Browsing by Author "Mateevici, Vera"

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ÎNDEPĂRTAREA CEFALEXINEI DIN SOLUȚII APOASE UTILIZÂND PROCESUL FOTOCATALITIC FENTON
(Academia de Ştiinţe a Moldovei, 2021) Mocanu, Larisa; Gonța, Maria; Mateevici, Vera; Duca, Gheorghe; Porubin-Schimbător, Veronica
This paper aims to study the degradation and oxidation/mineralization process of cephalexin in model systems using Fenton’s reagent for UV irradiation (λ = 254 nm). The effect of pH (2-11), concentration of H2O2 (0,3434 mg/L) and concentration of Fe(II) (0-28 mg/L) on the degradation of 50 mg/L CPX were investigated. It has been determined optimum conditions for photocatalytic oxidation of CPX. Increasing the amount of H2O2 plays an inhibitory role in the production of hydroxyl radicals and reduces the process efficiency. This can be attributed to the reaction of excess peroxide with •OH and the formation of HO2 •, which has less oxidizing power compared to free hydroxyl radical. And as the concentration of the catalyst increases to the optimum, the excess of Fe(II) ions reacts with the hydroxyl radical and, therefore, the efficiency of the process also is reduced. Accordingly, the optimum degradation efficiency of 88 % and 83% for COD was obtained under the following conditions: pH 2,5, H2O2 concentration – 3,4 mg/L, Fe(II) ions concentration – 5,6 mg/L, cephalexin concentration – 50 mg/L, and reaction time – 60 min. Thus, the current study demonstrated that the photo-Fenton reactor can be used effectively as an advanced oxidation treatment unit for degradation of cephalexin under optimized environmental conditions.
ÎNLĂTURAREA COLORANŢILOR DIRECŢI DIN APELE REZIDUALE TEXTILE PRIN METODE ELECTROCHIMICE
(CEP USM, 2007) Duca, Gheorghe; Mateevici, Vera; Gonţa, Maria; Coptu, Olga
The process of direct colorants removal from solutions on their electrochemical treatmentin the cells with soluble Al anodes has been studied. It was found that the effect of colorants removal depends on pH value. With the increase of anionic groups number, the pH value is decreased from 6,0 to 5,0. It was shown that the most effective direct colorants can be removed by the electrochemical coagulation, and the removal efficiency is dependent on the intensity of electric current.
STUDIEREA PROCESULUI DE DIMINUARE A CONCENTRAŢIEI COLORANŢILOR DIRECŢI DIN SOLUŢIILE-MODEL PRIN APLICAREA METODELOR FIZICO-CHIMICE
(CEP USM, 2011) Mateevici, Vera; Duca, Gheorghe; Gonța, Maria; Iambarțev, Viorica; Mocanu, Larisa
The process of removal of textile coloring agents from model solutions by means of consecutive electrochemical andcatalytic oxidative treatment in the presence of hydrogen peroxide, and its dependence of the amount of electrochemical coagulant, initial concentration and properties of the coloring agent as well as the iron ions (II) content was discussed incurrent paper. The obtained results prove that the removal of reactive colorants through electrical generation of coagulants is more effective and economically sound when carried out from more concentrated model solutions of textile residual waters (the initial concentration should between 150-200 mg/l). The application of catalytic oxidation procedure can be applied in case of removal of reactive colorants of less concentrated solutions (the amount of colorants should not exceed 50 mg/l). From the acquired results it was identified that combined methods of electrochemical removal and catalytic oxidation by hydrogen peroxide of reactive colorants assure their effective removal from model solutions of residual waters containing up to 200 mg/l of mentioned colorants. The mineralization and residues content were reduced by 97-98%, while the consumption of coagulant was lower by a factor of 2-2.5 in comparison with conventional methods of treatment.