Removal of fluoride by thermally activated carbon prepared from neem (Azadirachta indica) and kikar (Acacia arabica) leaves.

PubMed

Kumar, Sunil; Gupta, Asha; Yadav, J P

2008-03-01

The present investigation deals with fluoride removal from aqueous solution by thermally activated neem (Azadirachta indica) leaves carbon (ANC) and thermally activated kikar (Acacia arabica) leaves carbon (AKC) adsorbents. In this study neem leaves carbon and kikar leaves carbon prepared by heating the leaves at 400 degrees C in electric furnace was found to be useful for the removal of fluoride. The adsorbents of 0.3 mm and 1.0 mm sizes of neem and kikar leaves carbon was prepared by standard sieve. Batch experiments done to see the fluoride removal properties from synthetic solution of 5 ppm to study the influence of pH, adsorbent dose and contact time on adsorption efficiency The optimum pH was found to be 6 for both adsorbents. The optimum dose was found to be 0.5g/100 ml forANC (activated neem leaves carbon) and 0.7g/100 ml forAKC (activated kikar leaves carbon). The optimum time was found to be one hour for both the adsorbent. It was also found that adsorbent size of 0.3 mm was more efficient than the 1.0 mm size. The adsorption process obeyed Freundlich adsorption isotherm. The straight line of log (qe-q) vs time at ambient temperature indicated the validity of langergren equation consequently first order nature of the process involved in the present study. Results indicate that besides intraparticle diffusion there maybe other processes controlling the rate which may be operating simultaneously. All optimized conditions were applied for removal of fluoride from four natural water samples.

Aluminium removal from water after defluoridation with the electrocoagulation process.

PubMed

Sinha, Richa; Mathur, Sanjay; Brighu, Urmila

2015-01-01

Fluoride is the most electronegative element and has a strong affinity for aluminium. Owing to this fact, most of the techniques used for fluoride removal utilized aluminium compounds, which results in high concentrations of aluminium in treated water. In the present paper, a new approach is presented to meet the WHO guideline for residual aluminium concentration as 0.2 mg/L. In the present work, the electrocoagulation (EC) process was used for fluoride removal. It was found that aluminium content in water increases with an increase in the energy input. Therefore, experiments were optimized for a minimum energy input to achieve the target value (0.7 mg/L) of fluoride in resultant water. These optimized sets were used for further investigations of aluminium control. The experimental investigations revealed that use of bentonite clay as coagulant in clariflocculation brings down the aluminium concentration of water below the WHO guideline. Bentonite dose of 2 g/L was found to be the best for efficient removal of aluminium.

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.

Removal of lead and fluoride from contaminated water using exhausted coffee grounds based bio-sorbent.

PubMed

Naga Babu, A; Reddy, D Srinivasa; Kumar, G Suresh; Ravindhranath, K; Krishna Mohan, G V

2018-07-15

Water pollution by industrial and anthropogenic actives has become a serious threat to the environment. World Health Organization (WHO) has identified that lead and fluoride amid the environmental pollutants are most poisonous water contaminants with devastating impact on the human race. The present work proposes a study on economical bio-adsorbent based technique using exhausted coffee grounds in the removal of lead and fluoride contaminants from water. The exhausted coffee grounds gathered from industrial wastes have been acid-activated and examined for their adsorption capacity. The surface morphology and elemental characterization of pre-and-post adsorption operations by FESEM, EDX and FTIR spectral analysis confirmed the potential of the exhausted coffee ground as successful bio-sorbent. However, thermodynamic analysis confirmed the adsorption to be spontaneous physisorption with Langmuir mode of homogenous monolayer deposition. The kinetics of adsorption is well defined by pseudo second order model for both lead and fluoride. A significant quantity of lead and fluoride is removed from the synthetic contaminated water by the proposed bio-sorbent with the respective sorption capabilities of 61.6 mg/g and 9.05 mg/g. However, the developed bio-sorbent is also recyclable and is capable of removing the lead and fluoride from the domestic and industrial waste-water sources with an overall removal efficiency of about 90%. Copyright © 2018 Elsevier Ltd. All rights reserved.

Isolation and identification of Trichoderma harzianum from groundwater: An effective biosorbent for defluoridation of groundwater.

PubMed

Koshle, Shalini; Mahesh, S; Swamy, S Nanjunda

2016-01-01

The ability of non-viable form of Trichoderma harzianum, isolated from fluoride rich groundwater, was investigated as biosorbent for defluoridation of groundwater. Biosorption experiments were carried out at laboratory scale for removal of fluoride from groundwater. Significant effect of operational parameters on fluoride biosorption using Trichoderma harzianum as biosorbent was evaluated by varying operational parameters such as: initial fluoride concentration (2-8 mgl(-1)), biosorbent dose (0.4-1.6g/100ml), groundwater pH (6-10), temperature (30-50 degrees C) and biosorption time (30-120 min). The fluoride adsorption isotherms were modeled by Langmuir and Freundlich isotherms. Our result showed that fluoride biosorption, significantly increased with increase in groundwater pH, biosorbent dose, temperature and biosorption time, whereas increase in initial fluoride concentration reduced fluoride removal. The fluoride biosorption was rapid and maximum fluoride uptake was attained with 1.6g 100ml(-1) biosorbent within 60 min. Optimal pH 10 and temperature 50 degrees C gave maximum defluoridation efficiency. Freundlich isotherm fits well for defluoridation of groundwater using Trichoderma harzianum as biosorbent which indicated that biosorbent surface sites were heterogeneous in nature and fitted into heterogeneous site binding model.

Practical considerations, column studies and natural organic material competition for fluoride removal with bone char and aluminum amended materials in the Main Ethiopian Rift Valley.

PubMed

Brunson, Laura R; Sabatini, David A

2014-08-01

The fluoride removal capacities of three materials, bone char (BC), aluminum oxide coated bone char (ACBC) and aluminum oxide impregnated wood char (AIWC), along with activated alumina (AA) as a baseline material, were investigated in batch and column studies, including comparison between synthetic and natural groundwater. Results suggest that in all cases the laboratory column results exhibited higher fluoride removal efficiency than the field studies conducted in the Ethiopian Rift Valley. Further studies indicate that the reduced effectiveness in the field was likely due to a combination of the high pH of groundwater (8.2) and the presence of competing ions (sulfate). Batch studies testing potential competition from natural organic material (NOM) showed no statistical evidence of NOM competition with BC and minor evidence of competition with ACBC and AIWC. To provide evidence for using Rapid Scale Small Column Test (RSSCT) principles for BC two different column volume and particle sizes were used. The results indicate that RSSCT scaling equations, developed for activated carbon, are applicable for BC removal of fluoride. These results thus provide valuable insights for translating laboratory results of novel sorbents for mitigating fluoride tainted groundwater in the field. Copyright © 2013 Elsevier B.V. All rights reserved.

Arsenic and fluoride contaminated groundwaters: A review of current technologies for contaminants removal.

PubMed

Jadhav, Sachin V; Bringas, Eugenio; Yadav, Ganapati D; Rathod, Virendra K; Ortiz, Inmaculada; Marathe, Kumudini V

2015-10-01

Chronic contamination of groundwaters by both arsenic (As) and fluoride (F) is frequently observed around the world, which has severely affected millions of people. Fluoride and As are introduced into groundwaters by several sources such as water-rock interactions, anthropogenic activities, and groundwater recharge. Coexistence of these pollutants can have adverse effects due to synergistic and/or antagonistic mechanisms leading to uncertain and complicated health effects, including cancer. Many developing countries are beset with the problem of F and As laden waters, with no affordable technologies to provide clean water supply. The technologies available for the simultaneous removal are akin to chemical treatment, adsorption and membrane processes. However, the presence of competing ions such as phosphate, silicate, nitrate, chloride, carbonate, and sulfate affect the removal efficiency. Highly efficient, low-cost and sustainable technology which could be used by rural populations is of utmost importance for simultaneous removal of both pollutants. This can be realized by using readily available low cost materials coupled with proper disposal units. Synthesis of inexpensive and highly selective nanoadsorbents or nanofunctionalized membranes is required along with encapsulation units to isolate the toxicant loaded materials to avoid their re-entry in aquifers. A vast number of reviews have been published periodically on removal of As or F alone. However, there is a dearth of literature on the simultaneous removal of both. This review critically analyzes this important issue and considers strategies for their removal and safe disposal. Copyright © 2015 Elsevier Ltd. All rights reserved.

Water defluoridation by aluminium oxide-manganese oxide composite material.

PubMed

Alemu, Sheta; Mulugeta, Eyobel; Zewge, Feleke; Chandravanshi, Bhagwan Singh

2014-08-01

In this study, aluminium oxide-manganese oxide (AOMO) composite material was synthesized, characterized, and tested for fluoride removal in batch experiments. AOMO was prepared from manganese(II) chloride and aluminium hydroxide. The surface area of AOMO was found to be 30.7m2/g and its specific density was determined as 2.78 g/cm3. Detailed investigation of the adsorbent by inductively coupled plasma-optical emission spectrometry, inductively coupled plasma-mass spectrometry, and ion chromatography (for sulphate only) showed that it is composed of Al, Mn, SO4, and Na as major components and Fe, Si, Ca, and Mg as minor components. Thermogravimetric analysis was used to study the thermal behaviour of AOMO. X-ray diffraction analysis showed that the adsorbent is poorly crystalline. The point of zero charge was determined as 9.54. Batch experiments (by varying the proportion of MnO, adsorbent dose, contact time, initial F concentration, and raw water pH) showed that fluoride removal efficiency ofAOMO varied significantly with percentage of MnO with an optimum value of about I11% of manganese oxide in the adsorbent. The optimum dose of the adsorbent was 4 g/L which corresponds to the equilibrium adsorption capacity of 4.8 mg F-/g. Both the removal efficiency and adsorption capacity showed an increasing trend with an increase in initial fluoride concentration of the water. The pH for optimum fluoride removal was found to be in the range between 5 and 7. The adsorption data were analysed using the Freundlich, Langmuir, and Dubinirn-Radushkevich models. The minimum adsorption capacity obtained from the non-linear Freundlich isotherm model was 4.94 mg F-/g and the maximum capacity from the Langmuir isotherm method was 19.2mg F-/g. The experimental data of fluoride adsorption on AOMO fitted well to the Freundlich isotherm model. Kinetic studies showed that the adsorption is well described by a non-linear pseudo-second-order reaction model with an average rate constant of 3.1 x 10(-2) g/min mg. It is concluded that AOMO is a highly promising adsorbent for the removal of excess fluoride from drinking water.

Design Manual: Removal of Fluoride from Drinking Water ...

EPA Pesticide Factsheets

This document is an updated version of the Design Manual: Removal of Fluoride from Drinking Water Supplies by Activated Alumina (Rubel, 1984). The manual is an in-depth presentation of the steps required to design and operate a fluoride removal plant using activated alumina (AA), which is a reliable and cost-effective process for treating excess fluoride from drinking water supplies. Design Manual on removing fluoride from drinking water to support the fluoride MCL - manual

Design and development of sustainable remediation process for mitigation of fluoride contamination in ground water and field application for domestic use.

PubMed

Gwala, Poonam; Andey, Subhash; Nagarnaik, Pranav; Ghosh, Sarika Pimpalkar; Pal, Prashant; Deshmukh, Prashant; Labhasetwar, Pawan

2014-08-01

Decentralised household chemo defluoridation unit (CDU) was developed and designed based on a combination of coagulation and sorption processes. Chemo-defluoridation process was optimised to reduce use of chemicals and increase acceptability among beneficiaries without affecting palatability of water. Chemical dose optimization undertaken in the laboratory using jar test revealed the optimum calcium salt to initial fluoride ratio of 60 for fluoride removal. Performance of CDU was evaluated in the laboratory for removal efficiency, water quality parameters, filter bed cleaning cycle and desorption of fluoride. CDU evaluation in the laboratory with spiked water (5 mg/L) and field water (~4.2 mg/L) revealed treated water fluoride concentration of less than 1mg/L. Seventy five CDUs were installed in households at Sakhara Village, Yavatmal District in Maharashtra State of India. Monthly monitoring of CDUs for one year indicated reduction of the raw water fluoride concentration from around 4 mg/L to less than 1mg/L. Post implementation survey after regular consumption of treated drinking water by the users for one year indicated user satisfaction and technological sustainability. Copyright © 2014 Elsevier B.V. All rights reserved.

Removal of fluoride, SDS, ammonia and turbidity from semiconductor wastewater by combined electrocoagulation-electroflotation.

PubMed

Aoudj, S; Khelifa, A; Drouiche, N

2017-08-01

Semiconductor industry effluents contain organic and inorganic pollutants, such as sodium dodecyl sulfate (SDS), fluoride and ammonia, at high levels which consists a major environmental issue. A combined EC-EF process is proposed as a post-treatment after precipitation for simultaneous clarification and removal of pollutants. In EC step, a hybrid Fe-Al was used as the soluble anode in order to avoid supplementary EC step. EC-Fe is more suitable for SDS removal; EC-Al is more suitable for fluoride removal, while EC with hybrid Al-Fe makes a good compromise. Clarification and ammonia oxidation were achieved in the EF step. Effects of anodic material, initial pH, current, anion nature, chloride concentration and initial pollutant concentration were studied. The final concentrations may reach 0.27, 6.23 and 0.22 mg L -1 for SDS, fluoride and ammonia respectively. These concentrations are far lower than the correspondent discharge limits. Similarly, the final turbidity was found 4.35 NTU which is lower than 5NTU and the treated water does not need further filtration before discharge. Furthermore, the EC-EF process proves to be sufficiently energy-efficient with less soluble electrode consumption. Copyright © 2017 Elsevier Ltd. All rights reserved.

Removal of phosphorus, fluoride and metals from a gypsum mining leachate using steel slag filters.

PubMed

Claveau-Mallet, Dominique; Wallace, Scott; Comeau, Yves

2013-03-15

The objective of this work was to evaluate the capacity of steel slag filters to treat a gypsum mining leachate containing 11-107 mg P/L ortho-phosphates, 9-37 mg/L fluoride, 0.24-0.83 mg/L manganese, 0.20-3.3 zinc and 1.7-8.2 mg/L aluminum. Column tests fed with reconstituted leachates were conducted for 145-222 days and sampled twice a week. Two types of electric arc furnace (EAF) slags and three filter sequences were tested. The voids hydraulic retention time (HRT(v)) of columns ranged between 4.3 and 19.2 h. Precipitates of contaminants present in columns were sampled and analyzed with X-ray diffraction at the end of tests. The best removal efficiencies over a period of 179 days were obtained with sequential filters that were composed of Fort Smith EAF slag operated at a total HRT(v) of 34 h which removed 99.9% of phosphorus, 85.3% of fluoride, 98.0% of manganese and 99.3% of zinc. Mean concentration at this system's effluent was 0.04 mg P/L ortho-phosphates, 4 mg/L fluoride, 0.02 mg/L manganese, 0.02 zinc and 0.5 mg/L aluminum. Thus, slag filters are promising passive and economical systems for the remediation of mining effluents. Phosphorus was removed by the formation of apatite (hydroxyapatite, Ca(5)(PO(4))(3)OH or fluoroapatite, Ca(5)(PO(4))(3)F) as confirmed by visual and X-ray diffraction analyses. The growth rate of apatite was favored by a high phosphorus concentration. Calcite crystals were present in columns and appeared to be competing for calcium and volume needed for apatite formation. The calcite crystal growth rate was higher than that of apatite crystals. Fluoride was removed by precipitation of fluoroapatite and its removal was favored by a high ratio of phosphorus to fluoride in the wastewater. Copyright © 2012 Elsevier Ltd. All rights reserved.

Characterisation of a new adsorbent (beta cyclodextrin modified hybrid hydrous iron-zirconium oxide) to remove fluoride from aqueous solution

NASA Astrophysics Data System (ADS)

Saha, Indranil

2017-04-01

Prolonged use of fluoride contaminated water (>1.5mg L-1) causes serious problems to public health and ultimately leads to skeletal fluorosis. There is an urgent need to develop more efficient fluoride scavenging materials for designing water filters. A simple and efficient adsorbent (CHIZO, beta-Cyclodextrin (b-CD) amended hydrous iron-zirconium hybrid oxide), has been developed, characterised and tested. The results indicate the efficacy of CHIZO on fluoride removal from an aqueous solution. The agglomerated micro structured composite material has several new features such as very poor crystallinity confirmed from TEM images. BET experiment reveals a surface area of 0.2070 m2 g-1 and pore volume of 0.0476 cm3 g-1. The findings also indicate the highly pH dependent fluoride adsorption by CHIZO which decreases with an increase in pH, and pseudo-second order kinetics control the reaction.Isotherm study indicates Langmuir isotherm was the best fit model to describe the adsorption equilibrium. Significantly higher monolayer adsorption capacity of fluoride (31.35 mg g-1) than the host hydrous Fe-Zr oxide (8.21 mg g-1) at pH 7.0 and 303 K was observed. Thermodynamic parameter indicates spontaneous nature of CHIZO which is due to the exothermic nature of the reaction. Apart from this phosphate and sulphate have some impact (interference) on fluoride adsorption. b-CD forms inclusion complexes by taking up fluoride ions from water into its central cavity. Several factors are involved regarding high efficacy of the system such as the release of enthalpy-rich water molecules from its cavity, electrostatic interactions, hydrogen bonding and release of conformational strain. However, the regeneration is difficult because of probable entrapping of fluoride inside the cavity of b-CD with hydrogen bonding. It has been found that only 0.9 g of CHIZO is able to reduce the fluoride level to below 1.0 mg L-1 in one-litre of fluoride spiked (5.0 mg L-1) natural water sample. The study highlights the potentiality of the developed adsorbent. Examples are high adsorption capacity and economical viability.

Fluoride removal in water by a hybrid adsorbent lanthanum-carbon.

PubMed

Vences-Alvarez, Esmeralda; Velazquez-Jimenez, Litza Halla; Chazaro-Ruiz, Luis Felipe; Diaz-Flores, Paola E; Rangel-Mendez, Jose Rene

2015-10-01

Various health problems associated with drinking water containing high fluoride levels, have motivated researchers to develop more efficient adsorbents to remove fluoride from water for beneficial concentrations to human health. The objective of this research was to anchor lanthanum oxyhydroxides on a commercial granular activated carbon (GAC) to remove fluoride from water considering the effect of the solution pH, and the presence of co-existing anions and organic matter. The activated carbon was modified with lanthanum oxyhydroxides by impregnation. SEM and XRD were performed in order to determine the crystal structure and morphology of the La(III) particles anchored on the GAC surface. FT-IR and pK(a)'s distribution were determined in order to elucidate both the possible mechanism of the lanthanum anchorage on the activated carbon surface and the fluoride adsorption mechanism on the modified material. The results showed that lanthanum ions prefer binding to carboxyl and phenolic groups on the activated carbon surface. Potentiometric titrations revealed that the modified carbon (GAC-La) possesses positive charge at a pH lower than 9. The adsorption capacity of the modified GAC increased five times in contrast to an unmodified GAC adsorption capacity at an initial F(-) concentration of 20 mg L(-1). Moreover, the presence of co-existing anions had no effect on the fluoride adsorption capacity at concentrations below 30 mg L(-1), that indicated high F(-) affinity by the modified adsorbent material (GAG-La). Copyright © 2015 Elsevier Inc. All rights reserved.

Application of response surface methodology for optimization of biosorption of fluoride from groundwater using Shorea robusta flower petal

NASA Astrophysics Data System (ADS)

Biswas, G.; Kumari, M.; Adhikari, K.; Dutta, S.

2017-12-01

Fluoride pollution in groundwater is a major concern in rural areas. The flower petal of Shorea robusta, commonly known as sal tree, is used in the present study both in its native form and Ca-impregnated activated form to eradicate excess fluoride from simulated wastewater. Response surface methodology (RSM) was used for experimental designing and analyzing optimum condition for carbonization vis-à-vis calcium impregnation for preparation of adsorbent. During carbonization, temperature, time and weight ratio of calcium chloride to sal flower petal (SFP) have been considered as input factors and percentage removal of fluoride as response. Optimum condition for carbonization has been obtained as temperature, 500 °C; time, 1 h and weight ratio, 2.5 and the sample prepared has been termed as calcium-impregnated carbonized sal flower petal (CCSFP). Optimum condition as analyzed by one-factor-at-a-time (OFAT) method is initial fluoride concentration, 2.91 mg/L; pH 3 and adsorbent dose, 4 g/L. CCSFP shows maximum removal of 98.5% at this condition. RSM has also been used for finding out optimum condition for defluoridation considering initial concentration, pH and adsorbent dose as input parameters. The optimum condition as analyzed by RSM is: initial concentration, 5 mg/L; pH 3.5 and adsorbent dose, 2 g/L. Kinetic and equilibrium data follow Ho pseudo-second-order kinetic model and Freundlich isotherm model, respectively. Adsorption capacity of CCSFP has been found to be 5.465 mg/g. At optimized condition, CCSFP has been found to remove fluoride (80.4%) efficiently from groundwater collected from Bankura district in West Bengal, a fluoride-contaminated province in India.

Removing Fluoride Ions with Continously Fed Activated Alumina.

ERIC Educational Resources Information Center

Wu, Yeun C.; Itemaking, Isara Cholapranee

1979-01-01

Discussed is the mathematical basis for determining fluoride removal during water treatment with activated alumina. The study indicates that decreasing particle size decreases the pore diffusion effect and increases fluoride removal. (AS)

Acoustic cavitation induced synthesis of zirconium impregnated activated carbon for effective fluoride scavenging from water by adsorption.

PubMed

Mullick, Aditi; Neogi, Sudarsan

2018-07-01

Environmental concern associated with the side effects of high fluoride content in ground water and surface water has prompted the researchers to look for an efficient, convenient and easy method. Considering the potential of a good adsorbent, present study reports the synthesis of a composite by impregnating zirconium on powdered activated carbon (AC) using ultrasound as the tool for synthesis and applying it for fluoride adsorption from water. The nature of the composite was determined through characterization by scanning electron microscopy (SEM), energy dispersive Xray (EDX), Xray diffraction (XRD), N 2 adsorption analysis (BET) and Fourier Transform Infrared Spectroscopy (FTIR) analysis. The pH pzc (point of zero charge) of the adsorbent was found to be 5.03; with the optimum pH obtained at 4 for adsorption of strong electronegative fluoride ions. The initial fluoride concentration was varied from 2.5 up to 20 mg.L -1 and the maximum adsorption capacity of 5 mg.g -1 was obtained. A maximum fluoride removal of 94.4% was obtained for an initial concentration of 2.5 mg.L -1 within an equilibrium time of 180 min. The adsorption isotherm followed the Langmuir isotherm model indicating a monolayer adsorption process and the adsorption kinetics followed pseudo second order model. The effects of various coexisting ions (HCO 3 - , NO 3 - , SO 4 2- , Cl - ) commonly present in the water were found to have negligible impact on the process performance. Conducting the adsorption-desorption studies for five consecutive cycles for an initial fluoride concentration of 10 mg.L -1 , the removal efficiency reduced from 86.2 to 32.6%. The ultrasonic method provided an easy route to synthesize the composite in less time and significantly reduced energy consumption by more than 96% compared to the conventional method. Copyright © 2018 Elsevier B.V. All rights reserved.

Comparison of Fluoridated Miswak and Toothbrushing with Fluoridated Toothpaste on Plaque Removal and Fluoride Release.

PubMed

Baeshen, Hosam; Salahuddin, Sabin; Dam, Robel; Zawawi, Khalid H; Birkhed, Dowen

2017-04-01

Dental caries and periodontal diseases are all induced by oral biofilm (dental plaque). This study was conducted to evaluate if fluoride-impregnated miswak is as effective in plaque removal and fluoride release as toothbrushing with fluoride toothpaste. This single-blind, randomized, crossover study was conducted at the Department of Cariology, University of Gothenburg, Gothenburg, Sweden, from February 2010 to January 2011. Fifteen healthy subjects participated in this study. The participants were instructed to use the following: (1) 0.5% NaF-impregnated miswak, (2) nonfluoridated miswak, (3) toothbrush with nonfluoride toothpaste, and (4) toothbrush with 1450 ppm fluoride toothpaste. Each method was used twice a day for 1 week after which plaque amount and fluoride concentration in resting saliva were measured. There was a 1-week washout period between each method. No significant difference between miswak and tooth-brushing was found regarding plaque removal on buccal and lingual surfaces. A somewhat higher fluoride concentration in resting saliva was found after using impregnated miswak when compared with toothbrushing with fluoride toothpaste (p < 0.05). Miswak and toothbrushing showed the same plaque removing effect on buccal and lingual surfaces. Miswak impregnated with 0.5% NaF resulted in a higher concentration of fluoride in saliva than brushing with 1450 ppm fluoride toothpaste. Miswak impregnated with 0.5% NaF and toothbrushing results in comparable plaque removal and about the same fluoride concentration in saliva even it was somewhat higher for impregnated miswak.

An Experimental Test Facility to Support Development of the Fluoride Salt Cooled High Temperature Reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoder Jr, Graydon L; Aaron, Adam M; Cunningham, Richard Burns

2014-01-01

The need for high-temperature (greater than 600 C) energy exchange and delivery systems is significantly increasing as the world strives to improve energy efficiency and develop alternatives to petroleum-based fuels. Liquid fluoride salts are one of the few energy transport fluids that have the capability of operating at high temperatures in combination with low system pressures. The Fluoride Salt-Cooled High-Temperature Reactor design uses fluoride salt to remove core heat and interface with a power conversion system. Although a significant amount of experimentation has been performed with these salts, specific aspects of this reactor concept will require experimental confirmation during themore » development process. The experimental facility described here has been constructed to support the development of the Fluoride Salt Cooled High Temperature Reactor concept. The facility is capable of operating at up to 700 C and incorporates a centrifugal pump to circulate FLiNaK salt through a removable test section. A unique inductive heating technique is used to apply heat to the test section, allowing heat transfer testing to be performed. An air-cooled heat exchanger removes added heat. Supporting loop infrastructure includes a pressure control system; trace heating system; and a complement of instrumentation to measure salt flow, temperatures, and pressures around the loop. The initial experiment is aimed at measuring fluoride salt heat transfer inside a heated pebble bed similar to that used for the core of the pebble bed advanced high-temperature reactor. This document describes the details of the loop design, auxiliary systems used to support the facility, the inductive heating system, and facility capabilities.« less

Design Manual: Removal of Fluoride from Drinking Water Supplies by Activated Alumina

EPA Science Inventory

This document is an updated version of the Design Manual: Removal of Fluoride from Drinking Water Supplies by Activated Alumina (Rubel, 1984). The manual is an in-depth presentation of the steps required to design and operate a fluoride removal plant using activated alumina (AA)...

Adsorption process of fluoride from drinking water with magnetic core-shell Ce-Ti@Fe3O4 and Ce-Ti oxide nanoparticles.

PubMed

Abo Markeb, Ahmad; Alonso, Amanda; Sánchez, Antoni; Font, Xavier

2017-11-15

Synthesized magnetic core-shell Ce-Ti@Fe 3 O 4 nanoparticles were tested, as an adsorbent, for fluoride removal and the adsorption studies were optimized. Adsorption capacity was compared with the synthesized Ce-Ti oxide nanoparticles. The adsorption equilibrium for the Ce-Ti@Fe 3 O 4 adsorbent was found to occur in <15min and it was demonstrated to be stable and efficient in a wide pH range of 5-11 with high fluoride removal efficiency over 80% of all cases. Furthermore, isotherm data were fitted using Langmuir and Freundlich models, and the adsorption capacities resulted in 44.37 and 91.04mg/g, at pH7, for Ce-Ti oxides and Ce-Ti@Fe 3 O 4 nanoparticles, respectively. The physical sorption mechanism was estimated using the Dubinin-Radushkevich model. An anionic exchange process between the OH - group on the surface of the Ce-Ti@Fe 3 O 4 nanomaterial and the F - was involved in the adsorption. Moreover, thermodynamic parameters proved the spontaneous process for the adsorption of fluoride on Ce-Ti@Fe 3 O 4 nanoparticles. The reusability of the material through magnetic recovery was demonstrated for five cycles of adsorption-desorption. Although the nanoparticles suffer slight structure modifications after their reusability, they keep their adsorption capacity. Likewise, the efficiency of the Ce-Ti@Fe 3 O 4 was demonstrated when applied to real water to obtain a residual concentration of F - below the maximum contaminated level, 1.5mg/L (WHO, 2006). Copyright © 2017 Elsevier B.V. All rights reserved.

Combined electrocoagulation and electroflotation for removal of fluoride from drinking water.

PubMed

Zuo, Qianhai; Chen, Xueming; Li, Wei; Chen, Guohua

2008-11-30

A combined electrocoagulation (EC) and electroflotation (EF) process was proposed to remove fluoride from drinking water. Its efficacy was investigated under different conditions. Experimental results showed that the combined process could remove fluoride effectively. The total hydraulic retention time required was only 30 min. After treatment, the fluoride concentration was reduced from initial 4.0-6.0mg/L to lower than 1.0mg/L. The influent pH value was found to be a very important variable that affected fluoride removal significantly. The optimal influent pH range is 6.0-7.0 at which not only can effective defluoridation be achieved, but also no pH readjustment is needed after treatment. In addition, it was found that SO(4)(2-) had negative effect; Ca(2+) had positive effect; while Cl(-) had little effect on the fluoride removal. The EC charge loading, EF charge loading and energy consumption were 3.0 Faradays/m(3), 1.5 Faradays/m(3), and 1.2 kWh/m(3), respectively, under typical conditions where fluoride was reduced from initial 4.0 to 0.87 mg/L.

Removal of anionic pollutants by pine bark is influenced by the mechanism of retention.

PubMed

Paradelo, R; Conde-Cid, M; Arias-Estévez, M; Nóvoa-Muñoz, J C; Álvarez-Rodríguez, E; Fernández-Sanjurjo, M J; Núñez-Delgado, A

2017-01-01

The use of organic biosorbents for anion removal from water has been less studied than for cationic compounds. In this work, the removal capacity of pine bark for potential anionic pollutants (fluoride, phosphate, arsenate and dichromate) was assessed in column experiments, designed to study the process of transport. The results showed that pine bark has a very low retention capacity for phosphate, arsenate or fluoride, and in turn, very high for dichromate, with retention values close to 100% and less than 2% desorption of the adsorbed dichromate. The large differences observed between anions suggest that differences in the retention mechanism of each anion exist. In the case of phosphate and arsenate, electrostatic interactions with the mostly negatively charged functional groups of the pine bark determine the low retention capacity. Dichromate retention might proceed through reduction of chromium (VI) to chromium (III), what improves the efficiency of the removal. Copyright © 2016 Elsevier Ltd. All rights reserved.

Fixed bed column study for water defluoridation using neem oil-phenolic resin treated plant bio-sorbent.

PubMed

Manna, Suvendu; Saha, Prosenjit; Roy, Debasis; Adhikari, Basudam; Das, Papita

2018-04-15

Fluoride has both detrimental and beneficial effects on living beings depending on the concentration and consumption periods. The study presented in this article investigated the feasibility of using neem oil phenolic resin treated lignocellulosic bio-sorbents for fluoride removal from water through fixed bed column study. Results indicated that treated bio-sorbents could remove fluoride both from synthetic and groundwater with variable bed depth, flow rate, fluoride concentration and column diameter. Data obtained from this study indicated that columns with the thickest bed, lowest flow rate, and fluoride concentration showed best column performance. Bio-sorbents used in this study are regenerable and reusable for more than five cycles. The initial materials cost needed to remove one gram of fluoride also found to be lower than the available alternatives. This makes the process more promising candidate to be used for fluoride removal. In addition, the process is also technically advantageous over the available alternatives. Copyright © 2018 Elsevier Ltd. All rights reserved.

Preparation and characterization of γ-AlOOH @CS magnetic nanoparticle as a novel adsorbent for removing fluoride from drinking water.

PubMed

Wan, Zhen; Chen, Wei; Liu, Cheng; Liu, Yu; Dong, Changlong

2015-04-01

For this study, a novel adsorbent of γ-AlOOH @CS (pseudoboehmite and chitosan shell) magnetic nanoparticles (ACMN) with magnetic separation capabilities was developed to remove fluoride from drinking water. The adsorbent was first characterized, and then its performance in removing fluoride was evaluated. Kinetic data demonstrated rapid fluoride adsorption with more than 80% fluoride adsorption within the initial 20 min and equilibrium reached in 60 min. Based on the results of kinetic and isotherm models, the fluoride adsorption process on the ACMN's surface was a monolayer adsorption on a homogeneous surface. Thermodynamic parameters presented that the adsorption process is spontaneous and endothermic in nature. The mechanism for the adsorption involved electrostatic interaction and hydrogen bonding. Moreover, the calculated adsorption capacity of the ACMN for fluoride using the Langmuir model was 67.5 mg/g (20°C, pH=7.0±0.1), higher than other fluoride removal adsorbents. This nanoadsorbent performed well over a pH range of 4-10. The study found that PO4(3-) was the co-existing anion most able to hinder the nanoparticle's fluoride adsorption, followed by NO3(-) then Cl(-). Experimental results suggest that ACMN is a promising adsorbent for treating fluoride-contaminated water. Copyright © 2014 Elsevier Inc. All rights reserved.

Phosphorus removal characteristics in hydroxyapatite crystallization using converter slag.

PubMed

Kim, Eung-Ho; Hwang, Hwan-Kook; Yim, Soo-Bin

2006-01-01

This study was performed to investigate the phosphorus removal characteristics in hydroxyapatite (HAP) crystallization using converter slag as a seed crystal and the usefulness of a slag column reactor system. The effects of alkalinity, and the isomorphic-substitutable presence of ionic magnesium, fluoride, and iron on HAP crystallization seeded with converter slag, were examined using a batch reactor system. The phosphorus removal efficiencies of the batch reactor system were found to increase with increases in the iron and fluoride ion concentrations, and to decrease with increases in the alkalinity and magnesium ion concentration. A column reactor system for HAP crystallization using converter slag was found to achieve high, stable levels of phosphorus elimination: the average PO4-P removal efficiency over 414 days of operation was 90.4%, in which the effluent phosphorus concentration was maintained at less than 0.5 mg/L under the appropriate phosphorus crystallization conditions. The X-ray diffraction (XRD) patterns and Fourier transform infrared (FTIR) spectra of the crystalline material deposited on the seed particles exhibited peaks consistent with HAP. Scanning electron micrograph (SEM) images showed that finely distributed crystalline material was formed on the surfaces of the seed particles. Energy dispersive X-ray spectroscopy (EDS) mapping analysis revealed that the molar Ca/P composition ratio of the crystalline material was 1.72.

A biocompatible and novelly-defined Al-HAP adsorption membrane for highly effective removal of fluoride from drinking water.

PubMed

He, Junyong; Chen, Kai; Cai, Xingguo; Li, Yulian; Wang, Chengming; Zhang, Kaisheng; Jin, Zhen; Meng, Fanli; Wang, Xuguang; Kong, Lingtao; Liu, Jinhuai

2017-03-15

A biocompatible and novelly-defined adsorption membrane for rapid removal of fluoride was prepared. Both adsorption and membrane techniques were used in this research. Al(OH) 3 nanoparticles modified hydroxyapatite (Al-HAP) nanowires were developed and made into Al-HAP membrane. The adsorption data of Al-HAP adsorbent could be well described by Freundlich isotherm model while the adsorption kinetic followed pseudo-second-order model. The maximum of adsorption capacity was 93.84mg/g when the fluoride concentration was 200mg/L. The adsorption mechanism was anion exchanges and electrostatic interactions. The contribution rates of HAP nanowires and Al(OH) 3 nanoparticles in fluoride removal were 36.70% and 63.30%, respectively. The fixed-bed column test demonstrate that the Al-HAP was biocompatible and in a good stability during the process of water treatment. The fluoride removal abilities of Al-HAP membrane with 0.3mm thickness could reach 1568L/m 2 when fluoride concentrations were 5mg/L. This study indicated that the Al-HAP membrane could be developed into a very viable technology for highly effective removal of fluoride from drinking water. Copyright © 2016 Elsevier Inc. All rights reserved.

Batch technique to evaluate the efficiency of different natural adsorbents for defluoridation from groundwater

NASA Astrophysics Data System (ADS)

Kumar, Pankaj; Saraswat, Chitresh; Mishra, Binaya Kumar; Avtar, Ram; Patel, Hiral; Patel, Asha; Sharma, Tejal; Patel, Roshni

2017-09-01

Fluoride pollution (with concentration >1.0 mg/L) in groundwater has become a global threat in the recent past due to the lesser availability of potable groundwater resource. In between several defluoridation techniques discovered so far, the adsorption process proved to be most economic and efficient. This study is an effort to evaluate defluoridation efficiency of powdered rice husk, fine chopped rice husk and sawdust by the batch adsorption process. Optimum defluoridation capacity is achieved by optimizing various parameters, viz. dose of adsorbent, pH, contact time and initial concentration. It was found that all three materials can be employed for the defluoridation technique, but powdered rice husk is the best adsorbent in the midst of all three. Powdered rice husk showed fluoride removal efficiency ranging between 85 and 90 % in the contact period of 7 h only in conditions of all optimized parameter. Following this parameter optimization, adsorption efficiency was also evaluated at natural pH of groundwater to minimize the cost of defluoridation. No significant difference was found between fluoride adsorption at optimized pH (pH = 4) and natural one (pH = 7), which concludes that powdered rice husk can be efficiently used for the defluoridation technique at field scale. The adsorption isotherm using this adsorbent perfectly followed Langmuir isotherms. The value of calculated separation factor also suggests the favourable adsorption of fluoride onto this adsorbent under the conditions used for the experiments. The field application for defluoridation of groundwater using this adsorbent (based on pH of natural groundwater there and seasonal variation of temperature) showed the high success rate.

Fluoride bioaccumulation by hydroponic cultures of camellia (Camellia japonica spp.) and sugar cane (Saccharum officinarum spp.).

PubMed

Camarena-Rangel, Nancy; Rojas Velázquez, Angel Natanael; Santos-Díaz, María del Socorro

2015-10-01

The ability of hydroponic cultures of camellia and sugar cane adult plants to remove fluoride was investigated. Plants were grown in a 50% Steiner nutrient solution. After an adaptation period to hydroponic conditions, plants were exposed to different fluoride concentrations (0, 2.5, 5 and 10 mg L(-1)). Fluoride concentration in the culture medium and in tissues was measured. In sugar cane, fluoride was mainly located in roots, with 86% of it absorbed and 14% adsorbed. Sugar cane plants removed 1000-1200 mg fluoride kg(-1) dry weight. In camellia plants the highest fluoride concentration was found in leaf. Roots accumulated fluoride mainly through absorption, which was 2-5 times higher than adsorption. At the end of the experiment, fluoride accumulation in camellia plants was 1000-1400 mgk g(-1) dry weight. Estimated concentration factors revealed that fluoride bioaccumulation is 74-221-fold in camellia plants and 100-500-fold in sugar cane plants. Thus, the latter appear as a suitable candidate for removing fluoride from water due to their bioaccumulation capacity and vigorous growth rate; therefore, sugar cane might be used for phytoremediation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Household water treatment systems: A solution to the production of safe drinking water by the low-income communities of Southern Africa

NASA Astrophysics Data System (ADS)

Mwabi, J. K.; Adeyemo, F. E.; Mahlangu, T. O.; Mamba, B. B.; Brouckaert, B. M.; Swartz, C. D.; Offringa, G.; Mpenyana-Monyatsi, L.; Momba, M. N. B.

One of the United Nations Millennium Development Goals is to reduce to half by 2015 the number of people, worldwide, who lack access to safe water. Due to the numerous deaths and illnesses caused by waterborne pathogens, various household water treatment devices and safe storage technologies have been developed to treat and manage water at the household level. The new approaches that are continually being examined need to be durable, lower in overall cost and more effective in the removal of the contaminants. In this study, an extensive literature survey was conducted to regroup various household treatment devices that are suitable for the inexpensive treatment of water on a household basis. The survey has resulted in the selection of four household treatment devices: the biosand filter (BSF), bucket filter (BF), ceramic candle filter (CCF) and the silver-impregnated porous pot filter (SIPP). The first three filters were manufactured in a Tshwane University of Technology workshop, using modified designs reported in literature. The SIPP filter is a product of the Tshwane University of Technology. The performance of the four filters was evaluated in terms of flow rate, physicochemical contaminant (turbidity, fluorides, phosphates, chlorophyll a, magnesium, calcium and nitrates) and microbial contaminant ( Escherichia coli, Vibrio cholerae, Salmonella typhimurium, Shigella dysenteriae) removals. The flow rates obtained during the study period were within the recommended limits (171 l/h, 167 l/h, 6.4 l/h and 3.5 l/h for the BSF, BF, CCF and SIPP, respectively). Using standard methods, the results of the preliminary laboratory and field studies with spiked and environmental water samples indicated that all filters decreased the concentrations of contaminants in test water sources. The most efficiently removed chemical contaminant in spiked water was fluoride (99.9%) and the poorest removal efficiency was noted for magnesium (26-56%). A higher performance in chemical contaminant removal was noted with the BF. For pathogenic bacteria, the mean percentage removals ranged between 97% and 100%. Although the concentrations of most chemical parameters were within the recommended limits in raw surface water, poor removal efficiencies were recorded for all filters, with the poorest reduction noted with fluorides (16-48%). The average turbidity removals from surface water ranged between 90% and 95% for all filters. The highest bacterial removal efficiency was recorded by the SIPP (99-100%) and the lowest by the BF (20-45%) and the BSF (20-60%). Extensive experimental studies with various types of raw surface water will still determine the long-term performance of each filter, as well as the filters that can be recommended to the communities for household treatment of drinking water.

A Review on Adsorption of Fluoride from Aqueous Solution

PubMed Central

Habuda-Stanić, Mirna; Ergović Ravančić, Maja; Flanagan, Andrew

2014-01-01

Fluoride is one of the anionic contaminants which is found in excess in surface or groundwater because of geochemical reactions or anthropogenic activities such as the disposal of industrial wastewaters. Among various methods used for defluoridation of water such as coagulation, precipitation, membrane processes, electrolytic treatment, ion-exchange, the adsorption process is widely used. It offers satisfactory results and seems to be a more attractive method for the removal of fluoride in terms of cost, simplicity of design and operation. Various conventional and non-conventional adsorbents have been assessed for the removal of fluoride from water. In this review, a list of various adsorbents (oxides and hydroxides, biosorbents, geomaterials, carbonaceous materials and industrial products and by-products) and its modifications from literature are surveyed and their adsorption capacities under various conditions are compared. The effect of other impurities on fluoride removal has also been discussed. This survey showed that various adsorbents, especially binary and trimetal oxides and hydroxides, have good potential for the fluoride removal from aquatic environments. PMID:28788194

Preparation of fly ash based zeolite for removal of fluoride from drinking water

NASA Astrophysics Data System (ADS)

Panda, Laxmidhar; Kar, Biswabandita; Dash, Subhakanta

2018-05-01

Fluoride contamination of drinking water is a worldwide phenomenon and scientists are working relentlessly to find ways to remove fluoride from drinking water. Out of the different methods employed for removal fluoride from drinking water adsorption process is the most suitable because in this process the adsorbent is regenerated and the process is cost effective. In the present study fly ash is used as the raw material, which is treated with alkali (NaOH) to form NaP1 zeolite. This zeolite is then subjected to characterization by standard procedures. It is found that the synthesized zeolite has more crystalline character than the raw fly ash and has also more voids and channels on its surface. The surface of the synthesized zeolite is modified with calcium chloride and the same is employed for removal of fluoride under varying pH, contact time, initial concentration of fluoride, temperature and adsorbent dose etc so as to assess the suitably or otherwise of the synthesized product.

House hold unit for the treatment of fluoride, iron, arsenic and microorganism contaminated drinking water.

PubMed

Dhadge, Vijaykumar L; Medhi, Chitta Ranjan; Changmai, Murchana; Purkait, Mihir Kumar

2018-05-01

A first of its kind hybrid electrocoagulation-filtration prototype unit was fabricated for the removal of fluoride, iron, arsenic and microorganisms contaminated drinking water. The unit comprised of 3 chambers, chamber A consisting of an inlet for the water to be treated and an outlet for the treated water along with one block of aluminum electrodes. Chamber B consisted of ceramic membrane filtration assembly at the bottom over a metallic support which filters the flocs so produced in chamber A and chamber C consisting of space to collect the treated water. Operating parameters were maintained as current density of 625 A m -2 and an electrode distance of 0.005 m. Contaminated drinking water containing mixture of fluoride (10 mg L -1 ), iron (25 mg L -1 ), arsenic (200 μg L -1 ) and microorganisms (35 CFU ml -1 ) was used for the experiment. A removal of 98.74%, 95.65%, 93.2% and 100% were obtained for iron, arsenic, fluoride and microorganisms, respectively. The apparatus and method made it possible to efficiently treat contaminated drinking water to produce drinkable water as per WHO specification. By-products obtained from the electrocoagulation bath were analyzed using SEM, EDX and XRD and explained. Copyright © 2018 Elsevier Ltd. All rights reserved.

PILOT STUDY OF FLUORIDE AND ARSENIC REMOVAL FROM POTABLE WATER

EPA Science Inventory

Pilot plant studies were conducted on the removal of fluoride and arsenic from potable water using activated alumina as the adsorbent. The tests were run using water from the community of Why, Arizona, that contained 3 mg/L fluoride and 0.15 mg/L arsenic. The experimental data sh...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Da-Quan; Sun, Tian-Ying; Yu, Xue-Feng, E-mail: yxf@whu.edu.cn

Highlights: • The morphology and properties of Ce-doped yttrium hydroxide fluoride nanotubes (YHF:Ce NTs) were investigated. • YHF:Ce NTs were conjugated with Au nanoparticles to produce Au-YHF:Ce nanocomposites. • Au-YHF:Ce NTs showed excellent capability and efficiency in removing Congo red from solutions. • Au-YHF:Ce NTs were utilized to determine the concentration of Congo red based on SERS. - Abstract: Ce-doped yttrium hydroxide fluoride nanotubes (YHF:Ce NTs) with large surface area are synthesized and conjugated with Au nanoparticles (NPs) to produce Au-YHF:Ce nanocomposites. The Au-YHF:Ce NTs have a hollow structure, rough surface, polymer coating, and good surface-enhanced Raman spectroscopy (SERS) properties.more » They are applied to wastewater treatment to remove Congo red as a typical pollutant. The materials not only remove pollutants rapidly from the wastewater, but also detect trace amounts of the pollutants quantitatively. The multifunctional Au-YHF:Ce NTs have commercial potential as nano-absorbents and nano-detectors in water treatment and environmental monitoring.« less

SEPARATION OF PLUTONIUM

DOEpatents

Maddock, A.G.; Smith, F.

1959-08-25

A method is described for separating plutonium from uranium and fission products by treating a nitrate solution of fission products, uranium, and hexavalent plutonium with a relatively water-insoluble fluoride to adsorb fission products on the fluoride, treating the residual solution with a reducing agent for plutonium to reduce its valence to four and less, treating the reduced plutonium solution with a relatively insoluble fluoride to adsorb the plutonium on the fluoride, removing the solution, and subsequently treating the fluoride with its adsorbed plutonium with a concentrated aqueous solution of at least one of a group consisting of aluminum nitrate, ferric nitrate, and manganous nitrate to remove the plutonium from the fluoride.

In situ precipitation of nano-hydroxyapatite in gelatin polymatrix towards specific fluoride sorption.

PubMed

Pandi, Kalimuthu; Viswanathan, Natrayasamy

2015-03-01

This study investigates the synthesis of nano-hydroxyapatite (n-HAp) incorporated gelatin (Gel) biocomposite namely n-HAp@Gel composite for efficient removal of fluoride from aqueous solution. The results demonstrated that, the developed n-HAp@Gel biocomposite possess an enhanced defluoridation capacity (DC) of 4157 mgF-/kg. The batch experiments were optimized as a function of various influencing parameters like contact time, pH, co-ions, temperature and initial fluoride concentration. The physicochemical characteristics of n-HAp@Gel composite was examined by using different instrumental techniques like FTIR, XRD, TGA-DSC and SEM with EDAX analysis. The sorption data were fitted with various isotherm models. The acquired thermodynamic parameters showed that the sorption of fluoride onto the sorbent was endothermic and spontaneous in nature. The reaction-based and diffusion-based models were used to identify the kinetics of the reaction. At field conditions, n-HAp@Gel composite reduce the fluoride concentration below the tolerance limit. A regeneration technique was proposed in order to reuse the sorbent. Copyright © 2014 Elsevier B.V. All rights reserved.

Simultaneous arsenic and fluoride removal from synthetic and real groundwater by electrocoagulation process: Parametric and cost evaluation.

PubMed

Thakur, Lokendra Singh; Mondal, Prasenjit

2017-04-01

Co-existence of arsenic and fluoride in groundwater has raised severe health issues to living being. Thus, the present research has been conducted for simultaneous removal of arsenic and fluoride from synthetic groundwater by using electrocoagulation process with aluminum electrode. Effects of initial pH, current density, run time, inter electrode distance and NaCl concentration over percentage removal of arsenic and fluoride as well as operating cost have been studied. The optimum experimental conditions are found to be initial pH: 7, current density: 10 A/m 2 , run time: 95 min, inter electrode distance: 1 cm, NaCl concentration: 0.71 g/l for removal of 98.51% arsenic (initial concentration: 550 μg/l) and 88.33% fluoride (initial concentration: 12 mg/l). The concentration of arsenic and fluoride in treated water are found to be 8.19 μg/l and 1.4 mg/l, respectively, with an operating cost of 0.357 USD/m 3 treated water. Pseudo first and second order kinetic model of individual and simultaneous arsenic and fluoride removal in electrocoagulation have also been studied. Produced sludge characterization studies also confirm the presence of arsenic in As(III) form, and fluoride in sludge. The present electrocoagulation process is able to reduce the arsenic and fluoride concentration of synthetic as well as real groundwater to below 10 μg/l and 1.5 mg/l, respectively, which are maximum contaminant level of these elements in drinking water according to WHO guidelines. Copyright © 2016 Elsevier Ltd. All rights reserved.

Comparing activated alumina with indigenous laterite and bauxite as potential sorbents for removing fluoride from drinking water in Ghana

USGS Publications Warehouse

Craig, Laura; Stillings, Lisa; Decker, David L.; Thomas, James M.

2015-01-01

Fluoride is considered beneficial to teeth and bones when consumed in low concentrations, but at elevated concentrations it can cause dental and skeletal fluorosis. Most fluoride-related health problems occur in poor, rural communities of the developing world where groundwater fluoride concentrations are high and the primary sources of drinking water are from community hand-pump borehole drilled wells. One solution to drinking high fluoride water is to attach a simple de-fluoridation filter to the hand-pump; and indigenous materials have been recommended as low-cost sorbents for use in these filters. In an effort to develop an effective, inexpensive, and low-maintenance de-fluoridation filter for a high fluoride region in rural northern Ghana, this study conducted batch fluoride adsorption experiments and potentiometric titrations to investigate the effectiveness of indigenous laterite and bauxite as sorbents for fluoride removal. It also determined the physical and chemical properties of each sorbent. Their properties and the experimental results, including fluoride adsorption capacity, were then compared to those of activated alumina, which has been identified as a good sorbent for removing fluoride from drinking water. The results indicate that, of the three sorbents, bauxite has the highest fluoride adsorption capacity per unit area, but is limited by a low specific surface area. When considering fluoride adsorption per unit weight, activated alumina has the highest fluoride adsorption capacity because of its high specific surface area. Activated alumina also adsorbs fluoride well in a wider pH range than bauxite, and particularly laterite. The differences in adsorption capacity are largely due to surface area, pore size, and mineralogy of the sorbent.

Method for removing oxide contamination from silicon carbide powders

DOEpatents

Brynestad, J.; Bamberger, C.E.

1984-08-01

The described invention is directed to a method for removing oxide contamination in the form of oxygen-containing compounds such as SiO/sub 2/ and B/sub 2/O/sub 3/ from a charge of finely divided silicon carbide. The silicon carbide charge is contacted with a stream of hydrogen fluoride mixed with an inert gas carrier such as argon at a temperature in the range of about 200/sup 0/ to 650/sup 0/C. The oxides in the charge react with the heated hydrogen fluoride to form volatile gaseous fluorides such as SiF/sub 4/ and BF/sub 3/ which pass through the charge along with unreacted hydrogen fluoride and the carrier gas. Any residual gaseous reaction products and hydrogen fluoride remaining in the charge are removed by contacting the charge with the stream of inert gas which also cools the powder to room temperature. The removal of the oxygen contamination by practicing the present method provides silicon carbide powders with desirable pressing and sintering characteristics. 1 tab.

Factors affecting fluoride and natural organic matter (NOM) removal from natural waters in Tanzania by nanofiltration/reverse osmosis.

PubMed

Shen, Junjie; Schäfer, Andrea I

2015-09-15

This study examined the feasibility of nanofiltration (NF) and reverse osmosis (RO) in treating challenging natural tropical waters containing high fluoride and natural organic matter (NOM). A total of 166 water samples were collected from 120 sources within northern Tanzania over a period of 16 months. Chemical analysis showed that 81% of the samples have fluoride levels exceeding the WHO drinking guideline of 1.5mg/L. The highest fluoride levels were detected in waters characterized by high ionic strength, high inorganic carbon and on some occasions high total organic carbon (TOC) concentrations. Bench-scale experiments with 22 representative waters (selected based on fluoride concentration, salinity, origin and in some instances organic matter) and 6 NF/RO membranes revealed that ionic strength and recovery affected fluoride retention and permeate flux. This is predominantly due to osmotic pressure and hence the variation of diffusion/convection contributes to fluoride transport. Different membranes had distinct fluoride removal capacities, showing different raw water concentration treatability limits regarding the WHO guideline compliance. BW30, BW30-LE and NF90 membranes had a feed concentration limit of 30-40 mg/L at 50% recovery. NOM retention was independent of water matrices but is governed predominantly by size exclusion. NOM was observed to have a positive impact on fluoride removal. Several mechanisms could contribute but further studies are required before a conclusion could be drawn. In summary, NF/RO membranes were proved to remove both fluoride and NOM reliably even from the most challenging Tanzanian waters, increasing the available drinking water sources. Copyright © 2015 Elsevier B.V. All rights reserved.

Synthesis and performance evaluation of Al/Fe oxide coated diatomaceous earth in groundwater defluoridation: Towards fluorosis mitigation.

PubMed

Izuagie, Anthony A; Gitari, Wilson M; Gumbo, Jabulani R

2016-08-23

The quest to reduce fluoride in groundwater to WHO acceptable limit of 1.5 mg/L to prevent diseases such as teeth mottling and skeletal fluorosis was the motivation for this study. Al/Fe oxide-modified diatomaceous earth was prepared and its defluoridation potential evaluated by batch method. The sorbent with pHpzc 6.0 ± 0.2 is very reactive. The maximum 82.3% fluoride removal attained in 50 min using a dosage of 0.3 g/100 mL in 10 mg/L fluoride was almost attained within 5 min contact time; 81.3% being the percent fluoride removal at 5 min contact time. The sorbent has a usage advantage of not requiring solution pH adjustment before it can exhibit its fluoride removal potential. A substantial amount of fluoride (93.1%) was removed from solution when a sorbent dosage of 0.6 g/100 mL was contacted with 10 mg/L fluoride solution for 50 min at a mixing rate of 200 rpm. The optimum adsorption capacity of the adsorbent was 7.633 mg/g using a solution containing initially 100 mg/L fluoride. The equilibrium pH of the suspensions ranged between 6.77 and 8.26 for 10 and 100 mg/L fluoride solutions respectively. Contacting the sorbent at a dosage of 0.6 g/100 mL with field water containing 5.53 mg/L at 200 rpm for 50 min reduced the fluoride content to 0.928 mg/L-a value below the upper limit of WHO guideline of 1.5 mg/L fluoride in drinking water. The sorption data fitted to both Langmuir and Freundlich isotherms but better with the former. The sorption data obeyed only the pseudo-second-order kinetic, which implies that fluoride was chemisorbed.

Fluoride in drinking water and its removal.

PubMed

Meenakshi; Maheshwari, R C

2006-09-01

Excessive fluoride concentrations have been reported in groundwaters of more than 20 developed and developing countries including India where 19 states are facing acute fluorosis problems. Various technologies are being used to remove fluoride from water but still the problem has not been rooted out. In this paper, a broad overview of the available technologies for fluoride removal and advantages and limitations of each one have been presented based on literature survey and the experiments conducted in the laboratory with several processes. It has been concluded that the selection of treatment process should be site specific as per local needs and prevailing conditions as each technology has some limitations and no one process can serve the purpose in diverse conditions.

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 in...

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 in...

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 in...

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 in...

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 in...

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. Copyright © 2014 Elsevier Ltd. All rights reserved.

Titania-catalyzed radiofluorination of tosylated precursors in highly aqueous medium

DOE PAGES

Sergeev, Maxim E.; Morgia, Federica; Lazari, Mark; ...

2015-04-10

Nucleophilic radiofluorination is an efficient synthetic route to many positron-emission tomography (PET) probes, but removal of water to activate the cyclotron-produced [ 18F]fluoride has to be performed prior to reaction, which significantly increases overall radiolabeling time and causes radioactivity loss. In this paper, we demonstrate the possibility of 18F-radiofluorination in highly aqueous medium. The method utilizes titania nanoparticles, 1:1 (v/v) acetonitrile–thexyl alcohol solvent mixture, and tetra-n-butylammonium bicarbonate as a phase-transfer agent. Efficient radiolabeling is directly performed with aqueous [ 18F]fluoride without the need for a drying/azeotroping step to significantly reduce radiosynthesis time. High radiochemical purity of the target compound ismore » also achieved. Finally, the substrate scope of the synthetic strategy is demonstrated with a range of aromatic, aliphatic, and cycloaliphatic tosylated precursors.« less

Interaction between bacteriophage and pyrophyllite clay in aqueous solution

NASA Astrophysics Data System (ADS)

Park, Jeong-Ann; Kim, Jae-Hyun; Kang, Jin-Kyu; Son, Jeong-Woo; Yi, In-Geol; Kim, Song-Bae

2014-05-01

Viral contamination results in a degradation in drinking water quality and a threat to public health. Toprovide safe drinking water, water treatment alternatives using various adsorbents and filter media such as activated carbon, bituminous coal, quartz sand and clay have been considered. Pyrophyllite is a 2:1 clay mineral having dioctahedral layer structure with octahedrally coordinated Al ion sheets between two sheets of SiO4 tetrahedra. It is a hydrous aluminosilicate clay with the chemical composition AlSi2O5(OH). Pyrophyllite has recently been investigated as a potential low-cost and environmental friendly adsorbent for removing various contaminants. The aim of this study was to investigate the removal of the bacteriophage MS2 from aqueous solution using pyrophyllite. Batch experiments were conducted to examine the MS2 sorption to pyrophyllite. The influence of fluoride, a groundwater contaminant, on the removal of MS2 was also observed. Batch results demonstrated that pyrophyllite was effective in MS2 removal. The percent removal increased from 5.26% to 99.99% (= 4.0 log removal) as the pyrophyllite concentrations increased from 0.2 to 20 g/L. More than 99% of MS2 could be removed with a pyrophyllite concentration of ≥ 4 g/L. The sorption of MS2 to pyrophyllite was rapid. Within 15 min, approximately 99.98% (= 3.7 log removal) of MS2 was attained. More than 4.0 log removal was achieved after 180 min. The experimental data were analyzed with the pseudo first-order and pseudo second-order kinetic models. The correlation coefficient showed that pseudo second-order model was better than pseudo first-order model at describing the kinetic data. The amount of MS2 removed at equilibrium was determined to be 1.43 × 108 pfu/g from the pseudo second-order model. The experimental data were also analyzed with the Freundlich and Langmuir isotherm models. The correlation coefficients showed that the Langmuir model was more suitable than the Freundlich model for MS2 sorption data. The maximum amount of MS2 removed per unit mass of pyrophyllite was determined to be 5.01 × 108 pfu/g. Results also showed that at a pyrophyllite concentration of 20 g/L, the log removal in the presence of 5 mg/L fluoride was 3.05, which was lower than that for 0 mg/L fluoride. At the same concentration of pyrophyllite, the log removal in the presence of 10 mg/L fluoride was 2.54, which was lower than those for 0 and 5 mg/L fluoride. The removal of MS2 by pyrophyllite was thus shown to be influenced by fluoride ions. The results could be attributed to fluoride ions competing with MS2 for sorption sites on the pyrophyllite surfaces. Separate batch experiments indicated that the fluoride adsorption capacity of pyrophyllite was 0.124 mg/g at the given conditions (pyrophyllite concentration = 20 g/L; initial fluoride concentration = 5 mg/L; reaction time = 5 h), which indicated that fluoride could adsorb to pyrophyllite. This study can improve our knowledge on the application of pyrophyllite as adsorbents for virus removal in water treatment. Acknowledgement This research was supported by the Korea Ministry of Environment as GAIA project.

Mitigation of Fluorosis - A Review

PubMed Central

Dodamani, Arun S.; Jadhav, Harish C.; Naik, Rahul G.; Deshmukh, Manjiri A.

2015-01-01

Fluoride is required for normal development and growth of the body. It is found in plentiful quantity in environment and fluoride content in drinking water is largest contributor to the daily fluoride intake. The behaviour of fluoride ions in the human organism can be regarded as that of “double-edged sword”. Fluoride is beneficial in small amounts but toxic in large amounts. Excessive consumption of fluorides in various forms leads to development of fluorosis. Fluorosis is major health problem in 24 countries, including India, which lies in the geographical fluoride belt. Various technologies are being used to remove fluoride from water but still the problem has not been rooted out. The purpose of this paper is to review the available treatment modalities for fluorosis, available technologies for fluoride removal from water and ongoing fluorosis mitigation programs based on literature survey. Medline was the primary database used in the literature search. Other databases included: PubMed, Web of Science, Google Scholar, WHO, Ebscohost, Science Direct, Google Search Engine, etc. PMID:26266235

Apparatus and methods for purifying lead

DOEpatents

Tunison, Harmon M.

2016-01-12

Disclosed is an exemplary method of purifying lead which includes the steps of placing lead and a fluoride salt blend in a container; forming a first fluid of molten lead at a first temperature; forming a second fluid of the molten fluoride salt blend at a second temperature higher than the first temperature; mixing the first fluid and the second fluid together; separating the two fluids; solidifying the molten fluoride salt blend at a temperature above a melting point of the lead; and removing the molten lead from the container. In certain exemplary methods the molten lead is removed from the container by decanting. In still other exemplary methods the molten salt blend is a Lewis base fluoride eutectic salt blend, and in yet other exemplary methods the molten salt blend contains sodium fluoride, lithium fluoride, and potassium fluoride.

Enhanced fluoride adsorption by nano crystalline γ-alumina: adsorption kinetics, isotherm modeling and thermodynamic studies

NASA Astrophysics Data System (ADS)

Chinnakoti, Prathibha; Chunduri, Avinash L. A.; Vankayala, Ranganayakulu K.; Patnaik, Sandeep; Kamisetti, Venkataramaniah

2017-09-01

Nano materials in particular nano oxides with enhanced surface area and an excellent catalytic surface serve as potential adsorbents for defluoridation of water. In the present study nano γ-alumina was synthesized through a simple and low cost, surfactant assisted solution combustion method. As synthesized material was characterized by XRD and FESEM for its phase, size and morphological characteristics. Surface properties have been investigated by BET method. Nano γ-alumina was further used for a detailed adsorption study to remove fluoride from water. Batches of experiments were performed at various experimental conditions such as solution pH, adsorbent dose, initial fluoride concentration and contact time to test the defluoridation ability of γ-alumina. Fluoride Adsorption by nano sized γ-alumina was rapid and reached equilibrium within two hours. The adsorption worked well at pH 4.0, where ˜96 % of fluoride was found to be adsorbed on adsorbent. It was possible to reduce fluoride levels to as low as 0.3 mg/L (within the safe limit of WHO: ≤1.5 mg/L) from an initial fluoride levels of 10 mg/L. This could be achieved using a very small quantity, 1 g/L of γ-alumina at pH 4 within 1 h of contact time. Defluoridation capacity of nano γ-alumina was further investigated by fitting the equilibrium data to various isotherm as well as kinetic models. The present study revealed that γ-alumina could be an efficient adsorbent for treating fluoride contaminated water.

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.

Defluoridation of drinking water using a new flow column-electrocoagulation reactor (FCER) - Experimental, statistical, and economic approach.

PubMed

Hashim, Khalid S; Shaw, Andy; Al Khaddar, Rafid; Ortoneda Pedrola, Montserrat; Phipps, David

2017-07-15

A new batch, flow column electrocoagulation reactor (FCER) that utilises a perforated plate flow column as a mixer has been used to remove fluoride from drinking water. A comprehensive study has been carried out to assess its performance. The efficiency of fluoride removal (R%) as a function of key operational parameters such as initial pH, detention time (t), current density (CD), inter-electrode distance (ID) and initial concentration (C 0 ) has been examined and an empirical model has been developed. A scanning electron microscopy (SEM) investigation of the influence of the EC process on morphology of the surface of the aluminium electrodes, showed the erosion caused by aluminium loss. A preliminary estimation of the reactor's operating cost is suggested, allowing for the energy from recycling of hydrogen gas hydrogen gas produced amount. The results obtained showed that 98% of fluoride was removed within 25 min of electrolysis at pH of 6, ID of 5 mm, and CD of 2 mA/cm 2 . The general relationship between fluoride removal and operating parameters could be described by a linear model with R 2 of 0.823. The contribution of the operating parameters to the suggested model followed the order: t > CD > C 0  > ID > pH. The SEM images obtained showed that, after the EC process, the surface of the anodes, became non-uniform with a large number of irregularities due to the generation of aluminium hydroxides. It is suggested that these do not materially affect the performance. A provisional estimate of the operating cost was 0.379 US $/m 3 . Additionally, it has been found that 0.6 kW/m 3 is potentially recoverable from the H 2 gas. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Synthesis of hydroxyapatite/multi-walled carbon nanotubes for the removal of fluoride ions from solution

NASA Astrophysics Data System (ADS)

Ruan, Zhongyuan; Tian, Yaxi; Ruan, Jifu; Cui, Guijia; Iqbal, Kanwal; Iqbal, Anam; Ye, Herui; Yang, Zhangzhong; Yan, Shiqiang

2017-08-01

A novel composite material, hydroxyapatite (HA)-multi-walled carbon nanotubes (MWCNTs), was prepared using a simple in-situ sol-gel method, and was used for the first time to remove fluoride from water. The novel HA-MWCNTs were characterized using TEM, FT-IR, BET and XRD analysis. The TEM and SAED results revealed that the MWCNTs were uniformly encapsulated by hydroxyapatite nanoparticles. The synthesized HA-MWCNTs had a high specific surface area (180.504 m2 g-1), with an average pore width (14.607 nm) and pore volume (0.774 cm3 g-1), which produced a defluoridation capacity (DC) of 30.22 mgF- g-1. This value was greater than unmodified hydroxyapatite (HA), which exhibited a larger specific surface area (172.233 m2 g-1) and an excellent DC of 17.80 mgF- g-1. A number of pertinent parameters that could affect the defluoridation performance of the HA/MWCNTs including weight ratios of the two key materials, solution pH and competing anions were carefully and comprehensively examined. It was found that the adsorption results followed the Langmuir and Freundlich isotherm model, and the sorption kinetics of the F- appeared to exhibit a pseudo second order. Moreover, the adsorption reaction was spontaneous and endothermic and appeared to exhibit a higher initial adsorption rate. This reaction appeared to occur result from both anion exchange and electrostatic interactions. When the HA-MWCNTs (MH6) were at an adsorbent dose of 2.0 g L-1, they were able to decrease the fluoride concentration of actual nuclear industry wastewater from 8.79 mg L-1 to about 0.25 mg L-1 (97.15% removal efficiency). The experimental results of this study showed that the HA-MWCNTs composites have application potential for the removal of fluoride ions from wastewater.

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. Copyright © 2014 Elsevier Inc. All rights reserved.

The removal of fluoride from aqueous solution by a lateritic soil adsorption: Kinetic and equilibrium studies.

PubMed

Iriel, Analia; Bruneel, Stijn P; Schenone, Nahuel; Cirelli, Alicia Fernández

2018-03-01

The use of natural sorbents to remove fluoride from drinking water is a promising alternative because of its low-cost and easy implementation. In this article, fluoride adsorption on a latosol soil from Misiones province (Argentina) was studied regarding kinetic and equilibrium aspects. Experiments were conducted in batch at room temperature under controlled conditions of pH 4-8) and ionic strength (1-10mM KNO 3 ). Experimental data indicated that adsorption processes followed a PSO kinetic where initial rates have showed to be influenced by pH solution. The necessary time to reach an equilibrium state had resulted approximately 30min. Equilibrium adsorption studies were performed at pH 8 which is similar to the natural groundwater. For that, fluoride adsorption data were successfully adjusted to Dubinin-Ataskhov model determining that the fluoride adsorption onto soil particles mainly followed a physical mechanism with a removal capacity of 0.48mgg -1 . Finally, a natural groundwater was tested with laterite obtaining a reduction close to 30% from initial concentration and without changing significantly the physicochemical properties of the natural water. Therefore, it was concluded that the use of lateritic soils for fluoride removal is very promising on a domestic scale. Copyright © 2017 Elsevier Inc. All rights reserved.

Removal of fluoride ion by bone char produced from animal biomass.

PubMed

Kawasaki, Naohito; Ogata, Fumihiko; Tominaga, Hisato; Yamaguchi, Isao

2009-01-01

Bone char (BC) was prepared by carbonizing four types of animal biomass, and the adsorption of fluoride ions and elution of phosphate ions were investigated. It was found that the BC yield decreased as carbonization temperature increased, and that carbonization temperature had no significant effect on surface pH, base or acid consumptions. Fluoride ion adsorption was increased in BC produced at a low carbonization temperature. The adsorption mechanism of fluoride ion on BCs might be monolayer adsorption. BC can potentially be used to remove fluoride ions in drinking water. However, it was found that phosphate ions from BC are eluted due to adsorption of fluoride ions, and that ingestion of large amounts of phosphate ions inhibits reabsorption of calcium in the human body. Thus there is a need to study the elution behavior of phosphate ions. The adsorption mechanisms of fluoride ions onto BC would be a physical adsorption onto BC and phosphate ion in BC is exchanged to fluoride ion.

Method for cleaning bomb-reduced uranium derbies

DOEpatents

Banker, John G.; Wigginton, Hubert L.; Beck, David E.; Holcombe, Cressie E.

1981-01-01

The concentration of carbon in uranium metal ingots induction cast from derbies prepared by the bomb-reduction of uranium tetrafluoride in the presence of magnesium is effectively reduced to less than 100 ppm by removing residual magnesium fluoride from the surface of the derbies prior to casting. This magnesium fluoride is removed from the derbies by immersing them in an alkali metal salt bath which reacts with and decomposes the magnesium fluoride. A water quenching operation followed by a warm nitric acid bath and a water rinse removes the residual salt and reaction products from the derbies.

Method for cleaning bomb-reduced uranium derbies

DOEpatents

Banker, J.G.; Wigginton, H.L.; Beck, D.E.; Holcombe, C.E.

The concentration of carbon in uranium metal ingots induction cast from derbies prepared by the bomb-reduction of uranium tetrafluoride in the presence of magnesium is effectively reduced to less than 100 ppM by removing residual magnesium fluoride from the surface of the derbies prior to casting. This magnesium fluoride is removed from the derbies by immersing them in an alkali metal salt bath which reacts with and decomposes the magnesium fluoride. A water quenching operation followed by a warm nitric acid bath and a water rinse removes the residual salt and reaction products from the derbies.

Removal of fluoride from drinking water using aluminum hydroxide coated activated carbon prepared from bark of Morinda tinctoria

NASA Astrophysics Data System (ADS)

Amalraj, Augustine; Pius, Anitha

2017-10-01

The aim of this study is to design and develop a novel cost effective method for fluoride removal, applicable to rural areas of developing countries. Adsorption is widely considered as one of the appropriate technologies for water defluoridation. This study investigates the feasibility of using low-cost biomass based activated carbon from the bark of Morinda tinctoria coated with aluminum hydroxide (AHAC) for water defluoridation, at neutral pH range. Characterization of AHAC was done through IR, SEM with EDAX studies before and after fluoride treatment. The fluoride adsorption capacity of AHAC as a function of contact time, pH and initial fluoride concentration was investigated. The role of co-existing interfering ions also was studied. The isotherm and kinetic models were used to understand the nature of the fluoride adsorption onto AHAC. Freundlich isotherm and intra-particle diffusion were the best-fitting models for the adsorption of fluoride on AHAC. Fluoride adsorption kinetics well fitted with pseudo-second order model. The results showed excellent fluoride adsorption capacity was found to be 26.03 mg g-1 at neutral pH.

Efficient removal of sulfur hexafluoride (SF6) through reacting with recycled electroplating sludge.

PubMed

Zhang, Jia; Zhou, Ji Zhi; Liu, Qiang; Qian, Guangren; Xu, Zhi Ping

2013-06-18

This paper reports that recycled electroplating sludge is able to efficiently remove greenhouse gas sulfur hexafluoride (SF6). The removal process involves various reactions of SF6 with the recycled sludge. Remarkably, the sludge completely removed SF6 at a capacity of 1.10 mmol/g (SF6/sludge) at 600 °C. More importantly, the evolved gases were SO2, SiF4, and a limited amount of HF, with no toxic SOF4, SO2F2, or SF4 being detected. These generated gases can be readily captured and removed by NaOH solution. The reacted solids were further found to be various metal fluorides, thus revealing that SF6 removal takes place by reacting with various metal oxides and silicate in the sludge. Moreover, the kinetic investigation revealed that the SF6 reaction with the sludge is a first-order chemically controlled process. This research thus demonstrates that the waste electroplating sludge can be potentially used as an effective removal agent for one of the notorious greenhouse gases, SF6.

Sorption of fluoride using chemically modified Moringa oleifera leaves

NASA Astrophysics Data System (ADS)

Dan, Shabnam; Chattree, Amit

2018-05-01

Contamination of drinking water due to fluoride is a severe health hazard problem. Excess of fluoride (> 1.5 mg/L) in drinking water is harmful to human health. Various treatment technologies for removing fluoride from groundwater have been investigated. The present study showed that the leaves of Moringa oleifera, a herbal plant is an effective adsorbent for the removal of fluoride from aqueous solution. Acid treated Moringa oleifera leaves powder showed good adsorption capacity than alkali treated Moringa oleifera leaves powder. Batch sorptive defluoridation was conducted under the variable experimental condition such as pH, contact time, adsorbent dose and initial fluoride ion concentration. Maximum defluoridation was achieved at pH 1. The percentage of fluoride removal increases with adsorbent dose. The equilibrium sorption data were fitted into Langmuir, Freundlich and Temkin isotherms. Of the three adsorption isotherms, the R 2 value of Langmuir isotherm model was the highest. The maximum monolayer coverage ( Q max) from Langmuir isotherm model was determined to be 1.1441 mg/g, the separation factor indicating a favorable sorption experiment is 0.035. It was also discovered that the adsorption did not conform to the Freundlich adsorption isotherm. The heat of sorption process was estimated from Temkin Isotherm model to be - 0.042 J/mol which vividly proved that the adsorption experiment followed a physical process.

Multi-criteria assessment of community-based fluoride-removal technologies for rural Ethiopia.

PubMed

Osterwalder, Lars; Johnson, C Annette; Yang, Hong; Johnston, Richard B

2014-08-01

Elevated concentrations of naturally-occurring fluoride in groundwater pose a serious health risk to millions of people living in the Ethiopian Rift Valley. In the absence of low-fluoride water resources of sufficient capacity, fluoride removal from drinking water is the accepted mitigation option. To date, five different community-level fluoride-removal technologies have been implemented in Ethiopia, although only a few units have been found in a functional state in the field. Which technology should be promoted and up-scaled is the subject of controversial debate amongst key stakeholders. This paper describes a multi-criteria decision analysis exercise, which was conducted with the participation of stakeholders in Ethiopia during a one-day workshop, to assess in an objective and transparent manner the available technology options. Criteria for technology comparison were selected and weighted, thus enabling the participants to assess the advantages and disadvantages of the different technologies and hear the views of other stakeholders. It was shown that there is no single most-preferable, technical solution for fluoride removal in Ethiopia. Selection of the most suitable solution depends on location-specific parameters and on the relative importance given to different criteria by the stakeholders involved. The data presented in this paper can be used as reference values for Ethiopia. © 2013. Published by Elsevier B.V. All rights reserved.

Highly selective defluoridation of brick tea infusion by tea waste supported aluminum oxides.

