Objective In recent years, the birth time and evolution of the Three Gorges, Yangtze River has become a focused topic. Different from previous studies, this study used provenance analysis of Quaternary sediments to di...Objective In recent years, the birth time and evolution of the Three Gorges, Yangtze River has become a focused topic. Different from previous studies, this study used provenance analysis of Quaternary sediments to discuss this question. Among those minerals in Quaternary sediments, magnetite was rarely studied. This paper presents element geochemistry and backscatter images of detrital magnetites from the Quaternary sediments in the Yichang area of Hubei Province. By discussing the provenance changes of detratic magnetites, we suggested the birth time of the Three Gorges of the Yangtze River.展开更多
In this work, the effect of Cu2+ on the structural and magnetic properties of samples of magnetite is addressed. Samples of magnetite, both pure and Cu2+ doped, Fe3-xCuxO4, with x = 0, 5, 10 and 20 atm.% were synthesi...In this work, the effect of Cu2+ on the structural and magnetic properties of samples of magnetite is addressed. Samples of magnetite, both pure and Cu2+ doped, Fe3-xCuxO4, with x = 0, 5, 10 and 20 atm.% were synthesized hydrothermally. The two-lattice method was employed to measure the Mossbauer recoilless fraction of magnetite relative to hematite (fmag/fhem) of the samples, looking for evidence of substitution of Fe2+ by Cu2+. The relative recoilless fraction measurements were performed by taking room temperature Mossbauer spectra of mixtures of each sample with analytical grade hematite. The Mossbauer measurements were complemented with Atomic Absorption Spectroscopy (AAS) and Energy Dispersive X-ray Spectroscopy (EDS). The analyses by AAS and EDS showed that the copper concentration in the final products increases with increasing the content of Cu2+ in the starting solutions. The Mossbauer analyses showed a linear decrease trend of the relative Mossbauer recoilless fraction with increasing concentration of Cu2+in the samples, as well as a reduction in the hyperfine magnetic field, which was more significant in the octahedral sites than tetrahedral sites. The broadening of the Mossbauer spectral lines was more significant for the octahedral sub spectrum than for the tetrahedral sub spectrum. Our study points that Cu2+ occupies preferentially the octahedral sites, where it substitutes Fe2+ species, generating broadening in the lines of the octahedral sub spectrum and a reduction in the probability of having nuclear resonant absorption of Mossbauer gamma rays in the samples.展开更多
The geochemistry of magnetite provides constraints on the source(s) of the magnetite and other ore minerals. In this study, we constructed a magnetite distribution map, compared the chemical composition of magnetite p...The geochemistry of magnetite provides constraints on the source(s) of the magnetite and other ore minerals. In this study, we constructed a magnetite distribution map, compared the chemical composition of magnetite present in hard rocks with that present in sand beach and stream deposits to determine magnetite’s provenance,investigated relationships among different trace elements,examined variations in the concentrations of trace elements present in magnetite, and identified the type of studied magnetite. Laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS) and inductively coupled plasma mass spectrometry/inductively coupled plasma atomic emission spectroscopy was used to analyze samples available in small and large amounts, respectively. The average magnetite compositions of beach and river samples were substantially similar to those of andesite rocks,revealing that the magnetite samples may have originated from surrounding andesite rocks;this finding is consistent with the chemical composition of the samples analyzed using LA-ICP-MS. Some of the andesite rocks found in the study area were the primary source of magnetite aggregations in the beach sands and stream sands near or slightly away from these rocks. High Ti–V magnetites lie within the fields of Fe–Ti–V bearing magnetite and titanomagnetite(ulv?spinel). These titanomagnetites may be undergoing transformation to spinel minerals such as galaxite,gahnite, magnesiochromite, and chromite, which are characterized by the high concentrations of Al, Ti, Mg, Cr,Ni, Mn, and Zn. The positive correlation between Fe and Ti, Cr and Ni, and also the negative correlation between Fe and Mg, Mn and Zn can be attributed to various magnetite phases present in the study area. V, Co, Mo, Nb, Ga, Sn,and Ta exhibited a positive correlation with Fe and a negative correlation with Al. The positive correlation between Fe and these elements indicates the enrichment of these elements in the magnetite series. We observed a negative correlation between Fe and Li, Rb, Ca, Ba, Sr, Cu,Cd, Sb, As, Sc, Y, REE, U, and Th. A positive correlation between Al and these elements indicates the enrichment of these elements in the spinel series.展开更多
Conductive materials(CM)can improve methane production(MP)efficiency in many methanogenic systems.However,several types of CM exist,and there are uncertainties regarding whether they all improve MP efficiency to the s...Conductive materials(CM)can improve methane production(MP)efficiency in many methanogenic systems.However,several types of CM exist,and there are uncertainties regarding whether they all improve MP efficiency to the same extent and modulate microbial communities in a similar way.To investigate that,different microbial enrichments with and without activated carbon(AC),magnetite(Mag),and zeolites(Zeo)(at 0.5 g/L)were developed.MP profiles and microbial composition changes were compared among enrichments.The behavior of all enrichments was different,although the initial inoculum sludge was the same.Lag phase duration was lower in AC enrichment,while the complete conversion of butyrate to methane was faster in Mag enrichment.Syntrophomonas was the most abundant bacterial genus in all enrichments,but changes in the methanogenic community were evident.Acetoclastic methanogens were more diverse in Mag enrichment,with microorganisms assigned to Methanosarcina and Methanothrix gener1,but Methanothrix was the only acetoclastic methanogen in the other enrichments.On the other hand,different species of hydrogenotrophic methanogens prevailed in distinct enrichments.The metatranscriptomics results revealed that the dominant mechanism of interspecies electron transfer in the AC enrichment utilized hydrogen as the electron carrier,and no evidences of direct interspecies electron transfer(DIET)could be found.These results showed how different CM modulate microbial communities and affect MP efficiency through mechanisms that do not necessarily involve DIET or mediation via CM.展开更多
The production of vanadium-titanium magnetite(VTM)pellets has the problems of low consolidation strength and high energy consumption in the preheating and roasting process.High-pressure grinding roll(HPGR)pretreatment...The production of vanadium-titanium magnetite(VTM)pellets has the problems of low consolidation strength and high energy consumption in the preheating and roasting process.High-pressure grinding roll(HPGR)pretreatment process was used to increase the fine-grained content and specific surface area of VTM concentrates,to strengthen the oxidation consolidation process of VTM pellets,and oxidation kinetic experiments were carried out.The results showed that the specific surface area of VTM concentrates was increased from 872 to 1457 cm^(2)/g by HPGR and then pelletising and roasting.With preheating at 1000℃ for 10 min and roasting at 1260℃ for 10 min,the strengths of preheated pellets were increased from 329 to 535 N,and the strengths of roasted pellets were increased from 1010 to 2591 N.The limiting link in the early stage of VTM pellets oxidation was the control of chemical reaction,while the limiting link in the later stage of oxidation was the mixed control of chemical reaction and gas diffusion.The activation energies of VTM pellets before and after HPGR pretreatment were 53.07 and 40.03 kJ/mol in the early stage of oxidation reaction,while the activation energies in the later stage of oxidation were 29.24 and 22.75 kJ/mol,respectively.展开更多
