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Magnetic particles modified with a dicationic polymeric ionic liquid are described as a new adsorbent in magnetic solid-phase extraction. They were obtained through the copolymerization of a 1,8-di(3-vinylimidazolium)octane-based ionic liquid with vinyl-modified SiO2@Fe3O4, and were characterized by FTIR spectroscopy, X-ray diffraction, and vibrating sample magnetometry. The modified magnetic particles are effective in the extraction of organophosphate pesticides and polycyclic aromatic hydrocarbons. Also, they can provide different extraction performance for the selected analytes including fenitrothion, parathion, fenthion, phoxim, phenanthrene, and fluoranthene, where the extraction efficiency is found to be in agreement with the hydrophobicity of analytes. Various factors influencing the extraction efficiency, such as, the amount of adsorbent, extraction, and desorption time, and type and volume of the desorption solvent, were optimized. Under the optimized conditions, a good linearity ranging from 1-100 μg/L is obtained for all analytes, except for parathion (2-200 μg/L), where the correlation coefficients varied from 0.9960 to 0.9998. The limits of detection are 0.2-0.8 μg/L, and intraday and interday relative standard deviations are 1.7-7.4% ( n = 5) and 3.8-8.0% ( n = 3), respectively. The magnetic solid-phase extraction combined with high-performance liquid chromatography can be applied for the detection of trace targets in real water samples with satisfactory relative recoveries and relative standard deviations. [ABSTRACT FROM AUTHOR]

Spinel ferrite (SF) magnetic materials are an important class of composite metal oxides containing ferric ions and having the general structural formula M 2+ Fe 2 3+ O 4 (where M = Mg 2+ , Co 2+ , Ni 2+ , Zn 2+ , Fe 2+ , Mn 2+ , etc.). SFs possess unique physicochemical properties including excellent magnetic characteristics, high specific surface area, surface active sites, high chemical stability, tunable shape and size, and the ease with which they can be modified or functionalized. As a result of their multifunctional properties, affordability, and magnetic separation capability, SF adsorbents are a top choice for water purification applications that require high adsorption efficiencies and rapid kinetics. In this review, we discuss adsorption performance and possible applications of SFs and their derivatives for treating a wide range of aqueous pollutants such as metal ions, dyes, and pharmaceuticals. Key parameters influencing the sorption performance such as particle size, shape, annealing temperature, functionalization, and metal ion doping have been comprehensively discussed. In addition, adsorbate–adsorbent interactions, desorption, regeneration, and utilization of spent adsorbent have also been summarized. The review also covered, how SFs are prepared from industrial waste using green synthetic routes and general remarks about toxicological effects. [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]

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.

[Display omitted] • A magnetic, efficient, selective, and low-cost material was developed for gold recovery. • Reduction-recovery mechanism was thoroughly analyzed. • Comprehensive evaluation of magnetic iron sulfide materials for gold recovery. • Over 2000 mg/g gold recovery capacity. Gold is a highly valuable resource in our society, an efficient and selective recovery technology is necessary for gold recycling from wastes to alleviate resource shortage and environmental pollution caused by traditional mining activities. In this paper, Fe 3 S 4 /Fe 7 S 8 materials were applied for Au(III) recovery for the first time, one of the materials showed ultra-high capacity (2020.7 mg/g). Various characterizations and adsorption tests proved its excellent properties, including high capacity and selectivity, good magnetism, low cost, and reusability. Characterization results revealed Au(III) is recovered on the adsorbents through in-situ reduction, and the reduction mechanism was studied through intensive XRD and XPS analyses. This work introduced magnetic iron sulfide materials in Au(III) recovery, and demonstrated its promising features. [ABSTRACT FROM AUTHOR]

A novel triethylenetetramine-functionalized magnetic graphene oxide composite was prepared and used as a magnetic solid-phase extraction adsorbent for the fast detection of ten trace-level phenolic environmental estrogens in environmental water. The synthesized material was carefully characterized by scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, and X-ray photoelectron spectroscopy to confirm the structure and components. The adsorption and desorption conditions of the adsorbent toward phenolic environmental estrogens were optimized in detailed to obtain the best extraction recovery and elution efficiency. Under the optimum conditions, the limits of detection of the method for ten phenolic environmental estrogens were in range of 0.15-1.5 ng/L, which was lower than the reported methods for phenolic environmental estrogens detection in literatures. This could be contributed to the unique structure and property of the as-prepared material. The developed method was successfully applied for the determination of environmental water samples with recoveries ranging from 88.5 to 105.6%. [ABSTRACT FROM AUTHOR]

