Erol Ayranci

Antioxidant activities of rosemary (Rosmarinus Officinalis L.) extract, blackseed (Nigella sativa L.) essential oil, carnosic acid, rosmarinic acid and sesamol

Antioxidant activities of three pure compounds: carnosic acid, rosmarinic acid and sesamol, as well as two plant extracts: rosemary extract and blackseed essential oil, were examined by applying DPPH and ABTS(+) radical-scavenging assays and the ferric thiocyanate test. All three test methods proved that rosemary extract had a higher antioxidant activity than blackseed essential oil. The order of antioxidant activity of pure compounds showed variations in different tests. This was attributed to structural factors of individual compounds. Phenolic contents of blackseed essential oil and rosemary extract were also determined. Rosemary extract was found to have a higher phenolic content than blackseed essential oil. This fact was utilised in explaining the higher antioxidant activity of rosemary extract.

A method for the measurement of the oxygen permeability and the development of edible films to reduce the rate of oxidative reactions in fresh foods

Abstract A method involving the flow of O 2 and N 2 gasses from the two sides of an edible film coupled with a simple wet chemical analysis at the end, was developed to measure the oxygen permeability of edible films. The proposed method was employed to determine the oxygen permeability of methyl cellulose (MC)-based edible films of various composition with the aim of finding the optimum composition for minimising oxidative degradation of foods. The effects of the presence of stearic acid (SA), ascorbic acid (AA) and citric acid (CA), in varying amounts in the film composition, on the oxygen permeability (OP) of MC based edible films were examined. The OP increased with increasing SA content of the film and decreased with the inclusion of AA or CA in the film composition. The films, with various compositions and with the measured oxygen permeabilities, were then applied to mushrooms ( Agaricus bisporus ) and cauliflower ( Brassica botrytis ). It was found, from the analysis of these coated foods, that the coatings containing antioxidants slowed the browning reactions and reduced the vitamin C loss in both foods, the effects being greater in cauliflower. Moreover, the moisture loss of coated foods was less than that of uncoated.

Viscosities and apparent molar volumes of some amino acids in water and in 6M guanidine hydrochloride at 25°C

Apparent molar volumes and viscosity B- and D- coefficients of amino acids glycine, valine, proline, serine and arginine have been determined in water and in aqueous 6M guanidine hydrochloride (GuHCl) solution at 25°C. Transfer volumes and transfer viscosity B-coefficients were evaluated for the amino acids studied in going from water to 6M GuHCl. These transfer properties which were all positive were interpreted in terms of strong interactions of GuHCl molecules with the charged centers of amino acid molecules. A comparison of results obtained in this work for GuHCl and those obtained from literature for urea has shown that GuHCl has stronger interactions than urea with amino acids. This finding explained the previous experimental observations on GuHCl being a stronger denaturing agent than urea for proteins.

Removal of phenol, phenoxide and chlorophenols from waste-waters by adsorption and electrosorption at high-area carbon felt electrodes

The adsorption and electrosorption behavior of phenol, sodium phenoxide, 1-, 2- and 3-chlorophenol and 2,6-dichlorophenol were studied at high-area carbon-felt (C-felt) electrodes by in situ UV spectroscopy in relation to development of procedures for purification of industrial waste-waters. Spectral characteristics and calibration parameters were evaluated for the phenolic species studied. It was demonstrated that the initial concentrations (about 1 mM) of these compounds can be reduced by a factor of 3 or more from waste-waters by adsorption at the C-felt already at a level of small percentage coverage on the surface (<10%). It was also found that the rate of adsorption of these compounds can be enhanced by polarizing the C-felt electrode, especially in the presence of an inert supporting electrolyte such as Na2SO4. Suppression of hydrolysis of phenoxide in the presence of NaOH, associated with ionization of phenol, diminishes the adsorption of phenoxide probably due to its hydration, causing it to be more hydrophilic than phenol. However, in situ analysis of aqueous phenoxide solution, without NaOH, as a mixture of phenoxide anion and phenol, the hydrolysis product, is made possible by the experimental setup and the software used, and shows that both species were adsorbed and electrosorbed at the C-felt. Among the three monochlorophenols, 4-chlorophenol exhibited the lowest rate of adsorption with 2-chlorophenol having the highest according to a kinetically first-order treatment of the adsorption data, while 2,6-dichlorophenol was adsorbed at an intermediate rate.

Adsorption and electrosorption at high-area carbon-felt electrodes for waste-water purification: Systems evaluation with inorganic, S-containing anions

Removal or modification of pollutants in industrial or mineral-processing wastewaters by electrosorption at high specific-area carbon materials (felts or powders) has been envisaged in previous work. Electrodes based on high-area substrates behave as quasi-three-dimensional interfaces, thus minimizing diffusion limitation in removal of trace impurities in waters. In the present paper, processes of open-circuit adsorption and electrosorption at electrochemically polarized, high-area C-felt electrode modules are quantitatively examined by means of in situ electrical resistance and optical absorbance measurements made in appropriately designed cells. The effectiveness of the procedures is examined by application to the adsorption and electrosorption of a series of related S-containing anions and the kinetics of their adsorption at the C-felt electrodes have also been evaluated in two cases. The adsorbability of such impurity ions is related to their hydration properties in water.

