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1

Fluoride removal from groundwater by technological process optimization

Valentukeviciene Marina, Zurauskiene Ramune, Boussouga Youssef Amine

Ecological Chemistry and Engineering. S

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2019

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Vol. 26, nr 1

133--147

EN

Fluoride removal from aqueous solutions was studied using nanofiltration and sorption techniques which have always been best key ways to deal with water contaminated by fluoride. In this presented work, we were firstly interested on fluoridated rejected water overcoming the drawback of RO membrane process of groundwater treatment plant in Baltic region (Kretinga, Lithuania). Opoka sorbent has shown effective results of fluoride sorption with efficiency higher than 77 %. In order to understand the sorption phenomenon and to validate the results obtained, we have applied experimental data on Freundlich and Langmuir isotherms which allow us to determine isotherms parameters (KF; 1/n and KL; qmax) and to confirm the experiment. Because of the unacceptable tariff of drinking water treated by RO, defluoridation with nanofiltration method is proposed in this study as a solution which can replace reverse osmosis technique. For that, tests of nanofiltration for fluoride removal were carried out at laboratory scale by using nanofiltration flat sheet membranes (NF270 and NF90).

2

Seasonal variation in fluoride content in groundwaters of Langtang area, Northcentral Nigeria

Dibal H. U., Dajilak W. N., Lekmang I. C., Nimze L. W., Yenne E. Y.

Contemporary Trends in Geoscience

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2017

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Vol. 6, iss. 1

11--27

EN

Thirty groundwater samples were collected at the peak of the rainy season and analysed for fluoride and other cations and anions in drinking water sources of Langtang area. For comparative purposes, thirty seven groundwater samples were collected in the dry season. The aim of the study was to determine variation in fluoride content with respect to the seasons. Fluoride in water was determined by the Ion Selective Electrode (ISE) and the cations by the Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). The anion (sulphate) was determined by Multi – Ion Colorimeter, bicarbonate and chloride by titration method. In addition fluorine content in aquifer materials from a borehole section were determined by Fusion method. The two seasons show variation in content of fluoride in groundwater. Fluoride content in groundwater is higher in the dry season ranging from 0.13 – 10.3 mg/ l compared to the 0.06 – 4.60 mg/l values in the rainy season. Content of fluorine (0.01 wt %) in the aquifer materials (sands) is low from depth of 0 to 7.95 m. However, fluorine content increases with depth, from 7.95 to 10.60 m with concentration of 0.04 wt %, 0.05 wt % from 10.60 to 13.25m, and 0.07 wt % from 13.25 to 15.70 m, the content of fluorine however, decreased at depth 15.70 to18.55m with concentration of 0.02 wt % even with fluorite mineral in the aquifer material at this depth. Dilution of fluoride ion as a result of rain input which recharges the aquifer may be the main reason for lower values recorded in the rainy season. Over fifty and sixty percent of waters in both dry and rainy season have fluoride concentration above the WHO upper limit of 1.5 mg/l. Consumption of these elevated values of fluoride in groundwater of the study area, clearly manifests as symptoms of dental fluorosis.

3

Use of the electrodialysis process for fluoride ion and salt removal from multi-constituent aqueous solutions

Grzegorzek M., Majewska-Nowak K.

Architecture Civil Engineering Environment

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2016

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Vol. 9, no. 4

107--113

EN

Fluorine is a common chemical element. According to WHO guidelines, the F- ion content in drinking water cannot be higher than 1.5 mg/dm3. Excess of fluorine leads to many health problems: Alzheimer’s disease, neurological disorders or fluorosis (dental or skeletal). Fluoride can be removed from aqueous solutions by means of various methods (adsorption, precipitation, ion-exchange or membrane techniques). The aim of this paper was to evaluate the efficiency of electrodialysis in fluoride removal under the presence of organic substances. During experiments solutions containing fluorides (5, 10, 100 and 200 mg F-/dm3), mineral salt (0.5 g NaCl/dm3) and organic matter (5, 10 and 15 mg/dm3 of humic acids) were used. The research was conducted with the use of the PC Cell BED-1 System. The current density was equal to 1.72 mA/cm2. It has been shown that electrodialysis is an efficient technique of fluoride removal provided that the initial concentration of F- ions is not higher than 10 mg F-/dm3. The impact of organic matter on the process run and efficiency was dependent on the fluoride content in the treated solution.

PL

Fluor jest powszechnie występującym pierwiastkiem chemicznym. Zgodnie z wytycznymi WHO zawartość fluorków w wodzie do picia nie może być większa niż 1.5 mg/dm3. Nadmiar fluoru prowadzi do licznych problemów zdrowotnych (Alzheimer, problemy neurologiczne, fluoroza zębów lub szkieletu). Fluorki mogą być usunięte z roztworów wodnych z wykorzystaniem różnych metod (adsorpcja, strącanie, wymiana jonowa czy procesy membranowe). Celem pracy była ocena efektywności elektrodializy w usuwaniu jonów fluorkowych w obecności substancji organicznych. W trakcie doświadczeń zostały wykorzystane roztwory zawierające fluorki (5, 10, 100 i 200 mg F-/dm3), sól mineralną (0.5 g NaCl/dm3) oraz substancje organiczne (5, 10 i 15 mg/dm3 kwasów humusowych). Doświadczenia zostały przeprowadzone z wykorzystaniem instalacji PCCell BED-1 System. Gęstość prądu wynosiła 1.72 mA/cm2. Wykazano, że w procesie elektrodializy fluorki są skutecznie usuwane pod warunkiem, że ich początkowe stężenie nie przekracza 10 mg F-/dm3. Wpływ substancji organicznych na przebieg i efektywność procesu zależał od stężenia fluorków w oczyszczanym roztworze.

4

Spectrophotometric determination of tin as a ternary complex in matrices containing oxides of tantalum, iron and titanium

Saran R., Baishya N. K., Roy S.

Chemia Analityczna

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2002

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Vol. 47, No. 1

131-138

EN

A rapid spectrophotometric method employing the formation of a ternary complex of tin with Fe(II) and dimethylglyoxime, has been developed for the determination of tin in tantalum, iron and titanium bearing matrices. A novel method for the dissolution of samples has been proposed to avoid hydrolysis and subsequent loss of tin due to adsorption by the hydrolysed mass. The observation that Sn(IV) also forms a triple complex, besides Sn(II), with exactly overlapping spectra avoids the presence of tin in specific oxidation state. The molar absorptivity and the Sandell sensitivity of the complex formed at pH 0.8-2.0 in aqueous medium are 4.2 x 10(3) L mol(-1) cm'1 and 0.0242 ug cm(-2), respectively, in either oxi-dation state of Sn at absorption maximum 460 nm.

PL

Opracowano szybką metodę spektrofotometryczną oznaczania Sn w matrycach zawierających Ta, Fe i Ti. W metodzie wykorzystano powstawanie trój członowego kompleksu Sn(II) lub Sn(IV) z Fe(II). Kompleksy Sn(II) i Sn(lV) majądokładnie nakładające się widma z maksimum absorpcji przy 460 nm. Próbki rozpuszczono tak, aby nie powstawały osady zhydrolizowanych produktów, co eliminowało możliwość strat cyny wskutek adsorpcji na tych osadach. Wyznaczono molowy współczynnik absorpcji i czułość SandelPa dla trójczło-nowych kompleksów cyny; przy pH 0.8-2.0 wynosiły one odpowiednio 4.2x 10(3) L mol(-1) cm(-1) 0.0242 ug cm(-2).