We examined the use of polypyrrole/maghemite (PPY/γ-Fe 2 O 3 ) and polyaniline/maghemite (PANI/γ-Fe 2 O 3 ) magnetic nanocomposites (MNCs) as active agents for removal of heavy metals ions from aqueous media. We have used chemical co-precipitation methods to prepare the maghemite nanoparticles. Subsequently, we synthesized the MNCs through emulsion polymerization of pyrrole or aniline. We estimated the efficiency of these MNCs for Cr (VI) and Cu (II) removal by using batch methods and inductively coupled plasma-optical emission spectroscopy (ICP-OES) to measure the metal content in the solutions before and after use of the MNCs. We evaluated the adsorption capacity ( q e ) of each MNC as a function of the solution pH and of the time allowed for its interaction with the metallic ions in solution. In the Cr (VI) [Cu (II)] case, we determined the value of q e as 209 [171] mg/g, for the PPY/γ-Fe 2 O 3 MNC, and 196 [107] mg/g, for the PANI/γ-Fe 2 O 3 MNC. In the PPY/γ-Fe 2 O 3 [PANI/γ-Fe 2 O 3 ] MNC case, the time necessary for attaining the q e saturation limit was of the order of 15 [35] min for both Cr (VI) and Cu (II). These characteristics compare favorably to those of alternative agents for removal of dissolved metal ions reported in the literature. [ABSTRACT FROM AUTHOR]

Recently there has been considerable interest in magnetic sorbents materials, which is added excellent capabilities such as sorption and magnetic response to an applied field. Accordingly, palygorskite nanoparticles were covered by magnetite using a co-precipitation technique and characterized by: X-ray fluorescence (XRF), X-ray diffraction (XRD), surface analysing and scanning electron microscopy (SEM) with element analysis and mapping, particle size, pore surface area (BET), density, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and zeta potential. Additionally, magnetic properties were studied by SQUID magnetometer, magnetic force microscopy (MFM) and also using a simple experimental setup. Magnetic nanoparticles produced had average diameters in a nanometric range. The amount of iron present in the nanoparticles increased by six times after the magnetization and a superparamagnetic behavior was exhibited with high saturation magnetization, from 4.0 × 10 −4 Am 2 /kg to about 20 Am 2 /kg. A weight loss was also observed around 277 °C–339 °C by TGA, indicating a structural change from magnetite to maghemite, which confirms the magnetization of palygorskite. Batch adsorption experiments were carried out for the removal of methylene blue cationic dye from aqueous solution using pure and covered by magnetite palygorskite nanoparticles as adsorbents. Furthermore, about 90% of methylene blue was removed within 3 min using magnetized palygorskite. [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]

Abstract: Mechanochemical synthesis of various types of magnetically responsive materials from non-magnetic powdered precursors has been developed. The preparation is based on the mechanochemical conversion of ferrous and ferric ions at the presence of alkaline hydroxide into magnetic iron oxides nanoparticles (maghemite identified by XRD measurements). The presence of powdered nonmagnetic materials during the mechanochemical process led to the efficient deposition of magnetic nanoparticles on the surface of the treated materials in the form of individual nanoparticles and their aggregates. The prepared magnetically responsive materials have been used as adsorbents for xenobiotics removal and as a carrier for enzymes immobilization. [Copyright &y& Elsevier]

