Magnetic Separation Experiments Research Articles

Magnetic γ-Fe2O3/Fe-doped hydroxyapatite nanostructures as high-efficiency cadmium adsorbents

Nowadays, water pollution by industrial waste water that contains heavy metal elements, such as Cd, has become an urgent concern to be solved. In this work, magnetic γ-Fe2O3/Fe-doped hydroxyapatite (HAP) nanostructures are realized as Cd(II) adsorbents with outstanding adsorption performance. The Vibrating Sample Magnetometer (VSM) analysis and magnetic separation experiments reveal that γ-Fe2O3/Fe-doped HAP nanostructures can be effectively separated by external magnet. Compared with pure HAP, the γ-Fe2O3/Fe-doped HAP nanostructures show higher adsorbed concentration and adsorption rate. The maximum adsorbed concentration at the equilibrium is 258 mg g−1 (under initial concentration of 500 mg L−1, temperature = 25 °C and pH = 5.0), which is higher than values reported for most of HAP-based adsorbents. The adsorption data could be well fitted by the Freundlich model, and the adsorption kinetic follows the pseudo-second-order model. Furthermore, the study of adsorption mechanism reveals that both ion-exchange and electrostatic interaction are involved in process of Cd(II) adsorption.

Recovery of iron and lead from a secondary lead smelter matte by magnetic separation

A secondary Pb smelter matte with a total Fe grade of ca. 50% (as FeS, Fe3O4, FeO and metallic Fe), shows good potential for being used as a secondary Fe source. However, requirements for Fe ore are: a total Fe grade >60% and a sulphur content as low as possible. Therefore, further treatment steps are necessary to increase the Fe content in the matte. Dry low intensity, wet low intensity and wet high intensity magnetic separation experiments were performed on different particle size fractions of the matte. Mineral liberation analysis (MLA) was performed to explain different behaviours of Pb in the different size fractions during magnetic separation. Moreover, oxidizing roasting at 600 °C was carried out to transform FeS to Fe2O3, which is the more prefered form of Fe for pig iron production. Results show that by combining low and high intensity magnetic separation and oxidizing roasting, material with a total Fe grade of 61% (as oxide) can be recovered in the magnetic fraction representing circa 50% of the initial weight of the sample. Moreover, the sulphur content was reduced from initial 20 to 4% in the final magnetic fraction. Further reduction in sulphur content would require an additional desulphurization step.

Fabrication of microencapsulated phase change materials with TiO2/Fe3O4 hybrid shell as thermoregulatory enzyme carriers: A novel design of applied energy microsystem for bioapplications

This article reported the design and fabrication of a novel applied energy microsystem based on magnetic microencapsulated phase change materials (PCMs) as thermoregulatory enzyme carriers for bioapplications. The PCM-containing microcapsules used as enzyme carriers were first synthesized through the Pickering emulsion templating self-assembly of Fe3O4 nanoparticles onto an n-eicosane core, followed by interfacial polycondensation of titania precursors to form a crystalline TiO2/Fe3O4 hybrid shell. The chemical compositions and crystalline structures of the hybrid shell were examined by energy-dispersive X-ray spectroscopy, X-ray photoelectron (XPS) spectroscopy and X-ray powder diffraction. The microcapsules were found to present a regular spherical morphology with a prefect core-shell structure on the basis of transmission and scanning electronic microscopic observations. Thermal analysis indicated that the microencapsulated n-eicosane not only revealed reliable phase-change performance with a thermal energy-storage efficiency of 53.56% but also exhibited a good thermoregulatory capability. Most of all, Candida rugosa lipase (CRL) was immobilized onto these microcapsules by covalent bonds, and such covalent bonding immobilization was further testified by Fourier–transform infrared spectroscopy and XPS spectroscopy. The separability of the CRL-immobilized microcapsules was determined by magnetic characterization along with a visible magnetic separation experiment. The effect of temperature on biocatalytic activity, storage stability, thermal stability and reusability of free and immobilized CRL were investigated. Compared to conventional TiO2 carriers, the immobilized CRL on the microcapsules designed by this study exhibited a higher biocatalytic activity, longer storage stability, higher thermal stability and better reusability due to the thermoregulatory effectiveness of n-eicosane core. This study may open up a novel direction for the development and applications of microencapsulated PCMs in biotechnological and bioengineering areas.

