Chemistry Journal of Moldova. General, Industrial and Ecological Chemistry

14-18

Authors: Raluca Anamaria Cristache, Ana Maria Budu, Petronela Spiridon, Viorica Vasilache, Ion Sandu

The authentication of cultural heritage assets is a complex process of scientific investigation which regards obtaining information about: author (painter), the period when it was made, the owners and other data related to the main contexts of their evolution in time (routes travelled). In fact, the identification of specific archaeometric features is aimed, in determining the materials composition and the patina, then the study of artistic techniques and technology used in the making process of a work of art. Latest serves to define the patrimonial elements and the role of the artifact in time. The expertise of old panel painting icons requires an interdisciplinary approach, correlating the artistic style with technique and materials used. In this regard, the specific techniques of microscopy and spectroscopy are very useful tools for determining the composition of structural elements and their deterioration / degradation state. This work presents a comparative study of the paper used in the preparation layer of three icons painted in Russian style. As an analysis techniques were used the micro and macro photography assisted by Optical Microscopy (OM), SEMEDX and micro-FTIR. Based on the experimental data obtained, it was found that the icons belong to the first half of the 19th century.

26-31

Authors: Silvea Pruteanu, Petronela Spiridon, Viorica Vasilache, Ion Sandu

Old icons, especially those involved in liturgical rituals are affected in time by external agents factors (temperature, humidity, light, pollution, microbiological attack, abrasion etc.), resulting changes of the appearance and of the structural integrity, dirt deposits, altered varnish and painting layer, cracks, material loss etc. In order to remove the dirt deposits, there are used cleaning systems with dry wiping, vacuuming, scraping, washing with organic solvents, ion exchange solutions, polyelectrolyte, surfactants, and so on, by enzymatic systems or by laser pyrolysis. The last two processes being considered aggressive and highly invasive, although they do clean very well adherent dirt deposits, which strongly degraded the varnish to total blackening (the iconographic image cannot be seen). Based on the literature in the field, regarding the nature of the materials used during the painting process and of the types and structures of the deposits, a series of alcoholic solutions of different concentrations were made, as such or basified, which were compared with ecologic synergic systems based on organic uncolored vegetable juices and decoctions from dried plants. The cleaning effectiveness was done by visual analysis and CIE L*a*b* reflection colorimetry, space proposed by the CIE (International Commission on Illumination) in 1976, was used. This technique permitting to determine by color deviations the critical point where the patina and polychromes layer.

41-51

Authors: Оlga Covaliova, Alexandr Kоshev, Valery Varentsov

The main regularities of the electroactive components distribution, polarization and local current density within the depth of the three-dimensional fl ow-through electrode have been studied using the calculation method, in dependence on the overall current density, electrode thickness and degree of its compression, solution fl ow velocity through the electrode, initial concentration of Fe(III) ions in the solution and electrodes brand.

58-61

Authors: Tudor Lupascu, Mihail Ciobanu, Victor Botan

Processes of removal of divalent ions of iron and manganese and hydrogen sulfide from groundwater at various pH values and temperature were studied. Obtained results have been used in order to elaborate a process of groundwater purification from the mentioned pollutants. The use of elaborated process for natural water leads to the decrease of the content of iron, manganese and hydrogen sulfide below the maximum allowable concentrations.

67-73

Authors: Ana Popusoi, Nicanor Barba, Aurelian Gulea, Jenny Roy, Donald Poirier

3-(4-(Dimethylamino)phenyl-1-(4-isothiocyanatophenyl)prop-2-en-1-one was obtained from the corresponding N,N-dimethylthyoureas by elimination of dimethylamine at heating with gaseous hydrogen chloride in chloroform and 1-(4-isothiocyanatophenyl)-3-(pyridin-2-il)prop-2-en-1-one by treating 1,1-dimethyl-3-(4-(3- (pyridin-2-il)-acryloyl)-phenyl)thyourea with acetic anhydride. The difference in the reactivity of the groups >C=O and NCS in the synthesis with hydrazine hydrate and its derivatives allows the synthesis of some 1,3-disubstituted propenones with thiosemicarbazide groups (4- and 1,4-disubstituted) in good yields. From 4-substituted thiosemicarbazides and 2-formilpyridine thiosemicarbazones were obtained. In the case of some derivatives, the propenone group in the reaction with hydrazine hydrate allows the formation of pyrazole derivatives. All obtained compounds were investigated for antileukemia activity. It was found that this activity is more pronounced for thiosemicarbazide derivatives with two pyridine nuclei at concentrations 10-5-10-7 mol/L.

