Junwen Qi

Iron–copper bimetallic nanoparticles supported on hollow mesoporous silica spheres: an effective heterogeneous Fenton catalyst for orange II degradation

Iron–copper bimetallic nanoparticles supported on hollow mesoporous silica spheres as a composite catalyst (FeCu/HMS) was synthesized via a post-impregnation and sodium borohydride reduction strategy. The catalyst was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen physisorption, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and zeta potential. The results showed that the FeCu/HMS catalyst possessed hollow mesoporous structure with interior cavity transfixed by mesoporous silica shell. The iron–copper nanoparticles highly dispersed in the matrix of hollow mesoporous silica spheres. For comparison, three other catalysts, including solely iron nanoparticles supported on hollow mesoporous silica spheres (Fe/HMS), solely copper nanoparticles supported on hollow mesoporous silica spheres (Cu/HMS) and iron–copper nanoparticles supported on solid-core structured mesoporous silica spheres (FeCu/MS), were prepared by the similar procedure. To demonstrate the heterogeneous Fenton catalytic performance of the as-synthesized FeCu/HMS, orange II was chosen as a model contaminant. The results showed that 90.2% of 50 mg L−1 orange II was removed during 15 min at the reaction conditions of 1 g L−1 catalyst and 13.7 mM H2O2 in neutral pH and room temperature, and raised to 94.3% at 2 h. Kinetic analysis showed that the degradation of orange II follows the pseudo-first order and the apparent rate constant of FeCu/HMS was much higher than those of as comparison catalysts. Additionally, it was found that the addition of copper could make the catalyst less pH dependent and keep the high activity (93.8% orange II removal efficiency) even at alkaline circumstance (pH = 9). The remarkable catalytic performance of FeCu/HMS may be ascribed to the synergetic effect of iron and copper and “cavity effect” of the hollow structure. The stability and recoverability of the catalyst were assessed. The results indicated that the catalyst retained high catalytic activity (78.9% orange II removal efficiency) after 5 consecutive runs. The unique nanostructure and efficient catalytic activity make the catalyst to be a novel and prospective candidate in heterogeneous Fenton chemistry.

Synthesis of Ag@SiO2 yolk–shell nanoparticles for hydrogen peroxide detection

Yolk–shell nanostructures are a potential platform for the application of sensors and detection. In this paper, Ag@SiO2 yolk–shell nanoparticles (YSNs) were synthesized by a facile “two solvents” impregnation–reduction approach. XRD, SEM, TEM and N2 adsorption characterization results revealed that the resultant Ag@SiO2 YSNs possess distinctive structures, such as movable cores, perpendicular mesoporous channels, protective shells and hollow cavities. A nonenzymatic H2O2 sensor was constructed using Ag@SiO2 YSNs as sensing interface. A three-electrode system was used for the measurement. Electrochemical results indicate that the Ag@SiO2 YSNs modified electrode exhibits outstanding performance toward the H2O2 reduction, with a faster amperometric response, a lower detection limit (3.5 μM) and a wider linear range (0.1–15 mM) than that based on Ag@SiO2 composites, which was synthesized by a direct impregnation method.

Fabrication of ordered mesoporous carbon hollow fiber membranes via a confined soft templating approach

Ordered mesoporous carbon (OMC) membranes have broad applications such as size exclusion separation of molecules. In this work, a new method to prepare OMC hollow fiber membranes through a confined soft templating route is developed. In this method, commercialized polymeric hollow fiber ultrafiltration membranes were immersed in an ethanol solution containing a phenolic resin and a Pluronic triblock copolymer. Upon solvent evaporation, the phenolic resin and the surfactant self-assembled into the confined voids of the ultrafiltration membrane. After drying and pyrolysis, OMC hollow fiber membranes were obtained. The OMC hollow fiber membranes possess continuous membrane walls with an average thickness of 113 μm. The membrane wall has a hierarchical pore structure: one coming from hexagonally ordered mesoporous carbon with a pore diameter of ∼4.3 nm and the other being disordered defect holes with a size of 8–50 nm randomly distributed inside the OMC matrix. The gas permeance results indicate that the OMC hollow fiber membranes exhibit Knudsen diffusion behavior confirming their good quality.