PubMed

Peng, Chuanyi; Xi, Junjun; Chen, Guijie; Feng, Zhihui; Ke, Fei; Ning, Jingming; Li, Daxiang; Ho, Chi-Tang; Cai, Huimei; Wan, Xiaochun

2017-03-01

Brick tea usually contains very high fluoride, which may affect human health. Biosorbents have received much attention for selective removal of fluoride because of low cost, environmental friendliness, and relative safeness. In the present study, a highly selective fluoride tea waste based biosorbent, namely, aluminum (Al) oxide decorated tea waste (Tea-Al), was successfully prepared. The Tea-Al biosorbent was characterized by energy-dispersive spectrometry, Fourier transform infrared spectroscopy, powder X-ray diffraction and X-ray photoelectron spectroscopic analysis. The Tea-Al sample exhibited remarkably selective adsorption for fluoride (52.90%), but a weaker adsorption for other major constituents of brick tea infusion, such as catechins, polyphenols and caffeine, under the same conditions. Fluoride adsorption by Tea-Al for different times obeyed the surface reaction and adsorption isotherms fit the Freundlich model. In addition, the fluoride adsorption mechanism appeared to be an ion exchange between hydroxyl and fluoride ions. Results from this study demonstrated that Tea-Al is a promising biosorbent useful for the removal of fluoride in brick tea infusion. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Phosphate reduction in a hydroxyapatite fluoride removal system

NASA Astrophysics Data System (ADS)

Egner, A.

2012-12-01

Fluorosis is a widespread disease that occurs as a result of excess fluoride consumption and can cause severe tooth and bone deformations. To combat fluorosis, several previous studies have examined the potential to replace traditional bone char filters with synthetic hydroxyapatite. Calcite particles with a synthetic hydroxyapatite coating have been shown to effectively removed fluoride, yet the low-cost method for forming these particles leaves high amounts of phosphate both in synthesis waste-water and in filter effluent. High phosphate in filter effluent is problematic because consumption of extremely high phosphate can leach calcium from bones, further exacerbating the fluoride effect. This study examines ways of reducing and reusing waste. In particular, a method of fluoride removal is explored in which fluorapatite coatings may be formed directly. In preliminary studies, batches of 4.1g of Florida limestone (<710 μm) were equilibrated with 100 mL of 10ppm fluoride. In a control batch containing lime but no added phosphate, 14% treatment was achieved, but with added phosphate, 100% treatment was achieved in all batches. Batches with lower levels of phosphate took longer to reach 100% treatment, ranging from less than 24 hours in the highest phosphate batches to approximately 42 hours in the lowest batches. The lower levels tested were well within reasonable levels for drinking water and reached 0ppm fluoride in 42 hours or less.

Rational Design of Antifouling Polymeric Nanocomposite for Sustainable Fluoride Removal from NOM-Rich Water.

PubMed

Zhang, Xiaolin; Zhang, Lu; Li, Zhixian; Jiang, Zhao; Zheng, Qi; Lin, Bin; Pan, Bingcai

2017-11-21

The presence of natural organic matter (NOM) exerts adverse effects on adsorptive removal of various pollutants including fluoride from water. Herein, we designed a novel nanocomposite adsorbent for preferable and sustainable defluoridation from NOM-rich water. The nanocomposite (HZO@HCA) is obtained by encapsulating hydrous zirconium oxide nanoparticles (HZO NPs) inside hyper-cross-linked polystyrene anion exchanger (HCA) binding tertiary amine groups. Another commercially available nanocomposite HZO@D201, with the host of a cross-linked polystyrene anion exchanger (D201) binding ammonium groups, was involved for comparison. HZO@HCA features with abundant micropores instead of meso-/macropores of HZO@D201, resulting in the inaccessible sites for NOM due to the size exclusion. Also, the tertiary amine groups of HCA favor an efficient desorption of the slightly loaded NOM from HZO@HCA. As expected, Sigma-Aldrich humic acid even at 20 mg of DOC/L did not exert any observable effect on fluoride sequestration by HZO@HCA, whereas a significant inhibition was observed for HZO@D201. Cyclic adsorption runs further verified the superior reusability of HZO@HCA for defluoridation from NOM-rich water. In addition, the HZO@HCA column could generate ∼80 bed volume (BV) effluent from a synthetic fluoride-containing groundwater to meet the drinking water standard (<1.5 mg F/L), whereas HCA and HZO@D201 columns could only generate <5 and ∼40 BV effluents, respectively. This study is believed to shed new light on how to rationally design antifouling nanocomposites for water remediation.

Electrochemical degradation of 5-FU using a flow reactor with BDD electrode: Comparison of two electrochemical systems.

PubMed

Ochoa-Chavez, A S; Pieczyńska, A; Fiszka Borzyszkowska, A; Espinoza-Montero, P J; Siedlecka, E M

2018-06-01

In this study, the electrochemical degradation process of 5-fluorouracil (5-FU) in aqueous media was performed using a continuous flow reactor in an undivided cell (system I), and in a divided cell with a cationic membrane (Nafion ® 424) (system II). In system I, 75% of 5-FU degradation was achieved (50 mg L -1 ) with a applied current density j app  = 150 A m -2 , volumetric flow rate qv = 13 L h -1 , after 6 h of electrolysis (k app  = 0.004 min -1 ). The removal efficiency of 5-FU was higher (95%) when the concentration was 5 mg L -1 under the same conditions. Nitrates (22% of initial amount of N), fluorides (27%) and ammonium (10%) were quantified after 6 h of electrolysis. System II, 77% of 5-FU degradation was achieved (50 mg L -1 ) after 6 h of electrolysis (k app  = 0.004 min -1 ). The degradation rate of 5-FU was complete when the concentration was 5 mg L -1 under the same conditions. Nitrates (29% of initial amount of N), fluorides (25%) and ammonium (5%) were quantified after 6 h of electrolysis. In addition, the main organic byproducts identified by mass spectroscopy were aliphatic compound with carbonyl and carboxyl functionalities. Due to, the mineralization of 5-FU with acceptable efficiency of 88% found in system II (j app of 200 A m -2 ), this system seems to be more promising in the cytostatic drug removal. Moreover the efficiency of 5-FU removal in diluted solutions is better in system II than in system I. Copyright © 2018 Elsevier Ltd. All rights reserved.

Onsite defluoridation system for drinking water treatment using calcium carbonate.

PubMed

Wong, Elaine Y; Stenstrom, Michael K

2018-06-15

Fluoride in drinking water has several effects on teeth and bones. At concentrations of 1-1.5 mg/L, fluoride can strengthen enamel, improving dental health, but at concentrations above 1.5 to 4 mg/L can cause dental fluorosis. At concentrations of 4-10 mg/L, skeletal fluorosis can occur. There are many areas of the world that have excessive fluoride in drinking water, such as China, India, Sri Lanka, and the Rift Valley countries in Africa. Treatment solutions are needed, especially in poor areas where drinking water treatment plants are not available. On-site or individual treatment alternatives can be attractive if constructed from common materials and if simple enough to be constructed and maintained by users. Advanced on-site methods, such as under sink reserve osmosis units, can remove fluoride but are too expensive for developing areas. This paper investigates calcium carbonate as a cost effective sorbent for an onsite defluoridation drinking water system. Batch and column experiments were performed to characterize F - removal properties. Fluoride sorption was described by a Freundlich isotherm model, and it was found that the equilibrium time was approximately 3 h. Calcium carbonate was found to have comparable F - removal abilities as the commercial ion exchange resins and possessed higher removal effectiveness compared to calcium containing eggshells and seashells. It was also found that the anion Cl- did not compete with F - at typical drinking water concentrations, having little impact on the effectiveness of the treatment system. A fluoride removal system is proposed that can be used at home and can be maintained by users. Through this work, we can be a step closer to bringing safe drinking water to those that do not have access to it. Copyright © 2017 Elsevier Ltd. All rights reserved.

APPLICATION OF VACUUM SALT DISTILLATION TECHNOLOGY FOR THE REMOVAL OF FLUORIDE AND CHLORIDE FROM LEGACY FISSILE MATERIALS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pierce, R.; Peters, T.

2011-11-01

Between September 2009 and January 2011, the Savannah River National Laboratory (SRNL) and the Savannah River Site (SRS) HB-Line Facility designed, developed, tested, and successfully deployed a production-scale system for the distillation of sodium chloride (NaCl) and potassium chloride (KCl) from plutonium oxide (PuO{sub 2}). Subsequent efforts adapted the vacuum salt distillation (VSD) technology for the removal of chloride and fluoride from less-volatile halide salts at the same process temperature and vacuum. Calcium chloride (CaCl{sub 2}), calcium fluoride (CaF{sub 2}), and plutonium fluoride (PuF{sub 3}) were of particular concern. To enable the use of the same operating conditions for themore » distillation process, SRNL employed in situ exchange reactions to convert the less-volatile halide salts to compounds that facilitated the distillation of halide without removal of plutonium. SRNL demonstrated the removal of halide from CaCl{sub 2}, CaF{sub 2} and PuF{sub 3} below 1000 C using VSD technology.« less

Evaluation of early bone response to fluoride-modified and anodically oxidized titanium implants through continuous removal torque analysis.

PubMed

Kwon, Taek-Ka; Lee, Hyo-Jung; Min, Seung-Ki; Yeo, In-Sung

2012-10-01

To compare between a bioactive and a bioinert implant with different geometries by continuous measurement of the removal torque and calculation of the angular momentum of each surfaced implant. Six New Zealand white rabbits were used in the study. Each rabbit received 2 implants. A bioactive fluoride-modified implant with a conical connection and microthread design was inserted into one tibia, and a bioinert anodically oxidized implant with an external connection design was inserted into the other. After 2 weeks of implant insertion, the removal torque values were continuously measured according to time. Using the time-torque curve resulting from the measurements, the maximum values were determined, and the angular momenta were calculated. The anodically oxidized implant had significantly higher peak removal torque and angular momentum values than the fluoride-modified implant (P < 0.05). The impact of the fluoride-modified bioactive implant on early bone response remains unclear. Considering the angular momentum of dental implants may assist in the elucidation of the effect of implant geometry on bone response.

Preparation of novel alginate based anion exchanger from Ulva japonica and its application for the removal of trace concentrations of fluoride from water.

PubMed

Paudyal, Hari; Pangeni, Bimala; Inoue, Katsutoshi; Kawakita, Hidetaka; Ohto, Keisuke; Ghimire, Kedar Nath; Alam, Shafiq

2013-11-01

A green seaweed, Ulva japonica, was modified by loading multivalent metal ions such as Zr(IV) and La(III) after CaCl2 cross-linking to produce metal loaded cross-linked seaweed (M-CSW) adsorbents, which were characterized by elemental analysis, functional groups identification, and metal content determination. Maximum sorption potential for fluoride was drastically increased after La(III) and Zr(IV) loading, which were evaluated as 0.58 and 0.95 mmol/g, respectively. Loaded fluoride was quantitatively desorbed by using dilute alkaline solution for its regeneration. Mechanism of fluoride adsorption was inferred in terms of ligand exchange reaction between hydroxyl ion on co-ordination sphere of the loaded metal ions of M-CSW and fluoride ion in aqueous solution. Application of M-CSW for the treatment of actual waste plating solution exhibited successful removal of fluoride to clear the effluent and environmental standards in Japan, suggesting high possibility of its application for the treatment of fluoride rich waste water. Copyright © 2013 Elsevier Ltd. All rights reserved.

Selective separation of phosphate and fluoride from semiconductor wastewater.

PubMed

Warmadewanthi, B; Liu, J C

2009-01-01

Hydrofluoric acid (HF) and phosphoric acid (H(3)PO(4)) are widely used in semiconductor industry for etching and rinsing purposes. Consequently, significant amount of wastewater containing phosphate and fluoride is generated. Selective separation of phosphate and fluoride from the semiconductor wastewater, containing 936 mg/L of fluoride, 118 mg/L of phosphate, 640 mg/L of sulfate, and 26.7 mg/L of ammonia, was studied. Chemical precipitation and flotation reactions were utilized in the two-stage treatment processes. The first-stage reaction involved the addition of magnesium chloride (MgCl(2)) to induce selective precipitation of magnesium phosphate. The optimal condition was pH 10 and molar ratio, [Mg(2 + )]/[(PO(4) (3-))], of 3:1, and 66.2% of phosphate was removed and recovered as bobierrite (Mg(3)(PO(4))(2).8H(2)O). No reaction was found between MgCl(2) and fluoride. Calcium chloride (CaCl(2)) was used in the second-stage reaction to induce precipitation of calcium fluoride and calcium phosphate. The optimum molar ratio, [Ca(2 + )]/[F(-)], was 0.7 at pH 10, and residual fluoride concentration of 10.7 mg/L and phosphate concentration of lower than 0.5 mg/L was obtained. Thermodynamic equilibrium was modeled with PHREEQC and compared with experimental results. Sodium dodecylsulfate (SDS) was an effective collector for subsequent solid-liquid removal via dispersed air flotation (DiAF). The study demonstrated that phosphate can be selectively recovered from the wastewater. Potential benefits include recovery of phosphate for reuse, lower required dosage of calcium for fluoride removal, and less amount of CaF(2) sludge.

APPLICATION OF VACUUM SALT DISTILLATION TECHNOLOGY FOR THE REMOVAL OF FLUORIDE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pierce, R.; Pak, D.

2011-08-10

Vacuum distillation of chloride salts from plutonium oxide (PuO{sub 2}) and simulant PuO{sub 2} has been previously demonstrated at Department of Energy (DOE) sites using kilogram quantities of chloride salt. The apparatus for vacuum distillation contains a zone heated using a furnace and a zone actively cooled using either recirculated water or compressed air. During a vacuum distillation operation, a sample boat containing the feed material is placed into the apparatus while it is cool, and the system is sealed. The system is evacuated using a vacuum pump. Once a sufficient vacuum is attained, heating begins. Volatile salts distill frommore » the heated zone to the cooled zone where they condense, leaving behind the non-volatile materials in the feed boat. The application of vacuum salt distillation (VSD) is of interest to the HB-Line Facility and the MOX Fuel Fabrication Facility (MFFF) at the Savannah River Site (SRS). Both facilities are involved in efforts to disposition excess fissile materials. Many of these materials contain chloride and fluoride salt concentrations which make them unsuitable for dissolution without prior removal of the chloride and fluoride salts. Between September 2009 and January 2011, the Savannah River National Laboratory (SRNL) and HB-Line designed, developed, tested, and successfully deployed a system for the distillation of chloride salts. Subsequent efforts are attempting to adapt the technology for the removal of fluoride. Fluoride salts of interest are less-volatile than the corresponding chloride salts. Consequently, an alternate approach is required for the removal of fluoride without significantly increasing the operating temperature. HB-Line Engineering requested SRNL to evaluate and demonstrate the feasibility of an alternate approach using both non-radioactive simulants and plutonium-bearing materials. Whereas the earlier developments targeted the removal of sodium chloride (NaCl) and potassium chloride (KCl), the current activities are concerned with the removal of the halide ions associated with plutonium trifluoride (PuF{sub 3}), plutonium tetrafluoride (PuF{sub 4}), calcium fluoride (CaF{sub 2}), and calcium chloride (CaCl{sub 2}). This report discusses non-radioactive testing of small-scale and pilot-scale systems and radioactive testing of a small-scale system. Experiments focused on demonstrating the chemistry for halide removal and addressing the primary engineering questions associated with a change in the process chemistry.« less

Fluoride removal from water using a magnesia-pullulan composite in a continuous fixed-bed column.

PubMed

Ye, Yuanyao; Yang, Jing; Jiang, Wei; Kang, Jianxiong; Hu, Ying; Ngo, Huu Hao; Guo, Wenshan; Liu, Yiwen

2018-01-15

A magnesia-pullulan composite (MgOP) was previously shown to effectively remove fluoride from water. In the present study, a continuous fixed-bed column was used to examine the application of the composite at an industrial scale. The influencing parameters included bed mass (4.0, 6.0 and 8.0 g), influent flow rate (8, 16 and 32 mL/min), inlet fluoride concentration (5, 10 and 20 mg/L), reaction temperature (20, 30 and 40 °C), influent pH (4, 7 and 10) and other existing anions (HCO 3 - , SO 4 2- , Cl - and NO 3 - ), through which the breakthrough curves could be depicted for the experimental data analysis. The results indicated that MgOP is promising for fluoride removal with a defluoridation capacity of 16.6 mg/g at the bed mass of 6.0 g, influent flow rate of 16 mL/min and inlet fluoride concentration of 10 mg/L. The dynamics of the fluoride adsorption process were modeled using the Thomas and Yan models, in which the Yan model presented better predictions for the breakthrough curves than the Thomas model. Moreover, the concentration of magnesium in the effluent was monitored to determine Mg stability in the MgOP composite. Results indicated the effluent concentration of Mg 2+ ions could be kept at a safe level. Calcination of fluoride-loaded MgOP effectively regenerated the material. Copyright © 2017 Elsevier Ltd. All rights reserved.

Enhanced defluoridation and facile separation of magnetic nano-hydroxyapatite/alginate composite.

PubMed

Pandi, Kalimuthu; Viswanathan, Natrayasamy

2015-09-01

In this research study, a new magnetic biosorbent was developed by the fabrication of magnetic Fe3O4 particles on nano-hydroxyapatite(n-HAp)/alginate (Alg) composite (Fe3O4@n-HApAlg composite) for defluoridation in batch mode. The synthesized Fe3O4@n-HApAlg biocomposite possess an enhanced defluoridation capacity (DC) of 4050 mgF(-)/kg when compare to n-HApAlg composite, Fe3O4@n-HAp composite, n-HAp and Fe3O4 which possesses the DCs of 3870, 2469, 1296 and 1050 mgF(-)/kg respectively. The structural changes of the sorbent, before and after fluoride sorption were studied using FTIR, XRD and SEM with EDAX techniques. There are various physico-chemical parameters such as contact time, pH, co-existing anions, initial fluoride concentration and temperature were optimized for maximum fluoride removal. The equilibrium data was well modeled by Freundlich, Langmuir, Dubinin-Radushkevich (D-R) and Temkin isotherms. The present system follows Dubinin-Radushkevich isotherm model. The thermodynamic parameters reveals that the feasibility, spontaneity and endothermic nature of fluoride sorption. The performance and efficiency of the adsorbent material was examined with water samples collected from fluoride endemic areas namely Reddiyarchatram and Ammapatti in Dindigul District of Tamil Nadu using standard protocols. Copyright © 2015 Elsevier B.V. All rights reserved.

Removal of uranium and fluorine from wastewater by double-functional microsphere adsorbent of SA/CMC loaded with calcium and aluminum

NASA Astrophysics Data System (ADS)

Wu, Liping; Lin, Xiaoyan; Zhou, Xingbao; Luo, Xuegang

2016-10-01

A novel dual functional microsphere adsorbent of alginate/carboxymethyl cellulose sodium composite loaded with calcium and aluminum (SA/CMC-Ca-Al) is prepared by an injection device to remove fluoride and uranium, respectively, from fluoro-uranium mixed aqueous solution. Batch experiments are performed at different conditions: pH, temperature, initial concentration and contact time. The results show that the maximum adsorption amount for fluoride is 35.98 mg/g at pH 2.0, 298.15 K concentration 100 mg/L, while that for uranium is 101.76 mg/g at pH 4.0, 298.15 K concentration 100 mg/L. Both of the adsorption process could be well described by Langmuir model. The adsorption kinetic data is fitted well with pseudo-first-order model for uranium and pseudo-second-order model for fluoride. Thermodynamic parameters are also evaluated, indicating that the adsorption of uranium on SA/CMC-Ca-Al is a spontaneous and exothermic process, while the removal of fluoride is non-spontaneous and endothermic process. The mechanism of modification and adsorption process on SA/CMC-Ca-Al is characterized by FT-IR, SEM, EDX and XPS. The results show that Ca (II) and Al (III) are loaded on SA/CMC through ion-exchange of sodium of SA/CMC. The coordination reaction and ion-exchange happen during the adsorption process between SA/CMC-Ca-Al and uranium, fluoride. Results suggest that the SA/CMC-Ca-Al adsorbent has a great potential in removing uranium and fluoride from aqueous solution.

Micro- and Nano- Porous Adsorptive Materials for Removal of Contaminants from Water at Point-of-Use

NASA Astrophysics Data System (ADS)

Yakub, Ismaiel

Water is food, a basic human need and a fundamental human right, yet hundreds of millions of people around the world do not have access to clean drinking water. As a result, about 5000 people die each day from preventable water borne diseases. This dissertation presents the results of experimental and theoretical studies on three different types of porous materials that were developed for the removal of contaminants from water at point of use (household level). First, three compositionally distinct porous ceramic water filters (CWFs) were made from a mixture of redart clay and sieved woodchips and processed into frustum shape. The filters were tested for their flow characteristics and bacteria filtration efficiencies. Since, the CWFs are made from brittle materials, and may fail during processing, transportation and usage, the mechanical and physical properties of the porous clays were characterized, and used in modeling designed to provide new insights for the design of filter geometries. The mechanical/physical properties that were characterized include: compressive strength, flexural strength, facture toughness and resistance curve behavior, keeping in mind the anisotropic nature of the filter structure. The measured flow characteristics and mechanical/physical properties were then related to the underlying porosity and characteristic pore size. In an effort to quantify the adhesive interactions associated with filtration phenomena, atomic force microscopy (AFM) was used to measure the adhesion between bi-material pairs that are relevant to point-of-use ceramic water filters. The force microscopy measurements of pull-off force and adhesion energy were used to rank the adhesive interactions. Similarly, the adsorption of fluoride to hydroxyapatite-doped redart clay was studied using composites of redart clay and hydroxyapatite (C-HA). The removal of fluoride from water was explored by carrying out adsorption experiments on C-HA adsorbents with different ratios of clay to hydroxyapatite (and sintered at different temperatures). The overall adsorption was controlled using water with varying fluoride concentrations and adsorbent-adsorbate contact times. Prototype frustum-shaped C-HA filters were then fabricated and shown to remove both fluoride and E.coli bacteria from water. Finally, "buckyweb", which is a foam comprising carbon nanotubes and graphene was made via thermal ablation of graphite, and tested for its deflouridation capacity. Defluoridation was studied in terms of concentration of fluoride, contact time and pH. The structure and adsorption characteristics of buckyweb foams were elucidated via energy dispersive x-ray spectroscopy, transmission electron microscopy and scanning transmission electron microscopy. The implications of the results were then explored for potential applications in water filtration.

Synthesis of hydroxyapatite nanorods for application in water defluoridation and optimization of process variables: Advantage of ultrasonication with precipitation method over conventional method.

PubMed

Mehta, Dhiraj; Mondal, Poonam; Saharan, Virendra Kumar; George, Suja

2017-07-01

This research work presents the synthesis of hydroxyapatite (Hap) nanorods for defluoridation of drinking water by using both conventional (CM) and ultrasonication with precipitation (USPM) methods. Calcium nitrate was reacted with potassium phosphate in presence of ammonia for controlled pH to synthesize Hap nanorods, which was characterized using FTIR, XRD, SEM, TG-DTA, and TEM/EDS for determining its phase composition, structural and thermal decomposition behavior. When USPM method was used for synthesis, the yield of the Hap nanorods was improved from 83.24±1.0% to 90.2±1.0%, and complete phase transformation occurred with formation of elongated Hap nanorods. Effects of process parameters such as solution pH, contact time and adsorbent dose were studied through response surface methodology (RSM). A simple quadratic model was developed using Central Composite Design (CCD) and optimum parameters for fluoride adsorption process were determined to be pH 7, contact time 3h and adsorbent dose 7g/L for maximum removal capacity. Fluoride removal efficiency was predicted to be 93.64% which was very close to the experimental value obtained at 92.86% using ultrasonically prepared Hap. Fluoride adsorption isotherms fitted the Freundlich isotherm with an adsorption capacity of 1.49mg/g, while the kinetic studies revealed that the process followed pseudo-second order model. The treated water quality parameters such as residual fluoride, calcium leached, total hardness and alkalinity was investigated, and it was observed that all these parameters were within the permissible limits as per WHO and BIS standards. Copyright © 2017 Elsevier B.V. All rights reserved.

Removal of ammonium and heavy metals by cost-effective zeolite synthesized from waste quartz sand and calcium fluoride sludge.

PubMed

Zhang, Qian; Lin, Bing; Hong, Junming; Chang, Chang-Tang

2017-02-01

This study focuses on the effectiveness of zeolite (10% CF-Z [0.5]) hydrothermally synthesized from waste quartz sand and calcium fluoride (CF) for ammonium ion and heavy metal removal. Zeolite was characterized through powder X-ray diffraction, Fourier-transform infrared spectroscopy, micromeritics N 2 adsorption/desorption analysis, and field emission scanning electron microscopy. The effects of CF addition, Si/Al ratio, initial ammonium concentration, solution pH, and temperature on the adsorption of ammonium on 10% CF-Z (0.5) were further examined. Results showed that 10% CF-Z (0.5) was a single-phase zeolite A with cubic-shaped crystals and 10% CF-Z (0.5) efficiently adsorbs ammonium and heavy metals. For instance, 91% ammonium (10 mg L -1 ) and 93% lead (10 mg L -1 ) are removed. The adsorption isotherm, kinetics, and thermodynamics of ammonium adsorption on 10% CF-Z (0.5) were also theoretically analyzed. The adsorption isotherm of ammonium and lead on 10% CF-Z (0.5) in single systems indicated that Freundlich model provides the best fit for the equilibrium data, whereas pseudo-second-order model best describes the adsorption kinetics. The adsorption degree of ions on 10% CF-Z (0.5) in mixed systems exhibits the following pattern: lead > ammonium > cadmium > chromium.

Swift adsorptive removal of Congo red from aqueous solution by K1.33Mn8O16 nanowires.

PubMed

Wu, Junshu; Li, Hongyi; Wang, Jinshu; Li, Zhifei

2013-08-01

A swift and efficient approach to converting organic dye effluents into fresh water could be of substantial benefit. In this study, we presented facile hydrothermal synthesis of K1.33Mn8O16 nanowires in ammonium fluoride (NH4F) aqueous solution. The crystallization process of K1.33Mn8O16 nanowires was investigated. The as-obtained K1.33Mn8O16 nanowires were used for swift adsorptive removal of Congo red from aqueous solution without adjusting pH value at room temperature. Adsorption kinetic experimental data are well described by pseudo-second-order rate kinetic model, and the adsorption isotherm fits Langmuir isotherm model. The present investigation provides an efficient approach to designing and fabricating manganese-based nanomaterials for environmental remediation.

Boron removal from aqueous solution by direct contact membrane distillation.

PubMed

Hou, Deyin; Wang, Jun; Sun, Xiangcheng; Luan, Zhaokun; Zhao, Changwei; Ren, Xiaojing

2010-05-15

The removal of boron from aqueous solution by direct contact membrane distillation (DCMD) was studied with self-prepared polyvinylidene fluoride (PVDF) hollow fiber membranes in the present work. The effect of pH, boron concentration, temperature and salt concentration of the feed solution on the boron rejection was investigated. The experimental results indicated that boron rejection was less dependent on the feed pH and salt concentration. DCMD process had high boron removal efficiency (>99.8%) and the permeate boron was below the maximum permissible level even at feed concentration as high as 750 mg/L. Although the permeate flux was enhanced exponentially with the feed temperature increasing, the influence of feed temperature on the boron rejection could be neglected. Finally, the natural groundwater sample containing 12.7 mg/L of boron was treated by DCMD process. The permeate boron kept below 20 microg/L whether the feed was acidified or not, but pre-acidification was helpful to maintain the permeate flux stability. All the experimental results indicated that DCMD could be efficiently used for boron removal from aqueous solution. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Effect of phytate and zinc ions on fluoride toothpaste efficacy using an in situ caries model.

PubMed

Parkinson, Charles R; Burnett, Gary R; Creeth, Jonathan E; Lynch, Richard J M; Budhawant, Chandrashekhar; Lippert, Frank; Hara, Anderson T; Zero, Domenick T

2018-06-01

To compare and explore the dose-response of phytate-containing 1150 ppm fluoride toothpastes on model caries lesions and to determine the impact of zinc ions. This was a single-centre, randomised, blinded (examiner/laboratory analyst), six-treatment, four-period crossover, in situ study in adults with a removable bilateral maxillary partial denture. Study treatments were toothpastes containing: 0.425% phytate/F; 0.85% phytate/F; 0.85% phytate/Zn/F; F-only; Zn/F and a 0% F placebo. Where present, F was 1150 ppm as NaF; Zn was 0.3% as ZnCl 2 . Human enamel specimens containing early-stage, surface-softened (A-lesions) or more advanced, subsurface (B-lesions) caries lesions were placed into the buccal flanges of participants' modified partial denture (one of each lesion type per side). A-lesions were removed after 14 days of twice-daily treatment use; B-lesions were removed after a further 14 days. A-lesions were analysed for surface microhardness recovery. Both lesion types were analysed by transverse microradiography and for enamel fluoride uptake, with B-lesions additionally analysed by quantitative light-induced fluorescence. Comparison was carried out using an analysis of covariance model. Statistically significant differences between 1150 ppm F and the placebo toothpastes (p < 0.05) were shown for all measures, validating the model. No differences between fluoride toothpastes were observed for any measure with little evidence of a dose-response for phytate. Study treatments were generally well-tolerated. Results suggest phytate has little impact on fluoride's ability to promote early-stage lesion remineralisation or prevent more advanced lesion demineralisation in this in situ caries model. Similarly, results suggest zinc ions do not impair fluoride efficacy. Toothpastes may contain therapeutic or cosmetic agents that could interfere with fluoride's caries prevention efficacy. The present in situ caries study has demonstrated that phytate, added to provide enhanced extrinsic stain removal/prevention, and zinc, added to inhibit malodour, do not impair fluoride efficacy. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Phytoremediation of fluoride with garden ornamentals Nerium oleander, Portulaca oleracea, and Pogonatherum crinitum.

PubMed

Khandare, Rahul V; Desai, Shaileshkumar B; Bhujbal, Sourabh S; Watharkar, Anuprita D; Biradar, Shivtej P; Pawar, Pankaj K; Govindwar, Sanjay P

2017-03-01

Nursery grown plants of Nerium oleander, Pogonatherum crinitum, and Portulaca oleracea were observed to remove fluoride up to 92, 80, and 73%, respectively, from NaF solution at the concentration of 10 mg L -1 within 15 days. Concentration range of 10-50 mg L -1 of fluoride revealed a constant decrease of removal from 92 to 51% within 15 days by N. oleander, while the biomass (one to five plants) showed enhancement in removal from 74 to 98% in 10 days. Translocation and bioaccumulation factors calculated after fluoride contents in roots and leaves of N. oleander, P. crinitum, and P. oleracea were 1.85, 1.19, and 1.43, and 9.8, 3.6, and 2.2, respectively. P . oleracea, P. crinitum, and N. oleander showed reductions in chlorophyll contents by 40, 57 and 25 and 8%, carbohydrates by 50, 44, and 16%, and proteins by 38, 53, and 15%, respectively. Activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) in the roots of P. oleracea, P. crinitum, and N. oleander were observed to be induced by 400, 383, and 500%; 80, 105, and 424%; and 153, 77, and 71%, respectively, while the leaves showed induction in SOD, CAT, and GPX activities by 550, 315, and 165%; 196, 227, and 243%; and 280, 242, and 184%, respectively. Results endorsed the superiority of N. oleander for fluoride removal over other plant species.

Defluoridation by Bacteriogenic Iron Oxides: Sorption Studies

NASA Astrophysics Data System (ADS)

Evans, K.; Ferris, F.

2009-05-01

At concentrations above 1 mg/L, fluoride in drinking water can lead to dental and skeletal fluorosis, a disease that causes mottling of the teeth, calcification of ligaments, crippling bone deformities and many other physiological disorders that can, ultimately, lead to death. Conservative estimates are that fluorosis afflicts tens of millions of people worldwide. As there is no treatment for fluorosis, prevention is the only means of controlling the disease. While numerous defluoridation techniques have been explored, no single method has been found to be both effective and inexpensive enough to implement widely. Our research began in India, with a large-scale geochemical study of the groundwater in a fluoride-contaminated region of Orissa. Having developed a better understanding of the geochemical relationships that exist between fluoride and other parameters present in an affected area, as well as the complex relationships that arise among those parameters that can impact the presence of fluoride, we began investigating certain remediation scenarios involving iron oxides. A common approach to remediation involves the partitioning of fluoride from groundwater by sorption onto a variety of materials, one of the most effective of which is iron oxide whose surface area acts as a scavenger for fluoride. In the presence of iron oxidizing bacteria, the oxidation rate of iron has been shown to be ˜6 times greater than in their absence; fluoride should, therefore, be removed from an aqueous environment by bacteriogenic iron oxides (BIOS) much more quickly than by abiotic iron oxides. Most recently, sorption studies have been conducted using both BIOS and synthetic hydrous ferric oxides in order to compare the behavior between biotic and abiotic sorbents. These studies have provided sorption isotherms that allow comparison of fluoride removed by sorption to BIOS versus synthetic iron oxides. Sorption affinity constants have also been determined, which allow for the prediction of fluoride removal in a wide variety of groundwater systems. Sorption isotherms and affinity constants show the use of BIOS to be a promising technique for the remediation of fluoride in groundwater.

Biosorptive removal of inorganic arsenic species and fluoride from aqueous medium by the stem of Tecomella undulate.

PubMed

Brahman, Kapil Dev; Kazi, Tasneem Gul; Baig, Jameel Ahmed; Afridi, Hassan Imran; Arain, Sadaf Sadia; Saraj, Saima; Arain, Muhammad B; Arain, Salma Aslam

2016-05-01

Simultaneous removal of fluoride (F(-)), inorganic arsenic species, As(III) and As(V), from aqueous samples has been performed using an economic indigenous biosorbent (Stem of Tecomella undulata). The inorganic As species in water samples before and after biosorption were determined by cloud point and solid phase extraction methods, while F(-) was determined by ion chromatography. Batch experiments were carried out to evaluate the equilibrium adsorption isotherm studies for As(III), As(V) and F(-) in aqueous solutions. Several parameters of biosorption were optimized such as pH, biomass dosage, analytes concentration, time and temperature. The surface of biosorbent was characterized by SEM and FTIR. The FTIR study indicated the presence of carbonyl and amine functional groups which may have important role in the sorption/removal of these ions. Thermodynamic and kinetic study indicated that the biosorption of As(III), As(V) and F(-) were spontaneous, exothermic and followed by pseudo-second-order. Meanwhile, the interference study revealed that there was no significant effect of co-existing ions for the removal of inorganic As species and F(-) from aqueous samples (p > 0.05). It was observed that the indigenous biosorbent material simultaneously adsorbed As(III) (108 μg g(-1)), As(V) (159 μg g(-1)) and F(-) (6.16 mg g(-1)) from water at optimized conditions. The proposed biosorbent was effectively regenerated and efficiently used for several experiments, to remove the As(III), As(V) and F(-) from real water sample collected from endemic area of Pakistan. Copyright © 2016 Elsevier Ltd. All rights reserved.

Highly efficient solid phase synthesis of oligonucleotide analogs containing phosphorodithioate linkages.

PubMed

Capaldi, D C; Cole, D L; Ravikumar, V T

2000-05-01

A triester method for the synthesis of deoxynucleoside phosphorodithioate dimers is described. The phosphorodithioate linkage is introduced using a new dithiophosphorylating reagent DPSE-SP(S)Cl(2)where DPSE = 2-diphenylmethylsilylethyl. This group is removed quickly using tetra-butylammonium fluoride leading to the quantitative formation of phosphorodithioate diesters uncontaminated with the corresponding phosphorothioates. The utility of this group is demonstrated by the synthesis of a penta-decathymidylic acid, [T(PS(2))T(PO(2))](7)T, which contains alternating phosphorodithioate/phosphate diester internucleotide linkages.

Method of removing arsenic and other anionic contaminants from contaminated water using enhanced coagulation

DOEpatents

Teter, David M.; Brady, Patrick V.; Krumhansl, James L.; Khandaker, Nadim R.

2006-11-21

An improved water decontamination process comprising contacting water containing anionic contaminants with an enhanced coagulant to form an enhanced floc, which more efficiently binds anionic species (e.g., arsenate, arsenite, chromate, fluoride, selenate, and borate, and combinations thereof) predominantly through the formation of surface complexes. The enhanced coagulant comprises a trivalent metal cation coagulant (e.g., ferric chloride or aluminum sulfate) mixed with a divalent metal cation modifier (e.g., copper sulfate or zinc sulfate).

75 FR 2440 - Approval and Promulgation of Implementation Plans; Kentucky: Approval of Revisions to the State...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-15

... SIP provisions relating to, among other things, fluoride emission standards); 64 FR 7790 (removing... provisions from Wyoming SIP relating to, among other things, hydrogen sulfide and fluoride ambient standards...

Atmosphere purification of radon and radon daughter elements

DOEpatents

Stein, L.

1974-01-01

A method of removing radon and radon daughter elements from an atmosphere containing these elements by passing the atmosphere through a bed of fluorinating compound whereby the radon and radon daughters are oxidized to their respective fluorides is discussed. These fluorides adhere to the fluorinating compound and are thus removed from the atmosphere which may then be recirculated. A method for recovering radon and separating radon from its daughter elements is also described. (Official Gazette)

[The Nutrition Commission of the Austrian Society of Pediatrics and Adolescent Medicine. Prevention of caries].

PubMed

Haschke, F

1992-01-01

Effective preventive programs must be instituted early in the life of a child. The pediatrician plays an important role in preventive oral health care, because most children do not visit a dentist before 3 years of age. Fluoride therapy decreases the caries vulnerability of the tooth, oral hygiene measures are important to remove bacterial plaque, and dietary modifications reduce the number of carbohydrate exposures per day. Community water fluoridation is proposed in Austrian cities, because it continues to be the most cost-effective caries prevention measure available. As long as the population does not have access to optimally fluoridated water, dietary fluoride supplementation offers an effective alternative. The recommended dosage of fluoride supplements for children depends on the amount of fluoride present in their drinking water and on the child's age. Liquid fluoride supplements and chewable tablets are proposed for children between 0.5 and 3 years and children between 3 and 13 years, respectively. Home use topical fluorides and professionally applied topical fluorides are useful beyond 3 years of age. Teaching of oral hygiene measures should be continued in kindergarten and school. The 3-6 year-old children require parental assistance to achieve effective plaque removal. Semiannual dental visits should begin at the age of three and continue throughout childhood and adolescence. As far as the diet is concerned, the frequency of exposure to sugar appears to be the most important factor in the development of dental caries. It now appears that most sugars are nearly equally cariogenic in a pure form.

Low-Cost, Robust, and Field Portable Smartphone Platform Photometric Sensor for Fluoride Level Detection in Drinking Water.

PubMed

Hussain, Iftak; Ahamad, Kamal Uddin; Nath, Pabitra

2017-01-03

Groundwater is the major source of drinking water for people living in rural areas of India. Pollutants such as fluoride in groundwater may be present in much higher concentration than the permissible limit. Fluoride does not give any visible coloration to water, and hence, no effort is made to remove or reduce the concentration of this chemical present in drinking water. This may lead to a serious health hazard for those people taking groundwater as their primary source of drinking water. Sophisticated laboratory grade tools such as ion selective electrodes (ISE) and portable spectrophotometers are commercially available for in-field detection of fluoride level in drinking water. However, such tools are generally expensive and require expertise to handle. In this paper, we demonstrate the working of a low cost, robust, and field portable smartphone platform fluoride sensor that can detect and analyze fluoride concentration level in drinking water. For development of the proposed sensor, we utilize the ambient light sensor (ALS) of the smartphone as light intensity detector and its LED flash light as an optical source. An android application "FSense" has been developed which can detect and analyze the fluoride concentration level in water samples. The custom developed application can be used for sharing of in-field sensing data from any remote location to the central water quality monitoring station. We envision that the proposed sensing technique could be useful for initiating a fluoride removal program undertaken by governmental and nongovernmental organizations here in India.

Arsenic and fluoride removal from groundwater by electrocoagulation using a continuous filter-press reactor.

PubMed

Guzmán, Athziri; Nava, José L; Coreño, Oscar; Rodríguez, Israel; Gutiérrez, Silvia

2016-02-01

We investigated simultaneous arsenic and fluoride removal from ground water by electrocoagulation (EC) using aluminum as the sacrificial anode in a continuous filter-press reactor. The groundwater was collected at a depth of 320 m in the Bajío region in Guanajuato Mexico (arsenic 43 µg L(-1), fluoride 2.5 mg L(-1), sulfate 89.6 mg L(-1), phosphate 1.8 mg L(-1), hydrated silica 112.4 mg L(-1), hardness 9.8 mg L(-1), alkalinity 31.3 mg L(-1), pH 7.6 and conductivity 993 µS cm(-1)). EC was performed after arsenite was oxidized to arsenate by addition of 1 mg L(-1) hypochlorite. The EC tests revealed that at current densities of 4, 5 and 6 mA cm(-2) and flow velocities of 0.91 and 1.82 cm s(-1), arsenate was abated and residual fluoride concentration satisfies the WHO standard (CF < 1.5 mg L(-1)). Spectrometric analyses performed on aluminum flocs indicated that these are mainly composed of aluminum-silicates of calcium and magnesium. Arsenate removal by EC involves adsorption on aluminum flocs, while fluoride replaces a hydroxyl group from aluminum aggregates. The best EC was obtained at 4 mA cm(-2) and 1.82 cm s(-1) with electrolytic energy consumption of 0.34 KWh m(-3). Copyright © 2015 Elsevier Ltd. All rights reserved.

PILOT-SCALE REMOVAL OF FLUORIDE FROM LEGACY PLUTONIUM MATERIALS USING VACUUM SALT DISTILLATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pierce, R. A.; Pak, D. J.

2012-09-11

Between September 2009 and January 2011, the Savannah River National Laboratory (SRNL) and HB-Line designed, developed, tested, and successfully deployed a system for the distillation of chloride salts. In 2011, SRNL adapted the technology for the removal of fluoride from fluoride-bearing salts. The method involved an in situ reaction between potassium hydroxide (KOH) and the fluoride salt to yield potassium fluoride (KF) and the corresponding oxide. The KF and excess KOH can be distilled below 1000{deg}C using vacuum salt distillation (VSD). The apparatus for vacuum distillation contains a zone heated by a furnace and a zone actively cooled using eithermore » recirculated water or compressed air. During a vacuum distillation operation, a sample boat containing the feed material is placed into the apparatus while it is cool, and the system is sealed. The system is evacuated using a vacuum pump. Once a sufficient vacuum is attaned, heating begins. Volatile salts distill from the heated zone to the cooled zone where they condense, leaving behind the non-volatile material in the feed boat. Studies discussed in this report were performed involving the use of non-radioactive simulants in small-scale and pilot-scale systems as well as radioactive testing of a small-scale system with plutonium-bearing materials. Aspects of interest include removable liner design considerations, boat materials, in-line moisture absorption, and salt deposition.« less

Mineralization and defluoridation of 2,2,3,3-tetrafluoro -1-propanol (TFP) by UV oxidation in a novel three-phase fluidized bed reactor (3P-FBR).

PubMed

Shih, Yu-Jen; Tsai, Meng-Tso; Huang, Yao-Hui

2013-05-01

2,2,3,3-Tetrafluoro-1-propanol (TFP, C3H4F4O, M.W. = 132.06) is extensively used as the solvent in CD-R and DVD-R fabrication. Since it has a fluorinated alky-chain configuration and is non-biodegradable, its treatment by conventional oxidation methods is typically very inefficient. In this work, novel three-phase fluidized bed reactor (3P-FBR, 7.5 cm in diameter, 50 cm high) that combines photo oxidation (UV/H2O2, one of AOPs (Advanced Oxidation Process) and adsorption (BT5 iron oxide as adsorbent) processes is designed for mineralizing and defluorinizing TFP wastewater. The experimental results reveal that TFP can be efficiently mineralized, and the BT5 that is circulated by aeration in the 3P-FBR system can remove the released fluoride ions in the reaction period. Irradiation with 254 nm UV and a 10 mM H2O2 dose yield a TOC removal of TFP (1.39 mM, equivalent to an initial TOC of 50 ppm) of over 99.95% in 2 h, and 99% of fluoride was removed by BT5 with an adsorption capacity of 24.1 mg-F g(-1). Copyright © 2013 Elsevier Ltd. All rights reserved.

Simultaneous removal of arsenite and fluoride via an integrated electro-oxidation and electrocoagulation process.

PubMed

Zhao, Xu; Zhang, Baofeng; Liu, Huijuan; Qu, Jiuhui

2011-04-01

An integrated electro-oxidation and electrocoagulation system was designed and used to remove As(III) and F(-) ions from water simultaneously. Dimensionally stable anodes (DSA), Fe electrodes, and Al electrodes were combined into an electrochemical system. Two pieces of DSA electrodes were assigned as the outside of the Fe and Al electrodes and were directly connected to the power supply as anode and cathode, respectively. The Fe and Al ions were generated by electro-induced process simultaneously. Subsequently, hydroxides of Fe and Al were formed. Arsenic ions are mainly removed by iron hydroxides and F(-) ions are mainly removed by the Al oxides. At the initial concentration of 1.0 mg L(-1), most of As(III) was transferred into As(V) within 40 min at current density of 4 mA cm(-2), whereas F(-) ions can be efficiently removed simultaneously. The effect of the ratio of Fe and Al plate electrodes and current density on the removal of As(III) and F(-) was investigated. With one piece of Fe plate electrode and three pieces of Al plate electrodes, it is observed that As(III) with concentration of 1 mg L(-1) and F(-) with concentration of 4.5 mg L(-1) can be removed and their final concentrations were below the values of 10 μg L(-1) and 1.0 mg L(-1), respectively within 40 min. Removal efficiency of As(III) increases with the increase of solution pH. However, in the pH range of 6-7, removal efficiency of F(-) is the largest. Copyright © 2011 Elsevier Ltd. All rights reserved.

MANUFACTURE OF UF$sub 4$

DOEpatents

Calcott, W.S.

1959-10-13

The manufacture of uranium tetrafluoride from urarium dioxide is described. Uranium dioxide is heated to about 500 deg C in a reactor. Anhydrous hydrogen fluoride is passed through the reactor in contact with uranium dioxide for several hours, the flow of hydrogen fluoride is discontinued, and hydrogen passed through the reactor for less than an hour. The flow of hydrogen fluoride is resumed for several hours, and then nitrogen is passed for a few minutes to expel unreacted hydrogen fluoride as water vapor. The reactor is cooled to room temperature and the uranium tetrafluoride removed.

Defluoridation of drinking water by combined electrocoagulation: effects of the molar ratio of alkalinity and fluoride to Al(III).

PubMed

Zhao, Hua-Zhang; Yang, Wei; Zhu, Jun; Ni, Jin-Ren

2009-03-01

The defluoridation efficiency (epsilon(F)) of electrocoagulation (EC) is closely related to the pH level of the F(-)-containing solution. The pH level usually needs to be adjusted by adding acid in order to obtain the highest epsilon(F) for the F(-)-containing groundwater. The use of combined EC (CEC), which is the combination of chemical coagulation with EC, was proposed to remove fluoride from drinking water for the first time in this study. The optimal scheme for the design and operation of CEC were obtained through experiments on the treatment of F(-)-containing groundwater. It was found, with OH(-) being the only alkalinity of the raw water, that the highest efficiency would be obtained when the molar ratio of alkalinity and fluoride to Al(III) (gamma(Alkalinity+F)) was controlled at 3.0. However, when the raw water contained HCO(3)(-) alkalinity, a correction coefficient was needed to correct the concentration of HCO(3)(-) to obtain the optimal defluoridation condition of gamma(Alkalinity+F)=3.0 for CEC. The correction coefficient of HCO(3)(-) concentration was concluded as 0.60 from the experiment. For the practical F(-)-containing groundwater treatment, CEC can achieve similar epsilon(F) as an acid-adding EC process. The consumption of aluminum electrode was decreased in CEC. The energy consumption also declined greatly in CEC, which is less than one third of that in the acid-adding EC process.

Synthesis of adsorbent from Tamarix hispida and modified by lanthanum metal for fluoride ions removal from wastewater: Adsorbent characteristics and real wastewater treatment data.

PubMed

Habibi, Nasim; Rouhi, Parham; Ramavandi, Bahman

2017-08-01

This data article describes a facile method for production of an adsorbent from Tamarix hispida wasted wood and modified by lanthanum metal for fluoride ions removal from wastewater. The main characteristics of the adsorbent consist of BET surface area, functional groups, and elemental analysis is presented. The data for attenuating the pollutants from a real wastewater treatment which was provided from a glass factory is also represented. More than 90% of fluoride content of the real wastewater was treated by the adsorbent. Generally, these data would be informative for extend research aim to industrial wastewater treatment and those who work in the wastewater treatment plants.

Adsorption of fluoride to UiO-66-NH2 in water: Stability, kinetic, isotherm and thermodynamic studies.

PubMed

Lin, Kun-Yi Andrew; Liu, Yu-Ting; Chen, Shen-Yi

2016-01-01

To provide safe drinking water, fluoride in water must be removed and adsorption processes appear to be the most widely used method. Metal organic frameworks (MOFs) represent a new class of adsorbents that have been used in various adsorption applications. To study the adsorption mechanism of fluoride to MOFs in water and obtain related adsorption parameters, we synthesized a zirconium-based MOF with a primary amine group on its ligand, named UiO-66-NH2. The kinetics, adsorption isotherm and thermodynamics of fluoride adsorption to UiO-66-NH2 were investigated. The crystalline structure of UiO-66-NH2 remained intact and the local structure of zirconium in UiO-66-NH2 did not change significantly after being exposed to fluoride. The kinetics of the fluoride adsorption in UiO-66-NH2 could be well represented by the pseudo second order rate law. The enthalpy of the adsorption indicates that the F(-) adsorption to UiO-66-NH2 was classified as a physical adsorption. However, the comparison between the adsorption capacities of UiO-66-NH2 and UiO-66 suggests that the fluoride adsorption to UiO-66-NH2 might primarily involve a strong interaction between F(-) and the metal site. The fluoride adsorption capacity of UiO-66-NH2 was found to decrease when pH>7. While the presence of chloride/bromide ions did not noticeably change the adsorption capacity of UiO-66-NH2, the ionic surfactants slightly affected the adsorption capacity of UiO-66-NH2. These findings provide insights to further optimize the adsorption process for removal of fluoride using zirconium-based MOFs. Copyright © 2015 Elsevier Inc. All rights reserved.

Fluoride tracer test for the performance analysis of a basin used as a lagooning pre-treatment facility in a WTP.

PubMed

Ruffino, Barbara

2015-07-01

The water treatment plant (WTP) of the city of Torino (NW Italy), which treats about 40 · 10(6) m(3)/year of raw water from Po river, has a 15-ha basin used as a lagooning pre-treatment facility. Since the efficiency of the lagooning process in the removal of pollutants from raw water depends on the internal hydrodynamics of the basin, the hydraulic performance of the basin was studied by combining the results of a stimulus-response tracer test with the monitoring of the tracer (fluoride) concentration throughout the basin at different times. The outcomes of the test demonstrated that the system was efficiently mixed and could be assimilated to a continuous stirred reactor presenting no flow anomalies, with an actual mean residence time (RT) of 12.7 days, compared with a nominal RT of 18 days. This assured that dissolved contaminants (such as fluoride) coming from the river were efficiently diluted before entering the WTP. The axial dispersion coefficient calculated from the RT distribution was approximately 47,300 m(2)/day. Three of the most popular formulae developed for the calculation of the axial dispersion coefficient provided results spreading over three orders of magnitude, thus showing their limitations. Finally, because of the width extent of the basin and the characteristics of its inflow, the 1-D advection-dispersion model failed in predicting the tracer concentration values in time at the outlet channel. On the contrary, the analytical solution of the 2-D advection-dispersion model proved to be suitable to fit the tracer concentration data over time at the outlet channel but it failed in describing the tracer distribution throughout the basin on the monitoring dates.

Corrigendum to "Synthesis of hydroxyapatite/multi-walled carbon nanotubes for the removal of fluoride ions from solution" [Appl. Surf. Sci. 412 (2017) 578-590

NASA Astrophysics Data System (ADS)

Ruan, Zhongyuan; Tian, Yaxi; Ruan, Jifu; Cui, Guijia; Iqbal, Kanwal; Iqbal, Anam; Ye, Herui; Yang, Zhangzhong; Yan, Shiqiang

2018-04-01

In our recent paper [1], we reported the synthesis of hydroxyapatite/multi-walled carbon nanotubes (HA-MWCNTs) and studied their performance for the removal of fluoride ions from solution. However, we have made some writing mistakes, especially in the section on adsorption kinetics analysis. Our mistakes were spotted by Prof. Yuandong Huang, who graciously noticed these errors. We are grateful to him, and have decided to write a "Corrigendum".

Zirconium/polyvinyl alcohol modified flat-sheet polyvinyldene fluoride membrane for decontamination of arsenic: Material design and optimization, study of mechanisms, and application prospects.

PubMed

Zhao, Dandan; Yu, Yang; Chen, J Paul

2016-07-01

Arsenic contamination in industrial wastewater and groundwater has become an important environmental issue. In this study, a novel zirconium/polyvinyl alcohol (PVA) modified polyvinyldene fluoride (PVDF) membrane was developed for arsenate removal from simulated contaminated water. A PVDF flat-sheet membrane was first fabricated; it was then soaked in a zirconium-PVA solution and dried, and finally reacted with a glutaraldehyde solution, by which the zirconium ions were impregnated onto the PVDF surface through the ether and hydroxyl groups according to the cross-linkage mechanism. The fabrication procedure was optimized by the Box-Behnken experimental design approach. The adsorption kinetics study showed that most of uptake occurred in 5 h and the equilibrium was established in 24 h. The acidic condition was beneficial for the arsenate removal and the optimal removal efficiency can be obtained at pH 2.0. The experimental data of the adsorption isotherm was better described by Langmuir equation than Freundlich equation. The maximum adsorption capacity of 128 mg-As/g was achieved at pH 2.0. In the filtration study, the modified membrane with an area of 12.56 cm(2) could treat 15.6 L arsenate solution (equivalent to 75,150 bed volumes) with an influent concentration of 98.6 μg/L to meet the maximum contaminate level of 10 μg/L. Several instrumental studies revealed that the removal was mainly associated with ion exchange between chloride and arsenate ions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Highly efficient solid phase synthesis of oligonucleotide analogs containing phosphorodithioate linkages

PubMed Central

Capaldi, Daniel C.; Cole, Douglas L.; Ravikumar, Vasulinga T.

2000-01-01

A triester method for the synthesis of deoxynucleoside phosphorodithioate dimers is described. The phosphorodithioate linkage is introduced using a new dithiophosphorylating reagent DPSE-SP(S)Cl2 where DPSE = 2-diphenylmethylsilylethyl. This group is removed quickly using tetra-butylammonium fluoride leading to the quantitative formation of phosphorodithioate diesters uncontaminated with the corresponding phosphorothioates. The utility of this group is demonstrated by the synthesis of a pentadecathymidylic acid, [T(PS2)T(PO2)]7T, which contains alternating phosphorodithioate/phosphate diester internucleotide linkages. PMID:10756207

Electrospun and functionalized PVDF/PAN composite for the removal of trace metals in contaminated water

NASA Astrophysics Data System (ADS)

Nthumbi, R. M.; Adelodun, A. A.; Ngila, J. C.

2017-08-01

The electrospinning of a nanofiber composite of polyvinylidene fluoride (PVDF) and polyacrylonitrile (PAN) in a dimethylformamide (DMF) solvent was carried out prior to functionalization by free radical grafting of acrylic acid (AA) brushes. Subsequent application for the removal of Pb2+ and Cd2+ from contaminated water is reported. Free radicals were initiated on the polymeric nanofiber composite using 5% 2,2‧-Azobis(2-methylpropionitrile) (AIBN) in acetone. Upon solvent removal by air-drying, AA was added and grafting (in a methanol-water solvent system) was carried out in an oil bath at 70 °C for 5 h under nitrogen atmosphere. Structural and chemical characterization of the composite was done using scanning electron microscope (SEM), nitrogen sorption at 77 K (BET method), goniometer and Fourier transform infrared spectrometer (FTIR), while changes in metal ion concentration during batch adsorption were monitored using inductively coupled plasma optical emission spectrometer (ICP-OES). Through isotherm study, the adsorption was confirmed to follow both Langmuir and Freundlich models whilst adsorption kinetic studies showed that the adsorption rate is of pseudo-second order. In furtherance, the respective values for adsorption capacity and estimated removal efficiency for Pb2+ and Cd2+ were 1.585 and 0.164 mg g-1, 90% and 80% respectively, while a 5% loss in regeneration efficiency after 10 cycles was also observed. Consequently, the nanocomposite was found efficient when applied to the removal of Pb2+ and Cd2+ from contaminated water.

Removal of uranium from aqueous HF solutions

DOEpatents

Pulley, Howard; Seltzer, Steven F.

1980-01-01

This invention is a simple and effective method for removing uranium from aqueous HF solutions containing trace quantities of the same. The method comprises contacting the solution with particulate calcium fluoride to form uranium-bearing particulates, permitting the particulates to settle, and separting the solution from the settled particulates. The CaF.sub.2 is selected to have a nitrogen surface area in a selected range and is employed in an amount providing a calcium fluoride/uranium weight ratio in a selected range. As applied to dilute HF solutions containing 120 ppm uranium, the method removes at least 92% of the uranium, without introducing contaminants to the product solution.

Cow bones char as a green sorbent for fluorides removal from aqueous solutions: batch and fixed-bed studies.

PubMed

Nigri, Elbert M; Cechinel, Maria Alice P; Mayer, Diego A; Mazur, Luciana P; Loureiro, José M; Rocha, Sônia D F; Vilar, Vítor J P

2017-01-01

Cow bone char was investigated as sorbent for the defluoridation of aqueous solutions. The cow bone char was characterized in terms of its morphology, chemical composition, and functional groups present on the bone char surface using different analytical techniques: SEM, EDS, N 2 -BET method, and FTIR. Batch equilibrium studies were performed for the bone chars prepared using different procedures. The highest sorption capacities for fluoride were obtained for the acid washed (q = 6.2 ± 0.5 mg/g) and Al-doped (q = 6.4 ± 0.3 mg/g) bone chars. Langmuir and Freundlich models fitted well the equilibrium sorption data. Fluoride removal rate in batch system is fast in the first 5 h, decreasing after this time until achieving equilibrium due to pore diffusion. The presence of carbonate and bicarbonate ions in the aqueous solution contributes to a decrease of the fluoride sorption capacity of the bone char by 79 and 31 %, respectively. Regeneration of the F-loaded bone char using 0.5 M NaOH solution leads to a sorption capacity for fluoride of 3.1 mg/g in the second loading cycle. Fluoride breakthrough curve obtained in a fixed-bed column presents an asymmetrical S-shaped form, with a slow approach of C/C 0  → 1.0 due to pore diffusion phenomena. Considering the guideline value for drinking water of 1.5 mg F - /L, as recommended by World Health Organization, the service cycle for fluoride removal was of 71.0 h ([F - ] feed  ∼ 9 mg/L; flow rate = 1 mL/min; m sorbent  = 12.6 g). A mass transfer model considering the pore diffusion was able to satisfactorily describe the experimental data obtained in batch and continuous systems.

Low temperature route to uranium nitride

DOEpatents

Burrell, Anthony K.; Sattelberger, Alfred P.; Yeamans, Charles; Hartmann, Thomas; Silva, G. W. Chinthaka; Cerefice, Gary; Czerwinski, Kenneth R.

2009-09-01

A method of preparing an actinide nitride fuel for nuclear reactors is provided. The method comprises the steps of a) providing at least one actinide oxide and optionally zirconium oxide; b) mixing the oxide with a source of hydrogen fluoride for a period of time and at a temperature sufficient to convert the oxide to a fluoride salt; c) heating the fluoride salt to remove water; d) heating the fluoride salt in a nitrogen atmosphere for a period of time and at a temperature sufficient to convert the fluorides to nitrides; and e) heating the nitrides under vacuum and/or inert atmosphere for a period of time sufficient to convert the nitrides to mononitrides.

Methods of decontaminating surfaces and related compositions

DOEpatents

Demmer, Ricky L.; Crosby, Daniel; Norton, Christopher J.

2016-11-22

A composition of matter includes water, at least one acid, at least one surfactant, at least one fluoride salt, and ammonium nitrate. A method of decontaminating a surface includes exposing a surface to such a composition and removing the composition from the surface. Other compositions of matter include water, a fatty alcohol ether sulfate, nitrilotriacetic acid, at least one of hydrochloric acid and nitric acid, sodium fluoride, potassium fluoride, ammonium nitrate, and gelatin.

Pore Structure and Fluoride Ion Adsorption Characteristics of Zr (IV) Surface-Immobilized Resin Prepared Using Polystyrene as a Porogen

NASA Astrophysics Data System (ADS)

Mizuki, Hidenobu; Ito, Yudai; Harada, Hisashi; Uezu, Kazuya

Zr(IV) surface-immobilized resins for removal of fluoride ion were prepared by surface template polymerization using polystyrene as a porogen. At polymerization, polystyrene was added in order to increase mesopores (2-50 nm) and macropore (>50 nm) with large macropores (around 300 nm) formed with internal aqueous phase of W⁄O emulsion. The pore structure of Zr(IV) surface-immobilized resins was evaluated by measuring specific surface area, pore volume, and pore size distribution with volumetric adsorption measurement instrument and mercury porosimeter. The adsorption isotherms were well fitted by Langmuir equation. The removal of fluoride was also carried out with column method. Zr(IV) surface-immobilized resins, using 10 g⁄L polystyrene in toluene at polymerization, possessed higher volume of not only mesopores and macropores but also large macropores. Furethermore, by adding the polystyrene with smaller molecular size, the pore volume of mesopores, macropores and large macropores was significantly increased, and the fluoride ion adsorption capacity and the column utilization also increased.

Adsorbent synthesis of polypyrrole/TiO(2) for effective fluoride removal from aqueous solution for drinking water purification: Adsorbent characterization and adsorption mechanism.

PubMed

Chen, Jie; Shu, Chiajung; Wang, Ning; Feng, Jiangtao; Ma, Hongyu; Yan, Wei

2017-06-01

More than 20 countries are still suffering problems of excessive fluoride containing water, and greater than 8mg/L fluoride groundwater has been reported in some villages in China. In order to meet the challenge in the drinking water defluoridation engineering, a high efficiency and affinity defluoridation adsorbent PPy/TiO 2 composite was designed and synthetized by in-situ chemical oxidative polymerization. Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction Investigator (XRD), X-ray photoelectron spectroscopy (XPS), Thermogravimetric analysis (TG), N 2 isotherm analysis, Scanning Electron Microscopy (SEM) and Zeta potential analysis were conducted to characterize surface and textural properties of the as-prepared PPy/TiO 2 , and the possibility of fluoride adsorption was carefully estimated by adsorption isotherm and kinetic studies. Characterization investigations demonstrate the uniqueness of surface and textural properties, such as suitable specific surface area and abundant positively charged nitrogen atoms (N + ), which indicate the composite is a suitable material for the fluoride adsorption. Adsorption isotherms and kinetics follow better with Langmuir and pseudo-second-order model, respectively. The maximum adsorption capacity reaches 33.178mg/g at 25°C according to Langmuir model, and particular interest was the ability to reduce the concentration of fluoride from 11.678mg/L to 1.5mg/L for drinking water at pH of 7 within 30min. Moreover, the adsorbent can be easily recycled without the loss of adsorption capacity after six cycles, greatly highlighting its outstanding affinity to fluoride, low-cost and novel to be used in the purification of fluoride containing water for drinking. Furthermore, the adsorption mechanism was extensively investigated and discussed by FTIR investigation and batch adsorption studies including effect of pH, surface potential and thermodynamics. The adsorption is confirmed to be a spontaneous and exothermic process with decreasing entropy, which is prominently conducted through electrostatic attraction, and ionic exchange, and chelation may be also involved. Hydroxyls and positively charged nitrogen atoms play important roles in the adsorption. Copyright © 2017 Elsevier Inc. All rights reserved.

Effect of home-used water purifier on fluoride concentration of drinking water in southern Iran

PubMed Central

Jaafari-Ashkavandi, Zohreh; Kheirmand, Mehdi

2013-01-01

Background: Fluoride in drinking water plays a key role in dental health. Due to the increasing use of water-purifier, the effect of these devices on fluoride concentration of drinking water was evaluated. Materials and Methods: Drinking water samples were collected before and after passing through a home water-purifier, from four different water sources. The fluoride, calcium and magnesium concentration of the samples were measured using the quantitative spectrophotometery technique. Data were analyzed by the Wilcoxon test. P value < 0.1 was considered as significant. Results: The result showed that the concentration of fluoride was 0.05-0.61 ppm before purification and was removed completely afterward. Furthermore, other ions reduced significantly after treatment by the water purifier. Conclusion: This study revealed that this device decreases the fluoride content of water, an issue which should be considered in low and high-fluoridated water sources. PMID:24130584

Efficient adsorption and photocatalytic degradation of organic pollutants diluted in water using fluoride-modified hydrophobic mesoporous silica

NASA Astrophysics Data System (ADS)

Yamashita, Hiromi; Maekawa, Kazuhiro; Nakao, Hidetoshi; Anpo, Masakazu

2004-10-01

Using a mixture of tetraethylammonium fluoride and dodecylamine as templates, hydrophobic mesoporous silica supports were prepared. The fine anatase TiO 2 photocatalysts were prepared on the fluoride-modified hydrophobic mesoporous silica and the adsorption properties and the photocatalytic degradation of an aqueous 2-propanol or 2-hexanol solution into CO 2 and H 2O have been studied. The amount of adsorption and the photocatalytic reactivities increased with increasing the content of fluoride ions on these photocatalysts. 2-Hexanol diluted in water was adsorbed on the hydrophobic catalysts more efficiently than 2-propanol.

Quality of our groundwater resources: Arsenic and fluoride

USGS Publications Warehouse

Nordstrom, D. Kirk

2011-01-01

Groundwater often contains arsenic or fluoride concentrations too high for drinking or cooking. These constituents, often naturally occurring, are not easy to remove. The right combination of natural or manmade conditions can lead to elevated arsenic or fluoride which includes continental source rocks, high alkalinity and pH, reducing conditions for arsenic, high phosphate, high temperature and high silica. Agencies responsible for safe drinking water should be aware of these conditions, be prepared to monitor, and treat if necessary.

Potentiality of a fruit peel (banana peel) toward abatement of fluoride from synthetic and underground water samples collected from fluoride affected villages of Birbhum district

NASA Astrophysics Data System (ADS)

Mondal, Naba Kumar; Roy, Arunabha

2018-06-01

Contamination of underground water with fluoride (F) is a tremendous health hazard. Excessive F (> 1.5 mg/L) in drinking water can cause both dental and skeletal fluorosis. A fixed-bed column experiments were carried out with the operating variables such as different initial F concentrations, bed depths, pH and flow rates. Results revealed that the breakthrough time and exhaustion time decrease with increasing flow rate, decreasing bed depth and increasing influent fluoride concentration. The optimized conditions are: 10 mg/L initial fluoride concentration; flow rate 3.4 mL/min, bed depth 3.5 and pH 5. The bed depth service time model and the Thomas model were applied to the experimental results. Both the models were in good agreement with the experimental data for all the process parameters studied except flow rate, indicating that the models were appropriate for removal of F by natural banana peel dust in fix-bed design. Moreover, column adsorption was reversible and the regeneration was accomplished by pumping of 0.1 M NaOH through the loaded banana peel dust column. On the other hand, field water sample analysis data revealed that 86.5% fluoride can be removed under such optimized conditions. From the experimental results, it may be inferred that natural banana peel dust is an effective adsorbent for defluoridation of water.

Ceria modified activated carbon: an efficient arsenic removal adsorbent for drinking water purification

NASA Astrophysics Data System (ADS)

Sawana, Radha; Somasundar, Yogesh; Iyer, Venkatesh Shankar; Baruwati, Babita

2017-06-01

Ceria (CeO2) coated powdered activated carbon was synthesized by a single step chemical process and demonstrated to be a highly efficient adsorbent for the removal of both As(III) and As(V) from water without any pre-oxidation process. The formation of CeO2 on the surface of powdered activated carbon was confirmed by X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy. The percentage of Ce in the adsorbent was confirmed to be 3.5 % by ICP-OES. The maximum removal capacity for As(III) and As(V) was found to be 10.3 and 12.2 mg/g, respectively. These values are comparable to most of the commercially available adsorbents. 80 % of the removal process was completed within 15 min of contact time in a batch process. More than 95 % removal of both As(III) and As(V) was achieved within an hour. The efficiency of removal was not affected by change in pH (5-9), salinity, hardness, organic (1-4 ppm of humic acid) and inorganic anions (sulphate, nitrate, chloride, bicarbonate and fluoride) excluding phosphate. Presence of 100 ppm phosphate reduced the removal significantly from 90 to 18 %. The equilibrium adsorption pattern of both As(III) and As(V) fitted well with the Freundlich model with R 2 values 0.99 and 0.97, respectively. The material shows reusability greater than three times in a batch process (arsenic concentration reduced below 10 ppb from 330 ppb) and a life of at least 100 L in a column study with 80 g material when tested under natural hard water (TDS 1000 ppm, pH 7.8, hardness 600 ppm as CaCO3) spiked with 330 ppb of arsenic.

Assessment of the Use of Nitrogen Trifluoride for Purifying Coolant and Heat Transfer Salts in the Fluoride Salt-Cooled High-Temperature Reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scheele, Randall D.; Casella, Andrew M.

2010-09-28

This report provides an assessment of the use of nitrogen trifluoride for removing oxide and water-caused contaminants in the fluoride salts that will be used as coolants in a molten salt cooled reactor.

Removal of Fluorides and Chlorides from Zinc Oxide Fumes by Microwave Sulfating Roasting

NASA Astrophysics Data System (ADS)

Li, Zhiqiang; Zhang, Libo; Chen, Guo; Peng, Jinhui; Zhou, Liexing; Yin, Shaohua; Liu, Chenhui

2015-10-01

Dechlorination and defluorination from zinc oxide dust by microwave sulfating roasting was investigated in this study. According to proposed reactions in the process, detailed experiments were systematically conducted to study the effect of roasting temperature, holding time, air and steam flow rates on the efficiency of the removal of F and Cl. The results show that 92.3% of F and 90.5% of Cl in the fume could be purified when the condition of the roasting temperature of 650 °C, holding time at 60 min, air flow of 300 L/h and steam flow of 8 ml/min was optimized. Our investigation indicates that microwave sulfating roasting could be a promising new way for the dechlorination and defluorination from zinc oxide dust.

Characterization of a fluoride-resistant bacterium Acinetobacter sp. RH5 towards assessment of its water defluoridation capability

NASA Astrophysics Data System (ADS)

Mukherjee, Shraboni; Yadav, Vaibhav; Mondal, Madhumanti; Banerjee, Soumya; Halder, Gopinath

2017-07-01

The present study investigates the defluoridation capability of fluoride-resistant bacteria from contaminated groundwater collected from Asanjola and Madhabpur, West Bengal, India. Seven strains of fluoride-resistant bacteria were isolated employing culture media containing 10-250 mg/L of fluoride to evaluate their ability in reducing fluoride concentration in water. Five isolates exhibited significant amount of reduction in fluoride. Isolate RH5 achieved a maximum fluoride removal of 25.7 % from the media at 30 °C and pH 7 after 8 days of incubation. Based on morphological, physiological characteristics and analysis of 16S rDNA gene sequence, isolate RH5 was identified as Acinetobacter sp. RH5. Growth of RH5 was analysed at a diverse pH range, and it could thrive at pH 5-10. The present investigation revealed that the selective pressure of fluoride results in growth of fluoride-resistant bacteria capable of secreting high-affinity anion-binding compounds. This bacterium played a dominant bioremediative role by concentrating the anions so that they become less available. Hence, the fluoride-resistant bacteria, Acinetobacter sp. RH5, could be used as a promising strain for application in water defluoridation from contaminated sites.

Efficient defluoridation of water using reusable nanocrystalline layered double hydroxides impregnated polystyrene anion exchanger.

PubMed

Cai, Jianguo; Zhang, Yanyang; Pan, Bingcai; Zhang, Weiming; Lv, Lu; Zhang, Quanxing

2016-10-01

Water decontamination from fluoride is still a challenging task of global concern. Recently, Al-based layered double hydroxides (LDHs) have been extensively studied for specific fluoride adsorption from water. Unfortunately, they cannot be readily applied in scaled-up application due to their ultrafine particles as well as the regeneration issues caused by their poor stability at alkaline pHs. Here, we developed a novel (LDH)-based hybrid adsorbent, i.e., LALDH-201, by impregnating nanocrystalline Li/Al LDHs (LADLH) inside a commercial polystyrene anion exchanger D201. TEM image and XRD spectra of the resultant nanocomposite confirmed that the LDHs particles were nanosized inside the pores of D201 of highly crystalline nature and well-ordered layer structure. After impregnation, the chemical and mechanical stability of LALDH were significantly improved against pH variation, facilitating its application at a wide pH range (3.5-12). Fluoride adsorption onto LALDH-201 was compared to D201 and activated alumina, evidencing the preferable removal fluoride of LALDH-201. Fluoride adsorption onto LALDH-201 followed pseudo-second-order model, with the maximum capacity (62.5 mg/g from the Sips model) much higher than the other two adsorbents. Fixed-bed adsorption run indicated the qualified treatable volume of the fluoride contaminated groundwater (4.1 mg/L initially) with LALDH-201 was about 11 times as much as with the anion exchanger D201 when the breakthrough point was set as 1.5 mg/L. The capacity of LALDH-201 could be effectively refreshed for continuous column operation without observable loss by using the mixed solution of 0.01 M NaOH + 1 M NaCl. The above results suggested that the hybrid adsorbent LALDH-201 is very promising for water defluoridation in scaled-up application. Copyright © 2016 Elsevier Ltd. All rights reserved.

[Water fluoridation and public health].

PubMed

Barak, Shlomo

2003-11-01

Fluoridation in Israel was first mooted in 1973 and finally incorporated into law in November 2002 obligating the Ministry of Health to add fluoride to the nation's water supply. Epidemiology studies in the USA have shown that the addition of one part per million of fluoride to the drinking water reduced the caries rate of children's teeth by 50% to 60% with no side effects. Both the WHO in 1994 and the American Surgeon General's report of 2000 declared that fluoridation of drinking water was the safest and most efficient way of preventing dental caries in all age groups and populations. Opposition to fluoridation has arisen from "antifluoridation" groups who object to the "pollution" of drinking water by the addition of chemicals and mass medication in violation of the "Patient's Rights" law and the Basic Law of Human Dignity and Liberty. A higher prevalence of hip fractures in elderly osteoporotic women and osteosarcoma in teenagers has been reported in areas where excess fluoride exists in the drinking water. However, none of the many independent professional committees reviewing the negative aspects of fluoridation have found any scientific evidence associating fluoridation with any ill-effects or health problems. In Israel, where dental treatment is not included in the basket of Health Services, fluoridation is the most efficient and cheapest way of reducing dental disease, especially for the poorer members of the population.

Heat regeneration of hydroxyapatite/attapulgite composite beads for defluoridation of drinking water.

PubMed

Feng, Li; Xu, Weihua; Liu, Tengfei; Liu, Jason

2012-06-30

Regeneration is one of the key factors in evaluating an adsorbent. A novel heat regeneration method for hydroxyapatite/attapulgite (HAP/ATT) composite beads was studied. The investigation included heat regeneration temperature, regeneration time, and regeneration effects. A possible mechanism for the heat regeneration is described that explains the results of XPS, and SEM with EDAX. Exhausted HAP/ATT composite beads can be regenerated for more than 10 cycles using boiling water or steam. The total capacity increases by 10 times compared to a single defluoridation cycle. The regeneration process involves F(-) ions adsorbed on the surface of the beads to move quickly into the bulk of the HAP through the effect of heating this composite material. The surface active sites are thus re-exposed and the beads recover their fluoride sequestration properties. HAP/ATT composite beads were successfully used for the removal of fluoride from field water taken from a nearby village where fluoride contamination is endemic. Defluoridation and regeneration cycles performed in the same container provide a high efficient and simple operation. No chemical agents are used and no waste products are produced during the heat regeneration process, so this is a nearly zero emission process. This method can easily be up-scaled to a large throughput application. Copyright © 2012 Elsevier B.V. All rights reserved.

Study of TiO2 anatase nano and microstructures with dominant {001} facets for NO oxidation.