The novel process of hydrogen-based shaft furnaces(HSFs)has attracted considerable attention because of their significant reduction of CO_(2)emissions.In this study,the interaction of H_(2)and CO with Fe_(tet1)-and Fe...The novel process of hydrogen-based shaft furnaces(HSFs)has attracted considerable attention because of their significant reduction of CO_(2)emissions.In this study,the interaction of H_(2)and CO with Fe_(tet1)-and Fe_(oct2)-terminated Fe_(3)O_(4)(111)surfaces under HSF conditions,including their adsorption and reduction behaviors,was investigated using the density functional theory method.The results indicated that the H_(2)molecule adsorbed onto the Fe_(tet1)-terminated surface with an adsorption energy(AE)of-1.36 eV,whereas the CO molecule preferentially adsorbed on the Fe_(oct2)-terminated surface with an AE of-1.56 eV.Both H_(2)and CO can readily undergo reduction on the Fe_(tet1)-terminated surface(corresponding to energy barriers of 0.83 eV and 2.23 eV,respectively),but kinetically the reaction of H2is more favorable than that of CO.With regard to the thermodynamics at 400-1400 K,the H_(2)was easy to be adsorbed,while the CO would like to react on the Fe_(tet1)-terminated surface.These thermodynamically tendencies were reversed on the Fe_(oct2)-terminated surface.The thermodynamic disadvantage of the reaction of H_(2)on the Fe_(tet1)-terminated surface was offset by an increase in the temperature.Furthermore,the adsorption of H2 and CO on the Fe_(tet1)-terminated surface was competitive,whereas the adsorption of them on the Fe_(oct2)-terminated surface was synergistic.Therefore,iron ores with a higher proportion of Fe_(tet1)-terminated surface can be applied for the HSF process.In conjunction with the increases in the reduction temperature and the ratio of H_(2)in the reducing gas would promote efficient HSF smelting.These observations provide effective guidance for optimizing the practical operation parameters and advancing the development of the HSF process.展开更多
The steel industry’s transition to hydrogen-based ironmaking necessitates a deeper understanding of magnetite ore reduction,a crucial yet underexplored pathway for decarbonization.This study systematically investigat...The steel industry’s transition to hydrogen-based ironmaking necessitates a deeper understanding of magnetite ore reduction,a crucial yet underexplored pathway for decarbonization.This study systematically investigates the combined effects of particle size and gangue composition on hydrogen-based reduction behavior of four industrial magnetite ore concentrates with varying CaO and MgO con-tents.Thermogravimetric analysis at 973 K,interrupted reduction experiments,and post-reduction characterization steps are used to eval-uate reduction extent and phase transformations across different particle size fractions and bulk ores.The finer fractions generally exhibit faster and more complete reduction.However,this trend is overridden by gangue effects in certain ores.Magnetite ores with MgO as gangue tend to form magnesio-wustite solid solution(Mg,Fe)O during reduction,resulting in dense microstructures that impede hydrogen diffusion and limit reduction progress.In contrast,magnetite ores with CaO as gangue facilitate the formation of intermediate calcium fer-rites,which promote porous morphology and enhanced reducibility.Notably,even the finer particles of ore containing MgO show a lower reduction degree than the coarser particles of the ore containing CaO as gangue.This highlights the dominant role of gangue composition in governing reduction kinetics,intermediate phase formation and final product morphology.These findings contribute to the growing knowledge necessary to enable fossil-free ironmaking by emphasizing the importance of considering both granulometric characteristics and heterogeneity when evaluating magnetite ores for hydrogen-based reduction.展开更多
The equilibrium phase relations of the CaO–SiO_(2)–TiO_(2)–5wt%Fe_(3)O_(4)system were experimentally investigated at 1400℃ in air High-temperature equilibration-quenching techniques were employed in an electric Mo...The equilibrium phase relations of the CaO–SiO_(2)–TiO_(2)–5wt%Fe_(3)O_(4)system were experimentally investigated at 1400℃ in air High-temperature equilibration-quenching techniques were employed in an electric MoSi2resistance heated furnace,with phase composition analysis conducted using an electron probe microanalyzer and X-ray diffraction.A single liquid region,liquid–solid phase equilibria regions (including liquid–tridymite,liquid–rutile,liquid–perovskite,and liquid–wollastonite),and three-phase equilibria regions of liquid–tridymite–rutile and liquid–rutile–perovskite were found.The 1400℃ isothermal sections of the CaO-SiO_(2)-TiO_(2)-5wt%Fe_(3)O_(4)system in air were projected.The present experimental results exhibited good agreement with the calculation results obtained from FactSage.展开更多
To advance green ironmaking and expand the utilization of magnetite with complex gangues,the hydrogen reduction behavior and mechanisms of barite-containing magnetite pellets were investigated.The findings revealed th...To advance green ironmaking and expand the utilization of magnetite with complex gangues,the hydrogen reduction behavior and mechanisms of barite-containing magnetite pellets were investigated.The findings revealed that increasing barite led to the increased amount of Ba_(x)Fe_(3−x)O_(4)and Ba-containing silicates in oxidized pellets,which hindered the continuous crystallization of Fe_(2)O_(3).During the reduction process,the reduction of Ba_(x)Fe_(3−x)O_(4)to Ba and Fe by H_(2)was challenging,resulting in the formation of BaFeO_(2.64).Furthermore,Ba_(x)Fe_(3−x)O_(4)impeded the reaction between Fe_(2)O_(3)and H_(2),decreasing the reduction degree and metallization ratio of the pellets.Ba^(2+)diffused into the Fe_(2)O_(3)lattice during oxidation,stabilizing the crystal structure during the initial reduction stage(Fe_(2)O_(3)to Fe_(3)O_(4)).In the third reduction stage(Fe_(x)O to Fe),BaFeO_(2.64)inhibited the rapid precipitation of metallic iron,thus preventing the abnormal growth of iron whiskers.Consequently,BaSO_(4)reduced the reduction swelling index of barite-containing magnetite pellets in hydrogen.These findings offer a theoretical basis for the future implementation of barite-containing pellets in the hydrogen-based shaft furnace direct reduction process.展开更多
Cadmium(Cd)contamination of soil is a global environmental issue.Traditional remediation techniques such as immobilization,leaching,and phytoextraction have numerous shortcomings,which has led to growing interest in t...Cadmium(Cd)contamination of soil is a global environmental issue.Traditional remediation techniques such as immobilization,leaching,and phytoextraction have numerous shortcomings,which has led to growing interest in the development of low-cost,high-efficiency,and environmentally friendly agents for removing Cd from soil.In this study,four magnetite(Fe_(3)O_(4))/polyaniline(PANI)nanocomposites,Fe_(3)O_(4)(1.0)/PANI,Fe_(3)O_(4)(1.5)/PANI,Fe_(3)O_(4)(2.0)/PANI,and Fe_(3)O_(4)(2.5)/PANI,were developed using 4 mL aniline monomer and 1.0,1.5,2.0,and 2.5 g Fe_(3)O_(4),respectively,and used as remediation agents with magnetic separation and regeneration capabilities.The Cd adsorption isotherms showed a better fit to the Langmuir model,with Fe_(3)O_(4)(1.5)/PANI exhibiting the highest Cd adsorption capacity of 47.62 mg g^(-1) at 25℃.Then,Fe_(3)O_(4)(1.5)/PANI was used to remediate four Cd-contaminated soils typical in China(black,brown,cinnamon,and red),all with a Cd content of 180 mg kg^(-1) after spiking.The results showed that the total Cd removal efficiency was satisfactory at 25.25%–38.91%and the exchangeable Cd removal efficiency was 36.03%on average.In addition,soil basic properties did not show significant changes after remediation.Regarding the regeneration performance,a higher total Cd removal efficiency(27.89%–44.96%)was achieved after the first regeneration cycle of Fe_(3)O_(4)(1.5)/PANI.After two regeneration cycles,Fe_(3)O_(4)(1.5)/PANI exhibited decreased total Cd removal efficiency compared to after the first regeneration,but its efficiency remained above 95%of or higher than those of virgin Fe_(3)O_(4)(1.5)/PANI.The synthetic process of Fe_(3)O_(4)/PANI was simple and cost-effective,and Fe_(3)O_(4)/PANI exhibited a high Cd removal efficiency with easy recovery and recyclability.Therefore,Fe_(3)O_(4)/PANI is a promising solution for the sustainable and efficient remediation of Cd-contaminated soils,especially for the reclamation of highly contaminated development land.展开更多
