Magnetic Separation Characteristics Research Articles

Magnetic MnFe2O4/ZIF-67 nanocomposites with high activation of peroxymonosulfate for the degradation of tetracycline hydrochloride in wastewater.

Advanced oxidation processes (AOPs) based on PMS have been used to degrade various refractory pollutants such as drugs, endocrine disruptors, dyes and perfluorinated compounds due to their wide application range, mild reaction conditions, fast reaction rate and simple operation. In this study, tetracycline hydrochloride (TCH) was degraded based on this method. Magnetic MnFe2O4/ZIF-67 nanocomposites were successfully prepared by a hydrothermal method, which combined the magnetic separation characteristics of MnFe2O4 with the high catalytic activity of ZIF-67 and were used to activate peroxymonosulfate (PMS) to efficiently degrade TCH. Satisfactory removal results were obtained with this simple and readily available material, with 82.6% of TCH removed in 15 min. The effect of different conditions on the degradation effect was investigated, and the optimal catalyst concentration and PMS concentration were determined to be 0.1 g L-1 and 0.2 g L-1, respectively, and all had good degradation effects at pH 5 to 10. XPS, impedance test and radical quenching experiments were used to investigate the degradation mechanism. The results showed that sulfate radical (SO4-˙) was the main active species in the degradation process. In addition, the catalyst has good cyclic stability, which provides a new idea for the removal of TCH in wastewater. It is worth mentioning that the catalyst also has good degradation property for other pollutants.

An Efficient and Attractive Synthetic Protocol for Three-component Preparation of NH-1,2,3-Triazoles Using a Novel Magnetically Recoverable Copper Catalyst

Due to their magnetic separation and recycling characteristics, magnetic nanocatalysts are widely used in a wide variety of organic reactions. 1,2,3-Triazoles are heterocyclic compounds with broad applications in organic chemistry, including medicine, materials, and synthetic chemistry; a wide range of 1,2,3-triazoles exhibits many biological activities, including activity against fungal, viral, allergic, and microbial infections has been also reported in the literature. In this work, a magnetic Fe3O4@SiO2 nanocatalyst modified with pyridine-tetrazole ligand supported copper (II) acetate [MNPs-Py/Tet-Cu(OAc)2] was constructed and used to catalyze this one-pot three-component reaction of NH-1,2,3-triazoles. This nanocatalyst can act as an excellent catalyst for these three-component reactions. The [MNPs-Py/Tet-Cu(OAc)2] nanocatalyst, which demonstrated effective magnetization as 43 emu/g, can be easily separate from the reaction mixture and reused for 7 times while preserving their catalytic activity. Also the diameter of the nanoparticles is about 70–97 nm with spherical morphology.

Synthesis and characterization of a new magnetic composite MnFe2O4/clay based on a natural clay obtained from Turkestan deposit

The work is devoted to the development of a new method for the synthesis of magnetic composites based on manganese ferrite on a natural clay, coupling with their physico-chemical characterization. In the study, a natural clay of Kazakhstan obtained from the Turkestan deposit was used for the preparation of magnetic composites. The formation of materials with magnetic properties is an urgent task of our time, due to the needs of various applications of magnetically controlled materials for biomedical systems, electronic devices, catalytic and adsorption processes. The advantage of such materials is the ability to control them using a magnetic field for shaking, recovery, induction heating, among others. In this work, samples were prepared by co-precipitation of manganese and iron salts with 5 mol L-1 NaOH over the Turkestan clay (TC). Materials were characterized by various analyses, such as Fourier-Transform infrared spectroscopy (FTIR), X-ray diffractometric analysis (XRD), and elemental analysis. According to the results of physical and chemical studies of the XRD and thermal analysis, kaolinite is the main mineral in the composition of TC. Magnetic adsorbents MnFe2O4/clay with perfect magnetic separation characteristics were successfully obtained by chemical co-precipitation

Selective extraction of perfluorooctane sulfonate in real samples by superparamagnetic nanospheres coated with a polydopamine-based molecularly imprinted polymer.

