Behavior Of Fluoride Research Articles

Use of reaction path modelling to investigate the evolution of water chemistry in shallow to deep crystalline aquifers with a special focus on fluoride

Crystalline aquifers are layered systems in which the hydrogeological path of waters extends from highly weathered, shallow and porous rocks to poorly weathered, deep and fissured rocks. This varying hydrogeological setting influences the water chemistry in different ways. The paper aims to reconstruct the water-rock interaction process in these various environments starting from a solid reactant represented by an average granite rock and several waters from the shallow aquifer. Afterwards, the water-rock interaction processes occurring in the deep environment are reconstructed, varying the geochemical conditions (primary reactants, secondary mineral phases allowed to precipitate, fO2 and fCO2), with a special focus on fluoride (F-). The evolution from the F-poor, Ca-HCO3 facies to the F-rich, Na-HCO3 water type of high pH was simulated using reaction path modelling. The obtained results show that the theoretical evolution trends well reproduce both shallow and deep water samples providing detailed information on the behavior of fluoride and other relevant constituents (i.e., Na, K, Ca, Mg, SiO2). The performed model represents a flexible and powerful tool for environmental research, applicable in other areas hosting F-rich groundwater.

Fluoride Contamination in Groundwater, Around Bhopalpatnam Area, District-Bijapur, Chhattisgarh: Adverse Effect on Human Health

In India many cases of fluorosis (dental and skeletal) have been reported in Archaean and Proterozoic granitic and gneissic t errain from Andhra Pradesh, Rajasthan, Madhya Pradesh, and Chhattisgarh. The origin of hazardous fluoride is attributed to geological reasons. A systematic study is required to understand the behavior of fluoride in drinking water particularly in terms of hydrogeological settings, climatic conditions etc. The present study is an effort to assess hydrogeological study of groundwater in parts of Bhopalpatnam area, District-Bijapur, Chhattisgarh. The study is conducted to understand the fluoride contamination in groundwater and to infer the chemical parameters responsible for distribution of fluoride. The study area is underlain partly by crystalline basement and partly by Proterozoic sedimentary rocks (sandstone, shale and limestone). A total 57 water samples have been taken from dug cum bored wells from the study area in June 2015. The results of chemical analysis showed fluoride concentration from 0.12mg/l to 3.58mg/l. The fluoride bearing minerals in host rock interacted with groundwater and through chemical decomposition, dissociation, reactions dissolution fluoride concentration increased in groundwater. Chemical weathering with relatively high alkalinity favors high concentration of fluoride in Groundwater. Villagers have no option to drink high fluoride groundwater as a result they were badly suffered from dental and skeletal fluorosis.

Geochemistry of high concentrations of fluoride in groundwater at Oued Rmel aquifer (North-eastern Tunisia), and risks to human health from exposure through drinking water

The Oued Rmel aquifer, in Zaghouan city in north-eastern Tunisia, extends geographically between 36°18′ and 36°26′ North, and between 10°06′ and 10°24′ East. The groundwater of the Oued Rmel aquifer is exploited for drinking and irrigation purposes. To monitor the chemical water quality, and especially to identify the occurrence and behaviour of fluoride, 23 water samples were collected in January 2013, and analysed for chemicals parameters such as Na+, Ca2+, Mg2+, K+, Cl−, SO42−, HCO3− and F−. This study applied conventional techniques such as hydrochemical compositions, multivariate statistical methods, Geochemical Modeling and Geographical Information Systems (GIS). Concentrations of fluoride in samples from the Oued Rmel aquifer ranged from 4 to 22 mg/L. The highest values were observed in the surroundings of hydrothermal sources, especially from Hammam Zriba and Hammam Djedidi. Compared with international and national guidelines, all analysed samples exceeded the maximum permissible concentration, in drinking water, of WHO and Tunisian Standards (NT.09.14), which are 1.5 and 1.2 mg/L, respectively. Consequently, up to 75% of the population in the region who use groundwater as a source of drinking water are at risk of developing dental or skeletal fluorosis. Thus, the treatment of fluoridated water through methods such as precipitation, ion exchange, electrodialysis, and reverse osmosis is essential.

