Effect of magnetic nanoparticles and silver-loaded magnetic nanoparticles on advanced wastewater treatment and disinfection

Nanocatalysis is an emerging area of research that has attracted much attention over the past few years. It provides the advantages of both homogeneous as well as heterogeneous catalysis in terms of activity, selectivity, efficiency and reusability. Magnetically recoverable nanocatalysts provide a larger surface area for the chemical transformations where the organic groups can be anchored and lead to decrease in the reaction time, increase in the reaction output and improve the atom economy of the chemical reactions. Moreover, magnetic nanocatalysts provide a greener approach towards the chemical transformations and are easily recoverable by the aid of an external magnet for their reusability. This review aims to give an insight into the important work done in the field of magnetically recoverable nanocatalysts and their applications in carbon–carbon and carbon–heteroatom bond formation.

/pdf/overview-on-magnetically-recyclable-ferrite-nanoparticles-3w35m2ckye.pdf

Overview on magnetically recyclable ferrite nanoparticles: synthesis and their applications in coupling and multicomponent reactions

Visible light photodegradation of 4-nitrophenol by new high-performance and easy recoverable Fe3O4/Ag2O-LDH hybrid photocatalysts

Magnetically stabilized fluidized bed reactor (MSFBR) is a sustainable and cost-effective biotechnological process, which justifies the increasing search for biocatalytic superparamagnetic supports to enzyme immobilization. This work, investigates the effect of modified nanomagnetite, Fe3O4 (nM), for biocatalytic support on properties associated with catalytic behavior and potential use in MSFBR. The nM was either synthesized and then modified with 3-aminopropyltriethoxysilano (nM-APTES) or stabilized with oleic acid (nM-OA) and later modified with chitosan (nM-OA-Cs). A novel correlation study was carried out about the support dimension effect, enzymatic surface loading and retained activity. Both nM-based supports were morphologically, structurally and magnetically characterized by X-ray diffraction, thermogravimetry, Mossbauer and Fourier-transform Infrared spectroscopies, as well as vibration sample magnetometry, scanning (SEM) and transmission (TEM) electron microscopies. The nM-APTES and nM-OA samples disclosed crystal sizes of 8.07 and 8.69 nm, respectively. From TEM imagens, the average particles sizes were 10.9 nm for nM-APTES and 12.6 nm for nM-OA. The nM-OA-Cs displayed an average particles size of 918.6 μm. These magnetic supports displayed high saturated magnetization, 79.6 emu/g for nM-APTES and 72.7 emu/g for nM-OA. The amano lipase AK enzyme was immobilized on supports activated with glutaraldehyde. The enzyme loading density of nM-APTES-GA-Lip (122 mg/g) with 61% immobilization yield was higher than that of nM-OA-Cs-GA-Lip (46 mg/g) with 23% immobilization yield. The catalytic activity of nM-APTES-GA-Lip (85%) was higher than that of nM-OA-Cs-GA-Lip (46%), which reflected the correlation between enzyme loading efficiency on the magnetic nanosupports and their relative activity, essential to potential use in MSFBR.

Modified magnetite nanoparticle as biocatalytic support for magnetically stabilized fluidized bed reactors

Core-shell FexOy@C nanoparticles (NPs) modified with Ag were studied with x-ray diffraction, transmission electron microscopy, energy dispersive elemental mapping, Mossbauer spectroscopy, static magnetic measurements, and optical magnetic circular dichroism (MCD). FexOy@C NPs synthesized by the pyrolysis process of the mixture of Fe(NO3)3 · 9H2O with oleylamine and oleic acid were added to a heated mixture of oleylamine and AgNO3 in different concentrations. The final product was a mixture of iron oxide crystalline NPs in an amorphous carbon shell and Ag crystalline NPs. The iron oxide NPs were presented by two magnetic phases with extremely close crystal structures: Fe3O4 and γ-Fe2O3. Ag is shown to form crystalline NPs located very close to the iron oxide NPs. An assumption is made about the formation of hybrid FexOy@C-Ag NPs. Correlations were obtained between the Ag concentration in the fabricated samples, their magnetic properties and the MCD spectrum shape. Introducing Ag led to a approximately linear decrease of the NPs saturation magnetization depending upon the Ag concentration, it also resulted into the MCD spectrum shift to the lower light wave energies. MCD was also studied for the Fe3O4@C NPs synthesized earlier with the same one-step process using different heat treatment temperatures, and MCD spectra were compared for two series of NPs. A possible contribution of the surface plasmon excitation in Ag NPs to the MCD spectrum of the FexOy@C-Ag NPs is discussed.

/pdf/characterization-of-the-iron-oxide-phases-formed-during-the-3ocm51ojwx.pdf

C.-R. Lin

Papers

Magnetic and magneto-optical properties of Fe3O4 nanoparticles modified with Ag