Magnetic iron oxide nanoparticles(Fe_(x)O_(y) NPs,mainly Fe3O4 andγ-Fe2O_(3))are nanomaterials ubiquitously present in aquatic,terrestrial,and atmospheric environments,with a high prevalence and complex sources.Over ...Magnetic iron oxide nanoparticles(Fe_(x)O_(y) NPs,mainly Fe3O4 andγ-Fe2O_(3))are nanomaterials ubiquitously present in aquatic,terrestrial,and atmospheric environments,with a high prevalence and complex sources.Over the past decade,numerous reports have emerged on the presence of exogenous particles in human body,facilitated by the rapid development of separation and detection methods.The health risk associated with magnetic Fe_(x)O_(y) NP have garnered escalating attention due to their presence in human blood and brain tissues,especially for their potential association with neurodegenerative diseases like Alzheimer’s disease.In this paper,we provide a comprehensive overview of sources,analysis methods,environmental impacts,and health risks of magnetic Fe_(x)O_(y) NP.Currently,most researches are primarily based on engineered Fe_(x)O_(y) NP,while reports aboutmagnetic Fe_(x)O_(y) NP existing in real-world environments are still limited,especially for their occurrence levels in various environmental matrices,environmental transformation behavior,and biotoxic effects.Our study reviews this emerging pollutant,providing insights to address current research deficiencies and chart the course for future studies.展开更多
The effects of siderite,hematite,and goethite on pyrite reactions in sodium aluminate solution at high temperatures,based on the coexistence of pyrite and iron-bearing minerals in bauxite,were studied.The addition of ...The effects of siderite,hematite,and goethite on pyrite reactions in sodium aluminate solution at high temperatures,based on the coexistence of pyrite and iron-bearing minerals in bauxite,were studied.The addition of siderite,goethite,and hematite increases the concentrations of S_(2)O_(3)^(2−),SO_(3)^(2−)and SO_(4)^(2−),enhancing sulfur removal during desilication.Siderite and hematite facilitate nearly 100%magnetite formation from pyrite,whereas goethite leads to the formation of both hematite and magnetite from pyrite through a multiphase transformation process.Iron-bearing minerals significantly increase the iron content in residues and enhance iron recovery from the red mud.Siderite,goethite,and hematite produce a porous surface in the form of erosive holes due to electrochemical corrosion,improving reaction efficiency of pyrite.Additionally,electrochemical corrosion promotes the pyrite reaction in accordance with the Kröger and Ziegler models,controlled by interfacial diffusion and chemical reactions in the presence of siderite,hematite and magnetite.展开更多
Iron removal from zinc leachate in hydrometallurgy produces large volumes of low-grade,impurity-laden iron waste,posing significant environmental challenges.Magnetite precipitation offers a novel method for iron remov...Iron removal from zinc leachate in hydrometallurgy produces large volumes of low-grade,impurity-laden iron waste,posing significant environmental challenges.Magnetite precipitation offers a novel method for iron removal and resource recycling in zinc hydrometallurgy.However,the chemical similarity between ferrous and zinc ions,along with high zinc concentrations,causes zinc co-precipitation,challenging its application.To address this issue,this study utilized electron microscopy to observe key intermediate products in magnetite crystallization and employed EXAFS(extended X-ray absorption fine structure)to analyze their evolutionary mechanisms and zinc-binding configurations.The results indicate that the intermediate products during magnetite formation are sequentially green rust,feroxyhyte(δ-FeOOH),and weakly crystalline nanoparticles,and further analysis revealed that their transformation follows the dissolution-recrystallization mechanism.Furthermore,it was found that intermediate products such as green rust exhibit strong binding with zinc(via adsorption and lattice substitution),which was confirmed as a significant reason for the difficulty in separating zinc from magnetite.This study elucidates the transformation process of intermediate products during magnetite formation and,for the first time,reveals the binding configurations of zinc with these key intermediate products.This has significant implications for the development and optimization of new technologies for the efficient separation of iron and zinc during the magnetite precipitation process.展开更多
An approach for coal-based direct reduction of vanadium−titanium magnetite(VTM)raw ore was proposed.Under the optimal reduction conditions with reduction temperature of 1140℃,reduction time of 3 h,C-to-Fe molar ratio...An approach for coal-based direct reduction of vanadium−titanium magnetite(VTM)raw ore was proposed.Under the optimal reduction conditions with reduction temperature of 1140℃,reduction time of 3 h,C-to-Fe molar ratio of 1.2꞉1,and pre-oxidation temperature of 900℃,the iron metallization degree is 97.8%.Ultimately,magnetic separation yields an iron concentrate with an Fe content of 76.78 wt.%and efficiency of 93.41%,while the magnetic separation slag has a Ti grade and recovery of 9.36 wt.%and 87.07%,respectively,with a titanium loss of 12.93%.This new strategy eliminates the beneficiation process of VTM raw ore,effectively reduces the Ti content in the iron concentrate,and improves the comprehensive utilization of valuable metals.展开更多
The isothermal oxidation kinetics of vanadium–titanium magnetite(VTM)pellets prepared with 3Co-binder(coal-based colloidal composite binder)and F-binder(pulverized Funa binder)are compared.The oxidation process was a...The isothermal oxidation kinetics of vanadium–titanium magnetite(VTM)pellets prepared with 3Co-binder(coal-based colloidal composite binder)and F-binder(pulverized Funa binder)are compared.The oxidation process was analyzed using the first-order irreversible reaction,following the shrinking unreacted nucleus model.The results demonstrate that VTM pellets prepared with 3Co-binder exhibit a faster oxidation rate than those with F-binder across the temperatures ranging from 1073 to 1473 K.In both cases,the oxidation process was controlled by an interfacial chemical reaction during the pre-oxidation stage and by internal diffusion during the mid-oxidation stage.The type of binder did not influence the primary oxidation control mechanism of the VTM pellets.However,the apparent rate constants in the pre-oxidation stage and the internal diffusion coefficients in the mid-oxidation stage were higher for pellets with 3Co-binder compared to those with F-binder.The apparent activation energies for the 3Co-binder pellets were similar to those of bentonite,indicating favorable kinetic conditions without negative impacts on the oxidation process.Nonetheless,it is important to note that pellets with F-binder required a longer oxidation time than those with 3Co-binder.展开更多
A feasible criterion was established to determine the lower size limit of raw coal(d_(pRm))for efficient beneficiation in the air-fluidized bed with magnetite particles.The feasibility of using small magnetite particl...A feasible criterion was established to determine the lower size limit of raw coal(d_(pRm))for efficient beneficiation in the air-fluidized bed with magnetite particles.The feasibility of using small magnetite particles to accommodate the fine raw coal was demonstrated from the experimental perspective.The minimum size for the magnetite particles to be fluidized smoothly was clarified as 47.1μm,which corresponded to the border between Geldart-B and-A groups.Since the gangue and coal components in the raw coal were crushed into the same size,d_(pRm)depended on the greater one between d_(pGm)(minimum size required for the gangue particles to sink towards the bottom)and d_(pCm)(minimum size required for the coal particles to float towards the top).dpcm was determined as 259μm by supposing that provided the gangue particles accumulated in the lower half bed,they could be potentially extracted from the bottom.On the other hand,it was observed that the coal particles could always accumulate in the upper half bed.Under such circumstances,dpcm was revealed as 9.8μm since finer coal particles would be blown out by air before the 47.1μm sized magnetite particles became fluidized.Eventually,dpRm was clarified as 259μm,agreeing with the common view that raw coal coarser than 6 mm could be effectively beneficiated in the air-fluidized bed with magnetite particles.Additionally,the difficulty in beneficiating the fine raw coal was revealed to arise more from the remixing of sorted gangue particles than that of separated coal particles.展开更多
