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This study employed a template method to prepare a highly ordered and interconnected porous HOM-m MgFe2O4/MgO rare earth ion-efficient adsorbent. The specific surface area of the adsorbent was as high as 130 m2/g, with saturation adsorption capacities for Ce(Ⅲ) and La(Ⅲ) of 5689.69 mg/g and 2123.50 mg/g, respectively. The adsorbent exhibited superparamagnetism with efficient and rapid separation from an aqueous solution using a magnet. The adsorption results indicated that the adsorption mechanism of HOM-m MgFe2O4/MgO towards Ce(III) and La(III) primarily involved the ion exchange and redox reactions between Mg(II) hydrolyzed from MgO and Ce(III)/La(Ⅲ), as well as the electrostatic attraction between MgFe2O4 and Ce(Ⅲ)/La(Ⅲ). Density functional theory (DFT) calculations revealed that the adsorption process was driven by the interaction of Ce(III) and La(III) ions with the surface oxygen atoms of MgFe2O4/MgO. Moreover, MgFe2O4/MgO showed a higher affinity and stronger adsorption effect towards Ce(III) than La(III). Adsorption cycling experiments demonstrated that even after three cycles, HOM-m MgFe2O4/MgO maintained good removal efficiency for Ce(III) and La(III). Therefore, this adsorbent shows promise as an effective material for removing Ce(III) and La(III) and has significant implications for the remediation of water resources in ion adsorption-type rare earth mining areas. [ABSTRACT FROM AUTHOR]

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]

This study introduces a comprehensive experiment for the preparation of a magnetic adsorbent using Enteromorpha prolifera, focusing on its structural characterization and efficacy in purifying heavy metal-contaminated wastewater. Integrating fundamental theoretical knowledge and experimental skills from courses in physical chemistry, analytical chemistry, inorganic chemistry, and instrumental analysis, this experiment bridges these foundations with cutting-edge research in chemistry, materials science, environmental science and engineering. It enables students to deeply comprehend and apply the critical scientific principle that "structure determines properties, and properties dictate function", facilitating a transition from solidifying theoretical and practical foundations to enhancing innovative thinking. Moreover, this experiment embodies the principle of "treating waste with waste", subtly instilling the concept of ecological cultivation in students' minds. [ABSTRACT FROM AUTHOR]

In this article, FeNi3@MnO2 core–shell nanostructure has been used for the first time to remove Pb(II) and Cd(II) from aqueous solutions by adsorption. The MnO2-coated FeNi3 magnetic nanoparticles were synthesized by the hydrothermal method and characterized by various analytic methods such as X-ray diffraction, Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscope, transmission electron microscope, and atomic absorption spectrometry. Adsorption parameters such as pH, contact time, adsorbent amount, and initial concentration of metal ions were investigated and optimized. FTIR Spectrum of the nanostructure was used to analyze the adsorption mechanism. FeNi3@MnO2 adsorbent was shown to follow the Langmuir adsorption isotherm and the pseudo-second-order kinetic model. The thermodynamics of adsorption confirmed an endothermic and spontaneous process. The calculated maximum adsorption capacities of the adsorbent for Pb(II) and Cd(II) were 129.2 mg g−1 and 127.8 mg g−1 at room temperature, which confirmed a good adsorption performance, especially for Cd(II). The adsorbent had a good removal efficiency of more than 99% for both metal ions, which was achieved in only 20 minutes. [ABSTRACT FROM AUTHOR]

The utilization of gypsum and biomass in environmental remediation has become a novel approach to promote waste recycling. Generally, raw waste materials exhibit limited adsorption capacity for heavy metal ions (HMIs) and often result in poor solid–liquid separation. In this study, through co-pyrolysis with corncob waste, titanium gypsum (TiG) was transformed into magnetic adsorbents (GCx, where x denotes the proportion of corncob in the gypsum–corncob mixture) for the removal of Cd(II) and Pb(II). GC10, the optimal adsorbent, which was composed primarily of anhydrite, calcium sulfide, and magnetic Fe3O4, exhibited significantly faster adsorption kinetics (rate constant k1 was 218 times and 9 times of raw TiG for Cd(II) and Pb(II)) and higher adsorption capacity (Qe exceeded 200 mg/g for Cd(II) and 400 mg/g for Pb(II)) than raw TiG and previous adsorbents. Cd(II) removal was more profoundly inhibited in a Cd(II) + Pb(II) binary system, suggesting that GC10 showed better selectivity for Pb(II). Moreover, GC10 could be easily separated from purified water for further recovery, due to its high saturation magnetization value (6.3 emu/g). The superior removal capabilities of GC10 were due to adsorption and surface precipitation of metal sulfides and metal sulfates on the adsorbent surface. Overall, these waste-derived magnetic adsorbents provide a novel and sustainable approach to waste recycling and the deep purification of multiple HMIs.

