Chemistry of Glass Corrosion in High Saline Brines

1989 ◽  
Vol 176 ◽  
Author(s):  
B. Grambow ◽  
R. Müller
Keyword(s):  
Liquid Junction ◽  
Geochemical Model ◽  
Silicate Formation ◽  
Ph Values ◽  
Glass Corrosion ◽  
High Release ◽  
Constant Ph ◽  
Pitzer Formalism ◽  
Brine Chemistry ◽  
Salt Minerals

ABSTRACTExperimental data were obtained for conventional pH values corrected for liquid junction, amorphous silica solubility and glass corrosion in concentrated salt brines. The data were interpreted with a geochemical model. The brine chemistry was described with the Pitzer formalism [1] using a data base which allows calculation of brine compositions in equilibrium with salt minerals at temperatures up to 200°C.In MgCl2 dominated brines Mg silicates form and due to the consumption of Mg the pH decreases with proceeding reaction. A constant pH (about 4) and composition of alteration products is achieved, when the alkali release from the glass balances the Mg consumption. The low pH results in high release of rare earth elements REE and U from the glass. In the NaCl dominated brine MgCl2 becomes exhausted by Mg silicate formation. As long as there is still Mg left in solution the pH decreases. After exhaustion of Mg the pH rises with the alkali release from the glass and analcime is formed.

scholarly journals Production of butyric acid at constant pH by a solventogenic strain of Clostridium beijerinckii

2020 ◽  
Vol 38 (No. 3) ◽  
pp. 185-191 ◽  
Author(s):  
Marek Drahokoupil ◽  
Petra Patáková
Keyword(s):  
Flow Cytometry ◽  
Butyric Acid ◽  
Population Viability ◽  
Clostridium Beijerinckii ◽  
Clostridium Tyrobutyricum ◽  
Fluorescence Staining ◽  
Low Concentration ◽  
Ph Values ◽  
Constant Ph ◽  
Acetone Butanol Ethanol

A solventogenic strain of Clostridium beijerinckii, NRRL B-598, was cultured for the production of butyric acid as the main fermentation product. However, unlike typical acetone-butanol-ethanol (ABE) fermentations, where pH is not regulated, in this study the pH was kept constant during fermentation. From the five pH values tested, 6.0, 6.5, 7.0, 7.5 and 8.0, pH 6.5 and 7.0 resulted in the highest concentrations of butyric acid, at 9.69 ± 0.09 g L–1 and 11.5 ± 0.39 g L–1, respectively. However, a low concentration of solvents, 1.8 ± 0.22 g L–1, was only reached at pH 7.0. These results are comparable with those from typical butyric acid producers, i.e. Clostridium butyricum and Clostridium tyrobutyricum strains. At pH 7.0, we succeeded in suppressing sporulation and prolonging the population viability, which was confirmed by flow cytometry combined with double fluorescence staining.

Equilibrium and Kinetics of the Extraction of Gallium(III) from Sodium Hydroxide Solutions with 7-Dodecenyl-8-quinolinol (Kelex 100)

1993 ◽  
Vol 58 (5) ◽  
pp. 1093-1102 ◽  
Author(s):  
Aleksandra A. Mitrovic ◽  
Slobodan K. Milonjic ◽  
Zoja E. Ilic ◽  
Radomir V. Stevanovic
Keyword(s):  
Sodium Hydroxide ◽  
Sodium Hydroxide Solution ◽  
Aqueous Sodium Hydroxide ◽  
Sodium Concentration ◽  
Extraction Kinetics ◽  
Aqueous Sodium Hydroxide Solution ◽  
Ph Values ◽  
Constant Ph ◽  
Equilibrium And Kinetics ◽  
Kinetics Of

The influence of hydroxide ions concentration of the aqueous sodium hydroxide solution, at constant sodium concentrations, on the gallium extraction with Kelex 100 was examined in the hydroxide concentration range from 0.02 to 0.5 mol dm-3. The percentage of extracted gallium increases from 51% to 98% within the investigated hydroxide concentration range. The influence of sodium concentrations (from 1 to 6 mol dm-3) on the gallium extraction was also studied at constant pH values. The decrease of extracted gallium is slight for the sodium concentration up to 3 mol dm-3, while for the higher ones it is pronounced. The extraction kinetics was studied using a mixer-type apparatus. The rate expression of the extraction reaction of gallium with Kellex 100, for both lower and higher hydroxide concentrations are ascertained.

