The bastnaesite was defluorinated by steam roasting process,and fluorine was removed in the form of hydrogen fluoride to realize the separation from rare earth.The effects of particle size of raw material,roasting tem...The bastnaesite was defluorinated by steam roasting process,and fluorine was removed in the form of hydrogen fluoride to realize the separation from rare earth.The effects of particle size of raw material,roasting temperature and time on defluorination rate of bastnaesite were studied.The suitable conditions of steam roasting process are that the particle size of raw material is less than 74μm,the roasting temperature is 1000℃and the roasting time is 4 h.The defluorination rate of bastnaesite is close to 100%under above these conditions.When the temperature rises to 1000℃,the voids on the surface of the particles increase obviously,and there is a developed network of voids,which indicates that the fluorine oxides in bastnaesite react fully with the saturated water vapor at this stage,and a large amount of fluorine escapes in the form of hydrogen fluoride from the surface and inside of the mineral.X-ray diffraction results show that there are only rare-earth oxides in the form of Ce_(0.33)La_(0.33)Ca_(0.33)O_(1.5)and Ce_(7)O_(12)in the slag.The results of energy spectra and chemical analysis show that the fluorine in the baking sand was basically completely removed.展开更多
A systematic and green low-temperature sulfation roasting−water leaching strategy was put forward to achieve a very high fluorine removal rate of 97.82%for spent carbon cathode(SCC),which was believed as a hazardous s...A systematic and green low-temperature sulfation roasting−water leaching strategy was put forward to achieve a very high fluorine removal rate of 97.82%for spent carbon cathode(SCC),which was believed as a hazardous solid waste.And the carbon could be recycled with a purity of 90.29 wt.%in the flaky microstructure.Thermodynamic analysis and the results of SEM,XRD and EDS indicate that most of the fluoride could convert into water-soluble sulfate at low temperature.And the highest fluorine removal rate could be obtained when<0.15 mm SCC particles were mixed with sulfuric acid at a liquid-to-solid ratio of 1:1,and then roasted at 300℃ for 0.5 h.The sulfate was removed to purify the carbon via water-leaching process.Avrami exponents and corresponding activation energy for the roasting and leaching process demonstrated that both processes are controlled by diffusion.展开更多
Millions of people in poor areas are still under the threat of fluoride contamination.How to effectively separate fluorine in water is an important step to reduce the ecological risk.In this paper,we performed a syste...Millions of people in poor areas are still under the threat of fluoride contamination.How to effectively separate fluorine in water is an important step to reduce the ecological risk.In this paper,we performed a systematic DFT calculation focused on the defluorination behavior between the LiAl-and MgAl-LDHs.The results indicated that the LiAl-LDHs exhibited high chemical activity before the defluorination,because of the better electronic structure.After the defluorination,the LiAl-LDHs with adsorbed-F–were also more stable than the MgAl-LDHs.In addition,the existence of coordination covalent bond for the adsorbed-F–attached to the LiAl-LDHs was confirmed.This is an important reason for the high defluorination efficiency by the LiAl-LDHs.In addition,a series of weak interaction,including hydrogen bond and van der Waals interaction were also observed.Finally,a LiAl-LDHs with excellent fluoride removal properties were synthesized well by simple hydrothermal method.The results showed that our synthesized LiAl-LDHs with the capacity of 156.09 mg/g,could be effectively defluorinated in water.Notably,it surpasses most materials and has potential applications.展开更多
This study investigates the removal of fluorine(F)impurities from phosphogypsum(PG)using steam as the reaction medium.The effects of the reaction atmosphere,temperature,time,and steam velocity on F impurities removal ...This study investigates the removal of fluorine(F)impurities from phosphogypsum(PG)using steam as the reaction medium.The effects of the reaction atmosphere,temperature,time,and steam velocity on F impurities removal were systematically examined.The results showed that with a steam velocity of 0.0184 m·s^(-1),a reaction temperature of 700℃,and a reaction time of 60 min,the F removal rate reached 95.87%.Further investigations into the defluorination mechanism revealed that steam and SiO_(2) synergistically enhance fluoride removal,playing a crucial role in improving the defluorination efficiency.Kinetic analysis of the defluorination process,based on the shrinking core model(SCM),indicated that internal diffusion is the rate-controlling step,with the activation energy of 30.12 kJ·mol^(-1).This study identifies optimal conditions for PG defluorination and proposes a defluorination mechanism,contributing to the theoretical understanding of impurity removal through the thermal treatment of PG.展开更多
α-Trifluoromethyl ketones are a class of useful compounds with versatile applications.Their synthetic application via the transformation of the C—F bonds is of particular interest by allowing the synthesis of organi...α-Trifluoromethyl ketones are a class of useful compounds with versatile applications.Their synthetic application via the transformation of the C—F bonds is of particular interest by allowing the synthesis of organic compounds with diverse structures.Herein,the advances in the research areas ofα-trifluoromethyl ketone synthesis and their defluorination reactions are reviewed.Discussion on the mechanisms of the typical reactions has also been provided,in hope of affording some guides to the chemistry ofα-trifluoromethyl ketones in the synthetic methods toward themselves and their derivatives.展开更多
