Effect of ZrO2 on the glass durability

ABSTRACTBorosilicate glasses were prepared with the molar composition 70 SiO2-15 Na2O-15B2O3-n ZrO2 with n ranging from 0 to 10. The glasses were studied by conventional static dissolution tests of powders at 90°C in pure water and in buffered solutions for long times (months) and short times (minutes). During the first minutes of alteration in a buffered solution, sodium is rapidly leached until its loss becomes controlled by the silicon hydrolysis. The experimental data show that the introduction of zirconium drastically reduces the initial dissolution rate (Vo) of the glass. Zirconium strengthens the silica network but also strongly modifies the porous layer morphology. In the case of glasses with small Zr contents (less than 2%), the silica dissolution rate decreases but the formation of a passivating alteration layer is also delayed. As a result, small amounts of zirconium paradoxically decrease the loss of silica but increase the final loss of sodium and boron in the static leaching tests. Larger zirconium contents (above 5%) increase the durability of the glass regarding the initial dissolution rate and the final concentration of all elements.

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Cationic Corrosion Inhibitors for Alkaliborosilicate Glass

MRS Proceedings ◽

10.1557/proc-257-83 ◽

1991 ◽

Vol 257 ◽

Author(s):

H.U. Zwicky ◽

TH. Graber ◽

R. Grauer ◽

R. Restani

Keyword(s):

Dissolution Rate ◽

Corrosion Inhibitors ◽

Pure Water ◽

Reaction Rates ◽

Alkaline Solutions ◽

Lead Silicate ◽

Borosilicate Glasses ◽

Glass Dissolution ◽

Inhibiting Effect ◽

Solid Phases

ABSTRACTThe dissolution behaviour of two alkali borosilicate glasses has been investigated at 90°C in the presence of potential corrosion inhibitors. The added materials were selected on the basis of surface chemistry considerations: Since the dissolution rate of silicate solid phases in alkaline solutions increases with growing negative surface charge, it should be expected that sorbing cations reduce the reaction rates. Due to the formation of insoluble hydroxides and silicates and to the dominance of neutral or negatively charged hydroxo complexes in the pH range of interest, the selection of potential inhibitors is very restricted.The precipitated hydroxides of Al, Zn, Cd and Pb were chosen as the solid phases. Compared with the experiments in pure water, glass dissolution is enhanced in presence of Al(OH)3 and Zn(OH)2. The concentration of the aqua ions is too low for an inhibiting effect. Sorption of silicic acid on the hydroxide accelerates the glass dissolution. Addition of PbO had a strong inhibiting effect in a 28 days experiment. At longer times an insoluble lead silicate is formed and thereby the glass dissolution rate is increased. Cd on the other hand is still effective as an inhibitor after 365 days.Based on the present results, the possibility of using glass corrosion inhibitors in a repository is considered not to be worthwhile.

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Solid Dispersions as a Technological Strategy to Improve the Bio-Performance of Antiparasitic Drugs with Limited Solubility

Proceedings ◽

10.3390/iecp2020-08686 ◽

2020 ◽

Vol 78 (1) ◽

pp. 13

Author(s):

Santiago N. Campos ◽

Alicia G. Cid ◽

Analía I. Romero ◽

Mercedes Villegas ◽

Cintia A. Briones Nieva ◽

...

Keyword(s):

Dissolution Rate ◽

Solid Dispersions ◽

Poloxamer 407 ◽

Parasitic Infections ◽

Dissolution Tests ◽

Antiparasitic Drugs ◽

Dissolution Efficiency ◽

Time Required ◽

Low Solubility ◽

Initial Dissolution Rate

Albendazole (ABZ) and benznidazole (BZL) are drugs with low solubility used in parasitic infections treatment. In this research, solid dispersion (SD) technology was used to enhance ABZ and BZL performance by increasing their dissolution rate and solubility. SDs were prepared by the fusion method, employing Poloxamer 407 (P407) as carrier to disperse 32 of BZL or 50% w/w of ABZ. Furthermore, physical mixtures (PM) of P407 and either ABZ or BZL were also prepared, and then SDs and PMs were characterized. Dissolution tests of SDs, PMs and commercial formulations (CF) of ABZ and BZL were carried out and dissolution profiles were analyzed with the lumped mathematical model, which allowed parameters of pharmaceutical relevance to be obtained. The results indicated that ABZ SD presented an initial dissolution rate (IDR) 21-fold and 11-fold faster than PM and CF, respectively, while the IDR of BZL SD was 2.5-fold and 4.5-fold faster than PM and CF, respectively. For BZL formulations, the time required to reach 80% dissolution of the drug (t80%) was 4 (SD), 46 (PM), and 239 min (CF), while the dissolution efficiency (DE) at 30 min was 85 (DS), 71 (MF) and 65% (FC). For ABZ formulations, t80% was 2 (SD), value not reached (PM) and 40 min (CF), while the DE at 30 min was 85 (SD), 36 (MF) and 65% (CF). The SDs developed notably increased the dissolution rate, in consonance with the values obtained from the pharmaceutical parameters, which could lead to faster absorption and, consequently, increase the bioavailability of these drugs.

