Micro-and nano-to millimeter-scale magnetic matrix materials have gained widespread application due to their exceptional magnetic properties and favorable cost-effectiveness.With the rapid progress in condensed matter...Micro-and nano-to millimeter-scale magnetic matrix materials have gained widespread application due to their exceptional magnetic properties and favorable cost-effectiveness.With the rapid progress in condensed matter physics,materials science,and mineral separation technologies,these materials are now poised for new opportunities in theoretical research and development.This review provides a comprehensive analysis of these matrices,encompassing their structure,size,shape,composition,properties,and multifaceted applications.These materials,primarily composed of alloys of transition state metasl such as iron(Fe),cobalt(Co),titanium(Ti),and nickel(Ni),exhibit unique attributes like high magnetization rates,low eleastic modulus,and high saturation magnetic field strengths.Furthermore,the studies also delve into the complex mechanical interactions involved in the separation of magnetic particles using magnetic separator matrices,including magnetic,gravitational,centrifugal,and van der Waals forces.The review outlines how size and shape effects influence the magnetic behavior of matrices,offering new perspectives for innovative applications of magnetic matrices in various domains of materials science and magnetic separation.展开更多
The introduction of functionalized magnetizable particles and high-gradient magnetic separation represents a time and money saving alternative to conventional purification and separation unit operations in the biotech...The introduction of functionalized magnetizable particles and high-gradient magnetic separation represents a time and money saving alternative to conventional purification and separation unit operations in the biotechnical sector. This technique has some advantages especially for the recycling of immobilized enzymes. A new magnetic filter with sight glasses was constructed and produced to study the performance of high-gradient magnetic separation at varied parameters. By optical analysis the buildup of a clogging was identified as the major parameter which affected the separation performance. For the cleaning procedure, a two-phase flow of water with highly dispersed air bubbles was tested which led to a nearly complete cleaning of the filter chamber.展开更多
The changes of clay mineral association after high-gradient magnetic separation (HGMS) treatment, and the effects of chemical and physical technologies on concentrating Fe oxides for main soils in central and southern...The changes of clay mineral association after high-gradient magnetic separation (HGMS) treatment, and the effects of chemical and physical technologies on concentrating Fe oxides for main soils in central and southern China were investigated by means of X-ray diffraction (XRD) and chemical analysis methods. Results indicated that the concentrating times of Fe oxides by HGMS treatment were the largest for 0.2-2 μmsize fractions in the examined soils. For the soils in which 2: 1 phyllosilicates were dominant, concentrating times of iron oxides by HGMS treatment were larger than by 5 mol L-1 NaOH treatment. Phyllosili-cates were decreased after HGMS treatment; however, the decrease was less than that of kaorolinite. The goet bite / (goethite + hematie) values in Fe oxides of the soils kept virtually constant after HGMSt reatment.展开更多
The introduction of functionalized magnetizable particles for the purification of enzymes or for the multi-use of pre-immobilized biocatalysts offers a great potential for time and cost savings in biotechnological pro...The introduction of functionalized magnetizable particles for the purification of enzymes or for the multi-use of pre-immobilized biocatalysts offers a great potential for time and cost savings in biotechnological process design. The selective separation of the magnetizable particles is performed for example by a high-gradient magnetic separator. In this study FEM and CFD simulations of the magnetic field and the fluid flow field within a filter chamber of a magnetic separator were carried out, to find an optimal separator design. The motion of virtual magnetizable particles was calculated with a one-way coupled Lagrangian approach in order to test many geometric and parametric variations in reduced time. It was found that a flow homogenisator smoothed the fluid flow, so that the linear velocity became nearly equal over the cross section in the direction of flow. Furthermore the retention of magnetizable particles increases with a high total edge length within the filter matrix.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
Iron tailings are a common solid waste resource,posing serious environmental and spatial challenges.This study proposed a novel hydrogen-based reduction roasting(HRR)technology for the processing of iron tailings usin...Iron tailings are a common solid waste resource,posing serious environmental and spatial challenges.This study proposed a novel hydrogen-based reduction roasting(HRR)technology for the processing of iron tailings using a combined beneficiation and metallurgy approach.Pilot-cale experiment results indicated that under the gas composition of CO:H_(2)=1:3,and optimal roasting conditions at a reduction temperature of 520℃,the majority of weakly magnetic hematite transforms into strongly magnetic magnetite during the reduction process.Combining roasting products with a magnetic separation-grinding-magnetic selection process yields a final iron concentrate with a grade of 56.68%iron and a recovery rate of 86.54%.Theoretical calculations suggested the annual production value can reach 29.7 million USD and a reduction of 20.79 tons of CO_(2) emissions per year.This highlights that the use of HRR in conjunction with traditional beneficiation processes can effectively achieve comprehensive utilization of iron tailings,thereby reducing environmental impact.展开更多
A robust spontaneous exchange bias effect after zero-field cooling was observed in Co_(2)Sn_(1-x)Cr_(x)O_(4)system,which was driven by the transition from superspin-glass to superferromagnetic domain embedded in the f...A robust spontaneous exchange bias effect after zero-field cooling was observed in Co_(2)Sn_(1-x)Cr_(x)O_(4)system,which was driven by the transition from superspin-glass to superferromagnetic domain embedded in the ferrimagnetic matrix.Additionally,the exchange bias effect is gradually pronounced with the positive increase in the cooling field,known as the conventional exchange bias effect.However,as the cooling field gradually decreases and transits from positive to negative,the exchange bias effect can robustly remain positive in the low-negative-field region until the cooling field increases to be sufficiently large in the negative direction.展开更多