The C—F bond transformation of gem-difluorinated cyclopropanes without cleavage of the highly strained C—C bond is an intractable challenge. The synthesis of cyclopropanone ketals via double defluorination of gem-di...The C—F bond transformation of gem-difluorinated cyclopropanes without cleavage of the highly strained C—C bond is an intractable challenge. The synthesis of cyclopropanone ketals via double defluorination of gem-difluorinated cyclo-propanesunder transition-metal free and basic conditions has been developed. A broad range of gem-difluorinated cyclopro-panesand alcohols are amenable in present reaction to permit the synthesis of corresponding products in high yields. The reaction is elucidated to proceed via elimination and addition other than direct substitution based on the mechanistic studies. This transformation not only provides a new strategy for the construction of cyclopropanone ketals, but also reveals a new paradigm on C—F bond transformation without ring-opening of gem-difluorinated cyclopropanes.展开更多
Selective defluorinative functionalization of trifluoromethylarenes(ArCF3)to obtain the pharmaceutically commonα,α-difluorobenzylic motif is an attractive and elegant synthetic route.Over the past decade,although C(...Selective defluorinative functionalization of trifluoromethylarenes(ArCF3)to obtain the pharmaceutically commonα,α-difluorobenzylic motif is an attractive and elegant synthetic route.Over the past decade,although C(sp^(3))-F bonds functionalization have been greatly developed,catalytic cross-coupling of trifluoromethylarenes with C-H of terminal alkynes remains a challenge.Here,we report an approach to achieve Sonogashira-type cross-coupling of trifluoromethylarenes with terminal alkynes C(sp)-H bonds via photoredox and Cu/L dual catalysis.Tridentate anionic ligand is pivotal to realize this C-H sp-sp^(3) cross-coupling.Moreover,this unique catalytic system is also suitable for cross-coupling of C(sp^(3))-F bonds with azoles C(sp^(2))-H bonds.A series of trifluoromethylarenes,terminal alkynes and azoles with various functional groups are compatible with this protocol affording a variety of defluoroalkynylation or defluoroazolation products.Preliminary mechanistic studies indicated that deprotonated BINOL involved as a photocatalyst to activate ArCF3 rather than a ligand to the metal.展开更多
Perfluoroalkyl substances(PFASs)are typical persistent organic pollutants,and their removal is urgently required but challenging.Photocatalysis has shown potential in PFASs degradation due to the redox capabilities of...Perfluoroalkyl substances(PFASs)are typical persistent organic pollutants,and their removal is urgently required but challenging.Photocatalysis has shown potential in PFASs degradation due to the redox capabilities of photoinduced charge carriers in photocatalysts.Herein,hexagonal ZnIn_(2)S_(4)(ZIS)nanosheets were synthesized by a one-pot oil bath method and were well characterized by a series of techniques.In the degradation of sodium p-perfluorous nonenoxybenzenesulfonate(OBS),one kind of representative PFASs,the assynthesized ZIS showed activity superior to P25 TiO_(2) under both simulated sunlight and visible-light irradiation.The good photocatalytic performance was attributed to the enhanced light absorption and facilitated charge separation.The pH conditions were found crucial in the photocatalytic process by influencing the OBS adsorption on the ZIS surface.Photogenerated e−and h+were the main active species involved in OBS degradation in the ZIS system.This work confirmed the feasibility and could provide mechanistic insights into the degradation and defluorination of PFASs by visible-light photocatalysis.展开更多
Biochar,as an efficient,effective,and potential soil improver,has broad application prospects in the field of defluoridation.This study aimed to evaluate the defluoridation potential of iron(Fe)and manganese(Mn)co-mod...Biochar,as an efficient,effective,and potential soil improver,has broad application prospects in the field of defluoridation.This study aimed to evaluate the defluoridation potential of iron(Fe)and manganese(Mn)co-modified biochar from groundwater.The varied Fe/Mn molar ratio(2∶1 and 1∶2)modified biochar was prepared by corncob with the pyrolysis temperature of 300℃,400℃,and 500℃.Batch experiments for fluoride(F^(-))removal were performed by corncob biochar before and after Fe-Mn modified.Their composition,structure,and performance were analyzed by multiple characterization techniques to clarify F‒removal mechanisms.Our results indicated that unmodified corncob biochar produced at 400℃(BC400)exhibited the highest F‒adsorption efficiency(87.3%)among three unmodified samples,attributable to its largest specific surface area(2.55 m^(2)/g).Notably,F‒removal amounts by Fe-Mn modified BC400 were 2 times higher than BC400.The enhanced F⁻removal performance of Fe-Mn modified biochar can be attributed to several mechanisms:(1)the modification produced rougher surface textures,resulting in an increased specific surface area(about 3.50 m^(2)/g);(2)newly formed Fe-O and Mn-O bonds on the biochar surface facilitated the formation of complexes with F^(-);and(3)the adsorption results fitted well with pseudo-second-order and Freundlich models(R^(2)>0.98),indicating that the removal process involved physicochemical adsorption.These findings demonstrate that Fe-Mn modified biochar is a highly efficient and cost-effective material for F^(-)remediation and holds significant potential for application in contaminated groundwater and soil systems.展开更多
