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Sample records for acidic fluoride solutions

  1. Delayed fracture of Ni-Ti superelastic alloys in acidic and neutral fluoride solutions.

    PubMed

    Yokoyama, Ken'ichi; Kaneko, Kazuyuki; Moriyama, Keiji; Asaoka, Kenzo; Sakai, Jun'ichi; Nagumo, Michihiko

    2004-04-01

    Hydrogen-related degradation of the mechanical properties of a Ni-Ti superelastic alloy has been examined by means of delayed fracture tests in acidic and neutral fluoride solutions and hydrogen thermal desorption analysis. Delayed fracture took place in both solutions; the time to fracture was shorter in the acidic solutions than in the neutral solutions with the same fluoride concentration. The time to fracture was reduced in both solutions when applied stress exceeded the critical stress for martensite transformation. In the acidic solutions, Ni-Ti superelastic alloy underwent general corrosion and absorbed substantial amounts of hydrogen. Fractographic features suggested that the delayed fracture in the acidic solutions was attributable to hydrogen embrittlement, whereas in the neutral solutions, a different fracture mode appeared associated with localized corrosion only in the vicinity of the fracture initiation area. In the neutral solutions, the amount of absorbed hydrogen was much less than that in the acidic solutions, and the delayed fracture was likely to be induced by active path corrosion accompanying hydrogen absorption. The results of the present study imply that the hydrogen-related degradation of performance of Ni-Ti superelastic alloys occurs in the presence of fluoride. PMID:14999757

  2. The surface reactivity of a magnesium-aluminium alloy in acidic fluoride solutions studied by electrochemical techniques and XPS

    NASA Astrophysics Data System (ADS)

    Verdier, S.; van der Laak, N.; Delalande, S.; Metson, J.; Dalard, F.

    2004-08-01

    The behaviour of the 6% Al magnesium alloy AM60 in aqueous acid fluoride solutions was studied in situ by electrochemical techniques and the surface chemistry of the resulting film was examined by monochromatized XPS. The evolution of the corrosion potential and cyclic voltammograms showed that the aggressiveness of the solutions is mainly driven by their fluoride concentration, the pH having almost no detectable influence. The more concentrated and acidic fluoride solutions led to a higher degree of fluoride coverage of the surface. The surface film is composed of magnesium hydroxide and hydroxyfluoride Mg(OH) 2- xF x which approaches MgF 2 with increasing fluoride concentration in the film. The parameters governing the film evolution and their relation to surface reactions are discussed.

  3. Silicon oxidation in fluoride solutions

    NASA Technical Reports Server (NTRS)

    Sancier, K. M.; Kapur, V.

    1980-01-01

    Silicon is produced in a NaF, Na2SiF6, and Na matrix when SiF4 is reduced by metallic sodium. Hydrogen is evolved during acid leaching to separate the silicon from the accompanying reaction products, NaF and Na2SiF6. The hydrogen evolution reaction was studied under conditions simulating leaching conditions by making suspensions of the dry silicon powder in aqueous fluoride solutions. The mechanism for the hydrogen evolution is discussed in terms of spontaneous oxidation of silicon resulting from the cooperative effects of (1) elemental sodium in the silicon that reacts with water to remove a protective silica layer, leaving clean reactive silicon, and (2) fluoride in solution that complexes with the oxidized silicon in solution and retards formation of a protective hydrous oxide gel.

  4. An in vitro assessment of the mechanical characteristics of nickel-titanium orthodontic wires in Fluoride solutions with different acidities

    PubMed Central

    Alavi, Shiva; Barooti, Sara; Borzabadi-Farahani, Ali

    2015-01-01

    Objectives: The aim was to evaluate the in vitro effects of fluoride solutions with different acidities on load-deflection characteristics of nickel-titanium (NiTi) orthodontic wires. Materials and Methods: In this study, which lasted 30 days, 36 (3 cm long, 0.016 × 0.022 inches, SENT 1622, G & H wire Company, Greenwood, Indiana, USA) NiTi wires, were divided into three experimental groups of 12 each. Two groups were subjected to 0.05 topical fluoride mouthwash with different acidities (G1, pH 4; G2, pH 6.6) for 90 s, twice a day, and kept in normal saline after that. The third group (G3, the control group) was kept in normal saline only. Load and unload forces were measured with three bracket bending test in a universal testing machine (Testometric Co, Rochdale, UK). Loading and unloading plateaus and hysteresis were also recorded. Data were then analyzed using analysis of variance and honestly significant difference Tukey at P < 0.05. Results: During the loading phase, there was a significant difference between deflections (P < 0.001); but there was no interaction effect (P = 0.191) and no significant difference among three groups (P = 0.268). In the unloading phase, there was a significant difference between deflections (P < 0.001) and an interaction effect was also observed (P = 0.008). Further, significant differences noted among three groups (P = 0.037). Only in the unloading phase, at deflections of 2.2 through 0.2 mm, significant differences between the mean force values of the G1 and G3 groups were observed (P = 0.037). Conclusion: Based on this in-vitro study, compared to neutral fluoride solution, daily mouthwash with a fluoride solution with more acidic pH of 4 affected the NiTi wires load-deflection characteristics during the unloading phase. This finding may have clinical implications and can be further validated by in-vivo studies. PMID:26020039

  5. Inhibition of hydrogen embrittlement of Ni-Ti superelastic alloy in acid fluoride solution by hydrogen peroxide addition.

    PubMed

    Yokoyama, Ken'ichi; Yazaki, Yushin; Sakai, Jun'ichi

    2011-09-01

    Inhibition of the hydrogen embrittlement of Ni-Ti superelastic alloy in an acidulated phosphate fluoride (APF) solution has been attempted by adding various amounts of H(2)O(2). In a 0.2% APF solution, hydrogen absorption is markedly inhibited by adding H(2)O(2), although corrosion is slightly enhanced by increasing the amount of added H(2)O(2). By adding a small amount of H(2)O(2) (0.001 M), in the early stage of immersion, hydrogen embrittlement is inhibited and corrosion is only slightly enhanced. Upon adding H(2)O(2), it appears that the dominant cathodic reactions change from hydrogen evolution to H(2)O(2) reduction reactions, or the surface conditions of the alloy are changed by H(2)O(2) with a high oxidation capability, thereby inhibiting hydrogen absorption. The present study clearly indicates that infinitesimal addition of H(2)O(2) into acid fluoride solutions is effective for the inhibition of the hydrogen embrittlement of the alloy. PMID:21630433

  6. Interactions between variable-charge soils and acidic solutions containing fluoride: an investigation using repetitive extractions.

    PubMed

    Zhu, Mao-Xu; Jiang, Xin; Ji, Guo-Liang

    2004-08-01

    The reaction between two variable-charge soils and acidic solutions containing F was investigated with a repetitive extraction method. When added F concentration was 10(-4) mol/L, F did not markedly enhance solution pH in the whole prolonged extractions, in comparison with F-free acidic solution extractions. Most of the added F was adsorbed on soil surfaces and Al-F complexes were the dominant F species in solution. With increasing extractions, the fraction of Al-F slightly increased, arising from dissolution and/or desorption of Al. In comparison with F-free acidic solution extractions, F-induced Al dissolution did not significantly increase Al release, probably because of the modest reactivity of metal-F surface complexes at terminal sites at low F loading. The gradual decrease in Al release in the following extractions was due to the gradual depletion of readily reactive Al-containing mineral phases. In contrast to the low F loading, at an F concentration of 10(-3) mol/L, the pH was enhanced dramatically in the initial extraction and a high pH was maintained in the following extractions. In the initial extraction, the increase in negative surface charges and solution pH seemingly depressed proton-induced Al dissolution and enhanced readsorption of some positively charged Al-F complexes, resulting in low amounts of Al and F in solution. In the following several extractions, F-induced Al dissolution and desorption of Al-F complexes substantially enhanced the amounts of Al and F, and the fraction of Al-F complexes in solution. Several interconnected mechanisms such as ligand exchange, the release of OH(-) ions from soluble hydroxylated Al groups, desorption of Al as Al-F complexes, and F-induced breakdown of soil minerals were responsible for the alteration in pH, Al release, and the fraction of Al-F complexes in the later extractions. A molecular-level interpretation is needed in order to address the different impacts of varying F concentration levels on soil

  7. Preparation of conversion coating on Ti-6Al-4V alloy in mixed solution of phytic acid and ammonium fluoride through chemical modification

    NASA Astrophysics Data System (ADS)

    Li, Lanlan; He, Jian; Yang, Xu

    2016-05-01

    Conversion coatings on Ti-6Al-4V alloy was prepared through chemical modification in phytic acid and ammonium fluoride mixed solution. The influences of pH, time and the composition of solution on the microstructure of alloy surface were investigated. Scanning electron microscopy was used to observe the microstructure. The chemical composition of alloy surface before and after modification was investigated by energy dispersive X-ray spectroscopy. The results indicated that a conversion coating could be formed on the Ti-6Al-4V alloy in a mixed solution of phytic acid and ammonium fluoride, the growth and microstructure of the conversion coatings were critically dependent on the pH, time and concentration of phytic acid and ammonium fluoride. In 100 mg/ml phytic acid containing 125 mg/ml ammonium fluoride solution with a pH of 6, a compact conversion coating with the thickness of about 4.7 μm formed after 30 min immersion on Ti-6Al-4V alloy surface. The preliminary evaluation of bioactivity of conversion coating was performed by in vitro cell experiments. The results showed that this chemical modification method is a promising surface modification technique for Ti-6Al-4V alloy inplants.

  8. Xenon fluoride solutions effective as fluorinating agents

    NASA Technical Reports Server (NTRS)

    Hyman, H. H.; Quarterman, L. A.; Sheft, I.

    1967-01-01

    Solutions of xenon fluorides in anhydrous hydrogen fluoride have few disruptive effects and leave a residue consisting of gaseous xenon, which can be recovered and refluorinated. This mild agent can be used with materials which normally must be fluorinated with fluorine alone at high temperatures.

  9. Fluoride

    MedlinePlus

    Fluoride is used to prevent tooth decay. It is taken up by teeth and helps to strengthen teeth, resist acid, and block the cavity-forming action of bacteria. Fluoride usually is prescribed for children ...

  10. PRECIPITATION OF URANIUM PEROXIDE OF LOW FLUORIDE CONTENT FROM SOLUTIONS CONTAINING FLUORIDES

    DOEpatents

    King, E.J.; Clark, H.M.

    1958-08-12

    S>A method is described for the preparation of fluoride free uraniunn peroxide precipitates, even though the solution from which the precipitation is made is contaminated with fluorides. This is accomplished by add ing aluminum ions to the solution, where they complex any fluoride present and prevent its precipitation with the uramum peroxide.

  11. The ameliorative effect of ascorbic acid and Ginkgo biloba on learning and memory deficits associated with fluoride exposure

    PubMed Central

    Raghuveer, Vasudeva C.; Rao, Mallikarjuna C.; Somayaji, Nagabhooshana S.; Babu, Prakash B.

    2013-01-01

    Chronic exposure to fluoride causes dental and skeletal fluorosis. Fluoride exposure is also detrimental to soft tissues and organs. The present study aimed at evaluation of the effect of Ginkgo biloba and ascorbic acid on learning and memory deficits caused by fluoride exposure. Male Wistar rats were divided into five groups (n=6). Group 1 control. Groups 2 to 5 received 100 ppm of sodium fluoride over 30 days. Groups 3, 4 and 5 were further treated for 15 days receiving respectively 1% gum acacia solution, 100 mg/kg body weight ascorbic acid, and 100mg/kg body weight Ginkgo biloba extract. After 45 days, all animals were subjected to behavioural tests. The results showed that fluoride affected learning and memory. Fluoride causes oxidative stress and neurodegeneration, thereby affecting learning and memory. Ascorbic acid and Ginkgo biloba were found to augment the reversal of learning and memory deficits caused by fluoride ingestion. PMID:24678261

  12. Biogeochemistry of fluoride in a plant-solution system

    NASA Technical Reports Server (NTRS)

    Mackowiak, C. L.; Grossl, P. R.; Bugbee, B. G.

    2003-01-01

    Fluoride (F-) pollutants can harm plants and the animals feeding on them. However, it is largely unknown how complexing and chelating agents affect F bioavailability. Two studies were conducted that measured F- bioavailability and uptake by rice (Oryza sativa L.). In the first study, rice was grown in solution culture (pH 5.0) with 0, 2, or 4 mM F- as KF to compare the interaction of F- with humic acid (HA) and with a conventional chelating agent, N-hydroxyethylenthylenediaminetriacetic acid (HEDTA). In the second study, F was supplied at 0, 0.5, 1.0, and 2.0 mM KF with an additional 2 mM F- treatment containing solution Ca at 2x (2 mM Ca) the level used in the first study, to test the effect added Ca had on F- availability and uptake. Total biomass was greatest with HEDTA and F- < 1 mM. Leaf and stem F concentrations increased exponentially as solution F- increased linearly, with nearly no F partitioning into the seed. Results suggest that F was taken up as HF0 while F- uptake was likely restricted. Additionally, F- competed with HA for Ca, thus preventing the formation of Ca-HA flocculents. The addition of soluble Ca resulted in the precipitation of CaF2 solids on the root surface, as determined by tissue analysis and energy dispersive X-ray spectroscopy.

  13. TESTING OF 304L STAINLESS STEEL IN NITRIC ACID ENVIRONMENTS WITH FLUORIDES AND CHLORIDES

    SciTech Connect

    Mickalonis, J.

    2010-10-04

    Impure radioactive material processed in nitric acid solutions resulted in the presence of chlorides in a dissolver fabricated from 304L stainless steel. An experimental program was conducted to study the effects of chloride in nitric acid/fluoride solutions on the corrosion of 304L stainless steel. The test variables included temperature (80, 95, and 110 C) and the concentrations of nitric acid (6, 12, and 14 M), fluoride (0.01, 0.1, and 0.2 M) and chloride (100, 350, 1000, and 2000 ppm). The impact of welding was also investigated. Results showed that the chloride concentration alone was not a dominant variable affecting the corrosion, but rather the interaction of chloride with fluoride significantly affected corrosion.

  14. ANTICARIOGENIC POTENCIAL OF ACIDULATE SOLUTIONS WITH LOW FLUORIDE CONCENTRATION

    PubMed Central

    Delbem, Alberto Carlos Botazzo; Tiano, Gilberto Carlos; Alves, Karina Mirela Ribeiro Pinto; Cunha, Robson Frederico

    2006-01-01

    Objectives: The aim of this study was to verify the anticariogenic effect of acidulate solutions with low NaF concentration, using pH-cycling model and bovine enamel. Material and methods: Enamel blocks were submitted to the surface microhardness (SMH) test and randomly divided in 12 experimental and one placebo groups. The blocks were submitted to pH cycling for 7 days, with daily applications once/day of 0.05% NaF and 0.1% NaF and twice/day of 0.02% NaF solutions. Four different pH: 4.0, 5.0, 6.0 and 7.0 were used. Next, SMH test was again used to determine the surface microhardness percentage change (%SMH). Data obtained for %SMH were homogeneous and passed through variance analyses and Tukey's test (5%) as far as fluoride concentrations and pH. Results: The results showed that pH influenced %SMH in 0.02% NaF and 0.05% NaF solutions with pH 4.0, which had less mineral loss compared to pH 7.0 (p<0.05). The 0.02% NaF - pH 4.0, and 0.05% NaF – pH 7.0 groups showed similar results (p>0.05). A dose-response relationship was observed among the tested solutions, with better anticariogenic effect for the 0.1% NaF solution. Conclusion: The results suggest that the addition of citric acid to acidulate mouth rinses reduce mineral loss. PMID:19089268

  15. EQCM analysis of titanium corrosion in peroxide- or fluoride-containing solutions.

    PubMed

    Hattori, Masayuki; Oda, Yutaka

    2013-01-01

    Although offering superior resistance to corrosion, titanium is unable to withstand discoloration with exposure to peroxide or fluoride. The mechanism of this discoloration, however, remains to be clarified. The purpose of this study was to investigate the mechanism underlying discoloration of titanium with immersion in peroxide- or fluoride-containing solutions based on electrochemical quartz crystal microbalance (EQCM) analysis. A 9-MHz titanium-deposited quartz crystal was used as for the electrodes. Four test solutions were prepared for immersion of the electrodes: 154 mM (0.9%) NaCl; 150 mM H2O2+154 mM NaCl (pH=4 by addition of lactic acid); 150 mM H2O2+154 mM NaCl (pH=8 by addition of sodium hydroxide solution); and 48 mM (0.2%) NaF+154 mM NaCl (pH=5.0 by addition of lactic acid). A WinEchem electrochemistry software-controlled quartz crystal analyzer (QCA922) and the Potentiostat/Galvanostat (Princeton Applied Research) on Windows XP were used to measure concurrently the resonance frequency and potential of the electrodes. The EQCM data differed among solutions. In the acidulated fluoride-containing solution, the electrode showed lower open circuit potential and a gradual increase in electrode frequency, indicating a loss of mass by titanium dissolution. In the peroxide-containing solution, although open circuit potential showed no marked difference, electrode frequency showed a gentle decrease in acidic solution, indicating a gain in mass by oxidation; but an increase in alkaline solution, indicating a loss of mass by dissolution. These results confirmed that exposure to acidulated fluoride- or alkaline peroxide-containing solutions causes dissolution-induced discoloration, while that to acidulated peroxide-containing solutions resulted in the formation of an oxide film together with discoloration. PMID:24334626

  16. Serum fluoride and sialic acid levels in osteosarcoma.

    PubMed

    Sandhu, R; Lal, H; Kundu, Z S; Kharb, S

    2011-12-01

    Osteosarcoma is a rare malignant bone tumor most commonly occurring in children and young adults presenting with painful swelling. Various etiological factors for osteosarcoma are ionizing radiation, family history of bone disorders and cancer, chemicals (fluoride, beryllium, and vinyl chloride), and viruses. Status of fluoride levels in serum of osteosarcoma is still not clear. Recent reports have indicated that there is a link between fluoride exposure and osteosarcoma. Glycoproteins and glycosaminoglycans are an integral part of bone and prolonged exposure to fluoride for long duration has been shown to cause degradation of collagen and ground substance in bones. The present study was planned to analyze serum fluoride, sialic acid, calcium, phosphorus, and alkaline phosphatase levels in 25 patients of osteosarcoma and age- and sex-matched subjects with bone-forming tumours other than osteosarcoma and musculo-skeletal pain (controls, 25 each). Fluoride levels were analyzed by ISE and sialic acid was analyzed by Warren's method. Mean serum fluoride concentration was found to be significantly higher in patients with osteosarcoma as compared to the other two groups. The mean value of flouride in patients with other bone-forming tumors was approximately 50% of the group of osteosarcoma; however, it was significantly higher when compared with patients of group I. Serum sialic acid concentration was found to be significantly raised in patients with osteosarcoma as well as in the group with other bone-forming tumors as compared to the group of controls. There was, however, no significant difference in the group of patients of osteosarcoma when compared with group of patients with other bone-forming tumors. These results showing higher level of fluoride with osteosarcoma compared to others suggesting a role of fluoride in the disease. PMID:19390788

  17. Effect of strong acids on red mud structural and fluoride adsorption properties.

    PubMed

    Liang, Wentao; Couperthwaite, Sara J; Kaur, Gurkiran; Yan, Cheng; Johnstone, Dean W; Millar, Graeme J

    2014-06-01

    The removal of fluoride using red mud has been improved by acidifying red mud with hydrochloric, nitric and sulphuric acid. The acidification of red mud causes sodalite and cancrinite phases to dissociate, confirmed by the release of sodium and aluminium into solution as well as the disappearance of sodalite bands and peaks in infrared and X-ray diffraction data. The dissolution of these mineral phases increases the amount of available iron and aluminium oxide/hydroxide sites that are accessible for the adsorption of fluoride. However, concentrated acids have a negative effect on adsorption due to the dissolution of these iron and aluminium oxide/hydroxide sites. The removal of fluoride is dependent on the charge of iron and aluminium oxide/hydroxides on the surface of red mud. Acidifying red mud with hydrochloric, nitric and sulphuric acid resulted in surface sites of the form ≡SOH2(+) and ≡SOH. Optimum removal is obtained when the majority of surface sites are in the form ≡SOH2(+) as the substitution of a fluoride ion does not cause a significant increase in pH. This investigation shows the importance of having a low and consistent pH for the removal of fluoride from aqueous solutions using red mud. PMID:24703681

  18. Delayed fracture of beta titanium orthodontic wire in fluoride aqueous solutions.

    PubMed

    Kaneko, Kazuyuki; Yokoyama, Ken'ichi; Moriyama, Keiji; Asaoka, Kenzo; Sakai, Jun'ichi; Nagumo, Michihiko

    2003-05-01

    Hydrogen embrittlement of a beta titanium orthodontic wire has been examined by means of a delayed-fracture test in acid and neutral fluoride aqueous solutions and hydrogen thermal desorption analysis. The time to fracture increased with decreasing applied stress in 2.0% and 0.2% acidulated phosphate fluoride (APF) solutions. The fracture mode changed from ductile to brittle when the applied stress was lower than 500MPa in 2.0% APF solution. On the other hand, the delayed fracture did not occur within 1000h in neutral NaF solutions, although general corrosion was also observed similar to that in APF solutions. Hydrogen desorption of the delayed-fracture-tested specimens was observed with a peak at approximately 500 degrees C. The amount of absorbed hydrogen was 5000-6500 mass ppm under an applied stress in 2.0% APF solution for 24h. It is concluded that the immersion in fluoride solutions leads to the degradation of the mechanical properties and fracture of beta titanium alloy associated with hydrogen absorption. PMID:12628832

  19. Fluoride

    MedlinePlus

    Fluoride is used to prevent tooth decay. It is taken up by teeth and helps to strengthen ... and block the cavity-forming action of bacteria. Fluoride usually is prescribed for children and adults whose ...

  20. Corrosion resistance of stainless steels and high Ni-Cr alloys to acid fluoride wastes

    SciTech Connect

    Smith, H.D.; Mackey, D.B.; Pool, K.H. ); Schwenk, E.B. )

    1992-04-01

    TRUEX processing of Hanford Site waste will utilize potentially corrosive acid fluoride processing solutions. Appropriate construction materials for such a processing facility need to be identified. Toward this objective, candidate stainless steels and high Ni-Cr alloys have been corrosion tested in simulated acid fluoride process solutions at 333K. The high Ni-Cr alloys exhibited corrosion rates as low as 0.14 mm/y in a solution with an HF activity of about 1.2 M, much lower than the 19 to 94 mm/y observed for austenitic stainless steels. At a lower HF activity (about 0.008 M), stainless steels display delayed passivation while high Ni-Cr alloys display essentially no reaction.

  1. Inverted organic solar cells comprising a solution-processed cesium fluoride interlayer

    SciTech Connect

    Reinhard, Manuel; Zhang Zhenhao; Colsmann, Alexander; Lemmer, Uli; Hanisch, Jonas; Ahlswede, Erik

    2011-01-31

    We investigate the influence of solution-processed cesium fluoride (CsF) interlayers on the performance of inverted polymer solar cells comprising a blend of poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl C{sub 61}-butyric acid methyl ester. The thickness of the CsF layer is optimized in terms of current-voltage characteristics by a variation of the solid content in solution. Capacitance-voltage characteristics reveal a shift of the built-in voltage at the cathode interface by about 0.3 V as compared to devices without a CsF layer, giving rise to an increase in open-circuit voltage by the same value. The vertical distribution of Cs{sup +} and F{sup +} ions is studied by secondary ion mass spectroscopy, indicating a strong diffusion of the alkaline fluoride into the organic layer stack.

  2. Combined Tin-Containing Fluoride Solution and CO2 Laser Treatment Reduces Enamel Erosion in vitro.

    PubMed

    Esteves-Oliveira, Marcella; Witulski, Nadine; Hilgers, Ralf-Dieter; Apel, Christian; Meyer-Lueckel, Hendrik; Eduardo, Carlos de Paula

    2015-01-01

    The aim of this in vitro study was to evaluate the effect of combined CO2 laser and tin-containing fluoride treatment on the formation and progression of enamel erosive lesions. Ninety-six human enamel samples were obtained, stored in thymol solution and, after surface polishing, randomly divided into 6 different surface treatment groups (n = 16 in each group) as follows: no treatment, control (C); one CO2 laser irradiation (L1); two CO2 laser irradiations (L2); daily application of fluoride solution (F); combined daily fluoride solution + one CO2 laser irradiation (L1F), and combined daily fluoride solution + two CO2 laser irradiations (L2F). Laser irradiation was performed at 0.3 J/cm2 (5 µs/226 Hz/10.6 µm) on day 1 (L1) and day 6 (L2). The fluoride solution contained AmF/NaF (500 ppm F), and SnCl2 (800 ppm Sn) at pH 4.5. After surface treatment the samples were submitted to an erosive cycling over 10 days, including immersion in citric acid (2 min/0.05 M/pH = 2.3) 6 times daily and storage in remineralization solution (≥1 h) between erosive attacks. At the end of each cycling day, the enamel surface loss (micrometers) was measured using a 3D laser profilometer. Data were statistically analyzed by means of a 2-level mixed effects model and linear contrasts (α = 0.05). Group F (-3.3 ± 2.0 µm) showed significantly lower enamel surface loss than groups C (-27.22 ± 4.1 µm), L1 (-18.3 ± 4.4 µm) and L2 (-16.3 ± 5.3 µm) but higher than L1F (-1.0 ± 4.4 µm) and L2F (1.4 ± 3.2 µm, p < 0.05). Under the conditions of this in vitro study, the tin-containing fluoride solution caused 88% reduction of enamel surface loss, while its combination with CO2 laser irradiation at 0.3 J/cm2 hampered erosive loss almost completely. PMID:26418736

  3. Sulfonyl fluoride inhibitors of fatty acid amide hydrolase.

    PubMed

    Alapafuja, Shakiru O; Nikas, Spyros P; Bharathan, Indu T; Shukla, Vidyanand G; Nasr, Mahmoud L; Bowman, Anna L; Zvonok, Nikolai; Li, Jing; Shi, Xiaomeng; Engen, John R; Makriyannis, Alexandros

    2012-11-26

    Sulfonyl fluorides are known to inhibit esterases. Early work from our laboratory has identified hexadecyl sulfonylfluoride (AM374) as a potent in vitro and in vivo inhibitor of fatty acid amide hydrolase (FAAH). We now report on later generation sulfonyl fluoride analogs that exhibit potent and selective inhibition of FAAH. Using recombinant rat and human FAAH, we show that 5-(4-hydroxyphenyl)pentanesulfonyl fluoride (AM3506) has similar inhibitory activity for both the rat and the human enzyme, while rapid dilution assays and mass spectrometry analysis suggest that the compound is a covalent modifier for FAAH and inhibits its action in an irreversible manner. Our SAR results are highlighted by molecular docking of key analogs. PMID:23083016

  4. Inhibition of enamel erosion by stannous fluoride containing rinsing solutions.

    PubMed

    Rakhmatullina, Ekaterina; Beyeler, Barbara; Lussi, Adrian

    2013-01-01

    This in vitro study investigated the erosion-inhibiting properties of dental rinses during erosion in the presence of the salivary pellicle. The erosion inhibition by a Sn/F containing dental rinse (800 ppm Sn2+, 500 ppm F –, pH = 4.5) was compared with a fluoridated solution (500 ppm F –, pH = 4.5) and water(control). Calcium release and enamel softening were significantly reduced among enamel samples exposed to the Sn/F rinse (group SF)compared to those treated with the fluoride solution (group F) and the control (p 0.05). SEM showed slightly etched enamel interfaces in group SF, whereas the erosion was more pronounced in group F and even more severe in the control group. In conclusion, the Sn/F combination provided the best inhibition of erosion among tested solutions. This study demonstrates the application of different analytical tools for comparative erosion quantification.A strong correlation (r2 ≥ 0.783) was shown between calcium release and enamel softening during demineralization. PMID:23781557

  5. PRODUCTION OF THORIUM FLUORIDE

    DOEpatents

    Zachariasen, W.H.

    1959-08-11

    A process is presented for producing anhydrous thorium fluoride comprising the step of contacting a saturated aqueous solution of thorium nitrate with an aqueous solution of hydrofluoric acid having a concentration of about 45 to 50% by weight at a temperature above 70 deg C whereby anhydrous thorium fluoride precipitates.

  6. Corrosion behavior and surface characterization of titanium in solution containing fluoride and albumin.

    PubMed

    Takemoto, Shinji; Hattori, Masayuki; Yoshinari, Masao; Kawada, Eiji; Oda, Yutaka

    2005-03-01

    The objective of this study was to demonstrate the role of albumin on the corrosion behavior of titanium in a solution containing 2.0 g/l fluoride and either 0.1 or 1.0 g/l albumin. The corrosion behavior and surface characterization of passive films on titanium immersed in such a solution were examined. In addition, the change in pH and the concentration of dissolved titanium in the solution were examined. The results showed that the corrosion of titanium in a solution containing fluoride was distinct, and that adding albumin to the solution containing fluoride suppressed corrosion. Fluorine was detected on the titanium surface immersed in the solution containing fluoride, and dissolution of the titanium was confirmed. The titanium immersed in a solution containing both fluoride and albumin had an albumin film regardless of the albumin concentration. In addition, the amount of dissolved titanium from the titanium immersed in the solution was less than when the solution contained no albumin. It was suggested that the formation of adsorbed albumin films on or in the passive film acted to not only protect the titanium from attack by the fluoride but also suppressed dissolution of the titanium-fluoride compounds. PMID:15353194

  7. Corrosion behavior and surface characterization of Ti-20Cr alloy in a solution containing fluoride.

    PubMed

    Takemoto, Shinji; Hattori, Masayuki; Yoshinari, Masao; Kawada, Eiji; Asami, Katsuhiko; Oda, Yutaka

    2004-09-01

    The purpose of this study was to investigate the correlation between corrosion resistance and surface composition of an experimental Ti-20 mass% Cr casting alloy in a saline solution containing fluoride. The alloy had a greater resistance to corrosion in a fluoride-containing saline solution than did commercially pure titanium. However, with confirmed dissolution of titanium and chromium, it meant that the fluoride in the saline solution corroded the alloy slightly. X-ray photoelectron spectroscopy analysis revealed that the surface composition of the alloy consisted of titanium and chromium oxides containing hydroxide. The [Ti]/([Ti] + [Cr]) ratio in the surface oxide film decreased when immersed in fluoride-containing saline solution, that is, the surface oxide film became chromium-rich oxide. Therefore, the alloy obtained good corrosion resistance to fluoride due to formation of a chromium-rich oxide film. PMID:15510869

  8. Hydrogen embrittlement of Ni-Ti superelastic alloy in fluoride solution.

    PubMed

    Yokoyama, Ken'ichi; Kaneko, Kazuyuki; Moriyama, Keiji; Asaoka, Kenzo; Sakai, Jun'ichi; Nagumo, Michihiko

    2003-05-01

    Hydrogen embrittlement of Ni-Ti superelastic alloy in a fluoride solution (0.2% APF) has been investigated by means of a tensile test (after immersion) and hydrogen thermal desorption analysis. Upon immersion, the tensile strength of the alloy decreased to the critical stress level of martensite transformation. Hydrogen desorption of the immersed specimens appeared with a peak at around 500 degrees C. The amount of absorbed hydrogen in the alloy ranged from 100 to 1000 mass ppm when immersed in the fluoride solution for 2 to 24 h. The immersion in the fluoride solution led to the degradation of mechanical properties due to hydrogen embrittlement. The results of the present study imply that one reason that Ti and its alloys fracture in the oral cavity is the fact that hydrogen is absorbed in a fluoride solution, such as prophylactic agents. PMID:12734810

  9. Brushing abrasion of eroded dentin after application of sodium fluoride solutions.

    PubMed

    Attin, T; Zirkel, C; Hellwig, E

    1998-01-01

    The aim of the present in vitro study was to evaluate the influence of sodium fluoride solutions on brushing abrasion of eroded dentin. Dentin specimens were prepared from 60 bovine incisors. The specimens were embedded in acrylic resin, ground flat, polished and subsequently covered with tape exposing an area of 1.8 mm x 10.0 mm in the center of the exposed dentin. The samples were alternatingly stored in a demineralizing solution (5 min) and a remineralizing solution (1 min) for 5 times. The erosive soft drink Sprite light(R) served as a demineralizing solution and artificial saliva was used as a remineralizing solution. Prior to storage in artificial saliva 15 specimens were each treated for 1 min with 250 and 2,000 ppm fluoride solution, respectively. Fifteen specimens were treated with distilled water instead of the fluoride solution (= eroded controls). The remaining samples were neither eroded with the soft drink nor fluoridated (= uneroded controls). After each immersion in artificial saliva the specimens were submitted to abrasion in a toothbrushing machine. After 5 demineralization-remineralization brushing cycles the total amount of tooth wear due to erosion and subsequent abrasion was profilometrically evaluated. Statistical analysis revealed the significantly lowest wear in the uneroded controls and the highest amount of abrasion in the eroded controls. Application of the fluoride solutions increased the wear resistance of the eroded dentin specimens, showing significantly better protection by the high-concentration compared to the low-concentration solution. The susceptibility to abrasion of the eroded dentin specimens treated with the high-concentration fluoride solution did not differ significantly from the uneroded dentin samples. It is concluded that application of 2,000 ppm sodium fluoride solutions immediately before toothbrushing significantly reduces abrasion of eroded dentin in vitro. PMID:9701659

  10. Recovery of Acid Production in Streptococcus mutans Biofilms after Short-Term Fluoride Treatment.

    PubMed

    Dang, Minh-Huy; Jung, Ji-Eun; Lee, Dae-Woo; Song, Kwang-Yeob; Jeon, Jae-Gyu

    2016-01-01

    Fluoride is commonly used as an ingredient of topical oral hygiene measures. Despite the anti-acidogenic activities of fluoride against cariogenic biofilms, the recovery of the biofilms from fluoride damage is unclear. Herein, we investigated the recovery of acid production in Streptococcus mutans biofilms after short-term or during periodic 1-min fluoride treatments. For this study, 46-hour-old S. mutans biofilms were treated with fluoride (0-2,000 ppm F-) for 1-8 min and then incubated in saliva for 0-100 min. The 74-hour-old biofilms were also periodically treated with the fluoride concentration during biofilm formation (1 min/treatment). Changes in acidogenicity and viability were determined via pH drop and colony-forming unit assays, respectively. In this study, acid production after a 1-min fluoride treatment was recovered as saliva incubation time increased, which followed a linear pattern of concentration dependence (R = 0.99, R2 = 0.98). The recovery pattern was in a biphasic pattern, with an initial rapid rate followed by a second slow recovery. Furthermore, recovery from fluoride damage was retarded in a concentration-dependent manner as treatment time increased. In periodic 1-min fluoride treatments, acid production in the biofilms was not diminished during the non-fluoride treatment period; however, it was reduced in a concentration-dependent manner during the fluoride treatment period. The viability of the biofilm cells did not change, even at high fluoride concentrations. Collectively, our results suggest that brief fluoride treatment does not sustain anti-acidogenic activity against S. mutans in biofilms since the damage is recoverable with time. PMID:27355469

  11. [Uptake of fluoride into enamel and its effect on acid resistance by application of fluoride-releasing sealant--Part 2. Effect of application time and immersion time into buffer after its removal].

    PubMed

    Kato, K

    1991-03-01

    The purpose of this study was to investigate the relationship between the amount of fluoride in the enamel, taken from a fluoride-releasing sealant (F + sealant) and acid resistance. The F + sealant was applied to the bovine enamel from 1 week to 6 months. After the removal of the F + sealant, the bovine teeth were immersed in phosphate buffer from 1 month to 6 months. At each time period, the enamel was biopsied with acid and its fluoride and calcium concentration were analyzed. Results were as follows: (1) It was suitable to immerse the teeth in 1M KOH solution for 2 days in order to remove the loosely bound fluoride produced by the fluoride application from the enamel. (2) The amount of fluoride in the surface enamel increased in proportion to the application time of F + sealant. (3) The amount of calcium dissolved from the enamel showed the significant decrease by the F + sealant application, while no difference was shown by the application time. (4) The amount of fluoride in the surface enamel acquired by the F + sealant was maintained for 6 months after the removal of the F + sealant. (5) The amount of calcium dissolved from the enamel showed no difference in the period of immersion time. PMID:2066630

  12. CAN FLUORIDATION AFFECT LEAD (II) IN POTABLE WATER? HEXAFLUOROSILICATE AND FLUORIDE EQUILIBRIA IN AQUEOUS SOLUTION

    EPA Science Inventory

    Recent reports have attempted to show that fluoridating potable water is linked to increased levels of lead(II) in the blood. We examine these claims in light of the established science and critically evaluate their significance. The completeness of hexafluorosilicate hydrolysi...

  13. Effect of fluoride exposure on serum glycoprotein pattern and sialic acid level in rabbits.

    PubMed

    Ciftci, Gulay; Cenesiz, Sena; Yarim, Gul Fatma; Nisbet, Ozlem; Nisbet, Cevat; Cenesiz, Metin; Guvenc, Dilek

    2010-01-01

    This study describes the effects of fluoride exposure on the protein profile, glycoprotein pattern, and total sialic acid concentration of serum in rabbits. For this aim; 20 healthy New Zealand rabbits were used. The rabbits were divided into two equal groups each with ten animals according to their weighing: control group and experimental group. The rabbits in control group were given drinking tap water containing 0.29 mg/l sodium fluoride and experimental group received the same tap water to which was added 40 mg/l sodium fluoride for 70 days. Blood samples were taken from each rabbit on day 70. Serum fluoride concentrations were measured by a fluoride-specific ion electrode in serum. The fluoride levels in the serum were found as 18.4 (+/-1.58) microg/L in control and 301.3 (+/-52.18) microg/L in fluoride exposed rabbits. The sialic acid levels were found as 69.2 (+/-0.32) mg/dL in control and 43.4 (+/-0.13) mg/dL in fluoride exposed group. The electrophoretic patterns of serum proteins, glycoproteins, and total sialic acid concentration were determined. Fifteen different protein fractions with molecular weights ranging from 22 to 249 kDa were displayed in the serum protein electrophoretic gel of both groups. The raw concentrations of the protein fractions decreased in fluoride exposed rabbits as compared with the control rabbits. The serum glycoprotein pattern revealed seven major protein bands from 47 to 167 kDa in experimental and control groups. The slight decrease of raw concentration of the protein bands in glycoprotein pattern of serum was observed in fluoride toxication comparing to control. The results suggest that serum TSA determination and serum protein electrophoresis can be used to evaluate prognosis of fluoride exposure as a supplementary laboratory test in combination with clinical and other laboratory findings of fluorosis. PMID:19904501

  14. Studies on sorption of some geomaterials for fluoride removal from aqueous solutions.

    PubMed

    Sujana, M G; Pradhan, H K; Anand, S

    2009-01-15

    In the present study the defluoridation capacities of some of the naturally occurring materials like low and high iron containing lateritic ores, overburden from chromite mines of Orissa Mining Corporation (OMC) and Tata Steel have been estimated. The various experimental parameters studied for fluoride sorption from aqueous solutions were: time, pH, initial fluoride concentration, sorbent dose and temperature. The three geomaterials, namely chromite overburden from Orissa Mining Corporation, both low and high iron containing lateritic ores sorbed fluoride effectively. The sorption kinetics for these samples was found to follow first order rate expression and the experimental equilibrium sorption data fitted reasonably well to both Langmuir and Freundlich models. The negative values of DeltaG degrees suggest the sorption of fluoride onto three samples to be spontaneous and the exothermic nature of sorption is confirmed by the -DeltaH degrees values. The negative DeltaS degrees values for these sorbents point towards decreased randomness at the solid/solution interface. The sorption studies were also carried out at natural pH conditions for fluoride removal from ground water samples and the fluoride level could be reduced from 10.25 to <1.0mgL(-1) by multistage adsorption process using OMC and NH samples. PMID:18450373

  15. Fluoride removal from groundwater by limestone treatment in presence of phosphoric acid.

    PubMed

    Gogoi, Sweety; Nath, Suresh K; Bordoloi, Shreemoyee; Dutta, Robin K

    2015-04-01

    Fluoride removal from groundwater has been studied by addition of dilute phosphoric acid (PA) to the influent water before limestone treatment through laboratory plug-flow column experiments and bench-scale plug-flow pilot tests. In this PA-enhanced limestone defluoridation (PAELD) technique, fluoride is removed from 0.526 mM to 0.50-52.60 μM in 3 h with near neutral final pH. The presence of PA increases the fluoride removal capacity of limestone to 1.10 mg/g compared to 0.39 mg/g reported in its absence. The changes in fluoride removal with variation in initial PA concentration, initial fluoride concentration and the final pH have been found to be statistically significant with p < 0.05. The estimated recurring cost is US$ ≈0.58/m(3) water. Simple scrubbing and rinsing is a preferable method for regeneration of limestone as it is almost equally effective with lime or NaOH. Sorption of fluoride by calcium phosphates produced in situ in the reactor is the dominant mechanism of fluoride removal in the PAELD. Precipitation of CaF2 and sorption of fluoride by the limestone also contribute to the fluoride removal. High efficiency, capacity, safety, environment-friendliness, low cost and simplicity of operation make the PAELD a potential technique for rural application. PMID:25621387

  16. The influence of albumin on corrosion resistance of titanium in fluoride solution.

    PubMed

    Ide, Katsuhisa; Hattori, Masayuki; Yoshinari, Masao; Kawada, Eiji; Oda, Yutaka

    2003-09-01

    Proteins can interact with corrosion reactions in several ways. In this study, we investigated the effect of albumin on the corrosion resistance of titanium in the presence of fluoride. The effects of the NaF concentration, albumin concentration, and pH on the corrosion characteristics of commercially pure titanium (CP-Ti) were examined by means of electrochemical techniques. The corrosion resistance of titanium decreased as the NaF concentration increased and as pH decreased. The corrosion resistance of titanium in NaF solutions was improved in the presence of albumin. The natural electrode potential was elevated, and the passive current density was reduced by albumin at a concentration of 0.01%. The polarization resistance rose with increased concentrations of albumin in fluoride solution. These results showed that the albumin in saliva and dental plaque affected the corrosion resistance of CP-Ti in fluoride solution. PMID:14621001

  17. Remineralization of root surfaces demineralized in solutions of differing fluoride levels.

    PubMed

    Heilman, J R; Jordan, T H; Warwick, R; Wefel, J S

    1997-01-01

    The beneficial effects of fluoride on enamel have been well documented. However, limited data are available concerning the amount of fluoride required for beneficial effects on tooth root. Although studies have shown that fluoride inhibits root demineralization, the aim of this study was to investigate the location, extent and amount of remineralization on root dentin substrates after demineralization has occurred. The root surfaces of extracted human teeth were demineralized in a pure chemical buffer containing varying concentrations of sodium fluoride. After this lesion initiation, the same root sections were then placed into a remineralizing solution. The root sections were characterized after demineralization, and again after remineralization, by polarized light microscopy (PLM) and microradiography (MRG). Lesion depths after the demineralization phase were found to be inversely proportional to the fluoride concentration. When fluoride was present, bands or lines within the body of the lesion were observed with PLM and MRG. Using quantitative MRG, variations in mineral content and distribution were recorded. Examination of the root sections after the remineralization phase showed remineralization to have occurred on the remaining mineral and not on organic matrix devoid of mineral. The amount and location of mineral deposition may be of great significance in the arrestment and treatment of in vivo root surface caries. PMID:9353581

  18. Effect of temperature on the complexation of Uranium(VI) with fluoride in aqueous solutions

    SciTech Connect

    Tian, Guoxin; Rao, Linfeng

    2009-05-18

    Complexation of U(VI) with fluoride at elevated temperatures in aqueous solutions was studied by spectrophotometry. Four successive complexes, UO{sub 2}F{sup +}, UO{sub 2}F{sub 2}(aq), UO{sub 2}F{sub 3}{sup -}, and UO{sub 2}F{sub 4}{sup 2-}, were identified, and the stability constants at 25, 40, 55, and 70 C were calculated. The stability of the complexes increased as the temperature was elevated. The enthalpies of complexation at 25 C were determined by microcalorimetry. Thermodynamic parameters indicate that the complexation of U(VI) with fluoride in aqueous solutions at 25 to 70 C is slightly endothermic and entropy-driven. The Specific Ion Interaction (SIT) approach was used to obtain the thermodynamic parameters of complexation at infinite dilution. Structural information on the U(VI)/fluoride complexes was obtained by extended X-ray absorption fine structure spectroscopy.

  19. Separative recovery with lime of phosphate and fluoride from an acidic effluent containing H3PO4, HF and/or H2SiF6.

    PubMed

    Gouider, Mbarka; Feki, Mongi; Sayadi, Sami

    2009-10-30

    Fluoride content and flow-rate of fertilizer plant wastewater from phosphoric acid and/or triple superphosphate (TSP) production lead to the discharge of several thousand tons of fluoride (F(-)) per year and even more for phosphate (PO4(3-)). Since sustainability is an important environmental concern, the removal methods should allow phosphorus and fluoride to be recycled as a sustainable products for use as raw materials either in agricultural or industrial applications. In the present work, separative recovery with lime of these two target species was investigated. A preliminary speciation study, carried out on the crude effluent, showed that two forms of fluoride: HF and H2SiF6 are present in a highly acidic medium (pH approximately 2). Evidence that fluoride is present under both free (HF) and combined (H2SiF6) forms, in the phosphate-containing effluent, was provided by comparing potentiometric titration curves of a crude wastewater sample and synthetic acid mixtures containing H3PO4, HF and H2SiF6. In a second step synthetic effluent containing mixtures of the following acids: HF, H2SiF6 and H3PO4, were treated with lime. The behaviour of these compounds under lime treatment was analysed. The data showed that fluoride has a beneficial effect on phosphate removal. Moreover, by acting on the precipitation pH, a "selective" recovery of fluoride and phosphate ions was possible either from phosphoric acid/hydrofluoric acid or phosphoric acid/hexafluorosilicic acid mixtures. Indeed, the first stage of the separative recovery, led to a fluoride removal efficiency of 97-98% from phosphoric acid/hydrofluoric acid mixture. It was of 93-95% from phosphoric acid/hexafluorosilicic acid mixture. During the second stage, the phosphate precipitation reached 99.8% from both acidic mixtures whereas it did not exceed 82% from a solution containing H3PO4 alone. The XRD and IR analyses showed that during lime treatment, a H2SiF6 hydrolysis occurred, instead of CaSiF6 solid

  20. Calcium Fluoride Precipitation and Deposition From 12 mmol/L Fluoride Solutions With Different Calcium Addition Rates

    PubMed Central

    Markovic, M; Takagi, S; Chow, LC; Frukhtbeyn, S

    2009-01-01

    The effects of different Ca-addition rates on calcium fluoride (CaF2) precipitation and deposition were investigated in 12 mmol/L sodium fluoride solutions to which 0.1 mol/L calcium chloride solution was continuously added at average rates of (5, 7.5, 10, 12.5, 15 or 20) mmol L−1 min−1. The changes in ionic fluoride and calcium concentrations, as well as turbidity, were continuously recorded by F and Ca electrodes, and a fiber optic based spectrophotometer, respectively. The F− concentration decreased and turbidity increased with time indicating precipitation of CaF2. For the systems with Ca-addition rates of (5, 7.5, 10, 12.5, 15, and 20) mmol L−1 min−1, the 1 min CaF2 depositions in the model substrate (cellulose filter paper, pores 0.2 µm) expressed as mean ± SD of deposited F per substrate surface area were (3.78 ± 0.31, 11.45 ± 0.89, 9.31 ± 0.68, 8.20 ± 0.56, 6.63 ± 0.43, and 2.09 ± 0.28) µg/cm2, respectively (n = 10 for each group). The 1-min F depositions did not show positive correlation to Ca-addition rates. The lowest 1-min F deposition was obtained in the systems with the highest Ca-addition rate of 20 mmol L−1 min−1 for which CaF2 precipitation rate reached the maximum value of 0.31 mmol L−1 s−1 almost immediately after beginning of reaction (6 s). The largest 1-min F depositions were obtained from the systems with Ca addition rates of (7.5 to 12.5) mmol L−1 min−1 in which CaF2 precipitation rates continuously increased reaching the maximum values of (0.13 to 0.20) mmol L−1 s−1 after (18 to 29) s, respectively. The 1-min F depositions were greatly enhanced in comparison with the control F solutions that did not have continuous Ca-addition. This indicates that continuous Ca addition that controls the rate of CaF2 formation could be a critical factor for larger F depositions from F solutions. The efficacy of conventional F mouthrinses could be improved with addition of a substance that continuously releases Ca.

  1. Fatality due to acute systemic fluoride poisoning following a hydrofluoric acid skin burn.

    PubMed

    Tepperman, P B

    1980-10-01

    Reports indicate that death due to hydrofluoric acid exposure is usually the result of inhalation of vapor causing pulmonary edema and fluoride poisoning. Absorption via the skin route of fluoride ion sufficient to cause serious systemic problems and even death has rarely been reported. A fatality resulting from a severe facial burn, which produced acute systemic fluoride poisoning with profound hypocalcemia and hypomagnesemia, is presented. The importance of proper personal protective equipment as well as the immediate initiation of first aid and appropriate medical measures, including the monitoring and replacement of serum calcium and magnesium, are emphasized. PMID:7431138

  2. Roughness and morphology of composites: influence of type of material, fluoride solution, and time.

    PubMed

    de Oliveira, Ana Luísa Botta Martins; Giro, Elisa Maria Aparecida; Garcia, Patrícia Petromilli Nordi Sasso; Campos, Juliana Álvares Duarte Bonini; Phark, Jin-Ho; Duarte, Sillas

    2014-10-01

    This study evaluated the effect of fluoride solutions on surface roughness and morphology of composites in the short and long term. Specimens were randomly assigned to experimental groups (n=5) according to type of composite (nanofilled, microhybrid, microfilled) and immersion media (artificial saliva, 0.05% sodium fluoride solution, Fluordent Reach, Oral-B, and Fluorgard). Roughness was evaluated at time intervals: T 0 after 24 h in artificial saliva (baseline); T 60 after being in assigned immersion media for 1 min daily over 60 days; and T final after artificial aging (20,000 thermal cycles, 1,200,000 mechanical loading cycles, and continuous immersion for 1,825 min). Surface morphology was qualitatively analyzed by scanning electron microscopy (SEM) at T 60 and T final. Roughness data were submitted to analysis of variance for mixed repeated measures, Sidak, and Tukey tests at α=0.05. Micro-filled resin showed the highest roughness values. Fluoride solutions had no influence on roughness. Higher roughness values were observed after artificial aging. In SEM observations after the artificial aging, the specimens showed surface degradation, irrespective of immersion medium or type of composite. Nano-filled resin showed higher loss of resin matrix and protrusion of filler particles. Roughness was not influenced by fluoride solutions; however, it is material dependent and increases over time. PMID:25115976

  3. PRECIPITATION OF ZIRCONIUM AND FLUORIDE IONS FROM SOLUTIONS

    DOEpatents

    Newby, B.J.

    1963-06-11

    A process is given for removing zirconium and fluorine ions from aqueous solutions also containing uranium(VI). The precipitation is carried out with sodium formate, and the uranium remains in solution. (AEC)

  4. Spectroscopic and Crystal Field Consequences of Fluoride Binding by [Yb⋅DTMA]3+ in Aqueous Solution

    PubMed Central

    Blackburn, Octavia A; Chilton, Nicholas F; Keller, Katharina; Tait, Claudia E; Myers, William K; McInnes, Eric J L; Kenwright, Alan M; Beer, Paul D; Timmel, Christiane R; Faulkner, Stephen

    2015-01-01

    Yb⋅DTMA forms a ternary complex with fluoride in aqueous solution by displacement of a bound solvent molecule from the lanthanide ion. [Yb⋅DTMA⋅F]2+ and [Yb⋅DTMA⋅OH2]3+ are in slow exchange on the relevant NMR timescale (<2000 s−1), and profound differences are observed in their respective NMR and EPR spectra of these species. The observed differences can be explained by drastic modification of the ligand field states due to the fluoride binding. This changes the magnetic anisotropy of the YbIII ground state from easy-axis to easy-plane type, and this change is easily detected in the observed magnetic anisotropy despite thermal population of more than just the ground state. The spectroscopic consequences of such drastic changes to the ligand field represent important new opportunities in developing fluoride-responsive complexes and contrast agents. PMID:26223970

  5. Acidity of frozen electrolyte solutions.

    PubMed

    Robinson, Carmen; Boxe, C S; Guzman, M I; Colussi, A J; Hoffmann, M R

    2006-04-20

    Ice is selectively intolerant to impurities. A preponderance of implanted anions or cations generates electrical imbalances in ice grown from electrolyte solutions. Since the excess charges are ultimately neutralized via interfacial (H(+)/HO(-)) transport, the acidity of the unfrozen portion can change significantly and permanently. This insufficiently recognized phenomenon should critically affect rates and equilibria in frozen media. Here we report the effective (19)F NMR chemical shift of 3-fluorobenzoic acid as in situ probe of the acidity of extensively frozen electrolyte solutions. The sign and magnitude of the acidity changes associated with freezing are largely determined by specific ion combinations, but depend also on solute concentration and/or the extent of supercooling. NaCl solutions become more basic, those of (NH(4))(2)SO(4) or Na(2)SO(4) become more acidic, while solutions of the 2-(N-morpholino)ethanesulfonic acid zwitterion barely change their acidity upon freezing. We discuss how acidity scales based on solid-state NMR measurements could be used to assess the degree of ionization of weak acids and bases in frozen media. PMID:16610849

  6. METHOD FOR DISSOLVING LANTHANUM FLUORIDE CARRIER FOR PLUTONIUM

    DOEpatents

    Koshland, D.E. Jr.; Willard, J.E.

    1961-08-01

    A method is described for dissolving lanthanum fluoride precipitates which is applicable to lanthanum fluoride carrier precipitation processes for recovery of plutonium values from aqueous solutions. The lanthanum fluoride precipitate is contacted with an aqueous acidic solution containing dissolved zirconium in the tetravalent oxidation state. The presence of the zirconium increases the lanthanum fluoride dissolved and makes any tetravalent plutonium present more readily oxidizable to the hexavalent state. (AEC)

  7. Ion spatial distributions at the liquid-vapor interface of aqueous potassium fluoride solutions

    SciTech Connect

    Brown, M A; D'Auria, R; Kuo, I W; Krisch, M J; Starr, D E; Bluhm, H; Tobias, D J; Hemminger, J C

    2008-04-23

    X-ray photoemission spectroscopy operating under ambient pressure conditions is used to probe ion distributions throughout the interfacial region of a free-flowing aqueous liquid micro-jet of 6 M potassium fluoride. Varying the energy of the ejected photoelectrons by carrying out experiments as a function of x-ray wavelength measures the composition of the aqueous-vapor interfacial region at various depths. The F{sup -} to K{sup +} atomic ratio is equal to unity throughout the interfacial region to a depth of 2 nm. The experimental ion profiles are compared with the results of a classical molecular dynamics simulation of a 6 M aqueous KF solution employing polarizable potentials. The experimental results are in qualitative agreement with the simulations when integrated over an exponentially decaying probe depth characteristic of an APPES experiment. First principles molecular dynamics simulations have been used to calculate the potential of mean force for moving a fluoride anion across the air-water interface. The results show that the fluoride anion is repelled from the interface, and this is consistent with the depletion of F{sup -} at the interface revealed by the APPES experiment and polarizable force field-based molecular dynamics simulation. Together, the APPES and MD simulation data provide a detailed description of the aqueous-vapor interface of alkali fluoride systems. This work offers the first direct observation of the ion distribution at a potassium fluoride aqueous solution interface. The current experimental results are compared to those previously obtained for saturated solutions of KBr and KI to underscore the strong difference in surface propensity between soft/large and hard/small halide ions in aqueous solution.

  8. Study of actinide chemistry in saturated potassium fluoride solution

    NASA Technical Reports Server (NTRS)

    Cohen, D.; Thalmayer, C. E.

    1969-01-01

    Study concerning the chemistry of actinides in saturated KF solution included work with neptunium, uranium, and americium. Solubilities, absorption spectra, oxidation-reduction reactions, and solid compounds which can be produced in KF solution were examined. The information is used for preparation of various materials from salts of the actinides.

  9. Biochar enhances Aspergillus niger rock phosphate solubilization by increasing organic acid production and alleviating fluoride toxicity.

    PubMed

    Mendes, Gilberto de Oliveira; Zafra, David Lopez; Vassilev, Nikolay Bojkov; Silva, Ivo Ribeiro; Ribeiro, José Ivo; Costa, Maurício Dutra

    2014-05-01

    During fungal rock phosphate (RP) solubilization, a significant quantity of fluoride (F(-)) is released together with phosphorus (P), strongly inhibiting the process. In the present study, the effect of two F(-) adsorbents [activated alumina (Al2O3) and biochar] on RP solubilization by Aspergillus niger was examined. Al2O3 adsorbed part of the F(-) released but also adsorbed soluble P, which makes it inappropriate for microbial RP solubilization systems. In contrast, biochar adsorbed only F(-) while enhancing phosphate solubilization 3-fold, leading to the accumulation of up to 160 mg of P per liter. By comparing the values of F(-) measured in solution at the end of incubation and those from a predictive model, it was estimated that up to 19 mg of F(-) per liter can be removed from solution by biochar when added at 3 g liter(-1) to the culture medium. Thus, biochar acted as an F(-) sink during RP solubilization and led to an F(-) concentration in solution that was less inhibitory to the process. In the presence of biochar, A. niger produced larger amounts of citric, gluconic, and oxalic acids, whether RP was present or not. Our results show that biochar enhances RP solubilization through two interrelated processes: partial removal of the released F(-) and increased organic acid production. Given the importance of organic acids for P solubilization and that most of the RPs contain high concentrations of F(-), the proposed solubilization system offers an important technological improvement for the microbial production of soluble P fertilizers from RP. PMID:24610849

  10. Biochar Enhances Aspergillus niger Rock Phosphate Solubilization by Increasing Organic Acid Production and Alleviating Fluoride Toxicity

    PubMed Central

    Mendes, Gilberto de Oliveira; Zafra, David Lopez; Vassilev, Nikolay Bojkov; Silva, Ivo Ribeiro; Ribeiro, José Ivo

    2014-01-01

    During fungal rock phosphate (RP) solubilization, a significant quantity of fluoride (F−) is released together with phosphorus (P), strongly inhibiting the process. In the present study, the effect of two F− adsorbents [activated alumina (Al2O3) and biochar] on RP solubilization by Aspergillus niger was examined. Al2O3 adsorbed part of the F− released but also adsorbed soluble P, which makes it inappropriate for microbial RP solubilization systems. In contrast, biochar adsorbed only F− while enhancing phosphate solubilization 3-fold, leading to the accumulation of up to 160 mg of P per liter. By comparing the values of F− measured in solution at the end of incubation and those from a predictive model, it was estimated that up to 19 mg of F− per liter can be removed from solution by biochar when added at 3 g liter−1 to the culture medium. Thus, biochar acted as an F− sink during RP solubilization and led to an F− concentration in solution that was less inhibitory to the process. In the presence of biochar, A. niger produced larger amounts of citric, gluconic, and oxalic acids, whether RP was present or not. Our results show that biochar enhances RP solubilization through two interrelated processes: partial removal of the released F− and increased organic acid production. Given the importance of organic acids for P solubilization and that most of the RPs contain high concentrations of F−, the proposed solubilization system offers an important technological improvement for the microbial production of soluble P fertilizers from RP. PMID:24610849

  11. Fluoride removal from aqueous solution by Al(III)-Zr(IV) binary oxide adsorbent

    NASA Astrophysics Data System (ADS)

    Zhu, Jiuya; Lin, Xiaoyan; Wu, Pengwei; Zhou, Qiusheng; Luo, Xuegang

    2015-12-01

    In this study, a novel binary oxide adsorbent of Al2O3-ZrO2 was prepared via coprecipitation followed by calcination method, and the calcination temperatures were investigated. The adsorbent was characterized by XRD, EDX and XPS. The batch adsorption experiments were carried out at different parameters, such as solution pH, adsorbent dose, contact time, initial fluoride concentration and adsorption temperature, to evaluate the fluoride removal performance. The results showed that the adsorption isotherm was better described by the linear Langmuir model, and a maximum adsorption capacity was 114.54 mg/g. The adsorption kinetics was well fitted by the linear pseudo-second-order, and the correlation coefficient value (R2) was 0.997. The thermodynamic parameters of ΔH0, ΔS0 and ΔG0 were calculated, which showed that the fluoride adsorption process was spontaneous and exothermic. And the possible adsorption mechanism of the adsorbent for fluoride could involve the ligand-exchange and ion-exchange based on the results in the study.

  12. Criticality experiments and analysis of molybdenum reflected cylindrical uranyl fluoride water solution reactors

    NASA Technical Reports Server (NTRS)

    Fieno, D.; Fox, T.; Mueller, R.

    1972-01-01

    Clean criticality data were obtained from molybdenum-reflected cylindrical uranyl-fluoride-water solution reactors. Using ENDF/B molybdenum cross sections, a nine energy group two-dimensional transport calculation of a reflected reactor configuration predicted criticality to within 7 cents of the experimental value. For these reactors, it was necessary to compute the reflector resonance integral by a detailed transport calculation at the core-reflector interface volume in the energy region of the two dominant resonances of natural molybdenum.

  13. Corrosion investigations on zircaloy-4 and titanium dissolver materials for MOX fuel dissolution in concentrated nitric acid containing fluoride ions

    NASA Astrophysics Data System (ADS)

    Jayaraj, J.; Krishnaveni, P.; Krishna, D. Nanda Gopala; Mallika, C.; Mudali, U. Kamachi

    2016-05-01

    Aqueous reprocessing of plutonium-rich mixed oxide fuels require fluoride as a dissolution catalyst in boiling nitric acid for an effective dissolution of the spent fuel. High corrosion rates were obtained for the candidate dissolver materials zircaloy-4 (Zr-4) and commercial pure titanium (CP-Ti grade 2) in boiling 11.5 M HNO3 + 0.05 M NaF. Complexing the fluoride ions either with Al(NO3)3 or ZrO(NO3)2 aided in decreasing the corrosion rates of Zr-4 and CP-Ti. From the obtained corrosion rates it is concluded that CP-Ti is a better dissolver material than Zr-4 for extended service life in boiling 11.5 M HNO3 + 0.05 M NaF, when complexed with 0.15 M ZrO(NO3)2. XPS analysis confirmed the presence of TiO2 and absence of fluoride on the surface of CP-Ti samples, indicating that effective complexation had occurred in solution leading to passivation of the metal and imparting high corrosion resistance.

  14. Spectroscopic and Crystal Field Consequences of Fluoride Binding by [Yb⋅DTMA]3+ in Aqueous Solution

    PubMed Central

    Blackburn, Octavia A.; Chilton, Nicholas F.; Keller, Katharina; Tait, Claudia E.; Myers, William K.; McInnes, Eric J. L.; Kenwright, Alan M.; Beer, Paul D.; Timmel, Christiane R.

    2015-01-01

    Abstract Yb⋅DTMA forms a ternary complex with fluoride in aqueous solution by displacement of a bound solvent molecule from the lanthanide ion. [Yb⋅DTMA⋅F]2+ and [Yb⋅DTMA⋅OH2]3+ are in slow exchange on the relevant NMR timescale (<2000 s−1), and profound differences are observed in their respective NMR and EPR spectra of these species. The observed differences can be explained by drastic modification of the ligand field states due to the fluoride binding. This changes the magnetic anisotropy of the YbIII ground state from easy‐axis to easy‐plane type, and this change is easily detected in the observed magnetic anisotropy despite thermal population of more than just the ground state. The spectroscopic consequences of such drastic changes to the ligand field represent important new opportunities in developing fluoride‐responsive complexes and contrast agents. PMID:27478267

  15. WET FLUORIDE SEPARATION METHOD

    DOEpatents

    Seaborg, G.T.; Gofman, J.W.; Stoughton, R.W.

    1958-11-25

    The separation of U/sup 233/ from thorium, protactinium, and fission products present in neutron-irradiated thorium is accomplished by dissolving the irradiated materials in aqueous nitric acid, adding either a soluble fluoride, iodate, phosphate, or oxalate to precipltate the thorium, separating the precipltate from the solution, and then precipitating uranlum and protactinium by alkalizing the solution. The uranium and protactinium precipitate is removcd from the solution and dissolved in nitric acid. The uranyl nitrate may then be extracted from the acid solution by means of ether, and the protactinium recovered from the aqueous phase.

  16. A Descriptive in vitro Electron Microscopic Study of Acidic Fluoride-Treated Enamel: Potential Anti-Erosion Effects.

    PubMed

    Hjortsjö, Carl; Young, Alix; Kiesow, Andreas; Cismak, Andreas; Berthold, Lutz; Petzold, Matthias

    2015-01-01

    This study aimed to investigate the surface zones of acidic fluoride-treated enamel. Human teeth were each divided into three or four enamel specimens that were treated for 10 min with solutions of 0.2 and 0.4% HF (pH 3.09 and 2.94), 1.74% SnF2 (pH 2.9), 0.68% TiF4 (pH 1.6) and 0.84% NaF (pH 4.5). Untreated specimens functioned as negative controls. The microstructure and elemental composition of the surface zones were studied by scanning electron microscopy/energy-dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM) and nanospot-EDX following cross-sectional preparation using focused ion beam technology. TEM/EDX analyses of NaF-treated specimens showed a 500-nm-thick closed surface film containing 20-40 at% (atomic percent) F. HF-treated specimens had a distinct surface film 200-600 nm thick (dense, not globular) containing 45-47 at% F. TiF4-treated specimens had a surface film of 200-300 nm in thickness containing 8-11 at% Ti but no detectable fluoride. SnF2-treated specimens had a modified surface enamel layer varying in thickness from 200 to 800 nm with an inhomogeneous distribution of Sn. Local spots were detected with as high as 8 at% Sn (30 wt%, weight percent). The results suggest that the reaction mechanisms of SnF2 and TiF4 solutions with dental enamel differ from those occurring after enamel exposure to acidulated NaF and HF solutions. While the HF and NaF treatments resulted in the formation of CaF2-like material as shown by EDX, no significant surface fluoridation was found for SnF2 and TiF4 solutions within the TEM/EDX detection limits. These results suggest that the erosion-protective mechanisms of these latter compounds probably relate more to the formation of hardly soluble and acid-resistant reaction surface films and less to surface fluoride incorporation. PMID:26536617

  17. The role of fluoride in erosion therapy.

    PubMed

    Huysmans, Marie-Charlotte; Young, Alix; Ganss, Carolina

    2014-01-01

    The role of fluoride in erosion therapy has long been questioned. However, recent research has yielded positive results. In this chapter, an overview of the literature is provided regarding the application of fluorides in the prevention and treatment of erosion and erosive wear. The results are presented and discussed for different fluoride sources such as monovalent and polyvalent fluorides, and for different vehicles such as toothpastes, solutions and rinses, as well as varnishes and gels. It is concluded that fluoride applications are very likely to be of use in the preventive treatment of erosive wear. Most promising are high-concentration, acidic formulations and the polyvalent fluoride sources, with the best evidence available for stannous fluoride. However, the evidence base for clinical effectiveness is still small. PMID:24993271

  18. Corrosion behavior of pure titanium and titanium alloys in fluoride-containing solutions.

    PubMed

    Nakagawa, M; Matsuya, S; Udoh, K

    2001-12-01

    The effects of fluoride concentrations and pH on the corrosion behavior of pure titanium, Ti-6Al-4V, Ti-6Al-7Nb alloys and a new Ti alloy adding palladium, which is expected to promote a repassivation of Ti were examined by anodic polarization and corrosion potential measurements. The amount of dissolved Ti was analyzed by inductively coupled plasma mass spectroscopy. The surface of the specimen was analyzed by X-ray photoelectron spectroscopy before and after the measurement. Pure Ti, Ti-6Al-4V and Ti-6Al-7Nb alloys were easily corroded even in a low fluoride concentration in an acidic environment. The corrosion resistance of Ti-0.2Pd alloy was greater than those of pure Ti, Ti-6Al-4V and Ti-6Al-7Nb alloys in the wide range of pH and fluoride concentrations. The high corrosion resistance of Ti-0.2Pd alloy was caused by the surface enrichment of Pd promoting a repassivation of Ti. The Ti-0.2Pd alloy is expected to be useful as a new Ti alloy with high corrosion resistance in dental use. PMID:11915624

  19. Inhibition of enamel erosion by stannous and fluoride containing rinsing solutions.

    PubMed

    Rakhmatullina, Ekaterina; Beyeler, Barbara; Lussi, Adrian

    2013-01-01

    This in vitro study investigated the erosion-inhibiting properties of dental rinses during erosion in the presence of the salivary pellicle. The erosion inhibition by a Sn/F containing dental rinse (800 ppm Sn(2+), 500 ppm F(-), pH = 4.5) was compared with a fluoridated solution (500 ppm F(-), pH = 4.5) and water (control). Calcium release and enamel softening were significantly reduced among enamel samples exposed to the Sn/F rinse (group SF) compared to those treated with the fluoride solution (group F) and the control (p < 0.05). SEM showed slightly etched enamel interfaces in group SF, whereas the erosion was more pronounced in group F and even more severe in the control group. In conclusion, the Sn/F combination provided the best inhibition of erosion among tested solutions. This study demonstrates the application of different analytical tools for comparative erosion quantification. A strong correlation (r(2) ≥0.783) was shown between calcium release and enamel softening during demineralization. PMID:23519818

  20. Purex Processing of Dissolved Sand, Slag, and Crucible Containing High Levels of Boric Acid and Calcium Fluoride

    SciTech Connect

    Kyser, E.A.