PubMed

Sofianou, Maria-Veronica; Trapalis, Christos; Psycharis, Vassils; Boukos, Nikos; Vaimakis, Tiverios; Yu, Jiaguo; Wang, Wenguang

2012-11-01

TiO(2) anatase nanoplates and hollow microspheres were fabricated by a solvothermal-hydrothermal method using titanium isopropoxide as a titanium precursor and hydrofluoric acid as a capping agent in order to enhance the formation of the {001} crystal facets of the anatase nanocrystals. These different morphological structures of TiO(2) anatase can be achieved by only changing the solvent, keeping the amount of the precursor and of the capping agent identical during the solvothermal-hydrothermal process. After calcination of the samples, the adsorbed fluoride atoms on the {001} crystal facets of the TiO(2) anatase nanocrystals were completely removed from their surface according to XPS analysis. The calcined TiO(2) anatase structures were higher crystallized and the specific surface area of the catalysts increased, enhancing their photocatalytic activity in comparison to the non-calcined TiO(2) anatase structures. All TiO(2) anatase samples with adsorbed as well as non-adsorbed fluoride atoms on their {001} crystal facets, exhibited a higher photonic efficiency than Degussa P25, which was used as a reference. The fluoride free TiO(2) anatase nanoplates exhibited the best photocatalytic activity in oxidizing the NO gas to NO(2) and NO(3) (-).

Removal of fluoride from drinking water by cellulose@hydroxyapatite nanocomposites.

PubMed

Yu, Xiaolin; Tong, Shengrui; Ge, Maofa; Zuo, Junchao

2013-01-30

Cellulose@hydroxyapatite (HA) nanocomposites were prepared in NaOH/thiourea/urea/H(2)O solution via situ hybridization. The composite materials combine the advantage of cellulose and HA with the high specific surface area and the strong affinity toward fluoride. The composite materials were characterized by FTIR, SEM, XRD, TG and XPS, and the adsorption of fluoride was investigated. Adsorption kinetics indicated the adsorption equilibrium of fluoride was within 360 min and the adsorption process was well described by the pseudo-second-order kinetic model. The Langmuir and Freundlich isotherm models could fit the experimental data well. At the initial fluoride concentration of 10mg/L, the residual concentration using above 3g/L adsorbent dose could meet the drinking water standard of WHO norms. Furthermore, the coexisting anions had no significant effect on fluoride adsorption. Copyright © 2012 Elsevier Ltd. All rights reserved.

Toxicity of fluoride to microorganisms in biological wastewater treatment systems.

PubMed

Ochoa-Herrera, Valeria; Banihani, Qais; León, Glendy; Khatri, Chandra; Field, James A; Sierra-Alvarez, Reyes

2009-07-01

Fluoride is a common contaminant in a variety of industrial wastewaters. Available information on the potential toxicity of fluoride to microorganisms implicated in biological wastewater treatment is very limited. The objective of this study was to evaluate the inhibitory effect of fluoride towards the main microbial populations responsible for the removal of organic constituents and nutrients in wastewater treatment processes. The results of short-term batch bioassays indicated that the toxicity of sodium fluoride varied widely depending on the microbial population. Anaerobic microorganisms involved in various metabolic steps of anaerobic digestion processes were found to be very sensitive to the presence of fluoride. The concentrations of fluoride causing 50% metabolic inhibition (IC(50)) of propionate- and butyrate-degrading microorganisms as well as mesophilic and thermophilic acetate-utilizing methanogens ranged from 18 to 43 mg/L. Fluoride was also inhibitory to nitrification, albeit at relatively high levels (IC(50)=149 mg/L). Nitrifying bacteria appeared to adapt rapidly to fluoride, and a near complete recovery of their metabolic activity was observed after only 4d of exposure to high fluoride levels (up to 500 mg/L). All other microbial populations evaluated in this study, i.e., glucose fermenters, aerobic glucose-degrading heterotrophs, denitrifying bacteria, and H(2)-utilizing methanogens, tolerated fluoride at very high concentrations (>500 mg/L).

Laboratory investigations into the potential anticaries efficacy of fluoride varnishes.

PubMed

Lippert, Frank; Hara, Anderson Takeo; Martinez-Mier, Esperanza Angeles; Zero, Domenick T

2014-01-01

The purpose of this study was to investigate the potential anticaries efficacy of fluoride varnishes (FVs) by studying their ability to reharden and deliver fluoride to carious lesions and to release fluoride into saliva. Enamel carious lesions were created and allocated to 24 groups (11 FVs with two FV incubation times and two control groups) based on Knoop microhardness test values. FVs were applied to lesions, which were incubated in artificial saliva for two or six hours, with saliva being renewed hourly. FV was removed and lesions were remineralized in artificial saliva for 22 hours. Microhardness was measured and enamel fluoride uptake (EFU) was determined. Saliva samples (six-hour groups) were analyzed to determine fluoride release characteristics. Data were analyzed using analysis of variance. FVs differed considerably in their ability to reharden and deliver fluoride to carious lesions and in their fluoride release characteristics. Little consistency was found between investigated study variables for virtually all tested FVs. For example, a particular FV showed the highest EFU and fluoride release values but the lowest rehardening value. A longer FV contact time led to increased EFU for five of the 11 FVs. Some FVs delivered more fluoride to lesions in two hours than others did in six hours. Fluoride varnishes differ greatly in their in vitro anticaries efficacy.

Drinking water quality and fluoride concentration.

PubMed

Frazão, Paulo; Peres, Marco A; Cury, Jaime A

2011-10-01

This paper aimed to analyze the fluoride concentration in drinking water, taking into account the balance between the benefits and risks to health, in order to produce scientific backing for the updating of the Brazilian legislation. Systematic reviews studies, official documents and meteorological data were examined. The temperatures in Brazilian state capitals indicate that fluoride levels should be between 0.6 and 0.9 mg F/l in order to prevent dental caries. Natural fluoride concentration of 1.5 mg F/l is tolerated for consumption in Brazil if there is no technology with an acceptable cost-benefit ratio for adjusting/removing the excess. Daily intake of water with a fluoride concentration > 0.9 mg F/l presents a risk to the dentition among children under the age of eight years, and consumers should be explicitly informed of this risk. In view of the expansion of the Brazilian water fluoridation program to regions with a typically tropical climate, Ordinance 635/75 relating to fluoride added to the public water supply should be revised.

Fluoride adsorption properties of three modified forms of activated alumina in drinking water.

PubMed

Duan, Ying; Wang, Chenchen; Li, Xuede; Xu, Wei

2014-12-01

The study describes the removal of fluoride from drinking water using activated alumina (AA). AA was modified with H2SO4, FeCl3 and a combination of the two to enhance fluoride adsorption. The AA adsorbents were characterized using Brunauer-Emmett-Teller surface area analysis and X-ray fluorescence. The maximum adsorption capacity of H2SO4- and FeCl3-modified AA adsorbents was 4.98 mg/g, which is 3.4 times higher compared with that of normal AA. The results showed that the surface area of AA increased when modified with H2SO4. AA modified with FeCl3 enhanced fluoride adsorption ability through ion-exchange between chlorine ions and fluoride ions. The fluoride adsorption properties of AA modified with both H2SO4 and FeCl3 were consistent with the Langmuir model. The fluoride adsorption kinetics of the adsorbents were well described by the pseudo-second-order kinetic model.

Aqueous vinylidene fluoride polymer coating composition

NASA Technical Reports Server (NTRS)

Bartoszek, Edward J. (Inventor); Christofas, Alkis (Inventor)

1978-01-01

A water-based coating composition which may be air dried to form durable, fire resistant coatings includes dispersed vinylidene fluoride polymer particles, emulsified liquid epoxy resin and a dissolved emulsifying agent for said epoxy resin which agent is also capable of rapidly curing the epoxy resin upon removal of the water from the composition.

Synthesis, characterization, and potential application of Mn2+-intercalated bentonite in fluoride removal: adsorption modeling and mechanism evaluation

NASA Astrophysics Data System (ADS)

Mudzielwana, Rabelani; Gitari, Wilson M.; Akinyemi, Segun A.; Msagati, Titus A. M.

2017-12-01

The study synthesizes a low-cost adsorbent made from Mn2+-modified bentonite clay for groundwater defluoridation. The clays were characterized using X-ray diffraction, X-ray fluorescence, scanning electron microscopy, and Fourier transform infrared techniques. The fluoride adsorption capacity of the modified clay was evaluated using batch experiments. The adsorption kinetics results showed that the optimum fluoride (F-) uptake was achieved within the 30 min' contact time. The data fitted well to pseudo-second-order of reaction kinetics indicating that adsorption of F- occurred via chemisorption. In addition, the adsorption isotherm data fitted well to Langmuir isotherm model indicating that adsorption occurred on a mono-layered surface. Maximum F- removal of 57% was achieved from groundwater with an initial F- concentration of 5.4 mg L-1 and natural pH of 8.6 using adsorbent dosage of 1 g/100 mL. Fluoride adsorption occurred through ligands and ion exchange mechanisms. The synthesized adsorbent was successfully regenerated for up to five times. The study shows that Mn2+-intercalated bentonite clay has potential for application in defluoridation of groundwater.

Stabilization of arsenic and fluoride bearing spent adsorbent in clay bricks: Preparation, characterization and leaching studies.

PubMed

Rathore, Vineet Kumar; Mondal, Prasenjit

2017-09-15

The presence of arsenic and fluoride in groundwater has been observed throughout the world. Many technologies have been developed by various research groups in order to tackle this problem. Adsorption has emerged as one of the best possible technique for the removal of arsenic, fluoride and many other pollutants from drinking water. Although a considerable amount of work has been published on the adsorptive removal of arsenic and fluoride, the area related to the management of spent adsorbent is not well explored. Present paper deals with the adsorptive removal of arsenic and fluoride from aqueous solution by three different types of adsorbents, namely, thermally treated laterite (TTL), acid-base treated laterite (ABTL) and aluminum oxide/hydroxide nanoparticles (AHNP). Under the experimental conditions in batch operation, the adsorption capacities of TTL, ABLT and AHNP for arsenic are found to be 6.43 μg/g, 9.25 μg/g and 48.5 μg/g respectively, whereas for fluoride, these values are found as 0.21 mg/g, 0.85 mg/g and 4.65 mg/g respectively. After adsorption, the spent adsorbents have been stabilized in the form of clay bricks. The effects of spent adsorbent concentration on the properties of bricks and their leaching properties are investigated. The bricks have been tested for various properties like density, percentage water absorption, shrinkage, compressive strength and efflorescence. The maximum values of density and shrinkage of the bricks formed are found as 2.3 g/cm 3 and 10.2%, whereas the percentage water absorption and compressive strength of the bricks are found between 11 and 14% and 35 to 150 kgf/cm 2 respectively. All the test results are in accordance with the criteria set by Indian Standards. The leaching test of arsenic and fluoride from the bricks reveals that their maximum values in leachate are 510 μg/L and 2.1 mg/L respectively, which are below the permissible limits of USEPA standards. Copyright © 2017 Elsevier Ltd. All rights reserved.

Production efficiency of micellar casein concentrate using polymeric spiral-wound microfiltration membranes.

PubMed

Beckman, S L; Zulewska, J; Newbold, M; Barbano, D M

2010-10-01

Most current research has focused on using ceramic microfiltration (MF) membranes for micellar casein concentrate production, but little research has focused on the use of polymeric spiral-wound (SW) MF membranes. A method for the production of a serum protein (SP)-reduced micellar casein concentrate using SW MF was compared with a ceramic MF membrane. Pasteurized (79°C, 18s) skim milk (1,100 kg) was microfiltered at 50°C [about 3 × concentration] using a 0.3-μm polyvinylidene fluoride spiral-wound membrane, bleed-and-feed, 3-stage process, using 2 diafiltration stages, where the retentate was diluted 1:2 with reverse osmosis water. Skim milk, permeate, and retentate were analyzed for SP content, and the reduction of SP from skim milk was determined. Theoretically, 68% of the SP content of skim milk can be removed using a single-stage 3× MF. If 2 subsequent water diafiltration stages are used, an additional 22% and 7% of the SP can be removed, respectively, giving a total SP removal of 97%. Removal of SP greater than 95% has been achieved using a 0.1-μm pore size ceramic uniform transmembrane pressure (UTP) MF membrane after a 3-stage MF with diafiltration process. One stage of MF plus 2 stages of diafiltration of 50°C skim milk using a polyvinylidene fluoride polymeric SW 0.3-μm membrane yielded a total SP reduction of only 70.3% (stages 1, 2, and 3: 38.6, 20.8, and 10.9%, respectively). The SP removal rate for the polymeric SW MF membrane was lower in all 3 stages of processing (stages 1, 2, and 3: 0.05, 0.04, and 0.03 kg/m(2) per hour, respectively) than that of the comparable ceramic UTP MF membrane (stages 1, 2, and 3: 0.30, 0.11, and 0.06 kg/m(2) per hour, respectively), indicating that SW MF is less efficient at removing SP from 50°C skim milk than the ceramic UTP system. To estimate the number of steps required for the SW system to reach 95% SP removal, the third-stage SP removal rate (27.4% of the starting material SP content) was used to extrapolate that an additional 5 water diafiltration stages would be necessary, for a total of 8 stages, to remove 95% of the SP from skim milk. The 8-plus stages necessary to remove >95% SP for the SW MF membrane would create more permeate and a lengthier process than required with ceramic membranes. Copyright © 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Removal of Cu(II) ions from contaminated waters using a conducting microfiltration membrane.

PubMed

Wang, Xueye; Wang, Zhiwei; Chen, Haiqin; Wu, Zhichao

2017-10-05

Efficient removal of toxic metals using low-pressure membrane processes from contaminated waters is an important but challenging task. In the present work, a conducting microfiltration membrane prepared by embedding a stainless steel mesh in the active layer of a polyvinylidene fluoride membrane is developed to remove Cu(II) ions from contaminated waters. Results showed that the conducting membrane had favorable electrochemical properties and stability as cathode. Batch tests showed that Cu(II) removal efficiency increased with the increase of voltages and leveled off with the further enhancement of electric field. The optimal voltages were determined to be 1.0V and 2.0V for the influent Cu(II) concentrations of 5mg/L and 30mg/L, respectively. X-ray photoelectron spectroscopy and X-ray diffraction results demonstrated the presence of Cu(0) and Cu(OH) 2 on the membrane surface. The removal mechanisms involved the intrinsic adsorption of membrane, electrosorption of membrane, adsorption of deposited layer, chemical precipitation of Cu(OH) 2 and deposition of Cu(0) which were aided by electrophoresis and electrochemical oxidation-reduction. Long-term tests showed that the major contributors for Cu(II) removal were the deposition of Cu(0) by electrochemical reduction-oxidation (47.3%±8.5%) and chemical precipitation (41.1%±0.2%), followed by electrosorption, adsorption by the fouling layer and membrane intrinsic sorption. Copyright © 2017 Elsevier B.V. All rights reserved.

Evaluating the impact of municipal water fluoridation on the aquatic environment.

PubMed Central

Osterman, J W

1990-01-01

Although highly beneficial for dental health, low concentrations of fluoride in environmental waters may be toxic to several organisms. In an era of heightened public awareness about the environment, this may lead city officials to withhold implementing water fluoridation for environmental reasons. This paper presents a mass balance approach to evaluate this perceived risk. Generally speaking, fluoridated water loss during use, dilution of sewage by rain and ground water infiltrate, fluoride removal during secondary sewage treatment, and diffusion dynamics at effluent outfall combine to eliminate fluoridation-related environmental effects. In Montreal, water fluoridation would raise average aquatic fluoride levels in the waste water plume immediately below effluent outfall by only 0.05-0.09 mg/l. Downstream, these changes would be only 0.02-0.05 mg/l at 1 km, and 0.01-0.03 mg/l at 2 km below outfall. Overall river fluoride concentrations theoretically would be raised by 0.001-0.002 mg/l, a value not measurable by current analytical techniques. All resulting concentrations would be well below those recommended for environmental safety and would not exceed natural levels found elsewhere in Quebec. A literature review did not reveal any examples of municipal water fluoridation causing recommended environmental concentrations to be exceeded, although excesses occurred in several cases of severe industrial water pollution. PMID:2400035

Atmosphere purification of radon and radon daughter elements

DOEpatents

Stein, L.

1973-12-11

A method for purifying an atmosphere of radon and radon daughter elements which may be contained therein by contacting the atmosphere with a fluorinating solution, whereby the radon and radon daughters are oxidized to their respective fluorides is discussed. The fluorides dissolve in the fluorinating solutlon and are removed from the atmosphere, which may then be recirculated. (Official Gazette)

A ditopic fluorescent sensor for potassium fluoride.

PubMed

Koskela, Suvi J M; Fyles, Thomas M; James, Tony D

2005-02-21

The addition of potassium fluoride 'switches on' the fluorescence of sensors and while potassium chloride and bromide cause no fluorescence change; the fluorescence can be 'switched off' by removing the potassium cation from the benzocrown ether receptors of sensors and through the addition of [2.2.2]-cryptand and restored by the addition of the potassium cation as potassium chloride.

Removal of fluoride from water with powdered corn cobs.

PubMed

Parmar, S; Patel, Jignesh B; Sudhakar, Padmaja; Koshy, V J

2006-04-01

The adsorption of fluoride on corn cobs powder was investigated in the present study. Neat powdered corn cobs did not show remarkable adsorption but aluminium treated corn cobs had good adsorption capacity. The parameters studied include the contact time, concentration, temperature and pH. Near neutral pH was identified as the optimum condition of the medium, and 90 to 120 minutes was the best contact time for maximum fluoride adsorption. The adsorption process was found to follow Freundlich isotherm. The adsorption process was found to be exothermic as adsorption decreased with increasing temperature.

Removal of fluoride impurities from UF/sub 6/ gas

DOEpatents

Beitz, J.V.

1984-01-06

A method of purifying a UF/sub 6/ gas stream containing one or more metal fluoride impurities composed of a transuranic metal, transition metal or mixtures thereof, is carried out by contacting the gas stream with a bed of UF/sub 5/ in a reaction vessel under conditions where at least one impurity reacts with the UF/sub 5/ to form a nongaseous product and a treated gas stream, and removing the treated gas stream from contact with the bed. The nongaseous products are subsequently removed in a reaction with an active fluorine affording agent to form a gaseous impurity which is removed from the reaction vessel. The bed of UF/sub 5/ is formed by the reduction of UF/sub 6/ in the presence of uv light. One embodiment of the reaction vessel includes a plurality of uv light sources as tubes on which UF/sub 5/ is formed. 2 figures.

Removal of fluoride impurities from UF.sub.6 gas

DOEpatents

Beitz, James V.

1985-01-01

A method of purifying a UF.sub.6 gas stream containing one or more metal fluoride impurities composed of a transuranic metal, transition metal or mixtures thereof, is carried out by contacting the gas stream with a bed of UF.sub.5 in a reaction vessel under conditions where at least one impurity reacts with the UF.sub.5 to form a nongaseous product and a treated gas stream, and removing the treated gas stream from contact with the bed. The nongaseous products are subsequently removed in a reaction with an active fluorine affording agent to form a gaseous impurity which is removed from the reaction vessel. The bed of UF.sub.5 is formed by the reduction of UF.sub.6 in the presence of UV light. One embodiment of the reaction vessel includes a plurality of UV light sources as tubes on which UF.sub.5 is formed.

Efficiency of Silver Impregnated Porous Pot (SIPP) Filters for Production of Clean Potable Water

PubMed Central

Mahlangu, Oranso; Mamba, Bhekie; Momba, Maggie

2012-01-01

The Silver Impregnated Porous Pot (SIPP) filter is a product of the Tshwane University of Technology manufactured for the production of safe drinking water at a household (home) level. Two SIPP devices were assessed for the reduction efficiency of chemical contaminants such as calcium, magnesium, iron, arsenic, fluorides and total organic carbon (TOC) as well as microbial contaminants from environmental samples. Turbidity change after filtration, together with correlation between chlorophyll a in the feed water and SIPP’s flow rates were also evaluated in order to give comprehensive guidelines on the quality of intake water that could be filtered through the filter without causing a significant decrease in flow rate. The SIPP filters removed contaminants from environmental water samples as follows: 70% to 92% iron, 36% to 68% calcium, 42% to 82% arsenic, 39% to 98% magnesium, 39% to 95% fluorides, 12% to 35% TOC and 45% to 82% turbidity. The SIPP filters had initial flow rates of 1 L/h to 4 L/h but the flow rates dropped to 0.5 L/h with an increase in cumulative volume of intake water as the filter was used. Turbidity and chemical contaminant reduction rates decreased with accumulating volume of intake water but the filter removed Ca, Fe and Mg to levels that comply with the South African National Standards (SANS 241) and the World Health Organization (WHO) guideline values. However, the SIPP filters cannot produce enough water to satisfy the daily drinking water requirement of a typical household (25 L/p·d). Chlorophyll a was associated with a decrease in the flow rate through the SIPP filters. PMID:23202668

Efficiency of Silver Impregnated Porous Pot (SIPP) filters for production of clean potable water.

PubMed

Mahlangu, Oranso; Mamba, Bhekie; Momba, Maggie

2012-08-24

The Silver Impregnated Porous Pot (SIPP) filter is a product of the Tshwane University of Technology manufactured for the production of safe drinking water at a household (home) level. Two SIPP devices were assessed for the reduction efficiency of chemical contaminants such as calcium, magnesium, iron, arsenic, fluorides and total organic carbon (TOC) as well as microbial contaminants from environmental samples. Turbidity change after filtration, together with correlation between chlorophyll a in the feed water and SIPP's flow rates were also evaluated in order to give comprehensive guidelines on the quality of intake water that could be filtered through the filter without causing a significant decrease in flow rate. The SIPP filters removed contaminants from environmental water samples as follows: 70% to 92% iron, 36% to 68% calcium, 42% to 82% arsenic, 39% to 98% magnesium, 39% to 95% fluorides, 12% to 35% TOC and 45% to 82% turbidity. The SIPP filters had initial flow rates of 1 L/h to 4 L/h but the flow rates dropped to 0.5 L/h with an increase in cumulative volume of intake water as the filter was used. Turbidity and chemical contaminant reduction rates decreased with accumulating volume of intake water but the filter removed Ca, Fe and Mg to levels that comply with the South African National Standards (SANS 241) and the World Health Organization (WHO) guideline values. However, the SIPP filters cannot produce enough water to satisfy the daily drinking water requirement of a typical household (25 L/p·d). Chlorophyll a was associated with a decrease in the flow rate through the SIPP filters.

Chronic Fluoride Toxicity: Dental Fluorosis

PubMed Central

DenBesten, Pamela; Li, Wu

2012-01-01

Dental fluorosis occurs as a result of excess fluoride ingestion during tooth formation. Enamel fluorosis and primary dentin fluorosis can only occur when teeth are forming, and therefore fluoride exposure (as it relates to dental fluorosis) occurs during childhood. In the permanent dentition, this would begin with the lower incisors, which complete mineralization at approximately 2–3 years of age, and end after mineralization of the third molars. The white opaque appearance of fluorosed enamel is caused by a hypomineralized enamel subsurface; with more severe dental fluorosis, pitting and a loss of the enamel surface occurs, leading to secondary staining (appearing as a brown color). Many of the changes caused by fluoride are related to cell/matrix/mineral interactions as the teeth are forming. At the early maturation stage, the relative quantity of amelogenin protein is increased in fluorosed enamel in a dose-related manner. This appears to result from a delay in the removal of amelogenins as the enamel matures. In vitro, when fluoride is incorporated into the mineral, more protein binds to the forming mineral, and protein removal by proteinases is delayed. This suggests that altered protein/mineral interactions are in part responsible for retention of amelogenins and the resultant hypomineralization that occurs in fluorosed enamel. Fluoride also appears to enhance mineral precipitation in forming teeth, resulting in hypermineralized bands of enamel, which are then followed by hypomineralized bands. Enhanced mineral precipitation with local increases in matrix acidity may affect maturation stage ameloblast modulation, potentially explaining the doserelated decrease in cycles of ameloblast modulation from ruffleended to smooth-ended cells that occur with fluoride exposure in rodents. Specific cellular effects of fluoride have been implicated, but more research is needed to determine which of these changes are relevant to the formation of fluorosed teeth. As further studies are done, we will better understand the mechanisms responsible for dental fluorosis. PMID:21701193

Chronic fluoride toxicity: dental fluorosis.

PubMed

Denbesten, Pamela; Li, Wu

2011-01-01

Dental fluorosis occurs as a result of excess fluoride ingestion during tooth formation. Enamel fluorosis and primary dentin fluorosis can only occur when teeth are forming, and therefore fluoride exposure (as it relates to dental fluorosis) occurs during childhood. In the permanent dentition, this would begin with the lower incisors, which complete mineralization at approximately 2-3 years of age, and end after mineralization of the third molars. The white opaque appearance of fluorosed enamel is caused by a hypomineralized enamel subsurface. With more severe dental fluorosis, pitting and a loss of the enamel surface occurs, leading to secondary staining (appearing as a brown color). Many of the changes caused by fluoride are related to cell/matrix interactions as the teeth are forming. At the early maturation stage, the relative quantity of amelogenin protein is increased in fluorosed enamel in a dose-related manner. This appears to result from a delay in the removal of amelogenins as the enamel matures. In vitro, when fluoride is incorporated into the mineral, more protein binds to the forming mineral, and protein removal by proteinases is delayed. This suggests that altered protein/mineral interactions are in part responsible for retention of amelogenins and the resultant hypomineralization that occurs in fluorosed enamel. Fluoride also appears to enhance mineral precipitation in forming teeth, resulting in hypermineralized bands of enamel, which are then followed by hypomineralized bands. Enhanced mineral precipitation with local increases in matrix acidity may affect maturation stage ameloblast modulation, potentially explaining the dose-related decrease in cycles of ameloblast modulation from ruffle-ended to smooth-ended cells that occur with fluoride exposure in rodents. Specific cellular effects of fluoride have been implicated, but more research is needed to determine which of these changes are relevant to the formation of fluorosed teeth. As further studies are done, we will better understand the mechanisms responsible for dental fluorosis. Copyright © 2011 S. Karger AG, Basel.

Efficient colorimetric and fluorescent detection of fluoride in DMSO-water mixtures with arylaldoximes.

PubMed

Rosen, Christian B; Hansen, Dennis J; Gothelf, Kurt V

2013-12-07

Fluoride detection through hydrogen bonding or deprotonation is most commonly achieved using amide, urea or pyrrole derivatives. The sensor molecules are often complex constructs and several synthetic steps are required for their preparation. Here we report the discovery that simple arylaldoximes have remarkable properties as fluoride anion sensors, providing distinct colorimetric or fluorescent readouts, depending on the structure of the arylaldoxime. The oximes showed exceptional selectivity towards fluoride over other typical anions, and low detection limits for fluoride in both DMSO and DMSO-water mixtures were obtained.

Advanced Water Purification System for In Situ Resource Utilization

NASA Technical Reports Server (NTRS)

Anthony, Stephen M.; Jolley, Scott T.; Captain, James G.

2013-01-01

A main goal in the field of In Situ Resource Utilization is to develop technologies that produce oxygen from regolith to provide consumables to an extraterrestrial outpost. The processes developed reduce metal oxides in the regolith to produce water, which is then electrolyzed to produce oxygen. Hydrochloric and hydrofluoric acids are byproducts of the reduction processes, which must be removed to meet electrolysis purity standards. We previously characterized Nation, a highly water selective polymeric proton-exchange membrane, as a filtration material to recover pure water from the contaminated solution. While the membranes successfully removed both acid contaminants, the removal efficiency of and water flow rate through the membranes were not sufficient to produce large volumes of electrolysis-grade water. In the present study, we investigated electrodialysis as a potential acid removal technique. Our studies have shown a rapid and significant reduction in chloride and fluoride concentrations in the feed solution, while generating a relatively small volume of concentrated waste water. Electrodialysis has shown significant promise as the primary separation technique in ISRU water purification processes.

Advanced Water Purification System for In Situ Resource Utilization Project

NASA Technical Reports Server (NTRS)

Anthony, Stephen M.

2014-01-01

A main goal in the field of In Situ Resource Utilization is to develop technologies that produce oxygen from regolith to provide consumables to an extratrrestrial outpost. The processes developed reduce metal oxides in the regolith to produce water, which is then electrolyzed to produce oxygen. Hydrochloric and hydrofluoric acids are byproducts of the reduction processes, which must be removed to meet electrolysis purity standards. We previously characterized Nation, a highly water selective polymeric proton-exchange membrane, as a filtrtion material to recover pure water from the contaminated solution. While the membranes successfully removed both acid contaminants, the removal efficiency of and water flow rate through the membranes were not sufficient to produce large volumes of electrolysis-grade water. In the present study, we investigated electrodialysis as a potential acid removable technique. Our studies have show a rapid and significant reduction in chloride and fluoride concentrations in the feed solution, while generating a relatively small volume of concentrated waste water. Electrodialysis has shown significant promise as the primary separation technique in ISRU water purification processes.

TRANSURANIC ELEMENT, COMPOSITION THEREOF, AND METHODS FOR PRODUCING SEPARATING AND PURIFYING SAME

DOEpatents

Wahl, A.C.

1961-09-19

A process of separating plutonium from fission products contained in an aqueous solution is described. Plutonium, in the tri- or tetravalent state, and the fission products are coprecipitated on lanthanum fluoride, lanthanum oxalate, cerous fluoride, cerous phosphate, ceric iodate, zirconyl phosphate, thorium iodate, or thorium fluoride. The precipitate is dissolved in acid, and the plutonium is oxidized to the hexavalent state. The fission products are selectively precipitated on a carrier of the above group but different from that used for the coprecipitation. The plutonium in the solution, after removal of the fission product precipitate, is reduced to at least the tetravalent state and precipitated on lanthanum fluoride, lanthanum phosphate, lanthanum oxalate, lanthanum hydroxide, cerous fluoride, cerous phosphate, cerous oxalate, cerous hydroxide, ceric iodate, zirconyl phosphate, zirconyl iodate, zirconium hydroxide, thorium fluoride, thorium oxalate, thorium iodate, thorium peroxide, uranium iodate, uranium oxalate, or uranium peroxide, again using a different carrier than that used for the precipitation of the fission products.

Effects of fluoridated milk on root dentin remineralization.

PubMed

Arnold, Wolfgang H; Heidt, Bastian A; Kuntz, Sebastian; Naumova, Ella A

2014-01-01

The prevalence of root caries is increasing with greater life expectancy and number of retained teeth. Therefore, new preventive strategies should be developed to reduce the prevalence of root caries. The aim of this study was to investigate the effects of fluoridated milk on the remineralization of root dentin and to compare these effects to those of sodium fluoride (NaF) application without milk. Thirty extracted human molars were divided into 6 groups, and the root cementum was removed from each tooth. The dentin surface was demineralized and then incubated with one of the following six solutions: Sodium chloride NaCl, artificial saliva, milk, milk+2.5 ppm fluoride, milk+10 ppm fluoride and artificial saliva+10 ppm fluoride. Serial sections were cut through the lesions and investigated with polarized light microscopy and quantitative morphometry, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The data were statistically evaluated using a one-way ANOVA for multiple comparisons. The depth of the lesion decreased with increasing fluoride concentration and was the smallest after incubation with artificial saliva+10 ppm fluoride. SEM analysis revealed a clearly demarcated superficial remineralized zone after incubation with milk+2.5 ppm fluoride, milk+10 ppm fluoride and artificial saliva+10 ppm fluoride. Ca content in this zone increased with increasing fluoride content and was highest after artificial saliva+10 ppm fluoride incubation. In the artificial saliva+10 ppm fluoride group, an additional crystalline layer was present on top of the lesion that contained elevated levels of F and Ca. Incubation of root dentin with fluoridated milk showed a clear effect on root dentin remineralization, and incubation with NaF dissolved in artificial saliva demonstrated a stronger effect.

Hydrothermal synthesis and characterization of hydroxyapatite and fluorhydroxyapatite nano-size powders.

PubMed

Montazeri, Leila; Javadpour, Jafar; Shokrgozar, Mohammad Ali; Bonakdar, Shahin; Javadian, Sayfoddin

2010-08-01

Pure hydroxyapatite (HAp) and fluoride-containing apatite powders (FHAp) were synthesized using a hydrothermal method. The powders were assessed by x-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscope (SEM) and F-selective electrode. X-ray diffraction results revealed the formation of single phase apatite structure for all the compositions synthesized in this work. However, the addition of a fluoride ion led to a systematic shift in the (3 0 0) peak of the XRD pattern as well as modifications in the FTIR spectra. It was found that the efficiency of fluoride ion incorporation decreased with the increase in the fluoride ion content. Fluorine incorporation efficiency was around 60% for most of the FHAp samples prepared in the current study. Smaller and less agglomerated particles were obtained by fluorine substitution. The bioactivity of the powder samples with different fluoride contents was compared by performing cell proliferation, alkaline phosphatase (ALP) and Alizarin red staining assays. Human osteoblast cells were used to assess the cellular responses to the powder samples in this study. Results demonstrated a strong dependence of different cell activities on the level of fluoridation.

Preparation of drinking water used in water supply systems of the towns Zrenjanin and Temerin by electrochemical methods.

PubMed

Orescanin, Visnja; Kollar, Robert; Nad, Karlo; Mikulic, Nenad

2013-01-01

The aim of this work was the development and application of the pilot plant with the capacity of 1000 L/day for the purification of groundwater used for human consumption characterized with high concentration of arsenic and increased values of organic pollutants, ammonia, nitrites, color and turbidity. For that purpose, groundwater from the production wells supplying the towns Zrenjanin and Temerin (Vojvodina, Serbia) was used. Due to its complex composition, the purification system required the combination of the electroreduction/electrocoagulation, using iron and aluminum electrode plates with/without ozonation, followed by the electromagnetic treatment and the finally by the simultaneous ozonation/UV treatment. The electroreduction was used for the removal of nitrates, nitrites, and Cr(VI), while the removal of arsenic, heavy metals, suspended solids, color and turbidity required the application of the electrocoagulation with simultaneous ozonation. Organic contaminants and ammonia were removed completely in the last treatment step by applying the simultaneous ozonation/UV treatment. All measured parameters in the purified water were significantly lower compared to the regulated values. Under the optimum treatment conditions, the removal efficiencies for color, turbidity, suspended solids, total arsenic, total chromium, Ni(II), total copper, sulfates, fluorides, chemical oxygen demand, ammonia, nitrates, and nitrites were 100%. The removal efficiencies of the total manganese and iron were 85.19% and 97.44%, respectively, whilst the final concentrations were 4 and 7 μg/L, respectively.

Effect of baking soda in dentifrices on plaque removal.

PubMed

Myneni, Srinivas R

2017-11-01

The prevention of dental caries and periodontal diseases targets control of dental plaque biofilm. In this context, chemical agents could represent a valuable complement to mechanical plaque control by reducing and controlling biofilm formation. The literature on the effectiveness of different dentifrices has not, however, been carefully categorized. A lack of consensus exists among dental professionals on a recommendation for a universal dentifrice for plaque control. The authors reviewed the scientific data on the different properties of sodium bicarbonate (baking soda)-containing dentifrices and their effectiveness in plaque removal. The results of the literature search show that baking soda-containing dentifrices are ideal candidates to be considered as a universal dentifrice because baking soda is inexpensive, abundant in supply, highly biocompatible, exhibits specific antibacterial properties to oral microorganisms, has low abrasivity, and is effective in plaque biofilm removal. Although some patients may benefit from desensitizing or high fluoride-containing dentifrices, those with routine needs may find using dentifrices containing baking soda and fluoride effective. Baking soda and fluoride dentifrices, therefore, may perhaps be considered as a criterion standard for patients with routine oral hygiene needs. Copyright © 2017 American Dental Association. Published by Elsevier Inc. All rights reserved.

SEPARATION OF PLUTONIUM VALUES FROM URANIUM AND FISSION PRODUCT VALUES

DOEpatents

Maddock, A.G.; Booth, A.H.

1960-09-13

Separation of plutonium present in small amounts from neutron irradiated uranium by making use of the phenomenon of chemisorption is described. Plutonium in the tetravalent state is chemically absorbed on a fluoride in solid form. The steps for the separation comprise dissolving the irradiated uranium in nitric acid, oxidizing the plutonium in the resulting solution to the hexavalent state, adding to the solution a soluble calcium salt which by the common ion effect inhibits dissolution of the fluoride by the solution, passing the solution through a bed or column of subdivided calcium fluoride which has been sintered to about 8OO deg C to remove the chemisorbable fission products, reducing the plutonium in the solution thus obtained to the tetravalent state, and again passing the solution through a similar bed or column of calcium fluoride to selectively absorb the plutonium, which may then be recovered by treating the calcium fluoride with a solution of ammonium oxalate.

No calcium-fluoride-like deposits detected in plaque shortly after a sodium fluoride mouthrinse.

PubMed

Vogel, G L; Tenuta, L M A; Schumacher, G E; Chow, L C

2010-01-01

Plaque 'calcium-fluoride-like' (CaF(2)-like) and fluoride deposits held by biological/bacterial calcium fluoride (Ca-F) bonds appear to be the source of cariostatic concentrations of fluoride in plaque fluid. The aim of this study was to quantify the amounts of plaque fluoride held in these reservoirs after a sodium fluoride rinse. 30 and 60 min after a 228 microg/g fluoride rinse, plaque samples were collected from 11 volunteers. Each sample was homogenized, split into 2 aliquots (aliquots 1 and 2), centrifuged, and the recovered plaque fluid combined and analyzed using microelectrodes. The plaque mass from aliquot 1 was retained. The plaque mass from aliquot 2 was extracted several times with a solution having the same fluoride, calcium and pH as the plaque fluid in order to extract the plaque CaF(2)-like deposits. The total fluoride in both aliquots was then determined. In a second experiment, the extraction completeness was examined by applying the above procedure to in vitro precipitates containing known amounts of CaF(2)-like deposits. Nearly identical fluoride concentrations were found in both plaque aliquots. The extraction of the CaF(2)-like precipitates formed in vitro removed more than 80% of these deposits. The results suggest that either CaF(2)-like deposits were not formed in plaque or, if these deposits had been formed, they were rapidly lost. The inability to form persistent amounts of CaF(2)-like deposits in plaque may account for the relatively rapid loss of plaque fluid fluoride after the use of conventional fluoride dentifrices or rinses. (c) 2010 S. Karger AG, Basel.

Child-education program for the reduction of health risks due to fluoride in water sources in the Chiang Mai Basin, Thailand.

PubMed

Takizawa, S; Takeda, T; Wongrueng, A; Wattanachira, S

2010-01-01

Groundwater is the major source of drinking water in Lamphun Province in the Chiang Mai Basin, Thailand. However, groundwater contains high fluoride up to 16 mg F/L, which has caused dental and skeletal fluorosis. Although Thai Government installed RO membrane plants for the removal of fluoride from groundwater; and delivers RO-filtered bottled water that contains less fluoride than the Thai Standard of 0.7 mg F/L, it was found that the urinary fluoride levels are still high among the residents. To find the major sources of fluoride intake, fluoride contents in various water sources, such as village water supply, shallow and deep groundwaters, rain water and bottled water, were measured, and the local people's behavior on water uses was recorded by interview and questionnaire study. As a result, it was found that the highest risk of fluoride ingestion comes from cooking rice with fluoride-containing water because of a lack of knowledge on fluoride sources and fluoride chemistry. To reduce the health risks arising from fluoride intake, a hands-on educational program on the sources and risks of fluoride in water was developed and implemented in the local schools. The participatory educational program promoted active involvement of schoolchildren, but it was found that the effectiveness of education varied depending on the questions we asked. Therefore, it needs to be improved by an iterative and interactive educational program. In conclusion, it was found that the benefits of providing safe drinking water using such advanced technology as RO membrane can be maximized only when it comes along with a participatory educational program on fluoride sources and health risks.

No Calcium-Fluoride-Like Deposits Detected in Plaque Shortly after a Sodium Fluoride Mouthrinse

PubMed Central

Vogel, G.L.; Tenuta, L.M.A.; Schumacher, G.E.; Chow, L.C.

2010-01-01

Plaque ‘calcium-fluoride-like’ (CaF2-like) and fluoride deposits held by biological/bacterial calcium fluoride (Ca-F) bonds appear to be the source of cariostatic concentrations of fluoride in plaque fluid. The aim of this study was to quantify the amounts of plaque fluoride held in these reservoirs after a sodium fluoride rinse. 30 and 60 min after a 228 μg/g fluoride rinse, plaque samples were collected from 11 volunteers. Each sample was homogenized, split into 2 aliquots (aliquots 1 and 2), centrifuged, and the recovered plaque fluid combined and analyzed using microelectrodes. The plaque mass from aliquot 1 was retained. The plaque mass from aliquot 2 was extracted several times with a solution having the same fluoride, calcium and pH as the plaque fluid in order to extract the plaque CaF2-like deposits. The total fluoride in both aliquots was then determined. In a second experiment, the extraction completeness was examined by applying the above procedure to in vitro precipitates containing known amounts of CaF2-like deposits. Nearly identical fluoride concentrations were found in both plaque aliquots. The extraction of the CaF2-like precipitates formed in vitro removed more than 80% of these deposits. The results suggest that either CaF2-like deposits were not formed in plaque or, if these deposits had been formed, they were rapidly lost. The inability to form persistent amounts of CaF2-like deposits in plaque may account for the relatively rapid loss of plaque fluid fluoride after the use of conventional fluoride dentifrices or rinses. PMID:20185917

Application of response surface methodology and semi-mechanistic model to optimize fluoride removal using crushed concrete in a fixed-bed column.

PubMed

Gu, Bon-Wun; Lee, Chang-Gu; Park, Seong-Jik

2018-03-01

The aim of this study was to investigate the removal of fluoride from aqueous solutions by using crushed concrete fines as a filter medium under varying conditions of pH 3-7, flow rate of 0.3-0.7 mL/min, and filter depth of 10-20 cm. The performance of fixed-bed columns was evaluated on the basis of the removal ratio (Re), uptake capacity (qe), degree of sorbent used (DoSU), and sorbent usage rate (SUR) obtained from breakthrough curves (BTCs). Three widely used semi-mechanistic models, that is, Bohart-Adams, Thomas, and Yoon-Nelson models, were applied to simulate the BTCs and to derive the design parameters. The Box-Behnken design of response surface methodology (RSM) was used to elucidate the individual and interactive effects of the three operational parameters on the column performance and to optimize these parameters. The results demonstrated that pH is the most important factor in the performance of fluoride removal by a fixed-bed column. The flow rate had a significant negative influence on Re and DoSU, and the effect of filter depth was observed only in the regression model for DoSU. Statistical analysis indicated that the model attained from the RSM study is suitable for describing the semi-mechanistic model parameters.

40 CFR 421.32 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2010 CFR

2010-07-01

... CATEGORY Secondary Aluminum Smelting Subcategory § 421.32 Effluent limitations guidelines representing the... to the provisions of this subpart and which uses aluminum fluoride in its magnesium removal process... Fluoride 0.4 Ammonia (as N) 0.01 Aluminum 1.0 Copper 0.003 COD 1.0 pH (1) 1 Within the range of 7.5 to 9.0. ...

Purifying arsenic and fluoride-contaminated water by a novel graphene-based nanocomposite membrane of enhanced selectivity and sustained flux.

PubMed

Pal, Madhubonti; Mondal, Mrinal Kanti; Paine, Tapan Kanti; Pal, Parimal

2018-06-01

A novel graphene-based nanocomposite membrane was synthesized by interfacial polymerization (IP) through chemical bonding of the graphene oxide (GO) layer to polyethersulfone surface. Detailed characterization of the composite membrane through AFM, SEM, ATR-FTIR, XRD analysis, and Raman spectroscopy indicates strong potential of the membrane in highly selective removal of the toxic contaminants like arsenic and fluoride while permeating the essential minerals like calcium and magnesium. This makes the membrane suitable for production of safe drinking water from contaminated water. The membrane applied in a flat-sheet cross-flow module succeeded in removal of more than 98% arsenic and around 80% fluoride from contaminated water while selectively retaining the useful calcium and magnesium minerals in drinking water. A sustained pure water flux of around 150 LMH (liter per square meter per hour) during operation over long hours (> 150 h) with only 3-5% drop in flux indicates antifouling character of the membrane module.

Application of kinetic models to the design of a calcite permeable reactive barrier (PRB) for fluoride remediation.

PubMed

Cai, Qianqian; Turner, Brett D; Sheng, Daichao; Sloan, Scott

2018-03-01

The kinetics of fluoride sorption by calcite in the presence of metal ions (Co, Mn, Cd and Ba) have been investigated and modelled using the intra-particle diffusion (IPD), pseudo-second order (PSO), and the Hill 4 and Hill 5 kinetic models. Model comparison using the Akaike Information Criterion (AIC), the Schwarz Bayseian Information Criterion (BIC) and the Bayes Factor allows direct comparison of model results irrespective of the number of model parameters. Information Criterion results indicate "very strong" evidence that the Hill 5 model was the best fitting model for all observed data due to its ability to fit sigmoidal data, with confidence contour analysis showing the model parameters were well constrained by the data. Kinetic results were used to determine the thickness of a calcite permeable reactive barrier required to achieve up to 99.9% fluoride removal at a groundwater flow of 0.1 m.day -1 . Fluoride removal half-life (t 0.5 ) values were found to increase in the order Ba ≈ stonedust (a 99% pure natural calcite) < Cd < Co < Mn. A barrier width of 0.97 ± 0.02 m was found to be required for the fluoride/calcite (stonedust) only system when using no factor of safety, whilst in the presence of Mn and Co, the width increased to 2.76 ± 0.28 and 19.83 ± 0.37 m respectively. In comparison, the PSO model predicted a required barrier thickness of ∼46.0, 62.6 & 50.3 m respectively for the fluoride/calcite, Mn and Co systems under the same conditions. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

The influence of fluoride varnish on the attrition of dentine.

PubMed

Li, H; Watson, T F; Sherriff, M; Curtis, R; Bartlett, D W

2007-01-01

Previous investigations have shown the potential for fluoride to be protective in an abrasion/erosion laboratory model. The aim of this study was to investigate the effect of high concentrations of fluoride delivered in a varnish on attrition of dentine. Fifteen caries-free, intact lower third molar teeth were sectioned and the enamel removed by a water-cooled diamond disc. Polished dentine surfaces were divided into 8 areas, 4 of which were randomly covered with a high-concentration fluoride varnish for 24 h. The samples were subjected to 5,000 cycles of attrition bathed under artificial saliva. Microhardness testing adjacent to the wear scars showed no statistical difference between the fluoride-treated (71.42 KHN, SD 10.52) and control surfaces (72.66 KHN, SD 9.69). The volume of the wear scar was statistically greater for the fluoride-treated surface at 9.6 microm(3) (SD 4.92) and 8.13 microm(3) (SD 5.54) for the control areas (p = 0.029). The low pH of the fluoride varnish appears to have increased the amount of wear from attrition in this laboratory study. Copyright 2007 S. Karger AG, Basel.

Hydrous ZrO2 decorated polyaniline nanofibres: Synthesis, characterization and application as an efficient adsorbent for water defluoridation.

PubMed

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

2017-12-15

A new hybrid material comprising hydrous zirconium oxide (HZrO 2 ) supported onto polyaniline (PANI) nanofibres (HZrO 2 @PANI NFs) was prepared via the precipitation of HZrO 2 onto as-synthesized PANI NFs and tested for its defluoridation capabilities. The developed adsorbent (HZrO 2 @PANI NFs) was fully characterized by FTIR, BET, XRD, SEM-EDX, TEM-(S)TEM, XPS, and zeta potential measurements. HZrO 2 @PANI NFs achieved 2-fold BET surface area ∼86.64 m 2 /gas compared to PANI NFs ∼44.72 m 2 /g, implying that the incorporation of HZrO 2 onto the PANI nanofibres enhanced the available surface area for effective fluoride adsorption. Moreover, HZrO 2 @PANI NFs was found to be effective over a wide pH range (3-9) as designated by its high pH pzc ∼9.8. The adsorption kinetics obeyed the pseudo-second-order model well with equilibrium attainment in 30min. Adsorption isotherm was best described by the Langmuir model and the maximum adsorption capacities obtained were 83.23 and 28.77mg/g at pH 3 and 6.5, respectively, which is superior to most ZrO 2 based adsorbents reported in the literature and better than that of native PANI. Furthermore, the developed adsorbent manifested quite a selective fluoride uptake at pH 3 as compared to pH 6.5±0.1 wherein significant chemical affinity competition was presented by phosphate ions followed by bicarbonate and sulfate. The recyclability of HZrO 2 @PANI NFs for four cycles and its applicability to fluoride spiked ground water has also been demonstrated. The adsorption mechanism was interpreted with the help of FTIR, XPS and Zeta potential analysis and the results revealed the involvement of both anion exchange and electrostatic attraction in the adsorption of F - ions. Thus, a new efficient adsorbent with reasonably high adsorption capacity and superior pH tolerance has been developed for fluoride removal. Copyright © 2017 Elsevier Inc. All rights reserved.

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

2015-06-07

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.

Association between clinical and salivary microbial parameters during orthodontic treatment with removable appliances with or without use of fluoride mouth rinse.

PubMed

Zingler, S; Pritsch, M; Lux, C J; Kneist, S

2016-09-01

To evaluate the correlation between clinical and salivary microbial parameters during treatment with removable orthodontic appliances with or without use of fluoride mouth rinse. A group of 48 patients completed this randomized, controlled, parallel-group, clinical pilot study. 24 patients of the test group (TG) rinsed after tooth brushing with a fluoride mouth rinse (100 ppm AmF/150 ppm NaF) while 21 patients of the control group (CG) did not. Clinical parameters [Approximal Plaque Index (API), Papillary Bleeding Index (PBI)] as well as levels of salivary mutans streptococci (MS) and lactobacilli (LB) were assessed at baseline and after 3, 6, 9 and 12 months. Compliance was documented by participants. Appliance wear-times were estimated retrospectively by the patients. All participants received the same brushing instructions and were supplied with the same toothbrush/toothpaste. A significant correlation of API values with MS levels (p=0.0003) or with LB levels (p=0.001) was observed. Furthermore, appliance wear-times were significantly associated with API values (p=0.02). The changes of MS or LB levels between beginning and end of the study did not differ significantly between study groups. The changes of the API scores showed slightly different median values (-3.5 in the TG vs. 0 in the CG), the difference, however, was not significant. The results emphasise the need for a careful monitoring of the oral hygiene status in patients with removable orthodontic appliances. Larger controlled clinical trials are necessary to investigate treatment options such as use of supplementary fluoride mouth rinse.

Use of ferric-impregnated volcanic ash for arsenate (V) adsorption from contaminated water with various mineralization degrees.

PubMed

Chen, Rongzhi; Zhang, Zhenya; Yang, Yingnan; Lei, Zhongfang; Chen, Nan; Guo, Xu; Zhao, Chao; Sugiura, Norio

2011-01-15

Ferric-impregnated volcanic ash (FVA) which consisted mainly of different forms of iron and aluminum oxide minerals was developed for arsenate (V) removal from an aqueous medium. The adsorption experiments were conducted in both DI water samples and actual water (Lake Kasumigaura, Japan) to investigate the effects of solution mineralization degree on the As(V) removal. Kinetic and equilibrium studies conducted in actual water revealed that the mineralization of water greatly elevated the As(V) adsorption on FVA. The experiment performed in DI water indicated that the existence of multivalence metallic cations significantly enhanced the As(V) adsorption ability, whereas competing anions such as fluoride and phosphate greatly decreased the As(V) adsorption. It is suggested that FVA is a cost-effective adsorbent for As(V) removal in low-level phosphate and fluoride solution. It was important to conduct the batch experiment using the actual water to investigate the arsenic removal on adsorbents. Copyright © 2010 Elsevier Inc. All rights reserved.

Performance of granular zirconium-iron oxide in the removal of fluoride from drinking water.

PubMed

Dou, Xiaomin; Zhang, Yansu; Wang, Hongjie; Wang, Tingjie; Wang, Yili

2011-06-01

In this study, a granular zirconium-iron oxide (GZI) was successfully prepared using the extrusion method, and its defluoridation performance was systematically evaluated. The GZI was composed of amorphous and nano-scale oxide particles. The Zr and Fe were evenly distributed on its surface, with a Zr/Fe molar ratio of ∼2.3. The granular adsorbent was porous with high permeability potential. Moreover, it had excellent mechanical stability and high crushing strength, which ensured less material breakage and mass loss in practical use. In batch tests, the GZI showed a high adsorption capacity of 9.80 mg/g under an equilibrium concentration of 10 mg/L at pH 7.0, which outperformed many other reported granular adsorbents. The GZI performed well over a wide pH range, of 3.5-8.0, and especially well at pH 6.0-8.0, which was the preferred range for actual application. Fluoride adsorption on GZI followed pseudo-second-order kinetics and could be well described by the Freundlich equilibrium model. With the exception of HCO(3)(-), other co-existing anions and HA did not evidently inhibit fluoride removal by GZI when considering their real concentrations in natural groundwater, which showed that GZI had a high selectivity for fluoride. In column tests using real groundwater as influent, about 370, 239 and 128 bed volumes (BVs) of groundwater were treated before breakthrough was reached under space velocities (SVs) of 0.5, 1 and 3 h(-1), respectively. Additionally, the toxicity characteristic leaching procedure (TCLP) results suggested that the spent GZI was inert and could be safely disposed of in landfill. In conclusion, this granular adsorbent showed high potential for fluoride removal from real groundwater, due to its high performance and physical-chemical properties. Copyright © 2011 Elsevier Ltd. All rights reserved.

Current Progress of Capacitive Deionization for Removal of Pollutant Ions

NASA Astrophysics Data System (ADS)

Gaikwad, Mahendra S.; Balomajumder, Chandrajit

2016-08-01

A mini review of a recently developing water purification technology capacitive deionization (CDI) applied for removal of pollutant ions is provided. The current progress of CDI for removal of different pollutant ions such as arsenic, fluoride, boron, phosphate, lithium, copper, cadmium, ferric, and nitrate ions is presented. This paper aims at motivating new research opportunities in capacitive deionization technology for removal of pollutant ions from polluted water.

Summaries of Research, Fiscal Year 1992

DTIC Science & Technology

1992-01-01

needs, or between early exposure to fluoridated drinking water and treatment needs. - Three hundred seventy four female recruits have been surveyed at... fluoridated drinking water and treat- ment needs. An abstract was presented at the 1992 AADR Annual Meeting and Exhibition, July 1-4, Glasgow, Scotland...significant difference (p <.002) in subsequent root-canal (RCT) or extraction (EXT) when pulp capping was performed. When all caries could be removed

Defluoridation using biomimetically synthesized nano zirconium chitosan composite: kinetic and equilibrium studies.

PubMed

Prasad, Kumar Suranjit; Amin, Yesha; Selvaraj, Kaliaperumal

2014-07-15

The present study reports a novel approach for synthesis of Zr nanoparticles using aqueous extract of Aloe vera. Resulting nanoparticles were embedded into chitosan biopolymer and termed as CNZr composite. The composite was subjected to detailed adsorption studies for removal of fluoride from aqueous solution. The synthesized Zr nanoparticles showed UV-vis absorption peak at 420nm. TEM result showed the formation of polydispersed, nanoparticles ranging from 18nm to 42nm. SAED and XRD analysis suggested an fcc (face centered cubic) Zr crystallites. EDAX analysis suggested that Zr was an integral component of synthesized nanoparticles. FT-IR study indicated that functional group like NH, CO, CN and CC were involved in particle formation. The adsorption of fluoride on to CNZr composite worked well at pH 7.0, where ∼99% of fluoride was found to be adsorbed on adsorbent. Langmuir isotherm model best fitted the equilibrium data since it presented higher R(2) value than Freundlich model. In comparison to pseudo-first order kinetic model, the pseudo-second order model could explain adsorption kinetic behavior of F(-) onto CNZr composite satisfactorily with a good correlation coefficient. The present study revealed that CNZr composite may work as an effective tool for removal of fluoride from contaminated water. Copyright © 2014 Elsevier B.V. All rights reserved.

POINT-OF-USE TREATMENT OF DRINKING WATER IN SAN YSIDRO, NM

EPA Science Inventory

This study was conducted to determine whether point-of-use (POU) reverse osmosis (RO) units could satisfactorily function in lieu of central treatment to remove arsenic and fluoride from the drinking water supply of San Ysidro, NM. POU treatment was evaluated for removal efficien...

The cariostatic mechanisms of fluoride.

PubMed

Rošin-Grget, Kata; Peroš, Kristina; Sutej, Ivana; Bašić, Krešimir

2013-11-01

This article discusses the possible cariostatic mechanisms of the action of fluoride. In the past, fluoride inhibition of caries was ascribed to reduced solubility of enamel due to incorporation of fluoride (F-) into the enamel minerals. The present evidence from clinical and laboratory studies suggests that the caries-preventive mode of action of fluoride is mainly topical. There is convincing evidence that fluoride has a major effect on demineralisation and remineralisation of dental hard tissue. The source of this fluoride could either be fluorapatite (formed due to the incorporation of fluoride into enamel) or calcium fluoride (CaF2)-like precipitates, which are formed on the enamel and in the plaque after application of topical fluoride. Calcium fluoride deposits are protected from rapid dissolution by a phosphate -protein coating of salivary origin. At lower pH, the coating is lost and an increased dissolution rate of calcium fluoride occurs. The CaF2, therefore, act as an efficient source of free fluoride ions during the cariogenic challenge. The current evidence indicates that fluoride has a direct and indirect effect on bacterial cells, although the in vivo implications of this are still not clear. A better understanding of the mechanisms of the action of fluoride is very important for caries prevention and control. The effectiveness of fluoride as a cariostatic agent depends on the availability of free fluoride in plaque during cariogenic challenge, i.e. during acid production. Thus, a constant supply of low levels of fluoride in biofilm/saliva/dental interference is considered the most beneficial in preventing dental caries. Copyright © 2013 by Academy of Sciences and Arts of Bosnia and Herzegovina.

Emission beyond 4  μm and mid-infrared lasing in a dysprosium-doped indium fluoride (InF3) fiber.

PubMed

Majewski, Matthew R; Woodward, Robert I; Carreé, Jean-Yves; Poulain, Samuel; Poulain, Marcel; Jackson, Stuart D

2018-04-15

Optical emission from rare-earth-doped fluoride fibers has thus far been limited to less than 4 μm. We extend emission beyond this limit by employing an indium fluoride (InF 3 ) glass fiber as the host, which exhibits an increased infrared transparency over commonly used zirconium fluoride (ZBLAN). Near-infrared pumping of a dysprosium-doped InF 3 fiber results in broad emission centered around 4.3 μm, representing the longest emission yet achieved from a fluoride fiber. The first laser emission in an InF 3 fiber is also demonstrated from the 3 μm dysprosium transition. Finally, a frequency domain excited state lifetime measurement comparison between fluoride hosts suggests that multiphonon effects are significantly reduced in indium fluoride fiber, paving the way to more efficient, longer wavelength lasers compared to ZBLAN fibers.

Insights into the fluoride-resistant regulation mechanism of Acidithiobacillus ferrooxidans ATCC 23270 based on whole genome microarrays.

PubMed

Ma, Liyuan; Li, Qian; Shen, Li; Feng, Xue; Xiao, Yunhua; Tao, Jiemeng; Liang, Yili; Yin, Huaqun; Liu, Xueduan

2016-10-01

Acidophilic microorganisms involved in uranium bioleaching are usually suppressed by dissolved fluoride ions, eventually leading to reduced leaching efficiency. However, little is known about the regulation mechanisms of microbial resistance to fluoride. In this study, the resistance of Acidithiobacillus ferrooxidans ATCC 23270 to fluoride was investigated by detecting bacterial growth fluctuations and ferrous or sulfur oxidation. To explore the regulation mechanism, a whole genome microarray was used to profile the genome-wide expression. The fluoride tolerance of A. ferrooxidans cultured in the presence of FeSO4 was better than that cultured with the S(0) substrate. The differentially expressed gene categories closely related to fluoride tolerance included those involved in energy metabolism, cellular processes, protein synthesis, transport, the cell envelope, and binding proteins. This study highlights that the cellular ferrous oxidation ability was enhanced at the lower fluoride concentrations. An overview of the cellular regulation mechanisms of extremophiles to fluoride resistance is discussed.

Erosion Remineralization Efficacy of Gel-to-Foam Fluoride Toothpastes in situ: A Randomized Clinical Trial.

PubMed

Nehme, Marc; Jeffery, Peter; Mason, Stephen; Lippert, Frank; Zero, Domenick T; Hara, Anderson T

2016-01-01

This single-center, randomized, placebo-controlled, four-treatment, four-period crossover study compared the enamel remineralization effects of low- and medium-abrasivity gel-to-foam toothpastes and a reference toothpaste (all 1,450 ppm fluoride as NaF) versus placebo toothpaste (0 ppm fluoride) using a short-term in situ erosion model. Subjects (n = 56) wearing a palatal appliance holding acid-softened bovine enamel specimens brushed their teeth with the test toothpastes. Thereafter, the specimens were removed for analysis of percent surface microhardness recovery (%SMHR) and percent relative erosion resistance (%RER) at 2, 4, and 8 h. Both low- and medium-abrasivity gel-to-foam fluoride toothpastes and the reference toothpaste provided significantly greater %SMHR than placebo at all assessment time points (all p < 0.05). No statistically significant difference of %SMHR was observed between the fluoride treatment groups at any time point. Similarly, all fluoride products provided significantly superior %RER versus placebo (all p < 0.0001), whereas no significant difference of this parameter was noted between the fluoride treatment groups. Increasing numerical improvements of %SMHR and %RER were observed in all four treatment groups over time (2, 4, and 8 h). The present in situ model is a sensitive tool to investigate intrinsic and fluoride-enhanced rehardening of eroded enamel. All three fluoride toothpastes were more efficacious than placebo, and there were no safety concerns following single dosing in this short-term in situ model. © 2016 The Author(s) Published by S. Karger AG, Basel.

40 CFR 421.32 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2014 CFR

2014-07-01

... discharged by a point source subject to the provisions of this subpart and which uses water for metal cooling... to the provisions of this subpart and which uses aluminum fluoride in its magnesium removal process... Fluoride 0.4 Ammonia (as N) 0.01 Aluminum 1.0 Copper 0.003 COD 1.0 pH (1) 1 Within the range of 7.5 to 9.0. ...

40 CFR 421.32 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2012 CFR

2012-07-01

... discharged by a point source subject to the provisions of this subpart and which uses water for metal cooling... to the provisions of this subpart and which uses aluminum fluoride in its magnesium removal process... Fluoride 0.4 Ammonia (as N) 0.01 Aluminum 1.0 Copper 0.003 COD 1.0 pH (1) 1 Within the range of 7.5 to 9.0. ...

40 CFR 421.32 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2013 CFR

2013-07-01

... discharged by a point source subject to the provisions of this subpart and which uses water for metal cooling... to the provisions of this subpart and which uses aluminum fluoride in its magnesium removal process... Fluoride 0.4 Ammonia (as N) 0.01 Aluminum 1.0 Copper 0.003 COD 1.0 pH (1) 1 Within the range of 7.5 to 9.0. ...

40 CFR 421.32 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2011 CFR

2011-07-01

... discharged by a point source subject to the provisions of this subpart and which uses water for metal cooling... to the provisions of this subpart and which uses aluminum fluoride in its magnesium removal process... Fluoride 0.4 Ammonia (as N) 0.01 Aluminum 1.0 Copper 0.003 COD 1.0 pH (1) 1 Within the range of 7.5 to 9.0. ...

Energy dispersive X-ray spectrometry study of the protective effects of fluoride varnish and gel on enamel erosion.

PubMed

De Carvalho Filho, Antonio Carlos Belfort; Sanches, Roberto Pizarro; Martin, Airton Abrahão; Do Espírito Santo, Ana Maria; Soares, Luís Eduardo Silva

2011-09-01

Dental erosion is a risk factor for dental health, introduced by today's lifestyle. Topical fluoride applications in the form of varnishes and gel may lead to deposition of fluoride on enamel. This in vitro study aimed to evaluate the effect of two fluoride varnishes and one fluoride gel on the dissolution of bovine enamel by acids. Enamel samples (72) were divided (n = 8): artificial saliva (control-G1), Pepsi Twist® (G2), orange juice (G3), Duraphat® + Pepsi Twist® (G4), Duraphat® + orange juice (G5), Duofluorid® + Pepsi Twist® (G6), Duofluorid® + orange juice (G7), fluoride gel + Pepsi Twist® (G8), and fluoride gel + orange juice (G9). Fluoride gel was applied for 4 min and the varnishes were applied and removed after 6 h. The samples were submitted to six cycles (demineralization: Pepsi Twist® or orange juice, 10 min; remineralization: saliva, 1 h). Samples were analyzed by energy-dispersive X-ray fluorescence (144 line-scanning). The amount of Ca and P decreased significantly in the samples of G2 and G3, and the Ca/P ratio decreased in G3. Mineral gain (Ca) was greater in G9 samples than in G4 > G3 > G5 > G1, and (P) greater in G7 samples than in G9 > G4-6 > G2-3. The protective effect of Duofluorid® was significantly lower than fluoride gel against orange juice. The fluoride varnishes can interfere positively with the dissolution of dental enamel in the presence of acidic beverages. Fluoride gel showed the best protection level to extrinsic erosion with low costs. Copyright © 2010 Wiley-Liss, Inc.

Evidence-based tailoring of behavior-change campaigns: increasing fluoride-free water consumption in rural Ethiopia with persuasion.

PubMed

Huber, Alexandra C; Tobias, Robert; Mosler, Hans-Joachim

2014-03-01

Two hundred million people worldwide are at risk of developing dental and skeletal fluorosis due to excessive fluoride uptake from their water. Since medical treatment of the disease is difficult and mostly ineffective, preventing fluoride uptake is crucial. In the Ethiopian Rift Valley, a fluoride-removal community filter was installed. Despite having access to a fluoride filter, the community used the filter sparingly. During a baseline assessment, 173 face-to-face interviews were conducted to identify psychological factors that influence fluoride-free water consumption. Based on the results, two behavior-change campaigns were implemented: a traditional information intervention targeting perceived vulnerability, and an evidence-based persuasion intervention regarding perceived costs. The interventions were tailored to household characteristics. The campaigns were evaluated with a survey and analyzed in terms of their effectiveness in changing behavior and targeted psychological factors. While the intervention targeting perceived vulnerability showed no desirable effects, cost persuasion decreased the perceived costs and increased the consumption of fluoride-free water. This showed that altering subjective perceptions can change behavior even without changing objective circumstances. Moreover, interventions are more effective if they are based on evidence and tailored to specific households. © 2013 The International Association of Applied Psychology.

Freeze concentration of proteins in Antarctic krill wash water

NASA Astrophysics Data System (ADS)

Qi, Xiangming; Xu, Jing; Zhao, Kuo; Guo, Hui; Ma, Lei

2017-12-01

Water-washing removes fluoride from Antarctic krill but produces large volumes of wash water containing water- soluble proteins and fluoride. The freeze concentration method was tested to determine if it could be used to recover water-soluble proteins while leaving the fluoride in solution. After freezing and thawing the wash water, protein and fluoride contents of the thawed fractions were determined to explore the melting regularity of components in the wash water. The highest concentration factors of protein and fluoride were obtained after 80 min of thawing, such as 1.48 ± 0.06 and 1.35 ± 0.04 times, respectively. The free amino-nitrogen (FAN) content and sodium dodecyl sulfate-polyacrylamide gel electrophoresis pattern results revealed that the highest concentrations of all ingredients were obtained after 80 min of the process. The degree of hydrolysis of all fractions from the thawing process fluctuated in a narrow range around 12% during the entire process, indicating that the thawing order did not change with various proteins or time during the entire thawing course. These results demonstrate that the freeze concentration method can be used to concentrate protein solutions, even those with fluoride. It was concluded that condensation was achieved and no ingredient could be separated, regardless of fluoride, amino acids, or different proteins in the water.

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.

Fluoride glass starting materials - Characterization and effects of thermal treatment

NASA Technical Reports Server (NTRS)

Chen, William; Dunn, Bruce; Shlichta, Paul; Neilson, George F.; Weinberg, Michael C.

1987-01-01

The production of heavy metal fluoride (HMF) glasses, and the effects of thermal treatments on the HMF glasses are investigated. ZrF4, BaF2, AlF3, LaF3, and NaF were utilized in the synthesis of zirconium-barium-lanthanum-aluminum-sodium fluoride glass. The purity of these starting materials, in particular ZrF4, is evaluated using XRD analysis. The data reveal that low temperature heating of ZrF4-H2O is effective in removing the water of hydration, but causes the production of ZrF4 and oxyfluorides; however, dehydration followed by sublimation results in the production of monoclinic ZrFe without water or oxyfluoride contaminants.

Production of sintered porous metal fluoride pellets

DOEpatents

Anderson, L.W.; Stephenson, M.J.

1973-12-25

Porous pellets characterized by a moderately reactive crust and a softer core of higher reactivity are produced by forming agglomerates containing a metal fluoride powder and a selected amount ofwater. The metal fluoride is selected to be sinterable and essentially non-reactive with gaseous fluorinating agents. The agglomerates are contacted with a gaseous fluorinating agent under controlled conditions whereby the heat generated by localized reaction of the agent and water is limited to values effccting bonding by localized sintering. Porous pellets composed of cryolite (Na/sub 3/AlF/sub 6/) can be used to selectively remove trace quantities of niobium pentafluoride from a feed gas consisting predominantly of uranium hexafluoride. (Official Gazette)

Mechanism insight of PFOA degradation by ZnO assisted-photocatalytic ozonation: Efficiency and intermediates.

PubMed

Wu, Dan; Li, Xukai; Tang, Yiming; Lu, Ping; Chen, Weirui; Xu, Xiaoting; Li, Laisheng

2017-08-01

Zinc oxide (ZnO) nanorods were prepared by a directly pyrolysis method and employed as catalyst for perfluorooctanoic acid (PFOA) degradation. Comparative experiments were conducted to discuss the catalytic activity and flexibility of ZnO. After ZnO addition, the best PFOA degradation efficiency (70.5%) was achieved by ZnO/UV/O 3 system, only 9.5% by sole ozonation and 18.2% by UV 254 light irradiation. PFOA degradation was sensitive with pH value and temperature. The better PFOA removal efficiency was achieved at acidic condition. A novel relationship was found among PFOA degradation efficiency with hydroxyl radicals and photo-generated holes. Hydroxyl radicals generated on the surfaces of ZnO nanorods played dominant roles in PFOA degradation. PFOA degradation was found to follow the photo-Kolbe reaction mechanism. C 2 -C 7 shorter-chain perfluorocarboxylic acids and fluoride ion were detected as main intermediates during PFOA degradation process. Based on the results, a proposal degradation pathway was raised. Copyright © 2017 Elsevier Ltd. All rights reserved.

In Vitro Comparison of the Effects of Diode Laser and CO2 Laser on Topical Fluoride Uptake in Primary Teeth

PubMed Central

Bahrololoomi, Zahra; Sorouri, Milad

2015-01-01

Objectives: Fluoride therapy is important for control and prevention of dental caries. Laser irradiation can increase fluoride uptake especially when combined with topical fluoride application. The objective of this study was to compare the effects of CO2 and diode lasers on enamel fluoride uptake in primary teeth. Materials and Methods: Forty human primary molars were randomly assigned to four groups (n=10). The roots were removed and the crowns were sectioned mesiodistally into buccal and lingual halves as the experimental and control groups. All samples were treated with 5% sodium fluoride (NaF) varnish. The experimental samples in the four groups were irradiated with 5 or 7W diode or 1 or 2W CO2 laser for 15 seconds and were compared with the controls in terms of fluoride uptake, which was determined using an ion selective electrode after acid dissolution of the specimens. Data were analyzed by SPSS version 16 using ANOVA treating the control measurements as covariates. Results: The estimated amount of fluoride uptake was 59.5± 16.31 ppm, 66.5± 14.9 ppm, 78.6± 12.43 ppm and 90.4± 11.51 ppm for 5W and 7 W diode and 1W and 2 W CO2 lasers, respectively, which were significantly greater than the values in the conventional topical fluoridation group (P<0.005). There were no significant differences between 7W diode laser and 1W CO2 laser, 5W and 7W diode laser, or 1W and 2W CO2 laser in this regard. Conclusion: The results showed that enamel surface irradiation by CO2 and diode lasers increases the fluoride uptake. PMID:27123018

Water fluoridation and the quality of information available online.

PubMed

Frangos, Zachary; Steffens, Maryke; Leask, Julie

2018-02-13

The Internet has transformed the way in which people approach their health care, with online resources becoming a primary source of health information. Little work has assessed the quality of online information regarding community water fluoridation. This study sought to assess the information available to individuals searching online for information, with emphasis on the credibility and quality of websites. We identified the top 10 web pages returned from different search engines, using common fluoridation search terms (identified in Google Trends). Web pages were scored using a credibility, quality and health literacy tool based on Global Advisory Committee on Vaccine Safety (GAVCS) and Center for Disease Control and Prevention (CDC) criteria. Scores were compared according to their fluoridation stance and domain type, then ranked by quality. The functionality of the scoring tool was analysed via a Bland-Altman plot of inter-rater reliability. Five-hundred web pages were returned, of which 55 were scored following removal of duplicates and irrelevant pages. Of these, 28 (51%) were pro-fluoridation, 16 (29%) were neutral and 11 (20%) were anti-fluoridation. Pro, neutral and anti-fluoridation pages scored well against health literacy standards (0.91, 0.90 and 0.81/1 respectively). Neutral and pro-fluoridation web pages showed strong credibility, with mean scores of 0.80 and 0.85 respectively, while anti-fluoridation scored 0.62/1. Most pages scored poorly for content quality, providing a moderate amount of superficial information. Those seeking online information regarding water fluoridation are faced with comprehensible, yet poorly referenced, superficial information. Sites were credible and user friendly; however, our results suggest that online resources need to focus on providing more transparent information with appropriate figures to consolidate the information. © 2018 FDI World Dental Federation.

In Vitro Comparison of the Effects of Diode Laser and CO2 Laser on Topical Fluoride Uptake in Primary Teeth.

PubMed

Bahrololoomi, Zahra; Fotuhi Ardakani, Faezeh; Sorouri, Milad

2015-08-01

Fluoride therapy is important for control and prevention of dental caries. Laser irradiation can increase fluoride uptake especially when combined with topical fluoride application. The objective of this study was to compare the effects of CO2 and diode lasers on enamel fluoride uptake in primary teeth. Forty human primary molars were randomly assigned to four groups (n=10). The roots were removed and the crowns were sectioned mesiodistally into buccal and lingual halves as the experimental and control groups. All samples were treated with 5% sodium fluoride (NaF) varnish. The experimental samples in the four groups were irradiated with 5 or 7W diode or 1 or 2W CO2 laser for 15 seconds and were compared with the controls in terms of fluoride uptake, which was determined using an ion selective electrode after acid dissolution of the specimens. Data were analyzed by SPSS version 16 using ANOVA treating the control measurements as covariates. The estimated amount of fluoride uptake was 59.5± 16.31 ppm, 66.5± 14.9 ppm, 78.6± 12.43 ppm and 90.4± 11.51 ppm for 5W and 7 W diode and 1W and 2 W CO2 lasers, respectively, which were significantly greater than the values in the conventional topical fluoridation group (P<0.005). There were no significant differences between 7W diode laser and 1W CO2 laser, 5W and 7W diode laser, or 1W and 2W CO2 laser in this regard. The results showed that enamel surface irradiation by CO2 and diode lasers increases the fluoride uptake.

Seasonal variation of organic matter characteristics and fluoride concentration in the Maji ya Chai River (Tanzania): Impact on treatability by nanofiltration/reverse osmosis.

PubMed

Jeihanipour, Azam; Shen, Junjie; Abbt-Braun, Gudrun; Huber, Stefan A; Mkongo, Godfrey; Schäfer, Andrea I

2018-10-01

The Maji ya Chai River in Northern Tanzania, a fluoride-rich tropical area, shows a seasonal variation of natural organic matter (NOM) and fluoride concentration. Water samples collected monthly during one year from two locations of the River were characterized. High levels of precipitation in the rainy seasons increased the total organic carbon (TOC) concentration to as high as 36 mgC L -1 and diluted the fluoride concentration from a dry season high of 24 mg L -1 to <4 mg L -1 . A black water swamp in the Maji ya Chai River catchment was confirmed as the main source of NOM, fluoride, salinity, and inorganic carbon entering the River in the rainy season. The water samples were filtered by a number of nanofiltration/reverse osmosis (NF/RO) membranes to identify the retention mechanisms and the impact of varying water quality on treatability. While the denser membranes removed fluoride due to size exclusion, for the membranes with bigger pore radius charge repulsion was the dominant mechanism of fluoride retention. Regardless of the seasonal conditions a TOC concentration <2 mgC L -1 was achieved by all membranes at 50% recovery, as NF/RO membranes remove TOC mainly by size exclusion. Two swamp water samples, containing high TOC (79 and 183 mgC L -1 ), were filtered to determine the characteristics of NOM which permeate the NF/RO membranes. Liquid chromatography organic carbon detection (LC-OCD) was used to characterize the fractions in the permeates, consisting of about 1% of the original NOM. The average molecular weight of the permeate humic substances (HS) was more than four times larger than the membrane molecular weight cut-off. This suggests that large HS can permeate the NF/RO membranes through diffusion. Moreover, the relatively high aromaticity of the permeate HS (1.7-5.2 L mg -1  m -1 ) indicated the high content of hydrophobic-aromatic fractions. Copyright © 2018 Elsevier B.V. All rights reserved.