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]

Water pollution poses significant environmental and health challenges globally due to increasing industrialization and urbanization, which have led to a rise in wastewater discharges containing hazardous pollutants. These pollutants not only degrade aquatic ecosystems but also pose risks to human health. To address these issues, researchers have been exploring various treatment technologies, including adsorption, in which specific pollutants can be removed efficiently and selectively using adsorbents. Magnetic adsorbents, especially magnetite (Fe3O4), have emerged as a promising adsorbent material for water purification. Its high surface area, supermagnetism, and ease of functionalization make it suitable for the adsorption of many contaminants. In this Review, we highlight the recent developments in Fe3O4 nano adsorbents, including synthesis, properties, functionalization strategies, and challenges. The stability of Fe3O4 adsorbents was also discussed. A comparison of Fe3O4-based adsorbents and traditional adsorbents was then addressed. Finally, an outlook on the challenges and opportunities for the future advancement and practical application of these adsorbents is provided. Such an interdisciplinary research field is expected to stimulate further developments in nanoscience and advanced nanotechnology in water treatment.

Cr(VI), which has toxic effects, is a heavy metal and it must be removed from the environment due to the various damages it causes. In this study, the removal of Cr(VI) pollutants from aqueous solutions with Fe3O4-based materials using a batch adsorption technique was investigated. Magnetically modified graphene nanoplatelet (GNP)-based nanocomposites were prepared and their structures were characterized by FTIR, XRD, SEM, BET, and TGA techniques. The effects of various physicochemical parameters such as adsorbent dose, contact time, initial Cr(VI) solution concentration, pH, and the presence of coexisting ions (NaCl) on the adsorption process were investigated. Accordingly, the optimum conditions for Cr(VI) removal were determined. Nonlinear Langmuir, Freundlich, and Temkin isotherm models and pseudo-first-order, pseudo-second-order, and Bangham kinetic models were used to investigate the adsorption mechanism. The experimental data relatively fit the second-order kinetic model and the Freundlich isotherm model. The maximum adsorption capacities for pure Fe3O4 (Fe:GNP 1:0), Fe:GNP (2:1), and Fe:GNP (1:1) nanocomposite materials at 298 K and pH of approximately 5 were obtained as 12.71 mg/g, 27.03 mg/g, and 62.27 mg/g, respectively. This result showed that Cr(VI) removal increased as the amount of GNP in the composite material increased. Generally, the results confirmed that magnetically modified GNPbased adsorbents are functional and promising materials that can be used for the removal of pollutants such as Cr(VI) from aqueous media. [ABSTRACT FROM AUTHOR]

The new scheme of the rapid preconcentration of volatile organic substances followed by the thermodesorption and gas chromatographic determination by using a flame ionization detector is proposed for the analysis of air. The scheme implies a change in the geometry of the adsorbent layer in a column during the transition from adsorption to thermal desorption steps. The extraction of analytes is carried out in a wide tube, allowing quantitative adsorption at higher flow rates of the analyzed air passed through the magnetic sorbent held in a thin layer retained by a permanent magnet without any supporting frits. Novel magnetic adsorbents composed of magnetite or a zirconia/magnetite core and pyrocarbon shell are developed for this application. At the end of the adsorption step, the magnet moved out of the system, and the adsorbent transferred under the gravity force into a narrow tube, which provides the more efficient heating of the adsorbent and minimal blurring of the analyte zones during the subsequent thermal desorption. The proposed scheme allows a significant reduction (approximately 10 times) of the time required for the preconcentration of analytes, which is illustrated by the GC determination of alcohols (butanol-1, pentanol-1), phenol, and o-cresol in the air. [ABSTRACT FROM AUTHOR]

Gold is a valuable commodity with numerous industrial and technological applications. Traditional adsorbents for gold adsorption using activated carbon or ion exchange adsorption resin are limited by low capacity and selectivity. To overcome these limitations, this study introduces a core–shell structured magnetic adsorbent, Fe3O4@CuS, which can capture and recover gold through in situ reduction. The resulting gold-loaded adsorbent can be easily separated using an external magnet, offering significant advantages such as high efficiency, ease of operation, low cost, low materials consumption, and low waste generation. Results show that this adsorbent has a gold loading capacity of 407 mg/g within 4 h, and the maximum capacity can reach up to 558.7 mg/g. Moreover, this magnetic adsorbent exhibited good selectivity for gold in the presence of other base metals. This research shows the feasibility of using Fe3O4@CuS for efficient gold recovery and provides insights into its adsorption behavior and mechanism. [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]