    1998-05-01

    The plutonium solution obtained from the dissolution of SSC in F- Canyon will be high in fluoride. Flowsheet adjustments must be made to increase the plutonium extraction in the solvent extraction cycle to keep Pu losses from being excessive.

  1. Degradation in performance of orthodontic wires caused by hydrogen absorption during short-term immersion in 2.0% acidulated phosphate fluoride solution.

    PubMed

    Kaneko, Kazuyuki; Yokoyama, Ken'ichi; Moriyama, Keiji; Asaoka, Kenzo; Sakai, Jun'ichi

    2004-08-01

    The purpose of this study was to investigate the degradation in performance of four major alloys of orthodontic wires, namely nickel-titanium, beta titanium, stainless steel, and cobalt-chromium-nickel, caused by hydrogen absorption during short-term immersion in an acid fluoride solutions. The hydrogen-related degradation of orthodontic wires after immersion in 2.0% acidulated phosphate fluoride solution at 37 degrees C for 60 minutes was evaluated by a tensile test, scanning electron microscope observation, and hydrogen thermal desorption analysis. Upon immersion, the tensile strengths of the nickel-titanium and beta titanium wires decreased. Particularly, the nickel-titanium wire fractured before yielding, and the fracture mode changed from ductile to brittle. The amounts of absorbed hydrogen in the nickel-titanium and beta titanium wires were 200 and 100 mass ppm, respectively. On the other hand, the tensile strengths of the stainless steel and cobalt-chromium-nickel wires were only slightly affected by immersion. The results of this study suggest that degradation in performance of orthodontic wires of titanium alloys occurs because of hydrogen absorption even after a short-term immersion in fluoride solutions. PMID:15387026

  2. Solution properties of polygalacturonic acid

    PubMed Central

    Stoddart, R. W.; Spires, I. P. C.; Tipton, K. F.

    1969-01-01

    1. The specimen of polygalacturonic acid used in these studies was shown to contain very little neutral sugar, methyl ester groups or ash, and only residues of galacturonic acid. Its electrophoretic homogeneity was examined in pyridine–acetic acid buffer at pH6·5 and in borate buffer at pH9·2. The distribution of effective particle weights was shown to be fairly narrow. 2. The pH-titration curve of the polymer gave a pK value of 3·7. 3. The interaction of the polymer with Ruthenium Red was studied and titration curves were obtained for the spectral shifts associated with the formation of a complex. 4. Optical-rotatory-dispersion studies showed that the Drude constant, λc, was dependent on pH. 5. Polygalacturonic acid was shown to display non-Newtonian properties in solution and to have an anomalously high relative specific viscosity at low concentrations. 6. Studies were made of the pH-dependence of the sedimentation coefficient of the polymer. 7. These results are discussed in terms of the structure of the molecule and their relevance to the properties of pectic substances. PMID:5343801

  3. Ions in hyaluronic acid solutions

    NASA Astrophysics Data System (ADS)

    Horkay, Ferenc; Basser, Peter J.; Londono, David J.; Hecht, Anne-Marie; Geissler, Erik

    2009-11-01

    Hyaluronic acid (HA) is an anionic biopolymer that is almost ubiquitous in biological tissues. An attempt is made to determine the dominant features that account for both its abundance and its multifunctional role, and which set it apart from other types of biopolymers. A combination of osmotic and scattering techniques is employed to quantify its dynamic and static properties in near-physiological solution conditions, where it is exposed both to mono- and divalent counterions. An equation of state is derived for the osmotic pressure Π in the semidilute concentration region, in terms of two variables, the polymer concentration c and the ionic strength J of the added salt, according to which Π =1.4×103c9/4/J3/4 kPa, where c and J are expressed in mole. Over the physiological ion concentration range, the effect of the sodium chloride and calcium chloride on the osmotic properties of HA solutions is fully accounted for by their contributions to the ionic strength. The absence of precipitation, even at high CaCl2 concentrations, distinguishes this molecule from other biopolymers such as DNA. Dynamic light scattering measurements reveal that the collective diffusion coefficient in HA solutions exceeds that in aqueous solutions of typical neutral polymers by a factor of approximately 5. This property ensures rapid adjustment to, and recovery from, stress applied to HA-containing tissue. Small angle x-ray scattering measurements confirm the absence of appreciable structural reorganization over the observed length scale range 10-1000 Å, as a result of calcium-sodium ion exchange. The scattered intensity in the transfer momentum range q >0.03 Å-1 varies as 1/q, indicating that the HA chain segments in semidilute solutions are linear over an extended concentration range. The osmotic compression modulus c ∂Π/∂c, a high value of which is a prerequisite in structural biopolymers, is several times greater than in typical neutral polymer solutions.

  4. Single-crystalline ceramic whisker-reinforced carboxylic acid-resin composites with fluoride release.

    PubMed

    Xu, H H; Eichmiller, F C; Antonucci, J M; Flaim, G M

    2000-01-01

    Currently available glass-ionomer, resin-modified glass-ionomer, and compomer materials have relatively low strength and toughness and, therefore, are inadequate for use in large stress-bearing posterior restorations. In the present study, ceramic single-crystalline whiskers were mixed with fluorosilicate glass particles and used as fillers to reinforce experimental carboxylic acid-resin composites. The carboxylic acid was a monofunctional methacryloxyethyl phthalate (MEP). Five mass fractions of whisker/(whisker + fluorosilicate glass), and corresponding resin (resin + MEP), were evaluated. Four control materials were also tested for comparison: a glass ionomer, a resin-modified glass ionomer, a compomer, and a hybrid composite resin. Flexural specimens were fabricated to measure the flexural strength, elastic modulus, and work-of-fracture (an indication of toughness). Fluoride release was measured by using a fluoride ion selective electrode. The properties of whisker composites depended on the whisker/(whisker + fluorosilicate glass) mass fraction. At a mass fraction of 0.8, the whisker composite had a flexural strength in MPa (mean +/- sd; n = 6) of 150 +/- 16, significantly higher than that of a glass ionomer (15 +/- 7) or a compomer control (89 +/- 18) (Tukey's multiple comparison test; family confidence coefficient = 0.95). Depending on the ratio of whisker:fluorosilicate glass, the whisker composites had a cumulative fluoride release up to 60% of that of a traditional glass ionomer. To conclude, combining ceramic whiskers and fluorosilicate glass in a carboxylic acid-resin matrix can result in fluoride-releasing composites with significantly improved mechanical properties. PMID:11203805

  5. High efficient removal of fluoride from aqueous solution by a novel hydroxyl aluminum oxalate adsorbent.

    PubMed

    Wu, Shibiao; Zhang, Kaisheng; He, Junyong; Cai, Xingguo; Chen, Kai; Li, Yulian; Sun, Bai; Kong, Lingtao; Liu, Jinhuai

    2016-02-15

    A novel adsorbent, hydroxyl aluminum oxalate (HAO), for the high efficient removal of fluoride from aqueous solution was successfully synthesized. The adsorbent was characterized and its performance in fluoride (F(-)) removal was evaluated for the first time. Kinetic data reveal that the F(-) adsorption is rapid in the beginning followed by a slower adsorption process; 75.9% adsorption can be achieved within 1min and only 16% additional removal occurred in the following 239min. The F(-) adsorption kinetics was well described by the pseudo second-order kinetic model. The calculated adsorption capacity of this adsorbent for F(-) by Langmuir model was 400mgg(-1) at pH 6.5, which is one of the highest capabilities of today's materials. The thermodynamic parameters calculated from the temperature-dependent isotherms indicate that the adsorption reaction of F(-) on the HAO is a spontaneous process. The FT-IR spectra of HAO before and after adsorbing F(-) show adsorption mechanism should be hydroxyl and oxalate interchange with F(-). PMID:26624529

  6. How Lewis acidic is your cation? Putting phosphenium ions on the fluoride ion affinity scale.

    PubMed

    Slattery, John M; Hussein, Sharifa

    2012-02-14

    The fluoride ion affinities (FIAs) of 33 phosphenium ions with a range of substituents were calculated using ab inito and DFT methods. The use of these FIA data as a measure of the Lewis acidities of phosphenium ions is described and the FIAs of the species studied here are compared to FIA data for more commonly encountered Lewis acids. Phosphenium ions are often stronger Lewis acids than neutral species, but in many cases are less Lewis acidic than highly electrophilic cations such as [Me(3)C](+) or [Me(3)Si](+). The impact of mesomeric, inductive and steric substituent effects on FIAs are discussed and related to the underlying electronic structures of different cation types. A comparison between the FIAs of known "free" phosphenium ions with those that are currently unknown and other highly electrophilic cations suggests that some diaryl- and dialkylphosphenium ions may yet be accessible under the right conditions. PMID:22159000

  7. Sulfate, chloride and fluoride retention in Andosols exposed to volcanic acid emissions.

    PubMed

    Delmelle, Pierre; Delfosse, Thomas; Delvaux, Bruno

    2003-01-01

    The continuous emissions of SO(2), HCl and HF by Masaya volcano, Nicaragua, represent a substantial source of atmospheric S-, Cl- and F-containing acid inputs for local ecosystems. We report on the effects of such acid depositions on the sulfate, chloride and fluoride contents in soils (0-40 cm) from two distinct transects located downwind from the volcano. The first transect corresponds to relatively undifferentiated Vitric Andosols, and the second transect to more weathered Eutric Andosols. These soils are exposed to various rates of volcanogenic acid addition, with the Vitric sites being generally more affected. Prolonged acid inputs have led to a general pH decrease and reduced exchangeable base cation concentrations in the Andosols. The concentrations of 0.5 M NH(4)F- and 0.016 M KH(2)PO(4)-extractable sulfate (NH(4)F-S and KH(2)PO(4)-S, respectively) indicate that volcanic S addition has increased the inorganic sulfate content of the Vitric and Eutric soils at all depths. In this process, the rate of sulfate accumulation is also dependent on soil allophane contents. For all soils, NH(4)F extracted systematically more (up to 40 times) sulfate than KH(2)PO(4). This difference suggests sulfate incorporation into an aluminum hydroxy sulfate phase, whose contribution to total inorganic sulfate in the Vitric and Eutric Andosols is estimated from approximately 34 to 95% and approximately 65 to 98%, respectively. The distribution of KH(2)PO(4)-extractable chloride in the Vitric and Eutric Andosols exposed to volcanic Cl inputs reveals that added chloride readily migrates through the soil profiles. In contrast, reaction of fluoride with Al and Fe oxyhydroxides and allophanes is an important sink mechanism in the Masaya Andosols exposed to airborne volcanic F. Fluoride dominates the anion distribution in all soil horizons, although F is the least concentrated element in the volcanic emissions and depositions. The soil anion distribution reflects preferential retention

  8. Diffusion coefficients of sodium fluoride in aqueous solutions at 298.15 k and 310.15 k.

    PubMed

    Ribeiro, Ana C F; Lobo, Victor M M; Sobral, Abilio J F N; Soares, Helder T F C; Esteso, Ana R J; Esteso, Miguel A

    2010-06-01

    Mutual diffusion coefficients (interdiffusion coefficients) have been measured for sodium fluoride in water at 298.15 K and 310.15 K at concentrations between 0.003 mol dm-3 and 0.05 mol dm-3. The diffusion coefficients were measured using a conductimetric cell. The experimental mutual diffusion coefficients are discussed on the basis of the Onsager-Fuoss model. The limiting molar conductivity of the fluoride ion in these solutions at 310.15 K has been estimated using these results. PMID:24061738

  9. Stable Drop Formation and Deposition Control in Ink Jet Printing of Polyvinylidene Fluoride Solution

    NASA Astrophysics Data System (ADS)

    Thorne, Nathaniel; Yang, Xin; Sun, Ying; Complex Fluids and Multiphase Transport Lab-Drexel University Team

    2013-11-01

    Using inkjet printing as an additive fabrication method is an enabling technology for low-cost, high-throughput production of flexible electronics and photonics. Polymeric materials, such as Polyvinylidene fluoride (PVDF), are widely used as dielectric materials for microelectronics, batteries, among others. However, due to its large molecular weight and incompatibility with moisture in air, the stable drop formation of PVDF solution is quite challenging. In this study, we examine the effects of solute concentration, nozzle back pressure, ejection waveform, and ambient moisture on the formation of PVDF droplets. The deposition dynamics of inkjet-printed PVDF solutions are then examined as a function of the solvent concentration. Bi-solvents of different surface tensions and vapor pressures are used to induce Marangoni flows in order to suppress the coffee-ring effect. The deposition of a single droplet and the interactions between multiple drops are examined for a better control of the deposition uniformity. Printing of lines and patterns with reduced instability is also discussed.

  10. Hydrogen embrittlement of work-hardened Ni-Ti alloy in fluoride solutions.

    PubMed

    Yokoyama, Ken'ichi; Kaneko, Kazuyuki; Ogawa, Toshio; Moriyama, Keiji; Asaoka, Kenzo; Sakai, Jun'ichi

    2005-01-01

    Hydrogen embrittlement of work-hardened Ni-Ti alloy has been examined in acidulated phosphate fluoride (APF) solutions. Upon immersion in a 2.0% APF solution with a pH of 5.0, tensile strength decreased markedly with immersion time. Moreover, the fracture mode changed from ductile to brittle due to brittle layer formation at the peripheral part of the cross section of the specimen. The amount of absorbed hydrogen increased linearly with immersion time, and it reached above 5000 mass ppm after 24 h. The hydrogen desorption temperature of the immersed specimens shifted from 450 degrees C to a lower temperature with immersion time. As the amount of absorbed hydrogen was larger than 500 mass ppm, the degradation of mechanical properties was recognized. Although the tensile properties and fracture mode scarcely change in a 0.2% APF solution, the slight reduction in hardness and hydrogen absorption of several hundreds mass ppm were observed. The results of the present study imply that work-hardened Ni-Ti alloy is less sensitive to hydrogen embrittlement compared with Ni-Ti superelastic alloy. PMID:15193885

  11. Nitric acid recovery from waste solutions

    DOEpatents

    Wilson, A. S.

    1959-04-14

    The recovery of nitric acid from aqueous nitrate solutions containing fission products as impurities is described. It is desirable to subject such solutions to concentration by evaporation since nitric acid is regenerated thereby. A difficulty, however, is that the highly radioactive fission product ruthenium is volatilized together with the nitric acid. It has been found that by adding nitrous acid, ruthenium volatilization is suppressed and reduced to a negligible degree so that the distillate obtained is practically free of ruthenium.

  12. ELECTROLYTIC REDUCTION OF NITRIC ACID SOLUTIONS

    DOEpatents

    Alter, H.W.; Barney, D.L.

    1958-09-30

    A process is presented for the treatment of radioactivc waste nitric acid solutions. The nitric acid solution is neutralized with an alkali metal hydroxide in an amount sufficient to precipitate insoluble hydroxides, and after separation of the precipitate the solution is electrolyzed to convert the alkali nitrate formed, to alkali hydroxide, gaseous ammonla and oxygen. The solution is then reusable after reducing the volume by evaporating the water and dissolved ammonia.

  13. The solution of the Wertheim association theory for molecular liquids: Application to hydrogen fluoride

    NASA Astrophysics Data System (ADS)

    Fries, P. H.; Richardi, J.

    2000-11-01

    A general numerical method for solving the Wertheim association theory in the case of fully anisotropic polyatomic rigid molecules is proposed. In order to handle the nonspherical shapes of the molecules, the Wertheim association theory is combined with the rotational invariant approach of the molecular Ornstein-Zernike (MOZ) method. Therefore, this approach is called the WMOZ method. It is carried out in the association hypernetted chain (AHNC) approximation which is the only approximation and which consists of the neglect of the bridge functions. The method of solution is implemented by translating the set operations appearing in the Wertheim association theory into an algebraic formalism developed through a one-to-one correspondence between subsets and binary numbers. The Wertheim association theory is explicitly solved for hydrogen fluoride using two interaction site models. For these models, site-site distribution functions, internal excess energies, and dielectric constants obtained by the MOZ and WMOZ methods are compared to the exact molecular dynamics results. The WMOZ method strongly improves the structural description of the H bonding in comparison with the MOZ approximation. The quality of the dielectric and thermodynamic results obtained by the WMOZ approach is discussed in comparison with the simulation values. To our knowledge, this is the first solution of the Wertheim association theory for a liquid of particles of nonspherical shapes.

  14. Zirconium fluoride glass - Surface crystals formed by reaction with water

    NASA Technical Reports Server (NTRS)

    Doremus, R. H.; Bansal, N. P.; Bradner, T.; Murphy, D.

    1984-01-01

    The hydrated surfaces of a zirconium barium fluoride glass, which has potential for application in optical fibers and other optical elements, were observed by scanning electron microscopy. Crystalline zirconium fluoride was identified by analysis of X-ray diffraction patterns of the surface crystals and found to be the main constituent of the surface material. It was also found that hydrated zirconium fluorides form only in highly acidic fluoride solutions. It is possible that the zirconium fluoride crystals form directly on the glass surface as a result of its depletion of other ions. The solubility of zirconium fluoride is suggested to be probably much lower than that of barium fluoride (0.16 g/100 cu cm at 18 C). Dissolution was determined to be the predominant process in the initial stages of the reaction of the glass with water. Penetration of water into the glass has little effect.

  15. Superhydrophobicity of polyvinylidene fluoride membrane fabricated by chemical vapor deposition from solution

    NASA Astrophysics Data System (ADS)

    Zheng, Zhenrong; Gu, Zhenya; Huo, Ruiting; Ye, Yonghong

    2009-05-01

    Due to the chemical stability and flexibility, polyvinylidene fluoride (PVDF) membranes are widely used as the topcoat of architectural membrane structures, roof materials of vehicle, tent fabrics, and so on. Further modified PVDF membrane with superhydrophobic property may be even superior as the coating layer surface. The lotus flower is always considered to be a sacred plant, which can protect itself against water, dirt, and dust. The superhydrophobic surface of lotus leaf is rough, showing the micro- and nanometer scale morphology. In this work, the microreliefs of lotus leaf were mimicked using PVDF membrane and the nanometer scale peaks on the top of the microreliefs were obtained by the method of chemical vapor deposition from solution. The surface morphology of PVDF membrane was investigated by scanning electronic microscopy (SEM) and atomic force microscope (AFM). Elemental composition analysis by X-ray photoelectron spectroscopy (XPS) revealed that the material of the nanostructure of PVDF membrane was polymethylsiloxane. On the lotus-leaf-like PVDF membrane, the water contact angle and sliding angle were 155° and 4°, respectively, exhibiting superhydrophobic property.

  16. Characteristics of fluoride in pore-water at accidental hydrofluoric acid spillage site, Gumi, Korea

    NASA Astrophysics Data System (ADS)

    Kwon, E. H.; Lee, H. A.; Lee, J.; Kim, D.; Lee, S.; Yoon, H. O.

    2015-12-01

    A leakage accident of hydrofluoric acid (HF) occurred in Gumi, South Korea at Sep. 2012. The study site is located in the borderline between a large-scale industrial complex and a rural area. The HF plume was made immediately, and moved toward the rural area through air. After the accident, 212 ha of farm land were influenced and most of crops were withered. To recover the soil, CaO was applied after six months. Although several studies have done to estimate the extension and movement of HF plume in the air and to assess the impact on human health or plant after the incident, the long-term fate of fluoride (F) in the affected soils is not identified clearly. Thus, this study aimed to understand the behavior of F in the soil after HF releasing from accident site through chemical analysis and geochemical modeling. Within the radius of 1 km of accident site, 16 pore-water and soil samples were collected. The semi-quantitative soil composition (i.e., Al, Ca, Fe, K, Mg, Mn, Na, P, Si, Ti), total F, total P, OM contents in soil, and soil pH have already been measured, and pore-water compositions are also identified. From these experimental and modeling data, we could be evaluate if impact of accident exists until now, and also could be select and identify existing form of fluoride in soil and pore-water.

  17. Investigation of effect of fluoride on corrosion of 2S-0 aluminum and 347 stainless steel in fuming nitric acid at 170 F

    NASA Technical Reports Server (NTRS)

    Feiler, Charles E; Morrell, Gerald

    1954-01-01

    The effect of small additions of fluoride on the corrosion of 2S-0 aluminum and 347 stainless steel by fuming nitric acid at 170 degrees F has been evaluated quantitatively by the determination of the weight loss of metal specimens immersed in the acid. The ratio of metal surface area to volume of acid was approximately 7.5 inch (superscript)-1 in all cases. It was found that for acids containing no fluorides the weight loss of aluminum was approximately 1/5 that of stainless steel. Addition of 1 percent fluoride ion to the acid reduced the weight loss of both metals to practically zero even after 26 days of exposure to the acid at 170 degrees F. The minimum quantity of fluoride ion required to inhibit corrosion was found to be approximately 0.25 and 0.5 percent for aluminum and stainless steel, respectively, in white fuming nitric acid and 0.5 and 1 percent in red fuming nitric acid (18 percent nitrogen dioxide). These fluoride percentages were based on the total weight of acid. Provided the concentration of fluoride ion was sufficient to inhibit corrosion, the source of these ions was immaterial. Additional information concerning the effect of fluorides on corrosion was obtained by measuring the electrode potentials of the metals against a platinum reference electrode.

  18. DISSOLUTION OF LANTHANUM FLUORIDE PRECIPITATES

    DOEpatents

    Fries, B.A.

    1959-11-10

    A plutonium separatory ore concentration procedure involving the use of a fluoride type of carrier is presented. An improvement is given in the derivation step in the process for plutonium recovery by carrier precipitation of plutonium values from solution with a lanthanum fluoride carrier precipitate and subsequent derivation from the resulting plutonium bearing carrier precipitate of an aqueous acidic plutonium-containing solution. The carrier precipitate is contacted with a concentrated aqueous solution of potassium carbonate to effect dissolution therein of at least a part of the precipitate, including the plutonium values. Any remaining precipitate is separated from the resulting solution and dissolves in an aqueous solution containing at least 20% by weight of potassium carbonate. The reacting solutions are combined, and an alkali metal hydroxide added to a concentration of at least 2N to precipitate lanthanum hydroxide concomitantly carrying plutonium values.

  19. EVALUATION OF EMISSIONS AND CONTROL TECHNIQUES FOR REDUCING FLUORIDE EMISSIONS FROM GYPSUM PONDS IN THE PHOSPHORIC ACID INDUSTRY

    EPA Science Inventory

    The report gives results of a study of gaseous emissions from gypsum disposal and cooling water ponds to determine their potential as sources of airborne fluorides from the manufacture of phosphoric acid. A model of the chemistry within the pond environment was developed. Previou...

  20. Comparative study on corrosion behaviour of Nitinol and stainless steel orthodontic wires in simulated saliva solution in presence of fluoride ions.

    PubMed

    Mirjalili, M; Momeni, M; Ebrahimi, N; Moayed, M H

    2013-05-01

    Localized corrosion and effects of pre-passivation treatment of Nitinol and SS304 orthodontic wires in simulated saliva solution in the presence and absence of fluoride ions were investigated by means of potentiodynamic and potentiostatic polarisations. Results revealed that Nitinol does not show pitting corrosion in saliva solution however, SS304 shows pitting corrosion. Meanwhile fluoride ion has deteriorative effect on pitting corrosion of Nitinol, while its effect on SS304 was marginally constructive. Additionally, the presence of artificial crevice has no effect on corrosion behaviour in the presence of fluoride. Pre-passivation treatment has positive influence on pitting corrosion of both alloys in the presence of F(-) ions. PMID:23498236

  1. Salivary Streptococcus mutans count and gingivitis in children after rinsing with a chlorhexidine-fluoride solution with and without strontium.

    PubMed

    Spets-Happonen, S; Markkanen, H; Pöllänen, L; Kauppinen, T; Luoma, H

    1985-08-01

    Thirty schoolchildren, 9-12 yr old with high DMF score, rinsed their mouths twice a day for 3 days with a chlorhexidine-fluoride (CXF) solution or a chlorhexidine-fluoride-strontium (CXFSr) solution. Streptococcus mutans counts (CFU) were made from saliva incubated on MSB agar and the gingival bleeding was recorded both before and after the rinsing period. S. mutans count decreased significantly immediately after the rinsing with each of the solutions (from 650 X 10(3) to 170 X 10(3) CFU/ml by CXF and from 500 to 170 X 10(3) CFU/ml by CXFSr). Within about 18 days after the rinsing with each solution the salivary S. mutans counts returned to the original level. Gingival Bleeding Index (GBI) was significantly reduced by half through the CXF rinsing while the slight reduction by CXFSr was nonsignificant. Both of these changes were temporary. The results suggest that short rinsing periods with the CXF solution may be more advisable than daily rinses as a contribution to the maintenance of oral health in subjects or groups in need of such a prophylaxis. The weaker effect found with the CXFSr solution suggests that the cariostatic effect recently found in rats with the same solution may be due to other mechanisms than reduction of the oral S. mutans count. PMID:3862233

  2. Effects of copper, iron and fluoride co-crystallized with sugar on caries development and acid formation in deslivated rats.

    PubMed

    Rosalen, P L; Pearson, S K; Bowen, W H

    1996-11-01

    The purpose was to explore the effects of combinations of copper, iron and fluoride (Cu, Fe and F) incorporated in sucrose by co-crystallization on caries development in the deslivated rat model and to examine acid formation by bacteria in the rat mouth. Ninety-six Sprague-Dawley rats were infected with Streptococcus sobrinus 6715 and desalivated when aged 26 days. Eight groups were placed in a König-Höfer programmed feeder and received 17 meals daily at hourly intervals, and essential nutrition (NCP No. 2) by gavage twice daily for 21 days. The groups received (1) plain sucrose, (2) F (8 parts/10(6)) co-crystallized with sucrose, (3) Fe (88 parts/10(6)) sucrose, (4) Cu (75 parts/10(6)) sucrose, (5) Cu + F sucrose, (6) Cu + L Fe sucrose, (7) F + Fe sucrose, and (8) Cu + Fe + F sucrose. At death the jaws were removed and sonicated in 0.9% saline solution for microbial assessment. In addition, organic acid assays were performed for each animal. Keyes smooth-surface and sulcal caries scores were lowest in the Cu + Fe + F sucrose group, but not statistically significantly different from those of the other Cu groups. The numbers of Strep. sobrinus found in the groups that received Cu, Cu + Fe, Cu + F, F + Fe and Cu + Fe + F sugar were lower than in the control group. Lactic acid was found in lower concentrations in Fe, Cu, Cu + F, Cu + Fe and F + Fe groups than in the other groups. It appears that combinations of Cu; Fe and F co-crystallized with sugar may have an additive effect in reducing the cariogenic potential of sugar by affecting lactic acid formation and reducing bacterial colonization. PMID:9068864

  3. Effects of combined oleic acid and fluoride at sub-MIC levels on EPS formation and viability of Streptococcus mutans UA159 biofilms.

    PubMed

    Cai, Jian-Na; Kim, Mi-A; Jung, Ji-Eun; Pandit, Santosh; Song, Kwang-Yeob; Jeon, Jae-Gyu

    2015-01-01

    Despite the widespread use of fluoride, dental caries, a biofilm-related disease, remains an important health problem. This study investigated whether oleic acid, a monounsaturated fatty acid, can enhance the effect of fluoride on extracellular polysaccharide (EPS) formation by Streptococcus mutans UA159 biofilms at sub-minimum inhibitory concentration levels, via microbiological and biochemical methods, confocal fluorescence microscopy, and real-time PCR. The combination of oleic acid with fluoride inhibited EPS formation more strongly than did fluoride or oleic acid alone. The superior inhibition of EPS formation was due to the combination of the inhibitory effects of oleic acid and fluoride against glucosyltransferases (GTFs) and GTF-related gene (gtfB, gtfC, and gtfD) expression, respectively. In addition, the combination of oleic acid with fluoride altered the bacterial biovolume of the biofilms without bactericidal activity. These results suggest that oleic acid may be useful for enhancing fluoride inhibition of EPS formation by S. mutans biofilms, without killing the bacterium. PMID:26293974

  4. Protective effect of ascorbic acid and Ginkgo biloba against learning and memory deficits caused by fluoride.

    PubMed

    Jetti, Raghu; Raghuveer, C V; Mallikarjuna, Rao C

    2016-01-01

    Fluoride is present in the ground water, World Health Organization permitted level of fluoride in the ground water is 0.5 ppm. Tooth pastes, mouth washes, tea and sea fish are the sources of fluoride. Exposure to these multiple sources results in several adverse effects in addition to the fluorosis. The present study aimed to test the effect of vitamin C and Ginkgo biloba against the behavioural deficits caused by fluoride. Rats were divided into five groups with six animals in each group (n = 6). Control group received ordinary tap water with 0.5 ppm of fluoride, the remaining groups received 100 ppm of fluoride for 30 days prior to fluoride exposure. Two groups of animals received 100 mg/kg body weight of vitamin C and G. biloba for 15 days prior to fluoride exposure. After 45 days, behavioural studies (T-Maze, passive avoidance) were conducted on the experimental animals. The results of the present study showed no behavioural deficits in the control group of animals however, the rats that received fluoride water exhibited impairment in their spatial learning and memory deficits. The deficits are not marked in the vitamin C and G. biloba groups. To conclude chronic exposure to high levels of fluoride causes severe impairment in the spatial learning and memory, these deficits can be ameliorated with the vitamin C and G. biloba. PMID:24081631

  5. Degradation of ascorbic acid in ethanolic solutions.

    PubMed

    Hsu, Hsin-Yun; Tsai, Yi-Chin; Fu, Chi-Chang; Wu, James Swi-Bea

    2012-10-24

    Ascorbic acid occurs naturally in many wine-making fruits. The industry also uses ascorbic acid as an antioxidant and color stabilizer in the making of alcoholic beverages including white wine, wine cooler, alcopop, and fruit liqueur. However, the degradation of ascorbic acid itself may cause browning and the deterioration of color quality. This study was aimed to monitor the degradation of ascorbic acid, the formation of degradation products, and the browning in storage of ascorbic acid containing 0-40% (v/v) ethanolic solutions buffered at pH 3.2 as models of alcoholic beverages. The results show that ascorbic acid degradation in the ethanolic solutions during storage follows first-order reaction, that the degradation and browning rates increase with the increase of ethanol concentration, that the activation energy for the degradation of ascorbic acid is in the range 10.35-23.10 (kcal/mol), that 3-hydroxy-2-pyrone is an indicator and a major product of ascorbic acid degradation, and that aerobic degradation pathway dominants over anaerobic pathway in ascorbic acid degradation in ethanolic solutions. PMID:22994409

  6. Complexation of neptunium(V) with fluoride in aqueous solutions at elevated temperatures

    SciTech Connect

    Tian, Guoxin; Rao, Linfeng; Xia, Yuanxian; Friese, Judah I.

    2009-02-01

    summarizes the results of the complexation of Np(V) with fluoride in aqueous solutions at 10–70°C studied by spectrophotometry and microcalorimetry.

  7. Diffusion of sulfuric acid in concentrated solutions

    SciTech Connect

    Umino, S.; Newman, J. )

    1993-08-01

    Aqueous sulfuric acid is an economically important chemical reagent. It is one of the largest volume chemical commodities, finding uses in fertilizer production, petroleum refining, extraction of metals from their ores, production of inorganic pigments, pickling of iron and steel, synthesis of surface-active agents, and as a reactant in the lead-acid storage battery. The restricted diffusion method was used to measure the differential diffusion coefficient of sulfuric acid in water at 25 C for the concentration range from 0.3 to 7.5 molar. The concentration gradients of diffusing species were observed by Rayleigh interferometry. Experimental transport data are analyzed with concentrated solution theory of electrolytes in order to elucidate macroscopic transport characteristics of sulfuric acid in terms of specific binary interactions in solution. Results indicate that the transport properties of sulfuric acid are determined by the hydrogen ion-water molecule.

  8. Fluoridation Basics

    MedlinePlus

    ... Water Fluoridation Journal Articles for Community Water Fluoridation Water Fluoridation Basics Recommend on Facebook Tweet Share Compartir ... because of tooth decay. History of Fluoride in Water In the 1930s, scientists examined the relationship between ...

  9. Reference electrode for strong oxidizing acid solutions

    DOEpatents

    Rigdon, Lester P.; Harrar, Jackson E.; Bullock, Sr., Jack C.; McGuire, Raymond R.

    1990-01-01

    A reference electrode for the measurement of the oxidation-reduction potentials of solutions is especially suitable for oxidizing solutions such as highly concentrated and fuming nitric acids, the solutions of nitrogen oxides, N.sub.2 O.sub.4 and N.sub.2 O.sub.5, in nitric acids. The reference electrode is fabricated of entirely inert materials, has a half cell of Pt/Ce(IV)/Ce(III)/70 wt. % HNO.sub.3, and includes a double-junction design with an intermediate solution of 70 wt. % HNO.sub.3. The liquid junctions are made from Corning No. 7930 glass for low resistance and negligible solution leakage.

  10. ELECTRONIC SOLUTION SPECTRA FOR URANIUM AND NEPTUNIUM IN OXIDATION STATES (III) TO (VI) IN ANHYDROUS HYDROGEN FLUORIDE

    SciTech Connect

    Baluka, M.; Edelstein, N.; O'Donnell, T. A.

    1980-10-01

    Spectra have been recorded for solutions in anhydrous hydrogen fluoride (AHF) of uranium and neptunium in oxidation states (III) to (VI). The spectra for U(III), Np(III) and Np(IV) in AHF are very similar to those in acidified aqueous solution, but that for U(IV) suggests that the cationic species is UF{sub 2}{sup 2+}. The AHF spectra for the elements in oxidation states (V) and (VI) are not comparable with those of the formally analogous aqueous solutions, where the elements exist as well-defined dioxo-cations. However, the AHF spectra can be related to spectra in the gas phase, in the solid state or in non-aqueous solvents for each element in its appropriate oxidation state.

  11. Effect of fluoride on glucose incorporation and metabolism in biofilm cells of Streptococcus mutans.

    PubMed

    Balzar Ekenbäck, S; Linder, L E; Sund, M L; Lönnies, H

    2001-06-01

    The aim of this study was two-fold: firstly, to study the effect of high fluoride concentrations on carbohydrate metabolism in Streptococcus mutans present in biofilms on hydroxyapatite; and, secondly, to evaluate the effect of fluoride-bound hydroxyapatite on lactic acid formation in growing biofilms of Strep. mutans. Biofilms of a clinical strain of Strep. mutans on saliva-coated hydroxyapatite beads were incubated with sodium fluoride over a wide range of concentrations. At high fluoride concentrations (>10 mM) the incorporation of [14C]-labeled glucose decreased by 80-85%, at both pH 7.0 and 5.6. At lower fluoride concentrations, the effect of fluoride on the incorporation of labeled glucose was pH-dependent in both biofilm cells and in planktonic cells. At pH 7.0, fluoride at concentrations < 10 mM had little or no effect. Pretreatment of hydroxyapatite discs with fluoride varnish (Fluor Protector) or fluoride solutions caused a statistically significant reduction of lactic acid formation in associated, growing biofilms of Strep. mutans. Fluoride varnish and 0.2% (47.6 mM) sodium fluoride solution exhibited a statistically significant inhibitory effect on lactate production. PMID:11456349

  12. Electrical conductivity of acidic sulfate solution

    NASA Astrophysics Data System (ADS)

    Majima, Hiroshi; Peters, Ernest; Awakura, Yasuhiro; Park, Sung Kook

    1987-03-01

    The electrical conductivities of the aqueous solution system of H2SO4-MSO4 (involving ZnSO4, MgSO4, Na2SO4, and (NH4)2SO4), reported by Tozawa et al., were examined in terms of a (H2O) and H+ ion concentration. The equations to compute the concentrations of various species in aqueous sulfuric acid solutions containing metal sulfates were derived for a typical example of the H2SO4-ZnSO4-MgSO4-(Na2SO4)-H2O system. It was found that the H+ ion concentrations in concentrated sulfuric acid solutions corresponding to practical zinc electrowinning solutions are very high and remain almost constant with or without the addition of metal sulfates. The addition of metal sulfates to aqueous sulfuric acid solution causes a decrease in electrical conductivity, and this phenomenon is attributed to a decrease in water activity, which reflects a decrease in the amount of free water. The relationship between conductivity and water activity at a constant H+ ion concentration is independent of the kind of sulfates added. On the other hand, any increase in H+ ion concentration results in an increase in electrical conductivity. A novel method for the prediction of electrical conductivity of acidic sulfate solution is proposed that uses the calculated data of water activity and the calculated H+ ion concentration. Also, the authors examined an extension of the Robinson-Bower equation to calculate water activity in quarternary solutions based on molarity instead of molality, and found that such calculated values are in satisfactory agreement with those determined experimentally by a transpiration method.

  13. Degradation studies of transparent conductive electrodes on electroactive poly(vinylidene fluoride) for uric acid measurements

    NASA Astrophysics Data System (ADS)

    Cardoso, Vanessa F.; Martins, Pedro; Botelho, Gabriela; Rebouta, Luis; Lanceros-Méndez, Senentxu; Minas, Graca

    2010-08-01

    Biochemical analysis of physiological fluids using, for example, lab-on-a-chip devices requires accurate mixing of two or more fluids. This mixing can be assisted by acoustic microagitation using a piezoelectric material, such as the β-phase of poly(vinylidene fluoride) (β-PVDF). If the analysis is performed using optical absorption spectroscopy and β-PVDF is located in the optical path, the material and its conductive electrodes must be transparent. Moreover, if, to improve the transmission of the ultrasonic waves to the fluids, the piezoelectric transducer is placed inside the fluidic structures, its degradation must be assessed. In this paper, we report on the degradation properties of transparent conductive oxides, namely, indium tin oxide (ITO) and aluminum-doped zinc oxide, when they are used as electrodes for providing acoustic microagitation. The latter promotes mixing of chemicals involved in the measurement of uric acid concentration in physiological fluids. The results are compared with those for aluminum electrodes. We find that β-PVDF samples with ITO electrodes do not degrade either with or without acoustic microagitation.

  14. EXAFS study of the speciation of protactinium(V) in aqueous hydrofluoric acid solutions.

    PubMed

    De Sio, Stéphanie M; Wilson, Richard E

    2014-12-01

    The speciation of protactinium(V) in hydrofluoric acid (HF) solutions was studied using X-ray absorption spectroscopy. Extended X-ray absorption fine structure measurements were performed on an aqueous solution of 0.05 M protactinium(V) with various HF concentrations ranging from 0.5 to 27 M in order to probe the protactinium coordination sphere with respect to the identity and number of coordinating ligands. The resulting fits to the spectra suggest the presence of an eight-coordinate homoleptic fluoro complex in highly concentrated fluoride solutions (27 M), with equilibrium between seven- and eight-coordinate fluoro complexes at moderate acidities, and in more dilute solutions, results indicate that one water molecule is likely to replace a fluoride in the first coordination sphere, at a distance of 2.54-2.57 Å. Comparisons of this chemistry with group V metals, niobium and tantalum, are presented, and the potential implications for these results on the hydrolytic behavior of protactinium in aqueous systems are discussed. PMID:25389749

  15. Solution of rocks and refractory minerals by acids at high temperatures and pressures. Determination of silica after decomposition with hydrofluoric acid

    USGS Publications Warehouse

    May, I.; Rowe, J.J.

    1965-01-01

    A modified Morey bomb was designed which contains a removable nichromecased 3.5-ml platinium crucible. This bomb is particularly useful for decompositions of refractory samples for micro- and semimicro-analysis. Temperatures of 400-450?? and pressures estimated as great as 6000 p.s.i. were maintained in the bomb for periods as long as 24 h. Complete decompositions of rocks, garnet, beryl, chrysoberyl, phenacite, sapphirine, and kyanite were obtained with hydrofluoric acid or a mixture of hydrofluoric and sulfuric acids; the decomposition of chrome refractory was made with hydrochloric acid. Aluminum-rich samples formed difficultly soluble aluminum fluoride precipitates. Because no volatilization losses occur, silica can be determined on sample solutions by a molybdenum-blue procedure using aluminum(III) to complex interfering fluoride. ?? 1965.

  16. Polysaccharide-thickened aqueous fluoride solutions for rapid destruction of the nerve agent VX. Introducing the opportunity for extensive decontamination scenarios.

    PubMed

    Elias, Shlomi; Saphier, Sigal; Columbus, Ishay; Zafrani, Yossi

    2014-01-01

    Among the chemical warfare agents, the extremely toxic nerve agent VX (O-ethyl S-2-(diisopropylamino)ethyl methylphosphonothioate) is a target of high importance in the development of decontamination methods, due to its indefinite persistence on common environmental surfaces. Liquid decontaminants are mostly characterized by high corrosivity, usually offer poor coverage, and tend to flow and accumulate in low areas. Therefore, the development of a noncorrosive decontaminant, sufficiently viscous to resist dripping from the contaminated surface, is necessary. In the present paper we studied different polysaccharides-thickened fluoride aqueous solutions as noncorrosive decontaminants for rapid and efficient VX degradation to the nontoxic product EMPA (ethyl methylphosphonic acid). Polysaccharides are environmentally benign, natural, and inexpensive. Other known decontaminants cannot be thickened by polysaccharides, due to the sensitivity of the latter toward basic or oxidizing agents. We found that the efficiency of VX degradation in these viscous solutions in terms of kinetics and product identity is similar to that of KF aqueous solutions. Guar gum (1.5 wt %) with 4 wt % KF was chosen for further evaluation. The benign nature, rheological properties, adhering capabilities to different surfaces, and decontamination from a porous matrix were examined. This formulation showed promising properties for implementation as a spray decontaminant for common and sensitive environmental surfaces. PMID:24517492

  17. Comparative Evaluation of Tensile – Bond Strength of An Orthodontic Adhesive with and without Fluoride Application, After Acid Etching -An Invitro Study

    PubMed Central

    Yugandhar, G; Ramana, I Venkata; Srinivas, K; Yadav, S. Sarjeev Singh

    2015-01-01

    Background Fixed appliances hinder the effective control of plaque accumulation and white spot lesions may develop under the ill fitting bands or adjacent to the stainless steel brackets during orthodontic treatment particularly the etching process. Aims and Objectives Comparative study of tensile bond strength of an orthodontic adhesive with and without fluoride application after acid etching to know the effect of fluoride on bond strength. Materials and Methods This study is carried out on 90 non carious human premolar teeth, and divided in 6 groups with each group of 15 specimens. In those Groups I and IV were control group acid etch treatment, Group II and V is 1.23% APF gel (acid etch plus APF gel treatment,) and group III and VI is 8% SnF2 (acid etch plus SnF2 treatment). Samples of Group I, II and III bond strength were tested after 24 h and groups IV, V and VI after one month on microtechtensometer machine. The scanning electron microscope (SEM) investigation was carried out for the 2 specimens for the control group after acid etch and 4 specimens after acid etch with fluoride application for fluoride groups. Results Control and SnF2 treated groups was found to be nearly similar to the control group whereas APF treated group showed less focal holes than the other 2 groups. Conclusion Fluoride application after acid etching without having an adverse effect on bond strength but we can prevent the white spot lesions and caries. PMID:26023648

  18. Speciation in aqueous solutions of nitric acid.

    PubMed

    Hlushak, S; Simonin, J P; De Sio, S; Bernard, O; Ruas, A; Pochon, P; Jan, S; Moisy, P

    2013-02-28

    In this study, speciation in aqueous solutions of nitric acid at 25 °C was assessed in two independent ways. First, Raman experiments were carried out and interpreted in terms of free nitrate ions, ion pairs and neutral HNO(3) molecules. In parallel, a model was developed to account for the formation of these two kinds of pairs. It was based on an extension of the binding mean spherical approximation (BiMSA), or associative MSA (AMSA), in which the size and the charge of the ions in the chemical pair may differ from those of the free ions. A simultaneous fit of the osmotic coefficient and of the proportion of free ions (obtained from Raman spectroscopy experiments) led to an estimation of the speciation in nitric acid solutions. The result obtained using this procedure was compared with the estimation obtained from the Raman experiments. PMID:23258765

  19. Alkaline earth cation extraction from acid solution

    DOEpatents

    Dietz, Mark; Horwitz, E. Philip

    2003-01-01

    An extractant medium for extracting alkaline earth cations from an aqueous acidic sample solution is described as are a method and apparatus for using the same. The separation medium is free of diluent, free-flowing and particulate, and comprises a Crown ether that is a 4,4'(5')[C.sub.4 -C.sub.8 -alkylcyclohexano]18-Crown-6 dispersed on an inert substrate material.

  20. Optimal Fluoridation

    PubMed Central

    Lee, John R.

    1975-01-01

    Optimal fluoridation has been defined as that fluoride exposure which confers maximal cariostasis with minimal toxicity and its values have been previously determined to be 0.5 to 1 mg per day for infants and 1 to 1.5 mg per day for an average child. Total fluoride ingestion and urine excretion were studied in Marin County, California, children in 1973 before municipal water fluoridation. Results showed fluoride exposure to be higher than anticipated and fulfilled previously accepted criteria for optimal fluoridation. Present and future water fluoridation plans need to be reevaluated in light of total environmental fluoride exposure. PMID:1130041

  1. Fluoride toothpastes, rinses, and tablets.

    PubMed

    Stephen, K W

    1994-07-01

    Only from the mid-1950's has therapeutic benefit been obtained via dentifrices, initially with stannous fluoride-then monofluorophosphate-containing products which remained stable and efficacious. Altered abrasive systems followed, and both sodium fluoride and monofluorophosphate/sodium fluoride mixtures were introduced as active anti-caries agents, with recent meta-analysis indicating that sodium fluoride > monofluorophosphate/sodium fluoride > monofluorophosphate. With respect to fluoride levels, clear dose-response relationships have been demonstrated. However, at < 1000 ppm F, the situation is less certain. Since the mid-1980's, anticalculus fluoride dentifrices have been marketed, and have been shown to have similar caries-reducing potential as their non-calculus-inhibiting control formulae. Finally, one study has been described where a sodium fluoride dentifrice successfully reduced root caries. Of the many fluoride formulations used for caries-inhibiting mouthrinsing [e.g., acid phosphate fluoride (100-3000 ppm F), sodium fluoride (45-3000 ppm F), stannous fluoride (100-250 ppm F), ammonium fluoride (1000 ppm F), and amine fluoride (250 ppm F)], sodium fluoride would seem to be the preferred agent. Furthermore, rinse frequency is deemed more important than fluoride ion concentration, but caution is urged re the volumes and concentrations to be used by children, no rinsing being recommended below 4 years. Combination of a 440-pp-F sodium fluoride and 0.05% chlorhexidine school-administered rinse appears to have increased the caries-inhibiting benefit as compared with sodium fluoride alone. Fluoride supplements have reduced deciduous caries from 14 to 93%, and in the permanent dentition, from 20 to 81%.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7865074

  2. Acidities of Water and Methanol in Aqueous Solution and DMSO

    ERIC Educational Resources Information Center

    Gao, Daqing

    2009-01-01

    The relative acidities of water and methanol have been a nagging issue. In gas phase, methanol is more acidic than water by 36.0 kJ/mol; however, in aqueous solution, the acidities of methanol and water are almost identical. The acidity of an acid in solution is determined by both the intrinsic gas-phase ionization Gibbs energy and the solvent…

  3. Inhibition of nitrogen fixation in alfalfa by arsenate, heavy metals, fluoride, and simulated acid rain

    SciTech Connect

    Porter, J.R.; Sheridan, R.P.

    1981-07-01

    The acute effects of aqueous solutions of As, Cd, Cu, Pb, F, and Zn ions at concentrations from 0.01 to 100 micrograms per milliliter and solutions adjusted to pH 2 to 6 with nitric or sulfuric acid were studied with respect to acetylene reduction, net photosynthesis, respiration rate, and chlorophyll content in Vernal alfalfa. The effects of the various treatments on acetylene reduction varied from no demonstrable effect by any concentration of F/sup -/ and 42% inhibition by 100 micrograms Pb/sup 2 +/ per milliliter, to 100% inhibition by 10 micrograms Cd/sup 2 +/ per milliliter and 100 micrograms per milliliter As, Cu/sup 2 +/, and Zn/sup 2 +/ showed statistically significant inhibition of activity at 0.1 micrograms per milliliter. Acid treatments were not inhibitory above pH 2, at which pH nitric acid inhibited acetylene reduction activity more than did sulfuric acid. The inhibition of acetylene reduction by these ions was Zn/sup 2 +/ > Cd/sup 2 +/ > Cu/sup 2 +/ > AsO/sub 3//sup -/ > F/sup -/. The sensitivity of acetylene reduction to the ions was roughly equal to the sensitivity of photosynthesis, respiration, and chlorophyll content when Pb/sup 2 +/ was applied, but was 1000 times more sensitive to Zn/sup 2 +/. The relationship of the data to field conditions and industrial pollution is discussed.

  4. Inhibition of Nitrogen Fixation in Alfalfa by Arsenate, Heavy Metals, Fluoride, and Simulated Acid Rain

    PubMed Central

    Porter, John R.; Sheridan, Richard P.

    1981-01-01

    The acute effects of aqueous solutions of As, Cd, Cu, Pb, F, and Zn ions at concentrations from 0.01 to 100 micrograms per milliliter and solutions adjusted to pH 2 to 6 with nitric or sulfuric acid were studied with respect to acetylene reduction, net photosynthesis, respiration rate, and chlorophyll content in Vernal alfalfa (Medicago sativa L. cv. Vernal). The effects of the various treatments on acetylene reduction varied from no demonstrable effect by any concentration of F− and 42% inhibition by 100 micrograms Pb2+ per milliliter, to 100% inhibition by 10 micrograms Cd2+ per milliliter and 100 micrograms per milliliter As, Cu2+, and Zn2+ ions. Zn2+ showed statistically significant inhibition of activity at 0.1 micrograms per milliliter. Acid treatments were not inhibitory above pH 2, at which pH nitric acid inhibited acetylene reduction activity more than did sulfuric acid. The inhibition of acetylene reduction by these ions was Zn2+ > Cd2+ > Cu2+ > AsO3− > Pb2+ > F−. The sensitivity of acetylene reduction to the ions was roughly equal to the sensitivity of photosynthesis, respiration, and chlorophyll content when Pb2+ was applied, but was 1,000 times more sensitive to Zn2+. The relationship of the data to field conditions and industrial pollution is discussed. PMID:16661858

  5. Inhibition of nitrogen fixation in alfalfa by arsenate, heavy metals, fluoride, and simulated Acid rain.

    PubMed

    Porter, J R; Sheridan, R P

    1981-07-01

    The acute effects of aqueous solutions of As, Cd, Cu, Pb, F, and Zn ions at concentrations from 0.01 to 100 micrograms per milliliter and solutions adjusted to pH 2 to 6 with nitric or sulfuric acid were studied with respect to acetylene reduction, net photosynthesis, respiration rate, and chlorophyll content in Vernal alfalfa (Medicago sativa L. cv. Vernal). The effects of the various treatments on acetylene reduction varied from no demonstrable effect by any concentration of F(-) and 42% inhibition by 100 micrograms Pb(2+) per milliliter, to 100% inhibition by 10 micrograms Cd(2+) per milliliter and 100 micrograms per milliliter As, Cu(2+), and Zn(2+) ions. Zn(2+) showed statistically significant inhibition of activity at 0.1 micrograms per milliliter. Acid treatments were not inhibitory above pH 2, at which pH nitric acid inhibited acetylene reduction activity more than did sulfuric acid. The inhibition of acetylene reduction by these ions was Zn(2+) > Cd(2+) > Cu(2+) > AsO(3) (-) > Pb(2+) > F(-). The sensitivity of acetylene reduction to the ions was roughly equal to the sensitivity of photosynthesis, respiration, and chlorophyll content when Pb(2+) was applied, but was 1,000 times more sensitive to Zn(2+). The relationship of the data to field conditions and industrial pollution is discussed. PMID:16661858

  6. Hydrolysis of iron and chromium fluorides: mechanism and kinetics.

    PubMed

    Gálvez, José L; Dufour, Javier; Negro, Carlos; López-Mateos, Federico

    2008-06-15

    Fluoride complexes of metallic ions are one of the main problems when processing industrial effluents with high content of fluoride anion. The most important case is derived from pickling treatment of stainless steel, which is performed with HNO3/HF mixtures to remove oxides scale formed over the metal surface. Waste from this process, spent pickling liquor, must be treated for recovering metallic and acid content. Conventional treatments produce a final effluent with high quantity of fluoride complexes of iron and chromium. This work proposes a hydrolysis treatment of these solid metal fluorides by reacting them with a basic agent. Metal oxides are obtained, while fluoride is released to solution as a solved salt, which can be easily recovered as hydrofluoric acid. Solid iron and chromium fluorides, mainly K2FeF5(s) and CrF3(s), obtained in the UCM treatment process, were employed in this work. Optimal hydrolysis operating conditions were obtained by means of a factorial design: media must be basic but pH cannot be higher than 9.5, temperature from 40 to 70 degrees C and alkali concentration (potassium hydroxide) below 1.1 mol L(-1). Secondary reactions have been detected, which are probably due to fluoride adsorption onto obtained oxides surface. Mechanism of reaction consists of several stages, involving solid fluoride dissolution and complexes decomposition. Hydrolysis kinetics has been modeled with classical crystal dissolution kinetics, based on mass transfer phenomena. PMID:17988794

  7. Colorimetric and fluorimetric response of Schiff base molecules towards fluoride anion, solution test kit fabrication, logical interpretations and DFT-D3 study.

    PubMed

    Ghosh, Pritam; Roy, Biswajit Gopal; Jana, Saibal; Mukhopadhyay, Subhra Kanti; Banerjee, Priyabrata

    2015-08-21

    Two newly synthesized Schiff base molecules are herein reported as anion sensors. -NO2 substituted receptor (P1) is comparatively more acidic and can sense F(-), OAc(-) and H2PO4(-), whereas -CN substituted receptor (P2) is less acidic and is selective for F(-) only. Reversible UV-Vis response for both receptors with F(-) can mimic multiple logic gate functions, and several complex electronic circuits based on XNOR, XOR, OR, AND, NOT and NOR logic operations with 'Write-Read-Erase-Read' options have been executed. Interesting 'turn on and off' fluorescence responses were noticed for the receptors with F(-). Intracellular F(-) detection as a diagnosis of non-skeletal fluorosis was successful using a fluorescence microscope with Candida albicans (prokaryotic cell, a diploid fungus) and pollen grains of Tecoma stans (eukaryotic cell) incubated in 10(-6) M fluoride-contaminated hand-pump water collected from Bankura, West Bengal, India. Furthermore, a solution test kit was fabricated for easy and selective detection of F(-) in an aqueous solvent. PMID:26190641

  8. Pictorial Analogies XI: Concentrations and Acidity of Solutions.

    ERIC Educational Resources Information Center

    Fortman, John J.

    1994-01-01

    Presents pictorial analogies of several concepts relating to solutions for chemistry students. These include concentration of solution, strength of solution, supersaturated solution, and conjugate acid-base pairs. Among the examples are comparison of acid strength to percentage of strong soldiers or making supersaturated solution analogous to a…

  9. Rapid analysis of acid in etching and pickling solutions

    SciTech Connect

    Tumbina, V.P.; Chinokalov, V.Ya.

    1995-02-01

    A computational method for determining sulfuric and hydrochloric acids in two-component etching solutions has been proposed. The method makes use of linear relationships, assuming that the sum of free and bound acid in solution remains constant.

  10. Reactive solute transport in acidic streams

    USGS Publications Warehouse

    Broshears, R.E.

    1996-01-01

    Spatial and temporal profiles of Ph and concentrations of toxic metals in streams affected by acid mine drainage are the result of the interplay of physical and biogeochemical processes. This paper describes a reactive solute transport model that provides a physically and thermodynamically quantitative interpretation of these profiles. The model combines a transport module that includes advection-dispersion and transient storage with a geochemical speciation module based on MINTEQA2. Input to the model includes stream hydrologic properties derived from tracer-dilution experiments, headwater and lateral inflow concentrations analyzed in field samples, and a thermodynamic database. Simulations reproduced the general features of steady-state patterns of observed pH and concentrations of aluminum and sulfate in St. Kevin Gulch, an acid mine drainage stream near Leadville, Colorado. These patterns were altered temporarily by injection of sodium carbonate into the stream. A transient simulation reproduced the observed effects of the base injection.

  11. 49 CFR 173.163 - Hydrogen fluoride.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 2 2011-10-01 2011-10-01 false Hydrogen fluoride. 173.163 Section 173.163... Hydrogen fluoride. (a) Hydrogen fluoride (hydrofluoric acid, anhydrous) must be packaged as follows: (1) In... filling ratio of 0.84. (b) A cylinder removed from hydrogen fluoride service must be condemned...

  12. 49 CFR 173.163 - Hydrogen fluoride.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Hydrogen fluoride. 173.163 Section 173.163... Hydrogen fluoride. (a) Hydrogen fluoride (hydrofluoric acid, anhydrous) must be packaged as follows: (1) In... filling ratio of 0.84. (b) A cylinder removed from hydrogen fluoride service must be condemned...

  13. 49 CFR 173.163 - Hydrogen fluoride.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 2 2014-10-01 2014-10-01 false Hydrogen fluoride. 173.163 Section 173.163... Hydrogen fluoride. (a) Hydrogen fluoride (hydrofluoric acid, anhydrous) must be packaged as follows: (1) In... filling ratio of 0.84. (b) A cylinder removed from hydrogen fluoride service must be condemned...

  14. 49 CFR 173.163 - Hydrogen fluoride.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 2 2013-10-01 2013-10-01 false Hydrogen fluoride. 173.163 Section 173.163... Hydrogen fluoride. (a) Hydrogen fluoride (hydrofluoric acid, anhydrous) must be packaged as follows: (1) In... filling ratio of 0.84. (b) A cylinder removed from hydrogen fluoride service must be condemned...

  15. 49 CFR 173.163 - Hydrogen fluoride.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Hydrogen fluoride. 173.163 Section 173.163... Hydrogen fluoride. (a) Hydrogen fluoride (hydrofluoric acid, anhydrous) must be packaged as follows: (1) In... filling ratio of 0.84. (b) A cylinder removed from hydrogen fluoride service must be condemned...

  16. Process for the extraction of strontium from acidic solutions

    DOEpatents

    Horwitz, E. Philip; Dietz, Mark L.

    1994-01-01

    The invention is a process for selectively extracting strontium values from aqueous nitric acid waste solutions containing these and other fission product values. The extractant solution is a macrocyclic polyether in an aliphatic hydrocarbon diluent containing a phase modifier. The process will selectively extract strontium values from nitric acid solutions which are up to 6 molar in nitric acid.

  17. Process for the extraction of strontium from acidic solutions

    DOEpatents

    Horwitz, E.P.; Dietz, M.L.

    1993-01-01

    The invention is a process for selectively extracting strontium values from aqueous nitric acid waste solutions containing these and other fission product values. The extractant solution is a macrocyclic polyether in an aliphatic hydrocarbon diluent containing a phase modifier. The process will selectively extract strontium values from nitric acid solutions which are up to 6 molar in nitric acid.

  18. Process for the extraction of strontium from acidic solutions

    DOEpatents

    Horwitz, E.P.; Dietz, M.L.

    1994-09-06

    The invention is a process for selectively extracting strontium values from aqueous nitric acid waste solutions containing these and other fission product values. The extractant solution is a macrocyclic polyether in an aliphatic hydrocarbon diluent containing a phase modifier. The process will selectively extract strontium values from nitric acid solutions which are up to 6 molar in nitric acid. 4 figs.

  19. Containment of nitric acid solutions of Plutonium-238

    NASA Astrophysics Data System (ADS)

    Reimus, M. A. H.; Silver, G. L.; Pansoy-Hjelvik, L.; Ramsey, K. B.

    1999-01-01

    The corrosion of various metals that could be used to contain nitric acid solutions of Pu-238 has been studied. Tantalum and tantalum/2.5% tungsten resisted the test solvent better than 304L stainless steel and several INCONEL alloys. The solvent used to imitate nitric acid solutions of Pu-238 contained 70% nitric acid, hydrofluoric acid, and ammonium hexanitratocerate.

  20. Systemic fluoride.

    PubMed

    Sampaio, Fábio Correia; Levy, Steven Marc

    2011-01-01

    There is substantial evidence that fluoride, through different applications and formulas, works to control caries development. The first observations of fluoride's effects on dental caries were linked to fluoride naturally present in the drinking water, and then from controlled water fluoridation programs. Other systemic methods to deliver fluoride were later suggested, including dietary fluoride supplements such as salt and milk. These systemic methods are now being questioned due to the fact that many studies have indicated that fluoride's action relies mainly on its post-eruptive effect from topical contact with the tooth structure. It is known that even the methods of delivering fluoride known as 'systemic' act mainly through a topical effect when they are in contact with the teeth. The effectiveness of water fluoridation in many geographic areas is lower than in previous eras due to the widespread use of other fluoride modalities. Nevertheless, this evidence should not be interpreted as an indication that systemic methods are no longer relevant ways to deliver fluoride on an individual basis or for collective health programs. Caution must be taken to avoid excess ingestion of fluoride when prescribing dietary fluoride supplements for children in order to minimize the risk of dental fluorosis, particularly if there are other relevant sources of fluoride intake - such as drinking water, salt or milk and/or dentifrice. Safe and effective doses of fluoride can be achieved when combining topical and systemic methods. PMID:21701196

  1. Hepatotoxicity Induced by Subchronic Exposure of Fluoride and Chlorpyrifos in Wistar Rats: Mitigating Effect of Ascorbic Acid.

    PubMed

    Raina, Rajinder; Baba, Naseer Ahmad; Verma, Pawan K; Sultana, Mudasir; Singh, Maninder

    2015-08-01

    The aim of the study was to investigate the ameliorative properties of ascorbic acid against the subchronic effect of co-exposure of fluoride (F) and chlorpyrifos (CPF) on oxidative damage markers such as lipid peroxidation (MDA) and antioxidant defense system in the liver of adult Wistar rats. The animal groups were provided with either vehicle or ascorbic acid (60 mg/kg, b.w.) or NOAEL dose of fluoride (1 ppm) or CPF (1 mg/kg, b.w.) or ten times of such doses orally alone and in combination or pre-treated with ascorbic acid along with co-exposure of F and CPF every consecutive day for 28 days. Hepatic damage marker analysis in blood revealed that aspartate and alanine aminotransferases, alkaline phosphatase, and lactate dehydrogenase were significantly (P < 0.05) increased with single or combined exposure of F or CPF at either dose levels. Significant increased oxidative damage of hepatocytes as indicated by increased MDA levels with decrease in tissue ascorbate and free radical scavenging enzymes like catalase, superoxide dismutase, and glutathione peroxidase was observed in groups treated with either F or CPF as well as in combinedly treated animals as compared to control animals. Supplementation of ascorbic acid restored the hepatic specific marker enzymes in blood following co-exposure of F and CPF at lower doses which were otherwise increased in the F and CPF co-exposed rats. The results show that ascorbic acid supplementation with F and CPF prevents or diminishes the hepatic damage in rats co-exposed to toxicants and may act as a putative protective agent against toxicant-induced liver tissue injury. PMID:25669166

  2. Solution High-Energy Burst Assembly (SHEBA) results from subprompt critical experiments with uranyl fluoride fuel

    SciTech Connect

    Cappiello, C.C.; Butterfield, K.B.; Sanchez, R.G.; Bounds, J.A.; Kimpland, R.H.; Damjanovich, R.P.; Jaegers, P.J.

    1997-08-01

    Experiments were performed to measure a variety of parameters for SHEBA: behavior of the facility during transient and steady-state operation; characteristics of the SHEBA fuel; delayed-critical solution height vs solution temperature; initial reactor period and reactivity vs solution height; calibration of power level vs reactor power instrumentation readings; flux profile in SHEBA; radiation levels and neutron spectra outside the assembly for code verification and criticality alarm and dosimetry purposes; and effect on reactivity of voids in the fuel.

  3. In vivo remineralization of acid-etched enamel in non-brushing areas as influenced by fluoridated orthodontic adhesive and toothpaste.

    PubMed

    Praxedes-Neto, Otávio José; Borges, Boniek Castillo Dutra; Florêncio-Filho, Cícero; Farias, Arthur Costa Rodrigues; Drennan, John; De Lima, Kenio Costa

    2012-07-01

    This study aimed to evaluate the in vivo remineralization of acid-etched enamel in non-brushing areas as influenced by fluoridated orthodontic adhesive and toothpaste. One hundred and twenty teeth from 30 volunteers were selected. The teeth were assigned to four treatments: no treatment (negative control); 37% phosphoric acid-etching (PAE) (positive control); PAE + resin-modified glass ionomer cement (RMGIC); and, PAE + composite resin. Patients brushed teeth with fluoridated (n = 15) or non-fluoridated (n = 15) toothpastes, so that etched enamel was protected with screens and it was not in contact with the brush bristles. Remineralization was evaluated by means of laser fluorescence (LF), environmental scanning electronic microscopy, and energy dispersive spectrometry after extraction. The LF means were compared by means of Wilcoxon and Mann Whitney tests. Environmental scanning electron microscopy scores were compared among the groups using a Kruskal Wallis test, whereas the Ca/P ratio was evaluated by means of an Analysis of Variance with subparcels (treatments) and Tukey's post-hoc test. There were no statistically significant differences between the tooth pastes and between the orthodontic adhesives evaluated. Most teeth presented only partial enamel remineralization. Therefore, the fluoride released by the RMGIC was not enough to cause increased crystal regrowth in the acid-etched enamel. The use of fluoridated toothpaste did not provide positive additional effect. PMID:22298375

  4. Hopping rates and concentrations of mobile fluoride ions in Pb1-xSnxF2 solid solutions

    NASA Astrophysics Data System (ADS)

    Ahmad, Mohamad M.; Yamada, Koji

    2007-09-01

    In the present paper, the ion dynamics and relaxation of fluoride ions in Pb1-xSnxF2 (with x =0.2-0.6) solid solutions, prepared by mechanochemical milling, are studied in the conductivity formalism over wide ranges of frequencies and temperatures. The conductivity spectra of the investigated materials are analyzed by the Almond-West (AW) power-law model. The estimated values of the hopping rates and the dc conductivity of different compositions are thermally activated with almost the same activation energy. The calculated values of the concentration of mobile ions, nc, are almost independent of temperature and composition for x =0.2-0.4. The maximum value of nc is obtained for the x =0.6 sample, although it does not show the maximum conductivity. Therefore, the composition dependence of the ionic conductivity of these solid solutions could be explained based on the extracted parameters. The results presented in the current work indicate that the AW model represents a reasonable approximation of the overall frequency-dependent conductivity behavior of the investigated materials. The conductivity spectra at different temperatures for each composition are successfully scaled to a single master curve, indicating a temperature-independent relaxation mechanism. For different compositions, however, the conductivity spectra cannot be scaled properly, indicating composition-dependent relaxation dynamics.

