Facultatea de Chimie şi Tehnologie Chimică / Faculty of Chemistry and Chemical Technology
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Item INTENSIFICAREA FITOCHIMICĂ A EMISIEI BIOHIDROGENULUI ÎN PROCESELE DE FERMENTARE ANAEROBĂ A BIOMASEI(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 REMOVAL OF DIRECT DYES FROM TEXTILE WASTEWATER BY MEANS OF COMBINED METHODS(2009) Matveevici, Vera; Duca, Gheorghe; Gonța, Maria; Iambarțev, Viorica; Mocanu, LiliaItem THE DIMINISHING OF THE CONTENT OF TEXTILE DIRECT DYES AND AUXILIARY COMPOUNDS DURING THEIR CATALYTIC OXIDATION(2014) Gonța, Maria; Duca, Gheorghe; Matveevici, Vera; Mocanu, LarisaAdvanced 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.Item REGIONAL CLIMATE CHANGE AND SURFACE WATERS(2019) Duca, Gheorghe; Nedealcov, Maria; Travin, Serghei; Gladchi, VioricaThe actual period marred by the global warming requires expanding our knowledge on the regional particularities of climate changes manifestations as consequences of global climatic changes. It was stated that within the limits of Republic of Moldova’s territory the pace of warming is much more accelerated than the global one. These consequences, in their turn, had led to the increase in degree of evaporation of surface waters, which had conditioned the doubling of still water’s pollution in the region (Lake Beleu). We consider that the obtained results could contribute to the adequate management of water resources in the new climatic conditions.Item SELF-PURIFICATION OF AQUATIC MEDIA FROM HEXACHLOROCYCLOHEXANE IN A RADICAL PROCESS(2019) Travin, Serghei; Duca, Gheorghe; Gladchi, VioricaIt is known, that highly toxic pesticide hexachlorocyclohexane (HCH) is resistant to decomposition and has a long-term accumulating capacity. Nevertheless, it undergoes complete degradation in reactions with hydroxyl radicals in Fenton-like systems. The goal of this work was to study the influence of HCH on the processes of radical self-purification of water bodies and to explain the mechanisms of chemical transformation of substances occurring in natural waters, as well as to reveal the kinetic characteristics of the processes of radical self-purification of water bodies. It was found, that HCH plays a dual role for aquatic ecosystems – it is not only a scavenger of free radicals, but also an additional initiator. Under the influence of light in the surface layer of water, HCH generates radicals, thus contributing to the self-purification processes.Item SOLUŢII PENTRU PREVENIREA ŞI DIMINUAREA CONSECINŢELOR INUNDAŢIILOR(2010) Duca, Gheorghe; Furdui, Teodor; Melniciuc, Orest; Zubcov, Elena; Gladchi, Viorica; Moraru, Constantin; Bogdevici, Oleg; Arnăut, Nicolae; Bujac, VictorThe danger of floods is very up to date for the Republic of Moldova, so, two types of flood are characteristic: transboundary, caused by Dniester and Prut rivers, and local, caused by discharges of small streams, lakes, ponds. A group of experts from the Academy of Sciences of Moldova developed solutions to prevent damages caused by triggering floods. Among these are: the creation of National center of flood monitoring; the assessment of flood areas and the liable to inundation potential of Dniester and Prut rivers and small streams; the elaboration of “Scheme of protection of populated localities against flood”; the regular water sampling in flood areas to monitor the state of pollution; the implementation of flash flood model; the agreement between Ukraine-Republic of Moldova-Romania on monitoring, forecasting and sustainable exploitation of aquatic ecosystems etc.Item ASSESSMENT OF KINETIC PARAMETERS IN THE WATERS OF THE NISTRU COURSE IN THE SECTION NASLAVCEA – DUBASARI(2006) Bunduchi, Elena; Duca, Gheorghe; Gladchi, Viorica; Goreaceva, Nelli; Mardari, IgorThe current work represents the results of a monitoring executed on Nistru River waters between October 2003 and September 2005. The water quality was evaluated on the basis of such kinetic indicators as redox state and capacity of inhibition. The obtained results shows that Nistru River water in the segment Naslavcea village – Dubasari barrage are continuously polluted with reducing substances that diminish the H2O2 content, that actually determines the redox state of natural waters and the content of free radicalsItem THE WATER SPRINGS - SOURCES FOR WATER SUPPLY AND IRRIGATION IN THE NISTRU RIVER BASIN(2013) Sandu, Maria; Tărâță, Anatolie; Lozan, Raisa; Gladchi, Viorica; Duca, Gheorghe; Țurcan, Sergiu; Moșanu, Elena; Prepeliță, AfanasieThe present study estimates chemical composition and status of the groundwater from the Nistru (Dniester) river basin (about 360 springs and fountains). Research includes defining of springs/fountains location, evaluating physicochemical features of water, highlighting of main pollutants and pollution sources, establishing of water type and quality. It was established that springs/fountains with water that meets the criteria for drinking scope constitute 21%, sanitary acceptable for consumption is water from 129 springs/fountains, with high content of dissolved salts (mineralization >1000 mg/dm3) and hardness exceeding 10 me/dm3 (very hard water) were in 18.5% of sources and approximately 25% of the springs are water polluted with nitrates and its content is more than the MAC from 1 to 6 times.Item STUDY OF SPRINGS WATER QUALITY AS SOURCES OF POTABLE WATER AND FOR IRRIGATION IN REZINA DISTRICT(2010) Sandu, Maria; Moșanu, Elena; Gladchi, Viorica; Tărâță, Anatolie; Duca, Gheorghe; Spătaru, Petru; Lupașcu, Tudor; Sergentu, Efim; Lozan, Raisa; Jabin, Veaceslav; Țurcan, SergiuA spring is a component of the hydrosphere, where water flows on to the surface of the Earth from below the surface. This it is where the aquifer surface meets the ground surface. It may be the result of karsts topography where surface water has infiltrated the Earth’s surface, becoming part of the area groundwater. As sources of water supply in the Republic of Moldova underground waters constitute 15,2% (bore holes, springs and wells). The present work includes water quality investigations and aims to reveal local sources in river Nistru hydrographic basin (Rezina district) for drinking water provision in villages. Chemical composition of investigated spring’s water shows that in Rezina district 19% of springs are polluted with nitrogen compounds. Water of only 9% of springs is in conformity with the standard for drinking water. Water from 102 springs meets the requirements of irrigation that doesn’t present the risk of soil salinization (K > 18) – 1 383 L/min.Item CHEMICAL COMPOSITION FROM THE DNIESTER RIVER TRIBUTARIES(2013) Gladchi, Viorica; Duca, Gheorghe; Goreaceva, Nelli; Bunduchi, Elena; Lis, AngelaThis article presents the results obtained in the framework of the project 09.832.08.06A The role of the tributaries on formation of the Dniester river water and the study of the waters quality of sources/fountains in the catchment area of the Dniester river as sources of water supply and for irrigation in the State Program, Scientific Researches and of the management of waters quality.