Novel nanocomposite membranes prepared with PVC/ABS and silica nanoparticles for C<Subscript>2</Subscript>H<Subscript>6</Subscript>/CH<Subscript>4</Subscript> separation

Composite membranes based on polyvinyl chloride and acrylonitrile butadiene styrene (ABS) copolymer have been prepared and then filled with 2–8 wt % of silica nanoparticles. Membranes were fabricated by solution casting method using dimethylacetamide. The performance of prepared membranes were studied for methane and ethane at the feed pressure of 1.0, 1.5, 2.0, and 3.0 bar at 35°C. By increasing the percentage of ABS, permeability of methane and ethane increased. In addition, by adding the silica nanoparticles in the membrane, permeability of gas increased in all cases. The highest gas pair selectivity for C₂H₆/CH₄ could be obtained from PVC/BS (20 wt %) which loaded with 8 wt % of silica nanoparticles. The results of this study suggest that high performance gas separation nanocomposite membranes can be attained by adopting a judicious combination of blending technique for polymeric membrane, optimized loading percentage, and feed operating conditions.     

Preparation and characterization of (Pebax 1657 + silica nanoparticle)/PVC mixed matrix composite membrane for CO<Subscript>2</Subscript>/N<Subscript>2</Subscript> separation

In this work, the films of poly(ether-block-amide) (Pebax 1657) and hydrophilic/hydrophobic silica nanoparticles (0–10 wt%) were coated on a poly(vinyl chloride) (PVC) ultrafiltration membrane to form new mixed matrix composite membranes (MMCMs) for CO₂/N₂ separation. The membranes were characterized by SEM, FTIR, DSC and XRD. Successful formation of a non-porous defect-free dense top layer with ~4 μm of thickness and also uniform dispersion of silica nanoparticles up to 8 wt% loading in Pebax matrix were confirmed by SEM images. The gas permeation results showed an increase in the permeance of all gases and an increase in ideal CO₂/N₂ selectivity with the increase in silica nanoparticle contents. Comparison between the incorporation of hydrophilic and hydrophobic silica nanoparticle into Pebax matrix revealed that the great enhancement of CO₂ solubility is the key factor for the performance improvement of Pebax + silica nanoparticle membranes. The best separation performance of the hydrophilic silica nanoparticle-incorporated Pebax/PVC membrane for pure gases (at 1 bar and 25 °C) was obtained with a CO₂ permeability of 124 barrer and an ideal CO₂/N₂ selectivity of 76, i.e., 63 and 35% higher than those of neat Pebax membrane, respectively. The corresponding values for hydrophobic silica nanoparticle-incorporated Pebax/PVC membrane were 107 barrer for CO₂ permeability and 61 for ideal CO₂/N₂ selectivity. Also the performances of MMCMs improved upon pressure increase (1–10 bar) owing to the shift in plasticizing effect of CO₂ towards the higher pressures. In addition, an increase in permeabilities with a decrease in ideal selectivity was observed upon temperature increase (25–50 °C) due to the intensification of chain mobility.     

In situ synthesis of plate-like Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticles in porous cellulose films with obvious magnetic anisotropy

Nanocomposite cellulose films with obvious magnetic anisotropy have been prepared by in situ synthesis of plate-like Fe₂O₃ nanoparticles in the cellulose matrix. The influence of the concentrations of FeCl₂ and FeCl₃ solutions on the morphology and particle size of the synthesized Fe₂O₃ nanoparticles as well as on the properties of the composite films has been investigated. The Fe₂O₃ nanoparticles synthesized in the cellulose matrix was γ-Fe₂O₃, and its morphology was plate-like with size about 48 nm and thickness about 9 nm, which was totally different from those reported works. The concentration of FeCl₂ and FeCl₃ solution has little influence on the particle size and morphology of the Fe₂O₃ nanoparticles, while the content of Fe₂O₃ nanoparticles increased with the increase of the concentration of the precursor solution, indicating that porous structured cellulose matrix could modulate the growth of inorganic nanoparticles. The unique morphology of the Fe₂O₃ nanoparticles endowed the composite films with obvious magnetic anisotropy, which would expand the applications of the cellulose based nanomaterials.     

