First International Conference on MOLDAVIAN RISKS – FROM ...

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<strong>First</strong> <strong>International</strong> <strong>Conference</strong> on MOLDAVIAN RISKS - FROM GLOBAL TO LOCAL SCALE 16-19 May 2012, Bacau, Romania DEFICIENCIES AND POSSIBLE ENVIRONMENTAL RISKS OF PHOTOCATALYSIS USED FOR WATER AND AIR DEPOLLUTION Traian Vasilache, Gabriel Lazar, Marius Stamate “Vasile Alecsandri” University of Bacau, Department of Mechanical and Environmental Engineering Corresponding author: Traian Vasilache, traian.vasilache@ub.ro Abstract: This short review presents some deficiencies regarding photocatalysis use in water and air depollution, because the environmental risks have to be considered in order to minimize negative effects of the future applications. Since photocatalysis was discovered a couple of decades ago, it was intensively studied and many applications were developed. In the environmental engineering depollution ex-situ of water and air it seems to be revolutionary. Especially coupled processes involving photocatalysis coupled with ozonization, membrane filtration and microfiltration, adsorption, sonolysis, pulse discharge, flocculation, photolysis and microwave energy, were proving best results and possibilities for future commercial uses in industry and environmental protection. Deficiencies of these processes are concerning in formation of undesirable secondary products. In water depollution using membranes and photocatalysis the problem of presence of colloidal particles even after washing of membranes it was signalized. Another study found as problem the formation of cake layer on membrane surface. Adsorption on nanoporuos materials and photocatalysis used for wastewaters treatment was an acceptable method, but formation of colloidal particles decreased the efficiency of the process. Diclofenac is the disseminated medicine in water, potentially toxic for aquatic life and photocatalysis degraded it successfully; some of secondary products resulted are toxic, even more poisonous as primary pollutant. Degradation of 4-clorophenol under microwave energy couplet with photocatalysis in aqueous solutions occurs with formation of chlorobenzene, phenol, hydroquinone, benzoquinone and 4-chlorocatechol which are undesirable products. Textile dye Acid Red 88 was degraded by sonolysis and photocatalysis, but some intermediate products were not mineralized. The same problem occurred on degradation of diphenylamine from polluted water. Regarding air depollution, photocatalysis was applying in nasty smells removal; 2-butanone and methyl-ethyl-ketone were successfully oxidized, but acetaldehyde results as secondary product. A pulse discharge system combined with photocatalysis degraded phenols and the problem of sub products appears once again. Some insecticides as malathion, isomalathion and malaoxon were decomposed by photolysis coupled with photocatalysis and some undesirable secondary products formed. Also, trichoroethylene was decomposed succesfully by photocatalysis, but it results fosgene, chloroform and carbon tetrachoride. All the methods need improvement and future researches will find those materials and chemical reactions which have to be eco-friendly. Key words: photocatalysis, water depollution, air depollution, secondary products, environmental risk. 104
<strong>First</strong> <strong>International</strong> <strong>Conference</strong> on MOLDAVIAN RISKS - FROM GLOBAL TO LOCAL SCALE 16-19 May 2012, Bacau, Romania COMPOSITE MATERIALS WITH CARBON CLUSTERS AS ADSORBED MICRO-AND MACRO-MOLECULAR ELEMENTS Petru Lozovanu, Mihail Caraman, Alexandru Cresciuc Laboratory of Scientific Research "Photonics and Metrology Physics", Moldova State University Corresponding author: Petru Lozovanu, p_lozovanu@yahoo.com Abstract: Discovery of the new allotropic forms of carbon (fullerenes and nanotubes) led to broadening fields of practical use of carbon. Valence bonds of carbon atoms in fullerenes macromolecules (C60, C70...) are closed, but a small external excitation which can be induced by a molecule or cluster can lead to the formation of free bonds and their adsorption, respectively. A totally different interaction mechanism with external molecular environment have some modifications so-called nanotubes. Having free valence bonds at the edge, these attract strongly molecules and even polar clusters, and after their ionization it can be accumulated in large amounts by carbon clusters. These properties of carbon modification have been put into the basis of elaboration of the adsorbent elements with carbon clusters. Modern technologies allow to obtain industrial quantities of carbon cluster of different orders which have a wide range of physical properties. The paper presents experimental and technological research on the results about manufacturing the active filter elements to purify liquids and gases. By directing the carbon component concentration one can obtain the tiles, electrical conductivity of which varied in quite wide range from tens to hundreds of MOhms. We have done research on the variation of electrical conductivity for these micrometer elements made by these materials with different atmospheric pollutants (carbon and sulfur oxides and nitrites, vapor of organic compounds). A link between pollutant concentration in the atmosphere and the size of the electrical conductivity variation was established. As a result, experimental investigations of composites based on nanotubes and fullerenes, as well as the experimental methods form the basis of the work presented. Investigations were made in the Laboratory ”Metrology of the Environment and Astronomy”, Moldova State University Key words: cluster, fullerenes, nanotubes. 105
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