Operational and biological analyses of branched water-adjustment and combined treatment of wastewater from a chemical industrial park.

PubMed

Xu, Ming; Cao, Jiashun; Li, Chao; Tu, Yong; Wu, Haisuo; Liu, Weijing

2018-01-01

The combined biological processes of branched water-adjustment, chemical precipitation, hydrolysis acidification, secondary sedimentation, Anoxic/Oxic and activated carbon treatment were used for chemical industrial wastewater treatment in the Taihu Lake Basin. Full-scale treatment resulted in effluent chemical oxygen demand, total nitrogen, NH 3 -N and total phosphorus of 35.1, 5.20, 3.10 and 0.15 mg/L, respectively, with a total removal efficiency of 91.1%, 67.1%, 70.5% and 89.3%, respectively. In this process, short-circuited organic carbon from brewery wastewater was beneficial for denitrification and second-sulfate reduction. The concentration of effluent fluoride was 6.22 mg/L, which also met the primary standard. Gas Chromatography-Mass Spectrometry analysis revealed that many types of refractory compounds were present in the inflow. Microbial community analysis performed in the summer by PCR-denaturing gradient gel electrophoresis and MiSeq demonstrated that certain special functional bacteria, such as denitrificans, phosphorus-accumulating bacteria, sulfate- and perhafnate-reducing bacteria, aromatic compound-degrading bacteria and organic fluoride-degrading bacteria, present in the bio-tanks were responsible for the acceptable specific biological pollutant reduction achieved.

Improved Energetic-Behaviors of Spontaneously Surface-Mediated Al Particles.

PubMed

Kim, Dong Won; Kim, Kyung Tae; Min, Tae Sik; Kim, Kyung Ju; Kim, Soo Hyung

2017-07-05

Surface-mediated Al particles are synthesized by incorporating the stable fluoride reaction of Al-F on a pure Al surface in place of natural oxides. Al particles with fluoro-polymer directly adsorbed on the surface show a considerable capability to overcome limitations caused by the surface oxide. Here, we report that Al fluoride when spontaneously formed at the poly(vinylidene fluoride)/Al interface serves as an oxidation-protecting layer while also providing an efficient combustion path along which the internal Al rapidly reacts with external oxygen atoms. Both thermal oxidation and explosion tests of the poly(vinylidene fluoride)/Al particles show superior exothermic enthalpy energy and simultaneously rapid oxidation reactivity compared to those of Al 2 O 3 passivated Al particles. It is clearly elucidated that the enhanced energetic properties of Al particles mediated by poly(vinylidene fluoride) originate from the extraordinary pyrolytic process of Al fluoride occurring at a low temperature compared to Al 2 O 3 passivated Al. Hence, these results clarify that the surface mediation of Al particles can be significantly considered as advanced technology for many energetic applications.

Dentifrices, mouthwashes, and remineralization/caries arrestment strategies

PubMed Central

Zero, Domenick T

2006-01-01

While our knowledge of the dental caries process and its prevention has greatly advanced over the past fifty years, it is fair to state that the management of this disease at the level of the individual patient remains largely empirical. Recommendations for fluoride use by patients at different levels of caries risk are mainly based on the adage that more is better. There is a general understanding that the fluoride compound, concentration, frequency of use, duration of exposure, and method of delivery can influence fluoride efficacy. Two important factors are (1) the initial interaction of relatively high concentrations of fluoride with the tooth surface and plaque during application and (2) the retention of fluoride in oral fluids after application. Fluoride dentifrices remain the most widely used method of delivering topical fluoride. The efficacy of this approach in preventing dental caries is beyond dispute. However, the vast majority of currently marketed dentifrice products have not been clinically tested and have met only the minimal requirements of the FDA monograph using mainly laboratory testing and animal caries testing. Daily use of fluoride dental rinses as an adjunct to fluoride dentifrice has been shown to be clinically effective as has biweekly use of higher concentration fluoride rinses. The use of remineralizing agents (other than fluoride), directed at reversing or arresting non-cavitated lesions, remains a promising yet largely unproven strategy. High fluoride concentration compounds, e.g., AgF, Ag(NH3)2F, to arrest more advanced carious lesions with and without prior removal of carious tissue are being used in several countries as part of the Atraumatic Restorative Treatment (ART) approach. Most of the recent innovations in oral care products have been directed toward making cosmetic marketing claims. There continues to be a need for innovation and collaboration with other scientific disciplines to fully understand and prevent dental caries. PMID:16934126

The influence of salivary variables on fluoride retention in dental plaque exposed to a mineral-enriching solution.

PubMed

Kato, K; Nakagaki, H; Arai, K; Pearce, E I F

2002-01-01

This study was carried out to examine interindividual differences in salivary variables related to plaque accumulation and to estimate their influence on the fluoride retention in plaque in vivo by a mineral-enriching solution. Two saliva samples were taken from 10 subjects, once after brushing and once after 24 h without brushing. Calcium, phosphate and monofluorophosphatase (MFPase) activity in the saliva samples were determined. The salivary flow rate and the debris index were also recorded. After plaque had formed over 3 days within in situ plaque-generating devices, subjects were instructed to rinse with a mineral-enriching mouthrinse three times a day on 4 consecutive days. Plaque exposed to distilled water plus flavoring agents served as a control. Fluoride-free dentifrice was used during the experimental period. Twenty-four hours after the last rinsing, the samples were removed from the mouth, and fluoride and mineral distributions in plaque analyzed using a method previously reported by the authors. Salivary flow, MFPase activity and calcium concentration in saliva were significantly higher after 24 h of plaque accumulation. Rinsing with the mineral-enriching solution produced retention of fluoride and phosphate in the outer and middle layers of plaque. Salivary calcium concentration had a direct effect on fluoride uptake in plaque, but no obvious relationship was found between other salivary variables and the plaque fluoride retention. The salivary calcium effect may be due to enhanced bacterial cell wall binding of fluoride via calcium bridging. Copyright 2002 S. Karger AG, Basel

Comparison of linear and non-linear models for the adsorption of fluoride onto geo-material: limonite.

PubMed

Sahin, Rubina; Tapadia, Kavita

2015-01-01

The three widely used isotherms Langmuir, Freundlich and Temkin were examined in an experiment using fluoride (F⁻) ion adsorption on a geo-material (limonite) at four different temperatures by linear and non-linear models. Comparison of linear and non-linear regression models were given in selecting the optimum isotherm for the experimental results. The coefficient of determination, r², was used to select the best theoretical isotherm. The four Langmuir linear equations (1, 2, 3, and 4) are discussed. Langmuir isotherm parameters obtained from the four Langmuir linear equations using the linear model differed but they were the same when using the nonlinear model. Langmuir-2 isotherm is one of the linear forms, and it had the highest coefficient of determination (r² = 0.99) compared to the other Langmuir linear equations (1, 3 and 4) in linear form, whereas, for non-linear, Langmuir-4 fitted best among all the isotherms because it had the highest coefficient of determination (r² = 0.99). The results showed that the non-linear model may be a better way to obtain the parameters. In the present work, the thermodynamic parameters show that the absorption of fluoride onto limonite is both spontaneous (ΔG < 0) and endothermic (ΔH > 0). Scanning electron microscope and X-ray diffraction images also confirm the adsorption of F⁻ ion onto limonite. The isotherm and kinetic study reveals that limonite can be used as an adsorbent for fluoride removal. In future we can develop new technology for fluoride removal in large scale by using limonite which is cost-effective, eco-friendly and is easily available in the study area.

Geochemistry of fluoride in the Black Creek aquifer system of Horry and Georgetown Counties, South Carolina--and its physiological implications

USGS Publications Warehouse

Zack, Allen L.

1980-01-01

High concentrations of fluoride in ground-water supplies in certain areas of Horry and Georgetown Counties, S.C., have been the cause of dental fluorosis (tooth mottling) among persons who have lived in these areas and have ingested the water as children. Geochemical evidence and laboratory experiments demonstrate that fluorapatite in the form of fossil shark teeth is the source of fluoride, and that the fluoride ions are liberated to the ground-water system through anion exchange, rather than by dissolution. Calcite-cemented quartz sand in the upper third of the Black Creek Formation of Late Cretaceous age contains the fossil shark teeth. As ground water progresses downdip, the calcite matrix dissolves and hydrolyzes, releasing bicarbonate, hydroxyl, and calcium ions. The calcium ions are immediately exchanged for sodium ions adsorbed on sodium-rich clays, and the bicarbonate ions accumulate. As the shark teeth are exposed, the hydroxyl ions in solution exchange with fluoride ions on fluorapatite surfaces. Experiments using fossil shark teeth show that sodium chloride in solution inhibits the rate of exchange of fluoride ions from tooth surfaces for hydroxyl ions in solution. The amount of fluoride removed from water and exchanged for hydroxyl ions in the presence of pure hydroxylapatite (hog teeth) was greater in saline water than in freshwater.

Field Applicable Method to Reduce Dental Emergencies.

DTIC Science & Technology

1982-04-15

removed from a lower right 2nd molar and an orthodontic band was cemented and the tooth restored with the 70 percEnt SnF 2-polycarboxylate cement. 51 dAK...Martens & Mpqkin (1972) using only the buccal surfaces of 20 teeth (from 2nd premolars to 2nd pre - molars of both maxillary and mandibular arches). The...34 effect (Table 1, Fig. 3). Salivary and Urinary Fluoride Levels The pre -experimental baseline for salivary and urinary fluoride were 0.039 + 0.015 and

The status of community water fluoridation in the United States.

PubMed Central

Easley, M W

1990-01-01

Community water fluoridation has served the American public extremely well as the cornerstone of dental caries prevention activities for 45 years. The dental and general health benefits associated with the ingestion of water-borne fluorides have been well known by researchers for an even longer period. Continued research has repeatedly confirmed the safety, effectiveness, and efficiency of community water fluoridation in preventing dental caries for Americans regardless of age, race, ethnicity, religion, educational status, or socioeconomic level. Despite the obvious benefits associated with this proven public health measure, slow progress has been made toward achieving the 1990 national fluoridation objectives as listed in "Promoting Health/Preventing Disease: Objectives for the Nation." This paper documents the lagging pace of community fluoridation by reviewing and analyzing data reported in "Fluoridation Census, 1985," a document published in late 1988 by the Public Health Service's Centers for Disease Control. Failure to attain the 1990 objectives is attributable to a combination of circumstances, including their low priority within many local, State, and Federal health agencies, inadequate funding at all levels of government, lack of a coordinated and focused national fluoridation effort, failure of most States to require fluoridation, lack of Federal legislation mandating fluoridation, general apathy of most health professional organizations toward fluoridation, misconceptions by the public about effectiveness and safety and, finally, unrelenting opposition by a highly vocal minority of the lay public.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2116635

ARSENIC (III) AND ARSENIC (V) REMOVAL FROM DRINKING WATER IN SAN YSIDRO, NEW MEXICO

EPA Science Inventory

The removal of a natural mixture of As(III) (31 ug/L) and As(V) (57 ug/L) from a groundwater high in total dissolved solids (TDS), and also containing fluoride (2.0 mg/L), was studied in San Ysidro, NM using the University of Houston (UH)/U.S. Environmental Protection Agency (EPA...

Synthesis and evaluation of rare-earth doped glasses and crystals for optical refrigeration

NASA Astrophysics Data System (ADS)

Patterson, Wendy

This research focused on developing and characterizing rare-earth doped, solid-state materials for laser cooling. In particular, the work targeted the optimization of the lasercooling efficiency in Yb3+ and Tm3+ doped fluorides. The first instance of laser-induced cooling in a Tm3+-doped crystal, BaY2F8 was reported. Cooling by 3 degrees Kelvin below ambient temperature was obtained in a single-pass pump geometry at lambda = 1855 nm. Protocols were developed for materials synthesis and purification which can be applied to each component of ZBLANI:Yb 3+/Tm3+ (ZrF4 -- BaF2 -- LaF3 -- AlF3 -- NaF -- InF3: YbF3/TmF3) glass to enable a material with significantly reduced transition-metal impurities. A method for OH- impurity removal and ultra-drying of the metal fluorides was also improved upon. Several characterization tools were used to quantitatively and qualitatively verify purity, including inductively-coupled plasma mass spectrometry (ICP-MS). Here we found a more than 600-fold reduction in transition-metal impurities in a ZrCl2O solution. A non-contact spectroscopic technique for the measurement of laser-induced temperature changes in solids was developed. Two-band differential luminescence thermometry (TBDLT) achieved a sensitivity of ˜7 mK and enabled precise measurement of the zero-crossing temperature and net quantum efficiency. Several Yb3+-doped ZBLANI glasses fabricated from precursors of varying purity and by different processes were analyzed in detail by TBDLT. Laser-induced cooling was observed at room temperature for several of the materials. A net quantum efficiency of 97.39+/-0.01% at 238 K was found for the best ZBLANI:1%Yb 3+ laser-cooling sample produced from purified metal-fluoride precursors, and proved competitive with the best commercially procured material. The TBDLT technique enabled rapid and sensitive benchmarking of laser-cooling materials and provided critical feedback to the development and optimization of high-performance optical cryocooler materials. Also presented is an efficient and numerically stable method to calculate time-dependent, laser-induced temperature distributions in solids, including a detailed description of the computational procedure and its implementation. The model accurately predicted the zero-crossing temperature, the net quantum efficiency, and the functional shape of the transients, based on input parameters such as luminescence spectra, dopant concentration, pump properties, and several well-characterized material properties.

Synthesis, characterization, and evaluation of simple aluminum-based adsorbents for fluoride removal from drinking water.

PubMed

Du, Junyi; Sabatini, David A; Butler, Elizabeth C

2014-04-01

Simple aluminum (hydr)oxides and layered double hydroxides were synthesized using common chemicals and equipment by varying synthesis temperature, concentrations of extra sulfate and citrate, and metal oxide amendments. Aluminum (hydr)oxide samples were aged at either 25 or 200°C during synthesis and, in some cases, calcined at 600 °C. Despite yielding increased crystallinity and mineral phase changes, higher temperatures had a generally negative effect on fluoride adsorption. Addition of extra sulfate during synthesis of aluminum (hydr)oxides led to significantly higher fluoride adsorption capacity compared to aluminum (hydr)oxides prepared with extra citrate or no extra ligands. X-ray diffraction results suggest that extra sulfate led to the formation of both pseudoboehmite (γ-AlOOH) and basaluminite (Al4SO4(OH)10⋅4H2O) at 200 °C; energy dispersive X-ray spectroscopy confirmed the presence of sulfur in this solid. Treatment of aluminum (hydr)oxides with magnesium, manganese, and iron oxides did not significantly impact fluoride adsorption. While layered double hydroxides exhibited high maximum fluoride adsorption capacities, their adsorption capacities at dissolved fluoride concentrations close to the World Health Organization drinking water guideline of 1.5 mg L(-1) were much lower than those for the aluminum (hydr)oxides. Copyright © 2013 Elsevier Ltd. All rights reserved.

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

On the Use of Thermal NF3 as the Fluorination and Oxidation Agent in Treatment of Used Nuclear Fuels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scheele, Randall D.; McNamara, Bruce K.; Casella, Andrew M.

2012-05-01

This paper presents results of our investigation on the use of nitrogen trifluoride as the fluorination or fluorination/oxidation agent for use in a process for separating valuable constituents from used nuclear fuels by employing the volatility of many transition metal and actinide fluorides. Nitrogen trifluoride is less chemically and reactively hazardous than the hazardous and aggressive fluorinating agents used to prepare uranium hexafluoride and considered for fluoride volatility based nuclear fuels reprocessing. In addition, nitrogen trifluoride’s less aggressive character may be used to separate the volatile fluorides from used fuel and from themselves based on the fluorination reaction’s temperature sensitivitymore » (thermal tunability) rather than relying on differences in sublimation/boiling temperature and sorbents. Our thermodynamic calculations found that nitrogen trifluoride has the potential to produce volatile fission product and actinide fluorides from candidate oxides and metals. Our simultaneous thermogravimetric and differential thermal analyses found that the oxides of lanthanum, cerium, rhodium, and plutonium fluorinated but did not form volatile fluorides and that depending on temperature volatile fluorides formed from the oxides of niobium, molybdenum, ruthenium, tellurium, uranium, and neptunium. We also demonstrated near-quantitative removal of uranium from plutonium in a mixed oxide.« less

A randomised clinical study to evaluate experimental children's toothpastes in an in-situ palatal caries model in children aged 11-14 years.

PubMed

Newby, Evelyn E; Martinez-Mier, Esperanza A; Hara, Anderson; Lippert, Frank; Kelly, Sue A; Fleming, Nancy; Butler, Andrew; Bosma, Mary Lynn; Zero, Domenick T

2013-12-01

To compare three children's sodium fluoride toothpastes to placebo with respect to enamel remineralisation potential, enamel fluoride uptake and net acid resistance using an in situ palatal caries model in children aged 11-14 years following a single brushing. This was a randomised, single blind (laboratory analyst), single-centre, four-treatment, crossover study with a 7-day washout period between treatments. The treatments were 1,426 ppm fluoride, 1,000 ppm fluoride, 500 ppm fluoride and 0 ppm fluoride (placebo) toothpaste (NaF/silica). A custom made in situ palatal appliance was used by each subject in all treatment periods. At each of the four treatment visits subjects wore the appliance containing four partially demineralised human enamel specimens for 5 minutes and then brushed their teeth using a standardised procedure for 60 seconds under supervision using 1.0 g (±0.1 g) of their assigned toothpaste. After 4 hours the appliance was removed and enamel specimen recovered. This process was repeated until all subjects completed all four study treatment visits. Recovered enamel specimens were analysed for per cent surface microhardness recovery (%SMHR; Knoop) and enamel fluoride uptake (EFU; microdrill biopsy). Subsequently, specimens were demineralised in vitro to determine their % net acid resistance (%NAR; Knoop). All three fluoride toothpastes demonstrated significantly greater %SMHR, EFU and %NAR compared with 0 ppm F toothpaste. The model demonstrated a dose response over the range 0 to 1,426 ppm fluoride for %SMHR, EFU and %NAR. There was no significant difference between 500 ppm F and 1,000 ppm F for %SMHR and between 1,000 ppm F and 1,426 ppm F for %SMHR, EFU and %NAR. The present in situ study demonstrated that the children's fluoride toothpastes tested are capable of delivering cariostatic amounts of fluoride to early caries lesions following a single brushing. © 2013 FDI World Dental Federation.

Fluorine uptake into the human enamel surface from fluoride-containing sealing materials during cariogenic pH cycling

NASA Astrophysics Data System (ADS)

Yasuhiro, Matsuda; Katsushi, Okuyama; Hiroko, Yamamoto; Hisanori, Komatsu; Masashi, Koka; Takahiro, Sato; Naoki, Hashimoto; Saiko, Oki; Chiharu, Kawamoto; Hidehiko, Sano

2015-04-01

To prevent the formation of caries and reduce dentin hypersensitivity, sealing materials, either with or without fluoride, are generally applied on the tooth in clinical practice. Application of fluoride-free sealing materials results in the formation of an acid-resistant layer on the tooth surface. On the other hand, fluoride-containing sealing materials might not only form an acid-resistant layer but could possibly further provide fluoride to enhance remineralization and reduce demineralization. In this study, the demineralization prevention ability and fluorine uptake rate in human enamel of fluoride-containing sealing materials ["MS coats F" (MSF)] and fluoride-free sealing materials ("hybrid coats 2" [HI]) were evaluated using an automatic pH cycling system. Each material was applied to the original tooth surface, the cut surfaces were covered with sticky wax, and the automatic pH-cycling system simulated daily acid changes (pH 6.8-4.5) occurring in the oral cavity for 4 weeks. Caries progression was analyzed using transverse microradiography (TMR) taken pre and post the 4 weeks of pH cycling. The fluorine and calcium distributions in the carious lesion in each specimen were evaluated using the proton-induced gamma emission (PIGE) and proton-induced X-ray (PIXE) techniques, respectively. TMR analysis showed that both MSF and HI had a caries-preventing effect after 4 weeks of pH cycling. PIGE/PIXE analysis demonstrated that only MSF resulted in fluoride uptake in the enamel surface. Therefore, MSF can help to form an acid-resistant layer and provide fluoride to the enamel surface. The presence of fluoride on the enamel surface suggested that MSF could prevent demineralization, even if the acid-resistant layer was removed, in clinical settings. The data obtained using the PIGE and PIXE techniques are useful for understanding the benefits of the use of a fluoride-containing sealing material for preventing caries.

Transparent Glass-Ceramics Produced by Sol-Gel: A Suitable Alternative for Photonic Materials.

PubMed

Gorni, Giulio; Velázquez, Jose J; Mosa, Jadra; Balda, Rolindes; Fernández, Joaquin; Durán, Alicia; Castro, Yolanda

2018-01-30

Transparent glass-ceramics have shown interesting optical properties for several photonic applications. In particular, compositions based on oxide glass matrices with fluoride crystals embedded inside, known as oxyfluoride glass-ceramics, have gained increasing interest in the last few decades. Melt-quenching is still the most used method to prepare these materials but sol-gel has been indicated as a suitable alternative. Many papers have been published since the end of the 1990s, when these materials were prepared by sol-gel for the first time, thus a review of the achievements obtained so far is necessary. In the first part of this paper, a review of transparent sol-gel glass-ceramics is made focusing mainly on oxyfluoride compositions. Many interesting optical results have been obtained but very little innovation of synthesis and processing is found with respect to pioneering papers published 20 years ago. In the second part we describe the improvements in synthesis and processing obtained by the authors during the last five years. The main achievements are the preparation of oxyfluoride glass-ceramics with a much higher fluoride crystal fraction, at least double that reported up to now, and the first synthesis of NaGdF₄ glass-ceramics. Moreover, a new SiO₂ precursor was introduced in the synthesis, allowing for a reduction in the treatment temperature and favoring hydroxyl group removal. Interesting optical properties demonstrated the incorporation of dopant ions in the fluoride crystals, thus obtaining crystal-like spectra along with higher efficiencies with respect to xerogels, and hence demonstrating that these materials are a suitable alternative for photonic applications.

Health promotion and dental caries.

PubMed

Maltz, Marisa; Jardim, Juliana Jobim; Alves, Luana Severo

2010-01-01

The central idea of the Brazilian health system is to prevent the establishment of disease or detect it as early as possible. Prevention and treatment of dental caries are related to behavioral factors, including dietary and oral hygiene habits, which are related to many chronic diseases. Dental health promotion therefore should be fully integrated into broadly based health-promoting strategies and actions such as food and health policies, and general hygiene (including oral hygiene), among others. For decades, a linear relationship between sugar consumption and caries has been observed. Recent data has indicated that this relationship is not as strong as it used to be before the widespread use of fluoride. However, diet is still a key factor acting in the carious process. Oral hygiene is a major aspect when it comes to caries, since dental biofilm is its etiological factor. Oral hygiene procedures are effective in controlling dental caries, especially if plaque removal is performed adequately and associated with fluoride. An alternative to a more efficient biofilm control in occlusal areas is the use of dental sealants, which are only indicated for caries-active individuals. If a cavity is formed as a consequence of the metabolic activity of the biofilm, a restorative material or a sealant can be placed to block access of the biofilm to the oral environment in order to prevent caries progress. The prevention of dental caries based on common risk-factor strategies (diet and hygiene) should be supplemented by more disease-specific policies such as rational use of fluoride, and evidence-based dental health care.

Method for decontamination of nickel-fluoride-coated nickel containing actinide-metal fluorides

DOEpatents

Windt, Norman F.; Williams, Joe L.

1983-01-01

The invention is a process for decontaminating particulate nickel contaminated with actinide-metal fluorides. In one aspect, the invention comprises contacting nickel-fluoride-coated nickel with gaseous ammonia at a temperature effecting nickel-catalyzed dissociation thereof and effecting hydrogen-reduction of the nickel fluoride. The resulting nickel is heated to form a melt and a slag and to effect transfer of actinide metals from the melt into the slag. The melt and slag are then separated. In another aspect, nickel containing nickel oxide and actinide metals is contacted with ammonia at a temperature effecting nickel-catalyzed dissociation to effect conversion of the nickel oxide to the metal. The resulting nickel is then melted and separated as described. In another aspect nickel-fluoride-coated nickel containing actinide-metal fluorides is contacted with both steam and ammonia. The resulting nickel then is melted and separated as described. The invention is characterized by higher nickel recovery, efficient use of ammonia, a substantial decrease in slag formation and fuming, and a valuable increase in the service life of the furnace liners used for melting.

Advantages of liquid fluoride thorium reactor in comparison with light water reactor

NASA Astrophysics Data System (ADS)

Bahri, Che Nor Aniza Che Zainul; Majid, Amran Ab.; Al-Areqi, Wadeeah M.

2015-04-01

Liquid Fluoride Thorium Reactor (LFTR) is an innovative design for the thermal breeder reactor that has important potential benefits over the traditional reactor design. LFTR is fluoride based liquid fuel, that use the thorium dissolved in salt mixture of lithium fluoride and beryllium fluoride. Therefore, LFTR technology is fundamentally different from the solid fuel technology currently in use. Although the traditional nuclear reactor technology has been proven, it has perceptual problems with safety and nuclear waste products. The aim of this paper is to discuss the potential advantages of LFTR in three aspects such as safety, fuel efficiency and nuclear waste as an alternative energy generator in the future. Comparisons between LFTR and Light Water Reactor (LWR), on general principles of fuel cycle, resource availability, radiotoxicity and nuclear weapon proliferation shall be elaborated.

Advantages of liquid fluoride thorium reactor in comparison with light water reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bahri, Che Nor Aniza Che Zainul, E-mail: anizazainul@gmail.com; Majid, Amran Ab.; Al-Areqi, Wadeeah M.

2015-04-29

Liquid Fluoride Thorium Reactor (LFTR) is an innovative design for the thermal breeder reactor that has important potential benefits over the traditional reactor design. LFTR is fluoride based liquid fuel, that use the thorium dissolved in salt mixture of lithium fluoride and beryllium fluoride. Therefore, LFTR technology is fundamentally different from the solid fuel technology currently in use. Although the traditional nuclear reactor technology has been proven, it has perceptual problems with safety and nuclear waste products. The aim of this paper is to discuss the potential advantages of LFTR in three aspects such as safety, fuel efficiency and nuclearmore » waste as an alternative energy generator in the future. Comparisons between LFTR and Light Water Reactor (LWR), on general principles of fuel cycle, resource availability, radiotoxicity and nuclear weapon proliferation shall be elaborated.« less

Cr(VI) removal on visible light active TiO2 nanotube arrays

NASA Astrophysics Data System (ADS)

Bashirom, Nurulhuda; Zulkifli, Muhammad Afiq; Subagja, Subagja; Kian, Tan Wai; Matsuda, Atsunori; Lockman, Zainovia

2018-05-01

Self-organized TiO2 nanotube (TNT) arrays were fabricated by anodic oxidation of titanium foil in three different fluoride electrolytes: ethylene glycol (EG), glycerol, and sodium sulfate (Na2SO4) at different voltage and anodization time. In these electrolytes, the TNTs were produced in ˜ 2 µm long, but at the different diameter. The size of inner diameter can be arranged from the largest to the smallest value in the order of glycerol > EG > Na2SO4. Crystallization of the TNTs by annealing was led to the formation of anatase-TiO2. The sample can be activated under natural sunlight for reduction of hexavalent chromium, Cr(VI) into trivalent chromium, Cr(III). The reduction was thought to occur via synergistic reactions between adsorption and photoreduction. The result demonstrates 100 % of Cr(VI) removal efficiency over the TNTs grown in EG after 120 min. Whereas, only 48 % and 45 % of Cr(VI) can be removed over the TNTs fabricated in glycerol and Na2SO4, respectively. High photocatalytic activity of the TNTs-EG can be attributed to high crystallinity of anatase phase, enhanced Cr(VI) adsorption, and less electron-hole recombination due to smoother tube walls.

A specific chemodosimeter for fluoride ion based on a pyrene derivative with trimethylsilylethynyl groups.

PubMed

Lu, Hua; Wang, Qiuhong; Li, Zhifang; Lai, Guoqiao; Jiang, Jianxiong; Shen, Zhen

2011-06-21

Pyrene derivative 1 containing four trimethylsilylethynyl substituents was synthesized and investigated as a chromogenic and fluorescent chemodosimeter sensor for fluoride ions. 1 showed a high sensitivity and specific selectivity over a rapid response time toward fluoride anions compared to other anions, such as Cl(-), Br(-), ClO(4)(-), H(2)PO(4)(-) and HPO(4)(2-). TD-DFT calculations showed that the delocalization of the σ-electrons of the silicon destabilized the HOMO energy level of 1, thus red shifting both its absorption and emission spectrum. The addition of F(-) removed the trimethylsilyl substituents and resulted in a blue shift of both the absorption and fluorescent spectra of 1, which could be monitored by the color change with the naked-eye. Moreover, an easy to prepare test paper, which was obtained by immersing a filter paper into a THF solution of 1, could be utilized to detect and estimate the concentration of fluoride anions in water.

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)

Method for decontamination of nickel-fluoride-coated nickel containing actinide-metal fluorides

DOEpatents

Windt, N.F.; Williams, J.L.

In one aspect, the invention comprises contacting nickel-fluoride-coated nickel with gaseous ammonia at a temperature effecting nickel-catalyzed dissociation thereof and effecting hydrogen-reduction of the nickel fluoride. The resulting nickel is heated to form a melt and a slag and to effect transfer of actinide metals from the melt into the slag. The melt and slag are then separated. In another aspect, nickel contianing nickel oxide and actinide metals is contacted with ammonia at a temperature effecting nickel-catalyzed dissociation to effect conversion of the nickel oxide to the metal. The resulting nickel is then melted and separated as described. In another aspect nickel-fluoride-coated nickel containing actinide-metal fluorides is contacted with both steam and ammonia. The resulting nickel then is melted and separated as described. The invention is characterized by higher nickel recovery, efficient use of ammonia, a substantial decrease in slag formation and fuming, and a valuable increase in the service life of the furnace liners used for melting.

The Anticaries Efficacy of a 1.5% Arginine and Fluoride Toothpaste.

PubMed

Wolff, M S; Schenkel, A B

2018-02-01

Dental caries remains a world-wide disease despite the global distribution of fluoride. It has become apparent that the introduction of significant levels of sugar (fermentable carbohydrate) into the diet has resulted in a change in the biofilm, encouraging acid formation. Further, there has been a shift in the microbiota in the biofilm to a flora that produces acid, and thrives and reproduces in an acidic environment. The management of caries activity under these conditions has focused on brushing to remove the biofilm with fluoride pastes, and high-dose fluoride treatments. Kleinberg, in the 1970s, identified an arginine-containing compound in saliva that several oral biofilm bacterial species metabolize to produce base. Multiple in situ and in vivo studies have been conducted, and have discussed the ability of multiple bacteria to increase the resting pH of the biofilm and even reduce the decrease in pH when the biofilm is challenged with glucose. This shift in resting pH can shift the level of caries formation by the biofilm. Here, we present 8 clinical studies, with different clinical designs, measuring different clinical outcomes, for a diverse, world-wide population. Each of these studies demonstrates reductions in caries formation beyond that seen with fluoride alone and several demonstrate the reversal of early caries lesions. Significant clinical research has been shown that 1.5% arginine combined with fluoride toothpaste has superior anti-caries efficacy to toothpaste containing fluoride alone.

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.

Fast nitrate and fluoride adsorption and magnetic separation from water on α-Fe2O3 and Fe3O4 dispersed on Douglas fir biochar.

PubMed

Bombuwala Dewage, Narada; Liyanage, Achala S; Pittman, Charles U; Mohan, Dinesh; Mlsna, Todd

2018-05-02

α-Fe 2 O 3 and Fe 3 O 4 dispersed on high surface area (663 m 2 /g) Douglas fir biochar (BC) was prepared for fast nitrate and fluoride ion removal from water using magnetic separations. This biochar, made originally at 900 °C, was impregnated with FeCl 3 and converted by pyrolysis at 600 °C to magnetic (494 m 2 /g) biochar (MBC). MBC and its precursor BC were characterized using SEM, SEM-EDX, STEM, S BET , PZC measurements, XRD analysis, and XPS. Dispersed α-Fe 2 O 3 and Fe 3 O 4 particles caused magnetization and generated most adsorption sites, causing more nitrate and fluoride uptake than BC. Both nitrate and fluoride adsorption on MBC remained high over a pH range from 2 to 10. Sorption was evaluated from 298 to 318 K using the Langmuir and Freundlich isotherm models. Langmuir adsorption capacities were 15 mg/g for nitrate and 9 mg/g for fluoride, higher capacities than those reported for other biochar and iron oxide adsorbents. Published by Elsevier Ltd.

Fluoride-induced modulation of ionic transport in asymmetric nanopores functionalized with "caged" fluorescein moieties.

PubMed

Ali, Mubarak; Ahmed, Ishtiaq; Ramirez, Patricio; Nasir, Saima; Cervera, Javier; Niemeyer, Christof M; Ensinger, Wolfgang

2016-04-28

We demonstrate experimentally and theoretically a nanofluidic fluoride sensing device based on a single conical pore functionalized with "caged" fluorescein moieties. The nanopore functionalization is based on an amine-terminated fluorescein whose phenolic hydroxyl groups are protected with tert-butyldiphenylsilyl (TBDPS) moieties. The protected fluorescein (Fcn-TBDPS-NH2) molecules are then immobilized on the nanopore surface via carbodiimide coupling chemistry. Exposure to fluoride ions removes the uncharged TBDPS moieties due to the fluoride-promoted cleavage of the silicon-oxygen bond, leading to the generation of negatively charged groups on the fluorescein moieties immobilized onto the pore surface. The asymmetrical distribution of these groups along the conical nanopore leads to the electrical rectification observed in the current-voltage (I-V) curve. On the contrary, other halides and anions are not able to induce any significant ionic rectification in the asymmetric pore. In each case, the success of the chemical functionalization and deprotection reactions is monitored through the changes observed in the I-V curves before and after the specified reaction step. The theoretical results based on the Nernst-Planck and Poisson equations further demonstrate the validity of an experimental approach to fluoride-induced modulation of nanopore current rectification behaviour.

A novel sequential process for remediating rare-earth wastewater.

PubMed

Cui, Mingcan; Jang, Min; Kang, Kyounglim; Kim, Dukmin; Snyder, Shane A; Khim, Jeehyeong

2016-02-01

A novel and economic sequential process consisting of precipitation, adsorption, and oxidation was developed to remediate actual rare-earth (RE) wastewater containing various toxic pollutants, including radioactive species. In the precipitation step, porous air stones (PAS) containing waste oyster shell (WOS), PASWOS, was prepared and used to precipitate most heavy metals with >97% removal efficiencies. The SEM-EDS analysis revealed that PAS plays a key role in preventing the surface coating of precipitants on the surface of WOS and in releasing the dissolved species of WOS successively. For the adsorption step, a polyurethane (PU) impregnated by coal mine drainage sludge (CMDS), PUCMDS, was synthesized and applied to deplete fluoride (F), arsenic (As), uranium (U), and thorium (Th) that remained after precipitation. The continuous-mode sequential process using PAS(WOS), PU(CMDS), and ozone (O3) had 99.9-100% removal efficiencies of heavy metals, 99.3-99.9% of F and As, 95.8-99.4% of U and Th, and 92.4% of COD(Cr) for 100 days. The sequential process can treat RE wastewater economically and effectively without stirred-tank reactors, pH controller, continuous injection of chemicals, and significant sludge generation, as well as the quality of the outlet met the EPA recommended limits. Copyright © 2015 Elsevier Ltd. All rights reserved.

Utility of adsorbents in the purification of drinking water: a review of characterization, efficiency and safety evaluation of various adsorbents.

PubMed

Dubey, Shashi Prabha; Gopal, Krishna; Bersillon, J L

2009-05-01

Clean drinking water is one of the implicit requisites fora healthy human population. However the growing industrialization and extensive use of chemicals for various concerns, has increased the burden of unwanted pollutants in the drinking water of developing countries like India. The entry of potentially hazardous substances into the biota has been magnifying day by day. In the absence of a possible stoppage of these, otherwise, useful chemicals, the only way to maintain safer water bodies is to develop efficient purifying technologies. One such immensely beneficial procedure that has been in use is that of purification of water using 'adsorbents'. Indigenous minerals and natural plants products have potential for removing many pollutants viz. fluoride, arsenic, nitrate, heavy metals, pesticides as well as trihalomethanes. Adsorbents which are derived from carbon, alumina, zeolite, clay minerals, iron ores, industrial by products, and natural products viz. parts of the plants, herbs and algal biomass offer promising potential of removal. In the recent years attention has been paid to develop process involving screening/pretreatment/activation/impregnation using alkalies, acids, alum, lime, manganese dioxide, ferric chloride and other chemicals which are found to enhance their adsorbing efficiency. Chemical characterization of these adsorbents recapitulates the mechanism of the process. It is imperative to observe that capacities of the adsorbents may vary depending on the characteristics, chemical modifications and concentration of the individual adsorbent. Removal kinetics is found to be based on the experimental conditions viz. pH, concentration of the adsorbate, quantity of the adsorbent and temperature. It is suggested that isotherm model is suitable tool to assess the adsorption capacities in batch and column modes. Safety evaluation and risk assessment of the process/products may be useful to provide guidelines for its sustainable disposal.

The effect of a triclosan/copolymer/fluoride 
toothpaste on plaque formation, gingivitis, and 
dentin hypersensitivity: A single-blinded 
randomized clinical study.

PubMed

Al Habashneh, Rola; Farasin, Rawan; Khader, Yousef

2017-01-01

The daily removal of supragingival dental plaque is a key factor in the prevention of gingivitis. The aim of the study was to compare the gingival health benefits of a triclosan/copolymer/fluoride toothpaste (Colgate Total, a fluoride toothpaste containing an antiseptic) to a commercially available toothpaste containing 0.243% sodium fluoride in a silica base (Colgate Herbal, a conventional fluoride toothpaste with herbal extracts). A total of 50 patients with gingivitis and at least one sensitive tooth were included. The subjects were randomly stratified into two groups: Colgate Total toothpaste, and Colgate Herbal toothpaste. After a 4-week pre-experimental phase, baseline Plaque Index (Quigley-Hein Index) (PI), Gingival Index (GI), Gingival Bleeding Index (GBI), and Visual Analog Scale (VAS) were assessed. The PI, GI, GBI, and VAS were reexamined at weeks 4, 12, and 24 after the baseline. Fifty subjects complied with the protocol and completed the study. The conventional fluoride toothpaste with herbal extracts group and the fluoride toothpaste containing an antiseptic group exhibited significant reductions in PI, GI, GBI, and VAS over time. The amount of reduction after 6 months of the treatment was higher in the Total group compared to Herbal group (1.82 vs 1.39, P = .015 for PI; 0.67 vs 0.37, P < .005 for GI; and 56.64% vs 34.26%, P < .005 for GBI). No significant difference was seen for VAS. Twice daily brushing with a toothpaste containing 0.3% triclosan and polyvinyl methyl ether and maleic acid copolymer provides a more effective level of plaque control and gingival health with no effect on decreasing dentin hypersensitivity compared to conventional fluoride toothpaste. Toothpastes containing triclosan/copolymer, in addition to fluoride, result in a higher reduction in plaque, gingival inflammation, and gingival bleeding when compared with fluoride toothpastes without triclosan/copolymer.

Effect of Pre-Irradiation Annealing and Laser Modification on the Formation of Radiation-Induced Surface Color Centers in Lithium Fluoride

NASA Astrophysics Data System (ADS)

Voitovich, A. P.; Kalinov, V. S.; Novikov, A. N.; Radkevich, A. V.; Runets, L. P.; Stupak, A. P.; Tarasenko, N. V.

2017-01-01

It is shown that surface color centers of the same type are formed in the surface layer and in regions with damaged crystal structure inside crystalline lithium fluoride after γ-irradiation. Results are presented from a study of the effect of pre-irradiation annealing on the efficiency with which surface centers are formed in lithium fluoride nanocrystals. Raising the temperature for pre-irradiation annealing from room temperature to 250°C leads to a substantial reduction in the efficiency with which these centers are created. Surface color centers are not detected after γ-irradiation for pre-irradiation annealing temperatures of 300°C and above. Adsorption of atmospheric gases on the crystal surface cannot be regarded as a necessary condition for the formation of radiation-induced surface centers.

Performance evaluation of ALCAN-AASF50-ferric coated activated alumina and granular ferric hydroxide (GFH) for arsenic removal in the presence of competitive ions in an active well :Kirtland field trial - initial studies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neidel, Linnah L.; Krumhansl, James Lee; Siegel, Malcolm Dean

This report documents a field trial program carried out at Well No.15 located at Kirtland Air Force Base, Albuquerque, New Mexico, to evaluate the performance of two relatively new arsenic removal media, ALCAN-AASF50 (ferric coated activated alumina) and granular ferric hydroxide (US Filter-GFH). The field trial program showed that both media were able to remove arsenate and meet the new total arsenic maximum contaminant level (MCL) in drinking water of 10 {micro}g/L. The arsenate removal capacity was defined at a breakthrough effluent concentration of 5 {micro}g/L arsenic (50% of the arsenic MCL of 10 {micro}g/L). At an influent pH ofmore » 8.1 {+-} 0.4, the arsenate removal capacity of AASF50 was 33.5 mg As(V)/L of dry media (29.9 {micro}g As(V)/g of media on a dry basis). At an influent pH of 7.2 {+-} 0.3, the arsenate removal capacity of GFH was 155 mg As(V)/L of wet media (286 {micro}g As(V)/g of media on a dry basis). Silicate, fluoride, and bicarbonate ions are removed by ALCAN AASF50. Chloride, nitrate, and sulfate ions were not removed by AASF50. The GFH media also removed silicate and bicarbonate ions; however, it did not remove fluoride, chloride, nitrate, and sulfate ions. Differences in the media performance partly reflect the variations in the feed-water pH between the 2 tests. Both the exhausted AASF50 and GFH media passed the Toxicity Characteristic Leaching Procedure (TCLP) test with respect to arsenic and therefore could be disposed as nonhazardous waste.« less

Effects of fluoride on growth, body composition, and serum biochemical profile in a freshwater teleost, Cyprinus carpio.

PubMed

Chen, Jianjie; Cao, Jinling; Wang, Jundong; Jia, Ruhui; Xue, Wenjuan; Li, Yundong; Luo, Yongju; Xie, Lingtian

2013-10-01

Fluoride is ubiquitously distributed in natural waters. Elevated fluoride may cause histopathological changes and induce oxidative stress in the gills of the common carp (Cyprinus carpio). The present study further evaluates the effects of fluoride on growth performance, body composition, and biochemical measurements of C. carpio. The results showed that food intake, growth, serum osmolality, body composition, and biochemical measures in the blood were affected by fluoride. Weight gain rate and specific growth rate in the exposed fish decreased compared with those of the control fish. Levels of crude protein and crude lipids were reduced in the fluoride-exposed fish. The major ion levels in the sera of fluoride-exposed fish were severely disturbed, resulting in a lower osmolality. All the biochemical parameters measured in the blood were affected by the exposure to fluoride. Total protein, albumin, globulin, and glucose in fish exposed to 63.6 mg/L, 77.7 mg/L, and 124.4 mg/L were lower than those in the control fish. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were markedly increased in exposed fish compared with control. Taken together, the data showed that exposure to fluoride caused a suite of detrimental effects in C. carpio, which might lead to a decrease in growth and food utilization efficiency. The results of the present study indicated that high levels of fluoride could pose a threat to carp in the field. © 2013 SETAC.

Effect of theobromine-containing toothpaste on dentin tubule occlusion in situ.

PubMed

Amaechi, Bennett T; Mathews, Sapna M; Mensinkai, Poornima K

2015-01-01

Dentin hypersensitivity (DH) is treated by either occlusion of dentin tubules or nerve desensitization. This in situ study compared dentin tubules occlusion by theobromine-containing dentifrices with (Theodent-classic-F®, TCF) and without (Theodent-classic®, TC) fluoride with 1,500 ppm fluoride toothpaste, Colgate®-Regular (Fluoride) and Novamin®-containing toothpaste, Sensodyne®-5000-Nupro (Novamin®). Each subject wore four intraoral appliances bearing dentin blocks while using one of four test dentifrices (n = 20/dentifrice) twice daily for 7 days. The four appliances were removed successively after 1, 2, 3, and 7 days. Treated blocks and their control (untreated) blocks were examined with scanning electron microscopy (SEM). Effects were compared statistically (ANOVA/Tukey's) based on percentage of surface area covered by deposited precipitate layer (%DPL) and percentage of fully open (%FOT), partially occluded (%POT), and completely occluded (%COT) tubules in each block calculated relative to the number of tubules in their control blocks. SEM observation indicated an increased %COT and %DPL over time. After 1 and 2 days, %COT was comparable with TC and TCF, and significantly (p < 0.05) higher compared with Novamin® and Fluoride. Following 3 and 7 days, %COT was comparable among TC, TCF, and Novamin®, but remained significantly lower in Fluoride. At any time, %DPL was significantly (p < 0.05) higher in TC, TCF, and Novamin® compared with Fluoride. Theobromine-containing toothpastes with and without fluoride have equal potential in occluding dentin tubules within a shorter time period than Novamin®-containing toothpaste; however, the three demonstrated equal potential after 1 week, but not the fluoride toothpaste. Theobromine-containing toothpaste promoted dentin tubule occlusion thus shows potential to relief DH.

Preparation of sodium fluoride-loaded gelatin microspheres, characterization and cariostatic studies.

PubMed

Wu, H; Zhang, Z X; Zhao, H P; Wu, D C; Wu, B L; Cong, R

2004-12-01

Sodium fluoride-loaded gelatin microspheres (NaF-GMS) were prepared using double-phase emulsified condensation polymerization. The average diameter of microspheres was (11.33+/-5.56) microm. The drug content and encapsulation efficiency were 8.80% and 76.73%, respectively. The fluoride releasing profiles of NaF-GMS in physiological saline and artificial saliva (pH 4.5, pH 6.8) showed that NaF-GMS had a sustained-release property and fluoride release rate was increased in pH 4.5 artificial saliva. Experiments conducted in rabbits' oral cavity using NaF-GMS and NaF solution as control revealed NaF-GMS could maintain oral fluoride retention longer than NaF solution. Cariostatic abilities of NaF-GMS including demineralization prohibition in vitro, fluoride deposition in artificial dental plaque and the ability of targeting to cariogenic bacteria were investigated in artificial dental plaque. The results indicated NaF-GMS with lower fluoride concentrations could achieve equivalent cariostatic effect to the concentrated NaF solution, at the same time, could prolong fluoride retention in dental plaque. Microscopic observation showed that NaF-GMS carrying fusion protein of glucan-binding domain could adhere more bacteria than NaF-GMS and this might indicate the possibility of targeting to cariogenic bacteria when NaF-GMS were properly modified.

Non-woven PET fabric reinforced and enhanced the performance of ultrafiltration membranes composed of PVDF blended with PVDF-g-PEGMA for industrial applications

NASA Astrophysics Data System (ADS)

Wang, Shuai; Li, Tong; Chen, Chen; Chen, Sheng; Liu, Baicang; Crittenden, John

2018-03-01

Ultrafiltration (UF) membranes composed of poly(vinylidene fluoride) (PVDF) blended with poly(vinylidene fluoride)-graft-poly(ethylene glycol) methyl ether methacrylate (PVDF-g-PEGMA) can present high flux and excellent foulant removal efficiencies under suitable preparation conditions. However, these PVDF/PVDF-g-PEGMA blended membranes cannot be applied industrially because of the insufficient mechanical strength (strength-to-break value of 8.4 ± 0.6 MPa). We incorporated two types of non-woven polyethylene terephthalate (PET) fabrics (thin hydrophobic and thick hydrophilic fabrics) as support layers to improve the mechanical properties of the blended membranes. The thin and thick PET fabrics were able to significantly improve the tensile strength to 23.3 ± 3.7 MPa and 30.1 ± 1.4 MPa, respectively. The PET fabrics had a limited impact on the separation-related membrane performance such as hydrophilicity, foulant rejection, whereas the mechanical strength and pure water flux was improved several folds. The enhanced flux was attributed to the higher surface porosity and wider finger-like voids in the cross-section. The thin PET fabric with larger porosity was able to maintain a consistent toughness simultaneously; thus it is recommended as a support material for this blended membrane.

Effect of grinding and fluoride-gel exposure on strength of ion-exchanged porcelain.

PubMed

Anusavice, K J; Hojjatie, B; Chang, T C

1994-08-01

Strengthening of dental porcelain through a diffusion heat treatment at 450 degrees C of a potassium-enriched, ion-exchange surface coating has been demonstrated in several recent studies. However, little attention has been focused on the potential strength reduction of these materials when the treated surfaces are ground or etched under clinically simulated conditions. The objective of this study was to test the hypothesis that partial removal of the surface layers of ion-exchanged porcelains by grinding or exposure to acidulated fluoride gel will significantly reduce their flexure strength. Nine groups of body porcelain disks were ion-exchanged at 450 degrees C for 30 min. One of these groups was subjected to ion exchange and no further surface treatment. Eight specimen groups were subjected to the following procedures after ion exchange: grinding to depths of 50 microns, 100 microns, 150 microns, 200 microns, and 250 microns, and exposure to acidulated fluoride for 30 min, 60 min, and 300 min. A tenth group (FC) was fired at 960 degrees C and fast-cooled in air, but the disks were not subjected to the ion-exchange treatment. Surface stress was calculated from measured values of cracks induced in the treated surfaces. Fluoride exposure for up to 60 min resulted in a significant decrease in surface compression (P < or = 0.05), although this treatment had no effect on strength. Grinding to a depth of from 100 microns to 250 microns caused a significant decrease in strength, while removal of a 50-microns layer caused no significant change (P > 0.05).

Synthesis of Bisimidazole Derivatives for Selective Sensing of Fluoride Ion.

PubMed

Zhang, Liang; Liu, Fang

2017-09-11

Rapid and efficient analysis of fluoride ion is crucial to providing key information for fluoride ion hazard assessment and pollution management. In this study, we synthesized one symmetrical structure called 1,4-bis(4,5-diphenyl-1 H -imidazol-2-yl)benzene ( 1a ) and two asymmetrical structures, namely 2-(4-(4,5-diphenyl-1 H -imidazol-2-yl)phenyl)-1 H -phenanthro(9,10- d )imidazole ( 1b ) and 2-(4-(4,5-diphenyl-1 H -imidazol-2-yl)phenyl)-1 H -imidazo(4,5- f )(1,10)phenanthroline ( 1c ), which served as an efficient anion sensor for fluoride ion over a wide range of other anions (Cl - , Br - , I - , NO₃ - , ClO₄ - , HSO₄ - , BF₄ - , and PF₆ - ) owing to imidazole group in the main backbone. The absorption intensity of compound 1a at λ max 358 nm slightly decreased; however, a new band at λ max 414 nm appeared upon the addition of fluoride ion, while no evident change occurred upon the addition of eight other anions. The photoluminescence intensity of compound 1a at λ max 426 nm was nearly quenched and fluorescence emission spectra were broadened when fluoride ion was added into dimethyl sulfoxide (DMSO) solution of compound 1a . Compared with the optical behaviors of the DMSO solution of compound 1a in the presence of Bu₄N⁺F - , compounds 1b and 1c exhibited considerable sensitivity to fluoride ion due to the increase in coplanarity. Furthermore, compared with the fluorescence emission behaviors of the DMSO solutions of compounds 1a and 1b in the presence of Bu₄N⁺F - , compound 1c exhibited the most significant sensitivity to fluoride ion due to the charge transfer enhancement. Consequently, the detection limits of compounds 1a - 1 c increased from 5.47 × 10 -6 M to 4.21 × 10 -6 M to 9.12 × 10 -7 M. Furthermore, the largest red shift (75 nm) of the DMSO solution compound 1c in the presence of fluoride ion can be observed. Our results suggest that the increase in coplanarity and the introduction of electron-withdrawing groups to the imidazole backbone can improve the performance in detecting fluoride ion.

Spatial distribution mapping of drinking water fluoride levels in Karnataka, India: fluoride-related health effects.

PubMed

Chowdhury, Chitta R; Shahnawaz, Khijmatgar; Kumari, Divya; Chowdhury, Avidyuti; Bedi, Raman; Lynch, Edward; Harding, Stewart; Grootveld, Martin

2016-11-01

(1) To estimate the concentrations of fluoride in drinking water throughout different zones and districts of the state of Karnataka. (2) To investigate the variation of fluoride concentration in drinking water from different sources, and its relationships to daily temperature and rainfall status in the regional districts. (3) To develop an updated fluoride concentration intensity map of the state of Karnataka, and to evaluate these data in the context of fluoride-related health effects such as fluorosis and their prevalence. Aqueous standard solutions of 10, 100 and 1,000 ppm fluoride (F - ) were prepared with analytical grade Na + /F - and a buffer; TISAB II was incorporated in both calibration standard and analysis solutions in order to remove the potentially interfering effects of trace metal ions. This analysis was performed using an ion-selective electrode (ISE), and mean determination readings for n = 5 samples collected at each Karnataka water source were recorded. The F - concentration in drinking water in Karnataka state was found to vary substantially, with the highest mean values recorded being in the north-eastern zone (1.61 ppm), and the lowest in the south-western one (only 0.41 ppm). Analysis of variance (ANOVA) demonstrated that there were very highly significant 'between-zone' and 'between-districts-within-zones' sources of variation (p < 10 -5 -10 -9 ), results consistent with a substantial spatial variance of water source F - levels within this state. The southern part of Karnataka has low levels of F - in its drinking water, and may require fluoridation treatment in order to mitigate for dental caries and further ailments related to fluoride deficiency. However, districts within the north-eastern region have contrastingly high levels of fluoride, an observation which has been linked to dental and skeletal fluorosis. This highlights a major requirement for interventional actions in order to ensure maintenance of the recommended range of fluoride concentrations (0.8-1.5 ppm) in Karnataka's drinking water sources. © Royal Society for Public Health 2016.

Solution of heat removal from nuclear reactors by natural convection

NASA Astrophysics Data System (ADS)

Zitek, Pavel; Valenta, Vaclav

2014-03-01

This paper summarizes the basis for the solution of heat removal by natural convection from both conventional nuclear reactors and reactors with fuel flowing coolant (such as reactors with molten fluoride salts MSR).The possibility of intensification of heat removal through gas lift is focused on. It might be used in an MSR (Molten Salt Reactor) for cleaning the salt mixture of degassed fission products and therefore eliminating problems with iodine pitting. Heat removal by natural convection and its intensification increases significantly the safety of nuclear reactors. Simultaneously the heat removal also solves problems with lifetime of pumps in the primary circuit of high-temperature reactors.

Yeast Fex1p Is a Constitutively Expressed Fluoride Channel with Functional Asymmetry of Its Two Homologous Domains*

PubMed Central

Smith, Kathryn D.; Gordon, Patricia B.; Rivetta, Alberto; Allen, Kenneth E.; Berbasova, Tetyana; Slayman, Clifford; Strobel, Scott A.

2015-01-01

Fluoride is a ubiquitous environmental toxin with which all biological species must cope. A recently discovered family of fluoride export (FEX) proteins protects organisms from fluoride toxicity by removing it from the cell. We show here that FEX proteins in Saccharomyces cerevisiae function as ion channels that are selective for fluoride over chloride and that these proteins are constitutively expressed at the yeast plasma membrane. Continuous expression is in contrast to many other toxin exporters in yeast, and this, along with the fact that two nearly duplicate proteins are encoded in the yeast genome, suggests that the threat posed by fluoride ions is frequent and detrimental. Structurally, eukaryotic FEX proteins consist of two homologous four-transmembrane helix domains folded into an antiparallel dimer, where the orientation of the two domains is fixed by a single transmembrane linker helix. Using phylogenetic sequence conservation as a guide, we have identified several functionally important residues. There is substantial functional asymmetry in the effect of mutation at corresponding sites in the two domains. Specifically, mutations to residues in the C-terminal domain proved significantly more detrimental to function than did similar mutations in the N-terminal domain. Our data suggest particular residues that may be important to anion specificity, most notably the necessity of a positive charge near the end of TMH1 in the C-terminal domain. It is possible that a cationic charge at this location may create an electrostatic well for fluoride ions entering the channel from the cytoplasm. PMID:26055717

Transparent Glass-Ceramics Produced by Sol-Gel: A Suitable Alternative for Photonic Materials

PubMed Central

Gorni, Giulio; Mosa, Jadra; Balda, Rolindes; Fernández, Joaquin; Durán, Alicia; Castro, Yolanda

2018-01-01

Transparent glass-ceramics have shown interesting optical properties for several photonic applications. In particular, compositions based on oxide glass matrices with fluoride crystals embedded inside, known as oxyfluoride glass-ceramics, have gained increasing interest in the last few decades. Melt-quenching is still the most used method to prepare these materials but sol-gel has been indicated as a suitable alternative. Many papers have been published since the end of the 1990s, when these materials were prepared by sol-gel for the first time, thus a review of the achievements obtained so far is necessary. In the first part of this paper, a review of transparent sol-gel glass-ceramics is made focusing mainly on oxyfluoride compositions. Many interesting optical results have been obtained but very little innovation of synthesis and processing is found with respect to pioneering papers published 20 years ago. In the second part we describe the improvements in synthesis and processing obtained by the authors during the last five years. The main achievements are the preparation of oxyfluoride glass-ceramics with a much higher fluoride crystal fraction, at least double that reported up to now, and the first synthesis of NaGdF4 glass-ceramics. Moreover, a new SiO2 precursor was introduced in the synthesis, allowing for a reduction in the treatment temperature and favoring hydroxyl group removal. Interesting optical properties demonstrated the incorporation of dopant ions in the fluoride crystals, thus obtaining crystal-like spectra along with higher efficiencies with respect to xerogels, and hence demonstrating that these materials are a suitable alternative for photonic applications. PMID:29385706

Doxycycline-containing glass ionomer cement for arresting residual caries: an in vitro study and a pilot trial.

PubMed

Castilho, Aline Rogéria Freire de; Duque, Cristiane; Kreling, Paula Fernanda; Pereira, Jesse Augusto; Paula, Andreia Bolzan de; Sinhoreti, Mario Alexandre Coelho; Puppin-Rontani, Regina Maria

2018-01-01

In a previous study, we demonstrated that the incorporation of doxycycline hyclate (DOX) into resin-modified glass ionomer cement (RMGIC) inhibited important cariogenic microorganisms, without modifying its biological and mechanical characteristics. In this study, we keep focused on the effect of that experimental material as a potential therapy for arresting residual caries by analyzing other in vitro properties and conducting a pilot clinical trial assessing the in vivo effect of DOX-containing RMGIC on residual mutans streptococci after partial carious removal in primary molars. Specimens of the groups RMGIC (control); RMGIC + 1.5% DOX; RMGIC + 3% DOX; and RMGIC + 4.5% DOX were made to evaluate the effect of DOX incorporation on surface microhardness and fluoride release of RMGIC and against biofilm of Streptococcus mutans. Clinical intervention consisted of partial caries removal comparing RMGIC and RMGIC + 4.5% DOX as lining materials. After 3 months, clinical and microbiologic evaluations were performed. Data were submitted to ANOVA/Tukey or Wilcoxon/Mann-Whitney set as α=0.05. Fluoride release and surface microhardness was not influenced by the incorporation of DOX (p>0.05). There was a significant reduction of S. mutans biofilm over the material surface with the increase of DOX concentration. After clinical trial, the remaining dentin was hard and dry. Additionally, mutans streptococci were completely eliminated after 3 months of treatment with RMGIC + 4.5% DOX. The incorporation of DOX provided better antibiofilm effect, without jeopardizing fluoride release and surface microhardness of RMGIC. This combination also improved the in vivo shortterm microbiological effect of RMGIC after partial caries removal.

In vitro caries lesion rehardening and enamel fluoride uptake from fluoride varnishes as a function of application mode.

PubMed

Lippert, Frank; Hara, Anderson T; Martinez-Mier, Esperanza Angeles; Zero, Domenick T

2013-04-01

To study the laboratory predicted anticaries efficacy of five commercially available fluoride varnishes (FV) by determining their ability to reharden and to deliver fluoride to an early caries lesion when applied directly or in close vicinity to the lesion (halo effect). Early caries lesions were created in 80 polished bovine enamel specimens. Specimens were allocated to five FV groups (n = 16) based on Knoop surface microhardness (KHN) after lesion creation. All tested FV claimed to contain 5% sodium fluoride and were: CavityShield, Enamel Pro, MI Varnish, Prevident and Vanish. FV were applied (10 +/- 2 mg per lesion) to eight specimens per FV group (direct application); the remaining eight specimens received no FV but were later exposed to fluoride released from specimens which received a FV treatment (indirect application). Specimens were paired again and placed into containers (one per FV). Artificial saliva was added and containers placed into an incubator (27 hours at 37 degrees C). Subsequently, FV was carefully removed using chloroform. Specimens were exposed to fresh artificial saliva again (67 hours at 37 degrees C). KHN was measured and differences to baseline values calculated. Enamel fluoride uptake (EFU) was determined using the acid etch technique. Data were analyzed using two-way ANOVA. The two-way ANOVA highlighted significant interactions between FV vs. application mode, for both deltaKHN and EFU (P < 0.001). All FV were able to reharden and deliver fluoride to caries lesions, but to different degrees. Furthermore, considerable differences were found for both variables between FV when applied either directly or in close vicinity to the lesion: MI Varnish and Enamel Pro exhibited greater fluoride efficacy when applied in vicinity rather than directly to the lesion, whereas CavityShield and Vanish did not differ. Prevident exhibited a higher EFU when applied directly, but little difference in rehardening.

Fluoride and phosphate release from carbonate-rich fluorapatite during managed aquifer recharge

NASA Astrophysics Data System (ADS)

Schafer, David; Donn, Michael; Atteia, Olivier; Sun, Jing; MacRae, Colin; Raven, Mark; Pejcic, Bobby; Prommer, Henning

2018-07-01

Managed aquifer recharge (MAR) is increasingly used as a water management tool to enhance water availability and to improve water quality. Until now, however, the risk of fluoride release during MAR with low ionic strength injectate has not been recognised or examined. In this study we analyse and report the mobilisation of fluoride (up to 58 μM) and filterable reactive phosphorus (FRP) (up to 55 μM) during a field groundwater replenishment experiment in which highly treated, deionised wastewater (average TDS 33 mg/L) was injected into a siliciclastic Cretaceous aquifer. In the field experiment, maximum concentrations, which coincided with a rise in pH, exceeded background groundwater concentrations by an average factor of 3.6 for fluoride and 24 for FRP. The combined results from the field experiment, a detailed mineralogical characterisation and geochemical modelling suggested carbonate-rich fluorapatite (CFA: Ca10(PO4)5(CO3,F)F2) to be the most likely source of fluoride and phosphate release. An anoxic batch experiment with powdered CFA-rich nodules sourced from the target aquifer and aqueous solutions of successively decreasing ionic strength closely replicated the field-observed fluoride and phosphate behaviour. Based on the laboratory experiment and geochemical modelling, we hypothesise that the release of fluoride and phosphate results from the incongruent dissolution of CFA and the simultaneous formation of a depleted layer that has hydrated di-basic calcium phosphate (CaHPO4·nH2O) composition at the CFA-water interface. Disequilibrium caused by calcium removal following breakthrough of the deionised injectate triggered the release of fluoride and phosphate. Given the increasing use of highly treated, deionised water for MAR and the ubiquitous presence of CFA and fluorapatite (Ca10(PO4)6F2) in aquifer settings worldwide, the risk of fluoride and phosphate release needs to be considered in the MAR design process.

Fluoride exposure abates pro-inflammatory response and induces in vivo apoptosis rendering zebrafish (Danio rerio) susceptible to bacterial infections.

PubMed

Singh, Rashmi; Khatri, Preeti; Srivastava, Nidhi; Jain, Shruti; Brahmachari, Vani; Mukhopadhyay, Asish; Mazumder, Shibnath

2017-04-01

The present study describes the immunotoxic effect of chronic fluoride exposure on adult zebrafish (Danio rerio). Zebrafish were exposed to fluoride (71.12 mg/L; 1/10 LC 50 ) for 30 d and the expression of selected genes studied. We observed significant elevation in the detoxification pathway gene cyp1a suggesting chronic exposure to non-lethal concentration of fluoride is indeed toxic to fish. Fluoride mediated pro-oxidative stress is implicated with the downregulation in superoxide dismutase 1 and 2 (sod1/2) genes. Fluoride affected DNA repair machinery by abrogating the expression of the DNA repair gene rad51 and growth arrest and DNA damage inducible beta a gene gadd45ba. The upregulated expression of casp3a coupled with altered Bcl-2 associated X protein/B-cell lymphoma 2 ratio (baxa/bcl2a) clearly suggested chronic fluoride exposure induced the apoptotic cascade in zebrafish. Fluoride-exposed zebrafish when challenged with non-lethal dose of fish pathogen A. hydrophila revealed gross histopathology in spleen, bacterial persistence and significant mortality. We report that fluoride interferes with system-level output of pro-inflammatory cytokines tumour necrosis factor-α, interleukin-1β and interferon-γ, as a consequence, bacteria replicate efficiently causing significant fish mortality. We conclude, chronic fluoride exposure impairs the redox balance, affects DNA repair machinery with pro-apoptotic implications and suppresses pro-inflammatory cytokines expression abrogating host immunity to bacterial infections. Copyright © 2017 Elsevier Ltd. All rights reserved.

Hexamethyldisilazane Removal with Mesoporous Materials Prepared from Calcium Fluoride Sludge.

PubMed

Kao, Ching-Yang; Lin, Min-Fa; Nguyen, Nhat-Thien; Tsai, Hsiao-Hsin; Chang, Luh-Maan; Chen, Po-Han; Chang, Chang-Tang

2018-05-01

A large amount of calcium fluoride sludge is generated by the semiconductor industry every year. It also requires a high amount of fuel consumption using rotor concentrators and thermal oxidizers to treat VOCs. The mesoporous adsorbent prepared by calcium fluoride sludge was used for VOCs treatment. The semiconductor industry employs HMDS to promote the adhesion of photo-resistant material to oxide(s) due to the formation of silicon dioxide, which blocks porous adsorbents. The adsorption of HMDS (Hexamethyldisiloxane) was tested with mesoporous silica materials synthesized from calcium fluoride (CF-MCM). The resulting samples were characterized by XRD, XRF, FTIR, N2-adsorption-desorption techniques. The prepared samples possessed high specific surface area, large pore volume and large pore diameter. The crystal patterns of CF-MCM were similar with Mobil composite matter (MCM-41) from TEM image. The adsorption capacity of HMDS with CF-MCM was 40 and 80 mg g-1, respectively, under 100 and 500 ppm HMDS. The effects of operation parameters, such as contact time and mixture concentration, on the performance of CF-MCM were also discussed in this study.

High-power and highly efficient diode-cladding-pumped holmium-doped fluoride fiber laser operating at 2.94 microm.

PubMed

Jackson, Stuart D

2009-08-01

A high-power diode-cladding-pumped Ho(3+), Pr(3+)-doped fluoride glass fiber laser is demonstrated. The laser produced a maximum output power of 2.5 W at a slope efficiency of 32% using diode lasers emitting at 1,150 nm. The long-emission wavelength of 2.94 microm measured at maximum pump power, which is particularly suited to medical applications, indicates that tailoring of the proportion of Pr(3+) ions can provide specific emission wavelengths while providing sufficient de-excitation of the lower laser level.

Remediation of fluoride from drinking water using magnetic iron oxide coated hydrotalcite/chitosan composite.

PubMed

Pandi, Kalimuthu; Periyasamy, Soodamani; Viswanathan, Natrayasamy

2017-11-01

The present study was performed to examine the probability of magnetic iron oxide fabricated hydrotalcite/chitosan (Fe 3 O 4 @HTCS) composite for the removal of excess fluoride content from drinking water. The developed Fe 3 O 4 @HTCS composite not only demonstrate the good separation ability but also display an extreme enhanced defluoridation capacity (DC) when compared to other base components and composite. The DCs of Fe 3 O 4 @HTCS composite, Fe 3 O 4 @HT composite, Fe 3 O 4 , HT and CS was found to be 5032, 3041, 1050, 1030 and 52mgF - /kg respectively. The structure and morphology of the prepared adsorbent and fluoride sorbed adsorbent was analysed using FTIR, SEM and EDAX with mapping techniques. The dependence of DC on various parameters like initial fluoride concentration, pH, contact time, interfering anions and temperature was studied by batch method. From isotherm modeling, the equilibrium data is well described by Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. Thermodynamic parameters confirm the spontaneity and endothermic nature of the fluoride adsorption. The performance of Fe 3 O 4 @HTCS composite to field water sample designates its adaptable nature at field conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

Fluoride export (FEX) proteins from fungi, plants and animals are 'single barreled' channels containing one functional and one vestigial ion pore

PubMed Central

Berbasova, Tetyana; Nallur, Sunitha; Sells, Taylor; Smith, Kathryn D.; Gordon, Patricia B.; Tausta, Susan Lori

2017-01-01

The fluoride export protein (FEX) in yeast and other fungi provides tolerance to fluoride (F-), an environmentally ubiquitous anion. FEX efficiently eliminates intracellular fluoride that otherwise would accumulate at toxic concentrations. The FEX homolog in bacteria, Fluc, is a ‘double-barreled’ channel formed by dimerization of two identical or similar subunits. FEX in yeast and other eukaryotes is a monomer resulting from covalent fusion of the two subunits. As a result, both potential fluoride pores are created from different parts of the same protein. Here we identify FEX proteins from two multicellular eukaryotes, a plant Arabidopsis thaliana and an animal Amphimedon queenslandica, by demonstrating significant fluoride tolerance when these proteins are heterologously expressed in the yeast Saccharomyces cerevisiae. Residues important for eukaryotic FEX function were determined by phylogenetic sequence alignment and functional analysis using a yeast growth assay. Key residues of the fluoride channel are conserved in only one of the two potential fluoride-transporting pores. FEX activity is abolished upon mutation of residues in this conserved pore, suggesting that only one of the pores is functional. The same topology is conserved for the newly identified FEX proteins from plant and animal. These data suggest that FEX family of fluoride channels in eukaryotes are ‘single-barreled’ transporters containing one functional pore and a second non-functional vestigial remnant of a homologous gene fusion event. PMID:28472134

Synthesis and functional evaluation of a peptide derivative of 1-beta-D-arabinofuranosylcytosine.

PubMed

Balajthy, Z; Aradi, J; Kiss, I T; Elödi, P

1992-09-04

We have synthesized a peptidyl prodrug derivative of 1-beta-D-arabinofuranosylcytosine (1) designed to be a selective substrate of plasmin. D-Val-Leu-Lys-ara-C (2) was obtained by coupling the protected peptide Cbz-D-Val-Leu-(N6-Cbz)Lys-OH and ara-C (1) by a water-soluble carbodiimide (EDCI), followed by the removal of the Cbz groups by using catalytic hydrogenolysis over Pd/C. The kinetic constant of hydrolysis of 2 in the presence of plasmin demonstrated effective release of 1. The amino group of 1, which is sensitive to the removal by cytidine deaminase, is protected in 2 by the formation of the amide bond resulting in a prolonged half-life of 2 in biological milieu. The antiproliferative efficiency of 2 against L1210 leukemic cells was significantly higher than that of 1. The activity of 2 was abolished in the presence of serine proteinase inhibitor, (4-amidinopheny)methanesulfonyl fluoride. These data indicate that 2 is a prodrug form of 1 in systems generating plasmin.

The effect of normal pulsed Nd-YAG laser irradiation on pits and fissures in human teeth.

PubMed

Bahar, A; Tagomori, S

1994-01-01

The effects of normal pulsed Nd-YAG laser irradiation on the acid resistance of human dental enamel of pits and fissures, the cleaning of the pit and fissure contents and fluoride uptake into deep pits and fissures were examined. The acid resistance of the pit and fissure enamel was evaluated by the amount of dissolved calcium per square millimeter of the surface area. The pit and fissure enamel treated with laser irradiation obtained an acid resistance 30% higher than that of the unlased controls. The cleaning effect of laser irradiation on the pit and fissure contents was compared with chemicomechanical and mechanical methods. The laser irradiation was found to clean the pits and fissures to a greater depth without alterating the shape of pits and fissures, compared with the other two methods. The distribution of calcium, phosphorus and fluoride in the enamel of the pits and fissures was then measured by electron probe microanalyzer. At the entrance and in the deep part of the pits and fissures, the fluoride content of the enamel treated with acidulated phosphate fluoride after laser irradiation was higher than that of the enamel treated with acidulated phosphate fluoride alone. These results thus suggest that Nd-YAG laser irradiation might be effective in increasing the acid resistance of the pit and fissure enamel, while removing the pit and fissure debris contents and increasing the fluoride uptake into the pit and fissure enamel.

Removal of nitrate and phosphate using chitosan/Al2O3/Fe3O4 composite nanofibrous adsorbent: Comparison with chitosan/Al2O3/Fe3O4 beads.

PubMed

Bozorgpour, Farahnaz; Ramandi, Hossein Fasih; Jafari, Pooya; Samadi, Saman; Yazd, Shabnam Sharif; Aliabadi, Majid

2016-12-01

In the present study the chitosan/Al 2 O 3 /Fe 3 O 4 composite nanofibrous adsorbent was prepared by electrospinning process and its application for the removal of nitrate and phosphate were compared with chitosan/Al 2 O 3 /Fe 3 O 4 composite bead adsorbent. The influence of Al 2 O 3 /Fe 3 O 4 composite content, pH, contact time, nitrate and phosphate initial concentrations and temperature on the nitrate and phosphate sorption using synthesized bead and nanofibrous adsorbents was investigated in a single system. The reusability of chitosan/Al 2 O 3 /Fe 3 O 4 composite beads and nanofibers after five sorption-desorption cycles were carried out. The Box-Behnken design was used to investigate the interaction effects of adsorbent dosage, nitrate and phosphate initial concentrations on the nitrate and phosphate removal efficiency. The pseudo-second-order kinetic model and known Freundlich and Langmuir isotherm models were used to describe the kinetic and equilibrium data of nitrate and phosphate sorption using chitosan/Al 2 O 3 /Fe 3 O 4 composite beads and nanofibers. The influence of other anions including chloride, fluoride and sulphate on the sorption efficiency of nitrate and phosphate was examined. The obtained results revealed the higher potential of chitosan/Al 2 O 3 /Fe 3 O 4 composite nanofibers for nitrate and phosphate compared with chitosan/Al 2 O 3 /Fe 3 O 4 composite beads. Copyright © 2016 Elsevier B.V. All rights reserved.

Micronutrients in Parenteral Nutrition: Boron, Silicon, and Fluoride

USDA-ARS?s Scientific Manuscript database

Long-term parenteral nutrition (providing nutrients intravenously) is a life-saving treatment for patients with severe malabsorption of nutrients caused by intestinal failure, intestinal trauma (for example, gunshot or stab wounds), and intestinal removal. Metabolic bone disease characterized by min...

Formation of anodic TiO2 nanotube arrays in NaOH added fluoride-ethylene glycol electrolyte for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Nyein, Nyein; Tan, Wai Kian; Kawamura, Go; Matsuda, Atsunori; Lockman, Zainovia

2017-07-01

TiO2 nanotube (TNT) arrays were formed by anodizing titanium foil in fluoride-ethylene glycol (EG) electrolyte added to it either water (H2O) or sodium hydroxide (NaOH) as oxidant. In NaOH added fluoride-EG electrolyte, 10 µm long TNT arrays were formed compared to 5 μm long nanotubes in H2O added fluoride-EG electrolyte. When NaOH was added to EG, the electrolyte pH was 9. As the pH of the electrolyte was rather high, surface etching of the nanotubes was reduced resulting in tubes with longer length. Moreover, the addition of NaOH into fluoride-EG resulted in the crystallization of anatase in the as-made TNT arrays. Annealing obviously improved the crystallinity of the oxide. The TNT arrays were then used as a photoanode in a dye-sensitized solar cell (DSSC). A photoconversion efficiency of 2.4 % was recorded with photocurrent of 6.9 mA/cm2.

