A novel magnetic Fe3O4/SiO2 core-shell nanorods for the removal of arsenic

Magnetic mesoporous Fe3O4@nSiO2@mSiO2 nanoparticles for high-throughput mass spectrometry detection of hydrolyzed products of organophosphorus nerve agents

Rapid and accurate detection of hydrolyzed products of organophosphorus nerve agents (OPNAs) is an important method to effectively confirm the use of these agents. OPNAs are rapidly hydrolyzed to the methyl phosphonates (MPs) in the environment, which can be used as environmental traceability marker for OPNAs. Herein, magnetic mesoporous materials combined with real-time in situ mass spectrometry (MS) were used to achieve high-throughput detection of MPs. Novel magnetic mesoporous nanoparticles Fe3O4@nSiO2@mSiO2 were synthesized via co-condensation of tetraethyl orthosilicate and cetyltrimethylammonium bromide (CTAB) on the surface of nonporous silica-coated Fe3O4 under alkaline conditions. CTAB templates were removed by the reflux of ethanol (0.0375 mM ammonium nitrate) to form mesoporous SiO2, which has a large specific surface area of 549 m2 g-1 and an excellent magnetization strength of 59.6 emu g-1. A quick, cost-effective, rugged, and safe magnetic preparation method, magnetic QuEChERS, was established with magnetic mesoporous nanoparticles (Fe3O4@nSiO2@mSiO2) as adsorption materials for direct analysis in real-time and tandem MS (DART-MS/MS) of MPs in environmental samples. The method exhibits good linearity (R2 > 0.992) in the range of 20.0-4.00 μg mL-1, the limits of detection were <5.00 ng mL-1, the limits of quantification were <20.0 ng mL-1, and the extraction recoveries were 70.2-98.1%, with relative standard deviations (RSDs) in the range of 1.97-10.6%. Additionally, using this method, analysis of 70 environmental samples could be completed within 20 min. Then, the M-QuEChERS-DART-MS/MS method was applied to the 52nd Organisation for the Prohibition of Chemical Weapons (OPCW) environmental spiked samples analysis, where the accuracy was 95.2-116%, and the RSD was 1.16-7.83%. The results demonstrated that Fe3O4@nSiO2@mSiO2 based on the QuEChERS method can quickly and efficiently remove the matrix of environmental samples and when coupled with the DART-MS/MS can achieve high-throughput determination of MPs in environmental samples.

Chloride converts lead slag into a bifunctional material to remove heavy metals

Efficient and safe removal of arsenic and lead from industrial wastewater is essential for ecological protection. In this study, we developed a novel method using lead slag as a purifying agent and sodium chloride as a reinforcing agent to remove arsenic and lead from industrial wastewater. Through a combination of experiments and simulations, we elucidated the mechanisms involved in this reaction. The initial concentrations of As and Pb ions in the industrial wastewater were 4333 and 188 mg/L, respectively. After the reaction at 25 °C and a pH ranging from 9.7 to 10, the concentrations of arsenic and lead were reduced to 4.9 mg/L and 0.008 mg/L, respectively, achieving a removal rate of 99.9%. Our experimental results demonstrated that Pb2+ and AsO43- ions released from the lead slag and industrial wastewater reacted with Cl- ions to form Pb5(AsO4)3Cl precipitates, thus effectively eliminating a significant amount of As and Pb species. Simulation studies indicated that Pb5(AsO4)3Cl exhibited exceptional stability below 400 °C and could be directly stored. Additionally, the lead slag, which is rich in silica, played a crucial role in removing and stabilizing As and Pb ions. Under alkaline conditions, silica encapsulated the As and Pb species, adhering to the surface of the Pb-As co-precipitates and forming dense, irregular, small particles with internal and external structures that impeded the efflux of As and Pb ions. This phenomenon was confirmed through scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The kinetics of As and Pb ion removal was consistent with the pseudo-second-order kinetic model, indicating that the removal process was primarily governed by chemical interactions. Lead slag exhibits significant potential and advantages in the removal of As and Pb. This innovative method offers an effective approach to address heavy metal contamination in industrial wastewater, thus contributing to ecological protection.