Removal of fluoride from aqueous solution by aluminum-loaded Duolite C-467 resin

Our research interests were in the effects of pH, temperature, flow rate, and amount of resin on the kinetic behavior of fluoride removal using an aluminum-loaded synthetic resin, Duolite C-467, in batch reactors and fixed-bed adsorption columns, in order to obtain more practical design and operating data for a particular column. The results indicated that the removal efficiency was influenced significantly by solution pH and the optimum pH was found to be in the range 5.0–7.0. The removal of fluoride by the resin was interfered with by the presence of sulfate ions because of the competition for surface sites and neutralization of surface charge of resin. The Bed-Depth-Service-Time model can adequately describe the adsorption behavior of fluoride by aluminum-loaded Duolite C-467 resin in a fixed-bed column, also indicating that the adsorption rate of fluoride ion is mainly determined by the surface reaction step.

From Isocratic Data to a Gradient Elution Retention Model in IC: An Artificial Neural Network Approach

Gradient elution is used in ion chromatography to achieve rapid analysis with reasonable separation. Optimization and prediction of the gradient is clearly a multidimensional problem, however. One approach to prediction of gradient retention behavior is based on isocratic experimentation. In this work, a gradient model for simultaneous prediction of the retention behavior of fluoride, chlorite, chloride, chlorate, nitrate, and sulfate ions, on the basis of isocratic experimental data, is proposed. An artificial neural network was used to predict isocratic results; the network was optimized with regard to the number of data in the training set (25) and number of neurons in the hidden layer (6). A slight systematic error was observed in the isocratic prediction, but this did not effect gradient prediction. Good predictions were achieved for all the anions investigated (average error 1.79%). Deviations were somewhat higher for prediction of sulfate retention than for the other anions, probably because of the higher charge and larger size of sulfate in comparison with the other ions examined.

中国炭中フッ素の形態と燃焼時のフッ素の挙動

Research on fluoride emission from coal combustion is important to solve a serious fluoride pollution problem. Occurrence mode and behaviors of fluoride during coal combustion were investigated. XRD and XPS analysis showed that fluorides in chinese coal existed mainly as -CF2-, muscovite and apatite. Coal pyrolysis and combustion were carried out by TG-MS. HF was found to be released from both coal pyrolysis and combustion. Experimental result under different combustion conditions showed that fluoride content in flue gas and particles increased with increase in oxygen concentration or temperature, while fluoride content in residue decreased with it.

The removal of fluoride ion from aqueous solution by a cation synthetic resin

The removal of fluoride ion in aqueous solution by using an aluminum-formed synthetic resin, Amberlite IR-120 (MERCK, USA), was studied in this research. The experimental results indicated that the removal efficiency was influenced significantly by solution pH and the optimum operating pH was found to be in the range of 5–7. The removal of fluoride by Amberlite IR-120 resin was increased with the presence of sulfate ions in aqueous solution. The Langmuir and Freundlich isotherms can adequately describe the equilibrium behaviors of the adsorption processes. The surface reaction-limiting kinetic model can adequately describe the removal behaviors of fluoride ion by Amberlite IR-120 in batch systems. Results for column experiments indicate that the utilization of contact bed and the removal capacities improved with increasing empty bed contact time (EBCT). The Bed-Depth-Service-Time (BDST) model can describe the removal behavior of fluoride in the column adequately, indicating that the removal rate was possibly determined by the surface reaction step.

The Adsorption of Fluoride Ion from Aqueous Solution by Activated Alumina

The adsorption of fluoride ion in aqueous solution by using alumina was studied in this research. The experimental resultsindicated that the removal efficiency was influenced significantly by solution pH and the optimum operating pH wasfound to be in the range of 5 to 7. For neutral and acidic solutions, the adsorption capacities of fluoride by alumina wasinterfered by the presence of sulfate. The Langmuir and Freundlich isotherms can well describe the equilibrium behaviorsof the adsorption processes. The experimentally determined lowvalues of activation energy indicate nonspecific adsorption isthe predominant mechanism. The surface reaction-limiting batchkinetic model can adequately describe the removal behaviors offluoride ion by alumina adsorption in the batch system.

