The Zoujiashan uranium deposit in the Xiangshan ore field is the largest volcanic-related uranium deposit in China.Hematite-and fluorite-type ores are the predominant mineralization styles.Hematitization in the Xiangs...The Zoujiashan uranium deposit in the Xiangshan ore field is the largest volcanic-related uranium deposit in China.Hematite-and fluorite-type ores are the predominant mineralization styles.Hematitization in the Xiangshan ore field is closely associated with uranium mineralization,mainly occurring as hematitized rocks enclosing fluorite-type vein ores developed in pre-ore illitized porphyritic lava.Detailed petrographic and mass balance calculation studies were conducted to evaluate the mechanisms for uranium precipitation and mass transfer during hematitization.Petrographic observations suggest that in the hematitized rocks,orthoclase is more altered than plagioclase,and quartz dissolution is common,whereas in the illitized rocks,pyrite commonly occurs within the altered biotite grains,and chlorite grains are locally found.Mass balance calculations indicate that Na2O and U were gained,K2O,Ca O and Si O2were lost,whereas Fe2O3-t remained more or less constant during hematitization.These observations suggest that the hydrothermal fluids were Na-and U-rich and Ca-K-poor,and the Fe2+used for hematitization was locally derived,most likely from biotite,pyrite and chlorite in the host rocks.The Fe2+is inferred to have played the role of reductant to precipitate uranium,and calculation indicates that oxidation of Fe2+provided by host rocks is sufficient to form ores of economic significance.Consequently,the hematite-type ore is interpreted to be generated by the reaction between oxidized ore fluids and reduced components in host rocks.The development of calcite and pyrite in the fluorite ores suggests that perhaps mixing between the U-rich fluid and another fluid carrying reduced sulfur and carbon may have also contributed to uranium mineralization,in addition to temperature and pressure drop associated with the veining.展开更多
The significant effect of MgO in inhibiting the reduction swelling of iron ore pellets has been widely recognized.The swelling behaviors of pellets during the stepwise reduction by CO were assessed.The linear expansio...The significant effect of MgO in inhibiting the reduction swelling of iron ore pellets has been widely recognized.The swelling behaviors of pellets during the stepwise reduction by CO were assessed.The linear expansion of strip samples was measured using a linear dilatometer during the staged reduction process at a temperature of 900℃.The existence states of MgO in hematite,magnetite,and wüstite were investigated through thermodynamic calculations.The magnetite strip samples were subjected to oxidizing roasting at 1250℃ for 30 min to produce hematite strip samples.The strip samples with 0.49,1.49,2.49,and 3.49 wt.%MgO were analyzed for length change.It was observed that the sample with 2.49 wt.%MgO exhibited the least significant length change.The lengths of the samples with the initial length being 20 mm before reduction changed during the reduction stages of Fe_(2)O_(3)→Fe_(3)O_(4),Fe_(3)O_(4)→FeO,and FeO→Fe were 615,−25,and−378μm,respectively.The volume expansion of hematite to magnetite was primarily attributed to the crystal transformation.During the reduction stage from wüstite to metallic iron,a substantial contraction occurred,while the slag phase was able to retain its original basic shape.The enclosed areas,as indicated by the expansion change curves of the samples with 0.49,1.49,2.49,and 3.49 wt.%MgO,were measured at 3.76×10^(6),3.23×10^(6),3.05×10^(6),and 3.17×10^(6)μm s,respectively.展开更多
To explore the spontaneous magnetization of iron-bearing rare earth ores during suspension roasting,binary minerals containing hematite and bastnaesite were used to investigate the effects of the roasting temperature,...To explore the spontaneous magnetization of iron-bearing rare earth ores during suspension roasting,binary minerals containing hematite and bastnaesite were used to investigate the effects of the roasting temperature,roasting time,and bastnaesite-to-hematite mass ratio on in-situ reduction of hematite in a N_(2)atmosphere.Relevant analytical tests were used to explore the mineral phase evolution during roasting,the magnetism and microstructure of the roasted products,the phase composition,and the surface element valence of concentrate.It was found that magnetic separation of the iron concentrate afforded an iron grade of 68.87%and a recovery of 93.18%under the optimum roasting conditions.During roasting,bastnaesite decomposed to generate CO_(2)and CO,and the compact structure of hematite was gradually destroyed,resulting in microcracks.Subsequently,the CO entered the surface of the hematite through the microcracks and reacted to form a magnetite shell,and the magnetite-encapsulated hematite particles were recovered via low-intensity magnetic separation.展开更多
With the depletion of high-quality iron ore resources,high-phosphorus oolitic hematite(HPOH)has attracted great attention due to its large reserve and relatively high iron content.However,HPOH is very difficult to be ...With the depletion of high-quality iron ore resources,high-phosphorus oolitic hematite(HPOH)has attracted great attention due to its large reserve and relatively high iron content.However,HPOH is very difficult to be used in ironmaking process due to its special structure.A two-step method of gas-based direct reduction and magnetic separation was thus proposed to recover iron and reduce phosphorus.The results showed that the powdery reduced iron produced contained 92.31%iron and 0.1%phosphorus,and the iron recovery was 92.65%under optimum reduction condition,which is suitable for following steelmaking.The apatite will be reduced under long reduction time and a large reducing gas flow rate,resulting in more phosphorus found in the metallic iron.Increasing the hydrogen–carbon ratio will inhibit the formation and growth of iron particles and prevent the breakage of oolitic structure.Careful adjustment of reduction temperature is recommended as it affects the oolitic structure and reduction.展开更多