scholarly journals Chemical Reduction of Nitrate by Zero-Valent Iron: Shrinking-Core versus Surface Kinetics Models

2020 ◽  
Vol 17 (4) ◽  
pp. 1241 ◽  
Author(s):  
Maria Villen-Guzman ◽  
Juan Manuel Paz-Garcia ◽  
Brahim Arhoun ◽  
Maria del Mar Cerrillo-Gonzalez ◽  
Jose Miguel Rodriguez-Maroto ◽  
...  
Keyword(s):  
Nitrate Reduction ◽  
Chemical Reduction ◽  
Permeable Reactive Barriers ◽  
Zero Valent Iron ◽  
Sound Design ◽  
Surface Kinetics ◽  
Ph Values ◽  
Stirred Reactor ◽  
Constant Ph ◽  
Shrinking Core

Zero valent iron (ZVI) is being used in permeable reactive barriers (PRB) for the removal of oxidant contaminants, from nitrate to chlorinated organics. A sound design of these barriers requires a good understanding of kinetics. Here we present a study of the kinetics of nitrate reduction under relatively low values of pH, from 2 to 4.5. We use a particle size of 0.42 mm, which is within the recommended size for PRBs (0.2 mm to 2.0 mm). In order to avoid possible mass-transfer limitations, a well-stirred reactor coupled with a fluidized bed reactor was used. The experiments were performed at constant pH values using a pH controller that allows to accurately track the amount of acid added. Since the reduction of H + to H 2 by the oxidation of ZVI will always be present for these pH values, blank experiments (without nitrate) were performed and the rate of this H + reduction obtained. This rate of reduction was studied using three kinetic models: a regular empirical one, the Shrinking-Core Model (SCM), and the Surface Kinetics Model (SKM). The best performance was obtained from the SKM model. Therefore, this model was also used to study the results for the nitrate reduction, also with satisfactory results. In both cases, some assumptions are introduced to maintain a moderate number of fitting parameters.

Survival of Bacillus cereus Vegetative Cells and Spores during In Vitro Simulation of Gastric Passage

2012 ◽  
Vol 75 (4) ◽  
pp. 690-694 ◽  
Author(s):  
SIELE CEUPPENS ◽  
MIEKE UYTTENDAELE ◽  
KATRIEN DRIESKENS ◽  
ANDREJA RAJKOVIC ◽  
NICO BOON ◽  
...  
Keyword(s):  
Bacillus Cereus ◽  
Acid Resistance ◽  
In Vitro Experiments ◽  
Vegetative Cells ◽  
Ph Values ◽  
Constant Ph ◽  
In Vitro Simulation ◽  
Ph Range

The enteric pathogen Bacillus cereus must survive gastric passage in order to cause diarrhea by enterotoxin production in the small intestine. The acid resistance and the survival after gastric passage were assessed by in vitro experiments with acidified growth medium and gastric simulation medium with B. cereus NVH 1230-88 vegetative cells and spores. First, batch incubations at constant pH values for 4 h, which represented different physiological states of the stomach, showed that spores were resistant to any gastric condition in the pH range of 2.0 to 5.0, while vegetative cells were rapidly inactivated at pH values of ≤4.0. Second, a dynamic in vitro gastric experiment was conducted that simulated the continuously changing in vivo conditions due to digestion dynamics by gradually decreasing the pH from 5.0 to 2.0 and fractional emptying of the stomach 30 to 180 min from the start of the experiment. All of the B. cereus spores and 14% (±9%) of the vegetative cells survived the dynamic simulation of gastric passage.

The vertical gradient of bark pH of twigs and macrolichens in a Picea abies canopy not affected by acid rain

2001 ◽  
Vol 33 (4) ◽  
pp. 353-359 ◽  
Author(s):  
Thale Kermit ◽  
Yngvar Gauslaa
Keyword(s):  
Picea Abies ◽  
Species Composition ◽  
Acid Rain ◽  
Vertical Gradient ◽  
Small Scale ◽  
High Ph ◽  
Ph Values ◽  
Constant Ph ◽  
Horizontal Variation ◽  
Cyanobacterial Lichens

AbstractThe pH of 192 thin, even-aged twigs from 4 height levels of 12 randomly selected trees within a boreal Picea abies canopy naturally exposed to rainfall with a high pH (>5·2) was measured. The largest variation in bark pH was due to the height above the ground. However, a highly significant horizontal variation between trees was also found, apparently due to small-scale soil variations. The biomass of alectorioid lichens increased with increasing height above die ground to at least 12 m, a height interval with fairly constant pH values. The uppermost twigs had an unusually high pH and an abnormal species composition for P. abies, with dominance of the foliose Melanelia exasperatula. The canopy hosted several cyanobacterial lichens, but these were scattered and had low biomass, restricted to lower branches of the trees with the highest bark pH.

