Properties Of Fluoride Research Articles

The performance of calcined serpentine to simultaneously remove fluoride, iron and manganese

Abstract To solve the problem of high fluoride, iron and manganese concentrations in groundwater, serpentine (Srp) was modified by metal salt impregnation, acid–base activation and calcination, and the effects of these three modifications on the removal performance of Srp were compared. Specifically, the effects of the calcined serpentine (Csrp) dose, reaction time, pH, and temperature on the removal performance of F−, Fe2+ and Mn2+ on Csrp were analysed. An isothermal adsorption model and adsorption kinetic equation were established and confirmed through SEM, EDS, XRD and FTIR spectroscopy to analyse the mechanism of removing F−, Fe2+ and Mn2+ by Csrp. The results show that when 3 g/L Csrp was used to treat water samples with 5 mg/L F−, 20 mg/L Fe2+, and 5 mg/L Mn2+ (pH of 6, reaction temperature of 35 °C, and time of 150 min), the removal rates of F−, Fe2+, and Mn2+ were 94.3%, 99.0%, 98.9%, respectively. The adsorption of F−, Fe2+ and Mn2+ on Csrp follows the quasi-second-order kinetic equation and Langmuir isotherm adsorption model. After five cycles of regeneration of Csrp, Csrp can still maintain good properties of fluoride, iron and manganese removal.

Comparative Analysis of the Saturated Vapor Pressure of Halogenides of the Scandium Subgroup

Experimental values for saturated vapor pressure (Psat) of halides of the scandium subgroup are systematized for the purpose of analyzing and predicting unexplored Psat. Comparative calculations are used for analysis, making it possible to compare the sought Psat to basic values graphically (Psat for CaF2).. Generalized analytical expressions of the form $$\log P$$ −1/T for all halides of elements of the Sc subgroup and dependence $$\log P$$ − $$\log {{P}_{{{\text{Ca}}{{{\text{F}}}_{2}}}}}$$ at different temperatures are obtained using the least squares approach. Linear correlations of the form $$\log P$$ − $$\log {{P}_{{{\text{Ca}}{{{\text{F}}}_{2}}}}}$$ are used to estimate correctly unknown values Psat of halides of the subgroup Sc. The special position of scandium and fluorine in the subgroups of Mendeleev’s periodic table is confirmed by the considerable difference between the properties of fluorides and similar values for chlorides, bromides and iodides. It is shown that the properties of scandium halides differ from those of the corresponding lanthanum and yttrium halides, and the properties of fluorides differ sharply from those of chlorides, bromides, and iodides, which have close values. The possibility of estimating Psat for compounds of actinium and astatide is shown.

Optical and performance properties of fluoride and oxide films produced by vacuum evaporation

We discuss a range of issues related to optimization of industrial production processes used for deposition of metal fluoride and metal oxide films on optical components. We determine the optical and performance properties of films produced for commercially manufactured equipment via high-vacuum evaporation. We find that substrate temperature, vacuum chamber residual pressure, vacuum chamber working pressure, and ion source operating mode have an effect on these characteristics.

Influence of annealing temperature on optical properties of fluoride doped tin oxide films grown by the sol-gel spin-coating method

ABSTRACTFluoride-doped Tin Oxide (FTO) thin films were deposited on glass and silicon substrates by the sol-gel spin-coating method using stannic chloride pentahydrate (SnCl4·5H2O) and ammonium fluoride (NH4F) as starting precursors for Sn and F sources. As-deposited films were annealed at different temperatures ranging from 300–600°C. The effect of annealing temperature on structural and optical properties of FTO thin films including crystallinity, surface morphology, optical transparency, optical reflectivity and optical band gap are investigated by X-ray diffraction, scanning electron microscopy and UV-VIS spectrophotometry. The XRD results suggest that the prominent peak in the (110) orientation can be indexed to the polycrystalline SnO2 structure without any impurity phase caused by fluoride doping. The transmittance spectra of fluoride-doped tin oxide thin films show good transparency in the visible region with noticeable variation in its structural and optical reflectance properties depending on annealing temperature.

Properties of fluoride in wet phosphoric acid processes: Fluorosilicic acid in an aqueous solution of H2SiF6–H20 at temperatures ranging from 298.15 K to 353.15 K

The properties of fluoride in wet phosphoric acid processes were of interest us to understand the processes and roles that fluorosilicic acid plays in phosphoric acid solutions. The literature data indicate that some deficiencies exist in the thermodynamic properties of hexafluorosilicic acid aqueous solutions. In this investigation, the water activity and osmotic coefficients of H2SiF6(aq) were determined in the temperature range from T=298.15 to 353.15K. The measurements of the water activity were performed at molalities from 0.10 to 3.00molkg−1 of H2SiF6(aq) using the hygrometric method. The modelling approach based on the Pitzer model was developed to determine the thermodynamic properties. From these measurements, the ion interaction parameters in binary solution were evaluated at different temperatures ranging from 298.15K to 353.15K and were used to predict the solute activity coefficients. The development of a model for solution behaviour was also employed to determine the excess molal Gibbs energy, enthalpy, entropy and heat capacity of the H2SiF6 aqueous solution within the temperature range from 298.15K to 353.15K.

