• Journal of Environmental Science International
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• v.28 no.11
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• pp.943-950
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• 2019

The purpose of this study was to probe the influences of NaF oral administration on a dose-effect relationship between fluoride levels of serum enzyme activity such as alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) in rats fed experimental diets for 5 weeks. All groups increased the activity of serum ALP, AST, ALT, and LDH levels with increasing NaF. In addition the fluoride levels of serum and organ tissues (liver, brain, heart, lung, kidney) in oral NaF groups (NF3~NF50) were significantly increased by adding sodium fluoride in comparison with normal diet group (ND) (p<0.05). These results, a high concentration of sodium fluoride was determined that the toxicity to various organ tissues.

• The Journal of the Korean dental association
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• v.17 no.8 s.123
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• pp.627-631
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• 1979

• Environmental Engineering Research
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• v.24 no.2
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• pp.279-288
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• 2019

To obtain insightful knowledge of geochemical process controlling fluoride enrichment in groundwater of the villages near Shilabati river bank, West Bengal, India, multivariate statistical techniques were applied to a subgroup of the dataset generated from major ion analysis of groundwater samples. Water quality analysis of major ion chemistry revealed elevated levels of fluoride concentration in groundwater. Factor analysis (FA) of fifteen hydrochemical parameters demonstrated that fluoride occurrence was due to the weathering and dissolution of fluoride-bearing minerals in the aquifer. A strong positive loading (> 0.75) of fluoride with pH and bicarbonate for FA indicates an alkaline dominated environment responsible for leaching of fluoride from the source material. Mineralogical analysis of soli sediment exhibits the presence of fluoride-bearing minerals in underground geology. Hierarchical cluster analysis (HCA) was carried out to isolate the sampling sites according to groundwater quality. With HCA the sampling sites were isolated into three clusters. The occurrence of abundant fluoride in the higher elevated area of the observed three different clusters revealed that there was more contact opportunity of recharging water with the minerals present in the aquifer during infiltration through the vadose zone.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.124.2-124.2
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• 2016

Corrosion resistance and adhesion of electro-paint (E-paint) with fluoride conversion coating (FCC) on AZ31 Mg alloy were studied. Corrosion resistance and adhesion were studied as a function of FCC-treatment time and concentration of FCC-bath. Aqueous hydrogen fluoride (HF) solutions, with concentrations ranging from 0.5 M to 5 M, were used to form FCC on chemically polished AZ31 Mg alloy samples for six different times; 10, 30, 60, 90, 120, and 180s. The results from salt spray test (SST) showed that corrosion resistance of E-paint appeared to decrease with increasing FCC treatment times in low concentration FCC baths. The number of blisters formed on the FCC-treated samples increased with increasing FCC treatment time of more than 1 min in low concentration (0.5 M to 1 M) solutions. On the other hand, samples treated in the 5 M HF solution for 120s showed no delamination or blistering even after 1200h of SST.

• Journal of Oral Medicine and Pain
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• v.21 no.1
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• pp.115-122
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• 1996

This study was performed to compare the anticarious effect of the different fluoride adsorbed(Naf, $NH_4F, Na_2PO_3F, SnF_2, TiF_4$) on synthetic hydroxyapatite and enamel. The amount of fluoride adsorbed in synthetic hydroxyapatite under various concentrations and pH of these fluoride solutions was measured by specific electrode. Enamel samples treated with 5 kinds of 1,000ppm fluoride solutions for 10 minutes were evaluated for fluoride uptake and enamel soubility. The results were as follows. 1. The adsorption of fluoride on synthetic hydroxyapatite increased gradually by the concentration of the fluoride solution, In 1,000ppm fluoride solution, the adsorption of fluoride on synthetic hydroxyapatite treated with NH4F and NaF solutions at pH 4.0 was relatively higher than that of other fluoride solutions. In NH4F and NaF solutions, the adsorption of fluoride on powdered enamel was higher at pH 4.0 solution than at pH 7.0 solution. 2. Fluoride uptake from NH4F solution was relatively high. But that from $Na_2PO_3F$ solution was lower than those from other fluoride solutions. 3. Fluoride solutions were significantly effective on enhancing acid resistance. $NH_4F$ solution was relatively more effective than others on enhancing acid resistance. 4. $SnF_2 and TiF_4$ solutions had the same effect on fluoride adsorption, fluoride uptake, and enamel solubility.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.7
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• pp.730-737
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• 2010

It is very important to remove fluoride ion before treating semiconductor wastewater containing high concentration of ammonia, phosphates, and fluoride ions by struvite formation. Calcium ion was generally added for the removal of fluoride ion. However, calcium ions remained after removal of fluoride ion can deteriorate the performance of struvite crystalization. It should be removed completely before struvite formation. In this study, the effect of fluoride and calcium ion concentration on the struvite crystalization was investigated. Removal efficiencies of ortho-phosphate with struvite formation were more abruptly decreased than those of ammonium nitrogen, as increase of fluoride ion concentration in synthetic wastewater. The structures of struvite formed in synthetic wastewater containing calcium ion of up to 500 mg/L were identical. Purity of struvite was deteriorated as increase of calcium ion over 500 mg/L. Removal efficiencies of ammonium nitrogen were more decreased than those of phosphate ions as increase of cacium ion in synthetic wastewater.