Regulating the interfacial charge transfer is pivotal for elucidating the kinetics of engineering the interface between the light-harvesting semiconductor and the substrate/catalyst for photoelectrocatalytic water spl...Regulating the interfacial charge transfer is pivotal for elucidating the kinetics of engineering the interface between the light-harvesting semiconductor and the substrate/catalyst for photoelectrocatalytic water splitting.In this study,we constructed a superior Ti-doped hematite photoanode(TiFeO)by employing SnOx as an electron transfer mediator,partially oxidized graphene(pGO)as a hole transfer mediator,and molecular Co cubane as a water oxidation catalyst.The Co/pGO/TiFeO/SnO_(x)integrated system achieves a photocurrent density of 2.52 mA cm^(-2) at 1.23 VRHE,which is 2.4 times higher than bare photoanode(1.04 mA cm^(-2)),with operational stability up to 100 h.Kinetic measurements indicate that pGO can promote charge transfer from TiFeO to the Co cubane catalyst.In contrast,SnOx reduces charge recombination at the interface between TiFeO and the fluorinated tin oxide substrate.In-situ infrared spectroscopy shows the formation of an O–O bonded intermediate during water oxidation.This study highlights the crucial role of incorporating dual charge-transfer mediators into photoelectrodes for efficient solar energy conversion.展开更多
Cement production,while essential for global infrastructure,contributes significantly to carbon dioxide emissions,accounting for approximately 7%of total emissions.To mitigate these environmental impacts,flash calcina...Cement production,while essential for global infrastructure,contributes significantly to carbon dioxide emissions,accounting for approximately 7%of total emissions.To mitigate these environmental impacts,flash calcination of kaolinitic clays has been investigated as a sustainable alternative.This technique involves the rapid heating of clays,enabling their use as supplementary cementitious materials.The primary objective of this study was to modify the color of calcined clay in various atmospheres(oxidizing,inert,and reducing)to achieve a grayish tone similar to commercial cement while preserving its reactive properties.The experimental procedure employed a tubular reactor with precise control of gas flows(atmospheric air,nitrogen,and a carbon monoxide–nitrogen mixture).Physicochemical characterization of the raw clay was conducted before calcination,with analyses repeated on the calcined clays following experimentation.Results indicated that clay calcined in an oxidizing atmosphere acquired a reddish hue,attributed to the oxidation of iron in hematite.The Clay exhibited a pinkish tone in an inert atmosphere,while calcination in a reducing atmosphere yielded the desired grayish color.Regarding pozzolanic activity,clays calcined in oxidizing and inert atmospheres displayed robust strength,ranging from 82%to 87%.Calcination in a reducing atmosphere resulted in slightly lower strength,around 74%,likely due to the clay’s chemical composition and the calcination process,which affects compound formation and material reactivity.展开更多
Effects of stirring speed and time, pH and sodium oleate concentration on the shear hydrophobic flocculation of ultrafine Anshan hematite with sodium oleate as the surfactant were discussed. The results show that thes...Effects of stirring speed and time, pH and sodium oleate concentration on the shear hydrophobic flocculation of ultrafine Anshan hematite with sodium oleate as the surfactant were discussed. The results show that these parameters significantly affect the shear hydrophobic flocculation of ultrafine hematite. The optimum conditions for the flocculation are： stirring speed 1 400 r/min, flocculation time 20 min, pH 9 and sodium oleate concentration 3.94×10-4 mol/L; the flotation recovery of hematite flocs is remarkably high compared with non flocculated ultrafine hematite. According to the extended DLVO theory, the total interaction potential of Anshan ultrafine hematite was determined. The calculation results indicate that the hydrophobic flocculation state of the ultrafine hematite-sodium oleate system is mainly dominated by electric double layer repulsive interaction potential and hydrophobic interaction potential. A mechanical agitation is required to impart particles a kinetic energy to overcome potential barrier between them due to the existence of electric double layer repulsive interaction potential. Those particles further approach to form flocs due to the significant increase of the hydrophobic interaction potential.展开更多
High phosphorous oolitic hematite ore is one of typical intractable iron ores in China, and the conventional beneficiation methods are found to be impracticable to , remove phosphorus from the ore effectively. Better ...High phosphorous oolitic hematite ore is one of typical intractable iron ores in China, and the conventional beneficiation methods are found to be impracticable to , remove phosphorus from the ore effectively. Better beneficiation index were gotten by direct reduction roasting with dephosphorization agent followed by two stages of grinding and magnetic separation. P content decreases from 0.82% in the raw ore to 0.06% in the magnetic concentrate, and the total iron grade increases from 43.65% to 90.23%, the recovery of iron can reach 87%. Mechanisms of phosphorus removal in the beneficiation of high phosphorous oolitic hematite ore by direct reduction roasting with dephosphorization agent were studied using XRD, SEM and EPMA. The results showed that about 20% of the apatite in the raw ore transferred into phosphorus and volatilized with the gas in the process of reduction roasting, while the rest 80% apatite was not involved in the reaction of generation of phosphorus, and remained as apatite in the roasted products, which was removed to tailings by grinding and magnetic separation. A small amount of phosphorus existed in the magnetic concentrate as apatite. The oolitic texture of raw ore was partly changed during roasting, resulting in the formation of nepheline in the reaction between the dephosphorization agent, SiO2 and Al2O3 in the raw ore, which greatly improved the liberation degree of minerals in the roasted products, and it was beneficial to the subsequent grinding and magnetic separation.展开更多
