Efficient Magnetic Separation Research Articles

Sugarcane bagasse and iron ore tailings thermochemical conversion towards sustainable iron recovery with biogenic carbon and hydrogen production

The recovery of valuable chemical elements from industrial waste is essential for production processes' economic and environmental sustainability. The interaction between the iron ore tailings and sugarcane bagasse, both wastes, has the potential to provide a secondary iron source for future iron and steelmaking processes. This study evaluated the use of volatiles from sugarcane bagasse (SCB) and iron ore tailings (IOT) to the synergistic promotion of carbon deposition, H2 production and conversion of weak magnetic iron oxides in strong magnetic iron phases. The experiments were carried out at 400, 600, 800, and 1000 ºC with different SCB/IOT ratios under an N2 atmosphere. In all tests, SCB and IOT were heated simultaneously in separate beds to prevent direct contact between the materials. The combination of 600 ºC and higher SCB/IOT ratio resulted in a product with 96.7% magnetite, 98% magnetic fraction recovery, and 3.5% deposited carbon. The use of lower SCB/IOT ratio provided an increase in H2 production. Regardless of the mass ratio, heating the IOT and SCB simultaneously up to 1000 ºC led to significant mineralogical transformations, reaching reduced phases such as wüstite, fayalite and metallic iron, which impaired magnetic separation efficiency. The results indicate an alternative for recovering iron from IOT using biomass waste as a renewable reducing agent for the steel industry.

Polyoxometalate Derived Materials as Laccase‐Mimic Nanozyme and Reduction Catalyst for p‐Nitrophenol Remediation in Water

Abstractp‐Nitrophenol (PNP), a highly toxic water pollutant, poses significant risks to human health and the environment. For detecting PNP, a colorimetric method utilizing a nanozyme that mimics laccase activity presents a viable approach. In this study, PV14@MIL‐88A, a robust nanozyme with superior laccase‐mimic capabilities, was synthesized by incorporating Na7H2[PV14O42] (PV14) into MIL‐88A, a metal‐organic framework (MOF). This nanozyme demonstrates optimal laccase‐mimicking activity, enabling effective PNP detection via colorimetry and digital image colorimetry using smartphones. Theoretical analyses suggest that the outstanding laccase‐mimic activity of PV14@MIL‐88A is derived from the optimized d‐band center in PV14. Upon calcination with dicyandiamide (DCDA), PV14@MIL‐88A transforms into Fe2O3/VO2@NCNF. In the presence of NaBH4, Fe2O3/VO2@NCNF facilitates the conversion of PNP to p‐aminophenol (PAP), an essential precursor in paracetamol synthesis. The interaction between Fe2O3 and VO2 in Fe2O3/VO2@NCNF enhances adsorption and subsequent reduction of PNP. The saturation magnetization of Fe2O3/VO2@NCNF reaches 25 emu g−1, which supports efficient magnetic separation in the reduction process. This study not only advances an effective method for PNP detection but also facilitates its transformation from a hazardous pollutant into a valuable chemical precursor.

Magnetic-responsive sensors based on polydopamine macromolecules for highly sensitive detection of trace food colorant residues

As a kind of unique biomimetic macromolecule, polydopamine (PDA) have prominent in-situ reduction ability and interfacial adhesion. In this work, combined with in-situ reduction ability of PDA and excellent magnetic response performance of nickel foam (NF), a strategy was designed to fabricate a series of NF@PDA@AgNPs as magnetic-responsive surface enhancement Raman scattering (SERS) substrates for highly sensitive Rhodamine B (RhB) detection in chili powder. With crystal violet (CV) as probe molecule, the detection limit of SERS substrate could achieve 10−10 M, and the enhancement factor was as high as to 2.22 × 107. In addition, the NF@PDA@AgNPs SERS substrates showed excellent magnetic separation efficiency, good SERS uniformity and storage stability. More importantly, these substrates could achieve highly efficient collection and sensitive detection of RhB residues in chili powder by magnetic adsorption method, and the detection of limit was as low as to be 10−6 g/g. These NF@PDA@AgNPs substrates would be a great prospect for rapid and efficient pernicious contaminant detection in the chemical and biological fields.

