Papers by Ecaterina Stela Dragan
Molecules, Dec 5, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Die Makromolekulare Chemie
Polymers with tertiary amino groups were obtained by reaction of chloromethylated polystyrene (CM... more Polymers with tertiary amino groups were obtained by reaction of chloromethylated polystyrene (CMPS) with 3‐alkylaminopropionitriles (2a — e). The resulting polymers 3a — e were characterized by elemental analyses, IR and 1H NMR spectra. Kinetic investigation showed that the reaction is characterized by two rate constants, the rate change taking place at a conversion of 45–50%. Viscosimetric studies of the hydrochlorides of polymers 3a — e in water and methanol showed that they behave as polyelectrolytes only in methanol. The abnormal behaviour of water solutions was explained by hydrolysis reaction. To prove the conclusions on the molecular structures of 3a — e and the reactivity of CMPS, a study of the reaction of benzyl chloride with the same amines was performed.
Polymers, Feb 10, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Some cationic composite hydrogels based on chitosan (CS) and poly (N-2-aminoethyl acrylamide) (PA... more Some cationic composite hydrogels based on chitosan (CS) and poly (N-2-aminoethyl acrylamide) (PAEA) covalently cross-linked with glutaraldehyde (GA) were tested as novel sorbents for two dis-azo dyes: Congo Red and Direct Blue 1. Three CS-based composite hydrogels having different molar ratios between the primary amine groups and the cross-linking agent (GA/NH 2 = 5.3 and 12.5), the same total concentration of polycations (C PC = 2 wt%) and two molar ratios between polycations (PAEA:CS = 0.25 and 1.2) were used for this study. Pseudo-first order model, pseudo-second order model and the intraparticle diffusion model were used to analyze the experimental data in order to establish the mechanism of adsorption. The adsorption kinetics has been well described by the pseudo-second order model. The effect of temperature on the adsorption of both dyes has been also investigated.
Ionic hybrids based on chitosan and clinoptilolite with sorption capacity for copper(II) ions hig... more Ionic hybrids based on chitosan and clinoptilolite with sorption capacity for copper(II) ions higher than that of crosslinked chitosan are presented in the paper. Hybrids based on chitosan and clinoptilolite were characterized by swelling degree in water as a function of pH, and by the sorption and desorption of copper(II).
Molecules, Mar 20, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
ACS omega, Aug 23, 2022
The paper reports on the performances of cross-linked amidoxime hosted into mesoporous silica (AM... more The paper reports on the performances of cross-linked amidoxime hosted into mesoporous silica (AMOX) in the removal of As(III) and As(V). The optimum pH for sorption of As(III) and As(V) was pH 8 and pH 5, respectively. The PFO kinetic model and the Sips isotherm fitted the best the experimental data. The thermodynamic parameters were evaluated using the equilibrium constant values given by the Sips isotherm at different temperatures and found that the adsorption process of As(III) and As(V) was spontaneous and endothermic on all AMOX sorbents. The spent AMOX sorbents could be easily regenerated with 0.2 mol/L HCl solution and reused up to five sorption/desorption cycles with an average decrease of the adsorption capacity of 18%. The adverse effect of the co-existing inorganic anions on the adsorption of As(III) and As(V) onto the sorbent with the highest sorption capacity (AMOX3) was arranged in the following order: H2PO4– > HCO3– > NO3– > SO42–.
Chemical Engineering Journal
Molecules
In this paper, we present the synthesis of new polymeric adsorbents derived from macroporous chlo... more In this paper, we present the synthesis of new polymeric adsorbents derived from macroporous chloromethylated styrene–divinylbenzene (DVB) copolymers with different cross-linking degrees functionalized with the following aminobenzoic groups: styrene—6.7% DVB (PAB1), styrene—10% DVB (PAB2), and styrene—15% DVB (PAB3). The new polymeric products, PAB1, PAB2, and PAB3, were characterized by FTIR spectroscopy, thermogravimetric analysis, and EDX, SEM, and BET analysis, respectively. The evolution of the functionalization reaction was followed by FTIR spectroscopy, which revealed a decrease in the intensity of the γCH2Cl band at 1260 cm−1, and, simultaneously, the appearance of C=O carboxylic bands from 1685–1695 cm−1 and at 1748 cm−1. The thermal stability increased with the increase in the cross-linking degree. The data obtained from the EDX analysis of the novel cross-linked copolymers confirmed the functionalization with aminobenzoic groups through the presence and content of nitroge...