  5. pH effect of coagulation bath on the characteristics of poly(acrylic acid)-grafted and poly(4-vinylpyridine)-grafted poly(vinylidene fluoride) microfiltration membranes.

    PubMed

    Ying, Lei; Zhai, Guangqun; Winata, A Y; Kang, E T; Neoh, K G

    2003-09-15

    The poly(acrylic acid)-graft-poly(vinylidene fluoride) (PAAc-g-PVDF) and poly(4-vinylpyridine)-graft-poly(vinylidene fluoride) (P4VP-g-PVDF) copolymers were obtained by thermally induced molecular graft copolymerization of acrylic acid (AAc) and 4-vinylpyridine (4VP), respectively, with the ozone-pretreated poly(vinylidene fluoride) (PVDF) in N-methyl-2-pyrrolidone (NMP) solution. Microfiltration (MF) membranes were prepared from the respective copolymers by phase inversion in aqueous media. The effects of pH of the coagulation bath on the physicochemical and morphological characteristics of the membranes were investigated. The surface compositions of the membranes were determined by X-ray photoelectron spectroscopy (XPS). The surface graft concentration of the AAc polymer for the PAAc-g-PVDF MF membrane increased with decreasing pH value of the coagulation bath. Completely opposite pH-dependent behavior was observed for the surface graft concentration of the 4VP polymer in the P4VP-g-PVDF MF membranes. A substantial increase in mean pore size was observed for the PAAc-g-PVDF MF membranes cast in basic coagulation baths of increasing pH. In the case of the P4VP-g-PVDF MF membranes, a substantial increase in mean pore size was observed for membranes cast in low pH (acidic) baths. The permeation rate of aqueous solutions through the PAAc-g-PVDF and P4VP-g-PVDF MF membranes exhibited a reversible dependence on the pH of the solution, with the membranes cast near the neutral pH exhibiting the highest sensitivity to changes in permeate pH. PMID:12962674

  6. [Supervised daily mouth-rinsing with a 0.023% weak acid NaF solution. Results of a school-based program started at the age of four].

    PubMed

    Hirokawa, K

    1990-09-01

    The principal means of preventing dental caries in Japan are dietary control and tooth-brushing. However, these measures in public health have not been conducive to a definite reduction of dental caries, while the use of fluorides has led to a remarkable and rapid decrease in caries prevalence. Fluoride mouth-rinsing are usually incorporated into the school-based programs. Many trials were carried out in the elementary schools and a 30-50% reduction in caries increment was reported. To provide greater benefits to the permanent teeth, therefore, it is suggested that fluoride mouth-rinsing should be started earlier in the age. However, fluoride mouth-rinsing is not recommended generally for preschool children who cannot rinse out their mouths well. Among the solutions for mouth-rinsing, there are some different types in the fluoride used, the fluoride content and the frequency of application. The most commonly used fluoride mouth-rinsing solution for daily use is 0.05-0.1% NaF in neutral or weak acid solution. The present study was conducted to confirm the fluoride mouth-rinsing with a lower content of fluoride solution would have an additional cariostatic effect if it is started at the age of four. Participants rinsed with a weak acid (pH 5.0) NaF solution (100 ppm F) for 30 seconds 5 times a week. After all, they were received benefits from fluoride before eruption of the permanent teeth. In the present study, it was demonstrated that the effect of dental caries inhibition was greater than those in the previous study. Especially, many lower first molars were free from dental caries. After 7 years, the caries reduction rates were about 48% in DMFT and 54% in DMFS respectively. So far as 4 first molars, the caries reduction rate was about 41% in DMFT, and this figure was almost the same as all DMFT. It was recommended that the fluoride mouth-rinsing program with a lower fluoride content solution should be started at the age of four. PMID:2134272

  7. Optimizing the crystallinity and acidity of H-SAPO-34 by fluoride for synthesizing Cu/SAPO-34 NH3-SCR catalyst.

    PubMed

    Ma, Jing; Si, Zhichun; Wu, Xiaodong; Weng, Duan; Ma, Yue

    2016-03-01

    A series of H-SAPO-34 zeolites were synthesized by a hydrothermal method in fluoride media. The as-synthesized H-SAPO-34 zeolites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 physisorption, temperature-programmed desorption of NH3 (NH3-TPD) and nuclear magnetic resonance (NMR) measurements. The results showed that a certain concentration of F(-) anions promoted the nucleation and crystallization of H-SAPO-34. The H-SAPO-34 synthesized in the fluoride media showed high crystallinity, uniform particle size distribution, large specific surface area and pore volume, and enhanced acidity. Therefore, Cu/SAPO-34 based on the fluoride-assisted zeolite showed a broadened temperature window for the selective catalytic reduction of NO by NH3 (NH3-SCR) reaction due to the enhanced acidity of the zeolite and the improved dispersion of copper species. PMID:26969071

  8. Fluoride in UK rivers.

    PubMed

    Neal, Colin; Neal, Margaret; Davies, Helen; Smith, Jennifer

    2003-10-01

    Fluoride concentrations in eastern UK rivers (the Humber, Tweed, Wear, Great Ouse and Thames) are described based on information collected within the Land-Ocean Interaction Study (LOIS) and by the Environment Agency (EA) of England and Wales. The results show varied fluoride concentrations across the region, with a range from <0.01 to >10 mg l(-1); and mean, median and range in mean concentrations of 0.30, 0.21 and 0.05-3.38 mg l(-1) (excluding one outlier point), respectively. Within the main rivers and tributaries, the mean fluoride concentration varied from approximately 0.5 to over 2 mg l(-1) and the highest values occurred within the Don basin (Don, Dearne and Rother) and parts of the Trent basin (upper Tame and mid-upper Derbyshire Derwent) in highly industrialised and urbanised areas (Sheffield and Rotherham in the Don basin; Birmingham and Derby on the Trent). For localised inputs to the rivers, fluoride concentrations were slightly higher, and considerably higher in one outlier case. Correspondingly, the other rivers examined typically had mean fluoride concentrations between approximately 0.2 and 0.5 mg l(-1), but fluoride concentrations were lower in the headwater areas. As there is much less information on fluoride levels in upland areas, extensive data collected as part of an acid waters survey are used to show that fluoride concentrations are generally less than 0.1 mg l(-1) for the upland UK. The data are summarised in terms of both fluoride concentrations and flux, and the values are cross-referenced to other determinands collected within LOIS. The high positive correlation with boron and negative correlation with flow show the importance of point source (sewage) inputs of fluoride, while strong positive correlations between fluoride and barium indicate the relative importance of vein mineralisation in the bedrock in supplying fluoride to the waters of the Yorkshire Ouse and its tributaries. There seems to be some process that limits the fluoride

  9. Reactivity of fluoride dentifrices with artificial caries. III. Quantitative aspects of acquired acid resistance (AAR): F uptake, retention, surface hardening and remineralization.

    PubMed

    White, D J

    1991-01-01

    A pH cycling remineralization/dimineralization model has been used to compare remineralization and acid resistance benefits provided by commercial MFP and NaF dentifrices. Test results show that fluoride dentifrice systems were effective in enhancing lesion remineralization and providing acquired acid resistance (AAR) to carious lesions, with AAR benefits considerably greater in magnitude. Fluoride uptake into the carious lesions was associated with remineralization and AAR benefits. Dentifrices containing the highest levels of soluble ionic fluoride were found most effective in this protocol with MFP dentifrices showing significantly less activity. MFP dentifrice efficacy was enhanced slightly in calcium abrasives. The enhanced activity could be explained by increased levels of background ionic fluoride in the formulations. In contrast to the latter effects, a dual-active NaF+MFP dentifrice in a calcium abrasive system exhibited decreased efficacy relative to a silica abrasive formulation due to incompatibility of free fluoride ion. Comparison of analytical techniques for measurement of AAR in shallow lesions demonstrates that surface microhardness methods match radiographic measures and are thus adequate for ICT measurement of cariogenicity and F remineralization. PMID:1812910

  10. Solution High-Energy Burst Assembly (SHEBA) results from subprompt critical experiments with uranyl fluoride fuel

    SciTech Connect

    Cappiello, C.C.; Butterfield, K.B.; Sanchez, R.G.

    1997-10-01

    The Solution High-Energy Burst Assembly (SHEBA) was originally constructed during 1980 and was designed to be a clean free-field geometry, right-circular, cylindrically symmetric critical assembly employing U(5%)O{sub 2}F{sub 2} solution as fuel. A second version of SHEBA, employing the same fuel but equipped with a fuel pump and shielding pit, was commissioned in 1993. This report includes data and operating experience for the 1993 SHEBA only. Solution-fueled benchmark work focused on the development of experimental measurements of the characterization of SHEBA; a summary of the results are given. A description of the system and the experimental results are given in some detail in the report. Experiments were designed to: (1) study the behavior of nuclear excursions in a low-enrichment solution, (2) evaluate accidental criticality alarm detectors for fuel-processing facilities, (3) provide radiation spectra and dose measurements to benchmark radiation transport calculations on a low-enrichment solution system similar to centrifuge enrichment plants, and (4) provide radiation fields to calibrate personnel dosimetry. 15 refs., 37 figs., 10 tabs.

  11. Nitric acid uptake by sulfuric acid solutions under stratospheric conditions - Determination of Henry's Law solubility

    NASA Technical Reports Server (NTRS)

    Reihs, Christa M.; Golden, David M.; Tolbert, Margaret A.

    1990-01-01

    The uptake of nitric acid by sulfuric acid solutions representative of stratospheric particulate at low temperatures was measured to determine the solubility of nitric acid in sulfuric acid solutions as a function of H2SO4 concentration and solution temperature. Solubilities are reported for sulfuric acid solutions ranging from 58 to 87 wt pct H2SO4 over a temperature range from 188 to 240 K, showing that, in general, the solubility of nitric acid increases with decreasing sulfuric acid concentration and with decreasing temperature. The measured solubilities indicate that nitric acid in the global stratosphere will be found predominantly in the gas phase.

  12. Effects of fluoride on in vitro enamel demineralization analyzed by ¹⁹F MAS-NMR.

    PubMed

    Mohammed, N R; Kent, N W; Lynch, R J M; Karpukhina, N; Hill, R; Anderson, P

    2013-01-01

    The mechanistic action of fluoride on inhibition of enamel demineralization was investigated using (19)F magic angle spinning nuclear magnetic resonance (MAS-NMR). The aim of this study was to monitor the fluoride-mineral phase formed on the enamel as a function of the concentration of fluoride ions [F(-)] in the demineralizing medium. The secondary aim was to investigate fluorapatite formation on enamel in the mechanism of fluoride anti-caries efficacy. Enamel blocks were immersed into demineralization solutions of 0.1 M acetic acid (pH 4) with increasing concentrations of fluoride up to 2,262 ppm. At and below 45 ppm [F(-)] in the solution, (19)F MAS-NMR showed fluoride-substituted apatite formation, and above 45 ppm, calcium fluoride (CaF2) formed in increasing proportions. Further increases in [F(-)] caused no further reduction in demineralization, but increased the proportion of CaF2 formed. Additionally, the combined effect of strontium and fluoride on enamel demineralization was also investigated using (19)F MAS-NMR. The presence of 43 ppm [Sr(2+)] in addition to 45 ppm [F(-)] increases the fraction of fluoride-substituted apatite, but delays formation of CaF2 when compared to the demineralization of enamel in fluoride-only solution. PMID:23712030

  13. A simple ratiometric and colorimetric chemosensor for the selective detection of fluoride in DMSO buffered solution

    NASA Astrophysics Data System (ADS)

    Niu, Hu; Shu, Qinghai; Jin, Shaohua; Li, Bingjun; Zhu, Jiaping; Li, Lijie; Chen, Shusen

    2016-01-01

    A derivative of squaramide (cyclobuta[b]quinoxaline-1, 2(3H, 8H)-dione) has been synthesized for the ratiometric and colorimetric sensing of F- in aqueous solution in competitive fashion. With F-, probe 1 showed a highly selective naked-eye detectable color change along with a characteristic UV-Vis absorbance over other tested ions, which probably originates from the deprotonation occurred between 1 and F-, as proved by the 1H NMR titration experiments and DFT calculations.

  14. Chemical transformations of CO2 in trifluoroacetic acid solutions

    NASA Astrophysics Data System (ADS)

    Vishnetskaya, M. V.; Ivanova, M. S.; Svichkarev, O. M.; Budynina, E. M.; Mel'nikov, M. Ya.

    2013-05-01

    It is established that a conversion reaction of carbon dioxide takes place at room temperature and atmospheric pressure in aqueous solutions of trifluoroacetic acid (TFA), which leads to the formation of oxalic acid and heavier polymerized products.

  15. Zirconium-carbon hybrid sorbent for removal of fluoride from water: oxalic acid mediated Zr(IV) assembly and adsorption mechanism

    PubMed Central

    Halla, Velazquez-Jimenez Litza; Hurt Robert, H; Juan, Matos; Rene, Rangel-Mendez Jose

    2014-01-01

    When activated carbon (AC) is modified with zirconium(IV) by impregnation or precipitation, the fluoride adsorption capacity is typically improved. There is significant potential to improve these hybrid sorbent by controlling the impregnation conditions, which determine the assembly and dispersion of the Zr phases on carbon surfaces. Here, commercial activated carbon was modified with Zr(IV) together with oxalic acid (OA) used to maximize the zirconium dispersion and enhance fluoride adsorption. Adsorption experiments were carried out at pH 7 and 25 °C with a fluoride concentration of 40 mg L−1. The OA/Zr ratio was varied to determine the optimal conditions for subsequent fluoride adsorption. The data was analyzed using the Langmuir and Freundlich isotherm models. FTIR, XPS and the surface charge distribution were performed to elucidate the adsorption mechanism. Potentiometric titrations showed that the modified activated carbon (ZrOx-AC) possesses positive charge at pH lower than 7, and FTIR analysis demonstrated that zirconium ions interact mainly with carboxylic groups on the activated carbon surfaces. Moreover, XPS analysis demonstrated that Zr(IV) interacts with oxalate ions, and the fluoride adsorption mechanism is likely to involve –OH− exchange from zirconyl oxalate complexes. PMID:24359079

  16. Quantitative Assessment of Fluoride Release and Recharge Ability of Different Restorative Materials in Different Media: An in Vitro Study

    PubMed Central

    Pathak, Anuradha; Bajwa, Navroop Kaur; Sidhu, Haridarshan Singh

    2014-01-01

    Objective: To measure fluoride release and recharge ability of restorative materials in deionised water, artificial saliva and lactic acid. Materials and Methods: Pellets were prepared from GC2, Ketac N100 and Beautifil II. Each pellets were individually immersed in 10 ml deionised water, artificial saliva or lactic acid as per respective subgroup for 24 h and then elutes were collected. Specimens were reimmersed in respective container. Fluoride released was analysed after 24 h, 7th and 15th day. On 15th day all specimens were exposed to 1.23% APF gel and fluoride release in respective solution was measured on 16th, 22nd, 30th day. Result: Fluoride release was more after 24 h for all materials in all media then decrease gradually. GC2 shows more fluoride release than Ketac N100 at 24 hours and on 7th day but onwards Ketac N100 released significantly more fluoride. Beautifil II showed least fluoride release at all measured intervals in all media. Order of fluoride release in media was lactic acid > deionised water > artificial saliva for all materials. Conclusion: GICs are smart material which release more fluoride when environment become more acidic and also show tendency to recharge which helps clinically in caries risk children. PMID:25654027

  17. Sodium and potassium currents in squid axons perfused with fluoride solutions.

    PubMed

    Chandler, W K; Meves, H

    1970-12-01

    1. Axons perfused with a K-free solution containing 300 mM-NaF + sucrose to maintain isotonicity (referred to as 300 mM-NaF) and placed in K-free artificial sea-water usually depolarized spontaneously to around 0 mV. The membrane could be hyperpolarized to -70 to -100 mV with a small inwardly directed current; in one experiment the holding current was measured and was found to be less than 20 muA/cm(2).2. Membrane currents associated with a step depolarization from a potential which varied from -70 to -100 mV showed three phases: (a) an initial capacitative transient, (b) an early current which was inward for small depolarizations and outward for large ones, (c) a smaller maintained current. The currents in (b) and (c) are considered to be carried by Na ions since they both reversed direction at the same potential which was on the average within 0.3 mV of the equilibrium potential for Na ions, 10.4 mV at 0 degrees C and 11 mV at 16.5 degrees C, as estimated from measurements made with a cation-sensitive glass electrode.3. The instantaneous current-voltage relation was determined at the time of peak current and at the end of a long prepulse when the current had reached a steady level. In both cases the curve was approximately linear with a slight deviation at negative potentials.4. Prepulses, lasting 11-48 msec, to a potential of 33-64 mV (0-3.5 degrees C) produced a shift in the equilibrium potential of 0.6-3.3 mV. This small change can be accounted for by assuming that Na ions accumulate in the Frankenhaeuser-Hodgkin space.5. Both peak and steady-state components of Na current were blocked by tetrodotoxin (10(-7) g/ml.) in the external solution.6. The values of peak and steady-state Na conductance were strongly voltage-dependent for V less than -20 mV; for V more negative than -40 mV the peak and steady-state values increased e-fold for a change in potential of 4 and 6-8 mV respectively. At positive potentials the peak conductance was relatively independent of

  18. High concentration aqueous sodium fluoride certified reference materials for forensic use certified by complexometric titration.

    PubMed

    Archer, Marcellé; Brits, Martin; Prevoo-Franzsen, Désirée; Quinn, Laura

    2015-04-01

    Sodium fluoride in concentrations of 1 to 2 % is used to prevent the formation of ethanol in blood and urine samples that are to be analysed for ethanol content. The majority of such samples form part of forensic investigations into alleged drunken driving. In South Africa, the laboratory performing the tests is required to prove that the sodium fluoride concentration in the blood samples is above 1 g/100 ml on receipt. This is done by using a fluoride ion-selective electrode calibrated with external aqueous solutions of sodium fluoride. The National Metrology Institute of South Africa (NMISA) prepares sodium fluoride solutions in concentrations from 0.3 to 3.0 g/100 ml. No other certified sodium fluoride reference solutions in these concentrations are available commercially. The sodium fluoride is certified by precipitation of the fluoride as lead chlorofluoride (PbClF) through the addition of a known excess of lead nitrate. The excess lead is back-titrated with ethylenediamine tetraacetic acid (EDTA) using a photometric electrode to detect the endpoint. Aqueous sodium fluoride solutions are prepared and the concentrations verified by the precipitation/back-titration method. This paper shows the application of a classical complexometric method to the certification of reference materials and describes the procedures for the preparation of the sodium fluoride solutions, verification of the concentrations, homogeneity and stability by primary titrimetry. It also briefly covers the calculation of uncertainty, the establishment of traceability and the quality control measures applied to ensure the quality of the certified reference materials (CRMs). PMID:25326884

  19. Process for the recovery of strontium from acid solutions

    DOEpatents

    Horwitz, E. Philip; Dietz, Mark L.

    1992-01-01

    The invention is a process for selectively extracting strontium and technetium values from aqueous nitric acid waste solutions containing these and other fission product values. The extractant is a macrocyclic polyether in a diluent which is insoluble in water, but which will itself dissolve a small amount of water. The process will extract strontium and technetium values from nitric acid solutions which are up to 6 molar in nitric acid.

  20. Process for the recovery of strontium from acid solutions

    DOEpatents

    Horwitz, E.P.; Dietz, M.L.

    1992-03-31

    The invention is a process for selectively extracting strontium and technetium values from aqueous nitric acid waste solutions containing these and other fission product values. The extractant is a macrocyclic polyether in a diluent which is insoluble in water, but which will itself dissolve a small amount of water. The process will extract strontium and technetium values from nitric acid solutions which are up to 6 molar in nitric acid. 5 figs.

  1. Process for the recovery of strontium from acid solutions

    SciTech Connect

    Horwitz, E.P.; Dietz, M.L.

    1990-12-31

    The invention is a process for selectively extracting strontium and technetium values from aqueous nitric acid waste solutions containing these and other fission product values. The extractant is a macrocyclic polyether in a diluent which is insoluble in water, but which will itself dissolve a small amount of water. The process will extract strontium and technetium values from nitric acid solutions which are up to 6 molar in nitric acid.

  2. Dentifrice Fluoride

    NASA Astrophysics Data System (ADS)

    Rakita, Philip E.

    2004-05-01

    The effectiveness of the fluoride ion in lowering the incidence of dental caries is a major factor in the field of dental health. Observations and research studies in the first half of the 20th century have lead to the widespread adoption of fluoridated water and the use of inorganic fluoride compounds in oral care products, such as toothpaste and dental rinses. This article provides a brief review of the types of compounds used and the chemistry involved.

  3. REDUCTION OF ACIDITY OF NITRIC ACID SOLUTIONS BY USE OF FORMALDEHYDE

    DOEpatents

    Healy, T.V.

    1958-05-20

    A continuous method is described of concentrating by evaporation and reducing the nitrate ion content of an aqueous solution of metallic salts containing nitric acid not in excess of 8N. It consists of heating the solution and then passing formaldehyde into the heated solution to bring about decomposition of the nitric acid. The evolved gases containing NO are contacted countercurrently with an aqueous metal salt solution containing nitric acid in excess of 8N so as to bring about decomposition of the nitric acid and lower the normality to at least 8N, whereupon it is passed into the body of heated solution.

  4. Bottled Water and Fluoride

    MedlinePlus

    ... Fluoridation Journal Articles for Community Water Fluoridation Bottled Water Recommend on Facebook Tweet Share Compartir Consumers drink ... questions about bottled water and fluoride. Does bottled water contain fluoride? Bottled water products may contain fluoride, ...

  5. Mechanisms of fluoride release in sediments of Argentina's central region.

    PubMed

    Borgnino, L; Garcia, M G; Bia, G; Stupar, Y V; Le Coustumer, Ph; Depetris, P J

    2013-01-15

    We analyze the sources and mechanisms that control the release of fluoride from sediments collected from two types of aquatic reservoirs in the central region of Argentina: 1) mountainous rivers draining crystalline rocks from the Sierras Pampeanas ranges, and 2) shallow aquifers in loessic sediments. The assessment was performed on the basis of experimental work and the study of chemical and mineralogical characteristics of sediments in contact with F-rich waters of the studied region. The chemical and mineralogical compositions of sediments were analyzed by ICP/OES, DRX, and SEM-EDS. Batch experiments were conducted to evaluate the kinetics of fluoride release under variable pH and ionic composition of the solution. The enhanced release of fluoride at more acidic pH, the inhibition of release in Ca-rich solutions and the positive significant linear trends between Ca(2+) and fluoride concentrations suggest that the dissolution of a Ca/F-bearing phase (like fluorapatite) strongly controls the dynamics of fluoride in the early stages of water-sediment interaction, particularly under acidic conditions. Calculations revealed that the dissolution of an amount of FAp equivalent to that estimated in the studied sediments may widely account for the values measured in the leaching experiments at pH6, whatever the dominant cation in the solution. Under such conditions, dissolution of FAp (present as coatings onto glass surfaces or as detritic grains) is likely the major primary source of fluorine in the studied sediments. Contribution from biotite may be also considered as a source in fluvial sediments. When adequate surfaces are present the released anions may partially be scavenged from the solution by adsorption at acidic pH. Increasing alkalinity in the aquatic reservoirs may then release the adsorbed fluoride through desorption or through competition with other anionic species. Comparing both mechanisms, dissolution predominates at lower pH while desorption is the main

  6. Method for liquid chromatographic extraction of strontium from acid solutions

    DOEpatents

    Horwitz, E. Philip; Dietz, Mark L.

    1992-01-01

    A method and apparatus for extracting strontium and technetium values from biological, industrial and environmental sample solutions using a chromatographic column is described. An extractant medium for the column is prepared by generating a solution of a diluent containing a Crown ether and dispersing the solution on a resin substrate material. The sample solution is highly acidic and is introduced directed to the chromatographic column and strontium or technetium is eluted using deionized water.

  7. Decomposition Studies of Triphenylboron, Diphenylborinic Acid and Phenylboric Acid in Aqueous Alkaline Solutions Containing Copper

    SciTech Connect

    Crawford, C.L.; Peterson, R. A.

    1997-02-11

    This report documents the copper-catalyzed chemical kinetics of triphenylboron, diphenylborinic acid and phenylboric acid (3PB, 2PB and PBA) in aqueous alkaline solution contained in carbon-steel vessels between 40 and 70 degrees C.

  8. Magnesium fluoride recovery method

    DOEpatents

    Gay, Richard L.; McKenzie, Donald E.

    1989-01-01

    A method of obtaining magnesium fluoride substantially free from radioactive uranium from a slag containing the same and having a radioactivity level of at least about 7000 pCi/gm. The slag is ground to a particle size of about 200 microns or less. The ground slag is contacted with an acid under certain prescribed conditions to produce a liquid product and a particulate solid product. The particulate solid product is separated from the liquid and treated at least two more times with acid to produce a solid residue consisting essentially of magnesium fluoride substantially free of uranium and having a residual radioactivity level of less than about 1000 pCi/gm. In accordance with a particularly preferred embodiment of the invention a catalyst and an oxidizing agent are used during the acid treatment and preferably the acid is sulfuric acid having a strength of about 1.0 Normal.

  9. Nylon Dissolution in Nitric Acid Solutions

    SciTech Connect

    KESSINGER, GLENF.

    2004-06-16

    H Area Operations is planning to process Pu-contaminated uranium scrap in support of de-inventory efforts. Nylon bags will be used to hold materials to be dissolved in H-Canyon. Based on this set of twelve nylon dissolutions, it is concluded that (when other variables are held constant): increased acid concentration results in increased dissolution rates; increased acid concentration results in a lower dissolution onset temperature; little, if any, H plus is consumed during the depolymerization process; and 2.0-3.0 M HNO3, with 0.025 M KF and 2 g/L B, is satisfactory for the dissolution of nylon bag materials to be used during H-Canyon processing.

  10. Do Fluoride Ions Protect Teeth?

    ERIC Educational Resources Information Center

    Parkin, Christopher

    1998-01-01

    Begins with the procedure and results from an investigation on the effect of fluoride on the reaction between eggshell (substitute teeth) and dilute ethanoic acid. Describes an elegantly modified and improvised apparatus. (DDR)

  11. Raman spectra of amino acids and their aqueous solutions

    NASA Astrophysics Data System (ADS)

    Zhu, Guangyong; Zhu, Xian; Fan, Qi; Wan, Xueliang

    2011-03-01

    Amino acids are the basic "building blocks" that combine to form proteins and play an important physiological role in all life-forms. Amino acids can be used as models for the examination of the importance of intermolecular bonding in life processes. Raman spectra serve to obtain information regarding molecular conformation, giving valuable insights into the topology of more complex molecules (peptides and proteins). In this paper, amino acids and their aqueous solution have been studied by Raman spectroscopy. Comparisons of certain values for these frequencies in amino acids and their aqueous solutions are given. Spectra of solids when compared to those of the solute in solution are invariably much more complex and almost always sharper. We present a collection of Raman spectra of 18 kinds of amino acids ( L-alanine, L-arginine, L-aspartic acid, cystine, L-glutamic acid, L-glycine, L-histidine, L-isoluecine, L-leucine, L-lysine, L-phenylalanine, L-methionone, L-proline, L-serine, L-threonine, L-tryptophan, L-tyrosine, L-valine) and their aqueous solutions that can serve as references for the interpretation of Raman spectra of proteins and biological materials.

  12. Polymerization of beta-amino acids in aqueous solution

    NASA Technical Reports Server (NTRS)

    Liu, R.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

    1998-01-01

    We have compared carbonyl diimidazole (CDI) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC) as activating agents for the oligomerization of negatively-charged alpha- and beta-amino acids in homogeneous aqueous solution. alpha-Amino acids can be oligomerized efficiently using CDI, but not by EDAC. beta-Amino acids can be oligomerized efficiently using EDAC, but not by CDI. Aspartic acid, an alpha- and beta-dicarboxylic acid is oligomerized efficiently by both reagents. These results are explained in terms of the mechanisms of the reactions, and their relevance to prebiotic chemistry is discussed.

  13. Fluoride Programs in the School Setting: Preventive Dental Health.

    ERIC Educational Resources Information Center

    Rebich, Theodore, Jr.; And Others

    1982-01-01

    Two types of school-based programs that increase students' use of fluoride for preventive dental health are described. In fluoride mouthrinse programs, teachers give their students a fluoride solution once a week in a paper cup. In areas where the level of fluoride in the water supply is insufficient, the flouride tablet program is used. (JN)

  14. Vacuum-jacketed hydrofluoric acid solution calorimeter

    USGS Publications Warehouse

    Robie, R.A.

    1965-01-01

    A vacuum-jacketed metal calorimeter for determining heats of solution in aqueous HF was constructed. The reaction vessel was made of copper and was heavily gold plated. The calorimeter has a cooling constant of 0.6 cal-deg -1-min-1, approximately 1/4 that of the air-jacketed calorimeters most commonly used with HF. It reaches equilibrium within 10 min after turning off the heater current. Measurements of the heat of solution of reagent grade KCl(-100 mesh dried 2 h at 200??C) at a mole ratio of 1 KCl to 200 H2O gave ??H = 4198??11 cal at 25??C. ?? 1965 The American Institute of Physics.

  15. Method for incorporating radioactive phosphoric acid solutions in concrete

    DOEpatents

    Wolf, Gary A [Kennewick, WA; Smith, Jeffrey W [Lancaster, OH; Ihle, Nathan C [Walla Walla, WA

    1984-01-01

    A method for incorporating radioactive phosphoric acid solutions in concrete is described wherein the phosphoric acid is reacted with Ca(OH).sub.2 to form a precipitate of hydroxyapatite and the hydroxyapatite is mixed with portland cement to form concrete.

  16. Method for incorporating radioactive phosphoric acid solutions in concrete

    DOEpatents

    Wolf, G.A.; Smith, J.W.; Ihle, N.C.

    1982-07-08

    A method for incorporating radioactive phosphoric acid solutions in concrete is described wherein the phosphoric acid is reacted with Ca(OH)/sub 2/ to form a precipitate of hydroxyapatite and the hydroxyapatite is mixed with Portland cement to form concrete.

  17. Improved method for extracting lanthanides and actinides from acid solutions

    DOEpatents

    Horwitz, E.P.; Kalina, D.G.; Kaplan, L.; Mason, G.W.

    1983-07-26

    A process for the recovery of actinide and lanthanide values from aqueous acidic solutions uses a new series of neutral bi-functional extractants, the alkyl(phenyl)-N,N-dialkylcarbamoylmethylphosphine oxides. The process is suitable for the separation of actinide and lanthanide values from fission product values found together in high-level nuclear reprocessing waste solutions.

  18. RECOVERY OF ACTINIDES FROM AQUEOUS NITRIC ACID SOLUTIONS

    DOEpatents

    Ader, M.

    1963-11-19

    A process of recovering actinides is presented. Tetravalent actinides are extracted from rare earths in an aqueous nitric acid solution with a ketone and back-extracted from the ketone into an aqueous medium. The aqueous actinide solution thus obtained, prior to concentration by boiling, is sparged with steam to reduce its ketone to a maximum content of 3 grams per liter. (AEC)

  19. Phosphorylation of Glyceric Acid in Aqueous Solution Using Trimetaphosphate

    NASA Technical Reports Server (NTRS)

    Kolb, Vera; Orgel, Leslie E.

    1996-01-01

    The phosphorylation of glyceric acid is an interesting prebiotic reaction because it converts a simple, potentially prebiotic organic molecule into phosphate derivatives that are central to carbohydrate metabolism. We find that 0.05 M glyceric acid in the presence of 0.5 M trimetaphosphate in alkaline solution gives a mixture of 2- and 3-phosphoglyceric acids in combined yields of up to 40%.

  20. Polymorphic Crystallization and Crystalline Reorganization of Poly(l-lactic acid)/Poly(d-lactic acid) Racemic Mixture Influenced by Blending with Poly(vinylidene fluoride).

    PubMed

    Yu, Chengtao; Han, Lili; Bao, Jianna; Shan, Guorong; Bao, Yongzhong; Pan, Pengju

    2016-08-18

    The effects of poly(vinylidene fluoride) (PVDF) on the crystallization kinetics, competing formations of homocrystallites (HCs) and stereocomplexes (SCs), polymorphic crystalline structure, and HC-to-SC crystalline reorganization of the poly(l-lactic acid)/poly(d-lactic acid) (PLLA/PDLA) racemic mixture were investigated. Even though the PLLA/PDLA/PVDF blends are immiscible, blending with PVDF enhances the crystallization rate and SC formation of PLLA/PDLA components at different temperatures that are higher or lower than the melting temperature of the PVDF component; it also facilitates the HC-to-SC melt reorganization upon heating. The crystallization rate and degree of SC crystallinity (Xc,SC) of PLLA/PDLA components in nonisothermal crystallization increase after immiscible blending with PVDF. At different isothermal crystallization temperatures, the crystallization half-time of PLLA/PDLA components decreases; its spherulitic growth rate and Xc,SC increase as the mass fraction of PVDF increases from 0 to 0.5 in the presence of either a solidified or a molten PVDF phase. The HCs formed in primary crystallization of PLLA/PDLA components melt and recrystallize into SCs upon heating; the HC-to-SC melt reorganization is promoted after blending with PVDF. We proposed that the PVDF-promoted crystallization, SC formation, and HC-to-SC melt reorganization of PLLA/PDLA components in PLLA/PDLA/PVDF blends stem from the enhanced diffusion ability of PLLA and PDLA chains. PMID:27414064

  1. Reduction of Plutonium in Acidic Solutions by Mesoporous Carbons

    SciTech Connect

    Parsons-Moss, Tashi; Jones, Stephen; Wang, Jinxiu; Wu, Zhangxiong; Uribe, Eva; Zhao, Dongyuan; Nitsche, Heino

    2015-12-19

    Batch contact experiments with several porous carbon materials showed that carbon solids spontaneously reduce the oxidation state of plutonium in 1-1.5 M acid solutions, without significant adsorption. The final oxidation state and rate of Pu reduction varies with the solution matrix, and also depends on the surface chemistry and surface area of the carbon. It was demonstrated that acidic Pu(VI) solutions can be reduced to Pu(III) by passing through a column of porous carbon particles, offering an easy alternative to electrolysis with a potentiostat.

  2. Soil washing of fluorine contaminated soil using various washing solutions.

    PubMed

    Moon, Deok Hyun; Jo, Raehyun; Koutsospyros, Agamemnon; Cheong, Kyung Hoon; Park, Jeong-Hun

    2015-03-01

    Bench-scale soil washing experiments were conducted to remove fluoride from contaminated soils. Five washing solutions including hydrochloric acid (HCl), nitric acid (HNO3), sodium hydroxide (NaOH), sulfuric acid (H2SO4) and tartaric acid (C4H6O6) were tested. The concentration of the washing solutions used ranged from 0.1 to 3 M with a liquid to solid ratio of 10. The soil washing results showed that the most effective washing solution for the removal of fluoride from contaminated soils was HCl. The highest fluoride removal results of approximately 97 % from the contaminated soil were obtained using 3 M HCl. The fluoride removal efficiency of the washing solution increases in the following order: C4H6O6 < NaOH < H2SO4 < HNO3 < HCl. PMID:25552323

  3. REMOVAL OF CHLORIDE FROM ACIDIC SOLUTIONS USING NO2

    SciTech Connect

    Visser, A; Robert Pierce, R; James Laurinat, J

    2006-08-22

    Chloride (Cl{sup -}) salt processing in strong acids is used to recycle plutonium (Pu) from pyrochemical residues. The Savannah River National Laboratory (SRNL) is studying the potential application of nitrogen dioxide (NO{sub 2}) gas to effectively convert dissolved pyrochemical salt solutions to chloride-free solutions and improve recovery operations. An NO{sub 2} sparge has been shown to effectively remove Cl{sup -} from solutions containing 6-8 M acid (H{sup +}) and up to 5 M Cl{sup -}. Chloride removal occurs as a result of the competition of at least two reactions, one which is acid-dependent. Below 4 M H+, NO2 reacts with Cl- to produce nitrosyl chloride (ClNO). Between 6 M and 8 M H{sup +}, the reaction of hydrochloric acid (HCl) with nitric acid (HNO{sub 3}), facilitated by the presence of NO{sub 2}, strongly affects the rate of Cl{sup -} removal. The effect of heating the acidic Cl{sup -} salt solution without pre-heating the NO{sub 2} gas has minimal effect on Cl{sup -} removal rates when the contact times between NO{sub 2} and the salt solution are on the order of seconds.

  4. Evaluation of localized corrosion of zirconium in acidic chloride solutions

    SciTech Connect

    Fahey, J.; Holmes, D.; Yau, T.L.

    1997-01-01

    Zirconium is prone to localized corrosion in acidic chloride (Cl{sup {minus}}) solutions contaminated by oxidizing ions, such as ferric or cupric ions. This tendency can be reduced by ensuring that the zirconium surface is clean and smooth. The effect of surface condition on localized corrosion of zirconium in acidic chloride solutions was predicted using potentiodynamic polarization scans. Predictions were confirmed by mass-loss tests on various combinations of surface finish and acid concentrations. A real-time indication of localized corrosion was derived by monitoring electrochemical noise produced between two similar electrodes immersed in an acidic chloride solution. Electrochemical noise monitoring correlated well with predictions from the potentiodynamic polarization and mass-loss experiments. Electrochemical noise results showed a more anodic potential caused by ferric ion (Fe{sup 3+}) contamination might be necessary for localized corrosion but that it was not a sufficient condition. A clean zirconium surface reduced localized corrosion of zirconium.

  5. Divalent fluoride doped cerium fluoride scintillator

    DOEpatents

    Anderson, David F.; Sparrow, Robert W.

    1991-01-01

    The use of divalent fluoride dopants in scintillator materials comprising cerium fluoride is disclosed. The preferred divalent fluoride dopants are calcium fluoride, strontium fluoride, and barium fluoride. The preferred amount of divalent fluoride dopant is less than about two percent by weight of the total scintillator. Cerium fluoride scintillator crystals grown with the addition of a divalent fluoride have exhibited better transmissions and higher light outputs than crystals grown without the addition of such dopants. These scintillators are useful in radiation detection and monitoring applications, and are particularly well suited for high-rate applications such as positron emission tomography (PET).

  6. FLUORIDATION CHEMISTRY: EQUILIBRIA AND KINETICS OF FLUORIDE AND FLUORO-COMPLEXES

    EPA Science Inventory

    The most common fluoridating agents used by major American waterworks are hexafluorosilicic acid (H2SiF6) and sodium hexxafluorosilicate (Na2SiF6). According to the 1992 Water Fluoridation Census where 10,002 utilities responded affirmatively to fluoridating their water, 59
    % ...

  7. Removal of fluoride ions from water by adsorption onto carbonaceous materials produced from coffee grounds.

    PubMed

    Ogata, Fumihiko; Tominaga, Hisato; Yabutani, Hitoshi; Kawasaki, Naohito

    2011-01-01

    Carbonaceous material for the removal of fluoride ions from water was prepared from coffee grounds (CGs) by calcination and subsequent HCl treatment. The characteristics of the CGs, including the surface area, mean pore diameter, pore volume, and surface functional groups were determined, and the morphological characteristics were evaluated using scanning electron microscopy. The adsorption isotherms, saturated amount of fluoride ions adsorbed, and the effect of contact time and temperature on the adsorption of fluoride ions were investigated for a sample of tap water. The specific surface area of CG calcined at 600° (CG600) was larger than that of CGs calcined at 400, 800, and 1000°. Phenolic, lactonic, and carboxyl groups were detected on the CG600 surface. The adsorption capacity of the carbonized CGs for fluoride was ranked in the order CG400 < CG1000 < CG800 < CG600 (where the numeral indicates the carbonization temperature), whereas virgin CG and CG600-NAT (not treated with hydrochloric acid solution) did not exhibit any adsorption ability for fluoride ions. The amount of fluoride ions adsorbed onto CG600 increased with increasing temperature and was consistent with chemical adsorption. The mechanism of adsorption of fluoride ions onto CG600 proceeded via ion exchange with chloride ions (1:1) present on the surface of CG600. The adsorption isotherms were fitted to the Freundlich and Langmuir equations. Moreover, CG600 showed an acceptable adsorption capacity for fluoride ions present in tap water. PMID:22123243

  8. Direct determination of fluoride in aluminium reduction materials by using an ion-selective electrode.

    PubMed

    Palmer, T A

    1972-10-01

    Macro amounts of fluoride in aluminium reduction materials are successfully determined with a fluoride electrode. Except for anhydrous aluminium fluoride, which requires fusion with sodium hydroxide, samples are dissolved in aqueous media. Cryolite and sodium fluorosilicatc are dissolved in boiling sodium hydroxide solution. Other materials containing fluoride, such as fluorspar and the reduction cell bath and pot-lining, require dissolution in a hydrochloric acid solution of aluminium chloride. Potential interference from large amounts of aluminium (and calcium, if present) is eliminated and pH control attained by using ammoniacal sulphosalicylate (and EDTA). The procedures are reasonably rapid. Relative errors of less than 2% and a relative standard deviation of 1% are achieved. PMID:18961164

  9. Protic Acid Hydrogen Bonding in Chlorofluoroethylenes: the Hydrogen Fluoride-Vinyl Chloride Complex

    NASA Astrophysics Data System (ADS)

    Leung, Helen O.; Marshall, Mark D.

    2012-06-01

    Our studies of intermolecular complexes formed in the gas phase between protic acids (HX) and chlorofluoroethylene complexes to date have demonstrated a preference for HX binding to a F atom over hydrogen bond formation with the Cl atom. Ab initio calculations suggest that this may not be true for species with an increased degree of halogen substitution on the ethylene. To characterize the nature of hydrogen bond formation with the less electronegative, but more polarizable Cl atom, we have obtained the microwave spectrum of HF-vinyl chloride complex. Analysis of the spectra for the 35Cl and 37Cl isotopologues demonstrate that the complex is planar and provides structural parameters for this species. This allows comparisons to be made between the HX hydrogen bond to Cl and that to F.

  10. Efficient acid-catalyzed (18) F/(19) F fluoride exchange of BODIPY dyes.

    PubMed

    Keliher, Edmund J; Klubnick, Jenna A; Reiner, Thomas; Mazitschek, Ralph; Weissleder, Ralph

    2014-07-01

    Fluorine-containing fluorochromes are important validation agents for positron emission tomography imaging compounds, as they can be readily validated in cells by fluorescence imaging. In particular, the (18) F-labeled BODIPY-FL fluorophore has emerged as an important platform, but little is known about alternative (18) F-labeling strategies or labeling on red-shifted fluorophores. In this study we explore acid-catalyzed (18) F/(19) F exchange on a range of commercially available N-hydroxysuccinimidyl ester and maleimide BODIPY fluorophores. We show this method to be a simple and efficient (18) F-labeling strategy for a diverse span of fluorescent compounds, including a BODIPY-modified PARP-1 inhibitor, and amine- and thiol-reactive BODIPY fluorophores. PMID:24596307

  11. 137Cs desorption from lichen using acid solutions

    NASA Astrophysics Data System (ADS)

    Čučulović, A. A.; Veselinović, D.; Miljanić, S. S.

    2009-09-01

    Desoprtion of 137Cs from samples of Cetraria islandica lichen using HCl ( A) and HNO3 ( B) acid solutions with pH values from 2.00 to 3.75 was investigated. After five consecutive desorptions lasting 24 h it was shown that between 52.2% (solution B pH 3.28) and 72.2% (solution A pH 2.00) of 137Cs was desorbed from the lichen and the initial desorptions were the most successful. Lichen desorbed with the stated solutions did not undergo structural changes. The amount of absorbed water from solutions A and B, used for desorption from lichen, in relation to the starting volume (expressed in %) showed that solution concentration did not take place. Lichen act as neutralizing agents because the pH of the lichen thallus is higher than the pH value of the solution used

  12. 2-Acrylamido-2-methyl-1-propanesulfonic Acid Grafted Poly(vinylidene fluoride-co-hexafluoropropylene)-Based Acid-/Oxidative-Resistant Cation Exchange for Membrane Electrolysis.

    PubMed

    Pandey, Ravi P; Das, Arindam K; Shahi, Vinod K

    2015-12-30

    For developing acid-/oxidative-resistant aliphatic-polymer-based cation-exchange membrane (CEM), macromolecular modification of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) was carried out by controlled chemical grafting of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS). To introduce the unsaturation suitable for chemical grafting, dehydrofluorination of commercially available PVDF-co-HFP was achieved under alkaline medium. Sulfonated copolymer (SCP) was prepared by the free radical copolymerization of dehydofluorinated PVDF-co-HFP (DHPVDF-co-HFP) and AMPS in the presence of free radical initiator. Prepared SCP-based CEMs were analyzed for their morphological characteristics, ion-exchange capacity (IEC), water uptake, conductivity, and stabilities (mechanical, chemical, and thermal) in comparison with state-of-art Nafion117 membrane. High bound water content avoids the membrane dehydration, and most optimal (SCP-1.33) membrane exhibited about ∼2.5-fold high bound water content in comparison with that of Nafion117 membrane. Bunsen reaction of iodine-sulfur (I-S) was successfully performed by direct-contact-mode membrane electrolysis in a two-compartment electrolytic cell using different SCP membranes. High current efficiency (83-99%) confirmed absence of any side reaction and 328.05 kJ mol-H2(-1) energy was required for to produce 1 mol of H2 by electrolytic cell with SCP-1.33 membrane. In spite of low conductivity for reported SCP membrane in comparison with that of Nafion117 membrane, SCP-1.33 membrane was assessed as suitable candidate for electrolysis because of its low-cost nature and excellent stabilities in highly acidic environment may be due to partial fluorinated segments in the membrane structure. PMID:26642107

  13. Spectrophotometric determination of fluoride in fluoride-bearing minerals after decomposition by fusion with sodium hydroxide.

    PubMed

    Adelantado, J V; Martinez, V P; Moreno, A C; Reig, F B

    1985-03-01

    The decomposition of highly insoluble minerals (fluorspar and cryolite) by fusion with molten alkali-metal hydroxides is studied. The introduction of additives such as aluminium compounds or sodium peroxide to obtain total liberation of fluoride from calcium fluoride samples, is tested. The fusion is done in a silver crucible with a Bunsen burner. The cooled melt is easily soluble, giving solutions suitable for spectrophotometric fluoride determination by the Zr(IV)-fluoride-Erichrome Cyanine R method. PMID:18963832

  14. Dephosphorization of Steelmaking Slag by Leaching with Acidic Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Qiao, Yong; Diao, Jiang; Liu, Xuan; Li, Xiaosa; Zhang, Tao; Xie, Bing

    2015-12-01

    In the present paper, dephosphorization of steelmaking slag by leaching with acidic aqueous solution composed of citric acid, sodium hydroxide, hydrochloric acid and ion-exchanged water was investigated. The buffer solution of C6H8O7-NaOH-HCl system prevented changes in the pH values. Kinetic parameters including leaching temperature, slag particle size and pH values of the solution were optimized. The results showed that temperature has no obvious effect on the dissolution ratio of phosphorus. However, it has a significant effect on the dissolution ratio of iron. The dephosphorization rate increases with the decrease of slag particle size and the pH value of the solution. Over 90% of the phosphorus can be dissolved in the solution while the corresponding leaching ratio of iron was only 30% below the optimal condition. Leaching kinetics of dephosphorization follow the unreacted shrinking core model with a rate controlled step by the solid diffusion layer, the corresponding apparent activation energy being 1.233 kJ mol-1. A semiempirical kinetic equation was established. After leaching, most of the nC2S-C3P solid solution in the steelmaking slag was selectively dissolved in the aqueous solution and the iron content in the solid residue was correspondingly enriched.

  15. γ-Irradiation of malic acid in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Negron-Mendoza, Alicia; Graff, Rebecca L.; Ponnamperuma, Cyril

    1980-12-01

    The γ-irradiation of malic acid in aqueous solutions was studied under initially oxygenated and oxygen-free conditions in an attempt to determine the possible interconversion of malic acid into other carboxylic acids, specifically those associated with Krebs cycle. The effect of dose on product formation of the system was investigated. Gas-liquid chromatography combined with mass spectrometry was used as the principal means of identification of the non-volatile products. Thin layer chromotography and direct probe mass spectroscopy were also employed. The findings show that a variety of carboxylic acids are formed, with malonic and succinic acids in greatest abundance. These products have all been identified as being formed in the γ-irradiation of acetic acid, suggesting a common intermediary. Since these molecules fit into a metabolic cycle, it is strongly suggestive that prebiotic pathways provided the basis for biological systems.

  16. Fluoride uptake by Streptococcus mutans 6715.

    PubMed Central

    Whitford, G M; Schuster, G S; Pashley, D H; Venkateswarlu, P

    1977-01-01

    The short-term kinetics of fluoride uptake by cells from 20- to 22-h cultures of Streptococcus mutans strain 6715 were studied using rapid filtration and centrifugation techniques. Saline-suspended organisms were diluted with fluoride-containing solutions buffered at four different pH values (2.0, 4.0, 5.5, and 8.2). Fluoride disappearance from the medium was inversely related to pH and to the duration of the exposure at any given pH. The uptake was rapid and extensive at the lower pH values and decreased as the pH increased. Media fluoride concentrations subsequently increased; i.e., fluoride was released from the cells. The presence of glucose, cyanide, or iodoacetate did not influence the results. However, preincubation of the cells in fluoride-free buffers, followed by the addition of fluoride, reduced fluoride uptake markedly. Cell-to-media pH gradients were determined by the distribution of 14C-labeled 5,5-dimethyl-2,4-oxazolidinedione. Fluoride uptake was found to be a function of the magnitude of the pH gradient (P less than 0.001). It is hypothesized that fluoride uptake occurs by the diffusion of hydrogen fluoride and the subsequent trapping of ionic fluoride. PMID:22490

  17. Highly accurate boronimeter assay of concentrated boric acid solutions

    SciTech Connect

    Ball, R.M. )

    1992-01-01

    The Random-Walk Boronimeter has successfully been used as an on-line indicator of boric acid concentration in an operating commercial pressurized water reactor. The principle has been adapted for measurement of discrete samples to high accuracy and to concentrations up to 6000 ppm natural boron in light water. Boric acid concentration in an aqueous solution is a necessary measurement in many nuclear power plants, particularly those that use boric acid dissolved in the reactor coolant as a reactivity control system. Other nuclear plants use a high-concentration boric acid solution as a backup shutdown system. Such a shutdown system depends on rapid injection of the solution and frequent surveillance of the fluid to ensure the presence of the neutron absorber. The two methods typically used to measure boric acid are the chemical and the physical methods. The chemical method uses titration to determine the ionic concentration of the BO[sub 3] ions and infers the boron concentration. The physical method uses the attenuation of neutrons by the solution and infers the boron concentration from the neutron absorption properties. This paper describes the Random-Walk Boronimeter configured to measure discrete samples to high accuracy and high concentration.

  18. Polymerization of Pu(IV) in aqueous nitric acid solutions

    SciTech Connect

    Toth, L.M.; Friedman, H.A.; Osborne, M.M.

    1980-10-01

    The polymerization of Pu(IV) in aqueous nitric acid solutions has been studied spectrophotometrically both to establish the influence of large UO{sub 2}(NO{sub 3}){sub 2} concentrations on the polymerization rates and, more generally, to review the influence of the major parameters on the polymer reaction. Typically, experiments have been performed at 50{sup 0}C and with 0.05 M Pu in nitric acid solutions that vary in acidity from 0.07 to 0.4 M. An induction period usually precedes the polymer growth stage during which time nucleation of primary hydrolysis products occurs. Uranyl nitrate retards the polymerization reaction by approximately 35% in spite of the counteracting influence of the nitrate ions associated with this solute. The rate of polymer formation, expressed as d(percent polymer)/dt, has been shown to depend on the total plutonium concentration in reactions where the Pu(IV) concentration remained constant; and it is therefore suggested that the polymer reaction rate is not first order with respect to the concentration of plutonium as was previously thought. It has been shown further that accurate acid determinations on stock reagents are essential in order to obtain reliable polymerization experiments. Satisfactory procedures for these analyses did not exist, so appropriate modifications to the iodate precipitation methods were developed. The most ideal plutonium reagent material has been shown to be crystalline Pu(IV) nitrate because it can be added directly to acid solutions without the occurrence of unintentional hydrolysis reactions.

  19. Rapid and efficient removal of fluoride ions from aqueous solution using a polypyrrole coated hydrous tin oxide nanocomposite.

    PubMed

    Parashar, Kamya; Ballav, Niladri; Debnath, Sushanta; Pillay, Kriveshini; Maity, Arjun

    2016-08-15

    Polypyrrole/hydrous tin oxide nanocomposites (PPy/HSnO NC 1, 2, 3, 4 and 5) were synthesized through encapsulating HSnO by the PPy via an in situ polymerization for fluoride removal. The optimized adsorbent i.e. PPy/HSnO NC 3 was characterized using FE-SEM, HR-TEM, ATR-FTIR, XRD, BET, TGA and zeta sizer. Microscopic images revealed the encapsulation of HSnO by precipitating PPy during polymerization. The FTIR and XRD studies confirmed the presence of both constituents. The BET surface area and pHpzc of the adsorbent were estimated to be 65.758m(2)/g and 7.6, respectively. The fluoride adsorption followed pseudo-second-order model and was commendably rapid. The monolayer adsorption capacity was found to be 26.16-28.99mg/g at pH 6.5±0.1. The thermodynamic parameters indicated the sorption of F(-) was spontaneous, endothermic and that physisorption occurred. The calculated activation energy (Ea∼20.05kJ/mol) provided further evidence of a physisorption mechanism. Moreover, the adsorbent performed very well over a considerably wide pH range of 3.5-8.5 and in the presence of other co-existing ions. The regeneration of the F(-) laden PPy/HSnO NC 3 showed a high desorption efficiency of 95.81% up to 3 cycles. Ground water tested results also demonstrate the potential utility of the PPy/HSnO NC as an effective adsorbent. PMID:27209396

  20. Physiologic Conditions Affect Toxicity of Ingested Industrial Fluoride

    PubMed Central

    Sauerheber, Richard

    2013-01-01

    The effects of calcium ion and broad pH ranges on free fluoride ion aqueous concentrations were measured directly and computed theoretically. Solubility calculations indicate that blood fluoride concentrations that occur in lethal poisonings would decrease calcium below prevailing levels. Acute lethal poisoning and also many of the chronic effects of fluoride involve alterations in the chemical activity of calcium by the fluoride ion. Natural calcium fluoride with low solubility and toxicity from ingestion is distinct from fully soluble toxic industrial fluorides. The toxicity of fluoride is determined by environmental conditions and the positive cations present. At a pH typical of gastric juice, fluoride is largely protonated as hydrofluoric acid HF. Industrial fluoride ingested from treated water enters saliva at levels too low to affect dental caries. Blood levels during lifelong consumption can harm heart, bone, brain, and even developing teeth enamel. The widespread policy known as water fluoridation is discussed in light of these findings. PMID:23840230

  1. Methanol Uptake by Low Temperature Aqueous Sulfuric Acid Solutions

    NASA Technical Reports Server (NTRS)

    Iraci, L. T.; Essin, A. M.; Golden, D. M.; Hipskind, R. Stephen (Technical Monitor)

    2001-01-01

    The global methanol budget is currently unbalanced, with source terms significantly larger than the sinks terms. To evaluate possible losses of gaseous methanol to sulfate aerosols, the solubility and reactivity of methanol in aqueous sulfuric acid solutions representative of upper tropospheric and lower stratospheric aerosols is under investigation. Methanol will partition into sulfate aerosols according to its Henry's law solubility. Using standard uptake techniques in a Knudsen cell reactor, we have measured the effective Henry's law coefficient, H*, for cold (196 - 220 K) solutions ranging between 45 and 70 wt % H2SO4. We have found that methanol solubility ranges from approx. 10(exp 5) - 10(exp 7) M/atm for UT/LS conditions. Solubility increases with decreasing temperature and with increasing sulfuric acid content. Although methanol is slightly more soluble than are acetone and formaldehyde, current data indicate that uptake by clean aqueous sulfuric acid particles will not be a significant sink for methanol in the UT/LS. These solubility measurements include uptake due to physical solvation and any rapid equilibria which are established in solution. Reaction between primary alcohols and sulfuric acid does occur, leading to the production of alkyl sulfates. Literature values for the rate of this reaction suggest that formation of CH3OSO3H is not significant over our experimental time scale for solutions below 80 wt % H2SO4. To confirm this directly, results obtained using a complementary equilibrium measurement technique will also be presented.

  2. [Investigation on mechanism of pyrite oxidation in acidic solutions].

    PubMed

    Wang, Nan; Yi, Xiao-Yun; Dang, Zhi; Liu, Yun

    2012-11-01

    The mechanism of pyrite oxidation in acidic solutions was investigated by electrochemical analysis methods, such as open-circuit potential, cyclic voltammetry, Tafel polarization curve and anodic polarization curve, using a pyrite-carbon paste electrode as working electrode. The results showed that the oxidation process of pyrite in acidic solutions was via a two-step reaction: the first step was the dissolution of iron moiety and formation of a passivation film composed of elemental sulphur, metal-deficient sulfide and polysulfide; the second step was the further oxidation of these intermediate products to SO4(2-). The final reaction products of pyrite oxidation were Fe3+ and SO4(2-) in acidic solutions. In addition, the open-circuit potential and corrosion potential were positively shifted, the peak current and the corrosion current were increased with the increase in concentration of H2SO4 solutions. This indicated that increased acidity of the system was advantageous to the oxidation of pyrite. PMID:23323425

  3. PROCESS OF PREPARING A FLUORIDE OF TETRAVLENT URANIUM

    DOEpatents

    Wheelwright, E.J.

    1959-02-17

    A method is described for producing a fluoride salt pf tetravalent uranium suitable for bomb reduction to metallic uranium. An aqueous solution of uranyl nitrate is treated with acetic acid and a nitrite-suppressor and then contacted with metallic lead whereby uranium is reduced from the hexavalent to the tetravalent state and soluble lead acetate is formed. Sulfate ions are then added to the solution to precipitate and remove the lead values. Hydrofluoric acid and alkali metal ions are then added causing the formation of an alkali metal uranium double-fluoride in which the uranium is in the tetravalent state. After recovery, this precipitate is suitable for using in the limited production of metallic uranium.

  4. Stability of fluoride complex with silica and its distribution in natural water systems

    USGS Publications Warehouse

    Roberson, C.E.; Barnes, R.B.

    1978-01-01

    Fluoride reacts with silicic acid to form SiF2-6. A fluoride electrode was used to obtain an equilibrium constant of 1030.18 for the reaction:Si(OH) 0 6 + 6F-+4H+ = SiF 2- 6 + 4H2O at 25??C. Although there may be some experimental evidence for existence of traces of species containing less than six F- ions per silicon (n = 6), the species SiF2-6 predominates for n values from about 0.1 to 6. Silicic-acid complexing with fluoride is important only in solutions which have rather low pH and low concentrations of other cations which compete with silicon for fluoride. Computations for cold volcanic condensates from Hawaii indicate that for some samples much of the silicon is complexed by fluoride as SiF2-6. However, in most cooled acidic natural water samples Al and Fe are more important than Si in complexing fluoride. ?? 1978.

  5. Effect of fluoride toothpastes on enamel demineralization

    PubMed Central

    Arnold, Wolfgang H; Dorow, Andreas; Langenhorst, Stephanie; Gintner, Zeno; Bánóczy, Jolan; Gaengler, Peter

    2006-01-01

    Background It was the aim of this study to investigate the effect of four different toothpastes with differing fluoride compounds on enamel remineralization. Methods A 3 × 3 mm window on the enamel surface of 90 human premolars was demineralized in a hydroxyethylcellulose solution at pH 4.8. The teeth were divided into 6 groups and the lower half of the window was covered with varnish serving as control. The teeth were immersed in a toothpaste slurry containing: placebo tooth paste (group 1); remineralization solution (group 2); Elmex Anticaries (group 3); Elmex Sensitive (group 4); Blend-a-med Complete (group 5) and Colgate GRF (group 6). Ten teeth of each group were used for the determination of the F- content in the superficial enamel layer and acid solubility of enamel expressed in soluble phosphorus. Of 6 teeth of each group serial sections were cut and investigated with polarization light microscopy (PLM) and quantitative energy dispersive X-ray analysis (EDX). Results The PLM results showed an increased remineralization of the lesion body in the Elmex Anticaries, Elmex Sensitive and Colgate GRF group but not in the Blend-a-med group. A statistically significant higher Ca content was found in the Elmex Anticaries group. The fluoride content in the superficial enamel layer was significantly increased in both Elmex groups and the Blend-a-med group. Phosphorus solubility was significantly decreased in both Elmex groups and the Blend-a-med group. Conclusion It can be concluded that amine fluoride compounds in toothpastes result in a clearly marked remineralization of caries like enamel lesions followed by sodium fluoride and sodium monofluorophosphate formulations. PMID:16776820

  6. On-line flow injection solid sample introduction, leaching and potentiometric determination of fluoride in phosphate rock.

    PubMed

    Sweileh, Jamal A

    2007-01-01

    A flow injection method with on-line solid sample dissolution was developed for the determination of fluoride in phosphate rock. The fluoride was selectively leached (98-102.4 % recovery) from a 50-mg powdered phosphate rock sample with 0.50 M citric acid. Using the zone sampling technique the fluoride in the buffered leachate was determined by injecting 87 muL into the carrier stream using a fluoride ion-selective electrode detector. The sensing element of the electrode was housed in a home-made sleeve-type flow-through cell. On-line solid sample digestion with 0.50 M citric acid at 55 degrees C resulted in minimum dissolution of interfering iron and aluminum ions with improved accuracy and calibration linearity. The incorporation of relatively high level of fluoride in the carrier stream (40 microg mL(-1)) facilitated the determination of high levels of fluoride in phosphate rock (up to 4.1%) with out the need for excessive on-line dilution. The optimized flow system was applied for the determination of fluoride in phosphate rocks samples and a reference material at a rate of nine samples per hour with a relative standard deviation (n=5) of 2.95-4.0 %. Comparison of the proposed flow injection method with the standard method, which involves steam distillation from sulfuric acid solution and manual titration with thorium nitrate, showed no evidence of bias at the 95% confidence level. PMID:17386441

  7. Decontamination of soils and materials containing medium-fired PuO{sub 2} using inhibited fluorides with polymer filtration technology

    SciTech Connect

    Temer, D.J.; Villarreal, R.; Smith, B.F.

    1997-10-01

    The decontamination of soils and/or materials from medium-fired plutonium oxide (PuO{sub 2}) with an effective and efficient decontamination agent that will not significantly dissolve the matrix requires a new and innovative technology. After testing several decontamination agents and solutions for dissolution of medium-fired PuO{sub 2}, the most successful decontamination solutions were fluoride compounds, which were effective in breaking the Pu-oxide bond but would not extensively dissolve soil constituents and other materials. The fluoride compounds, tetra fluoboric acid (HBF{sub 4}) and hydrofluorosilicic acid (H{sub 2}F{sub 6}Si), were effective in dissolving medium-fired PuO{sub 2}, and did not seem to have the potential to dissolve the matrix. In both compounds, the fluoride atom is attached to a boron or silicon atom that inhibits the reactivity of the fluoride towards other compounds or materials containing atoms less attracted to the fluoride atom in an acid solution. Because of this inhibition of the reactivity of the fluoride ion, these compounds are termed inhibited fluoride compounds or agents. Both inhibited fluorides studied effectively dissolved medium-fired PuO{sub 2} but exhibited a tendency to not attack stainless steel or soil. The basis for selecting inhibited fluorides was confirmed during leaching tests of medium-fired PuO{sub 2} spiked into soil taken from the Idaho National Engineering Laboratory (INEL). When dissolved in dilute HNO{sub 3}, HCl, or HBr, both inhibited fluoride compounds were effective at solubilizing the medium-fired PuO{sub 2} from spiked INEL soil.

  8. Kinetics and equilibrium studies on Mg-Al oxide for removal of fluoride in aqueous solution and its use in recycling.

    PubMed

    Kameda, Tomohito; Oba, Jumpei; Yoshioka, Toshiaki

    2015-06-01

    Mg-Al oxide obtained by the thermal decomposition of Mg-Al layered double hydroxide (LDH) intercalated with CO3(2-) (CO3·Mg-Al LDH) was found to take up fluoride from aqueous solution. Fluoride was removed by rehydration of Mg-Al oxide accompanied by combination with F(-). Using five times the stoichiometric quantity of Mg-Al oxide, the residual concentration of F was decreased from 100 to 6.3 mg/L in 480 min, which was below the effluent standard in Japan (8 mg/L). Removal of F(-) can be represented by pseudo-second-order reaction kinetics. The apparent rate constants at 10 °C, 30 °C, and 60 °C were 2.3 × 10(-3), 2.2 × 10(-2), and 2.5 × 10(-1) g mmol(-1) min(-1), respectively. The apparent activation energy was 73.3 kJ mol(-1). The rate-determining step for F removal by Mg-Al oxide was consistent with chemical adsorption involving intercalation of F(-) into the reconstructed Mg-Al LDH due to electrostatic attraction. The adsorption of F by Mg-Al oxide follows a Langmuir-type adsorption. The values of the maximum adsorption and the equilibrium adsorption constant were 3.0 mmol g(-1) and 1.1 × 10(3), respectively, for Mg-Al oxide. The F(-) in the F·Mg-Al LDH thus produced was found to be anion-exchanged with CO3(2-) in solution. The Mg-Al oxide after regeneration treatment had excellent properties for removal of F in aqueous solution. In conclusion, the results of this study indicated that Mg-Al oxide has potential for use in recycling to remove F in aqueous solution. PMID:25867103

  9. Hydrolysis kinetics of lead silicate glass in acid solution

    NASA Astrophysics Data System (ADS)

    Rahimi, Rafi Ali; Sadrnezhaad, Sayed Khatibuleslam; Raisali, Gholamreza; Hamidi, Amir

    2009-06-01

    Hydrolysis kinetics of the lead silicate glass (LSG) with 40 mol% PbO in 0.5 N HNO 3 aqueous acid solution was investigated. The surface morphology and the gel layer thickness were studied by scanning electron microscopy (SEM) micrographs. Energy dispersive X-ray spectroscopy (EDS) and inductively coupled plasma spectroscopy (ICP) were used to determine the composition of the gel layer and the aqueous solution, respectively. The silicon content of the dissolution products was determined by using weight-loss data and compositions of the gel layer and the solution. The kinetic parameters were determined using the shrinking-core-model (SCM) for rate controlling step. The activation energy obtained for hydrolysis reaction was Qche = 56.07 kJ/mole. The diffusion coefficient of the Pb ions from the gel layer was determined by using its concentration in solution and in LSG. The shrinkage of the sample and the gel layer thickness during dissolution process were determined.

  10. A mechanistic study of copper electropolishing in phosphoric acid solutions

    NASA Astrophysics Data System (ADS)

    Mansson, Andrew

    The microelectronics industry is using copper as the interconnect material for microchips. A study of copper electropolishing is important for the process development of a new, low downforce approach, which is being developed to replace chemical mechanical polishing (CMP) of the copper overburden. A promising technology is a combination of electropolishing with conventional CMP. Electropolishing of copper in phosphoric acid has been studied for, more than 70 years. Previous work has shown that the polishing rate, as measured by current density is directly related to the viscosity of the electrolyte. Also, the limiting species is water. In this study, a multidimensional design of experiments was performed to develop an in-depth model of copper electropolishing. Phosphoric acid was mixed with alcohols of different molecular weight and related viscosity to investigate how the solvents' properties affected polishing. The alcohols used were methanol, ethanol, isopropanol, butanol, ethylene glycol, and glycerol. The limiting current densities and electrochemical behavior of each solution was measured by potentiodynamic and potentiostatic experiments. Also, the kinematic viscosity and density were measured to determine the dynamic viscosity to investigate the relationship of current density and viscosity. Water, methanol, ethanol, and isopropanol solutions were also examined at 20°C to 60°C. Next, the relative percentage of dissociated phosphoric acid was measured by Raman spectroscopy for each polishing solution. Raman spectroscopy was also used to measure the relative dissociation of phosphoric acid inside the polishing film. Additionally, wafers were electropolished and electrochemical mechanically polished to investigate the effects of the different solvents, fluid flow, current, and potential. The results of these experiments have shown that the molecular mass and the ability of the solvent to dissociate phosphoric acid are the primary electrolyte properties that

  11. Solution Preserves Nucleic Acids in Body-Fluid Specimens

    NASA Technical Reports Server (NTRS)

    Pierson, Duane L.; Stowe, Raymond P.

