered mixture in a glass vial by manual hand shaking method. The effect of excipients, surfactant, superdisintegrant, drug concentration and carrier particle size on dissolution rate was investigated. Dissolution rate studies of the prepared ordered mixtures revealed that all water soluble excipients increased the dissolution rate of piroxicam when compared to the dissolution rate of piroxicam or its suspension. Ordered mixture formulation PLF4, consisting of lactose as water soluble excipient, SSG (8% w/s) and SLS (1% w/w), released piroxcam at a very fast rate so much so that about 90% of the composition had passed into solution within 2 min. The order of the dissolution rate enhancement for ordered mixtures of various water soluble excipients was: lactose > mannitol > maltitol > sorbitol > sodium chloride. Carrier granules of size 355-710 µm were most effective in increasing the dissolution rate of drug from ordered mixtures. Decreasing the carrier particle size reduced drug dissolution from ordered mixtures. The dissolution rate of ordered mixtures consisting of 1-5% w/w piroxicam was superior to dissolution rate of piroxicam suspension. The dissolution data fitting and the resulting regression parameters indicated Hixson Crowell, cube root law, as the best fit to drug release data of ordered mixtures.

Improvement of database on glass dissolution

International Nuclear Information System (INIS)

Hayashi, Maki; Sasamoto, Hiroshi; Yoshikawa, Hideki

2008-03-01

In geological disposal system, high-level radioactive waste (HLW) glass is expected to retain radionuclide for the long term as the first barrier to prevent radionuclide release. The advancement of its performance assessment technology leads to the reliability improvement of the safety assessment of entire geological disposal system. For this purpose, phenomenological studies for improvement of scientific understanding of dissolution/alteration mechanisms, and development of robust dissolution/alteration model based on the study outcomes are indispensable. The database on glass dissolution has been developed for supporting these studies. This report describes improvement of the prototype glass database. Also, this report gives an example of the application of the database for reliability assessment of glass dissolution model. (author)

Dissolution of basaltic glass in seawater: Mechanism and rate

International Nuclear Information System (INIS)

Crovisier, J.L.; Honnorez, J.; Eberhart, J.P.

1987-01-01

Basaltic glasses are considered as natural analogues for nuclear waste glasses. Thermodynamic computer codes used to evaluate long term behavior of both nuclear waste and basaltic glasses require the knowledge of the dissolution mechanism of the glass network. The paper presents the results of a series of experiments designed to study the structure and chemical composition of alteration layers formed on the surface of artificial tholeiitic glass altered in artificial seawater. Experiments were performed at 60 degree C, 1 bar and 350 bars in non-renewed conditions. A natural sample from Palagonia (Sicily) has been studied by electron microscopy and comparison between natural and experimental palagonitic layers is made. The behavior of dissolved silica during experiments, and both the structure and the chemical composition of the palagonitic layers, indicate that they form by precipitation of secondary minerals from solution after a total breakdown of the glassy network, i.e., congruent dissolution of the glass. Hence the dissolution equation necessary for thermodynamic modelling of basaltic glass dissolution in seawater at low temperature must be written as a simple stoichiometric process. These experiments indicate that the transformation of glass to palagonitic material is not isovolumetric. Hence it is preferable to use Fe or Ti as conservative elements for chemical budget calculations

Dissolution of UO2 in redox conditions

International Nuclear Information System (INIS)

Casas, I.; Pablo de, J.; Rovira, M.

1998-01-01

The performance assessment of the final disposal of the spent nuclear fuel in geological formations is strongly dependent on the spent fuel matrix dissolution. Unirradiated uranium (IV) dioxide has shown to be very useful for such purposes. The stability of UO 2 is very dependent on vault redox conditions. At reducing conditions, which are expected in deep groundwaters, the dissolution of the UO 2 -matrix can be explained in terms of solubility, while under oxidizing conditions, the UO 2 is thermodynamically unstable and the dissolution is kinetically controlled. In this report the parameters which affect the uranium solubility under reducing conditions, basically pH and redox potential are discussed. Under oxidizing conditions, UO 2 dissolution rate equations as a function of pH, carbonate concentration and oxidant concentration are reported. Dissolution experiments performed with spent fuel are also reviewed. The experimental equations presented in this work, have been used to model independent dissolution experiments performed with both unirradiated and irradiated UO 2 . (Author)

Calcium Carbonate Dissolution Above the Lysocline: Implications of Copepod Grazing on Coccolithophores

Science.gov (United States)

White, M. M.; Waller, J. D.; Lubelczyk, L.; Drapeau, D.; Bowler, B.; Wyeth, A.; Fields, D.; Balch, W. M.

2016-02-01

Copepod-coccolithophore predator-prey interactions are of great importance because they facilitate the export of particulate inorganic and organic carbon (PIC and POC) from the surface ocean. Coccolith dissolution in acidic copepod guts has been proposed as a possible explanation for the paradox of PIC dissolution above the lysocline, but warrants further investigation. Using a new application of the 14C-microdiffusion technique, we investigated the dissolution of coccoliths in copepod guts. We considered both an estuarine predator-prey model (Acartia tonsa and Pleurochrysis carterae) and an open ocean predator-prey model (Calanus finmarchicus and Emiliania huxleyi). Additionally, we considered the impacts of pCO2 on this process to advance our understanding of the effects of ocean acidification on trophic interactions. In the estuarine predator-prey model, fecal pellets produced immediately after previously-starved copepods grazed on P. carterae had PIC/POC ratios 27-40 % lower than that of the algae, indicating PIC dissolution within the copepod gut, with no impact of pCO2 on this dissolution. Subsequent fecal pellets showed increasing PIC/POC, suggesting that calcite dissolution decreases as the gut fills. The open ocean predator-prey model showed equivocal results, indicating high variability among individual grazing behavior, and therefore no consistent impact of copepod grazing on coccolith dissolution above the lysocline in the open ocean. We will further discuss the effects of fecal pellet PIC/POC ratios on sinking rate.

An integrated system for dissolution studies and magnetic resonance imaging of controlled release, polymer-based dosage forms-a tool for quantitative assessment of hydrogel formation processes.

Science.gov (United States)

Kulinowski, Piotr; Dorozyński, Przemysław; Jachowicz, Renata; Weglarz, Władysław P

2008-11-04

Controlled release (CR) dosage forms are often based on polymeric matrices, e.g., sustained-release tablets and capsules. It is crucial to visualise and quantify processes of the hydrogel formation during the standard dissolution study. A method for imaging of CR, polymer-based dosage forms during dissolution study in vitro is presented. Imaging was performed in a non-invasive way by means of the magnetic resonance imaging (MRI). This study was designed to simulate in vivo conditions regarding temperature, volume, state and composition of dissolution media. Two formulations of hydrodynamically balanced systems (HBS) were chosen as model CR dosage forms. HBS release active substance in stomach while floating on the surface of the gastric content. Time evolutions of the diffusion region, hydrogel formation region and "dry core" region were obtained during a dissolution study of L-dopa as a model drug in two simulated gastric fluids (i.e. in fed and fasted state). This method seems to be a very promising tool for examining properties of new formulations of CR, polymer-based dosage forms or for comparison of generic and originator dosage forms before carrying out bioequivalence studies.

Experimental investigation of the dissolution of fractures. From early stage instability to phase diagram

Science.gov (United States)

Osselin, Florian; Budek, Agnieszka; Cybulski, Olgierd; Kondratiuk, Pawel; Garstecki, Piotr; Szymczak, Piotr

2016-04-01

Dissolution of natural rocks is a fundamental geological process and a key part of landscape formation and weathering processes. Moreover, in current hot topics like Carbon Capture and Storage or Enhanced Oil Recovery, mastering dissolution of the host rock is fundamental for the efficiency and the security of the operation. The basic principles of dissolution are well-known and the theory of the reactive infiltration instability has been extensively studied. However, the experimental aspect has proved very challenging because of the strong dependence of the outcome with pore network, chemical composition, flow rate... In this study we are trying to tackle this issue by using a very simple and efficient device consisting of a chip of pure gypsum inserted between two polycarbonate plates and subjected to a constant flow rate of pure water. Thanks to this device, we are able to control all parameters such as flow rate, fracture aperture, roughness of the walls... but also to observe in situ the progression of the dissolution thanks to the transparency of the polycarbonate which is impossible with 3D rocks. We have been using this experimental set-up to explore and investigate all aspects of the dissolution in a fracture, such as initial instability and phase diagram of different dissolution patterns, and to compare it with theory and simulations, yielding very good agreement and interesting feedbacks on the coupling between flow and chemistry in geological media

Uranium dissolution in hyper-alkaline TMA-OH solutions: Preliminary results

Energy Technology Data Exchange (ETDEWEB)

Cachoir, C.; Salah, S.; Mennecart, T.; Lemmens, K. [Belgian Research Nuclear Centre - SCK-CEN, Boeretang 200, 2400 Mol (Belgium)

2016-07-01

Leaching experiments were performed with depleted UO{sub 2} powders in tetramethylammonium solutions (TMA-OH) at pH 13.5 and 12.5, and at different UO{sub 2} surface area to volume of solution (SA/V) ratio's to determine the solubility and the dissolution kinetics of UO{sub 2} at high pH in absence of cations dominating cementitious waters (Ca, Na, K). The solubility of UO{sub 2} increased from pH 12.5 to 13.5 and by increasing the SA/V ratio up to 100 m{sup -1}. However, no known U secondary-phases were predicted by geochemical calculations to control the measured U-concentrations. We interpreted the UO{sub 2} dissolution process as a 2-step process. For all experiments, we observe a fast initial rate, hydroxo promoted and likely surface controlled. Afterwards the rate is apparently negative at low SA/V over time while it is positive at higher SA/V ratio's. The former is interpreted to be related to a sorption process, while the latter reveals a continuous residual dissolution process. No solubility enhancing effect of U-colloids was observed in the TMA-OH media. However, there is much less uranium colloid formation in TMA-OH tests with low Ca (Na, K) concentration than in previous tests with higher Ca (Na, K) concentrations. This suggests that the colloid formation is promoted by alkali and/or alkali-earth elements.

Modification of NaK (Na and K) dissolution device at the L.E.C.I

International Nuclear Information System (INIS)

Mansard, Bernard; Ducas, Serge; Riviere, Michel

1969-12-01

As three NaK dissolution devices had been operated since 1965 and as irradiation assemblies with a greater capacity (2 to 3 times) are now to be used, the modification of these dissolution devices is addressed. This requires a better control of the dissolution reaction (the NaK + alcohol reaction is highly exothermic and results in an effervescence which requires a greater volume). The objectives are therefore to delay the dissolution, to trigger it, to stop it, to control it at will, and to release heat. The new device is then described with its vessel, its cap, its ball valve, and its two tight sleeves. The operation principle is described, as well as the NaK draining process, and the NaK dissolution. Safety, time saving and raw matter saving issues are finally outlined

Effect of wet and dry cycles on dissolution of relatively insoluble particles containing Pu

International Nuclear Information System (INIS)

Mewhinney, J.A.; Eidson, A.F.; Wong, V.A.

1987-01-01

Dissolution of gross alpha emitter radioactivity from particles composed of mixed uranium and plutonium oxides or of plutonium dioxide continually immersed in solvent typically display at least a two-phase dissolution pattern. Rapid dissolution of a small fraction of the total particulate mass is followed by much slower dissolution for the majority of the particulate mass. In this study, respirable particles of (U, Pu)O 2 and PuO 2 were subjected to dissolution using an alternate wetting and drying cycle. Particles were continuously immersed in solvent for 4 d and then dried in air for 3 d. This cycle was repeated weekly for 7 wk. Four solvents were used to represent a range of potential environmental conditions and a fifth solvent was used for comparison to other continuous immersion studies. In contrast to dissolution studies involving continuous immersion over periods of two or more weeks that exhibit a three-phase dissolution process, the alternate wet-dry cycling resulted in repetition of the first two phases of the dissolution pattern for each cycle. This led to significantly enhanced dissolution of both particulate materials. The enhancement in total dissolution ranged from two to ten times larger during each wet-dry cycle compared to studies involving continuous immersion. The results indicate a potential need to re-evaluate environmental models of actinide element bioavailability for particulate materials released to environments where wet-dry cycling may be routine, i.e. intermittent rainfall in an otherwise arid climate or in stream beds with intermittent flow

Measurement of soluble nuclide dissolution rates from spent fuel

International Nuclear Information System (INIS)

Wilson, C.N.; Gray, W.J.

1990-01-01

Gaining a better understanding of the potential release behavior of water-soluble radionuclides is the focus of new laboratory spent fuel dissolution studies being planned in support of the Yucca Mountain Project. Previous studies have suggested that maximum release rates for actinide nuclides, which account for most of the long-term radioactivity in spent fuel, should be solubility-limited and should not depend on the characteristics or durability of the spent fuel waste form. Maximum actinide concentrations should be sufficiently low to meet the NRC (Nuclear Regulatory Commission) annual release limits. Potential release rates for soluble nuclides such as 99 Tc, 135 Cs, 14 C and 129 I, which account for about 1-2% of the activity in spent fuel at 1,000 years, are less certain and may depend on processes such as oxidation of the fuel in the repository air environment. Dissolution rates for several soluble nuclides have been measured from spent fuel specimens using static and semi-static methods. However, such tests do not provide a direct measurement of fuel matrix dissolution rates that may ultimately control soluble-nuclide release rates. Flow-through tests are being developed as a potential supplemental method for determining the matrix component of soluble-nuclide dissolution. Advantages and disadvantages of both semi-static and flow-through methods are discussed. Tests with fuel specimens representing a range of potential fuel states that may occur in the repository, including oxidized fuel, are proposed. Preliminary results from flow-through tests with unirradiated UO 2 suggesting that matrix dissolution rates are very sensitive to water composition are also presented

Freezing-Enhanced Dissolution of Iron Oxides: Effects of Inorganic Acid Anions.

Science.gov (United States)

Jeong, Daun; Kim, Kitae; Min, Dae Wi; Choi, Wonyong

2015-11-03

Dissolution of iron from mineral dust particles greatly depends upon the type and amount of copresent inorganic anions. In this study, we investigated the roles of sulfate, chloride, nitrate, and perchlorate on the dissolution of maghemite and lepidocrocite in ice under both dark and UV irradiation and compared the results with those of their aqueous counterparts. After 96 h of reaction, the total dissolved iron in ice (pH 3 before freezing) was higher than that in the aqueous phase (pH 3) by 6-28 times and 10-20 times under dark and UV irradiation, respectively. Sulfuric acid was the most efficient in producing labile iron under dark condition, whereas hydrochloric acid induced the most dissolution of the total and ferrous iron in the presence of light. This ice-induced dissolution result was also confirmed with Arizona Test Dust (AZTD). In the freeze-thaw cycling test, the iron oxide samples containing chloride, nitrate, or perchlorate showed a similar extent of total dissolved iron after each cycling while the sulfate-containing sample rapidly lost its dissolution activity with repeating the cycle. This unique phenomenon observed in ice might be related to the freeze concentration of protons, iron oxides, and inorganic anions in the liquid-like ice grain boundary region. These results suggest that the ice-enhanced dissolution of iron oxides can be a potential source of bioavailable iron, and the acid anions critically influence this process.

Diatom species abundance and morphologically-based dissolution proxies in coastal Southern Ocean assemblages

Science.gov (United States)

Warnock, Jonathan P.; Scherer, Reed P.

2015-07-01

Taphonomic processes alter diatom assemblages in sediments, thus potentially negatively impacting paleoclimate records at various rates across space, time, and taxa. However, quantitative taphonomic data is rarely included in diatom-based paleoenvironmental reconstructions and no objective standard exists for comparing diatom dissolution in sediments recovered from marine depositional settings, including the Southern Ocean's opal belt. Furthermore, identifying changes to diatom dissolution through time can provide insight into the efficiency of both upper water column nutrient recycling and the biological pump. This is significant in that reactive metal proxies (e.g. Al, Ti) in the sediments only account for post-depositional dissolution, not the water column where the majority of dissolution occurs. In order to assess the range of variability of responses to dissolution in a typical Southern Ocean diatom community and provide a quantitative guideline for assessing taphonomic variability in diatoms recovered from core material, a sediment trap sample was subjected to controlled, serial dissolution. By evaluating dissolution-induced changes to diatom species' relative abundance, three preservational categories of diatoms have been identified: gracile, intermediate, and robust. The relative abundances of these categories can be used to establish a preservation grade for diatom assemblages. However, changes to the relative abundances of diatom species in sediment samples may reflect taphonomic or ecological factors. In order to address this complication, relative abundance changes have been tied to dissolution-induced morphological change to the areolae of Fragilariopsis curta, a significant sea-ice indicator in Southern Ocean sediments. This correlation allows differentiation between gracile species loss to dissolution versus ecological factors or sediment winnowing. These results mirror a similar morphological dissolution index from a parallel study utilizing

Formalization of the kinetics for autocatalytic dissolutions. Focus on the dissolution of uranium dioxide in nitric medium

International Nuclear Information System (INIS)

Charlier, F.; Canion, D.; Gravinese, A.; Magnaldo, A.; Lalleman, S.; Borda, G.; Schaer, E.

2017-01-01

Uranium dioxide dissolution in nitric acid is a complex reaction. On the one hand, the dissolution produces nitrous oxides (NOX), which makes it a triphasic reaction. On the other hand, one of the products accelerates the kinetic rate; the reaction is hence called autocatalytic.The kinetics for these kinds of reactions need to be formalized in order to optimize and design innovative dissolution reactors. In this work, the kinetics rates have been measured by optical microscopy using a single particle approach. The advantages of this analytical technique are an easier management of species transport in solution and a precise following of the dissolution rate. The global rate is well described by a mechanism considering two steps: a non-catalyzed reaction, where the catalyst concentration has no influence on the dissolution rate, and a catalyzed reaction. The mass transfer rate of the catalyst was quantified in order to discriminate when the reaction was influenced by catalyst accumulated in the boundary layer or uncatalyzed. This first approximation described well the sigmoid dissolution curve profile. Moreover, experiments showed that solutions filled with catalyst proved to lose reactivity over time. Results pointed out that the higher the liquid-gas exchanges, the faster the kinetic rate decreases with time. Thus, it was demonstrated, for the first time, that there is a link between catalyst and nitrous oxides. The outcome of this study leads to new ways for improving the design of dissolvers. Gas-liquid exchanges are indeed a lever to impact dissolution rates. Temperature and catalyst concentration can be optimized to reduce residence times in dissolvers. (authors)

Novel designs of continuous process for dissolution of irradiated nuclear fuels

International Nuclear Information System (INIS)

Rance, P.J.W.; Tinsley, T.P.; Polyakov, A.S.; Raginsky, L.S.; Morkovnikov, V.E.; Morozov, N.V.; Eliseev, S.P.

1998-01-01

A novel design of continuous dissolver for the dissolution of irradiated nuclear fuels is described. The development of the dissolver has resulted from a successful collaboration over the last four years between British Nuclear Fuels plc (UK) and the A.A. Bochvar All-Russia Research Institute of Inorganic Materials (Russia). An overview of the development work carried out on three different models is presented, and results from each of these are discussed. The dissolver provides many advantages over current designs of dissolvers. (author)

On-line monitoring of lithium carbonate dissolution

Energy Technology Data Exchange (ETDEWEB)

Sun, Yuzhu; Song, Xingfu; Wang, Jin; Luo, Yan; Yu, Jianguo [National Engineering Research Center for Integrated Utilization Salt Lake Resources, East China University of Science and Technology, Shanghai (China)

2009-11-15

Dissolution of lithium carbonate (Li{sub 2}CO{sub 3}) in aqueous solution was investigated using three on-line apparatuses: the concentration of Li{sub 2}CO{sub 3} was measured by electrical conductivity equipment; CLD (Chord Length Distribution) was monitored by FBRM (Focused Beam Reflectance Measurement); crystal image was observed by PVM (Particle Video Microscope). Results show dissolution rate goes up with a decrease of particle size, and with an increase in temperature; stirring speed causes little impact on dissolution; ultrasound facilitates dissolution obviously. The CLD evolution and crystal images of Li{sub 2}CO{sub 3}powders in stirred fluid were observed detailedly by FBRM and PVM during dissolution. Experimental data were fitted to Avrami model, through which the activation energy was found to be 34.35 kJ/mol. PBE (Population Balance Equation) and moment transform were introduced to calculate dissolution kinetics, obtaining correlation equations of particle size decreasing rate as a function of temperature and undersaturation. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Dissolution of kinetics of nanoscale liquid Pb/Bi inclusions at a grain boundary in aluminium

DEFF Research Database (Denmark)

Prokofjev, Sergei I.; Johnson, Erik; Zhilin, Victor M.

2008-01-01

of the inclusions was observed until their complete disappearance. Digitized video recordings of the process of dissolution were used to obtain the dependence of the inclusion size with time. The kinetics of the dissolution of the grain boundary inclusions can be described with a model where it is assumed...

20(S-Protopanaxadiol Phospholipid Complex: Process Optimization, Characterization, In Vitro Dissolution and Molecular Docking Studies

Directory of Open Access Journals (Sweden)

Yiqiong Pu

2016-10-01

Full Text Available 20(S-Protopanaxadiol (PPD, a bioactive compound extracted from ginseng, possesses cardioprotective, neuroprotective, anti-inflammatory, antiestrogenic, anticancer and anxiolytic effects. However, the clinical application of PPD is limited by its weak aqueous solubility. In this study, we optimized an efficient method of preparing its phospholipid complex (PPD-PLC using a central composite design and response surface analysis. The prepared PPD-PLC was characterized by differential scanning calorimetric, powder X-ray diffraction, Fourier-transformed infrared spectroscopy and nuclear magnetic resonance analyses associated with molecular docking calculation. The equilibrium solubility of PPD-PLC in water and n-octanol increased 6.53- and 1.53-times, respectively. Afterwards, using PPD-PLC as the intermediate, the PPD-PLC-loaded dry suspension (PPD-PLC-SU was prepared with our previous method. In vitro evaluations were conducted on PPD-PLC and PPD-PLC-SU, including dissolution behaviors and stability properties under different conditions. Results of in vitro dissolution behavior revealed the improved dissolution extents and rates of PPD-PLC and PPD-PLC-SU (p < 0.05. Results of the formulation stability investigation also exposed the better stability of PPD-PLC-SU compared with free PPD. Therefore, phospholipid complex technology is a useful formulation strategy for BCS II drugs, as it could effectively improve their hydrophilicity and lipophilicity.

[Comparison in dissolution behavior of ethical and over-the counter scopolamine butylbromide].

Science.gov (United States)

Suzuki, Ichie; Miyazaki, Yasunori; Uchino, Tomonobu; Kagawa, Yoshiyuki

2011-01-01

Marketing authorization holders do not disclose any information on the pharmaceutical properties of over-the-counter drugs (OTC). When a drug is switched from a prescription drug to OTC, pharmacists can acquire that information from the corresponding ethical drug (ED) through the package insert, interview form, and so on. However, the pharmaceutical equivalence between ED and OTC is unclear. In this study, we examined the drug dissolution behavior of both ED and OTCs containing scopolamine butylbromide. Dissolution tests were performed by the paddle method using Japanese Pharmacopeia (JP) XV test fluids at pH 1.2, 4.0 and 6.8 and water based on the guidelines for bioequivalence studies of generic products. The dissolution profiles of OTCs differed significantly from ED showing a similarity factor (f2) value ranging from 8.9 to 42.9. Time until 85% dissolution ranged from 23 to 95 min and from 17 to 174 min at pH 1.2 and pH 6.8, respectively. Then JP XV disintegration tests were conducted to investigate differences in the disintegration process. The disintegration time of preparations showing delayed dissolution was prolonged compared to that of others, suggesting that the disintegration of the tablet or capsule is one of the important factors affecting the drug dissolution. These differences in the disintegration and drug dissolution might cause differences in the bioavailability of the drug. For patient safety, more detailed product information of OTCs should be supplied by the manufacturer, and not be assumed from that of corresponding ED.

Peroxide formation and kinetics of sodium dissolution in alcohols

International Nuclear Information System (INIS)

Muralidaran, P.; Chandran, K.; Ganesan, V.; Periaswami, G.

1997-01-01

Suitable techniques for sodium removal and decontamination of sodium wetted components of Liquid Metal Fast Reactors (LMFRs) are necessary both for repair, reuse and decommissioning of such components. Among the methods followed for sodium removal, alcohol dissolution is usually employed for small components like bellow sealed valves, gripping tools to handle core components and sodium sampling devices (primary and secondary). One of the concerns in the alcohol dissolution method is the possible role of peroxide formation in the ethoxy group during storage and handling leading to explosion. This paper describes the study of peroxide formation in ethyl carbitol and butyl cellosolve as well as some of the results of dissolution kinetic studies carried out in our laboratory using different alcohols. The peroxide formation of ethyl carbitol and butyl cellosolve were studied by iodometric technique. It has been found that the peroxide formation is less in sodium containing alcohol than in pure one. Ethyl carbitol, butyl cellosolve and Jaysol-SS (mixture of ethyl alcohol, methyl alcohol, isopropyl alcohol and methyl isobutyl ketone) were used in dissolution kinetics studies. The effects due to area and orientation of the fresh sodium surface have also been investigated. The reaction rates were studied in the temperature range of 303-343 K. The rate of dissolution was estimated by measuring the sodium content of alcohol at periodic intervals. It is found that the reaction rate varies in the order of ethyl alcohol-water mixture > Jaysol-SS > butyl cellosolve > ethyl carbitol. While cleaning sodium using alcohol, the concentration of alcohol is held essentially constant throughout the process. The rate of reaction depends only on the amount of sodium and follows pseudo-first order kinetics. Increase in surface area has a marked impact on the dissolution rate at lower temperatures while at higher temperatures, the temperature factor overrides the effect due to surface area

On the Impact of the Fuel Dissolution Rate Upon Near-Field Releases From Nuclear Waste Disposal

Directory of Open Access Journals (Sweden)

A Pereira

2016-09-01

Full Text Available Calculations of the impact of the dissolution of spent nuclear fuel on the release from a damaged canister in a KBS-3 repository are presented. The dissolution of the fuel matrix is a complex process and the dissolution rate is known to be one of the most important parameters in performance assessment models of the near-field of a geological repository. A variability study has been made to estimate the uncertainties associated with the process of fuel dissolution. The model considered in this work is a 3D model of a KBS-3 copper canister. The nuclide used in the calculations is Cs-135. Our results confirm that the fuel degradation rate is an important parameter, however there are considerable uncertainties associated with the data and the conceptual models. Consequently, in the interests of safety one should reduce, as far as possible, the uncertainties coupled to fuel degradation.

The kinetics of Dissolution of Biologically Formed Calcific Deposits.

Science.gov (United States)

Rokidi, Stamatia; Koutsoukos, Petros

2015-04-01

The calcification of aortic valves results in the formation of non stoichiometric apatitic deposits which may have serious health implications because of the fact that these minerals adhere tenaciously on tissues like heart valves and arteries causing permanent damage which is partly due to their low solubility. In the present work, calcium phosphate biominerals were extracted from clinically removed tissues and were characterized with respect to their mineralogical constituents and other properties including morphology, specific surface area analyses and thermogravimetric analysis. In all cases, the biominerals may be described as non stoichiometric apatitic materials, although traces of the precursor phase of octacalcium phosphate (Ca8H2(PO4)6•5H2O, OCP) were identified on the basis of their morphological examination. The kinetics of dissolution of the biomineral deposits was investigated in solutions undersaturated with respect to hydroxyapatite (Ca5(PO4)3OH, HAP) at conditions of constant undersaturation at pH 7.40, 37°C, 0.15M NaCl. Synthetic stoichiometric HAP was used as the control mineral. The experiments in the present work used solutions prepared from calcium chloride and sodium hydrogen phosphate and the relative undersaturation, σ, was in the range 0.38-0.74 with respect to HAP and 0.49-0.85 with respect to OCP (σ=1 in water). The dissolution process started immediately upon the introduction of an accurately weighted amount of powdered biomineral in the undersaturated solutions homogenized by magnetic stirring. Inert atmosphere was ensured with the bubbling of water vapor saturated nitrogen through the demineralizing solutions. A glass/Ag/AgCl combination electrode was used as a probe to monitor the process and to control the addition of diluent solutions with the stoichiometry of the dissolving mineral. The measurements of the rates of crystal dissolution, showed a parabolic dependence on the relative solution undersaturation for HAP and higher

Predicting dissolution patterns in variable aperture fractures: 1. Development and evaluation of an enhanced depth-averaged computational model

Energy Technology Data Exchange (ETDEWEB)

Detwiler, R L; Rajaram, H

2006-04-21

Water-rock interactions within variable-aperture fractures can lead to dissolution of fracture surfaces and local alteration of fracture apertures, potentially transforming the transport properties of the fracture over time. Because fractures often provide dominant pathways for subsurface flow and transport, developing models that effectively quantify the role of dissolution on changing transport properties over a range of scales is critical to understanding potential impacts of natural and anthropogenic processes. Dissolution of fracture surfaces is controlled by surface-reaction kinetics and transport of reactants and products to and from the fracture surfaces. We present development and evaluation of a depth-averaged model of fracture flow and reactive transport that explicitly calculates local dissolution-induced alterations in fracture apertures. The model incorporates an effective mass transfer relationship that implicitly represents the transition from reaction-limited dissolution to transport-limited dissolution. We evaluate the model through direct comparison to previously reported physical experiments in transparent analog fractures fabricated by mating an inert, transparent rough surface with a smooth single crystal of potassium dihydrogen phosphate (KDP), which allowed direct measurement of fracture aperture during dissolution experiments using well-established light transmission techniques [Detwiler, et al., 2003]. Comparison of experiments and simulations at different flow rates demonstrate the relative impact of the dimensionless Peclet and Damkohler numbers on fracture dissolution and the ability of the computational model to simulate dissolution. Despite some discrepancies in the small-scale details of dissolution patterns, the simulations predict the evolution of large-scale features quite well for the different experimental conditions. This suggests that our depth-averaged approach to simulating fracture dissolution provides a useful approach for

A multiphase interfacial model for the dissolution of spent nuclear fuel

Science.gov (United States)

Jerden, James L.; Frey, Kurt; Ebert, William

2015-07-01

The Fuel Matrix Dissolution Model (FMDM) is an electrochemical reaction/diffusion model for the dissolution of spent uranium oxide fuel. The model was developed to provide radionuclide source terms for use in performance assessment calculations for various types of geologic repositories. It is based on mixed potential theory and consists of a two-phase fuel surface made up of UO2 and a noble metal bearing fission product phase in contact with groundwater. The corrosion potential at the surface of the dissolving fuel is calculated by balancing cathodic and anodic reactions occurring at the solution interfaces with UO2 and NMP surfaces. Dissolved oxygen and hydrogen peroxide generated by radiolysis of the groundwater are the major oxidizing agents that promote fuel dissolution. Several reactions occurring on noble metal alloy surfaces are electrically coupled to the UO2 and can catalyze or inhibit oxidative dissolution of the fuel. The most important of these is the oxidation of hydrogen, which counteracts the effects of oxidants (primarily H2O2 and O2). Inclusion of this reaction greatly decreases the oxidation of U(IV) and slows fuel dissolution significantly. In addition to radiolytic hydrogen, large quantities of hydrogen can be produced by the anoxic corrosion of steel structures within and near the fuel waste package. The model accurately predicts key experimental trends seen in literature data, the most important being the dramatic depression of the fuel dissolution rate by the presence of dissolved hydrogen at even relatively low concentrations (e.g., less than 1 mM). This hydrogen effect counteracts oxidation reactions and can limit fuel degradation to chemical dissolution, which results in radionuclide source term values that are four or five orders of magnitude lower than when oxidative dissolution processes are operative. This paper presents the scientific basis of the model, the approach for modeling used fuel in a disposal system, and preliminary

Use of partial dissolution techniques in geochemical exploration

Science.gov (United States)

Chao, T.T.