• Magnetic MOFs with flexibility are fabricated as adsorbents for C 3 H 8 capture; • Magnetic-induced heating is utilized to realize temperature swing; • The obtained adsorbents show efficient uptake swing in magnetic-induced swing adsorption. Magnetic-induced swing adsorption is effective because of its easy operation, fast heat generation, and short distance of heat transfer. The energy efficiency of this adsorption method depends on the performance of magnetic adsorbents in alternative magnetic fields. In this work, we fabricated flexible MOF-based magnetic adsorbents and applied them in the magnetic-induced swing adsorption. When magnetic field is turned off, the adsorbents show open pores for C 3 H 8 uptake at room temperature. When magnetic field is turned on, C 3 H 8 is released because magnetic-induced heating drives the adsorbents loss their activity through conformational change of pores derived from aromatic rings tilting and rotation. The flexibility of the adsorbents decreases energy consumption to achieve desorption, which promote the energy efficiency of magnetic-induced swing adsorption. The optimal working capacity can reach 16.8 cm3 g−1, which is superior to various typical adsorbents such as F30/470 (9.32 cm3 g−1), MIL-91(Al) (3.36 cm3 g−1), and SSZ-13 zeolite (4.48 cm3 g−1). This work may open up a new avenue to address the issues caused by high energy consumption and slow heat transfer during desorption. [ABSTRACT FROM AUTHOR]

Magnetic microparticles functionalized with tailored ZnFeZr oxyhydroxide adsorbent were used for the reversible sorption of orthophosphate and recalcitrant organo-phosphonates from wastewater. The loaded particles were harvested magnetically from water, regenerated in an alkaline solution and reused numerous times. The applicability of the technology to treat brackish water reverse osmosis concentrates was tested under controlled synthetic conditions by investigating the influence of typical metals (Ca2+, Pb2+, Cu2+) on the removal of common phosphonates (HEDP, NTMP, EDTMP), and vice versa. When present at equimolar concentrations, metal cations enhanced the adsorption of phosphonates and were co-adsorbed at pH 4.0–4.5 (with removals of 83–93% for Pb2+ and 53–73% for Cu2+), likely through ternary complex formation. In the absence of metals, at pH > pHPZC ∼ 7 (the material point of zero charge), a drop in adsorption efficiency was observed for orthophosphate and all phosphonates. Thus, at pH 7, an increased adsorbent dose (>0.1 g/L) was necessary to remove 1 mg/L NTMP-P in 30 min. The reusability and effluent polishing potential of the ZnFeZr particles was demonstrated in a pilot test with municipal wastewater throughout 55 adsorption/desorption cycles without any drop in performance. Consistent removal of the non-reactive phosphorus species to ultra-low concentrations (

Aniline (benzenamine) is a very important substance used in industry even though it is classified as very toxic. The need for a practical solution to remove it from the environment is still a current topic. Aniline adsorption from water solution was evaluated using low-cost, magnetically responsive adsorbents of different type (plant derived materials, microbial and algae biomass, carbon-based and inorganic materials). Magnetic modification, based on the deposition of magnetic iron oxide particles on material surface, enabled rapid adsorbent separation from the analyzed solutions. Carbon-based materials including activated charcoal and biochars exhibited the best adsorption properties. Biochar pyrolysis temperature substantially influenced its affinity for aniline adsorption. Maximum adsorption capacity for magnetically modified spruce biochar pyrolyzed at 1200 °C was 75.7 mg/g.

