2. Articole
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Item Spectroscopic properties of ZnPc(COOH)4/Ch/Fe3O4 supramolecular architectures [Articol](CEP USM, 2024) Druță, Alexandrina; Lungu, Ion; Popușoi, Ana; Potlog, Tamara; Bulmaga, Petru; Rusnac, RomanThis paper presents the synthesis of ZnPc(COOH)4/Ch/Fe3O4 supramolecular architectures at various ZnPc(COOH)4 and Ch/Fe3O4 concentrations explored in the synthesis process. Ch/Fe3O4 composite was prepared by a simple solution mixing-evaporation method. The validation of the synthesis was achieved through FTIR analysis and UV-Vis spectroscopy. FTIR of composite indicated an interaction between chitosan and Fe3O4 NPs. The chemical interaction of ZnPc(COOH)4 with Ch/F3O4 composite is confirmed by the shift of the signal from ν(C=O)) of protonated COOH groups in the FTIR spectrum of ZnPc(COOH)4, associated with spitting, to (νsym(COO)) and (νasym(COO)) that correspond to deprotonated carboxylic group. The absorption spectra of ZnPc(COOH)₄ revealed IR Q band with two subbands situated at 640 nm 700 nm. Also, the effect of various ZnPc(COOH) and Ch/Fe3O4 concentrations on absorbance of ZnPc(COOH)4/Ch/Fe3O4 supramolecular architecture is discussed.Item Regenerarea cărbunelui activ ag-3 utilizat în procesele de potabilizare a apelor de suprafață [Articol](CEP USM, 2023) Ciobanu, Mihai; Lupașcu, Tudor; Țîmbaliuc, Nina; Boldurescu, NinaS-a studiat procesul termic de regenerare a cărbunelui activ AG-3 uzat de la stația de potabilizare a apei din municipiul Chișinău. Procesul de regenerare s-a efectuat la diferite temperaturi și la diferite intervale de timp cu vapori de apă. Pentru evaluarea gradului de regenerare a mostrelor de cărbuni activi s-au măsurat izotermele de adsorbție a benzenului și a albastrului de metilen din soluții apoase. S-a constatat că la temperaturi ridicate se produce regenerarea integrală a cărbunelui activ AG-3 uzat. Acest fapt se confirmă prin valorile adsorbției albastrului de metilen practic egale pe cărbunele activ regenerat și pe cel intact. La temperaturi apropiate de 8000 C, capacitatea adsorbțională a cărbunelui activ AG-3 uzat, dar regenerat este chiar mai mare decât a cărbunelui activ AG-3 intact, fapt care poate fi explicat prin oxidarea completă a carbonului amorf restant în carbonizat din structura poroasă.Item Adsorption of Lanthanide (III) Cations on Cross-Linked Ionic Polymer, Composition and Thermal Analysis of the Formed Composites [Articol](2021) Guțanu, Vasile; Lisă, Gabriela; Rusu, DanielaThe adsorption of lanthanide(III) cations by a strongly basic cross-linked polymer containing R4N+ groups was studied at 21 and 50°C. At both temperatures the sorption is best described with the Langmuir model. The maximum adsorption at both 21 and at 50°C increases in the series: La3+ < Eu3+ < Nd3+ < Er3+. The results show that polymers containing strongly basic groups can, under certain conditions, be used to separate lanthanide(III) cations in solutions containing mono- and bivalent cations. SEM EDX studies show that La3+, Nd3+, Eu3+ and Er3+ form composites in the polymer phase. The elemental composition of structural units of the composites is La1Cl13.7S64.3O287.7N122.6C2869, Nd1Cl27.4S50.7O391.6N169.3C2896, Eu1Cl8.5S50.8O285N130C2118 and Er1Cl36.8S263.9O1106N447C8657. The thermodynamic parameters of the sorption process are calculated: free energy, enthalpy, and entropy. Thermogravimetric