Recovery Of Fluorine Research Articles

Quantification of per‐ and polyfluoroalkyl substances with a modified total organic carbon analyzer and ion chromatography

AbstractQuantification of per‐ and polyfluoroalkyl substances (PFAS) via mass spectrometry is highly sensitive but targets a limited number of compounds and the instrumentation is not available in many laboratories. We developed a methodology to determine total organofluorine by modifying a total organic carbon analyzer, which is common in laboratories across disciplines. Evolved hydrogen fluoride was captured in an impinger and analyzed by ion chromatography. Recovery of fluorine from 20 PFAS was dependent on terminal functional group and alkyl chain length. The method detection limit based on perfluorooctanoic acid (PFOA) spiked samples was 36 μg‐F/L (52 μg PFOA/L). Fluorine recoveries of spiked PFAS in river water and wastewater were similar to those spiked in deionized water. The recovery of inorganic fluorine present in sodium fluoride was 91%. Therefore, researchers should be cautious when applying methods that pre‐combust samples to differentiate organo‐ and inorganic fluorine, because the combustion process may cause inadvertent losses of inorganic fluorine, resulting in an overestimation of organofluorine.Article Impact StatementResults enable the quantification of per‐ and polyfluoroalkyl substances using equipment present in a greater number of laboratories than mass spectrometry‐based methods.

Removal of Poly- and Per-Fluorinated Compounds from Ion Exchange Regenerant Still Bottom Samples in a Plasma Reactor.

"High-concentration" and "low-concentration" bench-scale batch plasma reactors were used to effectively degrade per- and polyfluoroalkyl substances (PFAS) at a high concentration (∼100 mg/L) and a low concentration (<1 μg/L), respectively, in ion exchange (IX) regenerant still bottom (SB) solutions. In the SBs, numerous PFAS were detected with a wide concentration range (∼0.01 to 100 mg/L; total oxidizable precursors (TOP) ∼4000 to 10000 mg/L). In the "high-concentration" plasma reactor, the concentrations of PFAS precursors and long-chain perfluoroalkyl acids (PFAAs) (≥6C for PFSAs and ≥8C for perfluorocarboxylic acids (PFCAs)) were decreased by >99.9% in 2 h, and short-chain PFAAs (<6C for perfluorocarboxylic acids (PFSAs) and <8C PFCAs) were decreased by >99% in 6 h of treatment. Subsequently, a "low concentration" plasma reactor was used to remove additional PFAAs. In this reactor, the addition of CTAB (cetrimonium bromide, a cationic surfactant) caused short-chain PFAAs, other than PFBA, to be removed to below detection limits in 90 min of treatment time. Overall, >99% of the TOP present in SBs was removed during the treatment. Fluorine recovery of 47 to 117% was obtained in six SB samples. Energy requirement (EE/O) for the treatment of PFOA and PFOS from SBs ranged from 380 to 830 kWh/m3.

Choosing sorbent for fluoride ion removal from zinc sulfate solutions

The process of zinc sulfate solution purification determines process, economic and environmental production results. Since recently there has been a constant increase in the content of halides in pregnant solutions of zinc production due to the processing of technogenic zinc-containing raw materials, it is relevant to search for methods for removing halides, in particular fluorine, from zinc solutions using a variety of materials. The purpose of this paper was to investigate the effectiveness of akaganeite as an sorbent for fluoride ion removal from zinc sulfate solutions. When using akaganeite, it is especially important to choose a carrier for the sorbent since the nanosized particles of akaganeite make it difficult to clean the solution from the sorbent. Most suitable carriers for this purpose in terms of surface characteristics and physicochemical properties are gypsum and red mud of alumina production. Experiments used a zinc sulfate solution (100 g/dm3 Zn2+, pH = 4.5) containing 26.8–111.4 mg/dm3 F–. The maximum fluoride ion capacity was shown by red mud due to the formation of F–Al complexes. The highest fluorine recovery was demonstrated by red mud with impregnated akaganeite at elevated temperature that facilitates showing akaganeite properties and accelerates the surface ОН– ↔ F– exchange process. The gypsum-based adsorbent successfully removed fluorine due to calcium ions released and calcium fluoride formed. The amount of fluorine removed depends on the sorbent material, its consumption, sorption duration and temperature. The optimal processing conditions were (at pH = 5.5): temperature – 60 °C, process duration – 120 min, composite sorbent consumption – 20÷30 g/dm3. It was shown that composite sorbents based on red mud or gypsum with impregnated akaganeite (β-FeOOH) are most suitable for cleaning zinc solutions from halides. These adsorbents make it possible to achieve the greatest capacity and degree of fluoride ion removal (up to 98–99 %) in the actual pH range of process solutions. The abovementioned sorbents can be regenerated in an alkali solution, and then reused (up to 3–4 cycles).