A novel magnetic, structured (with ordered pores) and hybrid imprinted polymer (HMMIP) was synthesized to selectively adsorb volatile fatty acids (VFAs) from aqueous matrices. Usual characterization techniques showed that a mesoporous adsorbent was obtained with relatively low specific areas but that could selectively (imprinting factor of 1.64) remove isovaleric acid (used as template) from aqueous solutions and effluents containing VFAs with a good capacity (Qe ~ 50 mg g−1). From kinetic studies a pseudo‐nth‐order model showed the best fit to the experimental data and resulted in kn = 3 equal to 8 × 10−4 g mg−1 min−1 whereas thermodynamic studies indicated that the adsorption of isovaleric acid onto HMMIP was endothermic and entropically driven. Reuse studies indicated that HMMIP loaded with VFA could be efficiently regenerated with acetone–water solution which led to an adsorption loss of ca 10% after three regeneration/reuse cycles and that the magnetic and specific adsorbent could be removed from complex matrices with an efficiency of ca 77%. Biochemical methane production assays showed that the addition of HMMIP to anaerobic batch reactors increased by four times the methane production due to the selective adsorption of VFAs. © 2020 Society of Chemical Industry [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 utilization of gypsum and biomass in environmental remediation has become a novel approach to promote waste recycling. Generally, raw waste materials exhibit limited adsorption capacity for heavy metal ions (HMIs) and often result in poor solid–liquid separation. In this study, through co-pyrolysis with corncob waste, titanium gypsum (TiG) was transformed into magnetic adsorbents (GC x , where x denotes the proportion of corncob in the gypsum–corncob mixture) for the removal of Cd(II) and Pb(II). GC 10 , the optimal adsorbent, which was composed primarily of anhydrite, calcium sulfide, and magnetic Fe 3 O 4 , exhibited significantly faster adsorption kinetics (rate constant k 1 was 218 times and 9 times of raw TiG for Cd(II) and Pb(II)) and higher adsorption capacity (Q e exceeded 200 mg/g for Cd(II) and 400 mg/g for Pb(II)) than raw TiG and previous adsorbents. Cd(II) removal was more profoundly inhibited in a Cd(II) + Pb(II) binary system, suggesting that GC 10 showed better selectivity for Pb(II). Moreover, GC 10 could be easily separated from purified water for further recovery, due to its high saturation magnetization value (6.3 emu/g). The superior removal capabilities of GC 10 were due to adsorption and surface precipitation of metal sulfides and metal sulfates on the adsorbent surface. Overall, these waste-derived magnetic adsorbents provide a novel and sustainable approach to waste recycling and the deep purification of multiple HMIs. [Display omitted] ● Raw TiG showed no obvious adsorption for Cd(II) but reduced Pb(II) below 4 mg/L. ● Co-pyrolysis with corncob transformed TiG to highly-efficient magnetic adsorbents. ● GC 10 showed higher selectivity for Pb(II) in Pb(II)+Cd(II) binary system. ● HMIs removal was governed by surface precipitation of PbS, CdS and PbSO 4. [ABSTRACT FROM AUTHOR]

A research study was conducted to establish the effect of the presence of sodium bis-2-ethyl-hexyl-sulfosuccinate (DOSS) surfactant on the size, shape, and magnetic properties of cobalt ferrite nanoparticles, and also on their ability to remove anionic dyes from synthetic aqueous solutions. The effect of the molar ratio cobalt ferrite to surfactant (1:0.1; 1:0.25 and 1:0.5) on the physicochemical properties of the prepared cobalt ferrite particles was evaluated using different characterization techniques, such as FT-IR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption analysis, and magnetic measurements. The results revealed that the surfactant has a significant impact on the textural and magnetic properties of CoFe2O4. The capacity of the synthesized CoFe2O4 samples to remove two anionic dyes, Congo Red (CR) and Methyl Orange (MO), by adsorption from aqueous solutions and the factors affecting the adsorption process, such as contact time, concentration of dyes in the initial solution, pH of the media, and the presence of a competing agent were investigated in batch experiments. Desorption experiments were performed to demonstrate the reusability of the adsorbents.

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]

Simultaneous extraction of basic, acidic and neutral compounds is an important goal in sample preparation. In this study, dispersive solid‐phase microextraction of three analyte types was carried out in a single step. The target compounds: aniline, phenol and naphthalene with surfactant modified magnetic graphene oxide sheets, before gas chromatography with flame ionization detection. The dispersive solid‐phase microextraction performed in both cationic and anionic modes by cetyltrimethylammonium bromide and sodium dodecyl sulfate respectively. First, the analytes were vortexed and adsorbed then the supernatant was decanted with a magnet and the sorbent was eluted with the proper solvent. The linearity was obtained over a wide concentration range; 0.044–0.50, 0.043–0.50 and 0.027–0.25 µg/mL for aniline, phenol and naphthalene respectively in both modes. The limit of detection and the limit of quantitation for target analytes were 0.008 –0.02 and 0.027–0.067 µg/mL, respectively in both modes. The method relative standard deviations for the analytes (0.1 µg/mL conc.) were ranged from 4.0 to 10.9% (n = 10). Enrichment factors ranged from 60 to 373. The method was successfully evaluated to simultaneously extract three different types of analytes (basic, acidic and neutral) from water samples. The recoveries ranged from 90.0 to 100.0%. [ABSTRACT FROM AUTHOR]

Highlights • The synthesis methods of iron oxide nanoparticles are reviewed. • Desirable characteristics of the magnetic sorbents for oil removal are crucial for the design of magnetic sorbents. • Magnetic oil sorbents could be synthesized by different materials and methods. • The removal efficiencies of the magnetic sorbents can reach up to 100%. Abstract Oil pollution has posed a great threat to marine ecosystems and human health. In recent years, many studies have focused on the functionalization of magnetic iron oxide nanoparticles to obtain efficient adsorbents for oil removal from water. This review focuses on recent studies on magnetic materials based on iron oxide nanoparticles and their applications as oil sorbents. The main techniques used to obtain iron oxide nanoparticles are also discussed. The aim of this literature review is to obtain a better understanding of the materials that could be used to obtain efficient oil adsorbents with magnetic iron oxide nanoparticles and suitable synthesis strategies by encapsulating iron oxides with organic or inorganic coatings or embedding them in a matrix/support. Another purpose is to identify the desirable characteristics of magnetic materials required for high oil removal efficiency. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

