Adsorptive and photocatalytic removal of phenol by layered niobates organically modified through intercalation and silylation

Layered hexaniobate K4Nb6O17 was modified with dodecylammonium ions and octadecyltrimethoxysilane molecules, which were held in the interlayer spaces by electrostatic interactions and covalent attachment to the layers, respectively. Interlayer spacing of the niobate was expanded by incorporation of the bulky organic species. Vapor adsorption isotherms of benzene and water indicated hydrophobic interlayer microenvironments of the organically modified niobates. Both of the modified niobates fairly adsorbed phenol dissolved in water. The photocatalytic activity of hexaniobate allowed the organically modified materials to photocatalytically decompose phenol upon UV irradiation. Decomposition time courses and quantitative analysis of phenol present in the system indicated that the phenol molecules adsorbed on the niobates were preferentially degraded. XRD and IR analyses of the modified niobates indicated that the silylated niobate was more durable than the ion-exchanged sample; the former kept the structure during the photocatalytic process while the latter was partly collapsed.     

Acceleration or Suppression of α-Phase Precipitation Using Isothermal ω Phase in Ti-20 at.pct Nb Alloy

Homogeneous precipitation of a fine α phase in the β matrix of Ti alloys is a promising method for obtaining a highly strengthened Ti-based alloy. Isothermal ω particles are known to be the nucleation sites for fine α-phase precipitation, but an understanding of the kinetics of α-phase formation on isothermal ω particles is still lacking. This study aimed to reveal the effect of isothermal ω particles on α-phase precipitation onset time. Two-step isothermal aging of a Ti-20 at.pct Nb alloy after solid solution treatment at 1273 K (1000 °C) was carried out. The first step of the aging at 633 K (360 °C) involved the formation of isothermal ω particles in the β matrix. This was followed by a second aging step at 673 K, 723 K, and 773 K (400 °C, 450 °C, and 500 °C) for α-phase precipitation. Suppression of α-phase nucleation on the isothermal ω particles occurred at 673 K (400 °C), whereas acceleration of α-phase nucleation on the isothermal ω particles was observed at 723 K and 773 K (450 °C and 500 °C). Thermodynamic stability of the isothermal ω particles and solute partitioning were controlling factors for the α-phase precipitation kinetics.     

Startup,performance, and microbial communities of an anammox reactor inoculated with indigenous sludge for the treatment of high-salinity and mesophilic underground brine

Clean Technologies and Environmental Policy - Anaerobic ammonium oxidation (anammox) has been implemented as a cost-effective nitrogen removal process in wastewater treatment. To apply the process...     

Intercalation of substituted alkylammonium ions into layered potassium niobate K4Nb6O17

Substituted alkylammonium ions (protonated hydroxy amine and diamine) were intercalated into layered niobate K₄Nb₆O₁₇in order to introduce functional substituents into the interlayer spaces of the niobate. In the case of reaction with 3-hydroxypropylammonium ion, the intercalation compound incorporated the ammonium ions in a bilayer arrangement, by which the hydroxyl substituents were located in the middle of the interlayer spaces to form intermolecular hydrogen bonding. For the intercalation compounds with alkyldiammonium ions, the intercalated alkyldiammonium ions were present in monolayer and oriented transversally with respect to the niobate layers.     

Structural response of organically modified layered niobate K4Nb6O17 to the adsorption of 2,4-dichlorophenol

We investigated structural alteration of organically modified layered hexaniobate K₄Nb₆O₁₇ upon adsorption of 2,4-dichlorophenol. Two adsorbents examined were hexaniobate intercalated with dodecylammonium (C₁₂N) or dioctadecyldimethylammonium (2C₁₈2MeN) ions. The adsorbent modified with the C₁₂N ions was structurally durable for the adsorption of 2,4-dichlorophenol from 0.4 to 10 mmol dm⁻³ aqueous solutions. The adsorbate molecules were accommodated among the pre-intercalated C₁₂N moieties. In contrast, the adsorbent intercalated with the 2C₁₈2MeN ions suffered from structural collapse with the uptake of adsorbate molecules from relatively concentrated solutions (10 mmol dm⁻³), although this sample adsorbed larger amount of 2,4-dichlorophenol than the niobate modified with C₁₂N ions. X-ray diffraction and IR spectroscopy showed that the 2C₁₈2MeN ions were deintercalated with the adsorption. However, liquid chromatography and total organic carbon analysis indicated that the deintercalated organic moiety stayed on the external surface of niobate to form an effective adsorption site of 2,4-dichlorophenol. The “deintercalative adsorption” was ascribed based on UV spectroscopy to a specific interaction between the adsorbate and 2C₁₈2MeN molecules. Such drastic structural response had not been reported for other organically modified layered adsorbents.     

Study on laser consolidation of metal powder with Yb:fiber laser—Evaluation of line consolidation structure

This study describes the consolidation characteristics of chromium molybdenum steel (SCM) based powder used for rapid tooling. The laser beam used was a Yb:fiber laser with a spot diameter of 45 μm and a maximum power of 40 W. In order to investigate the influence of irradiation conditions on the maximum temperature at the focal area, a two-color pyrometer developed by the authors was used. In addition, the cross section of the consolidated structure was analyzed with an electron probe microanalysis, and the cutting force was measured with a dynamometer. The result showed that the maximum temperature at the focal area was related to the consolidation characteristics of the metal powder. The main parameters which affected the consolidation characteristics were laser power and scan speed of the laser beam. The deposited powder and the plate surface were melted with generated heat and alloyed in the process of the solidification. The specific cutting force was greatly influenced by the consolidation conditions. The highest value of a specific cutting force was obtained when the melting of the powder and the solidification of the molten powder were performed repeatedly and the structure was consolidated linearly.     

Doped Ni Catalysts for Methane Reforming with CO<Subscript>2</Subscript>

Pb, Sb, Bi and Te doped Ni catalysts were prepared and used for methane reforming with CO₂ in order to diminish coke deposition. It was found that small amounts of Pb doped Ni catalysts exhibited excellent coke resistance ability with minor loss of the reforming activity. As the added amount of Pb increased from 0 to 0.015 (mole ratio between Pb/Ni), coke formation rate decreased from 166.7 mg-coke/g-cat h (on Ni/SiO₂) to 0, while the reforming activity decreased slightly from 73.2% to 63.3% (conversion of CO₂) at 800 °C, 60,000 ml(STP)/g-cat·h (CH₄ CO₂=1:1, no dilution gas in feed). Higher amounts of Pb and Sb, Bi, Te made Ni catalyst deactivated for methane reforming with CO₂.