Degradation mechanism of perfluorooctanoic acid (PFOA) during electrocoagulation using Fe electrode

In this study, the electrocoagulation of perfluorooctanoic acid (PFOA) in water using an iron (Fe) electrode was investigated. The effects of the current density, stirring speed, and electrolyte concentration (NaCl) on the corresponding removal rates of PFOA were examined. An increase in the current density from 2.4 to 80.0 mA cm−2 led to a significant increase in the removal efficiency of PFOA from 10.0 to 100.0% within 6 h. Formate (HCOO−) ions and three shorter-chain perfluorocarboxylates (i.e., perfluoropentanoic acid; PFPeA, perfluorohexanoic acid; PFHxA, and perfluoroheptanoic acid; PFHpA) were observed as organic byproducts during the electrocoagulation of PFOA, indicating that the C-C bond between C7F15 was first broken down and then was degraded into short carbon-chain compounds by PFOA decomposition. 65% of fluorine recovery as fluoride ions and organic fluorine in shorter-chain byproducts (PFPeA, PFHxA, and PFHpA) with 60% of total organic carbon (TOC) removal was achieved within 6 h during electrocoagulation, while the complete removal of PFOA was achieved. Our results imply that electrocoagulation using Fe electrode can effectively degrade PFOA into shorter-chain byproducts with significant mineralization.

Reaction mechanism of fluoride conversion into [formula omitted] during sulphuric acid leaching of roasted bastnaesite

The bastnaesite used in hydrometallurgy usually contains 7%–11% fluorine, and the conversion of fluorine into high-value products is the key to achieving green production of rare earths and improving the comprehensive utilization of bastnaesite. In order to recover fluorine from bastnaesite in the form of KBF4, the mechanism of F− conversion to BF4− in sulphuric acid leaching solution of roasted bastnaesite was studied by using Eh–pH diagram and simulation experiment. It shows that the formation of BF4− is affected by pH in the absence of rare earths. BF4− is hydrolyzed to BF3OH− and F− when the pH is greater than 3.9, and part of F− exists as HF2− when pH is lower than 2. In the presence of La3+, the formation of BF4− is mainly affected by LaF3 when pH is greater than 0, and in the case that the pH is lower than 2, it is mainly affected by HF2−. When Ce4+ is present in solution, CeF22+ can exist stably in sulphuric acid solution. Bringing down the pH can reduce the stability of CeF22+ and increase the BF4− conversion rate. Based on these results, KBF4 was prepared in the alkaline solution of bastnaesite, and the conversion of BF4− is 84.31%. This provides a theoretical basis for the recovery of fluorine from bastnaesite in the form of KBF4.

Solubility of ammonium fluoride in aqueous sodium fluoride solutions of various concentrations from dilute to saturated at 298.15 K for fluorine recovery from wet-process phosphoric acid

Recovery of fluorine from wet-process phosphoric acid (WPA) to produce ammonium fluoride (NH4F) and sodium fluoride (NaF) provides an environmentally-friendly route to purify WPA and produce high value-added fluoride salt. The solubility data and the related electrolyte thermodynamics are essential for a rational separation design of pure NH4F from aqueous NaF solution by crystallization. In this contribution, the solubilities of NH4F in aqueous NaF solutions of different concentrations from dilute to saturated were systematically measured at 298.15 K using a dynamic synthesis method. Experimental results show that the presence of NaF in the solution could significantly decrease the solubility of NH4F due to the common-ion effect which was decreased by 72.4% when the molality of NaF was only around 0.015 mol/kg. The data can be used to determine the yield of NH4F and liquid composition in the vacuum evaporative crystallization of NH4F. The mean activity coefficients of NH4F at saturation were determined from the experimental solubility data and then correlated with the extended Debye-Hükel equation and the Pitzer model. With four adjustable parameters, both models are able to accurately calculate the experimental data over a wide range of salt concentrations. The average relative deviations between the experimental and calculated logarithm of mean activity coefficients of NH4F from the two models are 1.43% and 2.29%, respectively. The binary and ternary ionic parameters for the Pitzer model are found to be concentration dependent and the correlations of them as functions of ionic strength are proposed.

