Browsing by Author "Covaliova, Olga"

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APPLICATION OF FLOW-THROUGH THREE-DIMENSIONAL ELECTRODES FOR REGENERATION OF PLATING IRON ELECTROLYTES: 1. MATHEMATICAL MODEL
(Institute of Chemistry of ASM, 2014) Koshev, Alexandr; Covaliova, Olga; Varentsov, Valery
The mathematical model of electrochemical processes distribution within the three-dimensional flow-through electrode for the system Fe(III)/Fe(II)/Fe is described in this paper, considering also the electrochemical reactions of hydrogen and molecular oxygen reduction. Possible dynamic changes in the parameters of electrode, electrolyte and the process are taken into account in the mathematical model, such as electro-conductivity of electrode material, electrolyte fl ow rate, material porosity and specific electrode surface, concentrations of electro-active substances and other characteristics within the local volume of electrode. Electrode and process characteristics are treated as time and coordinate functions within the electrode volume. The results of calculations and experimental studies of iron electroreduction are given, the analysis of the numerical modeling is provided.
APPLICATION OF FLOW-THROUGH THREE-DIMENSIONAL ELECTRODES FOR REGENERATION OF PLATING IRON ELECTROLYTES: 2. STUDY OF PROCESS REGULARITIES BY MATHEMATICAL MODELING
(Institute of Chemistry of ASM, 2014) Covaliova, Olga; Kоshev, Alexandr; Varentsov, Valery
The main regularities of the electroactive components distribution, polarization an d local current density within the depth of the threedimensional flow-through electrode have been studied using the calculation method, in dependence on the overall current density, electrode thickness and degree of its compression, solution flow velocity through the electrode, initial concentration of Fe(III) ions in the solution and electrodes brand.
AUTOCATALYTIC REDUCTION AND CHARACTERISTICS OF BORON-CONTAINING COATINGS
(Academia de Știinițe a Moldovei, 2013) Covaliov, Victor; Covaliova, Olga; Ivanov, Mikhail; Drovosekov, Andrey
The 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.
AUTOCATALYTIC REDUCTION AND CHARACTERISTICS OF BORON-CONTAINING COATINGS
(2013) Covaliov, Victor; Covaliova, Olga; Ivanov, Mihail; Drovosecov, Andrei
The 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.
AUTOCATALYTIC REDUCTION AND CHARACTERISTICS OF BORON-CONTAINING COATINGS
(Institute of Chemistry of ASM, 2013) Covaliov, V.; Covaliova, Olga; Ivanov, M.; Drovosekov, A.
The 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 ofthe 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.
BIOREACTOR PENTRU PRODUCEREA FITOCATALITICĂ A BIOHIDROGENULUI ÎN PROCESUL EPURĂRII ANAEROBE A APELOR REZIDUALE AGROINDUSTRIALE
(CEP USM, 2014) Covaliov, Victor; Covaliova, Olga; Nenno, Vladimir; Bobeică, Valentin
CLOSED-CYCLE INTENSIFIED TECHNOLOGY FOR SUSTAINABLE BIOCHEMICAL PRODUCTION OF ALTERNATIVE FUELS FROM AGRICULTURAL WASTES
(Academia de Ştiinţe a Moldovei, 2017) Covaliova, Olga; Covaliov, Victor; Bobeica, Valentin; Nenno, Vladimir; Duca, Gheorghe
CONDITIONING AND UTILIZATION OF ɋО2 FROM FERMENTATION INDUSTRIES FOR THE CULTIVATION OF MICROALGAE
(Academia de Ştiinţe a Moldovei, 2017) Covaliov, Victor; Covaliova, Olga
DEGRADAREA FERMENTATIVĂ A BIOMASEI LIGNOCELULOZICE PENTRU PRODUCEREA BIOGAZULUI: 1. Metode de preprocesare
(CEP USM, 2014) Covaliov, Victor; Ungureanu, Dumitru; Covaliova, Olga; Ioneţ, Ion
Biomasa lignocelulozică sub formă de plante energetice şi resturi/deşeuri vegetale atrage în ultimul timp atenţia specialiştilor în calitate de materie primă/sursă pentru fermentarea anaerobă şi obţinerea biogazului – combustibil netradi- ţional provenit din deşeuri regenerabile. Procesul de fermentare a biomasei lignocelulozice include dezintegrarea/ mărunţirea materiei prime, fermentarea propriu-zisă şi utilizarea produselor fermentării – a masei fermentate şi a biogazului. Datorită faptului că această biomasă este compusă din lignină, polizăharuri ale celulozei şi hemiceluloză – compuşi stabili şi rezistenţi la fermentare, această materie primă trebuie procesată în prealabil prin hidroliză, fiind transformată în zaharuri simple. În lucrare sunt analizate procesele de preprocesare a biomasei lignocelulozice în scopul intensificării fermentării anaerobe şi majorării producţiei de biogaz. Concomitent sunt prezentate rezultatele proceselor de obţinere a biogazului din fermentarea anaerobă a deşeurilor vegetale.
