Fluoride Carrier Research Articles

Process optimization of a closed-chamber distillation system for the recovery of FLiNaK molten salt

Low-pressure distillation has been proposed as a suitable technique for the recovery of carrier salt from molten salt reactor spent fuel. A closed-chamber distillation system, in which the pump is stopped and pressure-induced salt distillation is performed, was arranged for fluoride salt treatment. A stair-step optimization process was demonstrated to improve the recovery efficiency by up to 99%. The pressure change curve was feasible for estimating the distillation process, and a method for displaying the pressure value online in order to determine the end-point was also developed. The decontamination factor of Nd in the condensate salt was deduced to be greater than 100 with 1 wt% NdF3–FLiNaK distillation. The optimal conditions developed in this study showed a high recovery ratio for the fluoride carrier salt and a high separation efficiency for rare earth products.

Al(III)-NTA-fluoride: a simple model system for Al-F binding with interesting thermodynamics.

Al(iii) complexes are extensively studied as [18F]fluoride carriers in positron emission tomography. However, our limited knowledge on their thermodynamic and kinetic properties has hindered efforts to easily prepare radiochemically pure compounds while simultaneously reducing the overall labeling time. Thus, to improve our understanding of fluoride binding to coordinatively unsaturated Al(iii) complexes, we investigated the ternary system Al(iii)-H3NTA-F- (H3NTA = nitrilo-triacetic acid) by NMR, potentiometry and X-ray diffraction. Our results show that the [Al(NTA)] complex binds two water molecules, which are replaced by fluorides. Individual species and isomers show separate 19F NMR signals and different stability constants. The two available positions on the [Al(NTA)] complex feature significantly different properties in terms of basicity of the coordinated water molecules and preferential binding of fluoride anions. Fluorides are effectively bound in weakly acidic or neutral solutions, whereas hydroxido species are preferentially formed in alkaline solutions. Our experimental observations were rationalized by theoretical calculations: predictions of the energy ordering of complexes and isomers, interpretation of 19F NMR chemical shifts, and natural bonding orbital analysis. Radiolabeling of [Al(NTA)] with [18F]fluoride gave low yields that confirmed a high affinity of the complex for hydroxide anions.

Study of thermodynamic properties of SrThF6(s) in SrF2-ThF4 system using solid state electrochemical cell method

The fission product strontium (Sr), after generation in the reactor due to fission of 233U, might exist as SrF2 in the molten fluoride medium of molten salt reactor (MSR) using fluoride carrier salts. The high temperature interactions between the strontium fluoride (SrF2) with the fertile fuel component and thorium fluoride (ThF4) leads to form single ternary compound SrThF6(s). The Gibbs energy of formation is the driving force for formation of any compound. In the present study, standard molar Gibbs energy of formation SrThF6(s) has been determined using an e.m.f. technique using CaF2(s) as solid electrolyte. Using the experimental thermodynamic data, to study the stability domain of SrThF6(s), the chemical potential diagram of Sr-Th-F-O system and ternary phase diagram of Sr-Th-F2 system have been calculated.

Maxillofacial Prosthetics.

The treatment of head and neck cancers requires a team approach. Maxillofacial prosthetics and oncologic dentistry are involved in many phases of the treatment. After the cancer ablation surgery, if surgical reconstruction cannot not completely restore the surgical defect site, maxillofacial prostheses plays an important role to rehabilitate the patient's mastication, swallowing, and speech. For patients undergoing chemoradiation therapy, the outcome is enhanced by jaw positioning stent and fluoride carrier mouthpiece. This perioperative care by maxillofacial prosthetics improves the posttreatment outcomes and the patient's quality of life.