The population of surface broken bonds of some typical sulfide, oxide and salt-type minerals which may belong to cubic, tetragonal, hexagonal, or orthorhombic system, were calculated. In terms of the calculation resul...The population of surface broken bonds of some typical sulfide, oxide and salt-type minerals which may belong to cubic, tetragonal, hexagonal, or orthorhombic system, were calculated. In terms of the calculation results, the cleavage natures of these minerals were analyzed, and the relationship between surface broken bonds density and surface energy was also established. The results show that the surface broken bonds properties could be used to predict the cleavage nature of most of minerals, and the predicted cleavage planes agree well with those reported in previous literature. Moreover, this work explored a rule that, surface broken bonds density is directly related to surface energy with determination coefficient（R2） of over 0.8, indicating that the former is a dominant factor to determine the latter. Therefore, anisotropic surface broken bonds density can be used to predict the stability of mineral surface and the reactivity of surface atoms.展开更多
The adsorption of sodium acetohydroxamate on the goethite or hematite surface was investi- gated by Fourier transform infrared spectroscopy （FT-IR）, X-ray photoemission spectroscopy and periodic plane-wave density f...The adsorption of sodium acetohydroxamate on the goethite or hematite surface was investi- gated by Fourier transform infrared spectroscopy （FT-IR）, X-ray photoemission spectroscopy and periodic plane-wave density functional theory （DFT） calculations. The core-level shifts and charge transfers of the adsorbed surface iron sites calculated by DFT with periodic in- terfacial structures were confronted to the X-ray photoemission experiments. FT-IR results reveal that the interracial structure of sodium acetohydroxamate adsorbed on the goethite or hematite surface may be assigned to a five-membered ring complex. In agreement with the adsorption energies determined by the DFT calculations, a five-membered ring complex is formed via bonding of one surface iron atom of goethite （101） or （100） to both oxygen atoms of hydroxamate group, and these two oxygen atoms of the hydroxamate group correspond- ingly attach to two neighboring iron atoms of the goethite surface. But a five-membered ring complex between two oxygen atoms of the hydroxamate group and one surface iron atom of hematite （001） is formed without any extra attachments. The calculated core-level shifts of Fe2p for the interracial structures are correspondingly in good agreement with the experimental observed one, which confirmed the reliability of the calculated results.展开更多
The reverse flotation separation performance and mechanism of hematite and cellophane in the presence of RFP-138, a newly synthesized dephosphorization collector, were studied. Reverse flotation tests on monominerals ...The reverse flotation separation performance and mechanism of hematite and cellophane in the presence of RFP-138, a newly synthesized dephosphorization collector, were studied. Reverse flotation tests on monominerals and artificially mixed minerals of hematite and collophanite show that, this anionic collector performs excellently in reducing the phosphorus content in hematite. It can decrease the content of P in artificially mixed minerals from 1.05% to 0.12% and achieve the TFe recovery rate of 91.30%. The chemical behavior of solution and infrared spectra of RFP-138 were investigated to explore the selective collecting mechanism of RFP-138 to these two minerals.展开更多
The collecting performances of N-dodecylethylene-diamine （ND） to quartz and hematite were studied via single mineral flotation. Experimental results show that ND has stronger collecting ability to quartz than hemati...The collecting performances of N-dodecylethylene-diamine （ND） to quartz and hematite were studied via single mineral flotation. Experimental results show that ND has stronger collecting ability to quartz than hematite. Different floatability of quartz and hematite was presented in the existence of depressant. Compared with lauryl amine, ND has stronger collecting performances to quartz. Satisfied separation result of artificially mixed sample was acquired with iron grade of concentrate of 59.92% and iron recovery of 88.85% when pulp pH value was 7.27 with 41.7 mg/L collector and 3.33 mg/L starch. Polar group properties calculation results indicated that ND has stronger collecting capability and better selectivity than lauryl amine. Measurement results of zeta-potentials and infrared spectrum showed that hydrogen bonding adsorption and electrostatic adsorption occur between the surface of ND and quartz.展开更多
