Preparation of S-N co-doped CoFe2O4@rGO@TiO2 nanoparticles and their superior UV-Vis light photocatalytic activities.

A S-N co-doped CoFe2O4@rGO@TiO2 (CFGT-S/N) nanocomposite was successfully synthesized via a facile vapor-thermal method. XRD, XPS, FT-IR and FETEM results confirmed that N and S were co-doped into the lattice of TiO2. Photocatalytic tests indicated that CFGT-S/N exhibited excellent UV-Vis photocatalytic activity for decompositions of different organic dyes, including methyl orange (MO), rhodamine B (RhB) and methylene blue (MB). Particularly, the photocatalytic degradation rate of MO was about 33% higher than that when using P25 under visible light irradiation. The higher UV-Vis light photocatalytic activity of CFGT-S/N can be attributed to the synergetic effects of the strong absorption of visible light, the narrow band gap, improved separation of photo-generated electron/hole pairs, and the enhancement of the enrichment of pollutant dye molecules by S, N co-doping, CoFe2O4 and rGO. Moreover, this photocatalyst was superparamagnetic, which enables it to be easily recovered by an external magnetic field, and maintained stable photocatalytic efficiency over five cycles. Hence, CFGT-S/N with its highly efficient, recoverable and stable photocatalytic properties shows great potential for environmental treatment.

Enhanced photo-Fenton-like process over Z-scheme CoFe2O4/g-C3N4 Heterostructures under natural indoor light.

Low-cost catalysts with high activity and stability toward producing strongly oxidative species are extremely desirable, but their development still remains a big challenge. Here, we report a novel strategy for the synthesis of a magnetic CoFe2O4/C3N4 hybrid via a simple self-assembly method. The CoFe2O4/C3N4 was utilized as a photo-Fenton-like catalyst for degradation of organic dyes in the presence of H2O2 under natural indoor light irradiation, a green and energy-saving approach for environmental cleaning. It was found the CoFe2O4/C3N4 hybrid with a CoFe2O4: g-C3N4 mass ratio of 2:1 can completely degrade Rhodamine B nearly 100 % within 210 min under room-light irradiation. The effects of the amount of H2O2 (0.01-0.5 M), initial dye concentration (5-20 mg/L), solution pH (3.08-10.09), fulvic acid concentration (5-50 mg/L), different dyes and catalyst stability on the organic dye degradation were investigated. The introduction of CoFe2O4 on g-C3N4 produced an enhanced separation efficiency of photogenerated electron - hole pairs by a Z-scheme mechanism between the interfaces of g-C3N4 and CoFe2O4, leading to an excellent activity as compared with either g-C3N4 or CoFe2O4 and their mixture. This study demonstrates an efficient way to construct the low-cost magnetic CoFe2O4/C3N4 heterojunction as a typical Z-scheme system in environmental remediation.

Fe, Co, Ni nanocrystals encapsulated in nitrogen-doped carbon nanotubes as Fenton-like catalysts for organic pollutant removal.

Magnetic metal M (M=Fe, Co, Ni) nanocrystals encapsulated in nitrogen-doped carbon nanotubes (M@N-C) were fabricated conveniently using dicyandiamide as a C/N precursor, and exhibited varying activities toward Fenton-like reaction. The surface morphology and structure of the M@N-C catalysts were characterized and an efficient catalytic degradation performance, high stability, and excellent reusability were observed. In addition, several operational factors, such as initial dye concentration, oxidant type (peroxymonosulfate, peroxydisulfate and H2O2) and dosage, reaction temperature, and dye type as well as stability of the composite were extensively evaluated in view of the practical applications. The results showed that various transition metals M significantly affected the structures and performances of the catalysts, and specially, their activity followed the order of Co>Fe>Ni in the presence of peroxymonosulfate. Moreover, HO⁡ and SO4(-) radicals participating in the process were evidenced using quenching experiments, and a rational mechanism was proposed based on a non-radical process and the free radical process. Control experiments revealed that the enhanced active sites were mainly ascribed to the synergistic effects between the metal nanocrystals and nitrogen-doped carbon. The findings of this study elucidated that encapsulation of nanocrystals in nitrogen-doped carbon nanotubes was an effective strategy to enhance the overall catalytic activity.

Magnetic core-shell CuFe2O4@C3N4 hybrids for visible light photocatalysis of Orange II.