Magnetic Separation for Recovering Ni Compounds From Plating Waste With Use of HTS Bulk Magnets

A characteristic magnetic separation technique has been developed to recycle the Ni resource from the waste fluid of electroless Ni-plating processes. Since the plating waste still contains high concentration of Ni ions after several cycles of plating processes, the magnetic separation experiments were conducted to collect the precipitates containing Ni compounds. After extracting the fine NiHPO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> precipitate from the waste liquid, we synthesized the NiSO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> crystals from the NiHPO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> precipitates through the reaction with the concentrated sulfuric acid. The open-gradient magnetic separation was employed to separate the NiSO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> crystals from the mixed slurry composed of the NiSO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> and the NiHPO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> due to the difference between their magnetic properties. The experiments were practically conducted with use of the Gd123-based HTS bulk magnets with very steep gradient of magnetic field of over 100 T/m, which were activated to the magnetic fields of 1.53 and 1.95 T by the pulsed field magnetization process operated at 35 K. The ratio of NiSO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> content in the collected slurry attracted to the magnetic poles reached up to 98%, which suggests that the paramagnetic NiSO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> crystals are preferentially collected by the magnetic force from the mixed slurry in the strong magnetic field generated by the HTS bulk magnet.

Study on Volume Reduction of Cesium Contaminated Soil by Magnetic Separation

In this paper, we developed a new volume reduction method for contaminated soil by magnetic separation. We succeeded in selective separation of paramagnetic 2:1-type clay minerals, which strongly adsorb Cs, from 1:1-type clay minerals. As a result, it was shown that the radiation dose of 1:1-type clay minerals can be reduced. We examined magnetic separation conditions for efficient separation of 2:1-type clay minerals. First, the separation rate of each particle size of 2:1-type clay minerals was calculated by particle trajectory simulation because magnetic separation rate largely depends on the objective size. According to the calculation, 93.8% of 2:1-type of clay minerals could be separated at 7 T. Next, high-gradient magnetic separation experiment was conducted using superconducting magnet. Ninety-seven percent of 2:1-type clay minerals were separated under the condition of 7 T and 3 cm/s of flow rate. The separation experiment of 2:1-type clay minerals from the mixture of 1:1- and 2:1-type clay minerals was performed at 7 T. Ninety-seven percent of 2:1-type clay minerals were selectively separated from the model soil. It was shown that magnetic separation with superconducting magnet would contribute to the volume reduction of contaminated soil.

MLA-based partition curves for magnetic separation

Mineral liberation analysis (MLA) provides detailed information on the composition of single particles as well as particle populations exposed on the cross-sectioned surface of a grain mount. This information can be used to evaluate process efficiency related to the liberation distribution of valuables or to the distribution of a feature used for separation of valuable from barren particles. When separation processes are studied, the separation feature has to be added to the particle population data. In case of density separation (particle size and particle density) this is already been done by MLA software. For magnetic separation, however, the MLA data has to be combined with mineral susceptibilities using additional software.This contribution describes the calculation of partition curves for magnetic separation based on the liberation analysis of the feed and the products. Magnetic susceptibility data from measurements of pure minerals and from literature are combined with particle composition data from liberation analysis. Using sieved fractions in magnetic separation experiments the evolution of cut susceptibility and separation efficiency with particle size is studied. The effects of a stereological correction and of the width of susceptibility classes as well as of the mineral susceptibilities used in calculation are discussed.

Magnetic Field simulation and experimental tests of Special Cross-section Shape Matrices for High Gradient Magnetic Separation

The cross-sectional shape has great influence on the magnetic field characteristics of magnetic matrices in high gradient magnetic separation (HGMS). Suitable cross-sectional matrices can improve the recovery of fine weakly magnetic minerals and reduce mineral processing energy consumption. The performance of four types of cross-sectional shape matrices in the axial configuration of HGMS was studied through numerical simulation combined with experimental tests. The magnetic field generated by the matrices was simulated with ANSYS software, and the magnetic field strength, gradient, and magnetic force were analyzed and compared. The simulation results showed that diamond shaped, elliptical, square, and circular steel matrices reach magnetization saturation successively with increasing the magnetic induction, and the required magnetic induction is approximately 0.7, 0.8, 1, and 1.1 T, respectively. The magnetic field gradient increases with increasing the magnetic induction and then keeps constant when the matrices reach magnetization saturation. Within a wide range of the magnetic induction, the elliptical and square matrices present good magnetic field characteristics. The magnetic force near the surface of the square matrices is the largest but decreases rapidly and consequently has a small effect depth. The magnetic force near the surface of the elliptical matrices is relatively lower but decreases slowly and has a larger effect depth. The diamond-shaped matrices are easy to reach magnetization saturation, and the magnetic force decreases most rapidly. Magnetic matrices were manufactured, and magnetic separation experiments were conducted to verify the simulation results. The experimental results show that the elliptical and square matrices can obtain higher recovery in a wide range of magnetic induction, and the recovery of the elliptical matrices is the highest. The experimental results correspond well with the numerical simulation results, and the results indicate that the magnetic force effect depth is a very important factor influencing the performance of the matrices.

