Fluorine Compounds Research Articles

Fabrication of rGO/BiOI photocathode and its catalytic performance in the degradation of 4-Fluoroaniline

Organic fluorine compounds are acute carcinogenic and mutagenic to humans. Photoelectrocatalysis (PEC) treatment is an innovative technology in the field of the removal of fluorine compounds, and thus current research focused on improving stability and catalytic ability of photoanode. In this study, it has been synthesized a rGO/BiOI photocathode for the efficient degradation of 4-Fluoroaniline (4-FA). The physical characterization and photoelectrochemical properties of the photocathode was determined. The results indicate that the PEC treatment with the rGO/BiOI photocathode was more efficient compared with individual processes. During the optimization experiments, the PEC treatment achieved 99.58 % and 72.12 % of 4-FA degradation and defluorination within 1 h. Cyclic stability experiments show that rGO/BiOI photocathode was efficient and stable, which reached 96.91 % and 67.64 % of 4-FA degradation and defluorination after five cycles. Mechanism analysis indicates that the PEC process was based on an electrochemical reaction and photo-induced processes. The degradation product of 4-FA was mainly 2,4-di-t-butylphenol, and trapping experiments indicates that h+ is the primary oxidizing species. Therefore, PEC treatment with rGO/BiOI photocathode is a competitive green approach to remove fluorine compounds pollutants and brings new insights into development of PEC treatment.

Evaluation of fluorous affinity using fluoroalkyl-modified silica gel and selective separation of poly-fluoroalkyl substances in organic solvents.

In this study, we focused on the fluorous affinity acting among fluorine compounds, and then developed a new separation medium and evaluated their performance. We prepared the stationary phases for a column using silica gel-modified alkyl fluoride and investigated the characteristics of fluorous affinity by comparing them with a typical stationary phase, which does not contain fluorine, using high-performance liquid chromatography (HPLC). In HPLC measurements, we confirmed that while all non-fluorine compounds were not retained, retention of fluorine compounds increased as the number of fluorine increased with the stationary phase. It also revealed that the strength of fluorous affinity changes depending on the types of the organic solvent; the more polar the solvent, the stronger the effect. Additionally, the stationary phase was employed to compare the efficiency of our column with that of a commercially available column, Fluofix-II. The retention selectivity was almost the same, but the absolute retention strength was slightly higher on our column, indicating that the column is available for practical use.

Efforts toward the Recycling of Organic Fluorine Compounds

Efforts toward the Recycling of Organic Fluorine Compounds

Are Mouthwashes Really Effective against Candida spp.?

Oral candidiasis is an opportunistic infection caused by fungi of the genus Candida. Nystatin, fluconazole, and miconazole are the most widely used antifungal drugs in dentistry, but in recent years, they have been shown to be less effective due to the increase in the resistance to antifungal drugs. The growing challenge of antifungal resistance emphasizes the importance of exploring not only alternative strategies in the fight against Candida spp. infections but also supportive treatment for pharmacological treatment for oral candidiasis. This review aims to evaluate and compare the in vitro reports on antifungal efficacy against Candida spp. exhibited by mouthwashes distributed on the European market. The research question was elaborated through the PEO framework recommended by PRISMA 2020. A bibliographic search strategy was developed for the scientific online databases Pubmed and ScienceDirect. According to the eligibility criteria, 21 papers were included in this study over a 27-year period. Mouthwashes containing chlorhexidine digluconate, cetylpyridinium chloride, hexetidine, and fluorine compounds among others, and natural antimicrobials, such as menthol, thymol, eucalyptol, and Glycyrrhiza glabra extracts, have demonstrated antifungal effectiveness. Nonetheless, the methodological variance introduces ambiguity concerning the comparative efficacy of distinct molecules or mouthwash formulations and complicates the evaluation and the comparison of results between studies. Some mouthwashes commercially available in Europe have the potential to be used in anti-Candida therapy and prevention since they have shown antifungal effect.

A Review of Fluoride Removal from Phosphorous Gypsum: A Quantitative Analysis via a Machine Learning Approach.