The factors affecting the oxidation degree of vanadium–titanium magnetite (VTM) pellets were analyzed via the isothermal oxidation experiment. Furthermore, the oxidation kinetics of VTM pellets were explored through ...The factors affecting the oxidation degree of vanadium–titanium magnetite (VTM) pellets were analyzed via the isothermal oxidation experiment. Furthermore, the oxidation kinetics of VTM pellets were explored through linear fitting to the kinetic equations based on the shrinking unreacted-core model. The results reveal that VTM pellets undergo oxidation in three distinct phases: pre-oxidation, mid-oxidation, and final stable phase. Notably, the mid-oxidation phase is absent in magnetite oxidation. The shrinking unreacted-core model has been proven to be suitable for modeling the process of oxidizing VTM pellets. In the pre-oxidation stage, the rate-controlling step is determined by both the oxidation temperature and the effective oxygen concentration. The influence of the effective oxygen concentration on the rate of oxidation is more pronounced at temperatures between 1073 and 1273 K, especially when the oxygen content falls below 15 vol.%. For the production of oxidized VTM pellets, it is necessary to maintain a preheating temperature above 1173 K (to accelerate the oxidation reaction) and below 1473 K (to prevent the swift formation of compact Fe2TiO5 at the shell of the pellet) in an oxygen-enriched atmosphere.展开更多
Many researchers have focused on the behavior of fiber-reinforced concrete(FRC)in the construction of various defensive structures to resist against impact forces resulting from explosions and projectiles.However,the ...Many researchers have focused on the behavior of fiber-reinforced concrete(FRC)in the construction of various defensive structures to resist against impact forces resulting from explosions and projectiles.However,the lack of sufficient research regarding the resistance of functionally graded fiber-reinforced concrete against projectile impacts has resulted in a limited understanding of the performance of this concrete type,which is necessary for the design and construction of structures requiring great resistance against external threats.Here,the performance of functionally graded fiber-reinforced concrete against projectile impacts was investigated experimentally using a(two-stage light)gas gun and a drop weight testing machine.For this objective,12 mix designs,with which 35 cylindrical specimens and 30 slab specimens were made,were prepared,and the main variables were the magnetite aggregate vol%(55%)replacing natural coarse aggregate,steel fiber vol%,and steel fiber type(3D and 5D).The fibers were added at six vol%of 0%,0.5%,0.75%,1%,1.25%,and 1.5%in 10 specimen series(three identical specimens per each series)with dimensions of 40×40×7.5 cm and functional grading(three layers),and the manufactured specimens were subjected to the drop weight impact and projectile penetration tests by the drop weight testing machine and gas gun,respectively,to assess their performance.Parameters under study included the compressive strength,destruction level,and penetration depth.The experimental results demonstrate that using the magnetite aggregate instead of the natural coarse aggregate elevated the compressive strength of the concrete by 61%.In the tests by the drop weight machine,it was observed that by increasing the total vol%of the fibers,especially by increasing the fiber content in the outer layers(impact surface),the cracking resistance and energy absorption increased by around 100%.Note that the fiber geometry had little effect on the energy absorption in the drop weight test.Investigating the optimum specimens showed that using 3D steel fibers at a total fiber content of 1 vol%,consisting of a layered grading of 1.5 vol%,0 vol%,and 1.5 vol%,improved the penetration depth by 76%and lowered the destruction level by 85%.In addition,incorporating the 5D steel fibers at a total fiber content of 1 vol%,consisting of the layered fiber contents of 1.5%,0%,and 1.5%,improved the projectile penetration depth by 50%and lowered the damage level by 61%compared with the case of using the 3D fibers.展开更多
In response to the new mechanism of direct vortex melting reduction of vanadium–titanium magnetite,the reaction control mechanism and the migration regularity of valuable components in the process of direct melting r...In response to the new mechanism of direct vortex melting reduction of vanadium–titanium magnetite,the reaction control mechanism and the migration regularity of valuable components in the process of direct melting reduction were investigated using kinetic empirical equation by fitting and combining with X-ray diffraction,X-ray fluorescence,scanning electron microscopy,energy-dispersive spectrometry,and optical microscopy.The results show that iron reduction is controlled by the mass transfer process of(FeOx)in the slag,while vanadium reduction is controlled by both the mass transfer of(VOx)in the slag and the mass transfer of[V]in the molten iron,and the slag–metal interfacial reaction is the only pathway for vanadium reduction.The reduction of iron and vanadium is an obvious first-order reaction,with activation energy of 101.6051 and 197.416 kJ mol^(−1),respectively.Increasing the vortex rate and reaction temperature is beneficial to improving the reaction rate and reduction efficiency.The mineral phase variation of iron and vanadium in the slag during the reduction process is Fe_(2)O_(3)→Fe_(3)O_(4)/FeV_(2)O_(4)→FeTiO_(3) and FeV_(2)O_(4)→MgV_(2)O_(5);titanium in slag is mainly in the form of Mg_(x)Ti_(3−x)O_(5)(0≤x≤1)and CaTiO_(3).As the reaction time went on,the molar ratio(nTi/nMg)in Mg_(x)Ti_(3−x)O_(5)(0≤x≤1)and the Ti2O_(3) content in the slag gradually went up,while the area proportion of Mg_(x)Ti_(3−x)O_(5)(0≤x≤1)went up and then down,and the porosity of the slag and the grain size of Mg_(x)Ti_(3−x)O_(5)(0≤x≤1)got smaller.展开更多
Although previous researchers have attempted to decipher ore genesis and mineralization in the Erdaokan Ag-Pb-Zn deposit,some uncertainties regarding the mineralization process and evolution of both ore-forming fluids...Although previous researchers have attempted to decipher ore genesis and mineralization in the Erdaokan Ag-Pb-Zn deposit,some uncertainties regarding the mineralization process and evolution of both ore-forming fluids and magnetite types still need to be addressed.In this study,we obtained new EPMA,LA-ICP-MS,and in situ Fe isotope data from magnetite from the Erdaokan deposit,in order to better understand the mineralization mechanism and evolution of both magnetite and the ore-forming fluids.Our results identified seven types of magnetite at Erdaokan:disseminated magnetite(Mag1),coarse-grained magnetite(Mag2a),radial magnetite(Mag2b),fragmented fine-grained magnetite(Mag2c),vermicular gel magnetite(Mag3a1 and Mag3a2),colloidal magnetite(Mag3b)and dark gray magnetite(Mag4).All of the magnetite types were hydrothermal in origin and generally low in Ti(<400 ppm)and Ni(<800 ppm),while being enriched in light Fe isotopes(δ^(56)Fe ranging from−1.54‰to−0.06‰).However,they exhibit different geochemical signatures and are thus classified into high-manganese magnetite(Mag1,MnO>5 wt%),low-silicon magnetite(Mag2a-c,SiO_(2)<1 wt%),high-silicon magnetite(Mag3a-b,SiO_(2)from 1 to 7 wt%)and high-silicon-manganese magnetite(Mag4,SiO_(2)>1 wt%,MnO>0.2 wt%),each being formed within distinct hydrothermal environments.Based on mineralogy,elemental geochemistry,Fe isotopes,temperature trends,TMg-mag and(Ti+V)vs.(Al+Mn)diagrams,we propose that the Erdaokan Ag-Pb-Zn deposit underwent multi-stage mineralization,which can be broken down into four stages and nine sub-stages.Mag1,Mag2a-c,Mag3a-b and Mag4 were formed during the first sub-stage of each of the four stages,respectively.Additionally,fluid mixing,cooling and depressurization boiling were identified as the main mechanisms for mineral precipitation.The enrichment of Ag was significantly enhanced by the superposition of multi-stage ore-forming hydrothermal fluids in the Erdaokan Ag-Pb-Zn deposit.展开更多
基金financially supported by the National Natural Science Foundation of China (grants No.41072083 and 4157209)
文摘Objective In recent years, the birth time and evolution of the Three Gorges, Yangtze River has become a focused topic. Different from previous studies, this study used provenance analysis of Quaternary sediments to discuss this question. Among those minerals in Quaternary sediments, magnetite was rarely studied. This paper presents element geochemistry and backscatter images of detrital magnetites from the Quaternary sediments in the Yichang area of Hubei Province. By discussing the provenance changes of detratic magnetites, we suggested the birth time of the Three Gorges of the Yangtze River.