Nanocomposites of Magnetite and Layered Double Hydroxide for Recyclable Chromate Removal

Nanocomposites containing magnetic iron oxide (magnetite) nanoparticles and layered double hydroxide (LDH) nanosheets were prepared by two different methods, exfoliation-reassembly and coprecipitation, for aqueous chromate adsorbent. According to X-ray diffraction, scanning electron microscopy, and atomic force microscopy, both nanocomposites were determined to develop different nanostructures; LDH nanosheets well covered magnetite nanoparticles with house-of-cards-like structure in exfoliation-reassembly method, while coprecipitation resulted in LDH particle formation along with magnetite nanoparticles. Zeta-potential measurement also revealed that the magnetite surface was effectively covered by LDH moiety in exfoliation-reassembly compared with coprecipitation. Time, pH, concentration dependent chromate adsorption tests, and magnetic separation experiments exhibited that both nanocomposites effectively adsorb and easily collect chromate. However, exfoliation-reassembly nanocomposite was determined to be slightly effective in chromate removal by ~10%. Chromate adsorbed nanocomposites could be regenerated by treating with bicarbonate and the regenerated nanocomposites preserved ~80% of chromate adsorption efficacy after three times of recycling.

Study on Recovering Iron from Shandong Red Mud Based on Gas Reduction Reaction

Based on Shandong Renping Bayer red mud as the raw material, analyzing its basic characteristics, the result is that the content of total iron in red mud is 29.55%. Gas-based high-temperature direct reduction experiments are made by using a gas mixture of CO and H2O as a reducing agent. And then the reduction effect was investigated by magnetic separation experiments, to realize that separation of iron minerals from red mud. The results show that the consequent of the magnetic separation is improved obviously with the temperature rising. Under these conditions, namely, the roasting temperature being 1050°C, the roasting time lasting 90 minutes, the reduction gas rate being 0.7 m3/min, the magnetic field being 2.2A, and three magnetic separations, the iron recovery ratio in red mud is over 97%.

A novel method of synthesizing cyclodextrin grafted multiwall carbon nanotubes/iron oxides and its adsorption of organic pollutant

A novel methodology for the synthesis of the multiwalled carbon nanotubes/iron oxides modified by β-cyclodextrin (denoted as MWCNTs/iron oxides/β-CD) was proposed using 1,6-diisocyanatohexane as cross-linker in N,N-dimethyl formamide, which avoided complex steps in the link of β-cyclodextrin and MWCNTs/iron oxides via conventional synthetic methods. The characteristic results of Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and thermogravimetric analysis (TGA) showed that β-CD was grafted onto the MWCNTs/iron oxides successfully. In addition, vibrating sample magnetometer (VSM) and magnetic separation experiment suggested that the prepared composite exhibited preferable magnetic property and good dispersion property in aqueous solution. The effects of contact time, initial adsorbent content, solution pH and temperature on the adsorption of p-nitrophenol (PNP) were studied systematically. The adsorption kinetics and equilibrium isotherms data fitted well with pseudo-second-order kinetic equation and Langmuir isotherm model, respectively. Furthermore, the adsorption-desorption experiment of PNP demonstrated that MWCNTs/iron oxides/β-CD is a cost-effective material with high regeneration efficiency.