analysis made it possible to determine the stability of the formed composites, the stages of their decomposition and the corresponding kinetic parameters.Item 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, 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 STUDIUL PROCESELOR DE ADSORBȚIE A VITAMINEI B6 PE ADSORBANȚI CARBONICI AUTOHTONI(CEP USM, 2023) Țîmbaliuc, Nina; Petuhov, Oleg; Lupașcu, Tudor; Boldurescu, NinaÎn lucrare sunt prezentate rezultatele studiului adsorbției vitaminei B6 pe două mostre de cărbune activ autohton: AC-C și CAN-8. Datele cineticii de adsorbție, determinate la trei valori ale concentrației inițiale, denotă că rata imobilizare a adsorbatului crește odată cu creșterea timpului de contactare dintre cele două faze și este funcție de de concentrația inițială. Izotermele de adsorbție a vitaminei B6 au fost prelucrate utilizând ecuațiile de adsorbție Langmuir și Freundlich. S-a stabilit că imobilizarea vitaminei B6 pe adsorbanții cercetați este mai bine descrisă de modelul Langmuir. Valorile adsorbției maximale înregistrate pentru cărbunii activi AC-C și CAN-8 sunt în concordanță cu parametrii de structură a cărbunilor cercetați. Cercetările realizate atestă că contaminanții emergenți, cu o masă moleculară și proprietăți chimice similare cu vitamina B6, pot fi eficient imobilizați și îndepărtați din soluții apoase folosind cărbunii activi autohtoni AC-C și CAN-8 în calitate de adsorbanți obținuți din materie primă locală.Item ИЗУЧЕНИЕ АДСОРБЦИИ И КИНЕТИКИ АДСОРБЦИИ МЕТИЛЕНОВОГО СИНЕГО ИЗ ВОДНЫХ РАСТВОРОВ НА ТРЕПЕЛЕ(CEP USM, 2021) Тутован, Елена; Исак-Гуцул, ТатьянаA fost studiată adsorbția colorantului albastru de metilen (AM) pe tripol natural autohton. S-a stabilit că adsorbția AM pe tripol crește cu creșterea pH-ului. Forma izotermei de adsorbție a AM pe tripol este de tip Langmuir. Au fost determinate constantele din izoterma Langmuir (qmax = 107,527 mgг/g, K = 0,046 L/mg ) și Freundlich ( = 10,021 мг/г, 1/n = 0,517) și a fost stabilit că procesul de adsorbție este mai exact descris de modelul Langmuir. S-a observat că echilibrul se stabilește, practic, după 8 ore de contactare a soluției AM cu tripolul. Cinetica procesului de adsorbție a AM pe tripol este descrisă de modelul cinetic de ordinul pseudo-doi (к2 = 2,13 10-2 gh-1mg-1)Item NLĂTURA R EA COLORANTULUI PORTOCALIU ACTIV ȘI A ACIDUL UI 2, 2 - DIHIDROXIMETIL PROPIONIC PRIN METODE DE CONCENTRARE , LA PRIMA ETAPĂ , URMATE DE OXIDARE ŞI ADSORBŢIE(CEP USM, 2017) Gonța, Maria; Matveevici, Vera; Iambarțev, Viorica; Mocanu, Larisa; Duca, GheorgheA fost studiat procesul de diminuare a concentrației emolientului , acidul 2,2-dihidroximetil propionic (DMPA),în prezența colorantului textil portocaliu activ (PA).S-a constatat că efectul înlăturării componenților din amestecul de colorant şi emolient se măreşte la aplicarea metodei de electroflotare sau electroflotocoagulare, iar la aplicarea metodei de coagulare efectul înlăturării se micșorează . La fel, s-a stabilitcă sistemele cu concentraţii mici de colorant PA (100,0 mg/l) şi molient 20,0-80,0 mg/L)se epurează prin combinarea metodei de electroflotocoagulare şi adsorbţie.Odată cu mărirea concentraţiei compuşilor organici, este necesară combinarea metodelor de electroflotocoagulare şi oxidare.Item 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, LarisaAdvanced 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.