Ag@CoFe2O4/Fe2O3 nanorod arrays on carbon fiber cloth as SERS substrate and photo-Fenton catalyst for detection and degradation of R6G

In this study, Ag nanoparticles loaded CoFe₂O₄/Fe₂O₃ nanorod arrays on carbon fiber cloth have been successfully fabricated by a hydrothermal route followed by a calcination treatment and photochemical reduction process. The as-prepared composite has been characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The obtained Ag@CoFe₂O₄/Fe₂O₃ nanorod arrays show excellent SERS performance, which provides enhancement factors (EF) as high as about 1.2 × 10⁸ for Rhodamine 6G (R6G). The SERS signals collected over a 20?µm × 20?µm area show relative standard deviation lower than 12%, suggesting good SERS signal uniformity. In addition, the Ag@CoFe₂O₄/Fe₂O₃ nanorod arrays can be used as an effective photo-Fenton catalyst photocatalytical degradation of R6G. It was found that 99.15% of R6G can be degraded in an hour. This bifunctional composite that can act both as SERS substrates and as photo-Fenton catalyst would facilitate the cleaning and recycling of SERS substrates for reusing through a photocatalytic process, as well as facilitate the integration of rapid detection and effective degradation of organic pollutants.     

Intensifying the photocatalytic degradation of methylene blue by the formation of BiFeO3/Fe3O4 nanointerfaces

A novel highly efficient photocatalyst composite BiFeO₃/Fe₃O₄ has been synthesized by mechanosynthesis and applied to the degradation of Methylene Blue under visible light. Structural, optical and photocatalytic properties of the proposed photocatalyst composites are carefully investigated. The nanointerfaces, associated to ferrous Fe²⁺ ions of the Fe₃O₄ nanoparticles, improve the photocatalytic efficiency when compared with pure BiFeO₃ or Fe₃O₄. The time required to the complete degradation of Methylene Blue solution is 40 min for the sample with 20% of Fe₃O₄ which is more than 7 times faster than the time required using BiFeO₃ alone. Moreover, with the addition of H₂O₂ a complete degradation is achieved just after 10 min, which is faster than any other photocatalytic reaction reported for BiFeO₃-based materials. This enhancement is assumed to be related to an electron drain process due to the difference between energy levels of the conduction bands of BiFeO₃ and Fe₃O₄ combined with the direct Fenton-like process associated with the Fe²⁺ ions of the composites.     

Graphene oxide–Fe2O3 hybrid material as highly efficient heterogeneous catalyst for degradation of organic contaminants

Graphene oxide–Fe₂O₃ (GO–Fe₂O₃) hybrid material was synthesized as a heterogeneous catalyst for photo-Fenton degradation of organic contaminants by an easy and scalable impregnation. X-ray diffraction analysis and high-resolution transmission electron microscope analysis confirm the existence of the Fe₂O₃ nanoparticles in the GO–Fe₂O₃ catalyst. Fourier transform infrared spectroscopy analysis proves that the combination of Fe₂O₃ and GO sheet is due to the metal–carbonyl coordination. The catalytic activities of the GO–Fe₂O₃ catalyst were evaluated by the degradation of Rhodamine B and 4-nitrophenol under visible light irradiation (>420 nm) in the presence of hydrogen peroxide. The results show that the catalyst exhibited excellent catalytic property at a wide pH range of 2.09–10.09 and stable catalytic activity after seven recycles, which could be attributed to the synergetic effects of the adsorptive power of GO and the hydroxyl radicals produced by heterogeneous photo-Fenton reactions. The present results suggest that the GO–Fe₂O₃ hybrid material can act as an efficient heterogeneous catalyst for degradation of organic contaminants, which may provide insight into the design and development of high-efficiency visible-light photocatalyst for water treatment.     

