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In this article, we examine the recent uses of magnetic metal–organic frameworks (MMOFs). MMOFs can be used in various fields such as water purification, laboratory, food, environment, etc. Their materials can be composed of different metals and ligands, each of which has its own properties. Also, the presence of a magnetic property in these absorbents adds good features such as easy separation, faster absorption, and better interaction with other particles, which improves their application and performance. In recent years, various types of these compounds have been made, and, in this article, while classifying them, we will discuss the structure and application of some MMOFs. [ABSTRACT FROM AUTHOR]

The adsorption of toxic ions Be(II), Bi(III), Cd(II), Cr(III), and Pb(II), and also noble metals Ag(I), Au(III), and Pd(II), from aqueous solutions is studied using carbon nanotubes (CNTs), a magnetic nanosorbent composed of CNTs and magnetic nanoparticles (CNT@MNP), and activated carbon (AC). An advantage of CNT-based adsorbents over AC in terms of capacity was demonstrated, with an increase of approximately 1.5–2 times. The adsorption capacity of the synthesized magnetic adsorbent depends on the morphology of CNTs grown on iron subgroup catalysts: nickel (CNT(Ni)), cobalt (CNT(Co)), and iron (CNT(Fe)). CNT@MNP exhibited superior performance over other carbon adsorbents in magnetic solid-phase extraction, effectively separating solid and liquid phases. Additionally, composite adsorbents containing CNT(Co) and CNT(Fe) were noted for their cost-effectiveness, as they yielded satisfactory results, surpassed those obtained with the individual CNT-based adsorbents. Procedures were developed using these carbon adsorbents and their performance in the determination of elements in aqueous solutions by arc atomic emission spectrometry was estimated. [ABSTRACT FROM AUTHOR]

Recently, arsenic polluted groundwater water has become a big concern because it damages the health of humans as well as many dangers to drinking water supplies and ecosystems. Hence, an effective technique of simultaneous oxidation of As(III) to As(V), and removal of As(V) from water has gained growing attention. In this study, Rosemary extract was used in a precipitation/sonication one-pot method to synthesize Fe3O4/SiO2 nanocomposite. The capacity of the Fe3O4/SiO2 nanocomposite to remove arsenic from water as an adsorbent was studied. XRD, SEM, EDX, VSM, and FTIR techniques were used to characterize the final product. XRD pattern presented the absence of any impurities and minor, and SEM identified low agglomerated spherical particles. Reported image produced via nanosizer analysis depicts narrow size distribution. The saturation magnetization rate was 28.32 emu/g, suitable for collecting the nanocomposite from water by the magnetic field. Moreover, the isotherm and kinetics of arsenic removal from the nanocomposite were examined further. The Langmuir model best suited the acquired data, confirming an adsorption capacity of approximately 49 mg g−1. Additionally, the adsorption kinetic was identified to be in line with the pseudo-second-order kinetic model. Therefore, the synthesized magnetic nanocomposite is an effective adsorbent to remove arsenic from water. [ABSTRACT FROM AUTHOR]

This work shows that magnetic adsorbents with different porosity characteristics can be produced by carbonization and steam activation of a mixture of a furfuryl alcohol and iron-containing compound, such as ferrocene (PFA/ferrocene), FeCl3 (PFA/FeCl3) and FeSO4 (PFA/FeSO4). The materials obtained in this work possess magnetic properties that are revealed in the neodymium magnet balance test as an increase in weight loss with an increase in iron content in the material. In order to verify whether the magnetic properties facilitate the removal of the used adsorbent, the sedimentation test was carried out. The porous texture characteristics obtained from the N2 adsorption isotherms at 77 K show a huge differences in porosities depending on the type of iron compound used. The presence of ferrocene promotes the formation of mesoporosity, whereas the presence of iron(II) sulphate induces microporosity. XRD measurements reveal the presence of magnetite and hematite in all magnetic adsorbents. The intensity of the XRD peak designated to magnetite increases with an increase in the saturation magnetization. Adsorption of Congo red (CR), phenol (P), atrazine (A) and isoproturon (I) from aqueous solutions was carried out at a temperature of 24 °C in a static system. The magnetic properties accelerated the sedimentation processes and materials demonstrated a high adsorption ability toward organic contamination. The adsorption capacity on PFA-based MAC is strongly related to adsorbent porosity. [ABSTRACT FROM AUTHOR]

