Search results for "Distillation"

Adsorption of chlorinated volatile organic compounds on hydrophobic faujasite: correlation between the thermodynamic and kinetic properties and the p…

1998

This work deals with a thermodynamic and kinetic study of the adsorption of single volatile organic compounds (VOCs) (dichloromethane (DCM), 1,2-dichloroethane (DCA), trichloroethene (TCE) and tetrachloroethene (PCE)) on a dealuminated faujasite Y by simultaneous measurements of the adsorbed amounts, adsorption heats and diffusivities. The type V isotherms and the weak values of derivative enthalpies allowed us to predict that the competitive adsorption of their mixture would be similar to a distillation. This prediction was verified experimentally: the breakthrough curves of VOC mixtures showed that the adsorbate with the higher boiling point displaced the adsorbate with the lower boiling …

Effects of solvent-free microwave extraction on the chemical composition of essential oil of Calamintha nepeta (L.) Savi compared with the convention…

2008

The essential oil of Calamintha nepeta has been obtained by solvent-free microwave extraction (SFME) and by classical hydrodistillation (HD). A comparative qualitative-quantitative study on the composition of the oils was carried out. A total of 38 compounds, constituting 97.6% of the oil, were identified in the oil obtained by SFME, whereas 46 compounds, representing 95.4% of the oil, were characterized in the HD oil. SFME-distilled oil is richer in lightly oxygenated monoterpenes (LOM) than HD oil. It also has a higher amount of sesquiterpenes and a lower quantity of hydrocarbon monoterpenes. HD oil seems to be affected by chemical changes more than SFME oil.

Determination of fluoride after direct separation from acid medium by collection of its volatile compounds

1989

A method is proposed for determination of fluoride by separation in acid medium followed by ion-selective electrode measurement. The separation is done at temperatures up to 200 °C, without any previous treatment of the sample, in a PTFE reactor designed to ensure the complete absorption of volatile fluoride compounds. The distillation variables (temperature, time and acid concentration) have been optimized and the interference of other various species in the separation step has been studied. The method has been applied to geological samples. The results obtained are statistically satisfactory.

Determination of fluoride in rocks, soils, and fluoride-bearing minerals by separation using direct distillation in sulfuric acid medium and spectrop…

1989

Abstract An analytical method for fluoride determination in geological samples is proposed. It is based on a previous fluoride separation by distillation with a Teflon reactor. The variables that influence distillation quantitation (temperature, time, and acid concentration) are optimized. The influence of some species on fluoride recovery during distillation are studied, and conditions to avoid this influence are suggested. Fluoride determination is carried out by means of a spectrophotometric method [La(III)-F−-Alizarin complexone system] (N. T. Crosby, A. L. Dennis, and J. G. Stevens, Analyst (London), 1968, 93, 643–652). The method is applied to the analysis of soils, rocks, and fluorid…

Answer to the Letter to the Editor by Dr. Sanjay Pralhad Shirsat concerning the article “Separation of isobutyl alcohol and isobutyl acetate by extra…

2015

Efficient synthesis of 2-bromo-1-[18F]fluoroethane and its application in the automated preparation of 18F-fluoroethylated compounds

2002

An efficient synthesis of 2-bromo-1-[18F]fluoroethane from commercially available 1,2-dibromoethane and its integration into an automated preparation device was developed for the routine synthesis of 18F-fluoroethylated compounds. The 1,2-dibromoethane was reacted with the [18F]fluoride/Kryptofix 2.2.2./carbonate complex in acetonitrile at 70 degrees C for 3 min resulting in 60-70% radiochemical yields. The crude reaction mixture was diluted with water, loaded on a LiChrolute EN-cartridge, eluted with acetonitrile and passed through an AluminaB-cartridge. This method provides 2-bromo-1-[18F]fluoroethane with 98% radiochemical purity and <0.1 micromol of 1,2-dibromoethane within 10 min, thus…

Phase Equilibria Involved in the Extractive Distillation of Cyclohexane + Cyclohexene Using Diethyl Carbonate as an Entrainer

2011

Isobaric vapor–liquid equilibrium (VLE) data at 100 kPa have been measured for the ternary system cyclohexane + cyclohexene + diethyl carbonate and two constituent binary systems: cyclohexane + diethyl carbonate and cyclohexene + diethyl carbonate. Both binary systems show moderate positive deviations from ideal behavior and do not present an azeotrope. The VLE data have been correlated by the Wilson, universal quasichemical activity coefficient (UNIQUAC), and nonrandom two-liquid (NRTL) equations. The ternary system does not present an azeotrope and is well-estimated from binary interaction parameters. A prediction with the universal functional activity coefficient (UNIFAC)-Dortmund method…

The bactericidal effect of extracts from Humulus lupulus L Marynka variety on selected bacteria

2020

The aim of the research was to obtain extracts of Humulus lupulus L hop cones of the Marynka variety and to evaluate their antibacterial properties against three strains of gram-negative bacteria (Escherichia coli ATCC 10536, E. coli IPS and Pseudomonas aeruginosa ATCC 27853) and against two strains of gram-positive bacteria (Enterococcus hirae ATCC 10541 and Bacillus cereus ATCC 12826). The research material consisted of dried Marynka variety hop cones, from which extracts in the form essential oil (EO), infusion and decoction were obtained. EO was obtained in the process of hydrodistillation. The antibacterial activity of the extracts was evaluated by the plate-cylinder diffusion method a…

Characterization of commercial polymeric membranes for membrane distillation processes

2011

A no-carrier-added 72Se/72As radionuclide generator based on distillation

2004

Abstract Arsenic-72 is a positron emitting isotope with promising properties for syntheses of 72As-labelled radiopharmaceuticals for future application in positron emission tomography. This work describes the radiochemical separation of no-carrier-added 72Se from cyclotron irradiated germanium targets and the development of a 72Se/72As radionuclide generator, avoiding the addition of any selenium carrier. Using a vertical quartz tube device, no-carrier-added 72As is nearly quantitatively released from various chloride salt solutions containing 72Se within 10 min at a temperature of 100 °C in an HCl gas flow. The kinetics of the 72Se/72As isotope generator has been studied in relation to tem…