Определение оптимальных параметров выщелачивания фтора из угольной части отработанной футеровки демонтированных электролизеров производства алюминия

When aluminum is obtained by electrolysis of cryolite-alumina melts when the baths are sent for capital repairs, a solid technogenic product is formed – waste lining of electrolytic cells (WLEC). The volume of formation of WLEC is 30-50 kg per 1 ton of aluminum. Currently, it is mainly stored at landfills near industrial enterprises, causing harm to the environment. However, this technogenic raw material contains valuable components (fluorine, aluminum, sodium) that can be extracted to produce fluoride salts, which are in demand during the electrolytic production of aluminum. The objects of research were samples of the coal part of the waste lining of dismantled S-8BM (E) type electrolytic cells of «RUSAL Krasnoyarsk» JSC (Krasnoyarsk) of RUSAL company. According to the X-ray experiment diffraction analysis (using a Bruker D8 ADVANCE diffractometer) of the phase composition of the samples, it was found that the main fluorine-containing compounds are cryolite, chiolite, sodium and calcium fluorides. The total fluorine content in the studied samples averaged 13.1 %. We conducted studies on the leaching of fluorine from WLEC with a solution of caustic alkali (NaOH concentration – 17.5 g/dm3). The process was carried out in a mechanically agitated reactor using a BIOSAN MM-1000 top drive laboratory stirrer with a two-blade nozzle. By the method of mathematical planning of a three-factor experiment, the mutual influence of three leaching conditions on the optimization parameter was established – the extraction of fluorine in solution (in percent). The maximum recovery of fluorine from WLEC to the leach solution averaged 86.4 % and was achieved with the following indicators:processtemperature–95°C,theratio ofliquidtosolidphase–9:1,duration– 210 min.

Fluorine recovery from etching wastewater through CaF2-based near-infrared photocatalyst synthesis

Fluorine in etching wastewater is an important F resource, and the development of a high value-added fluorine based compounds could benefit for the fluoride resource saving and the reduction of fluoride effluent. In this work, F from etching wastewater was recovered by composites of CaF2 and CaSO4, which was used to prepare as the near infrared photocatalyst of Tm3+/Yb3+ co-doped ((CaF2/CaWO4)@Bi2WO6) (TY-CCB). It was found that CaWO4 was fabricated by the slow release of Ca2+ ions from CaSO4 particles according to XRD and XPS results, and the heterostructure between CaWO4 and Bi2WO6 were formed in the TY-CCB composite with flat-shape morphology, which could improve the photocatalytic activity. The upconverted UV (364 nm) and blue (484 nm) light were observed upon 980 nm NIR irradiation, combined with the extended absorption band of 519 nm in TY-CCB. For the degradation of methyl orange (MO) and salicylic acid (SA), the corresponding degradation rate of 0.44 and 0.42 mg L−1·h−1 were obtained after 3 h under NIR light irradiations, and both of them increased to 2.78 and 1.74 mg L−1·h−1 under UV–vis–NIR light irradiations, respectively. Fluorine recovery through the preparation of TY-CCB upconversion photocatalyst was a mutually beneficial approach.

Recovery of fluorine utilizing complex properties of cerium(IV) to obtain high purity CeF3 by solvent extraction

Abstract Utilizing complex properties of cerium(IV) with fluorine(I), this paper investigated the recovery of fluorine from nitrate solutions in the form of CeF 3 by solvent extraction. The extraction mechanism was studied firstly, and then CeF 3 was obtained from the extracted organic phase by reductive stripping. The effects of the main parameters such as HNO 3 concentration, extractant concentration, F(I) concentration, salting-out agent concentration and the temperature were examined and discussed. Showing that HNO 3 concentration, salting-out agent concentration and the temperature did not affect the extraction of Ce(IV). The presence of F(I) can decrease the extraction of Ce(IV). The extraction of HNO 3 , Ce(IV) and Ce(IV)-F have been studied respectively, and the extracted complexes are considered to be HNO 3 ·Cyanex923, Ce(NO 3 ) 4 ·2Cyanex923 and Ce(HF)(NO 3 ) 4 ·Cyanex923 individually. The extraction mechanisms were concluded according to slope analysis, and the loading capacities of Ce(IV) had been obtained. The Infrared Spectra of extracted complexes was determined, showing that the NO 3 − ion is a bidentate ligand. High purity CeF 3 nanoparticle was obtained and the size distribution, SEM and TEM images of the nanoparticle were given, CeF 3 nanoparticle was acquired also in H 2 SO 4 system and the difference between the two CeF 3 were compared.

