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Novel Fe3O4/polyacrylonitrile (PAN) composite nanofibers (NFs) were prepared by a simple two-step process, an electrospinning and solvothermal method. Characterization by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) demonstrated formation of a uniform nanoparticles coating (about 20 nm in thickness) on the PAN nanofiber backbone. The coating was constructed by well-crystallized cubic phase Fe3O4 nanoparticles as examined by X-ray diffraction spectroscopy (XRD). The coating doubled the specific surface area of NFs, from 8.4 to 17.8 m2 g(-1), as confirmed by nitrogen sorption isotherm analysis. To evaluate the feasibility of Fe3O4/PAN composite NFs as a potential adsorbent for antibiotic removal, batch adsorption experiments were conducted using tetracycline (TC) as the model antibiotic molecule. The results showed that Fe3O4/PAN composite NFs were effective in removing TC with no impactful loss of Fe in the pH regime of environmental interest (5-8). The adsorption of TC onto Fe3O4/PAN composite NFs better fitted the pseudo-second-order kinetics model, and the maximum adsorption capacity calculated from Langmuir isotherm model was 257.07 mg g(-1) at pH 6. The composite NFs also exhibited good regenerability over repeated adsorption/desorption cycles. Surface complexation between TC and the composite NFs contributed most to the adsorption as elucidated by X-ray photoelectron spectroscopy (XPS). This highly effective and novel adsorbent can be easily modularized and separated, promising its huge potential in drinking and wastewater treatment for antibiotic removal.

Low cost alternatives to the expensive and scarce Pt to catalyze the oxygen reduction reaction (ORR) in acid media are essential for the proton-exchange-membrane (PEM) fuel cells to become economically viable.Chemically doped nanocarbons are among the most promising candidates in this regard. We report the facile synthesis and superior electrocatalytic activity of an Fe-N doped nanocarbon composite of carbon nanotubes (CNTs) grown on/between graphene sheets. The structure and composition of the composite is characterized by using a variety of techniques including SEM, TEM, N 2 adsorption/desorption isotherms, XPS, XRD, and Mössbauer spectroscopy. It is shown that the in situ growth of CNTs in the presence of graphene sheets not only produces a tubes-on/between-sheets architecture that enhances the dispersion of CNTs and graphene sheets, but also leads to optimized doping and coordination of nitrogen and Fe which favour the ORR. The composite can catalyze the ORR much more efficiently than either of the single materials containing only CNTs or graphene synthesized under similar conditions, and similarly to Pt/C in both alkaline and acid media.

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