Yucheng Du

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.

α-Fe2O3 nanowires deposited diatomite: highly efficient absorbents for the removal of arsenic

α-Fe2O3 nanowires deposited diatomite was prepared using a precipitation–deposition method with FeCl3 as metal source and (NH2)2CO aqueous solution as precipitating agent. Physicochemical properties of the samples were characterized by means of numerous techniques, and their efficiency for the removal of As(III) and As(V) was determined. It is found that the solution pH value, reaction temperature, reaction time, and FeCl3 concentration had effects on the α-Fe2O3 amount loaded on the diatomite. Parameters, such as adsorbent amount, adsorption time, adsorption temperature, pH value, and initial As(III) or As(V) concentration, could influence the As(III) or As(V) removal efficiency of the α-Fe2O3 nanowires/diatomite sample (prepared with a 8 wt% FeCl3 aqueous solution at pH = 4.5 and 50 °C for 35 h) for the removal of As(III) and As(V). Over the α-Fe2O3/diatomite sample at pH = 3.5, the maximal As(III) and As(V) adsorption capacities were 60.6 and 81.2 mg g−1, and the maximal As(III) and As(V) removal efficiency was 99.98 and 100%, respectively. The Langmuir model was more suitable for the adsorption of As(V), whereas the Freundlich model was more suitable for the adsorption of As(III). The adsorption mechanism of the sample was also discussed.

Flower-, wire-, and sheet-like MnO2-deposited diatomites: Highly efficient absorbents for the removal of Cr(VI).

Flower-, wire-, and sheet-like MnO2-deposited diatomites have been prepared using a hydrothermal method with Mn(Ac)2, KMnO4 and/or MnSO4 as Mn source and diatomite as support. Physical properties of the materials were characterized by means of numerous analytical techniques, and their behaviors in the adsorption of chromium(VI) were evaluated. It is shown that the MnO2-deposited diatomite samples with different morphologies possessed high surface areas and abundant surface hydroxyl groups (especially the wire-like MnO2/diatomite sample). The wire-like MnO2/diatomite sample showed the best performance in the removal of Cr(VI), giving the maximum Cr(VI) adsorption capacity of 101 mg/g.

New fluorine-doped H2(H2O)Nb2O6 photocatalyst for the degradation of organic dyes

A new solid niobic acid phase, H2(H2O)Nb2O6, with fluorine (F) doping was crystallized using hydrothermal chemistry. F-doped H2(H2O)Nb2O6 octahedra could function as an efficient heterogeneous catalyst for the photodegradation of organic pollutants in water under UV light irradiation. The high photocatalytic activity of the F-doped H2(H2O)Nb2O6 materials is attributed to a synergistic effect of the specific surface area, the surface characteristics and the crystal structure. Our results suggest novel ways of controlling the crystallization of niobium oxides, further the fundamental understanding of their structure–property relationships, and may lead to their application in fields such as environmental protection and energy production.

Bouquet-like calcium sulfate dihydrate: a highly efficient adsorbent for Congo red dye

A unique bouquet-like calcium sulfate dihydrate (BCSD) was successfully synthesized from calcium chloride and aluminum potassium sulfate in aqueous sodium carboxymethyl cellulose (CMC) solution by means of a metathesis reaction. The morphology and structure of BCSD were characterized by scanning electron microscopy, powder X-ray diffraction and transmission electron microscopy. The adsorption of different organic dyes from aqueous solutions onto the as-synthesized BCSD was then investigated, taking into account the influences of adsorbent dose (1.0–3.5 g L−1), solution pH (5.0–12.0) and adsorption time. The results indicated that the temperature and agitation rate had no effect on the morphology of the samples. With the increase of CMC concentration from 0.10% to 0.50%, lamellar calcium sulfate dihydrate (LCSD) gradually transformed into rod-like calcium sulfate dihydrate (RCSD), and eventually generated BCSD. The as-prepared BCSD was monoclinic with preferential [021] and [041] orientations. Moreover, BCSD selectively adsorbed Congo red (CR) instead of rhodamine B and methyl orange. The adsorption equilibrium process of CR was an exothermic process and could adequately be described by the Langmuir isotherm model. The calculated maximum adsorption quantity (qmax) was 1224.09 mg g−1 at 303.5 K, which was almost 12 times larger than that onto LCSD (100.80 mg g−1). Additionally, the adsorption process of CR was a multi-step process, and the adsorption kinetics could be described in terms of a pseudo-second-order model. From attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy studies it was concluded that CR was chemisorbed on BCSD. These results indicate that BCSD is a promising candidate in wastewater treatment.

Effect of Particle Size Distribution of Calcined Diatomites on the Extinction Performance

Calcined diatomite was first investigated as matting agent for formulating high-performance coating. Jet milling and sieving or sedimentation methods were employed to obtain rational particle size distributions. It was found that the optimal size distribution of the particles with the diameters of D10 = 2.54 µm, D25 = 5.04 µm, D50 = 9.74 µm, D75 = 18.80 µm, and D90 = 31.66 µm showed the best extinction performance, with the gloss and extinction being 2.9 and 3.3 and 32.6% and 50.7% determined at incidence angles of 60° and 85°, respectively.

MgO-based nanosheets loaded with ZnxMg1−xO nanoparticles with UV light-driven photocatalytic performance

This paper reports the synthesis of MgO-based nanosheets loaded with UV-light absorbed, wurtzite ZnxMg1−xO nanoparticles based on calcining Zn2+-adsorbed Mg(OH)2 precursor, as evidenced by X-ray diffraction, UV-visible, X-ray photoelectron spectroscopy analyses, etc. The surface modification of magnesium oxide (MgO) sheet-like adsorbents by Zn–Mg–O alloys generates photocatalytic activity for the degradation removal of cationic dye Rhodamine B and anionic dye methyl orange under UV light irradiation. These findings provide a route to chemically controlled synthesis of new and highly robust MgO–ZnxMg1−xO materials for water purification. The endowed photocatalysis function of MgO makes it be easily recovered via photodegradation of adsorbed dyes rather than high-temperature calcination, thus extending the applications of MgO in dye wastewater treatment.

Nb 2 O 5 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.