Magnetic graphene oxide for rapid capture and efficient separation of cobalt from radioactive wastewater

The sequestration of Sr(II) and Cs(I) from aqueous solutions by magnetic graphene oxides

Studying the bonding nature of uranyl ion and graphene oxide (GO) is very important for understanding the mechanism of the removal of uranium from radioactive wastewater with GO-based materials. We have optimized 22 complexes between uranyl ion and GO applying density functional theory (DFT) combined with quasi-relativistic small-core pseudopotentials. The studied oxygen-containing functional groups include hydroxyl, carboxyl, amido, and dimethylformamide. It is observed that the distances between uranium atoms and oxygen atoms of GO (U-OG) are shorter in the anionic GO complexes (uranyl/GO(-/2-)) compared to the neutral GO ones (uranyl/GO). The formation of hydrogen bonds in the uranyl/GO(-/2-) complexes can enhance the binding ability of anionic GO toward uranyl ions. Furthermore, the thermodynamic calculations show that the changes of the Gibbs free energies in solution are relatively more negative for complexation reactions concerning the hydroxyl and carboxyl functionalized anionic GO complexes. Therefore, both the geometries and thermodynamic energies indicate that the binding abilities of uranyl ions toward GO modified by hydroxyl and carboxyl groups are much stronger compared to those by amido and dimethylformamide groups. This study can provide insights for designing new nanomaterials that can efficiently remove radionuclides from radioactive wastewater.

BackgroundIn recent days, solid-phase extraction methods are widely utilized for the extraction of drug molecules from plasma samples due to their easy operating procedures and low matrix effect. The trace-level solid-phase extraction of three structurally related antiepileptic drugs brivaracetam (BVC), eslicarbazepine acetate (ESL), and carbamazepine (CBZ) was investigated by using a magnetic porous material graphene oxide-β-cyclodextrin (MGO-CD). Morphology, magnetic properties, and structure of the synthesized MGO-CD were characterized by using FT-IR, SEM, XRD, and VSM.ResultsSolid-phase extraction (SPE) methods were used to extract the analytes from human plasma. Different extraction solvents such as acetonitrile (ACN), methanol (MeOH), acetone, chloroform (CHCl3), tertiary butyl diethyl ether (TBDE), and ethyl acetate (EtOAc) with variable polarities were used to extract drug molecules from MGO-CD. The linearity analysis showed good correlation coefficient values (R2) of 0.9989, 0.9995, and 0.9982 for BVC, ESL, and CBZ respectively. The LOD and LOQ ranges were found to be 6.14–28.32 ng mL−1 and 20.45–94.31 ng mL−1 respectively.ConclusionThe high accuracy and precision made the developed HPLC method with MGO-CD a suitable alternative for the bioequivalence study of BVC, ESL, and CBZ in human plasma. This developed HPLC-UV method has good efficiency for recoveries and good linearity and is simple to handle. And also, it gave low retention time for the three antiepileptic drugs within 8 min. It provides high efficiency for the extraction of trace-level substances from human plasma.

Hematoporphyrin-conjugated magnetic graphene oxide nanocomposite was designed and prepared as a novel promising model. Fe3O4 nanoparticles were dispersed on the surface and edges of the graphene oxide in a uniform size, and hematoporphyrin was effectively conjugated onto graphene oxide via hydrophobic interactions and π-π stacking. With the photosensitivity of hematoporphyrin and the magnetic properties of Fe3O4 nanoparticles, it can be applied for photodynamic therapy to increase the accumulation of hematoporphyrin in tumor cells. The cytotoxicity in vitro showed that hematoporphyrin conjugated magnetic graphene oxide nanocomposite irradiated at 671 nm generated cytotoxic singlet oxygen and exhibited a good inhibition to the human tumor cell HeLa (IC50 = 10.12 µg/ml), which suggested that the nanocomposite is potential for targeting photodynamic therapy as a promising drug delivery system.