Defluorination roasting of lepidolite ore in a fluidized bed reactor has been proposed for improving the extraction efficiency of lithium.In this paper,a vacuum was introduced to the fluidized bed reactor,which signif...Defluorination roasting of lepidolite ore in a fluidized bed reactor has been proposed for improving the extraction efficiency of lithium.In this paper,a vacuum was introduced to the fluidized bed reactor,which significantly improved the defluorination efficiency of lepidolite particles.This improvement could be attributed to an increase in the H2O/HF ratio.The highest defluorination rate for the lepidolite particles was obtained in the fluidized bed reactor under vacuum.The rate in the vacuum reactor was 1.5-2 times that in a fixed bed reactor or conventional fluidized bed reactor.The defluorination efficiency of the lepidolite particles also improved and the consumption of steam was greatly reduced by addition of coal char.This enhancement was mainly attributed to changes in the structures of the reduced lepidolite particles.This defluorination roasting method for high lithium extraction with low water steam consumption is a promising method for lithium ore treatment.展开更多
Perfluorooctanoic acid （PFOA） is a new-found hazardous persistent organic pollutant, and it is resistant to decomposition by hydroxyl radical （HO.） due to its stable chemical structure and the high electronegativi...Perfluorooctanoic acid （PFOA） is a new-found hazardous persistent organic pollutant, and it is resistant to decomposition by hydroxyl radical （HO.） due to its stable chemical structure and the high electronegativity of fluorine. Photocatalytic reduction of PFOA with β-Ga2O3 in anoxic aqueous solution was investigated for the first time, and the results showed that the photoinduced electron （ecb） coming from the β-Ga2O3 conduction band was the major degradation substance for PFOA, and shorter-chain perfluorinated carboxylic acids （PFCAs, CnF2n＋1COOH, 1 ≤ n ≤ 6） were the dominant products. Furthermore, the concentration of F- was measured by the IC technique and defluorination efficiency was calculated. After 3 hr, the photocatalytic degradation efficiency was 98.8% and defluorination efficiency was 31.6% in the presence of thiosulfate and bubbling N2. The degradation reaction followed first-order kinetics （k = 0.0239 min-1, t1/2 = 0.48 hr）. PFCAs （CnF2n＋xCOOH, 1 ≤ n≤ 7） were detected and measured by LC-MS and LC-MS/MS methods. It was deduced that the probable photocatalytic degradation mechanism involves ec-b attacking the carboxyl of CnF2n＋1COOH, resulting in decarboxylation and the generation of CnFzn＋1. The produced CnF2n＋1 reacted with H2O, forming CnF2n＋1OH, then CnF2n＋1OH underwent HF loss and hydrolysis to form CnF2,＋1COOH.展开更多
Nanophotocatalysts have shown great potential for degrading poly-and perfluorinated substances(PFAS).In light of the fact that most of these catalysts were studied in pure water,this study was designed to elucidate ef...Nanophotocatalysts have shown great potential for degrading poly-and perfluorinated substances(PFAS).In light of the fact that most of these catalysts were studied in pure water,this study was designed to elucidate effects from common environmental factors on decomposing and defluorinating perfluorooctanoic acid(PFOA)by In2O3 nanoparticles.Results from this work demonstrated that among the seven parameters,pH,sulfate,chloride,H2O2,In2O3 dose,NOM and O2,the first four had statistically significant negative effects on PFOA degradation.Since PFOA is a strong acid,the best condition leading to the highest PFOA removal was identified for two pH ranges.When pH was between 4 and 8,the optimal condition was:pH=4.2;sulfate=5.00 mg/L;chloride=20.43 mg/L;H2O2=0 mmol/L.Under this condition,PFOA decomposition and defluorination were 55.22 and 23.56%,respectively.When pH was between 2 and 6,the optimal condition was:pH=2;sulfate=5.00 mg/L;chloride=27.31 mg/L;H2O2=0 mmol/L.With this condition,the modeled PFOA decomposition was 97.59%with a defluorination of approximately 100%.These predicted results were all confirmed by experimental data.Thus,In2O3 nanoparticles can be used for degrading PFOA in aqueous solutions.This approach works best when the target contaminated water contains low concentrations of NOM,sulfate and chloride and at a low pH.展开更多
A method for stereoselective construction of Z-monofluoroalkenes by nickel-catalyzed defluorinative coupling of gem‑difluoroalkenes in mild conditions was described.The combination of lithium organoborate and ZnBr_(2)...A method for stereoselective construction of Z-monofluoroalkenes by nickel-catalyzed defluorinative coupling of gem‑difluoroalkenes in mild conditions was described.The combination of lithium organoborate and ZnBr_(2) generated in situ lithium aryl zincates,which facilitates the transmetalation step of the nickel-catalyzed cross coupling reaction.展开更多
tert-Butyl （R）-3-amino-3-（3-fluorophenyl）propanoate（5） was prepared with conventional debenzylation method. However, the tert-butyl （R）-3-[（S）-1-phenylethyl-amino]-3-（3-fluorophenyl） propanoate（6） and te...tert-Butyl （R）-3-amino-3-（3-fluorophenyl）propanoate（5） was prepared with conventional debenzylation method. However, the tert-butyl （R）-3-[（S）-1-phenylethyl-amino]-3-（3-fluorophenyl） propanoate（6） and tert-butyl （R）-3-amino-3-phenylpropanoate（7） were generated as the byproducts under the general catalytic hydrogenation Pd（OH）2/C-H2 conditions. So a series of experiments was performed to optimize the reaction conditions so that product 5 could be obtained with high purity and yield. Finally an effective catalytic system, Pd/C-HCOOH-CH3OH, was discovered.展开更多
NF3 decomposition over transition metal oxides coated MgO reagents in the absence of water is investigated. The results show that NF3 can be decomposed completely over pure MgO but the time of NF3 steady full conversi...NF3 decomposition over transition metal oxides coated MgO reagents in the absence of water is investigated. The results show that NF3 can be decomposed completely over pure MgO but the time of NF3 steady full conversion kept as short as 80 min, while the reactivities of coated MgO reagents were remarkably enhanced by transition metal oxides, for example the time of NF3 complete conversion over 12%Fe/MgO extended to 380 min. It is suggested that not only an increase in surface area but also a significant enhancement in the fluorination of MgO substrate caused by the surface transition metal oxides result in an improved reactivity of coated MgO reagents for NF3 decomposition.展开更多
