Yanming Shao

Preparation and Characterization of Magnetic Porous Carbon Microspheres for Removal of Methylene Blue by a Heterogeneous Fenton Reaction

High-specific-surface-area magnetic porous carbon microspheres (MPCMSs) were fabricated by annealing Fe(2+)-treated porous polystyrene (PS) microspheres, which were prepared using a two-step seed emulsion polymerization process. The resulting porous microspheres were then sulfonated, and Fe(2+) was loaded by ion exchange, followed by annealing at 250 °C for 1 h under an ambient atmosphere to obtain the PS-250 composite. The MPCMS-500 and MPCMS-800 composites were obtained by annealing PS-250 at 500 and 800 °C for 1 h, respectively. The iron oxide in MPCMS-500 mainly existed in the form of Fe3O4, which was concluded by characterization. The MPCMS-500 carbon microspheres were used as catalysts in heterogeneous Fenton reactions to remove methylene blue (MB) from wastewater with the help of H2O2 and NH2OH. The results indicated that this catalytic system has a good performance in terms of removal of MB; it could remove 40 mg L(-1) of MB within 40 min. After the reaction, the catalyst was conveniently separated from the media within several seconds using an external magnetic field, and the catalytic activity was still viable even after 10 removal cycles. The good catalytic performance of the composites could be attributed to synergy between the functions of the porous carbon support and the Fe3O4 nanoparticles embedded in the carrier. This work indicates that porous carbon spheres provide good support for the development of a highly efficient heterogeneous Fenton catalyst useful for environmental pollution cleanup.

Development of carbon nanotubes/CoFe2O4 magnetic hybrid material for removal of tetrabromobisphenol A and Pb(II).

Multi-walled carbon nanotubes (MWCNTs) coated with magnetic amino-modified CoFe2O4 (CoFe2O4-NH2) nanoparticles (denoted as MNP) were prepared via a simple one-pot polyol method. The MNP composite was further modified with chitosan (CTS) to obtain a chitosan-functionalized MWCNT/CoFe2O4-NH2 hybrid material (MNP-CTS). The obtained hybrid materials were characterized by Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectrogram (FT-IR) Analysis and X-ray Photoelectron Spectroscopy (XPS) Analysis, Vibrating Sample Magnetometer (VSM) Analysis and the Brunauer-Emmett-Teller (BET) surface area method, respectively. The composites were tested as adsorbents for tetrabromobisphenol A (TBBPA) and Pb(II), and were investigated using a pseudo-second-order model. The adsorption of TBBPA was well represented by the Freundlich isotherm; the Langmuir model better described Pb(II) absorption. MNP-CTS adsorbed both TBBPA and Pb(II) (maximum adsorption capacities of 42.48 and 140.1mgg(-1), respectively) better than did MNP without CTS. Magnetic composite particles with adsorbed TBBPA and Pb(II) could be regenerated using 0.2M NaOH solution and were separable from liquid media using a magnetic field.

Novel magnetic porous carbon spheres derived from chelating resin as a heterogeneous Fenton catalyst for the removal of methylene blue from aqueous solution.

Porous magnetic carbon spheres (MCS) were prepared from carbonized chelating resin composites derived from ethylenediaminetetraacetic acid-modified macroporous polystyrene (PS-EDTA) resin, and then loaded with iron composites via ion exchange. The resulting composites were characterized for this study using X-ray diffraction, MÖssbauer spectroscopy, and Raman spectroscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface area method, scanning electron microscopy, and vibrating sample magnetometry. The porous magnetic carbon spheres were then used, in the existence of H2O2 and NH2OH, with a view to remove methylene blue from the aqueous solution by catalyze a heterogeneous Fenton reaction. Results indicated excellent removal rates and removal efficiency for this catalytic system. Optimal degradation was achieved (nearly 100% within 10 min) using initial concentrations of 5 mmol H2O2 L(-1), 2.5 mmol L(-1) NH2OH and 40 mg L(-1) methylene blue. The catalyst retained its activity after six reuses, indicating strong stability and reusability. Porosity of the catalyst contributed to its high activity, suggesting its potential application for the industrial treatment of wastewater.

