Removal of arsenic from aqueous solution: A study of the effects of pH and interfering ions using iron oxide nanomaterials

Nanophase Fe₃O₄ and Fe₂O₃ were synthesized through a precipitation method and were utilized for the removal of either arsenic (III) or (V) from aqueous solution as a possible method for drinking water treatment. The synthesized nanoparticles were characterized using X-ray diffraction, which showed that the Fe₃O₄ and the Fe₂O₃ nanoparticles had crystal structures of magnetite and hematite, respectively. In addition, Secherrer's equation was used to determine that the grain size nanoparticles were 12 ± 1.0 nm and 17 ± 0.5 nm for the Fe₂O₃ and Fe₃O₄, respectively. Under a 1 h contact time, batch pH experiments were performed to determine the optimum pH for binding using 300 ppb of either As(III) or (V) and 10 mg of either Fe₃O₄ or Fe₂O₃. The binding was observed to be pH independent from pH 6 through pH 9 and a significant drop in the binding was observed at pH 10. Furthermore, batch isotherm studies were performed using the Fe₂O₃ and Fe₃O₄ to determine the binding capacity of As(III) and As(V) to the iron oxide nanomaterials. The binding was found to follow the Langmuir isotherm and the capacities (mg/kg) of 1250 (Fe₂O₃) and 8196 (Fe₃O₄) for As(III) as well as 20,000 (Fe₂O₃) and 5680 (Fe₃O₄) for As(III), at 1 and 24 h of contact time, respectively. The As(V) capacities were determined to be 4600 (Fe₂O₃), 6711(Fe₃O₄), 4904 (Fe₂O₃), and 4780 (Fe₃O₄) mg/kg for nanomaterials at contact times of 1 and 24 h respectively.     

Cancer cell detection and imaging: MRI-SERS bimodal splat-shaped Fe3O4/Au nanocomposites

In this paper, a kind of splat-shaped Fe₃O₄/Au nanocomposites was synthesized. The magnetic resonance imaging/surface-enhanced Raman scattering (MRI/SERS) studies demonstrated that as-synthesized Fe₃O₄/Au nanocomposites may be a promising MRI/SERS dual probe for the tumor detection.     

Magnetically recyclable Schiff-based palladium nanocatalyst [Fe3O4@SiNSB-Pd] and its catalytic applications in Heck reaction

A magnetically separable palladium nanocatalyst has been synthesized through the immobilization of palladium onto 3-aminopropylphenanthroline Schiff based functionalized silica coated superparamagnetic Fe₃O₄ nanoparticles. The nanocatalyst (Fe₃O₄@SiNSB-Pd) was fully characterized using several spectroscopic techniques, such as FT-IR, HR-SEM, TEM, XRD, ICP, and XPS. The microscopic image of Fe₃O₄ showed spherical shape morphology and had an average size of 150 nm. The Pd-nanoparticles exhibited an average size 3.5 ± 0.6 nm. The successful functionalization of Fe₃O₄@SiNSB-Pd was identified by FT-IR spectroscopy and the appearance of palladium species in Fe₃O₄@SiNSB-Pd was confirmed by XRD analysis. While XPS has been utilized for the determination of the chemical oxidation state of palladium species in Fe₃O₄@SiNSB-Pd. Several activated and deactivated arene halides and olefines were employed for Mizoroki-Heck cross-coupling reactions in the presence of Fe₃O₄@SiNSB-Pd, each of which produced the respective cross-coupling products with excellent yields. The Fe₃O₄@SiNSB-Pd shows good reactivity and reusability for up to seven consecutive cycles.     

Pectin mediated green synthesis of Fe3O4/Pectin nanoparticles under ultrasound condition as an anti-human colorectal carcinoma bionanocomposite