Vanadium Extraction from Shale via Sulfuric Acid Baking and Leaching

NASA Astrophysics Data System (ADS)

Shi, Qihua; Zhang, Yimin; Liu, Tao; Huang, Jing

2018-01-01

Fluorides are widely used to improve vanadium extraction from shale in China. Sulfuric acid baking-leaching (SABL) was investigated as a means of recovering vanadium which does not require the use of fluorides and avoids the productions of harmful fluoride-containing wastewater. Various effective factors were systematically studied and the experimental results showed that 90.1% vanadium could be leached from the shale. On the basis of phase transformations and structural changes after baking the shale, a mechanism of vanadium extraction from shale via SABL was proposed. The mechanism can be described as: (1) sulfuric acid diffusion into particles; (2) the formation of concentrated sulfuric acid media in the particles after water evaporation; (3) hydroxyl groups in the muscovite were removed and transient state [SO4 2-] was generated; and (4) the metals in the muscovite were sulfated by active [SO4 2-] and the vanadium was released. Thermodynamics modeling confirmed this mechanism.

Preparation and evaluation of GAC-based iron-containing adsorbents for arsenic removal.

PubMed

Gu, Zhimang; Fang, Jun; Deng, Baolin

2005-05-15

Granular activated carbon-based, iron-containing adsorbents (As-GAC) were developed for effective removal of arsenic from drinking water. Granular activated carbon (GAC) was used primarily as a supporting medium for ferric iron that was impregnated by ferrous chloride (FeCl2) treatment, followed by chemical oxidation. Sodium hypochlorite (NaClO) was the most effective oxidant, and carbons produced from steam activation of lignite were most suitable for iron impregnation and arsenic removal. Two As-GAC materials prepared by FeCl2 treatment (0.025 -0.40 M) of Dacro 20 x 50 and Dacro 20 x 40LI resulted in a maximum impregnated iron of 7.89% for Dacro 20 x 50 and 7.65% for Dacro 20 x 40Ll. Nitrogen adsorption-desorption analyses showed the BET specific surface area, total pore volume, porosity, and average mesoporous diameter all decreased with iron impregnation, indicating that some micropores were blocked. SEM studies with associated EDS indicated that the distribution of iron in the adsorbents was mainly on the edge of As-GAC in the low iron content (approximately 1% Fe) sample but extended to the center at the higher iron content (approximately 6% Fe). When the iron content was > approximately 7%, an iron ring formed at the edge of the GAC particles. No difference in X-ray diffraction patterns was observed between untreated GAC and the one with 4.12% iron, suggesting that the impregnated iron was predominantly in amorphous form. As-GAC could remove arsenic most efficiently when the iron content was approximately 6%; further increases of iron decreased arsenic adsorption. The removal of arsenate occurred in a wide range of pH as examined from 4.4 to 11, but efficiency was decreased when pH was higher than 9.0. The presence of phosphate and silicate could significantly decrease arsenate removal at pH > 8.5, while the effects of sulfate, chloride, and fluoride were minimal. Column studies showed that both As(V) and As(III) could be removed to below 10 microg/L within 6000 empty bed volume when the groundwater containing approximately 50 microg/L of arsenic was treated.

Dental fluorosis: chemistry and biology.

PubMed

Aoba, T; Fejerskov, O

2002-01-01

This review aims at discussing the pathogenesis of enamel fluorosis in relation to a putative linkage among ameloblastic activities, secreted enamel matrix proteins and multiple proteases, growing enamel crystals, and fluid composition, including calcium and fluoride ions. Fluoride is the most important caries-preventive agent in dentistry. In the last two decades, increasing fluoride exposure in various forms and vehicles is most likely the explanation for an increase in the prevalence of mild-to-moderate forms of dental fluorosis in many communities, not the least in those in which controlled water fluoridation has been established. The effects of fluoride on enamel formation causing dental fluorosis in man are cumulative, rather than requiring a specific threshold dose, depending on the total fluoride intake from all sources and the duration of fluoride exposure. Enamel mineralization is highly sensitive to free fluoride ions, which uniquely promote the hydrolysis of acidic precursors such as octacalcium phosphate and precipitation of fluoridated apatite crystals. Once fluoride is incorporated into enamel crystals, the ion likely affects the subsequent mineralization process by reducing the solubility of the mineral and thereby modulating the ionic composition in the fluid surrounding the mineral. In the light of evidence obtained in human and animal studies, it is now most likely that enamel hypomineralization in fluorotic teeth is due predominantly to the aberrant effects of excess fluoride on the rates at which matrix proteins break down and/or the rates at which the by-products from this degradation are withdrawn from the maturing enamel. Any interference with enamel matrix removal could yield retarding effects on the accompanying crystal growth through the maturation stages, resulting in different magnitudes of enamel porosity at the time of tooth eruption. Currently, there is no direct proof that fluoride at micromolar levels affects proliferation and differentiation of enamel organ cells. Fluoride does not seem to affect the production and secretion of enamel matrix proteins and proteases within the dose range causing dental fluorosis in man. Most likely, the fluoride uptake interferes, indirectly, with the protease activities by decreasing free Ca(2+) concentration in the mineralizing milieu. The Ca(2+)-mediated regulation of protease activities is consistent with the in situ observations that (a) enzymatic cleavages of the amelogenins take place only at slow rates through the secretory phase with the limited calcium transport and that, (b) under normal amelogenesis, the amelogenin degradation appears to be accelerated during the transitional and early maturation stages with the increased calcium transport. Since the predominant cariostatic effect of fluoride is not due to its uptake by the enamel during tooth development, it is possible to obtain extensive caries reduction without a concomitant risk of dental fluorosis. Further efforts and research are needed to settle the currently uncertain issues, e.g., the incidence, prevalence, and causes of dental or skeletal fluorosis in relation to all sources of fluoride and the appropriate dose levels and timing of fluoride exposure for prevention and control of dental fluorosis and caries.

High concentrations of fluoride and boron in drinking water wells in the Muenster region--results of a preliminary investigation.

PubMed

Queste, A; Lacombe, M; Hellmeier, W; Hillermann, F; Bortulussi, B; Kaup, M; Ott, K; Mathys, W

2001-03-01

In 1998, two cases of severe dental fluorosis in schoolchildren occurred in the Muenster region. These cases took place in one household, where fluoridated toothpaste, fluoridated salt, and fluoride tablets were consumed. Furthermore, the family used drinking water from its private well only. Analyses of the well water ordered by local health officials revealed very high amounts of fluoride, boron, and other electrolytes. This unusual combination of high amounts of fluoride and boron could also be found in the water of a great number of other private wells that are the only source for drinking water in this rural region of the Muensterland. Anthropogenic sources could be excluded. Because of this, the results of the water samples were collated to the specific geological situation in this area. In the Muenster region there are marl layers of the chalk era covered with quarternary sediments. The quarternary sediments are up to 10 to 20 metres thick and they usually conduct the groundwater. The marl contains high concentrations of fluoride and boron. In some places the groundwater has contact with these layers. To check the amount of fluoride and boron in the groundwater, indicator values were sought, which can give a hint of high contents of these trace elements. In this study the conductivity and acidity were identified as possible indicators of a high amount of fluoride and boron in the drinking water in this specific region. To work economically and efficiently, the drinking water should be checked for fluoride and boron on a regular basis only when these values are extraordinarily high. In the case of high concentrations, especially of fluoride, in the drinking water the persons concerned should be informed about their potential health risk, giving them the opportunity to optimise the total daily intake of fluoride.

The effect of tooth brushing and flossing sequence on interdental plaque reduction and fluoride retention: A randomized controlled clinical trial.

PubMed

Mazhari, Fatemeh; Boskabady, Marzie; Moeintaghavi, Amir; Habibi, Atieh

2018-05-09

Mechanical plaque control methods such as brushing and flossing are highly recommended to remove dental plaque. The aim of this study is to evaluate the efficacy of the sequence of brushing and flossing on reducing interdental plaque and increasing fluoride retention in that area. This randomized controlled crossover trial was conducted on 25 dental students. After prophylaxis, they were asked to discontinue all forms of oral hygiene for 48 hours. The study was performed in two phases with two-week washout intervals. In one phase, they first brushed, then flossed (sequence 1: brush-floss group). In the other phase they initially used dental floss then brushed (sequence 2: floss-brush group). At each phase, dental plaque (using the Rustogi Modified Navy Plaque Index) and fluoride concentrations (using a fluoride ion specific electrode) were measured before and after flossing and brushing, and the dental plaque reduction and fluoride increase were compared between the two groups using the mixed model test. A significance level of 5% was selected. In the floss-brush group interdental and whole plaque was reduced significantly more than the brush-floss group (p = 0.001, p = 0.009 respectively). However, marginal plaque did not show any statistically significant difference between the two groups (p = 0.2). Fluoride concentrations in interdental plaque were significantly higher in the floss-brush group than the other group (p = 0.027). The results showed that flossing followed by brushing is preferred to brushing then flossing in order to reduce interdental plaque and increase fluoride concentration in interdental plaque. This article is protected by copyright. All rights reserved. © 2018 American Academy of Periodontology.

Analysis of large soil samples for actinides

DOEpatents

Maxwell, III; Sherrod, L [Aiken, SC

2009-03-24

A method of analyzing relatively large soil samples for actinides by employing a separation process that includes cerium fluoride precipitation for removing the soil matrix and precipitates plutonium, americium, and curium with cerium and hydrofluoric acid followed by separating these actinides using chromatography cartridges.

Improved ultraviolet resonance lamp

NASA Technical Reports Server (NTRS)

Bass, A. M.

1970-01-01

Removal of the seal area from the path of the lamp discharge eliminates the gradual deterioration of lithium fluoride window surfaces from condensation of products formed by interaction of a resonant rare-gas discharge with window sealing materials. The discharge is confined to the inner tube.

[The effect of alternating administration of aluminum chloride and sodium fluoride in drinking water on the concentration of fluoride in serum and its content in bones of rats].

PubMed

Lubkowska, Anna; Chlubek, Dariusz; Machoy-Mokrzyniska, Anna

2006-01-01

Fluorine and aluminum remain a very interesting research topic due to equivocal and relatively unknown toxic action, role in the etiology of various diseases, and interactions of both elements. Fluorine and aluminum compounds are absorbed by organisms through the gastric and respiratory systems, although the latter route operates only at very high concentrations in air. Chronic exposure to fluorine and aluminum leads to accumulation of both elements, especially in bones and teeth, but also in lung, brain, kidney, and liver. Organisms excrete these elements with urine, faeces, and to a minor extent with sweat and bile. In the light of reports suggesting that aluminum has protective properties against fluorine toxicity during exposure to both elements, we decided to examine the effect of alternating doses of aluminum fluoride and sodium fluoride in drinking water on rats. Four female groups received: I--100 ppm fluorine ions during one month; II--100 ppm fluorine ions alternating every two days with 300 ppm aluminum ions during one month; III--100 ppm fluoride ions during four months; IV--100 ppm fluorine ions alternating every two days with 300 ppm aluminum ions during four months. The respective male groups called IA, IIA, IIIA, and IVA were treated identically. Subsequently, the animals were anesthetized and sacrificed. Blood was sampled from the heart and the right femur was removed for fluorine determination. Fluorine content in the femur and serum was determined with an ion-selective electrode (Orion). The results were analyzed statistically (Statistica 6). We observed higher fluoride concentrations in serum as compared with control values in all groups of female and male rats exposed to sodium fluoride only. Longer exposure time (4 months) did not result in further increase in serum fluoride concentration. However, longer exposure increased fluoride accumulation in the femur (p < 0.001). All groups exposed to NaF had significantly higher fluoride concentration in the femur as compared with control animals. Groups receiving NaF and AlCl3 showed lower fluoride concentration in serum and femur compared with those exposed to NaF only and higher in comparison with controls. Fluorine content in the femur of rats exposed to NaF and AlCI3 for four months was similar to the results obtained after one month of exposure.

A novel fluoride anion modified gelatin nanogel system for ultrasound-triggered drug release.

PubMed

Wu, Daocheng; Wan, Mingxi

2008-01-01

Controlled drug release, especially tumor-targeted drug release, remains a great challenge. Here, we prepare a novel fluoride anion-modified gelatin nanogel system and investigate its characteristics of ultrasound-triggered drug release. Adriamycin gelatin nanogel modified with fluoride anion (ADM-GNMF) was prepared by a modified co-precipitation method with fluoride anion and sodium sulfate. The loading and encapsulation efficiency of the anti-neoplastic agent adriamycin (ADM) were measured by high performance liquid chromatography (HPLC). The size and shape of ADM-GNMF were determined by electron microscopy and photo-correlation spectroscopy. The size distribution and drug release efficiency of ADM-GNMF, before and after sonication, were measured by two designed measuring devices that consisted of either a submicron particle size analyzer and an ultrasound generator as well as an ultrasound generator, automatic sampler, and HPLC. The ADM-GNMF was stable in solution with an average diameter of 46+/-12 nm; the encapsulation and loading efficiency of adriamycin were 87.2% and 6.38%, respectively. The ultrasound-triggered drug release and size change were most efficient at a frequency of 20 kHz, power density of 0.4w/cm2, and a 1~2 min duration. Under this ultrasound-triggered condition, 51.5% of drug in ADM-GNMF was released within 1~2 min, while the size of ADM-GNMF changed from 46 +/- 12 nm to 1212 +/- 35 nm within 1~2 min of sonication and restored to its previous size in 2~3 min after the ultrasound stopped. In contrast, 8.2% of drug in ADM-GNMF was released within 2~3 min without sonication, and only negligible size changes were found. The ADM-GNMF system efficiently released the encompassed drug in response to ultrasound, offering a novel and promising controlled drug release system for targeted therapy for cancer or other diseases.

Influence of fluoride varnish on shear bond strength of a universal adhesive on intact and demineralized enamel.

PubMed

Ortiz-Ruiz, Antonio José; Muñoz-Gómez, Iban Jesús; Pérez-Pardo, Ana; Germán-Cecilia, Concepción; Martínez-Beneyto, Yolanda; Vicente, Ascensión

2018-04-27

The aim was to evaluate the effect of fluoride varnish on the shear bond strength (SBS) on polished and non-polished intact and demineralized enamel. Bovine incisors (half demineralized) were used. Bifluorid 12™ was applied. Bonding was made with Futurabond ® M + and GrandioSO, 24 h and 7 days after varnishing. In some groups, varnish was removed by polishing before bonding. SBS was measured. Fracture type was determined by stereomicroscopy and scanning electron microscope (SEM) observations of the enamel surface were made. Between-group differences were determined by one-way ANOVA and the Tukey test. Associations between study factors and fracture modes were analysed using contingency tables and Pearson's chi-squared test. For intact enamel, SBS on varnished enamel at 24 h was significantly less than in the other groups. SBS recovered 7 days after varnishing. Varnish elimination after 24 h significantly increased the SBS. However, removal at 7 days did not modify SBS. SBS on demineralized enamel groups was significantly less than in intact enamel, except for demineralized enamel varnished and removed at 7 days. Demineralized enamel was associated with cohesive enamel fractures and intact enamel with cohesive fractures of the composite and adhesive fractures. SEM of varnish surfaces showed a homogenous layer scattered with amorphous precipitate. In conclusion, on intact enamel fluoride varnish had a negative effect on SBS at 24 h, which disappeared after 7 days. On demineralized enamel, varnish did not reduce SBS at either time. Polishing the varnished enamel surface showed a similar SBS to intact enamel after 7 days.

Doxycycline-containing glass ionomer cement for arresting residual caries: an in vitro study and a pilot trial

PubMed Central

Duque, Cristiane; Kreling, Paula Fernanda; Pereira, Jesse Augusto; de Paula, Andreia Bolzan; Sinhoreti, Mario Alexandre Coelho; Puppin-Rontani, Regina Maria

2018-01-01

Abstract In a previous study, we demonstrated that the incorporation of doxycycline hyclate (DOX) into resin-modified glass ionomer cement (RMGIC) inhibited important cariogenic microorganisms, without modifying its biological and mechanical characteristics. In this study, we keep focused on the effect of that experimental material as a potential therapy for arresting residual caries by analyzing other in vitro properties and conducting a pilot clinical trial assessing the in vivo effect of DOX-containing RMGIC on residual mutans streptococci after partial carious removal in primary molars. Specimens of the groups RMGIC (control); RMGIC + 1.5% DOX; RMGIC + 3% DOX; and RMGIC + 4.5% DOX were made to evaluate the effect of DOX incorporation on surface microhardness and fluoride release of RMGIC and against biofilm of Streptococcus mutans. Clinical intervention consisted of partial caries removal comparing RMGIC and RMGIC + 4.5% DOX as lining materials. After 3 months, clinical and microbiologic evaluations were performed. Data were submitted to ANOVA/Tukey or Wilcoxon/Mann-Whitney set as α=0.05. Fluoride release and surface microhardness was not influenced by the incorporation of DOX (p>0.05). There was a significant reduction of S. mutans biofilm over the material surface with the increase of DOX concentration. After clinical trial, the remaining dentin was hard and dry. Additionally, mutans streptococci were completely eliminated after 3 months of treatment with RMGIC + 4.5% DOX. The incorporation of DOX provided better antibiofilm effect, without jeopardizing fluoride release and surface microhardness of RMGIC. This combination also improved the in vivo shortterm microbiological effect of RMGIC after partial caries removal. PMID:29742263

Alternate Fuel Cycle Technologies/Thorium Fuel Cycle Technology Programs. Quarterly report for period 1 April--30 June 1978

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vondra, B.L.

1978-08-01

Voloxidation and dissolution studies: rotary-kiln heat-transfer tests are under way using a small rotary kiln along with the development of a mathematical model to determine kiln-heat-flux profiles necessary to maintain a desired temperature gradient. The erosion/corrosion test for evaluating materials of construction is operational. Fuel from a BWR (Big Rock Point) yielded more fine solid residue on dissolution than in previous tests with PWR fuel. Two additional parametric voloxidation tests with H.B. Robinson fuel compared air vs pure oxygen atmospheres at 550{sup 0}C; overall tritium release and subsequent fuel dissolution were equivalent. Thorium dissolution studies: the dissolution rate of thoriamore » in fluoride-catalyzed 8 to 14 M HNO{sub 3} (100{sup 0}C) was max between 0.04 to 0.06 M HF; at higher fluoride concentrations, ThF{sub 4}.5H{sub 2}O precipitated. The rate of zircaloy dissolution continued to increase with increasing fluoride concentration. Stainless-steel-clad (Th,U)0{sub 2} fuel rods irradiated in the NRX reactor were sheared, voloxidized, and dissolved. {le}10% of the tritium was released during voloxidation in air at 600{sup 0}C. Carbon-14 removal from off-gas and fixation: carbon dioxide removal with Linde 13X molecular sieves to less than 100 ppB was experimentally verified using 300 ppM CO in air. Decontamination factors from 3000 to 7500 were obtained for CO{sub 2} removal in the gas-slurry stirred-tank reactor with CA(OH){sub 2}.or Ba(0H){sub 2}/sup .8H2O./. With Ba(OH){sub 2}.H{sub 2}0{sup 2} in a fixed-bed column, decontamination factors of about 30,000 were obtained.« less

The differences in healthcare utilization for dental caries based on the implementation of water fluoridation in South Korea.

PubMed

Cho, Myung-Soo; Han, Kyu-Tae; Park, Sohee; Moon, Ki Tae; Park, Eun-Cheol

2016-11-08

There were some debates about the water fluoridation program in South Korea, even if the program had generally substantial effectiveness. Because the out-of-pocket expenditures for dental care were higher in South Korea than in other countries, an efficient solution was needed. Therefore, we examined the relationship between the implementation of water fluoridation and the utilization of dental care. We used the National Health Insurance Service National Sample Cohort. In this study, data finally included 472,250 patients who were newly diagnosed with dental caries during 2003-2013. We performed survival analysis using cox proportional hazard model, negative binomial-regression, and regression analyses using generalized estimating equation models. There were 48.49 % outpatient dental care visit during study period. Individuals with water fluoridation had a lower risk of dental care visits (HR = 0.949, 95 % CI = 0.928-0.971). Among the individuals who experienced a dental care visit, those with water fluoridation program had a lower number of dental care visits (β = -0.029), and the period of water fluoridation had an inverse association with the dental care expenditures. The implementation of water fluoridation programs and these periods are associated with reducing the utilization of dental health care. Considering these positive impacts, healthcare professionals must consider preventive strategies for activating water fluoridation programs, such as changes in public perception and relations, for the effective management of dental care in South Korea.

Comparison of fluoride intercalation/de-intercalation processes on graphite electrodes in aqueous and aqueous methanolic HF media

NASA Astrophysics Data System (ADS)

Noel, M.; Santhanam, R.; Francisca Flora, M.

The solvent can play a major role in the intercalation/de-intercalation process and the stability of graphite substrates towards this process. This fact is established in the present work that involves fluoride intercalation/de-intercatlation on graphite electrodes in aqueous and aqueous methanolic HF solutions where the HF concentration is varied between 1.0 and 18.0 M. In addition to cyclic voltammetry and potentiostatic polarization, open-circuit potential decay measurements, scanning electron microscopy and X-ray diffraction measurements have been employed. In general, addition of methanol and increasing concentration of HF raise the overall intercalation/de-intercalation efficiency. Methanol is adsorbed preferentially on the graphite lattice and, hence, suppresses both oxygen evolution and the formation of passive graphite oxides. In 15.0 M HF, the optimum methanol concentration is 5 vol.%. This suggests that, in addition to the adsorption effect, there is some weakening of the structured water molecules that facilitates the solvated fluoride ions for efficient intercalation.

REDUCTION OF FLUORIDE TO METAL

DOEpatents

Carlson, O.N.; Schmidt, F.A.; Spedding, F.H.

1960-08-30

A process is given for making yttrium metal by reducing yttrium fluoride with calcium plus magnesium. Calcium is added in an excess of from 10 to 20% and magnesium in a quantity to yield a magnesium--yttrium alloy containing from 12 to 25% magnesium when the reaction mass is heated in an inert atmosphere at from 900 to 1106 deg C, but preferably above the melting point of the alloy. Calcium chloride may be added so as to obtain a less viscous slag containing from 30 to 60% calcium chloride. After removal of the slag the alloy is vacuum-heated at about 1100 deg C for volatilization of the magnesium and calcium.

Perovskite-like fluorides and oxyfluorides: Phase transitions and caloric effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flerov, I. N., E-mail: flerov@iph.krasn.ru; Gorev, M. V., E-mail: gorev@iph.krasn.ru; Tressaud, A.

2011-01-15

An analysis of the effect that chemical and hydrostatic pressures have on the thermodynamic properties of perovskite-like fluorine-oxygen compounds A{sub 2}A Prime MeO{sub x}F{sub 6-x} has revealed that materials under-going order-disorder transitions and having significant external-pressure compliance have the highest caloric efficiency. Some of the fluorides and oxyfluorides under study can be considered promising solid coolants.

Electrochemical decomposition of fluorinated wetting agents in plating industry waste water.

PubMed

Fath, Andreas; Sacher, Frank; McCaskie, John E

2016-01-01

Electrochemical decomposition of fluorinated surfactants (PFAS, perfluorinated alkyl substances) used in the plating industry was analyzed and the decomposition process parameters optimized at the laboratory scale and production scale of a 500-liter reactor using lead electrodes. The method and system was successfully demonstrated under production conditions to treat PFAS) with up to 99% efficiency in the concentration range of 1,000-20,000 μg/l (1 ppm-20 ppm). The treatment also reduced hexavalent chromium (Cr(6+)) ions to trivalent chromium (Cr(3+)) ions in the wastewater. If the PFAS-containing wastewater is mixed with other wastewater streams, specifically from nickel plating drag out solution or when pH values >5, the treatment process is ineffective. For the short chain PFAS, (perfluorobutylsulfonate) the process was less efficient than C6-C8 PFAS. The process is automated and has safety procedures and controls to prevent hazards. The PFAS were decomposed to hydrogen fluoride (HF) under the strong acid electrochemical operating conditions. Analytical tests showed no evidence of organic waste products remaining from the process. Conventional alternative PFAS removal systems were tested on the waste streams and compared with each other and with the-E-destruct (electrochemical oxidation) process. For example, ion exchange resin (IX resin) treatment of wastewater to complex and remove PFAS was found to be seven times more efficient when compared to the conventional activated carbon absorption (C-treat) process. However, the E-destruct process is higher in capacity, exhibits longer service life and lower operating costs than either IX or C-treat methods for elimination of PFAS from these electroplating waste streams.

Catalase and sodium fluoride mediated rehabilitation of enamel bleached with 37% hydrogen peroxide.

PubMed

Thakur, Ruchi; Shigli, Anand L; Sharma, Divya; Thakur, Gagan

2015-01-01

Bleaching agents bring about a range of unwanted changes in the physical structure of enamel which needs to be restored qualitatively and timely. Catalase being an antioxidant ensures the effective removal of free radicals and improvement in fluoride mediated remineralization from the enamel microstructure which if retained may harm the integrity and affect the hardness of enamel. Thirty freshly extracted incisors were sectioned to 6 slabs which were divided into 5 groups: Group A, control; Group B, treatment with 37% hydrogen peroxide (HP); Group C, treatment with 37% HP and catalase, Group D, treatment with 37% HP and 5% sodium fluoride application, Group E, treatment with 37% HP followed by catalase and 5% sodium fluoride. Scanning electron microscope and microhardness analysis were done for all slabs. One-way ANOVA test was applied among different groups. Vicker's microhardness number (VHN) of Group B and C was significantly lower. No significant difference between VHN of Group B and C. VHN of Group D was significantly higher than Group A, B, and C; but significantly lower than Group E. VHN of Group E was significantly higher than any other experimental group. One-way ANOVA revealed a highly significant P value (P = 0.0001) and so Tukey's post-hoc Test for the group comparisons was employed. Subsequent treatment of bleached enamel with catalase and fluoride varnish separately results in repairing and significantly increasing the microhardness.

ENVIRONMENTALLY CONSCIOUS ELECTROCHEMICAL MACHINING FOR ZERO DISCHARGE AND METAL RECYCLING - PHASE I

EPA Science Inventory

Electrodeposition of molten silicon

DOEpatents

De Mattei, Robert C.; Elwell, Dennis; Feigelson, Robert S.

1981-01-01

Silicon dioxide is dissolved in a molten electrolytic bath, preferably comprising barium oxide and barium fluoride. A direct current is passed between an anode and a cathode in the bath to reduce the dissolved silicon dioxide to non-alloyed silicon in molten form, which is removed from the bath.

Method for selectively removing fluorine and fluorine-containing contaminants from gaseous UF.sub.6

DOEpatents

Jones, Robert L.; Otey, Milton G.; Perkins, Roy W.

1982-01-01

This invention is a method for effecting preferential removal and immobilization of certain gaseous contaminants from gaseous UF.sub.6. The contaminants include fluorine and fluorides which are more reactive with CaCO.sub.3 than is UF.sub.6. The method comprises contacting the contaminant-carrying UF.sub.6 with particulate CaCO.sub.3 at a temperature effecting reaction of the contaminant and the CaCO.sub.3.

Fluoride loaded polymeric nanoparticles for dental delivery.

PubMed

Nguyen, Sanko; Escudero, Carlos; Sediqi, Nadia; Smistad, Gro; Hiorth, Marianne

2017-06-15

The overall aim of the present paper was to develop fluoride loaded nanoparticles based on the biopolymers chitosan, pectin, and alginate, for use in dental delivery. First, the preparation of nanoparticles in the presence of sodium fluoride (NaF) as the active ingredient by ionic gelation was investigated followed by an evaluation of their drug entrapment and release properties. Chitosan formed stable, spherical, and monodisperse nanoparticles in the presence of NaF and tripolyphoshate as the crosslinker, whereas alginate and pectin were not able to form any definite nanostructures in similar conditions. The fluoride loading capacity was found to be 33-113ppm, and the entrapment efficiency 3.6-6.2% for chitosan nanoparticles prepared in 0.2-0.4% (w/w) NaF, respectively. A steady increase in the fluoride release was observed for chitosan nanoparticles prepared in 0.2% NaF both in pH5 and 7 until it reached a maximum at time point 4h and maintained at this level for at least 24h. Similar profiles were observed for formulations prepared in 0.4% NaF; however the fluoride was released at a higher level at pH5. The low concentration, but continuous delivery of fluoride from the chitosan nanoparticles, with possible expedited release in acidic environment, makes these formulations highly promising as dental delivery systems in the protection against caries development. Copyright © 2017 Elsevier B.V. All rights reserved.

One-pot palladium-catalyzed synthesis of sulfonyl fluorides from aryl bromides† †Electronic supplementary information (ESI) available: Experimental details and supporting characterisation data. See DOI: 10.1039/c6sc03924c Click here for additional data file.

PubMed Central

Davies, Alyn T.; Curto, John M.

2017-01-01

A mild, efficient synthesis of sulfonyl fluorides from aryl and heteroaryl bromides utilizing palladium catalysis is described. The process involves the initial palladium-catalyzed sulfonylation of aryl bromides using DABSO as an SO2 source, followed by in situ treatment of the resultant sulfinate with the electrophilic fluorine source NFSI. This sequence represents the first general method for the sulfonylation of aryl bromides, and offers a practical, one-pot alternative to previously described syntheses of sulfonyl fluorides, allowing rapid access to these biologically important molecules. Excellent functional group tolerance is demonstrated, with the transformation successfully achieved on a number of active pharmaceutical ingredients, and their precursors. The preparation of peptide-derived sulfonyl fluorides is also demonstrated. PMID:28451264

Red Mn4+-Doped Fluoride Phosphors: Why Purity Matters.

PubMed

Verstraete, Reinert; Sijbom, Heleen F; Joos, Jonas J; Korthout, Katleen; Poelman, Dirk; Detavernier, Christophe; Smet, Philippe F

2018-06-06

Traditional light sources, e.g., incandescent and fluorescent lamps, are currently being replaced by white light-emitting diodes (wLEDs) because of their improved efficiency, prolonged lifetime, and environmental friendliness. Much effort has recently been spent to the development of Mn 4+ -doped fluoride phosphors that can enhance the color gamut in displays and improve the color rendering index, luminous efficacy of the radiation, and correlated color temperature of wLEDs used for lighting. Purity, stability, and degradation of fluoride phosphors are, however, rarely discussed. Nevertheless, the typical wet chemical synthesis routes (involving hydrogen fluoride (HF)) and the large variety of possible Mn valence states often lead to impurities that drastically influence the performance and stability of these phosphors. In this article, the origins and consequences of impurities formed during synthesis and aging of K 2 SiF 6 :Mn 4+ are revealed. Both crystalline impurities such as KHF 2 and ionic impurities such as Mn 3+ are found to affect the phosphor performance. While Mn 3+ mainly influences the optical absorption behavior, KHF 2 can affect both the optical performance and chemical stability of the phosphor. Moisture leads to decomposition of KHF 2 , forming HF and amorphous hydrated potassium fluoride. As a consequence of hydrate formation, significant amounts of water can be absorbed in impure phosphor powders containing KHF 2 , facilitating the hydrolysis of [MnF 6 ] 2- complexes and affecting the optical absorption of the phosphors. Strategies are discussed to identify impurities and to achieve pure and stable phosphors with internal quantum efficiencies of more than 90%.

Synergistic effect of fluoride and laser irradiation for the inhibition of the demineralization of dental enamel

NASA Astrophysics Data System (ADS)

Lee, Raymond; Chan, Kenneth H.; Jew, Jamison; Simon, Jacob C.; Fried, Daniel

2017-02-01

Both laser irradiation and fluoride treatment alone are known to provide increased resistance to acid dissolution. CO2 lasers tuned to a wavelength of 9.3 μm can be used to efficiently convert the carbonated hydroxyapatite of enamel to a much more acid resistant purer phase hydroxyapatite (HAP). Further studies have shown that fluoride application to HAP yields fluoroapatite (FAP) which is even more resistant against acid dissolution. Previous studies show that CO2 lasers and fluoride treatments interact synergistically to provide significantly higher protection than either method alone, but the mechanism of interaction has not been elucidated. We recently observed the formation of microcracks or a "crazed" zone in the irradiated region that is resistant to demineralization using high-resolution microscopy. The microcracks are formed due to the slight contraction of enamel due to transformation of carbonated hydroxyapatite to the more acid resistant pure phase hydroxyapatite (HAP) that has a smaller lattice. In this study, we test the hypothesis that these small cracks will provide greater adhesion for topical fluoride for greater protection against acid demineralization.

Fluoride-fiber-based side-pump coupler for high-power fiber lasers at 2.8  μm.

PubMed

Schäfer, C A; Uehara, H; Konishi, D; Hattori, S; Matsukuma, H; Murakami, M; Shimizu, S; Tokita, S

2018-05-15

A side-pump coupler made of fluoride fibers was fabricated and tested. The tested device had a coupling efficiency of 83% and was driven with an incident pump power of up to 83.5 W, demonstrating high-power operation. Stable laser output of 15 W at a wavelength of around 2.8 μm was achieved over 1 h when using an erbium-doped double-clad fiber as the active medium. To the best of our knowledge, this is the first time a fluoride-glass-fiber-based side-pump coupler has been developed. A test with two devices demonstrated further power scalability.

Development of a portable, modular unit for the optimization of ultrasound-assisted oxidative desulfurization of diesel

NASA Astrophysics Data System (ADS)

Wan, Meng-Wei

Due to the stringent rules requiring ultra-low sulfur content in diesel fuels, it is necessary to develop alternative methods of desulfurization of fossil fuel derived oil, such as diesel. Current technology is not sufficient to solve this problem. Ultrasound applied to oxidative desulfurization which combined three complementary techniques: ultrasonication, phase transfer catalysis (PTC) and transition metal catalyzed oxidation, has accomplished high sulfur removal in a short contact time at ambient temperature and atmospheric pressure. This research has successfully demonstrated that the higher oxidation efficiency of BT to BTO and free of any by-products by using tetraoctylammonium fluoride as phase transfer agent. The oxidation rate of BT to BTO increased with increasing the carbon chain length of QAS cations. Under the same length of carbon chain, the oxidation rate of BT to BTO increased with decreasing the molecular size of QAS anions. Moreover, for diesel fuels containing various levels of sulfur content, UAOD process followed by solvent extraction has demonstrated that the sulfur reduction can reach above 95 % removal efficiency or final sulfur content below 15 ppm in mild condition. For large-scale commercial production, this research has successfully developed and operated a continuous desulfurization unit, which consists of a sonoractor, an RF amplifier, a function generator, a pretreatment tank, and a pipeline system. A single unit only needed 2' x 4' x 1' space for installation. The results indicated that the remarkable 92% removal efficiency for the sulfur in marine logistic diesel, even at a treatment rate as high as 25 lb/hour which is approximately 2 barrels per day. Therefore, this sonoreactor demonstrated the feasibility of large-scale operation even in a relatively small installation with low capital investment and maintenance cost. It also ensures the safety considerations by operating with diluted hydrogen peroxide under ambient temperature and pressure.

Ultrafast Self-Crystallization of High-External-Quantum-Efficient Fluoride Phosphors for Warm White Light-Emitting Diodes.

PubMed

Zhou, Wenli; Fang, Mu-Huai; Lian, Shixun; Liu, Ru-Shi

2018-05-30

In this study, we used HF (as good solvent) to dissolve K 2 GeF 6 and K 2 MnF 6 and added ethanol (as poor solvent) to cause ultrafast self-crystallization of K 2 GeF 6 :Mn 4+ crystals, which had an unprecedentedly high external quantum efficiency that reached 73%. By using the red phosphor, we achieved a high-quality warm white light-emitting diode with color-rendering index of R a = 94, R9 = 95, luminous efficacy of 150 lm W -1 , and correlated color temperature at 3652 K. Furthermore, the good-poor solvent strategy can be used to fast synthesize other fluorides.

Emissions of fluorides from welding processes.

PubMed

Szewczyńska, Małgorzata; Pągowska, Emilia; Pyrzyńska, Krystyna

2015-11-01

The levels of fluoride airborne particulates emitted from welding processes were investigated. They were sampled with the patented IOM Sampler, developed by J. H. Vincent and D. Mark at the Institute of Occupational Medicine (IOM), personal inhalable sampler for simultaneous collection of the inhalable and respirable size fractions. Ion chromatography with conductometric detection was used for quantitative analysis. The efficiency of fluoride extraction from the cellulose filter of the IOM sampler was examined using the standard sample of urban air particle matter SRM-1648a. The best results for extraction were obtained when water and the anionic surfactant N-Cetyl-N-N-N-trimethylammonium bromide (CTAB) were used in an ultrasonic bath. The limits of detection and quantification for the whole procedure were 8μg/L and 24μg/L, respectively. The linear range of calibration was 0.01-10mg/L, which corresponds to 0.0001-0.1mg of fluorides per m(3) in collection of a 20L air sample. The concentration of fluorides in the respirable fraction of collected air samples was in the range of 0.20-1.82mg/m(3), while the inhalable fraction contained 0.23-1.96mg/m(3) of fluorides during an eight-hour working day in the welding room. Copyright © 2015. Published by Elsevier B.V.

Method for selectively removing fluorine and fluorine-containing contaminants from gaseous UF/sub 6/. [ClF/sub 3/

DOEpatents

Jones, R.L.; Otey, M.G.; Perkins, R.W.

1980-11-24

This invention is a method for effecting preferential removal and immobilization of certain gaseous contaminants from gaseous UF/sub 6/. The contaminants include fluorine and fluorides which are more reactive with CaCO/sub 3/ than is UF/sub 6/. The method comprises contacting the contaminant-carrying UF/sub 6/ with particulate CaCO/sub 3/ at a temperature effecting reaction of the contaminant and the CaCO/sub 3/.

Surface phosphatase in Rhinocladiella aquaspersa: biochemical properties and its involvement with adhesion.

PubMed

Kneipp, Lucimar F; Magalhães, Andressa S; Abi-Chacra, Erika A; Souza, Lucieri O P; Alviano, Celuta S; Santos, André L S; Meyer-Fernandes, José R

2012-08-01

Rhinocladiella aquaspersa is an etiologic agent of chromoblastomycosis, a subcutaneous chronic infectious disease. In the present work, we found that the three morphological forms of this fungus (conidia, mycelia and sclerotic bodies) expressed different levels of ecto-phosphatase activity. Our results demonstrated that surface conidial enzyme is an acid phosphatase, inhibited by sodium salts of molybdate, orthovanadate and fluoride and that the inhibition caused by orthovanadate and molybdate was irreversible. The conidial ecto-phosphatase efficiently released phosphate groups from different phosphorylated substrates, causing a higher rate of phosphate removal when p-nitrophenylphosphate was used as substrate. This ecto-enzyme of R. aquaspersa is modulated by Co(2 +) ions and inorganic phosphate (Pi). Accordingly, removal of Pi from the culture medium resulted in a marked (121-fold) increase of ecto-phosphatase activity. Surface phosphatase activity is apparently involved in fungal adhesive properties, since the attachment of R. aquaspersa to epithelial cells was reversed by the pre-treatment of the conidia with orthovanadate, molybdate and anti-phosphatase antibody. Corroborating this finding, conidia with greater ecto-phosphatase activity (grown in Pi-depleted medium) showed higher adherence to epithelial cells than fungi cultivated in the presence of Pi.

Method for fluorination of actinide fluorides and oxyfluorides thereof using O.sub.2 F.sub.2

DOEpatents

Eller, Phillip G.; Malm, John G.; Penneman, Robert A.

1988-01-01

Method for fluorination of actinides and fluorides and oxyfluorides thereof using O.sub.2 F.sub.2 which generates actinide hexafluorides, and for removal of actinides and compounds thereof from surfaces upon which they appear as unwanted deposits. The fluorinating agent, O.sub.2 F.sub.2, has been observed to readily perform the above-described tasks at sufficiently low temperatures that there is virtually no damage to the containment vessels. Moreover, the resulting actinide hexafluorides are thereby not destroyed by high temperature reactions with the walls of the reaction vessel. Dioxygen difluoride is easily prepared, stored and transferred to the desired place of reaction.

Method for dissolving delta-phase plutonium

DOEpatents

Karraker, David G.

1992-01-01

A process for dissolving plutonium, and in particular, delta-phase plutonium. The process includes heating a mixture of nitric acid, hydroxylammonium nitrate (HAN) and potassium fluoride to a temperature between 40.degree. and 70.degree. C., then immersing the metal in the mixture. Preferably, the nitric acid has a concentration of not more than 2M, the HAN approximately 0.66M, and the potassium fluoride 0.1M. Additionally, a small amount of sulfamic acid, such as 0.1M can be added to assure stability of the HAN in the presence of nitric acid. The oxide layer that forms on plutonium metal may be removed with a non-oxidizing acid as a pre-treatment step.

Method for fluorination of actinide fluorides and oxyfluorides thereof using O[sub 2]F[sub 2

DOEpatents

Eller, P.G.; Malm, J.G.; Penneman, R.A.

1988-11-08

Method is described for fluorination of actinides and fluorides and oxyfluorides thereof using O[sub 2]F[sub 2] which generates actinide hexafluorides, and for removal of actinides and compounds thereof from surfaces upon which they appear as unwanted deposits. The fluorinating agent, O[sub 2]F[sub 2], has been observed to readily perform the above-described tasks at sufficiently low temperatures that there is virtually no damage to the containment vessels. Moreover, the resulting actinide hexafluorides are thereby not destroyed by high temperature reactions with the walls of the reaction vessel. Dioxygen difluoride is easily prepared, stored and transferred to the desired place of reaction.

PROCESS FOR THE RECOVERY OF PLUTONIUM

DOEpatents

Ritter, D.M.

1959-01-13

An improvement is presented in the process for recovery and decontamination of plutonium. The carrier precipitate containing plutonium is dissolved and treated with an oxidizing agent to place the plutonium in a hexavalent oxidation state. A lanthanum fluoride precipitate is then formed in and removed from the solution to carry undesired fission products. The fluoride ions in the reniaining solution are complexed by addition of a borate sueh as boric acid, sodium metaborate or the like. The plutonium is then reduced and carried from the solution by the formation of a bismuth phosphate precipitate. This process effects a better separation from unwanted flssion products along with conccntration of the plutonium by using a smaller amount of carrier.

Defluoridation of groundwater using aluminum-coated bauxite: Optimization of synthesis process conditions and equilibrium study.

PubMed

Salifu, Abdulai; Petrusevski, Branislav; Mwampashi, Emmanuel S; Pazi, Iddi A; Ghebremichael, Kebreab; Buamah, Richard; Aubry, Cyril; Amy, Gary L; Kenedy, Maria D

2016-10-01

There is no known effective treatment for fluoride-related health disorders, hence prevention through water defluoridation is necessary. This study explored the possibility of modifying the physico-chemical properties of bauxite, a locally available material in many countries including Ghana, by thermal treatment and an aluminum coating, for water defluoridation. The study mainly focused on investigating the effects of varying synthesis process conditions on the defluoridation efficiency of Granular Aluminum Coated Bauxite (GACB). GACB performed better than raw bauxite (RB) and was able to reduce fluoride concentration in groundwater from 5 ± 0.2 mg/L to ≤ 1.5 mg/L, World Health Organization (WHO) guideline. Based on nonlinear Chi-square (χ(2)) analysis, the best-fitting isotherm model for the fluoride-GACB system was in the order: Freundlich > Redlich-Perterson ≈ Langmuir > Temkin. The fluoride adsorption capacity of GACB (qmax = 12.29 mg/g) based on the Langmuir model was found to be either comparable or higher than the capacities of some reported fluoride adsorbents. Aluminum (Al) coating procedures optimized in this study could therefore be a useful approach for synthesizing an effective fluoride adsorbent using bauxite, a locally available material. Kinetic and isotherm analysis, thermodynamic calculations, as well as FTIR and Raman analysis suggested the mechanism of fluoride adsorption onto GACB was complex and involved both physical adsorption and chemisorption processes. Copyright © 2016 Elsevier Ltd. All rights reserved.

Fluoride varnishes with calcium glycerophosphate: fluoride release and effect on in vitro enamel demineralization.

PubMed

Carvalho, Thiago Saads; Peters, Bianca Glerean; Rios, Daniela; Magalhães, Ana Carolina; Sampaio, Fabio Correia; Buzalaf, Marília Afonso Rabelo; Bönecker, Marcelo José Strazzeri

2015-01-01

The aims of this study were (1) to assess the amount of fluoride (F) released from varnishes containing calcium glycerophosphate (CaGP) and (2) to assess the effect of the experimental varnishes on in vitro demineralization. Six test groups using 5 varnishes: base varnish (no active ingredients); Duraphat® (2.26% NaF); Duofluorid® (5.63% NaF/CaF2); experimental varnish 1 (1% CaGP/5.63% NaF/CaF2); experimental varnish 2 (5% CaGP/5.63% NaF/CaF2); and no varnish were set up. In stage 1, 60 acrylic blocks were randomly distributed into 6 groups (n = 10). Then 300 µg of each varnish was applied to each block. The blocks were immersed in deionized water, which was changed after 1, 8, 12, 24, 48 and 72 hours. Fluoride concentration in the water was analyzed using a fluoride electrode. In stage 2, 60 bovine enamel samples were distributed into 6 groups (n = 10), and treated with 300 µg of the respective varnish. After 6 h the varnish was removed and the samples were subjected to a 7-day in vitro pH cycle (6 h demineralization/18 h remineralization per day). The demineralization was measured using surface hardness. The results showed that both experimental varnishes released more fluoride than Duofluorid® and Duraphat® (p < 0.05), but Duraphat® showed the best preventive effect by decreasing enamel hardness loss (p < 0.05). Therefore, we conclude that even though (1) the experimental varnishes containing CaGP released greater amounts of F, (2) they did not increase in the preventive effect against enamel demineralization.

Protective effect of zinc-hydroxyapatite toothpastes on enamel erosion: An in vitro study.

PubMed

Poggio, Claudio; Gulino, Chiara; Mirando, Maria; Colombo, Marco; Pietrocola, Giampiero

2017-01-01

The aim of the present study was to test the impact of different toothpastes with Zinc-Hydroxyapatite (Zn-HAP) on preventing and repairing enamel erosion compared to toothpastes with and without fluoride. The following four toothpastes were tested: two toothpastes with Zn-HAP, one toothpaste with fluoride and one toothpaste without fluoride. An additional control group was used in which enamel specimens were not treated with toothpaste. Repeated erosive challenges were provided by immersing bovine enamel specimens (10 per group) in a soft drink for 2 min (6mL, room temperature) at 0, 8, 24 and 32 h. After each erosive challenge, the toothpastes were applied neat onto the surface of specimens for 3 min without brushing and removed with distilled water. Between treatments the specimens were kept in artificial saliva. Enamel hardness, after the erosive challenge and toothpaste treatment was monitored using surface micro-hardness measurements. As expected, repeated erosive challenge by a soft drink for total of 8 min significantly reduced enamel surface hardness (ANOVA, p < 0.05). No re-hardening of the surface softened enamel was observed in the group treated with fluoride-free toothpaste. Surface hardness of the softened enamel increased when the specimens were treated with the fluoride toothpaste and the two toothpastes with Zn-HAP ( p < 0.05). Toothpaste with Zn-HAP resulted in significant enamel remineralisation of erosively challenged enamel, indicating that these toothpastes could provide enamel health benefits relevant to enamel erosion. Key words: Enamel, erosion, remineralization, surface hardness, toothpastes.

Sensitivity of titanium brackets to the corrosive influence of fluoride-containing toothpaste and tea.

PubMed

Harzer, W; Schröter, A; Gedrange, T; Muschter, F

2001-08-01

Titanium brackets are used in orthodontic patients with an allergy to nickel and other specific substances. In recent studies, the corrosive properties of fluoride-containing toothpastes with different pH values were investigated. The present in vivo study tested how the surfaces of titanium brackets react to the corrosive influence of acidic fluoride-containing toothpaste during orthodontic treatment. Molar bands were placed on 18 orthodontic patients. In these same patients, titanium brackets were bonded on the left quadrants and stainless steel brackets on the right quadrants of the upper and lower arches. Fifteen patients used Gel Kam containing soluble tin fluoride (pH 3.2), whereas 3 used fluoride-free toothpaste. The brackets were removed for evaluation by light microscopy and scanning microscopy 5.5 to 7.0 months and 7.5 to 17 months after bonding. The quality and quantity of elements present were measured by scanning microscopy. Macroscopic evaluation showed the matte gray color of titanium brackets dominating over the silver gleam of the steel brackets. The plaque accumulation on titanium brackets is high because of the very rough surface. Pitting and crevices were observed in only 3 of the 165 brackets tested. The present in vivo investigation confirms the results of in vitro studies, but the changes are so minor that titanium brackets can safely be used for up to 18 months. Wing surfaces should be improved by modifying the manufacturing process.

Design of Complex Systems to Achieve Passive Safety: Natural Circulation Cooling of Liquid Salt Pebble Bed Reactors

NASA Astrophysics Data System (ADS)

Scarlat, Raluca Olga

This dissertation treats system design, modeling of transient system response, and characterization of individual phenomena and demonstrates a framework for integration of these three activities early in the design process of a complex engineered system. A system analysis framework for prioritization of experiments, modeling, and development of detailed design is proposed. Two fundamental topics in thermal-hydraulics are discussed, which illustrate the integration of modeling and experimentation with nuclear reactor design and safety analysis: thermal-hydraulic modeling of heat generating pebble bed cores, and scaled experiments for natural circulation heat removal with Boussinesq liquids. The case studies used in this dissertation are derived from the design and safety analysis of a pebble bed fluoride salt cooled high temperature nuclear reactor (PB-FHR), currently under development in the United States at the university and national laboratories level. In the context of the phenomena identification and ranking table (PIRT) methodology, new tools and approaches are proposed and demonstrated here, which are specifically relevant to technology in the early stages of development, and to analysis of passive safety features. A system decomposition approach is proposed. Definition of system functional requirements complements identification and compilation of the current knowledge base for the behavior of the system. Two new graphical tools are developed for ranking of phenomena importance: a phenomena ranking map, and a phenomena identification and ranking matrix (PIRM). The functional requirements established through this methodology were used for the design and optimization of the reactor core, and for the transient analysis and design of the passive natural circulation driven decay heat removal system for the PB-FHR. A numerical modeling approach for heat-generating porous media, with multi-dimensional fluid flow is presented. The application of this modeling approach to the PB-FHR annular pebble bed core cooled by fluoride salt mixtures generated a model that is called Pod. Pod. was used to show the resilience of the PB-FHR core to generation of hot spots or cold spots, due to the effect of buoyancy on the flow and temperature distribution in the packed bed. Pod. was used to investigate the PB-FHR response to ATWS transients. Based on the functional requirements for the core, Pod. was used to generate an optimized design of the flow distribution in the core. An analysis of natural circulation loops cooled by single-phase Boussinesq fluids is presented here, in the context of reactor design that relies on natural circulation decay heat removal, and design of scaled experiments. The scaling arguments are established for a transient natural circulation loop, for loops that have long fluid residence time, and negligible contribution of fluid inertia to the momentum equation. The design of integral effects tests for the loss of forced circulation (LOFC) for PB-FHR is discussed. The special case of natural circulation decay heat removal from a pebble bed reactor was analyzed. A way to define the Reynolds number in a multi-dimensional pebble bed was identified. The scaling methodology for replicating pebble bed friction losses using an electrically resistance heated annular pipe and a needle valve was developed. The thermophysical properties of liquid fluoride salts lead to design of systems with low flow velocities, and hence long fluid residence times. A comparison among liquid coolants for the performance of steady state natural circulation heat removal from a pebble bed was performed. Transient natural circulation experimental data with simulant fluids for fluoride salts is given here. The low flow velocity and the relatively high viscosity of the fluoride salts lead to low Reynolds number flows, and a low Reynolds number in conjunction with a sufficiently high coefficient of thermal expansion makes the system susceptible to local buoyancy effects Experiments indicate that slow exchange of stagnant fluid in static legs can play a significant role in the transient response of natural circulation loops. The effect of non-linear temperature profiles on the hot or cold legs or other segments of the flow loop, which may develop during transient scenarios, should be considered when modeling the performance of natural circulation loops. The data provided here can be used for validation of the application of thermal-hydraulic systems codes to the modeling of heat removal by natural circulation with liquid fluoride salts and its simulant fluids.

Fluoridated elastomers: effect on the microbiology of plaque.

PubMed

Benson, Philip E; Douglas, C W Ian; Martin, Michael V

2004-09-01

The objective of this study was to investigate the effect of fluoridated elastomeric ligatures on the microbiology of local dental plaque in vivo. This randomized, prospective, longitudinal, clinical trial had a split-mouth crossover design. The subjects were 30 patients at the beginning of their treatment with fixed orthodontic appliances in the orthodontic departments of the Liverpool and the Sheffield dental hospitals in the United Kingdom. The study consisted of 2 experimental periods of 6 weeks with a washout period between. Fluoridated elastomers were randomly allocated at the first visit to be placed around brackets on tooth numbers 12, 11, 33 or 22, 21, 43. Nonfluoridated elastomers were placed on the contralateral teeth. Standard nonantibacterial fluoridated toothpaste and mouthwash were supplied. After 6 weeks (visit 2), the elastomers were removed, placed in transport media, and plated on agar within 2 hours. Nonfluoridated elastomers were placed on all brackets for 1 visit to allow for a washout period. At visit 3, fluoridated elastomers were placed on the teeth contralateral to those that received them at visit 1. At visit 4, the procedures at visit 2 were repeated. Samples were collected on visits 2 and 4. A logistic regression was performed, with the presence or absence of streptococcal or anaerobic growth as the dependent variable. A mixed-effects analysis of variance was carried out with the percentage of streptococcal or anaerobic bacterial count as the dependent variable. The only significant independent variables were the subject variable (P =<.001) for the percentage of streptococcal and anaerobic bacterial count and the visit variable for the percentage of streptococcal count (P =<.001). The use of fluoridated or nonfluoridated elastomers was not significant for percentage of either streptococcal (P =.288) or anaerobic count (P =.230). Fluoridated elastomers are not effective at reducing local streptococcal or anaerobic bacterial growth after a clinically relevant time in the mouth.

Heat-activated persulfate oxidation of PFOA, 6:2 fluorotelomer sulfonate, and PFOS under conditions suitable for in-situ groundwater remediation.

PubMed

Park, Saerom; Lee, Linda S; Medina, Victor F; Zull, Aaron; Waisner, Scott

2016-02-01

PFOA (perfluorooctanoic acid) oxidation (0.121-6.04 μM) by heat-activated persulfate was evaluated at 20-60 °C with 4.2-84 mM [Formula: see text] and in the presence of soluble fuel components to assess feasibility for in-situ remediation of groundwater. 6:2 fluorotelomer sulfonic acid/sulfonate (6:2 FTSA) and PFOS (perfluorooctanesulfonic acid) persulfate oxidation was also evaluated in a subset of conditions given their co-occurrence at many sites. High performance liquid chromatography electron spray tandem mass spectrometry was used for organic analysis and fluoride was measured using a fluoride-specific electrode. PFOA pseudo-1st order transformation rates (k1,PFOA) increased with increasing temperature (half-lives from 0.1 to 7 d for 60 to 30 °C) sequentially removing CF2 groups ('unzipping') to shorter chain perfluoroalkyl carboxylic acids (PFCAs) and F(-). At 50 °C, a 5-fold increase in [Formula: see text] led to a 5-fold increase in k1,PFOA after which self-scavenging by sulfate radicals decreased the relative rate of increase with more [Formula: see text] . Benzene, toluene, ethylbenzene and xylene did not affect k1,PFOA even at 40 times higher molar concentrations than PFOA. A modeling approach to explore pathways strongly supported that for 6:2 FTSA, both the ethyl linkage and CF2-CH2 bond of 6:2 FTSA oxidize simultaneously, resulting in a ratio of ∼25/75 PFHpA/PFHxA. The effectiveness of heat-activated [Formula: see text] on PFOA oxidation was reduced in a soil slurry; therefore, repeated persulfate injections are required to efficiently achieve complete oxidation in the field. However, PFOS remained unaltered even at higher activation temperatures, thus limiting the sole use of heat-activated persulfate for perfluoroalkyl substances removal in the field. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of carbonated beverages, coffee, sports and high energy drinks, and bottled water on the in vitro erosion characteristics of dental enamel.

PubMed

Kitchens, Michael; Owens, Barry M

2007-01-01

This study evaluated the effect of carbonated and non-carbonated beverages, bottled and tap water, on the erosive potential of dental enamel with and without fluoride varnish protection. Beverages used in this study included: Coca Cola Classic, Diet Coke, Gatorade sports drink, Red Bull high-energy drink, Starbucks Frappuccino coffee drink, Dasani water (bottled), and tap water (control). Enamel surfaces were coated with Cavity Shield 5% sodium fluoride treatment varnish. Twenty-eight previously extracted human posterior teeth free of hypocalcification and caries were used in this study. The coronal portion of each tooth was removed and then sectioned transverse from the buccal to lingual surface using a diamond coated saw blade. The crown sections were embedded in acrylic resin blocks leaving the enamel surfaces exposed. The enamel surfaces were polished using 600 to 2000 grit abrasive paper and diamond paste. Test specimens were randomly distributed to seven beverage groups and comprised 4 specimens per group. Two specimens per beverage group were treated with a fluoride varnish while 2 specimens did not receive fluoride coating. Surface roughness (profilometer) readings were performed at baseline (prior to fluoride treatment and immersion in the beverage) and again, following immersion for 14 days (24 hours/day). The test beverages were changed daily and the enamel specimens were immersed at 37 degrees C. Surface roughness data was evaluated using multiple factor ANOVA at a significance level of p<0.05. Results showed that Coca-Cola Classic, Gatorade and Red Bull with/without fluoride revealed the highest post-treatment surface roughness measurements. Coca-Cola Classic, Diet Coke, Gatorade, and Red Bull all showed significantly higher post treatment readings than StarBucks coffee, Dasani water, and tap water. Fluoride varnish was not a significant impact factor; however, beverage (type) and exposure time were significant impact variables. Both carbonated and non-carbonated beverages displayed a significant erosive effect on dental enamel; however, fluoride varnish treatments did not demonstrate a significant protective influence on enamel surfaces.

The effect of CO2 laser irradiation plus fluoride dentifrice on the inhibition of secondary caries on root surfaces adjacent to glass ionomer cement or composite resin restorations

NASA Astrophysics Data System (ADS)

Rodrigues, S. R.; Moraes, M.; Hanashiro, F. S.; Youssef, M. N.; Brugnera Junior, A.; Nobre-dos-Santos, M.; de Souza-Zaroni, W. C.

2016-02-01

Although the cariostatic effects of CO2 laser on the root surface have been shown, there is scarce information regarding its effects on root secondary caries. The objective of this research was to investigate the effect of the association of CO2 laser and a fluoride dentifrice on the inhibition of secondary caries on root surfaces adjacent to composite-resin or glass-ionomer-cement restorations. Dental blocks of human roots were divided into two groups: composite resin (CR) or glass ionomer cement (GIC). Subsequently, the blocks were divided into four subgroups (n  =  10): C, non-fluoride dentifrice; FD, fluoride dentifrice; L, CO2 laser with an energy density of 6.0 J cm-2  +  non-fluoride dentifrice; and L  +  FD, CO2 laser  +  fluoride dentifrice. The blocks were subjected to pH cycling to simulate a high cariogenic challenge. Dental demineralization around the restorations was quantified by microhardness analysis. The results were subjected to analysis of variance (ANOVA) and the Tukey-Kramer test (p  ⩽  0.05). As for mineral loss, it can be observed that all the groups that were treated with a fluoride dentifrice and laser, used alone or not, were statistically similar and superior to the RC-C group. It was concluded that CO2 laser irradiation and a fluoride dentifrice used alone or combined with each other are efficient surface treatments for preventing secondary root caries, regardless of the restorative material used.

Immunoexcitotoxicity as the central mechanism of etiopathology and treatment of autism spectrum disorders: A possible role of fluoride and aluminum

PubMed Central

Strunecka, Anna; Blaylock, Russell L.; Patocka, Jiri; Strunecky, Otakar

2018-01-01

Our review suggests that most autism spectrum disorder (ASD) risk factors are connected, either directly or indirectly, to immunoexcitotoxicity. Chronic brain inflammation is known to enhance the sensitivity of glutamate receptors and interfere with glutamate removal from the extraneuronal space, where it can trigger excitotoxicity over a prolonged period. Neuroscience studies have clearly shown that sequential systemic immune stimulation can activate the brain's immune system, microglia, and astrocytes, and that with initial immune stimulation, there occurs CNS microglial priming. Children are exposed to such sequential immune stimulation via a growing number of environmental excitotoxins, vaccines, and persistent viral infections. We demonstrate that fluoride and aluminum (Al3+) can exacerbate the pathological problems by worsening excitotoxicity and inflammation. While Al3+ appears among the key suspicious factors of ASD, fluoride is rarely recognized as a causative culprit. A long-term burden of these ubiquitous toxins has several health effects with a striking resemblance to the symptoms of ASD. In addition, their synergistic action in molecules of aluminofluoride complexes can affect cell signaling, neurodevelopment, and CNS functions at several times lower concentrations than either Al3+ or fluoride acting alone. Our review opens the door to a number of new treatment modes that naturally reduce excitotoxicity and microglial priming. PMID:29721353

Hydrogeochemical processes controlling changes in fluoride ion concentration within alluvial and hard rock aquifers in a part of a semi-arid region of Northern India

NASA Astrophysics Data System (ADS)

Singh, Priyadarshini; Ashthana, Harshita; Rena, Vikas; Kumar, Pardeep; Mukherjee, Saumitra

2017-04-01

Geochemical signatures from alluvial and hard rock aquifers in a part of Northern India elucidate the chemical processes controlling fluctuations in fluoride ion concentration linked to changes in major ion groundwater chemistry. Majority of samples from the hard rock and the alluvial aquifers for pre-monsoon show both carbonate and silicate weathering, ion exchange, evaporation and rock water interaction as the processes controlling major ion chemistry whereas for post monsoon samples, contribution of silicate weathering and ion exchange process were observed. Evaporative processes causing the increase in Na+ ion concentration in premonsoon enhance the reverse ion exchange processes causing increase in Ca2+ ions which impedes fluorite mineral dissolution in the premonsoon groundwater samples within the study area. Alternately, it is observed that the removal of Ca2+ ion from solution plays a key role in increase in fluorite mineral dissolution despite its saturation in groundwater in the postmonsoon samples. Also, ion exchange process on clay surfaces is more pronounced in the postmonsoon samples leading to the uptake of Ca2+ ion upon release of Na+ and K+ ion in solution. Ca2+ ion concentration is inversely correlated with F- ion concentration in both the aquifers in the postmonsoon season validating the role of calcite precipitation as a major reason for the fluoride ion increase. Moreover, increase in silicate weathering in the postmonsoon samples leads to increase in clay particles acting as suitable sites for ion exchange enhancing Ca2+ removal from groundwater. Cationic dominance of Na+ ion in the post monsoon samples also validates the occurrence of this process. Collectively, these processes set the ideal conditions for increase in the fluoride ion concentration particularly in the alluvium aquifer waters in the postmonsoon season Keywords: geochemistry, ion-exchange, rock-water interaction, mineral dissolution, weathering.

Ternary metal fluorides as high-energy cathodes with low cycling hysteresis

PubMed Central

Wang, Feng; Kim, Sung-Wook; Seo, Dong-Hwa; Kang, Kisuk; Wang, Liping; Su, Dong; Vajo, John J.; Wang, John; Graetz, Jason

2015-01-01

Transition metal fluorides are an appealing alternative to conventional intercalation compounds for use as cathodes in next-generation lithium batteries due to their extremely high capacity (3–4 times greater than the current state-of-the-art). However, issues related to reversibility, energy efficiency and kinetics prevent their practical application. Here we report on the synthesis, structural and electrochemical properties of ternary metal fluorides (M1yM21-yFx: M1, M2=Fe, Cu), which may overcome these issues. By substituting Cu into the Fe lattice, forming the solid–solution CuyFe1-yF2, reversible Cu and Fe redox reactions are achieved with surprisingly small hysteresis (<150 mV). This finding indicates that cation substitution may provide a new avenue for tailoring key electrochemical properties of conversion electrodes. Although the reversible capacity of Cu conversion fades rapidly, likely due to Cu+ dissolution, the low hysteresis and high energy suggest that a Cu-based fluoride cathode remains an intriguing candidate for rechargeable lithium batteries. PMID:25808876

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Sungho, E-mail: shochoi@krict.re.kr; Park, Byung-Yoon; Jung, Ha-Kyun

Highlights: {yields} Systematic study of the fluorides doped solution-processed ZnO thin films via the luminescence and electrical behaviors. {yields} Defect-related visible emission bands are affected by annealing ambient and fluoride addition. {yields} Adding lithium fluoride followed by annealing in oxygen ambient leads to a controlled defect density with proper TFT performance. -- Abstract: To develop an efficient channel layer for thin film transistors (TFTs), understanding the defect-related luminescence and electrical property is crucial for solution-processed ZnO thin films. Film growth with the fluorides addition, especially using LiF, followed by the oxygen ambient post-annealing leads to decreased defect-related emission as wellmore » as enhanced switching property. The saturation mobility and current on/off ratio are 0.31 cm{sup 2} V{sup -1} s{sup -1} and 1.04 x 10{sup 3}. Consequently, we can visualize an optimized process condition and characterization method for solution-processed TFT based on the fluorine-doped ZnO film channel layer by considering the overall emission behavior.« less

Fabrication and Characterization of Polyvinylidene Fluoride Microfilms for Microfluidic Applications

NASA Astrophysics Data System (ADS)

Rao, Yammani Venkat Subba; Raghavan, Aravinda Narayanan; Viswanathan, Meenakshi

2016-10-01

The ability to create patterns of piezo responsive material on smooth substrate is an important method to develop efficient microfluidic mixers. This paper reports the fabrication of Poly vinylidene fluoride microfilms using spin-coating on smooth glass surface. The suitable crystalline phases, surface morphology and microstructural properties of the PVDF films have been investigated. We found that films of average thickness 10μm, had average roughness of 0.13μm. These PVDF films are useful in microfluidic mixer applications.

DISSOLUTION OF ZIRCONIUM-CONTAINING FUEL ELEMENTS

DOEpatents

Horn, F.L.

1961-12-12

Uranium is recovered from spent uranium fuel elements containing or clad with zirconium. These fuel elements are placed in an anhydrous solution of hydrogen fluoride and nitrogen dioxide. Within this system uranium forms a soluble complex and zirconium forms an insoluble complex. The uranium can then be separated, treated, and removed from solution as uranium hexafluoride. (AEC)

Novel uses of rice-husk-ash (a natural silica-carbon matrix) in low-cost water purification applications

NASA Astrophysics Data System (ADS)

Malhotra, Chetan; Patil, Rajshree; Kausley, Shankar; Ahmad, Dilshad

2013-06-01

Rice-husk-ash is used as the base material for developing novel compositions to deal with the challenge of purifying drinking water in low-income households in India. For example, rice-husk-ash cast in a matrix of cement and pebbles can be formed into a filtration bed which can trap up to 95% of turbidity and bacteria present in water. This innovation was proliferated in villages across India as a do-it-yourself rural water filter. Another innovation involves embedding silver nanoparticles within the rice husk ash matrix to create a bactericidal filtration bed which has now been commercialized in India as a low-cost for-profit household water purifier. Other innovations include the impregnation of rice-husk-ash with iron hydroxide for the removal of arsenic from water and the impregnation of rice-husk ash with aluminum hydroxide for the removal of fluoride ions from water which together have the potential to benefit over 100 million people across India who are suffering from the health effects of drinking groundwater contaminated with arsenic and fluoride.

Hydrogen mitigation in submerged arc welding

NASA Astrophysics Data System (ADS)

Klimowicz, Steven

With the role of hydrogen in weld metal well understood in its relation to cold cracking, there has been a push to produce welds with lower and lower diffusible hydrogen contents. The push for lower diffusible hydrogen contents has placed pressure on consumables manufactures to create consumables that can achieve the requirements for lower diffusible hydrogen content. Currently EM12K flux is produced so that it can achieve below 4 ml of diffusible hydrogen for every 100g of weld metal deposited (ml/100g) for submerged arc welding (SAW). The recent trend for industry is to preferentially achieve diffusible hydrogen contents below 3 ml/100g. Making it necessary to find a way to modify the flux to achieve a lower diffusible hydrogen content for the welds it produces. To achieve this goal a two phase plan was developed. The first phase was to characterize the entire welding system for hydrogen. Since the goal of the project is hydrogen mitigation, any amount of hydrogen that could be reduced is helpful and therefore must first be discovered. Sources of hydrogen may be found by analyzing the welding wire and base metal, as well as breaking the flux down into its components and production steps. The wire was analyzed for total hydrogen content as was the base metal. The flux and its components were analyzed using differential thermal analysis-simultaneous thermal analysis (DTA-STA) and later vacuum degassing for moisture content. The analysis of the wire showed that the copper coating on the wire was the largest contributor of hydrogen. There was lubricant present on the wire surface as well, but it did not contribute as much as the copper coating. It was found that a simple low temperature baking of the wire was enough to remove the lubricant and coating moisture. The base metal was found to have a similar total hydrogen content to that of the wire. The breakdown of the flux and production process for moisture content analysis revealed that the production process removes the moisture that is added by the water based binder. The second phase of the project was to modify the flux with fluoride additions to remove hydrogen from the arc while welding. The introduction of fluorine into the arc would lower the amount of hydrogen that may be absorbed as diffusible hydrogen by the weld metal. To select the fluorides a series of thermodynamic calculations were performed as well as simple tests to determine the fluorides behavior in a welding arc and flux. From these tests the following fluorides were selected to be used to be added to EM12K flux as oneweight percent additions: SrF 2, K2TiF6, K2SiF6, and LiF. Welds were then run with the experimental fluxes according to AWS A4.3 standard for diffusible hydrogen testing. From these tests it was found that none experimental fluxes were able to achieve a diffusible hydrogen content lower than the original EM12K flux. It was also found that fluoride reduction in a simple flux is a better predictor of fluoride effectiveness than decomposition temperature.

Development of high-efficiency solar cells on silicon web

NASA Technical Reports Server (NTRS)

Rohatgi, A.; Meier, D. L.; Campbell, R. B.; Seidensticker, R. G.; Rai-Choudhury, P.

1985-01-01

High-efficiency dendritic cells were discussed. The influence of twin planes and heat treatment on the location and effect of trace impurities was of particular interest. Proper heat treatment often increases efficiency by causing impurities to pile up at twin planes. Oxide passivation had a beneficial effect on efficiency. A very efficient antireflective (AR) coating of zinc selenide and magnesium fluoride was designed and fabricated. An aluminum back-surface reflector was also effective.

Noninvasive dentistry: a dream or reality?

PubMed

Clarkson, B H; Exterkate, R A M

2015-01-01

Various caries prevention and repair strategies are reviewed in this article ranging from the use of fluoride to nanohydroxyapatite particles. Several of the strategies which combine fluoride and calcium and phosphate treatments have both in vitro and in vivo data showing them to be efficacious if the surface integrity of the lesion is not breached. Once this has occurred, the rationale for cutting off the nutrient supplies to the pathogenic bacteria without the removal of the infected dentine, a noninvasive restorative technique, is discussed using existing clinical studies as examples. Finally two novel noninvasive restorative techniques using fluorohydroxyapatite crystals are described. The need for clinical data in support of emerging caries-preventive and restorative strategies is emphasized. 2015 S. Karger AG, Basel

DRY FLUORINE SEPARATION METHOD

DOEpatents

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

1959-05-19

Preparation and separation of U/sup 233/ by irradiation of ThF/sub 4/ is described. During the neutron irradiation to produce Pa/sup 233/ a fluorinating agent such as HF, F/sub 2/, or HF + F/sub 2/ is passed through the ThF/sub 4/ powder to produce PaF/sub 5/. The PaF/sub 5/, being more volatile, is removed as a gas and allowed to decay radioactively to U/sup 233/ fluoride. A batch procedure in which ThO/sub 2/ or Th metal is irradiated and fluorinated is suggested. Some Pa and U fluoride volatilizes away. Then the remainder is fluorinated with F/sub 2/ to produce very volatile UF/sub 6/ which is recovered. (T.R.H.)

Development of an all-metal thick film cost effective metallization system for solar cells

NASA Technical Reports Server (NTRS)

Ross, B.; Parker, J.

1982-01-01

Electrodes made with pastes produced under the previous contract were analyzed and compared with raw materials. A needle-like structure observed on the electroded solar cell was identified as eutectic copper-silicon, a phase considered to benefit the electrical and metallurgical properties of the contact. Electrodes made from copper fluorocarbon and copper silver fluoride also contained this phase but had poor adhesion. A liquid medium, intended to provide transport during carbon fluoride decomposition was incorporated into the paste resulting in better adhesion. The product survived preliminary environmental tests. A 2 cm by 2 cm solar cell made with fluorocarbon activated copper electrodes and gave 7% AMI efficiency (without AR coating). Both silver fluoride and fluorocarbon screened paste electrodes can be produced for approximately $0.04 per watt.

Ammonium fluoride as a mobile phase additive in aqueous normal phase chromatography.

PubMed

Pesek, Joseph J; Matyska, Maria T

2015-07-03

The use of ammonium fluoride as a mobile phase additive in aqueous normal phase chromatography with silica hydride-based stationary phases and mass spectrometry detection is evaluated. Retention times, peak shape, efficiency and peak intensity are compared to the more standard additives formic acid and ammonium formate. The test solutes were NAD, 3-hydroxyglutaric acid, α-ketoglutaric acid, p-aminohippuric acid, AMP, ATP, aconitic acid, threonine, N-acetyl carnitine, and 3-methyladipic acid. The column parameters are assessed in both the positive and negative ion detection modes. Ammonium fluoride is potentially an aggressive mobile phase additive that could have detrimental effects on column lifetime. Column reproducibility is measured and the effects of switching between different additives are also tested. Copyright © 2015 Elsevier B.V. All rights reserved.

Potential of nano-silver fluoride for tooth enamel caries prevention

NASA Astrophysics Data System (ADS)

Silva, Amitis V. C.; Mota, Cláudia C. B. O.; Teixeira, Joás. A.; Lins, Emery C.; Gomes, Anderson S. L.; Rosenblatt, Aronita

2018-02-01

This ex vivo study evaluated the efficiency of nano-silver fluoride (NSF) to enamel remineralization of deciduous teeth submitted to a high cariogenic challenge. 33 specimens of sound enamel were distributed into three groups: treated with sodium fluoride, with NSF, and deionized water. All specimens were submitted to microhardness test before chemical caries induction; post-induction of caries; and post-cariogenic challenge. The high cariogenic challenge was carried out in 14 daily cycles. There was no significant statistical difference (p=0.958) of enamel microhardness between NSFtreated and NaF-treated specimens. However, it presented significant difference between water-treated specimens and both NSF-treated and NaF-treated specimens (p=0.003).Furthermore, optical coherence tomography was employed for caries diagnosis, as it can be used in clinical environment.

Cariogenic potential of cows', human and infant formula milks and effect of fluoride supplementation.

PubMed

Peres, Regina Celia Rocha; Coppi, Luciane Cristina; Volpato, Maria Cristina; Groppo, Francisco Carlos; Cury, Jaime Aparecido; Rosalen, Pedro Luiz

2009-02-01

The aim of the present study was to evaluate the cariogenicity of cows', human and infant formula milks, supplemented or not with fluoride, in rats. Sixty female Wistar rats were desalivated and infected with Streptococcus sobrinus 6715.Animals were divided into six groups: group 1, sterilised deionised distilled water (SDW; negative control); group 2, 5 % sucrose added to SDW (positive control); group 3, human milk; group 4, cows' milk; group 5, Ninho(R) formula reconstituted with SDW; group 6, Ninho(R) formula reconstituted with 10 parts per million F and SDW. At day 21 the animals were killed and their jaws removed to quantify total cultivable microbiota, Strep. sobrinus and dental caries. The concentration of carbohydrate and fluoride in the milks was analysed. The Kruskal-Wallis test (alpha = 5 %) was used to analyse the data. The caries score by the milk formula was as high as that provoked by sucrose. Regarding smooth-surface caries, human milk was statistically more cariogenic than cows' milk, which did not differ from the SDW and the Ninho(R) with fluoride (P>0.05). Groups 2-6 showed higher Strep. sobrinus counts when compared with the negative control group (P < 0.05) but no statistically significant difference was found among them (P>0.05). HPLC analysis showed that infant formula had 9.3 % sucrose and 3.6 % reducing sugars. The infant formula should be considered cariogenic due to the sugars found in it, but fluoride supplementation reduced its cariogenic effect. The human milk was more cariogenic than the cows' milk but not as much as the formula milk.