Enhancement of fluoride activity against Streptococcus mutans biofilms by a substance separated from Polygonum cuspidatum

Polygonum cuspidatum is a plant with spreading rhizomes and numerous reddish-brown stems that has been used in Korean folk medicine to improve oral hygiene. Nevertheless, there are no reports related to its possible effect on the virulence of dental biofilms. In this study, the ability of a fraction (F1) separated from P. cuspidatum, alone or in combination with fluoride, to disrupt virulence factors and the composition of Streptococcus mutans biofilms was examined. F1 was mainly composed of resveratrol, emodin and physcion (approximately 16.2%, 18.9% and 2.07% of the weight of F1, respectively). F1 showed inhibitory effects on acid production and F-ATPase activity of S. mutans in biofilms, and could enhance fluoride activity against acid production and acid tolerance of S. mutans in biofilms. When S. mutans biofilms were briefly treated with F1 (10 min, a total of five times), the biomass accumulation, water-insoluble polysaccharides and intracellular iodophilic polysaccharides were reduced. Furthermore, the fluoride activity against biomass accumulation was enhanced by F1. These results suggest that F1 may be useful in the control of dental biofilms and in improving the cariostatic properties of fluoride without increasing its exposure.

Microstructure and Electrical Properties of Fluorides Added PMNT Ceramics

The effect of fluorides (MgF2 + LiF [MLF] and CaF2 + LiF [CLF]) on microstructure and electrical properties of 0.68Pb(Mg1/3Nb2/3)O3–0.32PbTiO3 (PMNT) ceramic was investigated. The results showed that the MLF sample exhibits a typical liquid phase sintering character, and the fluorides added PMNT ceramics exhibits a typical relaxation character, which may be ascribed to the difference of ionic radius and fluorides addition. The values of d33 and Kp for sample MLF arrive to 583 pC/N and 55%, respectively, which are far lager than those of pure PMNT sample (326 pC/N and 46%) and CLF sample (54 pC/N).

Radiation-induced defects in Pr3+-activated Liyf4 laser host

Rare earth doped fluorides have been used in laser applications. Not much is known about the effect of ionizing radiation on the lasing and other properties of fluorides. Therefore, in recent years much attention has been paid to the study of radiation-induced defects in laser materials, as they affect the optical and stimulated emission properties. The defect formation by γ-ray irradiation in Pr3+ activated LiYF4, powder prepared by melt method, have been studied by thermoluminescence and electron spin resonance techniques and are reported in this paper. It is shown that LiYF4:Pr3+ is sensitive to γ-ray radiation. Characterization of this laser material using ESR and photoluminescence techniques is also described.

Effect of In-Vitro Fluoride Ion Treatment on the Mechanical Properties of Bone Tissue

Cortical bone tissue has been modeled as a short fiber reinforced composite material. It is composed of an organic matrix comprised mainly of Type I collagen reinforced by a mineral crystal similar to carbonated hydroxyapatite. We have developed an in-vitro ion treatment method to alter mechanical properties of the bone tissue using fluoride ion solutions. When bone is exposed to a high ionic strength fluoride solution, part of the bone mineral dissolves and precipitates as calcium fluoride. Changes in the mechanical properties such as, elastic modulus, ultimate stress and ultimate strain are dependent on the concentration and the pH of the treatment. Mechanical properties of fluoride treated (high ionic strength) bone tissue showed that elastic modulus, yield stress and ultimate stress are reduced in comparison to the controls. However ultimate strain increased considerably as compare to controls indicating that there might be a slippage between the bone mineral and the organic phase.

Luminescence of Eu3+ ions in LaF3 laser host

Rare earth doped fluorides have been used in laser applications. Not much is known about the effect of ionizing radiation on the lasing and other properties of fluorides. The colour centre formation by γ-ray irradiation in pure and Eu3+ doped LaF3, studied by thermoluminescence measurements, is reported in this paper. It is shown that LaF3:Eu3+ is less sensitive to γ-ray irradiation. Characterization of this laser material using XRD and photoluminescence techniques is described.

Fluorides and Silicofluorides as Extreme Pressure Additives in Lubricating Fluids for Titanium

The extreme pressure properties of fluorides and silicofluorides as lubricants for titanium were studied using the Falex tester. With water solution of sodium fluoride and water soluble metallic and nonmetallic silica-fluorides, jaw loads of 1500 lb were attained without welding. Use of ceramic blocks in the Falex tester showed the efficacy of the fluorides and silicofluorides in preventing excessive metal build up on the ceramic blocks, or excessive wearing away of the ceramic blocks. Sodium fluoride was superior to potassium or ammonium fluoride, and ammonium silicofluoride was the best of the silicofluorides when combined with sodium fluoride. Alkaline additives were not effective in reducing corrosion of steel and copper and also caused a considerable increase in wear on the titanium. Corrosion was controlled by a mixture of a high molecular weight imidazoline and a rosin amine ethylene oxide adduct and in the concentrations used extreme pressure properties were only slightly affected. Presented as an...