Catalytic Properties of TiO<Subscript>2</Subscript>/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles in Plasma Chemical Treatment

We proposed here a new process coupling dielectric barrier discharge (DBD) plasma with magnetic photocatalytic material nanoparticles for improving yield in DBD degradation of methyl orange (MO). TiO₂ doped Fe₃O₄ (TiO₂/Fe₃O₄) was prepared by the sol-gel method and used as a new type of magnetic photocatalyst in DBD system. It was found that the introduction of TiO₂/Fe₃O₄ in DBD system could effectively make use of the energy generated in DBD process and improve hydroxyl radical contributed by the main surface Fenton reaction, photocatalytic reaction and catalytic decomposition of dissolved ozone. Most part of MO (88%) was degraded during 30 min at peak voltage of 13 kV and TiO₂/Fe₃O₄ load of 100 mg/L, with a rate constant of 0.0731 min^?1 and a degradation yield of 7.23 g/(kW h). The coupled system showed higher degradation efficiency for MO removal.     

Magnetic nanoparticles (Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> &amp; Co<Subscript>3</Subscript>O<Subscript>4</Subscript>) and their applications in urea biosensing

Nanobiotechnology has opened a new and exciting opportunities for exploring urea biosensor based on magnetic nanoparticles (NPs) mainly Fe₃O₄ and Co₃O₄. These NPs have been extensively exploited to develop biosensors with stability, selectivity, reproducibility and fast response time. This review gives an overview of the development of urea biosensor based on Fe₃O₄ and Co₃O₄ for in vitro diagnostic applications along with significant improvements over the last few decades. Additionally, effort has been made to elaborate properties of magnetic nanoparticles (MNPs) in biosensing aspects. It also gives details of recent developments in hybrid nanobiocomposite based urea biosensor.     

Synthesis and Characterization of the Superparamagnetic Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/Ag Nanocomposites

The study of superparamagnetic Fe₃O₄/Ag nanocomposites have received great research attention due to their wide range of potential applications in biomedicine. In this report, an easy microemulsion reaction was employed to synthesis Fe₃O₄/Ag nanocomposites with self-aggregated branch like nanostructures. The Fe₃O₄ nanoparticles were initially prepared and subsequently AgNO₃ was reduced as Ag by chemical reduction method. The results showed that the average size of the Fe₃O₄/Ag nanocomposites were in the range of 10 ± 2 nm. These nanoparticles were self-aggregated as a branch like nanostructure. The optical properties of Fe₃O₄ nanoparticles were modified with surface plasmon resonance of Ag nanoparticles. The observed saturation magnetization of superparamagnetic Fe₃O₄/Ag nanocomposites were 40 emu/g.     

Preparation and characterization of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>composite particles

Using Fe₃O₄ nano-particles as seeds, a new type of Fe₃O₄/Au composite particles with core/shell structure and diameter of about 170 nm was prepared by reduction of Au³⁺ with hydroxylamine in an aqueous solution. Particle size analyzer and transmission electron microscope were used to analyze the size distribution and microstructure of the particles in different conditions. The result showed that the magnetically responsive property and suspension stability of Fe₃O₄ seeds as well as reduction conditions of Au³⁺to Au⁰are the main factors which are crucial for obtaining a colloid of the Fe₃O₄/Au composite particles with uniform particle dispersion, excellent stability, homogeneity in particle sizes, and effective response to an external magnet in aqueous suspension solutions. UV-Vis analysis revealed that there is a characteristic peak of Fe₃O₄/Au fluid. For particles with d(0.5)=168 nm, the λmax is 625 nm.     

