Dechlorination of 3,3′,4,4′-tetrachlorobiphenyl in aqueous solution by hybrid Fe0/Fe3O4 nanoparticle system

The kinetics and efficiency of 3,3′,4,4′-tetrachlorobiphenyl (PCB77) degradation in aqueous solution by hybrid Fe⁰/Fe₃O₄ nanoparticle system were investigated. The results showed that nano-sized Fe⁰ and Fe₃O₄ could efficiently degrade PCB77, and the residual rate of PCB77 by nano-sized Fe⁰ and Fe₃O₄ were 67.70% ± 0.42% and 82.26% ± 2.96%, respectively after 240 min of reaction (for 5 mg·L^?1 PCB77 and 5 g·L^?1 nanoparticles). The combined use of nanoscale Fe⁰ and Fe₃O₄ could enhance the degradation of PCB77. The dose ratios of nano-sized Fe⁰ and Fe₃O₄ significantly affected the PCB77 degradation rate. At Fe⁰/Fe₃O₄ ratios of 1:0.1, 1:0.2 and 1:1, the residual rates of PCB77 were 6.46%, 10.23% and 38.20%, respectively. The PCB77 degradation efficiency was also greatly affected by solution pH, and was maximised at pH 6.8. The degradation of PCB77 by Fe⁰/Fe₃O₄ nanoparticle was a dechlorination process, and the chlorion concentration increased with the decreasing residual rate of PCB77 accordingly. Fe₃O₄ provided Fe²⁺ and Fe³⁺ for enhancing the PCB77 degradation by nanoscale Fe⁰, suggesting a synergy between Fe⁰ and Fe₃O₄.     

Effect of Cr doping on the phase structure,surface appearance and magnetic property of BiFeO<Subscript>3</Subscript> thin films prepared via sol–gel technology

Multiferroic BiFeO₃ (BFO) and BiFe_1?xCr_xO₃ (BF_1?xC_xO, x?=?0.05, 0.1, 0.15 and 0.2) thin films were successfully synthesized on silicon (111) substrates via sol–gel technology. The effect of Cr³⁺ ion doping on the phase structure, surface morphology, valence states for Fe element and magnetic property was investigated. The introduction for simulation images of ionic space arrangement was to better comprehend the substitution site and superexchange interaction between the Fe³⁺ (Cr³⁺) and O^2? ions. The phase structure of Cr-doping thin films transition from rhombohedral to orthorhombic was confirmed by the X-ray diffraction (XRD) and Raman measurements, and the obtained results also demonstrated that the Cr³⁺ ions successfully located in Fe²⁺ and Fe³⁺ ions sites of BFO lattice system. The Field Emission Scanning Electron Microscopy (FESEM) patterns clearly exhibited that the grains sizes were remarkably decreased by Cr³⁺ ions doping, and the surfaces textures got glossier and smoother judging from the Atomic Force Microscope (AFM) images. The dense surface structure can restrict the O^2? ions escaping from the lattices system, which is beneficial for the release of magnetic property due to superexchange interaction of improvement. It was found that the saturation magnetization (Ms) was significantly linearly increased accompanying the adding of Cr-doping due to destroying of spatial modulation helical structure and enhancing of superexchange interaction. Moreover, the Hall-effect results firstly revealed that the carrier concentration and mobility rate played significant roles in magnetoelectric effect behaviors.     