Enhancing Magnetic Micro- and Nanoparticle Separation with a Cost-Effective Microfluidic Device Fabricated by Laser Ablation of PMMA.

Superparamagnetic iron oxide micro- and nanoparticles have significant applications in biomedical and chemical engineering. This study presents the development and evaluation of a novel low-cost microfluidic device for the purification and hyperconcentration of these magnetic particles. The device, fabricated using laser ablation of polymethyl methacrylate (PMMA), leverages precise control over fluid dynamics to efficiently separate magnetic particles from non-magnetic ones. We assessed the device's performance through Multiphysics simulations and empirical tests, focusing on the separation of magnetite nanoparticles from blue carbon dots and magnetite microparticles from polystyrene microparticles at various total flow rates (TFRs). For nanoparticle separation, the device achieved a recall of up to 93.3 ± 4% and a precision of 95.9 ± 1.2% at an optimal TFR of 2 mL/h, significantly outperforming previous models, which only achieved a 50% recall. Microparticle separation demonstrated an accuracy of 98.1 ± 1% at a TFR of 2 mL/h in both simulations and experimental conditions. The Lagrangian model effectively captured the dynamics of magnetite microparticle separation from polystyrene microparticles, with close agreement between simulated and experimental results. Our findings underscore the device's robust capability in distinguishing between magnetic and non-magnetic particles at both micro- and nanoscales. This study highlights the potential of low-cost, non-cleanroom manufacturing techniques to produce high-performance microfluidic devices, thereby expanding their accessibility and applicability in various industrial and research settings. The integration of a continuous magnet, as opposed to segmented magnets in previous designs, was identified as a key factor in enhancing magnetic separation efficiency.

Separation and extraction of iron resources from hazardous electric arc furnace (EAF) steel slag: Aggregation of Fe-rich layers, magnetic separation, powder characterization

China's electric arc furnace (EAF) slag reserves are huge, the problems of EAF slag resource application need to be solved urgently. In this study, high temperature holding and slow cooling treatment were used to treat the slag. The phase and structure of the slag were analysed by means of X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. To analyse the migration pattern of iron elements and to study the interaction between EAF slag basicity and magnetic separation efficiency. The results show that, there is an obvious layering phenomenon during the cooling slag, and the top layer is the Fe-rich layer. The slow cooling treatment makes the Fe-rich phase grow sufficiently and improves the dissociation efficiency of the Fe-rich phase in the crushing process. As the basicity increases, the thickness of the iron-rich layer gradually decreases and the iron element is transferred to the RO phase, while the concentrate yield decreases. Multi-stage wet weak magnetic separation of treatment slag resulted in the highest concentrate yield of 49.05 % at an basicity of 1, with a T.Fe content of 56.711 %, and 70.32 % of the iron component entering the concentrate. The concentrate can be returned to the steelmaking process instead of the charge, and the tailings can be used to make high value-added products.