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Impact of boron complexation by Tris buffer on the initial dissolution rate of borosilicate glasses

Journal of Colloid and Interface Science ◽

10.1016/j.jcis.2013.03.009 ◽

2013 ◽

Vol 400 ◽

pp. 161-167 ◽

Cited By ~ 11

Author(s):

A. Tournié ◽

O. Majérus ◽

G. Lefèvre ◽

M.-N. Rager ◽

S. Walmé ◽

...

Keyword(s):

Dissolution Rate ◽

Tris Buffer ◽

Borosilicate Glasses ◽

Initial Dissolution Rate

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The reductive dissolution of synthetic goethite and hematite in dithionite

Clay Minerals ◽

10.1180/claymin.1987.022.3.07 ◽

1987 ◽

Vol 22 (3) ◽

pp. 329-337 ◽

Cited By ~ 83

Author(s):

J. Torrent ◽

U. Schwertmann ◽

V. Barron

Keyword(s):

Specific Surface ◽

Dissolution Rate ◽

Surface Area ◽

Reductive Dissolution ◽

Natural Environments ◽

Dissolution Rates ◽

Aluminium Substitution ◽

Initial Dissolution Rate

AbstractThe reductive dissolution by Na-dithionite of 28 synthetic goethites and 26 hematites having widely different crystal morphologies, specific surfaces and aluminium substitution levels has been investigated. For both minerals the initial dissolution rate per unit of surface area decreased with aluminium substitution. At similar aluminium substitution and specific surface, goethites and hematites showed similar dissolution rates. These results suggest that preferential, reductive dissolution of hematite in some natural environments, such as soils or sediments, might be due to the generally lower aluminium substitution of this mineral compared to goethite.

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The fate of Si and Fe while nuclear glass alters with steel and clay

npj Materials Degradation ◽

10.1038/s41529-021-00160-x ◽

2021 ◽

Vol 5 (1) ◽

Author(s):

C. Carriere ◽

P. Dillmann ◽

S. Gin ◽

D. Neff ◽

L. Gentaz ◽

...

Keyword(s):

Dissolution Rate ◽

Protective Layer ◽

Glass Dissolution ◽

A Value ◽

Waste Forms ◽

Controlling Mechanism ◽

Geological Repository ◽

The Mean ◽

High Level ◽

Initial Dissolution Rate

AbstractThe French concept developed to dispose high-level radioactive waste in geological repository relies on glassy waste forms, isolated from the claystone host rock by steel containers. Understanding interactions between glass and surrounding materials is key for assessing the performance of a such system. Here, isotopically tagged SON68 glass, steel and claystone were studied through an integrated mockup conducted at 50 °C for 2.5 years. Post-mortem analyses were performed from nanometric to millimetric scales using TEM, STXM, ToF-SIMS and SEM techniques. The glass alteration layer consisted of a crystallized Fe-rich smectite mineral, close to nontronite, supporting a dissolution/reprecipitation controlling mechanism for glass alteration. The mean glass dissolution rate ranged between 1.6 × 10−2 g m−2 d−1 to 3.0 × 10−2 g m−2 d−1, a value only 3–5 times lower than the initial dissolution rate. Thermodynamic calculations highlighted a competition between nontronite and protective gel, explaining why in the present conditions the formation of a protective layer is prevented.

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Initial Dissolution Rate Studies on Dental Enamel after CO2 Laser Irradiation

Journal of Dental Research ◽

10.1177/00220345920710070701 ◽

1992 ◽

Vol 71 (7) ◽

pp. 1389-1398 ◽

Cited By ~ 45

Author(s):

J.L. Fox ◽

D. Yu ◽

M. Otsuka ◽

W.I. Higuchi ◽

J. Wong ◽

...