    2004-01-01

    A solution has been formulated to preserve deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) in specimens of blood, saliva, and other bodily fluids. Specimens of this type are collected for diagnostic molecular pathology, which is becoming the method of choice for diagnosis of many diseases. The solution makes it possible to store such specimens at room temperature, without risk of decomposition, for subsequent analysis in a laboratory that could be remote from the sampling location. Thus, the solution could be a means to bring the benefits of diagnostic molecular pathology to geographic regions where refrigeration equipment and diagnostic laboratories are not available. The table lists the ingredients of the solution. The functions of the ingredients are the following: EDTA chelates divalent cations that are necessary cofactors for nuclease activity. In so doing, it functionally removes these cations and thereby retards the action of nucleases. EDTA also stabilizes the DNA helix. Tris serves as a buffering agent, which is needed because minor contaminants in an unbuffered solution can exert pronounced effects on pH and thereby cause spontaneous degradation of DNA. SDS is an ionic detergent that inhibits ribonuclease activity. SDS has been used in some lysis buffers and as a storage buffer for RNA after purification. The use of the solution is straightforward. For example, a sample of saliva is collected by placing a cotton roll around in the subject's mouth until it becomes saturated, then the cotton is placed in a collection tube. Next, 1.5 mL of the solution are injected directly into the cotton and the tube is capped for storage at room temperature. The effectiveness of the solution has been demonstrated in tests on specimens of saliva containing herpes simplex virus. In the tests, the viral DNA, as amplified by polymerase chain reaction, was detected even after storage for 120 days.

  12. Multiphase chemistry of ozone on fulvic acids solutions.

    PubMed

    Brigante, Marcello; D'Anna, Barbara; Conchon, Pierre; George, Christian

    2008-12-15

    By means of a wetted-wall flow tube, we studied the multiphase chemistry of ozone on aqueous solutions containing fulvic acids (FA), taken as proxies for atmospheric "humic like substances", so-called HULIS. In these experiments, the loss of gaseous O3 was monitored by UV-visible absorption spectroscopy at the reactor outlet (i.e., after contact between the gaseous and liquid phases). Measurements are reported in terms of dimensionless uptake coefficients (gamma) in the range from 1.6 x 10(-7) to 1.3 x 10(-5) depending on ozone gas phase concentration (in the range from 6.6 to 34.4 x 10(11) molecules cm(-3)) and fulvic acid aqueous concentration (in the range from 0.25 to 2.5 mg L(-1)) and pH (in the range from 2.5 to 9.2). The measured kinetics were observed to follow a Langmuir-Hinshelwood type mechanism, in which O3 first adsorbs on the liquid surface and then reacts with the Fulvic Acid molecules. The reported uptake coefficients are greatly increased over those measured on pure water, demonstrating that the presence in solution of fulvic acids does greatly enhance the uptake kinetics. Accordingly, the chemical interactions of fulvic acids (or HULIS) may be a driving force for the uptake of ozone on liquid organic aerosols and can also represent an important mechanism for the O3 deposition to the rivers and lakes. PMID:19174887

  13. Acid hydrolysis of cellulose in zinc chloride solution

    SciTech Connect

    Cao, N.J.; Xu, Q.; Chen, L.F.

    1995-12-31

    The efficient conversion of cellulosic materials to ethanol has been hindered by the low yield of sugars, the high energy consumption in pretreatment processes, and the difficulty of recycling the pre-treatment agents. Zinc chloride may provide an alternative for pre-treating biomass prior to the hydrolysis of cellulose. The formation of a zinc-cellulose complex during the pretreatment of cellulose improves the yield of glucose in both the enzymatic and acid hydrolysis of cellulose. Low-temperature acid hydrolysis of cellulose in zinc chloride solution is carried out in two stages, a liquefaction stage and a saccharification stage. Because of the formation of zinc-cellulose complex in the first stage, the required amount of acid in the second stage has been decreased significantly. In 67% zinc chloride solution, a 99.5% yield of soluble sugars has been obtained at 70{degrees}C and 0.5M acid concentration. The ratio of zinc chloride to cellulose has been reduced from 4.5 to 1.5, and the yield of soluble sugars is kept above 80%. The rate of hydrolysis is affected by the ratio of zinc chloride to cellulose, acid concentration, and temperature.

  14. Solution influence on biomolecular equilibria - Nucleic acid base associations

    NASA Technical Reports Server (NTRS)

    Pohorille, A.; Pratt, L. R.; Burt, S. K.; Macelroy, R. D.

    1984-01-01

    Various attempts to construct an understanding of the influence of solution environment on biomolecular equilibria at the molecular level using computer simulation are discussed. First, the application of the formal statistical thermodynamic program for investigating biomolecular equilibria in solution is presented, addressing modeling and conceptual simplications such as perturbative methods, long-range interaction approximations, surface thermodynamics, and hydration shell. Then, Monte Carlo calculations on the associations of nucleic acid bases in both polar and nonpolar solvents such as water and carbon tetrachloride are carried out. The solvent contribution to the enthalpy of base association is positive (destabilizing) in both polar and nonpolar solvents while negative enthalpies for stacked complexes are obtained only when the solute-solute in vacuo energy is added to the total energy. The release upon association of solvent molecules from the first hydration layer around a solute to the bulk is accompanied by an increase in solute-solvent energy and decrease in solvent-solvent energy. The techniques presented are expectd to displace less molecular and more heuristic modeling of biomolecular equilibria in solution.

  15. Electrodialysis synthesis of concentrated solutions of perrhenic acid

    NASA Astrophysics Data System (ADS)

    Palant, A. A.; Bryukvin, V. A.; Levin, A. M.; Reshetova, O. V.

    2011-03-01

    The presented results demonstrate the possibility of electrodialysis production of concentrated solutions of perrhenic acid (HReO4 concentration >400 g/l). KReO4 is used as a precursor. The investigations are performed in a three-chamber electrodialysis cell in a continuous mode. The optimal processing parameters are as follows: the current is 3-5 A, the voltage is 30-40 V, and the anode chamber temperature is 20-25°C. Grade AR-0 ammonium perrhenate is precipitated from the obtained HReO4 solution.

  16. Method for extracting lanthanides and actinides from acid solutions

    DOEpatents

    Horwitz, E. Philip; Kalina, Dale G.; Kaplan, Louis; Mason, George W.

    1985-01-01

    A process for the recovery of actinide and lanthanide values from aqueous acidic solutions with an organic extractant having the formula: ##STR1## where .phi. is phenyl, R.sup.1 is a straight or branched alkyl or alkoxyalkyl containing from 6 to 12 carbon atoms and R.sup.2 is an alkyl containing from 3 to 6 carbon atoms. The process is suitable for the separation of actinide and lanthanide values from fission product values found together in high level nuclear reprocessing waste solutions.

  17. Studies on the adsorption of americium on alumina from aqueous nitric acid-oxalic acid solutions

    SciTech Connect

    Subba Rao, M.; Gaikwad, A.M.; Rao, V.K.; Natarajan, P.R.

    1985-01-01

    This paper reports a study on the adsorption of Am(III) on alumina from oxalic acid-nitric acid solutions. Distribution coefficients for Am(III) on alumina at different oxalic acid-nitric acid concentrations have been determined and optimum conditions for loading and elution of Am from alumina columns have been established. Separation of Am from Pu and the effects of other ions, such as U(VI) and Fe(III), have also been studied. Am and Pu recoveries better than 99.5% were obtained. 3 references, 2 figures, 5 tables.

  18. DC diaphragm discharge in water solutions of selected organic acids

    NASA Astrophysics Data System (ADS)

    Vyhnankova, Edita J.; Hammer, Malte U.; Reuter, Stephan; Krcma, Frantisek

    2015-07-01

    Effect of four simple organic acids water solution on a DC diaphragm discharge was studied. Efficiency of the discharge was quantified by the hydrogen peroxide production determined by UV-VIS spectrometry of a H2O2 complex formed with specific titanium reagent. Automatic titration was used to study the pH behaviour after the plasma treatment. Optical emission spectroscopy overview spectra were recorded and detailed spectra of OH band and Hβ line were used to calculate the rotational temperature and comparison of the line profile (reflecting electron concentration) in the acid solutions. Contribution to the topical issue "The 14th International Symposium on High Pressure Low Temperature Plasma Chemistry (HAKONE XIV)", edited by Nicolas Gherardi, Ronny Brandenburg and Lars Stollenwark

  19. Interaction of Ethyl Alcohol Vapor with Sulfuric Acid Solutions

    NASA Technical Reports Server (NTRS)

    Leu, Ming-Taun

    2006-01-01

    We investigated the uptake of ethyl alcohol (ethanol) vapor by sulfuric acid solutions over the range approx.40 to approx.80 wt % H2SO4 and temperatures of 193-273 K. Laboratory studies used a fast flow-tube reactor coupled to an electron-impact ionization mass spectrometer for detection of ethanol and reaction products. The uptake coefficients ((gamma)) were measured and found to vary from 0.019 to 0.072, depending upon the acid composition and temperature. At concentrations greater than approx.70 wt % and in dilute solutions colder than 220 K, the values approached approx.0.07. We also determined the effective solubility constant of ethanol in approx.40 wt % H2SO4 in the temperature range 203-223 K. The potential implications to the budget of ethanol in the global troposphere are briefly discussed.

  20. Solubility of chlorine in aqueous hydrochloric acid solutions.

    PubMed

    Alkan, Mahir; Oktay, Münir; Kocakerim, M Muhtar; Copur, Mehmet

    2005-03-17

    The solubility of chlorine in aqueous hydrochloric acid solutions was studied. The effects of HCl concentration and temperature on the solubility were evaluated, and the thermodynamic parameters of the dissolution were calculated. It was found that the solubility isotherms had a minimum at about 0.5M HCl concentration at all the temperatures studied and that solubility decreased with the increase of temperature at all the HCl concentration range investigated. PMID:15752843

  1. Recovery of rhenium from sulfuric acid solutions with activated coals

    SciTech Connect

    Troshkina, I.D.; Naing, K.Z.; Ushanova, O.N.; P'o, V.; Abdusalomov, A.A.

    2006-09-15

    Equilibrium and kinetic characteristics of rhenium sorption from sulfuric acid solutions (pH 2) by activated coals produced from coal raw materials (China) were studied. Constants of the Henry equation describing isotherms of rhenium sorption by activated coals were calculated. The effective diffusion coefficients of rhenium in the coals were determined. The dynamic characteristics of rhenium sorption and desorption were determined for the activated coal with the best capacity and kinetic characteristics.

  2. Acid mine drainage: An economic total resource recovery solution

    SciTech Connect

    Clarke, R.L.; Clarke, S.R.; Brackenbury, D.R.

    1995-12-31

    A common feature of abandoned hard rock mines and subterranean coal mines is the creation of toxic and acidic solution often containing iron, copper, zinc, lead, cadmium, manganese and alkaline earth and alkali metals. A process is described which sequentially removes heavy metals using electrochemical ion exchange and rotating cylinder electrodes. Studies summarized indicate recovery of copper, zinc, iron, and aluminum oxide; selective stripping of arsenic, cadmium, chromium, and lead; and recovery of water acceptable for drinking after removal of heavy metals.

  3. Surface tensions of solutions containing dicarboxylic acid mixtures

    NASA Astrophysics Data System (ADS)

    Lee, Jae Young; Hildemann, Lynn M.

    2014-06-01

    Organic solutes tend to lower the surface tension of cloud condensation nuclei, allowing them to more readily activate. The surface tension of various dicarboxylic acid aerosol mixtures was measured at 20 °C using the Wilhelmy plate method. At lower concentrations, the surface tension of a solution with equi-molar mixtures of dicarboxylic acids closely followed that of a solution with the most surface-active organic component alone. Measurements of surface tension for these mixtures were lower than predictions using Henning's model and the modified Szyszkowski equation, by ˜1-2%. The calculated maximum surface excess (Γmax) and inverse Langmuir adsorption coefficient (β) from the modified Szyszkowski equation were both larger than measured values for 6 of the 7 mixtures tested. Accounting for the reduction in surface tension in the Köhler equation reduced the critical saturation ratio for these multi-component mixtures - changes were negligible for dry diameters of 0.1 and 0.5 μm, but a reduction from 1.0068 to 1.0063 was seen for the 4-dicarboxylic acid mixture with a dry diameter of 0.05 μm.

  4. Alimentary fluoride intake in preschool children

    PubMed Central

    2011-01-01

    Background The knowledge of background alimentary fluoride intake in preschool children is of utmost importance for introducing optimal and safe caries preventive measures for both individuals and communities. The aim of this study was to assess the daily fluoride intake analyzing duplicate samples of food and beverages. An attempt was made to calculate the daily intake of fluoride from food and swallowed toothpaste. Methods Daily alimentary fluoride intake was measured in a group of 36 children with an average age of 4.75 years and an average weight of 20.69 kg at baseline, by means of a double plate method. This was repeated after six months. Parents recorded their child's diet over 24 hours and collected duplicated portions of food and beverages received by children during this period. Pooled samples of food and beverages were weighed and solid food samples were homogenized. Fluoride was quantitatively extracted from solid food samples by a microdiffusion method using hexadecyldisiloxane and perchloric acid. The content of fluoride extracted from solid food samples, as well as fluoride in beverages, was measured potentiometrically by means of a fluoride ion selective electrode. Results Average daily fluoride intake at baseline was 0.389 (SD 0.054) mg per day. Six months later it was 0.378 (SD 0.084) mg per day which represents 0.020 (SD 0.010) and 0.018 (SD 0.008) mg of fluoride respectively calculated per kg bw/day. When adding the values of unwanted fluoride intake from the toothpaste shown in the literature (0.17-1.21 mg per day) the estimate of the total daily intake of fluoride amounted to 0.554-1.594 mg/day and recalculated to the child's body weight to 0.027-0.077 mg/kg bw/day. Conclusions In the children studied, observed daily fluoride intake reached the threshold for safe fluoride intake. When adding the potential fluoride intake from swallowed toothpaste, alimentary intake reached the optimum range for daily fluoride intake. These results showed that

  5. Dehydration and oxidation of cellulose hydrolysis products in acidic solution

    SciTech Connect

    Garves, K.

    1981-01-01

    The dehydration of cotton cellulose in aqueous solutions in the presence of Ac/sub 2/O, AcOH, HCl, H/sub 2/SO/sub 4/ or HBr proceeded by hydrolysis to carbohydrates with acetate groups, followed by conversion to 5-(hydroxymethyl)furfural (I) and then, to levulinic acid (II) accompanied by humic acids. For the formation of I, HCl was a more efficient and selective catalyst than H/sub 2/SO/sub 4/, and the formation of II was promoted by high acid and H/sub 2/O concentrations in the medium. The addition of FeCl/sub 3/ to the dehydration mixture with HCl and continuous distillation led to the isolation of furfural.

  6. Chemical emergency preparedness and prevention advisory: Hydrogen fluoride, series 8, No. 3

    SciTech Connect

    Not Available

    1993-07-01

    The advisory recommends ways Local Emergency Planning Committees (LEPCs) and chemical facilities can reduce risks posed by the presence of hydrogen fluoride (HF) in their communities. Hydrogen fluoride, a strong inorganic acid, is produced and used as a gas or liquid without water (i.e., in anhydrous form), or in a water (aqueous) solution. Inhalation of hydrogen fluoride vapor, either in anhydrous form or from water solutions, can cause irritation if the exposure is mild (i.e., low concentration in air for a short time), or severe damage to the respiratory system or death in the case of exposure to high concentrations. Contact with the liquid or vapor can severely burn the skin, eyes, and other tissue. The largest use of hydrogen fluoride is in the manufacture of fluorine-containing chemicals, particularly chlorofluorocarbons (CFCs). Hydrogen fluoride may be used in some petroleum refinery operations, aluminum production, nuclear applications, glass etching and polishing, and metal treating and cleaning. Hydrogen fluoride's acute toxicity prompted EPA to list it as an extremely hazardous substance (EHS), with a threshold planning quantity (TPQ) of 100 pounds, under Section 302 of the Emergency Planning and Community Right-to-Know Act (commonly known as SARA Title III).

  7. The Application of Electrodialysis to Desalting an Amino Acid Solution

    NASA Astrophysics Data System (ADS)

    García-García, Vicente; Montiel, Vicente; González-García, José; Expósito, Eduardo; Iniesta, Jesús; Bonete, Pedro; Inglés, Marina

    2000-11-01

    One of the main difficulties in preparing pharmaceutical products is isolating them from aqueous solutions of high salt concentration, as a high purity must be obtained. Several methods that employ organic solvents are normally used. In this paper, a novel method, electrodialysis, is presented together with its application to the desalting of an industrial effluent comprising an amino acid (p-hydroxyphenylglycine) with a high salt content (ammonium sulfate and sodium dihydrogenphosphate). It was possible to remove more than 70% of the initial salt content. From this solution with a low salt content, it is possible to isolate the amino acid with a higher purity. This experiment will enable the student to gain a useful knowledge of this technique and to work with typical figures of merit of electrodialysis such as current efficiency, electrical energy consumption, production of the process, removal of salt, and loss of amino acid. In addition the student learns the use of chromatographic techniques applied to the analysis of amino acids (HPLC) and salts (IC).

  8. Methanol Uptake By Low Temperature Aqueous Sulfuric Acid Solutions

    NASA Technical Reports Server (NTRS)

    Iraci, Laura T.; Essin, Andrew M.; Golden, David M.; Hipskind, R. Stephen (Technical Monitor)

    2001-01-01

    To evaluate the role of upper tropospheric and lower stratospheric aerosols in the global budget of methanol, the solubility and reactivity of CH3OH in aqueous sulfuric acid solutions are under investigation. Using standard uptake techniques in a Knudsen cell reactor, we have measured the effective Henry's law coefficient, H(*), for methanol dissolution into 45 to 70 percent by weight H2SO4. We find that methanol solubility ranges from 10(exp 5) to 10(exp 8) M/atm and increases with decreasing temperature and with increasing sulfuric acid content. These solubility measurements include uptake due to physical solvation and all rapid equilibria which are established in solution. Our data indicate that simple uptake by aqueous sulfuric acid particles will not be a significant sink for methanol in the UT/LS. These results differ from those recently reported in the literature, and an explanation of this disparity will be presented. In addition to solvation, reaction between primary alcohols and sulfuric acid does occur, leading to the production of alkyl sulfates. Literature values for the rate of this reaction suggest that formation of CH3OSO3H may proceed in the atmosphere but is not significant under our experimental conditions. Results obtained using a complementary equilibrium measurement technique confirm this directly. In addition, the extent of methanol sequestration via formation of mono- and dimethylsulfate will be evaluated under several atmospheric conditions.

  9. Experimental equilibrium between acid gases and ethanolamine solutions

    SciTech Connect

    Bhairi, A.M.

    1984-01-01

    The general subject area of this study is equilibrium solubility of carbon dioxide and hydrogen sulfide in solutions of some common ethanolamines. The amines studied are most widely used in the area of gas sweetening. They include monoethanolamine, diglycolamine, diethanolamine and methyldiethanolamine. Only limited data are available for some of these amines. The process involved developing simple apparatus and procedure for investigating the equilibrium solubility of carbon dioxide and hydrogen sulfide in aqueous alkanolamine solutions. The procedure uses a single equilibrium cell. No gas chromatograph nor liquid chemical analysis is required. Measurements of the solubility were made in different amine solution concentrations at acid gas partial pressures to 1000 psia and temperatures from 77 to 240{degree}F. The method used was found to be sound as indicated by the consistency and reproducibility of the data.

  10. Fluoride in diet

    MedlinePlus

    ... Infants can only get fluoride through drinking infant formulas. Breast milk has a negligible amount of fluoride ... of water to use in concentrated or powdered formulas. DO NOT use any fluoride supplement without talking ...

  11. Role of the P-F bond in fluoride-promoted aqueous VX hydrolysis: an experimental and theoretical study.

    PubMed

    Marciano, Daniele; Columbus, Ishay; Elias, Shlomi; Goldvaser, Michael; Shoshanim, Ofir; Ashkenazi, Nissan; Zafrani, Yossi

    2012-11-16

    Following our ongoing studies on the reactivity of the fluoride ion toward organophosphorus compounds, we established that the extremely toxic and environmentally persistent chemical warfare agent VX (O-ethyl S-2-(diisopropylamino)ethyl methylphosphonothioate) is exclusively and rapidly degraded to the nontoxic product EMPA (ethyl methylphosphonic acid) even in dilute aqueous solutions of fluoride. The unique role of the P-F bond formation in the reaction mechanism was explored using both experimental and computational mechanistic studies. In most cases, the "G-analogue" (O-ethyl methylphosphonofluoridate, Et-G) was observed as an intermediate. Noteworthy and of practical importance is the fact that the toxic side product desethyl-VX, which is formed in substantial quantities during the slow degradation of VX in unbuffered water, is completely avoided in the presence of fluoride. A computational study on a VX-model, O,S-diethyl methylphosphonothioate (1), clarifies the distinctive tendency of aqueous fluoride ions to react with such organophosphorus compounds. The facility of the degradation process even in dilute fluoride solutions is due to the increased reactivity of fluoride, which is caused by the significant low activation barrier for the P-F bond formation. In addition, the unique nucleophilicity of fluoride versus hydroxide toward VX, in contrast to their relative basicity, is discussed. Although the reaction outcomes were similar, much slower reaction rates were observed experimentally for the VX-model (1) in comparison to VX. PMID:23083335

  12. 40 CFR 60.212 - Standard for fluorides.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 6 2011-07-01 2011-07-01 false Standard for fluorides. 60.212 Section... Industry: Superphosphoric Acid Plants § 60.212 Standard for fluorides. (a) On and after the date on which... facility any gases which contain total fluorides in excess of 5.0 g/megagram (Mg) of equivalent P2O5...

  13. 40 CFR 60.212 - Standard for fluorides.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Standard for fluorides. 60.212 Section... Industry: Superphosphoric Acid Plants § 60.212 Standard for fluorides. (a) On and after the date on which... facility any gases which contain total fluorides in excess of 5.0 g/megagram (Mg) of equivalent P2O5...

  14. PROCESS FOR TREATING VOLATILE METAL FLUORIDES

    DOEpatents

    Rudge, A.J.; Lowe, A.J.

    1957-10-01

    This patent relates to the purification of uranium hexafluoride, made by reacting the metal or its tetrafluoride with fluorine, from the frequently contained traces of hydrofluoric acid. According to the present process, UF/sub 6/ containing as an impurity a small amount of hydrofluoric acid, is treated to remove such impurity by contact with an anhydrous alkali metal fluoride such as sodium fluoride. In this way a non-volatile complex containing hydrofluoric acid and the alkali metal fluoride is formed, and the volatile UF /sub 6/ may then be removed by distillation.

  15. Effect of phytic acid, ethylenediaminetetraacetic acid, and chitosan solutions on microhardness of the human radicular dentin

    PubMed Central

    Nikhil, Vineeta; Jaiswal, Shikha; Bansal, Parul; Arora, Rohit; Raj, Shalya; Malhotra, Pulkit

    2016-01-01

    Aim: The purpose of this study was to evaluate the effect of phytic acid, ethylenediaminetetraacetic acid (EDTA), and chitosan solutions on the microhardness of human radicular dentin. Materials and Methods: Thirty dentin specimens were randomly divided into three groups of 10 specimens each according to the irrigant used: G1 — 1% phytic acid, G2 — 17% EDTA, and G3 — 0.2% chitosan. A standardized volume of each chelating solution was used for 3 min. Dentin microhardness was measured before and after application at the cervical, middle, and apical levels with a Vickers indenter under a 200-g load and a 10-s dwell time. The results were analyzed using one-way analysis of variance (ANOVA) and Student's t test. Results: Microhardness of the radicular dentin varied at the cervical, middle, and apical levels. EDTA had the greatest overall effect, causing a sharp percentage reduction in dentin microhardness with a significant difference from phytic acid and chitosan (P = 0.002). However, phytic acid and chitosan differed insignificantly from each other (P = 0.887). Conclusion: All tested chelating solutions reduced microhardness of the radicular dentin layer at all the levels. However, reduction was least at the apical level. EDTA caused more reduction in dentin microhardness than chitosan while phytic acid reduced the least. PMID:27099428

  16. COMPLEX FLUORIDES OF PLUTONIUM AND AN ALKALI METAL

    DOEpatents

    Seaborg, G.T.

    1960-08-01

    A method is given for precipitating alkali metal plutonium fluorides. such as KPuF/sub 5/, KPu/sub 2/F/sub 9/, NaPuF/sub 5/, and RbPuF/sub 5/, from an aqueous plutonium(IV) solution by adding hydrogen fluoride and alkali-metal- fluoride.

  17. Toluene nitration in irradiated nitric acid and nitrite solution

    SciTech Connect

    Gracy Elias; Bruce J. Mincher; Stephen P. Mezyk; Jim Muller; Leigh R. Martin

    2011-04-01

    The kinetics, mechanisms, and stable products produced for the aryl alkyl mild ortho-para director - toluene, in irradiated nitric acid and neutral nitrite solutions were investigated using ?, and pulse radiolysis. Electron pulse radiolysis was used to determine the bimolecular rate constants for the reaction of toluene with different transient species produced by irradiation. HPLC with UV detection was primarily used to assess the stable reaction products. GC-MS and LC-MS were used to confirm the results from HPLC. Free-radical nitration reaction products were found in irradiated acidic and neutral media. In acidic medium, the ring substitution and side chain substitution and oxidation produced different nitro products. In ring substitution, nitrogen oxide radicals were added mainly to hydroxyl radical-produced cyclohexadienyl radical, and in side chain substitution they were added to the carbon-centered benzyl radical produced by H-atom abstraction. In neutral nitrite toluene solution, radiolytic ring nitration products approached a statistically random distribution, suggesting a free-radical reaction involving addition of the •NO2 radical.

  18. Concentration-Purification of Uranium from an Acid Leaching Solution

    NASA Astrophysics Data System (ADS)

    Guettaf, H.; Becis, A.; Ferhat, K.; Hanou, K.; Bouchiha, D.; Yakoubi, K.; Ferrad, F.

    2009-11-01

    Chemical processes for the elaboration of uranium concentrate from uranium ore have been studied. This process is composed of successive units operations: crushing, milling, acid conventional leaching, filtration-washing, purification-concentration by ion exchange resins and uranium precipitation. The acid leaching operating conditions allow us to obtain a recovery uranium rate of 93%. The uranium concentration of the pregnant solution is approximately of 1.2 g/l. This value justifies the use of ion exchange resins to the concentration-purification of our pregnant solution. We have noticed that the pregnant solution contains a relatively high phosphate concentration which causes a premature uranium precipitation at pH=1.8. This pH value is in general, considered optimal to obtain the highest amount of fixed uranium by the anionic resin. To avoid the precipitation of uranium, the pH=1.5 has been fixed. We have obtained at this condition a good adsorption capacity. A 75% uranium concentrate have been elaborated, but the filtration of this concentrate has been very difficult. We have also noticed an excessive sulphate concentration. In order to improve this process, we have tested nitrates as eluant at different operating conditions.

  19. Anodic dissolution of nickel in acidic chloride solutions

    NASA Astrophysics Data System (ADS)

    El Aal, E. E. Abd; Zakria, W.; Diab, A.; El Haleem, S. M. Abd

    2003-04-01

    The anodic dissolution of nickel was studied galvanostatically in hydrochloric acid solutions of various concentrations. The reaction orders of chloride ion and hydrogen ion concentrations were found to be 0.5 and 1.0, respectively. An anodic Tafel slope equal to 120 ± 10 mV · decade-1 was obtained. The dissolution rate of nickel at constant acid concentration was increased with stirring of the solution and increasing temperature. The activation energy, ΔH, for the anodic dissolution process was found to be 12 kcal · mol-1. The presence of oxygen in solutions assisted the passivation process. The effect of addition of aniline and some of its derivatives (o-, m-, and p-anisidine) as inhibitors on the dissolution kinetics of Ni in 1 M HCl was also investigated. These compounds inhibited the anodic dissolution of nickel without affecting the Tafel slope, indicating that the adsorption of such inhibitors could not interfere with the mechanism of metal dissolution.

  20. Sucrose and KF quenching system for solution phase parallel synthesis.

    PubMed

    Chavan, Sunil; Watpade, Rahul; Toche, Raghunath

    2016-01-01

    The KF, sucrose (table sugar) exploited as quenching system in solution phase parallel synthesis. Excess of electrophiles were covalently trapped with hydroxyl functionality of sucrose and due to polar nature of sucrose derivative was solubilize in water. Potassium fluoride used to convert various excess electrophilic reagents such as acid chlorides, sulfonyl chlorides, isocyanates to corresponding fluorides, which are less susceptible for hydrolysis and subsequently sucrose traps these fluorides and dissolves them in water thus removing them from reaction mixture. Various excess electrophilic reagents such as acid chlorides, sulfonyl chlorides, and isocyanates were quenched successfully to give pure products in excellent yields. PMID:27462506

  1. Sulfonic Acid- and Lithium Sulfonate-Grafted Poly(Vinylidene Fluoride) Electrospun Mats As Ionic Liquid Host for Electrochromic Device and Lithium-Ion Battery.

    PubMed

    Zhou, Rui; Liu, Wanshuang; Leong, Yew Wei; Xu, Jianwei; Lu, Xuehong

    2015-08-01

    Electrospun polymer nanofibrous mats loaded with ionic liquids (ILs) are promising nonvolatile electrolytes with high ionic conductivity. The large cations of ILs are, however, difficult to diffuse into solid electrodes, making them unappealing for application in some electrochemical devices. To address this issue, a new strategy is used to introduce proton conduction into an IL-based electrolyte. Poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) copolymer is functionalized with sulfonic acid through covalent attachment of taurine. The sulfonic acid-grafted P(VDF-HFP) electrospun mats consist of interconnected nanofibers, leading to remarkable improvement in dimensional stability of the mats. IL-based polymer electrolytes are prepared by immersing the modified mats in 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM(+)BF4(-)). It is found that the SO3(-) groups can have Lewis acid-base interactions with the cations (BMIM(+)) of IL to promote the dissociation of ILs, and provide additional proton conduction, resulting in significantly improved ionic conductivity. Using this novel electrolyte, polyaniline-based electrochromic devices show higher transmittance contrast and faster switching behavior. Furthermore, the sulfonic acid-grafted P(VDF-HFP) electrospun mats can also be lithiated, giving additional lithium ion conduction for the IL-based electrolyte, with which Li/LiCoO2 batteries display enhanced C-rate performance. PMID:26167794

  2. GADOLINIUM OXALATE SOLUBILITY MEASUREMENTS IN NITRIC ACID SOLUTIONS

    SciTech Connect

    Pierce, R.

    2012-02-22

    HB-Line will begin processing Pu solutions during FY2012 that will involve the recovery of Pu using oxalate precipitation and filtration. After the precipitation and filtration processes, the filtrate solution will be transferred from HB-Line to H-Canyon. The presence of excess oxalate and unfiltered Pu oxalate solids in these solutions create a criticality safety issue if they are sent to H-Canyon without controls in H-Canyon. One approach involves H-Canyon receiving the filtrate solution into a tank that is poisoned with soluble gadolinium (Gd). Decomposition of the oxalate will occur within a subsequent H-Canyon vessel. The receipt of excess oxalate into the H-Canyon receipt tanks has the potential to precipitate a portion of the Gd poison in the receipt tanks. Because the amount of Gd in solution determines the maximum amount of Pu solids that H-Canyon can receive, H-Canyon Engineering requested that SRNL determine the solubility of Gd in aqueous solutions of 4-10 M nitric acid (HNO{sub 3}), 4-12 g/L Gd, and 0.15-0.25 M oxalic acid (H{sub 2}C{sub 2}O{sub 4}) at 25 C. The target soluble Gd concentration is 6 g/L. The data indicate that the target can be achieved above 6 M HNO{sub 3} and below 0.25 M H{sub 2}C{sub 2}O{sub 4}. For 6 M HNO{sub 3}, 10.5 g/L and 7 g/L Gd are soluble in 0.15 M and 0.25 M H{sub 2}C{sub 2}O{sub 4}, respectively. In 4 M HNO{sub 3}, the Gd solubility drops significantly to 2 g/L and 0.25 g/L in 0.15 M and 0.25 M H{sub 2}C{sub 2}O{sub 4}, respectively. The solubility of Gd at 8-10 M HNO{sub 3} exceeds the solubility at 6 M HNO{sub 3}. The data for 4 M HNO{sub 3} showed good agreement with data in the literature. To achieve a target of 6 g/L soluble Gd in solution in the presence of 0.15-0.25 M oxalate, the HNO{sub 3} concentration must be maintained at or above 6 M HNO{sub 3}.

  3. Systems solutions by lactic acid bacteria: from paradigms to practice

    PubMed Central

    2011-01-01

    Lactic acid bacteria are among the powerhouses of the food industry, colonize the surfaces of plants and animals, and contribute to our health and well-being. The genomic characterization of LAB has rocketed and presently over 100 complete or nearly complete genomes are available, many of which serve as scientific paradigms. Moreover, functional and comparative metagenomic studies are taking off and provide a wealth of insight in the activity of lactic acid bacteria used in a variety of applications, ranging from starters in complex fermentations to their marketing as probiotics. In this new era of high throughput analysis, biology has become big science. Hence, there is a need to systematically store the generated information, apply this in an intelligent way, and provide modalities for constructing self-learning systems that can be used for future improvements. This review addresses these systems solutions with a state of the art overview of the present paradigms that relate to the use of lactic acid bacteria in industrial applications. Moreover, an outlook is presented of the future developments that include the transition into practice as well as the use of lactic acid bacteria in synthetic biology and other next generation applications. PMID:21995776

  4. Systems solutions by lactic acid bacteria: from paradigms to practice.

    PubMed

    de Vos, Willem M

    2011-08-30

    Lactic acid bacteria are among the powerhouses of the food industry, colonize the surfaces of plants and animals, and contribute to our health and well-being. The genomic characterization of LAB has rocketed and presently over 100 complete or nearly complete genomes are available, many of which serve as scientific paradigms. Moreover, functional and comparative metagenomic studies are taking off and provide a wealth of insight in the activity of lactic acid bacteria used in a variety of applications, ranging from starters in complex fermentations to their marketing as probiotics. In this new era of high throughput analysis, biology has become big science. Hence, there is a need to systematically store the generated information, apply this in an intelligent way, and provide modalities for constructing self-learning systems that can be used for future improvements. This review addresses these systems solutions with a state of the art overview of the present paradigms that relate to the use of lactic acid bacteria in industrial applications. Moreover, an outlook is presented of the future developments that include the transition into practice as well as the use of lactic acid bacteria in synthetic biology and other next generation applications. PMID:21995776

  5. Acid retardation method in analysis of strongly acidic solutions by inductively coupled plasma mass-spectrometry.

    PubMed

    Seregina, I F; Perevoznik, O A; Bolshov, M A

    2016-10-01

    Acid retardation on the sorbents as a technique for reduction of the acidity of the solutions prior to their analysis by inductively coupled plasma mass spectrometry was proposed and investigated. The proposed scheme provides substantial separation of the analytes and nitric acid, which allows direct introduction of the eluates in plasma without dilution. Two sorbents were examined - AV-17 anion-exchange resin and the Stirosorb 584 sorbent. Sorption and desorption of 38 elements on these sorbents were investigated. The efficiencies of the REEs' sorption on the anion-exchange and neutral sorbents were compared. The higher efficiency of the REEs and HNO3 separation was revealed for the neutral Stirosorb 584 sorbent. It was also found that most elements come out quantitatively of the column filled with the AV-17 resin after pumping 2-4mL of the solution. Wherein, the concentration of nitric acid decreased by 20 times. The anomalous behaviour of Ag, Pb, Th and U on the AV-17 resin was found. These analytes were eluted only after pumping 4 column volumes of deionized water. Na, K, Fe, Al and Li in concentrations within (50-1000mgL(-1)) range did not affect the recovery of REEs. The potential of ARM technique was demonstrate by the analysis of puriss. HNO3 and silverware. ARM enables to avoid dilution of highly acidic solutions prior to their introduction in ICP-MS. PMID:27474322

  6. Effects of acidic solutions on sexual reproduction of Pteridium aquilinum

    SciTech Connect

    Evans, L.S.; Conway, C.A.

    1980-01-01

    Experiments were performed to determine the effects of acidic solutions on spermatozoid motility and fertilization of gametophytes of Pteridium aquilinum. Buffered solutions (approx 0.0025 m) were used to simulate exposures to acidic precipitation for up to a 3.5 hr exposure. Experimental results suggest that the spermatozoid population can be subdivided into several groups with respect to pH sensitivity: About 25% spermatozoids are immobile one min after exposure to pH 6.1 buffer while about an equal percentage remain motile after 30 min exposure to buffer of pH 5.1. Between these two response extremes are two other subpopulations. One is quite sensitive to pH but shows some recovery if pH is between 5.6 and 6.1, while the second subpopulation does not seem to exhibit any motility recovery at all but is more resistant to acidity than the first subpopulation. To complement experiments that evaluate spermatozoid responses, experiments were performed to view the process of fertilization under controlled environmental conditions as well as under the canopy of a forest. Fertilization of gametophytes in uncovered petri dishes under a forest canopy was similar to results in aseptic culture after gametophytes were exposed to various pH levels and 86.6 micrometers sulfate. Fertilization at pH 4.5 and 3.6 was about one-half that occurring at pH 6.1. Fertilization in gametophytes exposed to pH 3.0 was about 10-20% of that occurring at pH 6.1. Addition of 86.6 micrometers sulfate decreased fertilization under all culture conditions. These experimental results suggest that fertilization in p. Aquilinum may be used as a bioindicator of contaminants in rainwater. The results demonstrate that spermatozoid motility (and the process of fertilization) is more acid sensitive than gametophytic and sporophytic tissues.

  7. How Does Fluoride Work?

    MedlinePlus

    ... Help White House Lunch Recipes How Does Fluoride Work? KidsHealth > For Kids > How Does Fluoride Work? Print A A A Text Size There's fluoride ... even in your water. But how does it work to keep teeth healthy? Let's find out. Fluoride ...

  8. Reduction of hexavalent chromium by ascorbic acid in aqueous solutions.

    PubMed

    Xu, Xiang-Rong; Li, Hua-Bin; Li, Xiao-Yan; Gu, Ji-Dong

    2004-11-01

    Hexavalent chromium is a priority pollutant in the USA and many other countries. Reduction of Cr(VI) to Cr(III) is environmentally favorable as the latter species is not toxic to most living organisms and also has a low mobility and bioavailability. Reduction of Cr(VI) by ascorbic acid (vitamin C) as a reductant was studied using potassium dichromate solution as the model pollutant. Effects of concentration of vitamin C, pH, temperature, irradiation and reaction time on the reduction of Cr(VI) were examined. Cr(VI) might be reduced by vitamin C not only in acidic conditions but also in weakly alkaline solutions. The reduction of Cr(VI) by vitamin C might occur not only under irradiation but also in the dark. Vitamin C is an important biological reductant in humans and animals, and not toxic. It is water-soluble and can easily permeate through various types of soils. The results indicate that vitamin C could be used in effective remediation of Cr(VI)-contaminated soils and groundwater in a wide range of pH, with or without sunlight. PMID:15488923

  9. Infrared optical constants of H2O ice, amorphous nitric acid solutions, and nitric acid hydrates

    NASA Technical Reports Server (NTRS)

    Toon, Owen B.; Koehler, Birgit G.; Middlebrook, Ann M.; Tolbert, Margaret A.; Jordon, Joseph

    1994-01-01

    We determined the infrared optical constants of nitric acid trihydrate, nitric acid dihydrate, nitric acid monohydrate, and solid amorphous nitric acid solutions which crystallize to form these hydrates. We have also found the infrared optical constants of H2O ice. We measured the transmission of infrared light throught thin films of varying thickness over the frequency range from about 7000 to 500/cm at temperatures below 200 K. We developed a theory for the transmission of light through a substrate that has thin films on both sides. We used an iterative Kramers-Kronig technique to determine the optical constants which gave the best match between measured transmission spectra and those calculated for a variety of films of different thickness. These optical constants should be useful for calculations of the infrared spectrum of polar stratospheric clouds.

  10. Removal of arsenious acid from sulfuric acidic solution using ultrasound oxidation and goethite

    NASA Astrophysics Data System (ADS)

    Okawa, Hirokazu; Yoshikawa, Tomohiro; Hosokawa, Ryota; Hangui, Shinji; Kawamura, Youhei; Sugawara, Katsuyasu

    2015-07-01

    We investigated the properties of synthetic goethite for the adsorption of As from strongly acidic solutions in ambient atmosphere under ultrasound irradiation. The goethite was successfully synthesized from iron-containing sulfuric acidic solution (1271 ppm) using an autoclave apparatus for 1 h at 0.12 MPa and 121 °C. The ratio of the iron eluted from the synthetic goethite to the acidic solution was only 0.58% at pH 2.1. Ultrasound irradiation (200 kHz, 200 W) was applied to oxidize 10 ppm of As(III) to As(V) at pH 2.2 for 60 min under various atmospheric conditions. Remarkably, the oxidation ratio of As(III) to As(V) is quite high (89.7%) at pH 2.2 in ambient atmosphere and is close to those obtained for Ar (95.3%) and O2 (95.9%) atmospheres. The As(III) removal ratio reached 94.5% after 60 min of irradiation. Therefore, goethite is a promising material for As adsorption using ultrasound oxidation in the acidic region in ambient atmosphere.

  11. Arsenic removal from acidic solutions with biogenic ferric precipitates.

    PubMed

    Ahoranta, Sarita H; Kokko, Marika E; Papirio, Stefano; Özkaya, Bestamin; Puhakka, Jaakko A

    2016-04-01

    Treatment of acidic solution containing 5g/L of Fe(II) and 10mg/L of As(III) was studied in a system consisting of a biological fluidized-bed reactor (FBR) for iron oxidation, and a gravity settler for iron precipitation and separation of the ferric precipitates. At pH 3.0 and FBR retention time of 5.7h, 96-98% of the added Fe(II) precipitated (99.1% of which was jarosite). The highest iron oxidation and precipitation rates were 1070 and 28mg/L/h, respectively, and were achieved at pH 3.0. Subsequently, the effect of pH on arsenic removal through sorption and/or co-precipitation was examined by gradually decreasing solution pH from 3.0 to 1.6 (feed pH). At pH 3.0, 2.4 and 1.6, the highest arsenic removal efficiencies obtained were 99.5%, 80.1% and 7.1%, respectively. As the system had ferric precipitates in excess, decreased arsenic removal was likely due to reduced co-precipitation at pH<2.4. As(III) was partially oxidized to As(V) in the system. In shake flask experiments, As(V) sorbed onto jarosite better than As(III). Moreover, the sorption capacity of biogenic jarosite was significantly higher than that of synthetic jarosite. The developed bioprocess simultaneously and efficiently removes iron and arsenic from acidic solutions, indicating potential for mining wastewater treatment. PMID:26705889

  12. Hydrogen production by photoelectrochemically splitting solutions of formic acid.

    PubMed

    Li, Lei; Guo, Wenliang; Zhu, Yusong; Wu, Yuping

    2011-10-17

    A TiO₂/FTO (FTO=fluorine-doped tin oxide) electrode was prepared by dip-coating FTO in a suspension of TiO₂ prepared from a sol-gel method and was used as a photoanode to split an aqueous solution of formic acid to produce hydrogen. The surface of the TiO₂/FTO film was covered with assemblies of TiO₂ nanoparticles with a diameter of approximately 20 nm. Under irradiation by using a Xe lamp, splitting of formic acid was performed at different applied current densities. Compared to splitting water or utilizing FTO and Pt foil as the anode, the splitting voltage is much lower and can be as low as -0.27 V. The results show that the splitting voltage is related to the concentration of free formate groups. The evolution rate of hydrogen measured by using gas chromatography is 130 μmol h⁻¹ at a current density of 20 mA cm⁻² and the energy-conversion efficiency can be 1.79 %. Photoelectrolysis of formic acid has the potential to be an efficient way to produce hydrogen with a high energy-conversion efficiency. PMID:21994155

  13. Conformation of poly(γ-glutamic acid) in aqueous solution.

    PubMed

    Muroga, Yoshio; Nakaya, Asami; Inoue, Atsuki; Itoh, Daiki; Abiru, Masaya; Wada, Kaori; Takada, Masako; Ikake, Hiroki; Shimizu, Shigeru

    2016-04-01

    Local conformation and overall conformation of poly(γ-DL-glutamic acid) (PγDLGA) and poly(γ-L-glutamic acid) (PγLGA) in aqueous solution was studied as a function of degree of ionization ε by (1) H-NMR, circular dichroism, and potentiometric titration. It was clarified that their local conformation is represented by random coil over an entire ε range and their overall conformation is represented by expanded random-coil in a range of ε > ε(*) , where ε(*) is about 0.3, 0.35, 0.45, and 0.5 for added-salt concentration of 0.02M, 0.05M, 0.1M, and 0.2M, respectively. In a range of ε < ε(*) , however, ε dependence of their overall conformation is significantly differentiated from each other. PγDLGA tends to aggregate intramolecularly and/or intermolecularly with decreasing ε, but PγLGA still behaves as expanded random-coil. It is speculated that spatial arrangement of adjacent carboxyl groups along the backbone chain essentially affects the overall conformation of PγGA in acidic media. PMID:26574908

  14. INTERACTION OF AQUEOUS SOLUTIONS OF CHLORINE WITH MALIC ACID, TARTARIC ACID, AND VARIOUS FRUIT JUICES, A SOURCE OF MUTAGENS

    EPA Science Inventory

    The interactions of aqueous solutions of chlorine with some fruit acids (citric acid, DL-malic acid, and L-tartaric acid) at different pH values were studied. iethyl ether extraction followed by GC/MS analysis indicated that a number of mutagens (certain chlorinated propanones an...

  15. Fluoride inhibition of proton-translocating ATPases of oral bacteria.

    PubMed Central

    Sutton, S V; Bender, G R; Marquis, R E

    1987-01-01

    The ATPases of isolated membranes of lactic acid bacteria were found to be inhibited by fluoride in a complex manner. Among the enzymes tested, that of Streptococcus mutans GS-5 was the most sensitive to fluoride, and the initial rate of hydrolysis of ATP was reduced 50% by approximately 3 mM fluoride. The enzyme of Lactobacillus casei ATCC 4646 was the most resistant, and about 25 mM fluoride was required for 50% inhibition. The response to fluoride appeared to involve reversible, noncompetitive inhibition during short exposure to low levels of fluoride and nonreversible inhibition at higher fluoride levels. In addition, kinetic studies of the effects of fluoride on the enzymes of membranes of S. mutans and L. casei indicated that reversible inhibition was at least partly overcome at high levels of either ATP or Mg. The effects of pH on fluoride inhibition of ATPases were markedly different from the effects of pH on inhibition of acid/base regulation of intact cells by fluoride. It appeared that formation of HF was not required for inhibition of the ATPases. F1 ATPases isolated from the membranes by washing with buffers of low ionic strength proved to be less sensitive to fluoride than the membrane-associated F1F0 holoenzymes, and it was concluded that the F0 or membrane sector of the holoenzyme is involved in fluoride inhibition. PMID:2889674

  16. A literature review on the chemical and physical properties of uranyl fluoride (UO sub 2 F sub 2 )

    SciTech Connect

    Myers, W.L. Illinois Univ., Urbana, IL . Dept. of Nuclear Engineering)

    1990-08-01

    This report reviews the preparation and properties of uranyl fluoride. Data are given on the crystal structure, solubility in water, specific gravity, density, specific heat, enthalpy, entropy, acidity, corrosion properties, and refractive indices. Empirical formulas are given to calculate specific gravity, density of aqueous solutions, molal volume, and refractive indices. 13 refs., 3 figs., 11 tabs.

  17. The extraction of actinides from nitric acid solutions with diamides of dipicolinic acid

    NASA Astrophysics Data System (ADS)

    Lapka, Joseph L.; Paulenova, Alena; Alyapyshev, Mikhail Yu; Babain, Vasiliy A.; Law, Jack D.; Herbst, R. Scott

    2010-03-01

    Diamides of dipicolinic acid (N,N'-diethyl-N,N'-ditolyl-dipicolinamide, EtTDPA) were synthesized and evaluated for their extraction capability for actinides. In this work the extractions of neptunium(V), protactinium(V), and thorium(IV) with EtTDPA in a polar fluorinated diluent from nitric acid were investigated. EtTDPA shows a high affinity for Th(IV) even at millimolar concentrations. Np(V) and Pa(V) are both reasonably extractable with EtTDPA; however, near saturated solutions are required to achieve appreciable distribution ratios. A comparison with previously published actinide extraction data is given.

  18. Radiolysis gases from nitric acid solutions containing HSA and HAN

    SciTech Connect

    Smith, J.R.

    1994-10-28

    The concentration of hydrogen (H{sub 2}) in the radiolytically produced off-gas from 2.76-4.25M HNO{sub 3}/PU solutions has been found to be greatly reduced in the presence of sulfamic acid (HSA) and hydroxylamine nitrate (HAN). The H{sub 2} concentration ([H{sub 2}]) is reduced from 35 percent to about 4 percent by dilution caused from an increase in the production rates of nitrogen (N{sub 2}), nitrous oxide (N{sub 2}O), and oxygen (O{sub 2}) gases. The generation rate of H{sub 2} was not affected by HSA or HAN giving a measured radiolytic yield, G(H{sub 2}), value of 0.201 molecules/100 eV for 2.765M NO{sub 3}{sup -} solution (a value of 0.213 is predicted from previous data). The G(H{sub 2}) values are dependent on the solution nitrate concentration ([NO{sub 3}{sup -}]). The generation rates of N{sub 2}, N{sub 2}O, and O{sub 2} are not dependent on the [NO{sub 3}{sup -}] in this narrow range, but are dependent on the presence of HSA and the concentration of HAN. The percentage [H{sub 2}] for the 2.5 to 3.0M NO{sub 3}{sup -} range expected in the off- from the FB-Line Pu{sup +3} Hold Tanks is conservatively estimated to be about 3.5 to 4.5 % for Pu + 3 solutions initially containing 0.023M HAN/0.165M HSA. The upper limit [H{sub 2}] may actually be about 4.1 % (4.3 % at 90 % confidence limits) but more {open_quotes}initial{close_quotes} off-gas rate data is needed at about 2.9M [NO{sub 3}{sup -}] in Pu{sup +3} solution for verification. Addition of ascorbic acid had no effect on the off-gas rate of Pu{sup +3} solutions containing HSA and NO{sub 3}{sup -} concentrations higher than those expected in the hold tanks. The maximum {open_quotes}hold time{close_quotes} for 50 grams/liter Pu{sup +3}/0.165M HSA/0.023M HAN/2.5-3.0M HNO{sub 3} solution is 20.3{+-}2.1 days. After this time the HSA initially present will become exhausted and the [H{sub 2}] will increase to 35 %. This hold time may be longer in [NO{sub 3}{sup -}] < 3.0M, but again more study is needed.

  19. GADOLINIUM OXALATE SOLUBILITY MEASUREMENTS IN NITRIC ACID SOLUTIONS

    SciTech Connect

    Pierce, R. A.

    2012-03-12

    HB-Line will begin processing Pu solutions during FY2012 that will involve the recovery of Pu using oxalate precipitation and filtration. After the precipitation and filtration processes, the filtrate solution will be transferred from HB-Line to H-Canyon. The presence of excess oxalate and unfiltered Pu oxalate solids in these solutions create a criticality safety issue if they are sent to H-Canyon without controls in H-Canyon. One approach involves H-Canyon receiving the filtrate solution into a tank that is poisoned with soluble gadolinium (Gd). Decomposition of the oxalate will occur within a subsequent H-Canyon vessel. The receipt of excess oxalate into the H-Canyon receipt tanks has the potential to precipitate a portion of the Gd poison in the receipt tanks. Because the amount of Gd in solution determines the maximum amount of Pu solids that H-Canyon can receive, H-Canyon Engineering requested that SRNL determine the solubility of Gd in aqueous solutions of 4-10 M nitric acid (HNO{sub 3}), 4-12 g/L Gd, and 0.15-0.25 M oxalic acid (H{sub 2}C{sub 2}O{sub 4}) at 25 °C. The target soluble Gd concentration is 6 g/L. The data indicate that the target can be achieved above 6 M HNO{sub 3} and below 0.25 M H{sub 2}C{sub 2}O{sub 4}. At 25 °C, for 6 M HNO{sub 3}, 11 g/L and 7 g/L Gd are soluble in 0.15 M and 0.25 M H{sub 2}C{sub 2}O{sub 4}, respectively. In 4 M HNO{sub 3}, the Gd solubility drops significantly to 2.5 g/L and 0.8 g/L in 0.15 M and 0.25 M H{sub 2}C{sub 2}O{sub 4}, respectively. The solubility of Gd at 8-10 M HNO{sub 3} exceeds the solubility at 6 M HNO{sub 3}. The data for 4 M HNO{sub 3} showed good agreement with data in the literature. To achieve a target of 6 g/L soluble Gd in solution in the presence of 0.15-0.25 M oxalate, the HNO{sub 3} concentration must be maintained at or above 6 M HNO{sub 3}. The solubility of Gd in 4 M HNO{sub 3} with 0.15 M oxalate at 10 °C is about 1.5 g/L. For 6 M HNO{sub 3} with 0.15 M oxalate, the solubility of Gd at 10

  20. Optical properties of chitosan in aqueous solution of L- and D-ascorbic acids

    NASA Astrophysics Data System (ADS)

    Malinkina, Olga N.; Shipovskaya, Anna B.; Kazmicheva, Olga F.

    2016-04-01

    The optical properties of aqueous chitosan solutions in L- and D-ascorbic acids were studied by optical rotatory dispersion and spectrophotometry. The specific optical rotation [α] of all chitosan solutions tested was positive, in contrast to aqueous solutions of the ascorbic acid enantiomers, which exhibit an inverse relationship of [α] values. Significant differences in the absolute values of [α] of the chitosan solutions at polymer-acid ratios exceeding the equimolar one were found.

  1. Functional and surface-active membranes from poly(vinylidene fluoride)-graft-poly(acrylic acid) prepared via RAFT-mediated graft copolymerization.

    PubMed

    Ying, L; Yu, W H; Kang, E T; Neoh, K G

    2004-07-01

    Poly (vinylidene fluoride) (PVDF) with "living" poly (acrylic acid) (PAAc) side chains (PVDF-g-PAAc) was prepared by reversible addition-fragmentation chain transfer (RAFT)-mediated graft copolymerization of acrylic acid (AAc) with the ozone-pretreated PVDF. The chemical composition and structure of the copolymers were characterized by elemental analysis, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The copolymer could be readily cast into pH-sensitive microfiltration (MF) membranes with enriched living PAAc graft chains on the surface (including the pore surfaces) by phase inversion in an aqueous medium. The surface composition of the membranes was determined by X-ray photoelectron spectroscopy. The morphology of the membranes was characterized by scanning electron microscopy. The pore size distribution of the membranes was found to be much more uniform than that of the corresponding membranes cast from PVDF-g-PAAc prepared by the "conventional" free-radical graft copolymerization process. Most important of all, the MF membranes with surface-tethered PAAc macro chain transfer agents, or the living membrane surfaces, could be further functionalized via surface-initiated block copolymerization with N-isopropylacrylamide (NIPAAM) to obtain the PVDF-g-PAAc-b-PNIPAAM MF membranes, which exhibited both pH- and temperature-dependent permeability to aqueous media. PMID:16459627

  2. The effect of stannous fluoride on human plaque acidogenicity in situ (Stephan curve).

    PubMed

    Svatun, B; Attramadal, A

    1978-01-01

    A system employing an Ingold glass electrode was shown to give reliable measurements of pH drops in dental plaque in situ (Stephan curve readings). The system was used to demonstrate that mouthrinses of 0.2 per cent aqueous solutions of stannous fluoride reduced the pH drops markedly for at least seven hours. A reduction of the stannous fluoride concentration increased the pH drops and decreased the duration of the inhibiting effect. A commercial toothpaste containing stannous fluoride and stannous pyrophosphate had an effect similar to the 0.2 per cent mouthrinse. It was shown that tin accumulated in dental plaque after application of solutions containing stannous fluoride. About 40 per cent of the amount of tin present in the plaque immediately after the mouthrinse was still retained seven hours later. It is suggested that the reduction in acid formation may be caused by stannous ions adsorbing to the bacterial cell wall thus disturbing membrane transport mechanisms, or through inhibition of enzyme systems essential in the fermentation of sugars. The observed effect may be a part of the mechanism involved in the caries preventive function of stannous fluoride. PMID:30252

  3. Fluoride metabolism in Acacia georginae Gidyea

    PubMed Central

    Peters, R. A.; Murray, L. R.; Shorthouse, M.

    1965-01-01

    1. The metabolism of fluoride in seedlings and small plants of Acacia georginae has been studied with the idea of finding the conditions under which the plant makes fluoroacetate in the laboratory. 2. Individual seedlings vary in the extent to which they take up fluoride and convert it into a form other than inorganic which is here called `organic' fluoride, F(org.). The differences between the toxicity of A. georginae Gidyea trees may therefore be genetic in origin. 3. The uptake of fluoride from solutions 0·525–1·05mm (10–20p.p.m.) was not large. In 1–4 days it reached 8 p.p.m. in the aerial parts and 16 p.p.m. in the roots. Unlike the distribution of the halogen in grass, total fluoride was greater than inorganic fluoride. It was almost a rule that more `organic' fluoride was present in the roots than in the aerial parts. 4. With higher concentrations of fluoride 10·5–15·75mm (200–300p.p.m.) much larger amounts of fluoride were taken up, especially by the roots, and much more apparent organic fluoride was formed. 5. pH had a large influence upon the intake, this being lowest at an initial pH8·4 and highest at pH4·0. The pH outside this range was not investigated. Some observations have been made with a view to clarifying the biochemical paths for the synthesis of the C–F bond. 6. There is no evidence that chloride is an intermediary in synthesis. 7. Succinate is not accumulated in fluoride-stressed plants, suggesting that succinate dehydrogenase is not inhibited. 8. Enolase does not appear to be inhibited in vivo. PMID:14342508

  4. Effects of acid-etching solutions on human enamel and dentin.

    PubMed

    Fanchi, M; Breschi, L

    1995-06-01

    Nine noncarious human molars were extracted and stored in saline solution. Three standard occlusal cavities with beveled enamel margins were prepared on each tooth and etched with the etching solutions of three dentinal adhesive systems: (1) 37% phosphoric acid solution, (2) 4.3% oxalic acid and 2.6% aluminum salts solution, and (3) 10% maleic acid solution. Scanning electron microscopic analysis revealed that all the etching solutions affected the enamel surface morphology. The solution of oxalic acid and aluminum salts removed primarily the prism core material and partially the periphery of the prisms, but did not affect the nonbeveled enamel surface. Phosphoric and maleic acids removed both prism core materials and prism periphery; these specimens also showed areas in which no prism morphology could be detected. These two acids also removed apatite crystals from the prism core of the intact enamel surface. PMID:8602425

  5. The effect of bicarbonate/fluoride dentifrices on human plaque pH.

    PubMed

    Blake-Haskins, J C; Gaffar, A; Volpe, A R; Bánóczy, J; Gintner, Z; Dombi, C

    1997-01-01

    The acidogenic response in dental plaque after rinsing with sodium bicarbonate/fluoride dentifrice slurries was studied using three intra-oral models. In the first model, resting plaque pH was monitored in mesiobuccal plaque on upper molars and premolars in six healthy subjects after abstinence from normal oral hygiene for three days. These measurements were followed by a three-minute rinse with 10% sucrose and, following a two-minute interval, a three-minute rinse with a test dentifrice slurry. After the test dentifrice rinse, pH was monitored at regular intervals up to 60 minutes. Flow rate, pH and buffer capacity of stimulated saliva were also determined. Changes in resting pH, plaque pH minima, and maximum pH drop were calculated. A clear elevation in the resting pH was observed after bicarbonate/fluoride dentifrice rinses, and a significant increase was obtained in the pH minima. The smallest pH drop also was found after treatment with the bicarbonate/fluoride dentifrice rinse treatment (p < 0.02). A second model using telemetric partial dentures with interproximally placed micro-antimony pH electrodes was used to study the effects of rinsing with increasing concentrations of sodium bicarbonate and calcium carbonate solutions, and with a fluoride dentifrice containing sodium bicarbonate. The response to these treatments was found to be rapid, dose-dependent, and was the greatest from the sodium bicarbonate. A third model used 24 subjects to assess the effects of sodium bicarbonate/fluoride dentifrice on plaque pH before and after a glucose challenge. The use of the bicarbonate/fluoride dentifrice resulted in significantly less measurable plaque acid than the fluoride dentifrice treatment. Collectively, these results indicate bicarbonate in dentifrice to be an effective buffering agent for stabilizing the pH and neutralizing plaque acids in dental plaque. PMID:9586535

  6. PROCESS FOR THE PRODUCTION OF AMMONIUM URANIUM FLUORIDE

    DOEpatents

    Ellis, A.S.; Mooney, R.B.

    1953-08-25

    This patent relates to the preparation of ammonium uranium fluoride. The process comprises adding a water soluble fluoride to an aqueous solution of a uranous compound containing an ammonium salt, and isolating the resulting precipitate. This patent relates to the manufacture of uranium tetnafluoride from ammonium uranium fluoride, NH/sub 4/UF/sub 5/. Uranium tetrafluoride is prepared by heating the ammonium uranium fluoride to a temperature at which dissociation occurs with liberation of ammonium fluoride. Preferably the process is carried out under reduced pressure, or in a current of an inert gas.

  7. Fluoride and Water (For Parents)

    MedlinePlus

    ... Things to Know About Zika & Pregnancy Fluoride and Water KidsHealth > For Parents > Fluoride and Water Print A ... to 19-year-olds continue Fluoride and the Water Supply For more than 60 years, water fluoridation ...

  8. Interaction of trace elements in acid mine drainage solution with humic acid.

    PubMed

    Suteerapataranon, Siripat; Bouby, Muriel; Geckeis, Horst; Fanghänel, Thomas; Grudpan, Kate

    2006-06-01

    The release of metal ions from a coal mining tailing area, Lamphun, Northern Thailand, is studied by leaching tests. Considerable amounts of Mn, Fe, Al, Ni and Co are dissolved in both simulated rain water (pH 4) and 10 mg L(-1) humic acid (HA) solution (Aldrich humic acid, pH 7). Due to the presence of oxidizing pyrite and sulfide minerals, the pH in both leachates decreases down to approximately 3 combined with high sulfate concentrations typical to acid mine drainage (AMD) water composition. Interaction of the acidic leachates upon mixing with ground- and surface water containing natural organic matter is simulated by subsequent dilution (1:100; 1:200; 1:300; 1:500) with a 10 mg L(-1) HA solution (ionic strength: 10(-3) mol L(-1)). Combining asymmetric flow field-flow fractionation (AsFlFFF) with UV/Vis and ICP-MS detection allows for the investigation of metal ion interaction with HA colloid and colloid size evolution. Formation of colloid aggregates is observed by filtration and AsFlFFF depending on the degree of the dilution. While the average HA size is initially found to be 2 nm, metal-HA complexes are always found to be larger. Such observation is attributed to a metal induced HA agglomeration, which is found even at low coverage of HA functional groups with metal ions. Increasing the metal ion to HA ratio, the HA bound metal ions and the HA entities are growing in size from <3 to >450 nm. At high metal ion to HA ratios, precipitation of FeOOH phases and HA agglomeration due to colloid charge neutralization by complete saturation of HA complexing sites are responsible for the fact that most of Fe and Al precipitate and are found in a size fraction >450 nm. In the more diluted solutions, HA is more relevant as a carrier for metal ion mobilization. PMID:16631855

  9. Characterization and adsorption properties of a lanthanum-loaded magnetic cationic hydrogel composite for fluoride removal.

    PubMed

    Dong, Shuoxun; Wang, Yili

    2016-01-01

    In this study, a novel lanthanum-loaded magnetic cationic hydrogel (MCH-La) was synthesized for fluoride adsorption from drinking water. The adsorption kinetics, isotherms, and effects of pH and co-existing anions on fluoride uptake by MCH-La were evaluated. FTIR, Raman and XPS were used to analyze the fluoride adsorption mechanism of MCH-La. Results showed that MCH-La had positive zeta potential values of 23.6-8.0 mV at pH 3.0-11.0, with the magnitude of saturation magnetization up to 10.3 emu/g. The fluoride adsorption kinetics by MCH-La fitted well with the fractal-like-pseudo-second-order model, and the adsorption capacity reached 93% of the ultimate adsorption capacity within the first 10 min. The maximum fluoride adsorption capacity for MCH-La was 136.78 mg F(-)/g at an equilibrium fluoride concentration of 29.3 mg/L and pH 7.0. Equilibrium adsorption data showed that the Sips model was more suitable than the Langmuir and Freundlich models. MCH-La still had more than 100 mg of F(-)/g adsorption capacity at a strongly alkaline solution (pH > 10). The adsorption process was highly pH-dependent, and the optimal adsorption was attained at pH 2.8-4.0, corresponding to ligand exchange, electrostatic interactions, and Lewis acid-base interactions. With the exception of both anions of HCO3(-) and SiO4(4-), Cl(-), NO3(-), and SO4(2-) did not evidently prevent fluoride removal by MCH-La at their real concentrations in natural groundwater. The fluoride adsorption capacity of the regenerated MCH-La approached 70% of the fresh MCH-La from the second to fifth recycles. FTIR and Raman spectra revealed that C-O and CO functional groups on MCH contributed to the fluoride adsorption, this finding was also confirmed by the XPS F 1s spectra. Deconvolution of C 1s spectra before and after fluoride adsorption indicated that the carboxyl, anhydride, and phenol groups of MCH were involved in the fluoride removal. PMID:26613180

  10. Dentifrice fluoride and abrasivity interplay on artificial caries lesions.

    PubMed

    Nassar, Hani M; Lippert, Frank; Eckert, George J; Hara, Anderson T

    2014-01-01

    Incipient caries lesions on smooth surfaces may be subjected to toothbrushing, potentially leading to remineralization and/or abrasive wear. The interplay of dentifrice abrasivity and fluoride on this process is largely unknown and was investigated on three artificially created lesions with different mineral content/distribution. 120 bovine enamel specimens were randomly allocated to 12 groups (n = 10), resulting from the association of (1) lesion type [methylcellulose acid gel (MeC); carboxymethylcellulose solution (CMC); hydroxyethylcellulose gel (HEC)], (2) slurry abrasive level [low (REA 4/ RDA 69); high (REA 7/RDA 208)], and (3) fluoride concentration [0/275 ppm (14.5 mM) F as NaF]. After lesion creation, specimens were brushed in an automated brushing machine with the test slurries (50 strokes 2×/day). Specimens were kept in artificial saliva in between brushings and overnight. Enamel surface loss (SL) was determined by optical profilometry after lesion creation, 1, 3 and 5 days. Two enamel sections (from baseline and post-brushing areas) were obtained and analyzed microradiographically. Data were analyzed by analysis of variance and Tukey's tests (α = 5%). Brushing with high-abrasive slurry caused more SL than brushing with low-abrasive slurry. For MeC and CMC lesions, fluoride had a protective effect on SL from day 3 on. Furthermore, for MeC and CMC, there was a significant mineral gain in the remaining lesions except when brushed with high-abrasive slurries and 0 ppm F. For HEC, a significant mineral gain took place when low-abrasive slurry was used with fluoride. The tested lesions responded differently to the toothbrushing procedures. Both slurry fluoride content and abrasivity directly impacted SL and mineral gain of enamel caries lesions. PMID:24993884

  11. Deposition of fluoride on enamel surfaces released from varnishes is limited to vicinity of fluoridation site

    PubMed Central

    Lennon, A. M.; Yakin, M.; Becker, K.; Buchalla, W.; Attin, R.; Wiegand, A.