80-89

Authors: Natalia Gorinchoy

The pseudo Jahn-Teller effect is employed to explain the origin of distortions of carbonyl fluoride, diazene and ketene molecules in the lowest singlet and triplet excited states. The ground state and the excited electronic states of considered molecules were calculated by ab initio SCF CI method with the use of the 631G-type basis set. The corresponding pseudo Jahn-Teller coupling constants are estimated by fitting the ab initio data for the adiabatic potential curves of the molecules to the general formula, obtained from the vibronic theory. With these data an explanation of both the larger instability of the triplet excited states as compared with the singlet ones and the elongation of the corresponding bond distances in the excited states is obtained.

99-106

Authors: Lilia Anghel

The multitude of physiological processes in which the binding of iron ions takes part makes its mechanism worth investigating. The multiple sequence alignment method was applied to investigate the structure similarities of five lactoferrin X-ray crystallographic structures and outline the differences and similarities between lactoferrin and serum transferrin. The results of this study provide useful insights into the mechanism of iron-binding of lactoferrin protein molecule.

14-32

Authors: Madalina Zanoaga, Fulga Tanasa

This article offers an overview of some contemporary antimicrobial agents used as functional finishing for textiles intended for biomedical applications. It reviews only synthetic agents, namely quaternary ammonium compounds, halogenated phenols, polybiguanides, N-halamines, and renewable peroxides. These agents can be divided into several groups according to their mechanism of antimicrobial activity, toxicity, durability and ecological acceptability. Examples of commercial antimicrobial products are presented herein, as well as the corresponding finishing methods.

37-41

Authors: Nikolay Kornilov, Elena Kornilova, Elena Stepanenko

In the article we give the results of comparative analysis of the composition of the Eurasian hydromineral resources and we implement the assessment of their impact on the physiological condition of an organism of the person according to biochemical studies of venous blood. Processing of initial data on the composition and properties of mineral waters chloride-hydrocarbonate, sulphate-hydrocarbonate and chloridesulphate types and venous blood are made using the method of mathematical modeling, developed by the authors of this article. It is shown that in the balneological impact hydromineral resources on the body hemoglobin and oxygen in the blood increases, glucose decreases, and acid-base pH shifts to high alkalinity.

53-58

Authors: Laura Bulgariu, Igor Cretescu, Dumitru Bulgariu, Matei Macoveanu

The adsorption on non-conventional and low-cost materials for removal of toxic heavy metals and oil products from aqueous media has become important in the last years, because is an efficient and cost-effective alternative compared to traditional chemical and physical remediation, and also other decontamination techniques. The good efficiency, minimization of secondary (chemical or biological) wastes and low cost of adsorbent materials, are only few main advantages of adsorption that can be used for the removal of such pollutants in high volumes of aqueous solutions, being thus more adequate for large scale applications. In this paper, are presented the adsorptive characteristics of a low-cost material that are abundant in our region, namely: Romanian peat moss from Poiana Stampei (Romania), for the removal of different toxic heavy metal ions (Pb(II), Hg(II), Co(II) and Ni(II)) and oil products from aqueous media. The experiments have concerned the influence of several experimental parameters (initial solution pH, adsorbent dose, initial heavy metals concentration, contact time, and temperature) on the heavy metals and oil products removal efficiency. The most important conditions for desorption of heavy metal ions from loaded-materials, required for their regeneration are also presented.

74-79

Authors: Carmen Zaharia, Victoria Fedorcea, Adrian Beda, Victor Amarandei Augustin Muresan

The paper presents some data from our laboratory-setup experiments of homogenous oxidative processes with hydrogen peroxide (i.e. advanced Fenton oxidation processes) applied for Remazol Rosso RB dye-containing aqueous systems, especially textile effluents. Therefore, some different operating parameters (including pH, concentration of dye, H2O2 and ferrous ions, oxidation time, temperature, stirring regime, among its) were tested for determination of the best performance in effluent discoloration and dye removal, meaning the optimal values of each studied parameters for highest discoloration or dye removal. For an effluent loaded with 50 mg/L Remazol Rosso RB dye, there were applied these optimal values that correspond to > 97 % discoloration efficiency performed with 88.24 mM H2O2, 0.18 mM FeSO4, at pH (5.16), temperature of 19-20°C, continuous stirring regime (30 rpm) and minimum 25-30 minutes of homogenous advanced oxidation treatment. If there are not used additional chemical reagents for pH adjustment (minimization reason of treatment operating cost), the performance of this oxidative treatment is closed to above mentioned efficiency by after a higher oxidation time (> 90 min). These results are encouraging and sustain this oxidative process application and optimization for reducing the environmental impact of effluent discharging directly in different natural aquatic receptors and compliance with admissible limits imposed by environmental legislation as well.