The effect of fatty acid content on water vapour and carbon dioxide transmissions of cellulose-based edible films

Abstract Water vapour and CO 2 transmissions of methyl cellulose (MC)-based edible films with varying amounts of the fatty acids, stearic acid (SA), palmitic acid (PA) and lauric acid (LA) were studied and the results were compared with those obtained for a film without added fatty acid. Water vapour transmission rate (WVTR), water vapour permeance (WVPN) and water vapour permeability (WVP) values of films were determined by measuring the amounts of water vapour transmitted through the film and then adsorbed on anhydrous CaCl 2 as a function of time, using a static method. A recently-developed static method which utilises ascarite to adsorb carbon dioxide transmitted through the film was employed for the determination of carbon dioxide transmission rate (CO 2 TR), carbon dioxide permeance (CO 2 PN) and carbon dioxide permeability (CO 2 P) of films. Among the three fatty acids studied, SA was found to be the most effective in decreasing both the water vapour and the CO 2 transmissions of films. In general, it was observed that WVTR, WVPN and WVP values of films decreased with increasing fatty acid content in the film composition. CO 2 transmission parameters also decreased with increasing SA and PA contents but increased with increasing LA content of films.

Attachment of benzo-crown ethers onto activated carbon cloth to enhance the removal of chromium, cobalt and nickel ions from aqueous solutions by adsorption.

This work consists of two stages. In the first stage, the adsorption of some monobenzo- and dibenzo-crown ethers onto activated carbon cloth (ACC) was investigated. Adsorption isotherm data were derived at 30 degrees C. Then the ACC surface was modified by saturating it with crown ethers. In the second stage, the adsorption of three metal ions, Cr(III), Co(II) and Ni(II), onto both the ACC and the ACC modified with crown ethers was investigated. The enhancement of adsorption of the ACC upon modification with crown ethers was examined for the three ions. The effects of the type and cavity size of crown ethers, the size and form of the ions on the extent of adsorption were discussed in terms of interactions of adsorbate species with the ACC surface. All the isotherm data were treated according to Langmuir and Freundlich models. Generally, Freundlich model was found to represent the experimental isotherm data better than Langmuir model.

In-Situ UV-Visible Spectroscopic Study on the Adsorption of some Dyes onto Activated Carbon Cloth

Abstract Adsorptive removal of the dyes C.I. Basic Blue 9, C.I. Basic Red 2, and C.I. Acid Blue 74 from aqueous solution onto the activated carbon cloth (ACC) has been investigated. The removal of each dye has been followed by in-situ UV-visible spectroscopic method using the so-called scanning kinetics technique. Kinetic data obtained in this way were tested according to pseudo-first order, pseudo-second order, Elovich, and intraparticle diffusion models. Pseudo-second order model was found to be the best in representing the experimental kinetic data. Adsorption isotherms at 30°C were derived for each dye. Isotherm data were found to fit best to Freundlich isotherm model among the three isotherm models tested; Langmuir, Freundlich, and Redlich-Peterson. High specific surface area of the ACC allowed almost complete removal of each dye under the experimental conditions applied. Adsorption capacity of the ACC for the three dyes was correlated with the dimensions of dye molecules and pore sizes of the ACC.

Use of quasi-3-dimensional porous electrodes for adsorption and electrocatalytic removal of impurities from waste-waters

Abstract The use of high-area C-felt electrodes as interfaces for in situ adsorptive or electrocatalytic removal, or modification of noxious pollutants in waste-waters is described. Such materials enable diffusion-limited rates of adsorption and electro-oxidative or reductive processes to be effectively enhanced in a major way. Applications are made to removal of pollutants such as salts of S-containing anions, K-ethylxanthate, phenol, aniline and its sulphate, and choline hydroxide from aqueous solutions at low concentrations. It is shown how the courses of the adsorptive and electrosorptive processes can be sensitively followed by means of in situ UV-visible spectrophotometry and, in the case of traces of S-containing anions, using in situ conductimetry. The spectrophotometry technique also provides accurate information on kinetics of the adsorption processes that are usually pseudo-first-order. Complementary studies of electrooxidation of ethylxanthate, choline hydroxide and phenol at Pt gauze electrodes by means of cyclic voltammetry and chronoamperometry are reported.

Adsorption/electrosorption of catechol and resorcinol onto high area activated carbon cloth.

Removal of catechol and resorcinol from aqueous solutions by adsorption and electrosorption onto high area activated carbon cloth (ACC) was investigated. Kinetics of both adsorption and electrosorption were followed by in-situ UV-spectroscopic method and the data were treated according to pseudo-first-order, pseudo-second-order and intraparticle diffusion models. It was found that the adsorption and electrosorption of these compounds onto ACC follows pseudo-second-order model. pH changes during adsorption and electrosorption were followed and discussed with regard to the interaction between ACC and adsorbate molecules, utilizing the pH(pzc) value of ACC. An electrodesorption experiment was conducted to explore the possibility of regeneration of ACC. Adsorption isotherms were derived at 25 degrees C on the basis of batch analysis. The fits of experimental isotherm data to the well-known Freundlich, Langmuir and Tempkin models were examined.