Given the gradual increase in the chlorite content of hematite ores, pulp properties seriously deteriorate during flotation. The traditional anion reverse flotation of hematite cannot effectively eliminate the effects...Given the gradual increase in the chlorite content of hematite ores, pulp properties seriously deteriorate during flotation. The traditional anion reverse flotation of hematite cannot effectively eliminate the effects of chlorite, leading to a significant decrease in the total Fe(TFe) grade of the concentrate. In this work, the effect of sodium alginate on the reverse flotation of hematite was systematically investigated. Flotation tests of artificially mixed ores were conducted, and the results showed that sodium alginate can significantly improve the removal rates of quartz and chlorite. The adsorption measurements, infrared spectroscopy, and contact angle tests demonstrated that sodium alginate adsorbs on the quartz surface by chelating with calcium ions, thereby weakening the steric hindrance of oleate ions and increasing the adsorption capacity of sodium oleate to ultimately improve the removal rate of quartz. Furthermore, owing to its lower density and fine particle size, chlorite is easily entrained into the foam layer. Sodium alginate dramatically increases the liquid-to-gas ratio of the foam layer by increasing pulp viscosity, thereby increasing the entrainment rate of chlorite and finally improving its removal rate. The core content of this thesis bears significance in improving the Fe grade in the reverse flotation of chlorite-containing hematite.展开更多
The efficient development and utilization of high-phosphorus oolitic hematite is of great strategic significance for the sustainable supply of iron-ore resources in China.In this paper,the mechanism of high-temperatur...The efficient development and utilization of high-phosphorus oolitic hematite is of great strategic significance for the sustainable supply of iron-ore resources in China.In this paper,the mechanism of high-temperature pretreatment for enhancing the effect of iron enrichment and dephosphorization in the magnetization roasting–leaching process was studied by X-ray diffraction(XRD),vibration sample magnetometer(VSM),scanning electron microscopy and energy dispersive spectrometry(SEM–EDS).Compared with the process without high-temperature pretreatment,the iron grade of the magnetic separation concentrate after high-temperature pretreatment had increased by 0.98%,iron recovery rate had increased by 1.33%,and the phosphorus content in the leached residue had decreased by 0.12%.High-temperature pretreatment resulted in the dehydration and decomposition of hydroxyapatite,the dehydration of limonite and the thermal decomposition of siderite,which can produce pores and cracks and weaken the compactness of the ore,improve the magnetization characteristics of roasted ore,and strengthen the iron enrichment and dephosphorization during the magnetization roasting and leaching process.展开更多
The reductive Bayer digestion by using iron powder as reductant is proposed to convert hematite to magnetite and further to dissociate iron minerals from sodium aluminosilicate hydrate(desilication product,DSP)based o...The reductive Bayer digestion by using iron powder as reductant is proposed to convert hematite to magnetite and further to dissociate iron minerals from sodium aluminosilicate hydrate(desilication product,DSP)based on the differences of their surface properties.The results show that the differences of surface properties between magnetite and DSP in zeta potential,wettability and solvation trend facilitate magnetite to agglomerate,grow up and thus to dissociate from DSP.The increments of reductant amount and alkali concentration favor the transformation of hematite in digestion with the relative alumina recovery of98.91%.Processing the resultant red mud can obtain qualified iron concentrate with iron grade of approximate60%and recovery of about86%through magnetic separation,resulting in reduction of red mud emission higher than70%.The results are potential to develop a novel technology for processing high iron diasporic bauxite efficiently and provide references for comprehensive utilization of high iron red mud.展开更多
A laboratory experiment was carried out to extract iron from oolitic iron ore by a deep reduction and magnetic separation technique. The raw coal with fixed carbon of 66.54% was used as the reductant. The iron was suc...A laboratory experiment was carried out to extract iron from oolitic iron ore by a deep reduction and magnetic separation technique. The raw coal with fixed carbon of 66.54% was used as the reductant. The iron was successfully extracted from the oolitic iron ore which otherwise is nearly impossible to be separated due to its extremely fine-grain and mosaic nature. The results showed that an iron recovery rate of 90.78% and an iron content of 92.53~ of iron concentrate could be obtained by such a technique. The optimized roast temperature is 1 200℃ and time is 60 min. The subsequent magnetic separation was performed by using a magnetic field intensity of 111 kA · m^-1 and a grinding fineness less than 45 μm of 96. 19% for the sintered product.展开更多
Magnetizing roasting of oolitic hematite ore from western Hubei Province was investigated.The mechanism for reduction roasting of oolitic hematite ore was discussed and analyzed.It is found that flash magnetizing roas...Magnetizing roasting of oolitic hematite ore from western Hubei Province was investigated.The mechanism for reduction roasting of oolitic hematite ore was discussed and analyzed.It is found that flash magnetizing roasting-magnetic separation process is a promising approach for the processing of oolitic hematite ore from western Hubei Province.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
Reverse flotation technology is one of the most efficient ways to improve the quality and reduce impurity of iron concentrate. Mineral processors dealing with hematite face a challenge that the flotation results of re...Reverse flotation technology is one of the most efficient ways to improve the quality and reduce impurity of iron concentrate. Mineral processors dealing with hematite face a challenge that the flotation results of reverse flotation of hematite are poor in presence of siderite using fatty acid as collector, starch as depressant of iron minerals and calcium ion as activator of quartz at strong alkaline pH. In this work, the effect of siderite on reverse anionic flotation of quartz from hematite was investigated. The effect mechanism of siderite on reverse flotation of hematite was studied by solution chemistry, ultraviolet spectrophotometry(UV) and Fourier transform infrared spectroscopy(FTIR). It was observed that siderite had strong depressive effect on quartz in flotation using sodium oleate as collector, corn starch as depressant of iron minerals and calcium chloride as activator of quartz at strong alkaline pH. The starch was adsorbed onto calcium carbonate by chemical reaction which was formed by CO^(2-)_3 from siderite dissolution and Ca^(2+) from calcium chloride as activator of quartz and precipitated on the surface of quartz, which resulted in improving the hydrophilic ability of quartz.展开更多
