Surface Of γ-Fe2O3 Research Articles

Carbon quantum dots can enable efficient photochemical interfacial activation of molecular oxygen in iron oxides/oxalate system

Photochemical reactions between natural iron oxides and oxalic acid (OA) have attracted wide attentions in environmental decontamination, but the critical interfacial ligand-to-metal charge transfer process (LMCT) is difficult to occur. In this study, carbon quantum dots modified maghemite (γ-Fe2O3/CQDs) with excellent photo-electrochemical properties has been successfully synthesized, which achieved rapid decomposition of sulfamethoxazole (SMX) with OA under UV. It was found that the complexed [≡FeIII(C2O4)n]3-2n on the γ-Fe2O3 surface could occur efficient interfacial LMCT, followed by fast internal transmission of electrons to CQDs part for activating its surface adsorbed O2 to efficiently produce O2•− and •OH. The heterogeneous LMCT would be dominant in UV/γ-Fe2O3/CQDs/OA system for the initial rapid SMX degradation, despite the non-reductive leaching of aqueous FeIII(C2O4)n3-2n would cause additional homogeneous LMCT. Bonded CQDs at iron oxides could highly improve utilization of the photo-generated electrons from complexed OA for O2 activation, and also broaden its application under visible light.

Transformation of chromium and its removal by Fe2O3 during the thermal disposal of municipal solid waste: A study based on density functional theory

Long-term exposure to chromium released during the thermal disposal of municipal solid waste (MSW) poses carcinogenic risks because of its volatility and biological toxicity. Experimental results showed that there was a strong interaction between γ-Fe2O3 and Cr species, but the specific mechanism of the interaction was unclear. In this study, reaction kinetics and density functional theory (DFT) were used to explore the homogeneous transformation pattern of Cr in flue gas and its adsorption on γ-Fe2O3 during the thermal disposal of MSW. It was found that H2O promoted the rapid transformation of CrOOH released from MSW into higher valence species such as CrO2(OH) and CrO2(OH)2. It was subsequently chlorinated by HCl to CrO2Cl and CrO2Cl2. During the heterogeneous reaction process, the adsorption energy of CrOOH, CrO2(OH), and CrO2Cl on the surface of γ-Fe2O3 (001) was CrOOH > CrO2(OH) > CrO2Cl. It mainly acted on surface oxygen sites. The adsorption energy and electron-loss capacity of CrOOH on the surface of γ-Fe2O3 (001) were enhanced with H2O. When HCl was present, although the adsorption energy of Cr on the surface of γ-Fe2O3 (001) was increased, the electron-losing ability was weakened and there was a tendency to be reduced. As for chlorination of CrOOH by HCl on the surface of γ-Fe2O3 (001), this process had two stages. In the first stage, CrOOH reacted with H2O to form CrO2(OH). In the second stage, CrO2(OH) was chlorinated into high-valence chlorides and chemically adsorbed on the surface of γ-Fe2O3 (001).

Progress toward Room-Temperature Synthesis and Functionalization of Iron-Oxide Nanoparticles.

Novel magnetic nanohybrids composed of nanomaghemite covered by organic molecules were successfully synthesized at room temperature with different functionalization agents (sodium polystyrene sulfonate, oxalic acid, and cetyltrimethylammonium bromide) in low and high concentrations. Structural, vibrational, morphological, electron energy-loss spectroscopy, magnetic, and Mössbauer characterizations unraveled the presence of mainly cubic inverse spinel maghemite (γ-Fe2O3), whilst X-ray diffraction and 57Fe Mössbauer spectroscopy showed that most samples contain a minor amount of goethite phase (α-FeOOH). Raman analysis at different laser power revealed a threshold value of 0.83 mW for all samples, for which the γ-Fe2O3 to α-Fe2O3 phase transition was observed. Imaging microscopy revealed controlled-size morphologies of nanoparticles, with sizes in the range from 8 to 12 nm. Organic functionalization of the magnetic nanoparticles was demonstrated by vibrational and thermogravimetric measurements. For some samples, Raman, magnetic, and Mössbauer measurements suggested an even more complex core-shell-like configuration, with a thin shell containing magnetite (Fe3O4) covering the γ-Fe2O3 surface, thus causing an increase in the saturation magnetization of approximately 11% against nanomaghemite. Field cooling hysteresis curves at 5 K did not evidence an exchange bias effect, confirming that the goethite phase is not directly interacting magnetically with the functionalized maghemite nanoparticles. These magnetic nanohybrids may be suitable for applications in effluent remediation and biomedicine.

