Search results for "chemistry [Water]"

Photocatalytic green synthesis of piperonal in aqueous TiO2 suspension

2014

Abstract Piperonal (heliotropine or 3,4-methylenedioxybenzaldehyde) has been synthesized by oxidizing piperonyl alcohol in aqueous UV-irradiated TiO2 suspensions. This compound was identified by GC–MS chromatography, 1H NMR and melting point determination. The other products of the photoprocess were 1,3-bis(3,4-(methylenedioxy)benzyl) ether (found in traces) and CO2, derived from the parallel pathway of photo-mineralization. Commercial and home-prepared TiO2 samples have been tested and the best selectivity (ca. 35%) was obtained by using the home-prepared ones. The reported green process allows to obtain an added value product (piperonal), upon partial oxidation of a cheap reagent.

Catalytic reduction of nitrates and nitrites in water solution on pumice-supported Pd–Cu catalysts

2000

Abstract Two series of pumice-supported palladium and palladium–copper catalysts, prepared by impregnation with different palladium and copper precursors, were tested for the hydrogenation of aqueous nitrate and nitrite solutions. Measurements were performed in a stirred tank reactor, operating in batch conditions, in buffered water solution at atmospheric pressure and at 293 K. The activities of the catalysts were calculated in terms of nitrate and/or nitrite removal. With the monometallic Pd/pumice, the reduction of nitrite is highly selective; only 0.2% of the initial nitrite content is converted to ammonium ions. The activity in terms of turn over frequency (TOF) is higher as compared t…

ZrO2SiO2 mixed oxides: surface aspects, photophysical properties and photoreactivity for 4-nitrophenol oxidation in aqueous phase

1996

Abstract Mixed oxides of ZrO2 and SiO2 were synthesized by a sol-gel technique by using zirconyl chloride and commercial silica gel as starting materials. The paper reports some surface features of the powders and the photoreactivity results obtained in the oxidation of 4-nitrophenol in aqueous suspensions of powdered photocatalyst. The optical characterization of the suspension was also performed by measuring the photon flows reflected and absorbed by the reacting system. The photoactivity exhibited by the ZrO2SiO2 samples is very scarce especially if compared with that shown by a TiO2 sample tested at equal experimental conditions. The low photoreactivity can be justified on the basis of…

Synthetic routes to novel fluorogenic pyronins and silicon analogs with far-red spectral properties and enhanced aqueous stability

2020

Fluorogenic detection of reactive (bio)analytes is often achieved with "smart" probes, whose activation mechanism causes the release of aniline-based fluorophores. Indeed, the protection-deprotection of their primary amino is the simplest way to induce dramatic and valuable changes in spectral features of the fluorogenic reporter. In this context, and due to their small size and intrinsic hydrophilicity, we focused on pyronin dyes and related heteroatom analogs (i.e., formal derivatives of 3-imino-3H-xanthen-6-amine and its silicon analog) for their use as optically tunable aniline-based fluorophores. To overcome some severe limitations associated with the use of such fluorogenic scaffolds …

The influence of ultrasound on the RuI3-catalyzed oxidation of phenol: Catalyst study and experimental design

2009

Abstract The influence of ultrasound at 24 kHz on the heterogeneous aqueous oxidation of phenol over RuI3 with hydrogen peroxide (H2O2) was studied isothermally at 298 K. Effect of ultrasound irradiation on catalytic properties and performance of RuI3 has been studied in details by means of scanning electron microscopy (SEM), X-ray powder diffraction (XRD), dispersion analyzer and a surface analyzer. Turn over frequency of the catalyst was also calculated. In this work, experimental design methodology was applied to optimize the degradation of phenol in aqueous solution, while minimizing an excessive consumption of chemical reagents. The independent variables considered were the catalyst lo…

Arsenic(III) Removal at Low Concentrations by Biosorption usingPhanerochaete chrysosporiumPellets

2013

As(III) removal from dilute aqueous solutions by biosorption onto pellets of the white rot fungus Phanerochaete chrysosporium was investigated. The As(III) uptake capacity was evaluated at low initial concentrations (0.2–1 mg/L) which revealed that the P. chrysosporium pellets were only slightly less efficient than the well studied adsorbent granular ferric hydroxide. Moreover, its performance was much more superior compared to anaerobic granular sludge, another cheaply available bacterial biosorbent. In the studied pH (5–9) and biomass concentration (0.25–1.5 g/L wet weight basis) ranges, no large differences in As(III) removal efficiency were observed. The influence of different ions, com…

Fixed‐Bed Removal of Free and Complexed Ni from Synthetic and Industrial Aqueous Solutions

2008

Abstract This paper evaluates the application of several biosorbents for Ni removal from aqueous solutions in the absence and in the presence of EDTA. Fixed bed experiments were performed (Ni influent concentration, 2 mg dm−3; EDTA doses, 0, 5, and 10 mg dm−3; pH=7) to study the process feasibility as refining after conventional physicochemical treatment. In absence of EDTA, uptake capacity followed the order peat > Posidonia oceanica > chitosan > chitin ≫ Scharlau AC. Maximum uptakes of 8.95 mg g−1 and 5.10 mg g−1 were found for peat and Posidonia oceanica, respectively. In the presence of EDTA, removal capacity decreased for all biosorbents; Ni was detected in the effluent from the beginn…

Halogen-containing BODIPY derivatives for photodynamic therapy

2019

Abstract Two iodinated (1 and 2) and two brominated (3 and 4) BODIPY-based photosensitizers are prepared and characterized using slightly modified synthetic procedures previously described. 1–4 present intense absorption bands in the 510–540 nm interval and very weak emissions due to the presence of halogen atoms in their structure. Irradiation of aqueous solutions of 1–4 with visible light (wavelength > 475 nm) induce the generation of singlet oxygen with quantum yields of ca. 0.62–0.66 for the photosensitizers containing iodine atoms (1 and 2) and of ca. 0.16–0.21 for the brominated counterparts (3 and 4). In vitro studies carried out with HeLa, SCC-13 and HaCaT cell lines and the four ph…

Subduction‐Induced Back‐Arc Extension Versus Far‐Field Stretching: Contrasting Modes for Continental Marginal Break‐Up

2021

Special Issue “Smart Urban Lighting Systems”

2020

The design and operation of multifunctional infrastructures for public lighting as well as their impact on the urban environment and citizens’ life is today of great interest. The cost of energy for public lighting is often an issue for the budget of municipalities. Furthermore, researchers’ and designers’ attention is increasingly focused on aspects of public lighting not directly valuable through economic factors. Starting from the “quality” of the light environment, looking at citizens’ visual comfort, the light has to be considered as an instrument to improve the urban context and objects therein (including buildings). Indeed, urban degradation (lack of infrastructures, maintenance, ser…