基金co-founded by the National Natural Science Foundation of China(Nos.42002090,41930428)the National Key Research and Development Program of China(No.2018YFC0604200)+5 种基金the Project of China Geological Survey(No.DD20190119)the Open Research Fund Program of State Key Laboratory of Nuclear Resources and Environment,East China University of Technology(No.NRE1915)the Open Research Fund Program of Jiangxi Engineering Laboratory on Radioactive Geoscience and Big Data Technology(No.JELRGBDT202006)the International Geoscience Programme(No.IGCP-675)the Jiangxi province graduate student innovation special fund project(YC2019-S271)the East China University of Technology graduate student innovation special fund project(No.DHYC-202001)。
文摘The Zoujiashan uranium deposit in the Xiangshan ore field is the largest volcanic-related uranium deposit in China.Hematite-and fluorite-type ores are the predominant mineralization styles.Hematitization in the Xiangshan ore field is closely associated with uranium mineralization,mainly occurring as hematitized rocks enclosing fluorite-type vein ores developed in pre-ore illitized porphyritic lava.Detailed petrographic and mass balance calculation studies were conducted to evaluate the mechanisms for uranium precipitation and mass transfer during hematitization.Petrographic observations suggest that in the hematitized rocks,orthoclase is more altered than plagioclase,and quartz dissolution is common,whereas in the illitized rocks,pyrite commonly occurs within the altered biotite grains,and chlorite grains are locally found.Mass balance calculations indicate that Na2O and U were gained,K2O,Ca O and Si O2were lost,whereas Fe2O3-t remained more or less constant during hematitization.These observations suggest that the hydrothermal fluids were Na-and U-rich and Ca-K-poor,and the Fe2+used for hematitization was locally derived,most likely from biotite,pyrite and chlorite in the host rocks.The Fe2+is inferred to have played the role of reductant to precipitate uranium,and calculation indicates that oxidation of Fe2+provided by host rocks is sufficient to form ores of economic significance.Consequently,the hematite-type ore is interpreted to be generated by the reaction between oxidized ore fluids and reduced components in host rocks.The development of calcite and pyrite in the fluorite ores suggests that perhaps mixing between the U-rich fluid and another fluid carrying reduced sulfur and carbon may have also contributed to uranium mineralization,in addition to temperature and pressure drop associated with the veining.
基金support from the 2023 Basic Research Foundation Project for Universities in the Inner Mongolia Autonomous Region(Grant No.2023RCTD006)the National Natural Science Foundation of China(Grant No.51864041,51664044).
文摘The significant effect of MgO in inhibiting the reduction swelling of iron ore pellets has been widely recognized.The swelling behaviors of pellets during the stepwise reduction by CO were assessed.The linear expansion of strip samples was measured using a linear dilatometer during the staged reduction process at a temperature of 900℃.The existence states of MgO in hematite,magnetite,and wüstite were investigated through thermodynamic calculations.The magnetite strip samples were subjected to oxidizing roasting at 1250℃ for 30 min to produce hematite strip samples.The strip samples with 0.49,1.49,2.49,and 3.49 wt.%MgO were analyzed for length change.It was observed that the sample with 2.49 wt.%MgO exhibited the least significant length change.The lengths of the samples with the initial length being 20 mm before reduction changed during the reduction stages of Fe_(2)O_(3)→Fe_(3)O_(4),Fe_(3)O_(4)→FeO,and FeO→Fe were 615,−25,and−378μm,respectively.The volume expansion of hematite to magnetite was primarily attributed to the crystal transformation.During the reduction stage from wüstite to metallic iron,a substantial contraction occurred,while the slag phase was able to retain its original basic shape.The enclosed areas,as indicated by the expansion change curves of the samples with 0.49,1.49,2.49,and 3.49 wt.%MgO,were measured at 3.76×10^(6),3.23×10^(6),3.05×10^(6),and 3.17×10^(6)μm s,respectively.
基金the financial support from the National Key R&D Program of China(No.2022YFC2905800)the National Natural Science Foundation of China(Nos.52174242,52130406)。
文摘To explore the spontaneous magnetization of iron-bearing rare earth ores during suspension roasting,binary minerals containing hematite and bastnaesite were used to investigate the effects of the roasting temperature,roasting time,and bastnaesite-to-hematite mass ratio on in-situ reduction of hematite in a N_(2)atmosphere.Relevant analytical tests were used to explore the mineral phase evolution during roasting,the magnetism and microstructure of the roasted products,the phase composition,and the surface element valence of concentrate.It was found that magnetic separation of the iron concentrate afforded an iron grade of 68.87%and a recovery of 93.18%under the optimum roasting conditions.During roasting,bastnaesite decomposed to generate CO_(2)and CO,and the compact structure of hematite was gradually destroyed,resulting in microcracks.Subsequently,the CO entered the surface of the hematite through the microcracks and reacted to form a magnetite shell,and the magnetite-encapsulated hematite particles were recovered via low-intensity magnetic separation.
