The clay mineral flocculation encapsulation poses a major technical challenge in the field of fine mineral separation.Enhancing the ability to separate clay minerals from target mineral surfaces is key to addressing t...The clay mineral flocculation encapsulation poses a major technical challenge in the field of fine mineral separation.Enhancing the ability to separate clay minerals from target mineral surfaces is key to addressing this issue.In the flotation process of ultrafine hematite,sodium polyacrylate(PAAS)was used as a selective flocculant for hematite,polyaluminum chloride(PAC)as a flocculant for kaolinite and chlorite,and sodium oleate(NaOL)as the collector to achieve asynchronous flocculation flotation.This study examines the flotation separation performance and validates it through experiments on actual mineral samples.The results indicate that with PAAS and PAC dosages of 1.25 and 50 mg·L^(-1),respectively,the iron grade and recovery of the actual mineral samples increased by 9.39%and 7.97%.Through Zeta potential,XPS analysis,infrared spectroscopy,and total organic carbon(TOC)testing,the study reveals the microscopic interaction mechanisms of different flocculants with minerals,providing insights for the clean and efficient utilization of ultrafine mineral resources.展开更多
1.Introduction Solar water splitting offers a promising approach for green hydrogen production[1].There are many ways to achieve solar water splitting,such as photocatalytic(PC)water splitting,photoelectrochemical(PEC...1.Introduction Solar water splitting offers a promising approach for green hydrogen production[1].There are many ways to achieve solar water splitting,such as photocatalytic(PC)water splitting,photoelectrochemical(PEC)water splitting,and photovoltaicelectrocatalytic(PV-EC)water splitting[2].展开更多
To enhance the performance of traditional cationic collector,a novel polyhydroxy amine collector N-(2,3-Propanediol)-N-dodecylamine(PDDA)was designed by introducing one propylene glycol group into dodecylamine(DDA).It...To enhance the performance of traditional cationic collector,a novel polyhydroxy amine collector N-(2,3-Propanediol)-N-dodecylamine(PDDA)was designed by introducing one propylene glycol group into dodecylamine(DDA).It was prepared by a nucleophilic substitution reaction,which showed better solubility and hydrophobicity than DDA and was firstly employed as the collector for the separation of hematite and quartz.Flotation tests showed that PDDA had an excellent flotation performance and significantly better selectivity than DDA.In addition,the flotation performance and adsorption mechanism of PDDA on hematite and quartz surfaces were studied using Fourier transform infrared spectroscopy(FTIR),zeta potential and X-ray photoelectron spectroscopy(XPS)tests.These results demonstrated that the interaction between PDDA and the minerals’surfaces was mainly electrostatic adsorption and hydrogen bond,while PDDA tended to adsorb on the surfaces of quartz more than that of hematite.Performance optimization of amine collectors by introducing hydroxyl was also verified,which was of great meaning to the design,development,and application of the polyhydroxy cationic collector.In conclusion,PDDA could be used as a potential collector in the flotation separation of quartz and hematite.展开更多
The adsorption of sodium oleate(NaOL)at the microfine hematite/aqueous solution interface was investigated in this paper.Experimental research indicated that negative effects stemmed from the dissolution of the microf...The adsorption of sodium oleate(NaOL)at the microfine hematite/aqueous solution interface was investigated in this paper.Experimental research indicated that negative effects stemmed from the dissolution of the microfine hematite(D50=19.21μm)could be effectively eliminated via the appropriate dosage of NaOL at alkali pH conditions.Solution chemistry calculation and adsorption test results indicated that RCOOand(RCOO)_(2)^(2-) ions were responsible for microfine hematite flotation at pH 8.2.Zeta potential and FTIR measurements confirmed the co-adsorption of molecular and ionic oleate species occurred at pH 8.2.X-ray photoelectron spectroscopy(XPS)results further indicated that oleate species interacted with hematite surfaces mainly through chemisorption,giving rise to molecule/colloid formation of oleate and Fe―OL complex compound.Time-of-flight secondary ion mass spectrometry(ToF-SIMS)results demonstrated that oleate species adsorbed onto the hematite surfaces with a thickness of a few nanometers.Furthermore,the normalized peak intensity of C4H7+ions on the hematite sample at pH 8.2 increased remarkably comparing with corresponding result of hematite sample at pH 6.8.The new findings of the present study well revealed the dissolution of microfine hematite and the pH effects on the hematite flotation,as well as the adsorption characteristics of oleate species.展开更多