Calcium poisoning mechanism on the selective catalytic reduction of NOx by ammonia over the γ-Fe2O3 (001) surface.

γ-Fe2O3 has an excellent low-temperature selective catalytic reduction (SCR) deNOx performance, but its resistance to alkaline earth metal calcium (Ca) is poor. In particular, the detailed mechanism of Ca poisoning on the γ-Fe2O3 catalyst at the atomic level is not clear. Hence, the density functional theory method was used in this research to investigate the influence mechanism of Ca poisoning on the NH3-SCR over the γ-Fe2O3 catalyst surface. The findings reveal that NH3, NO, and O2 molecules can bind to the γ-Fe2O3 (001) surface to generate coordinated ammonia, monodentate nitroso, and adsorption oxygen species, respectively. The main active site is Fe1-top. For the γ-Fe2O3 with Ca poisoning, the Ca atom has a high adsorption energy on the surface of γ-Fe2O3 (001), which covers the catalyst surface and reduces the active sites. The presence of Ca atom decreases the adsorption performance of NH3, while slightly improving the NO and O2 adsorption. In particular, the Ca atom restrains the NH3 activation and NH2 formation, which is detrimental to the NH3-SCR process.

Surface engineering of hematite nanorods photoanode towards optimized photoelectrochemical water splitting

Rapid charge recombination in hematite (Fe2O3) during photoelectrochemical water splitting is a major obstacle to achieving high-efficiency photoelectrodes. Surface defect engineering is considered as a viable strategy for enhancing photoelectrochemical activity of oxide photoanodes. Herein, a one-dimensional (1D) defective γ-Fe2O3 nanorods (DFNRs) photoanode is prepared using solvothermal and high-temperature hydrogenation strategies. The as-prepared DFNRs possess superior visible-light absorption capacity and exhibit excellent photoelectrochemical performance (0.98 mA cm−2), with approximately three-fold higher photocurrent density than that of pristine Fe2O3 (FNRs, 0.32 mA cm−2). The enhanced activity of the DFNRs results from the moderate formation of oxygen vacancy defects, which promotes spatial charge separation and transfer at the DFNRs/electrolyte interface, as well as the 1D nanorod structure, which favors rapid charge transfer. The surface of γ-Fe2O3 with hydroxyl (OH) groups provides sufficient surface-active sites. This result suggests that surface-oxygen deficiency of γ-Fe2O3 can not only expand the light absorption range but also facilitating photo-generated charge carriers separation. This surface engineering strategy provides an alternative method for preparing stable and highly active metal oxide photoanodes for photoelectrochemical water splitting.

Study on the adsorption and oxidation mechanism of mercury by HCl over γ-Fe2O3 catalyst

The mechanism of adsorption and oxidation of Hg0 by HCl on γ-Fe2O3 surface was investigated by density functional theory (DFT) calculation. The adsorption models of Hg0HCl, HgCl and HgCl2 on γ-Fe2O3(001) surface were constructed, and the reaction mechanism of catalytic oxidation of Hg0 by HCl on γ-Fe2O3 surface was analyzed. The results illustrate that the Hg0 tends to be chemically adsorbed at Feoct site. HCl can be dissociated and adsorbed on the surface of the catalyst to form adsorbed Cl and hydroxyl groups, and promote the adsorption of Hg0. HgCl can be molecularly chemisorbed upon γ-Fe2O3(001) and act as an intermediate. HgCl2 tends to be adsorbed in parallel on the surface of γ-Fe2O3. HCl oxidizes Hg0 on γ-Fe2O3(001) following the L-H mechanism: chemically adsorbed Hg0 reacts with dissociatively adsorbed HCl. By measuring the energy distribution of the reaction path, the oxidation process of Hg0 on the surface of γ-Fe2O3 was studied. The heterogeneous oxidation of Hg0 by HCl proceeds on a two-step reaction pathway: Hg0(ads)→HgCl(ads)→HgCl2(ads).