Multiple-metal-doped Fe3O4@Fe2O3 nanoparticles with enhanced photocatalytic performance for methyl orange degradation under UV/solar light irradiation

Waelz slag, which is a Fe-bearing hazardous waste, was applied as the raw material in the synthesis of M-Fe₃O₄@Fe₂O₃ (M = Al, Zn, Cu, and Mn) nanoparticles, which are potential photocatalysts. Through acidolysis, 97.23% of Fe and most of the valuable metals were extracted from this slag. Using sol-gel processes, designed Fe₃O₄@Fe₂O₃ nanoparticles doped with multiple elements were systematically synthesised and characterised using X-ray diffraction, field emission scanning electron microscopy, electron diffraction spectroscopy, transmission electron microscopy, and Brunauer–Emmett–Teller analysis. The photocatalytic activities of the synthesised particles and undoped Fe₂O₃ nanoparticles were compared through photocatalytic methyl orange degradation experiments under UV and simulated solar light. The results indicated that all of the slag-derived nanoparticles gave improved photocatalytic performances compared to the undoped sample, and the M-Fe₃O₄@Fe₂O₃ (M = Al, Zn, and Cu) sample exhibited the best photocatalytic activity. The enhancement can be attributed to grain refinement, doping, and the formation of a typical Fe₃O₄@Fe₂O₃ core-shell structure.     

Electrodeposition and corrosion behavior of Zn–Ni and Zn–Ni–Fe2O3 coatings

A thin film of Zn–Ni–Fe₂O₃ on steel substrates was prepared by electrodeposition technique using Zn–Ni alloy plating solution with nano-sized Fe₂O₃ particles. The cathodic polarization and cyclic voltammetry techniques were used to explain deposition process. The corrosion behavior of deposits was evaluated by polarization and impedance studies. Scanning electron microscope (SEM) images were used to study the surface morphology of coating. The grain size and amount of Fe₂O₃ particles present in composite coating were measured by X-ray diffraction pattern (XRD) and energy dispersive X-ray diffraction spectrometer (EDS), respectively.     

Tio2‐ or tio2/fe3o4‐containing PVA‐based microgels for controlled photocatalytic degradation of methyl orange

An inverse emulsion radical reaction was adopted to prepare poly(vinyl alcohol) (PVA)‐based microgels that contained titanium oxide (TiO₂) or TiO₂/Fe₃O₄, and the obtained microgels were applied to catalyze the degradation of methyl orange. First, well‐defined PVA was used to synthesize a PVA‐based macromonomer (PVAM) that contained carbon–carbon double bonds of tunable contents. Then, the composite microgels were prepared via the crosslinking reaction between PVAM and acrylic acid in the presence of TiO₂ or TiO₂/Fe₃O₄. Thermogravimetric analysis (TGA) and scanning electron microscope observation confirmed that the inorganic nanoparticles were well encapsulated within the microgels. TGA results showed that the loading efficiency of TiO₂ was able to be controlled by varying the structure of PVAM. It was found that the microgels can efficiently catalyze the degradation of methyl orange. Moreover, the composite microgels possessed controllable and returnable catalysis ability. In addition, the separation of the composite microgels from aqueous solution could be quite easily accomplished by incorporating magnetic particles. POLYM. COMPOS., 38:132–137, 2017. © 2015 Society of Plastics Engineers     

Enhanced sonocatalytic degradation of recalcitrant organic contaminants using a magnetically recoverable Ag/Fe-loaded activated biochar composite

Silverorthophosphate (Ag₃PO₄)-iron oxide (Fe₃O₄)@activated biochar (AB) composite was prepared by a co-precipitation method as a sonocatalyst for the degradation of recalcitrant organic contaminants. We characterized Ag₃PO₄–Fe₃O₄@AB to study the physicochemical properties using scanning electron microscopy, porosimetry, a vibrating sample magnetometer, and X-ray photoelectron spectroscopy. The specific surface area increased after loading Ag₃PO₄–Fe₃O₄ on AB compared to AB only. The high magnetic property of Ag₃PO₄–Fe₃O₄@AB was confirmed by vibrating sample magnetometer analysis, which could be attributed to the existence of Fe₃O₄. The Ag₃PO₄–Fe₃O₄@AB demonstrated excellent sonocatalytic performances for the degradation of rhodamine B (RhB) and bisphenol A (BPA) under an ultrasonic (US) irradiation. Synergetic sonocatalytic activity of Ag₃PO₄–Fe₃O₄@AB has been obtained from (i) enhanced pyrolysis conditions of water molecules on the surface of the sonocatalyst through a “hot spot” and (ii) photoinduced separation between electron-hole pairs of Ag₃PO₄ using sonoluminescence. The predominant active radical species was OH•, which was confirmed by a spin trapping study. The US/Ag₃PO₄–Fe₃O₄@AB system demonstrated successful application in the degradation of various organic contaminants including synthetic dyes, endocrine-disrupting compounds/pharmaceutical active chemicals, and chlorinated organic contaminants as well as excellent reusability without a significant loss of sonocatalytic performance.     