A large number of studies have shown that oolitic hematite is an iron ore that is extremely difficult to utilize because of its fine disseminated particle size, high harmful impurity content and oolitic structure.To r...A large number of studies have shown that oolitic hematite is an iron ore that is extremely difficult to utilize because of its fine disseminated particle size, high harmful impurity content and oolitic structure.To recover iron from oolitic hematite, we developed a novel multistage dynamic magnetizing roasting technology. Compared with traditional magnetizing roasting technologies, this novel technology has the following advantages: firstly, the oolitic hematite is dynamically reduced in a multi-stage roasting furnace, which shortens the reduction time and avoids ringing and over-reduction;secondly, the novel dynamic magnetizing roasting technology has strong raw material adaptability, and the size range of raw materials can be as wide as 0–15 mm;thirdly, the roasting furnace adopts a preheating-heating process, and the low-calorific value blast furnace gas can be used as the fuel and reductant, which greatly reduces the cost. The actual industrial production data showed that the energy consumption in the roasting process can be less than 35 kg of standard coal per ton of raw ore. The iron grade of the concentrate and iron recovery reached 65% and 90%, respectively.展开更多
Although there have been many reports of metal doping to ameliorate the drawbacks of hematite as the photoanode for water oxidation, most of them focused on monometallic doping, and only a few of them payed attention ...Although there have been many reports of metal doping to ameliorate the drawbacks of hematite as the photoanode for water oxidation, most of them focused on monometallic doping, and only a few of them payed attention to bimetallic doping. What is worse, the synergetic mechanism between two metal dopants was not sufficiently studied, especially the density functional theory(DFT) calculation. In this work, the n-type hematite was synthesized by introducing Ti dopant into hematite through the hydrothermal method, and dipping-sintering treatment was employed to further introduce homogeneously dispersed Zn dopant into that, forming the Ti, Zn co-doped hematite. Under the optimal condition, Tidoped hematite photoanode reached approximately 2-times enhancement of the photocurrent density compared with the pristine one at 1.23 V vs. RHE, while Ti, Zn co-doped hematite anode obtained another25% elevation. UV–Vis spectroscopy, Mott–Schottky plots, EIS analysis, photo-oxidation of hole scavenger(H2O2), and DFT calculation were employed to understand the role of Ti, Zn dopant. Based on the obtained results, the synergetic mechanism of two dopants was discussed, i.e., the improvement of PEC performance of Ti, Zn co-doped hematite photoanode was possibly attributed to greater carrier density and improved charge separation efficiency at the surface of hematite. This work provides new strategy and understanding of the improvement of PEC performance of hematite by doping engineering.展开更多
Hematite nanoparticles have been successfully synthesized via two processing routes：（i） conventional precipitation route and （ii） reverse microemulsion route.The particle precipitation was carried out in a semiba...Hematite nanoparticles have been successfully synthesized via two processing routes：（i） conventional precipitation route and （ii） reverse microemulsion route.The particle precipitation was carried out in a semibatch reactor.A microemulsion system consisting of water,chloroform,1-butanol and surfactant was loaded with iron nitrates to form iron nanoparticles precipitation.The precipitation was performed in the single-phase microemulsion operating region.Three technical surfactants,with different structure and HLB value are employed.The influence of surfactant characterization on the size of produced iron oxide particle has been studied to gain a deeper understanding of the important controlling mechanisms in the formation of nanoparticles in a microemulsion.Transmission electron microscopy （TEM）,surface area,pore volume,average pore diameter,pore size distribution and XRD were used to analyze the size,size distribution,shape and structure of precipitated iron nanoparticles.展开更多