A novel 3 D-graphene (3 D- G) magnetic nanomaterial was prepared and used as an adsorbent for the extraction of four neonicotinoid insecticides (acetamiprid, imidacloprid, thiacloprid, and thiamethoxam) from lemon juice sample. Then, HPLC with UV detection was applied for the determination of the neonicotinoid insecticides desorbed from the 3 D- G magnetic nanomaterial. The main experimental parameters that affect the extraction efficiencies such as the amount of 3 D- G magnetic nanomaterial, sample solution pH, extraction time, salting-out effect, and desorption conditions were studied and optimized. As a result, the linear concentration range of the method was from 0.3 to 100.0 ng/mL for thiacloprid, from 0.5 to 100.0 ng/mL for imidacloprid and acetamiprid, and from 1.0 to 100.0 ng/mL for thiamethoxam, with correlation coefficients of 0.9965-0.9985, respectively. The LODs of the method based on an S/ N of 3 were between 0.08 and 0.2 ng/mL. The enrichment factors obtained were between 67 and 427, and the RSDs ( n = 6) were in the range from 4.6 to 7.1%, and the recoveries of the method fell in the range of 88.75 to 111.60%. [ABSTRACT FROM AUTHOR]

Abstract: Magnetic chitosan composites (MCCs) are a novel material that exhibits good sorption behavior toward various toxic pollutants in aqueous solution. These magnetic composites have a fast adsorption rate and high adsorption efficiency, efficient to remove various pollutants and they are easy to recover and reuse. These features highlight the suitability of MCCs for the treatment of water polluted with metal and organic materials. This review outlines the preparation of MCCs as well as methods to characterize these materials using FTIR, XRD, TGA and other microscopy-based techniques. Additionally, an overview of recent developments and applications of MCCs for metal and organic pollutant removal is discussed in detail. Based on current research and existing materials, some new and futuristic approaches in this fascinating area are also discussed. The main objective of this review is to provide up-to-date information about the most important features of MCCs and to show their advantages as adsorbents in the treatment of polluted aqueous solutions. [Copyright &y& Elsevier]

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]

Abstract: Magnetic hydroxyapatite nanoparticles (MNHAP) adsorbents were synthesized and were used for the removal of Cd2+ and Zn2+ from aqueous solutions. The properties of this magnetic adsorbent were characterized by scanning electron microscopy (SEM), energy dispersive analysis system of X-ray (EDAX), X-ray powder diffraction (XRD) analysis, zeta potential, BET surface area measurements and magnetization curves. Experiments were carried out to investigate the influence of different sorption parameters, such as contact time, initial concentration of metal ions, the dosage of MNHAP, pH value of the solutions and competitive adsorption behavior. Kinetic data are well fitted by a pseudo second-order model and the equilibrium data are analyzed by Langmuir model very well with high correlation coefficient. From the Langmuir isotherms, the maximum adsorption capacities of MNHAP adsorbents towards Cd2+ and Zn2+ are 1.964 and 2.151mmolg−1, respectively. The results revealed that the most prominent advantage of the prepared MNHAP adsorbents consisted in their separation convenience compared to the other adsorbents. [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]

Abstract: Magnetic poly(2-hydroxyethyl methacrylate) (mPHEMA) beads were used in the removal of anti-dsDNA antibodies from systemic lupus erythematosus (SLE) patient plasma in a magnetically stabilized fluidized bed. mPHEMA beads, in the size range of 80–120μm, were produced by suspension technique. Then, DNA was immobilized onto mPHEMA beads by carbodiimide activation. Magnetic beads were contacted with blood in in vitro systems. Loss of blood cells and clotting times were followed. mPHEMA beads were characterized by scanning electron microscopy (SEM). Important results obtained in this study are as follows: the mPHEMA beads have a spherical shape and porous structure. Loss of cells in the blood contacting with mPHEMA/DNA was negligible. The anti-dsDNA adsorption capacity decreased significantly with the increase of the flow-rate. With increasing anti-dsDNA antibody concentration, the amount of antibody adsorbed per unit mass increased, then reached saturation. Maximum anti-dsDNA antibody adsorption capacity was found to be 97.8mg/g. Pathogenic antibody molecules could be repeatedly adsorbed and desorbed with these magnetic beads without noticeable loss in their antibody adsorption capacity. Because of the good blood-compatibility, mPHEMA is hopeful for the treatment of SLE by magnetically stabilized fluidized bed systems in the future. [Copyright &y& Elsevier]

Abstract: Magnetic solid phase extraction was tested for the preconcentration of non-ionic surfactants based on oxyethylated nonylphenol, aliphatic alcohols and hydrogenated fatty acid methyl esters from water. Magnetic hydrophobic adsorbents exhibited the best extraction characteristics. Surfactants with the middle oxyethylation level were extracted efficiently while the extraction of surfactants with low and high oxyethylation levels was very low. [Copyright &y& Elsevier]