A solid ternary mixture consisting of NaF, silicon and one of the metal oxides such as Al2O3, MgO, CaO, SrO, BaO was prepared and used as a defluorinated reagent for CF4 decomposition. The results show that the initia...A solid ternary mixture consisting of NaF, silicon and one of the metal oxides such as Al2O3, MgO, CaO, SrO, BaO was prepared and used as a defluorinated reagent for CF4 decomposition. The results show that the initial conversion of CF4 reached 100% over NaF-Si-MgO and NaF-Si-CaO at 850°C, and the reagent with NaF/Si/MgO molar ratio of 33/34/33 exhibited a high reactivity with a full conversion of CF4 lasting for 57 min. The plausible paths of CF4 decomposition over NaF-Si-Al2O3, NaF-Si-MgO, NaF-Si-CaO, NaF-Si-SrO and NaF-Si-BaO are proposed.展开更多
The N-H methylsulfoxidation of sulfoximines using DMso as a methylsulfinyl source,induced by electrochemistry,has been developed.This method is the first example of an electrochemical reaction in which DMso serves as ...The N-H methylsulfoxidation of sulfoximines using DMso as a methylsulfinyl source,induced by electrochemistry,has been developed.This method is the first example of an electrochemical reaction in which DMso serves as a methylsulfinyl source.Unlike previous electrochemical reactions involving DMsO as a substrate,which exclusively proceed via radical mechanisms,this reaction follows an S-cation pathway.A wide range of N-methylsulfinyl sulfoximines were successfully obtained.展开更多
A catalyst-free and additive-free ring-opening reaction of polyfluoroalkyl peroxides,triethylenediamine(DABCO),and 1,2-dichloroethane(DCE)has been developed for the defluorinative synthesis of structurally diverse pip...A catalyst-free and additive-free ring-opening reaction of polyfluoroalkyl peroxides,triethylenediamine(DABCO),and 1,2-dichloroethane(DCE)has been developed for the defluorinative synthesis of structurally diverse piperazines featuring a fluoroenone framework and a N-chloroethyl-substituent with high Z-stereoselectivity.The success of this three-component reaction is attributed to the in situ generation of an active 1-(2-chloroethyl)-1,4-diazabicyclo[2.2.2]octan-1-ium(DABCO·DCE)salt,which judiciously acts as a formal N-(2-chloroethyl)piperazine equivalent in the defluorinative coupling with less-studied aliphatic fluorinated substances.Impressively,this reaction accomplishes multi-activation of robust C(sp^(3))-F,C(sp^(3))-Cl,C(sp^(3))-O,and C(sp^(3))-N bonds in a one-pot process,offering a practical platform for the late-stage functionalization of complex molecules.Furthermore,the resulting products can not only serve as versatile building blocks for the synthesis of fluorinated heterocycles,but also undergo C—Cl bond displacement transformations with N-,O-,and S-nucleophiles.展开更多
Development of novel electrode materials with the integration of structural and compositional merits can essentially improve the electrosorption performance.Herein,we demonstrate a new strategy,named as carbothermal d...Development of novel electrode materials with the integration of structural and compositional merits can essentially improve the electrosorption performance.Herein,we demonstrate a new strategy,named as carbothermal diffusion reaction synthesis(CDRS),to fabricate binder-free CrN/carbon nanofiber electrodes for efficient electrosorption of fluoride ions from water.The CDRS strategy involves electrospinning MIL-101(Cr)particles with polyacrylonitrile(PAN)to form one-dimensional nanofiber,followed by spatial-confined pyrolysis process in which the nitridation reaction occurred between nitrogen element from PAN and chromium element from MIL-101(Cr),resulting macroscopic,free-standing electrodes with well dispersed ultrafine CrN nanoparticles on porous nitrogen enriched carbon matrix.As expected,the F-adsorption capacity reached 47.67 mg g-1 and there was no decrease in F-removal after 70 adsorption regenerations in 50 mg L-1 F-solution at 1.2 V.The adsorption mechanism of F-was explored by X-ray photoelectron spectroscopy(XPS)and density functional theory(DFT).The enhanced F-adsorption capacity was achieved by the reversible Cr4+/Cr3+redox pair provided by CrN and the electrical double layer capacitance produced by carbon skeleton.This study provides guidance on synergistic modulation of shaping and composition optimization of novel functional materials for electrosorption,catalysis,and supercapacitor applications.展开更多
Organic 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 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 ofthese methods.展开更多
基金Project supported by the National Key Research and Development Program of China(2020YFC1907500)the Fundamental Research Funds of the Ministry of Education of China(N2125033)。
文摘The bastnaesite was defluorinated by steam roasting process,and fluorine was removed in the form of hydrogen fluoride to realize the separation from rare earth.The effects of particle size of raw material,roasting temperature and time on defluorination rate of bastnaesite were studied.The suitable conditions of steam roasting process are that the particle size of raw material is less than 74μm,the roasting temperature is 1000℃and the roasting time is 4 h.The defluorination rate of bastnaesite is close to 100%under above these conditions.When the temperature rises to 1000℃,the voids on the surface of the particles increase obviously,and there is a developed network of voids,which indicates that the fluorine oxides in bastnaesite react fully with the saturated water vapor at this stage,and a large amount of fluorine escapes in the form of hydrogen fluoride from the surface and inside of the mineral.X-ray diffraction results show that there are only rare-earth oxides in the form of Ce_(0.33)La_(0.33)Ca_(0.33)O_(1.5)and Ce_(7)O_(12)in the slag.The results of energy spectra and chemical analysis show that the fluorine in the baking sand was basically completely removed.