The strong collecting performance of N-laurel-1,3-diaminopropane（ND13） with respect to quartz encouraged us to study its separation of hematite and quartz mixtures in a laboratory cell flotation test The results sho...The strong collecting performance of N-laurel-1,3-diaminopropane（ND13） with respect to quartz encouraged us to study its separation of hematite and quartz mixtures in a laboratory cell flotation test The results show that the best separation results can be achieved when the pulp pH is 7.27 and 58.3 mg/L collector plus 6.67 mg/L depressant are added to the mixture.Products with 58.45%,62.78%and 63.72% iron grades can be achieved respectively when mass ratio of hematite to quartz is 2：3,1：1,and 3：2.The adsorption mechanism of ND13 on a quartz surface was investigated by zeta-potential and X-ray photoelectron spectroscopy measurements.The results reveal that electrostatic and hydrogen bonding adsorption take place between ND13 and the quartz surface,and that ND13 mainly interacts with the oxygen atoms on the quartz surface.展开更多
There are a few studies on the use of ferro-nanofluids for enhanced oil recovery,despite their magnetic properties;hence,it is needed to study the adsorption of iron oxide(Fe2 O3 and Fe3 O4) nanoparticles(NPs) on rock...There are a few studies on the use of ferro-nanofluids for enhanced oil recovery,despite their magnetic properties;hence,it is needed to study the adsorption of iron oxide(Fe2 O3 and Fe3 O4) nanoparticles(NPs) on rock surfaces.This is important as the colloidal transport of NPs through the reservoir is subject to particle adsorption on the rock surface.Molecular dynamics simulation was used to determine the interfacial energy(strength) and adsorption of Fe2 O3 and Fe3 O4 nanofluids infused in reservoir sandstones.Fourier transform infrared spectroscopy and X-ray photon spectroscopy(XPS) were used to monitor interaction of silicate species with Fe2 O3 and Fe3 O4.The spectral changes show the variation of dominating silicate anions in the solution.Also,the XPS peaks for Si,C and Fe at 190,285 and 700 eV,respectively,are less distinct in the spectra of sandstone aged in the Fe3 O4 nanofluid,suggesting the intense adsorption of the Fe3 O4 with the crude oil.The measured IFT for brine/oil,Fe2 O3/oil and Fe3 O4/oil are 40,36.17 and 31 mN/m,respectively.Fe3 O4 infused with reservoir sandstone exhibits a higher silicate sorption capacity than Fe2 O3,due to their larger number of active surface sites and saturation magnetization,which accounts for the effectiveness of Fe3 O4 in reducing IFT.展开更多
Hematite is regarded as a promising photoanode for photoelectrochemical(PEC) water splitting.However,the charge recombination occurred at the interface of FTO/hematite strictly limits the PEC performance of hematite.H...Hematite is regarded as a promising photoanode for photoelectrochemical(PEC) water splitting.However,the charge recombination occurred at the interface of FTO/hematite strictly limits the PEC performance of hematite.Herein,we reported a Ti3C2 MXene underlayer modified hematite(Ti-Fe2O3) photoanode via a simple drop-casting followed by hydrothermal and annealing processes.Owing to the bifunctional role of Ti3C2 MXene underlayer in improving the interfacial properties of FTO/hematite and providing Ti source for the construction of Fe2 TiO5/Fe2O3 heterostructure in hematite nanostructure,the bulk and interfacial charge transfer dynamics of hematite are significantly enhanced,and consequently enhancing the PEC performance.Compared with the pristine hematite,the as-prepared Ti-Fe2O3 photoanode shows an increased photocurrent density from 0.80 mA/cm^(2) to 1.30 mA/cm^(2) at 1.23 V vs.RHE.Moreover,a further promoted PEC performance including a dramatically increased photocurrent density of 2.49 mA/cm^(2) at1.23 V vs.RHE and an obviously lowered onset potential is achieved for the Ti-Fe2O3 sample after the subsequent surface F-treatment and the loading of FeNiOOH cocatalyst.Such results suggest that the introduction of Ti3C2 MXene underlayer is a facile but effective approach to improve the PEC water splitting activity of hematite.展开更多