Superparamagnetic core-shell structured molecularly imprinted polydopamine nanospheres were constructed via self-polymerization of dopamine to attach the template onto the surface of magnetic Fe3 O4 substrate in tris-HCl solution. Then they were used for the specific recognition and extraction of perfluorooctane sulfonate from environmental water and human serum samples. The structural features and morphological characterization of the magnetic imprinting nanospheres were assessed, indicating that the magnetic polydopamine imprinted composite was successfully prepared and featured excellent magnetic separation characteristics. Adsorption experiments revealed that the magnetic adsorbents exhibited rapid adsorption kinetics and highly selective recognition properties toward perfluorooctane sulfonate. The stability and regeneration experiments indicated the materials had repeatable activity retention after repeated reuse. As a magnetic solid-phase extraction adsorbent, it was successfully applied for the extraction and quantification of perfluorooctane sulfonate in environmental water and human serum samples combined with liquid chromatography tandem mass spectrometry, with recoveries of ∼70-101.5% obtained in real samples. These results demonstrate that the prepared magnetic imprinting nanospheres are effective for the selective separation of perfluorooctane sulfonate from real samples. The synthesis technique is an effective and facile method that is conducted in aqueous solution and at ambient temperature, which is low cost, environmentally benign, and easy for scaling-up.

Facile fabrication of magnetic bio-derived chars by co-mixing with Fe3O4 nanoparticles for effective Pb2+ adsorption: Properties and mechanism

This study enlightened a green and novel method to prepare magnetic bio-derived chars by physical co-mixing and the Pb2+ adsorption behavior of these chars was investigated. Three kinds of magnetic chars were fabricated by wheat stalk biochar, rice husk biochar, and commercial coconut husk activated carbon co-mixing with magnetic nano-iron tetroxide (Fe3O4), respectively. The microstructure, magnetism properties, adsorption performance, and mechanism of magnetic chars were systematically investigated with multiple approaches. The experimental results showed that optimized Fe3O4 magnetic chars with the mass ratio of 1:3 (chars to Fe3O4) exhibited excellent Pb2+ adsorption ability and magnetic separation characteristics. The adsorption kinetics was well described by the pseudo-second order model indicating that the Pb2+ adsorption rate and amount of magnetic chars were enhanced. The maximum Pb2+ adsorption capacities of magnetic wheat stalk biochar, wheat stalk biochar, magnetic rice husk biochar, rice husk biochar, magnetic coconut husk activated carbon, and coconut husk activated carbon were 179.85, 160.39, 95.44, 73.34, 43.38, and 39.15 mg/g, respectively. Furthermore, the mechanism analysis indicated that the Pb2+ adsorption on Fe3O4 magnetic bio-derived chars included the co-precipitation reaction, complexation reaction, conjugation adsorption, ion exchange, and Fe–O coordination. This study presents an attractive method for preparing magnetic bio-derived chars for enhancing heavy metal adsorption without chemical processes and mechanical energy.

Boosting Aerobic Oxidation of Alcohols via Synergistic Effect between TEMPO and a Composite Fe3O4/Cu-BDC/GO Nanocatalyst.

Fabrication of a nanocomposite catalyst via a novel and efficient strategy remains a challenge; Fe3O4 nanoparticles anchored on graphene oxide (GO) sheet-supported metal-organic frameworks (MOFs). In this study, the physicochemical properties of the ensuing Fe3O4/Cu-BDC/GO are investigated using Fourier transform infrared spectrum, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, energy-dispersive X-ray detector, and atomic absorption spectroscopy. The salient features of the nanocomposite such as Cu-MOF, synergistic effect with GO sheets, and magnetic separation characteristics make it an excellent ternary heterostructure for aerobic oxidation of alcohols. The proposed nanocatalyst and co-catalyst 2,2,6,6-tetramethylpiperidine-N-oxyl substantially enhance the catalytic performance for the aerobic oxidation under very mild and sustainable reaction conditions. The heterogeneity of Fe3O4/Cu-BDC/GO composite catalyst is affirmed with the added advantage that the initial activity is well maintained even after seven cycles.

Magnetic beads separation characteristics of a microfluidic bioseparation chip based on magnetophoresis with lattice-distributed soft magnets

To continuously perform pretreatment operations of biological detection reagents, a kind of microfluidic bioseparation chip that integrates mixer, heater and soft magnets for detection of nucleic acid and extraction of molecular proteins with magnetic beads methods is presented in the paper. A specific magnetic field is formed in a desired chamber bonded with PDMS and PMMA sheets by embedding soft magnets of iron powders in the chip, and magnetized by an external magnetic field. Soft magnets distributed in different ways are designed respectively, and the characteristics of the magnetic field, as well as the magnetic trajectory of the magnetic beads are simulated by considering the magnetic-fluid coupling. An experimental platform to observe the capturing of magnetic beads is built and the capture phenomenon for magnetic beads with lattice-distributed soft magnets is also experimentally verified. Based on the experimental data, the capture efficiency of the magnetic beads is calculated with the image processing method. The results show that lattice-distributed soft magnets are more effective than the array-distributed soft magnets for separating the magnetic beads. Furthermore, the lattice-distributed soft magnets can improve the separation efficiency of the detected reagent maintained to be more than 80% when the inlet flow rate increases from 0.01 m/s to 0.05 m/s.