Development of an Fe3O4 Surface-Grafted Carboxymethyl Chitosan Molecularly Imprinted Polymer for Specific Recognition and Sustained Release of Salidroside

The choice of carrier material is critical in the study of natural drug release preparations and glycosylated magnetic molecularly imprinted materials. The stiffness and softness of the carrier material affect the efficiency of drug release and the specificity of recognition. The dual adjustable aperture-ligand in molecularly imprinted polymers (MIPs) provides the possibility of individualized design for sustained release studies. In this study, a combination of paramagnetic Fe₃O₄ and carboxymethyl chitosan (CC) was used to enhance the imprinting effect and improve drug delivery. A combination of tetrahydrofuran and ethylene glycol was used as a binary porogen to prepare MIP-doped Fe₃O₄-grafted CC (SMCMIP). Salidroside serves as the template, methacrylic acid acts as the functional monomer, and ethylene glycol dimethacrylate (EGDMA) serves as the crosslinker. Scanning and transmission electron microscopy were used to observe the micromorphology of the microspheres. The structural and morphological parameters of the SMCMIP composites were measured, including the surface area and pore diameter distribution. In an in vitro study, we found that the SMCMIP composite had a sustained release property of 50% after 6 h of release time in comparison to the control SMCNIP. The total amounts of SMCMIP released at 25 °C and 37 °C were 77% and 86%, respectively. In vitro results showed that the release of SMCMIP followed Fickian kinetics, meaning that the rate of release is dependent on the concentration gradient, with diffusion coefficients ranging from 3.07 × 10^-2 cm²/s to 5.66 × 10^-3 cm²/s. The results of cytotoxicity experiments showed that the SMCMIP composite did not have any harmful effects on cell growth. The survival rates of intestinal epithelial cells (IPEC-J2) were found to be above 98%. By using the SMCMIP composite, drugs may be delivered in a sustained manner, potentially leading to improved therapeutic outcomes and reduced side effects.

Understanding the adsorption of iron oxide nanomaterials in magnetite and bimetallic form for the removal of arsenic from water

Arsenic decontamination is a major worldwide concern as prolonged exposure to arsenic (&gt;10 µg L-1) through drinking water causes serious health hazards in human beings. The selection of significant, cost-effective, and affordable processes for arsenic removal is the need of the hour. For the last decades, iron-oxide nanomaterials (either in the magnetite or bimetallic form) based adsorptive process gained attention owing to their high arsenic removal efficiency and high regenerative capacity as well as low yield of harmful by-products. In the current state-of-the-art, a comprehensive literature review was conducted focused on the applicability of iron-based nanomaterials for arsenic removal by considering three main factors: (a) compilation of arsenic removal efficiency, (b) identifying factors that are majorly affecting the process of arsenic adsorption and needs further investigation, and (c) regeneration capacity of adsorbents without affecting the removal process. The results revealed that magnetite and bimetallic nanomaterials are more effective for removing Arsenic (III) and Arsenic (V). Further, magnetite-based nanomaterials could be used up to five to six reuse cycles, whereas this value varied from three to six reuse cycles for bimetallic ones. However, most of the literature was based on laboratory findings using decided protocols and sophisticated instruments. It cannot be replicated under natural aquatic settings in the occurrence of organic contents, fluctuating pH and temperature, and interfering compounds. The primary rationale behind this study is to provide a comparative picture of arsenic removal through different iron-oxide nanomaterials (last twelve yearsof published literature) and insights into future research directions.

Recent developments of magnetic nanoadsorbents for remediation of arsenic from aqueous stream

One of the emerging environmental concerns is the high levels of arsenic ions found in groundwater and other water sources. Decontaminating water that contains arsenic is crucial for environmental and health reasons. Nano-adsorbents have gained much interest recently for the adsorptive removal of arsenic species from wastewater. On the other hand, for their prospective use in natural water treatment, current nano-adsorbents must be separated from treated fluids. Researchers studied nanocomposite iron oxide-based adsorbents to overcome these problems and to design effective sorbents for removing arsenic. This study provides a summary of current developments in the field of magnetic nanoadsorbents for the removal of various arsenic compounds from wastewater. Adsorption of arsenic from groundwater has been found to be very promising for magnetic nanoadsorbents. In order to eliminate arsenic from the aqueous phase, magnetic nanocomposite adsorbents may offer practical and affordable water purification solutions.

Magnetic nanocomposite adsorbents for abatement of arsenic species from water and wastewater

The presence of high concentrations of arsenic species in drinking water and other water bodies has become one of the most critical environmental concerns. Therefore, decontamination of arsenic-containing water is essential for improved health and environmental concern. In recent years, nano-adsorbents have been widely used for the adsorptive removal of arsenic from water. Separating existing nano-adsorbents from treated waters, on the other hand, is a critical issue for their potential applications in natural water treatment. To address these issues and to effectively remove arsenic from water, researchers looked at iron oxide-based magnetic nanocomposite adsorbents. The magnetic nanoadsorbents have the benefit of surface functionalization, making it easier to target a specific pollutant for adsorption, and magnetic separation. In addition, magnetic nanoparticles have a large surface area, high chemical inertness, superparamagnetic, high magnetic susceptibility, small particle size, and large specific surface area, and are especially easily separated in a magnetic field. Magnetic nano-adsorbents have been discovered to have a lot of potential for eliminating arsenic from water. The recent advances in magnetic nano-absorbents for the cleanup of arsenic species from water are summarized in this paper. Future perspectives and directions were also discussed in this article. This will help budding researchers for the further advancement of magnetic nanocomposites for the treatment of water and wastewater contaminated with arsenic.