文摘In this work, the effect of Cu2+ on the structural and magnetic properties of samples of magnetite is addressed. Samples of magnetite, both pure and Cu2+ doped, Fe3-xCuxO4, with x = 0, 5, 10 and 20 atm.% were synthesized hydrothermally. The two-lattice method was employed to measure the Mossbauer recoilless fraction of magnetite relative to hematite (fmag/fhem) of the samples, looking for evidence of substitution of Fe2+ by Cu2+. The relative recoilless fraction measurements were performed by taking room temperature Mossbauer spectra of mixtures of each sample with analytical grade hematite. The Mossbauer measurements were complemented with Atomic Absorption Spectroscopy (AAS) and Energy Dispersive X-ray Spectroscopy (EDS). The analyses by AAS and EDS showed that the copper concentration in the final products increases with increasing the content of Cu2+ in the starting solutions. The Mossbauer analyses showed a linear decrease trend of the relative Mossbauer recoilless fraction with increasing concentration of Cu2+in the samples, as well as a reduction in the hyperfine magnetic field, which was more significant in the octahedral sites than tetrahedral sites. The broadening of the Mossbauer spectral lines was more significant for the octahedral sub spectrum than for the tetrahedral sub spectrum. Our study points that Cu2+ occupies preferentially the octahedral sites, where it substitutes Fe2+ species, generating broadening in the lines of the octahedral sub spectrum and a reduction in the probability of having nuclear resonant absorption of Mossbauer gamma rays in the samples.
文摘The geochemistry of magnetite provides constraints on the source(s) of the magnetite and other ore minerals. In this study, we constructed a magnetite distribution map, compared the chemical composition of magnetite present in hard rocks with that present in sand beach and stream deposits to determine magnetite’s provenance,investigated relationships among different trace elements,examined variations in the concentrations of trace elements present in magnetite, and identified the type of studied magnetite. Laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS) and inductively coupled plasma mass spectrometry/inductively coupled plasma atomic emission spectroscopy was used to analyze samples available in small and large amounts, respectively. The average magnetite compositions of beach and river samples were substantially similar to those of andesite rocks,revealing that the magnetite samples may have originated from surrounding andesite rocks;this finding is consistent with the chemical composition of the samples analyzed using LA-ICP-MS. Some of the andesite rocks found in the study area were the primary source of magnetite aggregations in the beach sands and stream sands near or slightly away from these rocks. High Ti–V magnetites lie within the fields of Fe–Ti–V bearing magnetite and titanomagnetite(ulv?spinel). These titanomagnetites may be undergoing transformation to spinel minerals such as galaxite,gahnite, magnesiochromite, and chromite, which are characterized by the high concentrations of Al, Ti, Mg, Cr,Ni, Mn, and Zn. The positive correlation between Fe and Ti, Cr and Ni, and also the negative correlation between Fe and Mg, Mn and Zn can be attributed to various magnetite phases present in the study area. V, Co, Mo, Nb, Ga, Sn,and Ta exhibited a positive correlation with Fe and a negative correlation with Al. The positive correlation between Fe and these elements indicates the enrichment of these elements in the magnetite series. We observed a negative correlation between Fe and Li, Rb, Ca, Ba, Sr, Cu,Cd, Sb, As, Sc, Y, REE, U, and Th. A positive correlation between Al and these elements indicates the enrichment of these elements in the spinel series.
基金supported by the Portuguese Foundation for Science and Technology(FCT)under the scope of the strategic funding of UIDB/04469/2020 unit and by the CM4Methane project(Ref:PTDC/BTA-BTA/2249/2021,DOI 10.54499/PTDC/BTABTA/2249/2021)FCT and European Union(EU),through the Portuguese State Budget and the European Social Fund under the scope of Norte2020-Programa Operacional Regional do Norte,also funded the SFRH/BD/132003/2017 and COVID/BD/152431/2022 grants held by Cátia S.N.Braga.,and the SFRH/BD/147271/2019 grant held by João C.Sequeira.M.SaloméDuarte acknowledges FCT for the Junior Research contract obtained under the scope of the Scientific Stimulus Employment 2022(ref:2022.06569.CEECIND/CP1718/CT0004,doi:https://doi.org/10.54499/2022.06569.CEECIND/CP1718/CT0004)PhD M.Fernando R.Pereira and PhD O.SaloméG.Soares from the Laboratory of Separation and Reaction Engineering-Laboratory of Catalysis and Materials,Faculty of Engineering(University of Porto),for providing the AC used in this study.
文摘Conductive materials(CM)can improve methane production(MP)efficiency in many methanogenic systems.However,several types of CM exist,and there are uncertainties regarding whether they all improve MP efficiency to the same extent and modulate microbial communities in a similar way.To investigate that,different microbial enrichments with and without activated carbon(AC),magnetite(Mag),and zeolites(Zeo)(at 0.5 g/L)were developed.MP profiles and microbial composition changes were compared among enrichments.The behavior of all enrichments was different,although the initial inoculum sludge was the same.Lag phase duration was lower in AC enrichment,while the complete conversion of butyrate to methane was faster in Mag enrichment.Syntrophomonas was the most abundant bacterial genus in all enrichments,but changes in the methanogenic community were evident.Acetoclastic methanogens were more diverse in Mag enrichment,with microorganisms assigned to Methanosarcina and Methanothrix gener1,but Methanothrix was the only acetoclastic methanogen in the other enrichments.On the other hand,different species of hydrogenotrophic methanogens prevailed in distinct enrichments.The metatranscriptomics results revealed that the dominant mechanism of interspecies electron transfer in the AC enrichment utilized hydrogen as the electron carrier,and no evidences of direct interspecies electron transfer(DIET)could be found.These results showed how different CM modulate microbial communities and affect MP efficiency through mechanisms that do not necessarily involve DIET or mediation via CM.
基金supports provided from Guangxi Science and Technology Major Project(AA24263047).
文摘The production of vanadium-titanium magnetite(VTM)pellets has the problems of low consolidation strength and high energy consumption in the preheating and roasting process.High-pressure grinding roll(HPGR)pretreatment process was used to increase the fine-grained content and specific surface area of VTM concentrates,to strengthen the oxidation consolidation process of VTM pellets,and oxidation kinetic experiments were carried out.The results showed that the specific surface area of VTM concentrates was increased from 872 to 1457 cm^(2)/g by HPGR and then pelletising and roasting.With preheating at 1000℃ for 10 min and roasting at 1260℃ for 10 min,the strengths of preheated pellets were increased from 329 to 535 N,and the strengths of roasted pellets were increased from 1010 to 2591 N.The limiting link in the early stage of VTM pellets oxidation was the control of chemical reaction,while the limiting link in the later stage of oxidation was the mixed control of chemical reaction and gas diffusion.The activation energies of VTM pellets before and after HPGR pretreatment were 53.07 and 40.03 kJ/mol in the early stage of oxidation reaction,while the activation energies in the later stage of oxidation were 29.24 and 22.75 kJ/mol,respectively.