Poly(sulfonamide-thiourea) grafted γ-Fe2O3@talc as a green catalyst for the synthesis of substituted tetrahydropyridines

Herein, we aim to study the role of template and polymers on the synthesis of tetrahydropyridine scaffolds, novel composite (γ-Fe2O3@[email protected]) was synthesized from immobilization of poly (sulfonamide-thiourea) on the surface of γ-Fe2O3@talc. Poly(sulfonamide-thiourea) (PBST) was synthesized for the first time as a polydentate nitrogen donor ligand and combined with the γ-Fe2O3@talc as a novel organic-inorganic catalyst in order to construct of tetrahydropyridine derivatives from the reaction of aromatic aldehydes, anilines and 1,3-dicarbonyl compounds in good to excellent yield. Additionally, γ-Fe2O3@[email protected] has shown a very good reusability up to six consecutive recycle tests and its activity has not changed significantly. The prepared γ-Fe2O3@[email protected] has an excellent catalytic activity, which is due to the combined effect of Brønsted acidity and high density functional groups.

Boosted Cr(VI) clean up over magnetically recoverable NiS/γ-Fe2O3/C type-II heterostructure derived from bimetal (Fe/Ni)-organic framework under visible light

Cr(VI), as a toxic species derived from processes such as electroplating, is harmful to humans, plants, animals, and microorganisms. Thus, it is required to remove and recycle Cr(VI) for chromium resource keeping and prevent toxicity issues. Here, a novel magnetically recoverable NiS/γ-Fe2O3/C type-II heterojunction was successfully prepared via one-pot calcination of MIL-101(Fe/Ni) nanoflakes as a propitiatory template in the presence of Na2S precursor. In this calcination process, the Ni/Fe in MIL-101 acts as a metallic source for simultaneous construction of NiS nanoparticles on the γ-Fe2O3 surface by an in-situ solid-state reaction and organic ligand in MIL-101 acts as an in-situ carbon source to form a C matrix for encapsulation of NiS/γ-Fe2O3 nanoparticles. NiS/γ-Fe2O3/C type-II heterojunction can adequately harvest visible light, boost the interfacial separation and quench the recombination of photogenerated charge transfer agents, proceeding significant photoreduction of Cr(VI). The proposed system exhibits a superior photocatalytic reduction activity of Cr(VI) with an efficiency of 83.85% and a DF value of 0.776 at optimum values of 20 mg/L of Cr(VI), 0.003 g NiS/γ-Fe2O3/C type II heterojunction and 35 min irradiation time. A scavenging experiment confirmed that holes and •OH radicals could be entirely trapped by tartaric acid and a photocatalytic mechanism based on the other electrochemical, optical, and physicochemical characterizations was proposed. These findings give a new approach and insight to synthesize high-performance type-II heterojunction-based photocatalysts for promising future applications.

SiO2 mediated templating synthesis of γ-Fe2O3/MnO2 as peroxymonosulfate activator for enhanced phenol degradation dominated by singlet oxygen

Cost-effective and low-toxicity of MnO2 is regarded as a promising alternative to Co-based catalyst for peroxymonosulfate (PMS) activation to degrade recalcitrant organic pollutants. However, the sluggish Mn(IV)/Mn(III) redox cycling and limited specific surface area greatly hampered its wide application. To solve this challenge, a mesoporous γ-Fe2O3@MnO2 magnetic catalyst with SiO2 assistance (s-γ-Fe2O3@MnO2) was synthesized. Physicochemical characterization confirmed part MnO2 was coated on γ-Fe2O3 surface while the other existed independently. Furthermore, BET surface area of s-γ-Fe2O3@MnO2 was more than two times that of the counterpart without SiO2 assistance (ws-γ-Fe2O3@MnO2). s-γ-Fe2O3@MnO2 exhibited enhanced PMS activation capacity with 97.6% phenol removal efficiency within 80 min, superior to other samples. Various influencing parameters on phenol oxidation were optimized. Reactive oxygen species (ROS) scavenging experiment and electron paramagnetic resonance (EPR) validated co-existence of hydroxyl radicals (·OH) and sulfate radicals (SO4·−) as well as singlet oxygen (1O2) during PMS activation. However, phenol degradation was a non-radical oxidation process dominated by 1O2. A rational reaction mechanism was proposed. Fe(II) promoted Mn(IV)/Mn(III) redox cycling and the enlarged surface area derived from SiO2 mediated templating synthesis were responsible for the enhanced phenol degradation. This strategy can give a guidance for synthesis of highly efficient catalyst for sewage remediation.