Mass transfer and equilibrium characteristics of defluorination from groundwater by emulsion liquid membrane

AbstractBACKGROUNDThe defluorination of fluoride contaminated groundwater by emulsion liquid membrane using primary amine LK‐N21 as fluoride carrier and Span 80 as surfactant has been investigated.RESULTSThe purification process comprised preparation of W/O emulsion, extraction and demulsification operations. The transport mechanism of fluoride by emulsion liquid membrane using primary amine LK‐N21 as fluoride carrier was determined. The extraction conditions, i.e. surfactant and carrier concentration, type and concentration of precipitant, emulsification time and speed, volume ratio of internal phase to organic membrane phase, external phase pH and volume ratio of external phase to W/O emulsion for purification of the fluoride contaminated groundwater were studied.CONCLUSIONSThe treated natural groundwater samples finally were found to have been treated with high extraction efficiency, thus meeting the limiting values of the quality standard of class II for groundwater in China. Equilibrium extraction correlation was found to represent well the fluorine equilibrium relation in the emulsion membrane extraction system from the experimental data. Optimization of the purification conditions and system enabled realization of the practical defluorination needs for fluoride contaminated groundwater. © 2016 Society of Chemical Industry

Theoretical and NMR experimental insights on urea, thiourea and diindolyurea as fluoride carriers

Urea and thiourea derivatives are widely known as anion transporters. The pristine urea and thiourea compounds were theoretically and spectroscopically evaluated as fluoride ligands, since transportation of F− is involved in many biochemical processes and this anion is suitable to be analyzed through NMR. Conformational changes induced by anions can be useful to probe ligand-anion complexation, but urea and thiourea do not undergo conformational isomerization. Thus, diindolylurea (DIU) was computationally investigated to search for its conformational preferences upon complexation with fluoride. Overall, the NMR proton signal for urea and thiourea moved downfield and broadened upon addition of one equivalent of fluoride anion in DMSO solution, indicating complexation. The 19F signal for the thiourea-F- mixture also shifted relative to the anion source. However, a J(N)H,F coupling constant was not observed, probably because of entropy and bulk solvation effects. In addition, the conformational preference of DIU changed drastically after simulated complexation with fluoride, in agreement with previous studies with other anions. This confirms the potential of urea derivatives as fluoride carriers.

The in vitro effect of fluoridated milk in a bacterial biofilm--enamel model.

The purpose of this study was to investigate the effect of milk and fluoridated milk on bacterially induced caries-like lesions. Extracted impacted human molars were cut in half and covered with a varnish leaving a 4*4 mm window. The samples were coated with biofilm of S. sobrinus and were further divided into three experimental groups of S. sobrinus, S. sobrinus and milk and S. sobrinus and fluoridated milk. As negative controls served teeth incubated in saline. Of twenty tooth halves serial ground sections were cut through the lesions and investigated with polarization light microscopy (PLM) and scanning electron microscopy (SEM) and EDX element analysis. The PLM photographs were used for 3D reconstruction, volumetric assessment and determination of the extension of the lesion zones. Of eight tooth halves the biofilm on the enamel surface was studied with SEM and EDX element analysis. Volumetric assessment showed a statistically significant difference in the volume of the body of the lesion and the translucent zone between the milk group and fluoridated milk group. Quantitative element analysis demonstrated significant differences between sound enamel and the superficial layer in the fluoridated milk group. The biofilm on the enamel surface showed an increased Ca content in the milk group and fluoridated milk group. Milk as a common nutrient seems to play a complex role in in-vitro biofilm--enamel interactions stimulating bacterial demineralization on one hand, and, as effective fluoride carrier, inhibits caries-like demineralization.

Fluoride release from microporous poly(2-hydroxyethyl methacrylate) membranes

Fluoride ion is commonly used in the preventive treatment of tooth decay and when provided with extra fluoride, children living in regions that lack fluoride benefit from it. In the present study, the clinical properties of an intraoral controlled release fluoride delivery system were considered. Poly(2-hydroxyethyl methacrylate) (PHEMA) was examined as a fluoride carrier. Membranes were prepared by photopolymerization and then characterised. Contact angles and swelling ratios of fluoride-loaded membranes were determined. The surface morphology of the membranes were examined by using scanning electron microscopy. In vitro fluoride release studies were carried out in an artificial saliva medium. The concentration of fluoride was measured with a fluoride-specific electrode. The amount of released fluoride was determined and the effects of fluoride loading, medium pH and temperature on fluoride release were investigated. The swelling ratio of the PHEMA membrane was 58.5%, that of the fluoride-loaded PHEMA membrane was 17.8%. Increasing in the fluoride loading amount in the PHEMA membrane accelerated the fluoride release. The fluoride release ratio was increased with increasing pH and temperature.