ACS Applied Materials & Interfaces, 2020
E: Crystallographic Communications, 76, 929-932 (2020) ൬൫. Crystal structure of catenapoly[[[diaq... more E: Crystallographic Communications, 76, 929-932 (2020) ൬൫. Crystal structure of catenapoly[[[diaqua[1,2-bis(pyridin-4yl)ethene]{4-[2-(pyridin-4-yl)ethenyl]pyridinium}gold(I)iron(II)]-di-μcyanido] bis[dicyanidogold(I)] 1,2bis(pyridin-4-yl)ethene dihydrate]
Revue Roumaine de Chimie, 2019
The paper follows the chemical modification of different sorts of starch after grafting and hydro... more The paper follows the chemical modification of different sorts of starch after grafting and hydrolysis reactions. The grafting reaction of acrylonitrile on the starches from potato, wheat and rice, took place using Ce(SO 4) 2 in H 2 SO 4 0.4 M, as initiator system. Even if the grafting reaction with this initiator system has been already discussed in the literature, this paper aims a comparison of the product characteristics as a function of starch source. The synthesis of water soluble polymers was performed by the basic hydrolysis of the grafted starches. The grafted and hydrolyzed copolymers were characterized by FT-IR and 1 H-NMR spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX).
Molecules, 2020
The authors wish to make a change to the published paper [...]
Molecules, 2020
Materials coming from renewable resources have drawn recently an increased attention in various a... more Materials coming from renewable resources have drawn recently an increased attention in various applications as an eco-friendly alternative in the synthesis of novel functional materials. Polysaccharides, with their prominent representative – chitosan (CS), are well-known for their sorption properties, being able to remove metal ions from dilute solutions either by electrostatic interactions or chelation. In this context, we proposed here a comparative study on Cu2+, Zn2+, Ni2+, Fe3+, and Cr3+ metal ions removal from industrial wastewaters by CS-based composite cryogels using batch technique. The composite cryogels consisting of CS embedding a natural zeolite, namely clinoptilolite, were synthesized by cryogelation, and their sorption performance were compared to those of CS cryogels and of acid-activated zeolite. A deeper analysis of thermodynamics and kinetics sorption data was performed to get insights into the sorption mechanism of all metal ions onto sorbents. Based on the opti...
Molecules, 2020
Removal of Cr(VI) from the environment represents a stringent issue because of its tremendous eff... more Removal of Cr(VI) from the environment represents a stringent issue because of its tremendous effects on living organisms. In this context, design of sorbents with high sorption capacity for Cr(VI) is getting a strong need. For this purpose, poly(vinylbenzyl chloride), impregnated into porous silica (PSi), was cross-linked with either N,N,N’,N’-tetramethyl-1,2-ethylenediamine (TEMED) or N,N,N’,N’-tetramethyl-1,3-propanediamine, followed by the reaction of the free -CH2Cl groups with N,N-diethyl-2-hydroxyethylamine to generate strong base anion exchangers (ANEX) inside the pores. The PSi/ANEX composite sorbents were deeply characterized by FTIR spectroscopy, SEM-energy dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), and water uptake. The sorption performances of composites against Cr(VI) were investigated as a function of pH, contact time, initial concentration of Cr(VI), and temperature. It was found that the cross-linker structure and the silica morphology ar...
Environmental Engineering and Management Journal, 2006
The flocculation efficiency of some polycations with quaternary ammonium salt groups located in t... more The flocculation efficiency of some polycations with quaternary ammonium salt groups located in the backbone, such as N,N-dimethyl-2-hydroxypropylenammonium chloride in PCA 5 , P CA 20, PCA 5 D 1 , PCA 5 H 1 , PCA 5 H 2, and poly(diallyldimethylammonium chloride) (PDADMAC), on the montmorillonite and silica nanoparticles contained in synthetic aqueous suspensions has been studied in this work. The influence of the charge density, polycation dose as well as of temperature on the separation of the inorganic particles was followed by turbidity measurements. Dual flocculation of dyes and flocculation of silica with preformed nonstoichiometric interpolyelectrolyte complexes as colloidal dispersions were also discussed comparative with single polycations.