In this work,a facile chelation-mediated route was developed to fabricate ultrathin cobalt(oxy)hydroxides(CoOOH)nanosheets on hematite photoanode(Fe_(2)O_(3)).The route contains two steps of the adsorption of[Co-EDTA]...In this work,a facile chelation-mediated route was developed to fabricate ultrathin cobalt(oxy)hydroxides(CoOOH)nanosheets on hematite photoanode(Fe_(2)O_(3)).The route contains two steps of the adsorption of[Co-EDTA]^(2-)species on Fe_(2)O_(3) nanorod array followed by the hydrolysis in alkaline solution.The resulting CoOOH/Fe_(2)O_(3) exhibits a remarkably improved photocurrent density of 2.10 mA cm^(-2) at 1.23 V vs.RHE,which is ca.2.8 times that of bare Fe_(2)O_(3).In addition,a negative shift of onset potential ca.200 mV is achieved.The structural characterizations reveal the chelate EDTA plays important roles that enhance the adsorption of Co species and the formation of contact between CoOOH and Fe_(2)O_(3).(Photo)electrochemical analysis suggests,besides providing active sites for water oxidation,CoOOH at large extent promotes the charge separation and the charge transfer via passivating surface states and suppressing charge recombination.It also found CoOOH possesses some oxygen vacancies,which could act as trapping centers for photogenerated holes and facilitate the charge separation.Intensity modulated photocurrent spectroscopy(IMPS)shows that,under low applied potential the water oxidation mainly occurs on CoOOH,while under high applied potential the water oxidation could occur on both CoOOH and Fe_(2)O_(3).The findings not only provide an efficient strategy for designing ultrathin(oxy)hydroxides on semiconductors for PEC applications but also put forward a new insight on the role of CoOOH during water oxidation.展开更多
A value of single-ionic magnetocrystalline anisotropy constant in hematite was recently calculated by Li Hua and others1,being estimated as 47.7×10^(5)erg/cm^(3) at T=0K.
A calculation of the magnetic single-ion anisotropy in hematite has been made.The results show that an equivalent single-ion anisotropy field Hsi(=103.8×10^(2) Oe)exists along the c-axis at T=0K.The Morin transit...A calculation of the magnetic single-ion anisotropy in hematite has been made.The results show that an equivalent single-ion anisotropy field Hsi(=103.8×10^(2) Oe)exists along the c-axis at T=0K.The Morin transition in hematite could be explained by our results in conjunction with the calculated H_(md) by Artman et al.展开更多
Hematite is an excellent catalyst for photoelectrochemical (PEC) water splitting but its performance has been highly limited by poor conductivity and high charge recombination.Here by a Zr-based treatment to create bu...Hematite is an excellent catalyst for photoelectrochemical (PEC) water splitting but its performance has been highly limited by poor conductivity and high charge recombination.Here by a Zr-based treatment to create bulk Fe_(2)ZrO_(5) in hematite and a F-based treatment to form an ultrathin surface FeF_(x) layer,the charge transfer can be highly improved and the charge recombination can be significantly suppressed.As a result,the FeF_(x) /Zr-Fe_(2)O_(3) photoanode presents an enhanced PEC performance with a photocurrent density of 2.43 m A/cm^(2)at 1.23 V vs.RHE,which is around 3 times higher than that of the pristine Fe_(2)O_(3) .The FeF_(x) /Zr-Fe_(2)O_(3) photoanode also shows a low onset potential of 0.77 V vs.RHE (100 mV lower than the pristine hematite).The performance is much higher than that of the sample treated by Zr or F alone,suggesting the synergistic effect between bulk Fe_(2)ZrO_(5) and surface FeF_(x) .By coupling with the FeNiOOH co-catalyst,the final photoanode can achieve a high photocurrent density of 2.81 mA/cm^(2) at 1.23 V vs.RHE.The novel design of Zr and F co-modified hematite can be used as a promising way to prepare efficient catalysts for solar water splitting.展开更多
基金funded by the National Natural Science Foundation of China(No.52374265)the Central Guided Local Science and Technology Development Funding Program(No.236Z4106G)+1 种基金the Natural Science Foundation of Hebei Province(No.E2022209108)Key Projects of Hebei Provincial Department of Education(No.ZD2022059)。