Novel CuFe2O4@C3N4 core-shell photocatalysts were fabricated through a self-assembly method and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, transmission electron microscopy and Uv-vis diffuse reflection spectroscopy. The photocatalytic performances of the CuFe2O4@C3N4 catalysts were evaluated in photo Fenton-like discoloration of Orange II dye using H2O2 as an oxidant under visible-light irradiation (λ>420 nm). It was found the CuFe2O4@C3N4 hybrid (mass ratio of CuFe2O4/g-C3N4 at 2:1) exhibits a superior activity as compared with single component of CuFe2O4 or g-C3N4 and the mixture of g-C3N4 and CuFe2O4, due to the elevation of the separation efficiency of photoinduced electron-hole pairs, resulted from the heterojunction between the interfaces of g-C3N4 and CuFe2O4. The quenching tests of different scavengers displayed that O2(•-), OH and h(+) are responsible for the Orange II decolorization. In addition, the effects of initial concentration of the dye contaminant (0.014-0.140 mM), different anions (Cl(-), SO4(2-), NO3(-), CH3COO(-) and HCO3(-)) and temperature (15-65 °C) in photoreaction were also investigated. The CuFe2O4@C3N4 sample exhibited stable performance without obvious loss of catalytic activity after five successive runs, showing a promising application for the photo-oxidative degradation of environmental contaminants.

Sulfate radicals induced from peroxymonosulfate by cobalt manganese oxides (Co(x)Mn(3-x)O4) for Fenton-Like reaction in water.

A series of CoxMn3-xO4 particles as Fenton-like solid catalysts were synthesized, and their catalytic performance in oxidative degradation of organic dye compounds in water was investigated. The surface morphology and structure of the CoxMn3-xO4 catalysts were characterized by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results showed that, as an oxide composite of Co and Mn elements, CoMn2O4 showed much stronger catalytic activity in peroxymonosulfate (PMS) oxidation than Co3O4, Mn2O3, and their physical mixture. Typically, the uses of 0.02 g/dm(3) CoMn2O4 and 0.2 g/dm(3) PMS yielded a nearly complete removal of Rhodamine B (0.03 g/dm(3)) in 80 min at 25 °C. The efficiency of Rhodamine B decomposition increased with increasing temperature (15-55 °C), but decreased with the increase of fulvic acid concentration (0-0.08 g/dm(3)). Furthermore, CoMn2O4 could maintain its catalytic activity in the repeated batch experiments. Moreover, HO· and SO4(·-) radicals participating in the process were evidenced using quenching experiments, and a rational mechanism was proposed. PMS oxidation with CoMn2O4 is an efficient technique for remediation of organic contaminants in wastewater.

One-pot approach for synthesis of N-doped TiO2/ZnFe2O4 hybrid as an efficient photocatalyst for degradation of aqueous organic pollutants.

N-doped TiO2/ZnFe2O4 catalysts were successfully prepared by coupling nitrogen modified TiO2 with ZnFe2O4 via a one-pot vapor-thermal method. The physicochemical properties of the as-prepared catalysts have been characterized using various spectroscopic and microscopic techniques. The UV-vis-light-driven photocatalytic activities of the hybrids were evaluated and the effects of the amount of photocatalyst, different types of dyes, catalyst stability on photodegradation of organic dyes were investigated. Moreover, degradation kinetics and mechanism as well as the roles of N doping, ZnFe2O4 and TiO2 have been analyzed. It was revealed that N-doped TiO2/ZnFe2O4 exhibited an improved performance compared with TiO2/ZnFe2O4 or ZnFe2O4 because of the formation of a heterostructure at the interface as well as the introduction of N species. Active species such as holes, electrons, hydroxyl radicals, and superoxide radicals involved in the photodegradation process were detected by using different types of scavengers. Because of ZnFe2O4 in the hybrid, the catalyst shows ferromagnetism, and thus, the hybrid catalyst is easily isolated from the reaction mixture after the photocatalytic experiments. This work not only offers a simple method for the fabrication of N doped TiO2/ZnFe2O4 hybrids, but also provides an effective and conveniently recyclable photocatalyst for the purification of water.

Magnetic recoverable MnFe2O4 and MnFe2O4-graphene hybrid as heterogeneous catalysts of peroxymonosulfate activation for efficient degradation of aqueous organic pollutants.