Simulation of Magnetic Separation of Metal Ions in Aqueous Electrolytes

The magnetic separation of metal ions provides an alternative solution to traditional separation techniques such as pyrometallurgy, hydrometallurgy, biometallurgy or electrodialysis. Compared to traditional techniques that either use large amounts of chemicals (usually inorganic acids combined with reducing agent), produce large amounts of sludge as solid waste, consume a large amount of energy, or are difficult to separate ions of different charges [1], the magnetic separation of the metal ions can separate ions based on their magnetic susceptibility. This method is environmentally friendly [2] and consumes a small amount of energy (particularly when the system is designed using permanent magnets instead of electromagnets). The goal of this presentation is twofold. First, we derive the set of transport equations that need to be used to simulate the magnetic separation of metal ions in aqueous solutions. Then, we use these transport equations to simulate the magnetic separation process in various magnetic systems and predict the efficiency of magnetic separation of different systems.The mathematical model developed here is based on coupling the three-dimensional Navier-Stokes equations for flow transport with the drift (migration)-diffusion equations of ion transport [3] in the presence of magnetic field gradients. Both the drift-diffusion model and the Navier-Stokes equations include the magnetic force term as an additional driving force. By solving the entire system of equations self-consistently we analyze the effect of the diffusivity, concentration gradients, magnetic field gradients and fluid velocity over the capturing properties of the system. A detailed presentation of the mathematical model, underlying assumptions of the model, limiting cases, numerical implementation in three-dimensional structures, and simulations results will be presented at the meeting. In addition, we will present predictions for the magnetic separation of Li, Fe, Ni, Mn, and Co from the solution phase. Fortunately, these ions have significantly different magnetic susceptibility, which vary over more than 3 orders of magnitude, and which allows for the efficient extraction and separation of the elements from the solution and from each other.

Construction of an efficient molecular enrichment and magnetic separation flow with Fe3O4@Ag@COF for ratiometric SERS detection of methamidophos

As a typical organophosphorus pesticide widely utilized in agricultural production with its residue as enormous threat to human health and environment, methamidophos (MTD) has gained increasing attention in recent years, so, it is necessary to develop an effective strategy to detect MTD from complex matrix. Here, an efficient molecular enrichment and magnetic separation flow was constructed through Fe3O4@Ag@COF (covalent organic framework) for ratiometric SERS detection of MTD. Specifically, Fe3O4@Ag@COF is shown to have a high-density hot-spot region and optimal SERS performance by adjusting the particle size and addition volume of Fe3O4@Ag. COF endows Fe3O4@Ag@COF with a platform for enriching MTD molecules and isolating impurities, allowing the separation of Fe3O4@Ag@COF with MTD molecules from complex matrix by magnetism. More importantly, due to its natural core–shell structure, the Raman peaks of COF can be employed as an internal standard for ratiometric SERS sensing, thereby increasing its analysis accuracy and reliability. Under the optimal extraction method and solvent conditions, the developed detection flow exhibited a wide linear range from 10-4 M to 10-9 M and a low MTD detection limit of 8.3 × 10-5 mg/kg. Furthermore, the SERS sensor had excellent reproducibility and long-term stability with a low relative standard deviation (RSD). In practical application, this detection flow was tested for quantifying trace MTD in green tea samples, with recoveries of 89.54 % to 101.89 % and RSDs below 5 % (n = 5), comparable to the performance of gas chromatography mass spectrometry (GC–MS).

On controllability of fluidized bed reduction of iron ore by CH4 for selective formation of magnetite

Magnetization roasting technology is one of the most representative ways to improve the magnetic separation efficiency and iron recovery of refractory weakly magnetic iron ores. However, utilization of CO-rich or H2-rich gas of strong reducibility as reducing agent for magnetization roasting would lead to over-reduction of Fe2O3 in the ore to non-magnetic FeO, which makes the magnetism of the roasted ore be lower than its maximum, and hence leads to a lower iron recovery than expected. To explore the possibility of using CH4 as reducing agent for controllable reduction of Fe2O3 in iron ores to selectively forming magnetic Fe3O4, i.e., for maximizing the magnetism of the reduced ore for efficient iron separation and recovery, a series of fluidized bed reduction tests in CH4 were carried out on two iron ores of 55 % and 33 % iron at different temperatures for different periods of time, and the resultant reduced ore particles were magnetically separated for recovery of iron concentrate. XRD and ICP analyses were performed on all recovered iron concentrates to identify the crystal forms of their iron species and to quantify their iron contents. The results have shown that the controllable reduction by CH4 of Fe2O3 in the iron ores to strongly magnetic Fe3O4 can be realized by controlling the reduction temperature and time condition applied. The resultant concentrates can be fully recovered by magnetic separation in a weak magnetic field of 60 kA/m to attain a maximum iron recovery of 98 % for the high-grade ore and that of 65 % for the low-grade ore. Besides, the results have also shown that the most critical factor affecting the controllability of the ore reduction process and the selectivity to the generation of magnetic Fe3O4-containing particles is the reduction temperature, and that the upper temperature threshold for the controllable reduction and selective generation of strongly magnetic iron concentrate is about 650℃.