This review comprehensively explores fluoride removal from phosphogypsum, focusing on its composition, fluorine-containing compounds, characterization methods, and defluorination techniques. It initially outlines the elemental composition of phosphogypsum prevalent in major production regions and infers the presence of fluorine compounds based on these constituents. The study highlights X-ray photoelectron spectroscopy (XPS) as a pivotal method for characterizing fluorine compounds, emphasizing its capability to determine precise binding energies essential for identifying various fluorine species. Additionally, the first-principle density functional theory (DFT) is employed to estimate binding energies of different fluorine-containing compounds. Significant correlations are observed between the total atomic energy of binary fluorides (e.g., of alkali metals, earth metals, and boron group metals) and XPS binding energies. However, for complex compounds like calcium fluorophosphate, correlations with the calculated average atomic total energy are less direct. The review categorizes defluorination methods applied to phosphogypsum as physical, chemical, thermal, and thermal-combined processes, respectively. It introduces neural network machine learning (ML) technology to quantitatively analyze and optimize reported defluorination strategies. Simulation results indicate potential optimizations based on quantitative analyses of process conditions reported in the literature. This review provides a systematic approach to understanding the phosphogypsum composition, fluorine speciation, analytical methodologies, and effective defluorination strategies. The attempts of adopting DFT simulation and quantitative analysis using ML in optimization underscore its potential and feasibility in advancing the industrial phosphogypsum defluorination process.

The Fate of Fluorine Post Per- and Polyfluoroalkyl Substances Destruction during the Thermal Treatment of Biosolids: A Thermodynamic Study

Per- and polyfluoroalkyl substances (PFAS) are a group of fluorinated synthetic chemicals that are highly recalcitrant, toxic, and bio-accumulative and have been detected in biosolids worldwide, posing potential risks to humans and the environment. Recent studies suggest that the organic C-F bond in PFAS can be destructed and potentially mineralised into inorganic fluorides during thermal treatment. This study focuses on thermodynamic equilibrium investigations and the fate of fluorine compounds post-PFAS destruction during biosolid thermal treatment. The results indicate that gas-phase fluorine compounds are mainly hydrogen fluoride (HF) and alkali fluorides, whereas solid-phase fluorine compounds include alkaline earth fluorides and their spinels. High moisture and oxygen content in the volatiles increased the concentration of HF in the gas phase. However, adding minerals reduced the emission of HF in the gas phase significantly and enhanced the capture of fluorine as CaF2 spinel in the solid phase. This study also investigates the effect of feedstock composition on the fate of fluorine. High ash content and low volatile matter in the feedstock reduced HF gas emissions and increased fluorine capture in the solid product. The findings of this work are useful in designing thermal systems with optimised operating conditions for minimising the release of fluorinated species during the thermal treatment of PFAS-containing biosolids.

Anti-icing performance of hydrophobic coatings on stainless steel surfaces

This study aims to prevent ice accumulation on the surface of drilling tools by investigating the effectiveness of hydrophobic coatings, which is one of the most promising methods to solve drilling difficulties in warm ice. Herein, four types of hydrophobic organic coatings that can be used on metal surfaces were tested to evaluate their anti-icing performance, service durability, and friction properties. All of them possess rough surfaces with microstructure characteristics such as pores, stripes, or micropapillae. They also exhibit hydrophobicity, with water contact angles of 101.6°, 100.0°, 103.1°, and 108.5°. They can significantly prolong the required freezing time of water droplets on their surfaces, effectively reduce ice adhesion, and decrease the friction between ice and their surface. The ice adhesion in the axial, tensile, and tangential directions can be reduced by 65.64 %, 56.31 %, and 72.11 %, respectively, for the coating with silicon (Si)-based and fluorine (F)-containin compounds (coating-C) at −30 °C; while it can be reduced by 85.05 %, 73.9 %, and 94.2 %, respectively, for the coatings with Si-based and polytetrafluoroethylene (PTFE) compounds (coating-D). The two coatings mentioned above lose their anti-icing performance after 20 icing and de-icing cycles, and their hydrophobicity after 120 abrasion cycles under a load of 6 N.

