Nb2O5 nanowires in-situ grown on carbon fiber: A high-efficiency material for the photocatalytic reduction of Cr(VI).

Niobium oxide nanowire-deposited carbon fiber (CF) samples were prepared using a hydrothermal method with amorphous Nb2O5·nH2O as precursor. The physical properties of the samples were characterized by means of numerous techniques, including X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), UV-visible spectroscopy (UV-vis), N2 adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy. The efficiency for the removal of Cr(VI) was determined. Parameters such as pH value and initial Cr(VI) concentration could influence the Cr(VI) removal efficiency or adsorption capacity of the Nb2O5/carbon fiber sample obtained after hydrothermal treatment at 160°C for 14hr. The maximal Cr(VI) adsorption capacity of the Nb2O5 nanowire/CF sample was 115mg/g. This Nb2O5/CF sample also showed excellent photocatalytic activity and stability for the reduction of Cr(VI) under UV-light irradiation: the Cr(VI) removal efficiency reached 99.9% after UV-light irradiation for 1hr and there was no significant decrease in photocatalytic performance after the use of the sample for 10 repeated cycles. Such excellent Cr(VI) adsorption capacity and photocatalytic performance was related to its high surface area, abundant surface hydroxyl groups, and good UV-light absorption ability.

CO2-assisted 'Weathering' of Steel Slag-Derived Calcium Silicate Hydrate: A Generalized Strategy for Recycling Noble Metals and Constructing SiO2-Based Nanocomposites.

The spent adsorbent loaded by toxic metals is a solid hazardous waste which could cause significant secondary pollution due to potential possible additional release of metal ions. Therefore, the main subject is direct reutilization of spent adsorbents which can further economically and realistically offer new features, like recycling metal adsorbed, or formation of functional SiO2-based nanocomposites. The nanoporous structure and negative surface charges enable steel slag-derived amorphous calcium silicate hydrate (CSH) to retain effectively the incoming metal ions (e. g. Au3+, Ag+, Pd2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Ce3+, Y3+, and Gd3+) by chemisorption. Sparked by natural carbonation 'weathering', which ultimately sequestrates atmospheric CO2 by alkaline silicate minerals to leach calcium from mineral matrix, the decalcification reactions of metal-bearing CSH results in successful recovery of noble metals (Ag, Au, Pd) upon NaOH etching the resultant SiO2 support. Further, SiO2-based heterostructures, containing nanocrystalline metals (e. g. Au0, Ag0, Pd0, Fe0, Co0, Ni0, Cu0, and Zn0) or rare-earth oxides (e. g. CeO2, Y2O3, and Gd2O3), are formed after reduction in H2/Ar (5 vol% H2) flow, which is also very important for the multipurpose immobilization of diverse hybrid materials on SiO2 surface (e. g. Cu0-Ag0@SiO2, Cu0-CeO2@SiO2, and Cu0-Ag0-CeO2@SiO2).

P123-PMMA dual-templating generation and unique physicochemical properties of three-dimensionally ordered macroporous iron oxides with nanovoids in the crystalline walls.

Three-dimensionally (3D) ordered macroporous (3DOM) iron oxides with nanovoids in the rhombohedrally crystallized macroporous walls were fabricated by adopting the dual-templating [Pluronic P123 and poly(methyl methacrylate) (PMMA) colloidal microspheres] strategy with ferric nitrate as the metal precursor in an ethanol or ethylene glycol and methanol mixed solution and after calcination at 550 °C. The possible formation mechanisms of such architectured materials were discussed. The physicochemical properties of the materials were characterized by means of techniques such as XRD, TGA/DSC, FT-IR, BET, HRSEM, HRTEM/SAED, UV-vis, XPS, and H(2)-TPR. The catalytic properties of the materials were also examined using toluene oxidation as a probe reaction. It is shown that 3DOM-structured α-Fe(2)O(3) without nanovoids in the macroporous walls was formed in the absence of P123 during the fabrication process, whereas the dual-templating strategy gave rise to α-Fe(2)O(3) materials that possessed high-quality 3DOM structures with the presence of nanovoids in the polycrystalline macropore walls and higher surface areas (32-46 m(2)/g). The surfactant P123 played a key role in the generation of nanovoids within the walls of the 3DOM-architectured iron oxides. There was the presence of multivalent iron ions and adsorbed oxygen species on the surface of each sample, with the trivalent iron ion and oxygen adspecies concentrations being different from sample to sample. The dual-templating fabricated iron oxide samples exhibited much better low-temperature reducibility than the bulk counterpart. The copresence of a 3DOM-structured skeleton and nanovoids in the macropore walls gave rise to a drop in the band-gap energy of iron oxide. The higher oxygen adspecies amounts, larger surface areas, better low-temperature reducibility, and unique nanovoid-containing 3DOM structures of the iron oxide materials accounted for their excellent catalytic performance in the oxidation of toluene.