A new magnetically separable zwitterionic copolymer hydrogel: Synthesis, characterization, and adsorption studies

In this study, a new magnetic organic–inorganic hydrogel composite was prepared and applied as an adsorbent for the removal of contaminants from aqueous media. The composite was prepared by loading FeCo nanoparticles on a zwitterionic copolymer hydrogel (poly(4-vinylbenzenesulfonate-co-[3-(methacryloylamino) propyl] trimethylammonium chloride), poly(MPTC-co-VBS)). Three composites with different FeCo contents were prepared to find the poly(MPTC-co-SVBS): FeCo ratio that achieves the highest adsorption of reactive yellow 160 (RY160) and Ni2+ ions. The prepared materials were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffractometer (XRD), and vibrating-sample magnetometer (VSM).The characterization results revealed that the FeCo nanoparticles, poly(MPTC-co-SVBS) zwitterionic copolymer hydrogel, and FeCo-zwitterionic copolymer hydrogel composites were successfully prepared. The VSM and SEM analysis showed the ferromagnetic nature and porous structure of the FeCo-zwitterionic copolymer hydrogel composite. According to the XRD and FTIR, the FeCo was partially oxidized to CoFe2O4 during the preparation of the FeCo-zwitterionic copolymer hydrogel composite. The composite with the ratio of 2 wt% of poly(MPTC-co-SVBS) to 1 wt% of FeCo (2ZCPH-1FeCo) achieved the highest removal of both RY160 and Ni2+. The optimum removal of RY160 (92 %) was attained using 0.5 g/L of 2ZCPH-1FeCo at pH 7 after 60 min., while the optimum removal of Ni2+ (92 %) was attained using 1.0 g/L at pH 6.5 after 60 min. The PFO and PSO kinetic models described accurately the adsorption of RY160 and Ni2+,respectively. While the isotherm data of RY160 dye and Ni2+ was best described by Freundlich and Temkin models, respectively. Overall, the new FeCo-zwitterionic copolymer hydrogel composite demonstrated remarkable adsorption efficiency and simple magnetic separation post-treatment which makes it a prime contender for practical application in water treatment.

Design and application of environmentally friendly composite magnetic particles for microplastic extraction from water media

The widespread presence of microplastic particles in aquatic environments requires methods of their extraction from water for counting and analysis and for water purification technologies. In this study, new magnetic composite nanoparticles (FNP) were designed, characterized and explored to be used as magnetic seeds for extracting polyethylene terephthalate microparticles (MPET, 5–30 μm) from water by magnetic sedimentation. The engineered seeds have a complex morphology, with magnetic cores of Fe3O4 dispersed in an environmentally compatible polymer matrix of silicon dioxide, chitosan or gelatine. Mechanisms of the heteroaggregation of FNP and MPET are considered and the main influencing factors (particles concentrations, major ions, duration of the preliminary exposure and of the sedimentation) are studied. The heteroaggregates are removed from water using a gradient magnetic field (Bzmax = 0.44 T) generated by a system of permanent magnets. The mass concentration of magnetic nanoseeds for more than 98 % capture of PET particles in pure and in salted water after 0.5 hour of magnetic sedimentation was detected to be 0.002 g/L. It is two orders of magnitude lower than that reported for uncovered magnetite-based particles. Using magnetic composite seeds with ecofriendly coatings allows to perform a high efficient magnetic separation of microplastic particles from water both for analytical purpose and for potential water cleaning technologies, while strongly reducing the synthetic flocculant sludge volume.