• Proceedings of the Korean Environmental Health Society Conference
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• 2004.06a
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• pp.213-216
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• 2004

This work was based on the hypotheses that fingernail clippings can be used as a biomarker for the subchronic exposure to fluoride. This study was conducted to prove the hypotheses and fingernail clippings were collected form 120 preschool children aged $3{\sim}6$ residing in Jumunjin(community water fluoridation area) and Kangnung(non-fluoridation area). The acid-diffusible fluoride in the fingernail clipping was isolated by the acid-diffusion technique and measured with a fluoride electrode. The mean fingernail fluoride as the children's living area were 4.49ug/g(SD 2.43) to Jumunjin and 2.68ug/g(SD 1.13) to Kangnung. As would be expected, the fluoride concentration in fingernail clippings were significantly different between the two geographical groups(p<0.001) determined by t-test.

• Journal of the Korean earth science society
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• v.42 no.5
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• pp.556-570
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• 2021

This study presents the data analysis results of groundwater chemistry and the occurrence of fluoride in groundwater obtained from the groundwater quality monitoring network of Korea. The groundwater data were collected from the National Groundwater Information Center and censored for erratic values and charge balance (±10%). From the geochemical graphs and various ionic ratios, it was observed that the Ca-HCO₃ type was predominant in Korean groundwater. In addition, water-rock interaction was identified as a key chemical process controlling groundwater chemistry, while precipitation and evaporation were found to be less important. According to a non-parametric trend test, at p=0.05, the concentration of fluoride in groundwater did not increase significantly and only 4.3% of the total groundwater exceeded the Korean drinking water standard of 1.5 mg/L. However, student t-tests revealed that the fluoride concentrations were closely associated with the lithologies of tuff, granite porphyry, and metamorphic rocks showing distinctively high levels. This study enhances our understanding of groundwater chemical composition and major controlling factors of fluoride occurrence and distribution in Korean groundwater.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.4
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• pp.210-217
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• 2015

Fluoride removal by acid and heat treated red mud were studied in batch and column system regarding contact time, initial concentration, pH, adsorbent dose, and filter depth. The results showed that acid treated with 0.8 M HCl, had highest adsorption capacity of fluoride and adsorption capacity decreased as heat treatment temperature increased. Sorption equilibrium reached in 30 min at a initial concentration of 50 mg-F/L but 1 h was required to reach the sorption equilibrium at the initial concentration of 500 mg-F/L by 0.8 M acid treated red mud (0.8 M-ATRM). Equilibrium adsorption data were fitted well to Langmuir isotherm model with maximum fluoride adsorption capacity of 23.162 mg/g. The fluoride adsorption decreased as pH increased due to the fluoride competition for favorable adsorption site with $OH^-$ at higher pH. Removal percentage was increased but the amount of adsorption per unit mass decreased by adding the amount of 0.8 M-ATRM. It was concluded that the 0.8 M-ATRM could be used as a potential adsorbent for the fluoride removal from aqueous solutions because of its high fluoride adsorption capacity and low cost.

• Restorative Dentistry and Endodontics
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• v.22 no.2
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• pp.560-574
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• 1997

The present study was undertaken to investigate the crystal growth onto human enamel mineral and synthetic hydroxyapatite(HA) seeds in media resembling the enamel fluid composition. Effects of fluoride at high concentrations on the precipitation were also examined in a bench-top crystal growth model adopting a miniaturized reaction column. The Ca, P and F concentrations and pH values of the inlet and outlet solutions were determined. The recovered solid samples were weighed to assess the amount of minerals precipitated during the experimental period, and finally viewed under a scanning electron microscope. Remarkable findings were that 1) both biological and synthetic seeds with the same total surface areas yielded similar amounts of crystal growth, 2) the amount of crystal growth was accelerated in a manner depending on fluoride concentrations in the media, 3) SEM observations disclosed that without the addition of fluoride, precipitation of thin, plate-like OCP crystals became prominent, but by increasing the fluoride concentration(beyond 1ppm F), rod-like crystals having a pointed edge were most frequently observed, without any evidence for precipitation of the plate-like crystals. Furthermore, the dimension of rod-like crystals was increased in proportion to fluoride concentrations, 4) there was no difference in the morphological feature of precipitated mineral phase upon seeding between human enamel seed and synthetic HA seed. The overall results support the view that the seeded crystal growth model is of value to gain insight into the mechanism of enamel crystal growth under fluoride regimens.