(1) Background: A comparative research study to remove Congo Red (CR) and Methyl Orange (MO) from single and binary solutions by adsorption onto cobalt ferrite (CoFe2O4) and cobalt ferrite–chitosan composite (CoFe2O4-Chit) prepared by a simple coprecipitation method has been performed. (2) Methods: Structural, textural, morphology, and magnetic properties of the obtained magnetic materials were examined by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, N2 adsorption–desorption analysis, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and magnetic measurements. The optimal operating conditions of the CR and MO removal processes were established in batch experiments. The mathematical models used to describe the processes at equilibrium were Freundlich and Langmuir adsorption isotherms. (3) Results: Cobalt ferrite–chitosan composite has a lower specific surface area (SBET) and consequently a lower adsorption capacity than cobalt ferrite. CoFe2O4 and CoFe2O4–Chit particles exhibited a superparamagnetic behavior which enabled their efficient magnetic separation after the adsorption process. The research indicates that CR and MO adsorption onto prepared magnetic materials takes place as monolayer onto a homogeneous surface. According to Langmuir isotherm model that best fits the experimental data, the maximum CR/MO adsorption capacity is 162.68/94.46 mg/g for CoFe2O4 and 15.60/66.18 mg/g for CoFe2O4–Chit in single solutions. The results of the kinetics study revealed that in single-component solutions, both pseudo-first-order and pseudo-second-order kinetics models represent well the adsorption process of CR/MO on both magnetic adsorbents. In binary solutions, adsorption of CR/MO on CoFe2O4 better follows the pseudo-second-order kinetics model, while the kinetic of CR/MO adsorption on CoFe2O4–Chit is similar to that of the dyes in single-component solutions. Acetone and ethanol were successfully used as desorbing agents. (4) Conclusions: Our study revealed that CoFe2O4 and CoFe2O4–Chit particles are good candidates for dye-contaminated wastewater remediation.

Chitosan is a kind of biodegradable natural polysaccharide, and it is a very promising adsorber material for removing metal ions from aqueous solutions. In this study, chitosan-based magnetic adsorbent CMC@Fe3O4 was synthesized by a one-step method using carboxymethyl chitosan (CMC) and ferric salts under relatively mild conditions. The Fe3O4 microspheres were formed and the core–shell structure of CMC@Fe3O4 was synthesized in the meantime, which was well characterized via SEM/TEM, XRD, VSM, FT-IR, thermo gravimetric analysis (TGA), XPS, size distribution, and zeta potential. The effects of initial arsenic concentration, pH, temperature, contact time, and ionic strength on adsorption quantity of inorganic arsenic was studied through batch adsorption experiments. The magnetic adsorbent CMC@Fe3O4 displayed satisfactory adsorption performance for arsenic in water samples, up to 20.1 mg/g. The optimal conditions of the adsorption process were pH 3.0, 30−50 °C, and a reaction time of 15 min. The adsorption process can be well described by pseudo-second-order kinetic model, suggesting that chemisorption was main rate-controlling step. The Langmuir adsorption model provided much higher correlation coefficient than that of Freundlich adsorption model, indicating that the adsorption behavior is monolayer adsorption on the surface of the magnetic adsorbents. The above results have demonstrated that chitosan-based magnetic adsorbent CMC@Fe3O4 is suitable for the removal of inorganic arsenic in water.

Under the influence of human activities, atmospheric mercury (Hg) concentrations have increased by 450% compared with natural levels. In the context of the Minamata Convention on Mercury, which came into effect in August 2017, it is imperative to strengthen Hg emission controls. Existing Air Pollution Control Devices (APCDs) combined with collaborative control technology can effectively remove Hg2+ and Hg p ; however, Hg0 removal is substandard. Compared with the catalytic oxidation method, Hg0 removal through adsorbent injection carries the risk of secondary release and is uneconomical. Magnetic adsorbents exhibit excellent recycling and Hg0 recovery performance and have recently attracted the attention of researchers. This review summarizes the existing magnetic materials for Hg0 adsorption and discusses the removal performances and mechanisms of iron, carbon, mineral-based, and magnetosphere materials. The effects of temperature and different flue gas components, including O 2 , NO, SO 2 , H 2 O, and HCl, on the adsorption performance of Hg0 are also summarized. Finally, different regeneration methods are discussed in detail. Although the research and development of magnetic adsorbents has progressed, significant challenges remain regarding their application. This review provides theoretical guidance for the improvement of existing and development of new magnetic adsorbents. [Display omitted] [ABSTRACT FROM AUTHOR]