Green palladium nanoparticles prepared with glycerol and supported on maghemite for dye removal application

This study aims to synthesize palladium nanoparticles (PdNPs) in presence of glycerol as green reducing/stabilizing agent, supported on γ-Fe2O3 (maghemite), as catalysts for dye removal. Three materials were prepared with different Pd loadings, from 0.43 to 0.63 wt%. PdNPs at the surface were composed of Pd0, Pd2+ and Pd4+ species, at average oxidation state of +1.6 and Pd2+:Pd0 atomic ratio up to 1:0.9, which showed that glycerol was able to partially reduce Pd2+. PdNPs of spherical shaped clumps morphology, predominantly well dispersed on the γ-Fe2O3 surface were formed. High resolution scanning transmission electron microscopy images of the materials with higher Pd content revealed PdNPs smaller than 5 nm with crystal interplanar distance compatible with Pd(0). The catalysts were applied in the adsorption as well as in the heterogeneous Fenton degradation of the azo dye methyl orange with 90% of decolourization after 240 min. It was possible to observe an improvement in the catalytic activity with the Pd content increase as well as with the PdNPs size distribution. The dye removal followed pseudo-first-order kinetics. The effect of catalyst dosage and temperature were evaluated. The acidic character of the iron compounds as well as of the glycerol acidic hydrogens constituents of the catalyst can be released in the reaction medium, being responsible to adjust the reaction pH to 3, which is the optimum pH for Fenton process.

Mechanism study of selenium retention by iron minerals during coal combustion

The interactions between selenium vapors and coal accessory Ca/Fe-minerals favor selenium emission control by transferring selenium into fly ash during coal combustion. Considering the complicated effects of iron transformation on selenium retention, iron species in fly ashes from seven coal-fired power plants were distinguished and the associations between selenium and iron minerals were assessed. Iron oxides (including Fe3O4, γ-Fe2O3 and ɑ-Fe2O3) were determined as the main form of iron minerals in fly ash. The adsorption of selenium vapors by different iron oxides was conducted at temperatures ranging from 300 to 900 °C and the species of captured selenium were identified. Furthermore, reaction sites on the surfaces of fresh and reacted iron oxides were compared to investigate the mechanism regarding selenium adsorption over these iron oxides, which were further clarified through density functional theory study. The results showed that iron oxides were surely to play a significant role in selenium retention mainly through chemisorption and the reactions probably occurred at temperatures below 900 °C. At 300 °C, ɑ-Fe2O3 had better selenium adsorption performance than Fe3O4/γ-Fe2O3. Regardless of iron species, Fe atoms on iron oxides participated in the selenium adsorption by forming a Se–O–Fe Structure. With temperature increasing, selenium adsorption by Fe atoms was suppressed, which caused a drop off in selenium capture capacity of Fe3O4 and ɑ-Fe2O3. Differently, increasing temperature promoted selenium adsorption over γ-Fe2O3, which owned a high selenium adsorption capacity even at 700 °C. Further analysis confirmed that the presence of O2/H2O(g) in the flue gas contributed to the formation of oxygen vacancies on the surface of γ-Fe2O3 at high temperatures and facilitated selenium vapors to react with Fe atoms.

Cerium Oxide-Decorated γ-Fe2O3 Nanoparticles: Design, Synthesis and in vivo Effects on Parameters of Oxidative Stress.