Epitaxial growth and exchange coupling of spinel ferrimagnet Ni0.3Zn0.7Fe2O4 on multiferroic BiFeO3

Thin films of the zinc nickel ferrite, Zn_0.7Ni_0.3Fe₂O₄ (ZNFO), were deposited by the RF magnetron sputtering on a number of substrates, including (001) oriented single crystals of LaAlO₃ (LAO) and SrTiO₃ (STO), polycrystalline Pt/Si, and epitaxial films of BiFeO₃ (BFO) and LaNiO₃ (LNO). Except for the films on Pt/Si, the ZNFO films grown on other substrates were epitaxial and their magnetic properties were affected by the heteroepitaxy induced strains. Typically, the coercivity (H_c) was increased with the strain, i.e. H_c varied from 31 Oe for the 150 nm thick polycrystalline films grown on Pt/Si, to 55 Oe and 155 Oe for the 20 nm thick epitaxial films grown on BFO and LAO, respectively. The saturation magnetization of the epitaxial films was reduced accordingly to about 470 emu/cm³ from 986 emu/cm³ in the polycrystalline films. The all-oxide architecture allowed field-annealing to perform at the temperature above the Neel temperature of BFO (~ 370 °C), after which clear exchange bias was observed.     

The degradation of landfill leachate in the presence of different catalysts by sonolytic and sonocatalytic processes

In the study, the degradation of landfill leachate by single ultrasound (sonolytic) and sonolytic combined with Fe²⁺ and TiO₂ catalysts was carried out in laboratory conditions. The effect of pH and ultrasonic wave amplitude was also investigated in terms of color removal, total organic carbon (TOC) and chemical oxygen demand (COD) from leachate by the sonolytic degradation process. In this process, the color removal efficiency was recorded as 81.81% at 620?nm, pH?=?2.0 and 70% wave amplitude. The sonocatalytic degradation of landfill leachate accompanied by different catalysts was studied by using the 70% wave amplitude at pH?=?2.0 and room temperature for 20?min. The sonocatalytic degradation of leachate by using Fe²⁺ and TiO₂ was found to be significantly higher than sonolytic degradation (p?2+ concentration increased from 1.0 to 3.0?mg/L, the COD and color removal of leachate significantly decreased (p?相似文献   

cis-1,3,4,6-Tetranitrooctahydroimidazo-[4,5-d]imidazole (BCHMX), its properties and initiation reactivity

Pre-treatment of simulated industrial wastewaters (SIM1, SIM2 and SIM3) containing organic and inorganic compounds (1,2-dichloroethane, sodium formate, sodium hydrogen carbonate, sodium carbonate and sodium chloride) by oxidative degradation using homogeneous Fenton type processes (Fe²⁺/H₂O₂ and Fe³⁺/H₂O₂) has been evaluated. The effects of initial Fe²⁺ and Fe³⁺ concentrations, [Fe^2+/3+], type of iron salt (ferrous sulfate vs. ferric chloride), initial hydrogen peroxide concentration, [H₂O₂], on mineralization extent, i.e., total organic content (TOC) removal, were studied. Response surface methodology (RSM), particularly Box–Behnken design (BBD) was used as modelling tool, and obtained predictive function was used to optimize the overall process by the means of desirability function approach (DFA). Up to 94% of initial TOC was removed after 120 min. Ferrous sulfate was found to be the most appropriate reagent, and the optimal doses of Fe²⁺ and H₂O₂ for reducing the pollutant content, in terms of final TOC and sludge production were assessed.     

Electron spin resonance study and improved magnetic and dielectric properties of Gd–Ti co-substituted BiFeO3 ceramics

Polycrystalline BiFeO₃ (BFO), Bi_0.90Gd_0.10FeO₃ (BGF), Bi_0.90Gd_0.10Fe_1?xTi_xO₃ (x = 0.03–0.10; BGFT_x) ceramics were prepared via solid state reaction method. X-ray diffraction studies reveal R3c symmetry for BFO and BGF samples and coexistence of R3c + Pn2 ₁ a symmetries for BGFT_x samples. The change in line width of Raman modes indicates the structural distortion and substitution of dopants ions in the BFO lattice. Magnetic studies show weak ferromagnetism in BGF and BGFT_x samples as a result of Gd³⁺–Fe³⁺, Gd³⁺–Gd³⁺ interactions and imbalance created between two antiparallel Fe³⁺ spin sublattices by Ti substitution. The maximum remnant magnetization of 0.141 emu/g is observed for BGFT_x=0.10 sample. Further, electron spin resonance study confirms the weak ferromagnetism of BGFT_x samples, associated with small grains and increase in anisotropy of particles distribution as found during SEM studies. UV–Visible absorption spectra in the spectral range from 1.6 to 3.5 eV showed one d–d crystal field transition and two charge-transfer transitions with optical band gap variation in visible region. Improved dielectric properties with very low values of dielectric loss have been observed for BGF and BGFT_x samples.     