Magnetic iron based materials are generally effective for many catalytic reactions and can be magnetically recovered after application, showing advantages than other metal oxides. In the present work, magnetic MnFe2O4 nanoparticle and MnFe2O4-reduced graphene oxide (rGO) hybrid were prepared and used as catalysts to activate peroxymonosulfate (PMS) to oxidatively degrade various organic pollutants in water. From a process of chemical deposition and reduction, MnFe2O4-rGO hybrids were produced with nanosized MnFe2O4 particles (ca. 13.2 nm). It was found that MnFe2O4 or MnFe2O4-rGO presented high activity in activating PMS to produce sulfate radicals for degradation of organic dyes (Methyl violet, Methyl orange, Methylene blue, Orange II and Rhodamine B) and could be separated with a magnet without any loss. The reaction kinetics, effect of different ion species CL(-),HCO3(-),CH3COO(-)and NO3(-) and Cl(-) strength, reaction temperature (25-65°C), catalytic stability, as well as degradation mechanism were comprehensively studied. The lower activation energy on MnFe2O4-rGO (25.7 kJ/mol) justify the higher chemical performance than that of MnFe2O4 (31.7 kJ/mol), suggesting that graphene plays a significant role in the enhanced degradation of dyes. More importantly, the as-prepared MnFe2O4 and MnFe2O4-rGO hybrid exhibited stable performance to remove the organic pollutants in wastewater with easy recycling and good stability by successive degradation experiments.

Facile synthesis of magnetic ZnFe2O4-reduced graphene oxide hybrid and its photo-Fenton-like behavior under visible iradiation.

A magnetic ZnFe2O4-reduced graphene oxide (rGO) hybrid was successfully developed as a heterogeneous catalyst for photo-Fenton-like decolorization of various dyes using peroxymonosulfate (PMS) as an oxidant under visible light irradiation. Through an in situ chemical deposition and reduction, ZnFe2O4 nanoparticles (NPs) with an average size of 23.7 nm were anchored uniformly on rGO sheets to form a ZnFe2O4-rGO hybrid. The catalytic activities in oxidative decomposition of organic dyes were evaluated. The reaction kinetics, effect of ion species and strength, catalytic stability, degradation mechanism, as well as the roles of ZnFe2O4 and graphene were also studied. ZnFe2O4-rGO showed to be a promising photocatalyst with magnetism for the oxidative degradation of aqueous organic pollutants and simple separation. The combination of ZnFe2O4 NPs with graphene sheets leads to a much higher catalytic activity than pure ZnFe2O4. Graphene acted as not only a support and stabilizer for ZnFe2O4 to prevent them from aggregation, largely improving the charge separation in the hybrid material, but also a catalyst for activating PMS to produce sulfate radicals at the same time. The ZnFe2O4-rGO hybrid exhibited stable performance without losing activity after five successive runs.

Preparation and characterization of N-S-codoped TiO(2) photocatalyst and its photocatalytic activity.

N-S-codoped anatase nanosized TiO(2) photocatalyst (NSTO) was successfully prepared by one-step hydrothermal method from a mixed aqueous solution of Ti(SO(4))(2) and thiourea. The samples were characterized by XRD, UV-vis, XPS, FT-IR and EA. From results of UV-vis, a red shift of the absorption edge was brought out owing to N and S codoping, and the extension for photoabsorption range of NSTO occurred. XRD, XPS, EA and FT-IR studies revealed that N and S were in situ codoped in the lattice of TiO(2) and N concentration decreased from the surface to the center of NSTO. Especially, the photocatalytic tests indicated that NSTO exhibited a high activity for decompositions of methyl orange both under UV-light and vis-light irradiation comparing to S-doped TiO(2) (STO) and undoped TiO(2) (TO). The high activity of NSTO can be related to the results of the synergetic effects of strong absorption in the UV-vis region, red shift in adsorption edge, oxygen vacancies and the enhancement of surface acidity induced by N and S codoping.

Childhood atypical meningioma with perineural spread: MR findings.

Meningiomas are uncommon in children. When they occur, they are frequently associated with neurofibromatosis type 2. Childhood meningiomas are generally large and commonly associated with cyst formation and an unusual location. Perineural tumor spread, occasionally associated with head and neck malignancies, is very rare in meningiomas. We present the MR findings of an atypical meningioma with perineural spread in a 4.5-year-old girl.