Preparation and adsorption of magnetic Co<Subscript>0.5</Subscript>Ni<Subscript>0.5</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript>-chitosan nanoparticles

In this paper, magnetic chitosan microspheres were prepared by the emulsification cross-linking technique, with glutaraldehyde as the cross-linking agent, liquid paraffin as the dispersant, and the Span-80 as emulsifier. The time of cross-linking and the ratio of Co_0.5Ni_0.5Fe₂O₄/chitosan were investigated. The morphology was studied by different instruments. The adsorption performance was investigated and the effects of initial concentration of methyl orange, the time of cross-linking, and the amount of adsorbent were discussed. It is found that the product has uniform morphology when the ratio of magnetic Co_0.5Ni_0.5Fe₂O₄/chitosan is 1 : 2 and the time of cross-linking is 5 h; At room temperature, magnetic Co_0.5Ni_0.5Fe₂O₄–chitosan has a good adsorption toward methyl orange when the magnetic Co_0.5Ni_0.5Fe₂O₄/chitosan dosage is 20 mg.     

Preparation of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>-C18 nano-magnetic composite materials and their cleanup properties for organophosphorous pesticides

Magnetic Fe₃O₄-C18 composite nanoparticles of approximately 5–10 nm in size were synthesized and characterized by IR spectroscopy, atomic absorption spectroscopy, X-ray diffraction, and transmission electron microscopy. The magnetic Fe₃O₄-C18 composite nanoparticles were applied for cleanup and enrichment of organophosphorous pesticides. Comparative studies were carried out between magnetic Fe₃O₄-C18 composite nanoparticles and common C18 materials. Residues of organophosphorous pesticides were determined by gas chromatography in combination with a nitrogen/phosphorus detector. The cleanup and enrichment properties of magnetic Fe₃O₄-C18 composite nanoparticles are comparable with those of common C18 materials for enrichment of organophosphorous pesticides, but the cleanup and enrichment are faster and easier to perform. Figure Presumed mechanism for the adhesion of the OPs to the Fe₃O₄-C18 magnetic nanoparticles     

Stabilization of Oil-in-Water Emulsions with SiO<Subscript>2</Subscript> and Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles

Stabilization of oil-in-water Pickering emulsions with SiO₂ and Fe₃O₄ nanoparticles has been studied. Emulsions containing three-dimensional gel networks formed by aggregated nanoparticles in the dispersion media have been shown to be stable with respect to flocculation, coalescence, and creaming. Concentration ranges in which emulsions are kinetically stable have been determined. Stabilization with mixed Ludox HS-30 and Ludox CL SiO₂ nanoparticles leads to the formation of stable emulsions at a weight ratio between the nanoparticles equal to 2 and pH 6.7. In the case of stabilization with Ludox CL and Fe₃O₄ nanoparticles, systems resistant to aggregation and sedimentation are obtained at pH 8. The use of mixed Ludox HS-30 and Fe₃O₄ nanoparticles has not resulted in the formation of emulsions stable with respect to creaming, with such emulsions appearing to be resistant only to coalescence at pH 2–6.     

Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/rice husk-based maco-/mesoporous carbon bone nanocomposite as superior high-rate anode for lithium ion battery

Rice husks (RHs), a kind of biowastes, are firstly hydrothermally pretreated by HCl aqueous solution to achieve promising macropores, facilitating subsequently impregnating ferric nitrate and urea aqueous solution, the precursor of Fe₃O₄ nanoparticles. A Fe₃O₄/rice husk-based maco-/mesoporous carbon bone nanocomposite is finally prepared by the high-temperature hydrothermal treatment of the precursor-impregnated pretreated RHs at 600 °C followed by NaOH aqueous solution treatment for dissolving silica and producing mesopores. The macro-/mesopores are able to provide rapid lithium ion-transferring channels and accommodate the volumetric changes of Fe₃O₄ nanoparticles during cycling as well. Besides, the macro-/mesoporous carbon bone can offer rapid electron-transferring channels through directly fluxing electrons between Fe₃O₄ nanoparticles and carbon bone. As a result, this nanocomposite delivers a high initial reversible capacity of 918 mAh g^?1 at 0.2 A g^?1 and a reversible capacity of 681 mAh g^?1 remained after 200 cycles at 1.0 A g^?1. The reversible capacities at high current densities of 5.0 and 10.0 A g^?1 still remain at high values of 463 and 221 mAh g^?1, respectively.     