Recovery of cryolite with high molar ratio from high fluorine-containing wastewater

The recovery of fluoride from wastewater has great economic and environmental significance for the fluorine industry. Cryolite is an optimal product for fluorine recovery from high fluorine-containing wastewater. The cryolite with a high molar ratio is more valuable and is extensively used in the aluminum electrolytic industry. The present study aims to recover cryolite with a high molar ratio from high fluorine-containing wastewater through the crystallization process. The crystallization conditions of cryolite with a high molar ratio were investigated by laboratory experiment and thermodynamic modeling. The results show that the composition of the cryolite products may be a mixture of Na3AlF6 and NaAlF4 for the Al3+–Na+–F−–H+–H2O system. Favorable conditions for the formation of AlF6 3− and Na3AlF6 include higher pH, higher influent concentration of fluorine, and lower reaction temperature. Cryolite products with a high molar ratio can be recovered from high-fluorine containing wastewater at a pH range of 3.69–8.39, a reaction temperature of 20–30 °C, and an α k of 3.11–4.44. The results can be used to predict and to guide the crystallization process of cryolite with a high molar ratio.

Leaching of fluorine and rare earths from bastnaesite calcined with aluminum hydroxide and the recovery of fluorine as cryolite

Bastnaesite is decomposed with aluminium hydroxide to avoid fluorine loss and contamination, to recover fluorine as cryolite.

Influence of microwave heating on the extractions of fluorine and Rare Earth elements from mixed rare earth concentrate

A novel process was proposed to treat the mixed rare earth concentrate by utilizing the microwave radiation. The influences of microwave heating on the mechanism of decomposition, microstructure of mixed rare earth concentrate, the behavior of fluorine leaching by water and the rare earth elements(REEs) leaching by hydrochloric acid were investigated. The results showed that bastnaesite and monazite were decomposed efficiently to rare earth oxide, and fluorine containing compounds were converted to fluoride after the microwave treatment. However, the bastnaesite and monazite were partly decomposed to REEs hydrate after treating with the conventional heating (convective heating). The recoveries of fluoride in the solutions of water and REEs in the solution of hydrochloric acid by leaching the concentrate treated with microwave radiation reached 67.1% and 82.5%, which were much higher than for those with conventional heating process (38.5% and 47.4% respectively). The increase in the recovery of fluorine and REEs is attributed to the phase transformation of REEs minerals due to the microwave characteristics of the rapid internal heating and energy transfer.

Treatment and resource recovery from inorganic fluoride-containing waste produced by the pesticide industry

The rapid development of the fluorinated pesticide industry has produced a large amount of fluorine-containing hazardous waste, especially inorganic fluoride-containing waste (IFCW). A two-step process, including extraction and recovery, was developed to recover fluorine as synthetic cryolite from IFCW produced by the pesticide industry. The optimum conditions for extraction were found to be a temperature of 75°C, an initial pH (pHi) of 12, a 4-hr incubation time and a liquid-to-solid ratio of 40mL/g; these conditions resulted in a fluorine extraction ratio of 99.0%. The effects of pH and the F/Al molar ratio on fluorine recovery and the compositional, mineralogical and morphological characteristics of the cryolite products were investigated. Field-emission scanning electron microscopy of recovered precipitates showed changes in morphology with the F/Al molar ratio. Coupling Fourier transform and infrared spectroscopy, X-ray diffraction indicated that the formation of AlF63− was restricted as increasing pH. Both the amount of fluorine recovered and the quality of the cryolite were optimized at initial pH=3 and a F/Al molar ratio 5.75. This study proposed a reliable and environmentally friendly method for the treatment of fluoride-containing wastes, which could be suitable for industrial applications.