Photocatalytic degradation of formaldehyde by nanostructured TiO2 composite films

Interest in the photocatalytic oxidation of formaldehyde from contaminated wastewater is growing rapidly. The photocatalytic activity of the nanocrystalline Fe³⁺/F^? co-doped TiO₂–SiO₂ composite film for the degradation of formaldehyde solution under visible light was discussed in this study. The films were characterised by field emission scanning electron microscopy (FE-SEM) equipped with energy-dispersive spectroscopy, X-ray diffraction (XRD), BET surface area, UV–Vis absorption spectroscopy, and photoluminescence spectroscopy. The FE-SEM results revealed that the Fe³⁺/F^? co-doped TiO₂–SiO₂ film was composed of uniform round-like nanoparticles or aggregates with the size range of 5–10 nm. The XRD results indicated that only the anatase phase was observed in the film. Compared with a pure TiO₂ film and a singly modified TiO₂ film, the Fe³⁺/F^? co-doped TiO₂–SiO₂ composite film showed the best photocatalytic properties due to its strong visible light adsorption and diminished electrons-holes recombination.     

Assembly of Fe3O4 nanoparticles on SiO2 monodisperse spheres

The assembly of superparamagnetic Fe₃O₄ nanoparticles on submicroscopic SiO₂ spheres have been prepared by an in situ reaction using different molar ratios of Fe³⁺/Fe²⁺ (50–200%). It has been observed that morphology of the assembly and properties of these hybrid materials composed of SiO₂ as core and Fe₃O₄ nanoparticles as shell depend on the molar ratio of Fe³⁺/Fe²⁺.     

Multiferroic properties of BiFeO3/Bi4Ti3O12 double-layered thin films fabricated by chemical solution deposition

Multiferroic BiFeO₃/Bi₄Ti₃O₁₂ (BFO/BTO) double-layered film was fabricated on a Pt(111)/Ti/SiO₂/Si(100) substrate by a chemical solution deposition method. The effect of an interfacial BTO layer on electrical and magnetic properties of BFO was investigated by comparing those of pure BFO and BTO films prepared by the same condition. The X-ray diffraction result showed that no additional phase was formed in the double-layered film, except BFO and BTO phases. The remnant polarization (2P_r) of the double-layered film capacitor was 100 μC/cm² at 250 kV/cm, which is much larger than that of the pure BFO film capacitor. The magnetization-magnetic field hysteresis loop revealed weak ferromagnetic response with remnant magnetization (2M_r) of 0.4 kA/m. The values of dielectric constant and dielectric loss of the double-layered film capacitor were 240 and 0.03 at 100 kHz, respectively. Leakage current density measured from the double-layered film capacitor was 6.1 × 10^− 7 A/cm² at 50 kV/cm, which is lower than the pure BFO and BTO film capacitors.     

Synthesis of nanostructured M/Fe3O4 (M = Ag,Cu) composites using hexamethylentetramine and their electrocatalytic properties

Nanoscaled Ag/Fe₃O₄ hybrids with different Ag contents and Cu/Fe₃O₄ nanoshpere and microsphere were successfully synthesized with assistance of sodium citrate and (CH₂)₆N₄ via a hydrothermal process. The as-prepared samples were identified and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS), respectively. All samples were used as electrocatalysts modified on a glassy carbon electrode for p-nitrophenol reduction in a basic solution. The catalytic activity of Ag/Fe₃O₄ samples increased first and then decreased by increasing Ag content from 0% to 8%, and the one with 6% Ag displayed the highest catalytic activity. All the Cu/Fe₃O₄ samples exhibited enhanced catalytic activity by comparison with a glassy carbon electrode, and the one prepared with the molar ratio of Cu²⁺, Fe³⁺, citrate anion, and (CH₂)₆N₄ with 1:1:3:5 exhibited the highest catalytic activity.     