The obvious grain refinement of the primary MnSb phase has been observed in the Mn-89.7 wt%Sb alloy directionally solidified under a high-gradient magnetic field.With the application of a high-gradient magnetic field,...The obvious grain refinement of the primary MnSb phase has been observed in the Mn-89.7 wt%Sb alloy directionally solidified under a high-gradient magnetic field.With the application of a high-gradient magnetic field,the morphology of the primary MnSb phase transformed from developed dendritic-like to equiaxed-like,and the grain size decreased by approximately 93%.Refinement of the primary MnSb phase can be attributed to the constituent supercooling in front of the solidification interface,which promoted nucleation of the primary MnSb phase.The constituent supercooling can be linked to the enrichment of the Mn solute induced by the magnetic force and the Lorentz force that drove Mn solute migration and suppressed convection.展开更多
Microfluidic combined with magnetic field have been demonstrated to be the promising solutions for fast and low-damage particles separation.However,the difficulties in the precise layout of magnets and accurate predic...Microfluidic combined with magnetic field have been demonstrated to be the promising solutions for fast and low-damage particles separation.However,the difficulties in the precise layout of magnets and accurate prediction of particle trajectories lead to under and over separation of target particles.A novel particle separation lab-on-chip(LOC)prototype integrated with microstructures and micropolar arrays is designed and characterized.Meanwhile,a numerical model for the separation of magnetic particles by the synergistic effect of geometry-induced hydrodynamics and magnetic field is constructed.The effect of geometry and magnetic field layout on particle deflection is systematically analyzed to implement accurate prediction of particle trajectories.It is found that the separation efficiency of magnetic particles increased from 50.2%to 91.7%and decreased from 88.6%to 85.7%in the range of depth factors from 15µm to 27µm and width factors from 30µm to 60µm,respectively.In particular,the combined effect of the offset distance of permanent magnets and the distance from the main flow channel exhibits a significant difference from the conventional perception.Finally,the developed LOC prototype was generalized for extension to arbitrary systems.This work provides a new insight and robust method for the microfluidic separation of magnetic particles.展开更多
In order to utilize slag discarded by nickel plants, the selective recovery of nickel and copper versus iron was investigated by selective reduction, which was achieved by controlling the reduction parameters and magn...In order to utilize slag discarded by nickel plants, the selective recovery of nickel and copper versus iron was investigated by selective reduction, which was achieved by controlling the reduction parameters and magnetic separation process on bench scale. The results show that increasing the basicity （mass ratio of CaO to SIO2） of nickel slag facilitates the enrichment of nickel and copper The process parameters for selective reduction were optimized as follows： basicity of 0.15, reducing at 1200 ~C for 20 min, 5% coal on a dried slag mass base. The grinding-magnetic separation results of reduced briquettes show that concentrate containing 3.25%Ni, 1.20%Cu and 75.26%Fe is obtained and selective enrichment is achieved with a recovery of 82.20%, 80.00% for nickel and copper respectively, while the recovery of iron is only 42.17%. The S and P contents are not reduced obviously and further research may be needed to examine the behaviors of S and P in the process.展开更多
The magnetism of pentlandite surface was enhanced through the selective precipitation of micro-fine magnetite fractions on pentlandite surfaces. This was achieved through adjustment of slurry pH and addition of surfac...The magnetism of pentlandite surface was enhanced through the selective precipitation of micro-fine magnetite fractions on pentlandite surfaces. This was achieved through adjustment of slurry pH and addition of surfactants. The results showed that at pH 8.8 with the addition of 100 g/t sodium hexametaphosphate, 4.5 L/t oleic acid, and 4.5 L/t kerosene, significant amount of fine magnetite particles adhered to the pentlandite surface, while trace amount of coating was found on serpentine surfaces. Thus, the magnetism of pentlandite was enhanced and pentlandite was well separated from serpentine by magnetic separation under the magnetic field intensity of 200 kA/m. Scanning electron microscopy （SEM） and zeta potential measurement were performed to characterize changes of mineral surface properties. Calculations of the extended Derjaguin-Landau-Verwey-Ocerbeek （EDLVO） theory indicated that, in the presence of surfactants the total interaction energy between magnetite and pentlandite became stronger than that between magnetite and serpentine. This enabled the selective adhesion of magnetite particles to pentlandite surfaces, thereby enhancing its magnetism.展开更多
The reduction behaviors of FeO·V2O3 and FeO·Cr2O3 during coal-based direct reduction have a decisive impact on the efficient utilization of high-chromium vanadium-bearing titanomagnetite concentrates. The ef...The reduction behaviors of FeO·V2O3 and FeO·Cr2O3 during coal-based direct reduction have a decisive impact on the efficient utilization of high-chromium vanadium-bearing titanomagnetite concentrates. The effects of molar ratio of C to Fe n(C)/n(Fe) and temperature on the behaviors of vanadium and chromium during direct reduction and magnetic separation were investigated. The reduced samples were characterized by X-ray diffraction(XRD), scanning election microscopy(SEM) and energy dispersive spectrometry(EDS) techniques. Experimental results indicate that the recoveries of vanadium and chromium rapidly increase from 10.0% and 9.6% to 45.3% and 74.3%, respectively, as the n(C)/n(Fe) increases from 0.8 to 1.4. At n(C)/n(Fe) of 0.8, the recoveries of vanadium and chromium are always lower than 10.0% in the whole temperature range of 1100-1250 °C. However, at n(C)/n(Fe) of 1.2, the recoveries of vanadium and chromium considerably increase from 17.8% and 33.8% to 42.4% and 76.0%, respectively, as the temperature increases from 1100 °C to 1250 °C. At n(C)/n(Fe) lower than 0.8, most of the FeO·V2O3 and FeO·Cr2O3 are not reduced to carbides because of the lack of carbonaceous reductants, and the temperature has little effect on the reduction behaviors of FeO·V2O3 and FeO·Cr2O3, resulting in very low recoveries of vanadium and chromium during magnetic separation. However, at higher n(C)/n(Fe), the reduction rates of FeO·V2O3 and FeO·Cr2O3 increase significatly because of the excess amount of carbonaceous reductants. Moreover, higher temperatures largely induce the reduction of FeO·V2O3 and FeO·Cr2O3 to carbides. The newly formed carbides are then dissolved in the γ(FCC) phase, and recovered accompanied with the metallic iron during magnetic separation.展开更多