Conjugation of Urokinase to Water-Soluble Magnetic Nanoparticles for Enhanced Thrombolysis

In this study, covalent conjugation of thrombolytic drug urokinase to water-soluble magnetic nanoparticles (NPs) is proposed to enhance the efficiency of thrombolysis. Hydrophobic NPs of oleic acid (OA)-coated Fe3O4 are first synthesized and then surface-modified with the amphipathic copolymer poly(maleic anhydride-alt-1-octadecylene) (PMAO) to form water-soluble NPs of PMAO-OA-Fe3O4 with monodispersed sizes. PMAO-OA-Fe3O4 NPs display a good water-based stability without aggregation at near neutral pH and show good magnetic separation characteristics. The thrombolytic drug urokinase is then covalently linked with the former product through dehydration condensation reaction between the amino and carboxyl produced by dehydration of the anhydride under N-Ethyl-N′-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). Transmission electron microscope (TEM) images and dynamic light scattering (DLS) results show that the urokinase@PMAO-OA-Fe3O4 NPs are uniformly dispersed in water. The in vitro thrombolytic effect based on the manipulation of magnetic coupling, combined with static and alternating current (AC) magnetic fields, in a mimic blood-vascular system was studied. Drug release test shows that AC magnetic field can be used as switch and accelerator for NPs to release drugs. In addition, thrombolytic efficiency is nearly four times that of pure urokinase. This indicates that the coupling magnetic field may be a promising method to improve thrombolytic effect of the prepared magnetic carrier drug conjugates.

Effect of microwave irradiation on the grinding and magnetic separation characteristics of vanadium titano-magnetite

In this study, the influence of microwave irradiation on the grinding characteristics and magnetic separation of vanadium titano-magnetite (VTM) was investigated, including the effects of microwave power, microwave irradiation time, and particle size of VTM. The particle size distribution of the ground product and Fe grade in magnetic fraction of the untreated and microwave-treated VTM were obtained. Grinding experiment showed that the microwave irradiation could improve the grindability of VTM, thus increasing the specific rate of breakage (S1) value and the weight percentage of the fine ground product significantly. With increasing microwave irradiation time and particle size of VTM, the increment in grindability of VTM was improved. No obvious difference was observed in the particle size distribution of the fine ground product between the untreated and microwave-treated VTM. The magnetic separation tests confirmed that the Fe grade of the magnetic fraction increased from 51.70% for untreated VTM to 53.78% by microwave irradiation. According to X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM) analyses, the dominant mechanisms that improved the grindability and liberation of VTM under microwave irradiation included the microwave selective heating the valuable mineral within the VTM and the micro-fractures between mineral and gangue that were induced by the thermal stress.

Shell thickness controlled hydrophilic magnetic molecularly imprinted resins for high-efficient extraction of benzoic acids in aqueous samples

Hydrophilic magnetic molecular imprinted resins (MMIRs) were firstly fabricated by one-pot copolycondensation of resorcinol, melamine, and formaldehyde in the pores of Fe3O4 @mSiO2. The porous structure of mSiO2 limited copolycondensation. After the removal of mSiO2, controllable imprinting shell thickness (about 5 nm) was formed, reducing the probability of embedded sites, favoring the efficient adsorption. Moreover, the reaction time (3 h) was just 1/5−1/8 of those synthesized by conventional heating method. The transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), vibrating sample magnetometer (VSM), thermo-gravimetric analysis (TGA), water contact angle analysis, and Brunauer‒Emmett‒Teller (BET) analysis indicated the successful preparation of MMIRs with excellent hydrophilic property, and magnetic separation characteristics. Steady-state adsorption studies showed that the resultant MMIRs had specific recognition for benzoic acids, GA, protocatechuic acid (PCA), vanillic acid (VA), 4-hydroxybenzoic acid (4-HBA), salicylic acid (SA), and benzoic acid (BA). MMIRs combination with high-performance liquid chromatography–ultraviolet (HPLC–UV) were then directly used for selective extraction and determination of benzoic acids in river water, fruit juices, and human serum. Obtained limits of detection (LOD) and recoveries were in the range of 0.02–1.0 μg/mL, and 81.8–108.7%, respectively, and the batch-to-batch relative standard deviation (RSD) was 5.9%. The proposed strategy showed excellent hydrophilicity and specificity, which was promising for detection of benzoic acids in real aqueous samples.