Lattice distortion and room-temperature ferroelectric properties of (Sm, Cr) co-doped BiFeO3 thin films

Pure BiFeO₃ (BFO) and Bi_0.85Sm_0.15Fe_0.97Cr_0.03O₃ (BSFCO) thin films were prepared on FTO/glass (SnO₂: F) substrates by using a chemical solution deposition method. The effects of (Sm, Cr) co-doping on the microstructure and ferroelectric properties of the BSFCO thin films were studied. The X-ray diffraction and Raman scattering spectra proved that the co-doped BSFCO thin film has a lattice distortion compared with the pure BFO thin film. The remnant polarization (2P _r) of the BSFCO thin film was 153.67 μC/cm² at 1 kHz in the applied electric field of 1,270 kV/cm. At an applied electric field of 100 kV/cm, the leakage current density of the co-doped BSFCO thin film (2.12 × 10^?6 A/cm²) was 3 orders lower than that of the pure BFO thin film (3.8 × 10^?3 A/cm²). The improved properties of the co-doped thin film could be attributed to lattices distortion, more grain boundaries, higher binding energy of Sm–O and the mixed-valence states of Cr³⁺ and Cr ⁶⁺.     

Iron promotion of the TiO2 photosensitization process towards the photocatalytic oxidation of azo dyes under solar-simulated light irradiation

The photocatalytic oxidation of the azo dye Orange-II (Or-II) using Fe loaded TiO₂ (Fe–TiO₂) was studied under ultraviolet (UV), visible (vis) and simultaneous UV–vis irradiations using a solar light simulator. Photocatalysts were characterized by means of XRD, SEM-EDX, FTIR and DRS. Fe³⁺ species, identified in XPS analyses, were responsible of the increased absorption of visible light. Moreover, DRS analyses showed a decrease in the bandgap due to Fe³⁺ loading. Photocatalystic tests proved that Fe modification enhanced the TiO₂ photocatalytic activity towards Or-II photodegradation under simultaneous UV–vis irradiation. Even so, the performance of the Fe–TiO₂ samples towards the photodegradation of phenol, under UV irradiation, was lower than TiO₂ suggesting the recombination of the UV photogenerated electron–hole pair. Therefore, results evidence a Fe³⁺ promotion of the electron caption in the photosensitization process of TiO₂ by Or-II acting as a sensitizer. Such process leads to the Or-II photooxidation under UV–vis irradiation by losing energy in electron transferring processes to sensitize TiO₂, and, the formation of reactive oxygen species promoted by the injected electron to the TiO₂ conduction band.     

Application of multi-functional chestnut shell in one-step preparing Fe3O4@C magnetic nanocomposite with high adsorption performance

Chestnut shell (CS) acts as a multi-functional material in the one-step preparation of Fe₃O₄@C nanocomposite via hydrothermal method by using Fe(NO₃)₃ as Fe source without adding any other additives. The characterized results show that under required hydrothermal conditions, a proper amount of CS can reduce a certain amount of adsorbed/enriched Fe³⁺ to Fe²⁺ to ensure the 2:1 molar ration of Fe³⁺ to Fe²⁺ and the in-situ formation of goal phase Fe₃O₄ on the surface of the CS. Meanwhile, CS is carbonized to C material similar to graphene oxide. In the preparation process of the composite of Fe₃O₄@C, CS plays multiple roles, such as promoter, reductive agent, C-source, and template, to endow a certain morphology of the nanocomposite Fe₃O₄@C. The composite material shows good magnetic separability and adsorption property for methylene blue (MB) solution. Furthermore, the adsorptive kinetic behavior of the Fe₃O₄@C is investigated. The method is simple, fast, low cost and green and really realizes the full use of wasteful resource CS.     