Phenol and its derivatives threaten human health and reduce ecosystem functions if these pollutants are released into the water. Adsorption of phenol and derivatives onto adsorbents has been considered as one of the easy operation, cost-effective as well as highly effective methods for water purification. In this work, four different biochar-based magnetic adsorbents including biochar/ZnFe2O4 (BC/ZnFe2O4), oxidized biochar/ZnFe2O4 (OX-BC/ZnFe2O4), ethylene glycol-functionalized biochar/ZnFe2O4 (EG-BC/ZnFe2O4) and polyethylene glycol-functionalized biochar/ZnFe2O4 (PEG-BC/ZnFe2O4) were successfully fabricated and used for adsorption of phenol from aqueous medium. The maximum adsorption capacity for phenol removal in the presence of BC/ZnFe2O4, OX-BC/ZnFe2O4, EG-BC/ZnFe2O4 and PEG-BC/ZnFe2O4 adsorbents was obtained 66.3, 84.8, 344.8 and 588.3 mg/g, respectively. The addition of ethylene glycol and polyethylene glycol functional groups into biochar matrix can enhance the surface area of biochar and create more active sites on the biochar surface as adsorbents. Moreover, the addition of ZnFe2O4 nanoparticles can help the synthesized adsorbents separate so easily from aqueous media. Also, the presence of ZnFe2O4 nanoparticles can increase hydrogen bonding and this can enhance removal efficiency. To optimize removal parameter such as mixture pH, contact time and dosage of adsorbent, the response surface methodology-Box–Behnken design (RSM-BBD) was employed. The optimal pH for all of the adsorbents was 7, while the optimal time as well as the optimal dosage of adsorbent was obtained 170, 60, 30 and 25 min as well as 0.7, 0.5, 0.4 and 0.15 g/L in the presence of BC/ZnFe2O4, OX-BC/ZnFe2O4, EG-BC/ZnFe2O4 and PEG-BC/ZnFe2O4 adsorbents, respectively. Kinetically, the empirical results of adsorption fitted with the second-order model and all the adsorbents followed the Langmuir isotherm model. Thermodynamic study exhibited that the adsorption of phenol on the all adsorbents was spontaneous. Also, enthalpy and entropy of all the adsorbents were positive. The obtained results showed that all of the synthesized adsorbents had good stability after six consecutive runs. [ABSTRACT FROM AUTHOR]

The adsorption of 2,4-dichlorophenoxyacetic acid on the samples of activated carbons modified with iron compounds to acquire magnetic properties of these samples was studied. The formation of the magnetic particles of iron oxide compounds, which make it possible to technologically simplify the phase separation system after adsorption, on the adsorbent surface was found by XRD analysis. A slight decrease in the adsorption capacity of the samples modified with iron compounds allows one to use them for wastewater treatment in order to remove the herbicide studied in the work. [ABSTRACT FROM AUTHOR]

We proposed a method for producing magnetic nanocomposite adsorbents, based on the adsorption of Fe3O4 magnetic nanoparticles (MNPs) on hydrophobized silicas with different structural characteristics. The magnetic properties, stability, and structural characteristics of the obtained magnetic adsorbents are studied. The effect of the incorporation of Fe3O4 nanoparticles into the adsorbent matrix on their adsorption capacity was studied. The adsorption properties of hydrophobized silicas modified by MNPs depend both on the structural parameters of the silica matrix and the sizes of adsorbate molecules. [ABSTRACT FROM AUTHOR]

The combination of two microextraction techniques (dispersive liquid-liquid microextraction [DLLME] and magnetic dispersive microsolid phase extraction [MDMSPE]) was developed and reported for atrazine and simazine preconcentration from wastewater samples. The proposal methodology involved the use of magnetite supports functionalized with different alkyl or phenyl groups. The magnetic adsorbents were synthesized by the solvothermal method assisted by microwave, characterized, and used in the sample preconcentration of atrazine and simazine. The method validation included parameters such as the wastewater matrix effect, repeatability, and recovery. The analyte separation and quantification were performed by high-performance liquid chromatography with ultraviolet detection (HPLC-DAD). Parameters, such as the polarity and mass of magnetic solids and pH, were evaluated to provide better extraction performance. The highest recoveries (> 95%) were obtained with 50 mg of the phenyl group support (CS2) at pH 5, using 5 mL of the sample and carbon tetrachloride and methanol, as extraction and dispersive solvents, respectively. The lowest limits of detection (LOD) achieved were 13.16 and 13.86 ng L−1, and the limits of quantification (LOQ) were 43.89 and 46.19 ng L−1 for simazine and atrazine, respectively, with repeatability (expressed as %RSD) below 5% in all cases. The developed method is simple, easy, and low cost for the analysis of two herbicides potentially dangerous for environmental and human health. [ABSTRACT FROM AUTHOR]