Solid-phase zirconium and fluoride species in alkaline zircaloy cladding waste at Hanford.

PubMed

Reynolds, Jacob G; Huber, Heinz J; Cooke, Gary A; Pestovich, John A

2014-08-15

The United States Department of Energy Hanford Site, near Richland, Washington, USA, processed plutonium between 1944 and 1987. Fifty-six million gallons of waste of various origins remain, including waste from removing zircaloy fuel cladding using the so-called Zirflex process. The speciation of zirconium and fluoride in this waste is important because of the corrosivity and reactivity of fluoride as well as the (potentially) high density of Zr-phases. This study evaluates the solid-phase speciation of zirconium and fluoride using X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). Two waste samples were analyzed: one waste sample that is relatively pure zirconium cladding waste from tank 241-AW-105 and another that is a blend of zirconium cladding wastes and other high-level wastes from tank 241-C-104. Villiaumite (NaF) was found to be the dominant fluoride species in the cladding waste and natrophosphate (Na7F[PO4]2 · 19H2O) was the dominant species in the blended waste. Most zirconium was present as a sub-micron amorphous Na-Zr-O phase in the cladding waste and a Na-Al-Zr-O phase in the blended waste. Some zirconium was present in both tanks as either rounded or elongated crystalline needles of Na-bearing ZrO2 that are up to 200 μm in length. These results provide waste process planners the speciation data needed to develop disposal processes for this waste. Copyright © 2014 Elsevier B.V. All rights reserved.

Intense laser beams; Proceedings of the Meeting, Los Angeles, CA, Jan. 23, 24, 1992

NASA Technical Reports Server (NTRS)

Wade, Richard C. (Editor); Ulrich, Peter B. (Editor)

1992-01-01

Various papers on intense laser beams are presented. Individual topics addressed include: novel methods of copper vapor laser excitation, UCLA IR FEL, lasing characteristics of a large-bore copper vapor laser (CVL), copper density measurement of a large-bore CVL, high-power XeCl excimer laser, solid state direct-drive circuit for pumping gas lasers, united energy model for FELs, intensity and frequency instabilities in double-mode CO2 lasers, comparison of output power stabilities of CO and CO2 lasers, increasing efficiency of sealed-off CO lasers, thermal effects in singlet delta oxygen generation, optical extraction from the chemical oxygen-iodine laser medium, generation and laser diagnostic analysis of bismuth fluoride. Also discussed are: high-Q resonator design for an HF overtone chemical lasers, improved coatings for HF overtone lasers, scaled atmospheric blooming experiment, simulation on producing conjugate field using deformable mirrors, paraxial theory of amplitude correction, potential capabilities of adaptive optical systems in the atmosphere, power beaming research at NASA, system evaluations of laser power beaming options, performance projections for laser beam power to space, independent assessment of laser power beaming options, removal of atmospheric CFCs by lasers, efficiency of vaporization cutting by CVL.

Optimizing adsorption of fluoride from water by modified banana peel dust using response surface modelling approach

NASA Astrophysics Data System (ADS)

Bhaumik, Ria; Mondal, Naba Kumar

2016-06-01

The present work highlighted the effective application of banana peel dust (BPD) for removal of fluoride (F-) from aqueous solution. The effects of operating parameters such as pH, initial concentration, adsorbent dose, contact time, agitation speed and temperature were analysed using response surface methodology. The significance of independent variables and their interactions were tested by the analysis of variance and t test statistics. Experimental results revealed that BPD has higher F- adsorption capacity (17.43, 26.31 and 39.5 mg/g). Fluoride adsorption kinetics followed pseudo-second-order model with high correlation of coefficient value (0.998). On the other hand, thermodynamic data suggest that adsorption is favoured at lower temperature, exothermic in nature and enthalpy driven. The adsorbents were characterised through scanning electron microscope, Fourier transform infrared spectroscopy and point of zero charges (pHZPC) ranges from pH 6.2-8.2. Finally, error analysis clearly demonstrates that all three adsorbents are well fitted with Langmuir isotherm compared to the other isotherm models. The reusable properties of the material support further development for commercial application purpose.

Infrared Emissivity of Tin upon Release of a 25 GPa Shock into a LiF Window

DOE Office of Scientific and Technical Information (OSTI.GOV)

Turley, W. D., Holtkamp, D. B., Marshall, B. R., Stevens, G. D., Veeser, L. R.

We measured the emissivity of a tin sample at its interface with a lithium-fluoride window upon release of a 25 GPa shock wave from the tin into the window. Measurements were made over four wavelength bands between 1.2 and 5.4 μm. Thermal emission backgrounds from the tin, glue, and lithium fluoride were successfully removed from the reflectance signals. Emissivity changes for the sample, which was initially nearly specular, were small except for the longest wavelength band, where uncertainties were high because of poor signal-to-noise ratio at that wavelength. A thin glue layer, which bonds the sample to the window, wasmore » found to heat from reverberations of the shock wave between the tin and the lithium fluoride. At approximately 3.4 μm the thermal emission from the glue was large compared to the tin, allowing a good estimate of the glue temperature from the thermal radiance. The glue appears to remain slightly colder than the tin, thereby minimizing heat conduction into or out of the tin immediately after the shock passage.« less

Innovative Monitoring of Atmospheric Gaseous Hydrogen Fluoride

PubMed Central

Bonari, Alessandro; Pompilio, Ilenia; Monti, Alessandro; Arcangeli, Giulio

2016-01-01

Hydrogen fluoride (HF) is a basic raw material for a wide variety of industrial products, with a worldwide production capacity of more than three million metric tonnes. A novel method for determining particulate fluoride and gaseous hydrogen fluoride in air is presented herewith. Air was sampled using miniaturised 13 mm Swinnex two-stage filter holders in a medium-flow pumping system and through the absorption of particulate fluoride and HF vapours on cellulose ester filters uncoated or impregnated with sodium carbonate. Furthermore, filter desorption from the holders and the extraction of the pentafluorobenzyl ester derivative based on solid-phase microextraction were performed using an innovative robotic system installed on an xyz autosampler on-line with gas chromatography (GC)/mass spectrometry (MS). After generating atmospheres of a known concentration of gaseous HF, we evaluated the agreement between the results of our sampling method and those of the conventional preassembled 37 mm cassette (±8.10%; correlation coefficient: 0.90). In addition, precision (relative standard deviation for n = 10, 4.3%), sensitivity (0.2 μg/filter), and linearity (2.0–4000 μg/filter; correlation coefficient: 0.9913) were also evaluated. This procedure combines the efficiency of GC/MS systems with the high throughput (96 samples/day) and the quantitative accuracy of pentafluorobenzyl bromide on-sample derivatisation. PMID:27829835

A novel smart supramolecular organic gelator exhibiting dual-channel responsive sensing behaviours towards fluoride ion via gel-gel states.

PubMed

Mehdi, Hassan; Pang, Hongchang; Gong, Weitao; Dhinakaran, Manivannan Kalavathi; Wajahat, Ali; Kuang, Xiaojun; Ning, Guiling

2016-07-07

A novel smart supramolecular organic gelator G-16 containing anion and metal-coordination ability has been designed and synthesized. It shows excellent and robust gelation capability as a strong blue fluorescent supramolecular organic gel OG in DMF. Addition of Zn(2+) produced Zn(2+)-coordinated supramolecular metallogel OG-Zn. Organic gel OG and organometallic gel OG-Zn exhibited efficient and different sensing behaviors towards fluoride ion due to the variation in self-assembling nature. Supramolecular metallogel OG-Zn displayed specific selectivity for fluoride ion and formed OG-Zn-F with dramatic color change from blue to blue green in solution and gel to gel states. Furthermore after directly addition of fluoride into OG produced fluoride containing organic gel OG-F with drastically modulation in color from blue to greenish yellow fluorescence via strong aggregation-induced emission (AIE) property. A number of experiments were conducted such as FTIR, (1)H NMR, and UV/Vis spectroscopies, XRD, SEM and rheology. These results revealed that the driving forces involved in self-assembly of OG, OG-Zn, OG-Zn-F and OG-F were hydrogen bonding, metal coordination, π-π interactions, and van der Waal forces. In contrast to the most anion responsive gels, particularly fluoride ion responsive gels showed gel-sol state transition on stimulation by anions, the gel state of OG and OG-Zn did not show any gel-to-sol transition during the whole F(-) response process.

Pyrrole based Schiff bases as colorimetric and fluorescent chemosensors for fluoride and hydroxide anions.

PubMed

Velmathi, Sivan; Reena, Vijayaraghavan; Suganya, Sivalingam; Anandan, Sambandam

2012-01-01

An efficient colorimetric sensor with pyrrole-NH moiety as binding site and nitro group as a signaling unit has been synthesized by a one step procedure and characterized by spectroscopic techniques, which displays excellent selectivity and sensitivity for fluoride and hydroxide ions. The hydrogen bonding with these anions provides remarkable colorimetric responses. (1)H NMR and FT IR studies has been carried out to confirm the hydrogen bonding. UV-vis and fluorescence spectral changes can be exploited for real time and on site application.

Pilot Plant Makes Oxygen Difluoride

NASA Technical Reports Server (NTRS)

Humphrey, Marshall F.; Lawton, Emil A.

1989-01-01

Pilot plant makes oxygen difluoride highly-energetic, space-storable oxidizer not made commercially. Designed to handle reactants, product, and byproduct, most of which highly reactive, corrosive, and toxic. Oxygen difluoride evolves continuously from reactor containing potassium hydroxide in water at 10 degree C. Collection tanks alternated; one filled while other drained to storage cylinder. Excess OF2 and F2 dissipated in combustion of charcoal in burn barrel. Toxic byproduct, potassium fluoride, reacted with calcium hydroxide to form nontoxic calcium fluoride and to regenerate potassium hydroxide. Equipment processes toxic, difficult-to-make substance efficiently and safely.

Role of Spirulina in mitigating hemato-toxicity in Swiss albino mice exposed to aluminum and aluminum fluoride.

PubMed

Sharma, Shweta; Sharma, K P; Sharma, Subhasini

2016-12-01

Aluminum is ingested through foods, water, air, and even drugs. Its intake is potentiated further through foods and tea prepared in aluminum utensils and Al salt added in the drinking water for removal of suspended impurities and also fluoride in the affected areas. The ameliorating role of a blue green alga Spirulina is well documented to various pollutants in the animal models. We, therefore, examined its protective role (230 mg/kg body weight) on the hematology of male Swiss albino mice treated with aluminum (sub-acute = 78.4 mg/kg body weight for 7 days, sub-chronic = 7.8 mg/kg body weight for 90 days) and aluminum fluoride (sub-acute = 103 mg/kg body weight, sub-chronic = 21 mg/kg body weight), along with their recovery after 90 days of sub-chronic exposure. This study revealed significant reduction in the values of RBC (5-18 %), Hb (15-17 %), PCV (8-14 %), and platelets (26-36 %), and increase in WBC (54-124 %) in the treated mice, particularly after sub-acute exposure. Aluminum fluoride was comparatively more toxic than aluminum. Further, Spirulina supplement not only alleviated toxicity of test chemicals in Swiss albino mice but also led to their better recovery after withdrawal.

Caries Epidemiology and Community Dentistry: Chances for Future Improvements in Caries Risk Groups. Outcomes of the ORCA Saturday Afternoon Symposium, Greifswald, 2014. Part 1.

PubMed

Splieth, Christian H; Christiansen, Jette; Foster Page, Lyndie A

2016-01-01

This paper reviews the first part of the outcomes of the ORCA Saturday Afternoon Symposium 2014 dealing with 'caries epidemiology and community dentistry: chances for future improvements in caries risk groups'. After the caries decline in many countries, there are remaining pockets of higher caries levels, mostly in the primary dentition and/or linked to a low socio-economic status (SES). The review into the evidence of caries-preventive measures clearly points to the use of fluorides, especially toothbrushing with fluoridated toothpaste and collective measures such as water fluoridation. In contrast to several unsuccessful high-risk approaches, community and public health programmes seem to be able to ensure a population-wide access and compliance in risk groups. Their simple and evidence-based measures mostly combine regular plaque removal and fluoride applications via toothbrushing, at least for children and adolescents. For the future, the common risk factor approach which addresses associations between oral health, social deprivation, diet, hygiene, smoking, alcohol use and stress should lead to combined efforts with other community health and education specialists. Further engagement with public policy, community leaders and administration is needed in order to strengthen healthy choices and behaviour, e.g. in 'healthy' schools and kindergartens. It seems advisable that these population programmes also aim at improving upstream factors. © 2016 S. Karger AG, Basel.

Porous Electrospun Fibers Embedding TiO2 for Adsorption and Photocatalytic Degradation of Water Pollutants.

PubMed

Lee, Chang-Gu; Javed, Hassan; Zhang, Danning; Kim, Jae-Hong; Westerhoff, Paul; Li, Qilin; Alvarez, Pedro J J

2018-04-03

Using a bipolymer system consisting of polyvinylpyrrolidone (PVP) and poly(vinylidene fluoride) (PVDF), P25-TiO 2 was immobilized into thin film mats of porous electrospun fibers. Pores were introduced by dissolving sacrificial PVP to increase surface area and enhance access to TiO 2 . The highest photocatalytic activity was achieved using a PVDF:PVP weight ratio of 2:1. Methylene blue (MB) was used to visualize contaminant removal, assess the sorption capacity (5.93 ± 0.23 mg/g) and demonstrate stable removal kinetics ( k MB > 0.045 min -1 ) under UVA irradiation (3.64 × 10 -9 einstein/cm 2 /s) over 10 cycles. Treatment was also accomplished via sequential MB sorption in the dark and subsequent photocatalytic degradation under UVA irradiation, to illustrate that these processes could be uncoupled to overcome limited light penetration. The photocatalytic mat degraded bisphenol A and 17α-ethynylestradiol in secondary wastewater effluent (17 mg TOC/L), and (relative to TiO 2 slurry) immobilization of TiO 2 in the mat mitigated performance inhibition by co-occurring organics that scavenge oxidation capacity. This significantly lowered the electrical energy-per-order of reaction (EEO) needed to remove such endocrine disruptors in the presence of oxidant scavenging/inhibitory organics. Thus, effective TiO 2 immobilization into polymers with affinity toward specific priority pollutants could both increase the efficiency and reduce energy requirements of photocatalytic water treatment.

Geogenic fluoride and arsenic contamination in the groundwater environments in Tanzania

NASA Astrophysics Data System (ADS)

Bhattacharya, Prosun; Lesafi, Fina; Filemon, Regina; Ligate, Fanuel; Ijumulana, Julian; Mtalo, Felix

2016-04-01

Adequate, safe and accessible drinking water is an important aspect to human health worldwide. Understanding this importance, the Tanzanian Government has initiated a number of programmes to ensure access to high quality water by the citizens. However, elevated concentration of geochemical pollutants in many drinking water sources pose a serious challenge to water suppliers and users in the country. Fluoride is a widespread drinking water contaminant of geogenic origin occuring in both surface- and groundwater around volcanic mountains and many parts within the East African Rift Valley in regions including Arusha (10 mg/L), Shinyanga (2.9 mg/L) and Singida (1.8 mg/L). An estimated 90% of the population living along the Rift Valley region are affected by dental or skeletal fluorosis and bone crippling because of long term exposure to very high levels of fluoride in drinking water sources. In the mining areas within Lake Victoria basin, groundwater wit elevated concentrations of arsenic has been discovered over an extended area. Most of these geochemical and naturally occurring drinking water pollutants are patchy with uncertainities in their spatial and temporal distribution patterns. The adverse health effects of skin disorder and cancer due to an elevated As concentration are reported from the North Mara gold and Geita mining areas in the Lake Victoria basin. About 30% of the water sources used for drinking in Tanzania exceed the WHO guideline values of fluoride (1.5 mg/L) and arsenic (10 μg/L). There is a scarcity of baseline information on the water quality data especially on geogenic contaminants in the groundwater and surface water as potable sources. This information is crucial in exploring sources of safe drinking water aquifers, associated human health risks of fluoride and arsenic pollution. using Laboratory based studies during the past two decades have shown promising results on the removal of fluoride and arsenic using locally available adsorbent materials such as pumice, bauxite, ferralsols and bone char. Developing innovative technologies, pilot-scale implementation and scaling-up water purification based on the locally available adsorbents is thus necessary to safeguard the public health for communities exposed to high levels of fluoride and arsenic in drinking water.

Reusable electrochemical cell for rapid separation of [18F]fluoride from [18O]water for flow-through synthesis of 18F-labeled tracers

PubMed Central

Sadeghi, Saman; Liang, Vincent; Cheung, Shilin; Woo, Suh; Wu, Curtis; Ly, Jimmy; Deng, Yuliang; Eddings, Mark; van Dam, R. Michael

2015-01-01

A brass-platinum electrochemical micro flow cell was developed to extract [18F]fluoride from an aqueous solution and release it into an organic based solution, suitable for subsequent radio-synthesis, in a fast and reliable manner. This cell does not suffer electrode erosion and is thus reusable while operating faster by enabling increased voltages. By optimizing temperature, trapping and release potentials, flow rates, and electrode materials, an overall [18F]fluoride trapping and release efficiency of 84±5% (n=7) was achieved. X-ray photoelectron spectroscopy (XPS) was used to analyze electrode surfaces of various metal-metal systems and the findings were correlated with the performance of the electrochemical cell. To demonstrate the reactivity of the released [18F]fluoride, the cell was coupled to a flow-through reactor and automated synthesis of [18F]FDG with a repeatable decay-corrected yield of 56±4% (n=4) was completed in <15 min. A multi-human dose of 5.92 GBq [18F]FDG was also demonstrated. PMID:23474380

Ternary metal fluorides as high-energy cathodes with low cycling hysteresis

DOE PAGES

Wang, Feng; Kim, Sung -Wook; Seo, Dong -Hwa; ...

2015-03-26

In this study, transition metal fluorides are an appealing alternative to conventional intercalation compounds for use as cathodes in next-generation lithium batteries due to their extremely high capacity (3–4 times greater than the current state-of-the-art). However, issues related to reversibility, energy efficiency and kinetics prevent their practical application. Here we report on the synthesis, structural and electrochemical properties of ternary metal fluorides (M 1 yM 2 1-yF x: M 1, M 2 = Fe, Cu), which may overcome these issues. By substituting Cu into the Fe lattice, forming the solid–solution Cu yFe 1-yF 2, reversible Cu and Fe redox reactionsmore » are achieved with surprisingly small hysteresis (<150 mV). This finding indicates that cation substitution may provide a new avenue for tailoring key electrochemical properties of conversion electrodes. In conclusion, although the reversible capacity of Cu conversion fades rapidly, likely due to Cu + dissolution, the low hysteresis and high energy suggest that a Cu-based fluoride cathode remains an intriguing candidate for rechargeable lithium batteries.« less

Manufacturing of Dysprosium-Iron Alloys by Electrolysis in Fluoride-Based Electrolytes: Oxide Solubility Determinations

NASA Astrophysics Data System (ADS)

Martinez, Ana Maria; Støre, Anne; Osen, Karen Sende

2018-04-01

Electrolytic production of light rare earth elements and alloys takes place in a fluoride-based electrolyte using rare earth oxides as raw material. The optimization of this method, mainly in terms of the energy efficiency and environmental impact control, is rather challenging. Anode effects, evolution of fluorine-containing compounds, and side cathode reactions could largely be minimized by a good control of the amount of rare earth oxide species dissolved in the fluoride-based electrolyte and their dissolution rate. The oxide content of the fluoride melts REF3-LiF (RE = Nd, Dy) at different compositions and temperatures were experimentally determined by carbothermal analysis of melt samples. The highest solubility values of oxide species, added as Dy2O3 and Dy2(CO3)3, were obtained to be of ca. 3 wt pct (expressed as Dy2O3) in the case of the equimolar DyF3-LiF melt at 1323 K (1050 °C). The oxide saturation values increased with the amount of REF3 present in the molten bath and the working temperature.

Antimicrobial efficacy of amine fluoride based tooth gels compared to a toothpaste in a phase 2/step 2 in-vitro test model

PubMed Central

Schiller, Anne; Großjohann, Beatrice; Welk, Alexander; Hübner, Nils-Olaf; Braun, Dagmar; Assadian, Ojan; Kramer, Axel

2012-01-01

Introduction: The aim of the present study was to determine the antimicrobial effect of various gel formulations on plaque formation; different tooth gels were compared to a toothpaste containing comparable antimicrobial ingredients with regard to its microbiocidal activity. The study was conducted under the assumption, that a chief requirement for the prevention of plaque formation is the combination of mechanical removal and antimicrobial activity, and not the sole capability of mechanical plaque removal. Methods: Ledermix® fluoride gel as commercially available with preservative, and without preservative and perfume oils, Elmex® gelée, and Meridol® toothpaste were tested in a standardized in-vitro test modification of the quantitative suspension test EN 1040. Instead of testing in a suspension, the respective product was directly placed on a standardized contaminated sterile stainless steel disk without adding any bio-burden. 50% egg yolk in Aqua dest. was used as a neutralizer. Results: Within 1 min, Elmex® gelée showed a RF >5 log10 against S. pyogenes and S. sanguinis. Against S. mutans, a log10 RF of ≥5 was achieved after 2 min, against C. albicans after 5 min, and against P. aeruginosa after 10 min S. aureus was the most difficult organisms to be reduced. After an application time of 10 min, only a log10 RF of 2.4 was achieved. Ledermix exceeded the antimicrobial efficacy of Elmex® gelée against S. mutans and C. albicans and was already effective against these organisms after 1 min, but did not show the same antimicrobial efficacy as Elmex® gelée against P. aeruginosa. Similar to Elmex® gelée, a required reduction of >5 log10 for antimicrobials under no organic challenge was not achieved against S. aureus. Ledermix® fluoride gel without preservatives and Ledermix® fluoride gel without preservatives and perfume oil did not show the antimicrobial efficacy of the standard Ledermix® fluoride gel formulation, indicating that the observed antimicrobial efficacy is chiefly based on the preservative, and possibly the perfume oil. Compared to the tested gels, Meridol® toothpaste was less effective and reached any antimicrobial effect >5 log10 only against S. sanguinis after 10 min. Conclusion: All unmodified tested gels showed an antimicrobial effect. Because no relevant antimicrobial efficacy against plaque forming bacteria was achieved within 2 min, in practice, an anti-plaque forming effect based on the antimicrobial action of gels cannot be assumed when used in the oral cavity. However, the results of the present study indicate that the antimicrobial efficacy of gels is determined by their formulation and that for the prevention of plaque formation the combination of mechanical removal and antimicrobial activity is not the chief requirement only, but a sustained antimicrobial effect may be of greater importance. PMID:22558041

Composition and method to remove asbestos

DOE Office of Scientific and Technical Information (OSTI.GOV)

Block, J.

A composition for transforming a chrysotile asbestos-containing material into a non-asbestos material is disclosed. The composition comprises water, at least about 30% by weight of phosphoric acid, and from about 0.1 to about 4% by weight of a source of fluoride ions. A method of transforming the asbestos-containing material into a non-asbestos material using the present composition also is disclosed.

Composition and method to remove asbestos

DOEpatents

Block, J.

1998-05-19

A composition for transforming a chrysotile asbestos-containing material into a non-asbestos material is disclosed. The composition comprises water, at least about 30% by weight of phosphoric acid, and from about 0.1 to about 4% by weight of a source of fluoride ions. A method of transforming the asbestos-containing material into a non-asbestos material using the present composition also is disclosed.

40 CFR 426.116 - Pretreatment standards for new sources.

Code of Federal Regulations, 2011 CFR

2011-07-01

... the recognition that animal and vegetable oils can be adequately removed in a publicly owned treatment... (animal and vegetable) (1) (1) Oil (mineral) 260.0 130.0 TSS (1) (1) Fluoride 120.0 60.0 Lead (1) (1) pH (1) (1) English units (lb/1,000 lb of furnace pull) Oil (animal and vegetable) (1) (1) Oil 0.26 0.13...

40 CFR 426.116 - Pretreatment standards for new sources.

Code of Federal Regulations, 2010 CFR

2010-07-01

... the recognition that animal and vegetable oils can be adequately removed in a publicly owned treatment... (animal and vegetable) (1) (1) Oil (mineral) 260.0 130.0 TSS (1) (1) Fluoride 120.0 60.0 Lead (1) (1) pH (1) (1) English units (lb/1,000 lb of furnace pull) Oil (animal and vegetable) (1) (1) Oil 0.26 0.13...

The effect of increasing sodium fluoride concentrations on erosion and attrition of enamel and dentine in vitro.

PubMed

Austin, R S; Rodriguez, J M; Dunne, S; Moazzez, R; Bartlett, D W

2010-10-01

To investigate the effect of an aqueous sodium fluoride solution of increasing concentration on erosion and attrition of enamel and dentine in vitro. Enamel and dentine sections from caries-free human third molars were polished flat and taped (exposing a 3 mm x 3 mm area) before being randomly allocated to 1 of 5 groups per substrate (n=10/gp): G1 (distilled water control); G2 (225 ppm NaF); G3 (1450 ppm NaF); G4 (5000 ppm NaF); G5 (19,000 ppm NaF). All specimens were subjected to 5, 10 and 15 cycles of experimental wear [1 cycle=artificial saliva (2h, pH 7.0)+erosion (0.3% citric acid, pH 3.2, 5 min)+fluoride/control (5 min)+attrition (60 linear strokes in artificial saliva from enamel antagonists loaded to 300 g)]. Following tape removal, step height (SH) in mum was measured using optical profilometry. When the number of cycles increased the amount of tooth surface loss increased significantly in enamel and dentine after attrition and erosion and for dentine after attrition. Attrition and erosion resulted in greater surface loss than attrition alone after 15 cycles of experimental wear of enamel. 5000 ppm and 19,000 ppm sodium fluoride solutions had a protective effect on erosive and attritional enamel tooth wear in vitro, however no other groups showed significant differences. The more intensive the fluoride regime the more protection was afforded to enamel from attrition and erosion. However, in this study no such protective effect was demonstrated for dentine. Copyright 2010 Elsevier Ltd. All rights reserved.

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.

Molecular imprinted polymer functionalized carbon nanotube sensors for detection of saccharides

NASA Astrophysics Data System (ADS)

Badhulika, Sushmee; Mulchandani, Ashok

2015-08-01

In this work, we report the synthesis and fabrication of an enzyme-free sugar sensor based on molecularly imprinted polymer (MIP) on the surface of single walled carbon nanotubes (SWNTs). Electropolymerization of 3-aminophenylboronic acid (3-APBA) in the presence of 10 M d-fructose and fluoride at neutral pH conditions resulted in the formation of a self-doped, molecularly imprinted conducting polymer (MICP) via the formation of a stable anionic boronic ester complex between poly(aniline boronic acid) and d-fructose. Template removal generated binding sites on the polymer matrix that were complementary to d-fructose both in structure, i.e., shape, size, and positioning of functional groups, thus enabling sensing of d-fructose with enhanced affinity and specificity over non-MIP based sensors. Using carbon nanotubes along with MICPs helped to develop an efficient electrochemical sensor by enhancing analyte recognition and signal generation. These sensors could be regenerated and used multiple times unlike conventional affinity based biosensors which suffer from physical and chemical stability.

Efficacy of a novel endotoxin adsorber polyvinylidene fluoride fiber immobilized with l-serine ligand on septic pigs*

PubMed Central

Gao, Jian-ping; Huang, Man; Li, Ning; Wang, Peng-fei; Chen, Huan-lin; Xu, Qiu-ping

2011-01-01

A novel adsorber, polyvinylidene fluoride matrix immobilized with l-serine ligand (PVDF-Ser), was developed in the present study to evaluate its safety and therapeutic efficacy in septic pigs by extracorporeal hemoperfusion. Endotoxin adsorption efficiency (EAE) of the adsorber was firstly measured in vitro. The biocompatibility and hemodynamic changes during extracorporeal circulation were then evaluated. One half of 16 pigs receiving lipopolysaccharide (Escherichia coli O111:B4, 5 μg/kg) intravenously in 1 h were consecutively treated by hemoperfusion with the new adsorber for 2 h. The changes of circulating endotoxin and certain cytokines and respiratory function were analyzed. The 72 h-survival rate was assessed eventually. EAE reached 46.3% (100 EU/ml in 80 ml calf serum) after 2 h-circulation. No deleterious effect was observed within the process. The plasma endotoxin, interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) levels were decreased during the hemoperfusion. Arterial oxygenation was also improved during and after the process. Furthermore, the survival time was significantly extended (>72 h vs. 47.5 h for median survival time). The novel product PVDF-Ser could adsorb endotoxin with high safety and efficacy. Early use of extracorporeal hemoperfusion with the new adsorber could reduce the levels of circulating endotoxin, IL-6, and TNF-α, besides improve respiratory function and consequent 72 h-survival rate of the septic pigs. Endotoxin removal strategy with blood purification using the new adsorber renders a potential promising future in sepsis therapy. PMID:21462381

SuFEx-Based Polysulfonate Formation from Ethenesulfonyl Fluoride-Amine Adducts

DOE PAGES

Wang, Hua; Zhou, Feng; Ren, Gerui; ...

2017-05-18

In this article, the SuFEx-based polycondensation between bisalkylsulfonyl fluorides (AA monomers) and bisphenol bis(t-butyldimethylsilyl) ethers (BB monomers) using [Ph 3P=N-PPh 3] +[HF 2] - as the catalyst is described. The AA monomers were prepared via the highly reliable Michael addition of ethenesulfonyl fluoride and amines/anilines while the BB monomers were obtained from silylation of bisphenols by t-butyldimethylsilyl chloride. With these reactions, a remarkable diversity of monomeric building blocks was achieved by exploiting readily available amines, anilines, and bisphenols as starting materials. The SuFEx-based polysulfonate formation reaction exhibited excellent efficiency and functional group tolerance, producing polysulfonates with a variety of sidemore » chain functionalities in >99 % conversion within 10 min to 1 h. When bearing an orthogonal group on the side chain, the polysulfonates can be further functionalized via click-chemistry-based post-polymerization modification.« less

Radiation Heat Transfer Modeling Improved for Phase-Change, Thermal Energy Storage Systems

NASA Technical Reports Server (NTRS)

Kerslake, Thomas W.; Jacqmin, David A.

1998-01-01

Spacecraft solar dynamic power systems typically use high-temperature phase-change materials to efficiently store thermal energy for heat engine operation in orbital eclipse periods. Lithium fluoride salts are particularly well suited for this application because of their high heat of fusion, long-term stability, and appropriate melting point. Considerable attention has been focused on the development of thermal energy storage (TES) canisters that employ either pure lithium fluoride (LiF), with a melting point of 1121 K, or eutectic composition lithium-fluoride/calcium-difluoride (LiF-20CaF2), with a 1040 K melting point, as the phase-change material. Primary goals of TES canister development include maximizing the phase-change material melt fraction, minimizing the canister mass per unit of energy storage, and maximizing the phase-change material thermal charge/discharge rates within the limits posed by the container structure.

An easy prepared dual-channel chemosensor for selective and instant detection of fluoride based on double Schiff-base

NASA Astrophysics Data System (ADS)

Leng, Yan-Li; Zhang, Jian-Hui; Li, Qiao; Zhang, You-Ming; Lin, Qi; Yao, Hong; Wei, Tai-Bao

2016-10-01

A colorimetric and fluorescent dual-channel fluoride chemosensor N,N‧-bis (4-diethylaminosalicylidene) hydrazine (sensor S) bearing two imine groups has been designed and synthesized. This structurally simple probe displays rapid response and high selectivity for fluoride over other common anions (Cl-, Br-, I-, AcO-, H2PO4-, HSO4-, ClO4-, CN- and SCN-) in a highly polar aqueous DMSO solution. Mechanism studies suggested that the sensor firstly combined with F- through hydrogen bonds and then experienced the deprotonation process at higher concentrations of F- anion to the two Ar-OH groups. The detection limit was 5.78 × 10- 7 M of F-, which points to the high detection sensitivity. Test strips based on sensor S were fabricated, which could act as a convenient and efficient F- test kit to detect F- for ;in-the-field; measurement.

Efficacy of chlorhexidine digluconate-containing formulations and other mouthrinses against periodontopathogenic microorganisms.

PubMed

Eick, Sigrun; Goltz, Susann; Nietzsche, Sandor; Jentsch, Holger; Pfister, Wolfgang

2011-09-01

To determine in vitro the action of chlorhexidine digluconate and different commercially available mouthrinses on oral microorganisms. Minimal inhibitory concentrations and possible induction of resistance by chlorhexidine digluconate, an essential oil-containing mouthwash and an amine fluoride/stannous fluoride solution, were determined against microorganisms normally found in the oral cavity (10 streptococci, 2 enterobacteria, 1 Candida albicans, 8 Porphyromonas gingivalis, 6 Aggregatibacter actinomycetemcomitans, and 1 Fusobacterium nucleatum). Further, the effect of a 1-minute exposure on cell and bacterial viability was studied. The susceptibility of the oral microorganisms to chlorhexidine digluconate ranged from 0.01% to 0.50%. Passages on agar plates containing subinhibitory concentrations of chlorhexidine digluconate resulted in a transitory moderate increase in the tolerance to chlorhexidine digluconate in five of the 24 isolates. After 1 minute of exposure, chlorhexidine digluconate solutions as well as the essential oil and the amine/stannous fluoride-containing solutions showed a high activity against the tested microorganisms. Commercially available chlorhexidine digluconate formulations (ie, those with antidiscoloration systems) were partly less efficient than the corresponding manually prepared chlorhexidine digluconate preparation. The determination of MTT resulted in a strong cytotoxicity of all tested preparations to gingival fibroblasts. The results indicate that most of the chlorhexidine digluconate formulations as well as essential oil and the amine fluoride/stannous fluoride solutions are active against oral microbes. Long-term use of these agents would not result in emergent antimicrobial resistance.

Volumetric determination of uranium using titanous sulfate as reductant before oxidimetric titration

USGS Publications Warehouse

Wahlberg, James S.; Skinner, Dwight L.; Rader, Lewis F.

1956-01-01

A new method for determining uranium in samples containing 0.05 percent or more U3O8, using titanous sulfate as reducing agent, is much shorter, faster, and has fewer interferences than conventional methods using reductor columns. The sample is dissolved with sulfuric, nitric, perchloric, and hydrofluoric acids. Elements that would otherwise form insoluble fluorides are kept in solution by complexing the fluoride ion with boric acid. A precipitation is made with cupferron to remove interfering elements. The solution is filtered to remove the precipitated cupferrates instead of extracting them with chloroform as is usually done. Filtration is preferred to extraction because any niobium that may be in solution forms an insoluble cupferrate that may be removed by filtering but is very difficult to extract with chloroform. Excess cupferron is destroyed by oxidizing with nitric and perchloric acids, and evaporating to dense fumes of sulfuric acid. The uranium is reduced to U(IV) by the addition of titanous sulfate, with cupric sulfate used as an indicator of the completeness of the reduction. Metallic copper is formed when all the uranium is reduced. The reduced copper is then reoxidized by the addition of mercuric perchlorate, an excess of ferric sulfate added, and the solution titrated immediately with standard ceric sulfate with ferroin as an indicator. Precision of the method compared favorable with methods in common use, both for uranium ores and for most types of uranium-rich materials.

BDD anodic treatment of 6:2 fluorotelomer sulfonate (6:2 FTSA). Evaluation of operating variables and by-product formation.

PubMed

Urtiaga, Ane; Soriano, Alvaro; Carrillo-Abad, Jordi

2018-06-01

The concerns about the undesired impacts on human health and the environment of long chain perfluorinated alkyl substances (PFASs) have driven industrial initiatives to replace PFASs by shorter chain fluorinated homologues. 6:2 fluorotelomer sulfonic acid (6:2 FTSA) is applied as alternative to PFOS in metal plating and fluoropolymer manufacture. This study reports the electrochemical treatment of aqueous 6:2 FTSA solutions on microcrystalline BDD anodes. Bench scale batch experiments were performed, focused on assessing the effect of the electrolyte and the applied current density (5-600 A m -2 ) on the removal of 6:2 FTSA, the reduction of total organic carbon (TOC) and the fluoride release. Results showed that at the low range of applied current density (J = 50 A m -2 ), using NaCl, Na 2 SO 4 and NaClO 4 , the electrolyte exerted a minimal effect on removal rates. The formation of toxic inorganic chlorine species such as ClO 4 - was not observed. When using Na 2 SO 4 electrolyte, increasing the applied current density to 350-600 A m -2 promoted a notable enhancement of the 6:2 FTSA removal and defluorination rates, pointing to the positive contribution of electrogenerated secondary oxidants to the overall removal rate. 6:2 FTSA was transformed into shorter-chain PFCAs, and eventually into CO 2 and fluoride, as TOC reduction was >90%. Finally, it was demonstrated that diffusion in the liquid phase was controlling the overall kinetic rate, although with moderate improvements due to secondary oxidants at very high current densities. Copyright © 2018 Elsevier Ltd. All rights reserved.

Standardization of fluorine-18 manufacturing processes: new scientific challenges for PET.

PubMed

Hjelstuen, Ole K; Svadberg, Anders; Olberg, Dag E; Rosser, Mark

2011-08-01

In [(18)F]fluoride chemistry, the minute amounts of radioactivity taking part in a radiolabeling reaction are easily outnumbered by other reactants. Surface areas become comparably larger and more influential than in standard fluorine chemistry, while leachables, extractables, and other components that normally are considered small impurities can have a considerable influence on the efficiency of the reaction. A number of techniques exist to give sufficient (18)F-tracer for a study in a pre-clinical or clinical system, but the chemical and pharmaceutical understanding has significant gaps when it comes to scaling up or making the reaction more efficient. Automation and standardization of [(18)F]fluoride PET tracers is a prerequisite for reproducible manufacturing across multiple PET centers. So far, large-scale, multi-site manufacture has been established only for [(18)F]FDG, but several new tracers are emerging. In general terms, this transition from small- to large-scale production has disclosed several scientific challenges that need to be addressed. There are still areas of limited knowledge in the fundamental [(18)F]fluoride chemistry. The role of pharmaceutical factors that could influence the (18)F-radiosynthesis and the gaps in precise chemistry knowledge are discussed in this review based on a normal synthesis pattern. Copyright © 2011 Elsevier B.V. All rights reserved.

Naturally occurring radioactive material (NORM) from a former phosphoric acid processing plant.

PubMed

Beddow, H; Black, S; Read, D

2006-01-01

In recent years there has been an increasing awareness of the radiological impact of non-nuclear industries that extract and/or process ores and minerals containing naturally occurring radioactive material (NORM). These industrial activities may result in significant radioactive contamination of (by-) products, wastes and plant installations. In this study, scale samples were collected from a decommissioned phosphoric acid processing plant. To determine the nature and concentration of NORM retained in pipe-work and associated process plant, four main areas of the site were investigated: (1) the 'Green Acid Plant', where crude acid was concentrated; (2) the green acid storage tanks; (3) the Purified White Acid (PWA) plant, where inorganic impurities were removed; and (4) the solid waste, disposed of on-site as landfill. The scale samples predominantly comprise the following: fluorides (e.g. ralstonite); calcium sulphate (e.g. gypsum); and an assemblage of mixed fluorides and phosphates (e.g. iron fluoride hydrate, calcium phosphate), respectively. The radioactive inventory is dominated by 238U and its decay chain products, and significant fractionation along the series occurs. Compared to the feedstock ore, elevated concentrations (< or =8.8 Bq/g) of 238U were found to be retained in installations where the process stream was rich in fluorides and phosphates. In addition, enriched levels (< or =11 Bq/g) of 226Ra were found in association with precipitates of calcium sulphate. Water extraction tests indicate that many of the scales and waste contain significantly soluble materials and readily release radioactivity into solution.

Selective radiative cooling with MgO and/or LiF layers

DOEpatents

Berdahl, P.H.

1984-09-14

A selective radiation cooling material which is absorptive only in the 8 to 13 microns wavelength range is accomplished by placing ceramic magnesium oxide and/or polycrystalline lithium fluoride on an infrared-reflective substrate. The reflecting substrate may be a metallic coating, foil or sheet, such as aluminum, which reflects all atmospheric radiation from 0.3 to 8 microns, the magnesium oxide and lithium fluoride being nonabsorptive at those wavelengths. <10% of submicron voids in the material is permissible in which case the MgO and/or LiF layer is diffusely scattering, but still nonabsorbing, in the wavelength range of 0.3 to 8 microns. At wavelengths from 8 to 13 microns, the magnesium oxide and lithium fluoride radiate power through the ''window'' in the atmosphere, and thus remove heat from the reflecting sheet of material and the attached object to be cooled. At wavelengths longer than 13 microns, the magnesium oxide and lithium fluoride reflects the atmospheric radiation back into the atmosphere. This high reflectance is only obtained if the surface is sufficiently smooth: roughness on a scale of 1 micron is permissible but roughness on a scale of 10 microns is not. An infrared-transmitting cover or shield is mounted in spaced relationship to the material to reduce convective heat transfer. If this is utilized in direct sunlight, the infrared transmitting cover or shield should be opaque in the solar spectrum of 0.3 to 3 microns.

Study on Treatment of acidic and highly concentrated fluoride waste water using calcium oxide-calcium chloride

NASA Astrophysics Data System (ADS)

Ren, T.; Gao, X. R.; Zheng, T.; Wang, P.

2016-08-01

There are problems with treating acidic waste water containing high concentration fluorine by chemical precipitation, including the low sludge setting velocity and the high difficulty of reaching the criterion. In Heilongjiang province, a graphite factory producing high-purity graphite generates acidic waste water with a high concentration of fluorine. In this paper, the effect of removals on the concentration of fluoride with the combined treatment of calcium oxide and calcium chloride were discussed with regard to acid waste water. The study improved the sludge characteristics by using polyacrylamide (PAM) and polymeric aluminum chloride (PAC). The effect of different coagulants on sludge was evaluated by the sludge settlement ratio (SV), sludge volume index (SVI) and sludge moisture content. The results showed that the optimal combination for 100 ml waste water was calcium oxide addition amount of 14 g, a calcium chloride addition amount of 2.5 g, a PAM addition amount of 350 mg/L, and the effluent fluoride concentration was below 6 mg/L. PAM significantly improved the sludge settling velocity. The sludge settlement ratio reduced from 87.6% to 60%. The process for wastewater treatment was easily operated and involved low expenditure.

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.

Groundwater arsenic and fluoride in Rajnandgaon District, Chhattisgarh, northeastern India

NASA Astrophysics Data System (ADS)

Patel, Khageshwar Singh; Sahu, Bharat Lal; Dahariya, Nohar Singh; Bhatia, Amarpreet; Patel, Raj Kishore; Matini, Laurent; Sracek, Ondra; Bhattacharya, Prosun

2017-07-01

The groundwater of Ambagarh Chouki, Rajnandgaon, India, shows elevated levels of As and F-, frequently above the WHO guidelines. In this work, the concentrations of As, F-, Na+, Mg2+, Ca2+, Cl-, SO4 2-, HCO3 -, Fe, dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in the groundwater of Ambagarh Chouki are described. The sources of dissolved components in the groundwater are investigated using the cluster and factor analysis. Five factors have been identified and linked to processes responsible for the formation of groundwater chemistry. High concentrations of dissolved As seems to be linked to high concentrations of DOC, suggesting reductive dissolution of ferric oxyhydroxides as arsenic mobilization process. Fluoride is found in shallow depth water, presumably as a consequence of evaporation of water and removal of Ca2+ by precipitation of carbonates.

Synthesis and characterization of barium fluoride substituted zinc tellurite glasses

NASA Astrophysics Data System (ADS)

Aishwarya, K.; Vinitha, G.; Varma, G. Sreevidya; Asokan, S.; Manikandan, N.

2017-12-01

Glasses in the TeO2-ZnO-BaF2 system were prepared by standard melt quenching technique and were characterized for their thermal, optical and structural properties. Samples were found to show good thermal stability with values ranging above 100 °C for all the compositions. Optical bandgap and refractive index values were calculated from linear optical measurements using UV-Vis spectroscopy. Infrared spectra showed the presence of hydroxyl groups in the glasses indicating that the effect of fluorine was negligible in removing the hydroxyl impurities for the experimental conditions and compositions used. Raman measurements showed the modification occurring in the glass network due to addition of barium fluoride in terms of increase in the formation of non-bridging oxygen atoms compared to strong Te-O-Te linkages in the glass matrix.

Composition and method to remove asbestos

DOE Office of Scientific and Technical Information (OSTI.GOV)

Block, Jacob

A composition for transforming a chrysotile asbestos-containing material into a non-asbestos material is disclosed, wherein the composition comprises water, at least about 30% by weight of phosphoric acid, and from about 0.1 to about 4% by weight of a source of fluoride ions. A method of transforming the asbestos-containing material into a non-asbestos material using the present composition also is disclosed.

Nephelometric determination of fluorine

USGS Publications Warehouse

Stevens, R.E.

1936-01-01

Fluorine in minerals may be determined with the nephelometer to about 1 per cent of the fluorine. The determination is made on an aliquot of the sodium chloride solution of the fluorine, obtained by the Berzelius method of extraction. The fluorine is precipitated as colloidal calcium fluoride in alcoholic solution, gelatin serving as a protective colloid. Arsenates, sulfates, and phosphates, which interfere with the determination, must be removed.

Water treatment plants assessment at Talkha power plant.

PubMed

El-Sebaie, Olfat D; Abd El-Kerim, Ghazy E; Ramadan, Mohamed H; Abd El-Atey, Magda M; Taha, Sahr Ahmed

2002-01-01

Talkha power plant is the only power plant located in El-Mansoura. It generates electricity using two different methods by steam turbine and gas turbine. Both plants drew water from River Nile (208 m3 /h). The Nile raw water passes through different treatment processes to be suitable for drinking and operational uses. At Talkha power plant, there are two purification plants used for drinking water supply (100 m3/h) and for water demineralization supply (108 m3/h). This study aimed at studying the efficiency of the water purification plants. For drinking water purification plant, the annual River Nile water characterized by slightly alkaline pH (7.4-8), high annual mean values of turbidity (10.06 NTU), Standard Plate Count (SPC) (313.3 CFU/1 ml), total coliform (2717/100 ml), fecal coliform (0-2400/100 ml), and total algae (3 x 10(4) org/I). The dominant group of algae all over the study period was green algae. The blue green algae was abundant in Summer and Autumn seasons. The pH range, and the annual mean values of turbidity, TDS, total hardness, sulfates, chlorides, nitrates, nitrites, fluoride, and residual chlorine for purified water were in compliance with Egyptian drinking water standards. All the SPC recorded values with an annual mean value of 10.13 CFU/1 ml indicated that chlorine dose and contact time were not enough to kill the bacteria. However, they were in compliance with Egyptian decree (should not exceed 50 CFU/1 ml). Although the removal efficiency of the plant for total coliform and blue green algae was high (98.5% and 99.2%, respectively), the limits of the obtained results with an annual mean values of 40/100 ml and 15.6 org/l were not in compliance with the Egyptian decree (should be free from total coliform, fecal coliform and blue green algae). For water demineralization treatment plant, the raw water was characterized by slightly alkaline pH. The annual mean values of conductivity, turbidity, and TDS were 354.6 microS/cm, 10.84 NTU, and 214.6 mg/I, respectively. There was an increase in the results of conductivity, turbidity, total hardness, and TDS in carbon filter effluent which was attributed to the desorption of adsorbed ions on the carbon media. The removal efficiencies of turbidity, total hardness, and TDS indicated the high efficiency of the cationic filter. The annual removal efficiencies of conductivity, turbidity, chloride, and TDS proved the efficiency of the anionic filter for removing the dissolved and suspended ions. All of the recorded values of the pH, conductivity, turbidity, chlorides, hardness, and TDS of the mixed bed effluent indicated that the water at this stage was of high quality for boiler feed. The study recommended adjustment of coagulant and residual chlorine doses as well as contact time, and continuous monitoring and maintenance of the different units.

Topography, wetting, and corrosion responses of electrodeposited hydroxyapatite and fluoridated hydroxyapatite on magnesium.

PubMed

Assadian, Mahtab; Jafari, Hassan; Ghaffari Shahri, Seyed Morteza; Idris, Mohd Hasbullah; Almasi, Davood

2016-08-12

In this study, different types of calcium-phosphate phases were coated on NaOH pre-treated pure magnesium. The coating was applied by electrodeposition method in order to provide higher corrosion resistance and improve biocompatibility for magnesium. Thickness, surface morphology and topography of the coatings were analyzed using optical, scanning electron and atomic-force microscopies, respectively. Composition and chemical bonding, crystalline structures and wettability of the coatings were characterized using energy-dispersive and attenuated total reflectance-Fourier transform infrared spectroscopies, grazing incidence X-ray diffraction and contact angle measurement, respectively. Degradation behavior of the coated specimens was also investigated by potentiodynamic polarization and immersion tests. The experiments proved the presence of a porous coating dominated by dicalcium-phosphate dehydrate on the specimens. It was also verified that the developed hydroxyapatite was crystallized by alkali post-treatment. Addition of supplemental fluoride to the coating electrolyte resulted in stable and highly crystallized structures of fluoridated hydroxyapatite. The coatings were found effective to improve biocompatibility combined with corrosion resistance of the specimens. Noticeably, the fluoride supplemented layer was efficient in lowering corrosion rate and increasing surface roughness of the specimens compared to hydroxyapatite and dicalcium-phosphate dehydrates layers.

Oral Hygiene Behaviors and Caries Experience in Northwest PRECEDENT Patients

PubMed Central

Rothen, Marilynn; Cunha-Cruz, Joana; Zhou, Lingmei; Mancl, Lloyd; Jones, Jackie S.; Berg, Joel

2014-01-01

Objectives To investigate the association between oral hygiene behaviors (toothbrushing, water rinsing after brushing, interproximal cleaning, and adjunctive use of fluoride products) and recent caries (past 24 months) in a random sample of patients in Northwest PRECEDENT practices. Methods Practitioner-members of Northwest PRECEDENT dental Practice-based Research Network (PBRN) conducted a longitudinal study on caries risk assessment. At baseline patients completed a questionnaire on oral self-care, snacking, health, and socio-demographics. A dental exam recorded readily-visible heavy plaque and DMFT; chart review captured new caries and treatments in the previous 24 months. Bivariate and multiple GEE log-linear regression models stratified by age groups were used to relate oral hygiene behaviors to the primary outcome of mean dental caries in the past 24 months on data from 1400 patients in 63 practices. The primary exposure of interest was fluoride toothbrushing frequency. Results Fluoride toothbrushing once per day or more by patients 9-17 was significantly associated with a 50% lower mean caries rate compared to fluoride toothbrushing less than once per day, after adjustment for age, gender, race, education, income, between-meal carbohydrate snacks, sugar-added beverages, alcohol consumption, smoking, BMI, exercise, stimulated salivary pH, number of teeth, and all other oral hygiene behaviors captured [Rate Ratio (RR)=0.5; 95% confidence interval (CI)=0.3-0.8]. After adjustment, for patients 18-64 fluoride toothbrushing two or more times per day was significantly associated with a 40% lower recent mean caries rate (RR=0.6; 95%CI=0.4-0.9); in patients 65+, twice a day or more fluoride toothbrushing was not associated with lower caries rates (RR=1.1; 95%CI=0.7-1.8). Of the other oral hygiene variables, after adjustment, patients 18-64 who rinsed with water after brushing had a 40% lower mean caries rate compared to no rinsing (RR=0.6; 95%CI=0.4-0.9) and the presence of readily-visible heavy plaque was significantly associated with an increase in the mean caries rate for patients 18-64 (RR=1.6; 95%CI=1.2-2.2) and 65+ (RR=2.5; 95%CI=1.8-3.5). Conclusions In the present study, the frequency of fluoride toothbrushing and the presence of readily-visible heavy plaque were the factors most strongly associated with mean caries rate. In young patients with permanent dentition the daily application of fluoride toothpaste appears more important than emphasis on thorough plaque removal. While for adults, the protective effect of twice daily fluoride toothbrushing disappears with advancing age and the presence of readily-visible heavy plaque becomes increasingly associated with caries risk. PMID:24766464

Ammonium boranes for the selective complexation of cyanide or fluoride ions in water.

PubMed

Hudnall, Todd W; Gabbaï, François P

2007-10-03

With the recognition of aqueous fluoride and cyanide ions as an objective, we have investigated the anion binding properties of two isomeric ammonium boranes, namely [p-(Mes2B)C6H4(NMe3)]+ ([1]+) and [o-(Mes2B)C6H4(NMe3)]+ ([2]+). These cationic boranes, which could be obtained by reaction of the known 4- and 2-dimesitylboryl-N,N-dimethylaniline with MeOTf, have been investigated both experimentally and computationally. They both react with fluoride and cyanide ions in organic solvents to afford the corresponding fluoroborate/ or cyanoborate/ammonium zwitterions 1F, 1CN, 2F, and 2CN. In aqueous solution, however, these cationic boranes behave as remarkably selective receptors. Indeed, [1]+ only complexes cyanide ions while [2]+ only complexes fluoride ions. In H2O/DMSO 60:40 vol (HEPES 6 mM, pH 7), the cyanide binding constant of [1]+ and the fluoride binding constant of [2]+ are respectively equal to 3.9 (+/-0.1) x 108 and 910 (+/-50) M-1. Structural and computational studies indicate that both steric and electronic effects contribute to the unusual selectivity displayed by these cationic boranes. Owing to favorable Coulombic effects, the para-derivative [1]+ has a very high affinity for cyanide; yet these effects are not sufficiently intense to allow complexation of the more efficiently hydrated and less basic fluoride anion. In the case of the ortho-derivative [2]+, the proximity of the ammonium moiety leads to an increase in the Lewis acidity of the boron center thus making fluoride binding possible. However, steric effects prevent cyanide coordination to the boron center of [2]+. Finally, cation [1]+ and [2]+ bind their dedicated anions reversibly and show a negligible response in the presence of other common anions including Cl-, Br-, I-, NO3-, OAc-, H2PO4-, and HSO4-.

A simple microfluidic platform for rapid and efficient production of the radiotracer [18F]fallypride.

PubMed

Zhang, Xin; Liu, Fei; Knapp, Karla-Anne; Nickels, Michael L; Manning, H Charles; Bellan, Leon M

2018-05-01

Herein, we report the development of a simple, high-throughput and efficient microfluidic system for synthesizing radioactive [18F]fallypride, a PET imaging radiotracer widely used in medical research. The microfluidic chip contains all essential modules required for the synthesis and purification of radioactive fallypride. The radiochemical yield of the tracer is sufficient for multiple animal injections for preclinical imaging studies. To produce the on-chip concentration and purification columns, we employ a simple "trapping" mechanism by inserting rows of square pillars with predefined gaps near the outlet of microchannel. Microspheres with appropriate functionality are suspended in solution and loaded into the microchannels to form columns for radioactivity concentration and product purification. Instead of relying on complicated flow control elements (e.g., micromechanical valves requiring complex external pneumatic actuation), external valves are utilized to control transfer of the reagents between different modules. The on-chip ion exchange column can efficiently capture [18F]fluoride with negligible loss (∼98% trapping efficiency), and subsequently release a burst of concentrated [18F]fluoride to the reaction cavity. A thin layer of PDMS with a small hole in the center facilitates rapid and reliable water evaporation (with the aid of azeotropic distillation and nitrogen flow) while reducing fluoride loss. During the solvent exchange and fluorination reaction, the entire chip is uniformly heated to the desired temperature using a hot plate. All aspects of the [18F]fallypride synthesis were monitored by high-performance liquid chromatography (HPLC) analysis, resulting in labelling efficiency in fluorination reaction ranging from 67-87% (n = 5). Moreover, after isolating unreacted [18F]fluoride, remaining fallypride precursor, and various by-products via an on-chip purification column, the eluted [18F]fallypride is radiochemically pure and of a sufficient quantity to allow for PET imaging (∼5 mCi). Finally, a positron emission tomography (PET) image of a rat brain injected with ∼300 μCi [18F]fallypride produced by our microfluidic chip is provided, demonstrating the utility of the product produced by the microfluidic reactor. With a short synthesis time (∼60 min) and a highly integrated on-chip modular configuration that allows for concentration, reaction, and product purification, our microfluidic chip offers numerous exciting advantages with the potential for applications in radiochemical research and clinical production. Moreover, due to its simplicity and potential for automation, we anticipate it may be easily integrated into a clinical environment.

Effectiveness of probiotic, chlorhexidine and fluoride mouthwash against Streptococcus mutans – Randomized, single-blind, in vivo study

PubMed Central

Jothika, Mohan; Vanajassun, P. Pranav; Someshwar, Battu

2015-01-01

Aim: To determine the short-term efficiency of probiotic, chlorhexidine, and fluoride mouthwashes on plaque Streptococcus mutans level at four periodic intervals. Materials and Methods: This was a single-blind, randomized control study in which each subject was tested with only one mouthwash regimen. Fifty-two healthy qualified adult patients were selected randomly for the study and were divided into the following groups: group 1- 10 ml of distilled water, group 2- 10 ml of 0.2% chlorhexidine mouthwash, group 3- 10 ml of 500 ppm F/400 ml sodium fluoride mouthwash, and group 4- 10 ml of probiotic mouthwash. Plaque samples were collected from the buccal surface of premolars and molars in the maxillary quadrant. Sampling procedure was carried out by a single examiner after 7 days, 14 days, and 30 days, respectively, after the use of the mouthwash. All the samples were subjected to microbiological analysis and statistically analyzed with one-way analysis of variance (ANOVA) and post-hoc test. Results: One-way ANOVA comparison among groups 2, 3, and 4 showed no statistical significance, whereas group 1 showed statistically significant difference when compared with groups 2, 3, and 4 at 7th, 14th, and 30th day. Conclusion: Chlorhexidine, sodium fluoride, and probiotic mouthwashes reduce plaque S. mutans levels. Probiotic mouthwash is effective and equivalent to chlorhexidine and sodium fluoride mouthwashes. Thus, probiotic mouthwash can also be considered as an effective oral hygiene regimen. PMID:25984467

Efficient removal of nickel(II) from high salinity wastewater by a novel PAA/ZIF-8/PVDF hybrid ultrafiltration membrane.

PubMed

Li, Ting; Zhang, Weiming; Zhai, Shu; Gao, Guandao; Ding, Jie; Zhang, Wenbin; Liu, Yang; Zhao, Xin; Pan, Bingcai; Lv, Lu

2018-06-15

The development of highly efficient membranes, especially those aimed at the removal of trace (ppm, 10 -6 ) heavy metals from high salinity wastewater, is one of the principal challenges in the wastewater treatment field. In this study, a new metal-organic frameworks-based hybrid ultrafiltration membrane (PAA/ZIF-8/PVDF membrane) was prepared, which outperformed some other adsorption materials and owned the first and highest reported nickel ion (Ni(II)) adsorption capacity (219.09 mg/g) in high salinity ([Na + ] = 15000 mg/L) wastewater. Novel and highly efficient hybrid ultrafiltration membrane was facilely fabricated by physically immobilizing zeolitic imidazolate framework-8 (ZIF-8) particles onto the surface of trimesoyl chloride (TMC)-modified polyvinylidene fluoride (PVDF) membrane under the protection of polyacrylic acid (PAA) layer, and possessed a relatively high water flux of ∼460 L m -2 h -1 . The XPS studies revealed that the Ni(II) uptake was mainly attributed to the specific hydrogen bonding interaction between Ni(II) and hydroxyl on ZIF-8 frameworks as well as the electrostatic adsorption by carboxyl groups in PAA layer. Especially, compared to PAA, ZIF-8 could selectively bind with Ni(II) effectively, which was almost not affected by concentrated sodium ion. The filtration study showed that the membrane with an area of 12.56 cm 2 could treat 5.76 L of Ni(II)-contained high salinity wastewater ([Ni(II) = 2 mg/L, [Na + ] = 15000 mg/L) to meet the maximum contaminant level of 0.1 mg/L Ni(II). Moreover, the hybrid membrane can be regenerated several times by HCl-NaCl solution (pH = 5.5) for repeated use under direct current electric field. Thus, the newly developed ZIF-8 hybrid ultrafiltration membrane showed a promising potential for heavy metals containing wastewater treatment. This work provides a worthy reference for designing highly efficient ultrafiltration membranes modified by metal-organic frameworks. Copyright © 2018 Elsevier Ltd. All rights reserved.

Chemical Composition and Microhardness of Human Enamel Treated with Fluoridated Whintening Agents. A Study in Situ

PubMed Central

Petta, Thais de Mendonça; do Socorro Batista de Lima Gomes, Yasmin; Antunes Esteves, Renata; do Carmo Freitas Faial, Kelson; Souza D`Almeida Couto, Roberta; Martins Silva, Cecy

2017-01-01

Background: Dental whitening has been increasingly sought out to improve dental aesthetics, but may cause chemical and morphological changes in dental enamel surfaces. Objective: Assess in situ the effects of high-concentration hydrogen peroxide with and without fluoride on human dental enamel using the ion chromatography test (IC) and the Knoop hardness test (KHN). Material and Methods: Nineteen enamel specimens were prepared using third human molars. These specimens were fixed on molars of volunteers and were divided into groups: OP38-Opalescence Boost PF38%, PO37-Pola Office 37.5% and CO-Control group. For chemical analysis (n= 3), the dentin layer was removed, keeping only the enamel, which was subjected to acidic digestion by microwave radiation. It was necessary to perform sample dilutions for the elements fluorine (F), calcium (Ca) and phosphorus (P) for quantification using the IC test. The KHN (n= 5) was performed before and after the treatments. Five indentations were made, separated by 100 µm, for each specimen using a load of 25 gf for 5 seconds in the microdurometer. The data were analyzed using ANOVA with a 5% significance level. Results: The OP38 group had the largest concentrations of F, Ca and P ions. The PO37 group showed the lowest concentrations of F and Ca ions. The average KHN was not significantly different between the OP38 and PO37 groups. Conclusion: Enamel whitened with hydrogen peroxide containing fluoride had greater concentrations of F, Ca and P ions. The presence of fluoride in the whitening agent did not influence the enamel microhardness. PMID:28405245

CONCENTRATION AND DECONTAMINATION OF SOLUTIONS CONTAINING PLUTONIUM VALUES BY BISMUTH PHOSPHATE CARRIER PRECIPITATION METHODS

DOEpatents

Seaborg, G.T.; Thompson, S.G.

1960-08-23

A process is given for isolating plutonium present in the tetravalent state in an aqueous solution together with fission products. First, the plutonium and fission products are coprecipitated on a bismuth phosphate carrier. The precipitate obtained is dissolved, and the plutonium in the solution is oxidized to the hexavalent state (with ceric nitrate, potassium dichromate, Pb/ sub 3/O/sub 4/, sodium bismuthate and/or potassium dichromate). Thereafter a carrier for fission products is added (bismuth phosphate, lanthanum fluoride, ceric phosphate, bismuth oxalate, thorium iodate, or thorium oxalate), and the fission-product precipitation can be repeated with one other of these carriers. After removal of the fission-product-containing precipitate or precipitates. the plutonium in the supernatant is reduced to the tetravalent state (with sulfur dioxide, hydrogen peroxide. or sodium nitrate), and a carrier for tetravalent plutonium is added (lanthanum fluoride, lanthanum hydroxide, lanthanum phosphate, ceric phosphate, thorium iodate, thorium oxalate, bismuth oxalate, or niobium pentoxide). The plutonium-containing precipitate is then dissolved in a relatively small volume of liquid so as to obtain a concentrated solution. Prior to dissolution, the bismuth phosphate precipitates first formed can be metathesized with a mixture of sodium hydroxide and potassium carbonate and plutonium-containing lanthanum fluorides with alkali-metal hydroxide. In the solutions formed from a plutonium-containing lanthanum fluoride carrier the plutonium can be selectively precipitated with a peroxide after the pH was adjusted preferably to a value of between 1 and 2. Various combinations of second, third, and fourth carriers are discussed.

Dental caries: strategies to control this preventable disease.

PubMed

Rugg-Gunn, Andrew

2013-11-01

To provide a brief commentary review of strategies to control dental caries. Dental decay is one of man's most prevalent diseases. In many counties, severity increased in parallel with importation of sugar, reaching its zenith about 1950s and 1960s. Since then, severity has declined in many countries, due to the wide use of fluoride especially in toothpaste, but dental caries remains a disease of medical, social and economic importance. Within the EU in 2011, the cost of dental treatment was estimated to be €79 billion. The pathogenesis is well understood: bacteria in dental plaque (biofilm) metabolise dietary sugars to acids which then dissolve dental enamel and dentine. Possible approaches to control caries development, therefore, involve: removal of plaque, reducing the acidogenic potential of plaque, reduction in sugar consumption, increasing the tooth's resistance to acid attack, and coating the tooth surface to form a barrier between plaque and enamel. At the present time, only three approaches are of practical importance: sugar control, fluoride, and fissure sealing. The evidence that dietary sugars are the main cause of dental caries is extensive, and comes from six types of study. Without sugar, caries would be negligible. Fluoride acts in several ways to aid caries prevention. Ways of delivering fluoride can be classed as: 'automatic', 'home care' and 'professional care': the most important of these are discussed in detail in four articles in this issue of the Acta Medica Academica. Dental caries is preventable - individuals, communities and countries need strategies to achieve this. Copyright © 2013 by Academy of Sciences and Arts of Bosnia and Herzegovina.

9,10-Azaboraphenanthrene-containing small molecules and conjugated polymers: synthesis and their application in chemodosimeters for the ratiometric detection of fluoride ions.

PubMed

Zhang, Weidong; Li, Guoping; Xu, Letian; Zhuo, Yue; Wan, Wenming; Yan, Ni; He, Gang

2018-05-21

The introduction of main group elements into conjugated scaffolds is emerging as a key route to novel optoelectronic materials. Herein, an efficient and versatile way to synthesize polymerizable 9,10-azaboraphenanthrene ( BNP )-containing monomers by aromaticity-driven ring expansion reactions between highly antiaromatic borafluorene and azides is reported, and the corresponding conjugated small molecules and polymers are developed as well. The BNP -containing small molecules and conjugated polymers showed good air/moisture stability and notable fluorescence properties. Addition of fluoride ions to the BNP -based small molecules and polymers induced a rapid change in the emission color from blue to green/yellow, respectively, accompanied by strong intensity changes. The conjugated polymers showed better ratiometric sensing performance than small molecules due to the exciton migration along the conjugated chains. Further experiments showed that the sensing process is fully reversible. The films prepared by solution-deposition of BNP -based compounds in the presence of polycaprolactone also showed good ratiometric sensing for fluoride ions.

Semiconductor saturable absorber mirror passively Q-switched 2.97 μm fluoride fiber laser

NASA Astrophysics Data System (ADS)

Li, Jianfeng; Luo, Hongyu; He, Yulian; Liu, Yong; Luo, Binbin; Sun, Zhongyuan; Zhang, Lin; Turitsyn, Sergei K.

2014-05-01

A diode-cladding-pumped mid-infrared passively Q-switched Ho3+-doped fluoride fiber laser using a reverse designed broad band semiconductor saturable mirror (SESAM) was demonstrated. Nonlinear reflectivity of the SESAM was measured using an in-house Yb3+-doped mode-locked fiber laser at 1062 nm. Stable pulse train was produced at a slope efficient of 12.1% with respect to the launched pump power. Maximum pulse energy of 6.65 μJ with a pulse width of 1.68 μs and signal to noise ratio (SNR) of ~50 dB was achieved at a repetition rate of 47.6 kHz and center wavelength of 2.971 μm. To the best of our knowledge, this is the first 3 μm region SESAM based Q-switched fiber laser with the highest average power and pulse energy, as well as the longest wavelength from mid-infrared passively Q-switched fluoride fiber lasers.

Semiconductor saturable absorber mirror passively Q-switched 2.97 μm fluoride fiber laser

NASA Astrophysics Data System (ADS)

Li, J. F.; Luo, H. Y.; He, Y. L.; Liu, Y.; Zhang, L.; Zhou, K. M.; Rozhin, A. G.; Turistyn, S. K.

2014-06-01

A diode-cladding-pumped mid-infrared passively Q-switched Ho3+-doped fluoride fiber laser using a reverse designed broad band semiconductor saturable mirror (SESAM) was demonstrated. Nonlinear reflectivity of the SESAM was measured using an in-house Yb3+-doped mode-locked fiber laser at 1062 nm. Stable pulse train was produced at a slope efficient of 12.1% with respect to the launched pump power. Maximum pulse energy of 6.65 µJ with a pulse width of 1.68 µs and signal-to-noise ratio (SNR) of ~50 dB was achieved at a repetition rate of 47.6 kHz and center wavelength of 2.971 µm. To the best of our knowledge, this is the first 3 µm region SESAM-based Q-switched fiber laser with the highest average power and pulse energy, as well as the longest wavelength from mid-infrared passively Q-switched fluoride fiber lasers.

Combined Raman and SEM study on CaF2 formed on/in enamel by APF treatments.

PubMed

Tsuda, H; Jongebloed, W L; Stokroos, I; Arends, J

1993-01-01

Raman spectra containing the distinct band at 322 cm-1 due to CaF2 or CaF2-like material formed in/on fluoridated bovine enamel were recorded using a micro-Raman spectrograph. Due to increasing levels of background fluorescence with increasing thickness of enamel, the Raman measurements were carried out on thin regions of wedged enamel sections. The distribution of the CaF2 or CaF2-like material was estimated using a simple model. The results indicate that 1/3 of the total CaF2 was concentrated within the narrow depth < 2 microns with high CaF2 concentrations (> 10 wt%), and that the majority of the CaF2 was distributed over the depths up to 26 microns (1 wt% CaF2). SEM observations on fractured fluoridated enamel confirmed that morphological changes were present in the depth range comparable to that of the high CaF2 concentration region expected from the Raman analysis. In deeper regions where lower concentration (< 10%) but a large amount of CaF2 was still expected, the SEM images failed to distinguish between the normal and fluoridated enamel. After KOH treatment, the Raman spectra did not show evidence of the CaF2 peak and the SEM micrographs also confirmed the removal of globules. The peak position of the Raman band of the CaF2 formed by the fluoridation was identical to that of pure CaF2. However, the linewidth was 23 cm-1 (FWHM) and a factor of 2 broader than that of pure CaF2 (12 cm-1). This implies that the lattice dynamics of the CaF2 formed by fluoridation is different from of pure CaF2, and that the material formed is 'CaF2-like' or 'disordered CaF2'.

Screening glycosynthase libraries with a fluoride chemosensor assay independently of enzyme specificity: identification of a transitional hydrolase to synthase mutant.

PubMed

Andrés, Eduardo; Aragunde, Hugo; Planas, Antoni

2014-03-01

Glycosynthases have become efficient tools for the enzymatic synthesis of oligosaccharides, glycoconjugates and polysaccharides. Enzyme-directed evolution approaches are applied to improve the performance of current glycosynthases and engineer specificity for non-natural substrates. However, simple and general screening methods are required since most of the reported assays are specific for each particular enzyme. In the present paper, we report a general screening assay that is independent of enzyme specificity, and implemented in an HTS (high-throughput screening) format for the screening of cell extracts in directed evolution experiments. Fluoride ion is a general by-product released in all glycosynthase reactions with glycosyl fluoride donors. The new assay is based on the use of a specific chemical sensor (a silyl ether of a fluorogenic methylumbelliferone) to transduce fluoride concentration into a fluorescence signal. As a proof-of-concept, it has been applied to a nucleophile saturation mutant library of Bacillus licheniformis 1,3-1,4-β-glucanase. Beyond the expected mutations at the glutamic acid (catalytic) nucleophile, other variants have been shown to acquire glycosynthase activity. Surprisingly, an aspartic acid for glutamic acid replacement renders a highly active glycosynthase, but still retains low hydrolase activity. It appears as an intermediate state between glycosyl hydrolase and glycosynthase.

Comparison of the incipient lesion enamel fluoride uptake from various prescription and OTC fluoride toothpastes and gels.

PubMed

Schemehorn, B R; DiMarino, J C; Movahed, N

2014-01-01

The objective of this in vitro study was to compare the fluoride uptake into incipient enamel lesions of a novel 970 ppm F- ion SnF2 over-the-counter (OTC) gel (Enamelon Preventive Treatment Gel) and a novel 1150 ppm F- ion OTC toothpaste (Enamelon), each delivering amorphous calcium phosphate (ACP), to the uptake from two different prescription strength, 5000 ppm F- ion dentifrices containing tri-calcium phosphate (TCP) and a prescription 900 ppm F- ion paste containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP). The test procedure followed method #40 in the US-FDA Anticaries Drug Products for OTC Human Use, Final Monograph testing procedures. Eight sets of twelve incisor enamel cores were mounted in Plexiglas rods and the exposed surfaces were polished. The indigenous fluoride levels of each specimen were determined prior to treatment. The treatments were performed using slurries of a negative control (water) and the following products applied to a set of sound enamel cores: 5000 ppm F- ion, sodium fluoride (NaF) prescription (Rx) dentifrice "A" containing TCP; 5000 ppm F- ion, NaF Rx dentifrice "B" containing TCP; 900 ppm F- ion, NaF Rx paste with CPP-ACP; 1150 ppm F- ion, NaF OTC toothpaste; 1150 ppm F- ion, stannous fluoride (SnF2) OTC toothpaste delivering ACP (Enamelon); 1100 ppm F- ion, SnF2 OTC toothpaste; and 970 ppm F- ion, SnF2 OTC gel delivering ACP (Enamelon Preventive Treatment Gel). The twelve specimens of each group were immersed into 25 ml of their assigned slurry with constant stirring (350 rpm) for 30 minutes. Following treatment, one layer of enamel was removed from each specimen and analyzed for fluoride and calcium. The pre-treatment fluoride (indigenous) level of each specimen was subtracted from the post-treatment value to determine the change in enamel fluoride due to the test treatment. The increase in the average fluoride uptake for treated enamel cores was: 10,263 ± 295 ppm for the 970 ppm F- ion, Enamelon Preventive Treatment Gel; 7,016 ± 353 ppm for the 1150 ppm F- ion Enamelon Toothpaste; 4,138 ± 120 ppm for the 5000 ppm F- ion, NaF prescription dentifrice "A" with TCP; 3801 ± 121 ppm for the 5000 ppm F- ion, NaF prescription dentifrice "B" with TCP; 2,647 ± 57 ppm for the 1100 ppm F- ion, SnF2 OTC toothpaste; 1470 ± 40 ppm for the 1150 ppm F- ion, NaF OTC toothpaste; and 316 ± 9 ppm for the 900 ppm F- ion, NaF paste with CPP-ACP. The differences among all the products tested were statistically significant (p < 0.05), except for the two 5000 ppm F- ion products with TCP that were not statistically different from one another, and the 900 ppm F ion, NaF paste with CPP-ACP that was not statistically different from the negative water control. The Enamelon products (970 ppm and 150 ppm F ion, SnF2OTC dentifrices) delivering ACP provide statistically significantly more fluoride to incipient enamel lesions than two prescription strength 5000 ppm F- ion toothpastes containing TCP, the 900 ppm F- ion prescription paste containing CPP-ACP, and the other OTC toothpastes compared in this study.

XPS analysis of the effect of fillers on PTFE transfer film development in sliding contacts

NASA Technical Reports Server (NTRS)

Blanchet, T. A.; Kennedy, F. E.; Jayne, D. T.

1993-01-01

The development of transfer films atop steel counterfaces in contact with unfilled and bronze-filled PTFE has been studied using X-ray photoelectron spectroscopy. The sliding apparatus was contained within the vacuum of the analytical system, so the effects of the native oxide, hydrocarbon, and adsorbed gaseous surface layers of the steel upon the PTFE transfer behavior could be studied in situ. For both the filled and the unfilled PTFE, cleaner surfaces promoted greater amounts of transfer. Metal fluorides, which formed at the transfer film/counterface interface, were found solely in cases where the native oxide had been removed to expose the metallic surface prior to sliding. These fluorides also were found at clean metal/PTFE interfaces formed in the absence of frictional contact. A fraction of these fluorides resulted from irradiation damage inherent in XPS analysis. PTFE transfer films were found to build up with repeated sliding passes, by a process in which strands of transfer filled in the remaining counterface area. Under these reported test conditions, the transfer process is not expected to continue atop previously deposited transfer films. The bronze-filled composite generated greater amounts of transfer than the unfilled PTFE. The results are discussed relative to the observed increase in wear resistance imparted to PTFE by a broad range of inorganic fillers.