基金the Natural Science Foundation of Hunan Province,China(No.2020JJ1007).
文摘A systematic and green low-temperature sulfation roasting−water leaching strategy was put forward to achieve a very high fluorine removal rate of 97.82%for spent carbon cathode(SCC),which was believed as a hazardous solid waste.And the carbon could be recycled with a purity of 90.29 wt.%in the flaky microstructure.Thermodynamic analysis and the results of SEM,XRD and EDS indicate that most of the fluoride could convert into water-soluble sulfate at low temperature.And the highest fluorine removal rate could be obtained when<0.15 mm SCC particles were mixed with sulfuric acid at a liquid-to-solid ratio of 1:1,and then roasted at 300℃ for 0.5 h.The sulfate was removed to purify the carbon via water-leaching process.Avrami exponents and corresponding activation energy for the roasting and leaching process demonstrated that both processes are controlled by diffusion.
基金supported by the National Science Fund for Distinguished Young Scholars (No.52022111)the Natural Science Foundation of China (No.51974379)the Scientific and Technological Innovation Program of Hunan Province,Huxiang Youth Talent Project (No.2020RC_(3)012)。
文摘Millions of people in poor areas are still under the threat of fluoride contamination.How to effectively separate fluorine in water is an important step to reduce the ecological risk.In this paper,we performed a systematic DFT calculation focused on the defluorination behavior between the LiAl-and MgAl-LDHs.The results indicated that the LiAl-LDHs exhibited high chemical activity before the defluorination,because of the better electronic structure.After the defluorination,the LiAl-LDHs with adsorbed-F–were also more stable than the MgAl-LDHs.In addition,the existence of coordination covalent bond for the adsorbed-F–attached to the LiAl-LDHs was confirmed.This is an important reason for the high defluorination efficiency by the LiAl-LDHs.In addition,a series of weak interaction,including hydrogen bond and van der Waals interaction were also observed.Finally,a LiAl-LDHs with excellent fluoride removal properties were synthesized well by simple hydrothermal method.The results showed that our synthesized LiAl-LDHs with the capacity of 156.09 mg/g,could be effectively defluorinated in water.Notably,it surpasses most materials and has potential applications.
基金funded by the National Key Research and Development Program of China(2018YFC1903500)the National Key Research and Development Program of China(2019YFC1905800)+1 种基金Hebei Provincial Key Research Projects(22373101D)the commercial project by Beijing Zhong Dian Hua Yuan Environment Protection Technology Co.,Ltd.(E01211200005)。
文摘This study investigates the removal of fluorine(F)impurities from phosphogypsum(PG)using steam as the reaction medium.The effects of the reaction atmosphere,temperature,time,and steam velocity on F impurities removal were systematically examined.The results showed that with a steam velocity of 0.0184 m·s^(-1),a reaction temperature of 700℃,and a reaction time of 60 min,the F removal rate reached 95.87%.Further investigations into the defluorination mechanism revealed that steam and SiO_(2) synergistically enhance fluoride removal,playing a crucial role in improving the defluorination efficiency.Kinetic analysis of the defluorination process,based on the shrinking core model(SCM),indicated that internal diffusion is the rate-controlling step,with the activation energy of 30.12 kJ·mol^(-1).This study identifies optimal conditions for PG defluorination and proposes a defluorination mechanism,contributing to the theoretical understanding of impurity removal through the thermal treatment of PG.
文摘α-Trifluoromethyl ketones are a class of useful compounds with versatile applications.Their synthetic application via the transformation of the C—F bonds is of particular interest by allowing the synthesis of organic compounds with diverse structures.Herein,the advances in the research areas ofα-trifluoromethyl ketone synthesis and their defluorination reactions are reviewed.Discussion on the mechanisms of the typical reactions has also been provided,in hope of affording some guides to the chemistry ofα-trifluoromethyl ketones in the synthetic methods toward themselves and their derivatives.