Effect of eddy currents on metal fine particles in high gradient magnetic separation using a superconducting magnet

Abstract Dry high gradient magnetic separation is one of the key technologies expected in removing magnetic metal fine particles as contaminations in the production process of various powders. However, the effect of eddy currents on such metal fine particles in dry high gradient magnetic separation has not been adequately explored in previous research. In order to understand this phenomenon more comprehensively, we conducted particle trajectory simulations using a finite element analysis with numerical methods and actual magnetic separation experiments to investigate the influence of eddy currents on magnetic separation efficiency. The results show that for both paramagnetic and diamagnetic metal particles, eddy currents can favourably influence the capture efficiency. Furthermore, these effects depend on the particle size, electrical conductivity, and the rate of change in the magnetic field. Therefore, by taking eddy currents into account, magnetic separation systems can be better optimized and their performance further improved.

Magnetic separation, sunlight-driven photocatalytic activity, and antibacterial studies of Sm-doped Co0.33Mg0.33Ni0.33Fe2O4 nanoparticles.

Magnetic nanoparticles have emerged as a promising tool for wastewater treatment due to their unique properties. In this regard, Co0.33Mg0.33Ni0.33SmxFe2-xO4 (0.00 x 0.08) nanoparticles were prepared to examine their magnetic separation efficiency (MSE), photocatalytic, antibacterial, and antibiofilm performances. Pure nanoparticles, having the highest saturation magnetization (Ms = 31.87emu/g), exhibit the highest MSE, where 95.6% of nanoparticles were separated after 20min of applying a magnetic field of 150 mT. The catalytic performance of the prepared samples is examined by the photodegradation of rhodamine B (RhB) dye exposed to direct sunlight radiation. Improved photocatalytic activity is exhibited by Co0.33Mg0.33Ni0.33Sm0.04Fe1.96O4 nanoparticles, labeled as Sm0.04, where the rate of the degradation reaction is enhanced by 4.1 times compared to pure nanoparticles. Rising the pH and reaction temperature improves the rate of the photodegradation reaction of RhB. The incorporation of 15 wt% reduced graphene oxide (rGO) with Sm0.04 enhanced the rate of the reaction by 1.7 and 2.4 times compared with pure Sm0.04 sample and rGO, respectively. The antibacterial and antibiofilm activities against Escherichia coli, Leclercia adecarboxylata, Staphylococcus aureus, and Enterococcus faecium are assessed by the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) broth microdilution, the agar well diffusion, the time-kill assays, the biofilm formation, and destruction assays. The bacteria used in these assessments are isolated from wastewater. The nanoparticles exhibit a bacteriostatic activity, with a better effect against the Gram-positive isolates. Co0.33Mg0.33Ni0.33SmxFe2O4 (x = 0.00) nanoparticles have the best effect. The effect is exerted after 2-3h of incubation. Gram-positive biofilms are more sensitive to nanoparticles.

Direct Affinity Ligand Immobilization onto Bare Iron Oxide Nanoparticles Enables Efficient Magnetic Separation of Antibodies.

Magnetic separation is a promising alternative to chromatography for enhancing the downstream processing (DSP) of monoclonal antibodies (mAbs). However, there is a lack of efficient magnetic particles for successful application. Aiming to fill this gap, we demonstrate the suitability of bare iron oxide nanoparticles (BION) with physical site-directed immobilization of an engineered Protein A affinity ligand (rSpA) as an innovative magnetic material. The rSpA ligand contains a short peptide tag that enables the direct and stable immobilization onto the uncoated BION surface without commonly required laborious particle activation. The resulting BION@rSpA have beneficial characteristics outperforming conventional Protein A-functionalized magnetic particles: a simple, fast, low-cost synthesis, a particle size in the nanometer range with a large effective specific surface area enabling large immunoglobulin G (IgG) binding capacity, and a high magnetophoretic velocity advantageous for fast processing. We further show rapid interactions of IgG with the easily accessible rSpA ligands. The binding of IgG to BION@rSpA is thereby highly selective and not impeded by impurity molecules in perfusion cell culture supernatant. Regarding the subsequent acidic IgG elution from BION@rSpA@IgG, we observed a hampering pH increase caused by the protonation of large iron oxide surfaces after concentrating the particles in 100 mM sodium acetate buffer. However, the pH can be stabilized by adding 50 mM glycine to the elution buffer, resulting in recoveries above 85% even at high particle concentrations. Our work shows that BION@rSpA enable efficient magnetic mAb separation and could help to overcome emerging bottlenecks in DSP.

