Browsing by Author "Guțanu, Vasile"

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ADSORPTION OF LANTHANIDE (III) CATIONS ON CROSS-LINKED IONIC POLYMER, COMPOSITION AND THERMAL ANALYSIS OF THE FORMED COMPOSITES
(2021) Guțanu, Vasile; Lisă, Gabriela; Rusu, Daniela
The 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.
THE IMMOBILIZATION OF LANTHANIDE (III) CATIONS ON A POLYMER CONTAINING QUATERNARY AMMONIUM NITROGEN: INFLUENCE OF THE TEMPERATURE AND pH, PROCESS KINETICS
(2020) Guțanu, Vasile; Grecu, Cristina
The immobilization of lanthanide (III) cations on the Purolite A-400, a cross-linked polymer containing –R4N+ groups, was investigated. This type of polymers theoretically cannot retain metal cations from solutions. We assume that cations sorption on this polymer takes place due to the formation of jarosite mineral–type compounds. By increasing the temperature in the range of 0–60 °C, the cations sorption increases slightly but in the pH range of 2–6, it increases more considerable in the following order: La3+˂ Nd3+ ˂ Eu3+ ≈ Er3+. The sorption at 21 and 50 °C is adequately described by the pseudo-first-order (PFO) kinetic model, and the limiting step of the rate which decreases in order Er3+ ˃ Eu3+ ˃ Nd3+ ˃ La3+ is internal diffusion.
INTERACTION OF L-ASCORBIC ACID WITH ACTIVATED CARBON: KINETIC STUDIES AND THE EFFECT OF pH
(2022) Guțanu, Vasile; Baerle, Natalia
This article investigates the interaction of vitamin C with commercial activated Granucol-type carbons and newly produced AC-C coal at 25 and 35°C. L-Ascorbic acid molecules have been shown to retain on the surface of coals due to physical interactions. The adsorption kinetics is perfectly described by the pseudo-second-order kinetic model. The adsorption rate is mainly determined by the intraparticle diffusion. The process of adsorption of vitamin C on activated carbon is accompanied by a change in the pH of the system. The absorption is highly dependent on the pH of the solution, decreasing as the pH of the solution increases prior to contact with the carbon. In the carbon phase, ascorbic acid oxidizes to dehydroascorbic acid.
IODIDE IONS SORPTION ON POLYMER AV-17(Cl) AND SORBENT AV-17(Bi)
(2014) Guțanu, Vasile
The iodide ions sorption from solutions of KI and KI in excess of KCl has been investigated. The strongly basic anion exchangers AV-17 in Cl- form and Varion AD in NO3 - form was used as sorbents. Also AV-17 polymer modifi ed with Bi(III)-containing compounds were used. The sorption was performed in static and dynamic conditions. Isotherms are approximated with BET sorption model. The sorption value of iodide ions in the KI solutions with KCl in excess is quite high. It was established that sorption of iodide ions in the form of polyiodide occurs both as a result of anion exchange and as a result of chemisorption.
METALLIC COMPOUNDS IN THE PHASE OF THE RETICULATED IONIC POLYMERS
(2010) Guțanu, Vasile; Turta, Constantin; Filoti, George
In this review there are described the results of studying of iron ions state in the ion-exchange resins (KU-2, AN-31, AV-17, Varian – AD, EDE-10P), obtained by Mossbauer spectroscopy. The iron ions have been sorbet on ion exchangers, from aqueous solutions at different temperatures and air conditions. The iron state in polymer phase depends of nature of electron donor groups - amine or carboxylic. To explain the form and temperature dependence of Mossbauer spectra of polymer phase containing iron it was proposed the presence of different compounds like β-FeOOH, α-Fe2O3, and jarosite mineral type compounds: (R4N,H3O)[Fe3(OH)6(SO4)2] or coordination modes: {RCOO-Fe(L4)-OOCR}1 , {R-CO2=Fe(X2)=O2C-R}n, {R-COO-Fe(X4)-OOC-R}n, and {(-NCH2CH2N-)= Fe(X2) =(-NCH2CH2N-)}, where X= H2O,OH-, SO42-., n= from 3- to 1 . In special conditions the ultraﬁne superparamagnetic particles of Fe2O3 have been obtained.
STRUCTURAL, MORPHOLOGICAL AND MAGNETIC CHARACTERIZATION OF METAL-CHITOSAN/POLY (VINYL AMINE) COMPLEXES
(2017) Cocârță, Ana Irina; Guțanu, Vasile; Drăgan, Ecaterina Stela
Cu2+ and Ni2+ complexes of chitosan/poly(vinyl amine) (CS/PVAm) composites were prepared. The metal-CS/PVAm complexes were characterized by FT-IR spectroscopy, SEM-EDX, X-ray diffraction (XRD), and magnetic moment determination. FT-IR spectra of the metal-CS/PVAm complexes showed the characteristic bands of anhidroglucose unit were affected by the metal complexation, and new bands assigned to Me–N and Me-O bonds were observed. SEM images of the surface of metal-composite complexes show the influence of metal ion on the morphology of the complexes, the strong binding of Cu2+ and Ni2+, involving most of the amino groups, leading to a dense surface structure. The chemical composition on the surface of metal-CS/PVAm complexes was determined from EDX measurements. XRD provided information about the amorphous or crystalline nature of the composite and metal-composite complexes. Using magnetic susceptibility method, the oxidation degree of metal ions from the polymer phase, the homogeneous distribution of the ligand groups from the volume of the CS/PVAm beads, and the existence of the antiferromagnetic interactions between the metal ions were determined.