Magnetic γ-Fe2O3/CeOx nanoparticles were obtained by basic coprecipitation/oxidation of iron chlorides with hydrogen peroxide, followed by precipitation of Ce(NO3)3 with ammonia. The appearance of CeOx on the magnetic particle surface was confirmed by X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), and elemental analysis; a magnetometer was used to measure the magnetic properties of γ-Fe2O3/CeOx. The relatively high saturation magnetization of the particles (41.1 A·m2/kg) enabled magnetic separation. The surface of γ-Fe2O3/CeOx particles was functionalized with PEG-neridronate of two different molecular weights to ensure colloidal stability and biocompatibility. The ability of the particles to affect oxidative stress in hereditary hypertriglyceridemic (HHTg) rats was tested by biological assay of the liver, kidney cortex, and brain tissues. An improvement was observed in both enzymatic [superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx)] and non-enzymatic (reduced (GSH) and oxidized (GSSG) glutathione) levels of antioxidant defense and lipid peroxidation parameters [4-hydroxynonenal (4-HNE) and malondialdehyde (MDA)]. The results corresponded with chemical determination of antioxidant activity based on 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, proving that in the animal model γ-Fe2O3/CeOx@PEG2,000 nanoparticles effectively scavenged radicals due to the presence of cerium oxide, in turn decreasing oxidative stress. These particles may therefore have the potential to reduce disorders associated with oxidative stress and inflammation.

Functionalized magnetic PAMAM dendrimer as an efficient nanocatalyst for a new synthetic strategy of xanthene pigments

A green protocol has been developed for preparation of the wide variety of colored xanthene derivatives using a new efficient magnetic solid acid catalyst bearing polyamidoamine dendrimer moiety as a nanoscopic compound. Dendrimers, highly symmetric molecules around a core and 3D spherical morphology, show interesting traits based on their functionalized groups on the branched surface. They can be designed to provide water soluble structures or pseudo-active sites of biomolecules. The catalyst was assembled via a polyamidoamine dendrimer immobilized on the surface of γ-Fe2O3 followed by the sulfonylation of the amine groups by chlorosulfonic acid resulting in γ-Fe2O3@PAMAM-SO3H. Herein, PAMAM dendrimer with repeating amine/amide branches as catchable sites of sulfonic acid groups was introduced as transformer of homogeneous to heterogeneous acidic catalysts. The physicochemical properties of synthesized catalyst were studied using by FT-IR, FE-SEM, XRD, VSM, EDS, TGA/DTG, and TEM. Finally, the catalytic activity of γ-Fe2O3@PAMAM-SO3H was evaluated for the preparation of xanthene derivatives via a one-pot, three components reaction of aromatic aldehydes with i) β-naphthol, ii) cyclic 1,3-dicarbonyl, iii) β-naphthol and cyclic 1,3-dicarbonyl compounds, iv) 2-hydroxy-1,4-naphthoquinone, leading to the eco-riendly preparation of the target compounds in good to excellent yields. The catalyst could be easily recycled for at least five consecutive runs without significant loss in its catalytic activity.

Metal-organic framework-templated synthesis of t-ZrO2 /γ-Fe2O3 supported AgPt nanoparticles with enhanced catalytic and photocatalytic properties

A highly selective and effective catalyst and photocatalyst based on Ag, Pt, AgPt nanoparticles (NPs) on the surface of γ-Fe2O3 /t-ZrO2 nanocomposite which was derived from Fe-metal organic framework (Fe-MIL-88A) and Zr-metal organic framework (Zr-UiO-66) was developed. A green synthesis method was used for synthesis of binary nanocomposite (M = Ag, Pt, and Ag@Pt NPs)@γ-Fe2O3/t-ZrO2 and a new composite of γ-Fe2O3, t-ZrO2 structures which was made up by annealing under a nitrogen gas flow. The catalytic potential of the as-synthesized samples were considered toward the reduction of 4-nitrophenol (4-Nip) to 4-aminophenol (4-Amp) by NaBH4 solution at 25 °C and different reaction times. For the investigation photoactivity of samples, we have tested the degradation of the anionic (AB92) and cationic (MB) dyes under visible radiation. The obtained results demonstrated that among these nanocomposite structures, AgPt@γ-Fe2O3/t-ZrO2 displayed the best catalytic and photocatalytic activity and excellent stability, reusability for different runs under the employed reaction conditions.

