Search results for "Adsorption"
showing 10 items of 1326 documents
Photoassisted Oxidation of the Recalcitrant Cyanuric Acid Substrate in Aqueous ZnO Suspensions
2007
The photoassisted oxidative transformation of the highly recalcitrant cyanuric acid was examined in the liquid−solid regime at pH 3 and natural pH 7.5 under UV irradiation in oxygen- and ozone-saturated ZnO suspensions using ZnO as a photomediator. Loss of cyanuric acid was assayed by HPLC UV absorption spectroscopy, whereas intermediates and final products were determined by HPLC ion chromatography (IC), by MS techniques using an electrospray ionization mass spectrometer operated in the negative-ion mode, and by FT-IR spectroscopy. Final reaction products were CO2 gas and NO3- ions. The measure of nitrate in solution quantified the degree of mineralization of the substrate; its concentrati…
Photocatalytic oxidation of phenol on TiO2 powders. A Fourier transform infrared study
1994
Abstract In the present paper a detailed investigation of a well known photoreaction, i.e. phenol photodegradation in the presence of TiO2, has been carried out. The Fourier transform infrared (FT-IR) technique has been used to characterize the catalyst surface and to follow the photoprocess by “in situ” measurements in a gas—solid regime, simulating the aqueous liquid—solid regime in which this photodegradation reaction has been usually carried out. The influence on the photoprocess of the surface hydroxylation of the catalyst has been investigated and the presence of some reaction intermediates has been revealed by FT-IR. The experimental results have demonstrated that the chosen gas—soli…
Influence of the dissolution of MnS inclusions under free corrosion and potentiostatic conditions on the composition of passive films and the electro…
2006
Abstract The influence of the dissolution of MnS inclusions at the OCP value and 400 mV versus SCE on the chemical composition of passive films and the electrochemical behaviour of resulfurized austenitic stainless steel was studied in 1 M NaClO 4 , pH 3, solution using SIMS, XPS, electrochemical impedance spectroscopy and the electrochemical microcell technique. The electrochemical dissolution (at 400 mV versus SCE) of inclusions occurred uniformly along the interface and this process was almost complete after 25 min immersion. A small amount of sulfur was detected on the matrix that exhibited a wide passive range. By contrast, the dissolution process under free corrosion was not uniform a…
Structure Sensitivity of 2-Methyl-3-butyn-2-ol Hydrogenation on Pd: Computational and Experimental Modeling
2014
In the frame of DFT paradigms, the adsorption of 2-methyl-3-butyn-2-ol (MBY) and 2-methyl-3-buten-2-ol (MBE) on a Pd-30 cluster, including both {100} and {111} faces, was studied along with the pathways involved in the hydrogenation, taking place on plane and low coordination (corner/edge) sites of given MBY/Pd-30 and MBE/Pd-30 surface configurations. The calculated energetics, further validated by gas-phase and water-assisted gas-phase MBY and MBE hydrogenation, performed on well-defined size and shape-controlled Pd nanoparticles supported on SiO2, were able to explain the origin of the structure sensitivity and the high selectivity characterizing the title reaction when occurring in aqueo…
A biocompatible ZnNa2-based metal–organic framework with high ibuprofen, nitric oxide and metal uptake capacity
2020
Metal organic frameworks (MOFs) have received significant attention in recent years in the areas of biomedical and environmental applications. Among them, mixed metal MOFs, although promising, are relatively few in number in comparison with their homometallic analogues. The employment of benzophenone-4,4′-dicarboxylic acid (bphdcH2) in mixed metal MOF chemistry provided access to a 3D MOF, [Na2Zn(bphdc)2(DMF)2]n (NUIG1). NUIG1 displays a new topology and is a rare example of a mixed metal MOF based on 1D rod secondary building units. UV-vis, HPLC, TGA, XRPD, solid state NMR and computational studies indicated that NUIG1 exhibits an exceptionally high Ibuprofen (Ibu) and nitric oxide adsorpt…
Molecular simulation studies of water physisorption in zeolites
2006
We report a series of Grand Canonical Monte Carlo simulations of water adsorption in NaY and NaX faujasite, as well as in silicalite-1. Computed adsorption isotherms and heats of adsorption were in good agreement with the available experiments. The existence of cyclic water hexamers in NaX located in the 12-ring windows, recently disclosed by neutron diffraction experiments (Hunger et al., J. Phys. Chem. B, 2006, 110, 342-353) was reproduced in our simulations. Interestingly enough, such cyclic hexamer clusters were also observed in the case of NaY, in which no stabilizing cation is present in the 12-ring window. We also report cation redistribution upon water adsorption for sodium faujasit…
Preparation of nanostructures composed of dextran sulfate/ruthenium nanoparticles and their interaction with phospholipid monolayers at a liquid–liqu…
2007
Abstract Nanostructures composed of dextran sulfate (DS)/ruthenium (Ru) nanoparticles (NPs) adsorbed on phospholipid monolayers at a liquid–liquid interface were prepared and characterized electrochemically in relation to their potential use in drug delivery systems. First, positively charged Ru NPs were prepared, and then negatively charged DS was adsorbed on the surface of the NPs, thus forming well-defined and organized structures, as observed under the transmission electron microscope, which are referred to composite nanoclusters. The lipid monolayers were formed by depositing either 1-palmitoyl-2-oleoyl- sn -glycero-3-phosphatidylcholine or 1-palmitoyl-2-oleoyl- sn -glycero-3-phospho- …
Use of SPME extraction to determine organophosphorus pesticides adsorption phenomena in water and soil matrices
2005
Solid-phase micro extraction (SPME) coupled with GC enables rapid and simple analysis of organophosphorus pesticides in a range of complex matrices. Investigations were made into the extraction efficiencies from water of six organophosphorus insecticides (methamidophos, omethoate, dimethoate, parathion methyl, malathion, and parathion ethyl) showing a wide range of polarities. Three SPME fibres coated with different stationary phases, polydimethylsiloxane, polyacrylate, and carbowax-divinylbenzene (CW-DVB), were investigated. Water was spiked with the pesticides at concentrations from 1 to 0.01 µg mL-1, and the solutions used for optimization of the procedure. The CW-DVB fibre, with a 65 µm…
Photocatalytic degradation of dyes by using a membrane reactor
2004
Abstract Dyes are organic compounds used in textile, food and drug industries, and their abatement represents one of the main problems in the treatment processes because generally they are very stable toxic compounds. In this work, two commercial azo-dyes, i.e. Congo Red (C32H22N6Na2O6S2) and Patent Blue (C27H31N2NaO6S2), in aqueous solution were degraded in a photocatalytic membrane reactor by using TiO2 Degussa P25 as the catalyst. Different system configurations and irradiating sources were studied, and the influence of some operational parameters such as the pressure in the membrane cell and the initial concentration of the substrates was determined. A comparison between suspended and e…
Photocatalytic Oxidation of Cyanides in Aqueous Titanium Dioxide Suspensions
1997
The photocatalytic oxidation of free cyanides in aqueous suspensions containing polycrystalline TiO2(anatase) powders irradiated in the near-UV region has been investigated. The rate of cyanide photooxidation has been studied by varying the following operative parameters: (i) initial cyanide concentration; (ii) catalyst concentration; (iii) initial pH; (iv) power of irradiation; and (v) chloride ion concentration in the reacting mixture. Under the used experimental conditions the photoreaction proceeded at a measurable rate until the complete disappearance of cyanides. The kinetics of cyanide photooxidation is affected by the catalyst concentration, the chloride ion concentration, and the p…