Polyhydroxyethylmethacrylate/polyhydroxybutyrate composite membranes for fluoride release

AbstractControlled release technology is a recent technology which has considerable potential in the fields of medicine, pharmacy, and agriculture. Fluoride ion is commonly used in the preventive treatment of decay, and when provided with extra fluoride, children living in regions that lack fluoride benefit from it. For the present study, clinical properties of an intraoral controlled release fluoride delivery system were considered. The preparation of a controlled release membrane system is described. Polyhydroxyethylmethacrylate/polyhydroxybutyrate composite systems were examined as fluoride carriers. Polymeric membranes were prepared by photopolymerization and then characterized. Contact angles and swelling ratios of fluoride‐loaded membranes were determined. The surface morphology of the microporous membranes were examined by using scanning electron microscopy (SEM). In vitro fluoride release studies were carried out in an artificial saliva medium. The amount of released fluoride was determined and the effect of medium pH and temperature on fluoride release was investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 976–981, 2003

Single-cell analysis of bacteria by Raman microscopy: spectral information on the chemical composition of cells and on the heterogeneity in a culture

In the acetone–butanol (ABE) fermentation process, the utilised organisms from the group of the solventogenic Clostridia go through a complex cell-cycle. The role of different cell types in product formation is not understood in detail yet. We aim to use Raman spectroscopy to characterise the population distribution in Clostridium cultures. Cell suspensions were dried on calcium fluoride carriers. Raman spectra of single cells were obtained using a confocal Raman microscope (Dilor, Lille, France). The laser beam was focused on individual cells through the microscope objective. Spectra with good signal-to-noise ratio were obtained. Cells of different morphology, but also apparently similar cells, showed different spectra. Several cell components could be detected and varied in quantity. Compared to other methods for single-cell analysis, the new method is much more time-consuming to analyse one individual cell. However, a large amount of chemical information is obtained from each single cell in a non-destructive, non-invasive way. Raman microscopy appears to be a suitable method for studying population distributions in bacterial cultures.

Fabrication of a space-stippled vacuum-formed bleaching or fluoride carrier tray

The procedure allows for a selected area of the carrier tray to have a stippled surface to aid in concentration to exact areas for bleaching or fluoride treatments.

Control of water coolant in the maxillectomy patient

Water-cooled operative procedures can be performed under a rubber dam for the maxillectomy patient. However, the use of the rubber dam is limited when crown preparations are being done. Water spray often enters the exposed maxillary and nasal cavities despite high-speed evacuation during tooth preparation. Use of a polypropylene vacuum-formed base (Mouthguard Material, Buffalo Dental Mfg. Co., Inc., Syosset, N.Y.) can prevent this problem. This material is available in most maxillofacial clinics for making fluoride carriers. The partially edentulous maxillectomy patient shown in

Modified topical steroid therapy for the treatment of oral mucous membrane pemphigoid

A modified approach to the treatment of two patients with oral mucous membrane pemphigoid, using an adaptation of a custom fluoride carrier, is described. The method provided for occlusive topical steroid therapy, overcoming many of the obstacles to such treatment for oral lesions. Response was excellent, with no adverse local or systemic effects. Further clinical trials to determine the applicability of this form of therapy in the treatment of patients with a number of infectious, ulcerative, and vesiculobullous oral diseases appear warranted.

An investigation of the reaction mechanism of copper fluoride carriers in the spectrochemical determination of boron and silicon

The reaction mechanism by which copper (II) difluoride dihydrate and copper hydroxy fluoride increase the sensitivity of boron and silicon in emission spectrochemical analysis has been studied with the aid of thermal gravimetric analysis. Both compounds decompose at relatively low temperature with the evolution of hydrogen fluoride. It is shown that when boron and silicon are present as their oxides, they are volatilised from the system and their removal coincides with the evolution of hydrogen fluoride. This supports the proposal that the increased sensitivity achieved in spectrochemical analysis is a result of volatile fluoride formation.