Toray commercializes PFAS-free mold release film

On May 22, 2024, Toray Industries, Inc., announced that it recently commercialized a mold release film for advanced semiconductor applications that is free of per- and polyfluoroalkyl substances (PFAS; see Glossary note 1). The film's material reportedly does not contain the organic fluorine compounds that European and other countries are looking to regulate. The film could reportedly help improve operational rates in advanced semiconductor manufacturing by slashing problematic mold contamination by more than 80%.

Physico-chemical features of acid decomposition and production of extraction phosphoric acid based on moroccan phosphorites

The results of research on the establishment of physicochemical features of acid processing of North African (Moroccan) phosphorites, as well as their influence on the technological process and technical and economic indicators of extraction phosphate acid (EPA) production are presented. Significant differences have been established in the nature of the acid decomposition process, syngony and the size of the formed calcium sulfate crystals for different grades of phosphorites, which is due to a significant influence on the decomposition process not only of the technological mode of the process, but to a large extent differences in the mineralogical composition of phosphate ores. Thus, the increased content of carbonate apatites in phosphorites of the K-9 and K-10 grades led to a higher reactivity in the region of low concentrations. At the same time, the high reactivity of carbonateapatites leads to a number of negative processes, in particular, abundant foaming and passivation of grains of phosphate raw materials with fine-crystalline calcium sulfate precipitate, formed due to the rapid supersaturation of the system, which in turn leads to a sharp decrease in the degree of decomposition. A significant difference in the nature of calcium sulfate crystallization for the conditions for obtaining EPA from the known data was established, which made it possible to conclude that the rate and nature of the process of calcium sulfate recrystallization in the CaO-P2O5- H2O system is determined not only by temperature, sulfate regime and P2O5 content in the liquid phase, but also by the nature and composition of phosphate raw materials. Based on experimental data, conclusions were drawn about a decrease in power during the transition from apatite to phosphorites from 21.89 to 24.23% (depending on the brand of Moroccan phosphorite), a significant increase in the load on filters and a decrease of 1.5–2 times in the amount of fluorine compounds released into the gas phase during decomposition.

Synthesis and Investigation of the Hydration Degree of CA2 Phase Modified with Boron and Fluorine Compounds.

This study investigated the effect of fluoride and boron compound additives on the synthesis and hydration process of calcium aluminate (CA2). The analysis showed that the temperature of the full synthesis of CA2 without mineralizing additives was 1500 °C. However, the addition of fluorine and boron compounds at 1% and 3% significantly reduced the synthesis temperature to a range of 1100-1300 °C. The addition of fluoride compounds did not result in the formation of fluoride compounds from CaO and Al2O3, except for the calcium borate phase (Ca3(BO3)2) under certain conditions. In addition, the cellular parameters of the synthesized calcium aluminate phases were not affected by the use of these additives. Hydration studies showed that fluoride additives accelerate the hydration process, potentially improving mechanical properties, while boron additives slow down the reaction with water. These results highlight the relevance of fluoride and boron additives to the synthesis process and hydration kinetics of calcium aluminate, suggesting the need for further research to optimize their application in practice. TG studies confirmed the presence of convergence with respect to X-ray determinations made. SEM, EDS and elemental concentration maps confirmed the presence of a higher Al/Ca ratio in the samples and also showed the presence of hexagonal and regular hydration products.