    2006-01-01

    The aim of the in-situ study was to determine fluoride uptake in non-fluoridated, demineralized enamel after application of fluoride varnishes on enamel samples located at various distances from the non-fluoridated samples. All enamel samples used were demineralized with acidic hydroxyethylcellulose before the experiment. Intra-oral appliances were worn by ten volunteers in three series: (1, Mirafluorid, 0.15% F; 2, Duraphat, 2.3% F and 3, unfluoridated controls) of 6 days each. Each two enamel samples were prepared from 30 bovine incisors. One sample was used for the determination of baseline fluoride content (BFC); the other was treated according to the respective series and fixed in the intra-oral appliance for 6 days. Additionally, from 120 incisors, each four enamel samples were prepared (one for BFC). Three samples (a–c) were placed into each appliance at different sites: (a) directly neighboured to the fluoridated specimen (=next), (b) at 1-cm distance (=1 cm) and (c) in the opposite buccal aspect of the appliance (=opposite). At these sites, new unfluoridated samples were placed at days 1, 3 and 5, which were left in place for 1 day. The volunteers brushed their teeth and the samples with fluoridated toothpaste twice per day. Both the KOH-soluble and structurally bound fluoride were determined in all samples to determine fluoride uptake and were statistically analyzed. One day, after fluoridation with Duraphat, KOH-soluble fluoride uptake in specimen a (=next) was significantly higher compared to the corresponding samples of both the control and Mirafluorid series, which in turn were not significantly different from each other. At all other sites and time points, fluoride uptake in the enamel samples were not different from controls for both fluoride varnishes. Within the first day after application, intra-oral-fluoride release from the tested fluoride varnish Duraphat leads to KOH-soluble fluoride uptake only in enamel samples located in close

  12. Comparison of peak shape in hydrophilic interaction chromatography using acidic salt buffers and simple acid solutions.

    PubMed

    Heaton, James C; Russell, Joseph J; Underwood, Tim; Boughtflower, Robert; McCalley, David V

    2014-06-20

    The retention and peak shape of neutral, basic and acidic solutes was studied on hydrophilic interaction chromatography (HILIC) stationary phases that showed both strong and weak ionic retention characteristics, using aqueous-acetonitrile mobile phases containing either formic acid (FA), ammonium formate (AF) or phosphoric acid (PA). The effect of organic solvent concentration on the results was also studied. Peak shape was good for neutrals under most mobile phase conditions. However, peak shapes for ionised solutes, particularly for basic compounds, were considerably worse in FA than AF. Even neutral compounds showed deterioration in performance with FA when the mobile phase water concentration was reduced. The poor performance in FA cannot be entirely attributed to the negative impact of ionic retention on ionised silanols on the underlying silica base materials, as results using PA at lower pH (where their ionisation is suppressed) were inferior to those in AF. Besides the moderating influence of the salt cation on ionic retention, it is likely that salt buffers improve peak shape due to the increased ionic strength of the mobile phase and its impact on the formation of the water layer on the column surface. PMID:24813934

  13. Release of nitrous acid and nitrogen dioxide from nitrate photolysis in acidic aqueous solutions.

    PubMed

    Scharko, Nicole K; Berke, Andrew E; Raff, Jonathan D

    2014-10-21

    Nitrate (NO3(-)) is an abundant component of aerosols, boundary layer surface films, and surface water. Photolysis of NO3(-) leads to NO2 and HONO, both of which play important roles in tropospheric ozone and OH production. Field and laboratory studies suggest that NO3¯ photochemistry is a more important source of HONO than once thought, although a mechanistic understanding of the variables controlling this process is lacking. We present results of cavity-enhanced absorption spectroscopy measurements of NO2 and HONO emitted during photodegradation of aqueous NO3(-) under acidic conditions. Nitrous acid is formed in higher quantities at pH 2-4 than expected based on consideration of primary photochemical channels alone. Both experimental and modeled results indicate that the additional HONO is not due to enhanced NO3(-) absorption cross sections or effective quantum yields, but rather to secondary reactions of NO2 in solution. We find that NO2 is more efficiently hydrolyzed in solution when it is generated in situ during NO3(-) photolysis than for the heterogeneous system where mass transfer of gaseous NO2 into bulk solution is prohibitively slow. The presence of nonchromophoric OH scavengers that are naturally present in the environment increases HONO production 4-fold, and therefore play an important role in enhancing daytime HONO formation from NO3(-) photochemistry. PMID:25271384

  14. A case study in the treatment of spent pickling acids for fluoride compliance at a metals finishing facility

    SciTech Connect

    Francis, J.T.; Walters, J.; Evans, D.

    1995-12-31

    A metal finishing facility located in the Los Angeles area processes coiled steel sheets (300 and 400 series) and other sheet metal alloys by annealing, pickling and cold rolling operations. The facility acquires steel from large manufacturers or mills and finishes to a prescribed thickness, hardness, and grade depending on customers needs, for sale to metal product manufacturers such as can manufacturers and prefabricated steel building industries. Specialty metal alloys such as nickel-cobalt or titanium are also processed for use in aerospace industry applications. The facility produces about 10,000 tons of metal sheets per year and in the process generates about 40,000 gallons per day (gpd) of wastewater that is pretreated for metals removal and discharged to the sewer. About 30,000 gallons per month of spent acid are generated--much of which is used for pH adjustment in the pretreatment system. Acids of concern are sulfuric acid, hydrofluoric acid and nitric acid. The wastewater treatment system (WWTS) is equipped for chromium reduction and metals precipitation and handles the wastewater, the spent acids and other alkaline wastes generated at the facility. An estimated 50 tons of hazardous waste sludge are generated and disposed of on a monthly basis.

  15. Compatible solute influence on nucleic acids: Many questions but few answers

    PubMed Central

    Kurz, Matthias

    2008-01-01

    Compatible solutes are small organic osmolytes including but not limited to sugars, polyols, amino acids, and their derivatives. They are compatible with cell metabolism even at molar concentrations. A variety of organisms synthesize or take up compatible solutes for adaptation to extreme environments. In addition to their protective action on whole cells, compatible solutes display significant effects on biomolecules in vitro. These include stabilization of native protein and nucleic acid structures. They are used as additives in polymerase chain reactions to increase product yield and specificity, but also in other nucleic acid and protein applications. Interactions of compatible solutes with nucleic acids and protein-nucleic acid complexes are much less understood than the corresponding interactions of compatible solutes with proteins. Although we may begin to understand solute/nucleic acid interactions there are only few answers to the many questions we have. I summarize here the current state of knowledge and discuss possible molecular mechanisms and thermodynamics. PMID:18522725

  16. Preparation and characterization of pH-sensitive and antifouling poly(vinylidene fluoride) microfiltration membranes blended with poly(methyl methacrylate-2-hydroxyethyl methacrylate-acrylic acid).

    PubMed

    Ju, Junping; Wang, Chao; Wang, Tingmei; Wang, Qihua

    2014-11-15

    Functional terpolymer of poly(methyl methacrylate-2-hydroxyethyl methacrylate-acrylic acid) (P(MMA-HEMA-AA)) was synthesized via a radical polymerization method. The terpolymer could be directly blended with poly(vinylidene fluoride) (PVDF) to prepare the microfiltration (MF) membranes via phase separate process. The synthesized polymers were characterized by Fourier transform infrared (FTIR), the nuclear magnetic resonance proton spectra ((1)H NMR). The membrane had the typical asymmetric structure and the hydrophilic side chains tended to aggregate on the membrane surface. The surface enrichment of amphiphilic copolymer and morphology of MF membranes were characterized by Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR) and scanning electron microscopy (SEM). The contact angle (CA) and water uptake were also tested to assess the hydrophilicity and wetting characteristics of the polymer surface. The water filtration properties were measured. It was found the modified membranes showed excellent pH-sensitivity and pH-reversibility behavior. Furthermore, the hydrophilicity of the blended membranes increased, and the membranes showed good protein antifouling property. PMID:25203908

  17. Fluoridation update 2014.

    PubMed

    Allukian, Myron; Wong, Chloe

    2014-01-01

    This year more than 4 million people living in 140 communities in Massachusetts will have the health and economic benefits of community water fluoridation. However Massachusetts is ranked only 37th in the country for fluoridation, with just 62 percent of the population on a public water supply living in fluoridated communities. Nationally, more than 210 million Americans, about 74.6 percent of the U.S. population on a community water supply live in fluoridated communities. PMID:25226771

  18. EXAFS Study on the Reactions Between Iron And Fulvic Acid in Acid Aqueous Solutions

    SciTech Connect

    Schaik, J.W.J.van; Persson, I.; Kleja, D.B.; Gustafsson, J.P.

    2009-05-26

    Iron(III) competes with trace metals for binding sites on organic ligands. We used X-ray absorption fine structure (EXAFS) spectroscopy to determine the binding mode and oxidation state of iron in solutions initially containing only iron(III) and fulvic acid at pHs 2 and 4. EXAFS spectra were recorded at different times after sample preparation. Iron was octahedrally configured with inner-sphere Fe-O interactions at 1.98-2.10 {angstrom}, depending on the oxidation state of iron. Iron(III) formed complexes with fulvic acid within 15 min. Iron(III) was reduced to iron(II) with time at pH 2, whereas no significant reduction occurred at pH 4. No signs of dimeric/trimeric hydrolysis products were found in any of the solution samples (<0.45 {mu}m). However, the isolated precipitate of the pH 2 sample (>0.45 {mu}m) showed Fe{hor_ellipsis}Fe distances, indicating the presence of tightly packed iron(III) trimers and/or clusters of corner-sharing octahedra. It is suggested that the binding mode of iron(III) to fulvic acid at low pH may be phase-dependent: in solution mononuclear complexes predominate, whereas in the solid phase hydrolyzed polynuclear iron(III) complexes form, even at very low pH values. The observed pH dependence of iron(III) reduction was consistent with expected results based on thermodynamic calculations for model ligands.

  19. A comparative study of removal of fluoride from contaminated water using shale collected from different coal mines in India.

    PubMed

    Biswas, Gargi; Dutta, Manjari; Dutta, Susmita; Adhikari, Kalyan

    2016-05-01

    Low-cost water defluoridation technique is one of the most important issues throughout the world. In the present study, shale, a coal mine waste, is employed as novel and low-cost adsorbent to abate fluoride from simulated solution. Shale samples were collected from Mahabir colliery (MBS) and Sonepur Bazari colliery (SBS) of Raniganj coalfield in West Bengal, India, and used to remove fluoride. To increase the adsorption efficiency, shale samples were heat activated at a higher temperature and samples obtained at 550 °C are denoted as heat-activated Mahabir colliery shale (HAMBS550) and heat-activated Sonepur Bazari colliery shale (HASBS550), respectively. To prove the fluoride adsorption onto different shale samples and ascertain its mechanism, natural shale samples, heat-activated shale samples, and their fluoride-loaded forms were characterized using scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction study, and Fourier transform infrared spectroscopy. The effect of different parameters such as pH, adsorbent dose, size of particles, and initial concentration of fluoride was investigated during fluoride removal in a batch contactor. Lower pH shows better adsorption in batch study, but it is acidic in nature and not suitable for direct consumption. However, increase of pH of the solution from 3.2 to 6.8 and 7.2 during fluoride removal process with HAMBS550 and HASBS550, respectively, confirms the applicability of the treated water for domestic purposes. HAMBS550 and HASBS550 show maximum removal of 88.3 and 88.5 %, respectively, at initial fluoride concentration of 10 mg/L, pH 3, and adsorbent dose of 70 g/L. PMID:26620857

  20. Large-scale production of anhydrous nitric acid and nitric acid solutions of dinitrogen pentoxide

    DOEpatents

    Harrar, Jackson E.; Quong, Roland; Rigdon, Lester P.; McGuire, Raymond R.

    2001-01-01

    A method and apparatus are disclosed for a large scale, electrochemical production of anhydrous nitric acid and N.sub.2 O.sub.5. The method includes oxidizing a solution of N.sub.2 O.sub.4 /aqueous-HNO.sub.3 at the anode, while reducing aqueous HNO.sub.3 at the cathode, in a flow electrolyzer constructed of special materials. N.sub.2 O.sub.4 is produced at the cathode and may be separated and recycled as a feedstock for use in the anolyte. The process is controlled by regulating the electrolysis current until the desired products are obtained. The chemical compositions of the anolyte and catholyte are monitored by measurement of the solution density and the concentrations of N.sub.2 O.sub.4.

  1. Uptake of Hypobromous Acid (HOBr) by Aqueous Sulfuric Acid Solutions: Low-Temperature Solubility and Reaction

    NASA Technical Reports Server (NTRS)

    Iraci, Laura T.; Michelsen, Rebecca R.; Ashbourn, Samatha F. M.; Rammer, Thomas A.; Golden, David M.

    2005-01-01

    Hypobromous acid (HOBr) is a key species linking inorganic bromine to the chlorine and odd hydrogen chemical families. We have measured the solubility of HOBr in 45 - 70 wt% sulfuric acid solutions representative of upper tropospheric and lower stratospheric aerosol composition. Over the temperature range 201 - 252 K, HOBr is quite soluble in sulfuric acid, with an effective Henry's law coefficient, H* = 10(exp 4) - 10(exp 7) mol/L/atm. H* is inversely dependent on temperature, with Delta H = -46.2 kJ/mol and Delta S = -106.2 J/mol/K for 55 - 70 wt% H2SO4 solutions. Our study includes temperatures which overlap both previous measurements of HOBr solubility. For uptake into aqueous 45 wt% H2SO4, the solubility can be described by log H* = 3665/T - 10.63. For 55 - 70 wt% H2SO4, log H* = 2412/T - 5.55. At temperatures colder than approx. 213 K, the solubility of HOBr in 45 wt% H2SO4 is noticeably larger than in 70 wt% H2SO4. The solubility of HOBr is comparable to that of HBr, indicating that upper tropospheric and lower stratospheric aerosols should contain equilibrium concentrations of HOBr which equal or exceed those of HBr. Our measurements indicate chemical reaction of HOBr upon uptake into aqueous sulfuric acid in the presence of other brominated gases followed by evolution of gaseous products including Br2O and Br2, particularly at 70 wt% H2SO4.

  2. 21 CFR 175.270 - Poly(vinyl fluoride) resins.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... polymerization of vinyl fluoride. (b) The poly(vinyl fluoride) basic resins have an intrinsic viscosity of not... Dilute Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference. Copies may be... Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference; see paragraph (b)...

  3. 21 CFR 175.270 - Poly(vinyl fluoride) resins.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... polymerization of vinyl fluoride. (b) The poly(vinyl fluoride) basic resins have an intrinsic viscosity of not... Dilute Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference. Copies may be... Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference; see paragraph (b)...

  4. 21 CFR 175.270 - Poly(vinyl fluoride) resins.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... polymerization of vinyl fluoride. (b) The poly(vinyl fluoride) basic resins have an intrinsic viscosity of not... Dilute Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference. Copies may be... Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference; see paragraph (b)...

  5. 21 CFR 175.270 - Poly(vinyl fluoride) resins.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... polymerization of vinyl fluoride. (b) The poly(vinyl fluoride) basic resins have an intrinsic viscosity of not... Dilute Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference. Copies may be... Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference; see paragraph (b)...

  6. Effect of Fluoride-Releasing Adhesive Systems on the Mechanical Properties of Eroded Dentin.

    PubMed

    Guedes, Ana Paula Albuquerque; Moda, Mariana Dias; Suzuki, Thaís Yumi Umeda; Godas, André Gustavo de Lima; Sundfeld, Renato Herman; Briso, André Luiz Fraga; Santos, Paulo Henrique dos

    2016-01-01

    The aim of the study was to evaluate the effect of erosive pH cycling with solutions that simulate dental erosion on Martens hardness (HMV) and elastic modulus (Eit) of dentin restored with fluoride-releasing adhesive systems. Twenty-seven bovine dentin slabs were restored with three adhesive systems: Adper Single Bond 2 total-etch adhesive system, One Up Bond F and Clearfil SE Protect fluoride-containing self-etching adhesive systems. The restorations were made with Filtek Z250. The HMV and Eit values at distances of 10, 30, 50 and 70 µm from the interface were evaluated using a dynamic ultra microhardness tester before and after immersion in deionized water, citric acid and hydrochloric acid (n=9). Data were submitted to repeated-measures ANOVA and Fisher's PLSD tests (=0.05). After erosive cycling, HMV values of dentin decreased in all groups. For dentin restored with Adper Single Bond 2, the lowest values were found closer to the hybrid layer, while for One Up Bond F and Clearfil SE Protect, the values remained unaltered at all distances. For dentin restored with fluoride-releasing adhesive systems, a decrease in Eit was found, but after 30 µm this difference was not significant. The acid substances were able to alter HMV and Eit of the underlying dentin. For fluoride-releasing adhesives, the greater the distance from bonded interface, the lower the Eit values. The fluoride in One Up Bond F and Clearfil SE Protect was able to protect the underlying dentin closer to the materials. In this way, the fluoride from adhesive systems could have some positive effect in the early stages of erosive lesions. PMID:27058377

  7. THE EQUILIBRIUM FLUORIDE CAPACITY OF ACTIVATED ALUMINA. DETERMINATION OF THE EFFECTS OF PH AND COMPETING IONS

    EPA Science Inventory

    This report describes research on the determination of the equilibrium fluoride adsorption capacity of small columns of acid pretreated activated alumina (Alcoa F-1 grade). The experimental observations verified the expectation that fluoride is very favorably adsorbed in preferen...

  8. Chemico-therapeutic approach to prevention of dental caries. [using stannous fluoride gel

    NASA Technical Reports Server (NTRS)

    Shannon, I. L.

    1975-01-01

    The program of chemical preventive dentistry is based primarily upon the development of a procedure for stabilizing stannous fluoride in solution by forcing it into glycerin. New topical fluoride treatment concentrates, fluoride containing gels and prophylaxis pastes, as well as a completely stable stannous fluoride dentifrice are made possible by the development of a rather complicated heat application method to force stannous fluoride into solution in glycerin. That the stannous fluoride is clinically effective in such a preparation is demonstrated briefly on orthodontic patients.

  9. Isothermal heat measurements of TBP-nitric acid solutions

    SciTech Connect

    Smith, J.R.; Cavin, W.S.

    1994-12-16

    Net heats of reaction were measured in an isothermal calorimeter for both single phase (organic) and two phase (organic and aqueous) TBP/HNO{sub 3} reacting solutions at temperatures above 100 C. The oxidation rate constant was determined to be 5.4E-4 min{sup {minus}1} at 110 C for an open ``vented`` system as compared to 1.33 E-3 min{sup {minus}1} in the closed system. The heat released per unit material oxidized was also reduced. The oxidation in both phases was found to be first order in nitric acid and pseudo-zero order in butylnitrate and water. The hydrolysis (esterification) rate constant determined by Nichols` (1.33E-3 min{sup {minus}1}) fit the experimental data from this work well. Forced evaporation of the volatile components by the product gases from oxidation resulted in a cooling mechanism which more than balanced the heat from the oxidation reaction in the two-phased systems. Rate expressions were derived and rate constants determined for both the single and two phase systems. An approximating mathematical model was developed to fit the experimental data and to extrapolate beyond the experimental conditions. This model shows that one foot of ``reacting`` 14.3M HNO{sub 3} aqueous phase solution at 121 C will transport sufficient water to the organic phase to replace evaporative losses, maintaining endothermicity, for organic layers up to 12.2 + 6.0 feet deep. If the pressure in a reacting system is allowed to increase due to insufficient venting the temperature of the organic phase would increase in temperature to reach a new equilibrium. The rate of oxidation would increase not only due to the increase in temperature but also from the increased concentration of dissolved HNO{sub 3} reduction products. Another important factor is that the cooling system described in this work becomes less effective as the total pressure increases. These factors probably contributed to the explosion at Tomsk.

  10. Synthesis of new optically active propargylic fluorides and application to the enantioselective synthesis of monofluorinated analogues of fatty acid metabolites.

    PubMed

    Prakesch, M; Grée, D; Grée, R

    2001-05-01

    A new approach to obtain optically active unsaturated or polyunsaturated systems with a single fluorine atom in an allylic or propargylic position is reported. Central to this strategy is the high regio- and stereocontrol observed during the fluorination of propargylic alcohols allowing a short and efficient synthesis of 1. Further, simple functional group transformations gave the enals 2 and 3. These three key intermediates were used for the preparation of optically active monofluorinated analogues of fatty acid metabolites. PMID:11325281

  11. Fluoride Plus Functionalized β-TCP

    PubMed Central

    Karlinsey, R.L.; Pfarrer, A.M.

    2012-01-01

    With more than 50 years of clinical success, fluoride serves as the gold standard agent for preventing tooth decay. In particular, the action of fluoride facilitates saliva-driven remineralization of demineralized enamel and alters solubility beneficially. Still, tooth decay remains problematic, and one way to address it may be through the development of new mineralizing agents. Laboratory and clinical studies have demonstrated that the combination of fluoride and functionalized β-tricalcium phosphate (fTCP) produces stronger, more acid-resistant mineral relative to fluoride, native β-TCP, or fTCP alone. In contrast to other calcium-based approaches that seem to rely on high levels of calcium and phosphate to drive remineralization, fTCP is a low-dose system designed to fit within existing topical fluoride preparations. The functionalization of β-TCP with organic and/or inorganic molecules provides a barrier that prevents premature fluoride-calcium interactions and aids in mineralization when applied via common preparations and procedures. While additional clinical studies are warranted, supplementing with fTCP to enhance fluoride-based nucleation activity, with subsequent remineralization driven by dietary and salivary calcium and phosphate, appears to be a promising approach. PMID:22899679

  12. Corrosion behavior of zirconia in acidulated phosphate fluoride.

    PubMed

    Thomas, Anie; Sridhar, Sathyanarayanan; Aghyarian, Shant; Watkins-Curry, Pilanda; Chan, Julia Y; Pozzi, Alessandro; Rodrigues, Danieli C

    2016-02-01

    Objective The corrosion behavior of zirconia in acidulated phosphate fluoride (APF) representing acidic environments and fluoride treatments was studied. Material and Methods Zirconia rods were immersed in 1.23% and 0.123% APF solutions and maintained at 37°C for determined periods of time. Surfaces of all specimens were imaged using digital microscopy and scanning electron microscopy (SEM). Sample mass and dimensions were measured for mass loss determination. Samples were characterized by powder X-ray diffraction (XRD) to detect changes in crystallinity. A biosensor based on electrochemical impedance spectroscopy (EIS) was used to detect ion dissolution of material into the immersion media. Results Digital microscopy revealed diminishing luster of the materials and SEM showed increased superficial corrosion of zirconia submerged in 1.23% APF. Although no structural change was found, the absorption of salts (sodium phosphate) onto the surface of the materials bathed in 0.123% APF was significant. EIS indicated a greater change of impedance for the immersion solutions with increasing bathing time. Conclusion Immersion of zirconia in APF solutions showed deterioration limited to the surface, not extending to the bulk of the material. Inferences on zirconia performance in acidic oral environment can be elucidated from the study. PMID:27008257

  13. Corrosion behavior of zirconia in acidulated phosphate fluoride

    PubMed Central

    Thomas, Anie; Sridhar, Sathyanarayanan; Aghyarian, Shant; Watkins-curry, Pilanda; Chan, Julia Y.; Pozzi, Alessandro; Rodrigues, Danieli C.

    2016-01-01

    ABSTRACT Objective The corrosion behavior of zirconia in acidulated phosphate fluoride (APF) representing acidic environments and fluoride treatments was studied. Material and Methods Zirconia rods were immersed in 1.23% and 0.123% APF solutions and maintained at 37°C for determined periods of time. Surfaces of all specimens were imaged using digital microscopy and scanning electron microscopy (SEM). Sample mass and dimensions were measured for mass loss determination. Samples were characterized by powder X-ray diffraction (XRD) to detect changes in crystallinity. A biosensor based on electrochemical impedance spectroscopy (EIS) was used to detect ion dissolution of material into the immersion media. Results Digital microscopy revealed diminishing luster of the materials and SEM showed increased superficial corrosion of zirconia submerged in 1.23% APF. Although no structural change was found, the absorption of salts (sodium phosphate) onto the surface of the materials bathed in 0.123% APF was significant. EIS indicated a greater change of impedance for the immersion solutions with increasing bathing time. Conclusion Immersion of zirconia in APF solutions showed deterioration limited to the surface, not extending to the bulk of the material. Inferences on zirconia performance in acidic oral environment can be elucidated from the study. PMID:27008257

  14. Acid Solutions for Etching Corrosion-Resistant Metals

    NASA Technical Reports Server (NTRS)

    Simmons, J. R.

    1982-01-01

    New study characterized solutions for etching austenitic stainless steels, nickel-base alloys, and titanium alloys (annealed). Solutions recommended for use remove at least 0.4 mil of metal from surface in less than an hour. Solutions do not cause intergranular attack on metals for which they are effective, when used under specified conditions.

  15. Design of Fe₃O₄@SiO₂@Carbon Quantum Dot Based Nanostructure for Fluorescence Sensing, Magnetic Separation, and Live Cell Imaging of Fluoride Ion.

    PubMed

    Mohapatra, Sasmita; Sahu, Swagatika; Nayak, Santoshi; Ghosh, Sudip K

    2015-07-28

    A robust reusable fluoride sensor comprised of a receptor in charge of the chemical recognition and a fluorophore responsible for signal recognition has been designed. Highly fluorescent carbon quantum dot (CD) and magnetically separable nickel ethylenediaminetetraacetic acid (EDTA) complex bound-silica coated magnetite nanoparticle (Fe3O4@SiO2-EDTA-Ni) have been used as fluorophore and fluoride ion receptor, respectively. The assay is based on the exchange reaction between the CD and F(-), which persuades the binding of fluoride to magnetic receptor. This method is highly sensitive, fast, and selective for fluoride ion in aqueous solution. The linear response range of fluoride (R(2) = 0.992) was found to be 1-20 μM with a minimum detection limit of 0.06 μM. Excellent magnetic property and superparamagnetic nature of the receptor are advantageous for the removal and well quantification of fluoride ion. The practical utility of the method is well tested with tap water. Because of high sensitivity, reusability, effectivity, and biocompatibility, it exhibits great promise as a fluorescent probe for intracellular detection of fluoride. PMID:26114840

  16. 49 CFR 173.229 - Chloric acid solution or chlorine dioxide hydrate, frozen.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 2 2011-10-01 2011-10-01 false Chloric acid solution or chlorine dioxide hydrate, frozen. 173.229 Section 173.229 Transportation Other Regulations Relating to Transportation PIPELINE AND... Than Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When...

  17. 49 CFR 173.229 - Chloric acid solution or chlorine dioxide hydrate, frozen.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 2 2013-10-01 2013-10-01 false Chloric acid solution or chlorine dioxide hydrate, frozen. 173.229 Section 173.229 Transportation Other Regulations Relating to Transportation PIPELINE AND... Than Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When...

  18. 49 CFR 173.229 - Chloric acid solution or chlorine dioxide hydrate, frozen.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 2 2014-10-01 2014-10-01 false Chloric acid solution or chlorine dioxide hydrate, frozen. 173.229 Section 173.229 Transportation Other Regulations Relating to Transportation PIPELINE AND... Than Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When...

  19. 49 CFR 173.229 - Chloric acid solution or chlorine dioxide hydrate, frozen.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Chloric acid solution or chlorine dioxide hydrate, frozen. 173.229 Section 173.229 Transportation Other Regulations Relating to Transportation PIPELINE AND... Than Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When...

  20. 49 CFR 173.229 - Chloric acid solution or chlorine dioxide hydrate, frozen.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Chloric acid solution or chlorine dioxide hydrate, frozen. 173.229 Section 173.229 Transportation Other Regulations Relating to Transportation PIPELINE AND... Than Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When...

  1. 40 CFR 60.202 - Standard for fluorides.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 6 2011-07-01 2011-07-01 false Standard for fluorides. 60.202 Section... Industry: Wet-Process Phosphoric Acid Plants § 60.202 Standard for fluorides. (a) On and after the date on... facility any gases which contain total fluorides in excess of 10.0 g/Mg of equivalent P2O5 feed (0.020...

  2. 40 CFR 60.202 - Standard for fluorides.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Standard for fluorides. 60.202 Section... Industry: Wet-Process Phosphoric Acid Plants § 60.202 Standard for fluorides. (a) On and after the date on... facility any gases which contain total fluorides in excess of 10.0 g/Mg of equivalent P2O5 feed (0.020...

  3. Novel fluorogenic probe for fluoride ion based on the fluoride-induced cleavage of tert-butyldimethylsilyl ether

    NASA Astrophysics Data System (ADS)

    Yang, Xiao-Feng

    2007-06-01

    A highly sensitive and selective fluorogenic probe for fluoride ion, 4-methylumbelliferyl tert-butyldimethylsilyl ether (4-MUTBS), was designed and synthesized. 4-MUTBS was a weakly fluorescent compound and was synthesized via the one-step reaction of 4-MU with tert-butyldimethylsilyl chloride. Upon incubation with fluoride ion in acetone-water solution (7:3, v/v), the Si-O bond of 4-MUTBS was cleaved and highly fluorescent 4-methylumbelliferone (4-MU) was released, hence leading to the fluorescence increase of the reaction solution. The fluorescence increase is linearly with fluoride concentration in the range 50-8000 nmol l -1 with a detection limit of 19 nmol l -1 (3 σ). Because of the high affinity of silicon toward fluoride ion, the proposed probe shows excellent selectivity toward fluoride ion over other anions. The method has been successfully applied to the fluoride determination in toothpaste and tap water samples.

  4. Chemical evaluation of soil-solution in acid forest soils

    USGS Publications Warehouse

    Lawrence, G.B.; David, M.B.

    1996-01-01

    Soil-solution chemistry is commonly studied in forests through the use of soil lysimeters.This approach is impractical for regional survey studies, however, because lysimeter installation and operation is expensive and time consuming. To address these problems, a new technique was developed to compare soil-solution chemistry among red spruce stands in New York, Vermont, New Hampshire, Maine. Soil solutions were expelled by positive air pressure from soil that had been placed in a sealed cylinder. Before the air pressure was applied, a solution chemically similar to throughfall was added to the soil to bring it to approximate field capacity. After the solution sample was expelled, the soil was removed from the cylinder and chemically analyzed. The method was tested with homogenized Oa and Bs horizon soils collected from a red spruce stand in the Adirondack Mountains of New York, a red spruce stand in east-central Vermont, and a mixed hardwood stand in the Catskill Mountains of New York. Reproducibility, effects of varying the reaction time between adding throughfall and expelling soil solution (5-65 minutes) and effects of varying the chemical composition of added throughfall, were evaluated. In general, results showed that (i) the method was reproducible (coefficients of variation were generally < 15%), (ii) variations in the length of reaction-time did not affect expelled solution concentrations, and (iii) adding and expelling solution did not cause detectable changes in soil exchange chemistry. Concentrations of expelled solutions varied with the concentrations of added throughfall; the lower the CEC, the more sensitive expelled solution concentrations were to the chemical concentrations of added throughfall. Addition of a tracer (NaBr) showed that the expelled solution was a mixture of added solution and solution that preexisted in the soil. Comparisons of expelled solution concentrations with concentrations of soil solutions collected by zero-tension and

  5. Ion release from, and fluoride recharge of a composite with a fluoride-containing bioactive glass

    PubMed Central

    Davis, Harry B.; Gwinner, Fernanda; Mitchell, John C.; Ferracane, Jack L.

    2014-01-01

    Objectives Materials that are capable of releasing ions such as calcium and fluoride, that are necessary for remineralization of dentin and enamel, have been the topic of intensive research for many years. The source of calcium has most often been some form of calcium phosphate, and that for fluoride has been one of several metal fluoride or hexafluorophosphate salts. Fluoride-containing bioactive glass (BAG) prepared by the sol-gel method acts as a single source of both calcium and fluoride ions in aqueous solutions. The objective of this investigation was to determine if BAG, when added to a composite formulation, can be used as a single source for calcium and fluoride ion release over an extended time period, and to determine if the BAG-containing composite can be recharged upon exposure to a solution of 5,000 ppm fluoride. Methods BAG 61 (61% Si; 31% Ca; 4% P; 3% F; 1% B) and BAG 81 (81% Si; 11% Ca; 4% P; 3% F; 1% B) were synthesized by the sol gel method. The composite used was composed of 50/50 Bis-GMA/TEGDMA, 0.8% EDMAB, 0.4% CQ, and 0.05% BHT, combined with a mixture of BAG (15%) and strontium glass (85%) to a total filler load of 72% by weight. Disks were prepared, allowed to age for 24 h, abraded, then placed into DI water. Calcium and fluoride release was measured by atomic absorption spectroscopy and fluoride ion selective electrode methods, respectively, after 2, 22, and 222 h. The composite samples were then soaked for 5 min in an aqueous 5,000 ppm fluoride solution, after which calcium and fluoride release was again measured at 2, 22, and 222 h time points. Results Prior to fluoride recharge, release of fluoride ions was similar for the BAG 61 and BAG 81 composites after 2 h, and also similar after 22 h. At the four subsequent time points, one prior to, and three following fluoride recharge, the BAG 81 composite released significantly more fluoride ions (p<0.05). Both composites were recharged by exposure to 5,000 ppm fluoride, although the BAG 81

  6. Enhanced removal of fluoride by polystyrene anion exchanger supported hydrous zirconium oxide nanoparticles.

    PubMed

    Pan, Bingcai; Xu, Jingsheng; Wu, Bing; Li, Zhigang; Liu, Xitong

    2013-08-20

    Here we fabricated a novel nanocomposite HZO-201, an encapsulated nanosized hydrous zirconium oxide (HZO) within a commercial porous polystyrene anion exchanger D201, for highly efficient defluoridation of water. HZO-201 exhibited much higher preference than activated alumina and D201 toward fluoride removal when competing anions (chloride, sulfate, nitrate, and bicarbonate) coexisted at relatively high levels. Fixed column adsorption indicated that the effective treatable volume of water with HZO-201 was about 7-14 times as much as with D201 irrespective of whether synthetic solution or groundwater was the feeding solution. In addition, HZO-201 could treat >3000 BV of the acidic effluent (around 3.5 mg F(-)/L) per run at pH 3.5, compared to only ∼4 BV with D201. The exhausted HZO-201 could be regenerated by NaOH solution for repeated use without any significant capacity loss. Such attractive performance of HZO-201 resulted from its specific hybrid structure, that is, the host anion exchanger D201 favors the preconcentration of fluoride ions inside the polymer based on the Donnan principle, and the encapsulated nanosized HZO exhibits preferable sequestration of fluoride through specific interaction, as further demonstrated by XPS spectra. The influence of solution pH, competitive anions, and contact time was also examined. The results suggested that HZO-201 has a great potential in efficient defluoridation of groundwater and acidic mine drainage. PMID:23909842

  7. Solution properties and taste behavior of lactose monohydrate in aqueous ascorbic acid solutions at different temperatures: Volumetric and rheological approach.

    PubMed

    Sarkar, Abhijit; Sinha, Biswajit

    2016-11-15

    The densities and viscosities of lactose monohydrate in aqueous ascorbic acid solutions with several molal concentrations m=(0.00-0.08)molkg(-1) of ascorbic acid were determined at T=(298.15-318.15)K and pressure p=101kPa. Using experimental data apparent molar volume (ϕV), standard partial molar volume (ϕV(0)), the slope (SV(∗)), apparent specific volumes (ϕVsp), standard isobaric partial molar expansibility (ϕE(0)) and its temperature dependence [Formula: see text] the viscosity B-coefficient and solvation number (Sn) were determined. Viscosity B-coefficients were further employed to obtain the free energies of activation of viscous flow per mole of the solvents (Δμ1(0≠)) and of the solute (Δμ2(0≠)). Effects of molality, solute structure and temperature and taste behavior were analyzed in terms of solute-solute and solute-solvent interactions; results revealed that the solutions are characterized predominantly by solute-solvent interactions and lactose monohydrate behaves as a long-range structure maker. PMID:27283672

  8. Fluoride and Oral Health.

    PubMed

    O'Mullane, D M; Baez, R J; Jones, S; Lennon, M A; Petersen, P E; Rugg-Gunn, A J; Whelton, H; Whitford, G M

    2016-06-01

    The discovery during the first half of the 20th century of the link between natural fluoride, adjusted fluoride levels in drinking water and reduced dental caries prevalence proved to be a stimulus for worldwide on-going research into the role of fluoride in improving oral health. Epidemiological studies of fluoridation programmes have confirmed their safety and their effectiveness in controlling dental caries. Major advances in our knowledge of how fluoride impacts the caries process have led to the development, assessment of effectiveness and promotion of other fluoride vehicles including salt, milk, tablets, toothpaste, gels and varnishes. In 1993, the World Health Organization convened an Expert Committee to provide authoritative information on the role of fluorides in the promotion of oral health throughout the world (WHO TRS 846, 1994). This present publication is a revision of the original 1994 document, again using the expertise of researchers from the extensive fields of knowledge required to successfully implement complex interventions such as the use of fluorides to improve dental and oral health. Financial support for research into the development of these new fluoride strategies has come from many sources including government health departments as well as international and national grant agencies. In addition, the unique role which industry has played in the development, formulation, assessment of effectiveness and promotion of the various fluoride vehicles and strategies is noteworthy. This updated version of 'Fluoride and Oral Health' has adopted an evidence-based approach to its commentary on the different fluoride vehicles and strategies and also to its recommendations. In this regard, full account is taken of the many recent systematic reviews published in peer reviewed literature. PMID:27352462

  9. Arsenic from community water fluoridation: quantifying the effect.

    PubMed

    Peterson, Emily; Shapiro, Howard; Li, Ye; Minnery, John G; Copes, Ray

    2016-04-01

    Community water fluoridation is a WHO recommended strategy to prevent dental carries. One debated concern is that hydrofluorosilicic acid, used to fluoridate water, contains arsenic and poses a health risk. This study was undertaken to determine if fluoridation contributes to arsenic in drinking water, to estimate the amount of additional arsenic associated with fluoridation, and compare this to the National Sanitation Foundation/American National Standards Institute (NSF/ANSI) standard and estimates from other researchers. Using surveillance data from Ontario drinking water systems, mixed effects linear regression was performed to examine the effect of fluoridation status on the difference in arsenic concentration between raw water and treated water samples. On average, drinking water treatment was found to reduce arsenic levels in water in both fluoridated and non-fluoridated systems by 0.2 μg/L. However, fluoridated systems were associated with an additional 0.078 μg/L (95% CI 0.021, 0.136) of arsenic in water when compared to non-fluoridated systems (P = 0.008) while controlling for raw water arsenic concentrations, types of treatment processes, and source water type. Our estimate is consistent with concentrations expected from other research and is less than 10% of the NSF/ANSI standard of 1 μg/L arsenic in water. This study provides further information to inform decision-making regarding community water fluoridation. PMID:27105409

  10. Process for the removal of radium from acidic solutions containing same

    DOEpatents

    Scheitlin, F.M.

    The invention is a process for the removal of radium from acidic aqueous solutions. In one aspect, the invention is a process for removing radium from an inorganic-acid solution. The process comprises contacting the solution with coal fly ash to effect adsorption of the radium on the ash. The radium-containing ash then is separated from the solution. The process is simple, comparatively inexpensive, and efficient. High radium-distribution coefficients are obtained even at room temperature. Coal fly ash is an inexpensive, acid-resistant, high-surface-area material which is available in large quantities throughout the United States. The invention is applicable, for example, to the recovery of /sup 226/Ra from nitric acid solutions which have been used to leach radium from uranium-mill tailings.

  11. Removal of radium from acidic solutions containing same by adsorption on coal fly ash

    DOEpatents

    Scheitlin, Frank M.

    1984-01-01

    The invention is a process for the removal of radium from acidic aqueous solutions. In one aspect, the invention is a process for removing radium from an inorganic-acid solution. The process comprises contacting the solution with coal fly ash to effect adsorption of the radium on the ash. The radium-containing ash then is separated from the solution. The process is simple, comparatively inexpensive, and efficient. High radium-distribution coefficients are obtained even at room temperature. Coal fly ash is an inexpensive, acid-resistant, high-surface-area material which is available in large quantities throughout the United States. The invention is applicable, for example, to the recovery of .sup.226 Ra from nitric acid solutions which have been used to leach radium from uranium-mill tailings.

  12. Separation of ions in acidic solution by capillary electrophoresis

    SciTech Connect

    Thornton, M.

    1997-10-08

    Capillary electrophoresis (CE) is an effective method for separating ionic species according to differences in their electrophoretic mobilities. CE separations of amino acids by direct detection are difficult due to their similar electrophoretic mobilities and low absorbances. However, native amino acids can be separated by CE as cations at a low pH by adding an alkanesulfonic acid to the electrolyte carrier which imparts selectivity to the system. Derivatization is unnecessary when direct UV detection is used at 185 nm. Simultaneous speciation of metal cations such as vanadium (IV) and vanadium (V) can easily be performed without complexation prior to analysis. An indirect UV detection scheme for acidic conditions was also developed using guanidine as the background carrier electrolyte (BCE) for the indirect detection of metal cations. Three chapters have been removed for separate processing. This report contains introductory material, references, and general conclusions. 80 refs.

  13. Reprocessing system with nuclide separation based on chromatography in hydrochloric acid solution

    SciTech Connect

    Suzuki, Tatsuya; Tachibana, Yu; Koyama, Shi-ichi

    2013-07-01

    We have proposed the reprocessing system with nuclide separation processes based on the chromatographic technique in the hydrochloric acid solution system. Our proposed system consists of the dissolution process, the reprocessing process, the minor actinide separation process, and nuclide separation processes. In the reprocessing and separation processes, the pyridine resin is used as a main separation media. It was confirmed that the dissolution in the hydrochloric acid solution is easily achieved by the plasma voloxidation and by the addition of oxygen peroxide into the hydrochloric acid solution.

  14. PROCESS OF SECURING PLUTONIUM IN NITRIC ACID SOLUTIONS IN ITS TRIVALENT OXIDATION STATE

    DOEpatents

    Thomas, J.R.

    1958-08-26

    >Various processes for the recovery of plutonium require that the plutonium be obtalned and maintained in the reduced or trivalent state in solution. Ferrous ions are commonly used as the reducing agent for this purpose, but it is difficult to maintain the plutonium in a reduced state in nitric acid solutions due to the oxidizing effects of the acid. It has been found that the addition of a stabilizing or holding reductant to such solution prevents reoxidation of the plutonium. Sulfamate ions have been found to be ideally suitable as such a stabilizer even in the presence of nitric acid.

  15. Ion-selective electrode in determining fluorine in binary fluorides of metals of groups II-V

    SciTech Connect

    Mishchenko, V.T.; Mukomel', V.L.; Polvektov, N.S.; Shilova, L.P.; Tselik, E.I.

    1986-01-01

    The authors have developed a method of determining fluorine by ion-selective electrode techniques in specimens containing mixtures of the fluorides of magnesium and the rare-earth elements (REE), as well as scandium and bismuth. The specimens after treatment at high temperatures are sparingly soluble at room temperature in water and also in aqueous solutions of acids and bases. The authors found that a mixture of KNaCO/sub 3/ and K/sub 2/S/sub 2/O/sub 8/ with a mass ratio of 2:1 was an effective flux for MgF/sub 2/-MeF/sub 3/ specimens, where Me is an REE ion. The combined method of analyzing binary mixtures of fluorides (Mg and REE, Sc and Bi) which provides satisfactory accuracy and reliability in determining the fluoride and two different metals whose compounds may have various ratios in the samples.

  16. Corrosion Behavior of Titanium Grade 7 in Fluoride-Containing NaCl Brines

    SciTech Connect

    Lian, T; Whalen, M T; Wong, L

    2004-10-25

    The effects of fluoride on the corrosion behavior of Titanium Grade 7 (0.12-0.25% Pd) have been investigated. Up to 0.1 mol/L fluoride was added to the NaCl brines at 95 C, and three pH values of 4, 8, and 11 were selected for studying pH dependence of fluoride effects. It was observed that fluoride significantly altered the anodic polarization behavior, at all three pH values of 4, 8, and 11. Under acidic condition fluoride caused active corrosion. The corrosion of Titanium grade 7 was increased by three orders of magnitude when a 0.1 mol/L fluoride was added to the NaCl brines at pH 4, and the Pd ennoblement effect was not observed in acidic fluoride-containing environments. The effects of fluoride were reduced significantly when pH was increased to 8 and above.

  17. Thermodynamic modeling of hydrogen fluoride production relevant to actinide residue treatment

    SciTech Connect

    West, M.H.; Axler, K.M.

    1995-02-01

    This report addresses issues specific to generation of hydrogen fluoride via reaction of calcium fluoride with sulfuric acid. This process has been established on a commercial scale and is under consideration for treatment of calcium fluoride residues from uranium processing. Magnesium fluoride slags are also available as a product of uranium processing. The technique of using sulfuric acid for the production of hydrogen fluoride from magnesium fluoride is also under consideration as a residue processing scheme. In the current study, thermodynamic modeling was used to investigate these chemical processing systems. Results presented herein reveal information relevant to selection of processing temperatures and conditions. Details include predicted effects in system composition based on operating temperatures for both the calcium fluoride and the magnesium fluoride systems.

  18. Multiple-acid equilibria in adsorption of carboxylic acids from dilute aqueous solution

    SciTech Connect

    Husson, S.M.; King, C.J.

    1999-02-01

    Equilibria were measured for adsorption of carboxylic acids from aqueous, binary-acid mixtures of lactic and succinic acids and acetic and formic acids onto basic polymeric sorbents. The experimentally determined adsorption isotherms compared well with model predictions, confirming that simple extensions from adsorption of individual acids apply. Fixed-bed studies were carried out that establish the efficacy of chromatographic fractionation of lactic and succinic acids using basic polymeric sorbents. Finally, sequential thermal and solvent regeneration of lactic and acetic acid-laden sorbents was investigated as a method to fractionate among coadsorbed volatile and nonvolatile acids. Essentially complete removal of the acetic acid from the acid-laden sorbent was achieved by vaporization under the conditions used; a small amount of loss of lactic acid (about 11%) was observed.

  19. Temperature dependence of hydrogen-bond dynamics in acetic acid-water solutions.

    PubMed

    D'Amico, Francesco; Bencivenga, Filippo; Gessini, Alessandro; Masciovecchio, Claudio

    2010-08-19

    An inelastic UV scattering experiment has been carried out on acetic acid-water solutions as a function of temperature and concentration. The analysis of experimental data indicates the presence of a crossover temperature (T(c) approximately 325 +/- 10 K). Above T(c), the energy of hydrogen bonds responsible for water-acetic acid and acetic acid-acetic acid interactions is strongly reduced. This leads to a reduction in the average number of water molecule interacting with acetic acid, as well as to a lower number of acetic acid clusters. The latter behavior can be mainly ascribed to a temperature change in the activation energy of carboxylic groups of acetic acid. These results may be also relevant to better understand the folding mechanism in protein-water solutions. PMID:20701390

  20. Mechanistic studies of nitrations and oxidations in solutions of dinitrogen pentaoxide in nitric acid

    SciTech Connect

    Willmer, R.F.

    1992-01-01

    Mechanisms of nitrations in solutions of dinitrogen pentaoxide in nitric acid of 1,2,4-trichloro-5-nitrobenzene and 1,2-dichloro-4-nitrobenzene have been proposed. The kinetics and products of the nitration, in the title medium, of substantially deactivated benzoic acids and benzaldehydes have been investigated. Kinetics of nitration of some substituted benzoic acids in nitric acid solutions containing dinitrogen pentaoxide or nitronium trifluoro-methanesulphonate (nitronium triflate) have been compared. Rate coefficients for reactions in dinitrogen pentaoxide solutions were generally similar to those from nitronium triflate solutions of the same estimated nitronium ion concentration. Yields of aromatic products of nitration of some benzoic acid derivatives in the nitric acid solutions have been determined. Nitrodecarboxylation of 4-fluorobenzoic acid occurs as a result of nitronium ion attach at C(1). The competition between oxidation to the corresponding benzoic acid and nitration in the aromatic ring of some substituted benzaldehydes has been probed by kinetic and product studies. 4-Carboxybenzaldehyde is nitrated but more deactivated substrates are predominantly oxidized. Rapid reversible gem-dinitrate formation occurs in concentrated dinitrogen pentaoxide solutions. The equilibrium extent of formation of [alpha]-deuterio-(4-nitropheny)-dinitratomethane from [alpha]-deuterio-4-nitrobenzaldehyde is reported. 4-nitrobenzaldehyde and the gem-dinitrate are oxidized in processes in which [alpha]-hydrogen loss is at least partially rate determining. The relative rates of oxidation in nitronium triflate solutions suggest that the [alpha]-hydrogen is removed as a hydride ion in that medium. There is evidence for the intrusion of a radical mechanism of nitration in concentrated solutions of dinitrogen pentaoxide. (4-Nitrophenyl)dinitratomethane was produced on the addition of 4-nitrobenzaldehyde to a solution of dinitrogen pentaoxide in dichloromethane.

  1. Effect of acidic solutions on the surface degradation of a micro-hybrid composite resin.

    PubMed

    Münchow, Eliseu A; Ferreira, Ana Cláudia A; Machado, Raissa M M; Ramos, Tatiana S; Rodrigues-Junior, Sinval A; Zanchi, Cesar H

    2014-01-01

    Composite resins may undergo wear by the action of chemical substances (e.g., saliva, alcohol, bacterial acids) of the oral environment, which may affect the material's structure and surface properties. This study evaluated the effect of acidic substances on the surface properties of a micro-hybrid composite resin (Filtek Z-250). Eighty specimens were prepared, and baseline hardness and surface roughness (KMN0 and Ra0, respectively) were measured. The specimens were subjected to sorption (SO) and solubility (SL) tests according to ISO 4049:2009, but using different storage solutions: deionized water; 75/25 vol% ethanol/water solution; lactic acid; propionic acid; and acetic acid. The acids were used in two concentrations: PA and 0.02 N. pH was measured for all solutions and final hardness (KMN1) and surface roughness (Ra1) were measured. Data were analyzed with paired t-tests and one-way ANOVA and Tukey's test (a=5%). All solutions decreased hardness and increased the Ra values, except for the specimens stored in water and 0.02 N lactic acid, which maintained the hardness. All solutions produced similar SO and SL phenomena, except for the 0.02 N lactic acid, which caused lower solubility than the other solutions. Ethanol showed the highest pH (6.6) and the 0.02 N lactic acid the lowest one (2.5). The solutions affected negatively the surface properties of the composite resin; in addition, an acidic pH did not seem to be a significant factor that intensifies the surface degradation phenomena. PMID:25250496

  2. Fluorides and non-fluoride remineralization systems.

    PubMed

    Amaechi, Bennett T; van Loveren, Cor

    2013-01-01

    Caries develops when the equilibrium between de- and remineralization is unbalanced favoring demineralization. De- and remineralization occur depending on the degree of saturation of the interstitial fluids with respect to the tooth mineral. This equilibrium is positively influenced when fluoride, calcium and phosphate ions are added favoring remineralization. In addition, when fluoride is present, it will be incorporated into the newly formed mineral which is then less soluble. Toothpastes may contain fluoride and calcium ions separately or together in various compounds (remineralization systems) and may therefore reduce demineralization and promote remineralization. Formulating all these compounds in one paste may be challenging due to possible premature calcium-fluoride interactions and the low solubility of CaF2. There is a large amount of clinical evidence supporting the potent caries preventive effect of fluoride toothpastes indisputably. The amount of clinical evidence of the effectiveness of the other remineralization systems is far less convincing. Evidence is lacking for head to head comparisons of the various remineralization systems. PMID:23817057

  3. Reactivity of the cadmium ion in concentrated phosphoric acid solutions.

    PubMed

    De Gyves, J; Gonzales, J; Louis, C; Bessiere, J

    1989-07-01

    The solvation transfer coefficients which characterize the changes of ion reactivity with phosphoric acid concentration have been calculated for cadmium from the constants of the successive chloride complexes, and for silver and diethyldithiophosphate from potentiometric measurements. They evidence the strong desolvation of the cadmium species in concentrated phosphoric acid media, causing a remarkable increase of its reactivity. They allow the results of liquid-liquid extraction, precipitation and flotation reactions to be correctly interpreted and their changes to be foreseen when the reagents are modified. PMID:18964794

  4. The Solubility of Xenon in Simple Organic Solvents and in Aqueous Amino Acid Solutions.

    NASA Astrophysics Data System (ADS)

    Himm, Jeffrey Frank

    We have measured the Ostwald solubility (L) of ('133)Xe in a variety of liquids, including normal alkanes, normal alkanols, and aqueous solutions of amino acids, NaCl, and sucrose. For the alkanes and alkanols, measurements were made in the temperature range from 10-50(DEGREES)C. Values of L were found to decrease with increasing temperature, and also with increasing chain length, for both series of solvents. Thermodynamic properties of solution (enthalpy and entropy of solution) are calculated using both mole fraction and number density scales. Results are interpreted using Uhlig's model of the solvation process. Measurements of L in aqueous amino acid solutions were made at 25(DEGREES)C. Concentrations of amino acids in solution varied from near saturation for each of the amino acids studied to pure water. In all solutions, except those with NaCl, L decreases linearly with increasing solution molarity. Hydration numbers (H), the mean number of water molecules associated with each solute molecule, were determined for each amino acid, for NaCl, and for sucrose. Values of H obtained ranged from near zero (arginine, H = 0.2 (+OR-) 0.5) to about 16 (NaCl, H = 16.25 (+OR-) 0.3).

  5. Moving single bubble sonoluminescence in phosphoric acid and sulphuric acid solutions.

    PubMed

    Troia, A; Ripa, D Madonna; Spagnolo, R

    2006-04-01

    The phenomenon of sonoluminescence still presents some unsolved aspects. Recently [Y.T. Didenko, K. Suslick, Molecular Emission during Single Bubble Sonoluminescence, Nature 407 (2000) 877-879.], it was found that a single cavitating air bubble in polar aprotic liquids (including formamide and adiponitrile) can produce very strong sonoluminescence while undergoing macroscopic translation movements in the resonator, a condition known as moving single bubble sonoluminescing (MSBSL). Here we describe some experiments conducted in aqueous solutions of phosphoric and sulphuric acid. In these liquid media, it is possible to reproduce MSBSL and luminescence is emitted even if a trapped bubble is subjected to a strong shape instability, named in the literature "jittering phase". When a moving and luminescing bubble was present and the acoustic pressure gradually increased, we observed the generation of a discrete lattice of trapped bubbles. The bubbles in the lattice emit very intense light flashes and can change their position while maintaining the overall spatial distribution in time. Some preliminary results, obtained from Mie-scattering and measurements of relative light intensity, are reported. PMID:16309944

  6. Massachusetts fluoridation update 2006.

    PubMed

    Allukian, Myron

    2006-01-01

    Massachusetts has a long history of activity with community water fluoridation. Although the state has 3.8 million people living in 137 fluoridated communities, there are more than 2 million people who do not have these benefits. The Bay State is ranked 35th in the country regarding the percent of people on public water supplies with fluoridation. We can do better than that. We have more than 60 years of experience receiving the health and economic benefits of fluoridation in our country; however, there is still a lot of misinformation about fluoridation, and the unreliable nature of information posted on the Internet exacerbates much of this misinformation. Dental professionals, their patients, and decision-makers must be continuously educated about the safety, health, and economic benefits of community water fluoridation. Patients from 6 months to 16 years of age living in nonfluoridated communities should be prescribed supplemental fluoride. Dental professionals in nonfluoridated communities should assist them to become fluoridated. All dental professionals need to become more involved in the leadership of their communities. PMID:16683510

  7. Standard addition method for free acid determination in solutions with hydrolyzable ions

    SciTech Connect

    Baumann, E.W.

    1981-01-01

    The free acid content of solutions containing hydrolyzable ions has been determined potentiometrically by a standard addition method. Two increments of acid are added to the sample in a 1M potassium thiocyanate solution. The sample concentration is calculated by solution of three simultaneous Nernst equations. The method has been demonstrated for solutions containing Al/sup 3 +/, Cr/sup 3 +/, Fe/sup 3 +/, Ni/sup 2 +/, Th/sup 4 +/, or UO/sub 2//sup 2 +/ with a metal-to-acid ratio of < 2.5. The method is suitable for determination of 10 ..mu..moles acid in 10 mL total volume. The accuracy is verifiable by reasonable agreement of the Nerst slopes found in the presence and absence of hydrolyzable ions. The relative standard deviation is < 2.5 percent.

  8. Thermodynamics of the complexation of arabinogalactan with salicylic and p-aminobenzoic acids in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Mudarisova, R. Kh.; Badykova, L. A.

    2016-03-01

    The thermodynamics of complexation of arabinogalactan with salicylic and p-aminobenzoic acids in aqueous solutions is studied by means spectroscopy. The standard thermodynamic characteristics (Δ H°; Δ G°; Δ S°) of complexation are calculated.

  9. Indium fluoride glass fibers

    NASA Astrophysics Data System (ADS)

    Saad, Mohammed

    2012-03-01

    Fluoride glasses are the only material that transmit light from ultraviolet to mid-infrared and can be drawn into industrial optical fibers. The mechanical and optical properties of new indium fluoride glass fibers have been investigated. Multimode fiber 190 microns, has very high mechanical strength greater than 100 kpsi and optical loss as low as 45 dB/km between 2 and 4 microns. Unlike chalcogenide glass fibers, indium fluoride fiber has a wide transmission window from 0.3 to 5.5 microns without any absorption peak. Indium fluoride glass fibers are the technology of choice for all application requiring transmission up to 5 micron such as infrared contour measure (IRCM) and chemical sensing. Furthermore, Indium fluoride glasses have low phonon energy and can be heavily doped and co-doped whit rare-earth elements. Therefore they are very promising candidates for infrared fiber lasers.

  10. Process for recovering uranium using an alkyl pyrophosphoric acid and alkaline stripping solution

    SciTech Connect

    Worthington, R.E.; Magdics, A.

    1987-03-24

    A process is described for stripping uranium for a pregnant organic extractant comprising an alkyl pyrophosphoric acid dissolved in a substantially water-immiscible organic diluent. The organic extractant contains tetravalent uranium and an alcohol or phenol modifier in a quantity sufficient to retain substantially all the unhydrolyzed alkyl pyrophosphoric acid in solution in the diluent during stripping. The process comprises adding an oxidizing agent to the organic extractant and thereby oxidizing the tetravalent uranium to the +6 state in the organic extractant, and contacting the organic extractant containing the uranium in the +6 state with a stripping solution comprising an aqueous solution of an alkali metal or ammonium carbonate or hydroxide thereby stripping uranium from the organic extractant into the stripping solution. The resulting barren organic extractant containing substantially all of the unhydrolyzed alkyl pyrophosphoric acid dissolved in the diluent is separated from the stripping solution containing the stripped uranium, the barren extractant being suitable for recycle.

  11. Process for recovering uranium using an alkyl pyrophosphoric acid and alkaline stripping solution

    SciTech Connect

    Worthington, R.E.; Magdics, A.

    1987-03-24

    A process is described for stripping uranium from a pregnant organic extractant comprising an alkyl pyrophosphoric acid dissolved in a substantially water-immiscible organic diluent. The organic extractant contains tetravalent uranium and an alcohol or phenol modifier in a quantity sufficient to retain substantially all the unhydrolyzed alkyl pyrophosphoric acid in solution in the diluent during stripping. The process comprises adding an oxidizing agent to the organic extractant to and thereby oxidizing the tetravalent uranium to the +6 state in the organic extractant, and contacting the organic extractant containing the uranium in the +6 state with a stripping solution comprising an aqueous solution of an alkali metal or ammonium carbonate, nonsaturated in uranium. The uranium is stripped from, the organic extractant into the stripping solution, and the resulting barren organic extractant containing substantially all of the unhydrolyzed alkyl pyrophosphoric acid dissolved in the diluent is separated from the stripping solution containing the stripped uranium, the barren extractant being suitable for recycle.

  12. Behaviors of acrylamide/itaconic acid hydrogels in uptake of uranyl ions from aqueous solutions

    SciTech Connect

    Karadag, E.; Saraydin, D.; Gueven, O.

    1995-12-01

    In this study, adsorptions of uranyl ions from two different aqueous uranyl solutions by acrylamide-itaconic acid hydrogels were investigated by a spectroscopic method. The hydrogels were prepared by irradiating with {gamma}-radiation. In the experiment of uranyl ions adsorption, Type II adsorption was found. One gram of acrylamide-itaconic acid hydrogels sorbed 178-219 mg uranyl ions from the solutions of uranyl acetate, 42-76 mg uranyl ions from the aqueous solutions of uranyl nitrate, while acrylamide hydrogel did not sorb any uranyl ion. For the hydrogel containing 40 mg of itaconic acid and irradiated to 3.73 kGy, swelling of the hydrogels was observed in water (1660%), in the aqueous solution of uranyl acetate (730%), and in the aqueous solution of uranyl nitrate (580%). Diffusions of water onto hydrogels were a non-Fickian type of diffusion, whereas diffusions of uranyl ions were a Fickian type of diffusion.

  13. Effect of various alkaline metal ions on electrochemical behavior of lead electrode in sulfuric acid solution

    NASA Astrophysics Data System (ADS)

    Hirai, Nobumitsu; Yamamoto, Yui

    2015-10-01

    The effect of various alkaline metal ions on electrochemical behavior of lead electrode in sulfuric acid solution has been investigated. It was found that "the specific anodic oxidation peak" appears at the cathodic scan in cyclic voltammogram of lead electrode in sulfuric acid solution containing Li2SO4, K2SO4, Na2SO4, Rb2SO4, or Cs2SO4. The height of the specific anodic oxidation peak varies with the alkaline sulfate in the solution; K2SO4 >> Na2SO4 > Cs2SO4 > Rb2SO4 > Li2SO4. It should be note that alkaline ions exist in lead sulfate formed on lead electrode in sulfuric acid solution containing potassium sulfate when the electrode was immersed in the solution at the rest potential for more than 1 h.

  14. Thermodynamic and Ultrasonic Properties of Ascorbic Acid in Aqueous Protic Ionic Liquid Solutions

    PubMed Central

    Singh, Vickramjeet; Sharma, Gyanendra; Gardas, Ramesh L.

    2015-01-01

    In this work, we report the thermodynamic and ultrasonic properties of ascorbic acid (vitamin C) in water and in presence of newly synthesized ammonium based protic ionic liquid (diethylethanolammonium propionate) as a function of concentration and temperature. Apparent molar volume and apparent molar isentropic compression, which characterize the solvation state of ascorbic acid (AA) in presence of protic ionic liquid (PIL) has been determined from precise density and speed of sound measurements at temperatures (293.15 to 328.15) K with 5 K interval. The strength of molecular interactions prevailing in ternary solutions has been discussed on the basis of infinite dilution partial molar volume and partial molar isentropic compression, corresponding volume of transfer and interaction coefficients. Result has been discussed in terms of solute-solute and solute-solvent interactions occurring between ascorbic acid and PIL in ternary solutions (AA + water + PIL). PMID:26009887

  15. Environment and solute-solvent interaction effects on photo-physical behaviors of Folic acid and Folinic acid drugs

    NASA Astrophysics Data System (ADS)

    Khadem Sadigh, M.; Zakerhamidi, M. S.; Seyed Ahmadian, S. M.; Johari-Ahar, M.; Zare Haghighi, L.

    2016-12-01

    In this paper, spectral properties of Folic acid and Folinic acid as widely used drugs in the treatment of some diseases have been studied in various environments with different polarity. Our results show that the absorption, emission and stokes shifts of solute molecules depend strongly on molecular surrounding characteristics, solute-solvent interactions and, different active groups in their chemical structures. In order to investigate the contribution of specific and nonspecific interactions on various properties of drug samples, the linear solvation energy relationships concept is used. Moreover, the calculated dipole moments by means of solvatochromic method show that the high values of dipole moments in excited state are due to local intramolecular charge transfer. Furthermore, the obtained results about molecular interactions can be extended to biological systems and can indicate completely the behaviors of Folic acid and Folinic acid in polar solvents such as water in body system.

  16. Electrochemical behaviour of titanium in ammine and stannous fluoride and chlorhexidine 0.2 percent mouthwashes.

    PubMed

    Quaranta, A; Ronconi, L F; Di Carlo, F; Vozza, I; Quaranta, M

    2010-01-01

    Titanium (Ti) is widely used in dentistry. Fluorides at acid pH could destabilize Ti oxide and make it susceptible to corrosion. The behaviour of IV grade machined Ti disks in 5 electrolytic solutions: Fusayama artificial saliva (Fas), ammine fluoride-stannous fluoride (Am-SnF2), 0.2 percent Chlorexidine (CHX) 0.20 percent, Fas with 20 percent Am-SnF2, and Fas with 20 percent CHX, was evaluated. Open circuit potential Ecorr was determined by immersing Ti disks for 24 hours in an electrochemical cell containing the solutions, potential changes were measured until a stable value was obtained. Examination by Scanning Electronic Microscope and Energy Dispersive X-ray Analysis were then performed. One way ANOVA analysis showed a significant difference of Ecorr values regarding the 5 solutions (p less than 0.001). The highest values were observed for Fas (-37.6 mV), intermediate for Am-SnF2 (-81mV) and lowest for CHX (-87.6mV). SEM analysis of disks after polarization curve in CHX showed a marked localized corrosion, while the other solutions showed no considerable corrosive action on Ti surface. When considering corrosive potential range in oral cavity, Ti had an excellent behaviour on both antiseptics evaluated. The results obtained in this study will enable us to recommend the use of Am-SnF2 mouthwash for patients with dental implants. PMID:20378020

  17. SAVANNAH RIVER SITE TANK CLEANING: CORROSION RATE FOR ONE VERSUS EIGHT PERCENT OXALIC ACID SOLUTION

    SciTech Connect

    Ketusky, E.; Subramanian, K.

    2011-01-20

    Until recently, the use of oxalic acid for chemically cleaning the Savannah River Site (SRS) radioactive waste tanks focused on using concentrated 4 and 8-wt% solutions. Recent testing and research on applicable dissolution mechanisms have concluded that under appropriate conditions, dilute solutions of oxalic acid (i.e., 1-wt%) may be more effective. Based on the need to maximize cleaning effectiveness, coupled with the need to minimize downstream impacts, SRS is now developing plans for using a 1-wt% oxalic acid solution. A technology gap associated with using a 1-wt% oxalic acid solution was a dearth of suitable corrosion data. Assuming oxalic acid's passivation of carbon steel was proportional to the free oxalate concentration, the general corrosion rate (CR) from a 1-wt% solution may not be bound by those from 8-wt%. Therefore, after developing the test strategy and plan, the corrosion testing was performed. Starting with the envisioned process specific baseline solvent, a 1-wt% oxalic acid solution, with sludge (limited to Purex type sludge-simulant for this initial effort) at 75 C and agitated, the corrosion rate (CR) was determined from the measured weight loss of the exposed coupon. Environmental variations tested were: (a) Inclusion of sludge in the test vessel or assuming a pure oxalic acid solution; (b) acid solution temperature maintained at 75 or 45 C; and (c) agitation of the acid solution or stagnant. Application of select electrochemical testing (EC) explored the impact of each variation on the passivation mechanisms and confirmed the CR. The 1-wt% results were then compared to those from the 8-wt%. The immersion coupons showed that the maximum time averaged CR for a 1-wt% solution with sludge was less than 25-mils/yr for all conditions. For an agitated 8-wt% solution with sludge, the maximum time averaged CR was about 30-mils/yr at 50 C, and 86-mils/yr at 75 C. Both the 1-wt% and the 8-wt% testing demonstrated that if the sludge was removed from

  18. Vapor-liquid equilibria for nitric acid-water and plutonium nitrate-nitric acid-water solutions

    SciTech Connect

    Maimoni, A.