Preparation of copper doped magnetic porous carbon for removal of methylene blue by a heterogeneous Fenton-like reaction

High-specific-surface-area copper doped magnetic porous carbon (CuFe2O4/Cu@C) was fabricated by annealing iron, copper and 1,3,5-benzenetricarboxylic ([Cu/Fe]-BTC) metal–organic coordination polymers, which were prepared via a one-pot solvothermal method. The novel CuFe2O4/Cu@C catalyst consists of Cu (3.80%), CuFe2O4 (64.84%), and C (31.36%). Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, elemental analysis, inductively coupled plasma, Brunauer–Emmett–Teller surface area measurement, and vibrating sample magnetometer analysis were used to characterize the materials. The as-prepared materials were employed as a heterogeneous Fenton’s reagent with the addition of H2O2 for degradation of methylene blue (MB). The results showed that the materials effectively catalyzed H2O2 to generate hydroxyl radicals (˙OH). And due to their magnetism, the materials can be easily separated from wastewater to achieve repeatability. It also turned out that CuFe2O4/Cu@C had a higher catalytic activity than Fe3O4@C, which proved the importance of copper doped into the catalyst. This work indicated that porous carbon composites provide good support for the development of a highly efficient heterogeneous Fenton catalyst, which is useful for environmental pollution cleanup.

Fe3O4/MWCNT as a heterogeneous Fenton catalyst: degradation pathways of tetrabromobisphenol A

Tetrabromobisphenol A (TBBPA) is the most widely used brominated flame retardant around the world. In this study, we report that iron oxide decorated on a magnetic nanocomposite (Fe3O4/MWCNT) was used as a heterogeneous Fenton catalyst for the degradation of TBBPA in the presence of H2O2. Fe3O4/MWCNT was prepared by a simple solvothermal method, whereby an iron source (Fe(acac)3) and a reductant (n-octylamine) were allowed to react in n-octanol solvent. Monodisperse Fe3O4 nanoparticles of consistent shape were uniformly dispersed on the nanotubes. Samples were characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller surface area measurement, and vibrating sample magnetometry. The samples effectively catalyzed the generation of hydroxyl radicals (·OH) from H2O2, which degraded and subsequently mineralized the TBBPA. The whole process took four hours at near neutral pH. A degradation pathway for the system was proposed following analysis of intermediate products by gas chromatography-mass spectrometry. The quantification of Fe2+ and Fe3+ distribution before and after the recycling test of the composite were explored by X-ray photoelectron spectroscopy, in order to explain the stability and recyclability of the composite. Analysis of the results indicated that the magnetic nanocomposite is a potentially useful and environmentally compatible heterogeneous Fentons reagent with promising applications related to pollution control.

Preparation of novel magnetic molecular imprinted polymers nanospheres via reversible addition – fragmentation chain transfer polymerization for selective and efficient determination of tetrabromobisphenol A

A well-defined molecularly imprinted polymer nanospheres with excellent specific recognition ability was prepared on Fe3O4 nanoparticles via the combination of click chemistry and surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization and using Tetrabromobisphenol A as template. Concretely, Fe3O4 nanoparticles were prepared by solvothermal method and then modified by 4-vinylbenylchloride through distillation-precipitation, which makes azide groups easily introduced on the surface of magnetic nanoparticles to form the relatively large amount of benzyl chloride groups. With high efficiency, alkyne terminated RAFT chain transfer agent were then immobilized onto the surface of Fe3O4 by means of click chemistry, which is Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC). The highly uniform imprinted thin film was finally fabricated on the surface of RAFT agent modified Fe3O4 nanoparticles. The binding results demonstrated that as-prepared imprinted beads exhibited remarkable molecular imprinting effects to the template molecule, fast rebinding kinetics and an excellent selectivity to compounds with similar configuration.

Palladium-loaded magnetic core–shell porous carbon nanospheres derived from a metal–organic framework as a recyclable catalyst

Separation and recycling of noble metal nanocatalysts after catalytic reactions are significant challenges to reduce catalyst cost and avoid waste generation in industrial applications. In this study, Pd-loaded magnetic porous carbon nanospheres (Fe3O4@MC-Pd) were prepared by annealing Fe3O4@MIL-100/PdCl2, which was fabricated through a facile one-pot solvothermal method, at 450 °C in a nitrogen atmosphere. The novel Fe3O4@MC-Pd catalyst consists of a superparamagnetic Fe3O4 core and a chemically inert porous carbon layer, which can protect the Fe3O4 core from extreme external environments and prevent the loss of Pd NPs. The resultant composite material showed excellent catalytic performance in reducing methylene blue with sodium borohydride as a reducing agent and superparamagnetic behavior that enabled the magnetic separation and convenient recovery of the nanocatalysts from the reaction mixture. Moreover, the composite material also showed good thermal and acid stability, fast regeneration ability, and high cyclic stability (>10 cycles without loss of catalytic efficiency). The result shows the nanocatalysts could overcome the drawbacks of MOF catalysts (chemical unstability). This study indicated that the as-prepared Fe3O4@MC-Pd composite material shows great potential for using in a wide range of applications.