文摘The clay mineral flocculation encapsulation poses a major technical challenge in the field of fine mineral separation.Enhancing the ability to separate clay minerals from target mineral surfaces is key to addressing this issue.In the flotation process of ultrafine hematite,sodium polyacrylate(PAAS)was used as a selective flocculant for hematite,polyaluminum chloride(PAC)as a flocculant for kaolinite and chlorite,and sodium oleate(NaOL)as the collector to achieve asynchronous flocculation flotation.This study examines the flotation separation performance and validates it through experiments on actual mineral samples.The results indicate that with PAAS and PAC dosages of 1.25 and 50 mg·L^(-1),respectively,the iron grade and recovery of the actual mineral samples increased by 9.39%and 7.97%.Through Zeta potential,XPS analysis,infrared spectroscopy,and total organic carbon(TOC)testing,the study reveals the microscopic interaction mechanisms of different flocculants with minerals,providing insights for the clean and efficient utilization of ultrafine mineral resources.
基金financially supported by the National Key R&D Program of China under contact No.2017YFA0204804the National Natural Science Foundation of China under contact Nos.21761142018,21473189 and 22088102 for supporting Fundamental Research Center of Artificial Photosynthesis (FReCAP)。
文摘1.Introduction Solar water splitting offers a promising approach for green hydrogen production[1].There are many ways to achieve solar water splitting,such as photocatalytic(PC)water splitting,photoelectrochemical(PEC)water splitting,and photovoltaicelectrocatalytic(PV-EC)water splitting[2].
基金supported by the National Natural Science Foun-dation of China(Nos.52104250,51874074,and 51874073)the Liaoning Revitalization Talents Program(No.XLYC1807089)the Fundamental Research Funds for the Central Universities(Nos.N2101029 and N2101047).
文摘To enhance the performance of traditional cationic collector,a novel polyhydroxy amine collector N-(2,3-Propanediol)-N-dodecylamine(PDDA)was designed by introducing one propylene glycol group into dodecylamine(DDA).It was prepared by a nucleophilic substitution reaction,which showed better solubility and hydrophobicity than DDA and was firstly employed as the collector for the separation of hematite and quartz.Flotation tests showed that PDDA had an excellent flotation performance and significantly better selectivity than DDA.In addition,the flotation performance and adsorption mechanism of PDDA on hematite and quartz surfaces were studied using Fourier transform infrared spectroscopy(FTIR),zeta potential and X-ray photoelectron spectroscopy(XPS)tests.These results demonstrated that the interaction between PDDA and the minerals’surfaces was mainly electrostatic adsorption and hydrogen bond,while PDDA tended to adsorb on the surfaces of quartz more than that of hematite.Performance optimization of amine collectors by introducing hydroxyl was also verified,which was of great meaning to the design,development,and application of the polyhydroxy cationic collector.In conclusion,PDDA could be used as a potential collector in the flotation separation of quartz and hematite.
基金supported by the Natural Science Foundation of China (No. 52164021)the Natural Science Foundation of Yunnan Province (No. 2019FB078)
文摘The adsorption of sodium oleate(NaOL)at the microfine hematite/aqueous solution interface was investigated in this paper.Experimental research indicated that negative effects stemmed from the dissolution of the microfine hematite(D50=19.21μm)could be effectively eliminated via the appropriate dosage of NaOL at alkali pH conditions.Solution chemistry calculation and adsorption test results indicated that RCOOand(RCOO)_(2)^(2-) ions were responsible for microfine hematite flotation at pH 8.2.Zeta potential and FTIR measurements confirmed the co-adsorption of molecular and ionic oleate species occurred at pH 8.2.X-ray photoelectron spectroscopy(XPS)results further indicated that oleate species interacted with hematite surfaces mainly through chemisorption,giving rise to molecule/colloid formation of oleate and Fe―OL complex compound.Time-of-flight secondary ion mass spectrometry(ToF-SIMS)results demonstrated that oleate species adsorbed onto the hematite surfaces with a thickness of a few nanometers.Furthermore,the normalized peak intensity of C4H7+ions on the hematite sample at pH 8.2 increased remarkably comparing with corresponding result of hematite sample at pH 6.8.The new findings of the present study well revealed the dissolution of microfine hematite and the pH effects on the hematite flotation,as well as the adsorption characteristics of oleate species.