Magnetite concentrate was recovered from ferrous sulphate by co-precipitation and magnetic separation. In co-precipitation process, the effects of reaction conditions on iron recovery were studied, and the optimal rea...Magnetite concentrate was recovered from ferrous sulphate by co-precipitation and magnetic separation. In co-precipitation process, the effects of reaction conditions on iron recovery were studied, and the optimal reaction parameters are proposed as follows： n（CaO）/n（Fe2＋） 1.4：1, reaction temperature 80 ℃, ferrous ion concentration 0.4 mol/L, and the final mole ratio of Fe3＋ to FJ＋ in the reaction solution 1.9-2.1. In magnetic separation process, the effects of milling time and magnetic induction intensity on iron recovery were investigated. Wet milling played an important part in breaking the encapsulated magnetic phases. The results showed that the mixed product was wet-milled for 20 min before magnetic separation, the grade and recovery rate of iron in magnetite concentrate were increased from 51.41% and 84.15% to 62.05% and 85.35%, respectively.展开更多
The mainstream silver recovery has problems such as resource waste,weak silver selectivity,and complicated operation.Here,self-propelled magnetic enhanced capture hydrogel(magnetic NbFeB/MXene/GO,MNMGH)was prepared by...The mainstream silver recovery has problems such as resource waste,weak silver selectivity,and complicated operation.Here,self-propelled magnetic enhanced capture hydrogel(magnetic NbFeB/MXene/GO,MNMGH)was prepared by self-crosslinking encapsulation method.MNMGH achieved high selectivity(K_(d)=23.31 mL/g)in the acidic range,and exhibited ultrahigh silver recovery capacity(1604.8 mg/g),which greatly improved by 66%with the assistance of in-situ magnetic field.The recovered silver crystals could be directly physically exfoliated,without acid/base additions.The selective sieving effect of adsorption,MNMGH preferentially adsorbed Ag(I),and then selectively reduced to Ag(0),realizing dual-selective recovery.The in-situ magnetic field enhanced selective adsorption by enhancing mass transfer,reactivity of oxygen-containing functional groups.Furthermore,density function theory simulations demonstrated that the in-situ magnetic field could lower the silver reduction reaction energy barrier to enhance the selective reduction.Three-drive synergy system(reduction drive,adsorption drive and magnetic drive)achieved ultrahigh silver recovery performance.This study pioneered an in-situ magnetic field assisted enhancement strategy for dual-selective(adsorption/reduction)recovery of precious metal silver,which provided new idea for low-carbon recovery of noble metal from industrial waste liquids.展开更多
Owing to the worldwide trend towards carbon neutrality,the number of Dy-containing heat-resistant Nd magnets used for wind power generation and electric vehicles is expected to increase exponentially.However,rare eart...Owing to the worldwide trend towards carbon neutrality,the number of Dy-containing heat-resistant Nd magnets used for wind power generation and electric vehicles is expected to increase exponentially.However,rare earth(RE)elements(especially Dy)are unevenly distributed globally.Therefore,an environmental-friendly recycling method for RE elements with a highly precise separation of Dy and Nd from end-of-life magnets is required to realize a carbon-neutral society.As an alternative to traditional hydrometallurgical RE separation techniques with a high environmental load,we designed a novel,highly efficient,and precise process for the separation and recycling of RE elements from magnet scrap.As a result,over 90%of the RE elements were efficiently extracted from the magnets using MgCl_(2)and evaporation loss was selectively suppressed by adding CaF_(2).The extracted RE elements were electrolytically separated based on the formation potential differences of the RE alloys.Nd and Dy metals with purities greater than 90%were estimated to be recovered at rates of 96%and 91%,respectively.Almost all the RE in the scraps could be separated and recycled as RE metals,and the byproducts were easily removed.Thus,this process is expected to be used on an industrial scale to realize a carbon-neutral society.展开更多
The development of efficient photocatalysts is of paramount importance for the photocatalytic degradation of organic compounds.An effective approach is to construct heterojunctions with tight interface structures in o...The development of efficient photocatalysts is of paramount importance for the photocatalytic degradation of organic compounds.An effective approach is to construct heterojunctions with tight interface structures in order to enhance interfacial charge transfer and achieve high photocatalytic activity.A magnetically recyclable photocatalytic composite,comprising Ag_(3)PO_(4)/CoFe_(1.95)Dy_(0.05)O_(4)(AP/CFDO)S-scheme heterojunction,was synthesized using a simple hydrothermal method.The composition,microstructure and photoelectrochemical properties of the nanocomposites were comprehensively characterized by various advanced characterization methods.The photocatalytic activity of the AP/CFDO nanocomposites was investigated by subjecting methylene blue(MB)to degradation.The results demonstrated that AP/CFDO exhibited high degradation efficiency in the catalytic degradation of MB,with a degradation efficiency of 99.8%achieved within 30 min under visible light irradiation.Furthermore,after five repeated experiments,the degradation efficiency of MB under visible light irradiation remained at 90%.Furthermore,the degradation process followed the first-order kinetic reaction model,with a rate constant of 0.14042 min^(-1),which was 2.47 and 10.77 times that of Ag_(3)PO_(4)(AP,0.05678 min^(-1))and CFDO(0.01304 min^(-1)).This phenomenon can be attributed to the S-scheme heterojunction constructed between AP and CFDO,which enables the effective spatial separation and transfer of photogenerated carriers.Finally,the reaction mechanism of photocatalytic degradation of MB was studied by adding different free radical scavengers.The results of capture experiments showed that superoxide radicals and hydroxyl radicals were the main active substances in the process of photocatalytic degradation.展开更多