    1980-01-01

    The liquid-vapor equilibrium data for nitric acid and nitric acid-plutnonium nitrate-water solutions were examined to develop correlations covering the range of conditions encountered in nuclear fuel reprocessing. The scanty available data for plutonium nitrate solutions are of poor quality but allow an order of magnitude estimate to be made. A formal thermodynamic analysis was attempted initially but was not successful due to the poor quality of the data as well as the complex chemical equilibria involved in the nitric acid and in the plutonium nitrate solutions. Thus, while there was no difficulty in correlating activity coefficients for nitric acid solutions over relatively narrow temperature ranges, attempts to extend the correlations over the range 25/sup 0/C to the boiling point were not successful. The available data were then analyzed using empirical correlations from which normal boiling points and relative volatilities can be obtained over the concentration ranges 0 to 700 g/l Pu, 0 to 13 M nitric acid. Activity coefficients are required, however, if estimates of individual component vapor pressures are needed. The required ternary activity coefficients can be approximated from the correlations.

  19. Antimicrobial and cytotoxic effects of phosphoric acid solution compared to other root canal irrigants

    PubMed Central

    PRADO, Maíra; da SILVA, Emmanuel João Nogueira Leal; DUQUE, Thais Mageste; ZAIA, Alexandre Augusto; FERRAZ, Caio Cezar Randi; de ALMEIDA, José Flávio Affonso; GOMES, Brenda Paula Figueiredo de Almeida

    2015-01-01

    Phosphoric acid has been suggested as an irrigant due to its effectiveness in removing the smear layer. Objectives : The purpose of this study was to compare the antimicrobial and cytotoxic effects of a 37% phosphoric acid solution to other irrigants commonly used in endodontics. Material and Methods : The substances 37% phosphoric acid, 17% EDTA, 10% citric acid, 2% chlorhexidine (solution and gel), and 5.25% NaOCl were evaluated. The antimicrobial activity was tested against Candida albicans, Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Actinomyces meyeri, Parvimonas micra, Porphyromonas gingivalis, and Prevotella nigrescens according to the agar diffusion method. The cytotoxicity of the irrigants was determined by using the MTT assay. Results : Phosphoric acid presented higher antimicrobial activity compared to the other tested irrigants. With regard to the cell viability, this solution showed results similar to those with 5.25% NaOCl and 2% chlorhexidine (gel and solution), whereas 17% EDTA and 10% citric acid showed higher cell viability compared to other irrigants. Conclusion : Phosphoric acid demonstrated higher antimicrobial activity and cytotoxicity similar to that of 5.25% NaOCl and 2% chlorhexidine (gel and solution). PMID:26018307

  20. [Effect of amino acid solutions on the blood ammonia level].

    PubMed

    Sanjo, K; Harihara, Y; Kawasaki, S; Umekita, N; Idezuki, Y

    1985-09-01

    We have carried out several basic experiments on artificial liver support and found that the plasma free amino acid balance was lost after treatment according to this procedure. Application of fluid therapy--Using conventional amino acid preparations available on the market--Is not adequate during and after the treatment with artificial liver. Fluid therapy using mainly special amino acid preparations should have been established; preparations, named Todai Hospital fluid (THF), are intended to correct the deranged aminogram, supply nutrition and promote the improvement in symptoms. Furthermore, experimental animals with acute hepatic insufficiency of diverse severity were prepared and basic experiments were performed which these animals to see how the efficacy of THF developed. In the basic experiments, psychoneurotic symptoms and the electroencephalogram were improved with the lowering of the blood ammonia level. Clinically, THF was not only used as a therapeutic agent after treatment by artificial liver support in patients with fulminant hepatitis, but is also served as a further indication in hepatic encephalopathy accompanying chronic liver diseases in late stages. Improvement in encephalopathy was observed immediately after the administration of THF and persisted while the aminogram pattern returned to the premedication representation. There was more improvement in patients in whom ammonemia was complicated, and the blood ammonia level was reduced markedly. PMID:4088243

  1. Interfacial structures of acidic and basic aqueous solutions

    SciTech Connect

    Tian, C.; Ji, N.; Waychunas, G.; Shen, Y.R.

    2008-10-20

    Phase-sensitive sum-frequency vibrational spectroscopy was used to study water/vapor interfaces of HCl, HI, and NaOH solutions. The measured imaginary part of the surface spectral responses provided direct characterization of OH stretch vibrations and information about net polar orientations of water species contributing to different regions of the spectrum. We found clear evidence that hydronium ions prefer to emerge at interfaces. Their OH stretches contribute to the 'ice-like' band in the spectrum. Their charges create a positive surface field that tends to reorient water molecules more loosely bonded to the topmost water layer with oxygen toward the interface, and thus enhances significantly the 'liquid-like' band in the spectrum. Iodine ions in solution also like to appear at the interface and alter the positive surface field by forming a narrow double-charge layer with hydronium ions. In NaOH solution, the observed weak change of the 'liquid-like' band and disappearance of the 'ice-like' band in the spectrum indicates that OH{sup -} ions must also have excess at the interface. How they are incorporated in the interfacial water structure is however not clear.

  2. Waste acid/metal solution reduction and recovery by vacuum distillation

    SciTech Connect

    Jones, E.O.; Wilcox, W.A.; Johnson, N.T.; Bowdish, F.W.

    1995-07-01

    Processes involving distillation under reduced pressure were developed at the Pacific Northwest Laboratory several years ago to recover spent acid solutions generated during the manufacture of nuclear fuel for the N-Reactor at the Hanford site. Following construction and testing of a pilot-plant, the technology was licensed to Viatec Recovery Systems, Inc. for commercialization. The technology developed included specialized distillation and rectification of volatile acids, removal of water and/or volatile acid from sulfuric acid, and precipitation of salts. A key feature of the Waste Acid Detoxification and Reclamation (WADR) technology is the development and use of advanced thermoplastic and fluoropolymer materials of construction in all critical process equipment. The technology was then expanded to include crystallization to recover metal salts for possible reuse. Economic and environmental advantages of the procedures include recovery of acids for reuse, simplification or elimination of the disposal of waste solutions, and possible recovery of metals. Industries expected to benefit from such applications include galvanizing, electroplating, sand leaching and any where metals are cleaned in acid solutions. Currently a modular system has been assembled for recovery of several different spent acid solutions.

  3. Part 2. Comparison of emergency washing solutions in 70% hydrofluoric acid-burned human skin in an established ex vivo explants model

    PubMed Central

    Burgher, François; Mathieu, Laurence; Lati, Elian; Gasser, Philippe; Peno-Mazzarino, Laurent; Blomet, Joël; Hall, Alan H; Maibach, Howard I

    2011-01-01

    Background: Hydrofluoric acid (HF) is a small and partially dissociated acid (pKa 3.2), able to deeply penetrate into human skin in addition to the corrosiveness of the hydrogen ion (H+) and the toxicity of the fluoride ion (F-). However, there has been a lack of experimental studies to objectively characterize the results of human HF skin exposure decontamination. Methodology/principal findings: A previously established experimental method using a human skin explants ex vivo model (Part 1. Experimental 70% hydrofluoric acid (HF) burns: Histological observations in an established human skin explants ex vivo model) described the lesions that appeared following 70% HF penetration. Within 5min, 70% HF penetrates to the dermis. Using the same experimental conditions, a comparison study of two different washing protocols was performed: water + topical calcium gluconate (CaG) versus Hexafluorine®. In these conditions, washing for 15min with running tap water followed by topical CaG ointment only delayed burn onset, while severe tissue damage appeared later. In contrast, after washing with Hexafluorine® over 10 min, no histological lesions developed. These results are in accordance with the results of accidental human industrial case reports. Conclusion/significance: Amphoteric and hypertonic Hexafluorine® can deactivate H+ and chelate F- ions. Based on these results, it should be considered as a promising first-aid decontamination solution to prevent or minimize significant local and systemic consequences of concentrated HF skin exposures. PMID:21083510

  4. Silver-Catalyzed Decarboxylative Allylation of Aliphatic Carboxylic Acids in Aqueous Solution.

    PubMed

    Cui, Lei; Chen, He; Liu, Chao; Li, Chaozhong

    2016-05-01

    Direct decarboxylative radical allylation of aliphatic carboxylic acids is described. With K2S2O8 as the oxidant and AgNO3 as the catalyst, the reactions of aliphatic carboxylic acids with allyl sulfones in aqueous CH3CN solution gave the corresponding alkenes in satisfactory yields under mild conditions. This site-specific allylation method is applicable to all primary, secondary, and tertiary alkyl acids and exhibits wide functional group compatibility. PMID:27065060

  5. Solution-phase secondary-ion mass spectrometry of protonated amino acids.

    PubMed

    Pettit, G R; Cragg, G M; Holzapfel, C W; Tuinman, A A; Gieschen, D P

    1987-04-01

    Although sulfolane proved unexpectedly to be a poor solvent for solution-phase secondary-ion mass spectrometry of underivatized amino acids in the presence of thallium(I) salts, glycerol was somewhat more effective. Also, the addition of trifluoromethanesulfonic acid proved more effective than addition of the metal in generating molecular ion complexes. A convenient and reliable method for rapidly determining amino acid molecular ions is based on these observations. PMID:3037939

  6. Fluoride release and uptake abilities of different fissure sealants

    PubMed Central

    Andenna, Gianluigi; Ceci, Matteo; Beltrami, Riccardo; Colombo, Marco; Cucca, Lucia

    2016-01-01

    Background The long-term capability of resin sealants and glass ionomer cements to release fluoride is associated to a reduction in pit and fissure caries. The regular use of fluoride varnishes/toothpastes can result in the absorption of fluoride into the sealant. The objective of the present study was to assess the fluoride release/uptake capacities of different fissure sealants. Material and Methods Three different fissure sealants (Fuji Triage/GC, Fissurit FX/Voco and Grandio Seal/Voco) were examined. Ten discs of each material were prepared. Each disc was incubated with distilled water and then the solution analyzed for diluted for fluoride concentration, using a combination of fluoride electrode (OrionGP 1 S/N 13824, Orion Research Inc, Boston, MA, USA) connected to an expandable ion analyzer (Orion 720A, Orion Research Inc, Boston, MA, USA). Standard curves between 1 and 100 ppm F- were used to calibrate the electrode. Cumulative fluoride release was measured on days 1, 2, 3, 5, 7, 21, 35 and 49, then two different fluoride varnishes/pastes (Profluorid Varnish/Voco, MI Paste Plus/GC), were applied to the sealants tested, and fluoride release (after reuptake) was measured on days 56, 70 and 84. Results Kruskal Wallis test confirmed significant differences in fluoride release between Fuji Triage/GC and Fissurit FX/Voco and Grandio Seal/Voco from day 1 (P < 0.001). The application of fluoride varnish Profluorid Varnish enhanced the fluoride release for all sealants (P < 0.05). MI Paste Plus enhanced the fluoride release for all sealants except for Fuji Triage/GC (P > 0.05). Conclusions The GIC-based sealant (Fuji Triage/GC) released significantly more fluoride than the resin sealants tested. The exposure to the fluoridated varnish (Profluorid Varnish) significantly recharged the sealants tested more than the CPP-ACPF toothpaste (MI Paste Plus). Key words:Fissure sealants, fluoride release, fluoride uptake, glass ionomer cements. PMID:27398179

  7. The solvent extraction of Americium(III) by 2,6-bis[(diphenylphosphino)-methyl]pyridine N,P,P` trioxide from nitric acid and hydrochloric acid solutions

    SciTech Connect

    Bond, E.M.; Engelhardt, U.; Deere, T.P.; Rapko, B.M.; Paine, R.T.

    1997-12-31

    The liquid/liquid extractions of Am(III) from nitric acid and hydrochloric acid solutions with chloroform solutions of 2,6-bis[(diphenylphosphino)methyl]pyridine N,P,P{prime} trioxide will be described. Americium(III) extracts well from high concentration nitric acid solutions (D>3000 at 6M nitric acid) and can be back extracted from the organic phase at 0.01M Nitric Acid. Americium(III) exhibits modest extraction from hydrochloric acid solutions (D=2.2 at 5M hydrochloric acid) and can be back extracted from the organic phase at 0.1M hydrochloric acid. The ligand dependency data suggest that two ligand molecules are coordinated to americium in the nitric acid system and three ligand molecules are coordinated to the americium in the hydrochloric acid system.

  8. Dissolution of Simulated and Radioactive Savannah River Site High-Level Waste Sludges with Oxalic Acid & Citric Acid Solutions

    SciTech Connect

    STALLINGS, MARY

    2004-07-08

    This report presents findings from tests investigating the dissolution of simulated and radioactive Savannah River Site sludges with 4 per cent oxalic acid and mixtures of oxalic and citric acid previously recommended by a Russian team from the Khlopin Radium Institute and the Mining and Chemical Combine (MCC). Testing also included characterization of the simulated and radioactive waste sludges. Testing results showed the following: Dissolution of simulated HM and PUREX sludges with oxalic and citric acid mixtures at SRTC confirmed general trends reported previously by Russian testing. Unlike the previous Russian testing six sequential contacts of a mixture of oxalic acid citric acids at a 2:1 ratio (v/w) of acid to sludge did not produce complete dissolution of simulated HM and PUREX sludges. We observed that increased sludge dissolution occurred at a higher acid to sludge ratio, 50:1 (v/w), compared to the recommended ratio of 2:1 (v/w). We observed much lower dissolution of aluminum in a simulated HM sludge by sodium hydroxide leaching. We attribute the low aluminum dissolution in caustic to the high fraction of boehmite present in the simulated sludge. Dissolution of HLW sludges with 4 per cent oxalic acid and oxalic/citric acid followed general trends observed with simulated sludges. The limited testing suggests that a mixture of oxalic and citric acids is more efficient for dissolving HM and PUREX sludges and provides a more homogeneous dissolution of HM sludge than oxalic acid alone. Dissolution of HLW sludges in oxalic and oxalic/citric acid mixtures produced residual sludge solids that measured at higher neutron poison to equivalent 235U weight ratios than that in the untreated sludge solids. This finding suggests that residual solids do not present an increased nuclear criticality safety risk. Generally the neutron poison to equivalent 235U weight ratios of the acid solutions containing dissolved sludge components are lower than those in the untreated

  9. RECOVERY OF PROTACTINIUM FROM AQUEOUS SOLUTIONS

    DOEpatents

    Elson, R.E.

    1959-07-14

    The recovery of fluoride complexed protactinium from aqueous acidic solutions by solvent extraction is described. Generally the prccess of the invention com rises mixing an aqueous solution containing protactinium in a complexed form with an organic solvent which is specific for protactinium, such as diisopropyl carbinol, then decomposing the protactinium complex by adjusting the acidity of the aqueous solution to between 0-3 to 0-9 M in hydrogen ion concentration, and introducing a source of aluminum ions in sufficient quantity to establish a concentration of 0.5 to 1.2 M aluminum ion, whereupon decomposition of the protactinium fluoride complex takes place and the protactinium ion is taken up by the organic solvent phase.

  10. Novel salicylic acid-oriented thiourea-type receptors as colorimetric chemosensor: Synthesis, characterizations and selective naked-eye recognition properties

    NASA Astrophysics Data System (ADS)

    Li, Shaowei; Cao, Xiufang; Chen, Changshui; Ke, Shaoyong

    2012-10-01

    Based on the salicylic acid backbone, three highly sensitive and selective colorimetric chemosensors with an acylthiourea binding unit have been designed, synthesized and characterized. These chemosensors have been utilized for selective recognition of fluoride anions in dry DMSO solution by typical spectroscopic titration techniques. Furthermore, the obtained chemosensors AR1-3 have shown naked-eye sensitivity for detection of biologically important fluoride ion over other anions in solution.

  11. Method for extracting lanthanides and actinides from acid solutions by modification of Purex solvent

    DOEpatents

    Horwitz, E.P.; Kalina, D.G.

    1984-05-21

    A process has been developed for the extraction of multivalent lanthanide and actinide values from acidic waste solutions, and for the separation of these values from fission product and other values, which utilizes a new series of neutral bi-functional extractants, the alkyl(phenyl)-N, N-dialkylcarbamoylmethylphosphine oxides, in combination with a phase modifier to form an extraction solution. The addition of the extractant to the Purex process extractant, tri-n-butylphosphate in normal paraffin hydrocarbon diluent, will permit the extraction of multivalent lanthanide and actinide values from 0.1 to 12.0 molar acid solutions.

  12. The amino acid's backup bone - storage solutions for proteomics facilities.

    PubMed

    Meckel, Hagen; Stephan, Christian; Bunse, Christian; Krafzik, Michael; Reher, Christopher; Kohl, Michael; Meyer, Helmut Erich; Eisenacher, Martin

    2014-01-01

    Proteomics methods, especially high-throughput mass spectrometry analysis have been continually developed and improved over the years. The analysis of complex biological samples produces large volumes of raw data. Data storage and recovery management pose substantial challenges to biomedical or proteomic facilities regarding backup and archiving concepts as well as hardware requirements. In this article we describe differences between the terms backup and archive with regard to manual and automatic approaches. We also introduce different storage concepts and technologies from transportable media to professional solutions such as redundant array of independent disks (RAID) systems, network attached storages (NAS) and storage area network (SAN). Moreover, we present a software solution, which we developed for the purpose of long-term preservation of large mass spectrometry raw data files on an object storage device (OSD) archiving system. Finally, advantages, disadvantages, and experiences from routine operations of the presented concepts and technologies are evaluated and discussed. This article is part of a Special Issue entitled: Computational Proteomics in the Post-Identification Era. Guest Editors: Martin Eisenacher and Christian Stephan. PMID:23722089

  13. Heterogeneous freezing of single sulphuric acid solution droplets: laboratory experiments utilising an acoustic levitator

    NASA Astrophysics Data System (ADS)

    Ettner, M.; Mitra, S. K.; Borrmann, S.

    2004-03-01

    The heterogeneous freezing temperatures of single binary sulphuric acid solution droplets were measured in dependency of acid concentration down to temperatures as low as -70°C. In order to avoid influence of supporting substrates on the freezing characteristics, the droplets were suspended by means of an acoustic levitator. The droplets contained immersed particles of graphite, kaolin or montmorillonite in order to study the influence of the presence of such contamination on the freezing temperature. The radii of the suspended droplets spanned the range between 0,4 and 1,1 mm and the concentration of the sulphuric acid solution varied between 5 and 25 weight percent. The presence of the particles in the solution raises the freezing temperature with respect to homogeneous freezing of these solution droplets. The pure solution droplets can be supercooled up to 40° below the ice-acid solution thermodynamic equilibrium curve. Depending on the concentration of sulphuric acid and the nature of the impurity the polluted droplets froze between -11°C and -35°C. The experimental set-up, combining a deep freezer with a movable ultrasonic levitator and suitable optics, proved to be a useful approach for such investigations on individual droplets.

  14. Heterogeneous freezing of single sulfuric acid solution droplets: laboratory experiments utilizing an acoustic levitator

    NASA Astrophysics Data System (ADS)

    Ettner, M.; Mitra, S. K.; Borrmann, S.

    2004-09-01

    The heterogeneous freezing temperatures of single binary sulfuric acid solution droplets were measured in dependency of acid concentration down to temperatures as low as -50°C. In order to avoid influence of supporting substrates on the freezing characteristics, a new technique has been developed to suspend the droplet by means of an acoustic levitator. The droplets contained immersed particles of graphite, kaolin or montmorillonite in order to study the influence of the presence of such contamination on the freezing temperature. The radii of the suspended droplets spanned the range between 0.4 and 1.1mm and the concentration of the sulfuric acid solution varied between 5 and 14 weight percent. The presence of the particles in the solution raises the freezing temperature with respect to homogeneous freezing of these solution droplets. The pure solution droplets can be supercooled up to 40 degrees below the ice-acid solution thermodynamic equilibrium curve. Depending on the concentration of sulfuric acid and the nature of the impurity the polluted droplets froze between -11°C and -35°C. The new experimental set-up, combining a deep freezer with a movable ultrasonic levitator and suitable optics, proved to be a useful approach for such investigations on individual droplets.

  15. In vivo effects of fluoride, chlorhexidine and zinc ions on acid formation by dental plaque and salivary mutans streptococcus counts in patients with irradiation-induced xerostomia.

    PubMed

    Giertsen, E; Scheie, A A

    1993-10-01

    Irradiation therapy including major salivary glands may result in xerostomia and enhanced susceptibility to dental caries. The present aim was to assess the ability of mouthrinses with F-, Zn2+, and chlorhexidine (CH), in various combinations, to reduce acidogenic potential of dental plaque and salivary mutans streptococcus counts (SMSC) in 7 patients with xerostomia secondary to irradiation. The patients rinsed twice daily for 3 weeks with the following test solutions: (1) 12 mmol/l NaF (F; control), (2) NaF + 20 mmol/l ZnCl2 (F-Zn), and (3) NaF + 1.1 mmol/l CH (F-CH). Resting periods (F) of varying lengths were incorporated. Acid formation by dental plaque was monitored as plaque pH response to a sucrose mouthrinse, at the end of each test period, 4 h after mouthrinsing with test solution. Plaque pH was measured repeatedly at 2-8 sites in each patient before, and up to 60 min after the sucrose mouthrinse using touch microelectrodes. SMSC were determined using Dentocult SM-Strip mutans. Compared with F, F-CH significantly (P < or = 0.02) reduced acid formation by plaque and SMSC, whereas F-Zn did not affect acid formation or SMSC significantly. Pilot experiments in 4 patients showed mouthrinses with NaF + 0.55 mmol/l CH + 10 mmol/l Zn2+ to be ineffective, whereas NaF + 2.2 mmol/l CH was highly effective, but no better than F-CH. Twice daily mouthrinses with 12 mmol/l NaF in combination with 1.1 mmol/l CH may be an effective regimen to prevent post-irradiation caries. PMID:11706427

  16. Hydrogen generation by tin corrosion in lactic acid solution promoted by sodium perchlorate

    NASA Astrophysics Data System (ADS)

    Deyab, M. A.

    2014-12-01

    A method to produce high purity hydrogen using the corrosion of tin metal in lactic acid solutions is studied. The addition of sodium perchlorate has been also investigated for promoting the tin-lactic acid reaction. The data reveal that the rate of hydrogen production increases with increasing lactic acid concentration. The presence of perchlorate ions in lactic acid solution enhances the active dissolution of tin metal and tends to breakdown the passive film and promoting the hydrogen generation rate. Polarization measurements show that the breakdown potential (Epit) decreases with increase in sodium perchlorate concentration. An increase in temperature accelerates the rate of solubility of passive layer on the tin surface. Moreover, a synergistic effect of sodium perchlorate in combination with increasing the solution temperature is key in promoting the hydrogen generation rate. Results obtained from hydrogen and polarization measurements are in good agreement. These measurements are complemented with SEM, EDX and XRD examinations of the electrode surface.

  17. Control and monitoring of the localized corrosion of zirconium in acidic chloride solutions

    SciTech Connect

    Fahey, J.; Holmes, D.; Yau, T.L.

    1995-09-01

    Zirconium in acidic chloride solutions which are contaminated with ferric or cupric cations is prone to localized corrosion. This tendency can be reduced by ensuring that the zirconium surface is clean and smooth. In this paper, the effect of surface condition on the localized corrosion of zirconium in acidic chloride solutions is predicted with potentiodynamic scans. These predictions are confirmed by weight loss tests on various combinations of surface finish and acid concentrations. A real time indication of localized corrosion is seen by monitoring the electrochemical noise produced between two similar electrodes immersed in an acidic chloride solutions. Electrochemical noise monitoring correlates well with the predictions from potentiodynamic and weight loss experiments. The electrochemical noise results show that while an elevated (more anodic) potential caused by ferric ion contamination may be a necessary condition for localized corrosion, it is not a sufficient condition: A smooth, clean zirconium surface reduces the localized corrosion of zirconium.

  18. Effect of doping of calcium fluoride nanoparticles on the photoluminescence properties of europium complexes with benzoic acid derivatives as secondary ligands and 2-aminopyridine as primary ligand

    NASA Astrophysics Data System (ADS)

    Sharma, Garima; Narula, Anudeep Kumar

    2015-08-01

    The present article reports the synthesis of three Eu(III) complexes [Eu(BA)3(2-ap)] (1), [Eu(HBA)3(2-ap)] (2) and [Eu(ABA)3(2-ap)] (3) (BA = benzoic acid, HBA = 2-hydroxy benzoic acid, ABA = 2-amino benzoic acid and 2-ap = 2-aminopyridine) carried out in ethanol solution. The complexes were further doped with CaF2 nanoparticles and a change in the photoluminescence properties was observed. The compositions and structural investigation of the complexes were determined by elemental analysis and Fourier transform infrared spectroscopy (FTIR) which suggest the coordination of ligands with the central Eu(III) ion. The optical properties of the complexes were studied by Ultraviolet Visible absorption spectroscopy (UV-Vis) and photoluminescence studies (PL). The relative PL intensity was enhanced in the Eu(III) complexes doped with CaF2 nanoparticles as compared to the pure Eu(III) complexes, however the increase in intensity varied in the order of ligands ABA > HBA > BA. The photoluminescence lifetime decay curves also revealed the longer lifetime (τ) and higher quantum efficiency (η) for europium complexes with ABA ligands suggesting the efficient energy transfer and better sensitizing ability of the ligand to europium ion. The morphology of the synthesized compounds were studied by Scanning Electron Microscopy (SEM) revealing spherical morphology with agglomeration of the nanoparticles.

  19. Growth behavior of anodic porous alumina formed in malic acid solution

    NASA Astrophysics Data System (ADS)

    Kikuchi, Tatsuya; Yamamoto, Tsuyoshi; Suzuki, Ryosuke O.

    2013-11-01

    The growth behavior of anodic porous alumina formed on aluminum by anodizing in malic acid solutions was investigated. High-purity aluminum plates were electropolished in CH3COOH/HClO4 solutions and then anodized in 0.5 M malic acid solutions at 293 K and constant cell voltages of 200-350 V. The anodic porous alumina grew on the aluminum substrate at voltages of 200-250 V, and a black, burned oxide film was formed at higher voltages. The nanopores of the anodic oxide were only formed at grain boundaries of the aluminum substrate during the initial stage of anodizing, and then the growth region extended to the entire aluminum surface as the anodizing time increased. The anodic porous alumina with several defects was formed by anodizing in malic acid solution at 250 V, and oxide cells were approximately 300-800 nm in diameter.

  20. Time dependent inhibition of xanthine oxidase in irradiated solutions of folic acid, aminopterin and methotrexate

    SciTech Connect

    Robinson, K.; Pilot, T.F.; Meany, J.E. )

    1990-01-01

    The xanthine oxidase catalyzed oxidation of hypoxanthine was followed by monitoring the formation of uric acid at 290 nm. Inhibition of xanthine oxidase occurs in aqueous solutions of folic acid methotrexate and aminopterin. These compounds are known to dissociate upon exposure to ultraviolet light resulting in the formation of their respective 6-formylpteridine derivatives. The relative rates of dissociation were monitored spectrophotometrically by determining the absorbance of their 2,4-dinitrophenylhydrazine derivatives at 500 nm. When aqueous solutions of folic acid, aminopterin and methotrexate were exposed to uv light, a direct correlation was observed between the concentrations of the 6-formylpteridine derivatives existing in solution and the ability of these solutions to inhibit xanthine oxidase. The relative potency of the respective photolysis products were estimated.

  1. Electrochemical protection of zirconium in oxidizing hydrochloric acid solutions

    SciTech Connect

    Yuu, T-L.; Maguire, M.

    1984-06-01

    An electrochemical protection technique using cathodic polarization to maintain zirconium below its critical repassivation potential was used to avoid pitting and stress corrosion cracking (SCC) in hydrochloric acid (HCI) containing ferric ions (Fe/sup +3/). Corrosion and pit penetration rates are reported for pickled, abraded, and as-received surface conditions in 10, 20, and 37% HCI containing 50, 100, or 500 ppm Fe/sup +3/ at temperatures to boiling. The pickled surface was the least susceptible to pitting in the 64 day tests. Electrochemical protection is then evaluated for total immersion, partial immersion, U-bend, and constant strain rate tensile tests. Protection is effective in eliminating pitting and SCC in 10 and 20% HCI containing Fe/sup +3/.

  2. Acid gas absorption in aqueous solutions of mixed amines

    SciTech Connect

    Rinker, E.B.; Ashour, S.S.; Sandall, O.C.

    1996-12-31

    A mass transfer model has been developed to describe the rate of absorption (or desorption) of H{sub 2}S and CO{sub 2} in aqueous blends of a tertiary and a secondary or a primary amine. The model is based on penetration theory, and all significant chemical reactions are incorporated in the model. The reactions are taken to be reversible, with reactions involving only a proton transfer considered to be at equilibrium. The particular amines studied in this research were methyldiethanolamine (MDEA), a tertiary amine, and diethanolamine (DEA), a secondary amine. Key physicochemical data needed in the model, such as diffusion coefficients, kinetic rate constants, and gas solubilities, were measured. Experimental absorption rates of CO{sub 2} and H{sub 2}S were measured in a model gas-liquid contacting device and were compared with model predictions. Experiments were carried out for single amine solutions (both MDEA and DEA) and for amine blends.

  3. Solute-enhanced production of gamma-valerolactone (GVL) from aqueous solutions of levulinic acid

    SciTech Connect

    Dumesic, James A; Wettstein, Stephanie G; Alonso, David Martin; Gurbuz, Elif Ispir

    2015-02-24

    A method to produce levulinic acid (LA) and gamma-valerolactone (GVL) from biomass-derived cellulose or lignocellulose by selective extraction of LA using GVL and optionally converting the LA so isolated into GVL, with no purifications steps required to yield the GVL.

  4. Metabolic engineering of yeast to produce fatty acid-derived biofuels: bottlenecks and solutions.

    PubMed

    Sheng, Jiayuan; Feng, Xueyang

    2015-01-01

    Fatty acid-derived biofuels can be a better solution than bioethanol to replace petroleum fuel, since they have similar energy content and combustion properties as current transportation fuels. The environmentally friendly microbial fermentation process has been used to synthesize advanced biofuels from renewable feedstock. Due to their robustness as well as the high tolerance to fermentation inhibitors and phage contamination, yeast strains such as Saccharomyces cerevisiae and Yarrowia lipolytica have attracted tremendous attention in recent studies regarding the production of fatty acid-derived biofuels, including fatty acids, fatty acid ethyl esters, fatty alcohols, and fatty alkanes. However, the native yeast strains cannot produce fatty acids and fatty acid-derived biofuels in large quantities. To this end, we have summarized recent publications in this review on metabolic engineering of yeast strains to improve the production of fatty acid-derived biofuels, identified the bottlenecks that limit the productivity of biofuels, and categorized the appropriate approaches to overcome these obstacles. PMID:26106371

  5. Metabolic engineering of yeast to produce fatty acid-derived biofuels: bottlenecks and solutions

    PubMed Central

    Sheng, Jiayuan; Feng, Xueyang

    2015-01-01

    Fatty acid-derived biofuels can be a better solution than bioethanol to replace petroleum fuel, since they have similar energy content and combustion properties as current transportation fuels. The environmentally friendly microbial fermentation process has been used to synthesize advanced biofuels from renewable feedstock. Due to their robustness as well as the high tolerance to fermentation inhibitors and phage contamination, yeast strains such as Saccharomyces cerevisiae and Yarrowia lipolytica have attracted tremendous attention in recent studies regarding the production of fatty acid-derived biofuels, including fatty acids, fatty acid ethyl esters, fatty alcohols, and fatty alkanes. However, the native yeast strains cannot produce fatty acids and fatty acid-derived biofuels in large quantities. To this end, we have summarized recent publications in this review on metabolic engineering of yeast strains to improve the production of fatty acid-derived biofuels, identified the bottlenecks that limit the productivity of biofuels, and categorized the appropriate approaches to overcome these obstacles. PMID:26106371

  6. Fluoride-Mediated Capture of a Noncovalent Bound State of a Reversible Covalent Enzyme Inhibitor: X-ray Crystallographic Analysis of an Exceptionally Potent α-Ketoheterocycle Inhibitor of Fatty Acid Amide Hydrolase

    PubMed Central

    Mileni, Mauro; Garfunkle, Joie; Ezzili, Cyrine; Cravatt, Benjamin F.; Stevens, Raymond C.; Boger, Dale L.

    2011-01-01

    Two cocrystal X-ray structures of the exceptionally potent α-ketoheterocycle inhibitor 1 (Ki = 290 pM) bound to a humanized variant of rat fatty acid amide hydrolase (FAAH) are disclosed, representing noncovalently and covalently bound states of the same inhibitor with the enzyme. Key to securing the structure of the noncovalently bound state of the inhibitor was the inclusion of fluoride ion in the crystallization conditions that is proposed to bind the oxyanion hole precluding inhibitor covalent adduct formation with stabilization of the tetrahedral hemiketal. This permitted the opportunity to detect important noncovalent interactions stabilizing the binding of the inhibitor within the FAAH active site independent of the covalent reaction. Remarkably, noncovalently bound 1 in the presence of fluoride appears to capture the active site in the same “in action” state with the three catalytic residues Ser241–Ser217–Lys142 occupying essentially identical positions observed in the covalently bound structure of 1, suggesting that this technique of introducing fluoride may have important applications in structural studies beyond inhibiting substrate or inhibitor oxyanion hole binding. Key insights to emerge from the studies include the observations that noncovalently bound 1 binds in its ketone (not gem diol) form, that the terminal phenyl group in the acyl side chain of the inhibitor serves as the key anchoring interaction overriding the intricate polar interactions in the cytosolic port, and that the role of the central activating heterocycle is dominated by its intrinsic electron-withdrawing properties. These two structures are also briefly compared with five X-ray structures of α-ketoheterocycle-based inhibitors bound to FAAH recently disclosed. PMID:21355555

  7. Fluoride-Mediated Capture of a Noncovalent Bound State of a Reversible Covalent Enzyme Inhibitor: X-ray Crystallographic Analysis of an Exceptionally Potent [alpha]-Ketoheterocycle Inhibitor of Fatty Acid Amide Hydrolase

    SciTech Connect

    Mileni, Mauro; Garfunkle, Joie; Ezzili, Cyrine; Cravatt, Benjamin F.; Stevens, Raymond C.; Boger, Dale L.

    2011-11-02

    Two cocrystal X-ray structures of the exceptionally potent {alpha}-ketoheterocycle inhibitor 1 (K{sub i} = 290 pM) bound to a humanized variant of rat fatty acid amide hydrolase (FAAH) are disclosed, representing noncovalently and covalently bound states of the same inhibitor with the enzyme. Key to securing the structure of the noncovalently bound state of the inhibitor was the inclusion of fluoride ion in the crystallization conditions that is proposed to bind the oxyanion hole precluding inhibitor covalent adduct formation with stabilization of the tetrahedral hemiketal. This permitted the opportunity to detect important noncovalent interactions stabilizing the binding of the inhibitor within the FAAH active site independent of the covalent reaction. Remarkably, noncovalently bound 1 in the presence of fluoride appears to capture the active site in the same 'in action' state with the three catalytic residues Ser241-Ser217-Lys142 occupying essentially identical positions observed in the covalently bound structure of 1, suggesting that this technique of introducing fluoride may have important applications in structural studies beyond inhibiting substrate or inhibitor oxyanion hole binding. Key insights to emerge from the studies include the observations that noncovalently bound 1 binds in its ketone (not gem diol) form, that the terminal phenyl group in the acyl side chain of the inhibitor serves as the key anchoring interaction overriding the intricate polar interactions in the cytosolic port, and that the role of the central activating heterocycle is dominated by its intrinsic electron-withdrawing properties. These two structures are also briefly compared with five X-ray structures of {alpha}-ketoheterocycle-based inhibitors bound to FAAH recently disclosed.

  8. PRODUCTION OF TRIFLUOROACETIC ACID COMPOUNDS

    DOEpatents

    Haworth, W.N.; Stacey, M.

    1949-08-30

    A process is described for the preparation of trifluoroacetic acid. Acetone vapor diluted wlth nitrogen and fluorine also diluted with nltrogen are fed separately at a temperature of about 210 deg C into a reaction vessel containing a catalyst mass selected from-the group consisting of silver and gold. The temperature in the reaction vessel is maintained in the range of 200 deg to 250 deg C. The reaction product, trifluoroacetyl fluoride, is absorbed in aqueous alkali solution. Trifluoroacetic acid is recovered from the solution by acidification wlth an acid such as sulfuric followed by steam distillation.

  9. Comparison of XAD macroporous resins for the concentration of fulvic acid from aqueous solution

    USGS Publications Warehouse

    Aiken, G.R.

    1979-01-01

    Five macroreticular, nonlonlc AmberlHe XAD resins were evaluated for concentration and Isolation of fulvlc acid from aqueous solution. The capacity of each resin for fulvlc acid was measured by both batch and column techniques. Elution efficiencies were determined by desorptlon with 0.1 N NaOH. Highest recoveries were obtained with the acrylic ester resins which proved to be most efficient for both adsorption and elution of fulvlc acid. Compared to the acrylic ester resins, usefulness of the styrene dvlnybenzene resins to remove fulvlc acid is limited because of slow diffusion-controlled adsorption and formation of charge-transfer complexes, which hinders elution. ?? 1979 American Chemical Society.

  10. Novel one-pot synthesis of dicarboxylic acids mediated alginate-zirconium biopolymeric complex for defluoridation of water.

    PubMed

    Prabhu, Subbaiah Muthu; Meenakshi, Sankaran

    2015-04-20

    The present investigation explains the fluoride removal from aqueous solution using alginate-zirconium complex prepared with respective dicarboxylic acids like oxalic acid (Ox), malonic acid (MA) and succinic acid (SA) as a medium. The complexes viz., alginate-oxalic acid-zirconium (Alg-Ox-Zr), alginate-malonic acid-zirconium (Alg-MA-Zr) and alginate-succinic acid-zirconium (Alg-SA-Zr) were synthesized and studied for fluoride removal. The synthesized complexes were characterized by FTIR, XRD, SEM with EDAX and mapping images. The effects of various operating parameters were optimized. The result showed that the maximum removal of fluoride 9653mgF(-)/kg was achieved by Alg-Ox-Zr complex at acidic pH in an ambient atmospheric condition. Equilibrium data of Alg-Ox-Zr complex was fitted well with Freundlich isotherm. The calculated values of thermodynamic parameters indicated that the fluoride adsorption is spontaneous and endothermic in nature. The mechanism of fluoride removal behind Alg-Ox-Zr complex has been proposed in detail. The suitability of the Alg-Ox-Zr complex has been tested with the field sample collected in a nearby fluoride endemic area. PMID:25662688

  11. Reaction behavior of Ni-Re alloys during direct current polarization in sulfuric acid solutions

    NASA Astrophysics Data System (ADS)

    Bryukvin, V. A.; Elemesov, T. B.; Levchuk, O. M.; Bol'shikh, A. O.

    2016-01-01

    The macrokinetic regularities of the reactivity of synthesized Ni-Re (20 and 60 wt %) alloys in a sulfuric acid solution (100 g/L, 25-40°C) during direct current polarization are studied using physicochemical methods. The phase composition of the synthesized alloys is determined by the formation of solid solutions as a function of the initial Ni/Re weight ratio. These are two types of nickel solid solutions (Ni16Re0.2 and Ni14Re0.9) and one rhenium solution (Ni1.1Re). These solid solutions are anodically oxidized in the sequence of their structural rearrangement Ni16Re0.2 → Ni14Re0.9 → Ni1.1Re with a combined transition of the metals into an electrolyte solution. These solid solutions provide the reduction of Ni3+ to Ni2+ due to the depolarization ability of rhenium, being their component.

  12. Fluoridation: strategies for success.

    PubMed

    Isman, R

    1981-07-01

    Of 19 referenda on community water fluoridation held in the first six months of 1980, 17 were defeated. Among the postulated reasons are a growing distrust of government and the health establishment. The public remains largely ignorant of the purpose and benefits of fluoridation. The emotionalism surrounding the issue has made it difficult to generate public support outside of the health professions. Opponents have also learned to fight fluoridation with increasingly sophisticated techniques. Some of the strategies used in recent successful campaigns in Oakland, California, and Portland, Oregon are described; recommendations that can be applied to communities considering fluoridation include careful wording of ballot measures so they are unequivocally clear and simple; timing ballot measures with elections likely to draw the largest voter turnout; broadening the base of political and financial support; using a figurehead if possible; and making maximum use of the media. PMID:7246838

  13. Fluoride in diet

    MedlinePlus

    ... broken through the gums have changes in the enamel that covers the teeth. Faint white lines or ... regarding fluoride intake from reconstituted infant formula and enamel fluorosis: a report of the American Dental Association ...

  14. Precipitation pathways for ferrihydrite formation in acidic solutions

    DOE PAGESBeta

    Zhu, Mengqiang; Khalid, Syed; Frandsen, Cathrine; Wallace, Adam F.; Legg, Benjamin; Zhang, Hengzhong; Morup, Steen; Banfield, Jillian F.; Waychunas, Glenn A.

    2015-10-03

    In this study, iron oxides and oxyhydroxides form via Fe3+ hydrolysis and polymerization in many aqueous environments, but the pathway from Fe3+ monomers to oligomers and then to solid phase nuclei is unknown. In this work, using combined X-ray, UV–vis, and Mössbauer spectroscopic approaches, we were able to identify and quantify the long-time sought ferric speciation over time during ferric oxyhydroxide formation in partially-neutralized ferric nitrate solutions ([Fe3+] = 0.2 M, 1.8 < pH < 3). Results demonstrate that Fe exists mainly as Fe(H2O)63+, μ-oxo aquo dimers and ferrihydrite, and that with time, the μ-oxo dimer decreases while the othermore » two species increase in their concentrations. No larger Fe oligomers were detected. Given that the structure of the μ-oxo dimer is incompatible with those of all Fe oxides and oxyhydroxides, our results suggest that reconfiguration of the μ-oxo dimer structure occurs prior to further condensation leading up to the nucleation of ferrihydrite. The structural reconfiguration is likely the rate-limiting step involved in the nucleation process.« less

  15. Precipitation pathways for ferrihydrite formation in acidic solutions

    SciTech Connect

    Zhu, Mengqiang; Khalid, Syed; Frandsen, Cathrine; Wallace, Adam F.; Legg, Benjamin; Zhang, Hengzhong; Morup, Steen; Banfield, Jillian F.; Waychunas, Glenn A.

    2015-10-03

    In this study, iron oxides and oxyhydroxides form via Fe3+ hydrolysis and polymerization in many aqueous environments, but the pathway from Fe3+ monomers to oligomers and then to solid phase nuclei is unknown. In this work, using combined X-ray, UV–vis, and Mössbauer spectroscopic approaches, we were able to identify and quantify the long-time sought ferric speciation over time during ferric oxyhydroxide formation in partially-neutralized ferric nitrate solutions ([Fe3+] = 0.2 M, 1.8 < pH < 3). Results demonstrate that Fe exists mainly as Fe(H2O)63+, μ-oxo aquo dimers and ferrihydrite, and that with time, the μ-oxo dimer decreases while the other two species increase in their concentrations. No larger Fe oligomers were detected. Given that the structure of the μ-oxo dimer is incompatible with those of all Fe oxides and oxyhydroxides, our results suggest that reconfiguration of the μ-oxo dimer structure occurs prior to further condensation leading up to the nucleation of ferrihydrite. The structural reconfiguration is likely the rate-limiting step involved in the nucleation process.

  16. Precipitation pathways for ferrihydrite formation in acidic solutions

    NASA Astrophysics Data System (ADS)

    Zhu, Mengqiang; Frandsen, Cathrine; Wallace, Adam F.; Legg, Benjamin; Khalid, Syed; Zhang, Hengzhong; Mørup, Steen; Banfield, Jillian F.; Waychunas, Glenn A.

    2016-01-01

    Iron oxides and oxyhydroxides form via Fe3+ hydrolysis and polymerization in many aqueous environments, but the pathway from Fe3+ monomers to oligomers and then to solid phase nuclei is unknown. In this work, using combined X-ray, UV-vis, and Mössbauer spectroscopic approaches, we were able to identify and quantify the long-time sought ferric speciation over time during ferric oxyhydroxide formation in partially-neutralized ferric nitrate solutions ([Fe3+] = 0.2 M, 1.8 < pH < 3). Results demonstrate that Fe exists mainly as Fe(H2O)63+, μ-oxo aquo dimers and ferrihydrite, and that with time, the μ-oxo dimer decreases while the other two species increase in their concentrations. No larger Fe oligomers were detected. Given that the structure of the μ-oxo dimer is incompatible with those of all Fe oxides and oxyhydroxides, our results suggest that reconfiguration of the μ-oxo dimer structure occurs prior to further condensation leading up to the nucleation of ferrihydrite. The structural reconfiguration is likely the rate-limiting step involved in the nucleation process.

  17. Extraction of palladium from acidic solutions with the use of carbon adsorbents

    SciTech Connect

    O.N. Kononova; N.G. Goryaeva; N.B. Dostovalova; S.V. Kachin; A.G. Kholmogorov

    2007-08-15

    We studied the sorption of palladium(II) on LKAU-4, LKAU-7, and BAU carbon adsorbents from model hydrochloric acid solutions and the solutions of spent palladium-containing catalysts. It was found that sorbents based on charcoal (BAU) and anthracite (LKAU-4) were characterized by high sorption capacities for palladium. The kinetics of the saturation of carbon adsorbents with palladium(II) ions was studied, and it was found that more than 60% of the initial amount of Pd(II) was recovered in a 1-h contact of an adsorbent with a model solution. This value for the solutions of spent catalysts was higher than 35%.

  18. Bis(mesitoyl)phosphinic acid: photo-triggered release of metaphosphorous acid in solution.

    PubMed

    Fast, David E; Zalibera, Michal; Lauer, Andrea; Eibel, Anna; Schweigert, Caroline; Kelterer, Anne-Marie; Spichty, Martin; Neshchadin, Dmytro; Voll, Dominik; Ernst, Hanna; Liang, Yu; Dietliker, Kurt; Unterreiner, Andreas-Neil; Barner-Kowollik, Christopher; Grützmacher, Hansjörg; Gescheidt, Georg

    2016-08-01

    Bis(mesitoyl)phosphinic acid and its sodium salt display a unique photo-induced reactivity: both derivatives stepwise release two mesitoyl radicals and, remarkably, metaphosphorous acid (previously postulated as transient species in the gas phase), providing a new phosphorus-based reagent. PMID:27431207

  19. Isotherm-Based Thermodynamic Models for Solute Activities of Organic Acids with Consideration of Partial Dissociation.

    PubMed

    Nandy, Lucy; Ohm, Peter B; Dutcher, Cari S

    2016-06-23

    Organic acids make up a significant fraction of the organic mass in atmospheric aerosol particles. The calculation of gas-liquid-solid equilibrium partitioning of the organic acid is therefore critical for accurate determination of atmospheric aerosol physicochemical properties and processes such as new particle formation and activation to cloud condensation nuclei. Previously, an adsorption isotherm-based statistical thermodynamic model was developed for capturing solute concentration-activity relationships for multicomponent aqueous solutions over the entire concentration range (Dutcher et al. J. Phys. Chem. C/A 2011, 2012, 2013), with model parameters for energies of adsorption successfully related to dipole-dipole electrostatic forces in solute-solvent and solvent-solvent interactions for both electrolytes and organics (Ohm et al. J. Phys. Chem. A 2015). However, careful attention is needed for weakly dissociating semivolatile organic acids. Dicarboxylic acids, such as malonic acid and glutaric acid are treated here as a mixture of nondissociated organic solute (HA) and dissociated solute (H(+) + A(-)). It was found that the apparent dissociation was greater than that predicted by known dissociation constants alone, emphasizing the effect of dissociation on osmotic and activity coefficient predictions. To avoid additional parametrization from the mixture approach, an expression was used to relate the Debye-Hückel hard-core collision diameter to the adjustable solute-solvent intermolecular distance. An improved reference state treatment for electrolyte-organic aqueous mixtures, such as that observed here with partial dissociation, has also been proposed. This work results in predictive correlations for estimation of organic acid and water activities for which there is little or no activity data. PMID:27222917

  20. Process for converting magnesium fluoride to calcium fluoride

    DOEpatents

    Kreuzmann, A.B.; Palmer, D.A.

    1984-12-21

    This invention is a process for the conversion of magnesium fluoride to calcium fluoride whereby magnesium fluoride is decomposed by heating in the presence of calcium carbonate, calcium oxide or calcium hydroxide. Magnesium fluoride is a by-product of the reduction of uranium tetrafluoride to form uranium metal and has no known commercial use, thus its production creates a significant storage problem. The advantage of this invention is that the quality of calcium fluoride produced is sufficient to be used in the industrial manufacture of anhydrous hydrogen fluoride, steel mill flux or ceramic applications.

  1. Ion chromatography detection of fluoride in calcium carbonate.

    PubMed

    Lefler, Jamie E; Ivey, Michelle M

    2011-09-01

    Fluoride in aquatic systems is increasing due to anthropogenic pollution, but little is known about how this fluoride affects organisms that live in and around aquatic habitats. Fluoride can bioaccumulate in structures comprised of calcium carbonate, such as shells and skeletons of both freshwater and saltwater species as diverse as snails, corals, and coccolithophorid algae. In this article, ion chromatography (IC) techniques are developed to detect and quantify fluoride in a matrix of calcium carbonate. Solid samples are dissolved in hydrochloric acid, pretreated to remove the majority of the chloride ions, and then analyzed using IC. With these methods, the 3σ limit of detection is 0.2 mg of fluoride/kg of calcium carbonate. PMID:21859530

  2. A method for determining thermophysical properties of organic material in aqueous solutions: Succinic acid

    NASA Astrophysics Data System (ADS)

    Riipinen, I.; Svenningsson, B.; Bilde, M.; Gaman, A.; Lehtinen, K. E. J.; Kulmala, M.

    2006-12-01

    A method for determining evaporation rates and thermodynamic properties of aqueous solution droplets is introduced. The method combines evaporation rate measurements using modified TDMA technique with data evaluation using an accurate evaporation model. The first set of data has been collected and evaluated for succinic acid aqueous solution droplets. Evaporation rates of succinic acid solution droplets have been measured using a TDMA system at controlled relative humidity (65%) and temperature (298 K). A temperature-dependent expression for the saturation vapour pressure of pure liquid phase succinic acid at atmospheric temperatures has been derived by analysing the evaporation rate data with a numerical model. The obtained saturation vapour pressure of liquid phase succinic acid is ln( p) = 118.41 - 16204.8/ T - 12.452ln( T). The vapour pressure is in unit of Pascal and the temperature in Kelvin. A linear expression for the enthalpy of vaporization for liquid state succinic acid is also presented. According to the results presented in the following, a literature expression for the vapour pressure of liquid phase succinic acid defined for temperatures higher than 461 K [Yaws, C.L., 2003. Yaws' Handbook of Thermodynamic and Physical Properties of Chemical Compounds, Knovel] can be extrapolated to atmospheric temperatures with very good accuracy. The results also suggest that at 298 K the mass accommodation coefficient of succinic acid is unity or very close to unity.

  3. Solid electrolytes for fluoride ion batteries: ionic conductivity in polycrystalline tysonite-type fluorides.

    PubMed

    Rongeat, Carine; Reddy, M Anji; Witter, Raiker; Fichtner, Maximilian

    2014-02-12

    Batteries based on a fluoride shuttle (fluoride ion battery, FIB) can theoretically provide high energy densities and can thus be considered as an interesting alternative to Li-ion batteries. Large improvements are still needed regarding their actual performance, in particular for the ionic conductivity of the solid electrolyte. At the current state of the art, two types of fluoride families can be considered for electrolyte applications: alkaline-earth fluorides having a fluorite-type structure and rare-earth fluorides having a tysonite-type structure. As regard to the latter, high ionic conductivities have been reported for doped LaF3 single crystals. However, polycrystalline materials would be easier to implement in a FIB due to practical reasons in the cell manufacturing. Hence, we have analyzed in detail the ionic conductivity of La(1-y)Ba(y)F(3-y) (0 ≤ y ≤ 0.15) solid solutions prepared by ball milling. The combination of DC and AC conductivity analyses provides a better understanding of the conduction mechanism in tysonite-type fluorides with a blocking effect of the grain boundaries. Heat treatment of the electrolyte material was performed and leads to an improvement of the ionic conductivity. This confirms the detrimental effect of grain boundaries and opens new route for the development of solid electrolytes for FIB with high ionic conductivities. PMID:24444763

  4. Fluoride release from fissure sealants.

    PubMed

    Garcia-Godoy, F; Abarzua, I; De Goes, M F; Chan, D C

    1997-01-01

    This 30-day study, compared the amounts and patterns of fluoride release from 5 commercially available fluoride-containing pit and fissure sealants: FluroShield, Helioseal-F, Ultraseal XT, Baritone L3, and Teethmate-F; Delton without fluoride, was used as control. Disc-shaped samples of each sealant were immersed in distilled water and the fluoride release was measured periodically until day 30. All the fluoridated sealants tested released measurable fluoride throughout the test period in a similar pattern: the greatest amount of fluoride was released in the first 24 hours after mixing, fell sharply on the second day and decreased slowly for the last days. On day one, Baritone L3 released significantly more fluoride than all other materials. Teethmate-F released the highest amount of fluoride during all the other time intervals from day 2, until day 30. PMID:9643204

  5. Gamma-irradiation of malic acid in aqueous solutions. [prebiotic significance

    NASA Technical Reports Server (NTRS)

    Negron-Mendoza, A.; Graff, R. L.; Ponnamperuma, C.

    1980-01-01

    The gamma-irradiation of malic acid in aqueous solutions was studied under initially oxygenated and oxygen-free conditions in an attempt to determine the possible interconversion of malic acid into other carboxylic acids, specifically those associated with Krebs cycle. The effect of dose on product formation of the system was investigated. Gas-liquid chromatography combined with mass spectrometry was used as the principal means of identification of the nonvolatile products. Thin layer chromatography and direct probe mass spectroscopy were also employed. The findings show that a variety of carboxylic acids are formed, with malonic and succinic acids in greatest abundance. These products have all been identified as being formed in the gamma-irradiation of acetic acid, suggesting a common intermediary. Since these molecules fit into a metabolic cycle, it is strongly suggestive that prebiotic pathways provided the basis for biological systems.

  6. Formation of amino acids by cobalt-60 irradiation of hydrogen cyanide solutions

    NASA Technical Reports Server (NTRS)

    Sweeney, M. A.; Toste, A. P.; Ponnamperuma, C.

    1976-01-01

    Experiments were conducted to study the pathway for the prebiotic origin of amino acids from hydrogen cyanide (HCN) under the action of ionizing radiation considered as an effective source of energy on the primitive earth. The irradiations were performed in a cobalt-60 source with a dose rate of 200,000 rad/hr. Seven naturally occurring amino acids are identified among the products formed by the hydrolysis of gamma-irradiated solutions of HCN: glycine, alanine, valine, serine, threonine, aspartic acid, and glutamic acid. The identity of these amino acids is established by gas chromatography and mass spectrometry. Control experiments provided evidence that the amino acids are not the result of contamination.

  7. Supercritical fluid extraction of uranium and thorium from nitric acid solutions with organophosphorus reagents

    SciTech Connect

    Lin, Y.; Wai, C.M.; Smart, N.G. |

    1995-10-01

    Extraction techniques for the recovery of uranium and transuranic elements from acid waste solutions are important in nuclear waste management. This paper examines the feasibility of extracting uranyl and thorium ions from nitric acid solutions with supercritical CO{sub 2} containing the different organophosphorus reagents. In this study, an organophosphorus reagent is dissolved in supercritical CO{sub 2} by passing the fluid through a reagent vessel placed upstream of the sample vessel in the extractor. Using TBPO or TOPO in supercritical CO{sub 2}, effective extraction of uranyl and thorium ions can be achieved even in dilute HNO{sub 3} solutions, thus yielding the possibility of reducing acidic waste volumes in nuclear waste treatment. The results may form the basis of a novel extraction process for the treatment of acidified nuclear wastes, while minimizing the production of secondary wastes. 12 refs., 2 figs., 2 tabs.

  8. Fluoride geochemistry of thermal waters in Yellowstone National Park: I. Aqueous fluoride speciation

    NASA Astrophysics Data System (ADS)

    Deng, Yamin; Nordstrom, D. Kirk; Blaine McCleskey, R.

    2011-08-01

    Thermal water samples from Yellowstone National Park (YNP) have a wide range of pH (1-10), temperature, and high concentrations of fluoride (up to 50 mg/l). High fluoride concentrations are found in waters with field pH higher than 6 (except those in Crater Hills) and temperatures higher than 50 °C based on data from more than 750 water samples covering most thermal areas in YNP from 1975 to 2008. In this study, more than 140 water samples from YNP collected in 2006-2009 were analyzed for free-fluoride activity by ion-selective electrode (ISE) method as an independent check on the reliability of fluoride speciation calculations. The free to total fluoride concentration ratio ranged from <1% at low pH values to >99% at high pH. The wide range in fluoride activity can be explained by strong complexing with H + and Al 3+ under acidic conditions and lack of complexing under basic conditions. Differences between the free-fluoride activities calculated with the WATEQ4F code and those measured by ISE were within 0.3-30% for more than 90% of samples at or above 10 -6 molar, providing corroboration for chemical speciation models for a wide range of pH and chemistry of YNP thermal waters. Calculated speciation results show that free fluoride, F -, and major complexes ( HF(aq)0, AlF 2+, AlF2+ and AlF30) account for more than 95% of total fluoride. Occasionally, some complex species like AlF4-, FeF 2+, FeF2+, MgF + and BF(OH)2- may comprise 1-10% when the concentrations of the appropriate components are high. According to the simulation results by PHREEQC and calculated results, the ratio of main fluoride species to total fluoride varies as a function of pH and the concentrations and ratios of F and Al.

  9. Fluoride geochemistry of thermal waters in Yellowstone National Park: I. Aqueous fluoride speciation

    USGS Publications Warehouse

    Deng, Y.; Nordstrom, D.K.; Blaine, McCleskey R.

    2011-01-01

    Thermal water samples from Yellowstone National Park (YNP) have a wide range of pH (1-10), temperature, and high concentrations of fluoride (up to 50mg/l). High fluoride concentrations are found in waters with field pH higher than 6 (except those in Crater Hills) and temperatures higher than 50??C based on data from more than 750 water samples covering most thermal areas in YNP from 1975 to 2008. In this study, more than 140 water samples from YNP collected in 2006-2009 were analyzed for free-fluoride activity by ion-selective electrode (ISE) method as an independent check on the reliability of fluoride speciation calculations. The free to total fluoride concentration ratio ranged from <1% at low pH values to >99% at high pH. The wide range in fluoride activity can be explained by strong complexing with H+ and Al3+ under acidic conditions and lack of complexing under basic conditions. Differences between the free-fluoride activities calculated with the WATEQ4F code and those measured by ISE were within 0.3-30% for more than 90% of samples at or above 10-6 molar, providing corroboration for chemical speciation models for a wide range of pH and chemistry of YNP thermal waters. Calculated speciation results show that free fluoride, F-, and major complexes (HF(aq)0, AlF2+, AlF2+ and AlF30) account for more than 95% of total fluoride. Occasionally, some complex species like AlF4-, FeF2+, FeF2+, MgF+ and BF2(OH)2- may comprise 1-10% when the concentrations of the appropriate components are high. According to the simulation results by PHREEQC and calculated results, the ratio of main fluoride species to total fluoride varies as a function of pH and the concentrations and ratios of F and Al. ?? 2011.

  10. Standard enthalpies of formation of α-aminobutyric acid and products of its dissociation in an aqueous solution

    NASA Astrophysics Data System (ADS)

    Lytkin, A. I.; Chernikov, V. V.; Krutova, O. N.

    2016-08-01

    Heats of solution of crystalline α-aminobutyric acid in water and in aqueous solutions of potassium hydroxide at 298.15 K are measured by means of direct calorimetry. Standard enthalpies of formation of the amino acid and products of its dissociation in an aqueous solution are calculated.

  11. Radiation-induced degradation of cyclohexanebutyric acid in aqueous solutions by gamma ray irradiation

    NASA Astrophysics Data System (ADS)

    Jia, Wenbao; He, Yanquan; Ling, Yongsheng; Hei, Daqian; Shan, Qing; Zhang, Yan; Li, Jiatong

    2015-04-01

    The radiation-induced degradation of cyclohexanebutyric acid under gamma ray irradiation was investigated. Degradation experiments were performed with 100 mL sealed Pyrex glass vessels loaded with 80 mL of cyclohexanebutyric acid solutions at various initial concentrations of 10, 20, and 40 mg L-1. The absorbed doses were controlled at 0, 0.65, 1.95, 3.25, 6.5, 9.75, and 13 kGy. The results showed that gamma ray irradiation could effectively degrade cyclohexanebutyric acid in aqueous solutions. The removal rate of cyclohexanebutyric acid increased significantly with the increase of absorbed dose and the decrease of its initial concentration. At the same time, the removal of chemical oxygen demand (COD) was as effective as that of cyclohexanebutyric acid. The kinetic studies showed that the degradation of cyclohexanebutyric acid followed pseudo first-order reaction. Above all, the proposed mechanism obtained when NaNO2, NaNO3 and tert-butanol were added showed that the •OH radical played a major role in the gamma degradation process of cyclohexanebutyric acid, while •H and eaq- played a minor role in the gamma degradation process. The degradation products were identified by Fourier transform infrared spectroscopy (FTIR) and gas chromatography/mass spectrometry (GC/MS) during cyclohexanebutyric acid degradation.

  12. Phase equilibria in a system of aqueous arginine with an octane solution of sulfonic acid

    NASA Astrophysics Data System (ADS)

    Kuvaeva, Z. I.; Koval'chuk, I. V.; Vodop'yanova, L. A.; Soldatov, V. S.

    2013-05-01

    The extraction of arginine (Arg) from aqueous salt (0.1 M NaCl) solutions with a sulfo extractant in a wide range of pH values and amino acid concentrations was studied. The 0.1 M solution of dinonylnaphthalenesulfonic acid (HD) in octane was used as an extractant. The degree of extraction was found to be high at pH 0.8-9.0. This can be explained by the effect of additional intermolecular interactions in the extractant phase involving the guanidine group of Arg.

  13. Distribution of zirconium in petroleum sulfoxides during extraction and sorption from nitric and hydrochloric acid solutions

    SciTech Connect

    Turanov, A.N.

    1988-11-20

    Petroleum sulfoxides (PSO) are effective extractants for several metals. We discussed the distribution of petroleum sulfoxides and zirconium between aqueous solutions of hydrochloric and nitric acid and organic solvents, and also the macroporous sorbent impregnated with PSO. For the investigation we used a macroposous copolymer of styrene with divinylbenzene. Our investigation showed a noticeable decrease in the contamination of the raffinates by petroleum sulfoxides and their more complete utilization as extractant of metals from solutions of acids when PSO is deposited on a macroporous copolymer of styrene with divinylbenzene.

  14. Distribution of trace impurities of metals during their adsorption from solutions of phosphoric acid

    SciTech Connect

    Toranov, A.N.; Evseeva, N.K.; Kremenskaya, I.N.

    1986-09-01

    The phase distribution of trace impurities of metals between solutions of phosphoric acid and a polymer adsorbent based on a copolymer of styrene with divinylbenzene, impregnated with di-2-ethylhexyldithiophosphoric acid, was investigated. The influence of the composition of the aqueous and solid phases on the distribution coefficients of trace impurities of metals is discussed. It was shown that the coefficients of interfacial distribution in the case of adsorption by an impregnated adsorbent is higher than in the case of liquid extraction.

  15. Enhancement of metastable zone width for solution growth of potassium acid phthalate

    NASA Astrophysics Data System (ADS)

    Srinivasan, K.; Meera, K.; Ramasamy, P.

    1999-09-01

    A new method has been developed in which the addition of a small amount of ethylenediamine tetra acetic acid (EDTA), a well-known chelating agent, enhances the metastable zone width significantly. Also, it has been found that this addition reduces the rate of nucleation and increases the growth rate of the crystal. This method has been employed for solution growth of potassium hydrogen phthalate (KC 8H 5O 4), which is also known as potassium acid phthalate (KAP).

  16. Stability of antimicrobial activity of peracetic acid solutions used in the final disinfection process.

    PubMed

    Costa, Solange Alves da Silva; Paula, Olívia Ferreira Pereira de; Silva, Célia Regina Gonçalves E; Leão, Mariella Vieira Pereira; Santos, Silvana Soléo Ferreira dos

    2015-01-01

    The instruments and materials used in health establishments are frequently exposed to microorganism contamination, and chemical products are used before sterilization to reduce occupational infection. We evaluated the antimicrobial effectiveness, physical stability, and corrosiveness of two commercial formulations of peracetic acid on experimentally contaminated specimens. Stainless steel specimens were contaminated with Staphylococcus aureus, Escherichia coli, Candida albicans, blood, and saliva and then immersed in a ready peracetic acid solution: 2% Sekusept Aktiv (SA) or 0.25% Proxitane Alpha (PA), for different times. Then, washes of these instruments were plated in culture medium and colony-forming units counted. This procedure was repeated six times per day over 24 non-consecutive days. The corrosion capacity was assessed with the mass loss test, and the concentration of peracetic acid and pH of the solutions were measured with indicator tapes. Both SA and PA significantly eliminated microorganisms; however, the SA solution was stable for only 4 days, whereas PA remained stable throughout the experiment. The concentration of peracetic acid in the SA solutions decreased over time until the chemical was undetectable, although the pH remained at 5. The PA solution had a concentration of 500-400 mg/L and a pH of 2-3. Neither formulation induced corrosion and both reduced the number of microorganisms (p = 0.0001). However, the differences observed in the performance of each product highlight the necessity of establishing a protocol for optimizing the use of each one. PMID:25715037

  17. Sequence of morphological transitions in two-dimensional pattern growth from aqueous ascorbic Acid solutions.

    PubMed

    Paranjpe, A S

    2002-08-12

    A sequence of morphological transitions in two-dimensional dehydration patterns of aqueous solutions of ascorbic acid is observed with humidity as a control parameter. Change in morphology occurs due to humidity induced variation in the concentration of the metastable supersaturated solution phase formed after initial solvent evaporation. As percent humidity is varied from 40 to 80, patterns change from compact circular --> radial --> density modulated radial (a new morphology) --> density modulated circular --> density modulated dendritic (a new morphology) --> dense branching. PMID:12190528

  18. Electrochemical formation of hydroxide for enhancing carbon dioxide and acid gas uptake by a solution

    DOEpatents

    Rau, Gregory Hudson

    2012-05-15

    A system is described for forming metal hydroxide from a metal carbonate utilizing a water electrolysis cell having an acid-producing anode and a hydroxyl-producing cathode immersed in a water solution of sufficient ionic content to allow an electric current to pass between the hydroxyl-producing cathode and the acid-producing anode. A metal carbonate, in particular water-insoluble calcium carbonate or magnesium carbonate, is placed in close proximity to the acid-producing anode. A direct current electrical voltage is provided across the acid-producing anode and the hydroxyl-producing cathode sufficient to generate acid at the acid-producing anode and hydroxyl ions at the hydroxyl-producing cathode. The acid dissolves at least part of the metal carbonate into metal and carbonate ions allowing the metal ions to travel toward the hydroxyl-producing cathode and to combine with the hydroxyl ions to form the metal hydroxide. The carbonate ions travel toward the acid-producing anode and form carbonic acid and/or water and carbon dioxide. Among other uses, the metal hydroxide formed can be employed to absorb acid gases such as carbon dioxide from a gas mixture. The invention can also generate hydrogen and oxidative gases such as oxygen or chlorine.