基金National Natural Science Foundation of China (No. 51974204)。
文摘A large number of studies have shown that oolitic hematite is an iron ore that is extremely difficult to utilize because of its fine disseminated particle size, high harmful impurity content and oolitic structure.To recover iron from oolitic hematite, we developed a novel multistage dynamic magnetizing roasting technology. Compared with traditional magnetizing roasting technologies, this novel technology has the following advantages: firstly, the oolitic hematite is dynamically reduced in a multi-stage roasting furnace, which shortens the reduction time and avoids ringing and over-reduction;secondly, the novel dynamic magnetizing roasting technology has strong raw material adaptability, and the size range of raw materials can be as wide as 0–15 mm;thirdly, the roasting furnace adopts a preheating-heating process, and the low-calorific value blast furnace gas can be used as the fuel and reductant, which greatly reduces the cost. The actual industrial production data showed that the energy consumption in the roasting process can be less than 35 kg of standard coal per ton of raw ore. The iron grade of the concentrate and iron recovery reached 65% and 90%, respectively.
基金supported by Major Science and Technology Project of Water Pollution Control and Management(No.2017ZX07101003)Zhejiang Provincial Natural Science Foundation of China under Grant no.LR17B060003financially supported by the Natural Science Foundation of China(Project Nos.21436007,21522606,21476201,21676246,U1462201,and 21776248)
文摘Although there have been many reports of metal doping to ameliorate the drawbacks of hematite as the photoanode for water oxidation, most of them focused on monometallic doping, and only a few of them payed attention to bimetallic doping. What is worse, the synergetic mechanism between two metal dopants was not sufficiently studied, especially the density functional theory(DFT) calculation. In this work, the n-type hematite was synthesized by introducing Ti dopant into hematite through the hydrothermal method, and dipping-sintering treatment was employed to further introduce homogeneously dispersed Zn dopant into that, forming the Ti, Zn co-doped hematite. Under the optimal condition, Tidoped hematite photoanode reached approximately 2-times enhancement of the photocurrent density compared with the pristine one at 1.23 V vs. RHE, while Ti, Zn co-doped hematite anode obtained another25% elevation. UV–Vis spectroscopy, Mott–Schottky plots, EIS analysis, photo-oxidation of hole scavenger(H2O2), and DFT calculation were employed to understand the role of Ti, Zn dopant. Based on the obtained results, the synergetic mechanism of two dopants was discussed, i.e., the improvement of PEC performance of Ti, Zn co-doped hematite photoanode was possibly attributed to greater carrier density and improved charge separation efficiency at the surface of hematite. This work provides new strategy and understanding of the improvement of PEC performance of hematite by doping engineering.
基金supported by the Ferdowsi University of Mashhad,Iran (P/15369/1-89/8/5)
文摘Hematite nanoparticles have been successfully synthesized via two processing routes：（i） conventional precipitation route and （ii） reverse microemulsion route.The particle precipitation was carried out in a semibatch reactor.A microemulsion system consisting of water,chloroform,1-butanol and surfactant was loaded with iron nitrates to form iron nanoparticles precipitation.The precipitation was performed in the single-phase microemulsion operating region.Three technical surfactants,with different structure and HLB value are employed.The influence of surfactant characterization on the size of produced iron oxide particle has been studied to gain a deeper understanding of the important controlling mechanisms in the formation of nanoparticles in a microemulsion.Transmission electron microscopy （TEM）,surface area,pore volume,average pore diameter,pore size distribution and XRD were used to analyze the size,size distribution,shape and structure of precipitated iron nanoparticles.