1984-01-01

Application of partial dissolution techniques to geochemical exploration has advanced from an early empirical approach to an approach based on sound geochemical principles. This advance assures a prominent future position for the use of these techniques in geochemical exploration for concealed mineral deposits. Partial dissolution techniques are classified as single dissolution or sequential multiple dissolution depending on the number of steps taken in the procedure, or as "nonselective" extraction and as "selective" extraction in terms of the relative specificity of the extraction. The choice of dissolution techniques for use in geochemical exploration is dictated by the geology of the area, the type and degree of weathering, and the expected chemical forms of the ore and of the pathfinding elements. Case histories have illustrated many instances where partial dissolution techniques exhibit advantages over conventional methods of chemical analysis used in geochemical exploration. ?? 1984.

A potentiostatic and galvanostatic study of the selective dissolution of Cd/Pb eutectic alloy

International Nuclear Information System (INIS)

Sokharev, N.P.; Rabdel, A.A.; Zhadanov, V.V.

1986-01-01

The authors consider the selective dissolution (SD) of the electronegative component of a two-phase, eutectic alloy (Cd/Pb) under galvanostatic conditions. Treating this process as the extraction of a solid substance from a porous matrix, the distribution of the concentration of EC ions, c(x, t), can be described by a differential equation (presented). Experimental data are presented in two equations which are applicable for the description of the selective dissolution process of the electronegative component of a eutectic alloy under conditions of concentration polarization

Selection of dissolution process for spent fuels and preparation of corrosion test solution simulated to dissolver (contract research)

International Nuclear Information System (INIS)

Motooka, Takafumi; Terakado, Shogo; Koya, Toshio; Hamada, Shozo; Kiuchi, Kiyoshi

2001-03-01

In order to evaluate the reliability of reprocessing equipment materials used in the Rokkasho Reprocessing Plant, we have proceeded a mock-up test and laboratory tests for getting corrosion parameters. In a dissolver made of zirconium, the simulation of test solutions to the practical solution which includes the high concentration of radioactive elements such as FP and TRU is one of the important issues with respect to the life prediction. On this experiment, the dissolution process of spent fuels and the preparation of test solution for evaluating the corrosion resistance of dissolver materials were selected. These processes were tested in the No.3 cell of WASTEF. The test solution for corrosion tests was prepared by adjusting the uranium and nitric acid concentrations. (author)

Development and Validation of a Dissolution Test Method for ...

African Journals Online (AJOL)

Purpose: To develop and validate a dissolution test method for dissolution release of artemether and lumefantrine from tablets. Methods: A single dissolution method for evaluating the in vitro release of artemether and lumefantrine from tablets was developed and validated. The method comprised of a dissolution medium of ...

Low temperature dissolution flowsheet for plutonium metal

Energy Technology Data Exchange (ETDEWEB)

Daniel, W. E. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Almond, P. M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Rudisill, T. S. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2016-05-01

The H-Canyon flowsheet used to dissolve Pu metal for PuO₂ production utilizes boiling HNO₃. SRNL was requested to develop a complementary dissolution flowsheet at two reduced temperature ranges. The dissolution and H₂ generation rates of Pu metal were investigated using a dissolving solution at ambient temperature (20-30 °C) and for an intermediate temperature of 50-60 °C. Additionally, the testing included an investigation of the dissolution rates and characterization of the off-gas generated from the ambient temperature dissolution of carbon steel cans and the nylon bags that contain the Pu metal when charged to the dissolver.

Dissolution behavior of irradiated mixed oxide fuel with short stroke shearing for fast reactor reprocessing

International Nuclear Information System (INIS)

Ikeuchi, Hirotomo; Sano, Yuichi; Shibata, Atsuhiro; Koizumi, Tsutomu; Washiya, Tadahiro

2013-01-01

An efficient dissolution process was established for future reprocessing in which mixed-oxide (MOX) fuels with high plutonium contents and dissolver solution with high heavy-metal (HM) concentrations (more than 500 g dm -3 ) will be treated. This dissolution process involves short stroke shearing of fuels (∼10 mm in length). The dissolution kinetics of irradiated MOX fuels and the effects of the Pu content, HM concentration, and fuel form on the dissolution rate were investigated. Irradiated fuel was found to dissolve as 10 2 -10 3 times fast as non-irradiated fuel, but the rate decreased with increasing Pu content. Kinetic analysis based on the fragmentation model, which considers the penetration and diffusion of nitric acid through fuel matrices prior to chemical reaction, indicated that the dissolution rate of irradiated fuel was affected not only by the volume ratio of liquid to solid (L/S ratio) but also by the exposed surface area per unit mole of nitric acid (A/m ratio). The penetration rate of nitric acid is expected to be decreased at high HM concentrations by a reduction in the L/S ratio, but enhanced by shearing the fuel pieces with short strokes and thus enlarging the A/m ratio. (author)

The dissolution rate of silicate glasses and minerals: an alternative model based on several activated complexes

International Nuclear Information System (INIS)

Berger, G.

1997-01-01

Most of the mineral reactions in natural water-rock systems progress at conditions close to the chemical equilibrium. The kinetics of these reactions, in particular the dissolution rate of the primary minerals, is a major constrain for the numerical modelling of diagenetic and hydrothermal processes. In the case of silicates, recent experimental studies have pointed out the necessity to better understand the elementary reactions which control the dissolution process. This article presents several models that have been proposed to account for the observed dissolution rate/chemical affinity relationships. The case of glasses (R7T7), feldspars and clays, in water, in near neutral pH aqueous solutions and in acid/basic media, are reviewed. (A.C.)

Evaluation of alkaline dissolution of Al 6061 and Al 1050 for the production of Mo-99 from LEU targets

International Nuclear Information System (INIS)

Mindrisz, Ana C.; Camilo, Ruth L.; Araujo, Izilda C.; Forbicini, Christina A.L.G. de O.

2013-01-01

Since 2008, due to the global crisis in the production of radioisotope 99 Mo, which product of decay, 99m Tc, is the tracer element most often used in nuclear medicine and accounts for about 80% of all diagnostic procedures in vivo. Studies on the alkaline dissolution to obtain 9 9M o from irradiated UAl x -Al LEU targets are under development. Processing time should be minimized, considering the short half-life of 99 Mo and 99m Tc, about 66 h and 6 h, respectively. This makes dissolution time a significant factor in the development of the process. This paper presents the results of alkaline dissolution of 'scraps' of Al 6061 and 1050, used to simulate the dissolution process of UAl x -Al targets. Dissolution time and gas releasing were evaluated using the following alkaline solutions: a) NaOH 3 mol.L -1 and NaNO 3 2 mol.L -1 , b) NaOH 3 mol.L -1 and NaNO 3 4 mol.L -1 . The initial temperature of dissolution was 85 deg C in all cases. Al 6061 showed values of dissolution time greater than that for Al 1050, 25% for NaNO 3 2 mol.L -1 and 104.55% for NaNO 3 4 mol.L -1 . The dissolution with NaNO 3 2 mol.L -1 showed that the gas releasing for Al 6061 was 2.7% greater than for Al 1050. However Al 1050 showed that gas releasing 9.92% greater than for Al 6061 during the dissolution with NaNO 3 4 mol.L -1 . The decision about what type of alloy has to be used, Al 1050 or Al 6061, it will be upto the group that will manufacture the targets for the RMB. (author)

Physical heterogeneity control on effective mineral dissolution rates

Science.gov (United States)

Jung, Heewon; Navarre-Sitchler, Alexis

2018-04-01

Hydrologic heterogeneity may be an important factor contributing to the discrepancy in laboratory and field measured dissolution rates, but the governing factors influencing mineral dissolution rates among various representations of physical heterogeneity remain poorly understood. Here, we present multiple reactive transport simulations of anorthite dissolution in 2D latticed random permeability fields and link the information from local grid scale (1 cm or 4 m) dissolution rates to domain-scale (1m or 400 m) effective dissolution rates measured by the flux-weighted average of an ensemble of flow paths. We compare results of homogeneous models to heterogeneous models with different structure and layered permeability distributions within the model domain. Chemistry is simplified to a single dissolving primary mineral (anorthite) distributed homogeneously throughout the domain and a single secondary mineral (kaolinite) that is allowed to dissolve or precipitate. Results show that increasing size in correlation structure (i.e. long integral scales) and high variance in permeability distribution are two important factors inducing a reduction in effective mineral dissolution rates compared to homogeneous permeability domains. Larger correlation structures produce larger zones of low permeability where diffusion is an important transport mechanism. Due to the increased residence time under slow diffusive transport, the saturation state of a solute with respect to a reacting mineral approaches equilibrium and reduces the reaction rate. High variance in permeability distribution favorably develops large low permeability zones that intensifies the reduction in mixing and effective dissolution rate. However, the degree of reduction in effective dissolution rate observed in 1 m × 1 m domains is too small (equilibrium conditions reduce the effective dissolution rate by increasing the saturation state. However, in large domains where less- or non-reactive zones develop, higher

Transient refractory material dissolution by a volumetrically-heated melt

Energy Technology Data Exchange (ETDEWEB)

Seiler, Jean Marie, E-mail: jean-marie.seiler@cea.fr [CEA, DEN, DTN, 17 Rue des Martyrs, 38054 Grenoble Cedex 9 (France); Ratel, Gilles [CEA, DEN, DTN, 17 Rue des Martyrs, 38054 Grenoble Cedex 9 (France); Combeau, Hervé [Institut Jean Lamour, UMR 7198, Lorraine University, Ecole des Mines de Nancy, Parc de Saurupt, 54042 Nancy Cedex (France); Gaus-Liu, Xiaoyang; Kretzschmar, Frank; Miassoedov, Alexei [Karlsruhe Institut of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

2014-12-15

, the liquid composition at the interface is concentrated in the refractory species. During the transient, the interface temperature is equal to the liquidus temperature corresponding to the local and instantaneous composition of the liquid at the interface. Regarding the design of a protective layer made of refractory materials, we can answer the question of how much ceramic can be dissolved and its impact on melt temperature evolution during the dissolution process. It also impacts on subsequent corium solidification since the additional mass of dissolved ceramic leads to increased volume of the molten material, significantly increasing the time required for complete solidification. For the long term, ceramic material does not offer better confinement than a crust made of solidified corium. This work served as support to a generalisation of the model of transient evolution of interface temperature in various severe accident situations (Seiler and Combeau, 2014)

An evaluation of the dissolution process of natural uranium ore as an analogue of nuclear fuel

International Nuclear Information System (INIS)

Stern, V.H.

1991-08-01

The assumption of congruent dissolution of uraninite as a mechanism for the dissolution behaviour of spent fuel was critically examined with regard to the fate of toxic radionuclides. The fission and daughter products of uranium are typically present in spent unreprocessed fuel rods in trace abundances. The principles of trace element geochemistry were applied in assessing the behaviour of these radionuclides during fluid/solid interactions. It is shown that the behaviour of radionuclides in trace abundances that reside in the crystal structure can be better predicted from the ionic properties of these nuclides rather than from assuming that they are controlled by the dissolution of uraninite. Geochemical evidence from natural uranium ore deposits (Athabasca Basin, Northern Territories of Australia, Oklo) suggests that in most cases the toxic radionuclides are released from uraninite in amounts that are independent of the solution behaviour of uranium oxide. Only those elements that have ionic and thus chemical properties similar to U 4+ , such as plutonium, americium, cadmium, neptunium and thorium can be satisfactorily modelled by the solution properties of uranium dioxide and then only if the environment is reducing. (84 refs., 7 tabs.)

Predicting long-term risk for relationship dissolution using nonparametric conditional survival trees.

Science.gov (United States)

Kliem, Sören; Weusthoff, Sarah; Hahlweg, Kurt; Baucom, Katherine J W; Baucom, Brian R

2015-12-01

Identifying risk factors for divorce or separation is an important step in the prevention of negative individual outcomes and societal costs associated with relationship dissolution. Programs that aim to prevent relationship distress and dissolution typically focus on changing processes that occur during couple conflict, although the predictive ability of conflict-specific variables has not been examined in the context of other factors related to relationship dissolution. The authors examine whether emotional responding and communication during couple conflict predict relationship dissolution after controlling for overall relationship quality and individual well-being. Using nonparametric conditional survival trees, the study at hand simultaneously examined the predictive abilities of physiological (systolic and diastolic blood pressure, heart rate, cortisol) and behavioral (fundamental frequency; f0) indices of emotional responding, as well as observationally coded positive and negative communication behavior, on long-term relationship stability after controlling for relationship satisfaction and symptoms of depression. One hundred thirty-six spouses were assessed after participating in a randomized clinical trial of a relationship distress prevention program as well as 11 years thereafter; 32.5% of the couples' relationships had dissolved by follow up. For men, the only significant predictor of relationship dissolution was cortisol change score (p = .012). For women, only f0 range was a significant predictor of relationship dissolution (p = .034). These findings highlight the importance of emotional responding during couple conflict for long-term relationship stability. (c) 2015 APA, all rights reserved).

Dissolution of Platinum in Hydrochloric Acid Under Industrial-Scale Alternating Current Polarization

Science.gov (United States)

Myrzabekov, B. E.; Bayeshov, A. B.; Makhanbetov, A. B.; Mishra, B.; Baigenzhenov, O. S.

2018-02-01

The electrochemical behavior of platinum in a hydrochloric acid solution under polarization by an industrial-scale alternating current has been investigated. For the electrical dissolution of platinum, titanium is used as an auxiliary electrode, which increases the yield of platinum dissolution by 12.5 pct. The influence of the concentration of hydrochloric acid, the current densities of the platinum and titanium electrodes, and the temperature of the electrolyte on the efficiency of the process of dissolving platinum have all been studied.

Simfuel dissolution studies in granitic groundwater

International Nuclear Information System (INIS)

Casas, I.; Caceci, M.S.; Bruno, J.; Sandino, A.; Ollila, K.

1991-09-01

The dissolution behavior of an unirradiated chemical analogue of spent nuclear fuel (SIMFUEL) has been studied in the presence of two different synthetic groundwater at 25 deg C and under both oxic and anoxic conditions. The release of U, Mo, Ba, Y and Sr was monitored during static (batch) leaching experiments of long duration (about 250 days). Preliminary results from continuous flow-through reactor experiments are also reported. The results obtained indicate the usefulness and limitations of SIMFUEL in the study of the kinetics and mechanism of dissolution of the minor components of spent nuclear fuel. Molybdenum, barium and strontium have shown a trend to congruent dissolution with the SIMFUEL matrix after a higher initial fractional release. Yttrium release has been found to be solubility controlled under the experimental conditions. A clear dependence on the partial pressure of O 2 of the rates of dissolution of uranium has been observed

SIMFUEL dissolution studies in granitic groundwater

International Nuclear Information System (INIS)

Casas, I.; Caceci, M.S.; Bruno, J; Sandino, A.

1991-09-01

The dissolution behavior of an unirradiated chemical analogue of spent nuclear fuel (SIMFUEL) has been studied in the presence of two different synthetic groundwaters at 25 degrees C and under both oxic and anoxic conditions. The release of U, Mo, Ba, Y and Sr was monitored during static (batch) leaching experiments of long duration (about 250 days). Preliminary results from continuous flow-through reactor experiments are also reported. The results obtained indicate the usefulness and limitations of SIMFUEL in the study of the kinetics and mechanism of dissolution of the minor components of spent nuclear fuel. Molybdenum, barium and strontium have shown a trend of congruent dissolution with the SIMFUEL matrix after a higher initial fractional release has been found to be solubility controlled under the experimental conditions. A clear dependence on the partial pressure of O 2 of the rate of dissolution of uranium has been observed. (au)

Overview of chemical modeling of nuclear waste glass dissolution

International Nuclear Information System (INIS)

Bourcier, W.L.

1991-02-01

Glass dissolution takes place through metal leaching and hydration of the glass surface accompanied by development of alternation layers of varying crystallinity. The reaction which controls the long-term glass dissolution rate appears to be surface layer dissolution. This reaction is reversible because the buildup of dissolved species in solution slows the dissolution rate due to a decreased dissolution affinity. Glass dissolution rates are therefore highly dependent on silica concentrations in solution because silica is the major component of the alteration layer. Chemical modeling of glass dissolution using reaction path computer codes has successfully been applied to short term experimental tests and used to predict long-term repository performance. Current problems and limitations of the models include a poorly defined long-term glass dissolution mechanism, the use of model parameters determined from the same experiments that the model is used to predict, and the lack of sufficient validation of key assumptions in the modeling approach. Work is in progress that addresses these issues. 41 refs., 7 figs., 2 tabs

Development and validation of dissolution test for Metoprolol ...

African Journals Online (AJOL)

The dissolution method which uses USP apparatus I (Basket) with rotating at 100 rpm, 900 ml of different dissolution medium, ultra violet spectroscopy for quantification was demonstrated to be robust, discriminating and transferable. Dissolution tests conditions were selected after it was demonstrated that the Metoprolol ...

Interactions between a poorly soluble cationic drug and sodium dodecyl sulfate in dissolution medium and their impact on in vitro dissolution behavior.

Science.gov (United States)

Huang, Zongyun; Parikh, Shuchi; Fish, William P

2018-01-15

In the pharmaceutical industry, in vitro dissolution testing ofsolid oral dosage forms is a very important tool for drug development and quality control. However, ion-pairing interaction between the ionic drugand surfactants in dissolution medium often occurs, resulting in inconsistent and incomplete drug release. The aim of this study is toevaluate the effects ofsodium dodecyl sulfate (SDS) mediated medium onthe dissolution behaviors of a poorly soluble cationic drug (Drug B). The study was carried out by measuring solubility of Drug B substance and dissolution rate of Drug B product in media containing SDS.Desolubilization of Drug B substance was observed at pH 4.5 in the presence of SDS at concentrations below critical micelle concentration (CMC) which is attributed to the formation of an insoluble di-dodecyl sulfate salt between SDS and Drug B. This ion-pairing effect is less significant with increasing medium pH where Drug B is less ionized and CMC of SDS is lower. In medium at pH 4.5, dissolution of Drug B product was found incomplete with SDS concentration below CMC due to the desolubilization of Drug B substance. In media with SDS level above CMC, the dissolution rate is rather slower with higher inter-vessel variations compared to that obtained in pH 4.5 medium without SDS. The dissolution results demonstrate that the presence of SDS in medium generates unexpected irregular dissolution profiles for Drug B which are attributed to incompatible dissolution medium for this particular drug. Therefore, non-ionic surfactant was selected for Drug B product dissolution method and ion-pairing effect in SDS mediated medium should be evaluated when developing a dissolution method for any poorly soluble cationic drugs. Copyright © 2017 Elsevier B.V. All rights reserved.

Initial Drug Dissolution from Amorphous Solid Dispersions Controlled by Polymer Dissolution and Drug-Polymer Interaction.

Science.gov (United States)

Chen, Yuejie; Wang, Shujing; Wang, Shan; Liu, Chengyu; Su, Ching; Hageman, Michael; Hussain, Munir; Haskell, Roy; Stefanski, Kevin; Qian, Feng

2016-10-01

); while drug released much slower than the polymer when molecular level mixing or drug-polymer interaction was absent (SDD-PB systems). For ASDs without drug-polymer interaction (i.e., KTZ/HPMC systems), the mixing homogeneity had little impact on the release rate of either the drug or the polymer thus SDD and SDD-PB demonstrated the same drug or polymer release rate, while the drug released slowly and independently of polymer release. The initial drug release from an ASD was controlled by 1) the polymer release rate; 2) the strength of drug-polymer interaction, including the intrinsic interaction caused by the chemistry of the drug and the polymer (measured by the χ value), as well as that the apparent interaction caused by the drug-polymer ratio (measure by the extent of peak shift on spectroscopic analysis); and 3) the level of mixing homogeneity between the drug and polymer. In summary, the selection of polymer, drug-polymer ratio, and ASD processing conditions have profound impacts on the dissolution behavior of ASDs. Graphical Abstract Relationship between initial drug and polymer dissolution rates from amorphous solid dispersions with different mixing uniformity and drug-polymer interactions.

Carbonate mineral dissolution kinetics in high pressure experiments

Science.gov (United States)

Dethlefsen, F.; Dörr, C.; Schäfer, D.; Ebert, M.

2012-04-01

reaction kinetics should be acknowledged when using reactive transport models, especially when modeling kinetically controlled pH-buffering processes between a CO2 leakage an a receptor like a ground water well. Currently, further experiments for the determination of the dolomite dissolution kinetics are being performed. Here, the knowledge of the dissolution rate constants can be even more important compared to the (still) fast calcite dissolution. This study is being funded by the German Federal Ministry of Education and Research (BMBF), EnBW Energie Baden-Württemberg AG, E.ON Energie AG, E.ON Gas Storage AG, RWE Dea AG, Vattenfall Europe Technology Research GmbH, Wintershall Holding AG and Stadtwerke Kiel AG as part of the CO2-MoPa joint project in the framework of the Special Program GEOTECHNOLOGIEN. Literature Lasaga, A. C., 1984. Chemical Kinetics of Water-Rock Interactions. Journal of Geophysical Research 89, 4009-4025. Palandri, J. L. and Kharaka, Y. K., 2004. A compilation of rate parameters of water-mineral interaction kinetics for application to geochemical modeling. USGS, Menlo Park, CA, USA. v. Grinsven, J. J. M. and Riemsdijk, W. H., 1992. Evaluation of batch and column techniques to measure weathering rates in soils. Geoderma 52, 41-57.

Dissolution testing of orally disintegrating tablets.

Science.gov (United States)

Kraemer, Johannes; Gajendran, Jayachandar; Guillot, Alexis; Schichtel, Julian; Tuereli, Akif

2012-07-01

For industrially manufactured pharmaceutical dosage forms, product quality tests and performance tests are required to ascertain the quality of the final product. Current compendial requirements specify a disintegration and/or a dissolution test to check the quality of oral solid dosage forms. These requirements led to a number of compendial monographs for individual products and, at times, the results obtained may not be reflective of the dosage form performance. Although a general product performance test is desirable for orally disintegrating tablets (ODTs), the complexity of the release controlling mechanisms and short time-frame of release make such tests difficult to establish. For conventional oral solid dosage forms (COSDFs), disintegration is often considered to be the prerequisite for subsequent dissolution. Hence, disintegration testing is usually insufficient to judge product performance of COSDFs. Given the very fast disintegration of ODTs, the relationship between disintegration and dissolution is worthy of closer scrutiny. This article reviews the current status of dissolution testing of ODTs to establish the product quality standards. Based on experimental results, it appears that it may be feasible to rely on the dissolution test without a need for disintegration studies for selected ODTs on the market. © 2012 The Authors. JPP © 2012 Royal Pharmaceutical Society.

Importance of surface structure on dissolution of fluorite

DEFF Research Database (Denmark)

Godinho, Jose; Piazolo, Sandra; Balic Zunic, Tonci

2014-01-01

forming the initial surface and its inclination to the closest stable planes, which are specific for each surface orientation. During an initial dissolution regime dissolution rates decrease significantly, even though the total surface area increases. During a second dissolution regime, some surfaces...... by the relative stability of the planes and type of edges that constitute a surface needs to be considered. Significant differences between dissolution rates calculated based on surface area alone, and based on surface reactivity are expected for materials with the fluorite structure....

Dissolution and compaction instabilities in geomaterials

Science.gov (United States)

Stefanou, I.; Sulem, J.; de Sauvage, J.

2014-12-01

Compaction bands play an important role in reservoir engineering and geological storage. Their presence in geological formations may also provide useful information on various geological processes. Several mechanisms can be involved at different scales and may be responsible for compaction band instabilities [1]. Compaction bands can be seen as a particular instability of the governing mathematical system leading to localization of deformation [2-4]. In a saturated porous rock, the progressive mechanical damage of the solid skeleton during compaction, results in the increase of the interface area of the reactants and consequently in the acceleration of the dissolution rate of the solid phase [2,5]. Thus, the solid skeleton is degraded more rapidly (mass removal because of dissolution), the overall mechanical properties of the system diminish (contraction of the elastic domain - chemical softening), deformations increase and the solid skeleton is further damaged (intergranular fractures, debonding, breakage of the porous network etc.). The stability of this positive feedback process is investigated analytically through linear stability analysis by considering the strong chemo-poro-mechanical coupling due to chemical dissolution. The post bifurcation behavior is then studied analytically and numerically revealing the compaction band thickness and periodicity. The effect of various parameters is studied as for instance the influence of the hydraulic diffusivity on the compaction band thickness. [1] P. Baud, S. Vinciguerra, C. David, A. Cavallo, E. Walker and T. Reuschlé (2009), Pure Appl. Geophys., 166(5-7), 869-898 [2] I. Stefanou and J. Sulem (2014), JGR: Solid Earth, 119(2), 880-899. doi:10.1002/2013JB010342I [3] J.W. Rudnicki and J.R. Rice (1975), Journal of the Mechanics and Physics of Solids 23(6),: 371-394 [4] K.A. Issen and J.W. Rudnicki (2000), JGR, 105(B9), 21529. doi:10.1029/2000JB900185 [5] R. Nova, R. Castellanza and C. Tamagnini (2003), International

The Relationship Between the Evolution of an Internal Structure and Drug Dissolution from Controlled-Release Matrix Tablets.

Science.gov (United States)

Kulinowski, Piotr; Hudy, Wiktor; Mendyk, Aleksander; Juszczyk, Ewelina; Węglarz, Władysław P; Jachowicz, Renata; Dorożyński, Przemysław

2016-06-01

In the last decade, imaging has been introduced as a supplementary method to the dissolution tests, but a direct relationship of dissolution and imaging data has been almost completely overlooked. The purpose of this study was to assess the feasibility of relating magnetic resonance imaging (MRI) and dissolution data to elucidate dissolution profile features (i.e., kinetics, kinetics changes, and variability). Commercial, hydroxypropylmethyl cellulose-based quetiapine fumarate controlled-release matrix tablets were studied using the following two methods: (i) MRI inside the USP4 apparatus with subsequent machine learning-based image segmentation and (ii) dissolution testing with piecewise dissolution modeling. Obtained data were analyzed together using statistical data processing methods, including multiple linear regression. As a result, in this case, zeroth order release was found to be a consequence of internal structure evolution (interplay between region's areas-e.g., linear relationship between interface and core), which eventually resulted in core disappearance. Dry core disappearance had an impact on (i) changes in dissolution kinetics (from zeroth order to nonlinear) and (ii) an increase in variability of drug dissolution results. It can be concluded that it is feasible to parameterize changes in micro/meso morphology of hydrated, controlled release, swellable matrices using MRI to establish a causal relationship between the changes in morphology and drug dissolution. Presented results open new perspectives in practical application of combined MRI/dissolution to controlled-release drug products.

Controlled precipitation for enhanced dissolution rate of flurbiprofen: development of rapidly disintegrating tablets.

Science.gov (United States)

Essa, Ebtessam A; Elmarakby, Amira O; Donia, Ahmed M A; El Maghraby, Gamal M

2017-09-01

The aim of this work was to investigate the potential of controlled precipitation of flurbiprofen on solid surface, in the presence or absence of hydrophilic polymers, as a tool for enhanced dissolution rate of the drug. The work was extended to develop rapidly disintegrated tablets. This strategy provides simple technique for dissolution enhancement of slowly dissolving drugs with high scaling up potential. Aerosil was dispersed in ethanolic solution of flurbiprofen in the presence and absence of hydrophilic polymers. Acidified water was added as antisolvent to produce controlled precipitation. The resultant particles were centrifuged and dried at ambient temperature before monitoring the dissolution pattern. The particles were also subjected to FTIR spectroscopic, X-ray diffraction and thermal analyses. The FTIR spectroscopy excluded any interaction between flurbiprofen and excipients. The thermal analysis reflected possible change in the crystalline structure and or crystal size of the drug after controlled precipitation in the presence of hydrophilic polymers. This was further confirmed by X-ray diffraction. The modulation in the crystalline structure and size was associated with a significant enhancement in the dissolution rate of flurbiprofen. Optimum formulations were successfully formulated as rapidly disintegrating tablet with subsequent fast dissolution. Precipitation on a large solid surface area is a promising strategy for enhanced dissolution rate with the presence of hydrophilic polymers during precipitation process improving the efficiency.

Handbook of divorce and relationship dissolution

CERN Document Server

Fine, Mark A

2013-01-01

This Handbook presents up-to-date scholarship on the causes and predictors, processes, and consequences of divorce and relationship dissolution. Featuring contributions from multiple disciplines, this Handbook reviews relationship termination, including variations depending on legal status, race/ethnicity, and sexual orientation. The Handbook focuses on the often-neglected processes involved as the relationship unfolds, such as infidelity, hurt, and remarriage. It also covers the legal and policy aspects, the demographics, and the historical aspects of divorce. Intended for researchers, practitioners, counselors, clinicians, and advanced students in psychology, sociology, family studies, communication, and nursing, the book serves as a text in courses on divorce, marriage and the family, and close relationships.

In vivo in vitro correlations for a poorly soluble drug, danazol, using the flow-through dissolution method with biorelevant dissolution media

DEFF Research Database (Denmark)

Sunesen, Vibeke Hougaard; Pedersen, Betty Lomstein; Kristensen, Henning Gjelstrup

2005-01-01

The purpose of the study was to design dissolution tests that were able to distinguish between the behaviour of danazol under fasted and fed conditions, by using biorelevant media. In vitro dissolution of 100mg danazol capsules was performed using the flow-through dissolution method. Flow rates w...

Improving the API dissolution rate during pharmaceutical hot-melt extrusion I: Effect of the API particle size, and the co-rotating, twin-screw extruder screw configuration on the API dissolution rate.

Science.gov (United States)

Li, Meng; Gogos, Costas G; Ioannidis, Nicolas

2015-01-15

The dissolution rate of the active pharmaceutical ingredients in pharmaceutical hot-melt extrusion is the most critical elementary step during the extrusion of amorphous solid solutions - total dissolution has to be achieved within the short residence time in the extruder. Dissolution and dissolution rates are affected by process, material and equipment variables. In this work, we examine the effect of one of the material variables and one of the equipment variables, namely, the API particle size and extruder screw configuration on the API dissolution rate, in a co-rotating, twin-screw extruder. By rapidly removing the extruder screws from the barrel after achieving a steady state, we collected samples along the length of the extruder screws that were characterized by polarized optical microscopy (POM) and differential scanning calorimetry (DSC) to determine the amount of undissolved API. Analyses of samples indicate that reduction of particle size of the API and appropriate selection of screw design can markedly improve the dissolution rate of the API during extrusion. In addition, angle of repose measurements and light microscopy images show that the reduction of particle size of the API can improve the flowability of the physical mixture feed and the adhesiveness between its components, respectively, through dry coating of the polymer particles by the API particles. Copyright © 2014. Published by Elsevier B.V.

DISSOLUTION OF ZIRCONIUM AND ALLOYS THEREFOR

Science.gov (United States)

Swanson, J.L.

1961-07-11

The dissolution of zirconium cladding in a water solution of ammonium fluoride and ammonium nitrate is described. The method finds particular utility in processing spent fuel elements for nuclear reactors. The zirconium cladding is first dissolved in a water solution of ammonium fluoride and ammonium nitrate; insoluble uranium and plutonium fiuorides formed by attack of the solvent on the fuel materiai of the fuel element are then separated from the solution, and the fuel materiai is dissolved in another solution.

Dissolution of FFTF vendor fuel

International Nuclear Information System (INIS)

Lerch, R.E.

1979-08-01

Dissolution experiments were performed on FFTF vendor fuel (both mechanically mixed and coprecipitated) during 1974, 1975, and 1976. A marked improvement was noted in the completeness of fuel dissolution from 1974 to 1976. The reason for this is unknown but may have been attributable to slight changes in fuel fabrication conditions. In general, the bulk of the fuel pellets tested dissolved to greater than 99.9% in nitric acid alone

Dissolution of FFTF vendor fuel

Energy Technology Data Exchange (ETDEWEB)

Lerch, R.E.

1979-08-01

Dissolution experiments were performed on FFTF vendor fuel (both mechanically mixed and coprecipitated) during 1974, 1975, and 1976. A marked improvement was noted in the completeness of fuel dissolution from 1974 to 1976. The reason for this is unknown but may have been attributable to slight changes in fuel fabrication conditions. In general, the bulk of the fuel pellets tested dissolved to greater than 99.9% in nitric acid alone.