비료공장의 인산 슬러리로부터 규불산 제조

일반적으로 비료용 인산은 황산과 인광석의 분해반응에 의해 생산되는데 이 반응은 발열반응으로써 온도가 상승하게 되면 생산수율 저하의 문제점이 따른다. 이를 해결하기 위해 인산제조공정에서는 불산(HF)과 사불화규소(SiF4)가 함유된 증기(vapor, <TEX>$80^{\circ}C$</TEX>)를 배출시키는 진공냉각기(vacuum cooler)를 운영하고 있으나, 이 과정에서 냉매 및 폴리실리콘 원료로 활용가능한 귀중한 자원(불소 & 규소)들이 버려지고 있다. 본 연구는 인산제조공정 부산물인 규불산(H2SiF6)으로 회수하기 위한 기초 실험연구로서, 불소회수 후 인산슬러리 내 불소 농도변화를 분석하여 규불산 회수가능량을 예측하였다. 회수 후 불소농도는 약 0.12wt% 감소하였고, 대상 비료공장의 생산규모를 고려할 경우 불소 회수가능량은 약 5,509 톤/년이었다. 한편 현장에서, 규불산의 농도는 0.35wt%에서 7.33wt%까지 농축되었고, 진공냉각기로부터 배출되는 증기유량은 <TEX>$51,000m^3/hr$</TEX>이었다. 또한 Pilot실험을 통한 불소 회수효율은 76.74%로 나타나, 실제 회수할 수 있는 규불산량은 5,340 톤/년으로 추정되었다. Phosphoric acid used for the production of phosphate fertilizers is synthesized by the reaction of phosphate rock and sulfuric acid. As the reaction is exothermic, yield of phosphoric acid is poor at elevated temperature. Therefore, enhancement in its yield requires the process temperature be maintained by releasing the vapor (<TEX>$80^{\circ}C$</TEX>) containing HF and SiF4 through a vacuum cooler. However, these valuable resources; Fand Si, which can be utilized for the manufacture of refrigerant and polysilicon, respectively, are being wasted in the treatment process. We performed lab-scale experiments to estimate the amount of recoverable H2SiF6, a by-product of phosphoric acid manufacturing process. The experimental results showed a decrease of fluorine concentration by 0.12wt% in the liquid phase. Preliminary estimation showed a possible recovery of 5,509 ton/yr of fluorine considering the scale of the fertilizer manufacturing plant. Furthermore, field-scale experiment showed that H2SiF6 could be enriched in liquid phase from 0.35wt% to 7.33wt% and the vapor flow-rate from vacuum cooler was estimated at <TEX>$51,000m^3/hr$</TEX>. Anew, the efficiency of fluorine recovery in the pilot-scale experiment was found to be 76.74% and the production of H2SiF6 was estimated at 5,340 ton/yr.

Recovery of fluorine from bastnasite as synthetic cryolite by-product

This paper investigates the development of a new environment friendly approach for treatment of bastnasite. A new process was developed to recover fluorine from bastnasite as synthetic cryolite by-product. The conditions affecting the fluorine removal and recovery in the process, including contact time, acidity, Al3+ concentration, Al/F molar ratio and different kinds of aluminum salts being used, were investigated. The results indicate that high acidity and large Al/F molar ratio were beneficial to fluoride removal, and that the reaction reached equilibrium after 15min. The effect of the initial Al3+ concentration at a certain total Al3+ amount was slight. Aluminum nitrate was more efficient than aluminum sulfate for the removal of fluoride. Optimum operation parameters for synthesizing cryolite have been obtained and proposed for industrial applications.

Study on Harmless and Resources Recovery Treatment Technology of Waste Cathode Carbon Blocks from Electrolytic Aluminum

The paper provides a brief introduction in the physical and chemical properties of waste aluminum cathodes, and its harmless treatment technology and resource comprehensive utilization technology. The main chemical composition of the waste cathode carbon blocks of electrolytic aluminum are carbon, fluorine, sodium, aluminum, calcium, silicon and etc. The main mineral components of waste cathode carbon include sodium fluoride, cryolite, calcium fluoride, silicate minerals and so on, therein the fluorine content is about 9.86%, and the content of cyanide ions (CN−) is 0.82 ppm, which are the most important reasons leading serious environmental hazards caused by the waste aluminum cathodes; and in which carbon has been graphitized mostly and the content of it is up to 58.56%, having a high recycling value. Using the flotation-chemical treatment process to recover fluorine and carbon, carbon powder was obtained with the carbon content of 88.00%, recovery of 95.90%; and the content of sodium and fluoride in sodium fluoride product are 49.33% and 38.53% respectively, the total recovery of fluorine in fluoride sodium and other products is 90.10%. It proves that the cyanide in the waste cathode carbon block of electrolytic aluminum has been completely decomposed. The process takes fully the factors of crushing, grinding, flotation, chemistry, waste gas absorption technology into account, and achieves the purpose of harmless treatment and comprehensive utilization of resources.