The mining of ion-adsorption rare earth minerals or ores generated a large amount of wastewater containing rare earth elements at low-concentration, resulting in continuous environmental pollution. For this problem, our study prepared an efficient, recyclable MgO/MgFe 2 O 4 magnetic adsorbent, synthesized by a template method and characterized using XRD, SEM-EDS, BET, and VSM. The isothermal adsorption experiments and adsorption kinetic experiments were carried out to evaluate the ability of MgO/MgFe 2 O 4 to remove La(Ⅲ) and Ce(Ⅲ), and the effects of the initial pH of the solution and the dosage were also investigated. FT-IR and XPS analyzed the ion-exchange mechanism between La(III) and Ce(III) ions and the hydroxyl functional groups present in the adsorbent, culminating in the formation of La/Ce-OH complexes. MgO/MgFe 2 O 4 demonstrated a theoretical adsorption capacity of 2002 mg/g and 5317 mg/g for La(III) and Ce(III), respectively, achieving removal rates of 97.2% and 98.7% in dilute solutions, marking it as a potent solution for rare earth element remediation in wastewater. This advancement holds substantial implications for environmental management within rare earth mining locales. [Display omitted] • Adsorbents showed excellent adsorption capacity for La(Ⅲ) and Ce(Ⅲ). • Efficient magnetic separation of adsorbents from water. • Analysis of adsorption mechanism by batch adsorption experiments. • Significant for the restoration of water resources in rare earth mining areas. [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]

Abstract: Functional polymers with a metal–coordination interaction have been fabricated for sample pretreatment. Poly(N‐4‐vinyl‐benzyl iminodiacetic acid‐co‐methacrylic acid‐co‐styrene)‐modified magnetic nanoparticles were prepared and used as solid‐phase extraction adsorbents for the analysis of quinolones by tuning the metal–coordination interaction. In the construction of the polymer‐based adsorbents, functional monomer (N‐(4‐vinyl)‐benzyl iminodiacetic acid) and comonomers (methacrylic acid and styrene) were fabricated onto the magnetic nanoparticles by free radical polymerization. Factors affecting the performance of the adsorbents were investigated, and the results revealed that Fe3+ played a vital role in the formation of metal–coordination adsorbents. Compared with other compounds, the resultant adsorbents displayed good selectivity to quinolones due to the metal–coordination complex (N‐4‐vinyl‐benzyl iminodiacetic acid‐Fe3+‐quinolones). Interestingly, the captured quinolones could be rapidly released by manipulating the metal–coordination interaction with Cu2+. The linearity range for analysis of the test quinolones was 0.025–2.0 μg/mL (R2 > 0.999), and the recovery varied from 80.0 to 100.7%. Further, the proposed adsorbents were combined with high‐performance liquid chromatography for the analysis of quinolones in real urine samples. The results demonstrated that the prepared adsorbents have good selectivity and sensitivity for quinolones, showing great potential for drug analysis in real samples. [ABSTRACT FROM AUTHOR]

In this review, the state of the art on the removal of malachite green dye from aqueous solution using adsorption technique is presented. The objective is to critically analyze different adsorbents available for malachite green dye removal. Hence, the available recent literature in the area is categorized according to the cost, feasibility, and availability of adsorbents. An extensive survey of the adsorbents, derived from various sources such as low cost biological materials, waste material from industry, agricultural waste, polymers, clays, nanomaterials, and magnetic materials, has been carried out. The review studies on different adsorption factors, such as pH, concentration, adsorbent dose, and temperature. The fitting of the adsorption data to various models, isotherms, and kinetic regimes is also reported. [ABSTRACT FROM AUTHOR]

In this work, two magnetic adsorbents Fe3O4@1 and Fe3O4@2 were prepared by combining Fe3O4 nanoparticles and polyoxometalate hybrids [Ni(HL)2]2H2[P2Mo5O23]·4H2O (1), [H2L]5H[P2Mo5O23]·12H2O (2) (HL = 2-acetylpyridine-thiosemicarbazone). The temperature-dependent zero-field-cooled (ZFC) and field-cooled (FC) measurements indicated the blocking temperature at 160 K and 180 K, respectively. The Brunauer–Emmett–Teller (BET) surface area of Fe3O4@1 and Fe3O4@2 is 8.106 m2/g and 1.787 m2/g, respectively. Cationic dye methylene blue (MB) and anionic dye methyl orange (MO) were investigated for selective dye adsorption on Fe3O4@1 and Fe3O4@2. The two adsorbents were beneficial for selective adsorption of cationic dyes. The adsorption efficiency of MB was 94.8% for Fe3O4@1, 97.67% for Fe3O4@2. Furthermore, the two adsorbents almost maintained the same adsorption efficiency after seven runs. The maximum MB adsorption capacity of Fe3O4@1 and Fe3O4@2 is 72.07 and 73.25 mg/g, respectively. The fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) spectra of the adsorbents collected after adsorption of MB are very similar to the initial as-synthesized Fe3O4@polyoxometalates indicating the high stability of the two adsorbents. The adsorption kinetics indicated that the MB removal followed the pseudo-second-order model. These results showed that the two adsorbents had a potential application in treating wastewater.

