Alumina decorated TiO2 nanotubes with ordered mesoporous walls as high sensitivity NO(x) gas sensors at room temperature.

Alumina (Al2O3) decorated anatase TiO2 nanotubes with ordered mesoporous pore walls (Al2O3/meso-TiO2 nanotubes) are successfully synthesized through vacuum pressure induction technology, and then combined with the thermal decomposition of a mesoporous TiO2 sol precursor, inside the cylindrical nanochannels of an anodic aluminium oxide (AAO) template. The decorated Al2O3 was formed by in situ deposition via direct reaction of the strong acid sol precursor and the nanochannel wall of the AAO template. The resultant Al2O3/meso-TiO2 nanotubes are characterized in detail by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and N2 adsorption-desorption. The experimental results reveal that the Al2O3/meso-TiO2 nanotubes have a tubular structure with an average diameter of ∼200 nm and highly ordered mesopores in the tubular walls. The Al2O3 is distributed evenly on the anatase TiO2 nanotubes. Moreover, the Al2O3/meso-TiO2 nanotubes possess a large specific surface area (136 m(2) g(-1)) and narrow mesopore size distribution (∼10 nm). By using NO(x) as a probe molecule, the Al2O3/meso-TiO2 nanotube films exhibit better sensing performance than that of mesoporous TiO2 nanotubes, in terms of their high sensitivity, fast response-recovery time, and good stability in air at room temperature. The outstanding performance in the gas sensing ability of Al2O3/meso-TiO2 nanotubes is a result of their one-dimensional tubular and mesoporous nanostructures, advantageous for the adsorption and diffusion of NO(x) gas. In addition, the sensing response is greatly improved by virtue of the decorated Al2O3 on the surfaces of the TiO2 nanotubes, which acts as an energy barrier to suppress charge recombination. The structural properties of the Al2O3/meso-TiO2 nanotubes makes them a viable novel gas sensor material at room temperature.

Structure and properties of noncrystalline nano-Al(OH)3 reclaimed from carbonized residual wastewater treatment sludge.

Performance of wastewater treatement sludge-carbon (SC) can be evidently improved by removing the inorganic fractions. A novel investigation for recovery of Al from acid leaching of SC and synthesis of nano-Al(OH)(3) has been conducted. Results show that the sodium aluminates with high purity can be obtained by effectively dissolving the inorganic fractions from SC and by further removing the impurities (Fe(3+), Ca(2+), Mg(2+), S(4+), and P(3+)). Highly dispersed Al(OH)(3) with high S(BET) is obtained at pH = 6. The peaks of -CH(2)- vibration and the C1s peaks (binding energies of 284.6 eV) imply that polyethylene glycol 1000 (PEG-1000) is chemically adsorbed on the surface of Al(OH)(3) samples, which is propitious to reduce the hydrogen bonds between water molecules and surface -OH groups to prevent hard agglomeration. The stretching vibration peaks of [AlO(2)](-) and the Na1s peaks confirm that a trace of sodium aluminate (NaAl(OH)(4), Na(+)(H(2)O)(4)[Al(OH)(4)(-)], or the dehydrated monomers) is retained in the prepared Al(OH)(3). The main phase transformation for calcination (≤800 °C) of the SC-derived Al(OH)(3) is from amorphous Al(OH)(3) to amorphous A1(2)O(3). Here we highlight that production of Al(OH)(3) and SC from sludge provides the potential application in significant quantities that can revolutionize the handling of such kinds of harmful waste.