EFFECT OF COMPLEX FORMAT ION ON ELECTROCHEMICAL BEHAVIOUR OF METAL-CONT AINING WASTE WATERS
(Academia de Știinițe a Moldovei, 2009) Covaliova, Olga
The problem of preventing the heavy metals and other toxic substances release in environment due to the discharges of untreated plating and rinsing solutions is actual from both ecologic and economic point of view. It is crucial to prevent the environmental pollution and uncontrolled losses of resources (metals and other substances). The treatment technologies used today are not always efficient and cost saving and in some cases they may even provoke the secondary pollution of environment. Electrochemical treatment of industrial waste waters is one of the most promising technologies as it implies the same principles as the main technological processes and does not require introducing of chemicals into the trea ted solution. However, until now this method was given insufficient attention, although there are ce rtain publications in this field [1]. The electrochemical behaviour of some d- metal complexes was studied and discussed from the viewpoint of water treatment requirements. The studies performed in th e model plating solutions of Zn, Ni, Cu ammonia and pyrophosphate complexes, polynuclear Cr complexes have shown that the application of conventional reagent waste water treatment methods for such solutions would be inefficient. Examination of potentio-dynamic polarization curves registered in studied solutions have s hown, that due to the formation of series of Zn ammonia complexes, alkaline treatment will not ensure Zn removal from such solutions, and application of electrocoagulation treatment method will not be efficient enough. It was also found that in case of Ni-, Cr- containing solutions electrochemical treatment can be used for Cu removal, whereas for the effective Cr(VI) removal the electrocoagulation would be required, which entails the redox processes resulted in the formation of hydroxides. The research has shown that the approach on the heavy metal removal from the used plating solutions may be different depending on the plating bath composition.
EFFECTS OF AMARANTHS’ SEEDS ON DEHYDROGENASE ACTIVITY AND GASES EMISSION IN METHANOGENIC BIOREACTORS
(CEP USM, 2015) Covaliov, Victor; Senicovscaia, Irina; Nenno, Vladimir; Bobeica, Valentin; Covaliova, Olga
The influence of amaranths‘ seeds as the source of squalene on the dehydrogenase activity and efficiency of methane production were investigated in methanogenic bench-scale (5000 ml) bioreactors used to treat the mixture of distillery wastes and farmyard manure. The adding of amaranth seeds to the methanogenic bioreactor has an inhibitory effect on the dehydrogenase activity and stimulates the process of methanogenesis. Dehydrogenase activity decreased with the increase of doses of squalene and its trend had a close connection with doses (R2 =0.77-0.78). The methane content in the total amount of gases is 65.3-71.3% in a bioreactor with the additive of amaranth seeds in a dose of 50 mg l-1, which is 22.1% higher than in the the control bioreactor without additives. The increase in squalene concentration higher than 0.0005% is not rational because its stimulating effect on the methanogenic process decreases. Anaerobic digestion of alcohol distillery industry wastes with manure is a complex nonlinear time-varying microbiological process. Dehydrogenase activity trends in the experiment are described by the power function for 5 hours observations and by the logarithmic function for 120 hours of observations. Trends of CH4 are described by the polynomial function in all periods of testing. Correlation coefficients are 0.37 and 0.70 for CH4 after 5 and 120 hours of the anaerobic digestion. Dehydrogenase activity is in the close negative connection with the amount of gases, including methane. Correlation analysis between dehydrogenase activity and the release of gases has revealed the moderate and strongly negative link during 24 hours after the start of the experiment.
INTENSIFICAREA FITOCHIMICĂ A EMISIEI BIOHIDROGENULUI ÎN PROCESELE DE FERMENTARE ANAEROBĂ A BIOMASEI
(2013) Covaliov, Victor; Duca, Gheorghe; Bobeică, Valentin; Covaliova, Olga
Se 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.
MODIFICATION OF TiO2 PARTICLES NANOSTRUCTURE FOR PHOTOCATALYTIC APPLICATIONS
(Academia de Ştiinţe a Moldovei, 2015) Covaliova, Olga; Covaliov, Victor; Duca, Gheorghe
MODIFIED PROCESS AND BIOREACTOR FOR CYANOCOBALAMINE (VITAMIN В12) AND BIOMETHANE PRODUCTION
(Academia de Ştiinţe a Moldovei, 2017) Covaliov, Victor; Covaliova, Olga
A NEW CONCEPT REGARDING THE SELECTION OF SEWERAGE SYSTEMS AND NATURAL TREATMENT OF MUNICIPAL WASTEWATERS
(2023) Covaliov, Victor; Ungureanu, Dumitru; Duca, Gheorghe; Covaliova, Olga; Romanciuc, Lidia
The 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.