基金Financial support for this research provided by the National Key Technology Development and Research Programs of China(Nos. 2008BAB32B14 and 2008BAB31B03)
文摘The strong collecting performance of N-laurel-1,3-diaminopropane（ND13） with respect to quartz encouraged us to study its separation of hematite and quartz mixtures in a laboratory cell flotation test The results show that the best separation results can be achieved when the pulp pH is 7.27 and 58.3 mg/L collector plus 6.67 mg/L depressant are added to the mixture.Products with 58.45%,62.78%and 63.72% iron grades can be achieved respectively when mass ratio of hematite to quartz is 2：3,1：1,and 3：2.The adsorption mechanism of ND13 on a quartz surface was investigated by zeta-potential and X-ray photoelectron spectroscopy measurements.The results reveal that electrostatic and hydrogen bonding adsorption take place between ND13 and the quartz surface,and that ND13 mainly interacts with the oxygen atoms on the quartz surface.
文摘There are a few studies on the use of ferro-nanofluids for enhanced oil recovery,despite their magnetic properties;hence,it is needed to study the adsorption of iron oxide(Fe2 O3 and Fe3 O4) nanoparticles(NPs) on rock surfaces.This is important as the colloidal transport of NPs through the reservoir is subject to particle adsorption on the rock surface.Molecular dynamics simulation was used to determine the interfacial energy(strength) and adsorption of Fe2 O3 and Fe3 O4 nanofluids infused in reservoir sandstones.Fourier transform infrared spectroscopy and X-ray photon spectroscopy(XPS) were used to monitor interaction of silicate species with Fe2 O3 and Fe3 O4.The spectral changes show the variation of dominating silicate anions in the solution.Also,the XPS peaks for Si,C and Fe at 190,285 and 700 eV,respectively,are less distinct in the spectra of sandstone aged in the Fe3 O4 nanofluid,suggesting the intense adsorption of the Fe3 O4 with the crude oil.The measured IFT for brine/oil,Fe2 O3/oil and Fe3 O4/oil are 40,36.17 and 31 mN/m,respectively.Fe3 O4 infused with reservoir sandstone exhibits a higher silicate sorption capacity than Fe2 O3,due to their larger number of active surface sites and saturation magnetization,which accounts for the effectiveness of Fe3 O4 in reducing IFT.
基金the support from the high-performance computing platform of Jiangsu UniversityThe Jiangsu University Foundation (18JDG019)+3 种基金the Postdoctoral Foundation of Jiangsu Province (2018K072C)Six Talent Peak Project of Jiangsu Province (XLC-158)the China Postdoctoral Science Foundation (2019M651727, 2019M651719)the National Natural Science Foundation of China (21808090, 51902139, U1932211) financially supported this work。
文摘Hematite is regarded as a promising photoanode for photoelectrochemical(PEC) water splitting.However,the charge recombination occurred at the interface of FTO/hematite strictly limits the PEC performance of hematite.Herein,we reported a Ti3C2 MXene underlayer modified hematite(Ti-Fe2O3) photoanode via a simple drop-casting followed by hydrothermal and annealing processes.Owing to the bifunctional role of Ti3C2 MXene underlayer in improving the interfacial properties of FTO/hematite and providing Ti source for the construction of Fe2 TiO5/Fe2O3 heterostructure in hematite nanostructure,the bulk and interfacial charge transfer dynamics of hematite are significantly enhanced,and consequently enhancing the PEC performance.Compared with the pristine hematite,the as-prepared Ti-Fe2O3 photoanode shows an increased photocurrent density from 0.80 mA/cm^(2) to 1.30 mA/cm^(2) at 1.23 V vs.RHE.Moreover,a further promoted PEC performance including a dramatically increased photocurrent density of 2.49 mA/cm^(2) at1.23 V vs.RHE and an obviously lowered onset potential is achieved for the Ti-Fe2O3 sample after the subsequent surface F-treatment and the loading of FeNiOOH cocatalyst.Such results suggest that the introduction of Ti3C2 MXene underlayer is a facile but effective approach to improve the PEC water splitting activity of hematite.