  19. New crystallization of fatty acids from aqueous ethanol solution combined with liquid-liquid extraction

    SciTech Connect

    Maeda, Kouji; Nomura, Yoshihisa; Tai, Kimihiko; Ueno, Yoshitaka; Fukui, Keisuke; Hirota, Syouji

    1999-06-01

    A new separation process of saturated fatty acids (lauric acid-myristic acid) using crystallization from an aqueous ethanol solution has been examined. There were two vessels in this separation process: an extraction vessel and a crystallization vessel. The fatty acids in the aqueous phase were first extracted from their organic phase (melt) in the extraction vessel. The fatty acids in the aqueous phase were continuously introduced to the crystallization vessel, and then the fatty acids were crystallized there. The crystals of the fatty acids were collected continuously above the aqueous phase in the crystallization vessel. In this process, the yield and the purity of the crystals over time were measured, and it was found that the purity of lauric acid increased unsteadily up to 0.98 mole fraction of lauric acid with an increase in the yield of the low yield range. The mole fraction of ethanol in the aqueous phase could be significant to control the relationship between the yield and the purity of the crystals. Three different mole fractions of lauric acid in the organic phase were used to be separated in this process. Moreover, the authors have considered the effective separations of this process, and the maximum yield and purity of the crystals have been estimated by a simple mass balance.

  20. Emergency cooling experiments with aqueous boric acid solution in the REWET-II facility

    SciTech Connect

    Kervinen, T.; Tuunanen, J.

    1987-01-01

    Although boron is widely used as soluble neutron poison in nuclear reactors (boric acid in pressurized water reactors, sodium pentaborate in boiling water reactors), there is a lack of experimental data about aqueous boron solution behavior during loss-of-coolant accidents. The main aims of the REWET boric acid experiments were to study the behavior of aqueous boric acid solution during long-term cooling of a nuclear reactor and to find out the circumstances in which boric acid crystallization takes place. In the experiments, carried out in the facility of a 19-fuel-rod simulator bundle, boric acid crystallization caused the uncovering of the bundle, which always occurred on the water surface. However, crossflows and backflows in a reactor presumably make the concentrations uniform and thus retard crystallization. Therefore, experimental investigations of aqueous boric acid solution behavior will be carried out for the next 2 yr in a larger scale experimental facility. The new facility will be a simulator of the Loviisa VVER-440 reactor with a scaling factor of 1:349 for power and volumes and 1:1 for elevations. The facility will contain a full-scale rod bundle.

  1. Alkali Treatment of Acidic Solution from Hanford K Basin Sludge Dissolution

    SciTech Connect

    AA Bessonov; AB Yusov; AM Fedoseev; AV Gelis; AY Garnov; CH Delegard; GM Plavnik; LN Astafurova; MS Grigoriev; NA Budantseva; NN Krot; SI Nikitenko; TP Puraeva; VP Perminov; VP Shilov

    1998-12-22

    Nitric acid solutions will be created from the dissolution of Hanford K Basin sludge. These acidic dissolver solutions must be made alkaline by treatment with NaOH solution before they are disposed to ~ the Tank Waste Remediation System on the Hanford Site. During the alkali treatments, sodium diuranate, hydroxides of iron and aluminum, and radioelements (uranium, plutonium, and americium) will precipitate from the dissolver solution. Laboratory tests, discussed here, were pefiormed to provide information on these precipitates and their precipitation behavior that is important in designing the engineering flowsheet for the treatment process. Specifically, experiments were conducted to determine the optimum precipitation conditions; the completeness of uranium, plutonium, and americium precipitation; the rate of sedimentation; and the physico-chemical characteristics of the solids formed by alkali treatment of simulated acidic dissolver solutions. These experiments also determined the redistribution of uranium, plutonium, and americium flom the sodium di~ate and iron and al&inurn hydroxide precipitates upon contact with carbonate- and EDTA-bearing simulated waste solutions. Note: EDTA is the tetrasodium salt of ethylenediaminetetraacetate.

  2. Laboratory evaluation of limestone and lime neutralization of acidic uranium mill tailings solution. Progress report

    SciTech Connect

    Opitz, B.E.; Dodson, M.E.; Serne, R.J.

    1984-02-01

    Experiments were conducted to evaluate a two-step neutralization scheme for treatment of acidic uranium mill tailings solutions. Tailings solutions from the Lucky Mc Mill and Exxon Highland Mill, both in Wyoming, were neutralized with limestone, CaCO/sub 3/, to an intermediate pH of 4.0 or 5.0, followed by lime, Ca(OH)/sub 2/, neutralization to pH 7.3. The combination limestone/lime treatment methods, CaCO/sub 3/ neutralization to pH 4 followed by neutralization with Ca(OH)/sub 2/ to pH 7.3 resulted in the highest quality effluent solution with respect to EPA's water quality guidelines. The combination method is the most cost-effective treatment procedure tested in our studies. Neutralization experiments to evaluate the optimum solution pH for contaminant removal were performed on the same two tailings solutions using only lime Ca(OH)/sub 2/ as the neutralizing agent. The data indicate solution neutralization above pH 7.3 does not significantly increase removal of pH dependent contaminants from solution. Column leaching experiments were performed on the neutralized sludge material (the precipitated solid material which forms as the acidic tailings solutions are neutralized to pH 4 or above). The sludges were contacted with laboratory prepared synthetic ground water until several effluent pore volumes were collected. Effluent solutions were analyzed for macro ions, trace metals and radionuclides in an effort to evaluate the long term effectiveness of attenuating contaminants in sludges formed during solution neutralization. Neutralized sludge leaching experiments indicate that Ca, Na, Mg, Se, Cl, and SO/sub 4/ are the only constituents which show solution concentrations significantly higher than the synthetic ground water in the early pore volumes of long-term leaching studies.

  3. Experimental Shock Chemistry of Aqueous Amino Acid Solutions and the Cometary Delivery of Prebiotic Compounds

    NASA Astrophysics Data System (ADS)

    Blank, Jennifer G.; Miller, Gregory H.; Ahrens, Michael J.; Winans, Randall E.

    2001-02-01

    A series of shock experiments were conducted to assess the feasibility of the delivery of organic compounds to the Earth via cometary impacts. Aqueous solutions containing near-saturation levels of amino acids (lysine, norvaline, aminobutyric acid, proline, and phenylalanine) were sealed inside stainless steel capsules and shocked by ballistic impact with a steel projectile plate accelerated along a 12-m-long gun barrel to velocities of 0.5-1.9 km sec^-1. Pressure-temperature-time histories of the shocked fluids were calculated using 1D hydrodynamical simulations. Maximum conditions experienced by the solutions lasted 0.85-2.7 μs and ranged from 5.1-21 GPa and 412-870 K. Recovered sample capsules were milled open and liquid was extracted. Samples were analyzed using high performance liquid chromatography (HPLC) and mass spectrometry (MS). In all experiments, a large fraction of the amino acids survived. We observed differences in kinetic behavior and the degree of survivability among the amino acids. Aminobutyric acid appeared to be the least reactive, and phenylalanine appeared to be the most reactive of the amino acids. The impact process resulted in the formation of peptide bonds; new compounds included amino acid dimers and cyclic diketopiperazines. In our experiments, and in certain naturally occurring impacts, pressure has a greater influence than temperature in determining reaction pathways. Our results support the hypothesis that significant concentrations of organic material could survive a natural impact process.

  4. Experimental shock chemistry of aqueous amino acid solutions and the cometary delivery of prebiotic compounds.

    PubMed

    Blank, J G; Miller, G H; Ahrens, M J; Winans, R E

    2001-01-01

    A series of shock experiments were conducted to assess the feasibility of the delivery of organic compounds to the Earth via cometary impacts. Aqueous solutions containing near-saturation levels of amino acids (lysine, norvaline, aminobutyric acid, proline, and phenylalanine) were sealed inside stainless steel capsules and shocked by ballistic impact with a steel projectile plate accelerated along a 12-m-long gun barrel to velocities of 0.5-1.9 km sec-1. Pressure-temperature-time histories of the shocked fluids were calculated using 1D hydrodynamical simulations. Maximum conditions experienced by the solutions lasted 0.85-2.7 microseconds and ranged from 5.1-21 GPa and 412-870 K. Recovered sample capsules were milled open and liquid was extracted. Samples were analyzed using high performance liquid chromatography (HPLC) and mass spectrometry (MS). In all experiments, a large fraction of the amino acids survived. We observed differences in kinetic behavior and the degree of survivability among the amino acids. Aminobutyric acid appeared to be the least reactive, and phenylalanine appeared to be the most reactive of the amino acids. The impact process resulted in the formation of peptide bonds; new compounds included amino acid dimers and cyclic diketopiperazines. In our experiments, and in certain naturally occurring impacts, pressure has a greater influence than temperature in determining reaction pathways. Our results support the hypothesis that significant concentrations of organic material could survive a natural impact process. PMID:11296518

  5. Length Scale Dependence of the Dynamic Properties of Hyaluronic Acid Solutions in the Presence of Salt

    SciTech Connect

    Horkay, Ferenc; Falus, Peter; Hecht, Anne-Marie; Geissler, Erik

    2010-12-07

    In solutions of the charged semirigid biopolymer hyaluronic acid in salt-free conditions, the diffusion coefficient D{sub NSE} measured at high transfer momentum q by neutron spin echo is more than an order of magnitude smaller than that determined by dynamic light scattering, D{sub DLS}. This behavior contrasts with neutral polymer solutions. With increasing salt content, D{sub DLS} approaches D{sub NSE}, which is independent of ionic strength. Contrary to theoretical expectation, the ion-polymer coupling, which dominates the low q dynamics of polyelectrolyte solutions, already breaks down at distance scales greater than the Debye-Hueckel length.

  6. REDUCTION OF PLUTONIUM VALUES IN AN ACIDIC AQUEOUS SOLUTION WITH FORMALDEHYDE

    DOEpatents

    Olson, C.M.

    1959-06-01

    A method is given for reducing Pu to the tetravalent state and lowering the high acidity of dissolver solutions containing U and Pu. Formaldehyde is added to the HNO/sub 3/ solution of U and Pu to effect a formaldehyde to HNO/sub 3/ molar ratio of 0.375:1 to 1.5:1. The Pu can then be removed from the solution by carrier precipitation using BiPO/sub 4/ or by ion exchange. (T.R.H.)

  7. Private Well Water and Fluoride

    MedlinePlus

    ... from my well has less than the recommended level of fluoride for preventing tooth decay? The recommended ... if the water from my well has fluoride levels that are higher than the recommended level for ...

  8. Citric Acid-Modified Fenton's Reaction for the Oxidation of Chlorinated Ethylenes in Soil Solution Systems

    SciTech Connect

    Seol, Yongkoo; Javandel, Iraj

    2008-03-15

    Fenton's reagent, a solution of hydrogen peroxide and ferrous iron catalyst, is used for an in-situ chemical oxidation of organic contaminants. Sulfuric acid is commonly used to create an acidic condition needed for catalytic oxidation. Fenton's reaction often involves pressure buildup and precipitation of reaction products, which can cause safety hazards and diminish efficiency. We selected citric acid, a food-grade substance, as an acidifying agent to evaluate its efficiencies for organic contaminant removal in Fenton's reaction, and examined the impacts of using citric acid on the unwanted reaction products. A series of batch and column experiments were performed with varying H{sub 2}O{sub 2} concentrations to decompose selected chlorinated ethylenes. Either dissolved iron from soil or iron sulfate salt was added to provide the iron catalyst in the batch tests. Batch experiments revealed that both citric and sulfuric acid systems achieved over 90% contaminant removal rates, and the presence of iron catalyst was essential for effective decontamination. Batch tests with citric acid showed no signs of pressure accumulation and solid precipitations, however the results suggested that an excessive usage of H{sub 2}O{sub 2} relative to iron catalysts (Fe{sup 2+}/H{sub 2}O{sub 2} < 1/330) would result in lowering the efficiency of contaminant removal by iron chelations in the citric acid system. Column tests confirmed that citric acid could provide suitable acidic conditions to achieve higher than 55% contaminant removal rates.

  9. Removal of ash from Indian Assam coking coal using sodium hydroxide and acid solutions

    SciTech Connect

    Kumar, M.; Shankar, R.H.

    2000-03-01

    Mineral matter (ash) removal from Assam coking coal by leaching with different concentrations of sodium hydroxide and acid (HCl, H{sub 2}SO{sub 4}, HNO{sub 3}, and HF) solutions has been investigated at a temperature of 75 C. The parameters tested were concentration of NaOH, type of acid, concentration of acids, and number of acid leaching steps. Total ash removed increased with increase of NaOH and acid concentrations up to the range studied. For the same experimental conditions, treatment of caustic leached coal in HCl acid resulted in better demineralization than in H{sub 2}SO{sub 4} or HNO{sub 3} acid. In the NaOH-HNO{sub 3} leaching method, a higher concentration (>20%) of HNO{sub 3} acid had an adverse effect on the de-ashing of coal. The NaOH-HF leaching process has been found to be the most effective method of coal de-ashing. The two acid treatment steps (HCl-H{sub 2}SO{sub 4}/HCl-HNO{sub 3}) after caustic leaching are the next most effective methods of coal de-ashing. The removal of mineral matter (including S) from coal is expected to decrease the graphite reactivity and thus the atmospheric pollution (due to the generation of smaller quantities of CO and SO{sub 2} gases).

  10. Electrochemical formation of hydroxide for enhancing carbon dioxide and acid gas uptake by a solution

    DOEpatents

    Rau, Gregory Hudson

    2014-07-01

    A system for forming metal hydroxide from a metal carbonate utilizes a water electrolysis cell having an acid-producing anode and a hydroxyl-producing cathode immersed in a water solution of sufficient ionic content to allow an electric current to pass between the hydroxyl-producing cathode and the acid-producing anode. A metal carbonate is placed in close proximity to the acid-producing anode. A direct current electrical voltage is provided across the acid-producing anode and the hydroxyl-producing cathode sufficient to generate acid at the acid-producing anode and hydroxyl ions at the hydroxyl-producing cathode. The acid dissolves at least part of the metal carbonate into metal and carbonate ions allowing the metal ions to travel toward the hydroxyl-producing cathode and to combine with the hydroxyl ions to form the metal hydroxide. The carbonate ions travel toward the acid-producing anode and form carbonic acid and/or water and carbon dioxide.

  11. [Diffuse x-ray wide-angle scattering of polyglutamic acid in solution].

    PubMed

    Fedorov, B A; Becker, M; Damaschun, G; Damaschun, H; Gedicke, C; Zirwer, D

    1977-01-01

    The diffuse wide angle x-ray scattering (WAXS) of polyglutamic acid (PGA) in solution was studied using an x-ray diffractometer with small aperture of the primary beam. The scattering curve was recorded at an angular interval from (article: see text). The experimental scattering intensity of PGA with alpha-helical CD spectrum showed a maximum at 14.4 nm-1. Unordered PGA in solution yielded no maximum at this scattering angle. The studies have proved that the scattering theory can be applied to globular proteins in solution as well as to chain molecules in solution in this angular interval. The differences between the calculated scattering curves and the experimental curves indicate minor movements of the side chains of PGA in solutions and slight structuring of the solvent at the surface of the polypeptide chain. PMID:25547

  12. The synthesis and structural characterization of novel transition metal fluorides

    SciTech Connect

    Casteel, W.J. Jr.

    1992-09-01

    High purity KMF[sub 6] and K[sub 2]MF[sub 6] salts (M = Mo,Re, Ru, Os, Ir, Pt) are obtained from reduction hexafluorides. A rhombohedral unit cell is observed for KReF[sub 6]. Fluoride ion capture by Lewis acids from the hexafluorometallate (IV) salts affords high purity tetrafluorides for M = Mo, Re, Ru, Os, and Pd. The structure of RuF[sub 4] is determined from X-ray synchrotron and neutron powder data. Unit cells based on theorthorhombic PdF[sub 4] type cell are derived from X-ray powder data for ReF[sub 4] and OsF[sub 4]. Fluoride ion capture from KAgF[sub 4] provides the thermally unstable trifluoride as a bright, red, diamagnetic solid. The structure solution of AgF[sub 3] and redetermination of the AuF[sub 3] structure from X-ray synchrotron and neutron powder data demonstrate that the two are isostnictural. Thermal decomposition product of AgF[sub 3] is the mixed valence compound Ag[sup II]Ag[sub 2][sup III]F[sub 8]. Several new salts containing the (Ag - F)[sub n][sup n+] chain cation are prepared. The first linear (Ag - F)[sub n][sup n+] chain is observed in AgF[sup +]BF[sub 4 [sup [minus

  13. IMPROVEMENT UPON THE CARRIER PRECIPITATION OF PLUTONIUM IONS FROM NITRIC ACID SOLUTIONS

    DOEpatents

    James, R.A.; Thompson, S.G.

    1958-12-23

    A process is reported for improving the removal of plutonlum by carrier precipitation by the addition of nitrite ions to a nitrlc acid solutlon of neutronirradiated unanium so as to destroy any hydrazine that may be present in the solution since the hydrazine tends to complex the tetravalent plutonium and prevents removal by the carrier precipltate, such as bismuth phospbate.

  14. Modification of vital wheat gluten with phosphoric acid to produce high free-solution capacity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wheat gluten reacts with phosphoric acid to produce natural superabsorbent gels. The gel properties are defined by Fourier Transform Infra-red (FTIR) spectroscopy, 2-dimensional gel electrophoresis (2DE), and uptake of water, salt solutions, and aqueous ethanol. Temperatures above 120'C and dry cond...

  15. 49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 2 2013-10-01 2013-10-01 false Hydrogen cyanide, anhydrous, stabilized... Hazardous Materials Other Than Class 1 and Class 7 § 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed...

  16. 49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Hydrogen cyanide, anhydrous, stabilized... Hazardous Materials Other Than Class 1 and Class 7 § 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed...

  17. 49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 2 2011-10-01 2011-10-01 false Hydrogen cyanide, anhydrous, stabilized... Hazardous Materials Other Than Class 1 and Class 7 § 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed...

  18. 49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 2 2014-10-01 2014-10-01 false Hydrogen cyanide, anhydrous, stabilized... Hazardous Materials Other Than Class 1 and Class 7 § 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed...

  19. [Effects of UV Radiation on the Physicochemical Properties and Coagulation Properties of Humic Acid Solution].

    PubMed

    Wang, Wen-dong; Zhang, Ke; Fan, Qing-hai; Zheng, Dan

    2016-03-15

    To investigate the mechanism of UV light in promoting the removal of humic acid ( HA) by coagulation, the variations of the physical and chemical properties of the HA solution before and after UV light radiation were investigated. The effects of the changes in water quality conditions on the removal performance of HA in coagulation were also observed. Experimental results showed that except zeta potential, pH, chromaticity and viscosity of the HA solution exhibited varying degrees of decline after UV radiation. Further study showed that the impact of changes in viscosity of the solution on humic acid coagulation performance was relatively small. Under acidic conditions, the coagulation performance of HA significantly increased. The increase of zeta potential led to easy gathering of colloidal particles and improved the coagulation performance. Furthermore, except for HA with relative molecular mass of between (10-30) x 10³ and less than 10³, there was little variation in the proportion of low molecular weight HA, which may be an important reason that the coagulation performance of the humic acid solution increased after UV radiation. PMID:27337892

  20. Long-term stability of earthen materials in contact with acidic tailings solutions

    SciTech Connect

    Peterson, S.R.; Erikson, R.L.; Gee, G.W.

    1982-11-01

    The objectives of the studies documented in this report were to use experimental and geochemical computer modeling tools to assess the long-term environmental impact of leachate movement from acidic uranium mill tailings. Liner failure (i.e., an increase in the permeability of the liner material) was not found to be a problem when various acidic tailings solutions leached through liner materials for periods up to 3 years. On the contrary, materials that contained over 30% clay showed a decrease in permeability with time in the laboratory columns. The high clay materials tested appear suitable for lining tailings impoundment ponds. The decreases in permeability are attributed to pore plugging resulting from the precipitation of minerals and solids. This precipitation takes place due to the increase in pH of the tailings solution brought about by the buffering capacity of the soil. Geochemical modeling predicts, and x-ray characterization confirms, that precipitation of solids from solution is occurring in the acidic tailings solution/liner interactions studied. In conclusion the same mineralogical changes and contaminant reactions predicted by geochemical modeling and observed in laboratory studies were found at a drained evaporation pond (Lucky Mc in Wyoming) with a 4 year history of acid attack.

  1. Effect of acid solutions on plants studied by the optical beam deflection method.

    PubMed

    Nie, Liangjiao; Kuboda, Mitsutoshi; Inoue, Tomomi; Wu, Xingzheng

    2013-12-01

    The optical beam deflection method was applied to study the effects of acid solution on both a terrestial and aquatic plants Egeria and Cerastium, which are common aquatic plant and terrestial weed respectively. A probe beam from a He-Ne laser was passed through a vicinity of a leaf of the plants, which were put in culture dishes filled with acid solutions. Deflection signals of the probe beam were monitored and compared for acid solutions with different pH values. The results of Egria showed that the deflection signals changed dramatically when pH values of acid solutions were 2.0 and 3.0, while little at pH of 4.0 and 5.0. For Cerastium when pH were below 3.0, deflection signals changed greatly with time at the begining. After a certain period of time, deflection signals changed little with time. When pH value was above 4.0, deflection signals of Cerastium were still changing with time even after 20 hours. The results suggested that the damage threshold of pH was between 3.0 and 4.0 for both the land and aquatic plants. PMID:25078849

  2. PHYSICAL SOLUTIONS FOR ACID ROCK DRAINAGE AT REMOTE SITES DEMONSTRATION PROJECT

    EPA Science Inventory

    This report summarizes the results of Mine Waste Technology Program, Activity III, Project 42, Physical Solutions for Acid Rock Drainage at Remote Sites, funded by the U.S. Environmental Protection Agency (EPA) and jointly administered by EPA and the U.S. Department of Energy. A...

  3. 49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Hydrogen cyanide, anhydrous, stabilized... Hazardous Materials Other Than Class 1 and Class 7 § 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed...

  4. SOLVENT EXTRACTION PROCESS FOR SEPARATING URANIUM AND PLUTONIUM FROM AQUEOUS ACIDIC SOLUTIONS OF NEUTRON IRRADIATED URANIUM

    DOEpatents

    Bruce, F.R.

    1962-07-24

    A solvent extraction process was developed for separating actinide elements including plutonium and uranium from fission products. By this method the ion content of the acidic aqueous solution is adjusted so that it contains more equivalents of total metal ions than equivalents of nitrate ions. Under these conditions the extractability of fission products is greatly decreased. (AEC)

  5. Spray washing carcasses with alkaline solutions of lauric acid to reduce bacterial contamination

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The ability of lauric acid (LA)-potassium hydroxide (KOH) solutions to reduce carcass bacterial contamination was examined. Skin of carcasses was inoculated with a cecal paste containing antibiotic resistant strains of Escherichia coli, Salmonella Typhimirum, and Campylobacter coli. In one trial, in...

  6. Solution blow spun Poly(lactic acid)/Hydroxypropyl methylcellulose nanofibers with antimicrobial properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Poly(lactic acid) (PLA) nanofibers containing hydroxypropyl methylcellulose (HPMC) and tetracycline hydrochloride (THC) were solution blow spun from two different solvents, chloroform/acetone (CA, 80:20 v/v) and 2,2,2-triflouroethanol (TFE). The diameter distribution, chemical, thermal, thermal stab...

  7. MOLTEN FLUORIDE NUCLEAR REACTOR FUEL

    DOEpatents

    Barton, C.J.; Grimes, W.R.

    1960-01-01

    Molten-salt reactor fuel compositions consisting of mixtures of fluoride salts are reported. In its broadest form, the composition contains an alkali fluoride such as sodium fluoride, zirconium tetrafluoride, and a uranium fluoride, the latter being the tetrafluoride or trifluoride or a mixture of the two. An outstanding property of these fuel compositions is a high coeffieient of thermal expansion which provides a negative temperature coefficient of reactivity in reactors in which they are used.

  8. Ion flotation behaviour of thirty-one metal ions in mixed hydrochloric/nitric acid solutions.

    PubMed

    Hualing, D; Zhide, H

    1989-06-01

    The ion flotation of 31 metal ions in hydrochloric/nitric acid solution with the cationic surfactant cetylpyridinium chloride was investigated. A 25-ml portion of 0.27-2.87 x 10(-4)M metal ion and 1.8-6.0 x 10(-4)M cetylpyridinium chloride solution in 0.17-3.4M acid mixture ([HCl]:[HNO(3)] = 2.4:1) was subjected to flotation in a cell, 22.5 cm high and 4.0 cm in diameter, for 5 min, with nitrogen bubbles. Ir(IV), Pt(IV), Ge(IV), Sn(IV), Bi(III), Au(III), Tl(III), Pd(II) and Sn(II) were floated from solution in 95-100% yield; Ru(III), Rh(III), Ir(III), Hg(II), Ag(I) and Tl(I) were partly floated, while Cr(VI), Ti(IV), Zr(IV), Ga(III), In(III), Fe(III), Sb(III), Al(III), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), CD(II) and Pb(II) were floated with less than 20% yield. The flotation behaviour of these metal ions in the mixed acid system was compared with that in hydrochloric acid. The flotation is more efficient in the mixed acid system. PMID:18964771

  9. Origins of conductivity improvement in fluoride-enhanced silicon doping of ZnO films.

    PubMed

    Rashidi, Nazanin; Vai, Alex T; Kuznetsov, Vladimir L; Dilworth, Jonathan R; Edwards, Peter P

    2015-06-01

    Fluoride in spray pyrolysis precursor solutions for silicon-doped zinc oxide (SiZO) transparent conductor thin films significantly improves their electrical conductivity by enhancing silicon doping efficiency and not, as previously assumed, by fluoride doping. Containing only earth-abundant elements, SiZO thus prepared rivals the best solution-processed indium-doped ZnO in performance. PMID:25879727

  10. Corrosion behavior of niobium coated 304 stainless steel in acid solution

    NASA Astrophysics Data System (ADS)

    Pan, T. J.; Chen, Y.; Zhang, B.; Hu, J.; Li, C.

    2016-04-01

    The niobium coating is fabricated on the surface of AISI Type 304 stainless steel (304SS) by using a high energy micro arc alloying technique in order to improvecorrosion resistance of the steel against acidic environments. The electrochemical corrosion resistance of the niobium coating in 0.7 M sulfuric acid solutions is evaluated by electrochemical impedance spectroscopy, potentiodynamic polarization and the open circuit potential versus time. Electrochemical measurements indicate that the niobium coating increases the free corrosion potential of the substrate by 110 mV and a reduction in the corrosion rate by two orders of magnitude compared to the substrate alone. The niobium coating maintains large impedance and effectively offers good protection for the substrate during the long-term exposure tests, which is mainly ascribed to the niobium coating acting inhibiting permeation of corrosive species. Finally, the corresponding electrochemical impedance models are proposed to elucidate the corrosion resistance behavior of the niobium coating in acid solutions.

  11. An in vitro study of the effect of aluminum and the combined effect of strontium, aluminum, and fluoride elements on early enamel carious lesions.

    PubMed

    Koletsi-Kounari, Haroula; Mamai-Homata, Eleni; Diamanti, Iliana

    2012-06-01

    The purpose of this in vitro study was to evaluate the effect of aluminum and of combined strontium, aluminum, and fluoride treatments on enamel demineralization and remineralization. During a 6-day pH-cycling protocol, pre-softened bovine enamel slabs were immersed twice daily for 1 min in the following experimental solutions: (a) distilled water [W] (negative control); (b) 1,000 ppm F [F] (positive control); (c) 1,000 ppm Al [Al]; (d) 1,000 ppm Al,1,000 ppm F applied interchangeably [Al-F]; (e) 1,000 ppm Al, 1,000 ppm F, applied in sequential order [Al+F]; (f) combined 1,000 ppm Al and 150 ppm Sr [Al+Sr]; and (g) combined 150 ppm Sr and 1,000 ppm F [Sr+F]. Subsequently, the specimens were subjected to a 5-day acid resistance test. Lesions were evaluated quantitatively by performing surface microhardness and qualitatively by using polarized light microscopy. According to the results, solutions [Sr+F] and [Al-F] enhanced remineralization and inhibited demineralization as effectively as the [F] solution and significantly superiorly compared to [Al+Sr] and [Al] solutions. All tested solution groups, except for the [Al+Sr] group, presented significantly increased resistance to acidic attack, compared to [W]. PLM examination revealed that all solution groups, except for the [W] group, developed an acid-resistant zone at lesion surfaces. In conclusion, under the present experimental conditions, the combined strontium-fluoride and aluminum-fluoride treatments presented similar anti-caries efficacy compared to fluoride treatment alone, but they did not show evidence of synergistic activity on pre-softened enamel. PMID:22286865

  12. Effective Removal of Tetracycline from Aqueous Solution by Organic Acid-Coated Magnetic Nanoparticles.

    PubMed

    Guo, Liang; Liang, Yuyan; Chen, Xuelan; Xu, Wei; Wu, Kesheng; Wei, Hua; Xiong, Yonghua

    2016-03-01

    Self-assembled iron oxide nanocomposites are good magnetic nano-adsorbents that can be prepared using simple methods. Four types of organic acid-functionalised (oleic acid, undecenoic acid, caprylic acid or hexanoic acid) magnetic nanoparticles (MNPs) were synthesised through a one-pot chemisorption method for the removal of tetracycline (TC) from aqueous solution. The undecenoic acid-coated MNPs (UA-MNPs) exhibited the highest adsorption efficiency and can be easily retrieved with a low-gradient magnetic separator (0.4 Tesla) at pH 5.0 aqueous solution. The TC adsorption process on the UA-MNPs followed the Langmuir isotherm and the maximum adsorption capacities increased from 86.96 mg g(-1) to 222.2 mg g(-1) with the increase in temperature from 288 K to 318 K. The kinetics of adsorption fits pseudo-second-order model perfectly with a rate constant, 5.946 g mg(-1) min(-1) at 298 K. The positive values of the enthalpy (AH) and the negative value of the free energy (AG) indicated an endothermic and spontaneous adsorption process of TC on the UA-MNPs. Moreover, the UA-MNPs possessed excellent ability to adsorb the other three major types of TC antibiotics, including chlortetracycline, oxytetracycline and doxycycline. PMID:27455621

  13. Detergent-assisted self assembly of fatty acid layers on mica in solution

    NASA Astrophysics Data System (ADS)

    Hand, Sean; Yang, Jie

    1997-03-01

    Fatty acids are well known for their ability to form monolayers at air-water interfaces. The conventional method to coat a solid surface with mono or multi layers of fatty acids uses a Langmuir trough, via X- or Y- type coatings. The major advantage of the Langmuir trough is the ability to control the monolayer pressure. The limiting factors are, however, the restricted size of the substrate, the physical size of the Langmuir trough, and the coating procedure. To circumvent some of these drawbacks, we have developed a method to cover a solid mica substrate with fatty acids by detergent assisted self assembly in aqueous solutions. It has been found that a molecular layer of fatty acids, possibly complexed with some detergent, are self-assembled on the mica surface. Thickness measurements of these self-assembled layers suggest that the layer is composed of two monolayers of fatty acids in a bilayer arrangement. The presence of cations in the solution has some effect on the assembly of the molecular layer, and may alter the orientation of individual fatty acids in the layer. Structural characteristics of such self assembled molecular layers are studied with atomic force microscopy. Details of the method of the detergent assisted self assembly and some structural features of the assembled molecular layers will be presented.

  14. Interaction of Atmospheric-Pressure Air Microplasmas with Amino Acids as Fundamental Processes in Aqueous Solution

    PubMed Central

    Zhou, Renwu; Zhou, Rusen; Zhuang, Jinxing; Zong, Zichao; Zhang, Xianhui; Liu, Dongping; Bazaka, Kateryna; Ostrikov, Kostya

    2016-01-01

    Plasma medicine is a relatively new field that investigates potential applications of cold atmospheric-pressure plasmas in bioengineering, such as for bacterial inactivation and degradation of organic molecules in water. In order to enunciate mechanisms of bacterial inactivation at molecular or atomic levels, we investigated the interaction of atmospheric-pressure air microplasmas with amino acids in aqueous solution by using high-resolution mass spectrometry (HRMS). Results show that the oxidation effect of plasma-induced species on the side chains of the amino acids can be categorized into four types, namely hydroxylation, nitration, dehydrogenation and dimerization. In addition, relative activities of amino acids resulting from plasma treatment come in descending order as follows: sulfur-containing carbon-chain amino acids > aromatic amino acids > five-membered ring amino acids > basic carbon-chain amino acids. Since amino acids are building blocks of proteins vital to the growth and reproduction of bacteria, these results provide an insight into the mechanism of bacterial inactivation by plasma. PMID:27183129

  15. Interaction of Atmospheric-Pressure Air Microplasmas with Amino Acids as Fundamental Processes in Aqueous Solution.

    PubMed

    Zhou, Renwu; Zhou, Rusen; Zhuang, Jinxing; Zong, Zichao; Zhang, Xianhui; Liu, Dongping; Bazaka, Kateryna; Ostrikov, Kostya

    2016-01-01

    Plasma medicine is a relatively new field that investigates potential applications of cold atmospheric-pressure plasmas in bioengineering, such as for bacterial inactivation and degradation of organic molecules in water. In order to enunciate mechanisms of bacterial inactivation at molecular or atomic levels, we investigated the interaction of atmospheric-pressure air microplasmas with amino acids in aqueous solution by using high-resolution mass spectrometry (HRMS). Results show that the oxidation effect of plasma-induced species on the side chains of the amino acids can be categorized into four types, namely hydroxylation, nitration, dehydrogenation and dimerization. In addition, relative activities of amino acids resulting from plasma treatment come in descending order as follows: sulfur-containing carbon-chain amino acids > aromatic amino acids > five-membered ring amino acids > basic carbon-chain amino acids. Since amino acids are building blocks of proteins vital to the growth and reproduction of bacteria, these results provide an insight into the mechanism of bacterial inactivation by plasma. PMID:27183129

  16. Adsorptions of some heavy metal ions in aqueous solutions by acrylamide/maleic acid hydrogels

    SciTech Connect

    Saraydin, D.; Karadag, E.; Gueven, O.

    1995-10-01

    In this study, acrylamide-maleic acid (AAm/MA) hydrogels in the form of rod have been prepared by {gamma}-radiation. They have been used for adsorption of some heavy metal ions such as uranium, iron, and copper. For the hydrogel containing 40 mg of maleic acid and irradiated at 3.73 kGy, maximum and minimum swellings in the aqueous solutions of the heavy metal ions have been observed with water (1480%) and the aqueous solution of iron(III) nitrate (410%), respectively. Diffusions of water and heavy metal ions onto hydrogels have been found to be of the non-Fickian type of diffusion. In experiments of uranyl ions adsorption, Type II adsorption has been found. One gram of AAa/MA hydrogels sorbed 14-86 mg uranyl ions from solutions of uranyl acetate, 14-90 mg uranyl ions from solutions of uranyl nitrate, 16-39 mg iron ions from solutions of iron(IV) nitrate, and 28-81 mg copper ions from solutions of copper acetate, while acrylamide hydrogel did not sorb any heavy metals ions.

  17. Infusion of branched-chain enriched amino acid solution in patients with hepatic encephalopathy.

    PubMed

    Freund, H; Dienstag, J; Lehrich, J; Yoshimura, N; Bradford, R R; Rosen, H; Atamian, S; Slemmer, E; Holroyde, J; Fischer, J E

    1982-08-01

    Hospitalized patients with hepatic insufficiency often suffer from severe catabolic states and are in urgent need of nutritional support during their acute illness. Protein intolerence, however, remains a significant problem with respect to the provision of adequate nutrition, either enterally or parenterally. The following report is an anecdotal series of 63 consecutive patients in a large urban hospital treated prospectively with nutritional support using a prototype high branched-chain amino acid solution (FO80) given by technique of total parenteral nutrition by the subclavian or internal jugular route with hypertonic dextrose. Sixty-three patients, of which 42 had chronic liver disease (cirrhosis) with acute decompensation and 17 with acute hepatic injury as well as four with hepatorenal syndrome, are the subject of this report. All required intravenous nutritional support and were either intolerant to commercially available parenteral nutrition solutions or were in hepatic encephalopathy at the time they were initially seen. The cirrhotic patients had been hospitalized for a mean of 14.5 +/- 1.9 days before therapy, had a mean bilirubin of 13 mg/100 ml, and had been in coma for 4.8 +/- 0.7 days despite standard therapy. Patients with acute hepatitis had been in the hospital for 16.2 +/- 4.1 days before therapy, had a mean bilirubin of 25 mg/100 ml, and had been in coma 5.2 +/- 1.6 days before therapy. Routine tests of liver function, blood chemistries, amino acids, EEGs, and complex neurological testing including Reitan trailmaking tests were used in the evaluation of these patients. Up to 120 grams of synthetic amino acid solution with hypertonic dextrose was tolerated in these patients with improvement noted in encephalopathy of at least one grade in 87% of the patients with cirrhosis and 75% of the patients with hepatitis. Nitrogen balance was achieved when 75 to 80 grams of synthetic amino acids were administered. Survival was 45% in the cirrhotic group

  18. Aquatic photolysis: photolytic redox reactions between goethite and adsorbed organic acids in aqueous solutions

    USGS Publications Warehouse

    Goldberg, M.C.; Cunningham, K.M.; Weiner, Eugene R.

    1993-01-01

    Photolysis of mono and di-carboxylic acids that are adsorbed onto the surface of the iron oxyhydroxide (goethite) results in an oxidation of the organic material and a reduction from Fe(III) to Fe(II) in the iron complex. There is a subsequent release of Fe2+ ions into solution. At constant light flux and constant solution light absorption, the factors responsible for the degree of photolytic reaction include: the number of lattice sites that are bonded by the organic acid; the rate of acid readsorption to the surface during photolysis; the conformation and structure of the organic acid; the degree of oxidation of the organic acid; the presence or absence of an ??-hydroxy group on the acid, the number of carbons in the di-acid chain and the conformation of the di-acid. The ability to liberate Fe(III) at pH 6.5 from the geothite lattice is described by the lyotropic series: tartrate>citrate> oxalate > glycolate > maleate > succinate > formate > fumarate > malonate > glutarate > benzoate = butanoate = control. Although a larger amount of iron is liberated, the series is almost the same at pH 5.5 except that oxalate > citrate and succinate > maleate. A set of rate equations are given that describe the release of iron from the goethite lattice. It was observed that the pH of the solution increases during photolysis if the solutions are not buffered. There is evidence to suggest the primary mechanism for all these reactions is an electron transfer from the organic ligand to the Fe(III) in the complex. Of all the iron-oxyhydroxide materials, crystalline goethite is the least soluble in water; yet, this study indicates that in an aqueous suspension, iron can be liberated from the goethite lattice. Further, it has been shown that photolysis can occur in a multiphase system at the sediment- water interface which results in an oxidation of the organic species and release of Fe2+ to solution where it becomes available for further reaction. ?? 1993.

  19. Development of a stable solution of 5-aminolaevulinic acid for intracutaneous injection in photodynamic therapy.

    PubMed

    de Blois, A W; Grouls, R J E; Ackerman, E W; Wijdeven, W J A

    2002-01-01

    Photodynamic therapy using 5-aminolaevulinic acid (ALA) as a photosensitiser is a new treatment modality for basal cell carcinomas. Until now ALA has been used topically as a cream. As this administration route leads sometimes to insufficient penetration in the skin, an intracutaneously injectable solution of ALA was developed. The influence of pH, concentration and temperature on the degradation of ALA in aqueous solution was investigated in order to optimise the formulation of the injection. In 0.1% ALA solutions with pH values between 4 and 8 a pH dependency of ALA degradation was shown, comprising fast decomposition at pH values higher than 7, whereas at a pH value of 6 or lower the solutions remained within the range of 90-110% of the initial concentration for at least 128 days. An increase of degradation rate with increasing concentrations became evident which is consistent with the supposed second-order degradation kinetics. After accelerated stability research at 63 degrees C and 85 degrees C a shelf life of 281 days for a 0.1% ALA solution pH 5 was calculated from an Arrhenius plot. A 2% ALA solution was proven to be isotonic. From our results a 0.1-2% ALA solution with pH 5 and an appropriate amount of sodium chloride to obtain isotonicity is recommended as an injectable solution. PMID:12181635

  20. Modeling Sucrose Hydrolysis in Dilute Sulfuric Acid Solutions at Pretreatment Conditions for Lignocellulosic Biomass

    SciTech Connect

    Bower, S.; Wickramasinghe, R.; Nagle, N. J.; Schell, D. J.

    2008-01-01

    Agricultural and herbaceous feedstocks may contain appreciable levels of sucrose. The goal of this study was to evaluate the survivability of sucrose and its hydrolysis products, fructose and glucose, during dilute sulfuric acid processing at conditions typically used to pretreat lignocellulose biomass. Solutions containing 25 g/l sucrose with 0.1-2.0% (w/w) sulfuric acid concentrations were treated at temperatures of 160-200 C for 3-12 min. Sucrose was observed to completely hydrolyze at all treatment conditions. However, appreciable concentrations of fructose and glucose were detected and glucose was found to be significantly more stable than fructose. Different mathematical approaches were used to fit the kinetic parameters for acid-catalyzed thermal degradation of these sugars. Since both sugars may survive dilute acid pretreatment, they could provide an additional carbon source for production of ethanol and other bio-based products.

  1. Radiolysis of aqueous solutions of acetic acid in the presence of Na-montmorillonite

    NASA Technical Reports Server (NTRS)

    Navarro-Gonzalez, R.; Negron-Mendoza, A.; Ramos, S.; Ponnamperuma, C.

    1990-01-01

    The gamma-irradiation of 0.8 mol dm-3 aqueous, oxygen-free acetic acid solutions was investigated in the presence or absence of Na-montmorillonite. H2, CH4, CO, CO2, and several polycarboxylic acids were formed in all systems. The primary characteristics observed in the latter system were: (1) Higher yield of the decomposition of acetic acid; (2) Lower yield of the formation of polycarboxylic acids; (3) No effect on the formation of methane; (4) Higher yield of the formation of carbon dioxide; and (5) The reduction of Fe3+ in the octahedral sites of Na-montmorillonite. A possible reaction scheme was proposed to account for the observed changes. The results are important in understanding heterogeneous processes in radiation catalysis and might be significant to prebiotic chemistry.

  2. Spectrofluorimetric study of the interaction of ciprofloxacin with amino acids in aqueous solution following solvatochromic studies

    NASA Astrophysics Data System (ADS)

    Alizadeh, Kamal; Mobarrez, Mahsa; Ganjali, Mohammad Reza; Norouzi, Parviz; Chaichi, Mohammad Javad

    Complexation of a fluoroquinolone derivative (ciprofloxacin), L, and some amino acids has been studied using spectrofluorimetric method. Results indicated that ciprofloxacin have a greater tendency to form a 1:1 complex with aspartic acid and arginine than the other tested molecules. The fluorescence of ciprofloxacin exhibits quenching process while it has been titrated with these amino acids. Formation constant values (Kf) for complex formed between ciprofloxacin and amino acids were also calculated. Thermodynamic parameters such as ΔG°, ΔH° and ΔS° were studied too. Possible reasons for the observed stability sequence were discussed based on the structures proposed for the resulting complexes. Besides the solution studies, solvatochromic properties of the ciprofloxacin are discussed by studying its spectra in a selection of different solvents.

  3. Extraction of nitric acid, uranyl nitrate, and bismuth nitrate from aqueous nitric acid solutions with CMPO

    SciTech Connect

    Spencer, B.B.

    1995-08-01

    DOE sponsored development of the transuranium extraction (TRUEX) process for removing actinides from radioactive wastes. The solvent is a mixture of CMPO and TBP. Since the extraction characteristics of CMPO are not as well understood as those of TBP, the extraction of nitric acid, uranyl nitrate, and bismuth nitrate with CMPO (dissolved in n-dodecane) were studied. Results indicate that CMPO extracts nitric acid with a 1:1 stoichiometry; equilibrium constant is 2. 660{plus_minus}0.092 at 25 C, and extraction enthalpy is -5. 46{plus_minus}0.46 kcal/mol. Slope analysis indicates that uranyl nitrate extracts with a mixed equilibria of 1:1 and 2:1 stoichiometries in nearly equal proportion. Equil. constant of the 2: 1 extraction was 1.213 {times} 10{sup 6}{plus_minus}3.56 {times} 10{sup 4} at 25 C; reaction enthalpy was -9.610{plus_minus}0.594 kcal/mol. Nitration complexation constant is 8.412{plus_minus}0.579, with an enthalpy of -10.72{plus_minus}1.87 kcal/mol. Bismuth nitrate also extracts with a mixed equilibria of (perhaps) 1:1 and 2:1 stoichiometries. A 2:1 extraction equilibrium and a nitrate complexation adequately model the data. Kinetics and enthalpies were also measured.

  4. Reorientation of the ‘free OH’ group in the top-most layer of air/water interface of sodium fluoride aqueous solution probed with sum-frequency generation vibrational spectroscopy

    SciTech Connect

    Feng, Ran-Ran; Guo, Yuan; Wang, Hongfei

    2014-09-17

    Many experimental and theoretical studies have established the specific anion, as well as cation effects on the hydrogen-bond structures at the air/water interface of electrolyte solutions. However, the ion effects on the top-most layer of the air/water interface, which is signified by the non-hydrogen-bonded so-called ‘free O-H’ group, has not been discussed or studied. In this report, we present the measurement of changes of the orientational angle of the ‘free O-H’ group at the air/water interface of the sodium fluoride (NaF) solutions at different concentrations using the interface selective sum-frequency generation vibrational spectroscopy (SFG-VS) in the ssp and ppp polarizations. The polarization dependent SFG-VS results show that the average tilt angle of the ‘free O-H’ changes from about 35.3 degrees ± 0.5 degrees to 43.4 degrees ± 2.1degrees as the NaF concentration increase from 0 to 0.94M (nearly saturated). Such tilt angle change is around the axis of the other O-H group of the same water molecule at the top-most layer at the air/water interface that is hydrogen-bonded to the water molecules below the top-most layer. These results provide quantitative molecular details of the ion effects of the NaF salt on the structure of the water molecules at the top-most layer of the air/water interfacial, even though both the Na+ cation and the F- anion are believed to be among the most excluded ions from the air/water interface.

  5. In-line System to Produce High-Purity Acid Solutions.

    PubMed

    Masunaga, Hiroto; Higo, Yuji; Ishii, Mizuo; Maruyama, Noboru; Yamazaki, Shigeo

    2016-01-01

    Herein, we report a new device that generates a high-purity acid solution. It comprises three compartments divided by anion-exchange membranes and filled with ion-exchange resins. Fluorochemical cation-exchange membranes, which tolerate electrochemical wear and permit bulk flow, are inserted between each electrode and the anion-exchange resin. A bipolar boundary is a composite boundary comprising anion and cation exchangers. This device has four bipolar boundaries to separate the location of acid generation from the location where water is electrolyzed. It can tolerate high pressures, resist degradation due to electrolysis at the electrodes, and produce high-purity acid solutions that are free from gases and cationic impurities. The acid solution is generated on the basis of an electrokinetic phenomenon at the surfaces of ion-exchange resins and membranes in an electric field; its concentration can be controlled at rates from 0.01 to 100 μmol/min by adjusting the electrical current applied to the device. PMID:27302592

  6. The infrared optical constants of sulfuric acid at 250 K. [spectral reflectance measurement of aqueous solutions

    NASA Technical Reports Server (NTRS)

    Pinkley, L. W.; Williams, D.

    1976-01-01

    Results are presented for measurements of the IR spectral reflectance at near-normal incidence of aqueous solutions of sulfuric acid with acid concentrations of 75% and 95.6% by weight. Kramers-Kronig analyses of the reflectance data are employed to obtain values of the optical constants n(nu) and k(nu) in the spectral range from 400 to 6000 cm to the -1 power. The optical constants of these solutions at 250 K and 300 K are compared. It is found that in spectral regions remote from strong absorption bands, the values of the n(nu) indices obtained at 250 K agree with the values given by Lorentz-Lorenz correction of the same indices at 300 K. All absorption bands observed at 300 K are found to be present at 250 K with slight shifts in frequency and with significant differences in the k(nu) indices at the band maxima. Based on these results, it is concluded that the clouds of Venus probably consist of droplets of aqueous solutions of sulfuric acid with acid concentrations of about 75% by weight.

  7. Effects of Solution Hydrodynamics on Corrosion Inhibition of Steel by Citric Acid in Cooling Water

    NASA Astrophysics Data System (ADS)

    Ashassi-Sorkhabi, H.; Asghari, E.; Mohammadi, M.

    2014-08-01

    Corrosion is a major problem in cooling water systems, which is often controlled using corrosion inhibitors. Solution hydrodynamics is one of the factors affecting corrosion inhibition of metals in these systems. The present work focuses on the study of the combined effects of citric acid concentration (as a green corrosion inhibitor) and fluid flow on corrosion of steel in simulated cooling water. Electrochemical techniques including Tafel polarization and electrochemical impedance spectroscopy were used for corrosion studies. Laminar flow was simulated using a rotating disk electrode. The effects of solution hydrodynamics on inhibition performance of citric acid were discussed. The citric acid showed low inhibition performance in quiescent solution; however, when the electrode rotated at 200 rpm, inhibition efficiency increased remarkably. It was attributed mainly to the acceleration of inhibitor mass transport toward metal surface. The efficiencies were then decreased at higher rotation speeds due to enhanced wall shear stresses on metal surface and separation of adsorbed inhibitor molecules. This article is first part of authors' attempts in designing green inhibitor formulations for industrial cooling water. Citric acid showed acceptable corrosion inhibition in low rotation rates; thus, it can be used as a green additive to the corrosion inhibitor formulations.

  8. [Studies on carbonization of saccharides by using aqueous solution of various acids].

    PubMed

    Zhang, Xin; He, An-Qi; Kang, Ting-Guo; Xia, Jin-Ming; Weng, Shi-Fu; Xu, Yi-Zhuang; Wu, Jin-Guang

    2014-09-01

    The authors tried to establish an approach to use acids to convert biomass into a fuel with higher carbon content and lower oxygen content in a zero-energy-consumption fashion. Considering that biomass is composed of monosaccharide, we used aqueous solutions of variation acids including hydrochloric acid, sulfuric acid and perchloric acid to treat 2-deoxy-ribose and fructose at ambient temperature and pressure. Black substances were produced after a period of time when 2-deoxy-ribose and fructose were mixed with aqueous solutions containing 8 mol · L(-1) acids. The black substance was collected and characterized by using elemental analysis, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Elemental analysis results indicate that the contents of carbon increases significantly in the black substances in comparison with 2-deoxy-ribose and fructose. Moreover, XPS results indicate that the content of oxygen in the black substance undergoes a significant decrease compared with pure 2-deoxy-ribose and fructose. In the XPS spectra, the is peaks of 2-deoxy-ribose, strong sub peak at 286. 05 eV, which is assigned to carbon linked to oxygen directly, dominate in the C is peak envelop. After treatment by HClO4, the peak decreased dramatically. This result also supports the conclusion that the content of oxygen in mono-saccharide is significantly reduced after treatment by acids. In the FTIR spectra of the black substances, strong peaks can be observed around 1 600 cm(-1), indicating that C==C bond is formed in the product. The above results suggest that treatments with acids may be developed as a new zero-energy-consumption approach to convert biomass in a new fuel with improved energy output efficiency. PMID:25532323

  9. Comparative behavior of titanium and zirconium in hydrofluoric-nitric acid pickling solutions

    SciTech Connect

    Sutter, E.M.M.; Hlawka, F.; Cornet, A. )

    1990-07-01

    The different behavior of titanium and zirconium in HF-HNO{sub 3} pickling solutions has been studied using electrochemical methods and Raman spectrometry. In each case, the depleting of the solutions during a pickling experiment could be correlated with the consumption of HF to form metal oxo or oxofluoro complexes. However, the mechanism of metal dissolution is quite different for the two metals. The titanium dissolution process in such solutions can be interpreted using a passivation model in which dissolution and passivation are two competing reactions at the surface of the bare metal. On the other hand, zirconium dissolution occurs through formation of an oxide film with ionic diffusion through the film being a rate-determining step. The particular role of strong acid added to the HF solution for pickling of titanium and zirconium is also discussed.

  10. Effect of tritium on corrosion behavior of chromium in 0.01 N sulfuric acid solution

    SciTech Connect

    Oyaidzu, M.; Isobe, K.; Hayashi, T.

    2015-03-15

    The effects of tritium on the corrosion behavior of chromium in 0.01 N sulfuric solution have been investigated in the present study. Electrochemical experiments have been carried our for pure chromium. At first, the concentration dependence of sulfuric acid solution on anodic polarization behavior of chromium was experimented, resulting in that 0.01 N one was found appropriate. The dependence of both dissolved oxygen and tritium concentration on anodic behavior of chromium were performed. It was found from that the self-passivation of chromium induced by dissolved oxygen was inhibited in tritiated solution resulting in the enhancement of the corrosion. As a consequence it is highly likely that the elution of chromium by highly oxidative radiolysis products would explain the passivation inhibitory effect of SUS304 stainless steel observed in tritiated solutions.

  11. Guanine and inosine nucleotides, nucleosides and oxypurines in snail muscles as potential biomarkers of fluoride toxicity.

    PubMed

    Rać, Monika E; Safranow, Krzysztof; Dołegowska, Barbara; Machoy, Zygmunt

    2007-01-01

    The aim of the present study was to determine the toxicity of fluorides on energy metabolism in muscles of the Helix aspersa maxima snail. Qualitative and quantitative analysis of purine compounds was performed in slices of foot from mature snails with high-performance liquid chromatography. Fluoride concentrations were measured using an ion-selective electrode and gas chromatography. The results show that exposure to fluoride pollution was accompanied by a statistically significant increase in fluoride concentrations in soft tissues. This effect was already noticeable with the smallest fluoride dose. Accumulation was greatest in the shell. There is a significant and positive correlation between fluoride concentrations in foot muscles and guanine and inosine nucleotides or uridine content. The content of low-energy guanylate, inosylate and oxypurine in foot muscles significantly increased with rising dose of fluoride. The difference as compared with controls was significant only for the highest dose of fluoride. Interestingly, uric acid, the final product of purine catabolism, dominated quantitatively in the foot muscles of snails. In conclusion, increased low-energy guanylate and inosylate as well as decreased xanthine concentrations in snail muscle can be indicators of the toxic influence of fluoride on the organism. The measuring of fluoride accumulation in the shell is the most suitable bioindicator of fluoride pollution in the environment. PMID:18274260

  12. Microbial shelf life determination of vacuum-packaged fresh beef treated with polylactic acid, lactic acid, and nisin solutions.

    PubMed

    Ariyapitipun, T; Mustapha, A; Clarke, A D

    1999-08-01

    The effectiveness of polylactic acid, lactic acid, nisin, and combinations of the acids and nisin on extending the shelf-life of raw beef was determined. Fresh beef pieces (5 by 5 by 2.5 cm) were dipped in a solution of 2% low molecular weight polylactic acid (LMW-PLA), 2% lactic acid (LA), 200 IU of nisin per ml, or the combinations of nisin in either 2% LMW-PLA or 2% LA. The samples were then drip-dried, vacuum-packaged, and stored at 4 degrees C for up to 56 days. The beef surface pH values and numbers of psychrotrophic aerobic bacteria, psychrotrophic and mesophilic Enterobacteriaceae, Pseudomonas, and Lactobacillus were determined weekly for 56 days. The average surface pH values of the beef samples treated with 2% LMW-PLA or the combination of 200 IU of nisin per ml and 2% LMW-PLA were significantly reduced to 5.19 and 5.17, respectively, at day 0 (P < or = 0.05), while those decontaminated with 2% LA or 200 IU of nisin per ml in 2% LA solution were significantly decreased from 5.62 to 4.98 and 4.96, respectively. The 2% LMW-PLA, 2% LA, or the combinations of each acid and nisin showed immediate inhibitory effects on psychrotrophic aerobic bacteria (1.94, 2.36, 2.59, and 1.76 log reduction, respectively), psychrotrophic Enterobacteriaceae (1.37, 1.86, 1.77, and 1.35 log reduction, respectively), mesophilic Enterobacteriaceae (1.00, 1.00, 0.82, and 0.68 log reduction, respectively), and Pseudomonas (1.77, 1.57, 1.76, and 1.41 log reduction, respectively) on fresh beef (P < or = 0.05). The reduction was evident up to 56 days as seen by the numbers of Enterobacteriaceae and Pseudomonas (P < or = 0.05). Because there was no interaction between treatments and storage times, the data in each period were combined and presented as effect of treatments on overall microbial counts of fresh beef. It was found that 2% LMW-PLA, 2% LA, and the combinations of each acid and nisin significantly lowered the population of the above organisms compared with the untreated control

  13. Ferrimyoglobin-Fluoride.

    ERIC Educational Resources Information Center

    Russo, Steven O.; Hanania, George I. H.

    1990-01-01

    Described is an experiment which is designed to investigate the reaction of the protein ferrimyoglobin with fluoride. The activity uses readily available apparatus and the technique of optical absorbance for measurement of concentrations. Experimental design, procedures, and treatment of the equilibrium data are detailed. (CW)

  14. Other Fluoride Products

    MedlinePlus

    ... in preventing tooth decay in people of all ages. Use the information listed below to compare the other fluoride products ... even among children younger than 6 years of age. Proper application technique ... cleared for marketing by the Food and Drug Administration (FDA) as ...

  15. Fluorine (soluble fluoride)

    Integrated Risk Information System (IRIS)

    Fluorine ( soluble fluoride ) ; CASRN 7782 - 41 - 4 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for No

  16. Collagen tissue treated with chitosan solutions in carbonic acid for improved biological prosthetic heart valves.

    PubMed

    Gallyamov, Marat O; Chaschin, Ivan S; Khokhlova, Marina A; Grigorev, Timofey E; Bakuleva, Natalia P; Lyutova, Irina G; Kondratenko, Janna E; Badun, Gennadii A; Chernysheva, Maria G; Khokhlov, Alexei R

    2014-04-01

    Calcification of bovine pericardium dramatically shortens typical lifetimes of biological prosthetic heart valves and thus precludes their choice for younger patients. The aim of the present work is to demonstrate that the calcification is to be mitigated by means of treatment of bovine pericardium in solutions of chitosan in carbonic acid, i.e. water saturated with carbon dioxide at high pressure. This acidic aqueous fluid unusually combines antimicrobial properties with absolute biocompatibility as far as at normal pressure it decomposes spontaneously and completely into H2O and CO2. Yet, at high pressures it can protonate and dissolve chitosan materials with different degrees of acetylation (in the range of 16-33%, at least) without any further pretreatment. Even exposure of the bovine pericardium in pure carbonic acid solution without chitosan already favours certain reduction in calcification, somewhat improved mechanical properties, complete biocompatibility and evident antimicrobial activity of the treated collagen tissue. The reason may be due to high extraction ability of this peculiar compressed fluidic mixture. Moreover, exposure of the bovine pericardium in solutions of chitosan in carbonic acid introduces even better mechanical properties and highly pronounced antimicrobial activity of the modified collagen tissue against adherence and biofilm formation of relevant Gram-positive and Gram-negative strains. Yet, the most important achievement is the detected dramatic reduction in calcification for such modified collagen tissues in spite of the fact that the amount of the thus introduced chitosan is rather small (typically ca. 1wt.%), which has been reliably detected using original tritium labelling method. We believe that these improved properties are achieved due to particularly deep and uniform impregnation of the collagen matrix with chitosan from its pressurised solutions in carbonic acid. PMID:24582232

  17. Recovery of water and acid from leach solutions using direct contact membrane distillation.

    PubMed

    Kesieme, Uchenna K; Milne, Nicholas; Cheng, Chu Yong; Aral, Hal; Duke, Mikel

    2014-01-01

    This paper describes for the first time the use of direct contact membrane distillation (DCMD) for acid and water recovery from a real leach solution generated by a hydrometallurgical plant. The leach solutions considered contained H2SO4 or HCl. In all tests the temperature of the feed solution was kept at 60 °C. The test work showed that fluxes were within the range of 18-33 kg/m(2)/h and 15-35 kg/m(2)/h for the H2SO4 and HCl systems, respectively. In the H2SO4 leach system, the final concentration of free acid in the sample solution increased on the concentrate side of the DCMD system from 1.04 M up to 4.60 M. The sulfate separation efficiency was over 99.9% and overall water recovery exceeded 80%. In the HCl leach system, HCl vapour passed through the membrane from the feed side to the permeate. The concentration of HCl captured in the permeate was about 1.10 M leaving behind only 0.41 M in the feed from the initial concentration of 2.13 M. In all the experiments, salt rejection was >99.9%. DCMD is clearly viable for high recovery of high quality water and concentrated H2SO4 from spent sulfuric acid leach solution where solvent extraction could then be applied to recover the sulfuric acid and metals. While HCl can be recovered for reuse using only DCMD. PMID:24569289

  18. Resistance to protein and oil fouling of sulfobetaine-grafted Poly(vinylidene Fluoride) hollow fiber membrane and the electrolyte-responsive behavior in NaCl solution

    NASA Astrophysics Data System (ADS)

    Li, Qian; Bi, Qiu-Yan; Liu, Tian-Yin; Wang, Xiao-Lin

    2012-07-01

    An excellent protein-fouling-resistance performance of the sulfobetaine-grafted PVDF hollow fiber membrane was obtained and the potential of sulfobetaine-grafted PVDF membrane to resist the oil fouling was confirmed in the filtration solution which contained inorganic electrolyte, sodium chloride (NaCl). The electrolyte-responsive behavior of the sulfobetaine-modified PVDF membrane was demonstrated by the filtration of NaCl aqueous solution. The grafting amount of the modified PVDF hollow fiber membrane showed a stable value as 680 μg/cm2. An almost complete coverage of the membrane surface by the grafted sulfobetaine polymer contributed to the high hydrophilicity and membrane strength. The membrane surface became denser and the permeate flux reduced with the increase of NaCl concentration. The cyclic filtration experiment showed that during the filtration of the protein solution with 0.05 mol/L of NaCl, the sulfobetaine-grafted PVDF membrane exhibited an excellent protein-fouling-resistance performance with a high relative flux recovery of 98.2% and a low irreversible fouling extent which was lower 10 times than that of the nascent PVDF hollow fiber membrane. In addition, the sulfobetaine-grafted PVDF hollow fiber membrane showed an oil-fouling-resistance property during the filtration experiment of the oil-in-water emulsion with 0.05 mol/L of NaCl, resulting in an relative flux recovery of about twice that of the nascent PVDF membrane. The results extended the application of poly(sulfobetaine)-g-PVDF hollow fiber membrane in the fields of bio-separation, artificial oil and wastewater treatment.

  19. Metal-particle-induced, highly localized site-specific etching of Si and formation of single-crystalline Si nanowires in aqueous fluoride solution.

    PubMed

    Peng, Kuiqing; Fang, Hui; Hu, Juejun; Wu, Yin; Zhu, Jing; Yan, Yunjie; Lee, ShuitTong

    2006-10-16

    A straightforward metal-particle-induced, highly localized site-specific corrosion-like mechanism was proposed for the formation of aligned silicon-nanowire arrays on silicon in aqueous HF/AgNO3 solution on the basis of convincing experimental results. The etching process features weak dependence on the doping of the silicon wafers and, thus, provides an efficient method to prepare silicon nanowires with desirable doping characteristics. The novel electrochemical properties between silicon and active noble metals should be useful for preparing novel silicon nanostructures and also new optoelectronic devices. PMID:16871502

  20. The effect of different fluoride application methods on the remineralization of initial carious lesions

    PubMed Central

    2016-01-01

    Objectives The purpose of this study was to assess the effect of single and combined applications of fluoride on the amount of fluoride release, and the remineralization and physical properties of enamel. Materials and Methods Each of four fluoride varnish and gel products (Fluor Protector, FP, Ivoclar Vivadent; Tooth Mousse Plus, TM, GC; 60 Second Gel, A, Germiphene; CavityShield, CS, 3M ESPE) and two fluoride solutions (2% sodium fluoride, N; 8% tin(ii) fluoride, S) were applied on bovine teeth using single and combined methods (10 per group), and then the amount of fluoride release was measured for 4 wk. The electron probe microanalysis and the Vickers microhardness measurements were conducted to assess the effect of fluoride application on the surface properties of bovine teeth. Results The amount of fluoride release was higher in combined applications than in single application (p < 0.05). Microhardness values were higher after combined applications of N with FP, TM, and CS than single application of them, and these values were also higher after combined applications of S than single application of A (p < 0.05). Ca and P values were higher in combined applications of N with TM and CS than single application of them (p < 0.05). They were also increased after combined applications of the S with A than after single application (p < 0.05). Conclusions Combined applications of fluoride could be used as a basis to design more effective methods of fluoride application to provide enhanced remineralization. PMID:27200280

  1. Degradation of hydroxycinnamic acid mixtures in aqueous sucrose solutions by the Fenton process.

    PubMed

    Nguyen, Danny M T; Zhang, Zhanying; Doherty, William O S

    2015-02-11

    The degradation efficiencies and behaviors of caffeic acid (CaA), p-coumaric acid (pCoA), and ferulic acid (FeA) in aqueous sucrose solutions containing the mixture of these hydroxycinnamic acids (HCAs) were studied by the Fenton oxidation process. Central composite design and multiresponse surface methodology were used to evaluate and optimize the interactive effects of process parameters. Four quadratic polynomial models were developed for the degradation of each individual acid in the mixture and the total HCAs degraded. Sucrose was the most influential parameter that significantly affected the total amount of HCA degraded. Under the conditions studied there was a <0.01% loss of sucrose in all reactions. The optimal values of the process parameters for a 200 mg/L HCA mixture in water (pH 4.73, 25.15 °C) and sucrose solution (13 mass %, pH 5.39, 35.98 °C) were 77% and 57%, respectively. Regression analysis showed goodness of fit between the experimental results and the predicted values. The degradation behavior of CaA differed from those of pCoA and FeA, where further CaA degradation is observed at increasing sucrose and decreasing solution pH. The differences (established using UV/vis and ATR-FTIR spectroscopy) were because, unlike the other acids, CaA formed a complex with Fe(III) or with Fe(III) hydrogen-bonded to sucrose and coprecipitated with lepidocrocite, an iron oxyhydroxide. PMID:25585639

  2. Selective extraction of cesium from acidic nitrate solutions with didodecylnaphthalenesulfonic acid synergized with bis(tert-butylbenzo)-21-crown-7

    SciTech Connect

    McDowell, W.J.; Case, G.N. ); McDonough, J.A.; Bartsch, R.A. )

    1992-12-01

    The behavior of other crown ether-synergized sulfonic acid extraction systems suggested that the title system would be selective for cesium. Synthesis of the new lipophilic crown ether, bis[4(5)-tert-butylbenzo]-21-crown-7 (D(tBB)21C7), allowed testing of this hypothesis. Under nonloading conditions, the distribution coefficient for cesium between a toluene solution 0.025 M in didodecylnaphthalenesulfonic acid (HDDNS) and D(tBB)21C7 and an aqueous phase 0.1 M in nitric acid is 100 with separation factors of 1.2 from rubidium, 5.6 from potassium, and 294 from sodium. Under loading and competitive extraction conditions, the distribution coefficients were lower (5 for cesium), but the separation factors remained in the same order and of useful magnitude, 1.5 from rubidium, 6.4 from potassium, and 192 from sodium. Increasing the concentrations of D(tBB)21C7 and HDDNS in the organic phase gives higher distribution coefficients for cesium as did lower aqueous acid concentrations. 23 refs., 8 figs., 1 tab.