In this work the adsorption features of NaY zeolite with the magnetic properties of iron oxides have been combined in a composite to produce a magnetic adsorbent. These magnetic composites can be used as an adsorbent for metallic contaminants in water and subsequently removed from the medium by a simple magnetic process. The zeolites:iron oxide magnetic composites, were prepared by using NaY with weight ratio of 3:1 and were characterized by powder X-ray diffraction (XRD), magnetization measurements, chemical analyses, N2 adsorption isotherms and Mössbauer spectroscopy. Nitrogen adsorption isotherms showed that the surface area decreased from 505m2g-1 for the pure NaY to 353m2g-1 for the NaY:Fe oxide 3:1 composite. The adsorption isotherms of metal ions Cr3+, Cu2+ and Zn2+ from aqueous solution onto the composites also showed that the presence of iron oxide does not affect the adsorption capacity. [Copyright &y& Elsevier]

In this work, the adsorption features of clays with the magnetic properties of iron oxides have been combined in a composite to produce a magnetic adsorbent. These magnetic composites can be used as adsorbent for contaminants in water and can be subsequently removed from the medium by a simple magnetic process. The bentonite–iron oxide magnetic composites have been prepared with weight ratios of 2:1, 1.5:1, and 1:1 and characterized by powder X-ray diffraction (XRD), thermogravimetric analysis (TG), magnetization measurements, chemical analyses, temperature-programmed reduction (TPR), N2 adsorption–desorption isotherms, Mo¨ssbauer spectroscopy, and scanning electron microscopy (SEM). The results suggest that the main magnetic phase present is maghemite (γ-Fe2O3). A magnetization enhancement can be produced by treatment with H2 at 600 °C to reduce maghemite to magnetite. Nitrogen adsorption isotherms showed that the surface area and microporosity increased from 7 m2 g−1 (Vmicropores=0.003 cm3 g−1) for the pure bentonite to 55 m2 g−1 (Vmicropores=0.009 cm3 g−1) for the composite clay/iron oxide (2:1). The adsorption isotherms of metal ions Ni2+, Cu2+, Cd2+, and Zn2+ from aqueous solution onto the composites also showed that the presence of iron oxide produced an increase on the adsorption capacity of the bentonite. [Copyright &y& Elsevier]

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]

Halloysite/biochar was prepared by co-pyrolysis at different temperatures using coconut shell and halloysite as raw materials. Magnetic adsorbents were prepared through ball-mill extrusion with Fe 3 O 4 and the halloysite/biochar and the capacity of the adsorbents to adsorb Pb(II) from water was evaluated and compared. The effects of pH, contact time, and initial Pb(II) concentration on the adsorption capacity of the magnetic adsorbents for Pb(II) were investigated. The pseudo-second-order (R 2 =0.9999) and Langmuir isothermal models (R 2 =0.9906) fit the experimental data well. The prepared samples denotes as MBM-HBC700 exhibited the highest Pb(II) adsorption capacity (833.33 ± 16.71 mg·g-1), and the removal efficiency of Pb(II) by the magnetic adsorbents was above 90% after four adsorption–desorption cycles. Complexation, cation exchange, cation–π interaction, precipitation, pore filling and electrostatic adsorption have been proposed as the main removal mechanisms. After applying MBM-HBCs to simulated electroplating wastewater, the contents of Pb(II), Cu(II), Zn(II), and Cr(VI) were significantly lower than the discharge standard of China. The magnetic adsorbents prepared in this study have wide application prospects in the treatment of Pb(II) in wastewater, thus providing a new approach for promoting waste recycling and utilization. [Display omitted] ● Magnetic halloysite/biochar were prepared through ball-mill extrusion with Fe 3 O 4 ● The modified biochar exhibited extraordinary Pb(II) adsorption capacity ● Remained great Pb(II) removal efficiency after four adsorption–desorption cycles ● Adsorption mechanisms: complexation, cation exchange, cation–π interaction, etc. ● Removed Pb(II), Cu(II), Zn(II), and Cr(VI) from simulated electroplating wastewater [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. [ABSTRACT FROM AUTHOR]