Precious metals which include the platinum group, gold, and silver, play indispensable roles in high technology industries of the modern world due to their outstanding physical and chemical properties. As a result of diminishing availability of mineral sources, increasing demand, and environmental concerns, the recovery of precious metals from both leaching and industrial waste solutions is becoming a very important technology. Magnetic solid phase extraction (MSPE) is a technique that has received substantial consideration in the separation and recovery of precious metals because of the many advantages it offers compared to conventional methods. This technique is based on the extraction of different analytes from solutions using solid adsorbents with magnetic properties. This review focuses on different types of magnetic adsorbents, the main procedures used for synthesis, characterization and their application in precious metals recovery based on recently published literatures. [ABSTRACT FROM AUTHOR]

In the current study on the basis of metal organic frameworks (MOFs) a new adsorbent is developed for efficient removal of Cs + from aqueous solutions. MOF, HKUST-1 prepared by a simple, rapid and efficient method was magnetized and the magnetized adsorbent was impregnated with potassium nickel hexacyanoferrate (KNiFC); a promising adsorbent for Cs + removal. The magnetic nanocomposite was characterized by X-ray diffraction (XRD), Fourier Transform Infra-Red (FTIR), Scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), Energy Dispersive Analytical X-ray (EDAX), Vibrating sample magnetometer (VSM) and Thermogravimetry Analysis (TGA) techniques. MOF/KNiFC adsorbent exhibited high adsorption affinity (K d = 1.5 × 10 3 ), high adsorption capacity (153 mg·g −1 ). The selectivity of the adsorbent towards Cs + in the presence of Na + and K + ions was excellent. The removal process was kinetically fast and the equilibration was established within 45 min. The used adsorbent was efficiently separated from the solution by applying external magnetic field. The regenerated adsorbent retained 85% of its initial capacity after five regeneration cycle. The adsorption data analyzed by Langmuir and Freundlich models. The data best fitted to the Langmuir equation indicating that the adsorption process was monolayer and homogeneous. The positive values of ΔH° indicated the endothermic nature of the sorption process and suggested that chemisorption was the predominant mechanism. The negative value of ΔG° indicated that the sorption reaction was spontaneous and more favorable at higher temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • Comprehensive discussion on synthesis & characterization of MNPs. • Mechanistic insights in pollutants and pathogens removal. • Critical remarks on pilot-scale magnetic separation technologies. • Focused on structure–property relationships between adsorbent and adsorbate. • Future research directions on MNPs are critically commented. Toxins released due to rapid industrialization and urbanization have significantly polluted the world's water resources. Current remediation technologies remain inadequate in terms of cost and effectiveness in removing low concentration pollutants. Nanomaterials have unique properties, such as precisely controllable surface areas, biocompatibility, and durability, and their surface properties can be easily modified to increase their specificity. Considering the variety of nanosorbent materials, creating economic and efficient adsorbents that could easily remove toxic pollutants from environmental water is one of the current challenges. Magnetic nanoparticles (MNPs) offer a low-maintenance and straightforward alternative to conventional adsorbents for the removal of contaminants from wastewater. This review critically evaluates recent advances in the use of magnetic materials for a variety of pollutants (anions, cations, organics, radioactive elements, and pathogens). Also, the technology developed using magnetic adsorbent for the treatment of large-scale wastewater treatment processes as magnetic separators have been reviewed in detail. The structure–property relationships between the MNPs and the pollutants were revealed based on the results of theoretical models. The challenges in developing highly stable MNPs and improvements in their practical use for the removal of toxic pollutants are also discussed in detail. Further, potential modeling for water pollutant removal, economic evaluations, toxicity and legality, and further research direction on MNPs for on-site remediation and pilot scale application are emphasized. The review bridges adsorption research and engineering science to facilitate efficient approaches for adsorption of various toxic pollutants on MNPs from wastewater. [ABSTRACT FROM AUTHOR]