Dissolution of aerosol particles collected from nuclear facility plutonium production process

International Nuclear Information System (INIS)

Ning Xu; Martinez, Alex; Schappert, Michael; Montoya, D.P.; Martinez, Patrick; Tandon, Lav

2016-01-01

A simple, robust analytical chemistry method has been developed to dissolve plutonium containing particles in a complex matrix. The aerosol particles collected on Marple cascade impactor substrates were shown to be dissolved completely with an acid mixture of 12 M HNO 3 and 0.1 M HF. A pressurized closed vessel acid digestion technique was utilized to heat the samples at 130 deg C for 16 h to facilitate the digestion. The dissolution efficiency for plutonium particles was 99 %. The resulting particle digestate solution was suitable for trace elemental analysis and isotope composition determination, as well as radiochemistry measurements. (author)

Dissolution study of tremolite and anthophyllite: pH effect on the reaction kinetics

International Nuclear Information System (INIS)

Rozalen, M.; Ramos, M.E.; Gervilla, F.; Kerestedjian, T.; Fiore, S.; Huertas, F.J.

2014-01-01

Highlights: • Dissolution rates strongly depend on pH and it is different for each mineral. • Anthophyllite dissolves up to 8 times faster than tremolite in similar conditions. • SEM images show different particle breakage and carbonation effects at basic pHs. • Our results are a good background to develop remediation processes of contaminated sites. - Abstract: The effect of pH on the kinetics of tremolite and anthophyllite dissolution was investigated at 25 °C in batch reactors over the pH range of 1–13.5, in inorganic buffered solutions. Dissolution rates were obtained based on the release of Si and Mg. Results obtained in this study show different behaviors for both minerals. For tremolite, dissolution rates show a noticeable dependence on pH between 1 and 8, decreasing as pH increases and reaching a minimum around neutral conditions. At basic pH this dependence becomes even stronger, but dissolution takes place together with collateral effects of saturation and carbonation. A preferential release of Ca and Mg is observed in acid media, lowering the Mg/Si ratio to the extent that Mg solubility decreases with pH. For anthophyllite, dissolution rates also show a strong dependence on pH, between 1 and 9.5. At the same pH, anthophyllite dissolves up to 8 times faster than tremolite. For pH > 9.5 this dependence is smooth, and it is probably associated with effects of saturation and carbonation. Dissolution is also non-stoichiometric with a faster release of Mg with respect to Si in acid media. SEM observations show differences in the breakage mechanism of the fibers. The anthophyllite particle breakage during dissolution consists of the splitting of bundle fibers parallel to the fiber longitudinal direction. However, for tremolite, other than fiber splitting, particles shorten induced by coalescence of etch pits developed perpendicular to c axe

Mathematical methods for quantification and comparison of dissolution testing data.

Science.gov (United States)

Vranić, Edina; Mehmedagić, Aida; Hadzović, Sabira

2002-12-01

In recent years, drug release/dissolution from solid dosage forms has been the subject of intense and profitable scientific developments. Whenever a new solid dosage form is developed or produced, it is necessary to ensure that drug dissolution occurs in an appropriate manner. The pharmaceutical industry and the registration authorities do focus, nowadays, on drug dissolution studies. The quantitative analysis of the values obtained in dissolution/release tests is easier when mathematical formulas that express the dissolution results as a function of some of the dosage forms characteristics are used. This work discusses the analysis of data obtained for dissolution profiles under different media pH conditions using mathematical methods of analysis described by Moore and Flanner. These authors have described difference factor (f1) and similarity factor (f2), which can be used to characterise drug dissolution/release profiles. In this work we have used these formulas for evaluation of dissolution profiles of the conventional tablets in different pH of dissolution medium (range of physiological variations).

Dissolution of thorium/uranium mixed oxide in nitric acid-hydrofluoric acid solution

International Nuclear Information System (INIS)

Filgueiras, S.A.C.

1984-01-01

The dissolution process of thorium oxide and mixed uranium-thorium oxide is studied, as a step of the head-end of the fuel reprocessing. An extensive bibliography was analysed, concerning the main aspects of the system, specially the most important process variables. Proposed mechanisms and models for the thorium oxide dissolution are presented. The laboratory tests were performed in two phases: at first, powdered thoria was used as the material to be dissolved. The objective was to know how changes in he concentrations of the dissolvent solution components HNO 3 , HF and Al(NO 3 ) 3 affect the dissolution rate. The tests were planned according to the fractional factorial method. Thes results showed that it is advantageous to work with powdered material, since the reaction occurs rapidly. And, if the Thorex solution (HNO 3 13M, HF 0.05M and Al(NO 3 ) 3 0.10M) is a suitable dissolvent, it was verified that it is possible to reduce the concentration of either nitric or fluoridric acid, without reducing the reaction rate to an undesirable value. It was also observed significant interaction between the components of the dissolvent solution. In the second phase of the tests, (Th, 5%U)O 2 sintered pellets were used. The main goals were to know the pellets dissolution behaviour and to compare the results for different pellets among themselves. It was observed that the metallurgical history of the material strongly influences its dissolution, specially the density and the microstructure. It was also studied how the (Th,U)O 2 mass/Thorex solution volume ratio affects the time needed to obtain an 1 M Th/liter solution. The activation energy for the reaction was obtained. (Author) [pt

Dissolution of copper and iron from malachite ore and precipitation of copper sulfate pentahydrate by chemical process

Directory of Open Access Journals (Sweden)

H. Kokes

2014-03-01

Full Text Available The present work describes an investigation of a chemical process for the recovery of copper and iron from malachite ore. For the dissolution of copper and iron, H2SO4 was employed as well as H2O2 as an oxidizing agent. The effects of reaction temperature and time, acid concentration, liquid-to-solid ratio and agitation rate on the copper and iron percentage were investigated. Following the steps of dissolving the copper and iron sulfate and filtering, iron (III hydroxide was precipitated by adjusting the pH level of the solution. Subsequently, copper sulfate pentahydrate was obtained by using various precipitants (i.e. ethanol, methanol and sulfuric acid.

Development of a Unified Dissolution and Precipitation Model and Its Use for the Prediction of Oral Drug Absorption.

Science.gov (United States)

Jakubiak, Paulina; Wagner, Björn; Grimm, Hans Peter; Petrig-Schaffland, Jeannine; Schuler, Franz; Alvarez-Sánchez, Rubén

2016-02-01

Drug absorption is a complex process involving dissolution and precipitation, along with other kinetic processes. The purpose of this work was to (1) establish an in vitro methodology to study dissolution and precipitation in early stages of drug development where low compound consumption and high throughput are necessary, (2) develop a mathematical model for a mechanistic explanation of generated in vitro dissolution and precipitation data, and (3) extrapolate in vitro data to in vivo situations using physiologically based models to predict oral drug absorption. Small-scale pH-shift studies were performed in biorelevant media to monitor the precipitation of a set of poorly soluble weak bases. After developing a dissolution-precipitation model from this data, it was integrated into a simplified, physiologically based absorption model to predict clinical pharmacokinetic profiles. The model helped explain the consequences of supersaturation behavior of compounds. The predicted human pharmacokinetic profiles closely aligned with the observed clinical data. In summary, we describe a novel approach combining experimental dissolution/precipitation methodology with a mechanistic model for the prediction of human drug absorption kinetics. The approach unifies the dissolution and precipitation theories and enables accurate predictions of in vivo oral absorption by means of physiologically based modeling.

Factors affecting the differences in reactivity and dissolution rates between UO2 and spent nuclear fuel

International Nuclear Information System (INIS)

Shoesmith, D.W.; Tait, J.C.; Sunder, S.; Steward, S.; Russo, R.E.; Rudnicki, J.D.

1996-08-01

Strategies for the permanent disposal of spent nuclear fuel are being investigated by the U.S. Department of Energy at the Yucca Mountain site and by Atomic Energy of Canada Limited (AECL) in plutonic rock formations in the Canadian Shield. Uranium dioxide is the primary constituent of spent nuclear fuel and dissolution of the matrix is regarded as a necessary step for the release of radionuclides to repository groundwaters. In order to develop models to describe the dissolution of the U0 2 fuel matrix and subsequent release of radionuclides, it is necessary to understand both chemical and oxidative dissolution processes and how they can be affected by parameters such as groundwater composition, pH, temperature, surface area, radiolysis and redox potential. This report summarizes both published and on-going dissolution studies of U0 2 and both LWR and CANDU spent fuels being conducted at the Pacific Northwest Laboratory, Lawrence Livermore National Laboratory and Lawrence Berkeley Laboratory in the U.S. and at AECL's Whiteshell Laboratories in Canada. The studies include both dissolution tests and electrochemical experiments to measure uranium dissolution rates. The report focuses on identifying differences in reactivity towards aqueous dissolution between U0 2 and spent fuel samples as well as estimating bounding values for uranium dissolution rates. This review also outlines the basic tenets for the development of a dissolution model that is based on electrochemical principles. (author). 49 refs., 2 tabs., 11 figs

Oxidative dissolution of ADOPT compared to standard UO2 fuel

International Nuclear Information System (INIS)

Nilsson, Kristina; Roth, Olivia; Jonsson, Mats

2017-01-01

In this work we have studied oxidative dissolution of pure UO 2 and ADOPT (UO 2 doped with Al and Cr) pellets using H 2 O 2 and gammaradiolysis to induce the process. There is a small but significant difference in the oxidative dissolution rate of UO 2 and ADOPT pellets, respectively. However, the difference in oxidative dissolution yield is insignificant. Leaching experiments were also performed on in-reactor irradiated ADOPT and UO 2 pellets under oxidizing conditions. The results indicate that the U(VI) release is slightly slower from the ADOPT pellet compared to the UO 2. This could be attributed to differences in exposed surface area. However, fission products with low UO 2 solubility display a higher relative release from ADOPT fuel compared to standard UO 2 -fuel. This is attributed to a lower matrix solubility imposed by the dopants in ADOPT fuel. The release of Cs is higher from UO 2 which is attributed to the larger grain size of ADOPT. - Highlights: •Oxidative dissolution of ADOPT fuel is compared to standard UO 2 fuel. •Only marginal differences are observed. •The main difference observed is in the relative release rate of fission products. •Differences are claimed to be attributed to a lower matrix solubility imposed by the dopants in ADOPT fuel.

Oxidation and dissolution of UO{sub 2} in bicarbonate media: Implications for the spent nuclear fuel oxidative dissolution mechanism

Energy Technology Data Exchange (ETDEWEB)

Gimenez, J. [Department of Chemical Engineering, Universitat Politecnica de Catalunya, Diagonal 647, 08028 Barcelona (Spain)]. E-mail: francisco.javier.gimenez@upc.edu; Clarens, F. [Department of Chemical Engineering, Universitat Politecnica de Catalunya, Diagonal 647, 08028 Barcelona (Spain); Casas, I. [Department of Chemical Engineering, Universitat Politecnica de Catalunya, Diagonal 647, 08028 Barcelona (Spain); Rovira, M. [CTM Centre Tecnologic, Avda. Bases de Manresa 1. 08240 Manresa (Spain); Pablo, J. de [Department of Chemical Engineering, Universitat Politecnica de Catalunya, Diagonal 647, 08028 Barcelona (Spain); Bruno, J. [Enresa-Enviros Environmental Science and Waste Management Chair, UPC, Jordi Girona 1-3 B2, 08034 Barcelona (Spain)

2005-10-15

The objective of this work is to study the UO{sub 2} oxidation by O{sub 2} and dissolution in bicarbonate media and to extrapolate the results obtained to improve the knowledge of the oxidative dissolution of spent nuclear fuel. The results obtained show that in the studied range the oxygen consumption rate is independent on the bicarbonate concentration while the UO{sub 2} dissolution rate does depend on. Besides, at 10{sup -4} mol dm{sup -3} bicarbonate concentration, the oxygen consumption rate is almost two orders of magnitude higher than the UO{sub 2} dissolution rate. These results suggest that at low bicarbonate concentration (<10{sup -2} mol dm{sup -3}) the alteration of the spent nuclear fuel cannot be directly derived from the measured uranium concentrations in solution. On the other hand, the study at low bicarbonate concentrations of the evolution of the UO{sub 2} surface at nanometric scale by means of the SFM technique shows that the difference between oxidation and dissolution rates is not due to the precipitation of a secondary solid phase on UO{sub 2}.

Frogging It: A poetic Analysis of Relationship Dissolution

Directory of Open Access Journals (Sweden)

Sandra L. Faulkner

2012-10-01

Full Text Available Often, themes in work and life intertwine; the author recognized that a cadre of poems she had written during the past several years were about relationship dissolution. The poems concerned romantic and friendship dissolution and the aspects of identity creation and loss this entails. The author presents the poems and makes an explicit connection to interpersonal relationship dissolution literature through the technique of poetic analysis. This analysis serves as an exemplar for how poetry as performative writing offers a valuable addition to interpersonal communication research through the poeticizing of relational dissolution as an everyday relational challenge.

Initial results for electrochemical dissolution of spent EBR-II fuel

International Nuclear Information System (INIS)

Li, S. X.

1998-01-01

Initial results are reported for the anode behavior of spent metallic nuclear fuel in an electrorefining process. The anode behavior has been characterized in terms of the initial spent fuel composition and the final composition of the residual cladding hulls. A variety of results have been obtained depending on the experimental conditions. Some of the process variables considered are average and maximum cell voltage, average and maximum anode voltage, amount of electrical charge passed (coulombs or amp-hours) during the experiment, and cell resistance. The main goal of the experiments has been the nearly complete dissolution of uranium with the retention of zirconium and noble metal fission products in the cladding hulls. Analysis has shown that the most indicative parameters for determining an endpoint to the process, recognizing the stated goal, are the maximum anode voltage and the amount of electrical charge passed. For the initial experiments reported here, the best result obtained is greater than 98% uranium dissolution with approximately 50% zirconium retention. Noble metal fission product retention appears to be correlated with zirconium retention

Haw-glass dissolution and radionuclide release: mechanism - modelling - source term

Energy Technology Data Exchange (ETDEWEB)

Grambow, B [Forschungszentrum Karlsruhe, Institut fur Nukleare, Karlsruhe (Germany)

1997-07-01

Important release controlling processes are: 1) kinetics of glass matrix dissolution (leaching), 2) formation of secondary alteration products (controlling thermodynamic solubility), 3) sorption on surfaces in the engineered barrier system and 4) formation of mobile species. Quantification of these processes requires assessment of the energetics and dynamics of the various reversible and irreversible processes within an overall open non-equilibrium system. Corrosion/dissolution of the waste matrices is not necessarily associated with a proportional release of radionuclides. The formation of new secondary phases, such as silicates, molybdates, uranates, carbonates... establishes a new geochemical barrier for re-immobilization of radionuclides dissolved from the waste matrices. The presence of iron (corroding canisters during glass alteration) reduces the solution concentration of redox sensitive radionuclides. Consequently, the container, after being corroded, constitutes an important geochemical barrier for radionuclide re-immobilization. Geochemical modelling of the long-term behaviour of glasses must be performed in an integrated way, considering simultaneous reactions of the glass, of container corrosion, of repository rock and of backfill material. Until now, only few attempts were made for integral systems modelling. (A.C.)

Uranium carbide dissolution in nitric solution: Sonication vs. silent conditions

International Nuclear Information System (INIS)

Virot, Matthieu; Szenknect, Stéphanie; Chave, Tony; Dacheux, Nicolas; Moisy, Philippe; Nikitenko, Sergey I.

2013-01-01

The dissolution of uranium carbide (UC) in nitric acid media is considered by means of power ultrasound (sonication) or magnetic stirring. The induction period required to initiate UC dissolution was found to be dramatically shortened when sonicating a 3 M nitric solution (Ar, 20 kHz, 18 W cm −2 , 20 °C). At higher acidity, magnetic stirring offers faster dissolution kinetics compared to sonication. Ultrasound-assisted UC dissolution is found to be passivated after ∼60% dissolution and remains incomplete whatever the acidity which is confirmed by ICP–AES, LECO and SEM–EDX analyses. In general, the kinetics of UC dissolution is linked to the in situ generation of nitrous acid in agreement with the general mechanism of UC dissolution; the nitrous acid formation is reported to be faster under ultrasound at low acidity due to the nitric acid sonolysis. The carbon balance shared between the gaseous, liquid, and solid phases is strongly influenced by the applied dissolution procedure and HNO 3 concentration

Uranium carbide dissolution in nitric solution: Sonication vs. silent conditions

Science.gov (United States)

Virot, Matthieu; Szenknect, Stéphanie; Chave, Tony; Dacheux, Nicolas; Moisy, Philippe; Nikitenko, Sergey I.

2013-10-01

The dissolution of uranium carbide (UC) in nitric acid media is considered by means of power ultrasound (sonication) or magnetic stirring. The induction period required to initiate UC dissolution was found to be dramatically shortened when sonicating a 3 M nitric solution (Ar, 20 kHz, 18 W cm-2, 20 °C). At higher acidity, magnetic stirring offers faster dissolution kinetics compared to sonication. Ultrasound-assisted UC dissolution is found to be passivated after ∼60% dissolution and remains incomplete whatever the acidity which is confirmed by ICP-AES, LECO and SEM-EDX analyses. In general, the kinetics of UC dissolution is linked to the in situ generation of nitrous acid in agreement with the general mechanism of UC dissolution; the nitrous acid formation is reported to be faster under ultrasound at low acidity due to the nitric acid sonolysis. The carbon balance shared between the gaseous, liquid, and solid phases is strongly influenced by the applied dissolution procedure and HNO3 concentration.

In vitro Dissolution Studies on Solid Dispersions of Mefenamic Acid.

Science.gov (United States)

Rao, K R S Sambasiva; Nagabhushanam, M V; Chowdary, K P R

2011-03-01

Solid dispersions of mefanamic acid with a water-soluble polymer polyvinyl pyrrolidine and a super disintegrant, primojel were prepared by common solvent and solvent evaporation methods employing methanol as the solvent. The dissolution rate and dissolution efficiency of the prepared solid dispersions were evaluated in comparison to the corresponding pure drug. Solid dispersions of mefenamic acid showed a marked enhancement in dissolution rate and dissolution efficiency. At 1:4 ratio of mefenamic acid-primojel a 2.61 fold increase in the dissolution rate of mefenamic acid was observed with solid dispersion. The solid dispersions in combined carriers gave much higher rates of dissolution than super disintegrants alone. Mefanamic acid-primojel-polyvinyl pyrrolidine (1:3.2:0.8) solid dispersion gave a 4.11 fold increase in the dissolution rate of mefenamic acid. Super disintegrants alone or in combination with polyvinyl pyrrolidine could be used to enhance the dissolution rate of mefenamic acid.

Biogenic silica dissolution in diatom aggregates: insights from reactive transport modelling

KAUST Repository

Moriceau, B

2014-12-15

© Inter-Research 2014. Diatom aggregates contribute significantly to the vertical sinking flux of particulate matter in the ocean. These fragile structures form a specific microhabitat for the aggregated cells, but their internal chemical and physical characteristics remain largely unknown. Studies on the impact of aggregation on the Si cycle led to apparent inconsistency. Despite a lower biogenic silica (bSiO2) dissolution rate and diffusion of the silicic acid (dSi) being similar in aggregates and in sea-water, dSi surprisingly accumulates in aggregates. A reaction-diffusion model helps to clarify this incoherence by reconstructing dSi accumulation measured during batch experiments with aggregated and non-aggregated Skeletonema marinoi and Chaetoceros decipiens. The model calculates the effective bSiO2 dissolution rate as opposed to the experimental apparent bSiO2 dissolution rate, which is the results of the effective dissolution of bSiO2 and transport of dSi out of the aggregate. In the model, dSi transport out of the aggregate is modulated by alternatively considering retention (decrease of the dSi diffusion constant) and adsorption (reversible chemical bonds between dSi and the aggregate matrix) processes. Modelled bSiO2 dissolution is modulated by the impact of dSi concentration inside aggregates and diatom viability, as enhanced persistence of metabolically active diatoms has been observed in aggregates. Adsorption better explains dSi accumulation within and outside aggregates, raising the possible importance of dSi travelling within aggregates to the deep sea (potentially representing 20% of the total silica flux). The model indicates that bSiO2 dissolution is effectively decreased in aggregates mainly due to higher diatom viability but also to other parameters discussed herein.

Simulation of uranium aluminide dissolution in a continuous aluminum dissolver system

International Nuclear Information System (INIS)

Evans, D.R.; Farman, R.F.; Christian, J.D.

1990-01-01

This paper reports on the Idaho Chemical Processing Plant (ICPP) which recovers highly-enriched uranium (uranium that contains at least 20 atom percent 235 U) from spent nuclear reactor fuel by dissolution of the fuel elements and extraction of the uranium from the aqueous dissolver product. Because the uranium is highly-enriched, consideration must be given to whether a critical mass can form at any stage of the process. In particular, suspended 235 U-containing particles are of special concern, due to their high density (6.8 g/cm 3 ) and due to the fact that they can settle into geometrically unfavorable configurations when not adequately mixed. A portion of the spent fuel is aluminum-alloy-clad uranium aluminide (UAl 3 ) particles, which dissolve more slowly than the cladding. As the aluminum alloy cladding dissolves in mercury-catalyzed nitric acid, UAl 3 is released. Under standard operating conditions, the UAl 3 dissolves rapidly enough to preclude the possibility of forming a critical mass anywhere in the system. However, postulated worst-case abnormal operating conditions retard uranium aluminide dissolution, and thus require evaluation. To establish safety limits for operating parameters, a computerized simulation model of uranium aluminide dissolution in the aluminum fuel dissolver system was developed

Kinetics of UO2(s) dissolution under reducing conditions: Numerical modelling

International Nuclear Information System (INIS)

Puigdomenech, I.; Casas, I.; Bruno, J.

1990-05-01

A numerical model is presented that describes the dissolution and precipitation of UO 2 (s) under reducing conditions. For aqueous solutions with pH>4, main reaction is: UO 2 (s)+2H 2 O↔U(OH) 4 (aq). The rate constant for the precipitation reaction is found to be log(k p )=-1.2±0.2 h -1 m -2 , while the value for the rate constant of the dissolution reaction is log(k d )=-9.0±0.2 mol/(1 h m 2 ). Most of the experiments reported in the literature show a fast initial dissolution of a surface film of hexavalent uranium oxide. Making the assumption that the chemical composition of the surface coating is U 3 O 7 (s), we have derived a mechanism for this process, and its rate constants have been obtained. The influence of HCO 3 - and CO 3 2- on the mechanism of dissolution and precipitation of UO 2 (s) is still unclear. From the solubility measurements reported, one may conclude that the identity of the aqueous complexes in solution is not well known. Therefore it is not possible to make a mechanistic interpretation of the kinetic data in carbonate medium. (orig.)

Dissolution behaviour of silicon nitride coatings for joint replacements

Energy Technology Data Exchange (ETDEWEB)

Pettersson, Maria [Materials in Medicine Group, Div. of Applied Materials Science, Dept. of Engineering Sciences, Uppsala University, Uppsala (Sweden); Bryant, Michael [Institute of Functional Surfaces (iFS), School of Mechanical Engineering, University of Leeds, Leeds (United Kingdom); Schmidt, Susann [Thin Film Physics, Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping (Sweden); Engqvist, Håkan [Materials in Medicine Group, Div. of Applied Materials Science, Dept. of Engineering Sciences, Uppsala University, Uppsala (Sweden); Hall, Richard M. [Institute of Medical and Biological Engineering (iMBE), School of Mechanical Engineering, University of Leeds, Leeds (United Kingdom); Neville, Anne [Institute of Functional Surfaces (iFS), School of Mechanical Engineering, University of Leeds, Leeds (United Kingdom); Persson, Cecilia, E-mail: cecilia.persson@angstrom.uu.se [Materials in Medicine Group, Div. of Applied Materials Science, Dept. of Engineering Sciences, Uppsala University, Uppsala (Sweden)

2016-05-01

In this study, the dissolution rate of SiN{sub x} coatings was investigated as a function of coating composition, in comparison to a cobalt chromium molybdenum alloy (CoCrMo) reference. SiN{sub x} coatings with N/Si ratios of 0.3, 0.8 and 1.1 were investigated. Electrochemical measurements were complemented with solution (inductively coupled plasma techniques) and surface analysis (vertical scanning interferometry and x-ray photoelectron spectroscopy). The dissolution rate of the SiN{sub x} coatings was evaluated to 0.2–1.4 nm/day, with a trend of lower dissolution rate with higher N/Si atomic ratio in the coating. The dissolution rates of the coatings were similar to or lower than that of CoCrMo (0.7–1.2 nm/day). The highest nitrogen containing coating showed mainly Si–N bonds in the bulk as well as at the surface and in the dissolution area. The lower nitrogen containing coatings showed Si–N and/or Si–Si bonds in the bulk and an increased formation of Si–O bonds at the surface as well as in the dissolution area. The SiN{sub x} coatings reduced the metal ion release from the substrate. The possibility to tune the dissolution rate and the ability to prevent release of metal ions encourage further studies on SiN{sub x} coatings for joint replacements. - Graphical abstract: Dissolution rates of SiN{sub 0.3}, SiN{sub 0.8}, and SiN{sub 1.1} coatings on CoCrMo compared to uncoated CoCrMo. Dissolution rates were obtained from i) electrochemical measurements of I{sub corr}, ii) the step height between covered and solution-exposed surfaces, measured using VSI, and iii) the ion concentration in the solution, measured with ICP. - Highlights: • The dissolution of SiN{sub x} coatings was investigated in comparison to (bulk) CoCrMo. • The coatings gave a lower or similar dissolution rate to CoCrMo, of 0.2–1.2 nm/day. • An increased nitrogen content in the coatings gave lower dissolution rates. • SiN{sub x} coatings on CoCrMo reduced the metal ion release

Dissolution of nuclear fuels; Disolucion de combustibles Nucleares

Energy Technology Data Exchange (ETDEWEB)

Uriarte Hueda, A; Berberana Eizmendi, M; Rainey, R

1968-07-01

A laboratory study was made of the instantaneous dissolution rate (IDR) for unirradiated uranium metal rods and UO{sub 2}, PuO{sub 2} and PuO{sub 2}-UO{sub 2} pellets in boiling nitric acid alone and with additives. The uranium metal and UO{sub 2} dissolved readily in nitric acid alone; PuO{sub 2} dissolved slowly even with the addition of fluoride; PuO{sub 2}-UO{sub 2} pellets containing as much as 35% PuO{sub 2} in UO{sub 2} gave values of the instantaneous dissolution rate to indicate can be dissolved with nitric acid alone. An equation to calculate the time for complete dissolution has been determinate in function of the instantaneous dissolution rates. The calculated values agree with the experimental. Uranium dioxide pellets from various sources but all having a same density varied in instantaneous dissolution rate. All the pellets, however, have dissolved ved in the same time. The time for complete dissolution of PuO{sub 2}-UO{sub 2} pellets, having the same composition, and the concentration of the used reagents are function of the used reagents are function of the fabrication method. (Author) 8 refs.

Dissolution Model Development: Formulation Effects and Filter Complications

DEFF Research Database (Denmark)

Berthelsen, Ragna; Holm, Rene; Jacobsen, Jette

2016-01-01

This study describes various complications related to sample preparation (filtration) during development of a dissolution method intended to discriminate among different fenofibrate immediate-release formulations. Several dissolution apparatus and sample preparation techniques were tested. The fl....... With the tested drug–formulation combination, the best in vivo–in vitro correlation was found after filtration of the dissolution samples through 0.45-μm hydrophobic PTFE membrane filters....

Bench Scale Saltcake Dissolution Test Report

International Nuclear Information System (INIS)

BECHTOLD, D.B.; PACQUET, E.A.

2000-01-01

A potential scenario for retrieving saltcake from single shell tanks is the ''Rainbird(reg s ign) sprinkler'' method. Water is distributed evenly across the surface of the saltcake and allowed to percolate by gravity through the waste. The salt dissolves in the water, forming a saturated solution. The saturated liquid is removed by a saltwell pump situated near the bottom of the tank. By this method, there is never a large inventory of liquid in the tank that could pose a threat of leakage. There are many variables or factors that can influence the hydrodynamics of this retrieval process. They include saltcake porosity; saltwell pumping rate; salt dissolution chemistry; factors that could promote flow channeling (e.g. tank walls, dry wells, inclusions or discontinuities in the saltcake); method of water distribution; plug formation due to crystal formations or accumulation of insoluble solids. A brief literature search indicates that very little experimental data exist on these aspects of saltcake dissolution (Wiersma 1996, 1997). The tests reported here were planned (Herting, 2000) to provide preliminary data and information for planning future, scaled-up tests of the sprinkler method

Biogenic silica dissolution in diatom aggregates: insights from reactive transport modelling

KAUST Repository

Moriceau, B; Laruelle, GG; Passow, U; Van Cappellen, P; Ragueneau, O

2014-01-01

, dSi transport out of the aggregate is modulated by alternatively considering retention (decrease of the dSi diffusion constant) and adsorption (reversible chemical bonds between dSi and the aggregate matrix) processes. Modelled bSiO2 dissolution

Dissolution characteristics of sericite in chalcopyrite bioleaching and its effect on copper extraction

Science.gov (United States)

Dong, Ying-bo; Li, Hao; Lin, Hai; Zhang, Yuan

2017-04-01

The effects of sericite particle size, rotation speed, and leaching temperature on sericite dissolution and copper extraction in a chalcopyrite bioleaching system were examined. Finer particles, appropriate temperature and rotation speed for Acidithiobacillus ferrooxidans resulted in a higher Al3+ dissolution concentration. The Al3+ dissolution concentration reached its highest concentration of 38.66 mg/L after 48-d leaching when the sericite particle size, temperature, and rotation speed were -43 μm, 30°C, and 160 r/min, respectively. Meanwhile, the sericite particle size, rotation speed, and temperature can affect copper extraction. The copper extraction rate is higher when the sericite particle size is finer. An appropriately high temperature is favorable for copper leaching. The dissolution of sericite fitted the shrinking core model, 1-(2/3) α-(1- α)2/3 = k 1 t, which indicates that internal diffusion is the decision step controlling the overall reaction rate in the leaching process. Scanning electron microscopy analysis showed small precipitates covered on the surface of sericite after leaching, which increased the diffusion resistance of the leaching solution and dissolved ions.

Towards a molecular understanding of cellulose dissolution in ionic liquids: anion/cation effect, synergistic mechanism and physicochemical aspects.

Science.gov (United States)

Li, Yao; Wang, Jianji; Liu, Xiaomin; Zhang, Suojiang

2018-05-07

Cellulose is one of the most abundant bio-renewable materials on the earth and its conversion to biofuels provides an appealing way to satisfy the increasing global energy demand. However, before carrying out the process of enzymolysis to glucose or polysaccharides, cellulose needs to be pretreated to overcome its recalcitrance. In recent years, a variety of ionic liquids (ILs) have been found to be effective solvents for cellulose, providing a new, feasible pretreatment strategy. A lot of experimental and computational studies have been carried out to investigate the dissolution mechanism. However, many details are not fully understood, which highlights the necessity to overview the current knowledge of cellulose dissolution and identify the research trend in the future. This perspective summarizes the mechanistic studies and microscopic insights of cellulose dissolution in ILs. Recent investigations of the synergistic effect of cations/anions and the distinctive structural changes of cellulose microfibril in ILs are also reviewed. Besides, understanding the factors controlling the dissolution process, such as the structure of anions/cations, viscosity of ILs, pretreatment temperature, heating rate, etc. , has been discussed from a structural and physicochemical viewpoint. At the end, the existing problems are discussed and future prospects are given. We hope this article would be helpful for deeper understanding of the cellulose dissolution process in ILs and the rational design of more efficient and recyclable ILs.