Enhancement in Magnetic Properties of Mg-Doped Strontium-Substituted Bismuth Ferrite Prepared by Solid-State and Sol-Gel Methods

We report a potential way to effectively improve the magnetic properties of BiSrFeO3 (BSFO) through Mg ²⁺ ion substitution at the Fe sites of BFO lattice. Polycrystalline Bi_0.95Sr_0.05Fe_0.98Mg_0.02 O ₃ (BSFMO) powder was prepared through optimized solid-state (SS) and sol-gel (SG) reaction methods. The effect of preparation routes on the crystal purity and multiferroic properties of the BSFMO was investigated. The purity and structural changes induced by Mg doping are confirmed by X-ray powder diffractometer and IR spectra. Enhanced magnetic properties are observed in Mg-substituted samples, which simultaneously exhibit ferromagnetic and superparamagnetic properties at room temperature. The improved magnetic properties and soft nature obtained by Mg doping in BSFO particles demonstrate the possibility of BFO particles to practical applications.     

Reducing dissolution of MnO2 nanofibers by doping with ferric ion

MnO₂ nanofiber was found to possess high adsorption capacities for heavy metal ions such as, arsenic and lead, in water due to its high specific surface area (SSA) and high surface activity. However, a significant amount of manganese was found to leach from MnO₂ nanofibers. Reducing MnO₂ dissolution is very important for improving its applications in drinking water treatment. In this study, MnO₂ nanofiber was doped with Fe³⁺ to reduce its dissolution in water. Dissolution tests were conducted on un-doped and Fe-doped MnO₂ nanofibers. The results revealed that doping with Fe³⁺ significantly reduced MnO₂ dissolution. SSA and defects of MnO₂ materials were analyzed by BET and XRD methods. The effects of Fe³⁺ on MnO₂ dissolution were discussed and the optimal dopant amount was identified.     

General strategy for embedding high quality Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> quantum dots and ZnS:Mn<Superscript>2+</Superscript> quantum dots in a silica matrix

In this paper, ZnS:Mn²⁺ quantum dots (QDs) Fe₃O₄ quantum dots (QDs)/SiO₂ nanocomposites were successfully synthesized by reverse microemulsion method. The average diameter of ZnS:Mn²⁺ QDs, Fe₃O₄ QDs and ZnS:Mn²⁺ QDs Fe₃O₄ QDs/SiO₂ nanocomposites was about 5.8, 9 and 29 nm, respectively. As the mass ratio of ZnS:Mn²⁺ to Fe₃O₄ QDs increased from 2.5:4 to 7.5:4, the intensity of the yellow–orange emission coming from Mn²⁺ ions was increased. The superparamagnetic property of ZnS:Mn²⁺ QDs Fe₃O₄ QDs/SiO₂ nanocomposites was observed at room temperature, and the saturation magnetization was decreased as the amount of ZnS:Mn²⁺ QDs increased.     

Structural, Dielectric, Ferroelectric and Magnetic Properties of Bi0.80A0.20FeO3 (A=Pr,Y) Multiferroics

Here we studied the effect of homovalent Pr³⁺ and Y³⁺ substitution on the crystal structure, dielectric, electronic polarization and magnetic properties of the BiFeO₃ multiferroic ceramic. The samples were synthesized by the conventional solid-state reaction method. Pure phase formation of Pr doped BiFeO₃ (BFO) has been obtained, while Y³⁺ doped BFO has shown a few impurity peaks. It has shown that the crystal structure of the compounds is described within the space group R3c. Pr³⁺ modified BFO has shown an anomaly in the ε _r vs. T plot around and a Néel temperature ‘T _N’～370 ^°C. P–E hysteresis loops have shown higher value of remnant polarization for Pr³⁺ modified BFO. Magnetic properties of ceramics are determined by the ionic radius of the substituting element. Experimental results propose that the increase in the radius of A-site ion leads to effective suppression of the spiral spin structure of BiFeO₃, resulting in the appearance of net magnetization.     

