Search results for " Chemical Engineering"
showing 10 items of 2965 documents
Facilitated SLM extraction of peptides with D2EHPA as a carrier
2004
Abstract The extraction of short peptides through a supported liquid membrane containing di-2-(ethylhexyl)phosphoric acid (D2EHPA) as a carrier was investigated. The extraction was carried out from the aqueous donor phase with pH 3 to amore acidic acceptor phase. The proton gradient between the donor and the acceptor phase was the main driving force of the mass transfer in this system. The influence of various parameters such as diluent of the carrier, pH of the donor and acceptor phase, peptide structure and concentration on the extraction efficiency was presented.
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- …
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…
Screening and authentication of herbal formulations based on microextraction-assisted voltammetry of microparticles
2015
A simple solid state electrochemical methodology for screening and authentication of herbal formulations is described. The proposed method is based on the recording of the voltammetric response, in contact with aqueous buffers, of microparticulate films of antioxidant compounds resulting from micro-extraction of dried herbal samples with ethanol or acetone. The obtained voltammetric responses led us to differentiate between diverse active components upon application of bivariate and multivariate chemometric techniques. Resolution of herbal preparations containing two or more components is possible when well-separated voltammetric signals are recorded. In favorable cases, such characteristic…
Influence of Phase Modifiers on the Degradation of Tri-n-octylamine/dodecane Extracting Mixture by an Acidic Solution of Vanadium (V)
2012
The kinetics of degradation of a mixture of tri-n-octylamine (extractant) and various alcoholic phase modifiers in n-dodecane in contact with acidic aqueous sulfate solutions containing vanadium (V) has been investigated. The nature of the modifier influences the kinetics of degradation and an improvement of the resistance against the chemical degradation is obtained when secondary alcohol (2-nonanol) or tertiary alcohols such as 9-octyl-9-heptadecanol are used as phase modifiers instead of 1-tridecanol. For instance, the kinetic constant of degradation is divided by one half when 9-octyl-9-heptadecanol is used as phase modifier instead of 1-tridecanol. On the contrary, the alcohols contain…
Reactor model for fast reactions in the micro-bubble column and validation
2007
A simple reactor model for predicting conversions in a micro-bubble column is described. It assumes fast reactions so that the gaseous component is readily consumed at the gas-liquid interface. Then, gas-liquid mass transfer becomes determining. As input parameters for the model, the hydrodynamics, specific interfacial area, and mass transport need to be described. Two fast model reactions, the catalytic oxidation of butyraldehyde and the absorption of CO2 in aqueous NaOH, show the applicability of the model but also its limits. The model was used for predicting reaction performance in dependence of operating conditions, in particular to get maximum conversion with the antagonistic paramete…
Photocatalytic oxidation of toluene on irradiated TiO2: comparison of degradation performance in humidified air, in water and in water containing a z…
2003
Photocatalytic degradation of toluene was carried out both in gas–solid and in liquid–solid regime by using polycrystalline samples of TiO2 Merck and TiO2 Degussa P25. For the gas–solid regime two types of continuous photoreactor were used, a fixed bed one of cylindrical shape and a Carberry type photoreactor, both irradiated by near-UV light. The inlet reacting mixture consisted of air containing toluene and water vapours. The influence of the gas flow rate and the presence of water vapour on the photocatalytic process was investigated. CO2 and benzaldehyde were the toluene degradation products detected in the gas phase by using TiO2 Merck. In the presence of water vapour this catalyst exh…
Characterization of Zirconium Phosphate/Polycation Thin Films Grown by Sequential Adsorption Reactions
1997
Monolayer and multilayer thin films consisting of anionic α-zirconium phosphate (α-ZrP) sheets and polycations (poly(allylamine hydrochloride) (PAH), cytochrome c) were characterized by transmission electron microscopy (TEM), ellipsometry, UV−visible absorbance spectroscopy, reflectance FT-IR, XPS, and X-ray diffraction. Titration and powder X-ray diffraction experiments confirm that exfoliation of α-ZrP begins to occur when enough tetra(n-butylammonium) hydroxide (TBA+OH-) has been added to exceed single-layer packing of TBA+ ions (x ≈ 0.50) in the intercalation compound Zr(HPO4)2-x(TBA+PO4-)x·nH2O. The identical contrast of many sheets in TEM micrographs suggests that the suspension is un…
Partial molar volumes of cobalt(II) chloride in ethanol + water at 298.15 K
1996
Densities of ethanol + water + cobalt(II) chloride mixtures have been measured with an oscillating-tube densimeter over a large range of concentrations of salt, at 298.15 K. From these densities, apparent molar volumes of the electrolyte in these mixtures have been calculated, and partial molar volumes at infinite dilution have been evaluated, at different concentrations of alcohol in the solvent.
CO2 capture from biogas: Absorbent selection
2013
The development of proper biogas upgrading technology offers a viable means to utilize biogas in conventional power systems. In this paper, various molecular and ionic solvent systems were evaluated for CO2 removal from biogas in a loop reactor system. The performance of amine solutions, ionic liquids and their mixtures, amino acid salts and solutions blended with piperazine was compared in terms of their CO2 loading capacity. The experimental results revealed that addition of small amounts of piperazine can increase on average by 30 vol% the efficiency of above-mentioned solutions. The CO2 capturing capacity achieved for the most promising solvents was in the range of 50–60 L CO2/L absorbe…