The Influence of Active Carbon Supports Toward the Electrocatalytic Behavior of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles for the Extended Energy Generation of Mediatorless Microbial Fuel Cells

Magnetite (Fe₃O₄) nanoparticles anchored over the different active carbon supports were developed by a simple wet solution method. The developed nanostructures were magnetically self-assembled over the electrode surface and exploited as anode catalysts in mediatorless microbial fuel cells (MFC). The morphological characterizations revealed that 3～8-nm-sized Fe₃O₄ nanoparticles were homogeneously anchored over the different carbon matrices and the obtained diffraction patterns ensured the cubic inverse spinel structure of prepared Fe₃O₄ nanoparticles. The morphology, size, and structure of Fe₃O₄ nanoparticles anchored over the different active carbon supports were maintained identical, and the influence of active carbon support toward the effectual MFC performances was evaluated under various electrochemical regimes and conditions by using Escherichia coli as a catalytic microorganism. The electrochemical characterizations revealed that carbon nanotube (CNT)-supported Fe₃O₄ nanoparticles exhibited lower charge transfer resistance and high coulombic efficiency in comparison with the graphene and graphite nanofiber-supported composites. Among the studied anode catalysts, Fe₃O₄/CNT composite exhibited the maximum MFC power density of 865 mW m^?2 associated with excellent durability performances, owing to the specific interaction exerted between the microorganisms and the Fe₃O₄/CNT composite. Thus, the binder-free electrode modification process, mediatorless environment, rapid electron transfer kinetics, high power generation, and long durability performances achieved for the developed system paved futuristic dimensions for the high performance MFCs.     

Synthesis of novel magnetic sulfur-doped Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles for efficient removal of Pb(II)

In this work, we report the synthesis of magnetic sulfur-doped Fe₃O₄ nanoparticles (Fe₃O₄:S NPs) with a novel simple strategy, which includes low temperature multicomponent mixing and high temperature sintering. The prepared Fe₃O₄:S NPs exhibit a much better adsorption performance towards Pb(II) than bare Fe₃O₄ nanoparticles. FTIR, XPS, and XRD analyses suggested that the removal mechanisms of Pb(II) by Fe₃O₄:S NPs were associated with the process of precipitation (formation of PbS), hydrolysis, and surface adsorption. The kinetic studies showed that the adsorption data were described well by a pseudo second-order kinetic model, and the adsorption isotherms could be presented by Freundlich isotherm model. Moreover, the adsorption was not significantly affected by the coexisting ions, and the adsorbent could be easily separated from water by an external magnetic field after Pb(II) adsorption. Thus, Fe₃O₄:S NPs are supposed to be a good adsorbents for Pb(II) ions in environmental remediation.     

Improving Pullulanase Catalysis via Reversible Immobilization on Modified Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@Polydopamine Nanoparticles

To improve the catalysis of pullulanase from Anoxybacillus sp.WB42, Fe₃O₄@polydopamine nanoparticles (Fe₃O₄@PDA) were prepared and modified with functional groups for immobilization of pullulanases via covalent binding or ionic adsorption. Immobilized pullulanases had lower thermal stability than that of free pullulanase, whereas their catalysis depended on the surface characteristics of nanoparticles. As for covalent immobilization of pullulanases onto Fe₃O₄@PDA derivatives, the spacer grafted onto Fe₃O₄@PDA made the catalytic efficiency of pullulanase increase up to the equivalence of free enzyme but dramatically reduced the pullulanase thermostability. In contrast, pullulanases bounded ionically to Fe₃O₄@PDA derivatives had higher activity recovery and catalytic efficiency, and their catalytic behaviors varied with the modifier grafted onto Fe₃O₄@PDA. Among these immobilized pullulanases, ionic adsorption of pullulanase on Fe₃O₄@PDA-polyethyleneimine-glycidyltrimethylammonium gave a high-performance and durable catalyst, which displayed not only 1.5-fold increase in catalytic efficiency compared to free enzyme but also a significant improvement in operation stability with a half of initial activity after 27 consecutive cycles with a total reaction time of 13.5 h, and was reversible, making this nanoparticle reusable for immobilization.     