  3. Zirconium complexes with lactic acid in the solution and solid states

    NASA Astrophysics Data System (ADS)

    Demkowicz, Paul Andrew

    Lactic acid complexes of zirconium are used in a great number of industrial applications. Among these is their use as crosslinking agents for hydraulic fracturing fluids used in secondary oil recovery operations. Because of a poor understanding of zirconium lactate complex chemistry and crosslinking reactions, however, the design of superior fluid systems is often not guided by sound chemical principles and leads to empirical guesswork. Zirconium lactate solutions were characterized using Fourier transform infrared (FT-IR) spectroscopy, 1H, 13C, and 17O nuclear magnetic resonance (NMR) spectroscopy, and potentiometry. The results indicate that lactic acid is coordinated bidentate to zirconium via the alcohol and carboxylate groups. The average number of lactate ligands per zirconium ion is approximately 2 and is demonstrated to be relatively constant from pH 4--9. The lability of the lactate complexes increases as the pH is decreased. The NMR data reveal that there are both large and small complex molecules present in solution, with the size of the complex depending on the extent of zirconium hydrolysis. Large complexes consist of lactic acid coordinated to polynuclear zirconium hydroxy ions. The molecular size of these complexes is sufficient to hinder their tumbling in solution and cause broadening of the measured NMR signals. Small complexes involve lactic acid coordinated to hydroxylated species containing fewer zirconium ions, such that the rotational motion in solution is sufficiently rapid to result in narrow NMR signals. Zirconium lactate complexes were precipitated from solution and analyzed in the solid state using FT-IR spectroscopy, 13C magic angle spinning (MAS) NMR spectroscopy, elemental analysis, thermal gravitational analysis, and x-ray diffraction. Two distinct types of crystalline compounds were synthesized with four lactate ligands per zirconium ion. The coordination of lactic acid to zirconium is different in the two compounds, with one showing

  4. PROCESS FOR EXTRACTING NEPTUNIUM AND PLUTONIUM FROM NITRIC ACID SOLUTIONS OF SAME CONTAINING URANYL NITRATE WITH A TERTIARY AMINE

    DOEpatents

    Sheppard, J.C.

    1962-07-31

    A process of selectively extracting plutonium nitrate and neptunium nitrate with an organic solution of a tertiary amine, away from uranyl nitrate present in an aqueous solution in a maximum concentration of 1M is described. The nitric acid concentration is adjusted to about 4M and nitrous acid is added prior to extraction. (AEC)

  5. The synthesis and structural characterization of novel transition metal fluorides

    SciTech Connect

    Casteel, W.J. Jr.

    1992-09-01

    High purity KMF{sub 6} and K{sub 2}MF{sub 6} salts (M = Mo,Re, Ru, Os, Ir, Pt) are obtained from reduction hexafluorides. A rhombohedral unit cell is observed for KReF{sub 6}. Fluoride ion capture by Lewis acids from the hexafluorometallate (IV) salts affords high purity tetrafluorides for M = Mo, Re, Ru, Os, and Pd. The structure of RuF{sub 4} is determined from X-ray synchrotron and neutron powder data. Unit cells based on theorthorhombic PdF{sub 4} type cell are derived from X-ray powder data for ReF{sub 4} and OsF{sub 4}. Fluoride ion capture from KAgF{sub 4} provides the thermally unstable trifluoride as a bright, red, diamagnetic solid. The structure solution of AgF{sub 3} and redetermination of the AuF{sub 3} structure from X-ray synchrotron and neutron powder data demonstrate that the two are isostnictural. Thermal decomposition product of AgF{sub 3} is the mixed valence compound Ag{sup II}Ag{sub 2}{sup III}F{sub 8}. Several new salts containing the (Ag - F){sub n}{sup n+} chain cation are prepared. The first linear (Ag - F){sub n}{sup n+} chain is observed in AgF{sup +}BF{sub 4 {sup {minus}}} which crystallizes in a tetragonal unit. AgFAuF{sub 4} has a triclinic unit cell and is isostructural with CuFAuF{sub 4}. AgFAuF{sub 6} has an orthorhombic unit cell and appears to be isostructural with AgFAsF{sub 6}. A second mixed valence silver fluoride, Ag{sup II}Ag{sup III}F{sub 5}, is prepared, which magnetic measurements indicate is probably an AgF{sup +} salt. Magnetic data for all of the AgF{sup +} salts exhibit low magnitude, temperature independent paramagnetism characteristic of metallic systems. Cationic AG(II) in acidic AHF solutions is a powerful oxidizer, capable of oxidizing Xe to Xe(II) and O{sub 2} to O{sub 2}{sup +}. Reactions with C{sub 6}F{sub 6} and C{sub 3}F{sub 6} suggest an electron capture mechanism for cationic AG(II) oxidations.

  6. Short-term fluoride release from various aesthetic restorative materials.

    PubMed

    Yap, Adrian U J; Tham, S Y; Zhu, L Y; Lee, H K

    2002-01-01

    The short-term fluoride release of a giomer (Reactmer), a compomer (Dyract AP), a conventional glass ionomer cement (Fuji II Cap) and a resin-modified glass ionomer cement (Fuji II LC) was evaluated and compared. Specimen discs (6 +/-0.2 mm diameter and 1 +/- 0.2 mm thick) were prepared for each material using custom molds. Each disc was placed in 1 ml of deionized for 24 hours at 37 degrees C. After one day, the water was extracted and analyzed. The specimen discs were then re-immersed into another 1 ml of fresh deionized water. The procedure of removing and refilling the water was repeated for 28 days. Sample solutions taken during the first seven days and at days 14, 21 and 28 were introduced into a capillary electrophoresis system using field amplified sample injection (FASI) to determine fluoride release. Data was analyzed using factorial ANOVA/Scheffe's post-hoc test at significance level 0.05. An initial fluoride "burst" effect was observed with glass ionomers. Both compomer and giomer did not show an initial fluoride "burst" effect. With the exception of the compomer, fluoride release at day one was generally significantly greater than at the other time intervals. The glass ionomers released significantly more fluoride than the compomer and giomer at day one. Although fluoride release of the giomer was significantly greater than the other materials at day seven, it became significantly lower at day 28. PMID:12022457

  7. Fluoride solid electrolytes: investigation of the tysonite-type solid solutions La1-xBaxF3-x (x < 0.15).

    PubMed

    Chable, Johann; Dieudonné, Belto; Body, Monique; Legein, Christophe; Crosnier-Lopez, Marie-Pierre; Galven, Cyrille; Mauvy, Fabrice; Durand, Etienne; Fourcade, Sébastien; Sheptyakov, Denis; Leblanc, Marc; Maisonneuve, Vincent; Demourgues, Alain

    2015-12-01

    Pure tysonite La1-xBaxF3-x solid solutions for x < 0.15 were prepared by solid state synthesis in a platinum tube under an azote atmosphere with subsequent quenching for 0.07 ≤x < 0.15. The solid solutions were studied by X-ray, electron and neutron diffractions and by (19)F NMR and impedance spectroscopy. The evolution of the cell parameters obeying Vegard's rule was determined for 0 < x≤ 0.15 and atomic position parameters were accurately refined for x = 0.03, 0.07 and 0.10. The chemical pressure induced by large Ba(2+) cations leads to an increase of the unit cell parameters. Fluorine environment and mobilities are discussed on the basis of the results of neutron diffraction and (19)F solid state NMR. The F1 subnetwork is lacunar; fluorine exchange occurs according to the order: F1-F1 and F1-F2,3. 2D EXSY NMR spectra of La0.97Ba0.03F2.97 reveal, for the first time, a chemical exchange between F2 and F3 sites that requires two successive jumps. The ionic conductivity was evaluated from sintered pellets and different shaping methods were compared. The only structural features which could explain the conductivity maximum are a crossover together with a smaller dispersion of F1-F1,2,3 distances at x = 0.05-0.07. PMID:26246328

  8. Copper-Sulfate Pentahydrate as a Product of the Waste Sulfuric Acid Solution Treatment

    NASA Astrophysics Data System (ADS)

    Marković, Radmila; Stevanović, Jasmina; Avramović, Ljiljana; Nedeljković, Dragutin; Jugović, Branimir; Stajić-Trošić, Jasna; Gvozdenović, Milica

    2012-12-01

    The aim of this study is synthesis of copper-sulfate pentahydrate from the waste sulfuric acid solution-mother liquor generated during the regeneration process of copper bleed solution. Copper is removed from the mother liquor solution in the process of the electrolytic treatment using the insoluble lead anodes alloyed with 6 mass pct of antimony on the industrial-scale equipment. As the result of the decopperization process, copper is removed in the form of the cathode sludge and is precipitated at the bottom of the electrolytic cell. By this procedure, the content of copper could be reduced to the 20 mass pct of the initial value. Chemical characterization of the sludge has shown that it contains about 90 mass pct of copper. During the decopperization process, the very strong poison, arsine, can be formed, and the process is in that case terminated. The copper leaching degree of 82 mass pct is obtained using H2SO4 aqueous solution with the oxygen addition during the cathode sludge chemical treatment at 80 °C ± 5 °C. Obtained copper salt satisfies the requirements of the Serbian Standard for Pesticide, SRPS H.P1. 058. Therefore, the treatment of waste sulfuric acid solutions is of great economic and environmental interest.

  9. Micellization properties of zwitterionic surfactants derived from nicotinic acid in aqueous solutions

    SciTech Connect

    Wiederkehr, N.A.; Kalyanasundaram, K.; Graetzel, M. ); Viscardi, G.; Savarino, P.; Barni, E. )

    1991-01-01

    Various properties of monomeric and micellar (aggregated) forms of a series of zwitterionic surfactants based on nicotinic acid (N-alkylnicotinic acids), R-NA (R = C{sub 8}, C{sub 10}, C{sub 12}, C{sub 14}, and C{sub 16}) have been determined in aqueous solution by utilization of a number of physical methods (visible light absorption, fluorescence probe analysis, surfactant tension measurements, and low-angle light scattering): protonation equilibria, extent of counterion adsorption, critical micellar temperature, critical micellar concentration, and micellar aggregation number.

  10. Composition and process for separating cesium ions from an acidic aqueous solution also containing other ions

    DOEpatents

    Dietz, Mark L.; Horwitz, E. Philip; Bartsch, Richard A.; Barrans, Jr., Richard E.; Rausch, David

    1999-01-01

    A crown ether cesium ion extractant is disclosed as is its synthesis. The crown ether cesium ion extractant is useful for the selective purification of cesium ions from aqueous acidic media, and more particularly useful for the isolation of radioactive cesium-137 from nuclear waste streams. Processes for isolating cesium ions from aqueous acidic media using the crown ether cesium extractant are disclosed as are processes for recycling the crown ether cesium extractant and processes for recovering cesium from a crown ether cesium extractant solution.

  11. Composition and process for separating cesium ions from an acidic aqueous solution also containing other ions

    DOEpatents

    Dietz, M.L.; Horwitz, E.P.; Bartsch, R.A.; Barrans, R.E. Jr.; Rausch, D.

    1999-03-30

    A crown ether cesium ion extractant is disclosed as is its synthesis. The crown ether cesium ion extractant is useful for the selective purification of cesium ions from aqueous acidic media, and more particularly useful for the isolation of radioactive cesium-137 from nuclear waste streams. Processes for isolating cesium ions from aqueous acidic media using the crown ether cesium extractant are disclosed as are processes for recycling the crown ether cesium extractant and processes for recovering cesium from a crown ether cesium extractant solution. 4 figs.

  12. Ferulic acid stabilizes a solution of vitamins C and E and doubles its photoprotection of skin.

    PubMed

    Lin, Fu-Hsiung; Lin, Jing-Yi; Gupta, Ravindra D; Tournas, Joshua A; Burch, James A; Selim, M Angelica; Monteiro-Riviere, Nancy A; Grichnik, James M; Zielinski, Jan; Pinnell, Sheldon R

    2005-10-01

    Ferulic acid is a potent ubiquitous plant antioxidant. Its incorporation into a topical solution of 15%l-ascorbic acid and 1%alpha-tocopherol improved chemical stability of the vitamins (C+E) and doubled photoprotection to solar-simulated irradiation of skin from 4-fold to approximately 8-fold as measured by both erythema and sunburn cell formation. Inhibition of apoptosis was associated with reduced induction of caspase-3 and caspase-7. This antioxidant formulation efficiently reduced thymine dimer formation. This combination of pure natural low molecular weight antioxidants provides meaningful synergistic protection against oxidative stress in skin and should be useful for protection against photoaging and skin cancer. PMID:16185284

  13. Direct determination of peracetic acid, hydrogen peroxide, and acetic acid in disinfectant solutions by far-ultraviolet absorption spectroscopy.

    PubMed

    Higashi, Noboru; Yokota, Hiroshi; Hiraki, Satoru; Ozaki, Yukihiro

    2005-04-01

    In this paper we propose a rapid and highly selective far-ultraviolet (FUV) spectroscopic method for the simultaneous determination of peracetic acid (PAA), hydrogen peroxide, and acetic acid (AA). For this purpose we developed a novel FUV spectrometer that enables us to measure the spectra down to 180 nm. Direct determination of PAA, H(2)O(2), and AA, the three main species in disinfectant solutions, was carried out by using their absorption bands in the 180-220-nm region. The proposed method does not require any reagents or catalysts, a calibration standard, and a complicated procedure for the analysis. The only preparation procedure requested is a dilution of H(2)O(2) with pure water to a concentration range lower than 0.2 wt % in the sample solutions. Usually, the required concentration range can be obtained by the 10 times volume dilution of the actual disinfectant solutions. As the measured sample does not leave any impurity for the disinfection, it can be reused completely by using a circulation system. The detection limit for PAA of the new FUV spectrometer was evaluated to be 0.002 wt %, and the dynamic ranges of the measured concentrations were from 0 to 0.05 wt %, from 0 to 0.2 wt %, and from 0 to 0.2 wt % for PAA, H(2)O(2), and AA, respectively. The response time for the simultaneous determination of the three species is 30 s, and the analysis is applicable even to the flowing samples. This method may become a novel approach for the continuous monitoring of PAA in disinfectant solutions on the process of sterilization. PMID:15801764

  14. Novel Regenerated Solvent Extraction Processes for the Recovery of Carboxylic Acids or Ammonia from Aqueous Solutions Part I. Regeneration of Amine-Carboxylic Acid Extracts

    SciTech Connect

    Poole, L.J.; King, C.J.

    1990-03-01

    Two novel regenerated solvent extraction processes are examined. The first process has the potential to reduce the energy costs inherent in the recovery of low-volatility carboxylic acids from dilute aqueous solutions. The second process has the potential for reducing the energy costs required for separate recovery of ammonia and acid gases (e.g. CO{sub 2} and H{sub 2}S) from industrial sour waters. The recovery of carboxylic acids from dilute aqueous solution can be achieved by extraction with tertiary amines. An approach for regeneration and product recovery from such extracts is to back-extract the carboxylic acid with a water-soluble, volatile tertiary amine, such as trimethylamine. The resulting trimethylammonium carboxylate solution can be concentrated and thermally decomposed, yielding the product acid and the volatile amine for recycle. Experimental work was performed with lactic acid, succinic acid, and fumaric acid. Equilibrium data show near-stoichiometric recovery of the carboxylic acids from an organic solution of Alamine 336 into aqueous solutions of trimethylamine. For fumaric and succinic acids, partial evaporation of the aqueous back extract decomposes the carboxylate and yields the acid product in crystalline form. The decomposition of aqueous solutions of trimethylammonium lactates was not carried out to completion, due to the high water solubility of lactic acid and the tendency of the acid to self-associate. The separate recovery of ammonia and acid gases from sour waters can be achieved by combining steam-stripping of the acid gases with simultaneous removal of ammonia by extraction with a liquid cation exchanger. The use of di-2,4,4-trimethylpentyl phosphinic acid as the liquid cation exchanger is explored in this work. Batch extraction experiments were carried out to measure the equilibrium distribution ratio of ammonia between an aqueous buffer solution and an organic solution of the phosphinic acid (0.2N) in Norpar 12. The concentration

  15. Organic amendments increase soil solution phosphate concentrations in an acid soil: A controlled environment study

    SciTech Connect

    Schefe, C.R.; Patti, A.F.; Clune, T.S.; Jackson, R.

    2008-04-15

    Soil acidification affects at least 4 million hectares of agricultural land in Victoria, Australia. Low soil pH can inhibit plant growth through increased soluble aluminum (Al) concentrations and decreased available phosphorus (P). The addition of organic amendments may increase P availability through competition for P binding sites, solubilization of poorly soluble P pools, and increased solution pH. The effect of two organic amendments (lignite and compost) on P solubility in an acid soil was determined through controlled environment (incubation) studies. Three days after the addition of lignite and compost, both treatments increased orthophosphate and total P measured in soil solution, with the compost treatments having the greatest positive effect. Increased incubation time (26 days) increased soil solution P concentrations in both untreated and amended soils, with the greatest effect seen in total P concentrations. The measured differences in solution P concentrations between the lignite- and compost-amended treatments were likely caused by differences in solution chemistry, predominantly solution pH and cation dynamics. Soil amendment with lignite or compost also increased microbial activity in the incubation systems, as measured by carbon dioxide respiration. Based on the results presented, it is proposed that the measured increase in soil solution P with amendment addition was likely caused by both chemical and biological processes, including biotic and abiotic P solubilization reactions, and the formation of soluble organic-metal complexes.

  16. Pulsed field capillary electrophoresis of multikilobase length nucleic acids in dilute methyl cellulose solutions.

    PubMed

    Kim, Y; Morris, M D

    1994-10-01

    Pulsed field capillary gel electrophoresis in dilute methyl cellulose solutions is used to separate nucleic acid fragments in the size range 75-23,000 base pairs. Field inversion is shown to increase resolution for fragments longer than about 500 base pairs. Methyl cellulose solutions as dilute as 0.01% can be used. Intermolecular hydrogen bonding is suggested as the cause of apparent cellulose fiber entanglement at concentrations below the calculated entanglement limit. The 1-kb DNA ladder and the lambda DNA/HindIII restriction fragment mixtures are each baseline resolved in a 28-cm capillary in less than 9 min at 180 V/cm (dc component). PMID:7978303

  17. Spectral and Acid-Base Properties of Hydroxyflavones in Micellar Solutions of Cationic Surfactants

    NASA Astrophysics Data System (ADS)

    Lipkovska, N. A.; Barvinchenko, V. N.; Fedyanina, T. V.; Rugal', A. A.

    2014-09-01

    It has been shown that the spectral characteristics (intensity, position of the absorption band) and the acid-base properties in a series of structurally similar hydroxyflavones depend on the concentration of the cationic surfactants miramistin and decamethoxin in aqueous solutions, and the extent of their changes is more pronounced for hydrophobic quercetin than for hydrophilic rutin. For the first time, we have determined the apparent dissociation constants of quercetin and rutin in solutions of these cationic surfactants (pKa1) over a broad concentration range and we have established that they decrease in the series water-decamethoxin-miramistin.

  18. Three-dimensional patterns from the thin-film drying of amino acid solutions.

    PubMed

    Zhang, Xuehua; Crivoi, Alexandru; Duan, Fei

    2015-01-01

    Experimental atomic force microscopy (AFM) images show the dried-in patterns from amino acid solutions which can be in the form of dots or networks. The three-dimensional lattice-gas Kinetic Monte Carlo (KMC) model is applied to simulate the formation of dot-like and network-like particle structures from the evaporating thin films of solutions. A sigmoidal jump in the chemical potential value is implemented to obtain dual-scale structures with the grain size distribution peaking at two distinctive values. The simulated and experimental results are qualitatively comparable. PMID:26039636

  19. Three-dimensional patterns from the thin-film drying of amino acid solutions

    PubMed Central

    Zhang, Xuehua; Crivoi, Alexandru; Duan, Fei

    2015-01-01

    Experimental atomic force microscopy (AFM) images show the dried-in patterns from amino acid solutions which can be in the form of dots or networks. The three-dimensional lattice-gas Kinetic Monte Carlo (KMC) model is applied to simulate the formation of dot-like and network-like particle structures from the evaporating thin films of solutions. A sigmoidal jump in the chemical potential value is implemented to obtain dual-scale structures with the grain size distribution peaking at two distinctive values. The simulated and experimental results are qualitatively comparable. PMID:26039636

  20. Electro-oxidation of methanol on Pt(111) in acid solutions: effects of electrolyte anions during electrocatalytic reactions

    NASA Astrophysics Data System (ADS)

    Ogasawara, Hirohito; Ito, Masatoki

    1995-10-01

    The electro-oxidation of methanol on a Pt(111) surface in both sulfuric and perchloric acid solutions was investigated by combined apparatus under both ultra-high vacuum and electrochemical environments. In sulfuric acid solution, a strong lateral interaction was observed between adsorbed bisulfate and CO derived from methanol. Coadsorption of CO derived from methanol with bisulfate ion yielded a (√7 × √7)-R19.1°-CO-bisulfate structure. In perchloric acid solution, however, no lateral interaction between adsorbed CO and perchlorate was seen. The difference in reaction rates of methanol oxidation in both solutions was explained by these specific anion adsorption effects.

  1. Plaque fluoride concentrations in a community without water fluoridation: effects of calcium and use of a fluoride or placebo dentifrice.

    PubMed

    Whitford, G M; Buzalaf, M A R; Bijella, M F B; Waller, J L

    2005-01-01

    The results of a recent study by Whitford et al. [Caries Res 2002;36:256-265] with subjects whose drinking water was fluoridated led to two major conclusions: (1) Compared to the use of a placebo dentifrice, plaque fluoride concentrations ([F]) throughout much of the day are not significantly increased by the use of an F dentifrice but (2) they are positively related to plaque [Ca] (p = 0.0001). The present double-blind, double-crossover study with 16 subjects used the same protocol and was done to: (1) determine the effects of the use of an F dentifrice on salivary and plaque [F] in a community without water fluoridation and (2) further examine the relationship between plaque [Ca] and [F]. Following the use of an F dentifrice or placebo for one week, whole saliva and plaque were collected 1.0 and 12 h after the last use of the products. The study was repeated to include rinsing with a 20 mmol/l CaCl(2) solution immediately before the use of the dentifrices. The CaCl(2) rinse had only minor effects on salivary [Ca] and [F] and none on the plaque concentrations. Unlike the results found in the fluoridated community, all salivary and plaque [F] associated with the use of the F dentifrice were significantly higher than those associated with the use of the placebo. The results suggest that the cariostatic effectiveness of an F dentifrice should be greater in areas without water fluoridation. As noted previously, plaque [F] were positively related to plaque [Ca] (p = 0.0001). PMID:15741721

  2. Color removal from acid and reactive dye solutions by electrocoagulation and electrocoagulation/adsorption processes.

    PubMed

    Bellebia, S; Kacha, S; Bouberka, Z; Bouyakoub, A Z; Derriche, Z

    2009-04-01

    In this study, electrocoagulation of Marine Blue Erionyl MR (acid dye) and electrocoagulation followed by adsorption of Brilliant Blue Levafix E-BRA (reactive dye) from aqueous solutions were investigated, using aluminum electrodes and granular activated carbon (GAC). In the electrocoagulation and adsorption of dyestuff solutions, the effects of current density, loading charge, pH, conductivity, stirring velocity, contact time, and GAC concentration were examined. The optimum conditions for the electrocoagulation process were identified as loading charges 7.46 and 1.49 F/m3, for a maximum abatement of 200 mg/L reactive and acid dye, respectively. The residual reactive dye concentration was completely removed with 700 mg/L GAC. The results of this investigation provide important data for the development of a combined process to remove significant concentrations of recalcitrant dyes from water, using moderate activated carbon energy and aluminum consumption, and thereby lowering the cost of treatment. PMID:19445327

  3. Uptake of formaldehyde by sulfuric acid solutions - Impact on stratospheric ozone

    NASA Technical Reports Server (NTRS)

    Tolbert, Margaret A.; Pfaff, Jeanne; Jayaweera, Indira; Prather, Michael J.

    1993-01-01

    The study investigates the uptake of CH2O by low temperature sulfuric acid solutions representative of global stratospheric particulate. It is argued that if similar uptake occurs under stratospheric pressures of CH2O, i.e., 1000 times lower than used in the present study, then the removal of CH2O from the gas phase can take away a significant source of odd hydrogen in the mid- and high-latitude lower stratosphere. It is shown that with the inclusion of this reaction, concentrations of OH and H2O are reduced by as much as 4 percent under background levels of aerosols and more than 15 percent under elevated (volcanic) conditions. The accumulation of CH2O in stratospheric aerosols over a season, reaching about 1 M solutions, will alter the composition and may even change the reactivity of these sulfuric acid-water mixtures.

  4. Evaluation of the Magnesium Hydroxide Treatment Process for Stabilizing PFP Plutonium/Nitric Acid Solutions

    SciTech Connect

    Gerber, Mark A.; Schmidt, Andrew J.; Delegard, Calvin H.; Silvers, Kurt L.; Baker, Aaron B.; Gano, Susan R.; Thornton, Brenda M.

    2000-09-28

    This document summarizes an evaluation of the magnesium hydroxide [Mg(OH)2] process to be used at the Hanford Plutonium Finishing Plant (PFP) for stabilizing plutonium/nitric acid solutions to meet the goal of stabilizing the plutonium in an oxide form suitable for storage under DOE-STD-3013-99. During the treatment process, nitric acid solutions bearing plutonium nitrate are neutralized with Mg(OH)2 in an air sparge reactor. The resulting slurry, containing plutonium hydroxide, is filtered and calcined. The process evaluation included a literature review and extensive laboratory- and bench-scale testing. The testing was conducted using cerium as a surrogate for plutonium to identify and quantify the effects of key processing variables on processing time (primarily neutralization and filtration time) and calcined product properties.

  5. Competitive adsorption of boric acid and chromate onto alumina in aqueous solutions.

    PubMed

    Demetriou, A; Pashalidis, I

    2014-01-01

    The competitive adsorption of boric acid and chromate from aqueous solutions by alumina has been investigated by spectrophotometry at pH 8, ionic strength = 0.0, 0.1 and 1.0 M NaClO4, T = 22 ± 3 °C and under normal atmospheric conditions. The experimental data show that addition of excess boric acid in the system leads to the increase of Cr(VI) concentration in solution, indicating the replacement of adsorbed chromate by boron on the alumina surface. Data evaluation results in the determination of the competition reaction constant and the formation constant of the Cr(VI) surface complexes, which are logKCr(VI)-B(III) = -3.5 ± 0.2 and logβ*Cr = 7.6 ± 0.3, respectively. PMID:24473309

  6. Separation of glycols from dilute aqueous solutions via complexation with boronic acids

    SciTech Connect

    Randel, L.A.; King, C.J.

    1991-07-01

    This work examines methods of separating low molecular weight glycols from dilute aqueous solution. Extraction into conventional solvents is generally not economical, since, in the literature reviewed, distribution ratios for the two- to four-carbon glycols are all less than one. Distribution ratios can be increased, however, by incorporating into the organic phase an extracting agent that will complex with the solute of interest. The extracting agent investigated in this work is 3-nitrophenylboronic acid (NPBA). NPBA, a boric acid derivative, reversibly complexes with many glycols. The literature on complexation of borate and related compounds with glycols, including mechanistic data, measurement techniques, and applications to separation processes, provides information valuable for designing experiments with NPBA and is reviewed herein. 88 refs., 15 figs., 24 tabs.

  7. Removal of transition metals from dilute aqueous solution by carboxylic acid group containing absorbent polymers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A new carboxylic acid group containing resin with cation exchange capacity, 12.67 meq/g has been used to remove Cu2+, Co2+ and Ni2+ ions from dilute aqueous solution. The resin has Cu2+, Co2+ and Ni2+ removal capacity, 216 mg/g, 154 mg/g and 180 mg/g, respectively. The selectivity of the resin to ...

  8. Shock wave synthesis of amino acids from solutions of ammonium formate and ammonium bicarbonate

    NASA Astrophysics Data System (ADS)

    Suzuki, Chizuka; Furukawa, Yoshihiro; Kobayashi, Takamichi; Sekine, Toshimori; Nakazawa, Hiromoto; Kakegawa, Takeshi

    2015-07-01

    The emergence of life's building blocks, such as amino acids and nucleobases, on the prebiotic Earth was a critical step for the beginning of life. Reduced species with low mass, such as ammonia, amines, or carboxylic acids, are potential precursors for these building blocks of life. These precursors may have been provided to the prebiotic ocean by carbonaceous chondrites and chemical reactions related to meteorite impacts on the early Earth. The impact of extraterrestrial objects on Earth occurred more frequently during this period than at present. Such impacts generated shock waves in the ocean, which have the potential to progress chemical reactions to form the building blocks of life from reduced species. To simulate shock-induced reactions in the prebiotic ocean, we conducted shock-recovery experiments on ammonium bicarbonate solution and ammonium formate solution at impact velocities ranging from 0.51 to 0.92 km/s. In the products from the ammonium formate solution, several amino acids (glycine, alanine, ß-alanine, and sarcosine) and aliphatic amines (methylamine, ethylamine, propylamine, and butylamine) were detected, although yields were less than 0.1 mol % of the formic acid reactant. From the ammonium bicarbonate solution, smaller amounts of glycine, methylamine, ethylamine, and propylamine were formed. The impact velocities used in this study represent minimum cases because natural meteorite impacts typically have higher velocities and longer durations. Our results therefore suggest that shock waves could have been involved in forming life's building blocks in the ocean of prebiotic Earth, and potentially in aquifers of other planets, satellites, and asteroids.

  9. Fluoride ion recognition by chelating and cationic boranes.

    PubMed

    Hudnall, Todd W; Chiu, Ching-Wen; Gabbaï, François P

    2009-02-17

    Because of the ubiquity of fluoride ions and their potential toxicity at high doses, researchers would like to design receptors that selectively detect this anion. Fluoride is found in drinking water, toothpaste, and osteoporosis drugs. In addition, fluoride ions also can be detected as an indicator of uranium enrichment (via hydrolysis of UF(6)) or of the chemical warfare agent sarin, which releases the ion upon hydrolysis. However, because of its high hydration enthalpy, the fluoride anion is one of the most challenging targets for anion recognition. Among the various recognition strategies that are available, researchers have focused a great deal of attention on Lewis acidic boron compounds. These molecules typically interact with fluoride anions to form the corresponding fluoroborate species. In the case of simple triarylboranes, the fluoroborates are formed in organic solvents but not in water. To overcome this limitation, this Account examines various methods we have pursued to increase the fluoride-binding properties of boron-based receptors. We first considered the use of bifunctional boranes, which chelate the fluoride anion, such as 1,8-diborylnaphthalenes or heteronuclear 1-boryl-8-mercurio-naphthalenes. In these molecules, the neighboring Lewis acidic atoms can cooperatively interact with the anionic guest. Although the fluoride binding constants of the bifunctional compounds exceed those of neutral monofunctional boranes by several orders of magnitude, the incompatibility of these systems with aqueous media limits their utility. More recently, we have examined simple triarylboranes whose ligands are decorated by cationic ammonium or phosphonium groups. These cationic groups increase the electrophilic character of these boranes, and unlike their neutral analogs, they are able to complex fluoride in aqueous media. We have also considered cationic boranes, which form chelate complexes with fluoride anions. Our work demonstrates that Coulombic and chelate

  10. Chemical durability of glaze on Zsolnay architectural ceramics (Budapest, Hungary) in acid solutions

    NASA Astrophysics Data System (ADS)

    Baricza, Ágnes; Bajnóczi, Bernadett; May, Zoltán; Tóth, Mária; Szabó, Csaba

    2015-04-01

    Zsolnay glazed architectural ceramics are among the most famous Hungarian ceramics, however, there is no profound knowledge about the deterioration of these building materials. The present study aims to reveal the influence of acidic solutions in the deterioration of Zsolnay ceramics. The studied ceramics are glazed roof tiles, which originate from two buildings in Budapest: one is located in the densely built-up city centre with high traffic rate and another one is in a city quarter with moderate traffic and more open space. The roof tiles represent the construction and the renovation periods of the buildings. The ceramics were mainly covered by lead glazes in the construction period and mainly alkali glazes in the renovation periods. The glaze of the tiles were coloured with iron (for yellow glaze) or chromium/copper/iron (for green glazes) in the case of the building located in the city centre, whereas cobalt was used as colorant and tin oxide as opacifier for the blue glaze of the ceramics of the other building. Six tiles were selected from each building. Sulphuric acid (H2SO4) solutions of pH2 and pH4 were used to measure the durability of the glazes up to 14 days at room temperature. The surfaces of the glazed ceramics after the treatment were measured by X-ray diffraction, Raman spectroscopy and SEM-EDS techniques to determine the precipitated phases on the surface of the glaze. Electron microprobe analysis was used to quantitatively characterise phases found and to determine the chemical composition of the treated glaze. The recovered sulphuric acid solutions were measured with ICP-OES technique in order to quantify the extent of the ion exchange between the glaze and the solutions. There is a significant difference in the dissolution rates in the treatments with sulphuric acid solutions of pH2 and pH4, respectively. The solution of pH2 induced greater ion exchange (approx. 7-10 times) from the glaze compared to the solution of pH4. Alkali and alkali earth

  11. Glucose metabolic flux distribution of Lactobacillus amylophilus during lactic acid production using kitchen waste saccharified solution

    PubMed Central

    Liu, Jianguo; Wang, Qunhui; Zou, Hui; Liu, Yingying; Wang, Juan; Gan, Kemin; Xiang, Juan

    2013-01-01

    The 13C isotope tracer method was used to investigate the glucose metabolic flux distribution and regulation in Lactobacillus amylophilus to improve lactic acid production using kitchen waste saccharified solution (KWSS). The results demonstrate that L. amylophilus is a homofermentative bacterium. In synthetic medium, 60.6% of the glucose entered the Embden–Meyerhof–Parnas (EMP) to produce lactic acid, whereas 36.4% of the glucose entered the pentose phosphate metabolic pathway (HMP). After solid–liquid separation of the KWSS, the addition of Fe3+ during fermentation enhanced the NADPH production efficiency and increased the NADH content. The flux to the EMP was also effectively increased. Compared with the control (60.6% flux to EMP without Fe3+ addition), the flux to the EMP with the addition of Fe3+ (74.3%) increased by 23.8%. In the subsequent pyruvate metabolism, Fe3+ also increased lactate dehydrogenase activity, and inhibited alcohol dehydrogenase, pyruvate dehydrogenase and pyruvate carboxylase, thereby increasing the lactic acid production to 9.03 g l−1, an increase of 8% compared with the control. All other organic acid by-products were lower than in the control. However, the addition of Zn2+ showed an opposite effect, decreasing the lactic acid production. In conclusion it is feasible and effective means using GC-MS, isotope experiment and MATLAB software to integrate research the metabolic flux distribution of lactic acid bacteria, and the results provide the theoretical foundation for similar metabolic flux distribution. PMID:23489617

  12. Adsorption of naphthalene from aqueous solution onto fatty acid modified walnut shells.

    PubMed

    Zhu, Mijia; Yao, Jun; Dong, Lifu; Sun, Jingjing

    2016-02-01

    The removal of polycyclic aromatic hydrocarbons (PAHs) from aqueous solution is challenging to environmental technologists. Agricultural waste is apparently the most attractive materials in removing PAHs because of its abundance, renewability, and economic advantage. The adsorption of PAHs (e.g., naphthalene) onto walnut shell (WNS) and its fatty acid (e.g., capric acid, lauric acid, palmitic acid, and oleic acid)-modified equivalent were investigated in this work to develop low-cost biosorbents for hydrophobic organic compounds. Compared with other modified sorbents, oleic acid graftted walnut shell (OWNS) showed the maximum partition coefficient (4330 ± 8.8 L kg(-1)) because of its lowest polarity and highest aromaticity. The adsorption capacity (7210 μg g(-1)) of OWNS at the temperature of 298 K was observed for an initial naphthalene concentration of 25 mg L(-1) with contact time of 40 h, sorbent dosage of 1 g L(-1), and in neutral condition. Furthermore, the regeneration capability of OWNS implied that it was a promising biosorbent for naphthalene removal. PMID:26517393

  13. Exceptionally crystalline and conducting acid doped polyaniline films by level surface assisted solution casting approach

    NASA Astrophysics Data System (ADS)

    Puthirath, Anand B.; Methattel Raman, Shijeesh; Varma, Sreekanth J.; Jayalekshmi, S.

    2016-04-01

    Emeraldine salt form of polyaniline (PANI) was synthesized by chemical oxidative polymerisation method using ammonium persulfate as oxidant. Resultant emeraldine salt form of PANI was dedoped using ammonia solution and then re-doped with camphor sulphonic acid (CSA), naphthaline sulphonic acid (NSA), hydrochloric acid (HCl), and m-cresol. Thin films of these doped PANI samples were deposited on glass substrates using solution casting method with m-cresol as solvent. A level surface was employed to get homogeneous thin films of uniform thickness. Detailed X-ray diffraction studies have shown that the films are exceptionally crystalline. The crystalline peaks observed in the XRD spectra can be indexed to simple monoclinic structure. FTIR and Raman spectroscopy studies provide convincing explanation for the exceptional crystallinity observed in these polymer films. FESEM and AFM images give better details of surface morphology of doped PANI films. The DC electrical conductivity of the samples was measured using four point probe technique. It is seen that the samples also exhibit quite high DC electrical conductivity, about 287 S/cm for CSA doped PANI, 67 S/cm for NSA doped PANI 65 S/cm for HCl doped PANI, and just below 1 S/cm for m-cresol doped PANI. Effect of using the level surface for solution casting is studied and correlated with the observed crystallinity.

  14. Health Effects Associated with Water Fluoridation.

    ERIC Educational Resources Information Center

    Richmond, Virginia L.

    1979-01-01

    Discussion is presented concerning fluoridation of water supplies. Correlation between fluoride in drinking water and improved dental health is reviewed. Relationship is expressed between fluoridation and reduced tooth decay. Use of fluoride in treating skeletal disorders is discussed. Author advocates fluoridating water supplies. (SA)

  15. Complexation of Plutonium (IV) with Fluoride at Variable Temperatures

    SciTech Connect

    Xia, Yuanxian; Rao, Linfeng; Friese, Judah I.; Moore, Dean A.; Bachelor, Paula P.

    2010-02-02

    The complexation of Pu(IV) with fluoride at elevated temperatures was studied by solvent extraction technique. A solution of NaBrO3 was used as holding oxidant to maintain the oxidation state of plutonium throughout the experiments. The distribution ratio of Pu(IV) between the organic and aqueous phases was found to decrease as the concentrations of fluoride were increased. Stability constants of the 1:1 and 1:2 Pu(IV)-F- complexes, dominant in the aqueous phase under the experimental conditions, were calculated from the effect of fluoride ions on the distribution ratio. The thermodynamic parameters, including enthalpy and entropy of complexation between Pu(IV) and fluoride at 25 degrees C - 55 degrees C were calculated from the stability constants at different temperatures by using the Van’t Hoff equation.

  16. Self-assembled polyaniline nanotubes grown from a polymeric acid solution

    NASA Astrophysics Data System (ADS)

    Zhang, Lijuan; Peng, Hui; Hsu, Chyong Fang; Kilmartin, Paul A.; Travas-Sejdic, Jadranka

    2007-03-01

    Polyaniline (PANI) nanotubes were obtained by a self-assembly process, from a solution containing poly(methyl vinyl ether-alt-maleic acid) (PMVEA) by oxidative polymerization using ammonium persulfate as the oxidant. The size of the nanotubes was greatly affected by the weight ratio of polymeric acid to aniline as measured by SEM images. The outer diameter of the nanotubes increased from 65 to 160 nm as the weight ratio of PMVEA to aniline increased from 1 to 4 wt/wt%. The structural features of the nanotubes were characterized by FTIR, XPS and EPR spectroscopies, which confirmed the presence of the polymeric acid in the PANI nanotubes and their electronic conductive nature. The electrochemical properties were further analysed using cyclic voltammetry.

  17. Thermosensitivity of bile acid-based oligo(ethylene glycol) stars in aqueous solutions.

    PubMed

    Strandman, Satu; Le Dévédec, Frantz; Zhu, X X

    2011-08-01

    Amphiphilic star-shaped oligo(ethylene glycol)s with a hydrophobic bile acid core and varying number of hydrophilic arms have been made. Their thermal behavior in aqueous solutions depends on the number rather than the length of the arms. The two-armed lithocholate derivative showed the strongest tendency for association and exhibited the lowest cloud point (79 °C) of the oligomers made, as well as another phase separation at a lower temperature (31 °C). The "double thermosensitivity" arising both from the salt-dependent LCST of the oligo(ethylene glycol) segments and the temperature-responsive self-assembly of amphiphilic bile acid derivative provides an interesting path in the design of bile acid-based smart materials. PMID:21661073

  18. The anodizing behavior of aluminum in malonic acid solution and morphology of the anodic films

    NASA Astrophysics Data System (ADS)

    Ren, Jianjun; Zuo, Yu

    2012-11-01

    The anodizing behavior of aluminum in malonic acid solution and morphology of the anodic films were studied. The voltage-time response for galvanostatic anodization of aluminum in malonic acid solution exhibits a conventional three-stage feature but the formation voltage is much higher. With the increase of electrolyte concentration, the electrolyte viscosity increases simultaneously and the high viscosity decreases the film growth rate. With the concentration increase of the malonic acid electrolyte, the critical current density that initiates local "burning" on the sample surface decreases. For malonic acid anodization, the field-assisted dissolution on the oxide surface is relatively weak and the nucleation of pores is more difficult, which results in greater barrier layer thickness and larger cell dimension. The embryo of the porous structure of anodic film has been created within the linear region of the first transient stage, and the definite porous structure has been established before the end of the first transient stage. The self-ordering behavior of the porous film is influenced by the electrolyte concentration, film thickness and the applied current density. Great current density not only improves the cell arrangement order but also brings about larger cell dimension.

  19. IMPACT OF FLUORIDE ON DENTAL HEALTH QUALITY

    PubMed Central

    Medjedovic, Eida; Medjedovic, Senad; Deljo, Dervis; Sukalo, Aziz

    2015-01-01

    Introduction: Fluoride is natural element that strengthens teeth and prevents their decay. Experts believe that the best way to prevent cavities is the use of fluoride from multiple sources. Studies even show that in some cases, fluoride can stop already started damage of the teeth. In children younger than 6 years fluoride is incorporated into the enamel of permanent teeth, making the teeth more resistant to the action of bacterial and acids in food. Goal: The aim of this study is to determine the effects of improving the health status of teeth after six months treatment with the use of topical fluoridation 0.5% NaF, and the level and quality of the impact of treatment with chemical 0.5% NaF on the dental health of children at age from 8 to 15 years, in relation to gender and chronological age. This study included school children aged 8 to 15 years who visited health and dental services dependent in Mostar. Results: It is obvious that after the implementation of treatment with 5% NaF by the method of topical fluoridation, health status of subjects from the experimental group significantly improved, so that at the final review 89.71% or 61 subjects of the experimental group had healthy (cured teeth), tooth with dental caries only 5.88% or 4 respondents tooth with dental caries and filling 4.41% or 3 respondents, extracted baby tooth 14.71% or 10 respondents, while for 13.24% of respondents was identified state with still unerupted teeth. Our findings are indirectly confirmed that the six-month treatment of fluoridation with 5% NaF, contributed to statistically significant improvement in overall oral health of the experimental group compared to the control group which was not treated by any dental treatment. Conclusion: It can be concluded that there is a statistically significant difference in the evaluated parameters of oral health of children in the control group compared to the studied parameters of oral health the experimental group of children at the final

  20. 21 CFR 175.270 - Poly(vinyl fluoride) resins.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...(vinyl fluoride) basic resins have an intrinsic viscosity of not less than 0.75 deciliter per gram as determined by ASTM method D1243-79, “Standard Test Method for Dilute Solution Viscosity of Vinyl Chloride... (ASTM method D1243-79, “Standard Test Method for Dilute Solution Viscosity of Vinyl Chloride...

  1. Properties of alkali-solubilized collagen solution crosslinked by N-hydroxysuccinimide activated adipic acid

    NASA Astrophysics Data System (ADS)

    Chen, Yihui; Zhang, Min; Liu, Wentao; Li, Guoying

    2011-03-01

    The effect of N-hydroxysuccinimide activated adipic acid (NHS-AA) on the properties of alkali-solubilized collagen solutions was examined. The residual amino group content in crosslinked collagen, determined by trinitrobenzensulfonic acid (TNBS) assay, was decreased with increasing NHS-AA concentration. The results from differential scanning calorimeter (DSC) indicated that the maximum denaturation temperature ( T d) of crosslinked collagen solution was about 4.2°C higher than that of un-crosslinked collagen solution (36.6°C). Moreover, the values of storage modulus ( G'), loss modulus ( G″) and complex viscosity ( η*), obtained by means of dynamic frequency sweeps, were increased as NHS-AA concentration added up to 1.5 mM, and then decreased slightly when further increased NHS-AA concentration. Besides, for collagen solution crosslinked with 1.5 mM NHS-AA, dynamic denaturation temperature ( T dd) was about 1.1°C lower than T d (40.8°C), and the Arrhenius-type time-temperature superposition (TTS) principle was applied to yield the activation energy to be 474.4 kJmol-1.

  2. Influence of D-Penicillamine on the Viscosity of Hyaluronic Acid Solutions

    NASA Astrophysics Data System (ADS)

    Liang, Jing; Krause, Wendy E.; Colby, Ralph H.

    2006-03-01

    Polyelectrolyte hyaluronic acid (HA, hyaluronan) is an important component in synovial fluid. Its presence results in highly viscoelastic solutions with excellent lubricating and shock-absorbing properties. In comparison to healthy synovial fluid, diseased fluid has a reduced viscosity. In osteoarthritis this reduction in viscosity results from a decline in both the molecular weight and concentration of hyaluronic acid HA. Initial results indicate that D-penicillamine affects the rheology of bovine synovial fluid, a model synovial fluid solution, and its components, including HA. In order to understand how D-penicillamine modifies the viscosity of these solutions, the rheological properties of sodium hyaluronate (NaHA) in phosphate-buffered saline (PBS) with D-penicillamine were studied as function of time, D-penicillamine concentration (0 -- 0.01 M), and storage conditions. Penicillamine has a complex, time dependent effect on the viscosity of NaHA solutions---reducing the zero shear rate viscosity of a 3 mg/mL NaHA in PBS by ca. 40% after 44 days.

  3. Dose rate dependence of the speciation of neptunium in irradiated solutions of nitric acid

    SciTech Connect

    Precek, M.; Paulenova, A.; Mincher, B.J.; Mezyk, S.P.

    2013-07-01

    The effects of radiation on the redox speciation of neptunium are of interest due to their impact on the performance of separation of neptunium from highly radioactive solutions of dissolved used nuclear fuel. In this study, the influence of dose rate change from 0.4 kGy/h to 6 kGy/h was examined during irradiation of solutions of initially hexavalent 2.0-2.5 mM neptunium in nitric acid of two different concentrations (0.5 and 1 M). Results indicate that the immediate radiolytic steady-state concentration of neptunium(V) were depressed and its initial radiolytic yield was up to 2-times lower (in 1 M HNO{sub 3} solutions)during irradiations with the higher dose rate. The finding is explained on the basis of the enhancement of the role of oxidizing radicals during the radiolytic process. (authors)

  4. Method for extracting lanthanides and actinides from acid solutions by modification of purex solvent

    DOEpatents

    Horwitz, E. Philip; Kalina, Dale G.

    1986-01-01

    A process for the recovery of actinide and lanthanide values from aqueous solutions with an extraction solution containing an organic extractant having the formula: ##STR1## where .phi. is phenyl, R.sup.1 is a straight or branched alkyl or alkoxyalkyl containing from 6 to 12 carbon atoms and R.sup.2 is an alkyl containing from 3 to 6 carbon atoms and phase modifiers in a water-immiscible hydrocarbon diluent. The addition of the extractant to the Purex process extractant, tri-n-butylphosphate in normal paraffin hydrocarbon diluent, will permit the extraction of multivalent lanthanide and actinide values from 0.1 to 12.0 molar acid solutions.

  5. Corrosion of some chromium-nickel steels and alloys in sulfuric acid solutions of sodium sulfite

    SciTech Connect

    Kopeliovich, D.K.; Glagolenko, Yu.V.; Ermolinskii, S.P.

    1988-05-01

    Steels 12Kh18N1OT and 10Kh17N13M3T and alloys 06KhN28MDT and 46KhNM were studied in sulfuric acid solutions containing sodium sulfite and sulfur dioxide to determine the effects of different concentrations of the corrosive constituents on the anodic and cathodic active and passive corrosion behavior of the metals. Polarization curves were obtained with a P-5827 M potentiostat. Addition of sulfite facilitated both electrode processes and the region of the reactive state was broadened due to the shift of passivation potentials to more positive values. The activating effect of sulfite reduction products were confirmed by tests of alloys in spent solutions. This increased likelihood of activation and the decrease of the solutions's own corrosion potential were both attributed to retardation of the cathodic process by lower valence sulfur compounds.

  6. Method for extracting lanthanides and actinides from acid solutions by modification of Purex solvent

    DOEpatents

    Horwitz, E.P.; Kalina, D.G.

    1986-03-04

    A process is described for the recovery of actinide and lanthanide values from aqueous solutions with an extraction solution containing an organic extractant having the formula as shown in a diagram where [phi] is phenyl, R[sup 1] is a straight or branched alkyl or alkoxyalkyl containing from 6 to 12 carbon atoms and R[sup 2] is an alkyl containing from 3 to 6 carbon atoms and phase modifiers in a water-immiscible hydrocarbon diluent. The addition of the extractant to the Purex process extractant, tri-n-butylphosphate in normal paraffin hydrocarbon diluent, will permit the extraction of multivalent lanthanide and actinide values from 0.1 to 12.0 molar acid solutions. 6 figs.

  7. Aqueous solutions of acidic ionic liquids for enhanced stability of polyoxometalate-carbon supercapacitor electrodes

    NASA Astrophysics Data System (ADS)

    Hu, Chenchen; Zhao, Enbo; Nitta, Naoki; Magasinski, Alexandre; Berdichevsky, Gene; Yushin, Gleb

    2016-09-01

    Nanocomposites based on polyoxometalates (POMs) nanoconfined in microporous carbons have been synthesized and used as electrodes for supercapacitors. The addition of the pseudocapacitance from highly reversible redox reaction of POMs to the electric double-layer capacitance of carbon lead to an increase in specific capacitance of ∼90% at 1 mV s-1. However, high solubility of POM in traditional aqueous electrolytes leads to rapid capacity fading. Here we demonstrate that the use of aqueous solutions of protic ionic liquids (P-IL) as electrolyte instead of aqueous sulfuric acid solutions offers an opportunity to significantly improve POM cycling stability. Virtually no degradation in capacitance was observed in POM-based positive electrode after 10,000 cycles in an asymmetric capacitor with P-IL aqueous electrolyte. As such, POM-based carbon composites may now present a viable solution for enhancing energy density of electrical double layer capacitors (EDLC) based on pure carbon electrodes.

  8. Complexation of U(VI) with 1-Hydroxyethane-1,1-diphosphonicAcid (HEDPA) in Acidic to Basic Solutions

    SciTech Connect

    Reed, W A; Rao, L; Zanonato, P; Garnov, A; Powell, B A; Nash, K L

    2007-01-24

    Complexation of U(VI) with 1-hydroxyethane-1,1-diphosphonic acid (HEDPA) in acidic to basic solutions has been studied with multiple techniques. A number of 1:1 (UO{sub 2}H{sub 3}L), 1:2 (UO{sub 2}H{sub j}L{sub 2} where j = 4, 3, 2, 1, 0 and -1) and 2:2 ((UO{sub 2}){sub 2}H{sub j}L{sub 2} where j = 1, 0 and -1) complexes form, but the 1:2 complexes are the major species in a wide pH range. Thermodynamic parameters (formation constants, enthalpy and entropy of complexation) were determined by potentiometry and calorimetry. Data indicate that the complexation of U(VI) with HEDPA is exothermic, favored by the enthalpy of complexation. This is in contrast to the complexation of U(VI) with dicarboxylic acids in which the enthalpy term usually is unfavorable. Results from electrospray ionization mass spectrometry (ESI-MS) and {sup 31}P NMR have confirmed the presence of 1:1, 1:2 and 2:2 U(VI)-HEDPA complexes.

  9. Influence of acidic and alkaline waste solution properties on uranium migration in subsurface sediments

    NASA Astrophysics Data System (ADS)

    Szecsody, Jim E.; Truex, Mike J.; Qafoku, Nikolla P.; Wellman, Dawn M.; Resch, Tom; Zhong, Lirong

    2013-08-01

    This study shows that acidic and alkaline wastes co-disposed with uranium into subsurface sediments have significant impact on changes in uranium retardation, concentration, and mass during downward migration. For uranium co-disposal with acidic wastes, significant rapid (i.e., hours) carbonate and slow (i.e., 100 s of hours) clay dissolution resulted, releasing significant sediment-associated uranium, but the extent of uranium release and mobility change was controlled by the acid mass added relative to the sediment proton adsorption capacity. Mineral dissolution in acidic solutions (pH 2) resulted in a rapid (< 10 h) increase in aqueous carbonate (with Ca2 +, Mg2 +) and phosphate and a slow (100 s of hours) increase in silica, Al3 +, and K+, likely from 2:1 clay dissolution. Infiltration of uranium with a strong acid resulted in significant shallow uranium mineral dissolution and deeper uranium precipitation (likely as phosphates and carbonates) with downward uranium migration of three times greater mass at a faster velocity relative to uranium infiltration in pH neutral groundwater. In contrast, mineral dissolution in an alkaline environment (pH 13) resulted in a rapid (< 10 h) increase in carbonate, followed by a slow (10 s to 100 s of hours) increase in silica concentration, likely from montmorillonite, muscovite, and kaolinite dissolution. Infiltration of uranium with a strong base resulted in not only uranium-silicate precipitation (presumed Na-boltwoodite) but also desorption of natural uranium on the sediment due to the high ionic strength solution, or 60% greater mass with greater retardation compared with groundwater. Overall, these results show that acidic or alkaline co-contaminant disposal with uranium can result in complex depth- and time-dependent changes in uranium dissolution/precipitation reactions and uranium sorption, which alter the uranium migration mass, concentration, and velocity.

  10. Influence of Acidic and Alkaline Waste Solution Properties on Uranium Migration in Subsurface Sediments

    SciTech Connect

    Szecsody, James E.; Truex, Michael J.; Qafoku, Nikolla; Wellman, Dawn M.; Resch, Charles T.; Zhong, Lirong

    2013-08-01

    This study shows that acidic and alkaline wastes co-disposed with uranium into subsurface sediments has significant impact on changes in uranium retardation, concentration, and mass during downward migration. For uranium co-disposal with acidic wastes, significant rapid (i.e., hours) carbonate and slow (i.e., 100s of hours) clay dissolution resulted, releasing significant sediment-associated uranium, but the extent of uranium release and mobility change was controlled by the acid mass added relative to the sediment proton adsorption capacity. Mineral dissolution in acidic solutions (pH 2) resulted in a rapid (< 10 h) increase in aqueous carbonate (with Ca2+, Mg2+) and phosphate and a slow (100s of hours) increase in silica, Al3+, and K+, likely from 2:1 clay dissolution. Infiltration of uranium with a strong acid resulted in significant shallow uranium mineral dissolution and deeper uranium precipitation (likely as phosphates and carbonates) with downward uranium migration of three times greater mass at a faster velocity relative to uranium infiltration in pH neutral groundwater. In contrast, mineral dissolution in an alkaline environment (pH 13) resulted in a rapid (< 10 h) increase in carbonate, followed by a slow (10s to 100s of hours) increase in silica concentration, likely from montmorillonite, muscovite, and kaolinite dissolution. Infiltration of uranium with a strong base resulted in uranium-silicate precipitation (presumed Na-boltwoodite) but also desorption of natural uranium on the sediment due to the high ionic strength solution, or 60% greater mass with greater retardation compared with groundwater. Overall, these results show that acidic or alkaline co-contaminant disposal with uranium can result in complex depth- and time-dependent changes in uranium dissolution/precipitation reactions and uranium sorption, which alter the uranium migration mass, concentration, and velocity.

  11. Silica precipitation in acidic solutions: mechanism, pH effect, and salt effect.

    PubMed

    Gorrepati, Elizabeth A; Wongthahan, Pattanapong; Raha, Sasanka; Fogler, H Scott

    2010-07-01

    This study is the first to show that silica precipitation under very acidic conditions ([HCl] = 2-8 M) proceeds through two distinct steps. First, the monomeric form of silica is quickly depleted from solution as it polymerizes to form primary particles approximately 5 nm in diameter. Second, the primary particles formed then flocculate. A modified Smoluchowski equation that incorporates a geometric population balance accurately describes the exponential growth of silica flocs. Variation of the HCl concentration between 2 and 8 M further showed that polymerization to form primary particles and subsequent particle flocculation become exponentially faster with increasing acid concentration. The effect of salt was also studied by adding 1 M chloride salts to the solutions; it was found that salts accelerated both particle formation and growth rates in the order: AlCl(3) > CaCl(2) > MgCl(2) > NaCl > CsCl > no salt. It was also found that ionic strength, over cation identity, determines silica polymerization and particle flocculation rates. This research reveals that precipitation of silica products from acid dissolution of minerals can be studied apart from the mineral dissolution process. Thus, silica product precipitation from mineral acidization follows a two-step process--formation of 5 nm primary particles followed by particle flocculation--which becomes exponentially faster with increasing HCl concentration and with salts accelerating the process in the above order. This result has implications for any study of acid dissolution of aluminosilicate or silicate material. In particular, the findings are applicable to the process of acidizing oil-containing rock formations, a common practice of the petroleum industry where silica dissolution products encounter a low-pH, salty environment within the oil well. PMID:20536253

  12. Influence of acidic and alkaline waste solution properties on uranium migration in subsurface sediments.

    PubMed

    Szecsody, Jim E; Truex, Mike J; Qafoku, Nikolla P; Wellman, Dawn M; Resch, Tom; Zhong, Lirong

    2013-08-01

    This study shows that acidic and alkaline wastes co-disposed with uranium into subsurface sediments have significant impact on changes in uranium retardation, concentration, and mass during downward migration. For uranium co-disposal with acidic wastes, significant rapid (i.e., hours) carbonate and slow (i.e., 100 s of hours) clay dissolution resulted, releasing significant sediment-associated uranium, but the extent of uranium release and mobility change was controlled by the acid mass added relative to the sediment proton adsorption capacity. Mineral dissolution in acidic solutions (pH2) resulted in a rapid (<10 h) increase in aqueous carbonate (with Ca(2+), Mg(2+)) and phosphate and a slow (100 s of hours) increase in silica, Al(3+), and K(+), likely from 2:1 clay dissolution. Infiltration of uranium with a strong acid resulted in significant shallow uranium mineral dissolution and deeper uranium precipitation (likely as phosphates and carbonates) with downward uranium migration of three times greater mass at a faster velocity relative to uranium infiltration in pH neutral groundwater. In contrast, mineral dissolution in an alkaline environment (pH13) resulted in a rapid (<10h) increase in carbonate, followed by a slow (10 s to 100 s of hours) increase in silica concentration, likely from montmorillonite, muscovite, and kaolinite dissolution. Infiltration of uranium with a strong base resulted in not only uranium-silicate precipitation (presumed Na-boltwoodite) but also desorption of natural uranium on the sediment due to the high ionic strength solution, or 60% greater mass with greater retardation compared with groundwater. Overall, these results show that acidic or alkaline co-contaminant disposal with uranium can result in complex depth- and time-dependent changes in uranium dissolution/precipitation reactions and uranium sorption, which alter the uranium migration mass, concentration, and velocity. PMID:23851265

  13. Effect of Organic Acid Additions on the General and Localized Corrosion Susceptibility of Alloy 22 in Chloride Solutions

    SciTech Connect

    Carranza, R M; Giordano, C M; Rodr?guez, M A; Ilevbare, G O; Rebak, R B

    2007-08-28

    Electrochemical studies such as cyclic potentiodynamic polarization (CPP) and electrochemical impedance spectroscopy (EIS) were performed to determine the corrosion behavior of Alloy 22 (N06022) in 1M NaCl solutions at various pH values from acidic to neutral at 90 C. All the tested material was wrought Mill Annealed (MA). Tests were also performed in NaCl solutions containing weak organic acids such as oxalic, acetic, citric and picric. Results show that the corrosion rate of Alloy 22 was significantly higher in solutions containing oxalic acid than in solutions of pure NaCl at the same pH. Citric and picric acids showed a slightly higher corrosion rate, and acetic acid maintained the corrosion rate of pure chloride solutions at the same pH. Organic acids revealed to be weak inhibitors for crevice corrosion. Higher concentration ratios, compared to nitrate ions, were needed to completely inhibit crevice corrosion in chloride solutions. Results are discussed considering acid dissociation constants, buffer capacity and complex formation constants of the different weak acids.

  14. Interfacial reactions and microstructure of BaTiO 3 films prepared using fluoride precursor method

    NASA Astrophysics Data System (ADS)

    Fujihara, Shinobu; Schneller, Theodor; Waser, Rainer

    2004-01-01

    Interfacial reactions of BaF 2 and TiO 2 were investigated in preparing BaTiO 3 thin films using a fluoride precursor method. Trifluoroacetate solutions were prepared from barium acetate, titanium tetraisopropoxide (TTIP), and trifluoroacetic acid (TFA, CF 3COOH) with additives such as water and acetylacetone. The solutions were deposited on platinized Si wafers by spin-coating, were pyrolysed at 400 °C in air and were finally heated typically at 700 °C in a water vapor atmosphere. The perovskite BaTiO 3 phase was obtained although a small portion of BaF 2 remained unreacted. Thus, the films were characterized as the mixture of BaTiO 3, BaF 2, and amorphous TiO 2. Influence of the solution chemistry on the phase evolution and microstructure was examined in order to discuss the reaction pathway of the perovskite phase.

  15. Protection of copper surface with phytic acid against corrosion in chloride solution.

    PubMed

    Peca, Dunja; Pihlar, Boris; Ingrid, Milošev

    2014-01-01

    Phytic acid (inositol hexaphosphate) was tested as a corrosion inhibitor for copper in 3% sodium chloride. Phytic acid is a natural compound derived from plants, it is not toxic and can be considered as a green inhibitor. Electrochemical methods of linear polarization and potentiodynamic polarization were used to study the electrochemical behaviour and evaluate the inhibition effectiveness. To obtain the optimal corrosion protection the following experimental conditions were investigated: effect of surface pre-treatment (abrasion and three procedures of surface roughening), pre-formation of the layer of phytic acid, time of immersion and concentration of phytic acid. To evaluate the surface pre-treatment procedures the surface roughness and contact angle were measured. Optimal conditions for formation of phytic layer were selected resulting in the inhibition effectiveness of nearly 80%. Morphology and composition of the layer were further studied by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The layer of phytic acid with thickness in the nanometer range homogeneously covers the copper surface. The obtained results show that this natural compound can be used as a mildly effective corrosion inhibitor for copper in chloride solution. PMID:25286201

  16. Solubility of HOBr in Acidic Solution and Implications for Liberation of Halogens Via Aerosol Processing

    NASA Technical Reports Server (NTRS)

    Iraci, Laura T.; Michelsen, R. R.; Rammer, T. A.; Ashbourn, S. F. M.

    2004-01-01

    Halogen species are known to catalytically destroy ozone in several regions of the atmosphere. In addition to direct catalytic losses, bromine compounds can indirectly enhance ozone loss through coupling to other radical families. Hypobromous acid (HOBr) is a key species in the linkage of BrOx to ClOx and HOx. The aqueous- phase coupling reaction HOBr + HCI (right arrow) BrCl + H2O may provide a pathway for chlorine activation on sulfate aerosols at temperatures warmer than those required for polar stratospheric cloud formation. We have measured t h e solubility of HOBr in 45 - 70 wt% sulfuric acid solutions. Over the temperature range 201 - 252 K, HOBr is quite soluble in sulfuric acid, H* = 10(exp 4) - 10(exp 7) mol dm(exp -3) atm(exp -1). The expected inverse dependence of H* on temperature was observed, but only a weak dependence on acidity was found. The solubility of HOBr is comparable to that of HBr, indicating that equilibrium concentrations of HOBr could equal or exceed those of HBr in upper tropospheric and lower stratospheric aerosols. Despite the high solubility of HOBr, aerosol volumes are not large enough to sequester a significant fraction of inorganic bromine from the gas phase. Our measurements of HOBr uptake in aqueous sulfuric acid in the presence of other brominated gases show the evolution of gaseous products including Br2O and Br2.

  17. Dissolution of nickel ferrite in aqueous solutions containing oxalic acid and ferrous salts

    SciTech Connect

    Figueroa, C.A.; Sileo, E.E.; Morando, P.J.; Blesa, M.A.

    2000-05-15

    The dissolution of nickel ferrite in oxalic acid and in ferrous oxalate-oxalic acid aqueous solution was studied. Nickel ferrite was synthesized by thermal decomposition of a mixed tartrate; the particles were shown to be coated with a thin ferric oxide layer. Dissolution takes place in two stages, the first one corresponding to the dissolution of the ferric oxide outer layer and the second one being the dissolution of Ni{sub 1.06}Fe{sub 1.96}O{sub 4}. The kinetics of dissolution during this first stage is typical of ferric oxides: in oxalic acid, both a ligand-assisted and a redox mechanism operates, whereas in the presence of ferrous ions, redox catalysis leads to a faster dissolution. The rate dependence on both oxalic acid and on ferrous ion is described by the Langmuir-Hinshelwood equation. In the second stage, Langmuir-Hinshelwood kinetics also describes the dissolution of iron and nickel from nickel ferrite. It may be concluded that oxalic acid operates to dissolve iron, and the ensuing disruption of the solid framework accelerates the release of nickel.

  18. Kinetic Study and Mathematical Model of Hemimorphite Dissolution in Low Sulfuric Acid Solution at High Temperature

    NASA Astrophysics Data System (ADS)

    Xu, Hongsheng; Wei, Chang; Li, Cunxiong; Deng, Zhigan; Li, Minting; Li, Xingbin

    2014-10-01

    The dissolution kinetics of hemimorphite with low sulfuric acid solution was investigated at high temperature. The dissolution rate of zinc was obtained as a function of dissolution time under the experimental conditions where the effects of sulfuric acid concentration, temperature, and particle size were studied. The results showed that zinc extraction increased with an increase in temperature and sulfuric acid concentration and with a decrease in particle size. A mathematical model able to describe the process kinetics was developed from the shrinking core model, considering the change of the sulfuric acid concentration during dissolution. It was found that the dissolution process followed a shrinking core model with "ash" layer diffusion as the main rate-controlling step. This finding was supported with a linear relationship between the apparent rate constant and the reciprocal of squared particle radius. The reaction order with respect to sulfuric acid concentration was determined to be 0.7993. The apparent activation energy for the dissolution process was determined to be 44.9 kJ/mol in the temperature range of 373 K to 413 K (100 °C to 140 °C). Based on the shrinking core model, the following equation was established:

  19. Water fluoridation and the environment: current perspective in the United States.

    PubMed

    Pollick, Howard F

    2004-01-01

    Evidence of water fluoridation's effects on plants, animals, and humans is considered based on reviews by scientific groups and individual communities, including Fort Collins, CO, Port Angeles, WA, and Tacoma-Pierce County, WA. The potential for corrosion of pipes and the use of fluoridation chemicals, particularly fluorosilicic acid, are considered, as is the debate about whether fluoridation increases lead in water, with the conclusion that there is no such increase. The arguments of anti-fluoridationists and fluoridation proponents are examined with respect to the politics of the issue. PMID:15473093

  20. Optimization of a Nafion Membrane-Based System for Removal of Chloride and Fluoride from Lunar Regolith-Derived Water

    NASA Technical Reports Server (NTRS)

    Anthony, Stephen M.; Santiago-Maldonado, Edgardo; Captain, James G.; Pawate, Ashtamurthy S.; Kenis, Paul J. A.

    2012-01-01

    A long-term human presence in space will require self-sustaining systems capable of producing oxygen and potable water from extraterrestrial sources. Oxygen can be extracted from lunar regolith, and water contaminated with hydrochloric and hydrofluoric acids is produced as an intermediate in this process. We investigated the ability of Nafion proton exchange membranes to remove hydrochloric and hydrofluoric acids from water. The effect of membrane thickness, product stream flow rate, and acid solution temperature and concentration on water flux, acid rejection, and water and acid activity were studied. The conditions that maximized water transport and acid rejection while minimizing resource usage were determined by calculating a figure of merit. Water permeation is highest at high solution temperature and product stream flow rate across thin membranes, while chloride and fluoride permeation are lowest at low acid solution temperature and concentration across thin membranes. The figure of merit varies depending on the starting acid concentration; at low concentration, the figure of merit is highest across a thin membrane, while at high concentration, the figure of merit is highest at low solution temperature. In all cases, the figure of merit increases with increasing product stream flow rate.