基金supported by the National Key R&D Program of China(Grant Nos.2021YFC2902400 and 2021YFC2902404)Interdisciplinary Research Project for Young Teachers of USTB(Fundamental Research Funds for the Central Universities)(FRF-IDRY-21-027 and FRF-IDRY-22-018).
文摘With the depletion of high-quality iron ore resources,high-phosphorus oolitic hematite(HPOH)has attracted great attention due to its large reserve and relatively high iron content.However,HPOH is very difficult to be used in ironmaking process due to its special structure.A two-step method of gas-based direct reduction and magnetic separation was thus proposed to recover iron and reduce phosphorus.The results showed that the powdery reduced iron produced contained 92.31%iron and 0.1%phosphorus,and the iron recovery was 92.65%under optimum reduction condition,which is suitable for following steelmaking.The apatite will be reduced under long reduction time and a large reducing gas flow rate,resulting in more phosphorus found in the metallic iron.Increasing the hydrogen–carbon ratio will inhibit the formation and growth of iron particles and prevent the breakage of oolitic structure.Careful adjustment of reduction temperature is recommended as it affects the oolitic structure and reduction.
文摘Regulating the interfacial charge transfer is pivotal for elucidating the kinetics of engineering the interface between the light-harvesting semiconductor and the substrate/catalyst for photoelectrocatalytic water splitting.In this study,we constructed a superior Ti-doped hematite photoanode(TiFeO)by employing SnOx as an electron transfer mediator,partially oxidized graphene(pGO)as a hole transfer mediator,and molecular Co cubane as a water oxidation catalyst.The Co/pGO/TiFeO/SnO_(x)integrated system achieves a photocurrent density of 2.52 mA cm^(-2) at 1.23 VRHE,which is 2.4 times higher than bare photoanode(1.04 mA cm^(-2)),with operational stability up to 100 h.Kinetic measurements indicate that pGO can promote charge transfer from TiFeO to the Co cubane catalyst.In contrast,SnOx reduces charge recombination at the interface between TiFeO and the fluorinated tin oxide substrate.In-situ infrared spectroscopy shows the formation of an O–O bonded intermediate during water oxidation.This study highlights the crucial role of incorporating dual charge-transfer mediators into photoelectrodes for efficient solar energy conversion.
基金financial support for the research and for the publication costs of the articlesupported by Santa Catarina State Research Support Foundation(FAPESC)National Council for Scientific and Technological Development(CNPq no 302903/2023-2).
文摘Cement production,while essential for global infrastructure,contributes significantly to carbon dioxide emissions,accounting for approximately 7%of total emissions.To mitigate these environmental impacts,flash calcination of kaolinitic clays has been investigated as a sustainable alternative.This technique involves the rapid heating of clays,enabling their use as supplementary cementitious materials.The primary objective of this study was to modify the color of calcined clay in various atmospheres(oxidizing,inert,and reducing)to achieve a grayish tone similar to commercial cement while preserving its reactive properties.The experimental procedure employed a tubular reactor with precise control of gas flows(atmospheric air,nitrogen,and a carbon monoxide–nitrogen mixture).Physicochemical characterization of the raw clay was conducted before calcination,with analyses repeated on the calcined clays following experimentation.Results indicated that clay calcined in an oxidizing atmosphere acquired a reddish hue,attributed to the oxidation of iron in hematite.The Clay exhibited a pinkish tone in an inert atmosphere,while calcination in a reducing atmosphere yielded the desired grayish color.Regarding pozzolanic activity,clays calcined in oxidizing and inert atmospheres displayed robust strength,ranging from 82%to 87%.Calcination in a reducing atmosphere resulted in slightly lower strength,around 74%,likely due to the clay’s chemical composition and the calcination process,which affects compound formation and material reactivity.
基金Project (20062026) supported by Natural Science Foundation of Liaoning Province, China
文摘Effects of stirring speed and time, pH and sodium oleate concentration on the shear hydrophobic flocculation of ultrafine Anshan hematite with sodium oleate as the surfactant were discussed. The results show that these parameters significantly affect the shear hydrophobic flocculation of ultrafine hematite. The optimum conditions for the flocculation are： stirring speed 1 400 r/min, flocculation time 20 min, pH 9 and sodium oleate concentration 3.94×10-4 mol/L; the flotation recovery of hematite flocs is remarkably high compared with non flocculated ultrafine hematite. According to the extended DLVO theory, the total interaction potential of Anshan ultrafine hematite was determined. The calculation results indicate that the hydrophobic flocculation state of the ultrafine hematite-sodium oleate system is mainly dominated by electric double layer repulsive interaction potential and hydrophobic interaction potential. A mechanical agitation is required to impart particles a kinetic energy to overcome potential barrier between them due to the existence of electric double layer repulsive interaction potential. Those particles further approach to form flocs due to the significant increase of the hydrophobic interaction potential.