Heavy metals in the water resources are one of the most important environmental problems of human societies. Up to now, various methods were considered for removal of heavy metals, which among them using of low cost adsorbents are more favorite but, separation of them from process is so difficult. In this study a novel magnetic adsorbent based on orange peel and iron oxides composite was synthesized and used for removal of cadmium ions from aqueous solution. Dry orange peels were milled and granulated in 0.125-0.250 mm by standard sieves. Magnetic iron oxide particles was separately synthesized and allowed to combine with granulated orange peels. Batch equilibrium absorption experiments were carried out at various initial Cd ion concentrations, contact times and adsorption dosages in constant temperature and pHzpc. At the end of each adsorption experiment, the separation of adsorbents from aqueous solution was performed by a magnetic bar. The results showed the magnetic orange peel iron oxide adsorbents had a high efficiency for adsorption of cadmium from aqueous solutions. The experimental adsorption isotherm of cadmium on magnetic orange peel adsorbents were determined and correlated with common isotherm equations such as Langmuir, Freundlich and Temkin models. The results indicated the Freundlich isotherm model was the best model for fitting the adsorption data.

The presence of hazardous chemicals in wastewater produced by industrial activities and human metropoles is threating the availability of safe drinking water. The development of a multifunctional material coupling adsorption and photocatalytic activity is hereby particularly promising for the removal of pollutants. We have proved the adsorption and catalytic activity of NiFe2O4-layered double hydroxide (LDH) composite through the degradation of methyl orange (MO) at room temperature under visible light. This degradation is enhanced by using a set of small light-emitting diodes (LEDs) providing a uniform 405 nm UV light. The remediation process is based on a first-step rapid adsorption of MO molecules by the LDH structures followed by the photocatalytic oxidation of the pollutant by the (·OH) radicals produced by the NiFe2O4 semiconductor nanoparticles (NPs). The magnetic properties of the ferrite NPs allow a facile separation of the composite from the liquid media via a simple magnet. NiFe2O4-LDH composite could find wide application as a highly effective adsorbent/oxidizing catalyst operating under visible or near UV light.

[Display omitted] • Co-presence of biomass lowered TiG decomposition temperature below 700 °C. • TiG decomposition correlated well with organic volatiles of biomass wastes. • No hazardous gases were released during adsorbent preparation. • GC 10 had high P adsorption (183 mg/g) and perfect magnetic separation property. • P adsorbed on GC 10 was plant-available and could be slowly released. A novel scheme was proposed to prepare magnetic adsorbents by co-pyrolysis of titanium gypsum (TiG) and agricultural biomass wastes for phosphate (P) recovery. Co-presence of biomass wastes could improve TiG decomposition in inert atmosphere to generate magnetic centers and active sites, and P adsorption correlated well with organic volatiles of biomass wastes. The adsorption process evolved from a biomass-controlled process to a TiG-controlled process when increasing the mass ratio of corncob above 10 %. The optimal adsorbent (i.e. GC 10) exhibited higher P adsorption capacity (Q m 183 mg/g) than many previous adsorbents; moreover, it can be magnetically separated from water after P adsorption. Active sites including CaO, CaS and Fe 3 O 4 were deemed as the main factors for P chemisorption and surface precipitation. Most of adsorbed P could be released continuously and slowly by dilute NaHCO 3. These results highlight potential applications of TiG and biomass waste derived adsorbents in P purification and recovery. [ABSTRACT FROM AUTHOR]

In this work the adsorption features of hydrotalcites (Al, Mg- CO3) and the magnetic properties of iron oxides have been combined in a composite to produce a magnetic adsorbent. These magnetic composites can be used as adsorbents for anionic contaminants in water and subsequently removed from the medium by a simple magnetic process. The magnetic hydrotalcites were characterized by XRD, magnetization measurements, N2 adsorption isotherms and Mössbauer spectroscopy. These magnetic adsorbents show remarkable adsorption capacity for anionic contaminants in water.

Preparation of polyethyleneimine functionalized magnetic Fe3O4 by using a one-step solvothermal method is reported in this paper. The effect of the amount of polyethyleneimine on the properties of the prepared materials including the shape, size, and adsorption performance was investigated in detail. The magnetic adsorbent with the best adsorption capacity was prepared and used for the removal of Pb(II) in an aqueous medium. Adsorption experiments were performed to evaluate the effect of different sorption parameters, such as pH, initial concentration of Pb2+, and contact time. Langmuir and pseudo-second-order models were used for isotherm and kinetic studies, through which a maximum adsorption capacity of 143 mg g−1 could be calculated. Pb(II) could be desorbed from magnetic Fe3O4 nanoparticles modified with polyethyleneimine by 0.5 mol L−1 HCl and used for five cycles without any adsorption performance loss, indicating that the polymeric magnetic adsorbent used in this work had good reusability and great potential for practical application. [ABSTRACT FROM AUTHOR]