Synthesis of N-Doped Magnetic Mesoporous Carbon Composites for Adsorption of Ag(I) in Aqueous Solution.

In this work, a novel N-doped magnetic mesoporous carbon (NMC) composite (Fe3O4/NMC) was synthesized by a two-step process. First, NMC was prepared by a template method using a melamine formaldehyde resin as nitrogen and carbon sources, and then, Fe3O4 nanoparticles were loaded into the as-prepared NMC via in-situ coprecipitation process. The morphology, structure, and magnetic properties of Fe3O4/NMC were characterized and its adsorption properties were investigated. It can be found that Fe3O4/NMC with saturation magnetization of 20 emu · g-1 features a mesoporous structure, and its specific surface area reaches 513 m² · g-1. These two excellent specificities are propitious to the adsorption and separation of Ag(I) from aqueous solution. The adsorption behavior of Fe3O4/NMC nanocomposite has been investigated by adsorption kinetics and isotherms adsorption analyses as well. The adsorption isotherm and the adsorption kinetics of Ag(I) onto Fe3O4/NMC agrees well with Langmuir model and pseudo-second-order model, respectively. Moreover, the Fe3O4/NMC was easily to recovery by applied magnetic field, the adsorption capacity of Fe3O4/NMC was about 90.3% of the initial saturation adsorption capacity after five continuous uses.

Synthesis of magnetic graphene oxide grafted polymaleicamide dendrimer nanohybrids for adsorption of Pb(II) in aqueous solution.

In this paper, using maleic anhydride and ethylenediamine as functional monomers, graphene oxide (GO) loaded magnetic Fe3O4 nanoparticles modified by (3-Aminopropyl) triethoxysilane as support, magnetic graphene oxide grafted polymaleicamide dendrimer (GO/Fe3O4-g-PMAAM) nanohybrids were fabricated by divergent method and magnetic separation technology. The obtained samples were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, elementary analyzer and vibrating sample magnetometer. The effects of PMAAM generations, solution pH, Pb(II) initial concentration, temperature and contact time on the adsorption property of the samples for Pb(II) in aqueous solution were studied. The results demonstrated that nitrogen content and adsorption capacity of the as-synthesized samples with amino terminal groups were all higher than their adjacent generations PMAAM with carboxyl terminal groups. Moreover, with increasing generations of PMAAM grafted on to the GO/Fe3O4, the nitrogen content and the adsorption capacity of the samples with the same terminal groups gradually increased. The maximum adsorption capacity of GO/Fe3O4-g-G3.0 for Pb(II) was 181.4mgg-1 at 298K. The rising of temperature was beneficial for the adsorption. The adsorption kinetics had a better agreement with pseudo-second-order equation, and equilibrium data followed the Langmuir model.

Preparation of polyamidoamine dendrimers functionalized magnetic graphene oxide for the adsorption of Hg(II) in aqueous solution.

In this study, using graphene oxide supported Fe3O4 nanoparticles as carriers, ethylenediamine and methyl acrylate as functional monomer, different generations of polyamidoamine dendrimers functionalized magnetic graphene oxide (MGO-PAMAM), up to generation 4.0, were successfully synthesized via step by step growth chemical grafting approach and magnetic separation technology. In the process of synthesizing dendrimers, the generation of dendrimers was increased with the increasing of reaction cycles. In other words, the dendrimers generation is determined from the number of branch iterations. The obtained MGO-PAMAM were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), elemental analysis, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), nitrogen adsorption/desorption isotherm and Zeta potential analysis. The adsorption properties of the synthesized products for Hg(II) in aqueous solution were investigated by batch experiments. The results showed that the MGO-PAMAM with generation 3.0 of dendrimers (MGO-PAMAM-G3.0) has the maximum adsorption capacity of 113.71mg·g-1. The adsorption process of MGO-PAMAM-G3.0 for Hg(II) was well described by the pseudo-second-order kinetics model and the Langmuir isotherm model. The Hg(II) adsorbed on the surface of MGO-PAMAM-G3.0 was reduced to Hg(I) in the adsorption process. In addition, the MGO-PAMAM possesse good magnetic separation performance.

Implementation of ultrafast X-ray diffraction at the 1W2B wiggler beamline of Beijing Synchrotron Radiation Facility.

The implementation of a laser pump/X-ray probe scheme for performing picosecond-resolution X-ray diffraction at the 1W2B wiggler beamline at Beijing Synchrotron Radiation Facility is reported. With the hybrid fill pattern in top-up mode, a pixel array X-ray detector was optimized to gate out the signal from the singlet bunch with interval 85 ns from the bunch train. The singlet pulse intensity is ∼2.5 × 10(6) photons pulse(-1) at 10 keV. The laser pulse is synchronized to this singlet bunch at a 1 kHz repetition rate. A polycapillary X-ray lens was used for secondary focusing to obtain a 72 µm (FWHM) X-ray spot. Transient photo-induced strain in BiFeO3 film was observed at a ∼150 ps time resolution for demonstration.