Oolitic iron ore is one of the most important iron resources. This paper reports the recovery of iron from high phosphorus oolitic iron ore using coal-based reduction and magnetic separation. The influences of reducti...Oolitic iron ore is one of the most important iron resources. This paper reports the recovery of iron from high phosphorus oolitic iron ore using coal-based reduction and magnetic separation. The influences of reduction temperature, reduction time, C/O mole ratio, and CaO content on the metallization degree and iron recovery were investigated in detail. Experimental results show that reduced products with the metallization degree of 95.82% could be produced under the optimal conditions （i.e., reduction temperature, 1250℃; reduction time, 50 min; C/O mole ratio, 2.0; and CaO content, 10wt%）. The magnetic concentrate containing 89.63wt% Fe with the iron recovery of 96.21% was obtained. According to the mineralogical and morphologic analysis, the iron minerals had been reduced and iron was mainly enriched into the metallic iron phase embedded in the slag matrix in the form of spherical particles. Apatite was also reduced to phosphorus, which partially migrated into the metallic iron phase.展开更多
Waste cutting emulsions are difficult to treat efficiently owing to their complex composition and stable emulsified structure.As an important treatment method for emulsions,chemical demulsification is faced with chall...Waste cutting emulsions are difficult to treat efficiently owing to their complex composition and stable emulsified structure.As an important treatment method for emulsions,chemical demulsification is faced with challenges such as low flocs-water separation rates and high sludge production.Hence,in this study,Fe3O4 magnetic nanoparticles(MNPs)were used to enhance chemical demulsification performance for treating waste cutting emulsions under a magnetic field.The addition of MNPs significantly decreased the time required to attain sludge-water separation and sludge compression equilibrium,from 210 to 20 min.In addition,the volume percentage of sludge produced at the equilibrium state was reduced from 45% to 10%.This excellent flocculation-separation performance was stable over a pH range of 3-11.The magnetization of the flocculants and oil droplets to form a flocculant-MNP-oil droplet composite,and the magnetic transfer of the composite were two key processes that enhanced the separation of cutting emulsions.Specifically,the interactions among MNPs,flocculants,and oil droplets were important in the magnetization process,which was controlled by the structures and properties of the three components.Under the magnetic field,the magnetized flocculant-MNP-oil droplet composites were considerably accelerated and separated from water,and the sludge was simultaneously compressed.Thus,this study expands the applicability of magnetic separation techniques in the treatment of complex waste cutting emulsions.展开更多
To achieve high efficiency utilization of Panzhihua vanadium titano-magnetite, a new process of metalizing reduction and magnetic separation based on hot briquetting is proposed, and factors that affect the cold stren...To achieve high efficiency utilization of Panzhihua vanadium titano-magnetite, a new process of metalizing reduction and magnetic separation based on hot briquetting is proposed, and factors that affect the cold strength of the hot-briquetting products and the efficiency of reduction and magnetic separation are successively investigated through laboratory experiments. The relevant mechanisms are elucidated on the basis of microstructural observations. Experimental results show that the optimal process parameters for hot briquetting include a hot briquetting temperature of 475°C, a carbon ratio of 1.2, ore and coal particle sizes of less than 74 μm. Additionally, with respect to metalizing reduction and magnetic separation, the rational parameters include a magnetic field intensity of 50 mT, a reduction temperature of 1350°C, a reduction time of 60 min, and a carbon ratio of 1.2. Under these above conditions, the crushing strength of the hot-briquetting agglomerates is 1480 N, and the recovery ratios of iron, vanadium, and titanium are as high as 91.19%, 61.82%, and 85.31%, respectively. The new process of metalizing reduction and magnetic separation based on hot briquetting demonstrates the evident technological advantages of high efficiency separation of iron from other valuable elements in the vanadium titano-magnetite.展开更多
A technique comprising coal-based direct reduction followed by magnetic separation was presented to recover iron and copper from copper slag flotation tailings.Optimal process parameters,such as reductant and additive...A technique comprising coal-based direct reduction followed by magnetic separation was presented to recover iron and copper from copper slag flotation tailings.Optimal process parameters,such as reductant and additive ratios,reduction temperature,and reduction time,were experimentally determined and found to be as follows：a limestone ratio of 25%,a bitumite ratio of 30%,and reduction roasting at 1473 Kfor 90 min.Under these conditions,copper-bearing iron powders（CIP）with an iron content of 90.11% and copper content of 0.86%,indicating iron and copper recoveries of87.25% and 83.44%respectively,were effectively obtained.Scanning electron microscopy and energy dispersive spectroscopy of the CIP revealed that some tiny copper particles were embedded in metal iron and some copper formed alloy with iron,which was difficult to achieve the separation of these two metals.Thus,the copper went into magnetic products by magnetic separation.Adding copper into the steel can produce weathering steel.Therefore,the CIP can be used as an inexpensive raw material for weathering steel.展开更多
基金Project(52174245)supported by the National Natural Science Foundation of ChinaProject(2021J01640)supported by the Natural Science Foundation of Fujian Province,ChinaProject(BGRIMM-KJSKL2022-03)supported by Open Foundation of the State Key Laboratory of Mineral Processing,China。
文摘Micro-and nano-to millimeter-scale magnetic matrix materials have gained widespread application due to their exceptional magnetic properties and favorable cost-effectiveness.With the rapid progress in condensed matter physics,materials science,and mineral separation technologies,these materials are now poised for new opportunities in theoretical research and development.This review provides a comprehensive analysis of these matrices,encompassing their structure,size,shape,composition,properties,and multifaceted applications.These materials,primarily composed of alloys of transition state metasl such as iron(Fe),cobalt(Co),titanium(Ti),and nickel(Ni),exhibit unique attributes like high magnetization rates,low eleastic modulus,and high saturation magnetic field strengths.Furthermore,the studies also delve into the complex mechanical interactions involved in the separation of magnetic particles using magnetic separator matrices,including magnetic,gravitational,centrifugal,and van der Waals forces.The review outlines how size and shape effects influence the magnetic behavior of matrices,offering new perspectives for innovative applications of magnetic matrices in various domains of materials science and magnetic separation.