The scrutinised DFT and MD studies on the adsorption of D-penicillamine drug on γ-Fe2O3 nanoparticle as a highly efficient carrier

ABSTRACTWe have theoretically explored the adsorption behaviour of D-penicillamine (PEN) on the surface of magnetic nanoparticle (NP) (γ-Fe2O3) with quantum mechanics calculation and molecular dynamics (MD) simulation. Possible molecular configurations between the PEN and γ-Fe2O3 NP were examined by density functional theory (DFT) using Fe6(OH)18(H2O)6 ring cluster. The stability of optimised complexes was determined on the basis of relative adsorption energy (ΔEads). The atoms in molecule (AIM) theory was employed to gain an in-depth understanding of the intermolecular interactions. From the DFT calculations, the adsorption of PEN on the magnetite NP surface was exothermic and thermodynamically stable. The AIM results indicated that drug was adsorbed molecularly via hydrogen bonds to the surface of the NP. The electronic structure analysis of PEN showed that the structure of the drug molecule did not change considerably during the adsorption process. Moreover, MD simulation was performed to study the dynamics and diffusion of the drug molecule. The obtained results of interaction energies and binding free energies indicated that the PEN/γ-Fe2O3 complex had good stability in the solution phase. The diffusion of drug molecule into the γ-Fe2O3 surface was slow, which is a crucial factor for the controlled drug releases.

Insights over Titanium Modified FeMgOx Catalysts for Selective Catalytic Reduction of NOx with NH3: Influence of Precursors and Crystalline Structures

Titanium modified FeMgOx catalysts with different precursors were prepared by coprecipitation method with microwave thermal treatment. The iron precursor is a key factor affecting the surface active component. The catalyst using FeSO4 and Mg(NO3)2 as precursors exhibited enhanced catalytic activity from 225 to 400 °C, with a maximum NOx conversion of 100%. Iron oxides existed as γ-Fe2O3 in this catalyst. They exhibited highly enriched surface active oxygen and surface acidity, which were favorable for low-temperature selective catalytic reduction (SCR) reaction. Besides, it showed advantage in surface area, spherical particle distribution and pores connectivity. Amorphous iron-magnesium-titanium mixed oxides were the main phase of the catalysts using Fe(NO3)3 as a precursor. This catalyst exhibited a narrow T90 of 200/250–350 °C. Side reactions occurred after 300 °C producing NOx, which reduced the NOx conversion. The strong acid sites inhibited the side reactions, and thus improved the catalytic performance above 300 °C. The weak acid sites appeared below 200 °C, and had a great impact on the low-temperature catalytic performance. Nevertheless, amorphous iron-magnesium-titanium mixed oxides blocked the absorption and activation between NH3 and the surface strong acid sites, which was strengthened on the γ-Fe2O3 surface.

Efficient removal of organic contaminant via activation of potassium persulfate by γ-Fe2O3/α-MnO2 nanocomposite

In this study, γ-Fe2O3/α-MnO2 nanocomposite, which possesses magnetism as well as excellent activation performance for potassium persulfate (PS) to degrade organic contaminants in water, was successfully fabricated through ultrasonic strategy. Noted, proportion between γ-Fe2O3 and α-MnO2 was optimized to achieve excellent magnetic and activation performance. Also, physicochemical properties of magnetic nanocomposite material (γ-Fe2O3/α-MnO2 1/7, FM1-7) are investigated by SEM, EDS, BET, XRD, TEM, XPS and vibrating sample magnetometer (VSM). Results show that γ-Fe2O3 nanoparticles is connected with α-MnO2 nanorods successfully, what’s more, FM1-7 nanocomposite crystal structure is intact and its crystallinity is excellent. Besides, in γ-Fe2O3/α-MnO2/PS reaction system, about 92.79% of Rhodamine B could be removed within 30 min. The result proves that when the γ-Fe2O3 content is 12.5%, γ-Fe2O3/α-MnO2 nanocomposite exhibits superior activation performance. γ-Fe2O3/α-MnO2/PS reaction shows the most excellent degradation towards Rhodamine B when it is compared with another reaction systems. Most importantly, in this study, the crucial role of γ-Fe2O3 and catalysis mechanism of γ-Fe2O3/α-MnO2 is also discussed in detail. In the Fenton-like system mediated by Fe(III) and Mn(IV), the redox reactions with the activation of PS happen on the surface of γ-Fe2O3/α-MnO2. Therefore, strong oxidizers of SRs (SO4−), hydroxyl radicals (OH) and even superoxide anion (O2−) may be generated and participated in the degradation of Rhodamine B. What’s more, the result of repetitive experiment illustrates that magnetic FM1-7 sample possesses good recycle and reusability capacities. This study not only provides a feasible strategy to prepare catalyst which could be used to active PS, but also is expected to be applied to deal with many kinds of contaminants removal problem according to the practical requirement.