The magnetic graphene oxide (MGO) composites were prepared by coprecipitation of FeCl3·6H2O and FeCl2·4H2O on graphene oxide (GO) nanosheets and characterized in detail. The Fe3O4 was uniformly deposited on the surface of GO. The synthesized MGO composites were used as a versatile adsorbent for As(V) removal from aqueous solutions. The results showed that the adsorption of As(V) on MGO is an endothermic process and the adsorption kinetic fitted the pseudo-second-order model well. The MGO composites had a good adsorption capability for As(V) removal and the adsorption isotherms were described by the Langmuir model better than by the Freundlich model. The adsorption of As(V) on MGO decreased with ascending pH due to the electrostatic interaction. In addition, the adsorption of As(V) on MGO was greatly affected by the nature and concentration of coexisting cations and anions. The presence of coexisting anions showed an inhibiting effect on As(V) adsorption, which was more efficient at low pH, whereas the presence of coexisting cations showed an enhancing effect on As(V) adsorption, which was more efficient at high pH. The results of this work indicated that the combination of the excellent adsorption capacity of GO and the magnetic properties of Fe3O4 nanoparticles is very important in drinking water treatment due to the easy magnetic separation of MGO from aqueous solutions.

Highly efficient recovery of heavy rare earth elements by using an amino-functionalized magnetic graphene oxide with acid and base resistance

The engineering of materials with controlled magnetic properties by means other than a magnetic field is of great interest in nanotechnology. In this study, we report engineered magnetic graphene oxide (MGO) in the nanocomposite form of iron oxide nanoparticles (IO)-graphene oxide (GO) with tunable core magnetism and magnetic resonance transverse relaxivity (r2). These tunable properties are obtained by varying the IO content on GO. The MGO series exhibits r2 values analogous to those observed in conventional single core and cluster forms of IO in different size regimes—motional averaging regime (MAR), static dephasing regime (SDR), and echo-limiting regime (ELR) or slow motion regime (SMR). The maximum r2 of 162 ± 5.703 mM−1s−1 is attained for MGO with 28 weight percent (wt%) content of IO on GO and hydrodynamic diameter of 414 nm, which is associated with the SDR. These findings demonstrate the clear potential of magnetic graphene oxide for magnetic resonance imaging (MRI) applications.

This study aims at the functionalization of magnetic graphene oxide nanosheets and the binding of humic acid as a lead complex ligand. Graphene oxide nanosheets possess a large surface area and various carboxylic acid groups which can be activated easily by activating agents. Therefore, they are suitable to be used for the extraction of heavy metals. To have a better process of extracting lead ions, magnetic graphene oxide was used in this research. Humic acid, as a lead metal complex agent, has an amine functional group which can be bound to modified graphene oxide from one side. The process of constructing the nano-adsorbent proposed for the preconcentration of lead ions as well as its characterization was studied by infrared spectroscopy (IR), ultraviolet-visible spectroscopy (UV-visible), field emission scanning electron microscopy (FESEM), and vibrating sample magnetometry (VSM). The designed nano-adsorbent was tested to measure lead ions in simulated and real samples of sea water, fish, and oysters. The detection limit obtained in the simulated samples was 0.07μg/L, and the linear range was 0.2-12μg/L. The apparatus used to measure the ions was a flame atomic absorption device. In the analysis of the real samples, the values obtained through flame atomic absorption were compared with those obtained through furnace atomic absorption. The proposed technique is advantageous due to being cheap, precise, and sensitive for the trace measurement of lead ions.