Preparation of doped TiO2 nanofiber membranes through electrospinning and their application for photocatalytic degradation of malachite green

Fe³⁺ doped TiO₂ composite nanofiber membranes and pure TiO₂ nanofiber membranes were prepared through electrospinning, and were applied to the photocatalytic degradation of malachite green (MG) in aqueous solutions under simulated sunlight. The effects of ferric ion content, initial concentration of MG, photocatalyst loading, and recycling behavior were studied. Microscopic characterization showed that the products have fiber morphology with bent property and favorable continuity. The degradation results showed that TiO₂ nanofiber membranes containing 0.8 mol% Fe³⁺ performed the best photocatalytic activity against MG under identical light irradiation. The TiO₂:Fe³⁺ composite nanofiber membranes maintained their photocatalytic efficiency through seven recycling processes.     

Synthesis,characterization, photocatalytic evaluation,and toxicity studies of TiO2–Fe3+ nanocatalyst

Based on our previous work on the green preparation of Ag–TiO₂ photocatalyst with bactericidal activity under visible light, we extended our studies to the synthesis of TiO₂–Fe³⁺ materials with enhanced photocatalytic activity for the degradation of recalcitrant organic pollutants in water. TiO₂–Fe³⁺ nanopowders were synthesized using a robust, environmentally friendly procedure. Established amounts of Fe(NO₃)₃·9H₂O and titanium tetraisopropoxide (TTIP) were mixed using glacial acetic acid as solvent. Hydrolysis of TTIP–Fe³⁺ was accomplished using a 30 % (W/V) Arabic gum aqueous solution. TiO₂–Fe³⁺ nanopowders were obtained by thermal treatment at 400 °C. In order to elucidate the structure of these photocatalysts, microscopic and spectroscopic characterization techniques were applied. The high resolution transmission electron microscopy (HRTEM) analysis indicated the presence of uniformly distributed particles with average particle size of about 9 nm. According to the HRTEM lattice fringes, ring pattern, and selected area electron diffraction pattern, the crystalline part of the samples consists of anatase (PDF 01-086-1157 with the lattice constant of 3.7852, 9.5139 Å and 90°) as dominant phase. X-ray photoelectron spectroscopy (XPS) was applied to determine the oxidation state of iron. The XPS provides evidence for Fe³⁺ surface species in the TiO₂–Fe³⁺ composite. Complete degradation of aqueous solutions (20 ppm) of methylene blue and/or methyl orange was accomplished after 4 h of treatment using 150 mg of TiO₂–Fe³⁺/150 mL of dye solution. The in vitro toxicity of the materials was tested. The materials showed no toxicity against human red blood cells.     

Magnetic properties of the mixed spinel Co1+x Si x Fe2−2x O4

The structural and magnetic properties of the mixed spinel Co_1+x Si _x Fe_2?2x O₄ system for 0·1≤x≤0·6 have been studied by means of X-ray diffraction, magnetization, and Mössbauer spectroscopy measurements. X-ray intensity calculations indicate that Si⁴⁺ ions occupy only tetrahedral (A) sites replacing Fe³⁺ ions, and the added Co²⁺ ions substitute for (B) site Fe³⁺ ions. The Mössbauer spectra at 300 K have been fitted with two sextets in the ferrimagnetic state corresponding to Fe³⁺ at the A and B sites, forx≤0·3. The Mössbauer intensity data shows that Si possesses a preference for the A site of the spinel. The variation of the saturation magnetic moment per formula unit measured at 300 K with the Si content, is explained on the basis of Neel’s collinear spin ordering model forx≤0·3 which is supported by Mössbauer, and X-ray data. The Curie temperature decreases nearly linearly with increase of the Si content, forx=0·1–0·6.