Nanosized amine-rich spheres embedded polymeric beads for Cr (VI) removal

Porous matrix immobilization is considered as an effective approach to address the engineering challenges during practical application of nanoadsorbent. In this work, polyethersulfone (PES) beads with diameter of around 2.5mm, in which nanosized amine-rich polymer spheres (APSs) with particle size of ∼400nm are immobilized, are fabricated via phase inversion route. APSs-PES beads possess asymmetric and hierarchical structure with an exterior porous surface dense layer and numerous inner interpenetrating fingerlike channels, which promote the transportation of molecule and prevent the leaching of nanoadsorbents. The well distributed APSs with nitrogen-containing functional groups provide abundant adsorption sites. The cooperative attributing of the hierarchical structure and APSs demmonstrates enhanced Cr (VI) adsorption efficiency. The adsorption capacity of Cr (VI) is 243.9mg/g at 298K by Langmuir fitting. The effects of pH, temperature, the ratio of adsorbents and coexisting ionic are further studied in detail. The Cr (VI) removal mechanism is further explored by the combination of SEM, XPS, FTIR measurements and the adsorption parameters, further revealing the synergistic contribution of electrostatic attraction and reduction process. Therefore, this kind of adsorbents may show promising prospects on elimination of hazardous Cr (VI) in wastewater treatment.

Nitrogen-enriched carbon sheet for Methyl blue dye adsorption

In this work, nitrogen-enriched carbon sheet (NECS) was successfully fabricated by using sodium gluconate as a carbon source via melamine assisted chemical blowing approach. The obtained material exhibits sheet-like morphology with ultra-thin thickness and has a high specific surface area of 604 m2g-1 and high nitrogen contents of 11.2 wt%. The NECS showed an excellent adsorption performance towards the removal of anionic dye Methyl blue (a-Mb). The adsorption of a-Mb onto NECS better fitted the Langmuir isotherm model with the highest adsorption capacity of 847 mg g-1. Interestingly, the NECS showed a pH-sensitive behavior towards the adsorption efficiency of a-Mb dye in which the adsorption capacity abruptly increased from 34 to 701 mg g-1 when the pH of the solution was decreased from 10 to 2. Furthermore, the adsorbed materials can be easily regenerated without obvious efficiency loss over a five adsorption-desorption cycles.

Enhanced heterogeneous Fenton-like systems based on highly dispersed Fe0-Fe2O3 nanoparticles embedded ordered mesoporous carbon composite catalyst

Acceleration of Fe3+/Fe2+ cycle and simultaneous reduction of particle size with enhanced stability is extremely important for iron-based heterogeneous Fenton catalysts. In this work, Fe0-Fe2O3 composite nanoparticles embedded ordered mesoporous carbon hybrid materials (Fe0-Fe2O3/OMC) were rationally designed as efficient heterogeneous Fenton catalysts. Because of the confinement and reduction of OMC, highly dispersed Fe0-Fe2O3 active species with diameter of ∼8 nm were generated by an optimized carbothermic reduction process. In addition, Fe0-Fe2O3/OMC possesses ordered mesoporous structure with uniform mesopore, high surface area and pore volume. For comparison, two other catalysts, including solely Fe0 nanoparticles supported on ordered mesoporous carbon (Fe0/OMC) and solely Fe2O3 nanoparticles supported on ordered mesoporous carbon (Fe2O3/OMC) were also prepared. The Fenton catalytic performance of synthesized catalysts was evaluated by using H2O2 as oxidizing agent to degrade Acid Orange II (AOII). The results show that almost 98.1% of 100 mg L-1 AOII was removed by Fe0-Fe2O3/OMC in condition of neutral pH and nearly room temperature, which is much higher than those of compared catalysts. The enhanced catalytic activity of Fe0-Fe2O3/OMC for AOII removal is due to the efficient electron transfer between the Fe0 and iron oxide and the accelerated Fe3+/Fe2+ cycle. The stability and reusability of the catalyst was also investigated, which showed a good performance even after five consecutive runs. The as-synthesized catalyst is proved to be an attractive candidate in heterogeneous Fenton chemistry and practical application.