Nanoparticles have been widely applied to treat emulsion-containing wastewater in the form of chemical demulsifiers, such as SiO2, Fe3O4, and graphene oxide (GO). Owing to their asymmetric structures and selective adsorption, Janus nanoparticles show greater application potential in many fields. In the present work, the novel magnetic Janus graphene oxide (MJGO) nanoparticle was successfully prepared by grafting magnetic Fe3O4 to the surface of the JGO, and its demulsifying ability to treat a crude oil-in-water emulsion was evaluated. The MJGO structure and its magnetic intensity were verified by Fourier-transform infrared spectra (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), and magnetization saturation (MS) tests. Compared with GO and JGO, MJGO displayed the superior efficiency (>96%) to demulsify the crude oil-in-water emulsion, which can be attributed to the reduced electrostatic repulsion between MJGO and the emulsion droplets. Furthermore, the effects of pH and temperature on the demulsification performance of MJGO were also studied. Lastly, the recyclability of MJGO largely reduced the cost of demulsifiers in separating crude oil and water. The current research presents an efficient and recyclable demulsifier, which provides a new perspective for the structural design of nanomaterials and their application in the field of demulsification.

Reduction of soluble U(VI) to insoluble U(IV) based on photocatalysts is a simple, environmentally friendly, and efficient method for treating radioactive wastewater. The present study involved the systematic comparison of the photoelectric properties of three metalloporphyrins with different metal centers and the synthesis of a novel porphyrin-based hydrogen-bonded organic framework (Ni-pHOF) photocatalyst by modulating the surface charge microenvironment in porphyrin for enhanced photocatalytic removal of U(VI) from wastewater. Compared to the metal-free HOF, the surface charge microenvironment around the Ni atom in Ni-pHOF accelerated the reduction kinetics of U(VI) under visible light illumination at the initial moment, showing a high removal rate, even in air. The removal rate of U(VI) from aqueous solution by Ni-pHOF can achieve over 98% in the presence of coexisting nonoxidizing cations and only decreased by less than 8% after five cycles, exhibiting high selectivity and good reusability. Furthermore, Ni-pHOF can remove 86.74% of U(VI) from real low-level radioactive wastewater after 120 min of illumination, showcasing practical application potential. Density functional theory (DFT) calculations and electron paramagnetic resonance (EPR) spectra indicated that modulating the surface charge microenvironment in Ni-pHOF through porphyrin metallization is conducive to improving the charge separation efficiency, prompting more e- and •O2- to participate in the reduction reaction of U(VI). This work provides new insights into the metallization of porphyrin-based HOFs and paves a new way for the tailoring of porphyrin-based HOFs/COFs by modulating the surface charge microenvironment to achieve efficient recovery of U(VI) from real radioactive wastewater.

The large-scale application of ionic surfactants in industrial and agricultural production has caused great harm to the environment due to by-products. In order to remove this pollutant from the environment, graphene oxide as an adsorption material has received extensive attention. However, practically, it is difficult to separate the GO from aqueous solutions, making water treatment on a large scale challenging. To allow the recycling of GO, as well as enhance its adsorption ability to remove surfactants from water, a composite of magnetic graphene oxide (MGO) and 1-dodecyl-3-methylimidazolium chloride ionic liquid (IL) was synthesized. The MGO was prepared by coprecipitation, and IL-MGO was prepared by ultrasonic impregnation. Nitrogen adsorption-desorption curves show that the specific surface area of the composite was increased by the addition of the IL, from 103.28 to 163.35 m2/g. Finally, the adsorption ability of MGO and IL-MGO for the nonionic surfactant NP10EO was investigated. The results showed that the adsorption of MGO on NP10EO fits the Langmuir isothermal model and the quasi-second-order kinetic model. In addition, the equilibrium adsorption capacity of NP10EO by MGO at 298K, 308K, and 318K can reach 87.03 mg/g, 156.25 mg/g, and 214.13 mg/g. The adsorption is an endothermic reaction that occurs spontaneously and is governed by physical adsorption. The adsorption of IL-MGO on NP10EO conforms to the Langmuir isotherm model and the quasi-second-order kinetic model. At 298K, 308K, and 318K, the equilibrium adsorption capacity of NP10EO by MGO reached 261.02 mg/g, 280.24 mg/g, and 295.03 mg/g, respectively. Compared with the two results, the incorporation of IL greatly improved the adsorption capacity of MGO to NP10EO.