This work described the one-pot synthesis of apple pectin encapsulated Fe₃O₄ nanoparticles (Fe₃O₄/Pectin NPs) which is prepared by co-precipitation of Fe(II/(III) ions in alkaline solution mediated by pectin under ultrasound condition. This process led to formation of magnetic nanoparticles within the network of pectin. Physicochemical characterization of the as-synthesized Fe₃O₄/Pectin NPs was carried out through electron microscopy (SEM and TEM), energy dispersive X-ray spectroscopy (EDX), vibrating sample magnetometer (VSM) and X-ray diffraction (XRD). The in vitro cytotoxic and anti-colorectal cancer effects of biologically synthesized Fe₃O₄/Pectin NPs against Ramos.2G6.4C10, HCT-8 [HRT-18], HCT 116, and HT-29 cancer cell lines were assessed. The anti-colorectal cancer properties of the Fe₃O₄/Pectin NPs could significantly remove Ramos.2G6.4C10, HCT-8 [HRT-18], HCT 116, and HT-29 cancer cell lines in a time and concentration-dependent manner by MTT assay. The IC₅₀ of the Fe₃O₄/Pectin NPs were 317, 337, 187, and 300 µg/mL against Ramos.2G6.4C10, HCT-8 [HRT-18], HCT 116, and HT-29 cancer cell lines. The antioxidant activity of Fe₃O₄/Pectin NPs was determined by DPPH method. The Fe₃O₄/Pectin NPs showed the high antioxidant activity according to the IC₅₀ value. It seems that the anti-human colorectal cancer effect of recent nanoparticles is due to their antioxidant effects.     

Magnetite/carbon core-shell nanorods as anode materials for lithium-ion batteries

Carbon coated magnetite (Fe₃O₄) core-shell nanorods were synthesized by a hydrothermal method using Fe₂O₃ nanorods as the precursor. Transmission electron spectroscopy (TEM) and high resolution TEM (HRTEM) analysis indicated that a carbon layer was coated on the surfaces of the individual Fe₃O₄ nanorods. The electrochemical properties of Fe₃O₄/carbon nanorods as anodes in lithium-ion cells were evaluated by cyclic voltammetry, ac impedance spectroscopy, and galvanostatic charge/discharge techniques. The as-prepared Fe₃O₄/C core-shell nanorods show an initial lithium storage capacity of 1120 mAh/g and a reversible capacity of 394 mAh/g after 100 cycles, demonstrating better performance than that of the commercial graphite anode material.     

Studies on Fe–Co spinel electrodes

FeCo₂O₄ spinel oxide pelleted electrodes were prepared from the respective powders, obtained by low-temperature coprecipitation method. X-ray diffraction studies suggest the coexistence of two spinel phases, with different a-cell parameters. The samples show semiconductor-type behaviour, in the range 530–340 K. The estimated activation energy for conduction is about 0.7 eV. These phases are stable, after being used as electrode materials, as the XRD and SEM/EDS results show. Cyclic voltammetry has been used to investigate the electrochemical behaviour of the FeCo₂O₄ electrodes in 1 mol dm⁻³ KOH aqueous solutions. The voltammetric data allowed finding out the redox reactions occurring at the electrode surface, namely Fe₃O₄·4H₂O/Fe(OH)₂ or Fe₃O₄/Fe₂O₃ and CoO₂/CoOOH by comparing the experimental results with those referred in the literature.     

Iron (III) nanocomposites for enzyme-less biomimetic cathode: A promising material for use in biofuel cells

In this paper, we discuss the synthesis and electrochemical properties of a new material based on iron oxide nanoparticles stabilized with poly(diallyldimethylammonium chloride) (PDAC); this material can be used as a biomimetic cathode material for the reduction of H₂O₂ in biofuel cells. A metastable phase of iron oxide and iron hydroxide nanoparticles (PDAC–FeOOH/Fe₂O₃-NPs) was synthesized through a single procedure. On the basis of the Stokes–Einstein equation, colloidal particles (diameter: 20 nm) diffused at a considerably slow rate (D = 0.9 × 10^? 11 m s^? 1) as compared to conventional molecular redox systems. The quasi-reversible electrochemical process was attributed to the oxidation and reduction of Fe³⁺/Fe²⁺ from PDAC–FeOOH/Fe₂O₃-NPs; in a manner similar to redox enzymes, it acted as a pseudo-prosthetic group. Further, PDAC–FeOOH/Fe₂O₃-NPs was observed to have high electrocatalytic activity for H₂O₂ reduction along with a significant overpotential shift, ΔE = 0.68 V from ? 0.29 to 0.39 V, in the presence and absence of PDAC–FeOOH/Fe₂O₃-NPs. The abovementioned iron oxide nanoparticles are very promising as candidates for further research on biomimetic biofuel cells, suggesting two applications: the preparation of modified electrodes for direct use as cathodes and use as a supporting electrolyte together with H₂O₂.     

