Facultatea de Chimie şi Tehnologie Chimică / Faculty of Chemistry and Chemical Technology
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Item Production, structure and photocatalytic properties of nanotubular TiO2 [Articol](2020) Duca, Gheorghe; Covaliov, Victor; Covaliova, OlgaPhotocatalytic processes are among the most efficient treatment methods of waters polluted with recalcitrant organic substances. Nanotubular TiO2 arrays with photocatalytic properties were obtained in the process of titanium anodic oxidation in the fluoridecontaining electrolyte. Under the proposed conditions of electrolysis, a coherent system of tightly adjoining nanotubes was formed with the internal diameter of 60-80 nm and walls thickness up to 60-65 nm, the tubes height being dependent on process duration, reaching over 200 mkm. It was shown that it is the specifics of the formation, destruction and renewal of the barrier layer that determines the tubular structure of anodic titanium coatings formed. Various anodizing regimes were proposed to obtain the different TiO2-containing structures-nanotubular and fine dispersed ones. Subsequent annealing of nanotubular titanium dioxide provokes the series of structural-phase transformations, modifying its photocatalytic properties. The nanotubular systems thus obtained were tested as photo-catalysts, both as compact coatings and as fine dispersed particles, in the especially developed integrated photoreactor. It was shown that using the proposed equipment and photocatalysts produced, the efficient photodestruction of the persistent organic pollutants such as benozhiazol (BT) can be reached due to the combination of chemical and physical effects.Item A new concept regarding the selection of sewerage systems and natural treatment of municipal wastewaters [Articol](2023) Covaliov, Victor; Ungureanu, Dumitru; Duca, Gheorghe; Covaliova, Olga; Romanciuc, LidiaThe article contains a review of methods and procedures of the municipal wastewater treatment, with the discussion of their specifics. A new concept is proposed related to the selection of municipal sewerage and wastewater treatment systems, considering the local/decentralized, semicentralized or centralized systems, especially those suitable to rural and suburban localities, in dependence on the advantages and disadvantages of these systems and local specifics. The concept of phytofilters is proposed for the biological treatment of wastewater in small towns. This technology is simple, inexpensive and requires relatively little maintenance. Biological ponds in the Republic of Moldova have proven to be very suitable for advanced wastewater treatment, being a cheap and natural purification system with a good potential for implementation. When choosing a sewer system, priority must be given to its functionality and practical considerations.Item Perfecționarea sistemelor de obținere a biogazului [Articol](2015) Covaliov, VictorAu fost elaborate o tehnologie ecologic pură şi un bioreactor integrat intensiv de nouă generaţie pentru producerea biogazului prin valorificarea deşeurilor agroindustriale periculoase pentru mediul natural. S-a dezvoltat o tehnologie eficientă, independentă de sursa de alimentare centralizată, sporind astfel fiabilitatea şi eficienţa costurilor aprovizionării cu energie în zonele rurale. Procesul propus este uşor de gestionat, ecologic şi acceptabil pentru populaţie. Această tehnologie este unică în lume şi se bazează pe utilizarea fito-catalizatorilor naturali introduşi în biomasa fermentată în micro-concentraţii. Ei sunt obţinuţi prin extracţie din materii prime vegetale naturale şi deşeuri. Conţinutul biometanului în biogaz a crescut de la 62%, cu o valoare calorica de 5 232 kcal/m3, până la 85-92%, cu o valoare calorica de 8 010 kcal/m3. În plus, reziduurile de biomasă stabilizate pot fi utilizate ca îngrăşăminte organice, în timp ce apa tratată este conformă cerinţelor pentru irigare. Tehnologia asigură generarea energiei regenerabile „verzi”, atât electrice, cât şi termice, şi contribuie la îmbunătăţirea securităţii energetice şi ecologice în conformitate cu standardele naţionale şi internaţionale existente.Item Intensificarea fitochimică a emisiei biohidrogenului în procesele de fermentare anaerobă a biomasei [Articol](2013) Covaliov, Victor; Duca, Gheorghe; Bobeică, Valentin; Covaliova, OlgaSe examinează problemele producerii şi utilizării hidrogenului ca agent energetic ecologic. Se analizează, în special, realizările înregistrate în ceea ce priveşte intensifi carea şi reducerea consumurilor materiale şi energetice pentru obţinerea biohidrogenului în procesul purificării deşeurilor agroindustriale lichide prin metoda fermentării anaerobe, utilizându-se procedeul original de redirecţionare cu ajutorul unor microstimulenţi fi tochimici a metanogenezei în vederea formării hidrogenului, optimizării funcţionale şi energetice a bioreactorului şi utilizării unor procedee ecologo-economice de purifi care a biohidrogenului.Item Autocatalytic reduction and characteristics of boron-containing coatings [Articol](2013) Covaliov, Victor; Covaliova, Olga; Ivanov, Mihail; Drovosecov, AndreiThe research results of the plating conditions, chemical composition and properties of Ni-B coatings and Ni-Re-B, Ni-Mo-B and Ni-W-B alloys are given. It was shown that introduction of alloying elements (Re, Моand W) in the composition of Ni-containing coatings modifi es the catalytic activity of the alloys’ surface, with regard to the parallel reactions of dimethylamino-borane(DMAB) heterogeneous hydrolysis, Ni reduction and evolving of the molecular hydrogen. It was found that with the increase in concentration of alloying element, boron contents in the coatings is decreased to the trace amounts. The effect of alloys composition on hydrogen evolving overvoltage was studied. Due to the low overvoltage of hydrogen evolving (HE) on the alloy Ni-Re-B surface (11 at.% Re), it can be used as electrode for hydrogen generation from water in the electrolytic cell with novel design and improved technical-economical indicators.Item Savant pe linia de avangardă a oenologiei şi biotehnologiei: Boris Găină [Articol](2007) Covaliov, VictorItem Procese tehnologice de obţinere a biogazului în sistemele de epurare anaerobă a apelor reziduale [Articol](2007) Ungureanu, Dumitru; Covaliov, VictorThe continuous development of the civilization stipulates for the increased consumption of the power resources, which determines the search of the new alternative sources of energy. Among the alternative sources of energy a great importance is accorded to the technology of obtaining the biogas. This problem is very actual, especially in the Republic of Moldova, while the natural energetic resources in this country are absent. However our republic possesses the important recovering organic resources which in most cases are not used but are thrown out in the environment together with the sewage.Item Bioreactor pentru producerea fitocatalitică a biohidrogenului în procesul epurării anaerobe a apelor reziduale agroindustriale [Articol](CEP USM, 2014) Covaliov, Victor; Covaliova, Olga; Nenno, Vladimir; Bobeică, ValentinItem A new method of cyancobalamin (vitamin B12) production and its practical uses [Articol](Academia de Ştiinţe a Moldovei, 2015) Covaliova, Olga; Covaliov, Victor; Duca, Gheorghe; Nenno, Vladimir; Bobeica, ValentinItem Modification of TiO2 particles nanostructure for photocatalytic applications [Articol](Academia de Ştiinţe a Moldovei, 2015) Covaliova, Olga; Covaliov, Victor; Duca, Gheorghe