Environmental Engineering and Management Journal, 2002
The dilute solution behavior of a polyelectrolyte with quaternary ammonium salt groups (N,N-dimet... more The dilute solution behavior of a polyelectrolyte with quaternary ammonium salt groups (N,N-dimethyl-2-hydroxypropylenammonium chloride) located along the main chain, (PCA 5), has been studied in order to obtain information about the effect of polymer concentration and polarity strength of the solvent onto its chain conformation in various mixtures of water/methanol. The conformational changes of polyelectrolyte chain were followed by viscometric and conductometric methods. The viscometric experimental data were plotted in the terms of Rao's equation. Straight lines were obtained in all cases, allowing the calculation of intrinsic viscosity, [η]. The intrinsic viscosity values decreased with increasing organic solvent content in the mixed solvents. Data from the conductometric studies emphasized the equivalent conductivity values, Λ, increase with decreasing concentration over the whole concentration range. At a given concentration the equivalent conductivity decreases with decreasing dielectric constant. The flocculating efficiency of this polycation on an aqueous suspension of bentonitic clay was also studied.
International Journal of Biological Macromolecules, 2019
Could the porous chitosan-based composite materials have a chance to a "NEW LIFE" after Cu(II) io... more Could the porous chitosan-based composite materials have a chance to a "NEW LIFE" after Cu(II) ion binding?
Reactive and Functional Polymers, 2018
Porous strong base anion exchanger (SBAEx) microspheres bearing either N,N-dimethyl 2-hydroxyethy... more Porous strong base anion exchanger (SBAEx) microspheres bearing either N,N-dimethyl 2-hydroxyethyl ammonium, or N,N-diethyl 2-hydroxyethyl ammonium functional groups attached to styrene-divinylbenzene matrix were comparatively used as sorbents for the removal of Cr(VI) oxyanions from aqueous solutions, in batch mode. The remarkable retention capacity of Cr(VI) ions was slightly influenced by the solution pH, when pH varied in the range 3-6, this being very convenient for the applications of these sorbents. Sorption kinetics results at 25°C, fitted with pseudo-first order, pseudo-second order (PSO), Elovich, and intra-particle diffusion models evidenced that the sorption of Cr(VI) onto SBAEx obeyed the PSO kinetic model, and this supports chemisorption as the main mechanism of sorption. The experimental data for the Cr(VI) sorption at equilibrium were fitted with five isotherm models, Langmuir, Freundlich, Dubinin-Radushkevich, Temkin, and Sips, and found that the Langmuir, Temkin and Sips isotherms described very well the sorption process. The maximum sorption capacity for Cr(VI) oxyanions, evaluated by the Langmuir isotherm, ranged from 278.2 mg/g to 323.7 mg/g, being higher when the functional groups were N,N-dimethyl 2-hydroxyethyl ammonium chloride than in the case of N,N-diethyl 2-hydroxyethyl ammonium chloride. The negative values of ΔG°showed that sorption process was spontaneous and thermodynamically favorable, while more negative values of ΔG°in the case of the SBAEx having methyl substituents indicated the preference of Cr(VI) oxyanions for this sorbent, at each temperature. A small decrease of the sorption capacity of Cr(VI) after five sorption/desorption cycles was observed, supporting the great potential of these SBAEx in the removal of Cr(VI) oxyanions.
Process Safety and Environmental Protection, 2017
Abstract In this article, we have presented the studies regarding the improvements of the adsorpt... more Abstract In this article, we have presented the studies regarding the improvements of the adsorption performance of a styrene-12% divinylbenzene copolymer functionalized with aminophosphonate groups in the removal process of thallium ions from aqueous solutions, by impregnation of the solid support with trihexyl(tetradecyl)phosphonium chloride (Cyphos IL-101). The use of ionic liquid impregnated polymer as adsorbent in the removal process of radionuclides presents higher adsorption performance because, in this case, the advantages of the ionic liquids are combined with the properties of the solid support. Until now the ionic liquids were intensive studied in the removal process of radionuclides from aqueous solutions but using the liquid–liquid extraction. In our case these are used in the solid–liquid separation process, a smaller quantity of ionic liquids being used (which decrease the cost of the adsorption process), and the loss of the ionic liquids in the aqueous phase being avoided. The ultrasonication method used for the impregnation of the ionic liquids onto the solid support is also a new and original one. The impregnation of the solid support with Cyphos IL-101 significantly increased its adsorption performance in the removal process of Tl(I) ions from aqueous solutions.
Uploads
Papers by Ecaterina Stela Dragan