Effect of Fe3O4 concentration on 3D gel-printed Fe3O4/CaSiO3 composite scaffolds for bone engineering

In this study, porous calcium silicate (CaSiO₃) scaffolds were prepared by 3D gel-printing (3DGP) method and Fe₃O₄ water-based magnetic fluids (WMFs) were prepared by phacoemulsification compound chemical coprecipitation method. Fe₃O₄ WMFs were coated on CaSiO₃ scaffolds surface to prepare Fe₃O₄/CaSiO₃ composite scaffolds. The effect of WMFs with different Fe₃O₄ concentrations on porous CaSiO₃ scaffolds was studied. The composition and morphological characteristics of porous scaffolds were analyzed by using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) analysis. The magnetic properties were tested by vibrating sample magnetometer (VSM). The stability of Fe₃O₄ WMFs coatings and the degradability of composite scaffolds were tested by immersing them in simulated body fluid (SBF). The results show that when Fe₃O₄ concentration was 5.4% (w/v), the composite scaffolds had the highest saturation magnetization of 69.6 emu/g and the best stability in dynamic SBF. It is obviously that Fe₃O₄ WMFs coatings can be used for bone tissue engineering scaffolds repairing.     

Hydrothermal synthesis and visible-light photocatalytic activity of porous peanut-like BiVO4 and BiVO4/Fe3O4 submicron structures

Porous peanut-like BiVO₄ and BiVO₄/Fe₃O₄ submicron structures were synthesized by a template-free hydrothermal process at 160 °C for 24 h. The as-synthesized samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM) and UV–vis spectroscopy. The photocatalytic activity of BiVO₄ and BiVO₄/Fe₃O₄ submicron structures were evaluated for the degradation of Rhodamine B (RhB) and methylene blue (MB) under visible light irradiation with and without the assistance of H₂O₂. According to the experimental results obtained, porous peanut-like BiVO₄/Fe₃O₄ composite photocatalyst shows higher photocatalytic activity in the H₂O₂-assisted system under visible light irradiation compared to BiVO₄. Recycling test on the BiVO₄/Fe₃O₄ composite photocatalyst for the degradation of RhB under visible light irradiation indicates that the composite photocatalyst is stable in the H₂O₂-assisted system in five cycles. Therefore, this composite photocatalyst will be beneficial for efficient degradation of organic pollutants present in water and air under solar light.     

Facile one‐pot preparation of superparamagnetic chitosan sphere and its derived hollow sphere

A facile and robust approach is presented to prepare superparamagnetic chitosan (CS) spheres by simply dropping iron ions and CS mixture solution to ammonia aqueous solution. Fourier transform infrared spectra, X‐ray diffractions, and thermogravimetric analyses of the obtained spheres indicate that the composite spheres consisted of CS and Fe₃O₄. The microstructures of the surface and the inner part of the sphere were observed by scanning electron microscope to indicate nano scale of the Fe₃O₄ component. The results suggest that the nano sized Fe₃O₄ particles can be stabilized by CS molecules in the matrix of sphere to avoid aggregation based on their binding interaction. Because of the nano scale distributed Fe₃O₄ particles, the composite spheres show superparamagnetic properties, and the saturation magnetization of the composite sphere increases linearly with the Fe₃O₄ content. An electron probe microanalyzer was employed to measure the energy dispersive spectra of the magnetic sphere, through which the element contents at different points along the radius of a magnetic CS sphere have been obtained. It has been found that the Fe₃O₄ content decreased gradually from outer surface to its inner core. Moreover, the composite sphere was calcined in air at 700°C to prepare spherical hollow sphere. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Magnetic-field-induced Fe3O4@CNTs/PES/SPSf composite membrane for efficient removal of methylene blue by adsorption and catalytic degradation