基金Project (51074016) support by the National Natural Science Foundation of China
文摘High phosphorous oolitic hematite ore is one of typical intractable iron ores in China, and the conventional beneficiation methods are found to be impracticable to , remove phosphorus from the ore effectively. Better beneficiation index were gotten by direct reduction roasting with dephosphorization agent followed by two stages of grinding and magnetic separation. P content decreases from 0.82% in the raw ore to 0.06% in the magnetic concentrate, and the total iron grade increases from 43.65% to 90.23%, the recovery of iron can reach 87%. Mechanisms of phosphorus removal in the beneficiation of high phosphorous oolitic hematite ore by direct reduction roasting with dephosphorization agent were studied using XRD, SEM and EPMA. The results showed that about 20% of the apatite in the raw ore transferred into phosphorus and volatilized with the gas in the process of reduction roasting, while the rest 80% apatite was not involved in the reaction of generation of phosphorus, and remained as apatite in the roasted products, which was removed to tailings by grinding and magnetic separation. A small amount of phosphorus existed in the magnetic concentrate as apatite. The oolitic texture of raw ore was partly changed during roasting, resulting in the formation of nepheline in the reaction between the dephosphorization agent, SiO2 and Al2O3 in the raw ore, which greatly improved the liberation degree of minerals in the roasted products, and it was beneficial to the subsequent grinding and magnetic separation.
基金Project(50831006)supported by the National Natural Science Foundation of ChinaProject(2012BAB10B05)supported by the National Key Technologies R&D Program of China
文摘The population of surface broken bonds of some typical sulfide, oxide and salt-type minerals which may belong to cubic, tetragonal, hexagonal, or orthorhombic system, were calculated. In terms of the calculation results, the cleavage natures of these minerals were analyzed, and the relationship between surface broken bonds density and surface energy was also established. The results show that the surface broken bonds properties could be used to predict the cleavage nature of most of minerals, and the predicted cleavage planes agree well with those reported in previous literature. Moreover, this work explored a rule that, surface broken bonds density is directly related to surface energy with determination coefficient（R2） of over 0.8, indicating that the former is a dominant factor to determine the latter. Therefore, anisotropic surface broken bonds density can be used to predict the stability of mineral surface and the reactivity of surface atoms.
文摘The adsorption of sodium acetohydroxamate on the goethite or hematite surface was investi- gated by Fourier transform infrared spectroscopy （FT-IR）, X-ray photoemission spectroscopy and periodic plane-wave density functional theory （DFT） calculations. The core-level shifts and charge transfers of the adsorbed surface iron sites calculated by DFT with periodic in- terfacial structures were confronted to the X-ray photoemission experiments. FT-IR results reveal that the interracial structure of sodium acetohydroxamate adsorbed on the goethite or hematite surface may be assigned to a five-membered ring complex. In agreement with the adsorption energies determined by the DFT calculations, a five-membered ring complex is formed via bonding of one surface iron atom of goethite （101） or （100） to both oxygen atoms of hydroxamate group, and these two oxygen atoms of the hydroxamate group correspond- ingly attach to two neighboring iron atoms of the goethite surface. But a five-membered ring complex between two oxygen atoms of the hydroxamate group and one surface iron atom of hematite （001） is formed without any extra attachments. The calculated core-level shifts of Fe2p for the interracial structures are correspondingly in good agreement with the experimental observed one, which confirmed the reliability of the calculated results.
基金Project (2010FJ3069) supported by Science and Technology Project of Hunan Province, China
文摘The reverse flotation separation performance and mechanism of hematite and cellophane in the presence of RFP-138, a newly synthesized dephosphorization collector, were studied. Reverse flotation tests on monominerals and artificially mixed minerals of hematite and collophanite show that, this anionic collector performs excellently in reducing the phosphorus content in hematite. It can decrease the content of P in artificially mixed minerals from 1.05% to 0.12% and achieve the TFe recovery rate of 91.30%. The chemical behavior of solution and infrared spectra of RFP-138 were investigated to explore the selective collecting mechanism of RFP-138 to these two minerals.
基金Projects (2008BAB32B14, 2008BAB31B03) supported by the National Key Technology R&D Program of China Project (51004027) supported by the National Natural Science Foundation of China
文摘The collecting performances of N-dodecylethylene-diamine （ND） to quartz and hematite were studied via single mineral flotation. Experimental results show that ND has stronger collecting ability to quartz than hematite. Different floatability of quartz and hematite was presented in the existence of depressant. Compared with lauryl amine, ND has stronger collecting performances to quartz. Satisfied separation result of artificially mixed sample was acquired with iron grade of concentrate of 59.92% and iron recovery of 88.85% when pulp pH value was 7.27 with 41.7 mg/L collector and 3.33 mg/L starch. Polar group properties calculation results indicated that ND has stronger collecting capability and better selectivity than lauryl amine. Measurement results of zeta-potentials and infrared spectrum showed that hydrogen bonding adsorption and electrostatic adsorption occur between the surface of ND and quartz.
基金financially supported by the National Natural Science Foundation of China(Nos.51504053 and 51374079)the Fundamental Research Funds for the Central Universities(No.N170107013)
文摘Given the gradual increase in the chlorite content of hematite ores, pulp properties seriously deteriorate during flotation. The traditional anion reverse flotation of hematite cannot effectively eliminate the effects of chlorite, leading to a significant decrease in the total Fe(TFe) grade of the concentrate. In this work, the effect of sodium alginate on the reverse flotation of hematite was systematically investigated. Flotation tests of artificially mixed ores were conducted, and the results showed that sodium alginate can significantly improve the removal rates of quartz and chlorite. The adsorption measurements, infrared spectroscopy, and contact angle tests demonstrated that sodium alginate adsorbs on the quartz surface by chelating with calcium ions, thereby weakening the steric hindrance of oleate ions and increasing the adsorption capacity of sodium oleate to ultimately improve the removal rate of quartz. Furthermore, owing to its lower density and fine particle size, chlorite is easily entrained into the foam layer. Sodium alginate dramatically increases the liquid-to-gas ratio of the foam layer by increasing pulp viscosity, thereby increasing the entrainment rate of chlorite and finally improving its removal rate. The core content of this thesis bears significance in improving the Fe grade in the reverse flotation of chlorite-containing hematite.