Experimental study of thermal breakdown products from halogenated extinguishing agents

Thermal breakdown products from four different fire extinguishing agents have been analysed. The agents studied were: bromotrifluoromethane (Halon 1301), pentafluoroethane (HFC 125), heptafluoropropane (HFC 227ea) and dodecafluoro-2-methyl-pentane-3-one (C 6F-ketone). In the tests, the studied agent was introduced into a propane flame in a diffusion flame burner. The combustion products were analysed using both conventional IR-techniques and FTIR. It could be concluded that for all four extinguishing agents that the extinguishing agent takes part in the combustion process resulting in production of CO and CO 2, which was also confirmed by the increase in smoke production with increasing amounts of agent introduced into the flame. Production of HF and COF 2 was found in experiments with all four extinguishing agents. In experiments with Halon 1301, the production of HBr was also determined. It was found that the main fraction of fluorine ends up as HF for HFC 227ea and HFC 125 at lower relative application rates. When approaching extinguishing concentrations, the fraction recovered as COF 2 increases, but the total recovery of fluorine, including HF and the remaining part of the fluorine, is found in various organic breakdown products. The recovery of fluorine as HF and COF 2 for the C 6F-ketone is lower compared to HFC 227ea and HFC 125. There is a clear difference in the recovery of fluorine for Halon 1301 where an almost quantitative recovery as HF or COF 2 is found. Halon 1301 additionally contains bromine, which, to a large extent, is recovered as HBr.

Decomposition of tetrafluoromethane by water plasma generated under atmospheric pressure

Tetrafluoromethane (CF 4) decomposition by water plasma generated under atmospheric pressure was investigated by means of thermodynamic analyses and experiments. Thermodynamic equilibrium calculations were performed between 300 and 6000 K at atmospheric pressure. Experimental results indicated that CF 4 was completely decomposed by water plasma, and recovery of fluorine can be achieved more than 99%. Influence of factors such as arc current and additive flow rate of O 2 on CF 4 decomposition was determined. Furthermore, the decomposition mechanism of CF 4 was investigated from chemical kinetics consideration. CF x ( x: 1–4) was thermally decomposed above 4000 K, oxidized in the temperature range of 4000–2400 K, and removed by H radical at temperatures below 2400 K.

EFFECT OF MgO CONCENTRATION IN SOLID REACTANTS ON DECOMPOSITION TREATMENT OF HALON 1301

Halon 1301 (bromotrifluoromethane) is known as both an ozone-depleting and global-warming substance. In this study, a drying treatment was developed for halon 1301 decomposition. Burnt lime, burnt dolomite, and burnt brucite were used as reactants. Halon 1301 is decomposed to gases containing halogen, and these gases react with the reactants simultaneously. The effects of the treatment temperatures, the treatment times, and the reactant compositions on the effective treatment process were investigated. Bromine in halon was almost completely recovered with the reactants. However, the recovery of fluorine was low. Burnt dolomite and burnt brucite were better reactants than burnt lime. The presence of MgO in the reactants plays an important role in this process.

Effect of Selected Conditions on Fluorine Recovery from a Soil, Using Electrokinetics

Definition and implementation of adapted conditions for decontamination a fluorine polluted soil, using an electrokinetic process are described. Chemical batch extractions were first performed to evaluate the efficiency of some parameters like pH, nature of reagents for fluorine removal from the soil. The results showed that fluorine mobilization in the soil studied was pH dependent. The alkaline pH was favorable to fluorine recovery. In this medium, F− was the only predominant species in solution. Three laboratory electromigration tests were subsequently performed under controlled pH conditions. The results indicated that the fluorine recovery from the soil was obtained using a simple addition of water at the cathode. In water added at the cathode allowed generation of hydroxide ions which were then transported by electromigration toward the anode, increasing pH in the soil in about 10 days. This in situ OH production has the advantage of limiting reagent addition. A pH control was then achieved at the anode (by flushing it with a dilute alkaline solution) in order to prevent an undesirable low pH resulting from generation of hydronium ions. With such conditions, the part of mobilizable fluorine was removed in less than 30 days.