Search results for "photodegradation"
showing 10 items of 153 documents
Photocatalytic activity of TiO2/SiO2 systems
2009
Silica-supported TiO(2) powders were synthesized by a wet method under mild conditions. The aim of the work was the preparation of TiO(2)/SiO(2) additives for photocatalytic cements. Three types of commercial SiO(2) were used as supports: Cabot, Axim and Fly Ash. Cabot silica was ultra-pure whereas the other two silica contained different percentages of various oxides. The TiO(2)/SiO(2) samples, denoted TiO(2)/Cabot, TiO(2)/Axim and TiO(2)/Fly Ash, were prepared by boiling suspensions obtained by addition of silica to a solution of TiCl(4) in water (volume ratio 1:10). The photocatalytic activity was evaluated in a gas-solid system both in batch and in continuous reactors using 2-propanol a…
Simulated solar UV-irradiation of endocrine disrupting chemical octylphenol.
2009
The photolysis of octylphenol (OP) was investigated using a solar simulator in the absence/presence of dissolved natural organic matter (DNOM), HCO(3)(-), NO(3)(-) and Fe(III) ions. The effects of different parameters such as initial pH, initial concentration of substrate, temperature, and the effect of hydrogen peroxide concentration on photodegradation of octylphenol in aqueous solution have been assessed. The results indicate that the oxidation rate increases in the presence of H(2)O(2), nitrate and DNOM. Phenol, 1,4-dihydroxylbenzene and 1,4-benzoquinone were identified as intermediate products of photodegradation of octylphenol, through an HPLC method. In addition, the disappearance of…
Studying the stability of Solvent Red 19 and 23 as excise duty components under the influence of controlled factors
2020
Abstract In this study, we examine the chemical stability of two disazo dyes, namely Solvent Red 19 and 23 (SR 19 and SR 23), under simulated conditions. Both dyes are considered to be chemically stable under normal exploitation conditions and therefore, are used extensively as excise duty components that enable a rapid visual verification of the tax levels that were imposed on fuel products as well as identifying fuel usage. However, the results from this study confirmed that the colour of the samples that had been fortified with either SR 19 or SR 23 fades under the influence of external conditions such as UV-A irradiation and temperature over time. The UV-A irradiation was the dominant f…
Surface characterization of metal ions loaded TiO2 photocatalysts: structure-activity relationship
2004
Transition metal loaded TiO2 powders were characterised and tested for the photodegradation of some organic acids. Both Lewis and Brønsted surface acid sites were present in the samples containing large amounts of Mo, V and W. The Brønsted sites are associated to the presence of the transition metals as they do not exist in the unloaded support, and in particular to the presence of these metals in high oxidation states. The trend of the pzc values of the various powders matches rather well both with the surface acidity of the samples experimentally determined by NH3 adsorption and with a scale of acidity/basicity for bulk binary oxides. XPS investigation indicates that only the presence of …
Flow injection biamperometric determination of metronidazole with on-line photodegradation
1999
Abstract The determination of metronidazole is performed in a flow injection assembly, provided with a 40 W low pressure mercury lamp and a home-made biamperometric flow-cell furnished with two platinum electrodes polarized at 100 mV. The sample solution after being irradiated is inserted into a pure water stream. It then merges with an in situ mixed solution containing potassium iodide in sulphuric acid. The calibration graph was linear over the range 0.2–8.0 mg l −1 metronidazole; the 3 σ limit of detection was 0.008 mg l −1 ; the relative standard deviation was 0.6% (for 4 mg l −1 n = 13) and the sample throughput 50 h −1 . The influence of foreign compounds is slight and the method is …
Photodegradation of Toluene, m-Xylene, and n-Butyl Acetate and Their Mixtures over TiO2 Catalyst on Glass Fibers
2012
The abatement of typical paint solvent compounds as individuals and in mixtures was carried out in an annular TiO2 supported reactor, for concentrations up to 900 mg C m–3. Two different fiberglass supports were compared, and the catalyst supported over a fiber mat showed better performance, with a lower pressure drop (>35% of reduction) and a slightly higher removal efficiency (about 2%) than that supported over glass wool. For every target compound in the whole range of relative humidity studied (4–75%), the photocatalytic activity increased with the air water content. The removal of the compounds in the binary and ternary mixtures was depressed, even >90% for toluene, compared with indiv…
Zn,Al hydrotalcites calcined at different temperatures: Preparation, characterization and photocatalytic activity in gas–solid regime
2011
Abstract Layered double hydroxides (LDH) containing zinc and aluminium within the brucite-like layers and carbonate as the interlayer anion have been used as precursors for the preparation of mixed metal oxides by calcination. Zinc oxide and the ZnAl 2 O 4 spinel were formed with different degree of crystallinity depending of two parameters, i.e., the Zn 2+ /Al 3+ molar ratio and the calcination temperature (500–800 °C) of the LDH precursor. A pure spinel phase was obtained to remove ZnO upon a basic post-treatment in NaOH solution of the samples calcined at 800 °C. All the samples were tested for the photodegradation of 2-propanol in gas–solid regime. All the samples resulted active as het…
Neutral solar photo-Fenton degradation of 4-nitrophenol on iron-enriched hybrid montmorillonite-alginate beads (Fe-MABs)
2014
Hybrid montmorillonite-alginate beads (MABs) were prepared by the ion-gelation method from alginate and montmorillonite clay suspension dropped in a calcium chloride solution. Similarly, iron-enriched beads (Fe-MABs) were prepared using iron-exchanged montmorillonite. All beads were characterized by atomic absorption and Fourier-transform infrared spectroscopy. The efficiency of Fe-MABs as catalysts for the solar photo-Fenton performed at initial pH = 7.0 was evaluated by varying the catalyst amount and hydrogen peroxide concentration, and monitoring the removal of 4-nitrophenol (4-NP) at initial concentration of 10 ppm. A kinetic analysis showed that the removal of 4-NP by Fe-MABs followed…
Novel Lipophilic Lanthanide Bis-Phthalocyanines Functionalized by Pentadecylphenoxy Groups: Synthesis, Characterization and UV-Photostability
2012
Novel sandwich-type phthalocyanines containing a rare earth metal core (Pr, Nd, Eu-Lu) and macrocycles peripherally substituted by pentadecylphenoxy groups were synthesized using a cardanol-based phthalonitrile precursor and the respective lanthanide acetate. Additionally, the metal free-base analog compound was studied for comparison. The purified reaction products were all found to be thick and viscous substances at room temperature, showing liquid crystalline behavior with a distinct increase in fluidity at ca. 40 ° C. The complexes are readily soluble in chloroalkyl solvents and dissolve fairly well in DMF with some tendency to form aggregates. Besides they are strongly hydrophobic and …
Photocatalytic membrane reactors for degradation of organic pollutants in water
2001
Abstract Different flowsheets (batch and continuous) of photocatalytic membrane reactors, to be used for degradation of organic pollutants present in water, together to some experimental results, are reported. 4-Nitrophenol (4NP) was used as a probe polluting agent and titanium dioxide in suspension was the catalyst. The photodegradation tests in the batch system were carried out without membrane changing the characteristic variables of the process (light intensity, TiO 2 concentration, 4NP concentration, O 2 concentration, pH) to find their optimum values. The batch system consisted of a water jacket thermostatted and stirred beaker irradiated from above with a UV–Vis lamp (light intensity…