Effect of blunging process on purification of halloysite ore from ferrous impurities by dry magnetic separation

The objective of this research is to study the effects of feed particle size, splitter angle, and washing process on Fe<sub>2</sub>O<sub>3</sub> removal efficiency in the separation of ferrous impurities from halloysite ore by dry magnetic separation in order to increase the purity of halloysite sample after crushing and blunging processes separately. Firstly, after crushing ore in a jaw crusher and sizing to -2+1 mm, -1+0.5 mm, and -0.5+0.212 mm fractions, the sized materials were fed to REMS-type dry magnetic separator at a constant belt speed of 300 rpm with the splitter angles of 0, 15, 30º separately. Maximum Fe<sub>2</sub>O<sub>3</sub> removal efficiency (FRE) (97.1%) was obtained in the nonmagnetic product at -0.5+0.212 mm size fraction and 0º splitter angle. The minimum Fe<sub>2</sub>O<sub>3</sub> content (1.3%) was reached in the nonmagnetic product obtained in the experiment with the feed size of -2+1 mm and a splitter angle of 0º. Secondly, dry magnetic separation was applied to the washed -2+0.212 mm size fraction after drying at room temperature to evaluate the coarse particle-sized halloysite ore that was gained by mechanical dispersion in the aqueous medium towards sodium hexametaphosphate (SHMP), while a significant part of the clay minerals went into fine size after the dispersion process. In the experiment performed with a 0º splitter angle after washing, it was determined that halloysite concentrate of 0.4% Fe<sub>2</sub>O<sub>3</sub> content could be obtained with 98.8% Fe<sub>2</sub>O<sub>3</sub> removal efficiency. As a result of dry magnetic separation experiments, it was seen that Fe<sub>2</sub>O<sub>3</sub> removal efficiency decreased as the splitter angle increased, while Fe<sub>2</sub>O<sub>3</sub> content in magnetic and nonmagnetic products increased. It was determined that washing and cleaning of fine-sized minerals plastered on particle surfaces after mechanical dispersion and particle release of minerals with different magnetic properties increased the dry magnetic separation efficiency, and nonmagnetic products with very low Fe<sub>2</sub>O<sub>3</sub> (0.4%) and high Al<sub>2</sub>O<sub>3</sub> (31.9%) content was obtained. The blunging process in the presence of dispersant caused the dispersion of clay minerals and allowed to liberating of the ferrous minerals from the halloysite ore, hence the increase in the FRE for the magnetic separation.

Recovery and regeneration of water-hardened magnetic composite biochar sphere for the removal of multiple heavy metals in contaminated soils

Biochar has exceeded expectations for immobilizing heavy metals (HMs), but the potential ecological risks of its long-term burial in soil limit its practical application on a large scale. To address this challenge, a novel separable water-hardened magnetic composite biochar sphere (WMBCS) was prepared and applied to remediate agricultural soils contaminated with Cd, Pb, and As. The first application of WMBCS is simultaneously effective in removing Cd (3.2–12.7%), Pb (3.3–13.1%), and As (5.0–25.6%) from soil, and the removal rates are enhanced with increasing soil moisture, application dose and incubation time. WMBCS is more efficient for removing Cd and Pb in mildly contaminated alkaline soils than in heavily contaminated acidic soils. Compared with other regeneration methods, shaking and ultrasound-assisted EDTA-2Na efficiently elutes HMs with a dissolution efficiency of over 75% within 4 h, accompanied by the lowest rate of mass loss (7.6%) and Fe leaching (475.1 mg kg−1). After 5 rounds of successive cyclic remediation, WMBCS exhibits high adsorption efficiency (26.5–30.6% for Cd, 25.4–30.2% for Pb, and 30.2–41.0% for As), magnetic separation efficiency (98.8–99.8%) and regeneration efficiency (92.3–95.4%). The main mechanisms involved in the adsorption and regeneration of WMBCS include ion exchange and chelation. WMBCS is an economical and eco-friendly material with vast unexplored potential for use in agriculture.