文摘The introduction of functionalized magnetizable particles and high-gradient magnetic separation represents a time and money saving alternative to conventional purification and separation unit operations in the biotechnical sector. This technique has some advantages especially for the recycling of immobilized enzymes. A new magnetic filter with sight glasses was constructed and produced to study the performance of high-gradient magnetic separation at varied parameters. By optical analysis the buildup of a clogging was identified as the major parameter which affected the separation performance. For the cleaning procedure, a two-phase flow of water with highly dispersed air bubbles was tested which led to a nearly complete cleaning of the filter chamber.
文摘The changes of clay mineral association after high-gradient magnetic separation (HGMS) treatment, and the effects of chemical and physical technologies on concentrating Fe oxides for main soils in central and southern China were investigated by means of X-ray diffraction (XRD) and chemical analysis methods. Results indicated that the concentrating times of Fe oxides by HGMS treatment were the largest for 0.2-2 μmsize fractions in the examined soils. For the soils in which 2: 1 phyllosilicates were dominant, concentrating times of iron oxides by HGMS treatment were larger than by 5 mol L-1 NaOH treatment. Phyllosili-cates were decreased after HGMS treatment; however, the decrease was less than that of kaorolinite. The goet bite / (goethite + hematie) values in Fe oxides of the soils kept virtually constant after HGMSt reatment.
文摘The introduction of functionalized magnetizable particles for the purification of enzymes or for the multi-use of pre-immobilized biocatalysts offers a great potential for time and cost savings in biotechnological process design. The selective separation of the magnetizable particles is performed for example by a high-gradient magnetic separator. In this study FEM and CFD simulations of the magnetic field and the fluid flow field within a filter chamber of a magnetic separator were carried out, to find an optimal separator design. The motion of virtual magnetizable particles was calculated with a one-way coupled Lagrangian approach in order to test many geometric and parametric variations in reduced time. It was found that a flow homogenisator smoothed the fluid flow, so that the linear velocity became nearly equal over the cross section in the direction of flow. Furthermore the retention of magnetizable particles increases with a high total edge length within the filter matrix.
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.
基金National Natural Science Foundation of China(52104249)Liaoning Joint Fund General Support Program Project(2023-MSBA-126)the Fundamental Research Funds for the Central Universities(N2401019).
文摘Iron tailings are a common solid waste resource,posing serious environmental and spatial challenges.This study proposed a novel hydrogen-based reduction roasting(HRR)technology for the processing of iron tailings using a combined beneficiation and metallurgy approach.Pilot-cale experiment results indicated that under the gas composition of CO:H_(2)=1:3,and optimal roasting conditions at a reduction temperature of 520℃,the majority of weakly magnetic hematite transforms into strongly magnetic magnetite during the reduction process.Combining roasting products with a magnetic separation-grinding-magnetic selection process yields a final iron concentrate with a grade of 56.68%iron and a recovery rate of 86.54%.Theoretical calculations suggested the annual production value can reach 29.7 million USD and a reduction of 20.79 tons of CO_(2) emissions per year.This highlights that the use of HRR in conjunction with traditional beneficiation processes can effectively achieve comprehensive utilization of iron tailings,thereby reducing environmental impact.
基金financially supported by the National Natural Science Foundation of China(Nos.11474111 and 11604281)the Young Elite Scientists Sponsorship Program by CAST(No.YESS20220618)the Hundreds of Talents program of Sun Yat-sen University(No.210192)
文摘A robust spontaneous exchange bias effect after zero-field cooling was observed in Co_(2)Sn_(1-x)Cr_(x)O_(4)system,which was driven by the transition from superspin-glass to superferromagnetic domain embedded in the ferrimagnetic matrix.Additionally,the exchange bias effect is gradually pronounced with the positive increase in the cooling field,known as the conventional exchange bias effect.However,as the cooling field gradually decreases and transits from positive to negative,the exchange bias effect can robustly remain positive in the low-negative-field region until the cooling field increases to be sufficiently large in the negative direction.
基金supported by the National Key R&D Program of China(Grant No.2021YFB3501404)the fund of the State Key Laboratory of Solidification Processing in NWPU(Grant No.SKLSP202101).