An inorganic CO2 diffusion and dissolution process explains negative CO2 fluxes in saline/alkaline soils

Science.gov (United States)

Ma, Jie; Wang, Zhong-Yuan; Stevenson, Bryan A.; Zheng, Xin-Jun; Li, Yan

2013-01-01

An ‘anomalous' negative flux, in which carbon dioxide (CO2) enters rather than is released from the ground, was studied in a saline/alkaline soil. Soil sterilization disclosed an inorganic process of CO2 dissolution into (during the night) and out of (during the day) the soil solution, driven by variation in soil temperature. Experimental and modeling analysis revealed that pH and soil moisture were the most important determinants of the magnitude of this inorganic CO2 flux. In the extreme cases of air-dried saline/alkaline soils, this inorganic process was predominant. While the diurnal flux measured was zero sum, leaching of the dissolved inorganic carbon in the soil solution could potentially effect net carbon ecosystem exchange. This finding implies that an inorganic module should be incorporated when dealing with the CO2 flux of saline/alkaline land. Neglecting this inorganic flux may induce erroneous or misleading conclusions in interpreting CO2 fluxes of these ecosystems. PMID:23778238

Effect of alteration phase formation on the glass dissolution rate

International Nuclear Information System (INIS)

Ebert, W.L.

1997-01-01

The dissolution rates of many glasses have been observed to increase upon the formation of certain alteration phases. While simulations have predicted the accelerating effect of formation of certain phases, the phases predicted to form in computer simulations are usually different than those observed to form in experiments. This is because kinetically favored phases form first in experiments, while simulations predict the thermodynamically favored phases. Static dissolution tests with crushed glass have been used to measure the glass dissolution rate after alteration phases form. Because glass dissolution rates are calculated on a per area basis, an important effect in tests conducted with crushed glass is the decrease in the surface area of glass that is available for reaction as the glass dissolves. This loss of surface area must be taken into account when calculating the dissolution rate. The phases that form and their effect on the dissolution rate are probably related to the glass composition. The impact of phase formation on the glass dissolution rate also varies according to the solubility products of the alteration phases and how the orthocilicic acid activity is affected. Insight into the relationship between the glass dissolution rate, solution chemistry and alteration phase formation is provided by the results of accelerated dissolution tests

Effect of alteration phase formation on the glass dissolution rate

Energy Technology Data Exchange (ETDEWEB)

Ebert, W L [Argonne National Laboratory, Chemical Technology Div. (United States)

1997-07-01

The dissolution rates of many glasses have been observed to increase upon the formation of certain alteration phases. While simulations have predicted the accelerating effect of formation of certain phases, the phases predicted to form in computer simulations are usually different than those observed to form in experiments. This is because kinetically favored phases form first in experiments, while simulations predict the thermodynamically favored phases. Static dissolution tests with crushed glass have been used to measure the glass dissolution rate after alteration phases form. Because glass dissolution rates are calculated on a per area basis, an important effect in tests conducted with crushed glass is the decrease in the surface area of glass that is available for reaction as the glass dissolves. This loss of surface area must be taken into account when calculating the dissolution rate. The phases that form and their effect on the dissolution rate are probably related to the glass composition. The impact of phase formation on the glass dissolution rate also varies according to the solubility products of the alteration phases and how the orthocilicic acid activity is affected. Insight into the relationship between the glass dissolution rate, solution chemistry and alteration phase formation is provided by the results of accelerated dissolution tests.

Electrochemical studies of the effect of H2 on UO2 dissolution

International Nuclear Information System (INIS)

King, F.; Shoesmith, D.W.

2004-09-01

This report summarises evidence for the effect of H 2 on the oxidation and dissolution of UO 2 derived from electrochemical studies. In the presence of γ-radiation or with SIMFUEL electrodes containing ε-particles, the corrosion potential (E CORR ) of UO 2 is observed to be suppressed in the presence of H 2 by up to several hundred milli volts. This effect has been observed at room temperature with 5 MPa H 2 (in the case of γ-irradiated solutions) and at 60 deg C with a H 2 partial pressure of only 0.002-0.014 MPa H 2 with the SIMFUEL electrode. The suppression of E CORR in the presence of H 2 indicates that the degree of surface oxidation and the rate of dissolution of UO 2 is lower in the presence of H 2 .The precise mechanism of the effect of H 2 is unclear at this time. The mechanism appears to involve a surface heterogeneous process, rather than a homogeneous solution process. Under some circumstances the value of E CORR approaches the equilibrium potential for the H 2 /H + couple, suggesting galvanic coupling between sites on which this electrochemical process is catalysed and the rest of the UO 2 surface. It is also possible that H* radical species, either produced radiolytically from H 2 O or by dissociation of H 2 on ε-particles or surface-active UO 2+x sites, reduce oxidised U(V)/U(VI) surface states to U(IV). The effect of H 2 on reducing the degree of surface oxidation is only partially reversible, since surfaces reduced in H 2 atmospheres (re-)oxidise more slowly and to a lesser degree than surfaces not previously exposed to H 2 . Homogeneous reactions between dissolved H 2 and either oxidants or dissolved U(VI) cannot explain the observed effects.Regardless of the precise mechanism, the suppression of the degree of surface oxidation results in lower UO 2 dissolution rates in the presence of H 2 . Application of an electro-chemical dissolution model to the observed E CORR values suggests that the fractional dissolution rate of used fuel in the

Chemical Dissolution of Simulant FCA Cladding and Plates

Energy Technology Data Exchange (ETDEWEB)

Daniel, G. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Pierce, R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); O' Rourke, P. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2017-11-08

The Savannah River Site (SRS) has received some fast critical assembly (FCA) fuel from the Japan Atomic Energy Agency (JAEA) for disposition. Among the JAEA FCA fuel are approximately 7090 rectangular Stainless Steel clad fuel elements. Each element has an internal Pu-10.6Al alloy metal wafer. The thickness of each element is either 1/16 inch or 1/32 inch. The dimensions of each element ranges from 2 inches x 1 inch to 2 inches x 4 inches. This report discusses the potential chemical dissolution of the FCA clad material or stainless steel. This technology uses nitric acid-potassium fluoride (HNO₃-KF) flowsheets of H-Canyon to dissolve the FCA elements from a rack of materials. Historically, dissolution flowsheets have aimed to maximize Pu dissolution rates while minimizing stainless steel dissolution (corrosion) rates. Because the FCA cladding is made of stainless steel, this work sought to accelerate stainless steel dissolution.

Montmorillonite dissolution kinetics: Experimental and reactive transport modeling interpretation

Science.gov (United States)

Cappelli, Chiara; Yokoyama, Shingo; Cama, Jordi; Huertas, F. Javier

2018-04-01

The dissolution kinetics of K-montmorillonite was studied at 25 °C, acidic pH (2-4) and 0.01 M ionic strength by means of well-mixed flow-through experiments. The variations of Si, Al and Mg over time resulted in high releases of Si and Mg and Al deficit, which yielded long periods of incongruent dissolution before reaching stoichiometric steady state. This behavior was caused by simultaneous dissolution of nanoparticles and cation exchange between the interlayer K and released Ca, Mg and Al and H. Since Si was only involved in the dissolution reaction, it was used to calculate steady-state dissolution rates, RSi, over a wide solution saturation state (ΔGr ranged from -5 to -40 kcal mol-1). The effects of pH and the degree of undersaturation (ΔGr) on the K-montmorillonite dissolution rate were determined using RSi. Employing dissolution rates farthest from equilibrium, the catalytic pH effect on the K-montmorillonite dissolution rate was expressed as Rdiss = k·aH0.56±0.05 whereas using all dissolution rates, the ΔGr effect was expressed as a non-linear f(ΔGr) function Rdiss = k · [1 - exp(-3.8 × 10-4 · (|ΔGr|/RT)2.13)] The functionality of this expression is similar to the equations reported for dissolution of Na-montmorillonite at pH 3 and 50 °C (Metz, 2001) and Na-K-Ca-montmorillonite at pH 9 and 80 °C (Cama et al., 2000; Marty et al., 2011), which lends support to the use of a single f(ΔGr) term to calculate the rate over the pH range 0-14. Thus, we propose a rate law that also accounts for the effect of pOH and temperature by using the pOH-rate dependence and the apparent activation energy proposed by Rozalén et al. (2008) and Amram and Ganor (2005), respectively, and normalizing the dissolution rate constant with the edge surface area of the K-montmorillonite. 1D reactive transport simulations of the experimental data were performed using the Crunchflow code (Steefel et al., 2015) to quantitatively interpret the evolution of the released cations

Chrysotile dissolution rates: Implications for carbon sequestration

International Nuclear Information System (INIS)

Thom, James G.M.; Dipple, Gregory M.; Power, Ian M.; Harrison, Anna L.

2013-01-01

Highlights: • Uncertainties in serpentine dissolution kinetics hinder carbon sequestration models. • A pH dependent, far from equilibrium dissolution rate law for chrysotile. • F chrysotile (mol/m 2 /s) = 10 −0.21pH−10.57 at 22 °C over pH 2–10. • Laboratory dissolution rates consistent with mine waste weathering observations. • Potential for carbon sequestration in mine tailings and aquifers is assessed. - Abstract: Serpentine minerals (e.g., chrysotile) are a potentially important medium for sequestration of CO 2 via carbonation reactions. The goals of this study are to report a steady-state, far from equilibrium chrysotile dissolution rate law and to better define what role serpentine dissolution kinetics will have in constraining rates of carbon sequestration via serpentine carbonation. The steady-state dissolution rate of chrysotile in 0.1 m NaCl solutions was measured at 22 °C and pH ranging from 2 to 8. Dissolution experiments were performed in a continuously stirred flow-through reactor with the input solutions pre-equilibrated with atmospheric CO 2 . Both Mg and Si steady-state fluxes from the chrysotile surface, and the overall chrysotile flux were regressed and the following empirical relationships were obtained: F Mg =-0.22pH-10.02;F Si =-0.19pH-10.37;F chrysotile =-0.21pH-10.57 where F Mg , F Si , and F chrysotile are the log 10 Mg, Si, and molar chrysotile fluxes in mol/m 2 /s, respectively. Element fluxes were used in reaction-path calculations to constrain the rate of CO 2 sequestration in two geological environments that have been proposed as potential sinks for anthropogenic CO 2 . Carbon sequestration in chrysotile tailings at 10 °C is approximately an order of magnitude faster than carbon sequestration in a serpentinite-hosted aquifer at 60 °C on a per kilogram of water basis. A serpentinite-hosted aquifer, however, provides a larger sequestration capacity. The chrysotile dissolution rate law determined in this study has

Waste form dissolution in bedded salt

International Nuclear Information System (INIS)

Kaufman, A.M.

1980-01-01

A model was devised for waste dissolution in bedded salt, a hydrologically tight medium. For a typical Spent UnReprocessed Fuel (SURF) emplacement, the dissolution rate wll be diffusion limited and will rise to a steady state value after t/sub eq/ approx. = 250 (1+(1-epsilon 0 ) K/sub D//epsilon 0 ) (years) epsilon 0 is the overpack porosity and K/sub d/ is the overpack sorption coefficient. The steady state dissolution rate itself is dominated by the solubility of UO 2 . Steady state rates between 5 x 10 -5 and .5 (g/year) are achievable by SURF emplacements in bedded salt without overpack, and rates between 5 x 10 -7 and 5 x 10 -3 (g/year) with an overpack having porosity of 10 -2

Electrochemical dissolution of fresh and passivated chalcopyrite electrodes. Effect of pyrite on the reduction of Fe3+ ions and transport processes within the passive film

International Nuclear Information System (INIS)

Olvera, O.G.; Quiroz, L.; Dixon, D.G.; Asselin, E.

2014-01-01

Graphical abstract: - Highlights: • FeS 2 increased the dissolution rate of fresh and passivated CuFeS 2 electrodes. • Fe 3+ reduction was the rate controlling step in the dissolution of fresh CuFeS 2 . • Diffusion within the passive film controlled the dissolution rate of passivated CuFeS 2 . - Abstract: The effect of pyrite (FeS 2 ) on the electrochemical dissolution of fresh and passivated chalcopyrite (CuFeS 2 ) electrodes has been studied. Current density values for the dissolution of CuFeS 2 were calculated from EIS measurements. FeS 2 increased the dissolution rate of fresh and passivated CuFeS 2 electrodes indicating that the galvanic effect continued even after the electrode was chemically passivated. The dissolution rate of CuFeS 2 decreased by a factor of 3 after the passivation treatment. Due to the low diffusion rates of ions within the CuFeS 2 passive film and due to an increase in the resistance to the transfer of electrons at the electrode/film interface, the activity of FeS 2 for the reduction of Fe 3+ ions was also reduced by a factor of 2.3 even though FeS 2 was not exposed to any chemical treatment. The results in this work indicate that the dissolution rate of the fresh CuFeS 2 electrode was controlled by the reduction of Fe 3+ ions whereas for the passivated CuFeS 2 electrode the dissolution rate was controlled by diffusion within the passive film

Emotional and Cognitive Coping in Relationship Dissolution

Science.gov (United States)

Wrape, Elizabeth R.; Jenkins, Sharon Rae; Callahan, Jennifer L.; Nowlin, Rachel B.

2016-01-01

Dissolution of a romantic relationship can adversely affect functioning among college students and represents one primary reason for seeking campus counseling. This study examined the associations among common coping strategies and distress following relationship dissolution. Avoidance and repetitive negative thinking (RNT) were significantly…

CALCIUM CARBONATE DISSOLUTION RATE IN LIMESTONE CONTACTORS

Science.gov (United States)

The rate of carbonate mineral dissolution from limestone was studied using a rotating disk apparatus and samples of limestone of varied composition. The purpose of this study was to determine the effect of limestone composition on the kinetics of carbonate mineral dissolution. Th...

Effect of glucosamine HCl on dissolution and solid state behaviours of piroxicam upon milling.

Science.gov (United States)

Al-Hamidi, Hiba; Edwards, Alison A; Douroumis, Dionysis; Asare-Addo, Kofi; Nayebi, Alireza Mohajjel; Reyhani-Rad, Siamak; Mahmoudi, Javad; Nokhodchi, Ali

2013-03-01

Piroxicam is a non-steroidal anti-inflammatory drug that is characterised by low solubility and high permeability. In order to improve the drug dissolution rate, the co-grinding method was used as an approach to prepare piroxicam co-ground in the carriers such as glucosamine hydrochloride. As, this amino sugar (glucosamine HCl) has been shown to decrease pain and improve mobility in osteoarthritis in joints, therefore, the incorporation of glucosamine in piroxicam formulations would be expected to offer additional benefits to patients. The effect of the order of grinding on the dissolution of piroxicam was also investigated. Co-ground drug and glucosamine were prepared in different ratios using a ball mill. The samples were then subjected to different grinding times. In order to investigate the effect of the grinding process on the dissolution behaviour of piroxicam, the drug was ground separately in the absence of glucosamine. Mixtures of ground piroxicam and unground D-glucosamine HCl were prepared. Physical mixtures of piroxicam and glucosamine were also prepared for comparison. The properties of prepared co-ground systems and physical mixtures were studied using a dissolution tester, FTIR, SEM, XRPD and DSC. These results showed that the presence of glucosamine HCl can increase dissolution rate of piroxicam compared to pure piroxicam. Generally, all dissolution profiles showed the fastest dissolution rate when ground piroxicam was mixed with unground glucosamine. This was closely followed by the co-grinding of piroxicam with glucosamine where lower grinding times showed the fastest dissolution. The solid state studies showed that the grinding of piroxicam for longer times had no effect on polymorphic form of piroxicam, whereas mixtures of piroxicam-glucosamine ground for longer times (60 min) converted piroxicam polymorph II to polymorph I. Copyright © 2012 Elsevier B.V. All rights reserved.

Dissolution corrosion of 316L austenitic stainless steels in contact with static liquid lead-bismuth eutectic (LBE) at 500 °C

Science.gov (United States)

Lambrinou, Konstantina; Charalampopoulou, Evangelia; Van der Donck, Tom; Delville, Rémi; Schryvers, Dominique

2017-07-01

This work addresses the dissolution corrosion behaviour of 316L austenitic stainless steels. For this purpose, solution-annealed and cold-deformed 316L steels were simultaneously exposed to oxygen-poor (steels than the solution-annealed steel, indicating the importance of the steel thermomechanical state. The thickness of the dissolution-affected zone was non-uniform, and sites of locally-enhanced dissolution were occasionally observed. The progress of LBE dissolution attack was promoted by the interplay of certain steel microstructural features (grain boundaries, deformation twin laths, precipitates) with the dissolution corrosion process. The identified dissolution mechanisms were selective leaching leading to steel ferritization, and non-selective leaching; the latter was mainly observed in the solution-annealed steel. The maximum corrosion rate decreased with exposure time and was found to be inversely proportional to the depth of dissolution attack.

Evaluating the role of re-adsorption of dissolved Hg(2+) during cinnabar dissolution using isotope tracer technique.

Science.gov (United States)

Jiang, Ping; Li, Yanbin; Liu, Guangliang; Yang, Guidi; Lagos, Leonel; Yin, Yongguang; Gu, Baohua; Jiang, Guibin; Cai, Yong

2016-11-05

Cinnabar dissolution is an important factor controlling mercury (Hg) cycling. Recent studies have suggested the co-occurrence of re-adsorption of the released Hg during the course of cinnabar dissolution. However, there is a lack of feasible techniques that can quantitatively assess the amount of Hg re-adsorbed on cinnabar when investigating cinnabar dissolution. In this study, a new method, based on isotope tracing and dilution techniques, was developed to study the role of Hg re-adsorption in cinnabar dissolution. The developed method includes two key components: (1) accurate measurement of both released and spiked Hg in aqueous phase and (2) estimation of re-adsorbed Hg on cinnabar surface via the reduction in spiked (202)Hg(2+). By adopting the developed method, it was found that the released Hg for trials purged with oxygen could reach several hundred μgL(-1), while no significant cinnabar dissolution was detected under anaerobic condition. Cinnabar dissolution rate when considering Hg re-adsorption was approximately 2 times the value calculated solely with the Hg detected in the aqueous phase. These results suggest that ignoring the Hg re-adsorption process can significantly underestimate the importance of cinnabar dissolution, highlighting the necessity of applying the developed method in future cinnabar dissolution studies. Copyright © 2016 Elsevier B.V. All rights reserved.

Transfer of drug dissolution testing by statistical approaches: Case study

Science.gov (United States)

AL-Kamarany, Mohammed Amood; EL Karbane, Miloud; Ridouan, Khadija; Alanazi, Fars K.; Hubert, Philippe; Cherrah, Yahia; Bouklouze, Abdelaziz

2011-01-01

The analytical transfer is a complete process that consists in transferring an analytical procedure from a sending laboratory to a receiving laboratory. After having experimentally demonstrated that also masters the procedure in order to avoid problems in the future. Method of transfers is now commonplace during the life cycle of analytical method in the pharmaceutical industry. No official guideline exists for a transfer methodology in pharmaceutical analysis and the regulatory word of transfer is more ambiguous than for validation. Therefore, in this study, Gauge repeatability and reproducibility (R&R) studies associated with other multivariate statistics appropriates were successfully applied for the transfer of the dissolution test of diclofenac sodium as a case study from a sending laboratory A (accredited laboratory) to a receiving laboratory B. The HPLC method for the determination of the percent release of diclofenac sodium in solid pharmaceutical forms (one is the discovered product and another generic) was validated using accuracy profile (total error) in the sender laboratory A. The results showed that the receiver laboratory B masters the test dissolution process, using the same HPLC analytical procedure developed in laboratory A. In conclusion, if the sender used the total error to validate its analytical method, dissolution test can be successfully transferred without mastering the analytical method validation by receiving laboratory B and the pharmaceutical analysis method state should be maintained to ensure the same reliable results in the receiving laboratory. PMID:24109204

Dissolution Threats and Legislative Bargaining

DEFF Research Database (Denmark)

Becher, Michael; Christiansen, Flemming Juul

2015-01-01

Chief executives in many parliamentary democracies have the power to dissolve the legislature. Despite a well-developed literature on the endogenous timing of parliamentary elections, political scientists know remarkably little about the strategic use of dissolution power to influence policymaking....... To address this gap, we propose and empirically evaluate a theoretical model of legislative bargaining in the shadow of executive dissolution power. The model implies that the chief executive's public support and legislative strength, as well as the time until the next constitutionally mandated election...

Sodium tetraphenylborate solubility and dissolution rates

International Nuclear Information System (INIS)

Barnes, M.J.; Peterson, R.A.; Swingle, R.F.; Reeves, C.T.

1995-01-01

The rate of solid sodium tetraphenylborate (NaTPB) dissolution in In-Tank Precipitation salt solutions has been experimentally determined. The data indicates that the dissolution rate of solid NaTPB is a minor contributor the lag time experienced in the 1983 Salt Decontamination Demonstration Test and should not be considered as the rate determining step. Current analytical models for predicting the time to reach the composite lower flammability limit assume that the lag time is not more than 6 hours, and the data supports this assumption (i.e., dissolution by itself requires much less than 6 hours). The data suggests that another step--such as mass transport, the reaction of a benzene precursor or the mixing behavior--is the rate determining factor for benzene release to the vapor space in Tank 48H. In addition, preliminary results from this program show that the degree of agitation employed is not a significant parameter in determining the rate of NaTPB dissolution. As a result of this study, an improved equation for predicting equilibrium tetraphenylborate solubility with respect to temperature and sodium ion concentration has been determined

Magnesite dissolution and precipitation rates at hydrothermal conditions

International Nuclear Information System (INIS)

Saldi, Giuseppe

2009-01-01

Magnesite (MgCO 3 ) is the stable anhydrous member of a series of Mg-carbonates with different degrees of hydration. Despite its relative scarcity in the natural environments, it constitutes an important mineral phase for the permanent sequestration of CO 2 as carbonate minerals. Experimental determination of magnesite precipitation and dissolution rates at conditions representative of the storage sites is therefore fundamental for the assessment of magnesite sequestration potential in basaltic and ultramafic rocks and the optimization of the techniques of CO 2 storage. Magnesite precipitation rates have been measured using mixed-flow and batch reactors as a function of temperature (100 ≤ T ≤ 200 deg. C), solution composition and CO 2 partial pressure (up to 30 bar). Rates were found to be independent of aqueous solution ionic strength at 0.1 M 3 2- activity at pH > 8. All rates obtained from mixed flow reactor experiments were found to be consistent with the model of Pokrovsky et al. (1999) where magnesite precipitation rates are proportional to the concentration of the >MgOH 2 + surface species. The study of magnesite crystallization using hydrothermal atomic force microscopy (HAFM) demonstrated the consistency of the rates derived from microscopic measurements with those obtained from bulk experiments and showed that these rates are also consistent with a spiral growth mechanism. According to AFM observations this mechanism controls magnesite growth over a wide range of temperatures and saturation states (15≤ Ω ≤200 for 80 ≤T 2 to accelerate the rate of the overall carbonation process, avoiding the inhibiting effect of carbonate ions on magnesite precipitation and increasing the rates of Mg-silicate dissolution via acidification of reacting solutions. Determination of magnesite dissolution rates by mixed flow reactor at 150 and 200 deg. C and at neutral to alkaline conditions allowed us to improve and extend to high temperatures the surface

Mathematical methods for quantification and comparison of dissolution testing data

Directory of Open Access Journals (Sweden)

Edina Vranić

2002-02-01

Full Text Available In recent years, drug release/dissolution from solid dosage forms has been the subject of intense and profitable scientific developments. Whenever a new solid dosage form is developed or produced, it is necessary to ensure that drug dissolutionoccurs in an appropriate manner. The pharmaceutical industry and the registration authorities do focus, nowadays, on drug dissolution studies. The quantitative analysis of the values obtained in dissolution/release tests is easier when mathematicalformulas that express the dissolution results as a function of some of the dosage forms characteristics are used. This work discusses the analysis of data obtained for dissolution profiles under different media pH conditions using mathematical methodsof analysis described by Moore and Flanner. These authors have described difference factor (f1 and similarity factor (f2, which can be used to characterise drug dissolution/release profiles. In this work we have used these formulas for evaluation of dissolution profiles of the conventional tablets in different pH of dissolution medium (range of physiological variations.

Preservation and Dissolution of the Target Firm's Embedded Ties in Acquisitions

NARCIS (Netherlands)

S. Spedale-Latimer (Simona); F.A.J. van den Bosch (Frans); H.W. Volberda (Henk)

2006-01-01

textabstractOur study builds on extant theory on embeddness to concentrate on the process of preservation and dissolution of the target firm’s embedded ties in acquisitions. We identify four critical areas - communication, idiosyncratic investments, inter-personal relations and, personnel turnover –

Status report on dissolution model development

International Nuclear Information System (INIS)

Jackson, D.D.

1983-07-01

The computer program PROTOCOL models the dissolution reactions of chemical species in water. It is being developed particularly to study the dissolution of proposed nuclear waste forms and related phases. Experimentally derived leaching rate functions are coupled to thermochemical equilibrium calculations and water flow rates. The program has been developed over a period of years. This report describes improvements that have been done in the past year

Radiolytic modelling of spent fuel oxidative dissolution mechanism. Calibration against UO2 dynamic leaching experiments

International Nuclear Information System (INIS)

Merino, J.; Cera, E.; Bruno, J.; Quinones, J.; Casas, I.; Clarens, F.; Gimenez, J.; Pablo, J. de; Rovira, M.; Martinez-Esparza, A.

2005-01-01

Calibration and testing are inherent aspects of any modelling exercise and consequently they are key issues in developing a model for the oxidative dissolution of spent fuel. In the present work we present the outcome of the calibration process for the kinetic constants of a UO 2 oxidative dissolution mechanism developed for using in a radiolytic model. Experimental data obtained in dynamic leaching experiments of unirradiated UO 2 has been used for this purpose. The iterative calibration process has provided some insight into the detailed mechanism taking place in the alteration of UO 2 , particularly the role of · OH radicals and their interaction with the carbonate system. The results show that, although more simulations are needed for testing in different experimental systems, the calibrated oxidative dissolution mechanism could be included in radiolytic models to gain confidence in the prediction of the long-term alteration rate of the spent fuel under repository conditions

Effect of magnesium stearate concentration on dissolution properties of ranitidine hydrochloride coated tablets.

Science.gov (United States)

Uzunović, Alija; Vranić, Edina

2007-08-01

Most pharmaceutical formulations also include a certain amount of lubricant to improve their flowability and prevent their adhesion to the surfaces of processing equipment. Magnesium stearate is an additive that is most frequently used as a lubricant. Magnesium stearate is capable of forming films on other tablet excipients during prolonged mixing, leading to a prolonged drug liberation time, a decrease in hardness, and an increase in disintegration time. It is hydrophobic, and there are many reports in the literature concerning its adverse effect on dissolution rates. The objective of this study was to evaluate the effects of two different concentrations of magnesium stearate on dissolution properties of ranitidine hydrochloride coated tablet formulations labeled to contain 150 mg. The uniformity content was also checked. During the drug formulation development, several samples were designed for choice of the formulation. For this study, two formulations containing 0,77 and 1,1% of magnesium stearate added in the manufacture of cores were chosen. Fraction of ranitidine hydrochloride released in dissolution medium was calculated from calibration curves. The data were analyzed using pharmacopeial test for similarity of dissolution profiles ( f2 equation), previously proposed by Moore and Flanner. Application of f2 equation showed differences in time-course of ranitidine hydrochloride dissolution properties. The obtained values indicate differences in drug release from analyzed ranitidine hydrochloride formulations and could cause differences in therapeutic response.

Dissolution studies of synthetic soddyite and uranophane

International Nuclear Information System (INIS)

Casas, I.; Perez, I.; Torrero, E.; Bruno, J.; Cera, E.; Duro, L.

1997-09-01

The dissolution of synthetically obtained soddyite and uranophane has been studied in solutions of low ionic strength. These are the likely final phases of the oxidative alternation pathway of uranium dioxide. The thermodynamic and kinetic dissolution properties of these phases have been determined at different bicarbonate concentrations. The solubilities determined in the experiments with soddyite correspond fairly well to the theoretical model calculated with a log K 0 s0 =3.9±0.7. For uranophane, the best fitting was obtained for a log K 0 s0 =11.7±0.6. The dissolution rate in the presence of bicarbonate gave for soddyite an average value of 6.8(±4.4) 10 -10 mol m -2 s -1 . For uranophane, under the same experimental conditions, the following dissolution rate equation has been derived: r 0 (mol m -2 s -1 )=10 -9±2. [HCO 3 - ] 0.69±0.09 2

Oxidative dissolution of ADOPT compared to standard UO{sub 2} fuel

Energy Technology Data Exchange (ETDEWEB)

Nilsson, Kristina [School of Chemical Science and Engineering, Applied Physical Chemistry, KTH Royal Institute of Technology, SE-100 44 Stockholm (Sweden); Roth, Olivia [Studsvik Nuclear AB, SE-611 82 Nyköping (Sweden); Jonsson, Mats, E-mail: matsj@kth.se [School of Chemical Science and Engineering, Applied Physical Chemistry, KTH Royal Institute of Technology, SE-100 44 Stockholm (Sweden)

2017-05-15

In this work we have studied oxidative dissolution of pure UO{sub 2} and ADOPT (UO{sub 2} doped with Al and Cr) pellets using H{sub 2}O{sub 2} and gammaradiolysis to induce the process. There is a small but significant difference in the oxidative dissolution rate of UO{sub 2} and ADOPT pellets, respectively. However, the difference in oxidative dissolution yield is insignificant. Leaching experiments were also performed on in-reactor irradiated ADOPT and UO{sub 2} pellets under oxidizing conditions. The results indicate that the U(VI) release is slightly slower from the ADOPT pellet compared to the UO{sub 2.} This could be attributed to differences in exposed surface area. However, fission products with low UO{sub 2} solubility display a higher relative release from ADOPT fuel compared to standard UO{sub 2}-fuel. This is attributed to a lower matrix solubility imposed by the dopants in ADOPT fuel. The release of Cs is higher from UO{sub 2} which is attributed to the larger grain size of ADOPT. - Highlights: •Oxidative dissolution of ADOPT fuel is compared to standard UO{sub 2} fuel. •Only marginal differences are observed. •The main difference observed is in the relative release rate of fission products. •Differences are claimed to be attributed to a lower matrix solubility imposed by the dopants in ADOPT fuel.

Does the dose-solubility ratio affect the mean dissolution time of drugs?

Science.gov (United States)

Lánský, P; Weiss, M

1999-09-01

To present a new model for describing drug dissolution. On the basis of the new model to characterize the dissolution profile by the distribution function of the random dissolution time of a drug molecule, which generalizes the classical first order model. Instead of assuming a constant fractional dissolution rate, as in the classical model, it is considered that the fractional dissolution rate is a decreasing function of the dissolved amount controlled by the dose-solubility ratio. The differential equation derived from this assumption is solved and the distribution measures (half-dissolution time, mean dissolution time, relative dispersion of the dissolution time, dissolution time density, and fractional dissolution rate) are calculated. Finally, instead of monotonically decreasing the fractional dissolution rate, a generalization resulting in zero dissolution rate at time origin is introduced. The behavior of the model is divided into two regions defined by q, the ratio of the dose to the solubility level: q 1 (saturation of the solution, saturation time). The singular case q = 1 is also treated and in this situation the mean as well as the relative dispersion of the dissolution time increase to infinity. The model was successfully fitted to data (1). This empirical model is descriptive without detailed physical reasoning behind its derivation. According to the model, the mean dissolution time is affected by the dose-solubility ratio. Although this prediction appears to be in accordance with preliminary application, further validation based on more suitable experimental data is required.

Kinetics of Inorganic Calcite Dissolution in Seawater under Pressure

Science.gov (United States)

Dong, S.; Subhas, A.; Rollins, N.; Berelson, W.; Adkins, J. F.