Recent Advances in the Electrochemical Defluorinative Transformations of C—F Bonds

Comprehensive SummaryOrganic fluorine compounds are ubiquitous and pivotally important organic molecules, yet their activation and transformation have long been a formidable challenge due to the high energy and low reactivity of C—F bonds. Organic electrosynthesis, an environmentally benign synthetic method in organic chemistry, enables a myriad of chemical transformations without the need for external redox reagents. In recent years, organic electrochemistry has emerged as a powerful tool for achieving the activation and transformation of C—F bonds in fluorine‐containing compounds. This review aims to succinctly recapitulate the latest advancements in the electrochemical defluorinative transformations of C—F bonds and to delve into the reaction design, mechanistic insights, and developmental prospects of these methods. Key ScientistsIn 1959, Lund was the first to pioneer the electroreduction of CF3 to CH3 group. Electrochemistry has lately provided new opportunities for efficient conversion of organic fluorides. In 2020, Zhou and coworkers discovered the electrochemical defluorinative carboxylation of α‐CF3 alkenes. Lambert and colleagues reported electrophotocatalytic defluorinative amination of aryl fluorides. Electrochemical hydrodefluorination of trifluoromethylketones was developed by Lennox and coworkers in 2021. In the same year, Wang and Guo disclosed electrochemical radical defluorinative alkylation of α‐CF3 alkenes with Katritzky salts as the alkyl radical precursors. Subsequently, Wu and Liao described a transition‐metal‐free, site‐selective C—F arylation of polyfluoroarenes with (het)arenes using paired electrophotocatalysis. In 2023, numerous efforts were made to achieve electrochemical C—F bond activation. Xia and Guo developed an organoboron‐controlled method for the chemoselective electrochemical sequential (deutero)hydrodefluorination of trifluoroacetamides.

Analysis of per- and polyfluoroalkyl substances (PFAS) in raw materials intended for the production of paper-based food contact materials – evaluating LC-MS/MS versus total fluorine and extractable organic fluorine

Per- and polyfluoroalkyl substances (PFAS) analysis has become crucial due to their presence in the environment, their persistence and potential health risks. These compounds are commonly used in food contact materials (FCM) as a coating to provide water and grease-repellent properties. One of the pathways for PFAS to enter the human body is either through direct consumption of contaminated food or indirectly through migration from FCM into food. The purpose of this study was to investigate where the initial contamination of paper FCM occurs. We analysed paper material consisting of fresh fibre and secondary materials, intended to produce food packaging for the presence of PFAS. The samples were extracted and analysed for 23 different PFAS substances using the targeted approach with LC tandem mass spectrometry (LC-MS/MS). This analytical technique detects specific, easily ionisable PFAS with high sensitivity. However, one drawback of this approach is that it allows the identification of less than 1% of the PFAS known today. For this reason, we used combustion ion chromatography (CIC) to determine the content of extractable organic fluorine compounds (EOF) and compare it to the total fluorine content. The targeted analysis using LC-MS/MS measured an average sum concentration of PFAS of 0.17 ng g−1 sample. Our research shows that the primary PFAS contamination happens during the recycling process since all of the samples in which the targeted PFAS were measured belonged to the secondary material. The most frequently detected analytes were PFOA and PFOS, detected in 90% and 62% of the samples, respectively, followed by PFBS (in 29% of the samples). CIC showed that measured PFAS via LC-MS/MS amount to an average of 2.7 × 10−4% of total fluorine content, whereas the EOF was under the LOD in all of the measured samples. This result highlights the complexity of the accurate determination of PFAS compounds, displaying what kind of information the chosen methods provide.

Investigation of Production Wastes Upon Roasting Mechanically Activated Phosphorite and Utilisation of Fluorine Compounds

Investigation of Production Wastes Upon Roasting Mechanically Activated Phosphorite and Utilisation of Fluorine Compounds

Supercritical fluid decontamination (SCFD) of poly(vinylidene fluoride) (PVDF) and further upcycling into highly porous aerogels with a well defined microstructure

