Original calcium alginate beads with porous structure and high adsorption surface are proposed. The beads were synthesized using sodium alginate in the presence of sodium dodecyl sulfate as foaming agent, NaCl as porogen agent and CaCl 2 as cross-linker. They were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and Brunauer-Emmett-Teller method. The adsorption capacity of beads was tested with methylene blue (MB). The data show that the adsorption efficiency increases with the amount of beads, decreases with pollutant concentration, and is maximal at pH = 9. The adsorption is fast in the first 3 hours, and slows down thereafter. The kinetic results show that the adsorption of MB on alginate porous beads obeys the Langmuir model. A scheme of MB adsorption taking into account the ionic interactions with calcium alginate beads has been proposed.
The synthesis of small particles through the interaction between chitosan (CS) and sodium lauryl ether sulfate (SLES) was studied. Depending on working condition, microparticles at atmospheric pressure and ultrafine particles at high pressure have been obtained. At atmospheric pressure, the microparticles were formed instantaneously when the CS solution was dripped into the SLES aqueous solution. To obtain ultrafine particles, the surfactant solution in contact with high pressure carbon dioxide was sprayed into chitosan solution. Fourier Transform Infrared Spectroscopy proves the interaction between the sulfate groups of SLES and the amino groups of CS. The Scanning Electron Microscopy reveals that the microparticles are quasi-spherical, but some of them can take the form of pellets depending on preparation conditions. The obtained microparticles were successfully used to uptake Cu(II) ions from aqueous solutions. The adsorption of Cu(II) depends on pH being maximum at pH 5 5.5. The kinetic experiments demonstrated that Cu(II) adsorption onto CS/SLES microparticles obeys the Langmuir model.
& Contemporary population shows a great tendency to consume food capable of generating an intense feeling. Each food contains substances that generate sensations of taste and aroma. Beer is a food with specific flavor, which is mostly appreciated if, is fresh. It is considered that the beer flavor is dependent on the nature and the concentration of carbonyl compounds that are formed during the fermentation of the malt; the most important is the diacetyl (butandione). Carbonyl compounds in beer can be analyzed after a selective preconcentration. The methods of partial isolation as head space method and membrane process are designed to provide only qualitative information. For quantitative determination of carbonyl compounds present in beer, full extraction methods are used. The gas chromatographic separation method is used in order to study the mixtures obtained after the isolation of carbonyl compounds in beer. When the electron capture detector is used, only vicinal diketones can be identified and dosed in beer. The mixtures of 2,4-dinitrophenylhidrazone precipitates can be analyzed by spectrophotometric study or by liquid chromatographic separation. The analytical focus is the identification and dosing of the butandione and pentandione that have a key role in generating the sensation of flavor of beer. Brewers need rapidly and accurate information on the concentration of diacetyl in beer. In order to help the process, a neural sensor was proposed. It is used to determine the intensity of flavor sensation and it should provide the possibility of differentiating the products that come from different beer suppliers.
Mixtures of small quantities of carbonyl compounds are presents in foods, concerning sensorial qualities. The inferior carbonyl compounds (C2-C4, boiling point <100°C) – mono and dicarbonyl – can be identified and measured their concentrations, after a separation by distillation on the water bath. They are transferred in a strongly acid solution of 2.4-dinitrophenylhidrazine (2.4-DNPH), generating a mixture of insoluble 2.4-dinitrophenylhidrazones (2.4-DNPH-ones). The 2.4-DNPH-ones are organic compounds with weak polarity, solids, crystallized, yellows and water insoluble, soluble in organic solvents. The mixture of 2.4dinitrophenylhidrazones may be separated by liquid chromatography, using the reverse phase mechanism [1-3]. This paper contains experimental and theoretical considerations to the means of separation through liquid chromatography of two synthetically and a natural mixtures that contain 2.4-DNPH-ones provided by inferior carbonyl compounds; to obtain conclude results, in the synthetically mixtures was introduce and 2.4-DNPH-ones provided by carbonyl compounds having three (acetone and propanal) and four (isobutyl aldehyde) atoms of carbon.
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