2016-02-01

While understanding calcium carbonate dissolution is vital in constructing global carbon cycles and predicting the effect of seawater acidification as a result of increasing atmospheric CO2, there is still a major debate over the basic formulation of a dissolution rate law. The kinetics of calcium carbonate dissolution are typically described by the equation: Rate=k(1-Ω)n, while Ω=[Ca2+][CO32-]/Ksp. In this study, 13C-labeled calcite is dissolved in unlabeled seawater and the evolving d13C composition of the fluid is traced over time to establish dissolution rate. Instead of changing ion concentration to obtain varying Ω (as in our previous study; Subhas et al. 2015), we changed Ksp by conducting experiments under different pressures (described in theory as ∂lnKsp/∂P=-ΔV/RT, where ΔV is partial molal volume). This involved the construction of a pressure vessel that could hold our sample bag and provide aliquots while remaining pressurized. Pressure experiments were conducted between 0-2000PSI. Results support the conclusion in our previous study that near-equilibrium dissolution rates are highly nonlinear, but give a disparate relationship between undersaturation and dissolution rate if Ω is calculated assuming the specific ΔV embedded in CO2SYS. A revised ΔV from -37cm3 to -65cm3 would make the dissolution formulation equation agree, but clearly appears unreasonable. Our results are explained by a pressure effect on carbonate dissolution kinetics over and above the influence of pressure on Ω. If this is a phenomenon that occurs in nature, then we would predict that dissolution should be occurring shallower in the water column (as sometimes observed) than indicated by standard Ω calculations.

Mechanisms and kinetics laws of inactive R7T7 reference glass dissolution in water at 90 deg C: initial dissolution rate measurements

International Nuclear Information System (INIS)

Advocat, T.; Ghaleb, D.; Vernaz, E.

1993-02-01

The initial dissolution rate of inactive R7T7 reference glass was measured at 90 deg C in dilute aqueous solutions first at unspecified pH, then with imposed pH values. In distilled water, R7T7 glass corrosion initially involved preferential extraction of boron and network modifier elements (Li, Na, Ca) as long as the solution pH remained acid. When the solution pH became alkaline, glass dissolution was stoichiometric. These two mechanisms were confirmed by dissolution tests in aqueous solutions at imposed pH values under acid and alkaline conditions. The initial dissolution rate r 0 in mole.cm -3 .s -1 also increased significantly in alkaline media when the pH of the aqueous phase increased: in slightly acid media, selective glass dissolution formed a residual, de-alkalinized, hydrated glass that was characterized by transmission electron microscopy and secondary ion mass spectrometry. Under steady-state dissolution conditions, the initial glass corrosion rate (in mole.cm -3 .s -1 ) was: in acid and alkaline media, amorphous and crystallized alteration products formed after complete dissolution of the silicated glass network. The first products formed consisted mainly of Zr, Rare Earths, Fe and Al. (author). 67 refs., 29 figs., 26 tabs., 21 plates

Actor bonds after relationship dissolution

DEFF Research Database (Denmark)

Skaates, Maria Anne

2000-01-01

Most of the presented papers at the 1st NoRD Workshop can be classified as belonging to the business marketing approach to relationship dissolution. Two papers were conceptual, and the remaining six were empirical studies. The first conceptual study by Skaates (2000) focuses on the nature...... of the actor bonds that remain after a business relationship has ended. The study suggests that an interdisciplinary approach would provide a richer understanding of the phenomenon; this could be achieved by using e.g. Bourdieu's sociological concepts in dissolution research....

Feasibility of Using Gluconolactone, Trehalose and Hydroxy-Propyl Gamma Cyclodextrin to Enhance Bendroflumethiazide Dissolution Using Lyophilisation and Physical Mixing Techniques

Directory of Open Access Journals (Sweden)

Ashraf Saleh

2018-02-01

Full Text Available Purpose: Hydrophobic drugs are facing a major challenge in dissolution rate enhancement and solubility in aqueous solutions; therefore, a variety of methods have been used to improve dissolution rate and/or solubility of bendroflumethiazide as a model hydrophobic drug. Methods: In this study, two main methods (physical mixing and lyophilisation were used with gluconolactone, hydroxyl propyl γ-ccyclodextrin, and trehalose to explore this challenge. Bendroflumethiazide, practically insoluble in water, was mixed with one of the three excipients gluconolactone, hydroxyl propyl γ-cyclodextrin, and trehalose in three different ratios 1:1, 1:2, 1:5. To the best of our knowledge, the dissolution of the drug has not been previously enhanced by using either these methods or any of the used excipients. Samples containing drug and each of the excipients were characterized via dissolution testing, Fourier Transform infra-red spectroscopy, differential scanning calorimetry, and scanning electron microscopy. Results: The used methods showed a significant enhancement in dug dissolution rate; physical mixing significantly, p < 0.05, increased the percentage of the drug released with time; for example, bendroflumethiazide dissolution in distilled water was improved from less than 20% to 99.79% within 90 min for physically mixed drug-cyclodextrin 1:5. The lyophilisation process was enhanced and the drug dissolution rate and the highest drug dissolution was achieved for (drug-gluconolactone 1:1 with 98.98% drug release within 90 min. Conclusions: the physical mixing and freeze drying processes significantly increased the percentage of drug release with time.

Novel silk fibroin films prepared by formic acid/hydroxyapatite dissolution method

International Nuclear Information System (INIS)

Ming, Jinfa; Liu, Zhi; Bie, Shiyu; Zhang, Feng; Zuo, Baoqi

2014-01-01

Bombyx mori silk fibroin from the silkworm was firstly found to be soluble in formic acid/hydroxyapatite system. The rheological behavior of silk fibroin solution was significantly influenced by HAp contents in dissolved solution. At the same time, silk fibroin nanofibers were observed in dissolved solution with 103.6 ± 20.4 nm in diameter. Moreover, the structure behavior of SF films prepared by formic acid/hydroxyapatite dissolution method was examined. The secondary structure of silk fibroin films was attributed to silk II structure (β-sheet), indicating that the hydroxyapatite contents in dissolved solution were not significantly affected by the structure of silk fibroin. The X-ray diffraction results exhibited obviously hydroxyapatite crystalline nature existing in silk fibroin films; however, when the hydroxyapatite content was 5.0 wt.% in dissolved solution, some hydroxyapatite crystals were converted to calcium hydrogen phosphate dehydrate in silk fibroin dissolution process. This result was also confirmed by Fourier transform infrared analysis and DSC measurement. In addition, silk fibroin films prepared by this dissolution method had higher breaking strength and extension at break. Based on these analyses, an understanding of novel SF dissolution method may provide an additional tool for designing and synthesizing advanced materials with more complex structures, which should be helpful in different fields, including biomaterial applications. - Highlights: • SF fibers were firstly successfully dissolved in FA/HAp solution. • The rheological behavior of SF solution was significantly influenced by HAp contents. • SF nanofibrils were observed in FA/HAp solution with 103.6 ± 20.4 nm in diameter. • SF films prepared by FA/HAp dissolution method had higher mechanical properties

Novel silk fibroin films prepared by formic acid/hydroxyapatite dissolution method

Energy Technology Data Exchange (ETDEWEB)

Ming, Jinfa, E-mail: jinfa.ming@gmail.com [National Engineering Laboratory for Modern Silk, Soochow University, Suzhou 215123 (China); College of Textile and Clothing Engineering, Soochow University, Suzhou 215021 (China); Liu, Zhi; Bie, Shiyu [National Engineering Laboratory for Modern Silk, Soochow University, Suzhou 215123 (China); College of Textile and Clothing Engineering, Soochow University, Suzhou 215021 (China); Zhang, Feng [Jiangsu Province Key Laboratory of Stem Cell Research, Medical College, Soochow University, Suzhou 215006 (China); Zuo, Baoqi, E-mail: bqzuo@suda.edu.cn [National Engineering Laboratory for Modern Silk, Soochow University, Suzhou 215123 (China); College of Textile and Clothing Engineering, Soochow University, Suzhou 215021 (China)

2014-04-01

Bombyx mori silk fibroin from the silkworm was firstly found to be soluble in formic acid/hydroxyapatite system. The rheological behavior of silk fibroin solution was significantly influenced by HAp contents in dissolved solution. At the same time, silk fibroin nanofibers were observed in dissolved solution with 103.6 ± 20.4 nm in diameter. Moreover, the structure behavior of SF films prepared by formic acid/hydroxyapatite dissolution method was examined. The secondary structure of silk fibroin films was attributed to silk II structure (β-sheet), indicating that the hydroxyapatite contents in dissolved solution were not significantly affected by the structure of silk fibroin. The X-ray diffraction results exhibited obviously hydroxyapatite crystalline nature existing in silk fibroin films; however, when the hydroxyapatite content was 5.0 wt.% in dissolved solution, some hydroxyapatite crystals were converted to calcium hydrogen phosphate dehydrate in silk fibroin dissolution process. This result was also confirmed by Fourier transform infrared analysis and DSC measurement. In addition, silk fibroin films prepared by this dissolution method had higher breaking strength and extension at break. Based on these analyses, an understanding of novel SF dissolution method may provide an additional tool for designing and synthesizing advanced materials with more complex structures, which should be helpful in different fields, including biomaterial applications. - Highlights: • SF fibers were firstly successfully dissolved in FA/HAp solution. • The rheological behavior of SF solution was significantly influenced by HAp contents. • SF nanofibrils were observed in FA/HAp solution with 103.6 ± 20.4 nm in diameter. • SF films prepared by FA/HAp dissolution method had higher mechanical properties.

Investigation of dissolution kinetics of a Nigerian columbite in ...

African Journals Online (AJOL)

Investigation of dissolution kinetics of a Nigerian columbite in hydrofluoric acid using the shrinking core model. ... Experimental results indicate that the dissolution rate is chemical reaction controlled, with reaction order of 0.57. Dissolution of over 90 % of the columbite was achieved in 5 h, using 20 M HF at 90 oC with 100 ...

Growth of rhombohedral insulin crystals and in vitro modeling of their dissolution in the blood stream

Energy Technology Data Exchange (ETDEWEB)

Nanev, C.N.; Dimitrov, I.L.; Hodzhaoglu, F.V. [Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences, Sofia (Bulgaria)

2011-02-15

Insulin is the only protein that is secreted in a crystalline form in a human healthy body. To mimic the secretion process we used NaCl salting-out to growing tiny rhombohedral Zn-insulin crystals. The dissolution of the insulin crystals is of special interest for the therapeutical praxis, because the human body is supplied with the physiologically active monomers of the insulin through dissolution of the crystalline granules secreted in the pancreatic {beta}-cells. Sets of tiny rhombohedral Zn-insulin crystals, which resembled the granules secreted in the {beta}-cells, were subjected to dissolution in blood plasma and model solutions. The impacts of the solution composition, flow rate, pH and ionic strength on the insulin crystal dissolution were investigated. The effect of the blood plasma was determinant because it dissolved the rhombohedral Zn-insulin crystals almost instantly, while the effects of solution's physicochemical characteristics were of minor importance. In addition, we found that the presence of abundant zinc ions suppressed the dissolution of the insulin crystals. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Aqueous dissolution of silver iodide and associated iodine release under reducing conditions with FeCl2 solution

International Nuclear Information System (INIS)

Inagaki, Yaohiro; Imamura, Toshitaka; Idemitsu, Kazuya; Arima, Tatsumi; Kato, Osamu; Nishimura, Tsutomu; Asano, Hidekazu

2008-01-01

An empirical and analytical study was performed on the aqueous dissolution of silver iodide (AgI) to release iodine under reducing conditions with Fe 2+ in order to understand the fundamental chemical and/or physical behavior of potential radioactive iodine waste forms under geological disposal conditions. Aqueous dissolution tests of AgI powder in FeCl 2 solutions (10 -6 M to 10 -3 M) were performed in a glove box purged with a gas mixture (Ar + 5% H 2 ). The test results showed that AgI dissolves to release iodine at extremely slow rates, being controlled by a diffusion process in any FeCl 2 solution. The comparison with thermodynamic calculations based on redox equilibria suggested that the AgI dissolution proceeds by redox reaction between Ag + and Fe 2+ ; however, it was far from the thermodynamic equilibrium. These results suggested that the form of AgI itself has a potential to immobilize iodine for a long time even under the disposal conditions. Solid-phase analysis for the reacted AgI by using SEM/EDS showed a certain amount of silver (maybe metallic silver) precipitated at the surface. On the basis of these results and discussion, a potential mechanism for the actual AgI dissolution was proposed as follows. The AgI dissolution proceeds by redox reaction between Ag + and Fe 2+ to release I - , which results in the precipitation of metallic silver as a reduction product of Ag + at the AgI surface to form a thin layer covering the AgI surface. The silver layer evolves to be protective against the transport of reactant species, by which the further dissolution to reach the equilibrium is suppressed. Consequently, the dissolution proceeds at extremely slow rates, being controlled by a diffusion process. (author)

Dissolution of calcium carbonate: observations and model results in the subpolar North Atlantic

Directory of Open Access Journals (Sweden)

K. Friis

2007-01-01

Full Text Available We investigate the significance of in situ dissolution of calcium carbonate above its saturation horizons using observations from the open subpolar North Atlantic [sNA] and to a lesser extent a 3-D biogeochemical model. The sNA is particularly well suited for observation-based detections of in situ, i.e. shallow-depth CaCO3 dissolution [SDCCD] as it is a region of high CaCO3 production, deep CaCO3 saturation horizons, and precisely-defined pre-formed alkalinity. Based on the analysis of a comprehensive alkalinity data set we find that SDCCD does not appear to be a significant process in the open sNA. The results from the model support the observational findings by indicating that there is not a significant need of SDCCD to explain observed patterns of alkalinity in the North Atlantic. Instead our investigation points to the importance of mixing processes for the redistribution of alkalinity from dissolution of CaCO3 from below its saturation horizons. However, mixing has recently been neglected for a number of studies that called for SDCCD in the sNA and on global scale.

Dissolution behavior of PFBR MOX fuel in nitric acid

International Nuclear Information System (INIS)

Kelkar, Anoop; Kapoor, Y.S.; Singh, Mamta; Meena, D.L.; Pandey, Ashish; Bhatt, R.B.; Behere, P.G.

2017-01-01

Present paper describes the dissolution characteristics of PFBR MOX fuel (U,Pu)O 2 in nitric acid. An overview of batch dissolution experiments, studying the percentage dissolution of uranium and plutonium in (U, Pu)O 2 MOX sintered pellets with different percentage of PuO 2 with reference to time and nitric acid concentration are described. 90% of uranium and plutonium of PFBR MOX gets dissolves in 2 hrs and amount of residue increases with the decrease in nitric acid concentration. Overall variation in percentage residue in PFBR MOX fuel after dissolution test also described. (author)

Do Workplace Sex Ratios Affect Partnership Formation and Dissolution?

DEFF Research Database (Denmark)

Svarer, Michael

In this paper, I analyse the association between workplace sex ratios and partnership formation and dissolution. I find that the risk of dissolution increases with the fraction of coworkers of the opposite sex at both the female and male workplace. On the other hand, workplace sex ratios are not ......In this paper, I analyse the association between workplace sex ratios and partnership formation and dissolution. I find that the risk of dissolution increases with the fraction of coworkers of the opposite sex at both the female and male workplace. On the other hand, workplace sex ratios...

CaCO3 dissolution by holothurians (sea cucumber): a case study from One Tree Reef, Great Barrier Reef

Science.gov (United States)

Schneider, K.; Silverman, J.; Kravitz, B.; Woolsey, E.; Eriksson, H.; Schneider-Mor, A.; Barbosa, S.; Rivlin, T.; Byrne, M.; Caldeira, K.

2012-12-01

Holothurians (sea cucumbers) are among the largest and most important deposit feeder in coral reefs. They play a role in nutrient and CaCO3 cycling within the reef structure. As a result of their digestive process they secrete alkalinity due to CaCO3 dissolution and organic matter degradation forming CO2 and ammonium. In a survey at station DK13 on One Three Reef we found that the population density of holothurians was > 1 individual m-2. The dominant sea cucumber species Holothuria leucospilota was collected from DK13. The increase in alkalinity due to CaCO3 dissolution in aquaria incubations was measured to be 47±7 μmol kg-1 in average per individual. Combining this dissolution rate with the sea cucumbers concentrations at DK13 suggest that they may account for a dissolution rate of 34.9±17.8 mmol m-2 day-1, which is equivalent to about half of night time community dissolution measured in DK13. This indicates that in reefs where the sea cucumber population is healthy and protected from fishing they can be locally important in the CaCO3 cycle. Preliminary result suggests that the CaCO3 dissolution rates are not affected by the chemistry of the sea water they are incubated in. Measurements of the empty digestive track volume of two sea cucumbers H. atra and Stichopus herrmanni were 36 ± 4 ml and 151 ± 14 ml, respectively. Based on these measurements it is estimated that these species process 19 ± 2kg and 80 ± 7kg CaCO3 sand yr-1 per individual, respectively. The annual dissolution rates of H. atra and S. herrmanni are 6.5±1.9g and 9.6±1.4g, respectively, suggest that 0.05±0.02% and 0.1±0.02% of the CaCO3 processed through their gut annually is dissolved. During the incubations the CaCO3 dissolution was 0.07±0.01%, 0.04±0.01% and 0.21±0.05% of the fecal casts for H. atra, H. leucospilota and S. herrmanni, respectively. Our result that the primary parameter determining the CaCO3 dissolution by sea cucumber is the amount of carbonate send in their gut

The complexity of nanoparticle dissolution and its importance in nanotoxicological studies

International Nuclear Information System (INIS)

Misra, Superb K.; Dybowska, Agnieszka; Berhanu, Deborah; Luoma, Samuel N.; Valsami-Jones, Eugenia

2012-01-01

Dissolution of nanoparticles (NPs) is an important property that alters their abundance and is often a critical step in determining safety of nanoparticles. The dissolution status of the NPs in exposure media (i.e. whether they remain in particulate form or dissolve — and to what extent), strongly affects the uptake pathway, toxicity mechanisms and the environmental compartment in which NPs will have the highest potential impact. A review of available dissolution data on NPs demonstrates there is a range of potential outcomes depending on the NPs and the exposure media. For example two nominally identical nanoparticles, in terms of size and composition, could have totally different dissolution behaviours, subject to different surface modifications. Therefore, it is imperative that toxicological studies are conducted in conjunction with dissolution of NPs to establish the true biological effect of NPs and hence, assist in their regulation. -- Graphical abstract: Various physicochemical factors affecting dissolution of nanoparticles. Highlights: ► In this study we discuss dissolution of nanoparticles. ► Physicochemical properties of nanoparticles influence dissolution. ► Measuring dissolution of nanoparticles can help to understand their biological response.

Composition and Dissolution of a Migratory, Weathered Coal Tar Creosote DNAPL

Directory of Open Access Journals (Sweden)

Kerstin E. Scherr

2016-09-01

Full Text Available Opaque, viscous tars derived from the carbonization of fossile carbon feedstocks, such coal tars and creosote, are long-term sources of groundwater contamination, predominantly with poly- and heterocyclic aromatic hydrocarbons (PAH. The dissolution, ageing and migratory behavior of dense, non aqueous phase liquid (DNAPL coal tar blobs and pools forming at the aquitard is not sufficiently understood to estimate the risk and adequately design groundwater treatment measures at a contaminated site. In this study, we investigate the composition and dissolution of a migrated, aged creosote DNAPL and corresponding experimental and groundwater profiles using comprehensive two-dimensional gas chromatography (GCxGC-MS. GC-FID unresolved compounds were attributed to methylated homocyclic species using GCxGC-MS in the Methylanthracene weight range. Equilibrium concentrations were estimated using Raoult’s law, assuming non-ideal behavior. Low molecular weight compounds were found to be prevalent even after decades of weathering, with Naphthalene (8% by mass representing the most abundant identified compound, contrary to the expected preferential depletion of hydrophilic compounds. Morevoer, dimethylnaphthalenes were relatively more abundant in the aqueous boundary layer than in the DNAPL. DNAPL migration over 400m with the groundwater flow effected lower viscosity and specific gravity of the migrated phase body in a superposition of weathering, transport and aquifer chromatography effects. Based on a decomposition of analysed and estimated constituents using the group contribution approach, reference DNAPL values for activity coefficients γi were used to model aqueous solubilities for selected compounds. Anthracene was close to its theoretical precipitation limit in the bulk DNAPL. While laboratory and modelled DNAPL dissolution behavior agree well, field data imply the presence of specific interfacial in situ processes significantly impacting dissolution

Evaluating the role of re-adsorption of dissolved Hg{sup 2+} during cinnabar dissolution using isotope tracer technique

Energy Technology Data Exchange (ETDEWEB)

Jiang, Ping [Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199 (United States); Li, Yanbin [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education/Qingdao Collaborative Innovation Center of Marine Science and Technology, Ocean University of China, Qingdao 266100 (China); Liu, Guangliang [Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199 (United States); Southeast Environmental Research Center, Florida International University, Miami, FL 33199 (United States); Yang, Guidi [College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002 (China); Lagos, Leonel [Applied Research Center, Florida International University, Miami, FL 33199 (United States); Yin, Yongguang [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China); Gu, Baohua [Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge TN 37831 (United States); Jiang, Guibin [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China); Cai, Yong, E-mail: cai@fiu.edu [Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199 (United States); Southeast Environmental Research Center, Florida International University, Miami, FL 33199 (United States)

2016-11-05

Highlights: • Develop a new method to study Hg re-adsorption in cinnabar. • Both isotope dilution and tracer techniques were adopted. • The presence of O{sub 2} can significantly enhance the dissolution of cinnabar. • Prove the necessity of including re-adsorption in estimating cinnabar dissolution. - Abstract: Cinnabar dissolution is an important factor controlling mercury (Hg) cycling. Recent studies have suggested the co-occurrence of re-adsorption of the released Hg during the course of cinnabar dissolution. However, there is a lack of feasible techniques that can quantitatively assess the amount of Hg re-adsorbed on cinnabar when investigating cinnabar dissolution. In this study, a new method, based on isotope tracing and dilution techniques, was developed to study the role of Hg re-adsorption in cinnabar dissolution. The developed method includes two key components: (1) accurate measurement of both released and spiked Hg in aqueous phase and (2) estimation of re-adsorbed Hg on cinnabar surface via the reduction in spiked {sup 202}Hg{sup 2+}. By adopting the developed method, it was found that the released Hg for trials purged with oxygen could reach several hundred μg L{sup −1}, while no significant cinnabar dissolution was detected under anaerobic condition. Cinnabar dissolution rate when considering Hg re-adsorption was approximately 2 times the value calculated solely with the Hg detected in the aqueous phase. These results suggest that ignoring the Hg re-adsorption process can significantly underestimate the importance of cinnabar dissolution, highlighting the necessity of applying the developed method in future cinnabar dissolution studies.

Resistive switching in ZrO2 films: physical mechanism for filament formation and dissolution

International Nuclear Information System (INIS)

Parreira, Pedro; McVitie, Stephen; MacLaren, D A

2014-01-01

Resistive switching devices, also called memristors, have attracted much attention due to their potential memory, logic and even neuromorphic applications. Multiple physical mechanisms underpin the non-volatile switching process and are ultimately believed to give rise to the formation and dissolution of a discrete conductive filament within the active layer. However, a detailed nanoscopic analysis that fully explains all the contributory events remains to be presented. Here, we present aspects of the switching events that are correlated back to tunable details of the device fabrication process. Transmission electron microscopy and atomically resolved electron energy loss spectroscopy (EELS) studies of electrically stressed devices will then be presented, with a view to understanding the driving forces behind filament formation and dissolution

Crystal modifications and dissolution rate of piroxicam.

Science.gov (United States)

Lyn, Lim Yee; Sze, Huan Wen; Rajendran, Adhiyaman; Adinarayana, Gorajana; Dua, Kamal; Garg, Sanjay

2011-12-01

Piroxicam is a nonsteroidal anti-inflammatory drug with low aqueous solubility which exhibits polymorphism. The present study was carried out to develop polymorphs of piroxicam with enhanced solubility and dissolution rate by the crystal modification technique using different solvent mixtures prepared with PEG 4000 and PVP K30. Physicochemical characteristics of the modified crystal forms of piroxicam were investigated by X-ray powder diffractometry, FT-IR spectrophotometry and differential scanning calorimetry. Dissolution and solubility profiles of each modified crystal form were studied and compared with pure piroxicam. Solvent evaporation method (method I) produced both needle and cubic shaped crystals. Slow crystallization from ethanol with addition of PEG 4000 or PVP K30 at room temperature (method II) produced cubic crystal forms. Needle forms produced by method I improved dissolution but not solubility. Cubic crystals produced by method I had a dissolution profile similar to that of untreated piroxicam but showed better solubility than untreated piroxicam. Cubic shaped crystals produced by method II showed improved dissolution, without a significant change in solubility. Based on the XRPD results, modified piroxicam crystals obtained by method I from acetone/benzene were cube shaped, which correlates well with the FTIR spectrum; modified needle forms obtained from ethanol/methanol and ethanol/acetone showed a slight shift of FTIR peak that may be attributed to differences in the internal structure or conformation.

Dissolution of cellulose in ionic liquid: A review

Science.gov (United States)

Mohd, N.; Draman, S. F. S.; Salleh, M. S. N.; Yusof, N. B.

2017-02-01

Dissolution of cellulose with ionic liquids (IL) and deep eutectic solvent (DES) lets the comprehensive dissolution of cellulose. Basically, cellulose can be dissolved, in some hydrophilic ionic liquids, such as 1-butyl-3-methylimidazolium chloride (BMIMCl) and 1-allyl-3-methylimidazolium chloride (AMIMCl). Chloride based ionic liquids are suitable solvents for cellulose dissolution. Although the ILs is very useful in fine chemical industry, its application in the pharmaceutical and food industry have been very limited due to issues with toxicity, purity, and high cost. Seeing to these limitations, new green alternative solvent which is DES was used. This green solvents, may be definitely treated as the next-generation reagents for more sustainable industrial development. Thus, this review aims to discuss the dissolution of cellulose either with ionic liquids or DES and its application.

Impact of vibration and agitation speed on dissolution of USP prednisone tablets RS and various IR tablet formulations.

Science.gov (United States)

Seeger, Nicole; Lange, Sigrid; Klein, Sandra

2015-08-01

Dissolution testing is an in vitro procedure which is widely used in quality control (QC) of solid oral dosage forms and, given that real biorelevant test conditions are applied, can also be used as a predictive tool for the in vivo performance of such formulations. However, if a dissolution method is intended to be used for such purposes, it has to deliver results that are only determined by the quality of the test product, but not by other variables. In the recent past, more and more questions were arising on how to address the effects of vibration on dissolution test results. The present study was performed to screen for the correlation of prednisone dissolution of USP Prednisone Tablets RS with vibration caused by a commercially available vibration source as well as to investigate how drug release from a range of immediate release formulations containing class 1-4 drugs of the biopharmaceutical classification scheme is affected by vibration when performing dissolution experiments at different agitation rates. Results of the present study show that the dissolution process of oral drug formulations can be affected by vibration. However, it also becomes clear that the degree of which a certain level of vibration impacts dissolution is strongly dependent on several factors such as drug properties, formulation parameters, and the design of the dissolution method. To ensure the establishment of robust and predictive dissolution test methods, the impact of variation should thus be considered in method design and validation.

The anodic dissolution of zinc and zinc alloys in alkaline solution. II. Al and Zn partial dissolution from 5% Al–Zn coatings

International Nuclear Information System (INIS)

Vu, T.N.; Mokaddem, M.; Volovitch, P.; Ogle, K.

2012-01-01

Graphical abstract: - Abstract: The polarization behavior of a 5 wt% Al–Zn steel coating (Galfan™) has been investigated in alkaline solution using atomic emission spectroelectrochemistry (AESEC). The instantaneous Zn and Al dissolution rates were measured as a function of time during a linear scan and potential step transients. The formation rate of insoluble oxides was determined from the difference between the convoluted total current and the sum of the elemental dissolution currents. It was found that, over a wide potential range, the zinc and aluminum partial currents behaved in a similar way to pure zinc and pure aluminum independently. However, during the period in which zinc was active, aluminum dissolution was inhibited. This is attributed to the inhibitive effect of the first and/or the second states of zinc oxide that are formed during the active potential domain. The third form of zinc oxide, observed at higher potential and responsible for the passivation of zinc dissolution, does not have a measurable effect on the Al dissolution rate.

Dilution physics modeling: Dissolution/precipitation chemistry

International Nuclear Information System (INIS)

Onishi, Y.; Reid, H.C.; Trent, D.S.

1995-09-01

This report documents progress made to date on integrating dilution/precipitation chemistry and new physical models into the TEMPEST thermal-hydraulics computer code. Implementation of dissolution/precipitation chemistry models is necessary for predicting nonhomogeneous, time-dependent, physical/chemical behavior of tank wastes with and without a variety of possible engineered remediation and mitigation activities. Such behavior includes chemical reactions, gas retention, solids resuspension, solids dissolution and generation, solids settling/rising, and convective motion of physical and chemical species. Thus this model development is important from the standpoint of predicting the consequences of various engineered activities, such as mitigation by dilution, retrieval, or pretreatment, that can affect safe operations. The integration of a dissolution/precipitation chemistry module allows the various phase species concentrations to enter into the physical calculations that affect the TEMPEST hydrodynamic flow calculations. The yield strength model of non-Newtonian sludge correlates yield to a power function of solids concentration. Likewise, shear stress is concentration-dependent, and the dissolution/precipitation chemistry calculations develop the species concentration evolution that produces fluid flow resistance changes. Dilution of waste with pure water, molar concentrations of sodium hydroxide, and other chemical streams can be analyzed for the reactive species changes and hydrodynamic flow characteristics

Determination of the dissolution slowness surface by study of etched shapes I. Morphology of the dissolution slowness surface and theoretical etched shapes

Science.gov (United States)

Leblois, T.; Tellier, C. R.

1992-07-01

We propose a theoretical model for the anisotropic etching of crystals, in order to be applied in the micromachining. The originality of the model is due to the introduction of dissolution tensors to express the representative surface of the dissolution slowness. The knowledge of the equation of the slowness surface allows us to determine the trajectories of all the elements which compose the starting surface. It is then possible to construct the final etched shape by numerical simulation. Several examples are given in this paper which show that the final etched shapes are correlated to the extrema of the dissolution slowness. Since the slowness surface must be determined from experiments, emphasis is placed on difficulties encountered when we correlate theory to experiments. Nous avons modélisé le processus de dissolution anisotrope des cristaux en vue d'une application à la simulation des formes obtenues par photolithogravure chimique. La principale originalité de ce modèle tient à l'introduction de tenseurs de dissolution pour exprimer la surface représentative de la lenteur de dissolution. La connaissance de l'équation de la lenteur de dissolution permet de calculer les trajectoires des différents éléments constituant la surface de départ puis de reconstituer par simulation la forme dissoute. Les simulations démontrent que les formes limites des cristaux dissous sont corrélées aux extrema de la lenteur de dissolution. La détermination de la surface de la lenteur se faisant à partir de mesures expérimetales, nous nous sommes efforcés de montrer toutes les difficultés attachées à cette analyse.

Dissolution kinetics of lead telluride in alkali solutions of hydrogen peroxide

International Nuclear Information System (INIS)

Danilova, M.G.; Sveshnikova, L.L.; Stavitskaya, T.A.; Repinskij, S.M.

1991-01-01

Dissolution kinetics of lead telluride in alkali solutions of hydrogen peroxide was investigated. Dependences of change of PbTe dissolution rate on concentration of hydrogen peroxide and alkali in the solution were obtained. It is shown that dissolution rate of lead telluride is affected by dissolution rate of lead oxide, representing the product of ReTe dissolution. The obtained regularities can be explained by change of solution structure with increase of KOH concentration and by the state of hydrogen peroxide in the solution

Dissolution Of 3013-DE Sample 10-16

International Nuclear Information System (INIS)

Taylor-Pashow, K.