Abstract: Works of researchers of the Division of Analytical Chemistry of Moscow State University on the use of hypercrosslinked polystyrenes for the preconcentration and separation of organic compounds and ions of elements for the purpose of their subsequent determination are systematized. The works are devoted to the study of the adsorption of compounds of various classes on these materials and a possibility of combining the preconcentration of substances with modern methods of chemical analysis for the determination of amines, phenols, methylxanthines, sulfonamides, tetracyclines, and other compounds and ions of elements (gold, platinum, and rare-earth elements). The issues of using hypercrosslinked polystyrenes as stationary phases in chromatography and the creation of magnetic adsorbents based on them are also discussed. [ABSTRACT FROM AUTHOR]

We summarize data published over the last five years on the approaches and methods used in the synthesis of magnetic adsorbents based on iron oxide nanoparticles. A classification of magnetic adsorbents is proposed; examples of their use in the magnetic solid-phase extraction of organic compounds in the analysis of environmental samples, food, and biological fluids are given. [ABSTRACT FROM AUTHOR]

Biogenic iron oxides have been collected from a water stream and subsequently magnetically modified using water-based magnetic fluid. Both natural and magnetically modified materials have been characterized in detail using wavelength dispersive X-ray fluorescence spectrometry, X-ray powder diffraction, Mössbauer spectroscopy, electron microscopy and BET surface area measurements. The natural material is composed of 2-line ferrihydrite, forming hollow microtubules-sheaths of Leptothrix ochracea, and detrital components. As a result of the ferrofluid modification, maghemite nanoparticles were identified on the surface of the treated material. The active surface area of the bulk, magnetically-modified sample was 148 m g. The magnetically modified material was tested as inexpensive magnetically responsive adsorbent for the removal of selected organic xenobiotics, namely organic dyes, from aqueous solutions. The observed maximum adsorption capacities ranged between 34.3 and 97.8 mg of dye per 1 g of adsorbent. [ABSTRACT FROM AUTHOR]

A novel magnetic chelating adsorbent (CPMS) with iminodiacetate functionality was prepared by polymerization of glycidyl methacrylate-iminodiacetic acid (GMA-IDA) monomer with N, N-methylenebisacrylamide as crosslinker in the presence of monodisperse magnetic silica microspheres (MS). CPMS was characterized by IR, SEM, VSM and TGA. The experimental results revealed that MS was embedded in the gel polymer, but the morphology of CPMS was irregular. The saturation magnetization for CPMS was found to be 28.4 emu/g, and the percentage of GMA-IDA polymer grafted on MS was about 46.5%. CPMS were shown to be efficient for the removal of Pb(II) ions at pH 3.0-6.0, and the adsorption data obeyed the Langmuir equation with a maximum adsorption capacity of 54.4 mg·g at pH 5.0. Moreover, the adsorption rate of CPMS was fast and it took about 5 minutes to achieve adsorption equilibrium in aqueous solution of lower lead ions concentration. [ABSTRACT FROM AUTHOR]

Magnetic separation technology was applied in the separation of flavonoids from the licorice root in this work. Licorice flavonoids (LF) displayed a remarkable array of biological and pharmacological activities. The magnetic adsorbents with functional —NH2 groups were synthesized by immobilization of amino-silane on the surface of the magnetic silica supports, which were prepared by co-precipitation method. The adsorption and desorption characteristics of the magnetic adsorbents for the separation of LF have been evaluated. The purity of an enriched extract with this method was 16.7% while the crude extract only had about 6.8% purity. Therefore, it can be concluded that these kinds of magnetic adsorbents have selectivity to the flavonoids to some extent. The affinity selectivity of the adsorbents is based on the formation of hydrogen bonding between the —NH2 on the magnetic adsorbents and —OH, —CO on the flavonoids. [ABSTRACT FROM AUTHOR]

Flat magnetic separator was used to separate magnetic bioaffinity adsorbents from litre volumes of suspensions. Both magnetic cross-linked erythrocytes and magnetic chitosan were efficiently separated; at least 95% adsorbent recovery was achieved at maximum flow rate (1680 ml min-1). Using this system low amounts of trypsin were concentrated from large sample volumes using magnetic erythrocytes as affinity adsorbent. [ABSTRACT FROM AUTHOR]

A Davis tube (a matrix-free, flow-through magnetic separator used mainly in mineral processing) has been tested for separation of magnetic affinity biopolymer adsorbents from larger volumes of suspensions. Both magnetic chitosan and magnetic cross-linked erythrocytes could be efficiently separated from litre volumes of suspensions. Up to 90% adsorbent recovery was achieved under optimised separation conditions. [ABSTRACT FROM AUTHOR]