Tolerance of Trifolium subterraneum cultivars to low pH

1985 ◽  
Vol 36 (4) ◽  
pp. 569 ◽  
Author(s):  
MK Kim ◽  
DG Edwards ◽  
CJ Asher
Keyword(s):  
Phosphorus Uptake ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Solution Culture ◽  
Nutrient Concentrations ◽  
Solution Ph ◽  
Ph Values ◽  
Phosphorus Absorption ◽  
Constant Ph ◽  
Effects Of Ph

Eleven cultivars of Trifolium subterraneum and Trifolium semipilosum cv. Safari were grown with adequate combined nitrogen for 27 days in flowing solution culture with controlled nutrient concentrations at constant pH values ranging from 3.5 to 6.5. A solution pH of 3.5 was lethal to all cultivars, but growth was in all cases vigorous at pH 4.0 (RGR 15.2-16.9 g 100 g-1 day-1). There were no significant effects of pH over the range of 4.0-6.5 on the yield of any clover cultivar. The results are discussed in relation to an earlier study suggesting greater tolerance of subterranean clover to pH values below 4.0. Phosphorus toxicity symptoms developed in all subterranean clover cultivars with the intensity of symptom development increasing with solution pH from 4.5 to 6.5. The concentration of phosphorus in the older leaves decreased as the solution pH was increased from 4.0 to 4.5, and then increased with further increase in pH, reaching values = 1.0%. Rates of phosphorus absorption followed a similar pattern of response to solution pH. Results are discussed with reference to previously reported effects of pH on phosphorus uptake.

Comparison of the free energy of transfer of electrolytes, measured with cells without transference, with the sum of the free energies of the corresponding cations and anions with the Owen-cell on standard conditions

1983 ◽  
Vol 36 (10) ◽  
pp. 1997 ◽  
Author(s):  
K Schwabe ◽  
W Hoffmann ◽  
C Queck
Keyword(s):  
Free Energy ◽  
Free Energies ◽  
Liquid Junction Potential ◽  
Liquid Junction ◽  
Ph Values ◽  
Liquid Junction Potentials ◽  
Free Energy Of Transfer ◽  
Energy Of Transfer ◽  
Very High ◽  
Junction Potential

The comparison of S2ΔS1G°tr(E1) with the sum of the values for the corresponding cation and anion S2ΔS1G°tr(Ct+)~S2ΔS1G°tr(X-) (measured) with Owen cells, gained by double extrapolation and by the assumption that the liquid junction potential at 1→0 may be neglected) gives values which differ by not more than ±5%. Most of the investigated acids allow the conclusion that the pH values, measured in cells with transference, and having the same electrodes, give good information on the acidity of the organic solvent and its water mixtures, referred to the standard state in water. That means that the pH, changed to the same H+ concentration in the solvent compared with that in water, is essentially an effect of the free energy of transfer of the hydrogen ion and not of very high liquid junction potentials.

THE DECOMPOSITION OF 2-METHYL-Δ2-OXAZOLINE IN AQUEOUS SOLUTION

1963 ◽  
Vol 41 (7) ◽  
pp. 1662-1670 ◽  
Author(s):  
R. Greenhalgh ◽  
R. M. Heggie ◽  
M. A. Weinberger
Keyword(s):  
Aqueous Solution ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Water Concentration ◽  
Acidity Function ◽  
First Order ◽  
Ph Values ◽  
Constant Ph ◽  
Kinetic Expression ◽  
Ph Range

Nuclear magnetic resonance has been used to follow the decomposition of aqueous solutions of 2-methyl-Δ2-oxazoline (0.29 M) at constant pH values in the range −1 to 14. The decomposition is first order with respect to total oxazoline at any specific pH, but deviates from the simple reaction of water with the protonated species above pH 5. At neutral pH values this is shown to be partially due to a second reaction involving 2-methyl-Δ2-oxazoline and O-acetylethanolamine which yields N-2-acetoxyethyl N′-2-hydroxyethyl acetamidate. The decrease in rate constant at pH < 2 is accounted for by variation in the water concentration, which is related to the acidity function. A kinetic expression is derived for the decomposition over the whole pH range studied. The decomposition of the amidate is also discussed.

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