In this study, two alternative synthesis routes for magnetic adsorbents were evaluated to remove Pb(II) and Cd(II) in an aqueous solution. First, activated carbon was prepared from argan shells (C). One portion was doped with magnetite (Fe3O4+C) and the other with cobalt ferrite (CoFe2O4+C). Characterization studies showed that C has a high surface area (1635 m2 g−1) due to the development of microporosity. For Fe3O4+C the magnetic particles were nano-sized and penetrated the material's texture, saturating the micropores. In contrast, CoFe2O4+C conserves the mesoporosity developed because most of the cobalt ferrite particles adhered to the exposed surface of the material. The adsorption capacity for Pb(II) was 389 mg g−1 (1.88 mmol g−1) and 249 mg g−1 (1.20 mmol g−1); while for Cd(II) was 269 mg g−1 (2.39 mmol g−1) and 264 mg g−1 (2.35 mmol g−1) for the Fe3O4+C and CoFe2O4+C, respectively. The predominant adsorption mechanism is the interaction between -FeOH groups with the cations in the solution, which are the main reason these adsorption capacities remain high in repeated adsorption cycles after regeneration with HNO3. The results obtained are superior to studies previously reported in the literature, making these new materials a promising alternative for large-scale wastewater treatment processes using batch-type reactors. [ABSTRACT FROM AUTHOR]

Four magnetic biochars (MBs) were prepared from two mixtures of Sappeli sawdust with NiCl 2 solution or Sappeli sawdust with NiCl 2 plus ZnCl 2 solutions. These mixtures formed two pastes that were dried and further pyrolyzed at 700 °C under nitrogen flow. The pyrolyzed material was leached out with 0.1 M HCl under conventional reflux (AL- 80 °C, 2 h) or assisted by ultrasound-leaching (US- 15 min, 600 W), obtaining four biochars: SNiAL, SNiUS, SNiZnAL, SNiZnUS. The biochars were characterized by VSM, XRD, FTIR, isotherms of adsorption and desorption of nitrogen, pH pzc , hydrophobically characteristics (HI), TGA, elemental analysis (CHN/O). The data show that using the leaching process assisted by ultrasound can obtain biochars that present good magnetization saturation, with a lower leaching time than conventional leaching. The four biochar were tested as adsorbents to remove ten emerging contaminants and four dyes of aqueous effluents. It was observed that the impregnation of zinc chloride in the samples led to an increase in the surface areas of the magnetic biochars, which influenced the most of sorption capacities of the adsorbents for the different sorbing species. Making a ratio of sorption capacities of SNiAL/SNiZnAL and SNiUS/SNiZnUS, it was obtained the values, respectively, of 0.9761, and 0.9710 (Acid Red 1), 2.057, and 3.030 (Reactive Blue 4), 4.192, and 1.971 (Basic Violet 3), 3.359, and 1.129 (Basic Green 1), 1.673, and 1.835 (Paracetamol), 3.612, and 3.779 (Propranolol), 5.871, and 5.171 (Sodium Diclofenac), 1.457, and 1.607 (Nicotinamide), 1.094 and 1.093 (Caffeine), 1.167, and 2.398 (4-chloroaniline), 1.009 and 0.9965 (2-nitrophenol), 1.156 and 1.341 (Resorcinol), 1.299 and 1.331 (Hydroquinone), 0.9975 and 1.019 (4-bromophenol). [Display omitted] [ABSTRACT FROM AUTHOR]

Graphene and its derivatives, especially graphene oxide (GO), are attracting considerable interest in the fabrication of new adsorbents that have the potential to remove various pollutants that have escaped into the aquatic environment. Herein, the development of GO/chitosan (GO/CS) composites as adsorbent materials is described and reviewed. This combination is interesting as the addition of graphene to chitosan enhances its mechanical properties, while the chitosan hydrogel serves as an immobilization matrix for graphene. Following a brief description of both graphene and chitosan as independent adsorbent materials, the emerging GO/CS composites are introduced. The additional materials that have been added to the GO/CS composites, including magnetic iron oxides, chelating agents, cyclodextrins, additional adsorbents and polymeric blends, are then described and discussed. The performance of these materials in the removal of heavy metal ions, dyes and other organic molecules are discussed followed by the introduction of strategies employed in the regeneration of the GO/CS adsorbents. It is clear that, while some challenges exist, including cost, regeneration and selectivity in the adsorption process, the GO/CS composites are emerging as promising adsorbent materials. [ABSTRACT FROM AUTHOR]