Per- and polyfluoroalkyl substances (PFAS) like polyvinylidene fluoride (PVDF) have a wide range of applications due to their high stability and persistency, but their production is increasingly being restricted because the mentioned outstanding properties simultaneously impose drawbacks in terms of poor (bio)degradability. The lack of appropriate and industrially established solutions for handling and reuse of PVDF after fulfilling its first purpose aggravates this environmental issue. The presented work outlines a novel approach for the upcycling of PVDF waste material by supercritical fluid decontamination of used PVDF and subsequent conversion into a value-added, highly porous PVDF-based material with an open-cell structure, a so-called aerogel, containing a well-defined pore morphology on the microscale. The work further shows that the synthesis of an aerogel from used PVDF tolerates impurities to a certain extent, for which the previous treatment does not necessarily have to render a material 100 % free of contaminations. As a result, a proof-of-concept is given for an industrially feasible process that is capable of upcycling a valuable high-performance polymer into a sophisticated porous material, thereby avoiding the release of potentially toxic fluorine compounds and opening a path towards a circular economy for contaminated PVDF.

Recent Advance in the C−F Bond Functionalization of Trifluoromethyl Aromatic and Carbonyl Compounds

AbstractThe selective C−F bonds functionalization in available trifluoromethyl compounds is an economic route for obtaining high‐value organic fluorine compounds. However, due to the high C−F bonds dissociation energy in trifluoromethyl group, the strength of the bond decreases continuously during defluorination, posing a challenge in modifying such molecules without over‐conversion. Over the past few years, there has been significant progress in developing efficient methods for constructing difluoromethylene unit, using approaches such as radical chemistry, photochemistry, electrochemistry, and organometallic chemistry. These methods involve difluorocarbon radicals, difluorocarbon cations, difluorocarbon anions, and trifluoromethyl carbenes as intermediates. In this review, we summarized the recent five years of research achievements in this field for selective single C−F bond cleavage in trifluoromethyl aromatic and carbonyl compounds to gain diverse difluoromethylene‐containing organic molecules via different intermediate strategies.

Fluoride and acid enrichment in coal fire sponges in the Wuda coalfield, Inner Mongolia, Northern China

Coal fire sponges (CFSs) are a type of sponge-like contaminated soil bulge common in coal fire areas. However, the impacts of CFSs on the local environment are not yet understood. Thus, this study investigated soil samples from CFSs in the Wuda coalfield, Inner Mongolia, China, focusing on the acidity, sulfate, and fluorine content. The results showed that the CFSs were highly acidic, with an average pH of 0.76, and contained high levels of SO42− (257.29 × 103 μg/g), total fluorine (TF, 2011.6 μg/g), and water-soluble fluorine (WF, 118.94 μg/g), significantly exceeding those in the regional background soil and indicating that CFSs are a point source of heavy pollution. Soils in the 8000 m2 reclamation zone showed elevated acidity and high SO42− (129.6 × 103 μg/g), TF (1237.8 μg/g), and WF (43.05 μg/g) levels, which was likely the result of the weathering and dissemination of CFS. The CFS samples were rich in hydrogen fluoride, releasing 202.05 ppb of it when heated to 40 °C. Correlation analysis indicated that the acid sulfate soils in CFSs are likely caused by HSO4−/SO42−. Time-of-flight secondary ion mass spectrometry detected four characteristic ions (F−, H3O+, H2SO4+, and HSO4−) in all micro-domains of each sample, indicating that ionic fluorine compounds and sulfuric acid hydrate were found in the CFS samples. Sulfate minerals detected in CFSs included CaSO4, Fe2(SO4)3, CdSO4, NH4HSO4, and Na2SO4. Thus, the results identified CFSs as a transmission channel for contamination, with erosional surface soils as the carrier, for the first time. CFSs pose a serious threat of contamination, albeit over limited areas.

Prediction of 19F NMR chemical shift by machine learning

Fluorine-19 (19F) is a nucleus of great importance in the field of Nuclear Magnetic Resonance (NMR) spectroscopy due to its high receptivity and wide chemical shift dispersion. 19F NMR plays crucial roles in both organic synthesis and biomedicine. Herein, a machine learning-based comprehensive 19F NMR chemical shift prediction model was established based on the experimental 19F NMR dataset from the book by Dolbier and the open NMR database nmrshiftdb2. Fluorine radical SMILES (Fr-SMILES) that reflected the fluorine chemical equivalence, was designed as the representation of fluorine in the molecule. Model trained with the graph convolution network (GCN) algorithm gave a low mean absolute error (MAE) of 3.636 ppm on the testing set. This model exhibits broad applicability and can effectively predict 19F NMR shifts for a wide range of organic fluorine molecules. We believe that the current work will provide a powerful tool for not only predicting 19F NMR shifts but also aiding in the analysis and identification of these shifts in diverse organic fluorine compounds. An online prediction platform was constructed based on the current model, which can be found at https://fluobase.cstspace.cn/fnmr.