文摘The C—F bond transformation of gem-difluorinated cyclopropanes without cleavage of the highly strained C—C bond is an intractable challenge. The synthesis of cyclopropanone ketals via double defluorination of gem-difluorinated cyclo-propanesunder transition-metal free and basic conditions has been developed. A broad range of gem-difluorinated cyclopro-panesand alcohols are amenable in present reaction to permit the synthesis of corresponding products in high yields. The reaction is elucidated to proceed via elimination and addition other than direct substitution based on the mechanistic studies. This transformation not only provides a new strategy for the construction of cyclopropanone ketals, but also reveals a new paradigm on C—F bond transformation without ring-opening of gem-difluorinated cyclopropanes.
基金support of this work by the National Natural Science Foundation of China(Nos.22371307,21971267)the program for Guangdong Introducing Innovative and Entrepreneurial Teams(No.2017ZT07C069).
文摘Selective defluorinative functionalization of trifluoromethylarenes(ArCF3)to obtain the pharmaceutically commonα,α-difluorobenzylic motif is an attractive and elegant synthetic route.Over the past decade,although C(sp^(3))-F bonds functionalization have been greatly developed,catalytic cross-coupling of trifluoromethylarenes with C-H of terminal alkynes remains a challenge.Here,we report an approach to achieve Sonogashira-type cross-coupling of trifluoromethylarenes with terminal alkynes C(sp)-H bonds via photoredox and Cu/L dual catalysis.Tridentate anionic ligand is pivotal to realize this C-H sp-sp^(3) cross-coupling.Moreover,this unique catalytic system is also suitable for cross-coupling of C(sp^(3))-F bonds with azoles C(sp^(2))-H bonds.A series of trifluoromethylarenes,terminal alkynes and azoles with various functional groups are compatible with this protocol affording a variety of defluoroalkynylation or defluoroazolation products.Preliminary mechanistic studies indicated that deprotonated BINOL involved as a photocatalyst to activate ArCF3 rather than a ligand to the metal.
基金supported by the National Natural Science Foundation of China (Nos.22206113 and 22376124)the Outstanding Youth Science Fund (Overseas)of Shandong Provincial Natural Science Foundation (No.2022HWYQ-015)+2 种基金the Taishan Scholars Project Special Fund (No.tsqn202211039)the Guangdong Basic and Applied Basic Research Foundation (No.2021A1515111137)Qilu Youth Talent Program of Shandong University (No.61440082163171).
文摘Perfluoroalkyl substances(PFASs)are typical persistent organic pollutants,and their removal is urgently required but challenging.Photocatalysis has shown potential in PFASs degradation due to the redox capabilities of photoinduced charge carriers in photocatalysts.Herein,hexagonal ZnIn_(2)S_(4)(ZIS)nanosheets were synthesized by a one-pot oil bath method and were well characterized by a series of techniques.In the degradation of sodium p-perfluorous nonenoxybenzenesulfonate(OBS),one kind of representative PFASs,the assynthesized ZIS showed activity superior to P25 TiO_(2) under both simulated sunlight and visible-light irradiation.The good photocatalytic performance was attributed to the enhanced light absorption and facilitated charge separation.The pH conditions were found crucial in the photocatalytic process by influencing the OBS adsorption on the ZIS surface.Photogenerated e−and h+were the main active species involved in OBS degradation in the ZIS system.This work confirmed the feasibility and could provide mechanistic insights into the degradation and defluorination of PFASs by visible-light photocatalysis.
基金financially supported by the National Natural Science Foundation of China(42007181)Chinese Academy of Geological Sciences Basal Research Fund(CSJ-2024-03)National Key Research and Development Program of China(2023YFC3709104).
文摘Biochar,as an efficient,effective,and potential soil improver,has broad application prospects in the field of defluoridation.This study aimed to evaluate the defluoridation potential of iron(Fe)and manganese(Mn)co-modified biochar from groundwater.The varied Fe/Mn molar ratio(2∶1 and 1∶2)modified biochar was prepared by corncob with the pyrolysis temperature of 300℃,400℃,and 500℃.Batch experiments for fluoride(F^(-))removal were performed by corncob biochar before and after Fe-Mn modified.Their composition,structure,and performance were analyzed by multiple characterization techniques to clarify F‒removal mechanisms.Our results indicated that unmodified corncob biochar produced at 400℃(BC400)exhibited the highest F‒adsorption efficiency(87.3%)among three unmodified samples,attributable to its largest specific surface area(2.55 m^(2)/g).Notably,F‒removal amounts by Fe-Mn modified BC400 were 2 times higher than BC400.The enhanced F⁻removal performance of Fe-Mn modified biochar can be attributed to several mechanisms:(1)the modification produced rougher surface textures,resulting in an increased specific surface area(about 3.50 m^(2)/g);(2)newly formed Fe-O and Mn-O bonds on the biochar surface facilitated the formation of complexes with F^(-);and(3)the adsorption results fitted well with pseudo-second-order and Freundlich models(R^(2)>0.98),indicating that the removal process involved physicochemical adsorption.These findings demonstrate that Fe-Mn modified biochar is a highly efficient and cost-effective material for F^(-)remediation and holds significant potential for application in contaminated groundwater and soil systems.
基金supported by the National Natural Scientific Foundation of China(Grant Nos.21978300,U1462128,and 91334108)the State Key Development Program for Basic Research of China(973 Program,Grant No.2015CB251402).