基金financially supported by the Key Program of National Natural Science Foundation of China(No.U23A20608)the Liaoning Province Science and Technology Plan Joint Program(Key Research and Development Program Project),China(No.2023JH2/101800058)+3 种基金the Science&Technology Plan Project of Hebei Province,China(No.23314601L)the Project of Hydrogen-Based Shaft Furnace Reduction-Electric Furnace Melting And Separation Technology Research and Application for High-Titanium Magnetite Iron Ore(No.HG2023239)the General Program of National Natural Science Foundation of China(No.52274253)the Special Project for Major Scientific and Technological Achievements Transformation in Hebei Province,China(No.23284101Z)。
文摘The novel process of hydrogen-based shaft furnaces(HSFs)has attracted considerable attention because of their significant reduction of CO_(2)emissions.In this study,the interaction of H_(2)and CO with Fe_(tet1)-and Fe_(oct2)-terminated Fe_(3)O_(4)(111)surfaces under HSF conditions,including their adsorption and reduction behaviors,was investigated using the density functional theory method.The results indicated that the H_(2)molecule adsorbed onto the Fe_(tet1)-terminated surface with an adsorption energy(AE)of-1.36 eV,whereas the CO molecule preferentially adsorbed on the Fe_(oct2)-terminated surface with an AE of-1.56 eV.Both H_(2)and CO can readily undergo reduction on the Fe_(tet1)-terminated surface(corresponding to energy barriers of 0.83 eV and 2.23 eV,respectively),but kinetically the reaction of H2is more favorable than that of CO.With regard to the thermodynamics at 400-1400 K,the H_(2)was easy to be adsorbed,while the CO would like to react on the Fe_(tet1)-terminated surface.These thermodynamically tendencies were reversed on the Fe_(oct2)-terminated surface.The thermodynamic disadvantage of the reaction of H_(2)on the Fe_(tet1)-terminated surface was offset by an increase in the temperature.Furthermore,the adsorption of H2 and CO on the Fe_(tet1)-terminated surface was competitive,whereas the adsorption of them on the Fe_(oct2)-terminated surface was synergistic.Therefore,iron ores with a higher proportion of Fe_(tet1)-terminated surface can be applied for the HSF process.In conjunction with the increases in the reduction temperature and the ratio of H_(2)in the reducing gas would promote efficient HSF smelting.These observations provide effective guidance for optimizing the practical operation parameters and advancing the development of the HSF process.
文摘The steel industry’s transition to hydrogen-based ironmaking necessitates a deeper understanding of magnetite ore reduction,a crucial yet underexplored pathway for decarbonization.This study systematically investigates the combined effects of particle size and gangue composition on hydrogen-based reduction behavior of four industrial magnetite ore concentrates with varying CaO and MgO con-tents.Thermogravimetric analysis at 973 K,interrupted reduction experiments,and post-reduction characterization steps are used to eval-uate reduction extent and phase transformations across different particle size fractions and bulk ores.The finer fractions generally exhibit faster and more complete reduction.However,this trend is overridden by gangue effects in certain ores.Magnetite ores with MgO as gangue tend to form magnesio-wustite solid solution(Mg,Fe)O during reduction,resulting in dense microstructures that impede hydrogen diffusion and limit reduction progress.In contrast,magnetite ores with CaO as gangue facilitate the formation of intermediate calcium fer-rites,which promote porous morphology and enhanced reducibility.Notably,even the finer particles of ore containing MgO show a lower reduction degree than the coarser particles of the ore containing CaO as gangue.This highlights the dominant role of gangue composition in governing reduction kinetics,intermediate phase formation and final product morphology.These findings contribute to the growing knowledge necessary to enable fossil-free ironmaking by emphasizing the importance of considering both granulometric characteristics and heterogeneity when evaluating magnetite ores for hydrogen-based reduction.
基金financially supported from the National Natural Science Foundation of China (No. 52204310)the National Key Research and Development Program of China (No. 2021YFC2901000)+4 种基金the China Postdoctoral Science Foundation (Nos. 2020TQ0059 and 2020M570967)the Natural Science Foundation of Liaoning Province, China (No. 2021-MS-083)the Fundamental Research Funds for the Central Universities, China (No. N2125010)the Open Project Program of Key Laboratory of Metallurgical Emission Reduction & Resources Recycling (Anhui University of Technology), Ministry of Education, China (No. JKF22-02)the Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, China。
文摘The equilibrium phase relations of the CaO–SiO_(2)–TiO_(2)–5wt%Fe_(3)O_(4)system were experimentally investigated at 1400℃ in air High-temperature equilibration-quenching techniques were employed in an electric MoSi2resistance heated furnace,with phase composition analysis conducted using an electron probe microanalyzer and X-ray diffraction.A single liquid region,liquid–solid phase equilibria regions (including liquid–tridymite,liquid–rutile,liquid–perovskite,and liquid–wollastonite),and three-phase equilibria regions of liquid–tridymite–rutile and liquid–rutile–perovskite were found.The 1400℃ isothermal sections of the CaO-SiO_(2)-TiO_(2)-5wt%Fe_(3)O_(4)system in air were projected.The present experimental results exhibited good agreement with the calculation results obtained from FactSage.
基金Science and Technology Innovation Program of Hunan Province(Nos.2023RC1025,and 2024RC3022)the Basic Science Center Project(72088101)Major Scientific Research Projects(HKF202300356).
文摘To advance green ironmaking and expand the utilization of magnetite with complex gangues,the hydrogen reduction behavior and mechanisms of barite-containing magnetite pellets were investigated.The findings revealed that increasing barite led to the increased amount of Ba_(x)Fe_(3−x)O_(4)and Ba-containing silicates in oxidized pellets,which hindered the continuous crystallization of Fe_(2)O_(3).During the reduction process,the reduction of Ba_(x)Fe_(3−x)O_(4)to Ba and Fe by H_(2)was challenging,resulting in the formation of BaFeO_(2.64).Furthermore,Ba_(x)Fe_(3−x)O_(4)impeded the reaction between Fe_(2)O_(3)and H_(2),decreasing the reduction degree and metallization ratio of the pellets.Ba^(2+)diffused into the Fe_(2)O_(3)lattice during oxidation,stabilizing the crystal structure during the initial reduction stage(Fe_(2)O_(3)to Fe_(3)O_(4)).In the third reduction stage(Fe_(x)O to Fe),BaFeO_(2.64)inhibited the rapid precipitation of metallic iron,thus preventing the abnormal growth of iron whiskers.Consequently,BaSO_(4)reduced the reduction swelling index of barite-containing magnetite pellets in hydrogen.These findings offer a theoretical basis for the future implementation of barite-containing pellets in the hydrogen-based shaft furnace direct reduction process.
基金financially supported by the National Natural Science Foundation of China(No.41807116)the Natural Science Foundation of Fujian Province,China(Nos.2023J01418,2019J05035,and 2022N0024)+2 种基金the Scientific and Technological Innovation Project of China Metallurgical Geology Bureau(No.CMGBKY202301)the Independent Innovation Foundation of Tianjin University and Fuzhou University,China(No.TF2023-3)the Fuzhou University Testing Fund of Precious Apparatus,China(No.2023T014).
文摘Cadmium(Cd)contamination of soil is a global environmental issue.Traditional remediation techniques such as immobilization,leaching,and phytoextraction have numerous shortcomings,which has led to growing interest in the development of low-cost,high-efficiency,and environmentally friendly agents for removing Cd from soil.In this study,four magnetite(Fe_(3)O_(4))/polyaniline(PANI)nanocomposites,Fe_(3)O_(4)(1.0)/PANI,Fe_(3)O_(4)(1.5)/PANI,Fe_(3)O_(4)(2.0)/PANI,and Fe_(3)O_(4)(2.5)/PANI,were developed using 4 mL aniline monomer and 1.0,1.5,2.0,and 2.5 g Fe_(3)O_(4),respectively,and used as remediation agents with magnetic separation and regeneration capabilities.The Cd adsorption isotherms showed a better fit to the Langmuir model,with Fe_(3)O_(4)(1.5)/PANI exhibiting the highest Cd adsorption capacity of 47.62 mg g^(-1) at 25℃.Then,Fe_(3)O_(4)(1.5)/PANI was used to remediate four Cd-contaminated soils typical in China(black,brown,cinnamon,and red),all with a Cd content of 180 mg kg^(-1) after spiking.The results showed that the total Cd removal efficiency was satisfactory at 25.25%–38.91%and the exchangeable Cd removal efficiency was 36.03%on average.In addition,soil basic properties did not show significant changes after remediation.Regarding the regeneration performance,a higher total Cd removal efficiency(27.89%–44.96%)was achieved after the first regeneration cycle of Fe_(3)O_(4)(1.5)/PANI.After two regeneration cycles,Fe_(3)O_(4)(1.5)/PANI exhibited decreased total Cd removal efficiency compared to after the first regeneration,but its efficiency remained above 95%of or higher than those of virgin Fe_(3)O_(4)(1.5)/PANI.The synthetic process of Fe_(3)O_(4)/PANI was simple and cost-effective,and Fe_(3)O_(4)/PANI exhibited a high Cd removal efficiency with easy recovery and recyclability.Therefore,Fe_(3)O_(4)/PANI is a promising solution for the sustainable and efficient remediation of Cd-contaminated soils,especially for the reclamation of highly contaminated development land.