Facile preparation of tiny gold nanoparticle loaded magnetic yolk–shell carbon nanoreactors for confined catalytic reactions

Yolk–shell magnetic nanoreactors consisting of a mesoporous carbon shell and Fe3O4 core coated by tiny gold nanoparticle loaded SiO2 were fabricated through a facile method. Fe3O4@SiO2@RF nanospheres were firstly prepared by a one-pot process that combined the sol–gel process of tetraethyl orthosilicate and condensation polymerization of resorcinol and formaldehyde in the mixed solvent of water and ethanol with the help of ammonia, based on the similar mechanism of these two processes. Au nanoparticles were in situ immobilized after the Fe3O4@SiO2@RF nanospheres were annealed under an inert atmosphere and the silica shell was partially etched. The Fe3O4 core not only provides sites for the immobilization of Au nanoparticles but also allows the nanoreactor to be easily recovered from liquid media by an external magnetic field. The outer mesoporous carbon shell protects the Au nanoparticles from aggregation and harsh external conditions. Furthermore, the reactants and products easily diffuse in and out of the cavities between the core and the shell because of their numerous channels. The obtained materials exhibit excellent catalytic activity for the reduction of p-nitrophenol to p-aminophenol in the presence of NaBH4 due to their special yolk–shell structure. No dramatic decrease in catalytic activity was noted, even after the synthesized catalyst was used 10 times. This work indicates that magnetic porous carbon yolk–shell spheres could provide the ideal support for noble metal nanospheres in the development of highly efficient catalysts.

Self-template synthesis of hierarchical magnetic porous carbon fibers derived from Fe(BTC)-coated bamboo fibers for fast removal of methylene blue

Hierarchical magnetic porous carbon fibers (MBFs) were fabricated by annealing Fe(BTC)-coated bamboo fibers, which were produced using a new synthesis route for growing Fe(BTC) on bamboo fiber materials, in a nitrogen atmosphere. The materials were characterized using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Mossbauer spectroscopy, Brunauer–Emmett–Teller surface area measurement, and vibrating sample magnetometry. The obtained MBF composites possess both high surface areas and magnetic characteristics. Their adsorption properties were preliminarily tested by the adsorptive removal of methylene blue from aqueous solution. Results demonstrated that the obtained hybrid materials possess high adsorption capacity and can be easily recycled from liquid media by using an external magnetic field. MBF adsorption reached equilibrium within approximately 1 min and the adsorption capacity rapidly reached 143 mg g−1. Most importantly, MBF can be reused after washing with ethanol. After six reuses, the removal efficiency could still reach 80%. Moreover, the low-cost raw material used (i.e., bamboo) is abundant and renewable. This study indicated that the as-prepared MBF composites show great potential for use in a wide range of applications.

Fabrication of magnetic amino-functionalized nanoparticles for S-arylation of heterocyclic thiols

A series of uniformed mono-disperse magnetic nanoligands (MNLs) (CoFe2O4–NH2 (MNL A), Fe3O4@Si(CH2)3NH2 (MNL B), Fe3O4@Si(CH2)3NHC(O) (CH2)2PEI (MNL C) and Fe3O4@Si(CH2)3NHC(O)PEI (MNL D)) were obtained by loading two ligands, an aminosilane coupling agent and PEI-600, onto magnetic nanoparticles prepared using a solvothermal method. The catalytic applications of the synthesized MNLs were explored for the cross-coupling reaction of heterocyclic thiols with aromatic iodides. The reactions were carried out in the presence of CuI (5 mol%), MNL (10 mol% N) and K2CO3 (1.3 eq.) in DMF at 120 °C. A variety of heterocyclic sulfides were afforded in good to excellent yields (up to 98%) when MNL B was used. The magnetic, crystal, organic matter structure and morphology of MNL B exhibited no obvious changes after five consecutive cycles. XPS characterization of MNL B revealed the combination of a small amount of Cu0 nanoparticles, but this had no significant effect on catalytic performance.