2011-01-01

The HB-Line Facility has a long-term mission to dissolve and disposition legacy fissile materials. HB-Line dissolves plutonium dioxide (PuO 2 ) from K-Area parting support of the 3013 Destructive Examination (DE) program. The PuO 2 -bearing solids originate from a variety of unit operations and processing facilities, but all of the material is assumed to be high-fired (i.e., calcined in air for a minimum of two hours at (ge) 750 C). The Savannah River National Laboratory (SRNL) conducted dissolution flowsheet studies on 3013 DE Sample 10-16 (can R610826), which contains weapons-grade plutonium (Pu) as the fissile material. The dissolution flowsheet study was performed for 4 hours at 108 C on unwashed material using 12 M nitric acid (HNO 3 ) containing 0.20 M potassium fluoride (KF). After 4 hours at 108 C, the 239 Pu Equivalent concentration was 32.5 g/L (gamma, 5.0% uncertainty). The insoluble residue comprised 9.88 wt % of the initial bulk weight, and contained 5.31-5.95 wt % of the initial Pu. The residue contained Pu in the highest concentration, followed by tungsten (W). Analyses detected 2,770 mg/L chloride (Cl - ) in the final dissolver solution (3.28 wt %), which is significantly lower than the amount of Cl - detected by prompt gamma (9.86 wt %) and the 3013 DE Surveillance program (14.7 wt %). A low bias in chloride measurement is anticipated due to volatilization during the experiment. Gas generation studies found approximately 60 mL of gas per gram of sample produced during the first 30 minutes of dissolution. Little to no gas was produced after the first 30 minutes. Hydrogen gas (H 2 ) was not detected in the sample. Based on detection limits and accounting for dilution, the generated gas contained 2 , which is well below the 4.0 vol % flammability limit for H 2 in air. Filtration of the dissolver solution occurred readily. When aluminum nitrate nonahydrate (ANN) was added to the filtered dissolver solution at a 3:1 Al:F molar ratio, and stored at room

Effect of dissolution on the load–settlement behavior of shallow foundations

KAUST Repository

Cha, Minsu

2016-03-10

Mineral dissolution and solid-liquid phase change may cause settlement or affect the bearing capacity of shallow foundations. The effect of gradual grain dissolution on small-scale shallow foundation behavior is investigated using the discrete element method. Results show that dissolution is most detrimental during early stages, as initially contacting particles shrink and force chains must reform throughout the medium. Porosity tends to increase during dissolution and force chains evolve into strong localized forces with a honeycomb topology. Higher settlements are required to mobilize bearing resistance in postdissolution sediments than in pre-dissolution ones. Subsurface mineral dissolution beneath a footing under load is the worst condition; in fact, settlements in such cases are higher than when a foundation load is applied on a sediment that has already experienced dissolution. © the author(s) or their institution(s).

Effect of dissolution on the load–settlement behavior of shallow foundations

KAUST Repository

Cha, Minsu; Santamarina, Carlos

2016-01-01

Mineral dissolution and solid-liquid phase change may cause settlement or affect the bearing capacity of shallow foundations. The effect of gradual grain dissolution on small-scale shallow foundation behavior is investigated using the discrete element method. Results show that dissolution is most detrimental during early stages, as initially contacting particles shrink and force chains must reform throughout the medium. Porosity tends to increase during dissolution and force chains evolve into strong localized forces with a honeycomb topology. Higher settlements are required to mobilize bearing resistance in postdissolution sediments than in pre-dissolution ones. Subsurface mineral dissolution beneath a footing under load is the worst condition; in fact, settlements in such cases are higher than when a foundation load is applied on a sediment that has already experienced dissolution. © the author(s) or their institution(s).

Dissolution rate measurements of sea water soluble pigments for antifouling paints

DEFF Research Database (Denmark)

Yebra, Diego Meseguer; Kiil, Søren; Erik Weinell, Claus

2006-01-01

The dissolution of soluble pigments from both tin-based and tin-free chemically active antifouling (AF) paints is a key process influencing their polishing and biocide leaching rates. In this context, a low time- and resources-consuming method capable of screening the pigment behaviour in the sea...

Mercury-free dissolution of aluminum-clad fuel in nitric acid

Science.gov (United States)

Christian, Jerry D.; Anderson, Philip A.

1994-01-01

A mercury-free dissolution process for aluminum involves placing the aluminum in a dissolver vessel in contact with nitric acid-fluoboric acid mixture at an elevated temperature. By maintaining a continuous flow of the acid mixture through the dissolver vessel, an effluent containing aluminum nitrate, nitric acid, fluoboric acid and other dissolved components are removed.

Effect of Acid Dissolution Conditions on Recovery of Valuable Metals from Used Plasma Display Panel Scrap

Directory of Open Access Journals (Sweden)

Kim Chan-Mi

2017-06-01

Full Text Available The objective of this particular study was to recover valuable metals from waste plasma display panels using high energy ball milling with subsequent acid dissolution. Dissolution of milled (PDP powder was studied in HCl, HNO3, and H2SO4 acidic solutions. The effects of dissolution acid, temperature, time, and PDP scrap powder to acid ratio on the leaching process were investigated and the most favorable conditions were found: (1 valuable metals (In, Ag, Mg were recovered from PDP powder in a mixture of concentrated hydrochloric acid (HCl:H2O = 50:50; (2 the optimal dissolution temperature and time for the valuable metals were found to be 60°C and 30 min, respectively; (3 the ideal PDP scrap powder to acid solution ratio was found to be 1:10. The proposed method was applied to the recovery of magnesium, silver, and indium with satisfactory results.

Recovery of uranium from (U,Gd)O{sub 2} nuclear fuel scrap using dissolution and precipitation in carbonate media

Energy Technology Data Exchange (ETDEWEB)

Kim, Kwang-Wook, E-mail: nkwkim@kaeri.re.kr [Korea Atomic Energy Research Institute, 1045 Daedeok daero, Yuseong, Daejeon 305-353 (Korea, Republic of); KEPCO NF 1047 Daedeok daero, Yuseong, Daejeon 305-353 (Korea, Republic of); Hyun, Jun-Taek; Lee, Eil-Hee; Park, Geun-Il; Lee, Kune-Woo [Korea Atomic Energy Research Institute, 1045 Daedeok daero, Yuseong, Daejeon 305-353 (Korea, Republic of); Yoo, Myung-June [KEPCO NF 1047 Daedeok daero, Yuseong, Daejeon 305-353 (Korea, Republic of); Song, Kee-Chan; Moon, Jei-Kwon [Korea Atomic Energy Research Institute, 1045 Daedeok daero, Yuseong, Daejeon 305-353 (Korea, Republic of)

2011-11-15

Highlights: > A treatment of (U,Gd)O{sub 2} scrap with a dissolution in carbonate solution with H{sub 2}O{sub 2}. > Partial dissolution of Gd together with uranium in carbonate solution. > Solubilities of Gd in solutions with and without carbonate at several pHs. > Purification of Gd-contaminated UO{sub 4} by dissolution and precipitation of UO{sub 4}. - Abstract: This work studied a process to recover uranium from contaminated (U,Gd)O{sub 2} scraps generated from nuclear fuel fabrication processes by using the dissolution of (U,Gd)O{sub 2} scraps in a carbonate with H{sub 2}O{sub 2} and the precipitation of the dissolved uranium as UO{sub 4}. The dissolution characteristics of uranium, Gd, and impurity metal oxides were tested, and the behaviors of UO{sub 4} precipitation and Gd solubility were evaluated with changes of the pH of the solution. A little Gd was entrained in the UO{sub 4} precipitate to contaminate the uranium precipitate. Below a pH of 3, the uranium dissolved in the form of uranyl peroxo-carbonato complex ions in the carbonate solution was precipitated as UO{sub 4} with a high precipitation yield, and the Gd had a very high solubility. Using these characteristics, the Gd-contaminated UO{sub 4} could be purified using dissolution in a 1-M HNO{sub 3} solution with heating and re-precipitation upon addition of H{sub 2}O{sub 2} to the solution. Finally, an environmentally friendly and economical process to recover pure uranium from contaminated (U,Gd)O{sub 2} scraps was suggested.

High temperature dissolution of chromium substituted nickel ferrite in nitrilotriacetic acid medium

Energy Technology Data Exchange (ETDEWEB)

Sathyaseelan, V.S.; Chandramohan, P.; Velmurugan, S., E-mail: svelu@igcar.gov.in

2016-12-01

High temperature (HT) dissolution of chromium substituted nickel ferrite was carried out with relevance to the decontamination of nuclear reactors by way of chemical dissolution of contaminated corrosion product oxides present on stainless steel coolant circuit surfaces. Chromium substituted nickel ferrites of composition, NiFe{sub (2−x)}Cr{sub x}O{sub 4} (x ≤ 1), was synthetically prepared and characterized. HT dissolution of these oxides was carried out in nitrilotriacetic acid medium at 160 °C. Dissolution was remarkably increased at 160 °C when compared to at 85 °C in a reducing decontamination formulation. Complete dissolution could be achieved for the oxides with chromium content 0 and 0.2. Increasing the chromium content brought about a marked reduction in the dissolution rate. About 40 fold decrease in rate of dissolution was observed when chromium was increased from 0 to 1. The rate of dissolution was not very significantly reduced in the presence of N{sub 2}H{sub 4}. Dissolution of oxide was found to be stoichiometric. - Highlights: • Dissolution of NiFe{sub (2−x)}Cr{sub x}O{sub 4} was remarkably increased at 160 °C in NTA medium. • The dissolution was significantly decreasing with the increase in Cr content in the oxide. • Dissolution rate is dependent on the lability of metal-oxo bonds. • The rate of dissolution was not significantly reduced in the presence of N{sub 2}H{sub 4.} • NTA at high temperature is effective for decontamination of stainless steel surfaces.

Dissolution performance of plutonium nitride based fuel materials

Energy Technology Data Exchange (ETDEWEB)

Aneheim, E.; Hedberg, M. [Nuclear Chemistry, Chemistry and Chemical Engineering, Chalmers University of Technology, Kemivaegen 4, Gothenburg, SE41296 (Sweden)

2016-07-01

Nitride fuels have been regarded as one viable fuel option for Generation IV reactors due to their positive features compared to oxides. To be able to close the fuel cycle and follow the Generation IV concept, nitrides must, however, demonstrate their ability to be reprocessed. This means that the dissolution performance of actinide based nitrides has to be thoroughly investigated and assessed. As the zirconium stabilized nitrides show even better potential as fuel material than does the pure actinide containing nitrides, investigations on the dissolution behavior of both PuN and (Pu,Zr)N has been undertaken. If possible it is desirable to perform the fuel dissolutions using nitric acid. This, as most reprocessing strategies using solvent-solvent extraction are based on a nitride containing aqueous matrix. (Pu,Zr)N/C microspheres were produced using internal gelation. The spheres dissolution performance was investigated using nitric acid with and without additions of HF and Ag(II). In addition PuN fuel pellets were produced from powder and their dissolution performance were also assessed in a nitric acid based setting. It appears that both PuN and (Pu,Zr)N/C fuel material can be completely dissolved in nitric acid of high concentration with the use of catalytic amounts of HF. The amount of HF added strongly affects dissolution kinetics of (Pu, Zr)N and the presence of HF affects the 2 solutes differently, possibly due to inhomogeneity o the initial material. Large additions of Ag(II) can also be used to facilitate the dissolution of (Pu,Zr)N in nitric acid. PuN can be dissolved by pure nitric acid of high concentration at room temperature while (Pu, Zr)N is unaffected under similar conditions. At elevated temperature (reflux), (Pu,Zr)N can, however, also be dissolved by concentrated pure nitric acid.

A critical evaluation of the local-equilibrium assumption in modeling NAPL-pool dissolution

Science.gov (United States)

Seagren, Eric A.; Rittmann, Bruce E.; Valocchi, Albert J.

1999-07-01

An analytical modeling analysis was used to assess when local equilibrium (LE) and nonequilibrium (NE) modeling approaches may be appropriate for describing nonaqueous-phase liquid (NAPL) pool dissolution. NE mass-transfer between NAPL pools and groundwater is expected to affect the dissolution flux under conditions corresponding to values of Sh'St (the modified Sherwood number ( Lxkl/ Dz) multiplied by the Stanton number ( kl/ vx))≈400, the NE and LE solutions converge, and the LE assumption is appropriate. Based on typical groundwater conditions, many cases of interest are expected to fall in this range. The parameter with the greatest impact on Sh'St is kl. The NAPL pool mass-transfer coefficient correlation of Pfannkuch [Pfannkuch, H.-O., 1984. Determination of the contaminant source strength from mass exchange processes at the petroleum-ground-water interface in shallow aquifer systems. In: Proceedings of the NWWA/API Conference on Petroleum Hydrocarbons and Organic Chemicals in Ground Water—Prevention, Detection, and Restoration, Houston, TX. Natl. Water Well Assoc., Worthington, OH, Nov. 1984, pp. 111-129.] was evaluated using the toluene pool data from Seagren et al. [Seagren, E.A., Rittmann, B.E., Valocchi, A.J., 1998. An experimental investigation of NAPL-pool dissolution enhancement by flushing. J. Contam. Hydrol., accepted.]. Dissolution flux predictions made with kl calculated using the Pfannkuch correlation were similar to the LE model predictions, and deviated systematically from predictions made using the average overall kl=4.76 m/day estimated by Seagren et al. [Seagren, E.A., Rittmann, B.E., Valocchi, A.J., 1998. An experimental investigation of NAPL-pool dissolution enhancement by flushing. J. Contam. Hydrol., accepted.] and from the experimental data for vx>18 m/day. The Pfannkuch correlation kl was too large for vx>≈10 m/day, possibly because of the relatively low Peclet number data used by Pfannkuch [Pfannkuch, H.-O., 1984. Determination

Chitosan and chitosan chlorhydrate based various approaches for enhancement of dissolution rate of carvedilol

Directory of Open Access Journals (Sweden)

Shete Amol S

2012-12-01

Full Text Available Abstract Background and the purpose of the study Carvedilol nonselective β-adrenoreceptor blocker, chemically (±-1-(Carbazol-4-yloxy-3-[[2-(o-methoxypHenoxy ethyl] amino]-2-propanol, slightly soluble in ethyl ether; and practically insoluble in water, gastric fluid (simulated, TS, pH 1.1, and intestinal fluid (simulated, TS without pancreatin, pH 7.5 Compounds with aqueous solubility less than 1% W/V often represents dissolution rate limited absorption. There is need to enhance the dissolution rate of carvedilol. The objective of our present investigation was to compare chitosan and chitosan chlorhydrate based various approaches for enhancement of dissolution rate of carvedilol. Methods The different formulations were prepared by different methods like solvent change approach to prepare hydrosols, solvent evaporation technique to form solid dispersions and cogrind mixtures. The prepared formulations were characterized in terms of saturation solubility, drug content, infrared spectroscopy (FTIR, differential scanning calorimetry (DSC, powder X-ray diffraction (PXRD, electron microscopy, in vitro dissolution studies and stability studies. Results The practical yield in case of hydrosols was ranged from 59.76 to 92.32%. The drug content was found to uniform among the different batches of hydrosols, cogrind mixture and solid dispersions ranged from 98.24 to 99.89%. There was significant improvement in dissolution rate of carvedilol with chitosan chlorhdyrate as compare to chitosan and explanation to this behavior was found in the differences in the wetting, solubilities and swelling capacity of the chitosan and chitosan salts, chitosan chlorhydrate rapidly wet and dissolve upon its incorporation into the dissolution medium, whereas the chitosan base, less water soluble, would take more time to dissolve. Conclusion This technique is scalable and valuable in manufacturing process in future for enhancement of dissolution of poorly water soluble

A dissolution-diffusion sliding model for soft rock grains with hydro-mechanical effect

Directory of Open Access Journals (Sweden)

Z. Liu

2018-06-01

Full Text Available The deformation and failure of soft rock affected by hydro-mechanical (HM effect are one of the most concerns in geotechnical engineering, which are basically attributed to the grain sliding of soft rock. This study tried to develop a dissolution-diffusion sliding model for the typical red bed soft rock in South China. Based on hydration film, mineral dissolution and diffusion theory, and geochemical thermodynamics, a dissolution-diffusion sliding model with the HM effect was established to account for the sliding rate. Combined with the digital image processing technology, the relationship between the grain size of soft rock and the amplitude of sliding surface was presented. An equation for the strain rate of soft rocks under steady state was also derived. The reliability of the dissolution-diffusion sliding model was verified by triaxial creep tests on the soft rock with the HM coupling effect and by the relationship between the inversion average disjoining pressure and the average thickness of the hydration film. The results showed that the sliding rate of the soft rock grains was affected significantly by the waviness of sliding surface, the shear stress, and the average thickness of hydration film. The average grain size is essential for controlling the steady-state creep rate of soft rock. This study provides a new idea for investigating the deformation and failure of soft rock with the HM effect. Keywords: Soft rock, Hydro-mechanical (HM effect, Mineral dissolution-diffusion, Grain sliding model

Effect of Magnesium Stearate Concentration on Dissolution Properties of Ranitidine Hydrochloride Coated Tablets

Directory of Open Access Journals (Sweden)

Alija Uzunović

2007-08-01

Full Text Available Most pharmaceutical formulations also include a certain amount of lubricant to improve their flowability and prevent their adhesion to the surfaces of processing equipment. Magnesium stearate is an additive that is most frequently used as a lubricant. Magnesium stearate is capable of forming films on other tablet excipients during prolonged mixing, leading to a prolonged drug liberation time, a decrease in hardness, and an increase in disintegration time. It is hydrophobic, and there are many reports in the literature concerning its adverse effect on dissolution rates.The objective of this study was to evaluate the effects of two different concentrations of magnesium stearate on dissolution properties of ranitidine hydrochloride coated tablet formulations labeled to contain 150 mg. The uniformity content was also checked.During the drug formulation development, several samples were designed for choice of the formulation. For this study, two formulations containing 0,77 and 1,1% of magnesium stearate added in the manufacture of cores were chosen. Fraction of ranitidine hydrochloride released in dissolution medium was calculated from calibration curves. The data were analyzed using pharmaco-peial test for similarity of dissolution profiles (f2 equation, previously proposed by Moore and Flanner.Application of f2 equation showed differences in time-course of ranitidine hydrochloride dissolution properties. The obtained values indicate differences in drug release from analyzed ranitidine hydrochloride formulations and could cause differences in therapeutic response.

Kozeny-Carman permeability relationship with disintegration process predicted from early dissolution profiles of immediate release tablets.

Science.gov (United States)

Kumari, Parveen; Rathi, Pooja; Kumar, Virender; Lal, Jatin; Kaur, Harmeet; Singh, Jasbir

2017-07-01

This study was oriented toward the disintegration profiling of the diclofenac sodium (DS) immediate-release (IR) tablets and development of its relationship with medium permeability k perm based on Kozeny-Carman equation. Batches (L1-L9) of DS IR tablets with different porosities and specific surface area were prepared at different compression forces and evaluated for porosity, in vitro dissolution and particle-size analysis of the disintegrated mass. The k perm was calculated from porosities and specific surface area, and disintegration profiles were predicted from the dissolution profiles of IR tablets by stripping/residual method. The disintegration profiles were subjected to exponential regression to find out the respective disintegration equations and rate constants k d . Batches L1 and L2 showed the fastest disintegration rates as evident from their bi-exponential equations while the rest of the batches L3-L9 exhibited the first order or mono-exponential disintegration kinetics. The 95% confidence interval (CI 95% ) revealed significant differences between k d values of different batches except L4 and L6. Similar results were also spotted for dissolution profiles of IR tablets by similarity (f 2 ) test. The final relationship between k d and k perm was found to be hyperbolic, signifying the initial effect of k perm on the disintegration rate. The results showed that disintegration profiling is possible because a relationship exists between k d and k perm . The later being relatable with porosity and specific surface area can be determined by nondestructive tests.

Diurnal variation in rates of calcification and carbonate sediment dissolution in Florida Bay

Science.gov (United States)

Yates, K.K.; Halley, R.B.

2006-01-01

Water quality and circulation in Florida Bay (a shallow, subtropical estuary in south Florida) are highly dependent upon the development and evolution of carbonate mud banks distributed throughout the Bay. Predicting the effect of natural and anthropogenic perturbations on carbonate sedimentation requires an understanding of annual, seasonal, and daily variations in the biogenic and inorganic processes affecting carbonate sediment precipitation and dissolution. In this study, net calcification rates were measured over diurnal cycles on 27 d during summer and winter from 1999 to 2003 on mud banks and four representative substrate types located within basins between mud banks. Substrate types that were measured in basins include seagrass beds of sparse and intermediate density Thalassia sp., mud bottom, and hard bottom communities. Changes in total alkalinity were used as a proxy for calcification and dissolution. On 22 d (81%), diurnal variation in rates of net calcification was observed. The highest rates of net carbonate sediment production (or lowest rates of net dissolution) generally occurred during daylight hours and ranged from 2.900 to -0.410 g CaCO3 m-2 d-1. The lowest rates of carbonate sediment production (or net sediment dissolution) occurred at night and ranged from 0.210 to -1.900 g CaCO3 m -2 night-1. During typical diurnal cycles, dissolution during the night consumed an average of 29% of sediment produced during the day on banks and 68% of sediment produced during the day in basins. Net sediment dissolution also occurred during daylight, but only when there was total cloud cover, high turbidity, or hypersalinity. Diurnal variation in calcification and dissolution in surface waters and surface sediments of Florida Bay is linked to cycling of carbon dioxide through photosynthesis and respiration. Estimation of long-term sediment accumulation rates from diurnal rates of carbonate sediment production measured in this study indicates an overall average

Diagenesis of a drapery speleothem from Castañar Cave: from dissolution to dolomitization

Directory of Open Access Journals (Sweden)

Martín-Pérez A.

2012-07-01

Full Text Available A drapery speleothem (DRA-1 from Castañar Cave in Spain was subjected to a detailed petrographical study in order to identify its primary and diagenetic features. The drapery’s present day characteristics are the result of the combined effects of the primary and diagenetic processes that DRA-1 underwent. Its primary minerals are calcite, aragonite and huntite. Calcite is the main constituent of the speleothem, whereas aragonite forms as frostwork over the calcite. Huntite is the main mineral of moonmilk which covers the tips of aragonite. These primary minerals have undergone a set of diagenetic processes, which include: 1 partial dissolution or corrosion that produces the formation of powdery matt-white coatings on the surface of the speleothem. These are seen under the microscope as dark and highly porous microcrystalline aggregates; 2 total dissolution produces pores of few cm2 in size; 3 calcitization and dolomitization of aragonite result in the thickening and lost of shine of the aragonite fibres. Microscopically, calcitization is seen as rhombohedral crystals which cover and replace aragonite forming mosaics that preserve relics of aragonite precursor. Dolomitization results in the formation of microcrystalline rounded aggregates over aragonite fibres. These aggregates are formed by dolomite crystals of around 1 μm size. The sequence of diagenetic processes follows two main pathways. Pathway 1 is driven by the increase of saturation degree and Mg/Ca ratio of the karstic waters and is visible in the NW side of the drapery. This sequence of processes includes: 1 aragonite and huntite primary precipitation and 2 dolomitization. Pathway 2 is driven by a decrease in the degree of saturation of calcite and aragonite and Mg/Ca ratio of the cave waters, and it is observed in the SE side of the drapery. The diagenetic processes of the second pathway include: 1 calcitization of aragonite; 2 incomplete dissolution (micritization of both

Plutonium dioxide dissolution in glass

International Nuclear Information System (INIS)

Vienna, J.D.; Alexander, D.L.; Li, Hong

1996-09-01

In the aftermath of the Cold War, the U.S. Department of Energy's (DOE) Office of Fissile Materials Disposition (OFMD) is charged with providing technical support for evaluation of disposition options for excess fissile materials manufactured for the nation's defense. One option being considered for the disposition of excess plutonium (Pu) is immobilization by vitrification. The vitrification option entails immobilizing Pu in a host glass and waste package that are criticality-safe (immune to nuclear criticality), proliferation-resistant, and environmentally acceptable for long-term storage or disposal. To prove the technical and economic feasibility of candidate vitrification options it is necessary to demonstrate that PuO 2 feedstock can be dissolved in glass in sufficient quantity. The OFMD immobilization program has set a Pu solubility goal of 10 wt% in glass. The life cycle cost of the vitrification options are strongly influenced by the rate at which PUO 2 dissolves in glass. The total number of process lines needed for vitrification of 50 t of Pu in 10 years is directly dependent upon the time required for Pu dissolution in glass. The objective of this joint Pacific Northwest National Laboratory (PNNL) - Savannah River Technology Center (SRTC) study was to demonstrate a high Pu solubility in glass and to identify on a rough scale the time required for Pu dissolution in the glass. This study was conducted using a lanthanide borosilicate (LaBS) glass composition designed at the SRTC for the vitrification of actinides

Plutonium dioxide dissolution in glass

Energy Technology Data Exchange (ETDEWEB)

Vienna, J.D.; Alexander, D.L.; Li, Hong [and others

1996-09-01

In the aftermath of the Cold War, the U.S. Department of Energy`s (DOE) Office of Fissile Materials Disposition (OFMD) is charged with providing technical support for evaluation of disposition options for excess fissile materials manufactured for the nation`s defense. One option being considered for the disposition of excess plutonium (Pu) is immobilization by vitrification. The vitrification option entails immobilizing Pu in a host glass and waste package that are criticality-safe (immune to nuclear criticality), proliferation-resistant, and environmentally acceptable for long-term storage or disposal. To prove the technical and economic feasibility of candidate vitrification options it is necessary to demonstrate that PuO{sub 2} feedstock can be dissolved in glass in sufficient quantity. The OFMD immobilization program has set a Pu solubility goal of 10 wt% in glass. The life cycle cost of the vitrification options are strongly influenced by the rate at which PUO{sub 2} dissolves in glass. The total number of process lines needed for vitrification of 50 t of Pu in 10 years is directly dependent upon the time required for Pu dissolution in glass. The objective of this joint Pacific Northwest National Laboratory (PNNL) - Savannah River Technology Center (SRTC) study was to demonstrate a high Pu solubility in glass and to identify on a rough scale the time required for Pu dissolution in the glass. This study was conducted using a lanthanide borosilicate (LaBS) glass composition designed at the SRTC for the vitrification of actinides.

In Vivo Predictive Dissolution: Comparing the Effect of Bicarbonate and Phosphate Buffer on the Dissolution of Weak Acids and Weak Bases.

Science.gov (United States)

Krieg, Brian J; Taghavi, Seyed Mohammad; Amidon, Gordon L; Amidon, Gregory E

2015-09-01

Bicarbonate is the main buffer in the small intestine and it is well known that buffer properties such as pKa can affect the dissolution rate of ionizable drugs. However, bicarbonate buffer is complicated to work with experimentally. Finding a suitable substitute for bicarbonate buffer may provide a way to perform more physiologically relevant dissolution tests. The dissolution of weak acid and weak base drugs was conducted in bicarbonate and phosphate buffer using rotating disk dissolution methodology. Experimental results were compared with the predicted results using the film model approach of (Mooney K, Mintun M, Himmelstein K, Stella V. 1981. J Pharm Sci 70(1):22-32) based on equilibrium assumptions as well as a model accounting for the slow hydration reaction, CO2 + H2 O → H2 CO3 . Assuming carbonic acid is irreversible in the dehydration direction: CO2 + H2 O ← H2 CO3 , the transport analysis can accurately predict rotating disk dissolution of weak acid and weak base drugs in bicarbonate buffer. The predictions show that matching the dissolution of weak acid and weak base drugs in phosphate and bicarbonate buffer is possible. The phosphate buffer concentration necessary to match physiologically relevant bicarbonate buffer [e.g., 10.5 mM (HCO3 (-) ), pH = 6.5] is typically in the range of 1-25 mM and is very dependent upon drug solubility and pKa . © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

Kinetics of dissolution of calcium phosphate (Ca-P bioceramics

Directory of Open Access Journals (Sweden)

Lukas Brazda

2008-06-01

Full Text Available Hydroxyapatite (HAp and β-tricalcium phosphate (β-TCP are widely used bioceramics for surgical or dental applications. This paper is dealing with dissolution kinetics of synthetically prepared β-TCP and four types of HAp granules. Two groups of HAp, treated at different temperatures, each of them with two different granule sizes, were tested. Three corrosive solutions with different pH and simulated body fluid (SBF were used for immersing of the samples. Changes in concentrations of calcium and phosphate ions, pH level and weight changes of the samples were observed. It was found that presence of TRIS buffer enhanced dissolution rate of the β-TCP approximately two times. When exposed to SBF solution, calcium phosphate (most probably hydroxyapatite precipitation predominates over β-TCP dissolution. Results from HAp samples dissolution showed some unexpected findings. Neither heat treatment nor HAp particle size made any major differences in dissolution rate of the same mass of each HAp sample.

Dynamic Self-Assembly Induced Rapid Dissolution of Cellulose at Low Temperatures

International Nuclear Information System (INIS)

Cai, J.; Zhang, L.; Liu, S.; Liu, Y.; Xu, X.; Chen, X.; Chu, B.; Guo, X.; Xu, J.

2008-01-01

Cellulose can be dissolved in precooled (-12 C) 7 wt % NaOH-12 wt % urea aqueous solution within 2 min. This interesting process, to our knowledge, represents the most rapid dissolution of native cellulose. The results from 13C NMR, 15N NMR, 1H NMR, FT-IR, small-angle neutron scattering (SANS), transmission electron microscopy (TEM), and wide-angle X-ray diffraction (WAXD) suggested that NaOH 'hydrates' could be more easily attracted to cellulose chains through the formation of new hydrogen-bonded networks at low temperatures, while the urea hydrates could not be associated directly with cellulose. However, the urea hydrates could possibly be self-assembled at the surface of the NaOH hydrogen-bonded cellulose to form an inclusion complex (IC), leading to the dissolution of cellulose. Scattering experiments, including dynamic and static light scattering, indicated that most cellulose molecules, with limited amounts of aggregation, could exist as extended rigid chains in dilute solution. Further, the cellulose solution was relatively unstable and could be very sensitive to temperature, polymer concentration, and storage time, leading to additional aggregations. TEM images and WAXD provided experimental evidence on the formation of a wormlike cellulose IC being surrounded with urea. Therefore, we propose that the cellulose dissolution at -12 C could arise as a result of a fast dynamic self-assembly process among solvent small molecules (NaOH, urea, and water) and the cellulose macromolecules.

Standard practice for preparation and dissolution of plutonium materials for analysis

CERN Document Server

American Society for Testing and Materials. Philadelphia

2008-01-01

1.1 This practice is a compilation of dissolution techniques for plutonium materials that are applicable to the test methods used for characterizing these materials. Dissolution treatments for the major plutonium materials assayed for plutonium or analyzed for other components are listed. Aliquants of the dissolved samples are dispensed on a weight basis when one of the analyses must be highly reliable, such as plutonium assay; otherwise they are dispensed on a volume basis. 1.2 The treatments, in order of presentation, are as follows: Procedure Title Section Dissolution of Plutonium Metal with Hydrochloric Acid 9.1 Dissolution of Plutonium Metal with Sulfuric Acid 9.2 Dissolution of Plutonium Oxide and Uranium-Plutonium Mixed Oxide by the Sealed-Reflux Technique 9.3 Dissolution of Plutonium Oxide and Uranium-Plutonium Mixed Oxides by Sodium Bisulfate Fusion 9.4 Dissolution of Uranium-Plutonium Mixed Oxides and Low-Fired Plutonium Oxide in Beakers 9.5 1.3 The values stated in SI units are to be re...

Reactive Transport at the Pore Scale with Applications to the Dissolution of Carbonate Rocks for CO2 Sequestration Operations

Science.gov (United States)

Boek, E.; Gray, F.; Welch, N.; Shah, S.; Crawshaw, J.