Preparation of core-shell magnetic Fe3O4@SiO2-dithiocarbamate nanoparticle and its application for the Ni2+, Cu2+ removal

A typical superparamagnetic nanoparticles-based dithiocarbamate absorbent (Fe₃O₄@SiO₂-DTC) with core-shell structure was applied for aqueous solution heavy metal ions Ni²⁺, Cu²⁺ removal.     

A comparative study for treatment of white liquor by different applications of Fenton process

In this paper, the treatability of white liquor by conventional (CFP), modified (MFP) and electro-Fenton oxidation processes (EFP) was investigated depending on the COD parameter. Based on the experimental results, up to 62.4%, 58.4% and 54.9% COD removals by the CFP, MFP and EFP were achieved, respectively. It was observed that adjustment of initial pH to acidic values is not required in the CFP. The optimal operational conditions were found to be [Fe²⁺] = 500 mg/L, [H₂O₂] = 1000 mg/L at pH 7.3 (original pH) in the CFP, [Fe⁰] = 1250 mg/L, [H₂O₂] = 1000 mg/L at pH 3 in the MFP, and I = 1.0 A, [H₂O₂] = 1500 mg/L at pH 3 in the EFP, respectively. As a result, the CFP has been determined as a more efficient alternative treatment method.     

Lithium insertion chemistry of some iron vanadates

Lithium insertion into various iron vanadates has been investigated. Fe₂V₄O₁₃ and Fe₄(V₂O₇)₃ · 3H₂O have discharge capacities approaching 200 mAh g⁻¹ above 2.0 V vs. Li⁺/Li. Although the potential profiles change significantly between the first and subsequent discharges, capacity retention is unexpectedly good. Other phases, structurally related to FeVO₄, containing copper and/or sodium ions were also studied. One of these, β-Cu₃Fe₄(VO₄)₆, reversibly consumes almost 10 moles of electrons per formula unit (ca. 240 mAh g⁻¹) between 3.6 and 2.0 V vs. Li⁺/Li, in a non-classical insertion process. It is proposed that both copper and vanadium are electrochemically active, whereas iron(III) reacts to form LiFe^IIIO₂. The capacity of the Cu₃Fe₄(VO₄)₆/Li system is nearly independent of cycling rate, stabilizing after a few cycles at 120–140 mAh g⁻¹. Iron vanadates exhibit better capacities than their phosphate analogues, whereas the latter display more constant discharge potentials.     

Synthesis and characterization of Fe3O4@SiO2@poly-l-alanine,peptide brush–magnetic microspheres through NCA chemistry for drug delivery and enrichment of BSA

A novel Fe₃O₄@SiO₂@poly-l-alanine peptide brush–magnetic microsphere (PBMMs) was synthesized from amine-functionalized Fe₃O₄ through the surface-initiated polymerization of N-carboxyanhydrides. Two materials with different peptide lengths were obtained from different amounts of N-carboxyanhydrides. These materials were characterized by Fourier transform infrared, transmission electron microscopy, large-angle powder X-ray diffraction, vibrating sample magnetometer and elemental analysis. Furthermore, the loading and release behavior of ibuprofen and the enrichment of bovine serum albumin on the two materials were investigated and it was shown that the PBMMs have a maximum uptake amount of ibuprofen of 40.3 mg g⁻¹, and an enrichment of bovine serum albumin of 20.9 mg g⁻¹. These materials are promising candidates for targeted drug delivery and protein enrichment.     

Recyclable Fenton-like catalyst based on zeolite Y supported ultrafine,highly-dispersed Fe2O3 nanoparticles for removal of organics under mild conditions

The active Fenton-like catalyst, obtained by highly dispersed Fe₂O₃ nanoparticles in size of 5 nm on the surface of zeolite Y, shows the excellent degradation efficiency to phenol higher than 90% under the mild conditions of room temperature and neutral solution, and the catalyst can be easily recovered with stable catalytic activity for 8 cycles.     

