Facultatea de Chimie şi Tehnologie Chimică / Faculty of Chemistry and Chemical Technology

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Start date: 2023Subject: search.filters.subject.inhibition capacity

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    Rolul cobalaminei în procesele de autopurificare radicalică în mediul acvatic [Articol]
    (CEP USM, 2024) Lis, Angela; Gladchi, Viorica; Blonschi, Vladislav; Cisteacov, Maxim; Bunduchi, Elena
    The main purpose of this research is to study the role of Cyanocobalamin (CNCbl) in aquatic ecosystems. The spectrophotometric method was used to determine the inhibition capacity and the concentration of OH radicals using PNDMA traps. As a result, it was found that, on the one hand, CNCbl is a reducing substance and leads to the consumption of oxidative equivalents, resulting in its oxidation. High inhibition capacity values and low OH radical values confirmed this. On the other hand, under irradiation, CNCbl can also act as a sensitizer. It actively absorbs photons in the UV and visible range, transitions to an excited state, and then transfers the electronic excitation energy to dissolved oxygen in water, forming active species such as singlet oxygen and superoxide radical anion. In the presence of protons, the superoxide radical anion is reduced to hydrogen peroxide, which generates OH radicals upon irradiation. From the obtained results, it can be seen that under the conditions of natural aquatic systems, CNCbl will not disturb the processes of radical self-purification.
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    Monitorizarea proceselor de autopurificare chimică a sistemelor acvatice în baza indicatorilor cinetici [Articol]
    (Editura USM, 2023) Bunduchi, Elena; Duca, Gheorghe; Gladchi, Viorica
    În lucrarea de față sunt aduse date privind conținutul și dinamica temporală a peroxidului de hidrogen [H2O2], a reducătorilor peroxidazici [Red], a stării redox cinetice (ox./inst./red.) și a constantei efective de întrerupere a lanțului radicalic în procesele de oxidare cu participarea radicalilor •OH, pentru unele ape naturale. Perioada de monitorizare a cuprins anii 2020-2022. Supravegherea a scos în evidenţă prezența unor cantităţi scăzute de H2O2 (˂ 10 μg/L), dar mai des lipsa acestui oxidant în toate apele investigate, fapt ce arată că din totalul de substanţe reducătoare prezente în ape prevalează constant substanţele care sunt oxidate preferenţial de către H2O2. Obiectele acvatice se confruntă constant cu deficit de peroxid de hidrogen. Ca rezultat starea redox cinetică a apelor a fost frecvent fie instabilă, fie reducătoare. Se menționează că apele monitorizate au fost poluate cu captori de radicali •OH. Gradul de poluare variază de la poluată ușor (≈ 2.0·105 s-1 ) până la poluată înalt (> 10.0·105 s-1). Râul Ichel și lacul Dănceni sunt obiectele acavatce în care procesele deautopurificare radicalică sunt încetinite. Datele nu relevă că apele afluenților mărescpoluarea apelor nistrene.
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    Redox self-purification mechanism of natural waters with the involvement of thioglycolic acid and thiourea [Articol]
    (Pennsylvania, USA, 2023) Lis, Angela; Duca, Gheorghe; Gladchi, Viorica; Bunduchi, Elena; Blonschi, Vladislav
    This chapter studied the influence of TGA and TU on the self-purification processes of aquatic systems on model systems, whose composition was modeled to be as close as possible to the natural waters. As a source of irradiation was used the DRT-400 lamp and the Solar Simulator, Oriel model 9119X, the emission spectra of which overlap with the emission spectrum of the Sun. The results of the research show that on irradiation, TGA can regenerate an additional amount of OH radicals, thus contributing to the intensification of water self-purification processes. But in the presence of transition metals, such as Cu (II) and Fe (III), it has been established that the intensity of self-purification processes decreases due to the formation of the mercaptides, whose catalytic activity is low. Unlike TGA, TU leads to decreasing the intensity of the self-purification processes of aquatic systems, through the intense consumption of OH radicals, and at the same time on the interaction with transition metals, such as Cu (II) and Fe (III), form stable complexes with low catalytic activity.