Novel composite membranes are successfully developed for adsorption and catalytic degradation of methylene blue (MB) by blending Fe₃O₄-coated CNTs (Fe₃O₄@CNTs) nanoparticles in polyethersulfone (PES) and sulfonated polysulfone (SPSf) matrix via nonsolvent-induced phase separation (NIPS) method assisted by magnetic field. Fe₃O₄@CNTs nanoparticles migrate to the separation layer under the induction of magnetic field, thus Fe₃O₄@CNTs/PES/SPSf composite membranes prepared under magnetic field exhibit a better dye removal ability compared with that without magnetic field. The MB removal ratio by Fe₃O₄@CNTs/PES/SPSf composite membrane containing 8 wt% Fe₃O₄@CNTs (M2−M) can reach up to 99% in 30 min under the conditions of 0.25 g composite membrane, 20 mg/L MB, 0.1 mol/L H₂O₂, pH = 3 and 80°C. Furthermore, the composite membranes show excellent recycling performance, as the MB removal capacity remains at 99% even after four cycles.     

Polypropylene as a carbon source for the synthesis of multi-walled carbon nanotubes via catalytic combustion

Multi-walled carbon nanotubes (MWCNTs) were efficiently synthesized by catalytic combustion of polypropylene (PP) using nickel compounds (such as Ni₂O₃, NiO, Ni(OH)₂ and NiCO₃ · 2Ni(OH)₂) as catalysts in the presence of organic-modified montmorillonite (OMMT) at 630-830 °C. Morphologies of the sample undergoing different combustion times were observed to investigate actual process producing MWCNTs by this method. The obtained MWCNTs were characterized by X-ray diffraction (XRD), transmission electron microscope and Raman spectroscopy. The yield of MWCNTs was affected by the composition of PP mixtures with OMMT and nickel compounds and the combustion temperature. The proton acidic sites from the degraded OMMT layers due to the Hoffman reaction of the modifiers at high temperature played an important role in the catalytic degradation of PP to supply carbon sources that are easy to be catalyzed by nickel catalyst for the growth of MWCNTs. The XRD measurements demonstrated that the nickel compounds were in situ reduced into the Ni(0) state with the aid of hydrogen gas and/or hydrocarbons in the degradation products of PP, and the Ni(0) was really the active site for the growth of MWCNTs. The combination of nickel compounds with OMMT was a key factor to efficiently synthesize MWCNTs via catalytic combustion of PP.     

Effect of surface modification of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles on the preparation of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/polystyrene composite particles via miniemulsion polymerization

Fe₃O₄ nanoparticles were modified by n-octadecyltrimethoxysilane (C18TMS) and 3-trimethoxysilylpropylmethacrylate (MPS). The modified Fe₃O₄ nanoparticles were used to prepare Fe₃O₄/polystyrene composite particles by miniemulsion polymerization. The effect of surface modification of Fe₃O₄ on the preparation of Fe₃O₄/polystyrene composite particles was investigated by transmission electron microscopy, Fourier transform infrared spectrophotometer (FT-IR), contact angle, and vibrating sample magnetometer (VSM). It was found that C18TMS modified Fe₃O₄ nanoparticles with high hydrophobic property lead to the negative effect on the preparation of the Fe₃O₄/polystyrene composite particles. The obtained composite particles exhibited asymmetric phase-separated structure and wide size distribution. Furthermore, un-encapsulated Fe₃O₄ were found in composite particles solution. MPS modified Fe₃O₄ nanoparticles showed poor hydrophobic properties and resulted in the obtained Fe₃O₄/polystyrene composite particles with regular morphology and narrow size distribution because the ended C=C of MPS on the surface of Fe₃O₄ nanoparticles could copolymerize with styrene which weakened the phase separation distinctly.     