Magnetic Cu-MOFs embedded within graphene oxide nanocomposites for enhanced preconcentration of benzenoid-containing insecticides

Hybrid magnetic nanocomposites based on Cu-MOFs, graphene oxide (GO), and Fe3O4 nanoparticles (NPs) were prepared via chemical bonding approach, which GO were used as platforms to load nanostructured Cu-MOFs and Fe3O4 NPs. The composite features both magnetic separation characteristics and high MOFs porosity, making it an excellent adsorbent for magnetic solid-phase extraction (MSPE). The as-synthesized nanocomposites are characterized by XRD, TGA, SEM, TEM, nitrogen adsorption-desorption analysis and FT-IR spectroscopy. The composites are used in MSPE of six aromatic insecticides from various real samples prior to their quantification by HPLC. Amount of adsorbent, extraction times, extraction temperature, desorption times and oscillation rate are optimized. Under the optimal conditions, the method has a relative standard deviations (RSDs) of 1.9–2.7%, and good linearity (correlation coefficients higher than 0.9931). The low LOD and LOQ for six insecticides are found to be 0.30–1.58μgL-1 and 1.0–5.2μgL-1, respectively. The RSDs of within batch extraction are 1.6–9.5% and 3.9–12% for batch to batch extraction. The experimental results suggest that the nanocomposites have potential application for removal of hazardous pollutants from effluents.

A study on the preparation and application of a core-shell surface imprinted uranyl magnetic chelating adsorbent.

A core–shell surface imprinted uranyl magnetic chelating adsorbent (UMCA) was synthesized by combining the sol–gel process with the surface molecular imprinting technique (SMIT). A specific salophen and uranyl–salophen were designed and synthesized. Then, the synthesized uranyl–salophen complex was used as a template (in which uranyl is the target analyte), 3-aminopropyltriethoxysilane as a functional monomer and tetraethylorthosilicate as a cross-linker. The obtained UMCA was characterized by a variety of modern analytical and detection techniques. The adsorbent can be used for the solid-phase extraction of uranyl with good selectivity, high adsorption capacity, magnetic separation characteristics and good reusability. The chelating sorbent was successfully applied for the separation of uranyl, followed by multiphase photocatalytic resonance fluorescence method determination in several environmental water samples with a relative standard deviation of <5.48% and spiked recoveries of 92.5% to 103.0%. The adsorption mechanism was preliminarily discussed.

Preparation of magnetic superhydrophilic molecularly imprinted composite resin based on multi-walled carbon nanotubes to detect triazines in environmental water

In this work, a superhydrophilic surface imprinting composite resin was constructed for selective enrichment of triazines, which was first fabricated by one-pot condensation of formaldehyde, resorcinol and melamine on the surface of the magnetic multi-walled carbon nanotubes (MWNTs@Fe3O4). The effect of the amount of template (ametryn) on the imprinting performance was investigated. The FT-IR, VSM, XRD, SEM and water contact test indicated that the magnetic multi-walled carbon nanotubes imprinting resin (MWNTs@Fe3O4@MIR) was successfully prepared and exhibited superhydrophilic and excellent magnetic separation characteristics. The isothermal adsorption, selectivity and adsorption kinetics tests indicated that the prepared MWNTs@Fe3O4@MIR had better specific recognition for triazines. The adsorption isotherm obeyed Freundlich isotherm model and adsorption kinetic matched pseudo-second-order kinetic model well. Under the optimized conditions, the MWNTs@Fe3O4@MIR was successfully applied as selective adsorbent for the direct enrichment and determination of triazines in environmental water samples combined with HPLC-MS/MS. The established method exhibited good linearity (R2 ≥ 0.9987), lower limit of detection (0.007–0.068 μg L−1), and excellent precision (RSD < 9%). The surface imprinted strategy based on MWNTs@Fe3O4 developed a new way for the preparation of superhydrophilic magnet imprinting nanocomposites, which exhibited a perspective in the determination of triazines in water.