Comparison of Fluoride Modified Zirconia with Ceramic Hydroxy-Apatite for Preparative Scale Purification of Immunoglobulin from Serum Albumin

The utility of 50 μm fluoride modified zirconia particles as an easily cleaned and steam sterilizable low pressure preparative scale stationary phase for immunoglobulin purification was investigated and its performance was compared with 40 μm ceramic hydroxyapatite type II (cHAp II) particles. The equilibrium batch binding capacity of both supports for bovine serum albumin decreases monotonically with increase in the adsorption pH, while that for bovine IgG is independent of pH, in the pH ranges studied. The dynamic binding capacity, as determined by breakthrough analysis, was 29 mg BSA/g zirconia for fluoride modified zirconia and 8.6 mg BSA/g cHAp II for cHAp II. Linear gradient conditions were developed for the separation of BSA and IgG on fluoride modified zirconia. The same separation could be accomplished in a shorter time and with better resolution on cHAp II. The analysis of retention data for a set of model proteins suggests that, even though both supports retain proteins by mixed mode interactions (cation, anion and ligand exchange), the retention behavior of fluoride modified zirconia is not analogous to that of cHAp II. The results also indicate that protein adsorption-desorption kinetics on fluoride modified zirconia are rate limiting and control the dispersion of the protein elution profile. There was no observable effect on the batch binding capacity for bovine serum albumin on cleaning with 0.25 M NaOH and steam sterilization for the two supports. Zirconia particles were routinely cleaned, in situ, with 0.25 M NaOH (a total of 700–1000 column volumes) without any observable effect on the chromatographic integrity.

Fluorides in Wastewater Discharges: Toxic Challenges to the St. Lawrence River Biological Community

Abstract This literature review examines the risk to fluvial organisms of fluoride released to the St. Lawrence River by the Montréal Urban Community waste-water treatment plant. The following key points are presented regarding the behaviour of fluoride in aquatic systems: fluoride is not removed by primary sewage treatment methods; fluoride from the treatment plant is rapidly diluted to background levels; aquatic plants do not accumulate significant levels of fluoride; fluoride is generally sequestered in the shell/exoskeleton/skeleton and skin of animals and released via the urinary system; fluoride ion is not very toxic in aquatic systems; there is rarely a large difference between acute and chronic (or lethal and sublethal) threshold levels of fluoride in aquatic systems; the most sensitive aquatic organisms are trout and fingernail clams; finally, the only significant evidence of synergistic action is with aluminium. It is concluded that fluoridation of the city of Montréal’s drinking water would not pose any significant additional risk to the biological community in the receiving waters of the St. Lawrence River.

Coprecipitation of fluoride with calcium carbonate

The behavior of fluoride during the precipitation of calcium carbonate from calcium bicarbonate solution was studied experimentally. Magnesium ions in parent solutions cause the coprecipitation of fluoride with calcium carbonate. The amount of fluoride coprecipitated with calcite increases with increasing concentration of magnesium ions in parent solutions, whereas the amount of fluoride coprecipitated with aragonite decreases. It may suggest that the mechanism of the coprecipitation of fluoride with calcite is different from that with aragonite. The amount of fluoride coprecipitated with aragonite is larger than that with calcite. The experimental result agrees with the observed fact that the fluoride contents of skeletal aragonite of marine organisms and of natural aragonite formed inorganically in sea water are higher than those of skeletal calcites. Fluoride in parent solutions greatly favors calcite formation.

Behavior of Fluoride in the Process of Concentrating Sea Water by Ion Exchange Membrane Method

Behavior of Fluoride in the Process of Concentrating Sea Water by Ion Exchange Membrane Method

The behaviour of fluoride as a labilizing and orienting ligand in substitutions of Bis(ethylenediamine)cobalt(III) complexes

The behaviour of fluoride as a labilizing and orienting ligand in substitutions of Bis(ethylenediamine)cobalt(III) complexes

Reactions in the Presence of Metallic Halides. II. The Behavior of Fluorides and the Reactivity of the Halogens1

Reactions in the Presence of Metallic Halides. II. The Behavior of Fluorides and the Reactivity of the Halogens¹