Separation and Recovery of Phosphorus from P-bearing Steelmaking Slag

In order to recycle the phosphorus from P-bearing steelmaking slag, the influences of magnetic field intensities, slag particle sizes and slag compositions were investigated by magnetic separation experiments. SiO2, Al2O3 and TiO2 melting modification of converter slag was made respectively and phosphorus-rich phase was extracted by magnetic separation. The results show that MgO, MnO, Na2O and CaF2 have little effect on the phosphorus recovery, whereas the addition of SiO2, Al2O3, and TiO2 has great effect on phosphorus enrichment in slag and magnetic separation. With adding the reagent of SiO2, Al2O3 and TiO2, recycled non-magnetic substances are increased obviously and P2O5 content in non-magnetic substances and phosphorus recovery rate are also increased. The phosphorus recovery rates of modified slag No. 8 (SiO2 modification), slag No. 10 (Al2O3 modification) and slag No. 11 (TiO2 modification) are 84. 75%, 82. 16% and 74. 46%, respectively. Then, most of phosphorus was recycled.

Experimental Study on Magnetic Separation of Oolitic Hematite Ore

To enhance effective use of resources, we use magnetic separation method on the experiment study of a refractory oolitic hematite ore. Research showed that: the grade of raw ore (TFe) was 47.44%, and magnetic iron grade (MFe) was 28.59%. Through magnetic separation experiment, three-step magnetic separation process was chosen. The magnetic field intensity (MFI) of three magnetic separation processes was 1200Oe800Oe400Oe, respectively. After first magnetic separation, the preliminary concentrates was reground to fineness of 87% (-500 mesh). Under the optimal experiment conditions, an iron ore concentrate with grade of 61.11% and a good recovery of 44.35% was obtained.

Collection of Ni-bearing material from electroless plating waste by magnetic separation with HTS bulk magnet

The magnetic separation experiment to collect the Ni compounds from the waste liquid of electroless plating processes was conducted in the open-gradient magnetic separation process with the high temperature superconducting bulk magnet system. The magnetic pole containing Gd-based bulk superconductors was activated to 3.45T at 35K in the static magnetic field of 5T with use of a superconducting solenoid magnet. The coarse Ni-sulfate crystals were formed by adding the concentrated sulfuric acid to the Ni-phosphite precipitates which yielded from the plating waste liquid by controlling the temperature and the pH value. The open-gradient magnetic separation technique was employed to separate the Ni-sulfate crystals from the mixture of the Ni-sulfate and Ni-phosphite compounds by the difference between their magnetic properties. And we succeeded in collecting Ni-sulfate crystals preferentially to the Ni-phosphite by attracting them to the magnetic pole soon after the Ni-sulfate crystals began to grow.

CaO 화합물이 다량 함유된 비산재의 수화 특성에 관한 연구

The purpose of this study was to examine a possibility that fly ash could be used as raw material for carbonation by conducting the experiment on magnetic separation and hydration of fly ash that contained a large amount of CaO composite. Wet magnetic separation experiment was performed to remove the component of magnetic substance that contained fly ash, which aimed at increasing the content of CaO in the non-magnetic domain. The selected fly ash was used for hydration experiment before the TGDTA, XRF and XRD analyses were made to confirm the Ca component that could be carbonated. Then, the fly ash was turned to a hydrate that was favorable to dissociation of Ca 2+ ion. As a result, the magnetic separation enabled detecting the content of CaO component by up to 61 wt% in the non-magnetic domain. Since the hydrate was confirmed, it is believed that the fly ash can be used as raw material for carbonation.

Magnetic precipitate separation for Ni plating waste liquid using HTS bulk magnets

The magnetic separation experiment for recycling the nickel-bearing precipitates in the waste liquid from the electroless plating processes has been practically conducted under the high gradient magnetic separation technique with use of the face-to-face HTS bulk magnet system. A couple of facing magnetic poles containing Sm123 bulk superconductors were activated through the pulsed field magnetization process to 1.86T at 38K and 2.00T at 37K, respectively. The weakly magnetized metallic precipitates of Ni crystals and Ni–P compounds deposited from the waste solution after heating it and pH controlling. The high gradient magnetic separation technique was employed with the separation channels filled with the stainless steel balls with dimension of 1 and 3mm in diameter, which periodically moved between and out of the facing magnetic poles. The Ni-bearing precipitates were effectively attracted to the magnetized ferromagnetic balls. We have succeeded in obtaining the separation ratios over 90% under the flow rates less than 1.35L/min.