Magnetic polyphenol nanocomposite of Fe3O4/SiO2/PP for Cd(II) adsorption from aqueous solution

In order to solve the water solubility and difficult re-use of plant polyphenol (PP) in Cd(II) adsorption, PP was immobilized on the surface of magnetic material in this study. A core-shell nanocomposite Fe₃O₄/SiO₂/PP (∼18 nm) was synthesized with 3-8 nm SiO₂ and 2-5 nm PP. TGA analysis revealed the PP coating amount was 2.39%. VSM detection suggested that saturation magnetization of Fe₃O₄/SiO₂/PP was 45.94 emu/g. The adsorption equilibrium was reached in 2 h and the adsorption kinetics followed a pseudo-second-order model. The adsorption data fitted well to a Langmuir isotherm, achieving a 98.6% of Cd(II) removal at 0.6 g, pH 7.0, 298 K and 160 rpm. The adsorption capacity of Cd(II) on Fe₃O₄/SiO₂/PP highly depended on the pH. The adsorption capacity increased as the initial solution pH was increased in the range of 3.0-8.0. The adsorbed Cd(II) on Fe₃O₄/SiO₂/PP could be effectively desorbed by 0.1 mol/L of HNO₃ and the Fe₃O₄/SiO₂/PP still maintained a stable adsorption capacity after five cycles. The adsorption mechanism of Cd(II) on Fe₃O₄/SiO₂/PP is mainly dependent on complexation and electrostatic adsorption from the FTIR and XPS analyses. This study provided a new way for PP to remove Cd(II) from aqueous solution.

Two Novel BODIPY-Functional Magnetite Fluorescent Nano-Sensors for Detecting of Cr(VI) Ions in Aqueous Solutions

In this study, we developed two different very sensitive magnetite fluorescent Fe₃O₄@SiO₂-TPED-BODIPY and Fe₃O₄@SiO₂-TMPTA-BODIPY nano-sensors for the selective detection of Cr(VI) ions. The Cr(VI) metal ions sensing is based on the fluorescent quenching of BODIPY functionalized with Fe₃O₄@SiO₂-TPED and Fe₃O₄@SiO₂-TMPTA nanoparticles in the ethanol-water environment. Characterization of the newly synthesized fluorescent BODIPY compound was performed on a ¹H and ¹³C-NMR spectrometer. The morphology, chemical and physical properties of the sensing nano-sensors were studied by transmission thermogravimetric analysis (TGA), X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscopy (SEM), FT-IR spectroscopy, and transmission electron microscopy (TEM). UV-visible and fluorescent spectroscopy were used to characterize BODIPY functionalized magnetite fluorescent nano-sensors. Characterization measurements revealed that the mean particle diameter of magnetite fluorescent Fe₃O₄@SiO₂-TPED-BODIPY and Fe₃O₄@SiO₂-TMPTA-BODIPY nano-sensors was 18.5 and 19 nm, respectively. The magnetite fluorescent Fe₃O₄@SiO₂-TPED-BODIPY and Fe₃O₄@SiO₂-TMPTA-BODIPY nano-sensors (0.1 gL^-1 in EtOH/H₂O, v/v (3/7)) showed fluorescence quenching responses towards Cr(VI) ions in the medium at pH:1. The fluorescence quenches of the magnetite fluorescent Fe₃O₄@SiO₂-TPED-BODIPY and Fe₃O₄@SiO₂-TMPTA-BODIPY nano-sensors by Cr(VI) were completed in first 5 and 3 min. Respectively. These features provide potential uses of BODIPY functionalized magnetite fluorescent nano-sensors (Fe₃O₄@SiO₂-TPED-BODIPY and Fe₃O₄@SiO₂-TMPTA-BODIPY) as a new class of non-toxic sensors for environmental applications. Graphical Abstract.