Development of hyperbranched polymer encapsulated magnetic adsorbent (Fe3O4@SiO2–NH2-PAA) and its application for decontamination of heavy metal ions

The water dispersible magnetic adsorbent was fabricated by functionalization of magnetic nanoparticles (MNPs) with 3-aminopropyl trimethoxysilane (APTMS) and dendrimer-like polyamidoamine; the sorbent is named as Fe3O4@SiO2–NH2-PAA. The amine rich Fe3O4@SiO2–NH2-PAA adsorbent was further used in retrieval of heavy metal ions such as Cd(II), Co(II), Zn(II), Pb(II) and Cu(II) from the aqueous medium. Fabrication of Fe3O4@SiO2–NH2-PAA involves a two-step process: (i) surface initiation of MNPs by ligand exchange reaction and condensation of APTMS (Fe3O4@SiO2-NH2), (ii) surface functionalization of MNPs by controlled/living polymerization. Surface functional groups, crystallization characteristics, surface morphologies and magnetic properties of the adsorbent were analyzed by FT-IR, XRD, SEM, TEM, and VSM. The characterization outcomes showed that functionalization improved the oxygen and nitrogen atomic percentages of adsorbent resulting enriched adsorption. Sorption isotherm and kinetic models illustrated that sorption data better fitted to Langmuir isotherm model and pseudo-second order kinetic model. These results suggest that sorption process is monolayer and is chemical in nature. The order of sorption capacities (mgg−1) based on Langmuir isotherm model are: Pb(II) (108.82)>Cd(II) (100.81)>Co(II) (95.40)>Zn(II) (89.62)> Cu(II)(87.82). These findings suggest that as developed magnetic sorbent can be replaceable for traditional adsorbents due its high sorption performance, rapid kinetics, and magnetic separation characteristics.

Determination of Tributyltin in Seafood Based on Magnetic Molecularly Imprinted Polymers Coupled with High-Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry

In this study, Fe3O4 was adopted as a carrier for surface molecular imprinting with two-stage polymerization. First, the functional monomer (methacrylic acid, MAA) was modified on the surface of Fe3O4, which was then polymerized with the template molecule (tributyltin, TBT), cross linking agent (ethylene glycol dimethacrylate, EGDMA), and porogen (acetonitrile), hereby successfully preparing Fe3O4@MIPs prone to specifically identify TBT. The physical properties of Fe3O4@MIPs were then characterized, and adsorption and selection capacities were also assessed. Compared with conventional imprinting polymers, this magnetic molecular imprinting polymer (MIP) displayed significantly increased and more specific adsorption. Meanwhile, its pretreatment was simpler and faster due to magnetic separation characteristics. Using magnetic MIPs as adsorbents for enrichment and separation, detection limit, recovery rate, and linear range were 1.0 ng g−1, 79.74–95.72%, and 5 ng g−1~1000 ng g−1, respectively, for a number of seafood samples. High-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) was used to analyze Tegillarca granosa, mussels, large yellow croaker, and other specimens, with recovery rates of 79.74–95.72% and RSD of 1.3%–4.7%. Overall, this method has a shorter total analysis time, lower detection limit, and wider linear range and can be more effectively applied to determine MAA in seawater and seafood.

Removal of Humic Acid in Water by Rice Hull Magnetic Activated Carbon and Magnetic Separation

We have newly developed a rice hull magnetic activated carbon (RH-MAC) and studied its adsorption property for humic acid from water and high-gradient magnetic separation (HGMS) characteristics. Rice hull was impregnated with an iron nitrate solution and heat-treated in both nitrogen and carbon dioxide atmosphere. In these processes, the rice hull changed to activated carbon that had a lot of mesopores and nanosize magnetite inside. Magnetization of RH-MAC increased with an increase in iron nitrate concentration during the process and reached 20.8 Am <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /kg at 0.5 T. In the adsorption examination, it was able to adsorb humic acid effectively, and the removal ratio achieved 97.6% from a humic acid solution of 50 mg/L. In HGMS studies, we used the magnetic wire filter rounded on a magnet drum with 0.5-T permanent magnet and the slurry of RH-MAC concentration of 100 mg/L. Consequently, 99.4% of RH-MAC in the slurry of 2 L was captured in the magnetic filter at flow rates of 230 mL/min. These results show that this water purification system has higher removal ratio of humic acid than that for current advanced water treatments.

