2. Articole

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    Oxidarea foto-catalitică cu reagentul Fenton a surfactantului anionic 2-etil-hexil sulfat de sodiu [Articol]
    (2021) Porubin-Schimbător, Veronica; Gonța, Maria; Mocanu, Larisa
    A fost studiat procesul degradării și mineralizării surfactantului anionic 2-etil-hexil sulfat de sodiu (2-EHS), utilizând procesul de oxidare foto-catalitică cu reagentul Fenton. Ca urmare a cercetărilor științifice s-a constatat că eficiența degradării surfactantului 2-EHS depinde de pH-ul mediului de reacție. S-a constatat că în intervalul de pH=2-2,5 concentrația remanentă a 2-EHS este minimală și crește odată cu creșterea pH-ului, iar un rol important în aceste procese îi revine concentrațiilor ionilor de Fe2+ și a H2O2. Au fost determinare condițiile optime de realizare a procesului de degradare foto-cataliticiă a 2EHS cu reagent Fenton: [H2O2] = 0,3 mM, [Fe2+] = 0,8 mM, pH=2,5. S-a stabilit ca în astfel de condiții procesul de oxidare foto-catalitică cu reagentul Fenton decurge cu o eficiență de 95%.
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    Procesele avansate de foto-oxidare (reagentul Fenton) pentru mineralizarea surfactantului anionic 2-etil-hexil sulfat de natriu [Articol]
    (US Cahul, 2021-06-04) Porubin-Schimbător, Veronica; Gonța, Maria; Mocanu, Larisa
    A fost studiat procesul degradării și mineralizării surfactantului anionic 2-etil-hexil sulfat de sodiu (2-EHS), utilizînd procesul de oxidare foto-catalitică cu reagentul Fenton. Cercetările experimentale au fost realizate pe sisteme model în soluții apoase. Au fost stabilite condițiile optime de degradare și mineralizare în funcție de pH, timpul de oxidare, concentrația peroxidului de hidrogen și a Fe (II). Concentrația remanentă a surfactantului 2-EHS în urma foto-oxidării cu reagentul Fenton a fost determinată folosind metoda spectrofotometrica cu Albastru de Metilen. Ca urmare a cercetărilor științifice s-a constatat că eficiența degradării și mineralizării surfactantului anionic 2-EHS depinde de parametrii fizico-chimici astfel ca: pH, concentrația peroxidului de hidrogen, de concentrația Fe(II) și timpul de oxidare. S-a stabilit ca procesul de oxidare foto-catalitică cu reagentul Fenton decurge cu o eficiență de 95%.
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    The diminishing of the content of textile direct dyes and auxiliary compounds during their catalytic oxidation [Articol]
    (2014) Gonța, Maria; Duca, Gheorghe; Matveevici, Vera; Mocanu, Larisa
    Advanced 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.
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    STUDIUL INFLUENŢEI SUBSTANŢELOR SURFACTANTE ANIONICE ASUPRA PROCESULUI DE ÎNLĂTURARE A COLORANŢILOR DIN SOLUŢIILE MODEL LA TRATAREA LOR PRIN METODE FIZICO-CHIMICE
    (CEP USM, 2012) Matveevici, Vera; Gonţa, Maria; Duca, Gheorghe; Mocanu, Larisa
    It was studied process of elimination of direct red dye inthe presence of anionic surfact ant (sodium lauryl sulphate) of model solution, with their combinated tratation with alum inium coagulant, catalytic oxidation with hydrogen peroxide and sorbtion of remain compounds from activated charcoal by depending of concentration of aluminium ions, dye, surfactant and time of catalytic oxidation. It was obtained that direct dye can be eliminated from model solution with initial concentration of dye from 50 to 200 mg/l in presence of anionic surfactant (only to 40 mg/l) by applyind of combinated methods of coagulation with aluminium coagulant and adsorbtion from activated charcoal. Consume of coagulant in presence of surfactant rise from 2-3 time comparated with removal of dyes in absence of surfactant. It was founded that catalytic oxidation the mixture of direct dyes and anionic surfactants, molecules of surfactant degrades more difficult than dye molecules at the catalytic oxidation in presence of hydrogen peroxide, catalysed by Fe (II), and concentration of remain organic compouds can be reduced only on adsorbtion by activated charcoal. Cleaning concentrated solution, that contain direct dye and anionic surfactant with 200 mg/l and 60 mg/l concentration, can be realize only with combination of coagulation, catalytic oxidation and adsorbtion with activated charcoal methods.
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    THE DIMINISHING OF THE CONTENT OF TEXTILE DIRECT DYES AND AUXILIARY COMPOUNDS DURING THEIR CATALYTIC OXIDATION
    (Institute of Chemistry of ASM, 2014) Gonta, Maria; Duca, Gheorghe; Matveevici, Vera; Mocanu, Larisa
    Advanced oxidation methods of organic compounds lead to their partial mineralization and increase of the adsorption process effi ciency 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.