Keyword(s):

Dissolution Rate ◽

Laser Irradiation ◽

Co2 Laser ◽

Dental Enamel ◽

Initial Dissolution Rate

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Difference in the Dissolution Behaviors of Tablets Containing Polyvinylpolypyrrolidone (PVPP) Depending on Pharmaceutical Formulation After Storage Under High Temperature and Humid Conditions

Journal of Pharmacy & Pharmaceutical Sciences ◽

10.18433/j3hw3q ◽

2016 ◽

Vol 19 (4) ◽

pp. 511 ◽

Cited By ~ 2

Author(s):

Yoh Takekuma ◽

Haruka Ishizaka ◽

Masato Sumi ◽

Yuki Sato ◽

Mitsuru Sugawara

Keyword(s):

High Temperature ◽

Benzoic Acid ◽

Dissolution Rate ◽

Simple Structure ◽

Pharmaceutical Formulations ◽

Magnesium Stearate ◽

Principal Agent ◽

Amino Groups ◽

Dissolution Tests ◽

Rosuvastatin Calcium

PURPOSE. Storage under high temperature and humid conditions has been reported to decrease the dissolution rate for some kinds of tablets containing polyvinylpolypyrrolidone (PVPP) as a disintegrant. The aim of this study was to elucidate the properties of pharmaceutical formulations with PVPP that cause a decrease in the dissolution rate after storage under high temperature and humid conditions by using model tablets with a simple composition. METHODS. Model tablets, which consisted of rosuvastatin calcium or 5 simple structure compounds, salicylic acid, 2-aminodiphenylmethane, 2-aminobiphenyl, 2-(p-tolyl)benzoic acid or 4.4’-biphenol as principal agents, cellulose, lactose hydrate, PVPP and magnesium stearate as additives, were made by direct compression. The model tables were wrapped in paraffin papers and stored for 2 weeks at 40°C/75% relative humidity (RH). Dissolution tests were carried out by the paddle method in the Japanese Pharmacopoeia 16th edition. RESULTS. Model tablets with a simple composition were able to reproduce a decreased dissolution rate after storage at 40°C/75% RH. These tablets showed significantly decreased water absorption activities after storage. In the case of tablets without lactose hydrate by replacing with cellulose, a decreased dissolution rate was not observed. Carboxyl and amino groups in the structure of the principal agent were not directly involved in the decreased dissolution. 2-Benzylaniline tablets showed a remarkably decreased dissolution rate and 2-aminobiphenyl and 2-(p-tolyl)benzoic acid tablets showed slightly decreased dissolution rates, though 4,4’-biphenol tablets did not show a decrease dissolution rate. CONCLUSIONS. We demonstrated that additives and structure of the principal agent were involved in the decreased in dissolution rate for tablets with PVPP. The results suggested that one of the reasons for a decreased dissolution rate was the inclusion of lactose hydrate in tablets. The results also indicated that compounds as principal agents with low affinity for PVPP may be easily affected by airborne water under high temperature and humid conditions. This article is open to POST-PUBLICATION REVIEW. Registered readers (see “For Readers”) may comment by clicking on ABSTRACT on the issue’s contents page.

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Thorium oxide dissolution in HNO3-HF mixture: kinetics and mechanism

Radiochimica Acta ◽

10.1515/ract-2018-3052 ◽

2019 ◽

Vol 107 (4) ◽

pp. 289-297 ◽

Cited By ~ 2

Author(s):

Marie Simonnet ◽

Nicole Barré ◽

Romuald Drot ◽

Claire Le Naour ◽

Vladimir Sladkov ◽

...

Keyword(s):

Experimental Data ◽

Dissolution Rate ◽

Hydrofluoric Acid ◽

Kinetics And Mechanism ◽

Dissolution Mechanism ◽

Oxide Dissolution ◽

Thorium Oxide ◽

Specific Focus ◽

Acid Effect ◽

Wide Range

Abstract This paper is an attempt to find out thorium oxide dissolution mechanism in HNO3-HF mixture. In a previous paper, several parameters effects on thorium oxide dissolution have been described, with specific focus on hydrofluoric acid effect, which can lead to an increase of the dissolution rate if present in small amount, but precipitates as ThF4 at higher content. Based on this previous study, experimental data were fitted using several dissolution models in order to find out the best one. Finally, a revisited model based on literature and considering the ThF4 formation was proposed. It describes the main steps of dissolution and is able to fit the experimental data for a wide range of solution compositions. This point is crucial since it allows considering an extrapolation of the established model to not-yet-studied conditions.

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