文摘Defluorination roasting of lepidolite ore in a fluidized bed reactor has been proposed for improving the extraction efficiency of lithium.In this paper,a vacuum was introduced to the fluidized bed reactor,which significantly improved the defluorination efficiency of lepidolite particles.This improvement could be attributed to an increase in the H2O/HF ratio.The highest defluorination rate for the lepidolite particles was obtained in the fluidized bed reactor under vacuum.The rate in the vacuum reactor was 1.5-2 times that in a fixed bed reactor or conventional fluidized bed reactor.The defluorination efficiency of the lepidolite particles also improved and the consumption of steam was greatly reduced by addition of coal char.This enhancement was mainly attributed to changes in the structures of the reduced lepidolite particles.This defluorination roasting method for high lithium extraction with low water steam consumption is a promising method for lithium ore treatment.
基金supported by the National Natural Science Foundation of China (No. 20907026)the High Level Talent Research Foundation of Qindao Technological University (No:C-10-210)
文摘Perfluorooctanoic acid （PFOA） is a new-found hazardous persistent organic pollutant, and it is resistant to decomposition by hydroxyl radical （HO.） due to its stable chemical structure and the high electronegativity of fluorine. Photocatalytic reduction of PFOA with β-Ga2O3 in anoxic aqueous solution was investigated for the first time, and the results showed that the photoinduced electron （ecb） coming from the β-Ga2O3 conduction band was the major degradation substance for PFOA, and shorter-chain perfluorinated carboxylic acids （PFCAs, CnF2n＋1COOH, 1 ≤ n ≤ 6） were the dominant products. Furthermore, the concentration of F- was measured by the IC technique and defluorination efficiency was calculated. After 3 hr, the photocatalytic degradation efficiency was 98.8% and defluorination efficiency was 31.6% in the presence of thiosulfate and bubbling N2. The degradation reaction followed first-order kinetics （k = 0.0239 min-1, t1/2 = 0.48 hr）. PFCAs （CnF2n＋xCOOH, 1 ≤ n≤ 7） were detected and measured by LC-MS and LC-MS/MS methods. It was deduced that the probable photocatalytic degradation mechanism involves ec-b attacking the carboxyl of CnF2n＋1COOH, resulting in decarboxylation and the generation of CnFzn＋1. The produced CnF2n＋1 reacted with H2O, forming CnF2n＋1OH, then CnF2n＋1OH underwent HF loss and hydrolysis to form CnF2,＋1COOH.
基金funding provided by University at Albany,State University of New York。
文摘Nanophotocatalysts have shown great potential for degrading poly-and perfluorinated substances(PFAS).In light of the fact that most of these catalysts were studied in pure water,this study was designed to elucidate effects from common environmental factors on decomposing and defluorinating perfluorooctanoic acid(PFOA)by In2O3 nanoparticles.Results from this work demonstrated that among the seven parameters,pH,sulfate,chloride,H2O2,In2O3 dose,NOM and O2,the first four had statistically significant negative effects on PFOA degradation.Since PFOA is a strong acid,the best condition leading to the highest PFOA removal was identified for two pH ranges.When pH was between 4 and 8,the optimal condition was:pH=4.2;sulfate=5.00 mg/L;chloride=20.43 mg/L;H2O2=0 mmol/L.Under this condition,PFOA decomposition and defluorination were 55.22 and 23.56%,respectively.When pH was between 2 and 6,the optimal condition was:pH=2;sulfate=5.00 mg/L;chloride=27.31 mg/L;H2O2=0 mmol/L.With this condition,the modeled PFOA decomposition was 97.59%with a defluorination of approximately 100%.These predicted results were all confirmed by experimental data.Thus,In2O3 nanoparticles can be used for degrading PFOA in aqueous solutions.This approach works best when the target contaminated water contains low concentrations of NOM,sulfate and chloride and at a low pH.
基金the National Natural Science Foundation of China(Nos.21625206.21632009,21421002,22061160465)for financial support.
文摘A method for stereoselective construction of Z-monofluoroalkenes by nickel-catalyzed defluorinative coupling of gem‑difluoroalkenes in mild conditions was described.The combination of lithium organoborate and ZnBr_(2) generated in situ lithium aryl zincates,which facilitates the transmetalation step of the nickel-catalyzed cross coupling reaction.
基金Supported by the National Key New Drug Creation Program of China(No.2009ZX09103-001)the Jiangsu Key Laboratory of Molecular Targeted Antitumor Drug Research Foundation China(No.BM2008201)
文摘tert-Butyl （R）-3-amino-3-（3-fluorophenyl）propanoate（5） was prepared with conventional debenzylation method. However, the tert-butyl （R）-3-[（S）-1-phenylethyl-amino]-3-（3-fluorophenyl） propanoate（6） and tert-butyl （R）-3-amino-3-phenylpropanoate（7） were generated as the byproducts under the general catalytic hydrogenation Pd（OH）2/C-H2 conditions. So a series of experiments was performed to optimize the reaction conditions so that product 5 could be obtained with high purity and yield. Finally an effective catalytic system, Pd/C-HCOOH-CH3OH, was discovered.