2014-12-01

In CO2 sequestration operations, CO2 injected into a brine aquifer dissolves in the liquid to create an acidic solution. This may result in dissolution of the mineral grains in the porous medium. Experimentally, it is hard to investigate this process at the pore scale. Therefore we develop a new hybrid particle simulation algorithm to study the dissolution of solid objects in a laminar flow field, as encountered in porous media flow situations. First, we calculate the flow field using a multi-relaxation-time lattice Boltzmann (LB) algorithm implemented on GPUs, which demonstrates a very efficient use of the GPU device and a considerable performance increase over CPU calculations. Second, using a stochastic particle approach, we solve the advection-diffusion equation for a single reactive species and dissolve solid voxels according to our reaction model. To validate our simulation, we first calculate the dissolution of a solid sphere as a function of time under quiescent conditions. We compare with the analytical solution for this problem [1] and find good agreement. Then we consider the dissolution of a solid sphere in a laminar flow field and observe a significant change in the sphericity with time due to the coupled dissolution - flow process. Second, we calculate the dissolution of a cylinder in channel flow in direct comparison with corresponding dissolution experiments. We discuss the evolution of the shape and dissolution rate. Finally, we calculate the dissolution of carbonate rock samples at the pore scale in direct comparison with micro-CT experiments. This work builds on our recent research on calculation of multi-phase flow [2], [3] and hydrodynamic dispersion and molecular propagator distributions for solute transport in homogeneous and heterogeneous porous media using LB simulations [4]. It turns out that the hybrid simulation model is a suitable tool to study reactive flow processes at the pore scale. This is of great importance for CO2 storage and

Thermodynamic and Kinetic Aspects of the Dissolution of Quartz-Kaolinite Mixtures by Alkalis Aspects thermodynamiques et cinétiques de la dissolution des mélanges quartz-kaolinite par les alcalis

Directory of Open Access Journals (Sweden)

Labrid J.

2006-11-01

Full Text Available Mineral-alkali interactions have received considerable attention in the recent literature dealing with enhanced oil recovery techniques and clay stabilization treatments. One of the critical factors to be considered is alkali consumption. Alkalinity decrease occurs through several mechanisms, which are ion exchange, precipitation, reaction with crude oil components, and dissolution of minerals. This paper describes the dissolution process. An original kinetic model is proposed to describe the alkaline dissolution of a clayey sandstone. This model is based first on results concerning quartz dissolution/condensation processes. It is also based on new experimental data, which demonstrate the inhibiting effect of aluminum and, as the reaction proceeds, the precipitation of an aluminosilicate whose the chemical composition has been determined. From these data, a kinetic scheme has been conceived in which adsorption of different chemical species is assumed to occur onto solid surfaces. These species play a more or less important role according to the extent of the reaction. In the mechanisms considered, the argillaceous fraction of the rock provides silicon and aluminum which inhibit the dissolution of the matrix while silicon coming from quartz interferes with clay attack. The kinetic model depicts the coupling of elementary dissolution processes and calculates dissolved silicon and aluminum. It has been tested for various operating conditions, providing initial reaction rates for quartz and clay. Results emphasize the definitive advantage of carbonate compared to other alkaline chemicals owing to the relative low pH of solutions, which is particularly favorable for promoting inhibition by aluminum and, as a general rule, for reducing mineral dissolution. Ce résumé contient des formules (*** qui ne peuvent s'afficher à l'écran L'emploi des agents alcalins pour améliorer la récupération du pétrole a été préconisé à l'origine dans le but

Successful topical dissolution of cholesterol gallbladder stones using ethyl propionate.

Science.gov (United States)

Hofmann, A F; Amelsberg, A; Esch, O; Schteingart, C D; Lyche, K; Jinich, H; Vansonnenberg, E; D'Agostino, H B

1997-06-01

Topical dissolution of cholesterol gallbladder stones using methyl tert-butyl ether (MTBE) is useful in symptomatic patients judged too ill for surgery. Previous studies showed that ethyl propionate (EP), a C5 ester, dissolves cholesterol gallstones rapidly in vitro, but differs from MTBE in being eliminated so rapidly by the liver that blood levels remain undetectable. Our aim was to test EP as a topical dissolution agent for cholesterol gallbladder stones. Five high-risk patients underwent topical dissolution of gallbladder stones by EP. In three patients, the solvent was instilled via a cholecystostomy tube placed previously to treat acute cholecystitis; in two patients, a percutaneous transhepatic catheter was placed in the gallbladder electively. Gallstone dissolution was assessed by chromatography, by gravimetry, and by catheter cholecystography. Total dissolution of gallstones was obtained in four patients after 6-10 hr of lavage; in the fifth patient, partial gallstone dissolution facilitated basketing of the stones. In two patients, cholesterol dissolution was measured and averaged 30 mg/min. Side effects were limited to one episode of transient hypotension and pain at the infusion site; no patient developed somnolence or nausea. Gallstone elimination was associated with relief of symptoms. EP is an acceptable alternative to MTBE for topical dissolution of cholesterol gallbladder stones in high-risk patients. The lower volatility and rapid hepatic extraction of EP suggest that it may be preferable to MTBE in this investigational procedure.

Dissolution rates of over-the-counter painkillers: a comparison among formulations.

Science.gov (United States)

Alemanni, Matteo; Gatoulis, Sergio C; Voelker, Michael

2016-06-01

We wanted to compare the dissolution profile of several over-the-counter analgesics to understand whether the different formulation techniques employed to enhance absorption were associated with variations in the dissolution rate, a parameter known to affect drug absorption. We considered 5 formulations currently marketed in Italy: aspirin tablets (Aspirina Dolore e Infiammazione®), ibuprofen tablets and liquid capsules (Moment®), ibuprofen lysine tablets (Nurofenimmedia®) and dexketoprofen trometamol tablets (Enantyum®). Dissolution tests were performed according to the current USP/NF monograph dissolution procedure. Drug dissolution was evaluated at 1, 3, 6, 15, and 30 minutes since the start of the test. Dissolution was evaluated at three different pH: 1.2, 4.5 and 6.8. Every test was repeated 12 times. The aspirin formulation was by far the most rapid dissolving formulation, among those tested, with more than 80% of the tablet dissolved at 6 minutes for every pH considered. At pH 1.2 and 4.5, only the dexketoprofen formulation was able to reach the dissolution level of aspirin at 30 minutes, but had lower levels of dissolution at the previous time points. Instead, at pH 6.8, most of the formulations approached aspirin dissolution level, but only after 15 minutes. Ibuprofen capsules had the slowest kinetics, with a lag phase the first 6 minutes. Different formulation strategies can lead to great differences in the dissolution rates even among drugs of the same class, suggesting that enhancements in the formulation of painkillers can lead to improvements in drug absorption, and thus in the onset of analgesia.

K Basin sludge dissolution engineering study

International Nuclear Information System (INIS)

Westra, A.G.

1998-01-01

The purpose of this engineering study is to investigate the available technology related to dissolution of the K Basin sludge in nitric acid. The conclusion of this study along with laboratory and hot cell tests with actual sludge samples will provide the basis for beginning conceptual design of the sludge dissolver. The K Basin sludge contains uranium oxides, fragments of metallic U, and some U hydride as well as ferric oxyhydroxide, aluminum oxides and hydroxides, windblown sand that infiltrated the basin enclosure, ion exchange resin, and miscellaneous materials. The decision has been made to dispose of this sludge separate from the fuel elements stored in the basins. The sludge will be conditioned so that it meets Tank Waste Remediation System waste acceptance criteria and can be sent to one of the underground storage tanks. Sludge conditioning will be done by dissolving the fuel constituents in nitric acid, separating the insoluble material, adding neutron absorbers for criticality safety, and then reacting the solution with caustic to co-precipitate the uranium and plutonium. There will be five distinct feed streams to the sludge conditioning process two from the K East (KE) Basin and three from the K West (KW) Basin. The composition of the floor and pit sludges which contain more iron oxides and sand than uranium is much different than the canister sludges which are composed of mostly uranium oxides. The sludge conditioning equipment will be designed to process all of the sludge streams, but some of the operating parameters will be adjusted as necessary to handle the different sludge stream compositions. The volume of chemical additions and the amount of undissolved solids will be much different for floor and pit sludge than for canister sludge. Dissolution of uranium metal and uranium dioxide has been studied quite thoroughly and much information is available. Both uranium metal and uranium dioxide have been dissolved on a large scale in nuclear fuel

Dissolution of the Mors salt dome

International Nuclear Information System (INIS)

Lindstroem Jensen, K.E.

1982-01-01

Regardless of the interpretation of the measured salinity profiles above the Mors salt dome, they can at most be the result of dissolution rates of about 0.004 mm per year. This means that it would take more than 2.5 mill. years to dissolve 10 m of salt. Variations in groun water velocity and cap rock porosity will not significantly change this condition. The stability of the Mors salt dome is therefore not affected by dissolution of the dome. (EG)

In vitro acellular dissolution of mineral fibres: A comparative study.

Science.gov (United States)

Gualtieri, Alessandro F; Pollastri, Simone; Bursi Gandolfi, Nicola; Gualtieri, Magdalena Lassinantti

2018-05-04

The study of the mechanisms by which mineral fibres promote adverse effects in both animals and humans is a hot topic of multidisciplinary research with many aspects that still need to be elucidated. Besides length and diameter, a key parameter that determines the toxicity/pathogenicity of a fibre is biopersistence, one component of which is biodurability. In this paper, biodurability of mineral fibres of social and economic importance (chrysotile, amphibole asbestos and fibrous erionite) has been determined for the first time in a systematic comparative way from in vitro acellular dissolution experiments. Dissolution was possible using the Gamble solution as simulated lung fluid (pH = 4 and at body temperature) so to reproduce the macrophage phagolysosome environment. The investigated mineral fibres display very different dissolution rates. For a 0.25 μm thick fibre, the calculated dissolution time of chrysotile is in the range 94-177 days, very short if compared to that of amphibole fibres (49-245 years), and fibrous erionite (181 years). Diffraction and SEM data on the dissolution products evidence that chrysotile rapidly undergoes amorphization with the formation of a nanophasic silica-rich fibrous metastable pseudomorph as first dissolution step whereas amphibole asbestos and fibrous erionite show minor signs of dissolution even after 9-12 months.

The effect of fuel chemistry on UO{sub 2} dissolution

Energy Technology Data Exchange (ETDEWEB)

Casella, Amanda, E-mail: amanda.casella@pnnl.gov [Pacific Northwest National Laboratory, PO Box 999, MSIN P7-25, Richland, WA 99352 (United States); Hanson, Brady, E-mail: brady.hanson@pnnl.gov [Pacific Northwest National Laboratory, PO Box 999, MSIN P7-27, Richland, WA 99352 (United States); Miller, William [University of Missouri Research Reactor, 1513 Research Park Drive, Columbia, MO 65211 (United States)

2016-08-01

The dissolution rate of both unirradiated UO{sub 2} and used nuclear fuel has been studied by numerous countries as part of the performance assessment of proposed geologic repositories. In the scenario of waste package failure and groundwater contact with the fuel, the effects of variables such as temperature, dissolved oxygen, and water and fuel chemistry on the dissolution rates of the fuel are necessary to provide a quantitative estimate of the potential release over geologic time frames. The primary objective of this research was to determine the influence these parameters, with primary focus on the fuel chemistry, have on the dissolution rate of unirradiated UO{sub 2} under oxidizing repository conditions and compare them to the rates predicted by current dissolution models. Both unirradiated UO{sub 2} and UO{sub 2} doped with varying concentrations of Gd{sub 2}O{sub 3}, to simulate used fuel composition after long time periods when radiolysis has minor contributions to dissolution, were examined. In general, a rise in temperature increased the dissolution rate of UO{sub 2} and had a larger effect on pure UO{sub 2} than on those doped with Gd{sub 2}O{sub 3}. Oxygen dependence was observed in the UO{sub 2} samples with no dopant and increased as the temperature rose; in the doped fuels less dependence was observed. The addition of gadolinia into the UO{sub 2} matrix resulted in a significant decrease in the dissolution rate. The matrix stabilization effect resulting from the dopant proved even more beneficial in lowering the dissolution rate at higher temperatures and dissolved O{sub 2} concentrations in the leachate where the rates would typically be elevated. - Highlights: • UO{sub 2} dissolution rates were measured for a matrix of repository relevant conditions. • Dopants in the UO{sub 2} matrix lowered the dissolution rate. • Reduction in rates by dopants were increased at elevated temperature and O{sub 2} levels. • UO{sub 2} may be overly

In situ controlled crystallization as a tool to improve the dissolution of Glibenclamide.

Science.gov (United States)

Elkordy, Amal Ali; Jatto, Ayobami; Essa, Ebtessam

2012-05-30

For pharmaceutical purpose, micro-sized drugs are needed for many delivery systems, such as pulmonary and oral drug delivery systems. Many strategies have been employed to reduce the particle size of poorly water soluble drugs. Microcrystals could be produced by controlled association of drug in order to obtain naturally grown particles. The aim of this work was to increase the aqueous solubility and dissolution of Glibenclamide. The in situ controlled crystallization process was conducted in the presence of the non-ionic surfactants, Cremophor RH40 and Solutol HS-15 (0.75 and 1.5%, w/v), as protective stabilizing agents against agglomeration. In addition, these surfactants inhibit P-glycoprotein that reduces intestinal absorption of Glibenclamide by efflux transportation. Crystal shape was changed and particle size was reduced by about 15-folds, compared to control untreated drug. Differential Scanning Calorimetry (DSC) results indicated no interaction between the drug and the stabilizer. Microcrystals showed marked increase in the drug dissolution, Solutol HS-15 at 1.5% (w/v) concentration showing the highest dissolution efficiency. It could be concluded that in situ controlled crystallization using surfactants are promising method to improve dissolution of Glibeclamide as a model poorly water soluble drug. Copyright © 2012 Elsevier B.V. All rights reserved.

Development of simulation code for FBR spent fuel dissolution with rotary drum type continuous dissolver

International Nuclear Information System (INIS)

Sano, Yuichi; Katsurai, Kiyomichi; Washiya, Tadahiro; Koizumi, Tsutomu; Matsumoto, Satoshi

2011-01-01

Japan Atomic Energy Agency (JAEA) has been studying rotary drum type continuous dissolver for FBR spent fuel dissolution. For estimating the fuel dissolution behavior under several operational conditions in this dissolver, we have been developing the simulation code, PLUM, which mainly consists of 3 modules for calculating chemical reaction, mass transfer and thermal balance in the rotary drum type continuous dissolver. Under the various conditions where dissolution experiments were carried out with the batch-wise dissolver for FBR spent fuel and with the rotary drum type continuous dissolver for UO 2 fuel, it was confirmed that the fuel dissolution behaviors calculated by the PLUM code showed good agreement with the experimental ones. Based on this result, the condition for obtaining the dissolver solution with high HM (heavy metal : U and Pu) concentration (∼500g/L), which is required for the next step, i.e. crystallization process, was also analyzed by this code and appropriate operational conditions with the rotary drum type continuous dissolver, such as feedrate, concentration and temperature of nitric acid, could be clarified. (author)

Investigation of the dissolution of uranium dioxide in nitric media: a new approach aiming at understanding interface mechanisms

International Nuclear Information System (INIS)

Delwaulle, Celine

2011-01-01

This research thesis deals with the back-end cycle of the nuclear fuel by improving, modernizing and optimizing the processes used for all types of fuels which are to be re-processed. After a presentation of the industrial context and of the state of the art concerning dissolution kinetic data for uranium dioxide and mixed oxide, the author proposes a model which couples dissolution kinetics and hydrodynamics of a solid in presence of auto-catalytic species, in order to better understand phenomena occurring at the solid-liquid-gas interface. The next part reports dissolution experiments on a non-radioactive material (copper) and out of a nuclear environment. Then, the author identifies steps which are required to transpose this experiment within a nuclear environment. The first results obtained on uranium dioxide are discussed. Recommendations for further studies conclude the report

Dissolution corrosion of 316L austenitic stainless steels in contact with static liquid lead-bismuth eutectic (LBE) at 500 °C

Energy Technology Data Exchange (ETDEWEB)

Lambrinou, Konstantina, E-mail: klambrin@sckcen.be [SCK-CEN, Boeretang 200, 2400 Mol (Belgium); Charalampopoulou, Evangelia [SCK-CEN, Boeretang 200, 2400 Mol (Belgium); University of Antwerp, Electron Microscopy for Materials Science (EMAT), Groenenborgerlaan 171, 2020 Antwerpen (Belgium); Van der Donck, Tom [KU Leuven, Department of Materials Engineering, Kasteelpark Arenberg 44, 3001 Leuven (Belgium); Delville, Rémi [SCK-CEN, Boeretang 200, 2400 Mol (Belgium); Schryvers, Dominique [University of Antwerp, Electron Microscopy for Materials Science (EMAT), Groenenborgerlaan 171, 2020 Antwerpen (Belgium)

2017-07-15

This work addresses the dissolution corrosion behaviour of 316L austenitic stainless steels. For this purpose, solution-annealed and cold-deformed 316L steels were simultaneously exposed to oxygen-poor (<10{sup −8} mass%) static liquid lead-bismuth eutectic (LBE) for 253–3282 h at 500 °C. Corrosion was consistently more severe for the cold-drawn steels than the solution-annealed steel, indicating the importance of the steel thermomechanical state. The thickness of the dissolution-affected zone was non-uniform, and sites of locally-enhanced dissolution were occasionally observed. The progress of LBE dissolution attack was promoted by the interplay of certain steel microstructural features (grain boundaries, deformation twin laths, precipitates) with the dissolution corrosion process. The identified dissolution mechanisms were selective leaching leading to steel ferritization, and non-selective leaching; the latter was mainly observed in the solution-annealed steel. The maximum corrosion rate decreased with exposure time and was found to be inversely proportional to the depth of dissolution attack. - Highlights: •Dissolution corrosion was more severe in cold-deformed than solution-annealed 316L steels. •LBE penetration occurred along preferential paths in the steel microstructure. •The maximum dissolution rate was inversely proportionate to the depth of dissolution.

Preparation, characterization, and dissolution studies of naproxen solid dispersions using polyethylene glycol 6000 and labrafil M2130

Directory of Open Access Journals (Sweden)

Jafar Akbari

2015-06-01

Full Text Available Naproxen is a poor water soluble, non-steroidal analgesic and anti-inflammatory drug. The enhancement of oral bioavailability of poor water soluble drugs remains one of the most challenging aspects of drug development. Although salt formation, solubilization and particle size reduction have commonly been used to increase dissolution rate and thereby oral absorption and bioavailability of low water soluble drugs, there are practical limitation of these techniques. However, the most attractive option for increasing the release rate is improvement of solubility through formulation approaches. In this study, solid dispersions (SD of naproxen were prepared by hot melt method using various ratios of drug to polymers (PEG6000 separately and characterized for physical appearance, FTIR, DSC, X-Ray crystallography, and in-vitro dissolution studies. The influence of several amounts of Labrafil M2130 was also studied. FTIR study revealed that drug was stable in SDs, and great state of amorphous formed particles was proofed by DSC analysis. The in vitro dissolution studies were carried using USP type II (paddle dissolution apparatus at medium (pH 1.5. Solubility of naproxen from SDs was increased in dissolution media. The prepared dispersion showed increase in the dissolution rate of naproxen comparing to that of physical mixtures of drug and polymers and pure drug. Percent of drug released in 60 minutes was 23.92% for pure naproxen witch is increased in SDs and reached to100% for best formulations of PEG6000 and labrafil based SDs respectively, considering ratio of drug to polymers.It is concluded that dissolution of the naproxen could be improved by the solid dispersion. Although physical mixtures have increased the rate of dissolution, dissolution shows faster release from SDs which would therefore be due to formation of amorphous particles through the hot melt process which was also revealed by DSC analysis and XRD.

Studies of dissolution solutions of ruthenium metal, oxide and mixed compounds in nitric acid

International Nuclear Information System (INIS)

Mousset, F.; Eysseric, C.; Bedioui, F.

2004-01-01

Ruthenium is one of the fission products generated by irradiated nuclear fuel. It is present throughout all the steps of nuclear fuel reprocessing-particularly during extraction-and requires special attention due to its complex chemistry and high βγ activity. An innovative electro-volatilization process is now being developed to take advantage of the volatility of RuO 4 in order to eliminate it at the head end of the Purex process and thus reduce the number of extraction cycles. Although the process operates successfully with synthetic nitrato-RuNO 3+ solutions, difficulties have been encountered in extrapolating it to real-like dissolution solutions. In order to better approximate the chemical forms of ruthenium found in fuel dissolution solutions, kinetic and speciation studies on dissolved species were undertaken with RuO 2 ,xH 2 O and Ru 0 in nitric acid media. (authors)

Development and Validation of Discriminating and Biorelevant Dissolution Test for Lornoxicam Tablets.

Science.gov (United States)

Anumolu, P D; Sunitha, G; Bindu, S Hima; Satheshbabu, P R; Subrahmanyam, C V S

2015-01-01

The establishment of biorelevant and discriminating dissolution procedure for drug products with limited water solubility is a useful technique for qualitative forecasting of the in vivo behavior of formulations. It also characterizes the drug product performance in pharmaceutical development. Lornoxicam, a BCS class-II drug is a nonsteroidal antiinflammatory drug of the oxicam class, has no official dissolution media available in the literature. The objective of present work was to develop and validate a discriminating and biorelevant dissolution test for lornoxicam tablet dosage forms. To quantify the lornoxicam in dissolution samples, UV spectrophotometric method was developed using 0.01M sodium hydroxide solution as solvent at λma×376 nm. After evaluation of saturation solubility, dissolution, sink conditions and stability of lornoxicam bulk drug in different pH solutions and biorelevant media, the dissolution method was optimized using USP paddle type apparatus at 50 rpm rotation speed and 500 ml simulated intestinal fluid as discriminating and biorelevant dissolution medium. The similarity factor (f2) were investigated for formulations with changes in composition and manufacturing variations, values revealed that dissolution method having discriminating power and method was validated as per standard guidelines. The proposed dissolution method can be effectively applied for routine quality control in vitro dissolution studies of lornoxicam in tablets and helpful to pharmacopoeias.

Dissolution of artemisinin/polymer composite nanoparticles fabricated by evaporative precipitation of nanosuspension.

Science.gov (United States)

Kakran, Mitali; Sahoo, Nanda Gopal; Li, Lin; Judeh, Zaher

2010-04-01

An evaporative precipitation of nanosuspension (EPN) method was used to fabricate composite particles of a poorly water-soluble antimalarial drug, artemisinin, with a hydrophilic polymer, polyethylene glycol (PEG), with the aim of enhancing the dissolution rate of artemisinin. We investigated the effect of polymer concentration on the physical, morphological and dissolution properties of the EPN-prepared artemisinin/PEG composites. The original artemisinin powder, EPN-prepared artemisinin nanoparticles and artemisinin/PEG composites were characterised by scanning electron microscopy, Fourier-transform infrared spectroscopy, differential scanning calorimetry (DSC), X-ray diffraction (XRD), dissolution testing and HPLC. The percentage dissolution efficiency, relative dissolution, time to 75% dissolution and mean dissolution time were calculated. The experimental drug dissolution data were fitted to various mathematical models (Weibull, first-order, Korsemeyer-Peppas, Hixson-Crowell cube root and Higuchi models) in order to analyse the release mechanism. The DSC and XRD studies suggest that the crystallinity of the EPN-prepared artemisinin decreased with increasing polymer concentration. The phase-solubility studies revealed an A(L)-type curve, indicating a linear increase in drug solubility with PEG concentration. The dissolution rate of the EPN-prepared artemisinin and artemisinin/PEG composites increased markedly compared with the original artemisinin powder. EPN can be used to prepare artemisinin nanoparticles and artemisinin/PEG composite particles that have a significantly enhanced dissolution rate. The mechanism of drug release involved diffusion and erosion.

Synthesis and characterization of alumina-coated aluminum sponges manufactured by sintering and dissolution process as possible structured reactors

International Nuclear Information System (INIS)

Méndez, Franklin J.; Rivero-Prince, Sayidh; Escalante, Yelisbeth; Villasana, Yanet; Brito, Joaquín L.

2016-01-01

Al_2O_3–Al sponges were manufactured by sintering and dissolution process with the aim of using these materials as structured catalytic reactors. For this purpose, several synthesis conditions were examined for the design of the cellular material, such as: particle size of NaCl, weight fraction of Al, compaction pressure, and sintering temperature or time. An alumina layers was grown on top of the aluminum surfaces during both: sintering and thermal treatment. The obtained results showed that the synthesized materials could be promising as structured reactors for endothermic or exothermic reactions. - Highlights: • An efficient method for manufactured of aluminum sponges is reported. • Methods for productions of superficial Al_2O_3 are studied. • Al_2O_3–Al sponges could be used as structured reactors.

A Study on the Anodic Dissolution of Aluminum(II)

International Nuclear Information System (INIS)

Nam, C. W.; Park, C. S.; Park, C. S.

1978-01-01

In many cases oxide films formed on metals in atmosphere or aqueous solution are chemically inactive, especially it is the case with aluminum. In this study, anodic dissolution of aluminum was done using various electrolyte and cathode, mechanism of which was examined. As a consequence, oxide film on aluminum surface was dissolved together with the dissolution reaction of metal by the anodic current. It was shown that the dissolution reaction due to the contact between electrolyte and metal happened in the same time

Impact of iron chelators on short-term dissolution of basaltic glass

Science.gov (United States)

Perez, Anne; Rossano, Stéphanie; Trcera, Nicolas; Verney-Carron, Aurélie; Huguenot, David; van Hullebusch, Eric D.; Catillon, Gilles; Razafitianamaharavo, Angelina; Guyot, François

2015-08-01

Although microorganisms seem to play an important role in the alteration processes of basaltic glasses in solution, the elementary mechanisms involved remain unclear in particular with regard to the role of organic ligands excreted by the cells. Two glasses, one with Fe and one without Fe were synthesized to model basaltic glass compositions. Fe in the glass was mostly Fe(III) for enhancing interaction with siderophores, yet with small but significant amounts of Fe(II) (between 10% and 30% of iron). The prepared samples were submitted to abiotic alteration experiments in buffered (pH 6.4) diluted solutions of metal-specific ligands, namely oxalic acid (OA, 10 mM), desferrioxamine (DFA, 1 mM) or 2,2‧-bipyridyl (BPI, 1 mM). Element release from the glass into the solution after short term alteration (maximum 1 week) was measured by ICP-OES, and normalized mass losses and relative release ratios (with respect to Si) were evaluated for each element in each experimental condition. The presence of organic ligands had a significant effect on the dissolution of both glasses. Trivalent metals chelators (OA, DFA) impacted on the release of Fe3+ and Al3+, and thus on the global dissolution of both glasses, enhancing all release rates and dissolution stoichiometry (release rates were increased up to 7 times for Al or Fe). As expected, the mostly divalent metal chelator BPI interacted preferentially with Ca2+, Mg2+ and Fe2+. This study thus allows to highlight the central roles of iron and aluminium in interaction with some organic ligands in the alteration processes of basaltic glasses. It thus provides a step toward understanding the biological contribution of this fundamental geological process.

Rapid and gradual modes of aerosol trace metal dissolution in seawater

Directory of Open Access Journals (Sweden)

Katherine Rose Marie Mackey

2015-01-01

Full Text Available Atmospheric deposition is a major source of trace metals in marine surface waters and supplies vital micronutrients to phytoplankton, yet measured aerosol trace metal solubility values are operationally defined and there are relatively few multi-element studies on aerosol-metal solubility in seawater. Here we measure the solubility of aluminum (Al, cadmium (Cd, cobalt (Co, copper (Cu, iron (Fe, manganese (Mn, nickel (Ni, lead (Pb, and zinc (Zn from natural aerosol samples in seawater over a 7 day period to (1 evaluate the role of extraction time in trace metal dissolution behavior and (2 explore how the individual dissolution patterns could influence biota. Dissolution behavior occurs over a continuum ranging from rapid dissolution, in which the majority of soluble metal dissolved immediately upon seawater exposure (Cd and Co in our samples, to gradual dissolution, where metals dissolved slowly over time (Zn, Mn, Cu, and Al in our samples. Additionally, dissolution affected by interactions with particles was observed in which a decline in soluble metal concentration over time occurred (Fe and Pb in our samples. Natural variability in aerosol chemistry between samples can cause metals to display different dissolution kinetics in different samples, and this was particularly evident for Ni, for which samples showed a broad range of dissolution rates. The elemental molar ratio of metals in the bulk aerosols was 23,189Fe: 22,651Al: 445Mn: 348Zn: 71Cu: 48Ni: 23Pb: 9Co: 1Cd, whereas the seawater soluble molar ratio after 7 days of leaching was 11Fe: 620Al: 205Mn: 240Zn: 20Cu: 14Ni: 9Pb: 2Co: 1Cd. The different kinetics and ratios of aerosol metal dissolution have implications for phytoplankton nutrition, and highlight the need for unified extraction protocols that simulate aerosol metal dissolution in the surface ocean.

Feldspar dissolution rates in the Topopah Spring Tuff, Yucca Mountain, Nevada

Science.gov (United States)

Bryan, C.R.; Helean, K.B.; Marshall, B.D.; Brady, P.V.

2009-01-01

Two different field-based methods are used here to calculate feldspar dissolution rates in the Topopah Spring Tuff, the host rock for the proposed nuclear waste repository at Yucca Mountain, Nevada. The center of the tuff is a high silica rhyolite, consisting largely of alkali feldspar (???60 wt%) and quartz polymorphs (???35 wt%) that formed by devitrification of rhyolitic glass as the tuff cooled. First, the abundance of secondary aluminosilicates is used to estimate the cumulative amount of feldspar dissolution over the history of the tuff, and an ambient dissolution rate is calculated by using the estimated thermal history. Second, the feldspar dissolution rate is calculated by using measured Sr isotope compositions for the pore water and rock. Pore waters display systematic changes in Sr isotopic composition with depth that are caused by feldspar dissolution. The range in dissolution rates determined from secondary mineral abundances varies from 10-16 to 10-17 mol s-1 kg tuff-1 with the largest uncertainty being the effect of the early thermal history of the tuff. Dissolution rates based on pore water Sr isotopic data were calculated by treating percolation flux parametrically, and vary from 10-15 to 10-16 mol s-1 kg tuff-1 for percolation fluxes of 15 mm a-1 and 1 mm a-1, respectively. Reconciling the rates from the two methods requires that percolation fluxes at the sampled locations be a few mm a-1 or less. The calculated feldspar dissolution rates are low relative to other measured field-based feldspar dissolution rates, possibly due to the age (12.8 Ma) of the unsaturated system at Yucca Mountain; because oxidizing and organic-poor conditions limit biological activity; and/or because elevated silica concentrations in the pore waters (???50 mg L-1) may inhibit feldspar dissolution. ?? 2009 Elsevier Ltd. All rights reserved.

Mongol Warfare in the Pre-Dissolution Period »

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Timothy May

2015-01-01

Full Text Available Although the Mongols used many of the tactics and strategies that steppe nomads had used for centuries, the Mongols refined steppe warfare so that this style of warfare reached its apogee during the Mongol Empire. Furthermore, the Mongols developed a style of warfare that made them possibly the greatest military force in history. This work examines several facets of the pre-dissolution period (1200–1260. With the dissolution of the Mongol Empire, Mongol warfare once again changed. In some areas it remained complex while in others it regressed to traditional forces of steppe warfare, still potent but not as effective as the pre-dissolution period.

Dissolution mechanism of aluminum hydroxides in acid media

Science.gov (United States)

Lainer, Yu. A.; Gorichev, I. G.; Tuzhilin, A. S.; Gololobova, E. G.

2008-08-01

The effects of the concentration, temperature, and potential at the hydroxide/electrolyte interface on the aluminum hydroxide dissolution in sulfuric, hydrochloric, and perchloric acids are studied. The limiting stage of the aluminum hydroxide dissolution in the acids is found to be the transition of the complexes that form on the aluminum hydroxide surface from the solid phase into the solution. The results of the calculation of the acid-base equilibrium constants at the oxide (hydroxide)/solution interface using the experimental data on the potentiometric titration of Al2O3 and AlOOH suspensions are analyzed. A mechanism is proposed for the dissolution of aluminum hydroxides in acid media.

Effects of alteration product precipitation on glass dissolution

Energy Technology Data Exchange (ETDEWEB)

Strachan, Denis M.; Neeway, James J.