An air-fluidized magnetic separator and its separation performance for steel slag

In order to address the issue of magnetic agglomeration leading to poor magnetic separation efficiency and low activity enhancement, resulting in limited utilization of steel slag fine powder material, this study proposes a novel dry magnetic separator with air fluidization as the feeding method. The new separator incorporates adjustable magnetic field strength based on the material’s magnetic properties, enabling individual particle separation through a magnetic mesh while simultaneously enhancing mechanical and ultrasonic composite vibration. In addition, it enhances competitiveness by incorporating negative pressure suction. Primary magnetic separation tests on a steel slag fine powder material demonstrate that the air fluidized dry magnetic separator effectively separates inert minerals from active minerals in the steel slag powder. The iron grade in the magnetic products reaches 21.81%, which is 6.88% higher than that of the original steel slag, while the iron grade in non-magnetic products decreases to 11.93%, representing a 3% reduction compared to the original steel slag composition. Further sweeping and selection processes are expected to further improve these results, ultimately achieving effective utilization of steel slag.

Preparation of magnetic DTPA-modified chitosan composite microspheres for enhanced adsorption of Pb(II) from aqueous solution

In this study, magnetic DTPA-modified chitosan composite microspheres (MDCM) were prepared by reverse emulsion-double crosslinking method (carbodiimide followed by glutaraldehyde) for removal of Pb(II) from aqueous solution. The obtained magnetic adsorbents were characterized by FTIR, SEM, XRD, VSM, BET, and 13C NMR. The effects of the pH, contact time, initial concentration, and competitive metal cations (Na(I), Ca(II), or Mg(II)) on Pb(II) adsorption were investigated. The results revealed that MDCM exhibited high removal performance over a wide pH range and in the presence of competitive metal cations. The maximum adsorption capacity of MDCM for Pb(II) is 214.63 mg g−1 at pH 3, which is higher than most recently reported magnetic adsorbents. Adsorption kinetics and isotherms can be described by the pseudo-second-order model and Langmuir model, respectively. In addition, MDCM is easy to regenerate and can be reused five cycles with high adsorption capacity. Finally, the adsorption mechanism was further revealed by FTIR and XPS analysis. Overall, MDCM has practical application potential in removing Pb(II) from contaminated wastewater due to its high adsorption efficiency, good reusability, and convenient magnetic separation.

Fabrication and characterization of magnetic mesoporous nanoparticles for efficient determination and magnetic separation of sulfonamides in food samples.

A magnetic, mesoporous core/shell structured Fe3O4@SiO2@mSiO2 nanocomposite was synthesized and employed as a magnetic solid phase extraction (MSPE) sorbent for the determination of trace sulfonamides (SAs) in food samples. The synthesized nanocomposite was characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, X-ray diffraction, N2 sorption analysis and vibrating sample magnetometry. The results showed that Fe3O4@SiO2@mSiO2 possessed a mesoporous structure with a large surface area. Batch experiments were carried out to investigate the adsorption ability for SAs. Fe3O4@SiO2@mSiO2 showed fast kinetics and high adsorption capacity, and the pseudo-second-order model and Langmuir adsorption isotherm are well fitted with the experimental data, indicating that chemical adsorption might be the rate-limiting step. Moreover, the high adsorption capacity can be maintained for at least 8 runs, indicating excellent stability and reusability. The proposed method exhibited good linearity in the range of 0.2-500 μg L-1, the R2 values of all the analytes were greater than 0.99 and the LODs were all lower than 0.2 μg L-1. Furthermore, real food samples were successfully analyzed with Fe3O4@SiO2@mSiO2 and high recoveries varying from 89.7% and 110.6% were obtained with low relative standard deviations ranging from 1.78% to 6.91%. The Fe3O4@SiO2@mSiO2 magnetic nanocomposite is a promising sorbent for the efficient extraction of SAs from complex food samples.