Eco-friendly porous composite of octaphenyl polyhedral oligomeric silsesquioxane and HKUST-1 with hydrophobic-oleophilic properties towards sorption of oils and organic solvents.

The degradation of water bodies caused by organic pollutants from industrial wastewater discharge has made it necessary to develop new functional materials like hydrophobic-oleophilic materials that can efficiently remediate water. It is factual that many of the synthetic methods for creating hydrophobic-oleophilic materials involve the use of toxic or harmful reactants, such as fluorine or sulfur compounds. However, these methods often have significant drawbacks, including being hazardous to the environment, expensive, and complex to utilize. Therefore, there is an urgent need to develop a hydrophobic/oleophilic material that is non-toxic and eco-friendly in order to overcome the existing drawbacks. In this regard, we have proposed a modest and eco-friendly approach for constructing a hydrophobic-oleophilic Ph-POSS@HKUST-1 composite material by solution-assisted self-assembly for the conversion of hydrophilic HKUST-1 into hydrophobic HKUST-1 for separation applications. The incorporation of fluorine-free, low surface energy and hydrophobic POSS into HKUST-1 increased the hydrophobicity and oleophilicity of the system. The synthesized Ph-POSS@HKUST-1 composite material has been thoroughly characterized through FT-IR, PXRD, HR-SEM, BET, and thermogravimetric analysis. It has been observed that the material exhibits a contact angle of 137 ± 4° and shows high selectivity and absorption capacity towards organic solvents and oils from water mixtures. Concurrently, the Ph-POSS@HKUST-1@PDA@sponge has been effectively utilized for the separation of solvents and oils and it has shown more than 95% separation efficiency for up to 15 cycles. It is interesting to note that Ph-POSS@HKUST-1 and the Ph-POSS@HKUST-1@PDA@sponge have outstanding stability in abrasive chemical environments which is due to the presence of a mechanically and chemically stable inorganic-organic hybrid POSS nanocage. In addition, ab initio and DFT calculations elicit that the Ph-POSS@HKUST-1 composite is stabilized through π⋯π stacking instead of the C-H⋯π mode of interaction at the HKUST-1⋯Ph-POSS interface. Further electron density features confirm the interfacial interaction at the interface. Our latest research has led us to propose an eco-friendly and non-toxic hybrid composite material for efficiently tackling the issue of organic solvent and oil pollution in water mixtures.

Evaluation Methods and Detection Cases of Fluorine Compounds in Textile Products

Evaluation Methods and Detection Cases of Fluorine Compounds in Textile Products

An analysis of the interaction of infiltration waters from tungsten ore processing tailings and limestone

An experimental plant designed to study the interaction of acidic pore waters in tailings ponds was developed. The study showed that processing tailings of the Dzhida tungsten-molybdenum plant contain residual ore mineralization, which decomposed during long-term storage. The filtrate obtained by washing sand with distilled water contains sulfur, aluminum, iron, manganese, zinc, copper, cadmium and other components. To displace all dissolved substances from the pore space of sand, the threefold volume of water is sufficient. When the filtrate is neutralized with limestone under the dynamic conditions, amorphous compounds of iron, calcium, aluminum, sulfur, silicon, and fluorine are precipitated and the minerals gypsum, dolomite, and smithsonite appear. In addition, precipitation of non-ferrous and rare earth elements occurs on the surface of limestone. The study revealed an europium anomaly. To precipitate rare earth elements from a solution, it is necessary to use substances with an active surface.