Hydrothermal development of magnetic-hydrochar nanocomposite from pineapple leaves and its performance as an adsorbent for the uptake of Mn2+ and reuse of the metal loaded adsorbent in latent fingerprint

Manganese is one of the heavy metals that is a major environmental concern when present in large amount. Manganese is discarded into water systems by numerous industries, including mining, batteries and electroplating etc. Pineapple leaves were applied as a biomass source to produce a magnetic hydrothermal treated hydochar nanocomposite; Fe₃O₄-HC. The BET surface area of Fe₂O₃-HC nanocomposite was 21.27 m²/g. Batch adsorption experiments revealed that the uptake of Mn²⁺ fit well in the pseudo second kinetics model, while the adsorption isotherm best fit the Freundlich model, with a maximum adsorption capacity of 2.99 mg/g at 25 °C and a pH of 5. The obtained thermodynamic parameters demonstrated that Mn²⁺ ion adsorption using the Fe₂O₃-HC nanocomposite was endothermic and nonspontaneous. Additionally, Fe₂O₃-HC nanocomposite demonstrated to be highly selective towards Mn²⁺ ions in the presence of other ions. The removal percentage of Mn²⁺ from a real water sample spiked with 50 mg/L Mn²⁺ was reported to be 53.2%. The spent adsorbent was then used to detect latent fingerprints, which revealed that Mn²⁺-Fe₂O₃-HC nanocomposite generated better and clear latent fingerprints than Fe₂O₃-HC nanocomposite.     

Synthesis and applications of Fe3O4-diisopropylaminoacetamide as a versatile and reusable magnetic nanoparticle supported N,N-diisopropylethylamine equivalent

A magnetic nanoparticle supported N,N-diisopropylaminoacetamide (Fe₃O₄-DIPA) was developed for application as a magnetic recoverable, and reusable N,N-diisopropylethylamine equivalent. The Fe₃O₄ nanoparticles were coated with a silica layer using the sol-gel method, followed by surface modification with 3-aminopropyltriethoxysilane. Subsequent acylation with chloroacetyl chloride and chlorine displacement with diisopropylamine afforded Fe₃O₄-DIPA in 90% yield with a loading of 0.96 mmol/g. The applicability of Fe₃O₄-DIPA was demonstrated in the synthesis of amine derivatives cv sulfonation, acylation, and N-alkylation reactions. The desired products were obtained in excellent yields and purities after scavenging the residual starting amines by treatment with silica-supported dichlorotriazine. Fe₃O₄-DIPA was readily recovered by separation using a magnet and could be reused several times without significant loss of reactivity.     

Investigation of thermal hazard during the hydrosilylation of 1,6-divinyl(perfluorohexane) with trichlorosilane

In this study, we examined the reaction hazard during the hydrosilylation reaction between trichlorosilane (TCS) and 1,6-divinyl(perfluorohexane) (FDV) in the presence of a butanol solution of chloroplatinic acid (Pt-Cat) as the catalyst. Assuming the three industrial risks of excessive addition of Pt-Cat, contamination by iron rust and mixing with cooling water, we observed the temperature and pressure change of TCS/FDV with an excessive amount of Pt-Cat, TCS/FDV/Pt-Cat with Fe₂O₃ and TCS/FDV/Pt-Cat with distilled water, using an accelerating rate calorimeter (ARC). The temperature and pressure greatly increased, especially in the sample with Fe₂O₃. For instance, in TCS/FDV/Pt-Cat with 1.5 wt.% Fe₂O₃, the heat release rate exceeded 624 K · min^?1 and the pressure rose above 25 MPa during the exothermic reaction.     

A WO3 nanorod-Cr2O3 nanoparticle composite for selective gas sensing of 2-butanone

The sensor based on WO₃-Cr₂O₃ nanocomposites show good selectivity to 2-butanone.     

Minerals from Macedonia: XVII. Vibrational spectra of some common appearing amphiboles

The vibrational (infrared and Raman) spectroscopy is used in order to identify and characterize the following amphibole minerals with general formula W_0–1X₂Y₅Z₈O₂₂(OH)₂ (W = Na, K; X = Na, Ca; Y = Mg, Fe²⁺, Fe³⁺, Al; Z = Si, Al) originating from the localities in the Republic of Macedonia: glaucophane, Na₂(Mg,Fe²⁺)₃(Fe³⁺,Al)₂Si₈O₂₂(OH)₂; tremolite–actinolite, Ca₂(Mg,Fe²⁺)₅Si₈O₂₂(OH)₂; hornblende (Na,K)_0–1Ca₂(Mg,Fe²⁺,Fe³⁺,Al)₅(Si,Al)₈ O₂₂(OH)₂ and arfvedsonite, NaNa₂(Mg,Fe²⁺)₄(Fe³⁺,Al)Si₈O₂₂(OH)₂. The chemical composition of these minerals is not necessarily fixed. It is due to the possibility to form solid solution series with other minerals being their end-members (for example, tremolite–ferro-actinolite series, Ca₂Mg₅Si₈O₂₂(OH)₂–Ca₂Fe²⁺₅Si₈O₂₂(OH)₂). In this context, it is shown that the intensity and especially the number of the IR bands in the ν(OH) region could serve as a tool for exact mineral identification. Namely, it is based on the presence of different Y cations in various octahedral sites (M1 and M3), which is manifested by different spectral view. On the other hand, the expressed similarities in the 1300–370 cm⁻¹ (IR) and 1200–100 cm⁻¹ regions (Raman) of the spectra are observed due to their common structural characteristics (double chains of SiO₄ tetrahedra). Thus, the bands in this region are tentatively prescribed mostly to the vibrations of the SiO₄ tetrahedra. The results of our study are compared with the corresponding literature data for the analogous mineral species originating all over the world.     