基金supported by the National Key R&D Program of China(No.2023YFC3708302)the National Natural Science Foundation of China(Nos.22188102 and 22306041)+1 种基金the Chinese Academy of Sciences Project for Young Scientists in Basic Research(No.YSBR-086)China Postdoctoral Science Foundation(No.2023M733679).
文摘Magnetic iron oxide nanoparticles(Fe_(x)O_(y) NPs,mainly Fe3O4 andγ-Fe2O_(3))are nanomaterials ubiquitously present in aquatic,terrestrial,and atmospheric environments,with a high prevalence and complex sources.Over the past decade,numerous reports have emerged on the presence of exogenous particles in human body,facilitated by the rapid development of separation and detection methods.The health risk associated with magnetic Fe_(x)O_(y) NP have garnered escalating attention due to their presence in human blood and brain tissues,especially for their potential association with neurodegenerative diseases like Alzheimer’s disease.In this paper,we provide a comprehensive overview of sources,analysis methods,environmental impacts,and health risks of magnetic Fe_(x)O_(y) NP.Currently,most researches are primarily based on engineered Fe_(x)O_(y) NP,while reports aboutmagnetic Fe_(x)O_(y) NP existing in real-world environments are still limited,especially for their occurrence levels in various environmental matrices,environmental transformation behavior,and biotoxic effects.Our study reviews this emerging pollutant,providing insights to address current research deficiencies and chart the course for future studies.
基金the National Key R&D Program of China(No.2022YFC2904404).
文摘The effects of siderite,hematite,and goethite on pyrite reactions in sodium aluminate solution at high temperatures,based on the coexistence of pyrite and iron-bearing minerals in bauxite,were studied.The addition of siderite,goethite,and hematite increases the concentrations of S_(2)O_(3)^(2−),SO_(3)^(2−)and SO_(4)^(2−),enhancing sulfur removal during desilication.Siderite and hematite facilitate nearly 100%magnetite formation from pyrite,whereas goethite leads to the formation of both hematite and magnetite from pyrite through a multiphase transformation process.Iron-bearing minerals significantly increase the iron content in residues and enhance iron recovery from the red mud.Siderite,goethite,and hematite produce a porous surface in the form of erosive holes due to electrochemical corrosion,improving reaction efficiency of pyrite.Additionally,electrochemical corrosion promotes the pyrite reaction in accordance with the Kröger and Ziegler models,controlled by interfacial diffusion and chemical reactions in the presence of siderite,hematite and magnetite.
基金Project(2022YFC3900200)supported by the Foundation for the National Key R&D Program of ChinaProjects(52404375,22276218)supported by the National Natural Science Foundation of ChinaProject(52121004)supported by the Innovative Research Groups of the National Natural Science Foundation of China。
文摘Iron removal from zinc leachate in hydrometallurgy produces large volumes of low-grade,impurity-laden iron waste,posing significant environmental challenges.Magnetite precipitation offers a novel method for iron removal and resource recycling in zinc hydrometallurgy.However,the chemical similarity between ferrous and zinc ions,along with high zinc concentrations,causes zinc co-precipitation,challenging its application.To address this issue,this study utilized electron microscopy to observe key intermediate products in magnetite crystallization and employed EXAFS(extended X-ray absorption fine structure)to analyze their evolutionary mechanisms and zinc-binding configurations.The results indicate that the intermediate products during magnetite formation are sequentially green rust,feroxyhyte(δ-FeOOH),and weakly crystalline nanoparticles,and further analysis revealed that their transformation follows the dissolution-recrystallization mechanism.Furthermore,it was found that intermediate products such as green rust exhibit strong binding with zinc(via adsorption and lattice substitution),which was confirmed as a significant reason for the difficulty in separating zinc from magnetite.This study elucidates the transformation process of intermediate products during magnetite formation and,for the first time,reveals the binding configurations of zinc with these key intermediate products.This has significant implications for the development and optimization of new technologies for the efficient separation of iron and zinc during the magnetite precipitation process.
基金funded by the National Natural Science Foundation of China(Nos.U20A20145,51774205)the Open Project from Engineering Research Center of the Ministry of Education,Sichuan University,China.
文摘An approach for coal-based direct reduction of vanadium−titanium magnetite(VTM)raw ore was proposed.Under the optimal reduction conditions with reduction temperature of 1140℃,reduction time of 3 h,C-to-Fe molar ratio of 1.2꞉1,and pre-oxidation temperature of 900℃,the iron metallization degree is 97.8%.Ultimately,magnetic separation yields an iron concentrate with an Fe content of 76.78 wt.%and efficiency of 93.41%,while the magnetic separation slag has a Ti grade and recovery of 9.36 wt.%and 87.07%,respectively,with a titanium loss of 12.93%.This new strategy eliminates the beneficiation process of VTM raw ore,effectively reduces the Ti content in the iron concentrate,and improves the comprehensive utilization of valuable metals.
基金supported by National Natural Science Foundation of China(No.52204302)Young Elite Scientist Sponsorship Program by CAST(No.YESS20220533)Hunan Provincial Natural Science Foundation of China(No.2022JJ40625).
文摘The isothermal oxidation kinetics of vanadium–titanium magnetite(VTM)pellets prepared with 3Co-binder(coal-based colloidal composite binder)and F-binder(pulverized Funa binder)are compared.The oxidation process was analyzed using the first-order irreversible reaction,following the shrinking unreacted nucleus model.The results demonstrate that VTM pellets prepared with 3Co-binder exhibit a faster oxidation rate than those with F-binder across the temperatures ranging from 1073 to 1473 K.In both cases,the oxidation process was controlled by an interfacial chemical reaction during the pre-oxidation stage and by internal diffusion during the mid-oxidation stage.The type of binder did not influence the primary oxidation control mechanism of the VTM pellets.However,the apparent rate constants in the pre-oxidation stage and the internal diffusion coefficients in the mid-oxidation stage were higher for pellets with 3Co-binder compared to those with F-binder.The apparent activation energies for the 3Co-binder pellets were similar to those of bentonite,indicating favorable kinetic conditions without negative impacts on the oxidation process.Nonetheless,it is important to note that pellets with F-binder required a longer oxidation time than those with 3Co-binder.
基金supported by Shandong Provincial Natural Science Foundation(ZR2023MB038)Youth Innovation Team Program of Shandong Higher Education Institution(2022KJ156)。
文摘A feasible criterion was established to determine the lower size limit of raw coal(d_(pRm))for efficient beneficiation in the air-fluidized bed with magnetite particles.The feasibility of using small magnetite particles to accommodate the fine raw coal was demonstrated from the experimental perspective.The minimum size for the magnetite particles to be fluidized smoothly was clarified as 47.1μm,which corresponded to the border between Geldart-B and-A groups.Since the gangue and coal components in the raw coal were crushed into the same size,d_(pRm)depended on the greater one between d_(pGm)(minimum size required for the gangue particles to sink towards the bottom)and d_(pCm)(minimum size required for the coal particles to float towards the top).dpcm was determined as 259μm by supposing that provided the gangue particles accumulated in the lower half bed,they could be potentially extracted from the bottom.On the other hand,it was observed that the coal particles could always accumulate in the upper half bed.Under such circumstances,dpcm was revealed as 9.8μm since finer coal particles would be blown out by air before the 47.1μm sized magnetite particles became fluidized.Eventually,dpRm was clarified as 259μm,agreeing with the common view that raw coal coarser than 6 mm could be effectively beneficiated in the air-fluidized bed with magnetite particles.Additionally,the difficulty in beneficiating the fine raw coal was revealed to arise more from the remixing of sorted gangue particles than that of separated coal particles.