基金the National Natural Science Foundation of China(Nos.51734005,51874071,and 51604063)the Fok Ying Tung Education Foundation for Young Teachers in the Higher Education Institutions of China(No.161045)+1 种基金the Liao Ning Revitalization Talents Program(No.XLYC1807111)the Fundamental Research Funds for the Central Universities of China(No.N180105030).
文摘The efficient development and utilization of high-phosphorus oolitic hematite is of great strategic significance for the sustainable supply of iron-ore resources in China.In this paper,the mechanism of high-temperature pretreatment for enhancing the effect of iron enrichment and dephosphorization in the magnetization roasting–leaching process was studied by X-ray diffraction(XRD),vibration sample magnetometer(VSM),scanning electron microscopy and energy dispersive spectrometry(SEM–EDS).Compared with the process without high-temperature pretreatment,the iron grade of the magnetic separation concentrate after high-temperature pretreatment had increased by 0.98%,iron recovery rate had increased by 1.33%,and the phosphorus content in the leached residue had decreased by 0.12%.High-temperature pretreatment resulted in the dehydration and decomposition of hydroxyapatite,the dehydration of limonite and the thermal decomposition of siderite,which can produce pores and cracks and weaken the compactness of the ore,improve the magnetization characteristics of roasted ore,and strengthen the iron enrichment and dephosphorization during the magnetization roasting and leaching process.
基金Project(51374239)supported by the National Natural Science Foundation of ChinaProject(201509048)supported by Environmental Protection’s Special Scientific Research for Chinese Public Welfare IndustryProject(2015CX001)supported by the Innovation-driven Plan in Central South University,China
文摘The reductive Bayer digestion by using iron powder as reductant is proposed to convert hematite to magnetite and further to dissociate iron minerals from sodium aluminosilicate hydrate(desilication product,DSP)based on the differences of their surface properties.The results show that the differences of surface properties between magnetite and DSP in zeta potential,wettability and solvation trend facilitate magnetite to agglomerate,grow up and thus to dissociate from DSP.The increments of reductant amount and alkali concentration favor the transformation of hematite in digestion with the relative alumina recovery of98.91%.Processing the resultant red mud can obtain qualified iron concentrate with iron grade of approximate60%and recovery of about86%through magnetic separation,resulting in reduction of red mud emission higher than70%.The results are potential to develop a novel technology for processing high iron diasporic bauxite efficiently and provide references for comprehensive utilization of high iron red mud.
基金Item Sponsored by National Natural Science Foundation of China(51074036)
文摘A laboratory experiment was carried out to extract iron from oolitic iron ore by a deep reduction and magnetic separation technique. The raw coal with fixed carbon of 66.54% was used as the reductant. The iron was successfully extracted from the oolitic iron ore which otherwise is nearly impossible to be separated due to its extremely fine-grain and mosaic nature. The results showed that an iron recovery rate of 90.78% and an iron content of 92.53~ of iron concentrate could be obtained by such a technique. The optimized roast temperature is 1 200℃ and time is 60 min. The subsequent magnetic separation was performed by using a magnetic field intensity of 111 kA · m^-1 and a grinding fineness less than 45 μm of 96. 19% for the sintered product.
文摘Magnetizing roasting of oolitic hematite ore from western Hubei Province was investigated.The mechanism for reduction roasting of oolitic hematite ore was discussed and analyzed.It is found that flash magnetizing roasting-magnetic separation process is a promising approach for the processing of oolitic hematite ore from western Hubei Province.
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Project(51374079) supported by the National Natural Science Foundation of China
文摘Reverse flotation technology is one of the most efficient ways to improve the quality and reduce impurity of iron concentrate. Mineral processors dealing with hematite face a challenge that the flotation results of reverse flotation of hematite are poor in presence of siderite using fatty acid as collector, starch as depressant of iron minerals and calcium ion as activator of quartz at strong alkaline pH. In this work, the effect of siderite on reverse anionic flotation of quartz from hematite was investigated. The effect mechanism of siderite on reverse flotation of hematite was studied by solution chemistry, ultraviolet spectrophotometry(UV) and Fourier transform infrared spectroscopy(FTIR). It was observed that siderite had strong depressive effect on quartz in flotation using sodium oleate as collector, corn starch as depressant of iron minerals and calcium chloride as activator of quartz at strong alkaline pH. The starch was adsorbed onto calcium carbonate by chemical reaction which was formed by CO^(2-)_3 from siderite dissolution and Ca^(2+) from calcium chloride as activator of quartz and precipitated on the surface of quartz, which resulted in improving the hydrophilic ability of quartz.