文摘The obvious grain refinement of the primary MnSb phase has been observed in the Mn-89.7 wt%Sb alloy directionally solidified under a high-gradient magnetic field.With the application of a high-gradient magnetic field,the morphology of the primary MnSb phase transformed from developed dendritic-like to equiaxed-like,and the grain size decreased by approximately 93%.Refinement of the primary MnSb phase can be attributed to the constituent supercooling in front of the solidification interface,which promoted nucleation of the primary MnSb phase.The constituent supercooling can be linked to the enrichment of the Mn solute induced by the magnetic force and the Lorentz force that drove Mn solute migration and suppressed convection.
基金supported by the National Natural Science Foundation of China(Nos.11502044,U1906233)the Fundamental Research Funds for the Central Universities(No.DUT22JC08)+1 种基金the Liaoning Province's Xing Liao Talents Program(No.XLYC2002108)the Dalian City Supports Innovation and Entrepreneurship Projects for High-level Talents(No.2021RD16).
文摘Microfluidic combined with magnetic field have been demonstrated to be the promising solutions for fast and low-damage particles separation.However,the difficulties in the precise layout of magnets and accurate prediction of particle trajectories lead to under and over separation of target particles.A novel particle separation lab-on-chip(LOC)prototype integrated with microstructures and micropolar arrays is designed and characterized.Meanwhile,a numerical model for the separation of magnetic particles by the synergistic effect of geometry-induced hydrodynamics and magnetic field is constructed.The effect of geometry and magnetic field layout on particle deflection is systematically analyzed to implement accurate prediction of particle trajectories.It is found that the separation efficiency of magnetic particles increased from 50.2%to 91.7%and decreased from 88.6%to 85.7%in the range of depth factors from 15µm to 27µm and width factors from 30µm to 60µm,respectively.In particular,the combined effect of the offset distance of permanent magnets and the distance from the main flow channel exhibits a significant difference from the conventional perception.Finally,the developed LOC prototype was generalized for extension to arbitrary systems.This work provides a new insight and robust method for the microfluidic separation of magnetic particles.
基金Project([2009]606)supported by the National Development and Reform Commission of ChinaProject(50974135)supported by the National Natural Science Foundation of China
文摘In order to utilize slag discarded by nickel plants, the selective recovery of nickel and copper versus iron was investigated by selective reduction, which was achieved by controlling the reduction parameters and magnetic separation process on bench scale. The results show that increasing the basicity （mass ratio of CaO to SIO2） of nickel slag facilitates the enrichment of nickel and copper The process parameters for selective reduction were optimized as follows： basicity of 0.15, reducing at 1200 ~C for 20 min, 5% coal on a dried slag mass base. The grinding-magnetic separation results of reduced briquettes show that concentrate containing 3.25%Ni, 1.20%Cu and 75.26%Fe is obtained and selective enrichment is achieved with a recovery of 82.20%, 80.00% for nickel and copper respectively, while the recovery of iron is only 42.17%. The S and P contents are not reduced obviously and further research may be needed to examine the behaviors of S and P in the process.
基金Project(51574061)supported by the National Natural Science Foundation of ChinaProject(N150106004)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2014SKY-WK011)supported by the Open Fund Project of Shaanxi Key Laboratory of Comprehensive Utilization of Tailings Resources,China
文摘The magnetism of pentlandite surface was enhanced through the selective precipitation of micro-fine magnetite fractions on pentlandite surfaces. This was achieved through adjustment of slurry pH and addition of surfactants. The results showed that at pH 8.8 with the addition of 100 g/t sodium hexametaphosphate, 4.5 L/t oleic acid, and 4.5 L/t kerosene, significant amount of fine magnetite particles adhered to the pentlandite surface, while trace amount of coating was found on serpentine surfaces. Thus, the magnetism of pentlandite was enhanced and pentlandite was well separated from serpentine by magnetic separation under the magnetic field intensity of 200 kA/m. Scanning electron microscopy （SEM） and zeta potential measurement were performed to characterize changes of mineral surface properties. Calculations of the extended Derjaguin-Landau-Verwey-Ocerbeek （EDLVO） theory indicated that, in the presence of surfactants the total interaction energy between magnetite and pentlandite became stronger than that between magnetite and serpentine. This enabled the selective adhesion of magnetite particles to pentlandite surfaces, thereby enhancing its magnetism.
基金Projects(2013CB632601,2013CB632604)supported by the National Basic Research Program of ChinaProject(51125018)supported by the National Science Foundation for Distinguished Young Scholars of China+1 种基金Project(KGZD-EW-201-2)supported by the Key Research Program of the Chinese Academy of SciencesProjects(51374191,21106167,51104139)supported by the National Natural Science Foundation of China
文摘The reduction behaviors of FeO·V2O3 and FeO·Cr2O3 during coal-based direct reduction have a decisive impact on the efficient utilization of high-chromium vanadium-bearing titanomagnetite concentrates. The effects of molar ratio of C to Fe n(C)/n(Fe) and temperature on the behaviors of vanadium and chromium during direct reduction and magnetic separation were investigated. The reduced samples were characterized by X-ray diffraction(XRD), scanning election microscopy(SEM) and energy dispersive spectrometry(EDS) techniques. Experimental results indicate that the recoveries of vanadium and chromium rapidly increase from 10.0% and 9.6% to 45.3% and 74.3%, respectively, as the n(C)/n(Fe) increases from 0.8 to 1.4. At n(C)/n(Fe) of 0.8, the recoveries of vanadium and chromium are always lower than 10.0% in the whole temperature range of 1100-1250 °C. However, at n(C)/n(Fe) of 1.2, the recoveries of vanadium and chromium considerably increase from 17.8% and 33.8% to 42.4% and 76.0%, respectively, as the temperature increases from 1100 °C to 1250 °C. At n(C)/n(Fe) lower than 0.8, most of the FeO·V2O3 and FeO·Cr2O3 are not reduced to carbides because of the lack of carbonaceous reductants, and the temperature has little effect on the reduction behaviors of FeO·V2O3 and FeO·Cr2O3, resulting in very low recoveries of vanadium and chromium during magnetic separation. However, at higher n(C)/n(Fe), the reduction rates of FeO·V2O3 and FeO·Cr2O3 increase significatly because of the excess amount of carbonaceous reductants. Moreover, higher temperatures largely induce the reduction of FeO·V2O3 and FeO·Cr2O3 to carbides. The newly formed carbides are then dissolved in the γ(FCC) phase, and recovered accompanied with the metallic iron during magnetic separation.