Comparison of the Solubility of ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript>, Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> and Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> in High Temperature Water

As the solubility is a direct measure of stability, this study compares the solubilities of ZnFe₂O₄, Fe₃O₄ and Fe₂O₃ in high temperature water. Through literature analysis and formula derivation, it is shown that it is reasonable to assume ZnFe₂O₄ and Fe(OH)₃ coexist when ZnFe₂O₄ is dissolved in water. Results indicated that the solubility of ZnFe₂O₄ is much lower than that of Fe₂O₃ or Fe₃O₄. The low solubility of ZnFe₂O₄ indicates that it is more protectively stable as an anticorrosion phase. Moreover, the gap between the solubility of ZnFe₂O₄ and that of Fe₃O₄ or Fe₂O₃ was enlarged with an increase of temperature. This means that ZnFe₂O₄ is more protective at higher temperatures. Further analysis indicated that with the increase of temperature, the solubility of ZnFe₂O₄ changed little while those of Fe₂O₃ or Fe₃O₄ changed a lot. Little change of the solubility of ZnFe₂O₄ with increase of temperature showed that ZnFe₂O₄ is stable. The very low and constant solubility of ZnFe₂O₄ suggests that it is more protective than Fe₂O₃ and Fe₃O₄, especially in water at higher temperature.     

Adsorption behavior of <Superscript>99</Superscript>Tc on Fe,Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> and Fe<Subscript>2</Subscript>O<Subscript>4</Subscript>

Summary The adsorption of ⁹⁹Tc on the adsorbers Fe, Fe₂O₃ and Fe₃O₄ was studied by batch experiments under aerobic and anoxic conditions. The effects of pH and CO₃^2- concentration of the simulated ground water on the adsorption ratios were also investigated, and the valences of Tc in solution after the adsorption equilibrium were studied by solvent extraction. The adsorption isotherms of TcO₄- on the adsorbers Fe, Fe₂O₃ and Fe₃O₄ were determined. Experimental results have shown that the adsorption ratio of Tc on Fe decreases with the increase of pH in the range of 5-12 and increases with the decrease of the CO₃^2- concentration in the range of 10^-8M-10^-2M. Under aerobic conditions, the adsorption ratios of ⁹⁹Tc on Fe₂O₃ and Fe₃O₄ were not influenced by pH and CO₃^2-concentration. When Fe was used as adsorbent, Tc existed mainly in the form of Tc(IV) after equilibrium and in the form of Tc(VII) when the adsorbent was Fe₂O₃ or Fe₃O₄ under aerobic conditions. The adsorption ratios of Tc on Fe, Fe₂O₃ and Fe₃O₄ decreased with the increase of pH in the range of 5-12 and increased with the decrease of the CO₃^2- concentration in the range of 10^-8M-10^-2M under anoxic conditions. Tc existed mainly in the form of Tc(IV) after equilibrium when Fe, Fe₂O₃ and Fe₃O₄ was the adsorbent under anoxic conditions. The adsorption isotherms of TcO_4- on the adsorbers Fe, Fe₂O₃ and Fe₃O₄ are fairly in agreement with the Freundlich’s equation under both aerobic and anoxic conditions.     