2014-06-01

Understanding the mechanisms that control the durability of nuclear waste glass is paramount if reliable models are to be constructed so that the glass dissolution rate in a given geological repository can be calculated. Presently, it is agreed that (boro)silicate glasses dissolve in water at a rate dependent on the solution concentration of orthosilicic acid (H₄SiO₄) with higher [H₄SiO₄] leading to lower dissolution rates. Once the reaction has slowed as a result of the buildup of H₄SiO₄, another increase in the rate has been observed that corresponds to the precipitation of certain silica-bearing alteration products. However, it has also been observed that the concentration of silica-bearing solution species does not significantly decrease, indicating saturation, while other glass tracer elements concentrations continue to increase, indicating that the glass is still dissolving. In this study, we have used the Geochemist’s Workbench code to investigate the relationship between glass dissolution rates and the precipitation rate of a representative zeolitic silica-bearing alteration product, analcime [Na(AlSi₂O₆)∙H₂O]. To simplify the calculations, we suppressed all alteration products except analcime, gibbsite (Al(OH)₃), and amorphous silica. The pseudo-equilibrium-constant matrix for amorphous silica was substituted for the glass pseudo-equilibrium-constant matrix because it has been shown that silicate glasses act as a silica-only solid with respect to kinetic considerations. In this article, we present the results of our calculations of the glass dissolution rate at different values for the analcime precipitation rate constant and the effects of varying the glass dissolution rate constant at a constant analcime precipitation rate constant. From the simulations we conclude, firstly, that the rate of glass dissolution is dependent on the kinetics of

Dissolution testing of intermediary products in uranium dioxide production by the sol-gel method

International Nuclear Information System (INIS)

Melichar, F.; Landspersky, H.; Urbanek, V.

1979-01-01

A method was developed of dissolving polyuranates and uranium dioxides in sulphuric acid and in carbonate solutions for testing intermediate products in the sol-gel process preparation of uranium dioxide. A detailed granulometric analysis of spherical particle dispersion was included as part of the tests. Two different production methods were used for the two types of studied materials. The test results show that the test method is suitable for determining temperature sensitivity of the materials to dissolution reaction. The geometrical distribution of impurities in the spherical particles can be determined from the dissolution kinetics. The method allows the determination of the effect of carbon from impurities on the process of uranium dioxide leaching and is thus applicable for testing materials prepared by the sol-gel method. (Z.M.)

Saltcake dissolution FY 1998 status report

International Nuclear Information System (INIS)

HERTING, D.L.

1999-01-01

A laboratory scouting study was completed on the dissolution characteristics of Hanford waste from three single-shell waste tanks: 241-BY-102, 241-BY-106, and 241-B-106. Gross dissolution behavior (percent undissolved solids as a function of dilution) is explained in terms of characteristics of individual salts in the waste. The percentage of the sodium inventory retrievable from the tanks by dissolving saltcake at reasonable dilution levels is estimated at 86% of the total sodium for tank BY-102, 98% for BY-106, and 79% for B-106

Dissolution test for glibenclamide tablets

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Elisabeth Aparecida dos Santos Gianotto

2007-10-01

Full Text Available The aim of this work is to develop and validate a dissolution test for glibenclamide tablets. Optimal conditions to carry out the dissolution test are 500 mL of phosphate buffer at pH 8.0, paddles at 75 rpm stirring speed, time test set to 60 min and using equipment with six vessels. The derivative UV spectrophotometric method for determination of glibenclamide released was developed, validated and compared with the HPLC method. The UVDS method presents linearity (r² = 0.9999 in the concentration range of 5-14 µg/mL. Precision and recoveries were 0.42% and 100.25%, respectively. The method was applied to three products commercially available on the Brazilian market.

Enhanced Dissolution of Platinum Group Metals Using Electroless Iron Deposition Pretreatment

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Taninouchi, Yu-ki; Okabe, Toru H.

2017-12-01

In order to develop a new method for efficiently recovering platinum group metals (PGMs) from catalyst scraps, the authors investigated an efficient dissolution process where the material was pretreated by electroless Fe deposition. When Rh-loaded alumina powder was kept in aqua regia at 313 K (40 °C) for 30 to 60 minutes, the Rh hardly dissolved. Meanwhile, after electroless Fe plating using a bath containing sodium borohydride and potassium sodium tartrate as the reducing and complexing agents, respectively, approximately 60 pct of Rh was extracted by aqua regia at 313 K (40 °C) after 30 minutes. Furthermore, when heat treatment was performed at 1200 K (927 °C) for 60 minutes in vacuum after electroless plating, the extraction of Rh approached 100 pct for the same leaching conditions. The authors also confirmed that the Fe deposition pretreatment enhanced the dissolution of Pt and Pd. These results indicate that an effective and environmentally friendly process for the separation and extraction of PGMs from catalyst scraps can be developed utilizing this Fe deposition pretreatment.

Dissolution and alteration of uraninite under reducing conditions

International Nuclear Information System (INIS)

Janeczek, J.; Ewing, R.C.

1992-01-01

The behavior of uraninite under hydrothermal, reducung conditions is discussed on the basis of data in the literature and the authors' investigation of samples from two natural analogue sites: Oklo, Gabon and Cigar Lake, Canada. Uraninite under reducing conditions, in the presence of saline hydrothermal solutions may be altered through dissolution, preferential loss of lead and/or Y + HREE, and coffinitization. Textural features indicative of dissolution or uraninite include embayed grain boundaries, corroded relicts of uraninite embedded in a clay matrix, and replacement of uraninite by clays and sulfides. The alteration textures and phase chemistries at Oklo and Cigar Lake are remarkably similar. Dissolution of uraninite at Cigar Lake and Oklo was associated with the precipitation or illite and was probably caused by saline, uraninite moderately acidic solutions at approximately 200deg C. Increased oxygen fugacity may have occured locally due to release of excess oxygen from uraninite during dissolution or by α-radiolysis of the solution. The formation of Pb-rich (up to 18 wt% Pb, uraninite-I) and Pb-depleted (approximately 7-8 wt% Pb, uraninite-II) uraninites at both Oklo and Cigar Lake resulted from the loss of Pb due to predominantly episodic volume diffusion related to regional geologic events. Lead loss was not associated with U mobilization. In addition to uraninite dissolution, coffinitization resulted in U, Pb and REE release. (orig.)

Mesoporous Silica Molecular Sieve based Nanocarriers: Transpiring Drug Dissolution Research.

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Pattnaik, Satyanarayan; Pathak, Kamla

2017-01-01

Improvement of oral bioavailability through enhancement of dissolution for poorly soluble drugs has been a very promising approach. Recently, mesoporous silica based molecular sieves have demonstrated excellent properties to enhance the dissolution velocity of poorly water-soluble drugs. Current research in this area is focused on investigating the factors influencing the drug release from these carriers, the kinetics of drug release and manufacturing approaches to scale-up production for commercial manufacture. This comprehensive review provides an overview of different methods adopted for synthesis of mesoporous materials, influence of processing factors on properties of these materials and drug loading methods. The drug release kinetics from mesoporous silica systems, the manufacturability and stability of these formulations are reviewed. Finally, the safety and biocompatibility issues related to these silica based materials are discussed. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Effect of exopolymers on oxidative dissolution of natural rhodochrosite by Pseudomonas putida strain MnB1: An electrochemical study

International Nuclear Information System (INIS)

Wang, Huawei; Zhang, Daoyong; Song, Wenjuan; Pan, Xiangliang; Al-Misned, Fahad A.; Golam Mortuza, M.

2015-01-01

Highlights: • The biogeochemical behavior of natural rhodochrosite was investigated by electrochemical methods. • Bacterial exopolymers contributed to the increasing dissolution of natural rhodochrosite. • Oxidative dissolution of natural rhodochrosite was well explained by Tafel and EIS analysis. - Abstract: Oxidative dissolution of natural rhodochrosite by the Mn(II) oxidizing bacterium Pseudomonas putida strain MnB1 was investigated based on batch and electrochemical experiments using natural rhodochrosite as the working electrode. Tafel curves and batch experiments revealed that bacterial exopolymers (EPS) significantly increased dissolution of natural rhodochrosite. The corrosion current significantly increased with reaction time for EPS treatment. However, the corrosion process was blocked in the presence of cells plus extra EPS due to formation of the passivation layer. Moreover, the scanning electron microscopy and the energy dispersive spectroscopy (SEM–EDS) results showed that the surface of the natural rhodochrosite was notably changed in the presence of EPS alone or/and bacterial cells. This study is helpful for understanding the role of EPS in bacterially oxidation of Mn(II). It also indicates that the Mn(II) oxidizing bacteria may exert their effects on Mn(II) cycle and other biological and biogeochemical processes much beyond their local ambient environment because of the catalytically dissolution of solid Mn(II) by EPS and the possible long distance transport of the detached EPS

Aluminosilicate Dissolution and Silicate Carbonation during Geologic CO2 Sequestration

Science.gov (United States)

Min, Yujia

Geologic CO2 sequestration (GCS) is considered a promising method to reduce anthropogenic CO2 emission. Assessing the supercritical CO2 (scCO2) gas or liquid phase water (g, l)-mineral interactions is critical to evaluating the viability of GCS processes. This work contributes to our understanding of geochemical reactions at CO 2-water (g, l)-mineral interfaces, by investigating the dissolution of aluminosilicates in CO2-acidified water (l). Plagioclase and biotite were chosen as model minerals in reservoir rock and caprock, respectively. To elucidate the effects of brine chemistry, first, the influences of cations in brine including Na, Ca, and K, have been investigated. In addition to the cations, the effects of abundant anions including sulfate and oxalate were also examined. Besides the reactions in aqueous phase, we also examine the carbonation of silicates in water (g)-bearing supercritical CO2 (scCO2) under conditions relevant to GCS. For the metal carbonation, in particular, the effects of particle sizes, water, temperature, and pressure on the carbonation of wollastonite were systematically examined. For understanding the cations effects in brine, the impacts of Na concentrations up to 4 M on the dissolution of plagioclase and biotite were examined. High concentrations of Na significantly inhibited plagioclase dissolution by competing adsorption with proton and suppressing proton-promoted dissolution. Ca has a similar effect to Na, and their effects did not suppress each other when Na and Ca co-existed. For biotite, the inhibition effects of Na coupled with an enhancing effect due to ion exchange reaction between Na and interlayer K, which cracked the basal surfaces of biotite. The K in aqueous phase significantly inhibited the dissolution. If the biotite is equilibrated with NaCl solutions initially, the biotite dissolved faster than the original biotite and the dissolution was inhibited by Na and K in brine. The outcomes improve our current knowledge of

Influence of pH and temperature on alunite dissolution rates and products

Science.gov (United States)

Acero, Patricia; Hudson-Edwards, Karen

2015-04-01

, leading to dissolved Al/K ratios between 0.5 and 2.5. This depletion of Al in the solution is especially clear for the experiments at pH 4.5-4.8 and 8 and it is consistent with the results of elemental quantifications of the same proportions in the reacted alunite surfaces using X-ray Photoelectron Spectroscopy (XPS). REFERENCES Flaten, T.P. (2001): Aluminium as a risk factor in Alzheimzer's disease, with emphasis on drinking water. Brain Research Bulletin 55: 187-196. Nordstrom, D.K. (2011): Hydrogeochemical processes governing the origin, transport and fate of major and trace elements from mine wastes and mineralized rock to surface waters. Applied Geochemistry 26: 1777-1791. Prietzel, J., & Hirsch, C. (1998). Extractability and dissolution kinetics of pure and soil-added synthesized aluminium hydroxy sulphate minerals. European journal of soil science, 49(4), 669-681. Swayze, G.A., Ehlmann, B.L., Milliken, R.E., Poulet, F., Wray, J.J., Rye, R.O., Clark, R.N., Desborough, G.A., Crowley, J.K., Gondet, B., Mustard, J.F., Seelos, K.D. and Murchie, S.L., 2008. Discovery of the Acid-Sulfate Mineral Alunite in Terra Sirenum, Mars, Using MRO CRISM: Possible Evidence for Acid-Saline Lacustrine Deposits?, American Geophysical Union, Fall Meeting 2008, abstract #P44A-04. Welch, S. A., Kirste, D., Christy, A. G., Beavis, F. R., & Beavis, S. G. (2008): Jarosite dissolution II'Reaction kinetics, stoichiometry and acid flux. Chemical Geology, 254(1), 73-86.

In situ Microscopic Observation of Sodium Deposition/Dissolution on Sodium Electrode

OpenAIRE

Yuhki Yui; Masahiko Hayashi; Jiro Nakamura

2016-01-01

Electrochemical sodium deposition/dissolution behaviors in propylene carbonate-based electrolyte solution were observed by means of in situ light microscopy. First, granular sodium was deposited at pits in a sodium electrode in the cathodic process. Then, the sodium particles grew linearly from the electrode surface, becoming needle-like in shape. In the subsequent anodic process, the sodium dissolved near the base of the needles on the sodium electrode and the so-called ?dead sodium? broke a...

Kaolinite, illite and quartz dissolution in the karstification of Paleozoic sandstones of the Furnas Formation, Paraná Basin, Southern Brazil

Science.gov (United States)

Melo, Mário Sérgio de; Guimarães, Gilson Burigo; Chinelatto, Adilson Luiz; Giannini, Paulo César Fonseca; Pontes, Henrique Simão; Chinelatto, Adriana Scoton Antonio; Atencio, Daniel

2015-11-01

Karstification processes in sandstones of the Furnas Formation, Silurian to Devonian of the Paraná Basin, have been described since the mid-twentieth century. However, some geologists still doubt the idea of true karst in sandstones. Studies carried out in the Campos Gerais region, Paraná State, Southern Brazil, aimed at investigating the nature of erosion processes in Furnas Formation and the role of the dissolution in the development of their notorious erosive features and underground cavities. These studies have led to the recognition of dissolution macro to micro features ('furnas', caves, ponds, sinks, ruiniform relief on cliffs and rocky surfaces, grain corrosion, speleothems, mineral reprecipitation and incrustation). The analysis (scanning electron microscopy, energy dispersive spectrometry and x-ray diffractometry) of sandstones and their alterites has indicated significant dissolution of clay cement along with discrete quartz grain dissolution. This mesodiagenetic cement (kaolinite and illite) is dissolved and reprecipitated as clay minerals with poorly developed crystallinity along with other minerals, such as variscite and minerals of the alunite supergroup, suggesting organic participation in the processes of dissolution and incrustation. The mineral reprecipitation usually forms centimetric speleothems, found in cavities and sheltered rocky surfaces. The cement dissolution associated with other factors (fractures, wet weather, strong hydraulic gradient, antiquity of the landforms) leads to the rock arenisation, the underground erosion and the appearance of the karst features. Carbonate rocks in the basement may locally be increasing the karst forms in the overlying Furnas Formation. The recognition of the karst character of the Furnas Formation sandstones has important implications in the management of underground water resources (increasingly exploited in the region), in the use of the unique geological heritage and in the prevention of geo

Carbonate dissolution rates in high salinity brines: Implications for post-Noachian chemical weathering on Mars

Science.gov (United States)

Phillips-Lander, Charity M.; Parnell, S. R.; McGraw, L. E.; Elwood Madden, M. E.

2018-06-01

A diverse suite of carbonate minerals including calcite (CaCO3) and magnesite (MgCO3) have been observed on the martian surface and in meteorites. Terrestrial carbonates usually form via aqueous processes and often record information about the environment in which they formed, including chemical and textural biosignatures. In addition, terrestrial carbonates are often found in association with evaporite deposits on Earth. Similar high salinity environments and processes were likely active on Mars and some areas may contain active high salinity brines today. In this study, we directly compare calcite and magnesite dissolution in ultrapure water, dilute sulfate and chloride solutions, as well as near-saturated sulfate and chloride brines with known activity of water (aH2O) to determine how dissolution rates vary with mineralogy and aH2O, as well as aqueous cation and anion chemistry to better understand how high salinity fluids may have altered carbonate deposits on Mars. We measured both calcite and magnesite initial dissolution rates at 298 K and near neutral pH (6-8) in unbuffered solutions containing ultrapure water (18 MΩ cm-1 UPW; aH2O = 1), dilute (0.1 mol kg-1; aH2O = 1) and near-saturated Na2SO4 (2.5 mol kg-1, aH2O = 0.92), dilute (0.1 mol kg-1, aH2O = 1) and near-saturated NaCl (5.7 mol kg-1, aH2O = 0.75). Calcite dissolution rates were also measured in dilute and near-saturated MgSO4 (0.1 mol kg-1, aH2O = 1 and 2.7 mol kg-1, aH2O = 0.92, respectively) and MgCl2 (0.1 mol kg-1, aH2O = 1 and 3 mol kg-1, aH2O = 0.73, respectively), while magnesite dissolution rates were measured in dilute and near-saturated CaCl2 (0.1 mol kg-1, aH2O = 1 and 9 mol kg-1, aH2O = 0.35). Initial calcite dissolution rates were fastest in near-saturated MgCl2 brine, while magnesite dissolution rates were fastest in dilute (0.1 mol kg-1) NaCl and CaCl2 solutions. Calcite dissolution rates in near-saturated Na2SO4 were similar to those observed in the dilute solutions (-8.00 ± 0

Dissolution experiments of unirradiated uranium dioxide pellets

International Nuclear Information System (INIS)

Ollila, K.

1985-01-01

The purpose of this study was to measure the dissolution rate of uranium from unirradiated uranium dioxide pellets in deionized water and natural groundwater. Moreover, the solubility limit of uranium in natural groundwater was measured. Two different temperatures, 25 and 60 deg C were used. The low oxygen content of deep groundwater was simulated. The dissolution rate of uranium varied from 10 -7 to 10 -8 g cm -2 d -1 . The rate in reionized water was one order of magnitude lower than in groundwater. No great difference was observed between the natural groundwaters with different composition. Temperature seems to have effect on the dissolution rate. The solubility limit of uranium in natural groundwater in reducing conditions, at 25 deg C, varied from 20 to 600 μg/l and in oxidizing conditions, at 60 deg C, from 4 to 17 mg/l

Controlled evaluation of silver nanoparticle dissolution using atomic force microscopy.

Science.gov (United States)

Kent, Ronald D; Vikesland, Peter J

2012-07-03

Incorporation of silver nanoparticles (AgNPs) into an increasing number of consumer products has led to concern over the potential ecological impacts of their unintended release to the environment. Dissolution is an important environmental transformation that affects the form and concentration of AgNPs in natural waters; however, studies on AgNP dissolution kinetics are complicated by nanoparticle aggregation. Herein, nanosphere lithography (NSL) was used to fabricate uniform arrays of AgNPs immobilized on glass substrates. Nanoparticle immobilization enabled controlled evaluation of AgNP dissolution in an air-saturated phosphate buffer (pH 7.0, 25 °C) under variable NaCl concentrations in the absence of aggregation. Atomic force microscopy (AFM) was used to monitor changes in particle morphology and dissolution. Over the first day of exposure to ≥10 mM NaCl, the in-plane AgNP shape changed from triangular to circular, the sidewalls steepened, the in-plane radius decreased by 5-11 nm, and the height increased by 6-12 nm. Subsequently, particle height and in-plane radius decreased at a constant rate over a 2-week period. Dissolution rates varied linearly from 0.4 to 2.2 nm/d over the 10-550 mM NaCl concentration range tested. NaCl-catalyzed dissolution of AgNPs may play an important role in AgNP fate in saline waters and biological media. This study demonstrates the utility of NSL and AFM for the direct investigation of unaggregated AgNP dissolution.

Dissolution Enhancement of Rosuvastatin Calcium by Liquisolid Compact Technique

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V. J. Kapure

2013-01-01

Full Text Available In present investigation liquisolid compact technique is investigated as a tool for enhanced dissolution of poorly water-soluble drug Rosuvastatin calcium (RVT. The model drug RVT, a HMG-Co A reductase inhibitor was formulated in form of directly compressed tablets and liquisolid compacts; and studied for in-vitro release characteristics at different dissolution conditions. In this technique, liquid medications of water insoluble drugs in non-volatile liquid vehicles can be converted into acceptably flowing and compressible powders. Formulated systems were assessed for precompression parameters like flow properties of liquisolid system, Fourior transform infra red spectra (FTIR analysis, X-ray powder diffraction (XRPD, differential scanning calorimetry (DSC, and post compression parameters like content uniformity, weight variation, hardness and friability, disintegration test, wetting time, in vitro dissolution studies, effect of dissolution volume on drug release rate, and estimation of fraction of molecularly dispersed drug in liquid medication. As liquisolid compacts demonstrated significantly higher drug release rates, we lead to conclusion that it could be a promising strategy in improving the dissolution of poor water soluble drugs and formulating immediate release solid dosage forms.

15 CFR 295.23 - Dissolution of joint research and development ventures.

Science.gov (United States)

2010-01-01

... Development Ventures § 295.23 Dissolution of joint research and development ventures. Upon dissolution of any joint research and development venture receiving funds under these procedures or at a time otherwise... 15 Commerce and Foreign Trade 1 2010-01-01 2010-01-01 false Dissolution of joint research and...

Frogging It: A Poetic Analysis of Relationship Dissolution

Science.gov (United States)

Faulkner, Sandra L.

2012-01-01

Often, themes in work and life intertwine; the author recognized that a cadre of poems she had written during the past several years were about relationship dissolution. The poems concerned romantic and friendship dissolution and the aspects of identity creation and loss this entails. The author presents the poems and makes an explicit connection…

Determining the dissolution rates of actinide glasses: A time and temperature Product Consistency Test study

International Nuclear Information System (INIS)

Daniel, W.E.; Best, D.R.

1995-01-01

Vitrification has been identified as one potential option for the e materials such as Americium (Am), Curium (Cm), Neptunium (Np), and Plutonium (Pu). A process is being developed at the Savannah River Site to safely vitrify all of the highly radioactive Am/Cm material and a portion of the fissile (Pu) actinide materials stored on site. Vitrification of the Am/Cm will allow the material to be transported and easily stored at the Oak Ridge National Laboratory. The Am/Cm glass has been specifically designed to be (1) highly durable in aqueous environments and (2) selectively attacked by nitric acid to allow recovery of the valuable Am and Cm isotopes. A similar glass composition will allow for safe storage of surplus plutonium. This paper will address the composition, relative durability, and dissolution rate characteristics of the actinide glass, Loeffler Target, that will be used in the Americium/Curium Vitrification Project at Westinghouse Savannah River Company near Aiken, South Carolina. The first part discusses the tests performed on the Loeffler Target Glass concerning instantaneous dissolution rates. The second part presents information concerning pseudo-activation energy for the one week glass dissolution process

Dissolution of oxide films on iron in aqueous solutions containing complexing anions

International Nuclear Information System (INIS)

Shoesmith, D.W.; Lee, W.; Owen, D.G.

1981-01-01

The dissolution, in oxalic acid and oxalic acid plus ethylenediaminetetraacetate, of magnetite films grown at high temperature on iron has been studied under varying conditions of pH and temperature. For oxalate concentrations greater than about 2 x 10 -3 mol dm -3 , magnetite dissolves by direct chemical dissolution. The mechanism appears to involve adsorption of oxalate ions at ferric ion sites in the oxide lattice, followed by proton attack and desorption of cationic species. Once metal dissolution starts, β-ferrous oxalate dihydrate is precipitated on the electrode, leading to erratic fluctuations in the electrode potential and eventually to inhibition of metal dissolution. For oxalate concentrations -3 mol dm -3 , the predominant dissolution mechanism appears to involve reduction by the metal. Also, once solution penetration to the underlying metal has occurred, and the electrode has returned to the active state, autoreductive dissolution appears to predominate even at higher oxalate concentrations. This change in mechanism from predominantly chemical dissolution to predominantly autoreductive dissolution may be due, at least in part, to the desorption of oxalate ions at the more negative potentials achieved in the active state. (author)

The Dissolution of Uranium Oxides in HB-Line Phase 1 Dissolvers

International Nuclear Information System (INIS)

Gray, J.H.

2003-01-01

A series of characterization and dissolution studies has been performed to define flowsheet conditions for the dissolution of uranium oxide materials in dissolvers. The samples selected for analysis were uranium oxide materials. The selection of these uranium oxide materials for characterization and dissolution studies was based on high enriched uranium content and trace levels of plutonium. Test results from the characterization study identified ferric oxide (Fe2O3) and iron/chromium/nickel (Fe/Cr/Ni) particles as impurities along with the tri-uranium oxide (U3O8) and uranium trioxide (UO3). The weight percent uranium in this material was found to vary depending on the impurity content. The trace impurity plutonium appears to be associated with the Fe/Cr/Ni particles. A small amount of absorbed moisture and waters of hydration is present. Most of the uranium oxides easily dissolved in low-molar nitric acid solutions without fluoride within one to two hours at solution temperature s between 60-80 degrees C. A small amount of residue remained following this dissolution step. To assure complete dissolution of uranium from these oxide materials, an additional dissolution step at 90 degrees C to boiling for at least one to two hours has been suggested. Only trace amounts of iron associated with Fe2O3 and Fe/Cr/Ni particles will dissolve during the dissolution steps. Neither hydrogen nor heat will be generated during the dissolution of these uranium oxide materials in nitric acid solutions. Some brown nitrogen dioxide (NO2) fumes will be generated during the dissolution of U3O8

Looking for the Self: Phenomenology, Neurophysiology and Philosophical Significance of Drug-induced Ego Dissolution

Directory of Open Access Journals (Sweden)

Raphaël Millière

2017-05-01

Full Text Available There is converging evidence that high doses of hallucinogenic drugs can produce significant alterations of self-experience, described as the dissolution of the sense of self and the loss of boundaries between self and world. This article discusses the relevance of this phenomenon, known as “drug-induced ego dissolution (DIED”, for cognitive neuroscience, psychology and philosophy of mind. Data from self-report questionnaires suggest that three neuropharmacological classes of drugs can induce ego dissolution: classical psychedelics, dissociative anesthetics and agonists of the kappa opioid receptor (KOR. While these substances act on different neurotransmitter receptors, they all produce strong subjective effects that can be compared to the symptoms of acute psychosis, including ego dissolution. It has been suggested that neuroimaging of DIED can indirectly shed light on the neural correlates of the self. While this line of inquiry is promising, its results must be interpreted with caution. First, neural correlates of ego dissolution might reveal the necessary neurophysiological conditions for the maintenance of the sense of self, but it is more doubtful that this method can reveal its minimally sufficient conditions. Second, it is necessary to define the relevant notion of self at play in the phenomenon of DIED. This article suggests that DIED consists in the disruption of subpersonal processes underlying the “minimal” or “embodied” self, i.e., the basic experience of being a self rooted in multimodal integration of self-related stimuli. This hypothesis is consistent with Bayesian models of phenomenal selfhood, according to which the subjective structure of conscious experience ultimately results from the optimization of predictions in perception and action. Finally, it is argued that DIED is also of particular interest for philosophy of mind. On the one hand, it challenges theories according to which consciousness always involves

Looking for the Self: Phenomenology, Neurophysiology and Philosophical Significance of Drug-induced Ego Dissolution

Science.gov (United States)

Millière, Raphaël

2017-01-01

There is converging evidence that high doses of hallucinogenic drugs can produce significant alterations of self-experience, described as the dissolution of the sense of self and the loss of boundaries between self and world. This article discusses the relevance of this phenomenon, known as “drug-induced ego dissolution (DIED)”, for cognitive neuroscience, psychology and philosophy of mind. Data from self-report questionnaires suggest that three neuropharmacological classes of drugs can induce ego dissolution: classical psychedelics, dissociative anesthetics and agonists of the kappa opioid receptor (KOR). While these substances act on different neurotransmitter receptors, they all produce strong subjective effects that can be compared to the symptoms of acute psychosis, including ego dissolution. It has been suggested that neuroimaging of DIED can indirectly shed light on the neural correlates of the self. While this line of inquiry is promising, its results must be interpreted with caution. First, neural correlates of ego dissolution might reveal the necessary neurophysiological conditions for the maintenance of the sense of self, but it is more doubtful that this method can reveal its minimally sufficient conditions. Second, it is necessary to define the relevant notion of self at play in the phenomenon of DIED. This article suggests that DIED consists in the disruption of subpersonal processes underlying the “minimal” or “embodied” self, i.e., the basic experience of being a self rooted in multimodal integration of self-related stimuli. This hypothesis is consistent with Bayesian models of phenomenal selfhood, according to which the subjective structure of conscious experience ultimately results from the optimization of predictions in perception and action. Finally, it is argued that DIED is also of particular interest for philosophy of mind. On the one hand, it challenges theories according to which consciousness always involves self-awareness. On

The anodic dissolution of SIMFUEL (UO2) in slightly alkaline sodium carbonate/bicarbonate solutions

International Nuclear Information System (INIS)

Keech, P.G.; Goldik, J.S.; Qin, Z.; Shoesmith, D.W.

2011-01-01

The corrosion of nuclear fuel under waste disposal conditions is likely to be influenced by the bicarbonate/carbonate content of the groundwater since it increases the solubility of the U VI corrosion product, [UO 2 ] 2+ . As one of the half reactions involved in the corrosion process, the anodic dissolution of SIMFUEL (UO 2 ) has been studied in bicarbonate/carbonate solutions (pH 9.8) using voltammetric and potentiostatic techniques and electrochemical impedance spectroscopy. The reaction proceeds by two consecutive one electron transfer reactions (U IV → U V → U VI ). At low potentials (≤250 mV (vs. SCE) the rate of the first electron transfer reaction is rate determining irrespective of the total carbonate concentration. At potentials >250 mV (vs. SCE) the formation of a U VI O 2 CO 3 surface layer begins to inhibit the dissolution rate and the current becomes independent of potential indicating rate control by the chemical dissolution of this layer.

Oxidative dissolution of ruthenium deposits onto stainless steel by permanganate ions in alkaline medium

Energy Technology Data Exchange (ETDEWEB)

Floquet, S.; Eysseric, C.; Maurel, D. [Commissariat a l' Energie Atomique (CEA/Valrho), Bagnols-sur-Ceze (France)

2008-07-01

During spent nuclear fuel reprocessing ruthenium is liable to form black ruthenium deposits on the stainless steel walls of process equipments. These deposits promote corrosion and can eventually obstruct the off-gas lines. The results of decontamination of 304L stainless steel test specimens covered with RuO(OH){sub 2} . xH{sub 2}O deposits by permanganate ions in alkaline medium are described. The ruthenium deposits were dissolved by oxidation of RuO(OH){sub 2} to RuO{sub 4}{sup 2-} ions, while the permanganate ions were reduced to MnO{sub 4}{sup 2-} ions and then to manganese dioxide MnO{sub 2}. The parameters affecting the kinetics of oxidative dissolution of these deposits were examined. The results indicate that the oxidative dissolution kinetics depends on the instantaneous surface area of the deposit, and that the dissolution rate increases with the concentrations of MnO{sub 4}{sup -} and OH{sup -} ions. (orig.)

Numerical modelling of glass dissolution: gel layer morphology

Energy Technology Data Exchange (ETDEWEB)

Devreux, F. E-mail: fd@pmc.polytechnique.fr; Barboux, P

2001-09-01

Numerical simulations of glass dissolution are presented. The glass is modelized as a random binary mixture composed of two species representing silica and soluble oxides, such as boron and alkali oxides. The soluble species are dissolved immediately when they are in contact with the solution. For the species which represents silica, one introduces dissolution and condensation probabilities. It is shown that the morphology and the thickness of the surface hydration layer (the gel) are highly dependent on the dissolution model, especially on the parameter which controls the surface tension. Simulations with different glass surface area to solution volume ratio (S/V) show that this experimental parameter has important effects on both the shrinkage and the gel layer thickness.

USE OF AN EQUILIBRIUM MODEL TO FORECAST DISSOLUTION EFFECTIVENESS, SAFETY IMPACTS, AND DOWNSTREAM PROCESSABILITY FROM OXALIC ACID AIDED SLUDGE REMOVAL IN SAVANNAH RIVER SITE HIGH LEVEL WASTE TANKS 1-15

International Nuclear Information System (INIS)

KETUSKY, EDWARD

2005-01-01