A NEW METHOD OF CYANCOBALAMIN (VITAMIN B12) PRODUCTION AND ITS PRACTICAL USES
(Academia de Ştiinţe a Moldovei, 2015) Covaliova, Olga; Covaliov, Victor; Duca, Gheorghe; Nenno, Vladimir; Bobeica, Valentin
NEW USES OF BIOACTIVE PHYTOCOMPOUNDS DEPENDING ON MOLECULAR STRUCTURE
(Academia de Ştiinţe a Moldovei, 2015) Bobeica, Valentin; Covaliov, Victor; Ivancic, Albert; Nenno, Vladimir; Covaliova, Olga
PROCEDEUL MODIFICAT DE PRODUCERE BIOCHIMICĂ A CIANCOBALAMINEI (VITAMINA B12) DIN DEŞEURI AGROINDUSTRIALE 1. MODIFICĂRI TEHNOLOGICE PRIVIND INTENSIFICAREA PROCESULUI DE OBŢINERE A ADAOSULUI FURAJER
(CEP USM, 2015) Covaliov, Victor; Bobeică, Valentin; Covaliova, Olga
Aplicarea combinată a unor soluţii tehnologice noi, precum: stimularea chimică a metanogenezei, adaosul de compuşi predecesori ai biosintezei vitaminei B12, recircularea CO2 şi suplimentarea acestuia cu H2, a condus la îmbogăţirea sedimentelor epurării fermentativ-anaerobe a borhotului postdistilare alcoolică cu vitamina B12 de 1,5-2 ori. Drept rezultat, a fost ridicată calitatea concentratului furajer vitaminizat, concomitent cu intensificarea producerii biometanului, astfel mărind eficienţa ecologo-economică a epurării anaerobe a borhotului. O parte a cobalaminei se adsorbă pe particulele sedimentului în procesul de formare a lui, iar o parte rămasă în soluţie se supune epurării avansate prin sorbţie pe sorbentul mineral – diatomită. Produsul format poate fi utilizat în calitate de adaos furajer pentru animale şi păsări din agricultură.
PRODUCTION, STRUCTURE AND PHOTOCATALYTIC PROPERTIES OF NANOTUBULAR TiO2
(2020) Duca, Gheorghe; Covaliov, Victor; Covaliova, Olga
Photocatalytic 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.
STUDIUL PROCESELOR REDOX ÎN SISTEME BIOCHIMICE ÎN PREZENȚA ANTIOXIDANȚILOR
(Editura USM, 2023) Duca, Gheorghe; Covaliov, Victor; Covaliova, Olga; Romanciuc, Lidia; Tasca, Corina
Deșeurile din sectorul agroindustrial, datorită efectelor toxice asupra plantelor și organismelor vii, nu pot fi aruncate în sol. Totodată, ele pot servi și ca sursă regenerabilă de produse cu valoare adăugată, care pot fi obținute în urma tratării biochimice specifice. Această cercetare s-a concentrat pe studiile proceselor de fermentare a biomasei în prezența substanțelor bioactive introduse direct în biomasa digestată. Studiul efectelor substanțelor bioactive cu posibile proprietăți antioxidante asupra biomasei din sectorul vitivinicol cu identificarea mecanismelor acestor procese reprezintă o direcție de perspectivă, sugerând noi modalități de valorificare a deșeurilor. Rezultatele obţinute arată că substanţele biologic active de origine naturală utilizate ca aditivi în procesul de digestie a vinasei demonstrează efectele pronunţate asupra fermentaţiei alcoolice a vinasei în condiţii mezofile. Evaluarea comparativă a acțiunii diferiților adaosuri în procesele studiate a demonstrat că acidul dihidroxifumaric a determinat emisia de 266 cm3 CO2 în 76 ore, aescinum – 251 cm3 în 55 ore, tomatin – 233 cm3 în 78 ore, sclareol – 232 cm3 în 55 ore. ore, vanilină – 229 cm3 timp de 69 de ore, în timp ce catechina – 180 cm3 pe parcursul a 61 de ore de fermentație, până la finalizarea procesului de fermentație. A fost arătat că adăugarea compușilor complexși de Co(III) permite obținerea cobalaminei (vitamin B12) în fracția semi-solidă formată după fermentare. În rezultatul tratării, valorile CCOCr și CBO5 s-au redus cu 96,6-97,8%. Deasemenea, au fost elaborate două preparate pentru tratarea deșeurilor organice: unul pentru înlăturarea mirosului neplăcut a nămolurilor semi-solide rezultate din epurarea apelor uzate municipal, prin inhibiție a dezvoltării substanțelor tiolice formate în rezultatul acțiunii vitale a microorganismelor din digestatul format, și cel de-al doilea preparat - pentru deparazitare a nămolurilor de epurare stabilizate a apelor uzate cu folosirea juglonului. Ambele procese tehnologice pot fi recomandate pentru aplicare în practică.