Adsorption behavior of methylene blue on Fe3O4-embedded hybrid magnetic metal–organic framework

A magnetic hybrid material (Fe3O4-embedded-MOF) consisting of a stable metal–organic framework HKUST-1 embedded with poly(N-vinyl-2-pyrrolidone) coated Fe3O4 microspheres was simply prepared under refluxing conditions for 4 h. The as-synthesized material was characterized using powder X-ray diffraction, scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), energy dispersive spectroscopy (EDS) and N2 adsorption–desorption at 77 K. The hybrid material was studied for the adsorption of methylene blue from aqueous solution. The effects of dye concentration, adsorbent dose, and initial pH on the adsorption of methylene blue were measured, and from these experimental data, adsorption isotherms, kinetics, and thermodynamics were obtained. The results showed that a pseudo-second-order kinetic model and Langmuir isotherm (with R2 = 0.937) matched well for the adsorption of methylene blue onto Fe3O4-embedded-MOF. Thermodynamic parameters including free energy, enthalpy, and entropy of methylene blue adsorption were calculated, and the results showed that the adsorption of methylene blue were favorable on Fe3O4-embedded-MOF. The magnetic hybrid Fe3O4-embedded-MOF material features both magnetic separation characteristics as well as excellent adsorption performance for methylene blue in aqueous solution. The results of the present study demonstrate that Fe3O4-embedded-MOF is a promising adsorbent for the removal of dye from wastewater.

Optimization of High Gradient Magnetic Separation Filter Units for the Purification of Fermentation Products

High gradient magnetic separation (HGMS) has been established since the early 1970s. A more recent application of these systems is the use in bioprocesses. To integrate the HGMS in a fermentation process, it is necessary to optimize the separation matrix with regard to the magnetic separation characteristics and permeability of the non-magnetizable components of the fermentation broth. As part of the work presented here, a combined fluidic and magnetic force finite element model simulation was created using the software COMSOL Multiphysics and compared with separation experiments. Finally, as optimal lattice orientation of the separation matrix, a transversal rhombohedral arrangement was defined. The high suitability of the new filter matrix has been verified by separation experiments.

Effect of microwave irradiation on selective heating behavior and magnetic separation characteristics of Panzhihua ilmenite

The influences of microwave irradiation on the surface characteristics of Panzhihua ilmenite were systematically investigated. The crystal structures, surface morphology and surface chemical functional groups of ilmenite were characterized before and after microwave irradiation and magnetic separation for different microwave treatment times by using various methods, such as XRD, SEM, and FT-IR, respectively. XRD analysis showed that the microwave treated ilmenite has the strongest peaks of phase more than that of raw samples, indicates that the crystalline compound of ilmenite increased with the microwave irradiation time. SEM analysis showed the micro-cracking appeared at many grain boundaries of ilmenite after being pretreated by microwave treatment. The separations of ilmenite from gangue minerals were completed and the micro-fissure within ilmenite minerals were also formed, which could be attributed to the microwave selective heating characteristics of the different minerals and compounds, and the thermal stresses were caused by the uniform heat rate disturbed under microwave irradiation. The mineral processing results showed that the magnetic separation characteristics and properties of microwave treated ilmenite samples were better than that of microwave untreated ilmenite samples. It was concluded that microwave irradiation can be applied effectively and efficiently to the irradiation processes of Panzhihua ilmenite.

Facile fabrication of magnetically separable graphitic carbon nitride photocatalysts with enhanced photocatalytic activity under visible light

Because of their potential application in the conversion of solar energy to chemical energy, the development of semiconductor photocatalysts that have high reactivity under visible light has received great attention. In the present work, we illustrate the design and fabrication of magnetically separable polymeric carbon nitride photocatalysts, i.e. Fe2O3/g-C3N4 composite photocatalysts, a novel type of visible light driven photocatalyst with a cost-effective recovery manner. The obtained Fe2O3/g-C3N4 composite catalysts with different Fe2O3 contents were characterized by powder X-ray diffraction (PXRD), high-resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflection spectroscopy (DRS), vibration sample magnetometry (VSM) and thermogravimetric analysis (TGA). The saturation magnetization at 300 K varies from 0.37 to 1.56 emu g−1, depending on the different Fe2O3 contents (2.8–11.6 wt%) in the Fe2O3/g-C3N4 composites, clearly indicating the excellent magnetic separation characteristics of the as-prepared photocatalysts. Remarkably, the photocatalytic activity of the magnetic Fe2O3/g-C3N4 photocatalysts under visible light irradiation was increased up to 1.8 times for the photodegradation of Rhodamine B (RhB) under visible light irradiation compared with the conventional pure g-C3N4 photocatalyst. A possible mechanism for the enhanced photocatalytic activity of the Fe2O3/g-C3N4 composite photocatalyst was also proposed to guide the further improvement of their photocatalytic activity.