基金Project(2013A090100013)supported by the Special Project on the Integration of Industry,Education and Research of Guangdong Province,ChinaProject(201407300993)supported by the High Technology Research and Development Program of Xinjiang Uygur Autonomous Region,China
文摘Magnetite concentrate was recovered from ferrous sulphate by co-precipitation and magnetic separation. In co-precipitation process, the effects of reaction conditions on iron recovery were studied, and the optimal reaction parameters are proposed as follows： n（CaO）/n（Fe2＋） 1.4：1, reaction temperature 80 ℃, ferrous ion concentration 0.4 mol/L, and the final mole ratio of Fe3＋ to FJ＋ in the reaction solution 1.9-2.1. In magnetic separation process, the effects of milling time and magnetic induction intensity on iron recovery were investigated. Wet milling played an important part in breaking the encapsulated magnetic phases. The results showed that the mixed product was wet-milled for 20 min before magnetic separation, the grade and recovery rate of iron in magnetite concentrate were increased from 51.41% and 84.15% to 62.05% and 85.35%, respectively.
基金supported by The National Natural Science Foundation of China(52170087,22276137).
文摘The mainstream silver recovery has problems such as resource waste,weak silver selectivity,and complicated operation.Here,self-propelled magnetic enhanced capture hydrogel(magnetic NbFeB/MXene/GO,MNMGH)was prepared by self-crosslinking encapsulation method.MNMGH achieved high selectivity(K_(d)=23.31 mL/g)in the acidic range,and exhibited ultrahigh silver recovery capacity(1604.8 mg/g),which greatly improved by 66%with the assistance of in-situ magnetic field.The recovered silver crystals could be directly physically exfoliated,without acid/base additions.The selective sieving effect of adsorption,MNMGH preferentially adsorbed Ag(I),and then selectively reduced to Ag(0),realizing dual-selective recovery.The in-situ magnetic field enhanced selective adsorption by enhancing mass transfer,reactivity of oxygen-containing functional groups.Furthermore,density function theory simulations demonstrated that the in-situ magnetic field could lower the silver reduction reaction energy barrier to enhance the selective reduction.Three-drive synergy system(reduction drive,adsorption drive and magnetic drive)achieved ultrahigh silver recovery performance.This study pioneered an in-situ magnetic field assisted enhancement strategy for dual-selective(adsorption/reduction)recovery of precious metal silver,which provided new idea for low-carbon recovery of noble metal from industrial waste liquids.
基金supported by a Grant-in-Aid from the Japan Society for the Promotion of Science(JSPS)Fellows(19J20301).
文摘Owing to the worldwide trend towards carbon neutrality,the number of Dy-containing heat-resistant Nd magnets used for wind power generation and electric vehicles is expected to increase exponentially.However,rare earth(RE)elements(especially Dy)are unevenly distributed globally.Therefore,an environmental-friendly recycling method for RE elements with a highly precise separation of Dy and Nd from end-of-life magnets is required to realize a carbon-neutral society.As an alternative to traditional hydrometallurgical RE separation techniques with a high environmental load,we designed a novel,highly efficient,and precise process for the separation and recycling of RE elements from magnet scrap.As a result,over 90%of the RE elements were efficiently extracted from the magnets using MgCl_(2)and evaporation loss was selectively suppressed by adding CaF_(2).The extracted RE elements were electrolytically separated based on the formation potential differences of the RE alloys.Nd and Dy metals with purities greater than 90%were estimated to be recovered at rates of 96%and 91%,respectively.Almost all the RE in the scraps could be separated and recycled as RE metals,and the byproducts were easily removed.Thus,this process is expected to be used on an industrial scale to realize a carbon-neutral society.
基金Supported by 2023 Anhui Modern Coal Processing Technology Research Institute Open Fund Project(MTY202305)。
文摘The development of efficient photocatalysts is of paramount importance for the photocatalytic degradation of organic compounds.An effective approach is to construct heterojunctions with tight interface structures in order to enhance interfacial charge transfer and achieve high photocatalytic activity.A magnetically recyclable photocatalytic composite,comprising Ag_(3)PO_(4)/CoFe_(1.95)Dy_(0.05)O_(4)(AP/CFDO)S-scheme heterojunction,was synthesized using a simple hydrothermal method.The composition,microstructure and photoelectrochemical properties of the nanocomposites were comprehensively characterized by various advanced characterization methods.The photocatalytic activity of the AP/CFDO nanocomposites was investigated by subjecting methylene blue(MB)to degradation.The results demonstrated that AP/CFDO exhibited high degradation efficiency in the catalytic degradation of MB,with a degradation efficiency of 99.8%achieved within 30 min under visible light irradiation.Furthermore,after five repeated experiments,the degradation efficiency of MB under visible light irradiation remained at 90%.Furthermore,the degradation process followed the first-order kinetic reaction model,with a rate constant of 0.14042 min^(-1),which was 2.47 and 10.77 times that of Ag_(3)PO_(4)(AP,0.05678 min^(-1))and CFDO(0.01304 min^(-1)).This phenomenon can be attributed to the S-scheme heterojunction constructed between AP and CFDO,which enables the effective spatial separation and transfer of photogenerated carriers.Finally,the reaction mechanism of photocatalytic degradation of MB was studied by adding different free radical scavengers.The results of capture experiments showed that superoxide radicals and hydroxyl radicals were the main active substances in the process of photocatalytic degradation.
