An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The application of photo-catalysis combined with membrane filtration for the oxidation of humic acid substances (HA) which is one of the major natural organic matters (NOMs) is discussed in this paper. Theoretical model shows a potential advantage of photo-catalytic filtration under low flux conditions. Cross-flow filtration is applied for HA removal using a TiO2 membrane under UV conditions. An increase of the flux through the membrane was observed by applying UV light.
Photocatalytic activity of Ag/TiO2 composites obtained by photoreduction treatment (PRT) was investigated. The composite materials, containing 1.0 and 2.1 wt% of silver nanoparticles were obtained by depositing silver on the Evonic–Degussa P25 titania surface. Ag/TiO2 samples were examined by SEM, XPS and BET techniques. The XPS measurements revealed that silver particles were obtained mainly in metallic form. The photocatalytic activity of pure P25 and Ag/TiO2 composites was compared in photooxidation reaction of some model compound like: formic acid (FA), rhodamine B (RhB) and methylene blue (MB). Photodecomposition reaction was investigated in a batch reactor containing aqueous suspension of a photocatalyst illuminated by either UV or artificial sunlight (halogen lamp). The tests proved that small amount of silver nanoparticles deposited on titania surface triggers the increase in photocatalytic activity, this increase depends however on the type of substrate. The relation between the type of substrate and the activity of the composite was discussed.
Photocatalytic activity of Ag/TiO2 composites obtained by photoreduction treatment (PRT) was investigated. The composite materials, containing various ratio of silver nanoparticles (0.6−3.7 wt %) were obtained by depositing silver on the Evonic-Degussa P25 titania surface. Selected samples whose color varied between light rose and purple brown were examined by SEM, TEM, XPS, DRS, and BET techniques. Flat band potential was determined using Roy method. TEM analysis showed spherically shaped silver nanoparticles of the diameter 4−12 nm. The XPS measurements revealed that silver particles were obtained mainly in metallic form. DRS spectra and photovoltage measurements showed that silver nanoparticles modified the P25 spectral properties but they changed neither the band gap nor the location of flat band potential. The photocatalytic activity of Ag/P25 composite was compared to the photocatalytic activity of pure P25 in the photooxidation reaction of an important potable water contaminant humic acid (HA) and two model compounds, oxalic acid (OxA) and formic acid (FA). The photodecomposition reaction was investigated in a batch reactor containing aqueous suspension of a photocatalyst illuminated by either UV or artificial sunlight (halogen lamp). The tests proved that a small amount of silver nanoparticles deposited on the titania surface triggers the increase in photocatalytic activity; this increase depends, however, on the decomposed substance.
Polyelectrolyte films structure formed by the "layer-by-layer" (LbL) technique can be enriched by addition of charged nanoparticles like carbon nanotubes and silver or hydroxyapatite nanoparticles, which can improve properties of the polyelectrolyte films or modify their functionality. In our paper we examined the formation and properties of model polyelectrolyte multilayers containing a synthetic layered silicate, Laponite. The Laponite nanoparticles were incorporated into multilayer films, which were formed from weak, branched polycation PEI and strong polyanion PSS. Since charge of PEI is pH-dependent, we build up multilayer films in two deposition conditions: pH = 6 when PEI was strongly charged and pH = 10.5 when charge density of PEI was low. Thicknesses of the films constructed with various numbers of Laponite layers were measured by single wavelength ellipsometry. We also determined the differences in permeability for selected electroactive molecules using cyclic voltamperometry. Properties of the films containing clay nanoparticles were compared with model polyelectrolyte multilayer films PEI/PSS formed at the same conditions. We found that Laponite nanoparticles strongly influenced PEI/PSS multilayer film properties. Replacement of PSS by Laponite eliminated the oscillations of the film thickness in the case when PEI was weakly charged. PSS layer adsorbed on top of PEI/Laponite bilayers increased the thickness of multilayer films and improved their barrier properties so synergistic effects between these properties for polyelectrolytes and Laponite nanoparticles could be observed.
We investigate the distinctly different interaction of thiolate-protected cluster Au38(SC2H4Ph)24 with two diverse support materials Al2O3 and CeO2. The catalytic surfaces have been heated in different atmospheres, and the removal of the thiolate ligands has been studied. Thermogravimetry (TG), temperature-programmed process coupled with mass spectrometer (TPRDO-MS), and X-ray absorption spectroscopy (XAFS) studies were performed to understand the desorption of thiol ligands depending on conditions and support material. Depending on the atmosphere and the support material the fate of the thiol ligands is different upon heating, leading to metallic Au in the case of Al2O3 and to cationic Au with CeO2. The thiolate removal seems to be a two-step procedure. The catalytic activity of these Au38-supported clusters was studied for the aerobic oxidation of cyclohexane. Conversion was higher for the gold clusters supported on CeO2. Surprisingly, a significant amount of cyclohexanethiol was found, revealing the active participation of the thiolate ligand in catalytic reactions. The observation also indicates that breaking and formation of C–S bonds can be catalyzed by the gold clusters.
The possibility of application of the process of photocatalytic decomposition of humic substances (humic acid – HA) to their removal from water was investigated. Commercial TiO2 (Evonic-Degussa P-25) and the periodic reactor were used in the experiments. The decomposition under artificial sunlight (ASL) and UV irradiation was tested. It was stated that ASL irradiation is not sufficient to cause significant decomposition of HA whereas TiO2 appeared to be very effective under the UV irradiation. Strong adsorption of HA on the surface of TiO2 was observed.
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