Gabriela Apostolescu

The physicochemical properties of polyurethane membranes determined by swelling measurements

In this work, we have dispersed SAPO-5 zeolite particles in polyurethane matrix for preparation of porous mixed matrix membranes. The goal of work is the determination of the cohesive energy density for unfilled- and zeolite - filled polyurethane membranes. Experimental determination of cohesive energy density values for the prepared membranes is obtained by measuring the swelling coefficients in water and several alcohols (methanol, ethanol, propanol and butanol). The solubility parameters of the membranes are also calculated. For the unfilled membranes the corresponded values of cohesive energy density and solubility parameter increase in comparison to those of the filled membranes. All the tested membranes show a tendency to swell with ethanol.

The Effect of Storage Time on the Composition of the Olive and Sunflower Oils

The effect of storage time on the composition of the olive and sunflower oils has been investigated. It were studied parameters like free fatty acids (FFA), anisidine value (AV), iodine value (IV), saponification number (SN) and identification of the molecular structure through FT-IR method. During storage (48 months) an increasing in the values of parameters FFA and AV took place that measures the oxidative degradation of oils. The oxidative stability of olive oil stored at room temperature was less than of sunflower oil. Also, significant differences were found among the olive oil and sunflower oil during storage period.

A GREEN ROUTE TO SYNTHESIZE CeO2 NANOPARTICLES

The paper presents the surfactant-assisted solvo-thermal route to synthesize nanoparticles of cerium oxide with different shape and morphology. The precursor was calcined at 400°C for 4 h in order to obtain CeO2 nanoparticles. The obtained samples were characterized by means of thermal analysis and FTIR spectroscopy. The UV-Vis analysis was used to study the optical properties. The morphologies and nano-structures were characterized by scanning electron microscopy (SEM) and XRD. It was found that nature and concentration of template agents played important roles in the formation of the novel morphology. A possible formation mechanism was proposed based on the controlling reaction parameters.

New coordination compounds of Cr(III) used in leather tanning

Some new coordination compounds of Cr(III) using as ligand N-hydroxy - succinimide, were obtained and studied. The combination ratio, central atom: ligand were 1:1; 1:2 and 1:3. The new complex compounds were studied using UV-Vis spectroscopy, conductance and pH measurements. The studies of obtaining and of stability of the new compounds were accomplished in aqueous solutions using methods characteristic for coordination compounds: conductance and pH measurements. The combination ratios and the stability constants were determined with methods characteristic for studies in solutions.

Hydrotalcite-like anionic clays substituted with iron / laccase, composites for biosensors applications

Laccase - based biosensors are important for the selective determination of the phenolic compounds in the environmental matrices. The features of the enzyme immobilisation process and the characteristics of the inorganic porous matrix adsorbed on the electrode surface are both important for establishing the biosensor performances. This work presents the synthesis and physical-chemical characteristics of new hybrid materials based on iron containing layered double hydroxides / laccase. XRD and TGA-DTA analyses give information about the structural characteristics and thermal behaviour of the tested hybrids. The SEM images show the presence of a well crystallized texture of organized ensembles of platelets-like particles stacking on top of one another. The presence of iron in the substituted clay matrix is able to give rise to the specific redox properties that can be further used to tailor not only the laccase immobilisation process but also the biological sensing response of the biohybrid-transducer device.

NITROUS OXIDE DECOMPOSITION OVER Fe-ZSM-5 CATALYSTS PREPARED BY DIFFERENT METHODS

Two different methods of preparation (solid state exchange and aqueous exchange) with two different iron precursors (ferrous chloride, respectively ferric oxalate) have been used to introduce iron species in the zeolite ZSM-5. A special attention was devoted to the aqueous exchange method. The catalysts thus prepared were tested for direct N2O decomposition. The results of catalytic tests show that the Fe-ZSM-5 catalyst prepared by aqueous exchange in ferric oxalate solutions is much more active than the one prepared by solid state exchange.

Structural Considerations on Some Inorganic Polymers of Fe(III) with Phosphorus Containing Rings

The compounds were synthesised by the reactions between Fe(III) acetylacetonate with each of the following acids: diphenylphosphinic, diphenyltiophosphinic and diphenylditiophosphinic, diethylphosphinic, diethyltiophosphinic, diethylditiophosphinic. The studies were performed by means of Mössbauer, IR and ESR spectroscopy and X-ray diffraction.