基金supported by the National Natural Science Foundation of China(Nos.51134002 and 51074036)
文摘Oolitic iron ore is one of the most important iron resources. This paper reports the recovery of iron from high phosphorus oolitic iron ore using coal-based reduction and magnetic separation. The influences of reduction temperature, reduction time, C/O mole ratio, and CaO content on the metallization degree and iron recovery were investigated in detail. Experimental results show that reduced products with the metallization degree of 95.82% could be produced under the optimal conditions （i.e., reduction temperature, 1250℃; reduction time, 50 min; C/O mole ratio, 2.0; and CaO content, 10wt%）. The magnetic concentrate containing 89.63wt% Fe with the iron recovery of 96.21% was obtained. According to the mineralogical and morphologic analysis, the iron minerals had been reduced and iron was mainly enriched into the metallic iron phase embedded in the slag matrix in the form of spherical particles. Apatite was also reduced to phosphorus, which partially migrated into the metallic iron phase.
基金supported by the National Natural Science Foundation of China (Nos.51608375,51978490)the China Major Science and Technology Project of Water Pollution Control and Management,China (No.2017ZX07202-003).
文摘Waste cutting emulsions are difficult to treat efficiently owing to their complex composition and stable emulsified structure.As an important treatment method for emulsions,chemical demulsification is faced with challenges such as low flocs-water separation rates and high sludge production.Hence,in this study,Fe3O4 magnetic nanoparticles(MNPs)were used to enhance chemical demulsification performance for treating waste cutting emulsions under a magnetic field.The addition of MNPs significantly decreased the time required to attain sludge-water separation and sludge compression equilibrium,from 210 to 20 min.In addition,the volume percentage of sludge produced at the equilibrium state was reduced from 45% to 10%.This excellent flocculation-separation performance was stable over a pH range of 3-11.The magnetization of the flocculants and oil droplets to form a flocculant-MNP-oil droplet composite,and the magnetic transfer of the composite were two key processes that enhanced the separation of cutting emulsions.Specifically,the interactions among MNPs,flocculants,and oil droplets were important in the magnetization process,which was controlled by the structures and properties of the three components.Under the magnetic field,the magnetized flocculant-MNP-oil droplet composites were considerably accelerated and separated from water,and the sludge was simultaneously compressed.Thus,this study expands the applicability of magnetic separation techniques in the treatment of complex waste cutting emulsions.
基金financially supported by the National High-Tech Research and Development Program of China (No. 2012AA062302)the Major Program of the National Natural Science Foundation of China (No. 51090384)the Fundamental Research Funds of the Central Universities of China (No. N110202001)
文摘To achieve high efficiency utilization of Panzhihua vanadium titano-magnetite, a new process of metalizing reduction and magnetic separation based on hot briquetting is proposed, and factors that affect the cold strength of the hot-briquetting products and the efficiency of reduction and magnetic separation are successively investigated through laboratory experiments. The relevant mechanisms are elucidated on the basis of microstructural observations. Experimental results show that the optimal process parameters for hot briquetting include a hot briquetting temperature of 475°C, a carbon ratio of 1.2, ore and coal particle sizes of less than 74 μm. Additionally, with respect to metalizing reduction and magnetic separation, the rational parameters include a magnetic field intensity of 50 mT, a reduction temperature of 1350°C, a reduction time of 60 min, and a carbon ratio of 1.2. Under these above conditions, the crushing strength of the hot-briquetting agglomerates is 1480 N, and the recovery ratios of iron, vanadium, and titanium are as high as 91.19%, 61.82%, and 85.31%, respectively. The new process of metalizing reduction and magnetic separation based on hot briquetting demonstrates the evident technological advantages of high efficiency separation of iron from other valuable elements in the vanadium titano-magnetite.
基金the Natural Science Foundation of China(No.51304012)the State Key Laboratory of High-Efficient Mining and Safety of Metal Mines for the financial support for this research
文摘A technique comprising coal-based direct reduction followed by magnetic separation was presented to recover iron and copper from copper slag flotation tailings.Optimal process parameters,such as reductant and additive ratios,reduction temperature,and reduction time,were experimentally determined and found to be as follows：a limestone ratio of 25%,a bitumite ratio of 30%,and reduction roasting at 1473 Kfor 90 min.Under these conditions,copper-bearing iron powders（CIP）with an iron content of 90.11% and copper content of 0.86%,indicating iron and copper recoveries of87.25% and 83.44%respectively,were effectively obtained.Scanning electron microscopy and energy dispersive spectroscopy of the CIP revealed that some tiny copper particles were embedded in metal iron and some copper formed alloy with iron,which was difficult to achieve the separation of these two metals.Thus,the copper went into magnetic products by magnetic separation.Adding copper into the steel can produce weathering steel.Therefore,the CIP can be used as an inexpensive raw material for weathering steel.