基金financially supported by the National Natural Science Foundation of China(No.20976149)
文摘NF3 decomposition over transition metal oxides coated MgO reagents in the absence of water is investigated. The results show that NF3 can be decomposed completely over pure MgO but the time of NF3 steady full conversion kept as short as 80 min, while the reactivities of coated MgO reagents were remarkably enhanced by transition metal oxides, for example the time of NF3 complete conversion over 12%Fe/MgO extended to 380 min. It is suggested that not only an increase in surface area but also a significant enhancement in the fluorination of MgO substrate caused by the surface transition metal oxides result in an improved reactivity of coated MgO reagents for NF3 decomposition.
基金financially supported by the National Natural Science Foundation of China(No.20976149)
文摘A solid ternary mixture consisting of NaF, silicon and one of the metal oxides such as Al2O3, MgO, CaO, SrO, BaO was prepared and used as a defluorinated reagent for CF4 decomposition. The results show that the initial conversion of CF4 reached 100% over NaF-Si-MgO and NaF-Si-CaO at 850°C, and the reagent with NaF/Si/MgO molar ratio of 33/34/33 exhibited a high reactivity with a full conversion of CF4 lasting for 57 min. The plausible paths of CF4 decomposition over NaF-Si-Al2O3, NaF-Si-MgO, NaF-Si-CaO, NaF-Si-SrO and NaF-Si-BaO are proposed.
基金the Key Project of Provincial Natural Science Research Foundation of Anhui Universities,China(Nos.2022AH050406,2023AH050346)Anhui Province Research Funding for Outstanding Young Talents in Colleges and Universities,China(No.gxyq2022021)+3 种基金the Autonomous Project of Key Laboratory of Green and Precise Synthetic Chemistry and Applications,Ministry of Education(KLGPSCA202307,KLGPSCA202111)the Project of Graduate Innovation Fund(CX2024016)the Laboratory Open Project of Huaibei Normal University(Nos.2023syskf017,2023syskf027)the Industry-University-Research Horizontal Project(Nos.2023340603000039,22100370)forfinancial support.
文摘The N-H methylsulfoxidation of sulfoximines using DMso as a methylsulfinyl source,induced by electrochemistry,has been developed.This method is the first example of an electrochemical reaction in which DMso serves as a methylsulfinyl source.Unlike previous electrochemical reactions involving DMsO as a substrate,which exclusively proceed via radical mechanisms,this reaction follows an S-cation pathway.A wide range of N-methylsulfinyl sulfoximines were successfully obtained.
基金the financial support from the National Natural Science Foundation of China(22001121)Nanjing Tech University。
文摘A catalyst-free and additive-free ring-opening reaction of polyfluoroalkyl peroxides,triethylenediamine(DABCO),and 1,2-dichloroethane(DCE)has been developed for the defluorinative synthesis of structurally diverse piperazines featuring a fluoroenone framework and a N-chloroethyl-substituent with high Z-stereoselectivity.The success of this three-component reaction is attributed to the in situ generation of an active 1-(2-chloroethyl)-1,4-diazabicyclo[2.2.2]octan-1-ium(DABCO·DCE)salt,which judiciously acts as a formal N-(2-chloroethyl)piperazine equivalent in the defluorinative coupling with less-studied aliphatic fluorinated substances.Impressively,this reaction accomplishes multi-activation of robust C(sp^(3))-F,C(sp^(3))-Cl,C(sp^(3))-O,and C(sp^(3))-N bonds in a one-pot process,offering a practical platform for the late-stage functionalization of complex molecules.Furthermore,the resulting products can not only serve as versatile building blocks for the synthesis of fluorinated heterocycles,but also undergo C—Cl bond displacement transformations with N-,O-,and S-nucleophiles.
基金financially supported by National Natural Science Foundation of China(Grant No.22276096).
文摘Development of novel electrode materials with the integration of structural and compositional merits can essentially improve the electrosorption performance.Herein,we demonstrate a new strategy,named as carbothermal diffusion reaction synthesis(CDRS),to fabricate binder-free CrN/carbon nanofiber electrodes for efficient electrosorption of fluoride ions from water.The CDRS strategy involves electrospinning MIL-101(Cr)particles with polyacrylonitrile(PAN)to form one-dimensional nanofiber,followed by spatial-confined pyrolysis process in which the nitridation reaction occurred between nitrogen element from PAN and chromium element from MIL-101(Cr),resulting macroscopic,free-standing electrodes with well dispersed ultrafine CrN nanoparticles on porous nitrogen enriched carbon matrix.As expected,the F-adsorption capacity reached 47.67 mg g-1 and there was no decrease in F-removal after 70 adsorption regenerations in 50 mg L-1 F-solution at 1.2 V.The adsorption mechanism of F-was explored by X-ray photoelectron spectroscopy(XPS)and density functional theory(DFT).The enhanced F-adsorption capacity was achieved by the reversible Cr4+/Cr3+redox pair provided by CrN and the electrical double layer capacitance produced by carbon skeleton.This study provides guidance on synergistic modulation of shaping and composition optimization of novel functional materials for electrosorption,catalysis,and supercapacitor applications.
基金the Natural Science Foundation of Zhejiang Province(LQ22B020005,LZ22B020003)the National Natural Science Foundation of China(22101201,22071171)for financial support of this work.
文摘Organic 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 ofthese methods.