In this study, the electrochemical characteristics of magnetic particle-filled conductive polyaniline-doped graphene oxide nanocomposites (MDiPG) were investigated. The graphene oxide was chemically exfoliated from natural graphite flakes by the modified Hummer's method. The nanocomposite was characterised through thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy and X-ray diffraction. Its electrochemical characteristics were evaluated by cyclic voltammetry and galvanostatic charge/discharge tests. The nanocomposite electrode material was obtained through in situ polymerisation of polyaniline-doped graphene oxide combined with the mixing of a magnetic substance. The supercapacitor cell was composed of symmetric magnetic-derived electrodes, polypropylene separator, and 6M KOH as an electrolyte. The cyclic voltammetry curve study showed a good relation of both materials, where a high specific gravimetric capacitance was achieved at 303 F/g.

Aedes-borne diseases are of worldwide concern due to the lack of effective medicine and vaccination. Frequent use of chemical intervention has developed insecticide resistance in mosquitoes and posed health risks to humans and the environment, necessitating an effective and safer intervention. Graphene Oxide (GO) is an efficient material that can absorb pesticide particles and release pesticide macromolecules in a controlled manner. With the proposition that magnetic graphene oxide (MGO)-based nanoformulations can be an eco-safe and effective material for pesticide conjugation, the present study synthesized these nanoformulations conjugated with a pyrethroid, deltamethrin (DL) through chemical co-precipitation method. The formulations were validated using biophysical techniques and investigated for their efficacy against Aedes aegypti. The X-ray diffraction (XRD) pattern of nanocomposites showed six intense diffraction peaks of Fe3O4 particles, X-ray photoelectron spectroscopy (XPS) displayed the C1s, O1s, and Fe2p photoelectron lines in the MGO nanocomposite's spectra, while Field Emission Scanning Electron Microscopy (FESEM) revealed the small size and uniformity of Fe3O4 nanoparticles on the GO surface. The individual MGO and DL, as well as MGO-DL binary combinations (1:1, 1:2, and 1:3) imparted significant larval toxicity, demonstrating 30%, 50%, and 85% CTC (Co-toxicity coefficient), respectively. High corresponding Synergistic factor (SF) values indicated significant synergism increasing with the rise in deltamethrin proportion. The MGO-DL combinations also increased irritancy and flight response in adults, the notable synergistic effects imparted by the 1:3 combination. The effective actions of MGO-DL nanoformulations against mosquitoes suggest their possible use for mosquito management as a safer and more operative intervention.

Graphene oxide (GO) is a nanomaterial with excellent physico‐chemical properties widely used in a high variety of technological applications. However, conventional protocols for GO preparation rely on wet synthesis, involving extreme chemical conditions. Recently, mechanochemical synthesis has been postulated as a rapid and sustainable dry alternative for the preparation of new materials. In this work, an optimization of the mechanochemical synthesis of GO from graphite is carried out. To characterize the materials, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X‐Ray photoelectron microscopy (XPS), elemental analysis, and nitrogen adsorption–desorption isotherms are employed. The GO synthesized via dry protocol (d‐GO) and GO prepared via wet synthesis (w‐GO) are coupled with magnetic nanoparticles (MNPs) to prepare magnetic graphene oxide sorbents (d‐M@GO and w‐M@GO). Subsequently, the adsorption properties of the prepared materials toward inorganic and organic pollutants are determined and compared. The results indicated excellent adsorption efficiency for d‐M@GO, demonstrating the successful application of the mechanochemical method in magnetic sorbents preparation. To the best of the available knowledge, this is the first work to investigate the applicability of dry mechanochemical GO for the synthesis of a magnetic sorbent (d‐M@GO) and its use toward emerging concern and priority pollutants (PFAS and metal ions).

From signal amplification to restrained background: Magnetic graphene oxide assisted homogeneous electrochemiluminescence aptasensor for highly sensitive detection of okadaic acid