85-92

Authors: Maria Gonta, Gheorghe Duca, Vera Matveevici, Larisa Mocanu

Advanced oxidation methods of organic compounds lead to their partial mineralization and increase of the adsorption process efficiency on the surface of oxidized activated carbon. We have studied the oxidation process using model solutions containing mixture of dye direct brown (DB), ethylene glycol (EGL) and sodium lauryl sulfate (SLS) under the action of Fenton reagent, in the presence and absence of UV irradiation or under the action of electric current (in the electrochemical cell). The same studies were performed by replacing the iron (II) ion with titanium dioxide. We have found that the degree of oxidation and mineralization increases by photocatalytic oxidation and decreases the concentration of organic compounds. Due to the oxidation of dye molecules and other auxiliary components, by strong oxidation ability of free OH* radicals, which evolve to the formation of carbon dioxide, water and low molecular organic compounds (alcohols, ketones, organic acids) are forming. The decrease of the concentration of mixture of organic compounds (for the values of COD-Cr) depends on the nature of catalysts and the presence of electric current. The degree of oxidation is greater in the presence of iron (II) ions than in the presence of titanium dioxide after oxidation of the mixture of organic compounds with hydrogen peroxide in model solutions. This is explained by the fact that UV irradiation increases the concentration of free OH* radicals as iron ions further decompose hydrogen peroxide, but in the presence of titanium dioxide, the leading band electrons are accepted by free OH* radicals, converting these radicals to ions, as shown in the mechanism by Garcia J., et al. This leads to a decrease of the concentration of OH* radicals in model solution and reducing the effect of oxidation, respectively. On the contrary, in the presence of electric current electrons are accepted by the electrode, and the OH* radicals concentration does not decrease, but increases, and this leads to the enhancement of the oxidation effect and mineralization of organic compounds.

100-105

Authors: Masahiro Mikuriya, Nobuyuki Nagao, Satoshi Kurahashi, Atsushi Tabuchi, Seiki Tomohara, Motohiro Tsuboi, Daisuke Yoshioka, Hiroshi Sakiyama, Akira Fuyuhiro

Mixed-valent tetranuclear MnIIMnIII 3 complex with 1,3-diamino-2-hydroxypropane-N,N’,N”,N”’-tetraacetic acid (H5dhpta), Ca2[Mn4{μ-OHO}(dhpta)2(CH3COO)2], was synthesized and characterized by elemental analysis, IR and UV-vis-NIR spectroscopy, and temperature dependence of magnetic susceptibilities (4.5—300 K). Single-crystal X-ray crystallography revealed a trapezoid tetranuclear core with μ-(OHO), μ-alkoxido, μ-acetato bridges. Magnetic data analysis showed considerable antiferromagnetic interactions among these four manganese atoms with J(MnIIIMnIII) of –35.02 cm–1, J’(MnIII(MnII)-MnIII) of –4.82 cm–1 , and J”(MnII-MnIII) of –4.61 cm–1.

112-116

Authors: Irina Davidenko

Azobenzene polymer compositions are extensively studied now due to wide perspectives of their applications in optoelectronics and information technologies. Some possibilities of modification of their properties by chemical methods are analyzed in the present work. These methods allow to improve information characteristics of the media. Electrooptical effect is investigated and possibilities of polarization sensitive holographic recording is demonstrated in copolymer octyl methacrylate with incorporated azo dyes and its complex with Co ions.

123-127

Authors: Inna Melnyk

Current paper focuses on the analysis of influence of main factors (stages of the synthesis, the ratio of the reacting components, the order of their introduction, the concentration of water and ammonia, the synthesis temperature) on the morphology, size and content of functional groups of aminosilica nano- and submicrospheres. The recommendations for the synthesis of particles with predetermined properties were done. It is shown, that the ratio of the reacting components mainly affects the content of 3-aminopropyl functional groups and the temperature of the hydrolytic polycondensation reaction - the size of the particles.

132-135

Authors: Gabriela Ciobanu, Constantin Luca, Octavian Ciobanu

In this study, the porous hydroxyapatite-fi lled cellulose acetate scaffolds were prepared via dry-wet phase inversion method by dispersing hydroxyapatite nanoparticles in the polymeric matrix. The calcined hydroxyapatite prepared by wet precipitation method has the crystal size smaller than 50 nm. The unfi lled and hydroxyapatite-fi lled cellulose acetate scaffolds have an asymmetric structure consisting of two layers, the dense top layer (active layer) supported by the porous sub-layer (substructure). The cross-sectional SEM images revealed that hydroxyapatite nanoparticles were well dispersed in the cellulose acetate matrix.