Dandan Zhu

Efficient removal of pathogenic bacteria and viruses by multifunctional amine-modified magnetic nanoparticles

A novel amine-functionalized magnetic Fe3O4-SiO2-NH2 nanoparticle was prepared by layer-by-layer method and used for rapid removal of both pathogenic bacteria and viruses from water. The nanoparticles were characterized by TEM, EDS, XRD, XPS, FT-IR, BET surface analysis, magnetic property tests and zeta-potential measurements, respectively, which demonstrated its well-defined core-shell structures and strong magnetic responsivity. Pathogenic bacteria and viruses are often needed to be removed conveniently because of a lot of co-existing conditions. The amine-modified nanoparticles we prepared were attractive for capturing a wide range of pathogens including not only bacteriophage f2 and virus (Poliovirus-1), but also various bacteria such as S. aureus, E. coli O157:H7, P. aeruginosa, Salmonella, and B. subtilis. Using as-prepared amine-functionalized MNPs as absorbent, the nonspecific removal efficiency of E. coli O157:H7 or virus was more than 97.39%, while it is only 29.8% with Fe3O4-SiO2 particles. From joint removal test of bacteria and virus, there are over 95.03% harmful E. coli O157:H7 that can be removed from mixed solution with polyclonal anti-E. coli O157:H7 antibody modified nanoparticles. Moreover, the synergy effective mechanism has also been suggested.

Facile preparation of MnO2 doped Fe2O3 hollow nanofibers for low temperature SCR of NO with NH3

A series of MnO2 doped Fe2O3 hollow nanofibers with different Mn/Fe molar ratios were successfully synthesized by the electrospinning method for the low temperature selective catalytic reduction (SCR) of NO with NH3 in the presence of excess O2. The SEM and TEM images showed obvious hollow tubular structure of electrospun nanofibers. The hollow nanofibers with Mn/Fe molar ratio of 0.15 exhibited the highest catalytic activity, nearly 100% of NO conversion from 150 to 300 °C, among the catalysts investigated. The TPR, XPS and in situ FTIR results revealed that Mn4+ was the main active species for SCR reaction, and the addition of Mn species enhanced the surface concentration and acidity of Lewis acid sites.

Highly Efficient Removal of Pathogenic Bacteria with Magnetic Graphene Composite

Magnetic Fe3O4/graphene composite (abbreviated as G-Fe3O4) was synthesized successfully by solvothermal method to effectively remove both bacteriophage and bacteria in water, which was tested by HRTEM, XRD, BET, XPS, FTIR, CV, magnetic property and zeta-potential measurements. Based on the result of HRTEM, the single-sheet structure of graphene oxide and the monodisperse Fe3O4 nanoparticles on the surface of graphene can be observed obviously. The G-Fe3O4 composite were attractive for removing a wide range of pathogens including not only bacteriophage ms2, but also various bacteria such as S. aureus, E. coli, Salmonella, E. Faecium, E. faecalis, and Shigella. The removal efficiency of E. coli for G-Fe3O4 composite can achieve 93.09%, whereas it is only 54.97% with pure Fe3O4 nanoparticles. Moreover, a detailed verification test of real water samples was conducted and the removal efficiency of bacteria in real water samples with G-Fe3O4 composite can also reach 94.8%.

Highly efficient removal of NO with ordered mesoporous manganese oxide at low temperature

Highly ordered mesoporous MnO2 was prepared using KIT-6 as a hard template, for selective catalytic reduction (SCR) of NO with NH3 at low temperature, which was characterized using TEM, XRD, BET, XPS, H2-TPR, NH3-TPD and in situ DRIFT. Based on the results of HRTEM, the ordered mesoporous channels of MnO2 can be observed clearly. The SCR activity of NO with NH3 at low temperature was evaluated using these ordered mesoporous MnO2 as catalysts, and it was found that 100% NO conversion efficiency could be achieved at temperatures from 150 to 250 °C. For comparison, mesoporous Mn2O3 and bulk MnO2 were synthesized and their NO conversions were tested using the same parameters. The mechanism of improved SCR performance was investigated using XPS, H2-TPR, NH3-TPD and in situ DRIFT, and it was indicated that specific surface area, surface chemisorbed oxygen, reducibility and acid sites have great effect on the SCR reaction. In addition, the effects of H2O and GHSV on NO conversion were investigated.

Coaxial-electrospun magnetic core-shell Fe@TiSi nanofibers for the rapid purification of typical dye wastewater.

Magnetic mesoporous γ-Fe2O3@Ti0.9Si0.1O2 (abbreviated as Fe@TiSi) core-shell nanofibers were prepared using sol-gel chemistry combined with coaxial-electrospinning technology by adjusting the inner and outer feed ratios. The properties of these novel core-shell nanofibers were characterized by SEM, HRTEM, XRD, FTIR, BET, XPS, and UV-vis spectra. To evaluate the chemical properties of the nanofibers for cleaning typical organic wastewater, methylene blue (MB) was used as a target organic pollutant and was cleaned under irradiation with sunlight and visible light. The Fe@TiSi hierarchical nanofibers composed of a 1:10 feed ratio displayed a mesoporous structure and showed the highest photocatalytic activity for the degradation of MB in water. Furthermore, 86.8% and 71.1% of the MB, which was added at an original concentration of 1 mg/L, was removed after 60 min of irradiation with sunlight and visible light in the presence of Fe@TiSi at a concentration of 0.2 g/L, and 100% of the MB was removed after 75 min. It is very important that the magnetic nanofibers could be recycled rapidly with an outside magnet, and the actual water treatment process was easy to achieve. Moreover, the mechanism of MB degradation by Fe@TiSi core-shell nanofibers was proposed.