Preparation of hyperbranched polyglycerol groups modified by sulfonic acid tags supported on magnetized kappa-carrageenan: A sustainable solid acid for the synthesis of 1-amidoalkyl-2-naphthols

In this study, the magnetization of kappa-carrageenan (Carr) and its modification by hyperbranched polyglycerol-sulfonic acid tags (PGly-SO3H) was found to be a good strategy to fabricate a bio-inspired solid acid as a heterogeneous nanocatalyst for the synthesis of 1-amidoalkyl-2-naphthols from aldehydes, 2-naphthol, and acetamide. The catalyst was produced by embedding Fe3O4 nanoparticles into carrageenan shell and modifying the as-produced Fe3O4@Carr with PGly tags. Then, the Fe3O4@Carr was modified by chlorosulfonic acid (Cl-SO3H) to obtain the Fe3O4@Carr-PGly-SO3H nanoparticles. The morphology and structure of Fe3O4@Carr-PGly-SO3H nanoparticles were studied by FT–IR, XRD, FE-SEM, EDX-mapping, TEM, VSM, and TGA. Aromatic aldehydes with electron-donor/ electron-acceptor substituents, heterocyclic aldehydes, and enolizable aldehyde gave the corresponding 1-amidoalkyl-2-naphthols with 85–96 % isolated yields within 15–35 min, under solvent-free conditions. The acidic content of Fe3O4@Carr-pPGly-SO3H nanoparticles was found to be 3.5 mmol H+/g, which determined by titration. As shown by TEM images, the Fe3O4 core facilitates the efficient magnetic separation. The use of a benign support material, ease of catalyst preparation and recovery, heterogeneous nature (on the basis of hot-filtration experiment), solvent-free conditions, and reusability of the nanoparticles (5 times) are some of the green aspects of the present study.

A light-driving magnetic nanocomposite based on Zn/Fe/Cu embedded in HKUST-1 applied for adsorption/degradation of Indigo carmine and pathogens

An environmentally friendly photocatalytic system (type-II heterojunction) is designed and utilized for rapid removal of Indigo carmine (IC) and pathogens from aqueous samples. This photocatalyst contains ZnFe2O4 magnetic NPs, CuO semiconductor, β-cyclodextrin (β-CD) charge transferor, and HKUST-1 light harvester. After the adsorption and photodegradation process, the nanocomposite was separated magnetically, and the supernatant was taken for the UV-Vis analysis. The maximum adsorption and photodegradation efficiency of 94.45% and 97.67% (pH = 5, in 35 min) were obtained under blue LED light (7.0 W) irradiation, due to the calculations based on UV-Vis spectrophotometer results. Simple preparation via a self-assembly route and facile separation through a superparamagnetic behavior (leading to great recovery) can be mentioned as the most brilliant excellence. Moreover, the photocatalytic performance of this magnetic nanocomposite was preserved after five recycle runs without any substantial reduction in photocatalytic activity. Also, employing a biopolymer, affordability, availability of the raw materials, good thermal stability, facile magnetic separation, simple operation, and high efficiency are upsides of the prepared nanocomposite, making it a superior photocatalyst to previous analogous systems. This nanocomposite (formulated as ZnFe2O4-CuO@β-CD)/HKUST-1) also exhibited antibacterial activity against Gram-positive and -negative strains. Based on BET (porosity) evaluations, the nanocomposite has rendered a surface area of 451.52 m2/g, which led to great adsorption results representing first-order and pseudo-second-order (Freundlich isotherm) kinetic models for the degradation and adsorption processes, respectively.