Study on High Gradient Magnetic Separation for Selective Removal of Impurity From Highly Viscous Fluid

There is an issue of contamination by metallic wear debris in the industrial plants processing highly viscous fluid. It is necessary to remove the ferromagnetic impurities such as metallic wear debris. In the case several kinds of ferromagnetic particles exist in the highly viscous fluid, it is required to remove the object material selectively. In this study, the selective separation from several kinds of ferromagnetic particles was examined by the high gradient magnetic separation (HGMS) experiment by using superconducting magnet and the particle trajectory simulation. We succeeded in separating the object particle at the flow velocity around 100 mm/s by the magnetic separation experiment. The possibility of the selective magnetic separation from several kinds of ferromagnetic particles was also confirmed by particle trajectory simulation.

Measurement of the adhesion force between particles for high gradient magnetic separation of pneumatic conveyed powder products

In the industrial plants such as foods, medicines or industrial materials, there are big amount of issues on contamination by metallic wear debris originated from pipes of manufacturing lines. In this study, we developed a high gradient magnetic separation system (HGMS) under the dry process by using superconducting magnet to remove the ferromagnetic particles. One of the major problems of dry HGMS systems is, however, the blockage of magnetic filter caused by particle coagulation or deposition. In order to actualize the magnetic separation without blockage, we introduced pneumatic conveyance system as a new method to feed the powder. It is important to increase the drag force acting on the sufficiently dispersed particles, which require strong magnetic fields. To generate the strong magnetic fields, HGMS technique was examined which consists of a magnetic filter and a superconducting solenoid magnet.As a result of the magnetic separation experiment, it was shown that the separation efficiency changes due to the difference of the cohesive property of the particles. On the basis of the result, the adhesion force which acts between the ferromagnetic particles and the medium particles used for the magnetic separation was measured by Atomic Force Microscope (AFM), and cohesion of particles was studied from the aspect of interparticle interaction. We assessed a suitable flow velocity for magnetic separation according to the cohesive property of each particle based on the result.

Development of superconducting high gradient magnetic separation system for highly viscous fluid for practical use

In the industrial plants processing highly viscous fluid such as foods or industrial products, it is necessary to remove the metallic wear debris originating from pipe in manufacturing line which triggers quality loss. In this study, we developed a high gradient magnetic separation (HGMS) system which consists of superconducting magnet to remove the metallic wear debris. The magnetic separation experiment and the particle trajectory simulation were conducted with polyvinyl alcohol (PVA) as a model material (viscosity coefficient was 10Pas, which is 10,000 times higher than that in water). In order to develop a magnetic separation system for practical use, the particle trajectory simulation by using solenoidal superconducting magnet was conducted, and the possibility of the magnetic separation for removing ferromagnetic stainless steel (SUS) particles in highly viscous fluid of 10Pas was indicated. Based on the results, the number of filters to obtain required separation efficiency was examined to design the practical separation system.

Development of Superconducting Magnets and its Applications in IHEP

This paper mainly described the work of Superconducting Magnet Engineering Center (SMEC), Institute of High Energy Physics (IHEP), Beijing, and its future development directions. During the last several years, the SMEC has successfully developed three big superconducting magnets, 1.0 T Beijing Spectrometer III (BESIII) Magnet, 3.0 T Superconducting Electromagnetic Iron Separator (SEIS) and 1.5 T Magnetic Resonance Image (MRI). And, there are some other Superconducting (SC) magnets under construction. With the help of SEIS magnet, arsenic magnetic separation experiments and turbid wastewater treatment experiments were carried out at IHEP.

Magnetic Separation of Nickel from Electroless Plating Waste Fluid using a HTS Bulk Magnet

A magnetic separation experiment to recycle nickel from the waste fluid of electroless plating processes was conducted using the open-gradient magnetic separation technique and a HTS bulk magnet system. A magnetic pole containing Gd123-based bulk superconductors was activated to 3.44 T at 34.9 K using a 5 T superconducting solenoid and the field cooling method. The coarse precipitates of nickel sulfate are composed of phosphite ions, which are yielded during the plating reaction by controlling the temperature and pH. Next, the open-gradient magnetic separation technique was employed, with use of water channels to separate the nickel-sulfate crystals from the mixture of the nickel sulfate and phosphite compounds based on the difference in magnetic properties. From the concentrations of each precipitate attracted to the magnetic pole, we succeeded in collecting nickel-sulfate crystals preferentially to the phosphite ions soon after crystal growth began.