A Taguchi analysis on structural properties of polypropylene microcellular nanocomposite foams containing Fe2O3 nanoparticles in batch process

Polypropylene (PP) as a thermoplastic polymer has been foamed using batch foaming process. CO₂ is used as the blowing agent of the foaming. Ferrous oxide nanoparticles (nano Fe₂O₃) are also added as reinforcement. Effect of different parameters including nanoparticle weight percentage, foaming temperature and time on the structural properties of PP/nano Fe₂O₃ nanocomposites is investigated using Taguchi approach. Scanning electron microscope results depict that an appropriate microcellular structure is obtained with the cell density of 10⁹ cells/cm³ and almost 1 μm of cell size. Analysis of variance results indicated that foaming temperature is the most significant parameter on the structural properties. Cell density and expansion ratio are decreased by increasing foaming temperature. This phenomenon could be due to the reducing melt strength of polymer/gas mixture. It was also inferred that adding 2 wt% of nanoparticles leads to 80% improvement in cell density while cell size and expansion ratio was decreased.     

Ultrafine palladium nanoparticle-bonded to polyetheylenimine grafted reduced graphene oxide nanosheets: Highly active and recyclable catalyst for degradation of dyes and pigments

Much attention has been increasingly focused on the applications of noble metal nanoparticles (NPs) for the catalytic degradation of various dyes and pigments in industrial wastewater. We have demonstrated that Pd NPs/Fe₃O₄-PEI-RGO nanohybrids exhibit high catalytic activity and excellent durability in reductive degradation of MO, R6G, RB. Specific surface area was successfully prepared by simultaneous reduction of Pd(OAc)₂ chelating to PEI grafted graphene oxide nanosheets modified with Fe₃O₄. The as-prepared Pd NPs/Fe₃O₄-PEI-RGO nanohybrids were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, high-resolution TEM and energy dispersive X-ray spectroscopy, and UV-lambda 800 spectrophotometer, respectively. The catalytic activity of Pd NPs/Fe₃O₄-PEI-RGO nanohybrids to the degradation of MO, R6G, RB with NaBH4 was tracked by UV-visible spectroscopy. It was clearly demonstrated that Pd NPs/Fe₃O₄-PEI-RGO nanohybrids exhibited high catalytic activity toward the degradation of dyes and pigments, which could be relevant to the high surface areas of Pd NPs and synergistic effect on transfer of electrons between reduced graphene oxide (RGO), PEI and Pd NPs. Notably, Pd NPs/Fe₃O₄-PEI-RGO nanohybrids were easily separated and recycled thirteen times without obvious decrease in system. Convincingly, Pd NPs/Fe₃O₄-PEI-RGO nanohybrids would be a promising catalyst for treating industrial wastewater.     

Heterogeneous Fenton degradation of Orange II by immobilization of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles onto Al-Fe pillared bentonite

A novel catalyst, Fe₃O₄ nanoparticle decorated Al-Fe pillared bentonite (Fe₃O₄/Al-Fe-P-B), was prepared by in situ precipitation oxidization method. The catalyst was characterized by SEM, XRD and Raman spectroscopy. The Fe₃O₄ nanoparticles mainly exist on the surface or enter into the pore of bentonite, with better dispersing and less coaggregation. The catalytic activity of Fe₃O₄/Al-Fe-P-B was investigated in the degradation of Orange II (OII) by heterogeneous Fenton-like process. The effects of initial concentration of hydrogen peroxide, catalyst loading, temperature and initial pH on the degradation of OII were investigated. The Fe₃O₄/Al-Fe-P-B showed higher degradation efficiency of OII than bare Fe₃O₄ or Al-Fe-P-B in the degradation experiment. The enhanced catalytic activity of Fe₃O₄/Al-Fe-P-B in heterogeneous Fenton system was due to the synergistic effect between Al-Fe-P-B and Fe₃O₄. The novel catalyst can achieve solid-liquid separation easily by sample magnetic separation and has a good reusability and stability.     