• A concept of composable paper-based analytical devices has been proposed. • The concept of composable μPADs is illustrated by the determination of flavonoids. • The detection principle includes reduction of silver nitrate to silver nanoparticles. • Architectures for the determination of high and low concentrations flavonoids are reported. • A composable μPAD utilizing preconcentration on a magnetic adsorbent is described. A concept of composable paper-based analytical devices (composable μPADs) is proposed. The key idea of composable μPADs is to develop a paper-based analytical platform that can be easily and quickly assembled into a desired architecture from standard pre-made paper-based parts. Here it is illustrated by the determination of several flavonoids, as an important class of natural polyphenol antioxidants. Two methods for the determination of flavonoids, at high (a two-part configuration) and at low (a three-part configuration including an additional preconcentration zone) concentrations, were developed. The principle for flavonoid detection was based on their ability to reduce silver nitrate to silver nanoparticles (AgNPs) producing an intense surface plasmon resonance band. The effects of main factors on the formation of AgNPs and the analytical response in proposed μPADs were studied. The concentration limits of detection were 2.3, 5.2, 14 μg mL−1 and the absolute limits of detection were 0.12, 0.26, 0.70 μg for quercetin, morin and dihydroquercetin, respectively. To determine flavonoids at low concentration level, a three-part configuration of a composable μPAD utilizing preconcentration on magnetic hypercrosslinked polystyrene was used. It was shown that such preconcentration increases 5 times sensitivity of morin determination. The method was applied to the analysis of hawthorn tincture and onion peel. [ABSTRACT FROM AUTHOR]

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. [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. [ABSTRACT FROM AUTHOR]

The utilization and repurposing of waste materials from mining and minerals industry as low-cost adsorbents for valuable metals have received significant attention due to increasing drive for waste valorization, environmental protection and sustainable development. This study investigates the ability of magnetic nickeliferous pyrrhotite obtained from nickel sulphide mine tailings in Western Australia as adsorbent for gold (Au) from chloride solution. The influence of different variables, such as pH, contact time, initial Au concentration, and chloride (Cl–) concentrations on Au adsorption were examined. The use of magnetic adsorbents is considered as an emerging technology in the recovery of precious metals from aqueous solutions and offers a number of advantages related to ease of solid-liquid separation. The nickeliferrous pyrrhotite samples, composed of pyrrhotite (Fe (1-X) S, 65%), pentlandite ((Fe,Ni) 9 S 8 , 32%) and trace impurities of alumino-silicate minerals (3%), were collected manually using a permanent magnet, and were prepared by crushing and grinding to the desired particle size. Complete Au recovery (100%) was achieved after 15 min of contact time at acidic pH. It was also found that the magnetic adsorbent exhibited high loading capacity as evident by 100% Au recovery achieved even at higher initial Au concentrations and after eight times re-use of loaded particles. High Cl– concentration was observed to have a negative effect on Au uptake. The galvanic interaction between pentlandite and pyrrhotite as the possible mechanism for Au recovery is discussed. Repurposing nickeliferous pyrrhotite from mine wastes as magnetic adsorbent for Au offers a very attractive application for the material. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Magnetic solid-phase extraction (MSPE), an emerging sample pretreatment technique, has received much attention because of its environment friendliness, rapid separation process, excellent adsorption efficiency, and easily automated assay. This paper reviews the nature of MSPE, and the types and preparation of magnetic adsorbents. It also discusses recent application of MSPE to the analysis of trace contaminants in food samples, such as pesticides and veterinary drug residuals, polymer additives, and heavy metals ions. The future development trends of MSPE in food safety analysis are also investigated. High efficiency, low cost, and environmental-friendly food safety detection techniques are expected with the application of MSPE. • Recent applications of MSPE in food safety analysis are reviewed. • Different preparation strategies for modified magnetic nanoparticles are discussed. • The analysis of various pollutants in food is overviewed. • The possible adsorption mechanisms are discussed. [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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]