基金supported by the National Natural Science Foundation of China(No.52204302)Young Elite Scientist Sponsorship Program by CAST(No.YESS20220533)+1 种基金Hunan Provincial Natural Science Foundation of China(No.2022JJ50274)China Baowu Low Carbon Metallurgy Innovation Foundation(No.BWLCF202103).
文摘The factors affecting the oxidation degree of vanadium–titanium magnetite (VTM) pellets were analyzed via the isothermal oxidation experiment. Furthermore, the oxidation kinetics of VTM pellets were explored through linear fitting to the kinetic equations based on the shrinking unreacted-core model. The results reveal that VTM pellets undergo oxidation in three distinct phases: pre-oxidation, mid-oxidation, and final stable phase. Notably, the mid-oxidation phase is absent in magnetite oxidation. The shrinking unreacted-core model has been proven to be suitable for modeling the process of oxidizing VTM pellets. In the pre-oxidation stage, the rate-controlling step is determined by both the oxidation temperature and the effective oxygen concentration. The influence of the effective oxygen concentration on the rate of oxidation is more pronounced at temperatures between 1073 and 1273 K, especially when the oxygen content falls below 15 vol.%. For the production of oxidized VTM pellets, it is necessary to maintain a preheating temperature above 1173 K (to accelerate the oxidation reaction) and below 1473 K (to prevent the swift formation of compact Fe2TiO5 at the shell of the pellet) in an oxygen-enriched atmosphere.
文摘Many researchers have focused on the behavior of fiber-reinforced concrete(FRC)in the construction of various defensive structures to resist against impact forces resulting from explosions and projectiles.However,the lack of sufficient research regarding the resistance of functionally graded fiber-reinforced concrete against projectile impacts has resulted in a limited understanding of the performance of this concrete type,which is necessary for the design and construction of structures requiring great resistance against external threats.Here,the performance of functionally graded fiber-reinforced concrete against projectile impacts was investigated experimentally using a(two-stage light)gas gun and a drop weight testing machine.For this objective,12 mix designs,with which 35 cylindrical specimens and 30 slab specimens were made,were prepared,and the main variables were the magnetite aggregate vol%(55%)replacing natural coarse aggregate,steel fiber vol%,and steel fiber type(3D and 5D).The fibers were added at six vol%of 0%,0.5%,0.75%,1%,1.25%,and 1.5%in 10 specimen series(three identical specimens per each series)with dimensions of 40×40×7.5 cm and functional grading(three layers),and the manufactured specimens were subjected to the drop weight impact and projectile penetration tests by the drop weight testing machine and gas gun,respectively,to assess their performance.Parameters under study included the compressive strength,destruction level,and penetration depth.The experimental results demonstrate that using the magnetite aggregate instead of the natural coarse aggregate elevated the compressive strength of the concrete by 61%.In the tests by the drop weight machine,it was observed that by increasing the total vol%of the fibers,especially by increasing the fiber content in the outer layers(impact surface),the cracking resistance and energy absorption increased by around 100%.Note that the fiber geometry had little effect on the energy absorption in the drop weight test.Investigating the optimum specimens showed that using 3D steel fibers at a total fiber content of 1 vol%,consisting of a layered grading of 1.5 vol%,0 vol%,and 1.5 vol%,improved the penetration depth by 76%and lowered the destruction level by 85%.In addition,incorporating the 5D steel fibers at a total fiber content of 1 vol%,consisting of the layered fiber contents of 1.5%,0%,and 1.5%,improved the projectile penetration depth by 50%and lowered the damage level by 61%compared with the case of using the 3D fibers.
基金supported by the National Natural Science Foundation of China(U1908225)the Fundamental Research Funds for Central Universities(N2225012 and N232405-06).
文摘In response to the new mechanism of direct vortex melting reduction of vanadium–titanium magnetite,the reaction control mechanism and the migration regularity of valuable components in the process of direct melting reduction were investigated using kinetic empirical equation by fitting and combining with X-ray diffraction,X-ray fluorescence,scanning electron microscopy,energy-dispersive spectrometry,and optical microscopy.The results show that iron reduction is controlled by the mass transfer process of(FeOx)in the slag,while vanadium reduction is controlled by both the mass transfer of(VOx)in the slag and the mass transfer of[V]in the molten iron,and the slag–metal interfacial reaction is the only pathway for vanadium reduction.The reduction of iron and vanadium is an obvious first-order reaction,with activation energy of 101.6051 and 197.416 kJ mol^(−1),respectively.Increasing the vortex rate and reaction temperature is beneficial to improving the reaction rate and reduction efficiency.The mineral phase variation of iron and vanadium in the slag during the reduction process is Fe_(2)O_(3)→Fe_(3)O_(4)/FeV_(2)O_(4)→FeTiO_(3) and FeV_(2)O_(4)→MgV_(2)O_(5);titanium in slag is mainly in the form of Mg_(x)Ti_(3−x)O_(5)(0≤x≤1)and CaTiO_(3).As the reaction time went on,the molar ratio(nTi/nMg)in Mg_(x)Ti_(3−x)O_(5)(0≤x≤1)and the Ti2O_(3) content in the slag gradually went up,while the area proportion of Mg_(x)Ti_(3−x)O_(5)(0≤x≤1)went up and then down,and the porosity of the slag and the grain size of Mg_(x)Ti_(3−x)O_(5)(0≤x≤1)got smaller.
基金financially supported by the Heilongjiang Provincial Key R&D Program Project(No.GA21A204)Heilongjiang Provincial Natural Science Foundation of China(No.LH2022D031)the Research Project of Heilongjiang Province Bureau of Geology and Mineral Resources(No.HKY202302).
文摘Although previous researchers have attempted to decipher ore genesis and mineralization in the Erdaokan Ag-Pb-Zn deposit,some uncertainties regarding the mineralization process and evolution of both ore-forming fluids and magnetite types still need to be addressed.In this study,we obtained new EPMA,LA-ICP-MS,and in situ Fe isotope data from magnetite from the Erdaokan deposit,in order to better understand the mineralization mechanism and evolution of both magnetite and the ore-forming fluids.Our results identified seven types of magnetite at Erdaokan:disseminated magnetite(Mag1),coarse-grained magnetite(Mag2a),radial magnetite(Mag2b),fragmented fine-grained magnetite(Mag2c),vermicular gel magnetite(Mag3a1 and Mag3a2),colloidal magnetite(Mag3b)and dark gray magnetite(Mag4).All of the magnetite types were hydrothermal in origin and generally low in Ti(<400 ppm)and Ni(<800 ppm),while being enriched in light Fe isotopes(δ^(56)Fe ranging from−1.54‰to−0.06‰).However,they exhibit different geochemical signatures and are thus classified into high-manganese magnetite(Mag1,MnO>5 wt%),low-silicon magnetite(Mag2a-c,SiO_(2)<1 wt%),high-silicon magnetite(Mag3a-b,SiO_(2)from 1 to 7 wt%)and high-silicon-manganese magnetite(Mag4,SiO_(2)>1 wt%,MnO>0.2 wt%),each being formed within distinct hydrothermal environments.Based on mineralogy,elemental geochemistry,Fe isotopes,temperature trends,TMg-mag and(Ti+V)vs.(Al+Mn)diagrams,we propose that the Erdaokan Ag-Pb-Zn deposit underwent multi-stage mineralization,which can be broken down into four stages and nine sub-stages.Mag1,Mag2a-c,Mag3a-b and Mag4 were formed during the first sub-stage of each of the four stages,respectively.Additionally,fluid mixing,cooling and depressurization boiling were identified as the main mechanisms for mineral precipitation.The enrichment of Ag was significantly enhanced by the superposition of multi-stage ore-forming hydrothermal fluids in the Erdaokan Ag-Pb-Zn deposit.