Investigation of the photodegradation properties of iron oxide doped mesoporous SBA-15 silica

Mesoporous silica (SBA-15) and iron oxide incorporated silica (Fe₂O₃-SBA-15) were synthesized by co-operative self-assembly technique. Samples were characterized using nitrogen adsorption–desorption isotherm, electron microscopic and spectroscopic techniques. The results confirm the uniform distribution of pores, presence of metal oxides in the pores as well as in the surface of the mesoporous wall and oxidation state of iron in the Fe₂O₃-SBA-15. The photocatalytic degradation of methylene blue (MB), sulphorhodamine B (SR-B) and methyl orange (MO) by Fe₂O₃-SBA-15 was investigated. It was observed that Fe₂O₃-SBA-15 degraded 98 % of MB, 96 % of SR-B and 99 % of MO within 3 h after exposure to sunlight. SBA-15 does not exhibit any photocatalytic effect. These results demonstrate the potential of Fe₂O₃-SBA-15 for environmental pollution control.     

Crystallinity,conductivity, and magnetic properties of PVDF‐Fe3O4 composite films

The formation of Fe₃O₄ nanoparticles by hydrothermal process has been studied. X‐ray Diffraction measurements were carried out to distinguish between the phases formed during the synthesis. Using the synthesized Fe₃O₄ nanoparticles, poly(vinyledene fluoride)‐Fe₃O₄ composite films were prepared by spin coating method. Scanning electron microscopy of the composite films showed the presence of Fe₃O₄ nanoparticles in the form of aggregates on the surface and inside of the porous polymer matrix. Differential Scanning calorimetry revealed that the crystallinity of PVDF decreased with the addition of Fe₃O₄. The conductitivity of the composite films was strongly influenced by the Fe₃O₄ content; conductivity increased with increase in Fe₃O₄ content. Vibration sample magnetometry results revealed the ferromagnetic behavior of the synthesized iron oxide nanoparticles with a Ms value of 74.50 emu/g. Also the presence of Fe₃O₄ nanoparticles rendered the composite films magnetic. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synergistic effects of nano‐Mn0.4Zn0.6Fe2O4 on intumescent flame‐retarded polypropylene

The melamine salt of 5,5‐dimethyl‐1,3,2‐dioxaphos‐phorinane‐2‐oxide‐2‐hydroxide (IFR100) was used as an intumescent flame retardant in flame‐retarded polypropylene (PP). As a synergistic agent, nano‐Mn_0.4Zn_0.6Fe₂O₄ was incorporated into the PP/IFR100 composite at different proportions. The synergistic effects of nano‐Mn_0.4Zn_0.6Fe₂O₄ were studied by the limiting oxygen index (LOI) test, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X‐ray diffraction (XRD). The synergistic effect of the nano‐Mn_0.4Zn_0.6Fe₂O₄ additive with IFR100 was clearly observed by LOI. The TGA results showed that nano‐Mn_0.4Zn_0.6Fe₂O₄ improved the thermal stability of the PP/IFR100 system above 400°C. On the basis of the FTIR and XRD results, it was evident that nano‐Mn_0.4Zn_0.6Fe₂O₄ efficiently promoted the formation of a charred layer containing phosphocarbonaceous structures. The SEM micrographs indicated that nano‐Mn_0.4Zn_0.6Fe₂O₄ strengthened the structure of the char layer remaining after combustion. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers     

Synthesis of AgCl/Bi3O4Cl composite and its photocatalytic activity in RhB degradation under visible light

This work presents a novel composite photocatalyst, AgCl/Bi₃O₄Cl, which was prepared using an ion-exchange method. The synthesized composite was characterized by various techniques and its photocatalytic activity was investigated in RhB degradation under visible light irradiation. Results indicated that the introduction of AgCl into Bi₃O₄Cl promoted the specific surface area, light absorption performance and the separation efficiency of electron–hole pairs, which resulted in a high photocatalytic activity of the composite. The optimal AgCl/Bi₃O₄Cl sample showed a RhB degradation rate of 0.048 min^− 1, which was 2.2 and 2.4 times higher than those of AgCl and Bi₃O₄Cl, respectively.