Rice-panicle-like γ-Fe2O3@C nanofibers as high-rate anodes for superior lithium-ion batteries

We synthesized nanoarchitectures comprising γ-Fe2O3@C nanofibers with one-dimensional rice-panicle-like morphologies via a facile electrospinning and annealing process for use as anodes in lithium-ion batteries (LIBs). A thin carbon layer grown on the surface of γ-Fe2O3 provides a synergistic effect to relieve the stress and alleviate the volume expansion occurring during the lithium-ion insertion/extraction process. The unique structure not only offers good electron transport routes, but also enhances the lithium-ion conductive channels, resulting in excellent electrochemical activity and electrical conductivity of the LIB anode material. A high reversible specific capacity of 1252 mAh g−1 was achieved after 200 cycles even at the current density of 10 A g−1. When examined at the scan rate of 5 mV s−1, a high capacitive contribution ratio of 88.5% was achieved. The short lithium-ion diffusion pathways avoid structural damage to the active material and provide excellent rate capacities. This work suggests a new method to improve the electrochemical performance of LIBs through the synergistic design of uniquely structured metal oxides.

Impact of inorganic ions and natural organic matter on arsenates removal by ferrate(VI): Understanding a complex effect of phosphates ions

Arsenic compounds are carcinogenic to humans and are typically removed from contaminated water using various sorbents. The ionic composition plays a significant role in arsenate removal efficiency during the process of water remediation. Here, we quantify the effects of natural ions (chlorides, nitrates, carbonates, sulfates, and phosphates) and humic acid on the removal of arsenates by ferrate(VI) at pH = 6.6. In the experiments, the initial concentration of arsenates was 10 mg L−1 (as As) and the concentrations of ions varied in the range from 5 to 100 mg L−1 of element in ionic form and humic acid. The achieved results show that only phosphate ions had principle influence on the efficiency of arsenate removal by ferrate(VI). The effect of phosphates was elucidated by applying transmission electron microscopy, energy-dispersive X-ray spectroscopy, and low temperature in-field 57Fe Mössbauer spectroscopy to solid samples, prepared under different weight ratios of ferrate(VI), arsenates, and phosphates. These results show three crucial effects of phosphates on the arsenate removal mechanisms. At low P:As weight ratio (up to 1:1), the incorporation of arsenate ions into the crystalline structure of γ-Fe2O3/γ-FeOOH nanoparticles was found to be suppressed by the presence of phosphates. Thus, arsenates were mainly adsorbed onto the surface of γ-Fe2O3/γ-FeOOH nanoparticles. Further increase in the P:As weight ratio (more than 1:1) resulted in the competition between arsenates and phosphates sorption. With the increased concentration of phosphate ions, the number of arsenates on the surface of γ-Fe2O3/γ-FeOOH nanoparticles was reduced. Finally, the complexation of iron(III) ions with phosphate ions occurred, leading to a decrease in the arsenates removal efficiency, which resulted from a lower content of precipitated γ-Fe2O3/γ-FeOOH nanoparticles. All these aspects need to be considered prior to application of ferrate(VI) for arsenates removal in real natural waters.

The effect of Fe2O3 crystal phases on CO2 hydrogenation.

The effect of Fe2O3 crystal phases on their performance in CO2 hydrogenation was studied. α-Fe2O3 crystal was prepared by precipitation method from Fe(NO3)3·9H2O and (NH4)2CO3, and γ-Fe2O3 was prepared by grinding Fe(NO3)3·9H2O and L(+)-Tartaric acid in agate mortar completely. The crystal phases of Fe2O3 influence the distribution of promoter Zn, K and Cu on catalysts. The dispersity of K on γ-Fe2O3 surface is higher than α-Fe2O3. On the contrary, Cu and Zn are more dispersive on α-Fe2O3 surface than γ-Fe2O3. The catalyst in γ-Fe2O3 phase is easily reduced relative to the catalyst in α-Fe2O3 phase. The former presents higher CO2 conversion and C2+ hydrocarbon selectivity than the latter in CO2 hydrogenation.