基金supported by the National Natural Science Foundation of China(51502078)the Major Project of Science and Technology,Education Department of Henan Province(19A150019 and 19A150018)+2 种基金the Science and Technology Research Project of Henan Province(192102310490 and 182102410090)the program for Science&Technology Innovation Team in Universities of Henan Province(19IRTSTHN029)supported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences,Chemical Sciences,Geosciences,and Biosciences Division,Catalysis Science program。
文摘In this work,a facile chelation-mediated route was developed to fabricate ultrathin cobalt(oxy)hydroxides(CoOOH)nanosheets on hematite photoanode(Fe_(2)O_(3)).The route contains two steps of the adsorption of[Co-EDTA]^(2-)species on Fe_(2)O_(3) nanorod array followed by the hydrolysis in alkaline solution.The resulting CoOOH/Fe_(2)O_(3) exhibits a remarkably improved photocurrent density of 2.10 mA cm^(-2) at 1.23 V vs.RHE,which is ca.2.8 times that of bare Fe_(2)O_(3).In addition,a negative shift of onset potential ca.200 mV is achieved.The structural characterizations reveal the chelate EDTA plays important roles that enhance the adsorption of Co species and the formation of contact between CoOOH and Fe_(2)O_(3).(Photo)electrochemical analysis suggests,besides providing active sites for water oxidation,CoOOH at large extent promotes the charge separation and the charge transfer via passivating surface states and suppressing charge recombination.It also found CoOOH possesses some oxygen vacancies,which could act as trapping centers for photogenerated holes and facilitate the charge separation.Intensity modulated photocurrent spectroscopy(IMPS)shows that,under low applied potential the water oxidation mainly occurs on CoOOH,while under high applied potential the water oxidation could occur on both CoOOH and Fe_(2)O_(3).The findings not only provide an efficient strategy for designing ultrathin(oxy)hydroxides on semiconductors for PEC applications but also put forward a new insight on the role of CoOOH during water oxidation.
文摘A value of single-ionic magnetocrystalline anisotropy constant in hematite was recently calculated by Li Hua and others1,being estimated as 47.7×10^(5)erg/cm^(3) at T=0K.
文摘A calculation of the magnetic single-ion anisotropy in hematite has been made.The results show that an equivalent single-ion anisotropy field Hsi(=103.8×10^(2) Oe)exists along the c-axis at T=0K.The Morin transition in hematite could be explained by our results in conjunction with the calculated H_(md) by Artman et al.
基金supported by the National Key R&D Program of China (2020YFA0406103)the National Natural Science Foundation of China (U1932211)+1 种基金the Collaborative Innovation Center of Suzhou Nano Science & Technology, the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)the 111 Project。
文摘Hematite is an excellent catalyst for photoelectrochemical (PEC) water splitting but its performance has been highly limited by poor conductivity and high charge recombination.Here by a Zr-based treatment to create bulk Fe_(2)ZrO_(5) in hematite and a F-based treatment to form an ultrathin surface FeF_(x) layer,the charge transfer can be highly improved and the charge recombination can be significantly suppressed.As a result,the FeF_(x) /Zr-Fe_(2)O_(3) photoanode presents an enhanced PEC performance with a photocurrent density of 2.43 m A/cm^(2)at 1.23 V vs.RHE,which is around 3 times higher than that of the pristine Fe_(2)O_(3) .The FeF_(x) /Zr-Fe_(2)O_(3) photoanode also shows a low onset potential of 0.77 V vs.RHE (100 mV lower than the pristine hematite).The performance is much higher than that of the sample treated by Zr or F alone,suggesting the synergistic effect between bulk Fe_(2)ZrO_(5) and surface FeF_(x) .By coupling with the FeNiOOH co-catalyst,the final photoanode can achieve a high photocurrent density of 2.81 mA/cm^(2) at 1.23 V vs.RHE.The novel design of Zr and F co-modified hematite can be used as a promising way to prepare efficient catalysts for solar water splitting.