Highly efficient gel-state dye-sensitized solar cells prepared using propionitrile and poly(vinylidene fluoride-co-hexafluoropropylene)

NASA Astrophysics Data System (ADS)

Venkatesan, Shanmuganathan; Hidayati, Noor; Liu, I.-Ping; Lee, Yuh-Lang

2016-12-01

Propionitrile (PPN) solvent based iodide/triiodide liquid-electrolyte is utilized to prepare highly efficient poly (vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) polymer gel electrolytes (PGEs) of dye-sensitized solar cells, aiming at improving the energy conversion efficiency as well as the stability of gel-state DSSCs. The concentrations effect of the PVdF-HFP on the properties of PGEs and the performance of the corresponding cells are studied. The results show that the in-situ gelation is performed for the PVdF-HFP concentration range of 8-18% at room temperature. However, increasing the concentration of polymer in the PGEs triggers a decrease in the diffusivity and conductivity of the PGEs, but an increase in the phase transition temperature of the PGEs. A high phase transition temperature is obtained for the PGEs with 18 wt% PVdF-HFP, which increase the long-term stability of the gel-state DSSC. By using the 18 wt% PVdF-HFP in the presence of 5 wt% TiO2 nanofillers (NFs), gel-state cells with an efficiency of 8.38% can be obtained, which is higher than that achieved by liquid-state cells (7.55%). After 1000 h test at room temperature (RT) and 50 °C, the cell can retain 96% and 82%, respectively, of its initial efficiency.

Sunlight activated anodic freestanding ZrO2 nanotube arrays for Cr(VI) photoreduction.

PubMed

Bashirom, Nurulhuda; Tan, Wai Kian; Go, Kawamura; Matsuda, Atsunori; Abdul Razak, Khairunisak; Lockman, Zainovia

2018-06-14

Visible-light-active freestanding zirconia (ZrO2) nanotube (FSZNT) arrays were fabricated by a facile electrochemical anodization method in fluoride containing ethylene glycol electrolyte added to it 1 vol.% of potassium carbonate (K2CO3) at 60 V for 1 h. Poor adhesion at metal|oxide interface was induced by K2CO3 leading to formation of the FSZNT flakes. The effect of crystal structures of FSZNTs e.g., amorphous, amorphous/tetragonal, and tetragonal/monoclinic was investigated towards the photocatalytic reduction of 10 ppm hexavalent chromium, Cr(VI) at pH 2 under sunlight. The results demonstrate the amorphous FSZNTs exhibited the highest Cr(VI) removal efficiency than the crystalline FSZNTs (95 % versus 33 % after 5 h). The high photocatalytic activity of the amorphous FSZNTs can be attributed to enhanced Cr(VI) adsorption, high visible light absorption, and better charge carriers separation. The low photocatalytic activity of the crystalline FSZNTs annealed at 500 °C was mainly attributed to poor Cr(VI) adsorption, low visible light absorption, and less photoactive monoclinic-ZrO2. © 2018 IOP Publishing Ltd.

Heuristic method of fabricating counter electrodes in dye-sensitized solar cells based on a PEDOT:PSS layer as a catalytic material

NASA Astrophysics Data System (ADS)

Edalati, Sh; Houshangi far, A.; Torabi, N.; Baneshi, Z.; Behjat, A.

2017-02-01

Poly(3,4-ethylendioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) was deposited on a fluoride-doped tin oxide glass substrate using a heuristic method to fabricate platinum-free counter electrodes for dye-sensitized solar cells (DSSCs). In this heuristic method a thin layer of PEDOT:PPS is obtained by spin coating the PEDOT:PSS on a Cu substrate and then removing the substrate with FeCl3. The characteristics of the deposited PEDOT:PSS were studied by energy dispersive x-ray analysis and scanning electron microscopy, which revealed the micro-electronic specifications of the cathode. The aforementioned DSSCs exhibited a solar conversion efficiency of 3.90%, which is far higher than that of DSSCs with pure PEDOT:PSS (1.89%). This enhancement is attributed not only to the micro-electronic specifications but also to the HNO3 treatment through our heuristic method. The results of cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and Tafel polarization plots show the modified cathode has a dual function, including excellent conductivity and electrocatalytic activity for iodine reduction.

Photovoltaic and thermal properties of electrolytes based on electrospun poly(vinylidene fluoride-hexafluoro propylene)/poly(methyl methacrylate) nanofibers for dye-sensitized solar cells.

PubMed

Jang, Young-Wook; Won, Du-Hyun; Kim, Young-Keun; Hwang, Won-Pill; Jang, Sung-Il; Jeong, Sung-Hoon; Kim, Mi-Ra; Lee, Jin-Kook

2014-08-01

We prepared electrospun polymer nanofibers by electrospnning method and investigated about their applications to dye-sensitized solar cells (DSSCs). Electrospun polymer nanofibers applied to the polymer matrix in electrolyte for DSSCs. To improve the stiffness of polymer nanofiber, poly(vinylidene fluoride-hexafluoro propylene)/Poly(methyl methacrylate) (PVDF-HFP/PMMA) blend nanofibers were prepared and examined. In the electrospun PVDF-HFP/PMMA (1:1) blend nanofibers, the best results of VOC, JSC, FF, and efficiency of the DSSC devices showed 0.71 V, 12.8 mA/cm2, 0.61, and 5.56% under AM 1.5 illumination.

Efficient 41Ca measurements for biomedical applications

NASA Astrophysics Data System (ADS)

Vockenhuber, C.; Schulze-König, T.; Synal, H.-A.; Aeberli, I.; Zimmermann, M. B.

2015-10-01

We present the performance of 41Ca measurements using low-energy Accelerator Mass Spectrometry (AMS) at the 500 kV facility TANDY at ETH Zurich. We optimized the measurement procedure for biomedical applications where reliability and high sample throughput is required. The main challenge for AMS measurements of 41Ca is the interfering stable isobar 41K. We use a simplified sample preparation procedure to produce calcium fluoride (CaF2) and extract calcium tri-fluoride ions (CaF3-) ions to suppress the stable isobar 41K. Although 41K is not completely suppressed we reach 41Ca/40Ca background level in the 10-12 range which is adequate for biomedical studies. With helium as a stripper gas we can use charge state 2+ at high transmission (∼50%). The new measurement procedure with the approximately 10 × improved efficiency and the higher accuracy due to 41K correction allowed us to measure more than 600 samples for a large biomedical study within only a few weeks of measurement time.

Spectral engineering of optical fiber through active nanoparticle doping

NASA Astrophysics Data System (ADS)

Lindstrom-James, Tiffany

The spectral engineering of optical fiber is a method of intentional doping of the core region in order to absorb/emit specific wavelengths of light therby providing enhanced performance over current fibers. Efforts here focused on developing an understanding of optically active nanoparticles based on alkaline earth fluorides that could be easily and homogeneously incorporated into the core of a silica based optical fiber preform and result in efficient and tailorable spectral emissions. Doped and undoped calcium, strontium and barium fluoride nanoparticles were successfully synthesized and characterized for their physical, chemical, and optical behavior. Distinct spectroscopic differences as a result of different host materials, varying rare earth doping levels and processing conditions, indicated the ability to influence the spectral behavior of the doped nanoparticle. By using photoluminescence to predict diffusion behavior, the application of a simple one dimensional model for diffusion provided a method for predicting the diffusion coefficient of europium ions in alkaline earth fluorides with order of magnitude accuracy. Modified chemical vapor deposition derived silica preforms were individually solution doped with europium doped alkaline earth fluoride nanoparticles. By using the rare earth doped alkaline earth fluoride nanoparticles as the dopant materials in the core of optical fiber preforms, the resultant optical properties of the glass were significantly influenced by their presence in the core. The incorporation of these rare earth doped alkaline earth fluoride nanoparticles was found to significantly influence the local chemical and structural environment about the rare earth ion, demonstrated homogeneity and uniform distribution of the rare earth dopant and resulted in specifically unique spectral behavior when compared to conventional doping methods. A more detailed structural model of the doped core glass region has been developed based on the spectral behavior of these active fiber preforms. It has been shown that rare earth doping of alkaline earth fluoride nanoparticles provides a material which can be 'tuned' to specific applications through the use of different host materials, processing conditions and doping levels of the rare earth and when used as dopant materials for active optical fibers, provides a means to tailor the optical behavior.

Fluorine-fixing efficiency on calcium-based briquette: pilot experiment, demonstration and promotion.

PubMed

Yang, Jiao-lan; Chen, Dong-qing; Li, Shu-min; Yue, Yin-ling; Jin, Xin; Zhao, Bing-cheng; Ying, Bo

2010-02-05

The fluorosis derived from coal burning is a very serious problem in China. By using fluorine-fixing technology during coal burning we are able to reduce the release of fluorides in coal at the source in order to reduce pollution to the surrounding environment by coal burning pollutants as well as decrease the intake and accumulating amounts of fluorine in the human body. The aim of this study was to conduct a pilot experiment on calcium-based fluorine-fixing material efficiency during coal burning to demonstrate and promote the technology based on laboratory research. A proper amount of calcium-based fluorine sorbent was added into high-fluorine coal to form briquettes so that the fluorine in high-fluorine coal can be fixed in coal slag and its release into atmosphere reduced. We determined figures on various components in briquettes and fluorine in coal slag as well as the concentrations of indoor air pollutants, including fluoride, sulfur dioxide and respirable particulate matter (RPM), and evaluated the fluorine-fixing efficiency of calcium-based fluorine sorbents and the levels of indoor air pollutants. Pilot experiments on fluorine-fixing efficiency during coal burning as well as its demonstration and promotion were carried out separately in Guiding and Longli Counties of Guizhou Province, two areas with coal burning fluorosis problems. If the calcium-based fluorine sorbent mixed coal was made into honeycomb briquettes the average fluorine-fixing ratio in the pilot experiment was 71.8%. If the burning calcium-based fluorine-fixing bitumite was made into a coalball, the average of fluorine-fixing ratio was 77.3%. The concentration of fluoride, sulfur dioxide and PM10 of indoor air were decreased significantly. There was a 10% increase in the cost of briquettes due to the addition of calcium-based fluorine sorbent. The preparation process of calcium-based fluorine-fixing briquette is simple yet highly flammable and it is applicable to regions with abundant bitumite coal. As a small scale application, villagers may make fluorine-fixing coalballs or briquettes by themselves, achieving the optimum fluorine-fixing efficiency and reducing indoor air pollutants providing environmental and social benefits.

A randomised clinical evaluation of a fluoride mouthrinse and dentifrice in an in situ caries model.

PubMed

Parkinson, Charles R; Hara, Anderson T; Nehme, Marc; Lippert, Frank; Zero, Domenick T

2018-03-01

Fluoride mouthrinses provide advantages for fluoride delivery by maintaining elevated intra-oral fluoride concentrations following fluoride dentifrice use. This in situ caries study investigated potential anti-caries efficacy of a 220 ppm fluoride mouthrinse. This was an analyst-blinded, four-treatment, randomised, crossover study using partially demineralised, gauze-wrapped, human enamel samples mounted in a mandibular partial denture. Participants brushed twice daily for 14 days with either a 1150 ppm fluoride or a fluoride-free placebo dentifrice and either rinsed once daily with the 220 ppm fluoride mouthrinse or not. Following each treatment period, percent surface microhardness recovery (%SMHR) and enamel fluoride uptake (EFU) were assessed. Fifty three participants completed the study. Compared with the placebo dentifrice/no rinse treatment, the fluoride-containing regimens demonstrated greater enamel remineralisation (%SMHR) and fluoridation (EFU): fluoride dentifrice/fluoride rinse (%SMHR difference: 21.55 [95% CI: 15.78,27.32]; EFU difference 8.35 [7.21,9.29]); fluoride dentifrice/no rinse: 19.48 [13.81,25.15]; 6.47 [5.35,7.60]; placebo dentifrice/fluoride rinse: 16.76 [11.06,22.45]; 5.87 [4.72,7.00] (all P < .0001). There were no significant differences in%SMHR between fluoride regimens. The fluoride dentifrice/fluoride rinse regimen was associated with higher EFU than the fluoride dentifrice/no rinse (1.88 [0.75,3.01], P = .0013) and placebo dentifrice/fluoride rinse regimens (2.48 [1.34,3.62], P < .0001). Treatments were generally well-tolerated. The in situ caries model demonstrated that the fluoride mouthrinse is effective in promoting enamel caries lesion remineralisation and fluoridation whether used following a fluoride or non-fluoride dentifrice. Additive (potential) anti-caries benefits of a fluoride rinse after a fluoride dentifrice were confined to enhancements in lesion fluoridation (EFU). In conjunction with a fluoride dentifrice, fluoride mouthrinses enhance enamel fluoridation, which may be useful in caries prevention. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Contemporary biological markers of exposure to fluoride.

PubMed

Rugg-Gunn, Andrew John; Villa, Alberto Enrique; Buzalaf, Marília Rabelo Afonso

2011-01-01

Contemporary biological markers assess present, or very recent, exposure to fluoride: fluoride concentrations in blood, bone surface, saliva, milk, sweat and urine have been considered. A number of studies relating fluoride concentration in plasma to fluoride dose have been published, but at present there are insufficient data on plasma fluoride concentrations across various age groups to determine the 'usual' concentrations. Although bone contains 99% of the body burden of fluoride, attention has focused on the bone surface as a potential marker of contemporary fluoride exposure. From rather limited data, the ratio surface-to-interior concentration of fluoride may be preferred to whole bone fluoride concentration. Fluoride concentrations in the parotid and submandibular/sublingual ductal saliva follow the plasma fluoride concentration, although at a lower concentration. At present, there are insufficient data to establish a normal range of fluoride concentrations in ductal saliva as a basis for recommending saliva as a marker of fluoride exposure. Sweat and human milk are unsuitable as markers of fluoride exposure. A proportion of ingested fluoride is excreted in urine. Plots of daily urinary fluoride excretion against total daily fluoride intake suggest that daily urinary fluoride excretion is suitable for predicting fluoride intake for groups of people, but not for individuals. While fluoride concentrations in plasma, saliva and urine have some ability to predict fluoride exposure, present data are insufficient to recommend utilizing fluoride concentrations in these body fluids as biomarkers of contemporary fluoride exposure for individuals. Daily fluoride excretion in urine can be considered a useful biomarker of contemporary fluoride exposure for groups of people, and normal values have been published. Copyright © 2011 S. Karger AG, Basel.

Development of the FHR advanced natural circulation analysis code and application to FHR safety analysis

DOE PAGES

Guo, Z.; Zweibaum, N.; Shao, M.; ...

2016-04-19

The University of California, Berkeley (UCB) is performing thermal hydraulics safety analysis to develop the technical basis for design and licensing of fluoride-salt-cooled, high-temperature reactors (FHRs). FHR designs investigated by UCB use natural circulation for emergency, passive decay heat removal when normal decay heat removal systems fail. The FHR advanced natural circulation analysis (FANCY) code has been developed for assessment of passive decay heat removal capability and safety analysis of these innovative system designs. The FANCY code uses a one-dimensional, semi-implicit scheme to solve for pressure-linked mass, momentum and energy conservation equations. Graph theory is used to automatically generate amore » staggered mesh for complicated pipe network systems. Heat structure models have been implemented for three types of boundary conditions (Dirichlet, Neumann and Robin boundary conditions). Heat structures can be composed of several layers of different materials, and are used for simulation of heat structure temperature distribution and heat transfer rate. Control models are used to simulate sequences of events or trips of safety systems. A proportional-integral controller is also used to automatically make thermal hydraulic systems reach desired steady state conditions. A point kinetics model is used to model reactor kinetics behavior with temperature reactivity feedback. The underlying large sparse linear systems in these models are efficiently solved by using direct and iterative solvers provided by the SuperLU code on high performance machines. Input interfaces are designed to increase the flexibility of simulation for complicated thermal hydraulic systems. In conclusion, this paper mainly focuses on the methodology used to develop the FANCY code, and safety analysis of the Mark 1 pebble-bed FHR under development at UCB is performed.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Z.; Zweibaum, N.; Shao, M.

The University of California, Berkeley (UCB) is performing thermal hydraulics safety analysis to develop the technical basis for design and licensing of fluoride-salt-cooled, high-temperature reactors (FHRs). FHR designs investigated by UCB use natural circulation for emergency, passive decay heat removal when normal decay heat removal systems fail. The FHR advanced natural circulation analysis (FANCY) code has been developed for assessment of passive decay heat removal capability and safety analysis of these innovative system designs. The FANCY code uses a one-dimensional, semi-implicit scheme to solve for pressure-linked mass, momentum and energy conservation equations. Graph theory is used to automatically generate amore » staggered mesh for complicated pipe network systems. Heat structure models have been implemented for three types of boundary conditions (Dirichlet, Neumann and Robin boundary conditions). Heat structures can be composed of several layers of different materials, and are used for simulation of heat structure temperature distribution and heat transfer rate. Control models are used to simulate sequences of events or trips of safety systems. A proportional-integral controller is also used to automatically make thermal hydraulic systems reach desired steady state conditions. A point kinetics model is used to model reactor kinetics behavior with temperature reactivity feedback. The underlying large sparse linear systems in these models are efficiently solved by using direct and iterative solvers provided by the SuperLU code on high performance machines. Input interfaces are designed to increase the flexibility of simulation for complicated thermal hydraulic systems. In conclusion, this paper mainly focuses on the methodology used to develop the FANCY code, and safety analysis of the Mark 1 pebble-bed FHR under development at UCB is performed.« less

Blend-electrospun graphene oxide/Poly(vinylidene fluoride) nanofibrous membranes with high flux, tetracycline removal and anti-fouling properties.

PubMed

Park, Jeong-Ann; Nam, Aram; Kim, Jae-Hyun; Yun, Seong-Taek; Choi, Jae-Woo; Lee, Sang-Hyup

2018-09-01

Graphene oxide (GO)/poly(vinylidene fluoride) (PVDF) electrospun nanofibrous membranes (ENMs) have been fabricated to remove tetracycline (TC) from water via adsorptive-filtration. The pure water permeation flux of GO/PVDF ENMs (27,407-29,337 LMH/bar) was increased compared with that of PVDF ENMs. The flow pore diameter was steadily reduced by increasing the GO content from 0 to 1.5 wt% in the GO/PVDF ENMs. The maximum TC adsorption capacity of GO is 720.26 mg/g (Langmuir model) and GO retained its TC adsorption property after incorporation into GO/PVDF ENMs during water filtration (transmembrane pressure = 0.91 bar). The maximum experimental TC removal capacity (q a , exp ) was 17.92 mg/g with 1.5 wt% of GO (GO 1.5 /PVDF) ENMs, which was similar to the modified dose-response model value of 18.03 mg/g. In the presence of natural organic matter, TC adsorption was enhanced, because hydrophobic organic carbon improved hydrophobic and π-π interactions. The presence of Cu(II) further improved the TC adsorption capacity of GO 1.5 /PVDF ENMs through cation bridging. However, the presence of Ca(II) hindered TC adsorption by an electron shielding effect. For examining anti-fouling activity of GO 1.5 /PVDF ENMs, the log removal values of both bacteria, Escherichia coli and Staphylococcus aureus, were maintained at over 5 during water filtration. In addition, incorporation of GO in PVDF ENMs prevents bovine serum albumin (BSA) adsorption by both increasing the hydrophilicity of the ENMs forming hydration layer on the surface and electrostatic repulsion between both negatively charged BSA and GO in GO 1.5 /PVDF ENMs (zeta potential = - 14.14 mV, deionized water at pH 6). Copyright © 2018 Elsevier Ltd. All rights reserved.

Effectiveness of fluoride sealant in the prevention of carious lesions around orthodontic brackets: an OCT evaluation

PubMed Central

Pithon, Matheus Melo; Santos, Mariana de Jesus; de Souza, Camilla Andrade; Leão, Jorge César Borges; Braz, Ana Karla Souza; de Araujo, Renato Evangelista; Tanaka, Orlando Motohiro; Oliveira, Dauro Douglas

2015-01-01

Abstract Objective: This article aimed to evaluate in vitro the efficiency of Pro Seal fluoride sealant application in the prevention of white spot lesions around orthodontic brackets. Material and Methods: Brackets were bonded to the buccal surface of bovine incisors, and five groups were formed (n = 15) according to the exposure of teeth to oral hygiene substances and the application of enamel sealant: G1 (control), only brushing was performed with 1.450 ppm fluoride; G2 (control) brushing associated with the use of mouthwash with 225 ppm fluoride; G3, only Pro Seal sealant application was performed with 1.000 ppm fluoride; G4 Pro Seal associated with brushing; G5 Pro Seal associated with brushing and mouthwash. Experimental groups alternated between pH cycling and the procedures described. All specimens were kept at a temperature of 37 °C throughout the entire experiment. Both brushing and immersion in solutions were performed within a time interval of one minute, followed by washing in deionized water three times a day for 28 days. Afterwards, an evaluation by Optical Coherence Tomography (OCT) of the spectral type was performed. In each group, a scanning exam of the white spot lesion area (around the sites where brackets were bonded) and depth measurement of carious lesions were performed. Analysis of variance (ANOVA) was applied to determine whether there were significant differences among groups. For post hoc analysis, Tukey test was used. Results: There was statistically significant difference between groups 1 and 2 (p = 0.003), 1 and 3 (p = 0.008), 1 and 4 (p = 0.000) and 1 and 5 (p = 0.000). The group in which only brushing was performed (Group 1) showed deeper enamel lesion. Conclusion: Pro Seal sealant alone or combined with brushing and/or brushing and the use of a mouthwash with fluoride was more effective in protecting enamel, in comparison to brushing alone. PMID:26691968

Sulfonyl fluoride-based prosthetic compounds as potential 18F labelling agents.

PubMed

Inkster, James A H; Liu, Kate; Ait-Mohand, Samia; Schaffer, Paul; Guérin, Brigitte; Ruth, Thomas J; Storr, Tim

2012-08-27

Nucleophilic incorporation of [(18)F]F(-) under aqueous conditions holds several advantages in radiopharmaceutical development, especially with the advent of complex biological pharmacophores. Sulfonyl fluorides can be prepared in water at room temperature, yet they have not been assayed as a potential means to (18)F-labelled biomarkers for PET chemistry. We developed a general route to prepare bifunctional 4-formyl-, 3-formyl-, 4-maleimido- and 4-oxylalkynl-arylsulfonyl [(18)F]fluorides from their sulfonyl chloride analogues in 1:1 mixtures of acetonitrile, THF, or tBuOH and Cs[(18)F]F/Cs(2)CO(3(aq.)) in a reaction time of 15 min at room temperature. With the exception of 4-N-maleimide-benzenesulfonyl fluoride (3), pyridine could be used to simplify radiotracer purification by selectively degrading the precursor without significantly affecting observed yields. The addition of pyridine at the start of [(18)F]fluorination (1:1:0.8 tBuOH/Cs(2)CO(3(aq.))/pyridine) did not negatively affect yields of 3-formyl-2,4,6-trimethylbenzenesulfonyl [(18)F]fluoride (2) and dramatically improved the yields of 4-(prop-2-ynyloxy)benzenesulfonyl [(18)F]fluoride (4). The N-arylsulfonyl-4-dimethylaminopyridinium derivative of 4 (14) can be prepared and incorporates (18)F efficiently in solutions of 100 % aqueous Cs(2)CO(3) (10 mg mL(-1)). As proof-of-principle, [(18)F]2 was synthesised in a preparative fashion [88(±8) % decay corrected (n=6) from start-of-synthesis] and used to radioactively label an oxyamino-modified bombesin(6-14) analogue [35(±6) % decay corrected (n=4) from start-of-synthesis]. Total preparation time was 105-109 min from start-of-synthesis. Although the (18)F-peptide exhibited evidence of proteolytic defluorination and modification, our study is the first step in developing an aqueous, room temperature (18)F labelling strategy. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fluoride mechanisms.

PubMed

ten Cate, J M; van Loveren, C

1999-10-01

This article discusses fluoride mechanisms in relation to dental caries. The authors specifically address firmly bound versus loosely bound fluoride; different fluoride active ingredients; fluoride and demineralization and remineralization; fluoride slow-release devices and F-releasing dental materials; antimicrobial effects of fluoride; the uptake of fluoride by oral bacteria; inhibition of enolase, protein-intruding ATPase and sugar transport; the various aspects of plaque as it relates to fluoride; and the rational use of fluoride.

Morphological, Thermal, Electrical and Electromechanical Properties of Polyvinylidene Fluoride (PVDF)-Functionalized Carbon Nanotube Composites (Preprint)

DTIC Science & Technology

2012-03-01

several times with deionized water and ethanol to remove undissolved chemicals. Finally the solution was filtered through 0.2 µm cellulose nitrate...was recorded for 3 times and average was used. To observe the morphology of the synthesized samples, FESEM (Quanta 3D ) was performed. Powder was...linear within elastic region and start going to plastic region with further increment in load. For testing electromechanical properties of these f-CNT

Identification of V-type nerve agents in vapor samples using a field-portable capillary gas chromatography/membrane-interfaced electron ionization quadrupole mass spectrometry instrument with Tri-Bed concentrator and fluoridating conversion tube.

PubMed

Ohrui, Y; Nagoya, T; Kurimata, N; Sodeyama, M; Seto, Y

2017-07-01

A field-portable gas chromatography-mass spectrometry (GC-MS) system (Hapsite ER) was evaluated for the detection of nonvolatile V-type nerve agents (VX and Russian VX (RVX)) in the vapor phase. The Hapsite ER system consists of a Tri-Bed concentrator gas sampler, a nonpolar low thermal-mass capillary GC column and a hydrophobic membrane-interfaced electron ionization quadrupole mass spectrometer evacuated by a non-evaporative getter pump. The GC-MS system was attached to a VX-G fluoridating conversion tube containing silver nitrate and potassium fluoride. Sample vapors of VX and RVX were converted into O-ethyl methylphosphonofluoridate (EtGB) and O-isobutyl methylphosphonofluoridate (iBuGB), respectively. These fluoridated derivatives were detected within 10 min. No compounds were detected when the VX and RVX samples were analyzed without the conversion tube. A vapor sample of tabun (GA) was analyzed, in which GA and O-ethyl N,N-dimethylphosphoramidofluoridate were detected. The molar recovery percentages of EtGB and iBuGB from VX and RVX vapors varied from 0.3 to 17%, which was attributed to variations in the vaporization efficiency of the glass vapor container. The conversion efficiencies of the VX-G conversion tube for VX and RVX to their phosphonate derivatives were estimated to be 40%. VX and RVX vapors were detected at concentrations as low as 0.3 mg m -3 . Gasoline vapor was found to interfere with the analyses of VX and RVX. In the presence of 160 mg m -3 gasoline, the detection limits of VX and RVX vapor were increased to 20 mg m -3 . Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Retention of long-term interim restorations with sodium fluoride enriched interim cement

NASA Astrophysics Data System (ADS)

Strash, Carolyn

Purpose: Interim fixed dental prostheses, or "provisional restorations", are fabricated to restore teeth when definitive prostheses are made indirectly. Patients undergoing extensive prosthodontic treatment frequently require provisionalization for several months or years. The ideal interim cement would retain the restoration for as long as needed and still allow for ease of removal. It would also avoid recurrent caries by preventing demineralization of tooth structure. This study aims to determine if adding sodium fluoride varnish to interim cement may assist in the retention of interim restorations. Materials and methods: stainless steel dies representing a crown preparation were fabricated. Provisional crowns were milled for the dies using CAD/CAM technology. Crowns were provisionally cemented onto the dies using TempBond NE and NexTemp provisional cements as well as a mixture of TempBond NE and Duraphat fluoride varnish. Samples were stored for 24h then tested or thermocycled for 2500 or 5000 cycles before being tested. Retentive strength of each cement was recorded using a universal testing machine. Results: TempBond NE and NexTemp cements performed similarly when tested after 24h. The addition of Duraphat significantly decreased the retention when added to TempBond NE. NexTemp cement had high variability in retention over all tested time periods. Thermocycling for 2500 and 5000 cycles significantly decreased the retention of all cements. Conclusions: The addition of Duraphat fluoride varnish significantly decreased the retention of TempBond NE and is therefore not recommended for clinical use. Thermocycling significantly reduced the retention of TempBond NE and NexTemp. This may suggest that use of these cements for three months, as simulated in this study, is not recommended.

Corrosion-fatigue life of commercially pure titanium and Ti-6Al-4V alloys in different storage environments.

PubMed

Zavanelli, R A; Pessanha Henriques, G E; Ferreira, I; De Almeida Rollo, J M

2000-09-01

Removable partial dentures are affected by fatigue because of the cyclic mechanism of the masticatory system and frequent insertion and removal. Titanium and its alloys have been used in the manufacture of denture frameworks; however, preventive agents with fluorides are thought to attack titanium alloy surfaces. This study evaluated, compared, and analyzed the corrosion-fatigue life of commercially pure titanium and Ti-6Al-4V alloy in different storage environments. For each metal, 33 dumbbell rods, 2.3 mm in diameter at the central segment, were cast in the Rematitan system. Corrosion-fatigue strength test was carried out through a universal testing machine with a load 30% lower than the 0.2% offset yield strength and a combined influence of different environments: in air at room temperature, with synthetic saliva, and with fluoride synthetic saliva. After failure, the number of cycles were recorded, and fracture surfaces were examined with an SEM. ANOVA and Tukey's multiple comparison test indicated that Ti-6Al-4V alloy achieved 21,269 cycles (SD = 8,355) against 19,157 cycles (SD = 3, 624) for the commercially pure Ti. There were no significant differences between either metal in the corrosion-fatigue life for dry specimens, but when the solutions were present, the fatigue life was significantly reduced, probably because of the production of corrosion pits caused by superficial reactions.

Understanding Polymorphism Formation in Electrospun Fibers of Immiscible Poly(vinylidene fluoride) Blends

DOE Office of Scientific and Technical Information (OSTI.GOV)

G Zhong; L Zhang; R Su

2011-12-31

Effects of electric poling, mechanical stretching, and dipolar interaction on the formation of ferroelectric ({beta} and/or {gamma}) phases in poly(vinylidene fluoride) (PVDF) have been studied in electrospun fibers of PVDF/polyacrylonitrile (PAN) and PVDF/polysulfone (PSF) blends with PVDF as the minor component, using wide-angle X-ray diffraction and Fourier transform infrared techniques. Experimental results of as-electrospun neat PVDF fibers (beaded vs. bead-free) showed that mechanical stretching during electrospinning, rather than electric poling, was effective to induce ferroelectric phases. For as-electrospun PVDF blend fibers with the non-polar PSF matrix, mechanical stretching during electrospinning again was capable of inducing some ferroelectric phases in additionmore » to the major paraelectric ({alpha}) phase. However, after removing the mechanical stretching in a confined melt-recrystallization process, only the paraelectric phase was obtained. For as-electrospun PVDF blend fibers with the polar (or ferroelectric) PAN matrix, strong intermolecular interactions between polar PAN and PVDF played an important role in the ferroelectric phase formation in addition to the mechanical stretching effect during electrospinning. Even after the removal of mechanical stretching through the confined melt-recrystallization process, a significant amount of ferroelectric phases persisted. Comparing the ferroelectric phase formation between PVDF/PSF and PVDF/PAN blend fibers, we concluded that the local electric field-dipole interactions were the determining factor for the nucleation and growth of polar PVDF phases.« less

Comparative assessment of fluoride varnish and fluoride film for remineralization of postorthodontic white spot lesions in adolescents and adults over a 6-month period: A single-center, randomized controlled clinical trial.

PubMed

He, Tao; Li, Xue; Dong, Ying; Zhang, Na; Zhong, Yisi; Yin, Wei; Hu, Deyu

2016-06-01

The objective of this 3-arm parallel randomized trial was to evaluate the effects of a fluoride varnish and a fluoride film on the remineralization of white spot lesions around orthodontic brackets after orthodontic treatment. Patients who had recently completed orthodontic treatment were randomly assigned to the varnish, film, and control groups. Eligibility criteria included age of 12 to 25 years, good general health, and at least 1 maxillary anterior tooth with a white spot lesion. The primary outcome was the decrease in the lesion volume of each patient after 6 months of treatment; fluorescence loss and area were the secondary outcome measures. Randomization was accomplished according to a computer-generated randomization schedule, and allocation concealment was achieved with nontransparent concealed envelopes. Blinding was applicable for the treatments only. The test groups received fluoride varnish or film treatment once a month for 6 months, and the control group received a placebo treatment. All patients received oral hygiene education and were required to use fluoride toothpaste daily. Quantitative light-induced fluorescence images were taken at baseline and at the 3-month and 6-month follow-ups. A mixed-effects linear model was used to analyze quantitative light-induced fluorescence parameters with confounders integrated into the model. Two hundred forty patients (mean age, 16.9 years; range, 12-25 years) with 597 teeth with a white spot lesion were randomized 1:1:1 to the varnish, film, and control groups. Baseline demographics were similar between groups, and 29 patients were lost to follow-up. The primary analysis was carried out on a per-protocol basis involving 72 patients in the control group, 69 patients in the varnish group, and 70 patients in the film group who completed the study. The product of fluorescence loss and lesion area values were statistically associated with time (estimate, -4.58; 95% confidence interval [CI], -5.84 to -3.31; P <0.0001), and a significant decrease in the product of fluorescence loss and lesion area was observed in all groups after 6 months with each treatment. The interaction between group and time in the statistical analysis indicated that the product of fluorescence loss and lesion area values of the 3 groups followed different trends over time. Further pair-wise comparisons showed that the decreases in the 2 test groups were significantly greater than those in the control group (varnish vs control: estimate, -11.83; 95% CI, -15.39 to -8.26; P <0.0001; film vs control, estimate: -7.72; 95% CI, -11.34 to 4.10; P <0.0001) in the analysis for 6 months. In addition, the decrease in the varnish group was significantly greater than that in the film group (estimate, 4.11; 95% CI, 0.48 to 7.73; P = 0.0266) in the analysis for 6 months. No serious adverse effects associated with the use of the tested varnish, film, or placebo occurred. After removal of the orthodontic brackets, some natural remineralization of white spot lesions occurred, and daily use of fluoride toothpaste may be helpful for this process. However, not all patients experienced this remineralization, and treatment with fluoride varnish or fluoride film induced greater remineralization of white spot lesions. In addition, our results suggest that fluoride varnish may be slightly more effective than fluoride film. However, further similar clinical trials with more patients are needed to definitively determine which fluoride treatment is most effective. This trial was registered on the Chinese Clinical Trial Register, number ChiCTR-TRC-13003764. The details of the trial protocol are posted online at: http://apps.who.int/trialsearch/Trial.aspx?TrialID=ChiCTR-TRC-13003764. Copyright © 2016 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

Occurrence and removal of microbial indicators from municipal wastewaters by nine different MBR systems.

PubMed

Hirani, Zakir M; Decarolis, James F; Lehman, Geno; Adham, Samer S; Jacangelo, Joseph G

2012-01-01

Nine different membrane bioreactor (MBR) systems with different process configurations (submerged and external), membrane geometries (hollow-fiber, flat-sheet, and tubular), membrane materials (polyethersulfone (PES), polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE)) and membrane nominal pore sizes (0.03-0.2 μm) were evaluated to assess the impact of influent microbial concentration, membrane pore size and membrane material and geometries on removal of microbial indicators by MBR technology. The log removal values (LRVs) for microbial indicators increased as the influent concentrations increased. Among the wide range of MBR systems evaluated, the total and fecal coliform bacteria and indigenous MS-2 coliphage were detected in 32, 9 and 15% of the samples, respectively; the 50th percentile LRVs were measured at 6.6, 5.9 and 4.5 logs, respectively. The nominal pore sizes of the membranes, membrane materials and geometries did not show a strong correlation with the LRVs.

Defluoridation of drinking water by electrocoagulation/electroflotation in a stirred tank reactor with a comparative performance to an external-loop airlift reactor.

PubMed

Essadki, A H; Gourich, B; Vial, Ch; Delmas, H; Bennajah, M

2009-09-15

Defluoridation using batch electrocoagulation/electroflotation (EC/EF) was carried out in two reactors for comparison purpose: a stirred tank reactor (STR) close to a conventional EC cell and an external-loop airlift reactor (ELAR) that was recently described as an innovative reactor for EC. The respective influences of current density, initial concentration and initial pH on the efficiency of defluoridation were investigated. The same trends were observed in both reactors, but the efficiency was higher in the STR at the beginning of the electrolysis, whereas similar values were usually achieved after 15min operation. The influence of the initial pH was explained using the analyses of sludge composition and residual soluble aluminum species in the effluents, and it was related to the prevailing mechanisms of defluoridation. Fluoride removal and sludge reduction were both favored by an initial pH around 4, but this value required an additional pre-treatment for pH adjustment. Finally, electric energy consumption was similar in both reactors when current density was lower than 12mA/cm(2), but mixing and complete flotation of the pollutants were achieved without additional mechanical power in the ELAR, using only the overall liquid recirculation induced by H(2) microbubbles generated by water electrolysis, which makes subsequent treatments easier to carry out.

Using microabrasive material to remove fluorosis stains.

PubMed

Allen, Kenneth; Agosta, Claudine; Estafan, Denise

2004-03-01

Increased public access to fluoride has decreased the prevalence of caries and increased the prevalence of fluorosis staining. This article provides a case report involving a conservative method of removing fluorosis stain, as well as describes an in vitro test of the method. A healthy man sought treatment at New York University College of Dentistry for removal of severe, dark brown fluorosis staining on his anterior teeth. To remove the stain, the treating clinician used a microabrasive material, which leaves enamel intact, instead of a tooth-whitening agent, which requires removal of all affected enamel. To demonstrate that enamel structure is not disturbed by the microabrasive material, the authors performed a study using scanning electron microscopy, or SEM. They viewed enamel structure under SEM at x1,000 magnification. They viewed untreated microabraded enamel and compared it with enamel that had been treated for 20 seconds with 37 percent phosphoric acid. An etch pattern was not discernible on the tooth treated with the microabrasive material. The enamel prisms remained intact and the cores were not exposed. Microabrasion removes intrinsic fluorosis stain effectively while protecting enamel. In this case, an enamel shade of brown not in the range of any tooth color shade guide was reduced.

Highly efficient fluoride adsorption from aqueous solution by nepheline prepared from kaolinite through alkali-hydrothermal process.

PubMed

Wang, Hao; Feng, Qiming; Liu, Kun; Li, Zishun; Tang, Xuekun; Li, Guangze

2017-07-01

A direct alkali-hydrothermal induced transformation process was adopted to prepare nepheline from raw kaolinite (shortened form RK in this paper) and NaOH solution in this paper. Structure and morphology characterizations of the synthetic product showed that the nepheline possessed high degree of crystallinity and uniform surface morphology. Specific surface area of nepheline is 18 m 2 /g, with a point of zero charge at around pH 5.0-5.5. The fluoride (F - ions) adsorption by the synthetic nepheline (shortened form SN in this paper) from aqueous solution was also investigated under different experimental conditions. The adsorption process well matched the Langmuir isotherm model with an amazing maximum adsorption capacity of 183 mg/g at 323 K. The thermodynamic parameters (ΔG 0 , ΔH 0 , and ΔS 0 ) for adsorption on SN were also determined from the temperature dependence. The adsorption capacities of fluoride on SN increased with increasing of temperature and initial concentration. Initial pH value also had influence on adsorption process. Adsorption of fluoride was rapidly increased in 5-60 min and thereafter increased slowly to reach the equilibrium in about 90-180 min under all conditions. The adsorption followed a pseudo-second order rate law. Copyright © 2017 Elsevier Ltd. All rights reserved.

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).

Positive influence of Tm3+ on effective Er3+: 3 μm emission in fluoride glass under 980 nm excitation

NASA Astrophysics Data System (ADS)

Huang, Feifei; Wang, Tao; Guo, Yanyan; Lei, Ruoshan; Xu, Shiqing

2017-05-01

Er3+ and Tm3+ singly doped and codoped new fluoride glasses were prepared by traditional melt-quenching method. Efficient 3 μm emission was obtained under 980 nm laser excitation. It is worthy to notice that one of the two ions can be the sensitizer to the other one by depressing the Er3+: 1.5 μm emission through the energy transfer process from Er3+:4I13/2 level to Tm3+:3F4 level. On the basis of measured absorption spectra, the Judd-Ofelt intensity parameters and radiation emission probability were calculated to evaluate the spectroscopic properties. Additionally, the micro-parameters together with the phonon assistance of Er3+:4I13/2 → Tm3+:3F4 and Er3+:4I11/2 → Tm3+:3H5 processes were quantitatively analyzed by using Dexter model. The theoretical micro-parameters results meet well with the experiments which indicates that Er3+/Tm3+ codoped fluoride glass is a potential kind laser glass for 3 μm laser.

A comparative in vitro study investigating the occlusion and mineralization properties of commercial toothpastes in a four-day dentin disc model.

PubMed

Parkinson, Charles R; Willson, Richard J

2011-01-01

The objective of this study was to evaluate the relative level of dentin tubule occlusion and dentin mineralization conferred by a 5% w/w calcium sodium phosphosilicate (45S5)/1450 ppm fluoride toothpaste in comparison to a range of commercial toothpastes reported to occlude dentin tubules. Two separate experiments were employed to (i) determine the level of dentin tubule occlusion, and (ii) explore the change in dentin mineralization conferred by a number of marketed toothpastes and controls, following twice-daily brushing in a longitudinal, acid challenge-based, dentin disc model. In Study I, 192 bovine dentin discs, polished and etched in citric acid to provide a smooth dentin surface with patent tubules, were divided into eight treatment groups and subjected to brushing with one of seven test toothpastes or deionized water over four days. Prior to and between treatments, the dentin samples were stored in saliva. The test products were fluoridated toothpastes containing: calcium sodium phosphosilicate (45S5); strontium acetate; arginine/calcium carbonate; amine fluoride; calcium sulphate/diphosphate; stannous fluoride; casein stabilized amorphous calcium phosphate toothpaste; and a non-occluding negative control, deionized water. At the end of each treatment day (1 though 4), one group of samples was removed for scanning electron microscopy (SEM) analysis and graded on a categorical visual scale to assess the level of dentin tubule occlusion. A subset of samples from Study I was also cross-sectioned and examined using SEM. For the exploratory mineralization study (Study II), 120 dentin specimens were prepared as previously described and divided into four treatment groups consisting of A, C, F, and a tooth sealant varnish (I), and subjected to the treatment regimen described in Study I. The dentin samples were assessed for changes in surface microhardness using an indenter fitted with a Knoop probe and the level of dentin occlusion. In Study I, the 5% w/w calcium sodium phosphosilicate/1450 ppm fluoride-containing toothpaste (A), the stannous fluoride-containing toothpaste (F), and the strontium acetate-containing toothpaste (B) delivered the highest level of occlusion following four days of twice-daily brushing and a twice-daily acid challenge on days 3 and 4. Surface analysis of a subset of Study I samples, following four days of treatment, indicated that the 5% w/w calcium sodium phosphosilicate/1450 ppm fluoride-containing toothpaste formed a distinct layer at the surface of dentin. For Study II, surface microhardness analysis revealed that the 5% w/w calcium sodium phosphosilicate/1450 ppm fluoride-containing toothpaste (A) delivered significantly more surface hardening then the control or competitor toothpastes on days 2 and 4. Desensitizing toothpastes reported to operate by an occlusion mechanism have been observed to confer varying degrees of dentin tubule occlusion and dentin mineralization over four days in an acid challenge-based in vitro model. A 5% w/w calcium sodium phosphosilicate/1450 ppm fluoride-containing toothpaste was observed to impart a significant level of dentin tubule occlusion and surface hardening, and form durable occlusive deposits following four days of twice-daily brushing in vitro.

Fluoride intake of infants living in non-fluoridated and fluoridated areas.

PubMed

Zohoori, F V; Whaley, G; Moynihan, P J; Maguire, A

2014-01-01

Data on fluoride exposure of infants are sparse. This study aimed to estimate total daily fluoride intake (TDFI) of infants aged 1-12 months, living in non-fluoridated and fluoridated areas in north-east England. Daily dietary fluoride intake was assessed using a three-day food diary coupled with analysis of fluoride content of food/drink consumed, using a F-ISE and diffusion method. A questionnaire with an interview was used to collect information on toothbrushing habits. TDFI was estimated from diet, plus fluoride supplements and dentifrice ingestion where used. Thirty-eight infants completed the study; 19 receiving fluoridated water (mean 0.97 mgF/l) and 19 receiving non-fluoridated water (mean 0.19 mgF/l). Mean (SD) TDFI for the infants living in fluoridated and non-fluoridated areas was 0.107 (0.054) and 0.024 (0.015) mg/kg body weight per day, respectively. Diet was the only fluoride source for 87% of infants and none used fluoride supplements. For infants for whom mouth/teeth cleaning was undertaken, dentifrice contribution to TDFI ranged from 24 to 78%. Infants living in fluoridated areas, in general, may receive a fluoride intake, from diet only, of more than the suggested optimal range for TDFI. This emphasises the importance of estimating TDFI at an individual level when recommendations for fluoride use are being considered.

Abatement of sulfur hexafluoride emissions from the semiconductor manufacturing process by atmospheric-pressure plasmas.

PubMed

Lee, How Ming; Chang, Moo Been; Wu, Kuan Yu

2004-08-01

Sulfur hexafluoride (SF6) is an important gas for plasma etching processes in the semiconductor industry. SF6 intensely absorbs infrared radiation and, consequently, aggravates global warming. This study investigates SF6 abatement by nonthermal plasma technologies under atmospheric pressure. Two kinds of nonthermal plasma processes--dielectric barrier discharge (DBD) and combined plasma catalysis (CPC)--were employed and evaluated. Experimental results indicated that as much as 91% of SF6 was removed with DBDs at 20 kV of applied voltage and 150 Hz of discharge frequency for the gas stream containing 300 ppm SF6, 12% oxygen (O2), and 40% argon (Ar), with nitrogen (N2) as the carrier gas. Four additives, including Ar, O2, ethylene (C2H4), and H2O(g), are effective in enhancing SF6 abatement in the range of conditions studied. DBD achieves a higher SF6 removal efficiency than does CPC at the same operation condition. But CPC achieves a higher electrical energy utilization compared with DBD. However, poisoning of catalysts by sulfur (S)-containing species needs further investigation. SF6 is mainly converted to SOF2, SO2F4, sulfur dioxide (SO2), oxygen difluoride (OF2), and fluoride (F2). They do not cause global warming and can be captured by either wet scrubbing or adsorption. This study indicates that DBD and CPC are feasible control technologies for reducing SF6 emissions.

Estimated dietary fluoride intake for New Zealanders.

PubMed

Cressey, Peter; Gaw, Sally; Love, John

2010-01-01

Existing fluoride concentration and consumption data were used to estimate fluoride intakes from the diet and toothpaste use, for New Zealand subpopulations, to identify any population groups at risk of high-fluoride intake. For each sub-population, two separate dietary intake estimates were made--one based on a non-fluoridated water supply (fluoride concentration of 0.1 mg/L), and the other based on a water supply fluoridated to a concentration of 1.0 mg/L. Fluoride concentration data were taken from historical surveys, while food consumption data were taken from national 24-hour dietary recall surveys or from simulated diets. Mean and 95th percentile estimations of dietary fluoride intake were well below the upper level of intake (UL), whether intakes were calculated on the basis of a non-fluoridated or fluoridated water supply. The use of fluoride-containing toothpastes provides additional fluoride intake. For many of the population groups considered, mean fluoride intakes were below the adequate intake (AI) level for caries protection, even after inclusion of the fluoride contribution from toothpaste. Intake of fluoride was driven by consumption of dietary staples (bread, potatoes),beverages (particularly tea, soft drinks, and beer), and the fluoride status of drinking water. Estimates of fluoride intake from the diet and toothpaste did not identify any groups at risk of exceeding the UL, with the exception of infants (6-12 months) living in areas with fluoridated water supplies and using high-fluoride toothpaste. In contrast, much of the adult population may be receiving insufficient fluoride for optimum caries protection from these sources, as represented by the AI.

Serum protein removal from skim milk with a 3-stage, 3× ceramic Isoflux membrane process at 50°C.

PubMed

Adams, Michael C; Barbano, David M

2013-04-01

Small pore microfiltration (MF) can be used to remove serum proteins (SP) from skim milk. The process's SP removal efficiency directly influences the technology's economic feasibility. Our objective was to quantify the capacity of 0.14μm ceramic Isoflux MF membranes (TAMI, Nyons, France) to remove SP from skim milk. A 3-stage, 3×, feed-and-bleed MF study with diafiltration in the latter 2 stages was conducted at 50°C using Isoflux membranes to determine cumulative SP removal percentages and SP removal rates at each processing stage. The experiment was replicated 3 times starting with 3 separate lots of raw milk. In contrast to 3× MF theoretical cumulative SP removal percentages of 68, 90, and 97% after 1, 2, and 3 stages, respectively, the 3× Isoflux MF process removed only 39.5, 58.4, and 70.2% of SP after 1, 2, and 3 stages, respectively. Previous research has been published that provides the skim milk SP removal capacities of 3-stage, 3× 0.1μm ceramic Membralox (Pall Corp., Cortland, NY) uniform transmembrane pressure (UTP), 0.1μm ceramic Membralox graded permeability (GP), and 0.3μm polymeric polyvinylidene fluoride spiral-wound (PVDF-SW) MF systems (Parker-Hannifin, Process Advanced Filtration Division, Tell City, IN) at 50°C. No difference in cumulative SP removal percentage after 3 stages was detected between the Isoflux and previously published PVDF-SW values (70.3%), but SP removal was lower than published GP (96.5%) and UTP (98.3%) values. To remove 95% of SP from 1,000kg of skim milk in 12h it would take 7, 3, 3, and 7 stages with 6.86, 1.91, 2.82, and 17.98m(2) of membrane surface area for the Isoflux, GP, UTP, and PVDF-SW systems, respectively. The MF systems requiring more stages would produce additional permeate at lower protein concentrations. The ceramic MF systems requiring more surface area would incur higher capital costs. The authors hypothesize that SP removal with the Isoflux membranes was lower than theoretical for the following reasons: a range of membrane pore sizes existed (i.e., some pores were too small to pass SP), the selective layer modification and reverse flow conditions at the membrane outlet combined to reduce the effective membrane surface area, and the geometric shape of the Isoflux flow channels promoted early fouling of the membrane and rejection of SP by the foulant. Copyright © 2013 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

A novel UV-photolysis approach with acetone and isopropyl alcohol for the rapid determination of fluoride in organofluorine-containing drugs by spectrophotometry.

PubMed

Mullapudi, Venkata Balarama Krishna; Dheram, Karunasagar

2018-01-01

A UV photolysis decomposition (UVPD) method for the determination of fluoride in fluorine containing pharmaceuticals by spectrophotometry is reported. It is based on the use of high intensity UV-irradiation in the presence of a digesting solution comprising a mixture of acetone and isopropanol. For the optimization of the UVPD procedure, three bulk drugs (levofloxacin, nebivolol and efavirenz) were chosen as representatives of three diverse compounds containing a single fluorine atom, two fluorine atoms, and trifluoromethyl groups respectively. Operational conditions of the UVPD method, such as concentration and volume of reagents (acetone and isopropyl alcohol), and UV irradiation time (1-6 minutes) were optimized. The efficiency of digestion was evaluated by the determination of fluoride in sample digests. Using the developed method, it was possible for complete conversion of the organofluoride to free fluoride ion for its subsequent determination by spectrophotometry based on bleaching of Zr-xylenol orange-color complex. Quantitative recovery (>98%) of the fluorine in the drug samples could be achieved using a mixture of 2% acetone + 2% isopropyl alcohol + 0.003% Na 2 CO 3 in just 5 minutes of UV irradiation, which can be considered an important aspect considering the difficulties involved in the cleavage of the CF bond. Accuracy was evaluated by comparison of results obtained by the UVPD method with the values estimated using formula weight of the compound and no statistical difference was observed between the results. Therefore, the proposed method is suitable for application in routine analysis of fluoride in organofluorine-containing drugs. Copyright © 2016. Published by Elsevier B.V.

Fluoride exposure changed the structure and the expressions of Y chromosome related genes in testes of mice.

PubMed

Cao, Jinling; Chen, Yan; Chen, Jianjie; Yan, Hanghang; Li, Meiyan; Wang, Jundong

2016-10-01

It is known that during spermatogenesis, pluripotent germ cells differentiate to become efficient delivery vehicles to the oocyte of paternal DNA, and the process is easily damaged by external poison. In this study, the effects of fluoride on the body weight, fluoride content in femur, testosterone levels in serum and testis, sperm quality, and the expressions of Y chromosome microdeletion genes and protein levels were examined in testes of Kunming male mice treated with different concentrations of 0, 25, 50, 100 mg/L of NaF in drinking water for 11 weeks, respectively. The results showed that compared with the control group, fluoride contents in three treatment groups were significantly increased and the structure of testes was seriously injured. The testosterone contents and the sperm count were decreased. Sperm malformation ratio was distinctly elevated. The expressions of Sly and HSF2 mRNA were markedly reduced in 100 mg/L NaF group and Ssty2 mRNA expression was dramatically decreased in 50 and 100 mg/L NaF groups. Meanwhile, the protein levels of Ssty2 and Sly were significantly reduced in 50 and 100 mg/L NaF groups and HSF2 protein levels were significantly decreased in 100 mg/L NaF group. These studies indicated that fluoride had toxic effects on male reproductive system by reducing the testosterone and sperm count, and increasing the sperm malformation ratio, supported by the damage of testicular structure, as a consequence of depressed HSF2 level, which resulted in the down-regulation of Ssty2 and Sly mRNA and protein. Copyright © 2016 Elsevier Ltd. All rights reserved.

Influence of sodium content on the properties of bioactive glasses for use in air abrasion.

PubMed

Farooq, Imran; Tylkowski, Maxi; Müller, Steffen; Janicki, Tomasz; Brauer, Delia S; Hill, Robert G

2013-12-01

Air abrasion is used in minimally invasive dentistry for preparing cavities, while removing no or little sound dentine or enamel, and the use of bioactive glass (rather than alumina) as an abrasive could aid in tooth remineralization. Melt-derived bioactive glasses (SiO2-P2O5-CaO-CaF2-Na2O) with low sodium content (0 to 10 mol% Na2O in exchange for CaO) for increased hardness, high phosphate content for high bioactivity and fluoride content for release of fluoride and formation of fluorapatite were produced, and particles between 38 and 80 µm in size were used for cutting soda-lime silicate glass microscope slides and human enamel. Vickers hardness increased with decreasing Na2O content, owing to a more compact silicate network in low sodium content glasses, resulting in shorter cutting times. Cutting times using bioactive glass were significantly longer than using the alumina control (29 µm) when tested on microscope slides; however, glasses showed more comparable results when cutting human enamel. The bioactive glasses formed apatite in Tris buffer within 6 h, which was significantly faster than Bioglass® 45S5 (24 h), suggesting that the hardness of the glasses makes them suitable for air abrasion application, while their high bioactivity and fluoride content make them of interest for tooth remineralization.

The activity of calcium in calcium-metal-fluoride fluxes

NASA Astrophysics Data System (ADS)

Ochifuji, Yuichiro; Tsukihashi, Fumitaka; Sano, Nobuo

1995-08-01

The standard Gibbs energy of reaction Ca (1) + O (mass pct, in Zr) = CaO (s) has been determined as follows by equilibrating molten calcium with solid zirconium in a CaO crucible: Δ G° = -64,300(±700) + 19.8(±3.5) T J/mol (1373 to 1623 K) The activities of calcium in the CaOsatd-Ca- MF2 ( M: Ca, Ba, Mg) and CaOsatd-Ca-NaF systems were measured as a function of calcium composition at high calcium contents at 1473 K on the basis of the standard Gibbs energy. The activities of calcium increase in the order of CaF2, BaF2, and MgF2 at the same calcium fraction of these fluxes. The observed activities are compared with those estimated by using the Temkin model for ionic solutions. Furthermore, the possibility of the removal of tramp elements such as tin, arsenic, antimony, bismuth, and lead from carbon-saturated iron by using calcium-metal-fluoride fluxes is discussed.

Difluoromethane, a new and improved inhibitor of methanotrophy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, L.G.; Sasson, C.; Oremland, R.S.

1998-11-01

Difluoromethane (HFC-32; DFM) is compared to acetylene and methyl fluoride as an inhibitor of methanotrophy in cultures and soils. DFM was found to be a reversible inhibitor of CH{sub 4} oxidation by Methylococcus capsulatus (Bath). Consumption of CH{sub 4} in soil was blocked by additions of low levels of DFM (0.03 kPa), and this inhibition was reversed by DFM removal. Although a small quantity of DFM was consumed during these incubations, its remaining concentration was sufficiently elevated to sustain inhibition. Methanogenesis in anaerobic soil slurries, including acetoclastic methanogenesis, was unaffected by levels of DFM which inhibit methanotrophy. Low levels ofmore » DFM (0.03 kPa) also inhibited nitrification and N{sub 2}O production by soils. DFM is proposed as an improved inhibitor of CH{sub 4} oxidation over acetylene and/or methyl fluoride on the basis of its reversibility, its efficacy at low concentrations, its lack of inhibition of methanogenesis, and its low cost.« less

Fluoride toothpastes and fluoride mouthrinses for home use.

PubMed

Rugg-Gunn, Andrew; Bánóczy, Jolán

2013-11-01

To provide a brief commentary review of fluoride-containing toothpastes and mouthrinses with emphasis on their use at home. Toothpastes and mouthrinses are just two of many ways of providing fluoride for the prevention of dental caries. The first investigations into incorporating fluoride into toothpastes and mouthrinses were reported in the middle 1940s. Unlike water fluoridation (which is 'automatic fluoridation'), fluoride-containing toothpastes and fluoridecontaining mouthrinses are, primarily, for home use and need to be purchased by the individual. By the 1960s, research indicated that fluoride could be successfully incorporated into toothpastes and clinical trials demonstrated their effectiveness. By the end of the 1970s, almost all toothpastes contained fluoride. The widespread use of fluoride- containing toothpastes is thought to be the main reason for much improved oral health in many countries. Of the many fluoride compounds investigated, sodium fluoride, with a compatible abrasive, is the most popular, although amine fluorides are used widely in Europe. The situation is similar for mouthrinses. Concentrations of fluoride (F), commonly found, are 1500 ppm (1500 μg F/g) for toothpastes and 225 ppm (225 μg F/ml) for mouthrinse. Several systematic reviews have concluded that fluoride-containing toothpastes and mouthrinses are effective, and that there is added benefit from their use with other fluoride delivery methods such as water fluoridation. Guidelines for the appropriate use of fluoride toothpastes and mouthrinses are available in many countries. Fluoride toothpastes and mouthrinses have been developed and extensive testing has demonstrated that they are effective and their use should be encouraged. Copyright © 2013 by Academy of Sciences and Arts of Bosnia and Herzegovina.

Oral fluoride retention after use of fluoride dentifrices.

PubMed

Duckworth, R M; Morgan, S N

1991-01-01

Fluoride is the only extensively clinically proven means of reducing dental caries. Despite a large body of epidemiological data on the effectiveness of fluoride, delivered in the form of dentifrices, mouthrinses, drinking water, etc., the precise mode of action of fluoride is not completely understood. The purpose of this paper is to report an investigation of the link between oral fluoride levels and applied fluoride dose from dentifrices. Human salivary fluoride clearance studies and equilibrium baseline studies of fluoride in saliva and plaque have been carried out with dentifrices which contained 1,000, 1,500 and 2,500 micrograms fluoride per gram as sodium monofluorophosphate. After a single brushing with a fluoride dentifrice, salivary fluoride decreased in two distinct phases: an initial rapid phase which lasted for 40-80 min, depending on the individual, and a second slow phase lasting for several hours. The latter phase is believed to be due to fluoride released from an oral fluoride reservoir. During regular repeated use of the test dentifrices, the equilibrium baseline fluoride concentration, attained in both saliva and plaque between one application and the next, increased significantly compared with placebo values. Such elevated baseline fluoride concentrations also increased with increasing Na2FPO3 content of the dentifrices. The present work supports the concept that labile fluoride, stored in an oral fluoride reservoir at the time of treatment application, may maintain a prolonged protective effect against dental caries.

Calibration of equipment for analysis of drinking water fluoride: a comparison study.

PubMed

Quock, Ryan L; Chan, Jarvis T

2012-03-01

Current American Dental Association evidence-based recommendations for prescription of dietary fluoride supplements are based in part on the fluoride concentration of a pediatric patient's drinking water. With these recommendations in mind, this study compared the relative accuracy of fluoride concentration analysis when a common apparatus is calibrated with different combinations of standard values. Fluoride solutions in increments of 0.1 ppm, from a range of 0.1 to 1.0 ppm fluoride, as well as 2.0 and 4.0 ppm, were gravimetrically prepared and fluoride concentration measured in pentad, using a fluoride ion-specific electrode and millivolt meter. Fluoride concentrations of these solutions were recorded after calibration with the following 3 different combinations of standard fluoride solutions: 0.1 ppm and 0.5 ppm, 0.1 ppm and 1.0 ppm, 0.5 ppm and 1.0 ppm. Statistical analysis showed significant differences in the fluoride content of water samples obtained with different two-standard fluoride solutions. Among the two-standard fluoride solutions tested, using 0.5 ppm and 1.0 ppm as two-standard fluoride solutions provided the most accurate fluoride measurement of water samples containing fluoride in the range of 0.1 ppm to 4.0 ppm. This information should be valuable to dental clinics or laboratories in fluoride analysis of drinking water samples.

Fabrication of an optical component

DOEpatents

Nichols, Michael A.; Aikens, David M.; Camp, David W.; Thomas, Ian M.; Kiikka, Craig; Sheehan, Lynn M.; Kozlowski, Mark R.

2000-01-01

A method for forming optical parts used in laser optical systems such as high energy lasers, high average power lasers, semiconductor capital equipment and medical devices. The optical parts will not damage during the operation of high power lasers in the ultra-violet light range. A blank is first ground using a fixed abrasive grinding method to remove the subsurface damage formed during the fabrication of the blank. The next step grinds and polishes the edges and forms bevels to reduce the amount of fused-glass contaminants in the subsequent steps. A loose abrasive grind removes the subsurface damage formed during the fixed abrasive or "blanchard" removal process. After repolishing the bevels and performing an optional fluoride etch, the surface of the blank is polished using a zirconia slurry. Any subsurface damage formed during the loose abrasive grind will be removed during this zirconia polish. A post polish etch may be performed to remove any redeposited contaminants. Another method uses a ceria polishing step to remove the subsurface damage formed during the loose abrasive grind. However, any residual ceria may interfere with the optical properties of the finished part. Therefore, the ceria and other contaminants are removed by performing either a zirconia polish after the ceria polish or a post ceria polish etch.

Application of thermogravimetric studies for optimization of lithium hexafluorophosphate production

NASA Astrophysics Data System (ADS)

Smagin, A. A.; Matyukha, V. A.; Korobtsev, V. P.

Lithium hexafluorophosphate, isolated from hydrogen fluoride solution (anhydrous) by decanting and filtering, is an adduct of composition LiPF 6*HF. By thermogravimetric investigations the dynamics of HF removal from LiPF 6 by LiPF 6*HF thermal decomposition was studied. Based on the experimental data the constants entering into the equations as C = C0*exp( t*K0* exp(- E/RT)) were calculated, explaining the thermal decomposition processes of LiPF 6*HF and LiPF 6.

METHOD FOR REMOVING CONTAMINATION FROM PRECIPITATES

DOEpatents

Stahl, G.W.

1959-01-01

An improvement in the bismuth phosphate carrier precipitation process is presented for the recovery and purification of plutonium. When plutonium, in the tetravalent state, is carried on a bismuth phosphate precipitate, amounts of centain of the fission products are carried along with the plutonium. The improvement consists in washing such fission product contaminated preeipitates with an aqueous solution of ammonium hydrogen fluoride. since this solution has been found to be uniquely effective in washing fission production contamination from the bismuth phosphate precipitate.

Urinary fluoride excretion in preschool children after intake of fluoridated milk and use of fluoride-containing toothpaste.

PubMed

Norman, M; Twetman, S; Hultgren Talvilahti, A; Granström, E; Stecksén-Blicks, C

2017-03-01

To assess the urinary fluoride excretion in preschool children after drinking fluoridated milk with 0.185 mg F and 0.375 mg F and to study the impact of use of fluoride toothpaste. Double-blind cross-over study. Nine healthy children, 2.5-4.5 years of age. In a randomized order, participants drank 1.5 dl milk once daily for 7 days with no fluoride added (control), 0.185 mg fluoride added and 0.375 mg fluoride added. The experiment was performed twice with (Part I) and without (Part II) parental tooth brushing with 1,000 ppm fluoride toothpaste. The fluoride content in the piped drinking water was 0.5 mg F/L. Urinary fluoride excretion. The 24-hour urinary fl uoride excretion/kg body weight varied from 0.014 mg F for the placebo intervention and non-fluoride toothpaste to 0.027 mg F for the 0.375 mg intervention with use of 1,000 ppm fluoride toothpaste. The difference compared with the placebo intervention was not statistically significant for any of the interventions when fluoride toothpaste was used (p⟩0.05) while it was statistically significantly different when non-fluoride toothpaste was used (p⟨0.05). All sources of fluoride must be considered when designing community programs. With 0.5 mg F/L in the drinking water and daily use of fluoride toothpaste, most children had a fluoride intake optimal for dental health. In this setting, additional intake of fluoride milk was within safe limits up to 0.185 mg/day while conclusions about the safety of 0.375 mg/day were uncertain. Copyright© 2017 Dennis Barber Ltd

Determining the optimal fluoride concentration in drinking water for fluoride endemic regions in South India.

PubMed

Viswanathan, Gopalan; Jaswanth, A; Gopalakrishnan, S; Siva Ilango, S; Aditya, G

2009-10-01

Fluoride ion in drinking water is known for both beneficial and detrimental effects on health. The prevalence of fluorosis is mainly due to the intake of large quantities of fluoride through drinking water owing to more than 90% bioavailability. The objective of this study is to predict optimal fluoride level in drinking water for fluoride endemic regions by comprising the levels of fluoride and other water quality parameters in drinking water, prevalence of fluorosis, fluoride intake through water, food and beverages such as tea and coffee and also considering the progressive accumulation of fluoride in animal bones, by comparing with non fluoride endemic areas comprise of the same geological features with the aid of regression analysis. Result of this study shows that increase of fluoride level above 1.33 mg/l in drinking water increases the community fluorosis index (CFI) value more than 0.6, an optimum index value above which fluorosis is considered to be a public health problem. Regression plot between water fluoride and bone fluoride levels indicates that, every increase of 0.5mg/l unit of water fluoride level increases the bone fluoride level of 52 mg/kg unit within 2 to 3 years. Furthermore, the consumption of drinking water containing more than 0.65 mg/l of fluoride can raise the total fluoride intake per day more than 4 mg, which is the optimum fluoride dose level recommended for adults by the Agency for Toxic Substances and Disease Registry. From the result, the people in fluoride endemic areas in South India are advised to consume drinking water with fluoride level within the limit of 0.5 to 0.65 mg/l to avoid further fluorosis risk.

Assessing changes in the physico-chemical properties and fluoride adsorption capacity of activated alumina under varied conditions

USGS Publications Warehouse

Craig, Laura; Stillings, Lisa; Decker, David L.

2017-01-01

Adsorption using activated alumina is a simple method for removing fluoride from drinking water, but to be cost effective the adsorption capacity must be high and effective long-term. The intent of this study was to assess changes in its adsorption capacity under varied conditions. This was determined by evaluating the physico-chemical properties, surface charge, and fluoride (F−) adsorption capacity and rate of activated alumina under conditions such as hydration period, particle size, and slow vs. fast titrations. X-ray diffraction and scanning electron microscopy analyses show that the mineralogy of activated alumina transformed to boehmite, then bayerite with hydration period and a corresponding reduction in adsorption capacity was expected; while surface area analyses show no notable changes with hydration period or particle size. The pH dependent surface charge was three times higher using slow potentiometric titrations as compared to fast titrations (due largely to diffusion into pore space), with the surface acidity generally unaffected by hydration period. Results from batch adsorption experiments similarly show no change in fluoride adsorption capacity with hydration period. There was also no notable difference in fluoride adsorption capacity between the particle size ranges of 0.5–1.0 mm and 0.125–0.250 mm, or with hydration period. However, adsorption rate increased dramatically with the finer particle sizes: at an initial F− concentration of 0.53 mmol L−1 (10 mg L−1), 90% was adsorbed in the 0.125–0.250 mm range after 1 h, while the 0.5–1.0 mm range required 24 h to achieve 90% adsorption. Also, the pseudo-second-order adsorption rate constants for the finer vs. larger particle sizes were 3.7 and 0.5 g per mmol F− per min respectively (24 h); and the initial intraparticle diffusion rate of the former was 2.6 times faster than the latter. The results show that adsorption capacity of activated alumina remains consistent and high under the conditions evaluated in this study, but in order to increase adsorption rate, a relatively fine particle size is recommended.

Adverse effects associated with the clinical use of 4% TiF₄ on teeth enamel: case report.

PubMed

Pedro, Rafael de Lima; Pomarico, Luciana; Villardi, Michele; Maia, Lucianne Cople

2011-05-01

Titanium tetrafluoride (TiF₄) has been studied in dentistry as a promissory alternative for prevention and treatment of carious lesions. However, there are few in vivo studies concerning the consequences of its use on tooth enamel. The goal of this study was to report the effects of a 4% TiF₄ application on the remineralization of an incipient carious lesion of a permanent tooth. This research found an unexpected clinical outcome. A patient with active white spots had two of these lesions treated with 4% TiF₄ associated with fluoridated dentifrice and another lesion treated with fluoridated dentifrice only, thus the remineralization of the two kinds of treatment administered could be observed and compared. An extrinsic pigment appeared in the regions that received the TiF₄ treatment, which was partially removed by professional prophylaxis. Also, regular recidivists of this pigmentation in the review consultations were noted. The authors concluded that although the use of 4% TiF₄ was effective in treating incipient carious lesions on enamel, it was also responsible for an undesired pigmented layer on the tooth to which it was applied. Beyond the varied fluoridated materials used in dentistry, titanium tetrafluoride (TiF₄) deserves attention. This compound has the common properties of fluorides, and researchers are exploring its role in carious lesion prevention, fissure sealing, and tooth erosion prevention in in vitro and in situ studies. Research is also exploring its use for microinfiltration prevention in tooth restoration and hypersensitivity treatment. However, when compared to other fluoridated products TiF₄ demonstrates additional, specific particularities, such as the formation of a titanium dioxide (TiO₂) layer, which is tough, hydrophobic, and resistant in acidic environments. Nevertheless, there are insufficient in vivo studies concerning the consequences of TiF₄-containing products affecting tooth enamel. Thus, the goals of this study were to report the effects of a 4% TiF₄ application on the remineralization of an incipient carious lesion of a permanent tooth and to show the results of a backscattered scanning electron (BSE) analysis that was performed on the primary tooth. The clinical outcome was unexpected.

[The dose-effect relationship of water fluoride levels and renal damage in children].

PubMed

Liu, Jun-Ling; Xia, Tao; Yu, Yao-Yong; Sun, Xian-Zhong; Zhu, Qilong; He, Weihong; Zhang, Ming; Wang, Aiguo

2005-05-01

To explore the dose-effect relationship of water fluoride levels and renal damage in children and observe the difference of renal function between high-loaded fluoride people and dental fluorosis people in the same water fluoride level region. 210 children were divided into seven groups in term of drinking water fluoride levels and whether they suffered from dental fluorosis. Fluoride concentrations in urine and serum and activities of urine NAG and gamma-GT were determined. The urine and serum fluoride of high-loaded fluoride people and dental fluorosis people increased compared with control, moreover fluoride contents in urine and serum increased gradually with the increase of fluoride level in drinking water. Urine NAG and gamma-GT activities significantly increased in dental fluorosis people from area of 2.58 mg/L fluoride in drinking water and in those two groups from area of 4.51 mg/L fluoride in drinking water. Moreover, there existed an obvious dose-effect relationship between the drinking water fluoride concentration and NAG and gamma-GT activity. Over 2.0 mg/L fluoride in drinking water can cause renal damage in children, and the damage degree increases with the drinking water fluoride content. Renal damage degree is not related to whether the children suffered from dental fluorosis and mainly due to water fluoride concentration.

Urinary Fluoride Concentration in Children with Disabilities Following Long-Term Fluoride Tablet Ingestion

ERIC Educational Resources Information Center

Liu, Hsiu-Yueh; Chen, Jung-Ren; Hung, Hsin-Chia; Hsiao, Szu-Yu; Huang, Shun-Te; Chen, Hong-Sen

2011-01-01

Urine is the most commonly utilized biomarker for fluoride excretion in public health and epidemiological studies. Approximately 30-50% of fluoride is excreted from urine in children. Urinary fluoride excretion reflects the total fluoride intake from multiple sources. After administering fluoride tablets to children with disabilities, urinary…

Fluoride content of tank water in Australia.

PubMed

Cochrane, N J; Hopcraft, M S; Tong, A C; Thean, H l; Thum, Y S; Tong, D E; Wen, J; Zhao, S C; Stanton, D P; Yuan, Y; Shen, P; Reynolds, E C

2014-06-01

The aims of this study were to: (1) analyse the fluoride content of tank water; (2) determine whether the method of water collection or storage influenced fluoride content; and (3) survey participant attitudes towards water fluoridation. Plastic tubes and a questionnaire were distributed through dentists to households with water tanks in Victoria. A midstream tank water sample was collected and fluoride analysed in triplicate using ion chromatography All samples (n = 123) contained negligible amounts of fluoride, with a mean fluoride concentration of <0.01 ppm (range: <0.01-0.18 ppm). No statistically significant association was found between fluoride content and variables investigated such as tank material, tank age, roof material and gutter material. Most people did not know whether their tank water contained fluoride and 40.8% preferred to have access to fluoridated water. The majority thought fluoride was safe and more than half of the respondents supported fluoridation. Fluoride content of tank water was well below the optimal levels for caries prevention. People who rely solely on tank water for drinking may require additional exposure to fluoride for optimal caries prevention. © 2014 Australian Dental Association.

Kinetics of fluoride bioavailability in supernatant saliva and salivary sediment.

PubMed

Naumova, E A; Sandulescu, T; Bochnig, C; Gaengler, P; Zimmer, S; Arnold, W H

2012-07-01

The assessment of the fluoride kinetics in whole saliva as well as in the different salivary phases (supernatant saliva and sediment) is essential for the understanding of fluoride bioavailability. To assess the fluoride content, provided by sodium fluoride and amine fluoride, in the supernatant saliva and in salivary sediment. Seven trained volunteers were randomly attributed to 2 groups in a cross-over design and brushed their teeth in the morning for 3 min with a product containing either sodium fluoride or amine fluoride. Saliva was collected before, immediately after tooth brushing and 30, 120, and 360 min later and measured. The samples were centrifuged 10 min at 3024 × g. Fluoride content of the supernatant saliva and of the sediment was analysed using a fluoride sensitive electrode. All subjects repeated the study cycles 2 times, and statistical analyses were made using the nonparametric sign test for related samples, the Wilcoxon-Mann-Whitney-test for independent samples. There was a significant increase in fluoride immediately after tooth brushing in both groups in saliva and sediment. The distribution of fluoride between salivary sediment and supernatant saliva (ratio) varied considerably at the different collection times: decreased from 17.87 in baseline samples of saliva to 0.07 immediately and to 0.86 half an hour after tooth brushing in the sodium fluoride group and from 14.33 to 2.85 and to 3.09 in the amine fluoride group. Furthermore after 120 min and after 360 min after tooth brushing the ratio increased from 17.6 to 31.6 in the sodium fluoride group and from 20.5 to 25.76 in the amine fluoride group. No difference was found in the sediment-supernatant saliva ratio between the sodium fluoride and the amine fluoride groups 360 min after tooth brushing. For the assessment of fluoride kinetics in whole saliva it is necessary to pay attention to at least four factors: fluoride formulation, time after fluoride application, fluoride concentration in supernatant saliva and fluoride concentration in salivary sediment. This study was approved by the Ethical Committee of the University of Witten/Herdecke permission 21/2008. Copyright © 2012 Elsevier Ltd. All rights reserved.

Boric-Acid-Functional Lanthanide Metal-Organic Frameworks for Selective Ratiometric Fluorescence Detection of Fluoride Ions.

PubMed

Yang, Zhong-Rui; Wang, Man-Man; Wang, Xue-Sheng; Yin, Xue-Bo

2017-02-07

Here, we report that boric acid is used to tune the optical properties of lanthanide metal-organic frameworks (LMOFs) for dual-fluorescence emission and improves the selectivity of LMOFs for the determination of F - ions. The LMOFs are prepared with 5-boronoisophthalic acid (5-bop) and Eu 3+ ions as the precursors. Emission mechanism study indicates that 5-bop is excited with UV photons to produce its triplet state, which then excites Eu 3+ ions for their red emission. This is the general story of the antenna effect, but electron-deficient boric acid decreases the energy transfer efficiency from the triplet state of 5-bop to Eu 3+ ions, so dual emission from both 5-bop and Eu 3+ ions is efficiently excited at the single excitation of 275 nm. Moreover, boric acid is used to identify fluoride specifically as a free accessible site. The ratiometric fluorescent detection of F - ions is validated with the dual emission at single excitation. The LMOFs are very monodisperse, so the determination of aqueous F - ions is easily achieved with high selectivity and a low detection limit (2 μM). For the first time, we reveal that rational selection of functional ligands can improve the sensing efficiency of LMOFs through tuning their optical property and enhancing the selectivity toward targets.