Study on the valence fluctuation and the magnetism of an iron mixed-valence complex, (n-C4H9)4N[FeIIFeIII(mto)3](mto = C2O3S)

In the case of iron mixed-valence complexes whose spin states are situated in the spin-crossover region, conjugated phenomena coupled with spin and charge are expected. In general, the Fe site coordinated by six S atoms is in the low-spin state, while the Fe site coordinated by six O atoms is in the high-spin state. From this viewpoint, we have synthesized and investigated physical properties for an monothiooxalato-bridged (mto = C₂O₃S) iron mixed-valence complex, (n-C₄H₉)₄N[Fe^IIFe^III(mto)₃], consisting of Fe^IIIO₃S₃ and Fe^IIO₆ octahedra, which behaves as a ferrimagnet with its magnetic transition temperature of T_N = 38 K and Weiss temperature of θ = ?93 K. From the analysis of ⁵⁷Fe Mössbauer spectra of ⁵⁷Fe enriched complexes, (n-C₄H₉)₄N[⁵⁷Fe^IIFe^III(mto)₃] and (n-C₄H₉)₄N[Fe^II57Fe^III(mto)₃], the charge transfer between Fe^II and Fe^III exists in the paramagnetic phase. Considering the time window of ⁵⁷Fe Mössbauer spectroscopy, the time scale of the valence fluctuation is at least slower than 10^?7 s. In order to confirm the valence fluctuation between Fe^II and Fe^III, we investigated the dielectric constant and found an anomalous enhancement attributed to the Fe valence fluctuation between 170 and 250 K.     

Synthesis and characterization of amino-functionalized single magnetic core–silica shell composites

The thermal decomposition approach, reverse micro-emulsion system and surface modification technique had been successfully used to synthesis single magnetic core Fe₃O₄@Organic Layer@SiO₂–NH₂ complex microspheres. The magnetization of the magnetic microspheres core could be easily tuned between 28 and 56 emu/g by adjusting the amount of 2-mercaptobarbituric acid. It was found that the Organic Layer to some extent had a protective effect on avoiding Fe₃O₄ being oxidized into Fe₂O₃. Each Fe₃O₄@Organic Layer microsphere could be coated uniformly by about 30 nm of silica shell. The average diameter of the Fe₃O₄@Organic Layer@SiO₂ composites was about 538 nm. The saturation magnetization of the Fe₃O₄@Organic Layer@SiO₂ complex microspheres was 12.5% less than magnetic microspheres cores. The Fe₃O₄@Organic Layer@SiO₂–NH₂ composites possessed a huge application potentiality in specificity enriching and separating biological samples.     

Fabrication of a non-enzymatic glucose sensor field-effect transistor based on vertically-oriented ZnO nanorods modified with Fe2O3

Herein, we report a non-enzymatic glucose sensor field-effect transistor (FET) based on vertically-oriented zinc oxide nanorods modified with iron oxide (Fe₂O₃-ZNRs). Compared with ZnO-based non-enzymatic glucose sensors, which show poor sensing performances, modification of ZnO with Fe₂O₃ dramatically enhances the sensing behavior of the fabricated non-enzymatic FET glucose sensor due to the excellent electrocatalytic nature of Fe₂O₃. The fabricated non-enzymatic FET sensor showed excellent catalytic activity for glucose detection under optimized conditions with a linear range up to 18 mM, detection limits down to ~ 12 μM, excellent selectivity, good reproducibility and long-term stability. Moreover, the fabricated FET sensor detected glucose in freshly drawn mouse whole blood and serum samples. The developed FET sensor has practical applications in real samples and the solution-based synthesis process is cost effective.