Magnetic molecularly imprinted specific solid-phase extraction for determination of dihydroquercetin from Larix griffithiana using HPLC

The naturally occurring quercetin flavonoid, dihydroquercetin, is widely distributed in plant tissues and has a variety of biological activities. Herein, a magnetic molecularly imprinted solid-phase extraction was tailor made for selective determination of dihydroquercetin in Larix griffithiana using high-performance liquid chromatography. Amino-functionalized core-shell magnetic nanoparticles were prepared and characterized using scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, and infrared spectroscopy. The polymer had an average diameter of 250 ± 2.56 nm and exhibited good stability and adsorption for template molecule, which is enriched by hydrogen bonding interaction. Multiple factors for extraction, including loading, washing, elution solvents, and extraction time, were optimized. The limit of detection was 1.23 μg/g. The precision determined at various concentration of dihydroquercetin was less than 4% and the mean recovery was between 74.64 and 101.80%. It has therefore been shown that this protocol can be used as an alternative extraction to quantify dihydroquercetin in L. griffithiana and purify quercetin flavonoid from other complex matrices.

Magnetic molecularly imprinted polymers doped with graphene oxide for the selective recognition and extraction of four flavonoids from Rhododendron species

Herein, a novel magnetic molecularly imprinted polymer doped with reticular graphene oxide (Fe₃O₄@SiO₂-GO@MIPs) was synthesized for the selective recognition and extraction of 4 flavonoids (farrerol, taxifolin, kaempferol, and hyperin) from Rhododendrons species. The Fe₃O₄@SiO₂-GO@MIPs with lamellar membranes showed outstanding adsorption capacity. The 3D cavities complementary to the "shape" of farrerol were "imprinted" on the polymer framework after removal of farrerol template. Competitive binding assays showed that the polymer has a higher selectivity for farrerol compared with other analogues and references. The Fe₃O₄@SiO₂-GO@MIPs as solid-phase extraction adsorbents combined with liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS) was used for selective determination of four flavonoids from Rhododendrons samples. The limits of detection (LOD) were 0.07, 0.08, 0.06, and 0.08 μg L^-1 for farrerol, taxifolin, kaempferol, and hyperin, respectively. These results suggest that the prepared Fe₃O₄@SiO₂-GO@MIPs have the potential applicability to extract, purify, and enrich flavonoids from herbs, supplements, and other natural products.

Synthesis of magnetic orderly mesoporous α-Fe2O3 nanocluster derived from MIL-100(Fe) for rapid and efficient arsenic(III,V) removal

A calcination time regulation method has been unprecedentedly used to adjust the orderly meso-structure of novel α-Fe₂O₃ nanoclusters derived from MIL-100(Fe) (MIL: Materials of Institute Lavoisier). The as-synthesized magnetic orderly mesoporous α-Fe₂O₃ nanoclusters were characterized by XRD, SEM, TEM, TGA, N₂ adsorption-desorption isotherms, VSM, Zeta potential, FTIR and XPS. The 6h calcinated α-Fe₂O₃ nanocluster exhibited the optimal properties, including the high specific surface area and the orderly mesoporous properties, which facilitate the arsenic(III,V) adsorption capacity. The maximum adsorption capacities of As(III) and As(V) were 109.89 and 181.82mgg^-1, respectively, and adsorption equilibrium can be reached just within 30min. The kinetics intra-particle diffusion model and adsorption isotherms reveal that the adsorption rate is controlled by pore diffusion and the adsorption process belongs to Langmuir monolayer adsorption. These results indicate that the orderly mesoporous structure of α-Fe₂O₃ nanoclusters plays a key role in rapid and efficient adsorption for arsenic(III,V). Meanwhile, adsorption mechanism verifies that arsenic can react with active sites (Fe-OH) to form complexes by Fe-O-As bond. Moreover, α-Fe₂O₃ nanocluster can be separated easily due to its excellent magnetism. Above all, the magnetism orderly mesoporous α-Fe₂O₃ nanocluster is a promising adsorbent for emergent treatment of arsenic in practice.

Adsorption characteristics of arsenic from micro-polluted water by an innovative coal-based mesoporous activated carbon

An innovative coal-based mesoporous activated carbon (NCPAC) was prepared by re-agglomeration, oxidation and two-step activation using coal-blending as precursor. Adsorption capacities of As(III) and As(V) ions (<0.5mg/L) onto NCPAC as a function of pH, adsorbent dose, initial arsenic concentrations, contact time, and adsorption isotherms at 7°C was investigated. The innovative methods promoted total pore volume (1.087cm(3)/g), mesoporosity (64.31%), iodine numbers (1104mg/g), methylene blue (251.8mg/g) and ash contents (15.26%). The adsorption capacities of NCPAC for As(III) and As(V) were found to be strongly dependent on pH and contact time. The optimal pH value was 6. The equilibrium time was 60min for adsorption of As(III) and As(V) by NCPAC. The Langmuir model fitted the experimental data well for both As(III) (R(2)=0.9980) and As(V) (R(2)=0.9988). Maximum adsorption capacities of As(III) and As(V) (C0=0.50mg/L) by NCPAC were 1.491 and 1.760mg/g, respectively.