Performance characteristics of proximity focused ultraviolet image converters

NASA Technical Reports Server (NTRS)

Williams, J. T.; Feibelman, W. A.

1973-01-01

Performance characteristics of Bendix type BX 8025-4522 proximity focused image tubes for ultraviolet to visible light conversion are presented. Quantum efficiency, resolution, background, geometric distortion, and environmental test results are discussed. The converters use magnesium fluoride input windows with Cs - Te photocathodes, and P-11 phosphors on fiber optic output windows.

Performance characteristics of proximity focused ultraviolet image converters

NASA Technical Reports Server (NTRS)

Williams, J. T.; Feibelman, W. A.

1973-01-01

Performance characteristics of Bendix type BX 8025-4522 proximity focused image tubes for UV to visible light conversion are presented. Quantum efficiency, resolution, background, geometric distortion, and environmental test results are discussed. The converters use magnesium fluoride input windows with Cs-Te photocathodes and P-11 phosphors on fiber optic output windows.

Mid-infrared supercontinuum generation in fluoride fiber amplifiers: current status and future perspectives

NASA Astrophysics Data System (ADS)

Gauthier, Jean-Christophe; Robichaud, Louis-Rafaël; Fortin, Vincent; Vallée, Réal; Bernier, Martin

2018-06-01

The quest for a compact and efficient broadband laser source able to probe the numerous fundamental molecular absorption lines in the mid-infrared (3-8 µm) for various applications has been going on for more than a decade. While robust commercial fiber-based supercontinuum (SC) systems have started to appear on the market, they still exhibit poor energy conversion into the mid-infrared (typically under 30%) and are generally not producing wavelengths exceeding 4.7 µm. Here, we present an overview of the results obtained from a novel approach to SC generation based on spectral broadening inside of an erbium-doped fluoride fiber amplifier seeded directly at 2.8 µm, allowing mid-infrared conversion efficiencies reaching up to 95% and spectral coverage approaching the transparency limit of ZrF4 (4.2 µm) and InF3 (5.5 µm) fibers. The general concept of the approach and the physical mechanisms involved are presented alongside the various configurations of the system to adjust the output characteristics in terms of spectral coverage and output power for different applications.

Focus on Fluorides: Update on the Use of Fluoride for the Prevention of Dental Caries

PubMed Central

Carey, Clifton M.

2014-01-01

Declarative Title: Improving the efficacy of fluoride therapies reduces dental caries and lowers fluoride exposure. Background Fluoride is delivered to the teeth systemically or topically to aid in the prevention of dental caries. Systemic fluoride from ingested sources is in blood serum and can be deposited only in teeth that are forming in children. Topical fluoride is from sources such as community water, processed foods, beverages, toothpastes, mouthrinses, gels, foams, and varnishes. The United States Centers for Disease Control and Prevention (CDC) and the American Dental Association (ADA) have proposed changes in their long standing recommendations for the amount of fluoride in community drinking water in response to concerns about an increasing incidence of dental fluorosis in children. Current research is focused on the development of strategies to improve fluoride efficacy. The purpose of this update is to inform the reader about new research and policies related to the use of fluoride for the prevention of dental caries. Methods Reviews of the current research and recent evidence based systematic reviews on the topics of fluoride are presented. Topics discussed include: updates on community water fluoridation research and policies; available fluoride in dentifrices; fluoride varnish compositions, use, and recommendations; and other fluoride containing dental products. This update provides insights into current research and discusses proposed policy changes for the use of fluoride for the prevention of dental caries. Conclusions The dental profession is adjusting their recommendations for fluoride use based on current observations of the halo effect and subsequent outcomes. The research community is focused on improving the efficacy of fluoride therapies thus reducing dental caries and lowering the amount of fluoride required for efficacy. PMID:24929594

Focus on fluorides: update on the use of fluoride for the prevention of dental caries.

PubMed

Carey, Clifton M

2014-06-01

Improving the efficacy of fluoride therapies reduces dental caries and lowers fluoride exposure. Fluoride is delivered to the teeth systemically or topically to aid in the prevention of dental caries. Systemic fluoride from ingested sources is in blood serum and can be deposited only in teeth that are forming in children. Topical fluoride is from sources such as community water, processed foods, beverages, toothpastes, mouthrinses, gels, foams, and varnishes. The United States Centers for Disease Control and Prevention (CDC) and the American Dental Association (ADA) have proposed changes in their long standing recommendations for the amount of fluoride in community drinking water in response to concerns about an increasing incidence of dental fluorosis in children. Current research is focused on the development of strategies to improve fluoride efficacy. The purpose of this update is to inform the reader about new research and policies related to the use of fluoride for the prevention of dental caries. Reviews of the current research and recent evidence based systematic reviews on the topics of fluoride are presented. Topics discussed include: updates on community water fluoridation research and policies; available fluoride in dentifrices; fluoride varnish compositions, use, and recommendations; and other fluoride containing dental products. This update provides insights into current research and discusses proposed policy changes for the use of fluoride for the prevention of dental caries. The dental profession is adjusting their recommendations for fluoride use based on current observations of the halo effect and subsequent outcomes. The research community is focused on improving the efficacy of fluoride therapies thus reducing dental caries and lowering the amount of fluoride required for efficacy. Copyright © 2014 Elsevier Inc. All rights reserved.

Fluoride Supplementation Adherence and Barriers in a Community Without Water Fluoridation.

PubMed

Flood, Shannon; Asplund, Karin; Hoffman, Benjamin; Nye, Allison; Zuckerman, Katharine E

2017-04-01

To prevent early childhood caries, the American Dental Association recommends oral fluoride supplementation for children in communities lacking water fluoridation who are at high caries risk. However, patient adherence to oral fluoride supplementation has not been studied in this population. This study assessed adherence to oral fluoride and barriers to adherence in a community lacking water fluoridation. A self-administered survey was completed in a systematic sample of 209 parents of children aged 6 months to 4 years, during a primary care visit in an urban academic medical center. Participants reported frequency of administering oral fluoride to their children, as well as agreement or disagreement with proposed barriers to supplementation. Bivariate and multivariate analyses were used to assess adherence with oral supplementation and the association of barriers to supplementation and child receipt of fluoride on the day before. More than half of parents either had not or did not know if their child had received fluoride on the day before. Approximately 1 in 4 of parents had given fluoride in 0 of the previous 7 days. Difficulty remembering to give fluoride and agreeing that the child does not need extra fluoride were associated with not receiving fluoride on the day before. Adherence to oral fluoride supplementation in the primary care setting is low. Difficulty remembering to give fluoride daily is the greatest barrier to adherence. Further research on interventions to reduce common barriers is needed to increase fluoride administration and reduce early childhood caries in communities lacking water fluoridation. Copyright © 2016 Academic Pediatric Association. Published by Elsevier Inc. All rights reserved.

Oral fluoride levels 1 h after use of a sodium fluoride rinse: effect of sodium lauryl sulfate.

PubMed

Vogel, Gerald L; Schumacher, Gary E; Chow, Laurence C; Tenuta, Livia M A

2015-01-01

Increasing the concentration of free fluoride in oral fluids is an important goal in the use of topical fluoride agents. Although sodium lauryl sulfate (SLS) is a common dentifrice ingredient, the influence of this ion on plaque fluid and salivary fluid fluoride has not been examined. The purpose of this study was to investigate the effect of SLS on these parameters and to examine the effect of this ion on total (or whole) plaque fluoride, an important source of plaque fluid fluoride after a sufficient interval following fluoride administration, and on total salivary fluoride, a parameter often used as a surrogate measure of salivary fluid fluoride. Ten subjects accumulated plaque for 48 h before rinsing with a 12 mmol/l NaF (228 µg/g F) rinse containing or not containing 0.5% (w/w) SLS. SLS had no statistically significant effect on total plaque and total saliva fluoride but significantly increased salivary fluid and plaque fluid fluoride (by 147 and 205%, respectively). These results suggest that the nonfluoride components of topical agents can be manipulated to improve the fluoride release characteristics from oral fluoride reservoirs and that statistically significant change may be observed in plaque fluid and salivary fluid fluoride concentrations that may not be observed in total plaque and total saliva fluoride concentrations.

The effect of fluoridation and its discontinuation on fluoride profiles in the alveolar bone of rat.

PubMed

Ohmi, Kyohei; Nakagaki, Haruo; Tsuboi, Shinji; Okumura, Akihiro; Sugiyama, Tomoko; Thuy, Tran Thu; Robinson, Colin

2005-10-01

We investigated the effect of fluoridation and its discontinuation on fluoride content in the alveolar portion of the mandible in rats. Drinking water with three different fluoride contents (0, 50, 100 ppmF) was given to rats for three different periods (4, 13 and 25 weeks). Fluoride concentrations were measured in the crest, the middle, and the apical parts of the alveolar bone and in the body of the mandible. Furthermore, after fluoridated drinking water was given to rats for 4 or 13 weeks, distilled water was given to them for 21 or 12 weeks respectively; and the effect of the discontinuation on fluoride profiles was investigated. Layer samples were analyzed by abrasive microsampling. Fluoride and phosphorus concentrations were determined by ion-specific electrode and colorimetric procedures, respectively. There was an increase in fluoride concentrations in the mandible in proportion to the fluoride content in the drinking water and the duration of fluoridation. After fluoridation was discontinued, fluoride concentrations in the surface layers of the mandible presented a decrease. Among the four different parts of the mandible, the upper part of the alveolar bone and the alveolar crest part presented the highest rates of reduction. The relative reduction rate of fluoride concentration was closely related to the duration of discontinuation. The alveolar crest was affected most by the discontinuation of fluoridation, presenting the greatest reduction.

Simultaneous removal of phosphorus and EfOM using MIEX, coagulation, and low-pressure membrane filtration.

PubMed

Kim, Hyun-Chul; Timmes, Thomas C; Dempsey, Brian A

2015-01-01

The feasibility of using magnetic ion exchange (MIEX) treatment, in-line alum coagulation, and low-pressure membrane filtration was investigated for the simultaneous removal of total phosphorus (TP) and effluent organic matter (EfOM) from biologically treated wastewater. The focus was also placed on minimizing fouling of polyvinylidene fluoride and polyethersulfone membranes, which are the most commonly used low-pressure membranes in new and retrofit wastewater treatment plants. MIEX alone was effective for the removal of EfOM, and MIEX plus a small alum dose was very effective in removing both EfOM and TP. MIEX removed phosphorus, but organic acids in EfOM were preferentially removed, and the effects of competing anions on the removal of EfOM were insignificant. All the pretreatment strategies decreased the resistance to filtration. The greatest decrease in fouling was achieved by using MIEX (15 mL L⁻¹) plus a very low dose of alum (∼0.5 mg Al L⁻¹). Sweep floc coagulation using alum and without MIEX also significantly decreased fouling but did not effectively remove EfOM and produced high floc volume that could be problematic for inside-out hollow-fibre modules. The addition of these reagents into rapid mix followed by membrane filtration would provide operational simplicity and could be easily retrofitted at existing membrane filtration facilities.

Fluoride barriers in Nb/Pb Josephson junctions

NASA Astrophysics Data System (ADS)

Asano, H.; Tanabe, K.; Michikami, O.; Igarashi, M.; Beasley, M. R.

1985-03-01

Josephson tunnel junctions are fabricated using a new class of artificial barriers, metal fluorides (Al fluoride and Zr fluoride). These fluoride barriers are deposited on the surface of a Nb base electrode, which are previously cleaned using a CF4 cleaning process, and covered by a Pb counterelectrode. The junctions with both Al fluoride and Zr fluoride barriers exhibit good tunneling characteristics and have low specific capacitance. In the case of Zr fluoride, it is observed that reasonable resistances are obtained even at thickness greater than 100 A. This phenomenon might be explained by tunneling via localized states in Zr fluoride.

Eukaryotic resistance to fluoride toxicity mediated by a widespread family of fluoride export proteins.

PubMed

Li, Sanshu; Smith, Kathryn D; Davis, Jared H; Gordon, Patricia B; Breaker, Ronald R; Strobel, Scott A

2013-11-19

Fluorine is an abundant element and is toxic to organisms from bacteria to humans, but the mechanisms by which eukaryotes resist fluoride toxicity are unknown. The Escherichia coli gene crcB was recently shown to be regulated by a fluoride-responsive riboswitch, implicating it in fluoride response. There are >8,000 crcB homologs across all domains of life, indicating that it has an important role in biology. Here we demonstrate that eukaryotic homologs [renamed FEX (fluoride exporter)] function in fluoride export. FEX KOs in three eukaryotic model organisms, Neurospora crassa, Saccharomyces cerevisiae, and Candida albicans, are highly sensitized to fluoride (>200-fold) but not to other halides. Some of these KO strains are unable to grow in fluoride concentrations found in tap water. Using the radioactive isotope of fluoride, (18)F, we developed an assay to measure the intracellular fluoride concentration and show that the FEX deletion strains accumulate fluoride in excess of the external concentration, providing direct evidence of FEX function in fluoride efflux. In addition, they are more sensitive to lower pH in the presence of fluoride. These results demonstrate that eukaryotic FEX genes encode a previously unrecognized class of fluoride exporter necessary for survival in standard environmental conditions.

Eukaryotic resistance to fluoride toxicity mediated by a widespread family of fluoride export proteins

PubMed Central

Li, Sanshu; Smith, Kathryn D.; Davis, Jared H.; Gordon, Patricia B.; Breaker, Ronald R.; Strobel, Scott A.

2013-01-01

Fluorine is an abundant element and is toxic to organisms from bacteria to humans, but the mechanisms by which eukaryotes resist fluoride toxicity are unknown. The Escherichia coli gene crcB was recently shown to be regulated by a fluoride-responsive riboswitch, implicating it in fluoride response. There are >8,000 crcB homologs across all domains of life, indicating that it has an important role in biology. Here we demonstrate that eukaryotic homologs [renamed FEX (fluoride exporter)] function in fluoride export. FEX KOs in three eukaryotic model organisms, Neurospora crassa, Saccharomyces cerevisiae, and Candida albicans, are highly sensitized to fluoride (>200-fold) but not to other halides. Some of these KO strains are unable to grow in fluoride concentrations found in tap water. Using the radioactive isotope of fluoride, 18F, we developed an assay to measure the intracellular fluoride concentration and show that the FEX deletion strains accumulate fluoride in excess of the external concentration, providing direct evidence of FEX function in fluoride efflux. In addition, they are more sensitive to lower pH in the presence of fluoride. These results demonstrate that eukaryotic FEX genes encode a previously unrecognized class of fluoride exporter necessary for survival in standard environmental conditions. PMID:24173035

Fluoride metabolism when added to salt.

PubMed

Whitford, Gary M

2005-01-01

The purpose of this review is to present the general characteristics of the metabolism of fluoride particularly as it occurs when ingested with fluoridated salt. Following the absorption of salt-borne fluoride from the stomach and intestines, its metabolism is identical to that of water-borne fluoride or other vehicles containing ionized fluoride. Because fluoridated salt is almost always ingested with food, however, absorption from the gastrointestinal tract may be delayed or reduced. Reports dealing with this subject have shown that fluoride absorption is delayed and, therefore, peak plasma concentrations are lower than when fluoride is ingested with water. The amount of ingested fluoride that is finally absorbed, however, is not appreciably affected unless the meal is composed mainly of components with high calcium concentrations. In this case, the extent of absorption can be reduced by as much as 50%. Fluoridated salt is also ingested less frequently than fluoridated water. Data are presented to show that the dose size and frequency of ingestion have only minor effects on fluoride retention in the body and on the concentrations in plasma, bone and enamel. Finally, calculations are presented to show that the risk of acute toxicity from fluoridated salt is virtually non-existent.

Fluoride content of still bottled water in Australia.

PubMed

Cochrane, N J; Saranathan, S; Morgan, M V; Dashper, S G

2006-09-01

Recently there has been a considerable increase in the consumption of bottled water in Australia. Overseas studies have found the fluoride levels in many bottled waters are well below levels considered optimal for preventing dental caries. This raises the concern that if bottled water is regularly consumed an effective means of preventing dental caries is unavailable. The aim of this study was to determine the fluoride concentration in 10 popular brands of still bottled water currently sold in Australia. The fluoride content of water samples were determined using an ion analyser and compared to a fluoride standard. The fluoride concentration of all bottled waters was less than 0.08 ppm. Only three of the 10 brands indicated the fluoride content on their labels. Melbourne reticulated water was found to be fluoridated at 1.02 ppm. All bottled waters tested contained negligible fluoride which justifies the concern that regular consumption of bottled water may reduce the benefits gained from water fluoridation. It is recommended that all bottled water companies should consider stating their fluoride content on their labels. This will inform consumers and dental care providers of the levels of fluoride in bottled water and allow an informed decision regarding consumption of fluoridated versus non-fluoridated drinking water.

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)

Determination of total fluoride in HF/HNO3/H2SiF6 etch solutions by new potentiometric titration methods.

PubMed

Weinreich, Wenke; Acker, Jörg; Gräber, Iris

2007-03-30

In the photovoltaic industry the etching of silicon in HF/HNO(3) solutions is a decisive process for cleaning wafer surfaces or to produce certain surface morphologies like polishing or texturization. With regard to cost efficiency, a maximal utilisation of etch baths in combination with highest quality and accuracy is strived. To provide an etch bath control realised by a replenishment with concentrated acids the main constituents of these HF/HNO(3) etch solutions including the reaction product H(2)SiF(6) have to be analysed. Two new methods for the determination of the total fluoride content in an acidic etch solution based on the precipitation titration with La(NO(3))(3) are presented within this paper. The first method bases on the proper choice of the reaction conditions, since free fluoride ions have to be liberated from HF and H(2)SiF(6) at the same time to be detected by a fluoride ion-selective electrode (F-ISE). Therefore, the sample is adjusted to a pH of 8 for total cleavage of the SiF(6)(2-) anion and titrated in absence of buffers. In a second method, the titration with La(NO(3))(3) is followed by a change of the pH-value using a HF resistant glass-electrode. Both methods provide consistent values, whereas the analysis is fast and accurate, and thus, applicable for industrial process control.

Ammonium Fluoride Mediated Synthesis of Anhydrous Metal Fluoride-Mesoporous Carbon Nanocomposites for High-Performance Lithium Ion Battery Cathodes.

PubMed

Chun, Jinyoung; Jo, Changshin; Sahgong, Sunhye; Kim, Min Gyu; Lim, Eunho; Kim, Dong Hyeon; Hwang, Jongkook; Kang, Eunae; Ryu, Keun Ah; Jung, Yoon Seok; Kim, Youngsik; Lee, Jinwoo

2016-12-28

Metal fluorides (MF x ) are one of the most attractive cathode candidates for Li ion batteries (LIBs) due to their high conversion potentials with large capacities. However, only a limited number of synthetic methods, generally involving highly toxic or inaccessible reagents, currently exist, which has made it difficult to produce well-designed nanostructures suitable for cathodes; consequently, harnessing their potential cathodic properties has been a challenge. Herein, we report a new bottom-up synthetic method utilizing ammonium fluoride (NH 4 F) for the preparation of anhydrous MF x (CuF 2 , FeF 3 , and CoF 2 )/mesoporous carbon (MSU-F-C) nanocomposites, whereby a series of metal precursor nanoparticles preconfined in mesoporous carbon were readily converted to anhydrous MF x through simple heat treatment with NH 4 F under solventless conditions. We demonstrate the versatility, lower toxicity, and efficiency of this synthetic method and, using XRD analysis, propose a mechanism for the reaction. All MF x /MSU-F-C prepared in this study exhibited superior electrochemical performances, through conversion reactions, as the cathode for LIBs. In particular, FeF 3 /MSU-F-C maintained a capacity of 650 mAh g -1 FeF3 across 50 cycles, which is ∼90% of its initial capacity. We expect that this facile synthesis method will trigger further research into the development of various nanostructured MF x for use in energy storage and other applications.

Development of bimetal oxide doped multifunctional polymer nanocomposite for water treatment

NASA Astrophysics Data System (ADS)

Saxena, Swati; Saxena, Umesh

2016-08-01

Bimetal oxide doped polymer nanocomposite was developed using Alumina and Iron (III) Oxide as nanoparticles with Nylon 6, 6 and Poly (sodium-4-styrenesulphonate) as polymer matrix for removal of pollutants from water. The blend sample of polymers was prepared by well established solution blending technique and their nanocomposite samples were prepared through dispersion technique during the solution casting of blend sample. The fabricated composites were characterized adopting FTIR, XRD, FESEM and EDX techniques. XRD and FESEM were used for morphological characterization of nano phase, while FTIR and EDX analysis were adopted for characterization of chemical moieties in composites. In the study of pollutant removal capacities of prepared composites, 6 % nanocomposite provided the best results. It exhibited the maximum removal of all parameters. The removal of total alkalinity was 66.67 %, total hardness 42.85 %, calcium 66.67 %, magnesium 25 %, chloride 58.66 %, nitrate 34.78 %, fluoride 63.85 %, TDS 41.27 % and EC was up to the level of 41.37 % by this composite. The study is a step towards developing multifunctional, cost-effective polymer nanocomposites for water remediation applications.

Encapsulation of ZnO particles by metal fluorides: Towards an application as transparent insulating coatings for windows

NASA Astrophysics Data System (ADS)

Trenque, Isabelle; Mornet, Stéphane; Duguet, Etienne; Majimel, Jérôme; Brüll, Annelise; Teinz, Katharina; Kemnitz, Erhard; Gaudon, Manuel

2013-01-01

Because ZnO is a promising candidate for getting efficient films or varnishes with thermal insulating abilities for windows applications, the effect of the encapsulation of ZnO particles in shells of low refractive index material on the improvement of the visible light transmission was investigated. ZnO-MgF2 core-shell particles were synthesized by deposition of fluoride sols on ZnO particles through a vacuum slip casting process like. The transmission behaviours were first indirectly studied by diffuse reflexion measurements on powder beds. Then, particle films were elaborated by a screen printing process which ensured direct transmission measurements. The encapsulation of ZnO particles with a coating shell of 1.3 wt.% of MgF2 improves the visible light transmission of 32%.

Absorption, distribution and excretion of inhaled hydrogen fluoride in the rat

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morris, J.B.

1979-01-01

Rats were subjected to whole body HF exposure for 6 hrs or to nose-only HF exposure for 1 hr. Total and/or ionic fluoride concentrations in selected tissues were determined at various times following exposure. In rats sacrificed 6 hrs after whole body exposure, dose-dependent increases in lung, plasma, and kidney total and ionic fluoride concentration occurred. Rats excreted more fluoride in the urine after whole body exposure than could be explained by the amount of HF inhaled. Considerable evidence suggests that airborne HF deposits on fur and is then ingested due to preening activity. Urinary fluoride excretion was increased bymore » nose-only exposure. The urinary fluoride excretion accounted for approximately twice the fluoride estimated to be inhaled during exposure. Tissue fluoride concentrations were elevated immediately after nose-only exposure. Fluoride concentrations in lung and kidney returned to control levels within 12 hrs. Plasma fluoride concentration was slightly elevated 24 hrs after the start of the 1 hr exposure but was at control levels at 96 hrs. Immediately following nose-only exposure, lung ionic fluoride concentrations were less than plasma ionic fluoride concentrations suggesting that the fluoride in the lung had reached that site via plasma transport rather than by inhalation. A dose-dependent increase in plasma ionic fluoride concentration occurred after upper respiratory tract HF exposure providing strong evidence that fluoride is absorbed systemically from that site. The plasma ionic fluoride concentration after upper respiratory tract exposure was of sufficient magnitude to account for the plasma fluoride concentrations observed in intact nose-only exposed rats. (ERB)« less

Exposure to water fluoridation and caries increment.

PubMed

Spencer, A J; Armfield, J M; Slade, G D

2008-03-01

The objective of this cohort study was to examine the association between exposure to water fluoridation and the increment of dental caries in two Australian states: Queensland (Qld)--5 per cent fluoridation coverage; and South Australia (SA)--70 per cent fluoridation coverage. Stratified random samples were drawn from fluoridated Adelaide and the largely non-fluoridated rest-of-state in SA, and fluoridated Townsville and non-fluoridated Brisbane in Qld. Children were enrolled between 1991 and 1992 (SA: 5-15 yrs old, n = 9,980; Qld: 5-12 yrs old, n = 10,695). Follow-up caries status data for 3 years (+/- 1/2 year) were available on 8,183 children in SA and 6,711 children in Qld. Baseline data on lifetime exposure to fluoridated water, use of other fluorides and socio-economic status (SES) were collected by questionnaire, and tooth surface caries status by dental examinations in school dental service clinics. Higher per cent lifetime exposure to fluoridated water (6 categories: 0;1-24; 25-49; 50-74; 75-99; 100 per cent) was a significant predictor (ANOVA, p < 0.01) of lower annualised Net Caries Increment (NCI) for the deciduous dentition in SA and Qld, but only for Qld in the permanent dentition. These associations persisted in multiple linear regression analyses controlling for age, gender, exposure to other fluorides and SES (p < 0.05). Water fluoridation was effective in reducing caries increment, even in the presence of a dilution effect from other fluorides. The effect of fluoridated water consumption was strongest in the deciduous dentition and where diffusion of food and beverages from fluoridated to non-fluoridated areas was less likely.

SULPHUR DIOXIDE LEACHING OF URANIUM CONTAINING MATERIAL

DOEpatents

Thunaes, A.; Rabbits, F.T.; Hester, K.D.; Smith, H.W.

1958-12-01

A process is described for extracting uranlum from uranium containing material, such as a low grade pitchblende ore, or mill taillngs, where at least part of the uraniunn is in the +4 oxidation state. After comminuting and magnetically removing any entrained lron particles the general material is made up as an aqueous slurry containing added ferric and manganese salts and treated with sulfur dioxide and aeration to an extent sufficient to form a proportion of oxysulfur acids to give a pH of about 1 to 2 but insufficient to cause excessive removal of the sulfur dioxide gas. After separating from the solids, the leach solution is adjusted to a pH of about 1.25, then treated with metallic iron in the presence of a precipitant such as a soluble phosphate, arsonate, or fluoride.

Removal of nanoaerosol during the bubbling of the salt melt of beryllium and lithium fluorides for the preparation of reactor radioisotopes

NASA Astrophysics Data System (ADS)

Zagnit'ko, A. V.; Chuvilin, D. Yu.

2010-06-01

The parameters of aerosol particles formed in the course of the spontaneous thermal condensation of vapors and bubbling a 66LiF-34BeF2 (mol %) eutectic salt mixture with helium have been studied. For this purpose, a vertical bubbling mode at T ≈ 900 K and an ampule device for obtaining reactor radioisotopes for medical applications were used. The rate of the bulk removal and the chemical composition of aerosols were measured. The size distribution of the aerosol particles was bimodal, and the mass concentration of the particles exceeded by far the maximum permissible concentration (MPC). The characteristics of regenerated nickel multilayer nanofilters for ultrahigh filtration of aerosols from the salt liquid melt were analyzed.

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

Physiologic conditions affect toxicity of ingested industrial fluoride.

PubMed

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.

21 CFR 177.2510 - Polyvinylidene fluoride resins.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Polyvinylidene fluoride resins. 177.2510 Section... Repeated Use § 177.2510 Polyvinylidene fluoride resins. Polyvinylidene fluoride resins may be safely used... fluoride resins consist of basic resins produced by the polymerization of vinylidene fluoride. (b) The...

Comparison of in vitro fluoride uptake from whitening toothpastes and a conventional toothpaste in demineralised enamel.

PubMed

Altenburger, Markus J; Bernhart, Jasmin; Schicha, Thurid D; Wrbas, Karl-Thomas; Hellwig, Elmar

2010-01-01

Studies on the compatibility of abrasives and fluoride compounds deal exclusively with fluoride uptake and remineralization after storing the enamel specimens in a toothpaste-saliva mixture. The influence of brushing on the fluoride uptake when highly abrasive toothpastes are used has hardly been investigated so far. The aim of the present study was to investigate fluoride uptake in initially demineralised dental enamel after storage in, or brushing with, whitening toothpaste slurries, compared to a conventional toothpaste. For this purpose two widely available whitening toothpastes with ionically bound fluoride (sodium fluoride NaF), two with covalently-bound fluoride toothpastes (sodium monofluorophosphate, NaMFP) and a conventional amine fluoride toothpaste (AmF) were compared. The fluoride uptake after use of the AmF toothpaste was shown to be statistically significantly higher than that after application of the NaF toothpastes, which in turn was statistically significantly higher than the uptake resulting from NaMFP application. The fluoride uptake was slightly higher when the enamel samples were brushed with NaF toothpaste, rather than just stored in the respective toothpaste slurry. Brushing with highly abrasive toothpastes did not negatively influence fluoride uptake in demineralised dental enamel. The ionic form of the fluoride in toothpastes appears to be critical for increased fluoride uptake. The acidic components of the AmF toothpaste improved fluoride uptake compared to alkaline NaF toothpastes.

The effective use of fluorides in public health.

PubMed Central

Jones, Sheila; Burt, Brian A.; Petersen, Poul Erik; Lennon, Michael A.

2005-01-01

Dental caries remain a public health problem for many developing countries and for underprivileged populations in developed countries. This paper outlines the historical development of public health approaches to the use of fluoride and comments on their effectiveness. Early research and development was concerned with waterborne fluorides, both naturally occurring and added, and their effects on the prevalence and incidence of dental caries and dental fluorosis. In the latter half of the 20th century, the focus of research was on fluoride toothpastes and mouth rinses. More recently, systematic reviews summarizing these extensive databases have indicated that water fluoridation and fluoride toothpastes both substantially reduce the prevalence and incidence of dental caries. We present four case studies that illustrate the use of fluoride in modern public health practice, focusing on: recent water fluoridation schemes in California, USA; salt fluoridation in Jamaica; milk fluoridation in Chile; and the development of "affordable" fluoride toothpastes in Indonesia. Common themes are the concern to reduce demands for compliance with fluoride regimes that rely upon action by individuals and their families, and the issue of cost. We recommend that a community should use no more than one systemic fluoride (i.e. water or salt or milk fluoridation) combined with the use of fluoride toothpastes, and that the prevalence of dental fluorosis should be monitored in order to detect increases in or higher-than-acceptable levels. PMID:16211158

Efficient suppression of nanograss during porous anodic TiO2 nanotubes growth

NASA Astrophysics Data System (ADS)

Gui, Qunfang; Yu, Dongliang; Li, Dongdong; Song, Ye; Zhu, Xufei; Cao, Liu; Zhang, Shaoyu; Ma, Weihua; You, Shiyu

2014-09-01

When Ti foil was anodized in fluoride-containing electrolyte for a long time, undesired etching-induced "nanograss" would inevitably generate on the top of porous anodic TiO2 nanotubes (PATNTs). The nanograss will hinder the ions transport and in turn yield depressed (photo) electrochemical performance. In order to obtain nanograss-free nanotubes, a modified three-step anodization and two-layer nanostructure of PATNTs were designed to avoid the nanograss. The first layer (L1) nanotubes were obtained by the conventional two-step anodization. After washing and drying processes, the third-step anodization was carried out with the presence of L1 nanotubes. The L1 nanotubes, serving as a sacrificed layer, was etched and transformed into nanograss, while the ultralong nanotubes (L2) were maintained underneath the L1. The bi-layer nanostructure of the nanograss/nanotubes (L1/L2) was then ultrasonically rinsed in deionized water to remove the nanograss (L1 layer). Then much longer nanotubes (L2 layer) with intact nanotube mouths could be obtained. Using this novel approach, the ultralong nanotubes without nanograss can be rationally controlled by adjusting the anodizing times of two layers.

Solid state electrochemical current source

DOEpatents

Potanin, Alexander Arkadyevich; Vedeneev, Nikolai Ivanovich

2002-04-30

A cathode and a solid state electrochemical cell comprising said cathode, a solid anode and solid fluoride ion conducting electrolyte. The cathode comprises a metal oxide and a compound fluoride containing at least two metals with different valences. Representative compound fluorides include solid solutions of bismuth fluoride and potassium fluoride; and lead fluoride and potassium fluoride. Representative metal oxides include copper oxide, lead oxide, manganese oxide, vanadium oxide and silver oxide.

76 FR 37129 - Determination That SODIUM FLUORIDE F 18 (Sodium Fluoride F-18) Injection, 10 to 200 Millicuries...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-24

...] Determination That SODIUM FLUORIDE F 18 (Sodium Fluoride F-18) Injection, 10 to 200 Millicuries per Milliliter... FLUORIDE F 18 (sodium fluoride F-18) injection, 10 to 200 millicuries per milliliter (mCi/mL), was not... abbreviated new drug applications (ANDAs) for SODIUM FLUORIDE F 18 injection, 10 to 200 mCi/mL, if all other...

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.

Health effects of groundwater fluoride contamination.

PubMed

Nayak, Bishwajit; Roy, Madan Mohan; Das, Bhaskar; Pal, Arup; Sengupta, Mrinal Kumar; De, Shankar Prasad; Chakraborti, Dipankar

2009-04-01

The people in Berhait block, Sahibganj district, Jharkhand state, India, have been exposed chronically to fluoridecontaminated groundwater. Hereby, we report the clinical effects of chronic exposure to fluoride. The study population was a convenience sample of 342 adults and 258 children living in the affected area. All volunteers filled out questionnaires and were examined. Well water from the six affected villages and urine samples were analyzed for fluoride using an ion-sensitive electrode. Twenty nine percent of 89 well water samples had fluoride concentrations above the Indian permissible limit of fluoride in drinking water. Eighty-five children and 72 adults had clinical fluorosis. Urine fluoride concentrations in children were 0.758-2.88 mg/L whereas in adults they were 0.331-10.36 mg/L. Clinical effects of fluoride included abnormal tooth enamel in children; adults had joint pain and deformity of the limbs and spine, along with ligamentous calcifications and exostosis formations in seven patients. Elevated urine fluoride concentrations supported the clinical diagnosis of fluorosis. Owing to insufficient fluoride-safe wells and lack of awareness of the danger of fluoride toxicity, villagers often drink fluoride-contaminated water. Villagers of Berhait block, including children, are at risk from chronic fluoride toxicity. To combat the situation, villagers need fluoride-safe water, education, and awareness of the danger about fluoride toxicity.

Microbial Removal of Atmospheric Carbon Tetrachloride in Bulk Aerobic Soils▿

PubMed Central

Mendoza, Y.; Goodwin, K. D.; Happell, J. D.

2011-01-01

Atmospheric concentrations of carbon tetrachloride (CCl4) were removed by bulk aerobic soils from tropical, subtropical, and boreal environments. Removal was observed in all tested soil types, indicating that the process was widespread. The flux measured in field chamber experiments was 0.24 ± 0.10 nmol CCl4 (m2 day)−1 (average ± standard deviation [SD]; n = 282). Removal of CCl4 and removal of methane (CH4) were compared to explore whether the two processes were linked. Removal of both gases was halted in laboratory samples that were autoclaved, dry heated, or incubated in the presence of mercuric chloride (HgCl2). In marl soils, treatment with antibiotics such as tetracycline and streptomycin caused partial inhibition of CCl4 (50%) and CH4 (76%) removal, but removal was not affected in soils treated with nystatin or myxothiazol. These data indicated that bacteria contributed to the soil removal of CCl4 and that microeukaryotes may not have played a significant role. Amendments of methanol, acetate, and succinate to soil samples enhanced CCl4 removal by 59%, 293%, and 72%, respectively. Additions of a variety of inhibitors and substrates indicated that nitrification, methanogenesis, or biological reduction of nitrate, nitrous oxide, or sulfate (e.g., occurring in possible anoxic microzones) did not play a significant role in the removal of CCl4. Methyl fluoride inhibited removal of CH4 but not CCl4, indicating that CH4 and CCl4 removals were not directly linked. Furthermore, CCl4 removal was not affected in soils amended with copper sulfate or methane, supporting the results with MeF and suggesting that the observed CCl4 removal was not significantly mediated by methanotrophs. PMID:21724884

[Optimization and comparison of nitrogen and phosphorus removal by different aeration modes in oxidation ditch].

PubMed

Guo, Chang-Zi; Peng, Dang-Cong; Cheng, Xue-Mei; Wang, Dan

2012-03-01

The oxidation ditch operation mode was simulated by sequencing batch reactor (SBR) system with alternate stirring and aeration. The nitrogen and phosphorus removal efficiencies were investigated in two different aeration modes: point aeration and step aeration. Experimental results show that oxygen is dissolved more efficiently in point aeration mode with a longer aerobic region in the same air supply capacity, but dissolved oxygen (DO) utilization efficiency for nitrogen and phosphorus removal is high in step aeration mode. Nitrification abilities of the two modes are equal with ammonia-nitrogen (NH4(+) -N) removal efficiency of 96.68% and 97.03%, respectively. Nitrifier activities are 4.65 and 4.66 mg x (g x h)(-1) respectively. When the ratio of anoxic zones and the aerobic zones were 1, the total nitrogen (TN) removal efficiency of point aeration mode in 2, 4 or 7 partitions was respectively 60.14%, 47.93% and 33.7%. The total phosphorus (TP) removal efficiency was respectively 28.96%, 23.75% and 24.31%. The less the partitions, the higher the nitrogen and phosphorus removal efficiencies, but it is in more favor of TN removal. As for step aeration mode with only one partitioning zone, the TN and TP removal efficiencies are respectively 64.21% and 49.09%, which is better than in point aeration mode, but more conducive to the improvement of TP removal efficiency. Under the condition of sufficient nitrification in step aeration mode, the nitrogen and phosphorus removal is better with the increase of anoxic zone. The removal efficiencies of TN and TP respectively rose to 73.94% and 54.18% when the ratio of anoxic zones and the aerobic zones was increased from 1 : 1 to 1. 8 : 1. As the proportion of anoxic zones was enlarged further, nitrification and operation stability were weakened so as to affect the nitrogen and phosphorus removal efficiencies.

Appropriate uses of fluorides for children: guidelines from the Canadian Workshop on the Evaluation of Current Recommendations Concerning Fluorides.

PubMed Central

Clark, D C

1993-01-01

OBJECTIVE: To prevent fluorosis caused by excessive fluoride ingestion by revising recommendations for fluoride intake by children. OPTIONS: Limiting fluoride ingestion from fluoridated water, fluoride supplements and fluoride dentifrices. OUTCOMES: Reduction in the prevalence of dental fluorosis and continued prevention of dental caries. EVIDENCE: Before the workshop, experts prepared comprehensive literature reviews of fluoride therapies, fluoride ingestion and the prevalence and causes of dental fluorosis. The papers, which were peer-reviewed, revised and circulated to the workshop participants, formed the basis of the workshop discussions. VALUES: Recommendations to limit fluoride intake were vigorously debated before being adopted as the consensus opinion of the workshop group. BENEFITS, HARMS AND COSTS: Decrease in the prevalence of dental fluorosis with continuing preventive effects of fluoride use. The only significant cost would be in preparing new, low-concentration fluoride products for distribution. RECOMMENDATIONS: Fluoride supplementation should be limited to children 3 years of age and older in areas where there is less than 0.3 ppm of fluoride in the water supply. Children in all areas should use only a "pea-sized" amount of fluoride dentifrice no more than twice daily under the supervision of an adult. VALIDATION: These recommendations are almost identical to changes to recommendations for the use of fluoride supplements recently proposed by a group of European countries. SPONSORS: The workshop was organized by Dr. D. Christopher Clark, of the University of British Columbia, and Drs. Hardy Limeback and Ralph C. Burgess, of the University of Toronto, and funded by Proctor and Gamble Inc., Toronto, the Medical Research Council of Canada and Health Canada (formerly the Department of National Health and Welfare). The recommendations were formally adopted by the Canadian Dental Association in April 1993. PMID:8261348

Review on fluoride-releasing restorative materials--fluoride release and uptake characteristics, antibacterial activity and influence on caries formation.

PubMed

Wiegand, Annette; Buchalla, Wolfgang; Attin, Thomas

2007-03-01

The purpose of this article was to review the fluoride release and recharge capabilities, and antibacterial properties, of fluoride-releasing dental restoratives, and discuss the current status concerning the prevention or inhibition of caries development and progression. Information from original scientific full papers or reviews listed in PubMed (search term: fluoride release AND (restorative OR glass-ionomer OR compomer OR polyacid-modified composite resin OR composite OR amalgam)), published from 1980 to 2004, was included in the review. Papers dealing with endodontic or orthodontic topics were not taken into consideration. Clinical studies concerning secondary caries development were only included when performed in split-mouth design with an observation period of at least three years. Fluoride-containing dental materials show clear differences in the fluoride release and uptake characteristics. Short- and long-term fluoride releases from restoratives are related to their matrices, setting mechanisms and fluoride content and depend on several environmental conditions. Fluoride-releasing materials may act as a fluoride reservoir and may increase the fluoride level in saliva, plaque and dental hard tissues. However, clinical studies exhibited conflicting data as to whether or not these materials significantly prevent or inhibit secondary caries and affect the growth of caries-associated bacteria compared to non-fluoridated restoratives. Fluoride release and uptake characteristics depend on the matrices, fillers and fluoride content as well as on the setting mechanisms and environmental conditions of the restoratives. Fluoride-releasing materials, predominantly glass-ionomers and compomers, did show cariostatic properties and may affect bacterial metabolism under simulated cariogenic conditions in vitro. However, it is not proven by prospective clinical studies whether the incidence of secondary caries can be significantly reduced by the fluoride release of restorative materials.

Streptozotocin Aggravated Osteopathology and Insulin Induced Osteogenesis Through Co-treatment with Fluoride.

PubMed

Yang, Chen; Zhang, Mengmeng; Li, Yagang; Wang, Yan; Mao, Weixian; Gao, Yuan; Xu, Hui

2015-12-01

The role of insulin in the mechanism underlying the excessive fluoride that causes skeletal lesion was studied. The in vitro bone marrow stem cells (BMSC) collected from Kunming mice were exposed to varying concentrations of fluoride with or without insulin. The cell viability and early differentiation of BMSC co-treated with fluoride and insulin were measured by using cell counting kit-8 and Gomori modified calcium-cobalt method, respectively. We further investigated the in vivo effects of varying dose of fluoride on rats co-treated with streptozotocin (STZ). Wistar rats were divided into six groups which included normal control, 10 mg fluoride/kg day group, 20 mg fluoride/kg day group, STZ control, STZ+10 mg fluoride/kg day group, and STZ+20 mg fluoride/kg day group. The rats were administered with sodium fluoride (NaF) by gavage with water at doses 10 and 20 mg fluoride/kg day for 2 months. In a period of one month, half of rats in every group were treated with streptozotocin (STZ) once through intraperitoneal injection at 52 mg/kg body weight. The serum glucose, HbA1c, and insulin were determined. Bone mineral content and insulin release were assessed. The results showed insulin combined with fluoride stimulated BMSC cell viability in vitro. The bone mineral content reduced in rats treated with higher dose of fluoride and decreased immensely in rat co-treated with fluoride and STZ. Similarly, a combination treatment of a high dose of fluoride and STZ decreased insulin sensitivity and activity. To sum up, these data indicated fluoride influenced insulin release, activity, and sensitivity. Furthermore, the insulin state in vivo interfered in the osteogenesis in turn and implied there was a close relation between insulin and bone pathogenesis in the mechanism of fluoride toxicity.

FLUORIDE: A REVIEW OF USE AND EFFECTS ON HEALTH.

PubMed

Kanduti, Domen; Sterbenk, Petra; Artnik, Barbara

2016-04-01

Appropriate oral health care is fundamental for any individual's health. Dental caries is still one of the major public health problems. The most effective way of caries prevention is the use of fluoride. The aim of our research was to review the literature about fluoride toxicity and to inform physicians, dentists and public health specialists whether fluoride use is expedient and safe. Data we used in our review were systematically searched and collected from web pages and documents published from different international institutions. Fluoride occurs naturally in our environment but we consume it in small amounts. Exposure can occur through dietary intake, respiration and fluoride supplements. The most important factor for fluoride presence in alimentation is fluoridated water. Methods, which led to greater fluoride exposure and lowered caries prevalence, are considered to be one of the greatest accomplishments in the 20th century`s public dental health. During pregnancy, the placenta acts as a barrier. The fluoride, therefore, crosses the placenta in low concentrations. Fluoride can be transmitted through the plasma into the mother's milk; however, the concentration is low. The most important action of fluoride is topical, when it is present in the saliva in the appropriate concentration. The most important effect of fluoride on caries incidence is through its role in the process of remineralization and demineralization of tooth enamel. Acute toxicity can occur after ingesting one or more doses of fluoride over a short time period which then leads to poisoning. Today, poisoning is mainly due to unsupervised ingestion of products for dental and oral hygiene and over-fluoridated water. Even though fluoride can be toxic in extremely high concentrations, it`s topical use is safe. The European Academy of Paediatric Dentistry (EAPD) recommends a preventive topical use of fluoride supplements because of their cariostatic effect.

FLUORIDE CONTENT OF COMMERCIALLY AVAILABLE BOTTLED DRINKING WATER IN BANGKOK, THAILAND.

PubMed

Rirattanapong, Praphasri; Rirattanapong, Opas

2016-09-01

The use of bottled drinking water may be a source of fluoride and could be a risk factor for fluorosis among infants and young children. The aim of this study was to evaluate the fluoride content of commercially available bottled drinking water in Bangkok, Thailand. Forty-five water samples (15 samples of plain water and 30 samples of mineral water) were purchased from several supermarkets in Bangkok, Thailand. Three bottles of each water sample were purchased, and the fluoride content of each sample was measured twice using a combination fluoride-ion selective electrode. The average reading for each sample was then calculated. Data were analyzed by descriptive statistics. Differences between mineral and plain water samples were determined by Student’s t-test. The mean (±SD) fluoride content for all the water samples was 0.17 (±0.17) mg F/l (range: 0.01-0.89 mg F/l). Six brands (13%) tested stated the fluoride content on the label. The actual fluoride content in each of their brands varied little from the label. Eight samples (18%) had a fluoride content >0.3 mg F/l and two samples (4%) had a fluoride content >0.6 mg F/l. The mean mineral water fluoride concentration was significantly higher than the mean fluoride concentration of plain water (p=0.001). We found commercially sold bottled drinking water in Bangkok, Thailand contained varying concentrations of fluoride; some with high concentrations of fluoride. Health professions need to be aware this varying fluoride content of bottled drinking water and educate the parents of infants and small children about this when prescribing fluoride supplements. Consideration should be made to have fluoride content put on the label of bottled water especially among brands with a content >0.3 mg F/l.

Evaluation of the direct and diffusion methods for the determination of fluoride content in table salt

PubMed Central

Martínez-Mier, E. Angeles; Soto-Rojas, Armando E.; Buckley, Christine M.; Margineda, Jorge; Zero, Domenick T.

2010-01-01

Objective The aim of this study was to assess methods currently used for analyzing fluoridated salt in order to identify the most useful method for this type of analysis. Basic research design Seventy-five fluoridated salt samples were obtained. Samples were analyzed for fluoride content, with and without pretreatment, using direct and diffusion methods. Element analysis was also conducted in selected samples. Fluoride was added to ultra pure NaCl and non-fluoridated commercial salt samples and Ca and Mg were added to fluoride samples in order to assess fluoride recoveries using modifications to the methods. Results Larger amounts of fluoride were found and recovered using diffusion than direct methods (96%–100% for diffusion vs. 67%–90% for direct). Statistically significant differences were obtained between direct and diffusion methods using different ion strength adjusters. Pretreatment methods reduced the amount of recovered fluoride. Determination of fluoride content was influenced both by the presence of NaCl and other ions in the salt. Conclusion Direct and diffusion techniques for analysis of fluoridated salt are suitable methods for fluoride analysis. The choice of method should depend on the purpose of the analysis. PMID:20088217

[Estimation of exposure to fluoride in "Los Altos de Jalisco", México].

PubMed

Hurtado-Jiménez, Roberto; Gardea-Torresdey, Jorge

2005-01-01

To estimate the level of fluoride exposure and human health risks in Los Altos de Jalisco (Jalisco State Heights) region. This study was conducted between May and July 2002. The fluoride concentrations of 105 water wells and six tap water samples were electrochemically measured. Exposure doses to fluoride and total intake of fluoride were estimated for babies (10 kg), children (20 kg), and adults (70 kg). The fluoride concentration of the water samples ranged from 0.1 to 17.7 mg/l. More than 45% of the water samples exceeded the national guideline value for fluoride of 1.5 mg/l. The estimated values of the exposure doses to fluoride and total intake of fluoride were in the range of 0.04-1.8 mg/kg/d and 0.5-18.4 mg/d, respectively. Dental fluorosis, skeletal fluorosis, and bone fractures are some of the potential health risks due to the intake of high doses of fluoride for the population of Los Altos de Jalisco. In order to reduce health risks, fluoridated salt,fluoridated toothpastes, and drinking water containing more than 0.7 mg/l of fluoride should be avoided.

Fluoride in the environment and its metabolism in humans.

PubMed

Jha, Sunil Kumar; Mishra, Vinay Kumar; Sharma, Dinesh Kumar; Damodaran, Thukkaram

2011-01-01

The presence of environmental fluoride and its impact on human health is well documented. When consumed in adequate quantity, fluoride prevents dental caries, assists in the formation of dental enamels, and prevents deficiencies in bone mineralization. At excessive exposure levels, ingestion of fluoride causes dental fluorosis skeletal fluorosis, and manifestations such as gastrointestinal, neurological, and urinary problems. The distribution of fluoride in the environment is uneven and largely is believed to derive from geogenic causes. The natural sources of fluoride are fluorite, fluorapatite, and cryolite, whereas anthropogenic sources include coal burning, oil refining, steel production, brick-making industries, and phosphatic fertilizer plants, among others. Among the various sources of fluoride in the environment, those of anthropogenic origin have occasionally been considered to be major ones. The gourndwater is more susceptible to fluoride accumulation and contamination than are other environmental media, primarily because of its contact with geological substrates underneath. The high fluoride concentration in water usually reflects the solubility of fluoride (CaF₂). High concentrations are also often associated with soft, alkaline, and calcium-deficient waters. The fluoride compounds that occur naturally in drinking water are almost totally bioavailable (90%) and are completely absorbed from the gastrointestinal tract. As a result, drinking water is considered to be the potential source of fluoride that causes fluorosis. Because the bioavailability of fluoride is generally reduced in humans when consumed with milk or a calcium-rich diet, it is highly recommended that the inhabitants of fluoride-contaminated areas should incorporate calcium-rich foods in their routine diet. Guidelines for limiting the fluoride intake from drinking water have been postulated by various authorities. Such limits are designed to protect public health and should reflect all fluoride intake sources, including dietary fluoride. The toxicological risks posed by fluoride could be better understood if epidemiological surveillance for dental and skeletal fluorosis would be systematically conducted in fluoride-affected areas. Such input would greatly improve understanding of the human dose-response relationship. Such surveillance of potentially high fluoride areas is also important because it would help to delineate, much earlier, the remedial measures that are appropriate for those areas.

Sodium fluoride-assisted modulation of anodized TiO₂ nanotube for dye-sensitized solar cells application.

PubMed

Yun, Jung-Ho; Ng, Yun Hau; Ye, Changhui; Mozer, Attila J; Wallace, Gordon G; Amal, Rose

2011-05-01

This work reports the use of sodium fluoride (in ethylene glycol electrolyte) as the replacement of hydrofluoric acid and ammonium fluoride to fabricate long and perpendicularly well-aligned TiO₂ nanotube (TNT) (up to 21 μm) using anodization. Anodizing duration, applied voltage and electrolyte composition influenced the geometry and surface morphologies of TNT. The growth mechanism of TNT is interpreted by analyzing the current transient profile and the total charge density generated during anodization. The system with low water content (2 wt %) yielded a membrane-like mesoporous TiO₂ film, whereas high anodizing voltage (70 V) resulted in the unstable film of TNT arrays. An optimized condition using 5 wt % water content and 60 V of anodizing voltage gave a stable array of nanotube with controllable length and pore diameter. Upon photoexcitation, TNTs synthesized under this condition exhibited a slower charge recombination rate as nanotube length increased. When made into cis-diisothiocyanato-bis(2,2̀-bipyridyl-4,4̀-dicarboxylato) ruthenium(II) bis (tetrabutyl-ammonium)(N719) dye-sensitized solar cells, good device efficiency at 3.33 % based on the optimized TNT arrays was achieved with longer electron time compared with most mesoporous TiO₂ films.

Potential fluoride toxicity from oral medicaments: A review.

PubMed

Ullah, Rizwan; Zafar, Muhammad Sohail; Shahani, Nazish

2017-08-01

The beneficial effects of fluoride on human oral health are well studied. There are numerous studies demonstrating that a small amount of fluoride delivered to the oral cavity decreases the prevalence of dental decay and results in stronger teeth and bones. However, ingestion of fluoride more than the recommended limit leads to toxicity and adverse effects. In order to update our understanding of fluoride and its potential toxicity, we have described the mechanisms of fluoride metabolism, toxic effects, and management of fluoride toxicity. The main aim of this review is to highlight the potential adverse effects of fluoride overdose and poorly understood toxicity. In addition, the related clinical significance of fluoride overdose and toxicity has been discussed.

SEPARATION OF METAL VALUES FROM NUCLEAR REACTOR

DOEpatents

Campbell, D.O.; Cathers, G.I.

1962-06-19

A method is given for separating beryllium fluoride and an alkali metal fluoride from a mixture containing same and rare earth fluorides. The method comprises contacting said mixture with a liquid hydrogen fluoride solvent containing no more than about 30 per cent water by weight and saturated with a fluoride salt characterized by its solubility in anhydrous hydrogen fluoride for a period of time sufficient to dissolve said beryllium fluoride in said solvent. (AEC)

Thirty years of fluoridation: a review.

PubMed

Richmond, V L

1985-01-01

Fluoride contributes to stability of both teeth and bones and to reduction of caries, especially if ingested before eruption of teeth. Reduction of caries continues at about 60% in persons drinking fluoridated water only as long as fluoride washes over teeth. One-half the population of the US does not have access to water with an optimal fluoride concentration of about 1 mg/L. Misinformation about fluoridation contributes to reluctance of communities to supplement the natural but inadequate fluoride of those water supplies. Fluoridation of water has no positive or negative effect on incidence or mortality rates due to cancer, heart disease, intracranial lesions, nephritis, cirrhosis, mongoloid births, or from all causes together. The collective decision to increase the natural fluoride content of water supplies is not an infringement of civil rights, nor does it establish a precedent in the binding sense of the law. Supplemental fluoride in water makes it available to all members of the community in a safe, practical, economical and reliable manner. Fluoridation saves money in dental costs and time lost from work. Fluoridation is an appropriate action of government in promoting the health and welfare of society.

Pr3 + -doped GeSx-based glasses for fiber amplifiers at 1.3 µm

NASA Astrophysics Data System (ADS)

Simons, D. R.; Faber, A. J.; de Waal, H.

1995-03-01

The photoluminescence properties of Pr3+ -doped GeS x -based glasses are studied and compared with those of other sulfide and fluoride glasses. The possibility of highly pump-power-efficient fiber amplifiers based on these GeSx-containing glasses in the telecommunications window at 1.3 mu m is discussed.

Fluoride in groundwater: toxicological exposure and remedies.

PubMed

Jha, S K; Singh, R K; Damodaran, T; Mishra, V K; Sharma, D K; Rai, Deepak

2013-01-01

Fluoride is a chemical element that is found most frequently in groundwater and has become one of the most important toxicological environmental hazards globally. The occurrence of fluoride in groundwater is due to weathering and leaching of fluoride-bearing minerals from rocks and sediments. Fluoride when ingested in small quantities (<0.5 mg/L) is beneficial in promoting dental health by reducing dental caries, whereas higher concentrations (>1.5 mg/L) may cause fluorosis. It is estimated that about 200 million people, from among 25 nations the world over, may suffer from fluorosis and the causes have been ascribed to fluoride contamination in groundwater including India. High fluoride occurrence in groundwaters is expected from sodium bicarbonate-type water, which is calcium deficient. The alkalinity of water also helps in mobilizing fluoride from fluorite (CaF2). Fluoride exposure in humans is related to (1) fluoride concentration in drinking water, (2) duration of consumption, and (3) climate of the area. In hotter climates where water consumption is greater, exposure doses of fluoride need to be modified based on mean fluoride intake. Various cost-effective and simple procedures for water defluoridation techniques are already known, but the benefits of such techniques have not reached the rural affected population due to limitations. Therefore, there is a need to develop workable strategies to provide fluoride-safe drinking water to rural communities. The study investigated the geochemistry and occurrence of fluoride and its contamination in groundwater, human exposure, various adverse health effects, and possible remedial measures from fluoride toxicity effects.

Near surface mechanical properties of optical single crystals and surface response to deterministic microgrinding

NASA Astrophysics Data System (ADS)

Randi, Joseph A., III

2005-12-01

This thesis makes use of microindentation, nanoindentation and nanoscratching methods to better understand the mechanical properties of single crystalline silicon, calcium fluoride, and magnesium fluoride. These properties are measured and are used to predict the material's response to material removal, specifically by grinding and polishing, which is a combination of elastic, plastic and fracture processes. The hardness anisotropy during Knoop microindentation, hardness from nanoindentation, and scratch morphology from nanoscratching are reported. This information is related to the surface microroughness from grinding. We show that mechanical property relationships that predict the surface roughness from lapping and deterministic microgrinding of optical glasses are applicable to single crystals. We show the range of hardness from some of the more common crystallographic faces. Magnesium fluoride, having a tetragonal structure, has 2-fold hardness anisotropy. Nanoindentation, as expected provides higher hardness than microindentation, but anisotropy is not observed. Nanoscratching provides the scratch profile during loading, after the load has been removed, and the coefficient of friction during the loading. Ductile and brittle mode scratching is present with brittle mode cracking being orientation specific. Subsurface damage (SSD) measurements are made using a novel process known as the MRF technique. Magnetorheological finishing is used to polish spots into the ground surface where SSD can be viewed. SSD is measured using an optical microscope and knowledge of the spot profile. This technique is calibrated with a previous technique and implemented to accurately measure SSD in single crystals. The data collected are compared to the surface microroughness of the ground surface, resulting in an upper bound relationship. The results indicate that SSD is always less than 1.4 times the peak-to-valley surface microroughness for single crystals regardless of the grinding conditions or mechanical properties. Single crystals have greater strain rate effects associated than optical glasses. Hence, the strain rate is investigated during grinding by applying more aggressive process parameters and measuring the resulting surface finish. It is observed that while there are weak materials and crystallographic orientation effects from process parameters, the changes in strain rate do not affect the surface finish of these materials.

40 CFR 63.9323 - How do I determine the add-on control device emission destruction or removal efficiency?

Code of Federal Regulations, 2011 CFR

2011-07-01

... device emission destruction or removal efficiency? 63.9323 Section 63.9323 Protection of Environment... determine the add-on control device emission destruction or removal efficiency? You must use the procedures... removal efficiency as part of the performance test required by § 63.9310. You must conduct three test runs...

40 CFR 63.9323 - How do I determine the add-on control device emission destruction or removal efficiency?

Code of Federal Regulations, 2010 CFR

2010-07-01

... device emission destruction or removal efficiency? 63.9323 Section 63.9323 Protection of Environment... determine the add-on control device emission destruction or removal efficiency? You must use the procedures... removal efficiency as part of the performance test required by § 63.9310. You must conduct three test runs...

40 CFR 63.4166 - How do I determine the add-on control device emission destruction or removal efficiency?

Code of Federal Regulations, 2011 CFR

2011-07-01

... device emission destruction or removal efficiency? 63.4166 Section 63.4166 Protection of Environment....4166 How do I determine the add-on control device emission destruction or removal efficiency? (a) For... device organic emissions destruction or removal efficiency, using Equation 2 of this section. ER23JY02...

40 CFR 63.3966 - How do I determine the add-on control device emission destruction or removal efficiency?

Code of Federal Regulations, 2010 CFR

2010-07-01

... device emission destruction or removal efficiency? 63.3966 Section 63.3966 Protection of Environment... or removal efficiency? You must use the procedures and test methods in this section to determine the add-on control device emission destruction or removal efficiency as part of the performance test...

40 CFR 63.4965 - How do I determine the add-on control device emission destruction or removal efficiency?

Code of Federal Regulations, 2011 CFR

2011-07-01

... device emission destruction or removal efficiency? 63.4965 Section 63.4965 Protection of Environment....4965 How do I determine the add-on control device emission destruction or removal efficiency? You must... destruction or removal efficiency as part of the performance test required by § 63.4960. You must conduct...

40 CFR 63.3966 - How do I determine the add-on control device emission destruction or removal efficiency?

Code of Federal Regulations, 2011 CFR

2011-07-01

... device emission destruction or removal efficiency? 63.3966 Section 63.3966 Protection of Environment... or removal efficiency? You must use the procedures and test methods in this section to determine the add-on control device emission destruction or removal efficiency as part of the performance test...

Chronologic Trends in Studies on Fluoride Mechanisms of Action.

PubMed

Oh, H J; Oh, H W; Lee, D W; Kim, C H; Ahn, J Y; Kim, Y; Shin, H B; Kim, C Y; Park, S H; Jeon, J G

2017-11-01

Fluoride has been widely used for the prevention of dental caries since the mid-20th century. The aim of this study was to investigate the chronologic trends in studies on fluoride mechanisms of action against dental caries during the years 1950 to 2015. To this aim, queries such as "fluoride," "fluoride and demineralization," "fluoride and remineralization," "fluoride and (plaque or biofilms)," and "fluoride and (bacteria or microbials)" were submitted to PubMed to collect research article information, including titles, abstracts, publication dates, author affiliations, and publication journals. The article information that PubMed produced was then collected by an automatic web crawler and examined through informetrics and linguistic analyses. We found that the number of articles concerned with fluoride mechanisms of action against dental caries was 6,903 and gradually increased over time during the years 1950 to 2015. They were published by 1,136 journals-most notably, Caries Research and Journal of Dental Research. Of the articles published, those related to bacteria/microbials had a higher percentage (44%) than those dealing with plaque/biofilms, demineralization, and remineralization. With regard to the geographic distribution of authors, Europe and North America accounted for 65% of the articles during the years 1987 to 2015, although the number of authors in Asia sharply increased in recent years. Among the fluoride compounds, NaF was mentioned more frequently than SnF 2 , Na 2 PO 3 F, amine fluoride, and acidulated phosphate fluoride during the years 1986 to 2015. Water fluoridation received the most attention among the various fluoride application methods (toothpastes, mouthwashes, fluoride varnishes, and fluoride gels) during the same period. These results, obtained from employing informetrics and linguistic analyses, suggest that in studies on fluoride mechanisms of action, 1) the unbalanced geographic distribution of articles and 2) the heavy concentration of articles on particular fluoride compounds and application methods should be overcome in future research.

Pyroprocess for processing spent nuclear fuel

DOEpatents

Miller, William E.; Tomczuk, Zygmunt

2002-01-01

This is a pyroprocess for processing spent nuclear fuel. The spent nuclear fuel is chopped into pieces and placed in a basket which is lowered in to a liquid salt solution. The salt is rich in ZrF.sub.4 and containing alkali or alkaline earth fluorides, and in particular, the salt chosen was LiF-50 mol % ZrF.sub.4 with a eutectic melting point of 500.degree. C. Prior to lowering the basket, the salt is heated to a temperature of between 550.degree. C. and 700.degree. C. in order to obtain a molten solution. After dissolution the oxides of U, Th, rare earth and other like oxides, the salt bath solution is subject to hydro-fluorination to remove the oxygen and then to a fluorination step to remove U as gaseous UF.sub.6. In addition, after dissolution, the basket contains PuO.sub.2 and undissolved parts of the fuel rods, and the basket and its contents are processed to remove the Pu.

Fluoride content of infant formulas prepared with deionized, bottled mineral and fluoridated drinking water.

PubMed

Buzalaf, M A; Granjeiro, J M; Damante, C A; de Ornelas, F

2001-01-01

Usually infant milk formula is the major source of fluoride in infancy. Fluoride concentrations in ten samples of powdered milk formulas, prepared with deionized, bottled mineral, and fluoridated drinking water were determined after HMDS-facilitated diffusion, using a fluoride ion specific electrode(Orion 9609). Fluoride concentrations ranged from 0.01 to 0.75 ppm; from 0.02 to 1.37 ppm and from 0.91 to 1.65 ppm for formulas prepared with deionized, bottled mineral (0.02 to 0.69 ppm F) and fluorinated drinking water (0.9 ppm F), respectively. Possible fluoride ingestion per Kg body mass ws estimated. With deionized water, only the soy-based- formulas should provide a daily fluoride intake of above the suggested threshold for fluorosis. With water containing 0.9 ppm F, however, all of them would provide it. Hence, to limit fluoride intakes to amounts <0.1 mg/kg/day, it is necessary to avoid use fo fluoridated water (around 1 ppm) to dilute powdered infant formulas.

The fractional urinary fluoride excretion of adults consuming naturally and artificially fluoridated water and the influence of water hardness: a randomized trial.

PubMed

Villa, A; Cabezas, L; Anabalón, M; Rugg-Gunn, A

2009-09-01

To assess whether there was any significant difference in the average fractional urinary fluoride excretion (FUFE) values among adults consuming (NaF) fluoridated Ca-free water (reference water), naturally fluoridated hard water and an artificially (H2SiF6) fluoridated soft water. Sixty adult females (N=20 for each treatment) participated in this randomized, double-blind trial. The experimental design of this study provided an indirect estimation of the fluoride absorption in different types of water through the assessment of the fractional urinary fluoride excretion of volunteers. Average daily FUFE values (daily amount of fluoride excreted in urine/daily total fluoride intake) were not significantly different between the three treatments (Kruskal-Wallis; p = 0.62). The average 24-hour FUFE value (n=60) was 0.69; 95% C.I. 0.65-0.73. The results of this study suggest that the absorption of fluoride is not affected by water hardness.

Does fluoride in the water close the dental caries gap between Indigenous and non-Indigenous children?

PubMed

Lalloo, R; Jamieson, L M; Ha, D; Ellershaw, A; Luzzi, L

2015-09-01

Indigenous children experience significantly more dental caries than non-Indigenous children. This study assessed if access to fluoride in the water closed the gap in dental caries between Indigenous and non-Indigenous children. Data from four states and two territories were sourced from the Child Dental Health Survey (CDHS) conducted in 2010. The outcomes were dental caries in the deciduous and permanent dentitions, and the explanatory variables were Indigenous status and access to fluoridated water (≥0.5 mg/L) prior to 2008. Dental caries prevalence and severity for Indigenous and non-Indigenous children, in both dentitions, was lower in fluoridated areas compared to non-fluoridated areas. Among non-Indigenous children, there was a 50.9% difference in mean dmft scores in fluoridated (1.70) compared to non-fluoridated (2.86) areas. The difference between Indigenous children in fluoridated (3.29) compared to non-fluoridated (4.16) areas was 23.4%. Among non-Indigenous children there was a 79.7% difference in the mean DMFT scores in fluoridated (0.68) compared to non-fluoridated (1.58) areas. The difference between Indigenous children in fluoridated (1.59) and non-fluoridated (2.23) areas was 33.5%. Water fluoridation is effective in reducing dental caries, but does not appear to close the gap between non-Indigenous children and Indigenous children. © 2015 Australian Dental Association.

Fluoride bioavailability in saliva and plaque

PubMed Central

2012-01-01

Background Different fluoride formulations may have different effects on caries prevention. It was the aim of this clinical study to assess the fluoride content, provided by NaF compared to amine fluoride, in saliva and plaque. Methods Eight trained volunteers brushed their teeth in the morning for 3 minutes with either NaF or amine fluoride, and saliva and 3-day-plaque-regrowth was collected at 5 time intervals during 6 hours after tooth brushing. The amount of collected saliva and plaque was measured, and the fluoride content was analysed using a fluoride sensitive electrode. All subjects repeated all study cycles 5 times, and 3 cycles per subject underwent statistical analysis using the Wilcoxon-Mann-Whitney test. Results Immediately after brushing the fluoride concentration in saliva increased rapidly and dropped to the baseline level after 360 minutes. No difference was found between NaF and amine fluoride. All plaque fluoride levels were elevated after 30 minutes until 120 minutes after tooth brushing, and decreasing after 360 minutes to baseline. According to the highly individual profile of fluoride in saliva and plaque, both levels of bioavailability correlated for the first 30 minutes, and the fluoride content of saliva and plaque was back to baseline after 6 hours. Conclusions Fluoride levels in saliva and plaque are interindividually highly variable. However, no significant difference in bioavailability between NaF and amine fluoride, in saliva, or in plaque was found. PMID:22230722

Gramicidin D enhances the antibacterial activity of fluoride.

PubMed

Nelson, James W; Zhou, Zhiyuan; Breaker, Ronald R

2014-07-01

Fluoride is a toxic anion found in many natural environments. One of the major bacterial defenses against fluoride is the cell envelope, which limits passage of the membrane-impermeant fluoride anion. Accordingly, compounds that enhance the permeability of bacterial membranes to fluoride should also enhance fluoride toxicity. In this study, we demonstrate that the pore-forming antibiotic gramicidin D increases fluoride uptake in Bacillus subtilis and that the antibacterial activity of this compound is potentiated by fluoride. Polymyxin B, another membrane-targeting antibiotic with a different mechanism of action, shows no such improvement. These results, along with previous findings, indicate that certain compounds that destabilize bacterial cell envelopes can enhance the toxicity of fluoride. Copyright © 2014 Elsevier Ltd. All rights reserved.

The effect on human salivary fluoride concentration of consuming fluoridated salt-containing baked food items.

PubMed

Macpherson, L M; Stephen, K W

2001-10-01

Salt fluoridation is recognised world-wide as a proven and viable alternative means of consumer choice-related, community-based fluoridation where water fluoridation is either technically or politically impossible. However, as most salt consumed is contained within cooked food products, rather than sprinkled over prepared food at the table, the purpose of this study was to investigate the effects on salivary fluoride concentration of consuming baked food products prepared with 250 and 350 ppm fluoridated salt (as KF). Six food items were baked with (a) normal non-fluoridated salt, (b) 250 mg F/kg salt and (c) 350 mg F/kg salt. Eleven adult volunteers consumed these foodstuffs on separate occasions and salivary samples were collected for fluoride analyses before and at various time points (1-30 min) after eating. For most foodstuffs, small but significant increases in salivary fluoride concentration occurred for at least 5 min after ingestion of the fluoridated salt-containing items. Salivary fluoride concentrations peaked 1 or 2 min after eating, with highest values for the six test foods ranging from 0.16 to 0.25 ppm F, and from 0.18 to 0.44 ppm F for the 250 and 350 mg F/kg salt products, respectively. In all cases, salivary fluoride concentrations had returned to baseline by 20 min. The clinical significance of such small, short-term increases in salivary fluoride is uncertain, but the findings suggest that a more frequent intake of foods with fluoridated salt substituted for normal salt could help sustain slightly elevated salivary fluoride concentrations for more prolonged periods of the day, and might thus potentiate the cariostatic effects of saliva on tooth mineral.

Concentration of Fluoride in Cow's and Buffalo's Milk in Relation to Varying Levels of Fluoride Concentration in Drinking Water of Mathura City in India- A Pilot Study.

PubMed

Gupta, Prahlad; Gupta, Nidhi; Meena, Komal; Moon, Ninad Joshirao; Kumar, Puneet; Kaur, Ravneet

2015-05-01

To estimate fluoride concentration in drinking water, cow's milk and buffalo's milk and to correlate the concentration of fluoride in cow's milk and buffalo's milk with varying levels of fluoride concentration in drinking water. Ten households having both cows and buffalo's were selected by convenience in each of the 3 zones (below optimum fluoride <0.7 ppm (parts per million), optimum fluoride 0.7-1.2 ppm and above optimum fluoride areas > 1.2 ppm). From these selected households, 200 ml of fresh milk of both cows and buffaloes was collected along with 200 ml of drinking water for estimation of fluoride concentration by using a fluoride ion selective electrode method. The data was analysed using SPSS, version 11.5 for windows. The mean fluoride concentration of drinking water, cow's milk and buffalo's milk in three different fluoride zones was 0.89±0.39, 0.09±0.07, 0.09±0.08 respectively. Pearson's correlation found a statistically significant correlation between fluoride concentrations in cow's and buffalo's milk with varying levels of fluoride concentration in drinking water in zone B and zone C. However, this correlation was not statistically significant in zone A. With an increase in fluoride concentration in drinking water there was an increase in concentration of fluoride in cow's and buffalo's milk. We conclude that this association is seen in conjunction to not only a single factor but rather due to culmination of several other aspects. So, there is a need to elucidate the other factors that might be contributing to this increase and dental fluorosis.

Level of Fluoride in Soil, Grain and Water in Jalgaon District, Maharashtra, India.

PubMed

Naik, Rahul Gaybarao; Dodamani, Arun Suresh; Vishwakarma, Prashanth; Jadhav, Harish Chaitram; Khairnar, Mahesh Ravindra; Deshmukh, Manjiri Abhay; Wadgave, Umesh

2017-02-01

Fluoride has an influence on both oral as well as systemic health. The major source of fluoride to body is through drinking water as well as through diet. Staple diet mainly depends on local environmental factors, food grains grown locally, its availability etc. Determination of fluoride level in these food grains is important. So, estimation of the amount of fluoride in grains and its relation to the sources of fluoride used for their cultivation viz., soil and water is important. To estimate the relation of fluoride concentration in grains (Jowar) with respect to that of soil and water used for their cultivation. Fifteen samples each of soil, water and grains were collected using standardized method from the same farm fields of randomly selected villages of Jalgaon district. Fluoride ion concentration was determined in laboratory using SPADNS technique. Mean difference in fluoride levels in between the groups were analyzed using ANOVA and Post-Hoc Tukey test. Linear regression method was applied to analyse the association of the fluoride content of grain with water and soil. There was a significant difference in between mean fluoride levels of soil and water (p<0.001) and in between soil and grain (p<0.001); however, difference in between mean fluoride levels of water and grain was found to be non significant (p=0.591). Also fluoride levels in all the three groups showed significant association with each other. Fluoride level of soil, grains and water should be adjusted to an optimum level. Soil has positive correlation with respect to uptake of fluoride by Jowar grains. So, Jowar grains with optimum fluoride content should be made available in the commercial markets so that oral and general health can be benefitted.

Development of resistance of mutans streptococci and Porphyromonas gingivalis to chlorhexidine digluconate and amine fluoride/stannous fluoride-containing mouthrinses, in vitro.

PubMed

Kulik, Eva M; Waltimo, Tuomas; Weiger, Roland; Schweizer, Irene; Lenkeit, Krystyna; Filipuzzi-Jenny, Elisabeth; Walter, Clemens

2015-07-01

The aim if this study was to determine the minimal inhibitory concentrations of chlorhexidine digluconate and an amine fluoride/stannous fluoride-containing mouthrinse against Porphyromonas gingivalis and mutans streptococci during an experimental long-term subinhibitory exposition. Five P. gingivalis strains and four mutans streptococci were subcultivated for 20-30 passages in subinhibitory concentrations of chlorhexidine digluconate or an amine fluoride/stannous fluoride-containing mouthrinse. Pre-passaging minimal inhibitory concentrations for chlorhexidine ranged from 0.5 to 2 mg/l for mutans streptococci and from 2 to 4 mg/l for the P. gingivalis isolates. For the amine fluoride/stannous fluoride-containing mouthrinse minimal inhibitory values from 0.125 to 0.25% for the mutans streptococci and from 0.063 to 0.125% for the P. gingivalis isolates were determined. Two- to fourfold increased minimal inhibitory concentrations against chlorhexidine were detected for two of the five P. gingivalis isolates, whereas no increase in minimal inhibitory concentrations was found for the mutans streptococci after repeated passaging through subinhibitory concentrations. Repeated exposure to subinhibitory concentrations of the amine fluoride/stannous fluoride-containing mouthrinse did not alter the minimally inhibitory concentrations of the bacterial isolates tested. Chlorhexidine and the amine fluoride/stannous fluoride-containing mouthrinse are effective inhibitory agents against the oral bacterial isolates tested. No general development of resistance against chlorhexidine or the amine fluoride/stannous fluoride-containing mouthrinse was detected. However, some strains showed potential to develop resistance against chlorhexidine after prolonged exposure. The use of chlorhexidine should be limited to short periods of time. The amine fluoride/stannous fluoride-containing mouthrinse appears to have the potential to be used on a long-term basis.