Obtaining of Ni<Subscript>0.65</Subscript>Zn<Subscript>0.35</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript>/SiO<Subscript>2</Subscript> nanocomposites by thermal decomposition of complex compounds embedded in silica matrix

This article presents the results of our investigation on the obtaining of Ni_0.65Zn_0.35Fe₂O₄ ferrite nanoparticles embedded in a SiO₂ matrix using a modified sol–gel synthesis method, starting from tetraethylorthosilicate (TEOS), metal (Fe^III,Ni^II,Zn^II) nitrates and ethylene glycol (EG). This method consists in the formation of carboxylate type complexes, inside the silica matrix, used as forerunners for the ferrite/silica nanocomposites. We prepared gels with different compositions, in order to obtain, through a suitable thermal treatment, the nanocomposites (Ni_0.65Zn_0.35Fe₂O₄)_x–(SiO₂)_100–x (where x=10, 20, 30, 40, 50, 60 mass%). The synthesized gels were studied by differential thermal analysis (DTA), thermogravimetry (TG) and FTIR spectroscopy. The formation of Ni–Zn ferrite in the silica matrix and the behavior in an external magnetic field were studied by X-ray diffraction (XRD) and quasi-static magnetic measurements (50 Hz).     

H<Subscript>3</Subscript>PMo<Subscript>12</Subscript>O<Subscript>40</Subscript> immobilized chitosan/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> as a novel efficient,green and recyclable nanocatalyst in the synthesis of pyrano-pyrazole derivatives

A novel nanomagnetic composite heteropolyacid immobilized chitosan/Fe₃O₄ was prepared via a facile one-pot synthetic approach. This magnetically recoverable nanocatalyst, H₃PMo₁₂O₄₀/chitosan/Fe₃O₄ (PMo/chit/Fe₃O₄), was fully characterized by XRD, FTIR, SEM and EDX analysis methods. A rapid, efficient and the chemoselective synthesis of different pyrano-pyrazole derivatives was achieved in excellent yields via a one-pot four-component reaction in the presence of catalytic amount of PMo/Chit/Fe₃O₄.     

Thermal oxide synthesis and characterization of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanorods and Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> nanowires

Fe₃O₄ nanorods and Fe₂O₃ nanowires have been synthesized through a simple thermal oxide reaction of Fe with C₂H₂O₄ solution at 200–600°C for 1 h in the air. The morphology and structure of Fe₃O₄ nanorods and Fe₂O₃ nanowires were detected with powder X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The influence of temperature on the morphology development was experimentally investigated. The results show that the polycrystals Fe₃O₄ nanorods with cubic structure and the average diameter of 0.5–0.8 μm grow after reaction at 200–500°C for 1 h in the air. When the temperature was 600°C, the samples completely became Fe₂O₃ nanowires with hexagonal structure. It was found that C₂H₂O₄ molecules had a significant effect on the formation of Fe₃O₄ nanorods. A possible mechanism was also proposed to account for the growth of these Fe₃O₄ nanorods. Supported by the Fund of Weinan Teacher’s University (Grant No. 08YKZ008), the National Natural Science Foundation of China (Grant No. 20573072) and the Doctoral Fund of Ministry of Education of China (Grant No. 20060718010)     

Synthesis and characterization of Co<Subscript>0.8</Subscript>Zn<Subscript>0.2</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles

Cobalt zinc ferrite, Co_0.8Zn_0.2Fe₂O₄, nanoparticles have been synthesized via autocatalytic decomposition of the precursor, cobalt zinc ferrous fumarato hydrazinate. The X-ray powder diffraction of the ‘as prepared’ oxide confirms the formation of single phase nanocrystalline cobalt zinc ferrite nanoparticles. The thermal decomposition of the precursor has been studied by isothermal, thermogravimetric and differential thermal analysis. The precursor has also been characterized by FTIR, and chemical analysis and its chemical composition has been determined as Co_0.8Zn_0.2Fe₂(C₄H₂O₄)₃·6N₂H_4. The Curie temperature of the ‘as-prepared oxide’ was determined by AC susceptibility measurements.