CHEMISTRY

INFLUENCE OF THE QUATERNARY AMMONIUM SALT ANION ON THE SYNERGISTIC SOLVENT EXTRACTION OF LANTANOIDS WITH MIXTURES OF THENOILTRIFLUOROACETONE AND ALIQUAT 336
M.Atanasova, V.Jordanov, I.Dukov

University of Chemical Technology and Metallurgy, 8 Kl. Ohridski, 1756 Sofia, Bulgaria E-mail dukov@uctm.edu

Received 25 January 2001 Accepted 30 January 2001

ABSTRACT
The influence of the quaternary ammonium salt anion on the synergistic extraction of La and Eu with mixtures of thenoyltrifluoroacetone (HTTA) and Aliquat 336 in chloride (QCl) and perclorate (QClO4 ) forms in C6H6 has been studied. The formation of mixed anionic complexes of the type Q[Ln(TTA)4] has been determined. The values of the equilibrium constants have been calculated. It was found that the change of the anion of the salt from Cl- to ClO4- exerted a considerable influence on the metal extraction.
These resuts are explained by the fact that the formation of the anionic mixed complexes is connected with the breaking of the bond between the cation and the anion of the quaternary ammonium salt .As the bond energy is much larger for QClO4, the metal extraction decreases significantly for HTTA - QClO4 mixtures. On the basis of the experimental data a conclusion is made that the synergistic agent is not the ion-pair obtained as a result of the interaction of the extractants but the quaternary ammonium salt itself.

Keywords: Lanthanoids, Thenoyltrifluoroacetone, Quaternary Ammonium Salt, Synergistic Extraction .

A PHASE COMPOSITION OF FERROMAGNETIC POWDERSPRECIPITATED FROM
Fe-NITRATES
S. Deneva, M. Dimitrov

 

University of Chemical Technology and Metallurgy, 8 Kl. Ohridski, 1756 Sofia, Bulgaria

Received 25 April 2001 Accepted 30 May 2001

ABSTRACT
Ferromagnetic powders were precepitated from Fe-nitrates at room conditions. The samples were prepared by two different routes: from Fe(NO3)2 and Fe(NO3)3 solutions (variant I) and only from Fe(NO3)2 solutions with addition of HNO3 as an oxidant (variant II). The characterisation of the phase composition of the powders was done by means of chemical, thermal analyses, X-ray diffraction and Moessbauer spectroscopy. In the two groups of samples, equivalent basic components Fe3O4 and g-Fe2O3 were identified (94-100%) whose ratio varied from about 30% : 70% to about 70% : 30%.
The Moessbauer data showed unsignificant amounts of a secondary phase a-Fe2O3 (a-FeOOH) in the samples of the second group. The mass % of that phase was 2 - 6%, that means below the accuracy limit of the method.
Keywords: magnetite, g-Fe2O3, precipitation, phase composition

 

IR SPECTROSCOPY STUDY OF NANOPARTICLES AND COMPOSITES
I. Markova - Deneva, K. Alexandrova, G. Ivanova, M. Pankova, I. Dragieva

 

University of Chemical Technology and Metallurgy, 8 Kl. Ohridski, 1756 Sofia, Bulgaria e-mail: vania@uctm.edu

Received 27 April 2001 Accepted 06 June 2001

ABSTRACT
Investigations by means of infrared spectroscopy (IR-spectroscopy) of amorphous and crystalline CoxByHz nanoparticles and their composites with AlN in the 4000 - 400 cm-1 range are carried out. Proofs for creation of chemical bonds between boron and oxygen atoms and a formation of BO3 and BO4 type of groups incorporated in boroxol rings (B3O4,5) x and structured as diborate, triborate and tetraborate units are given. Three modes of vibration in the frequency region typical for the B-O-B bonds in the BO3 and BO4 groups forming diferent structural units have revealed: symmertic stretching n1 (BO4) at 750 cm-1 , asymmetric stretching n3 (BO3) at 1020 cm-1 and deformation mode n4 (BO4) at 520 cm-1. The bands of absorption grow in intensity and shift to lower frequencies with increasing of the heat-treatment temperatures from 200 to 850oC At lower temperatures (200-500oC) the bands are broad while at higher temperatures (550-850oC) they are intensive and sharp. Composites with AlN which are heat-treated at high temperatures show the existence of chemical bonds between aluminum and oxygen atoms forming coordination groups of the types AlO4 and AlO6. The IR studies of the composites with AlN have characteristic stretching vibrations typical for the Al-O bonds in the AlO4 tetrahedra (900-650 cm-1) and AlO6 octahedra (650-500 cm-1).The increasing of the quantity of the AlN in the prepared isotropic composites has a opposite effect to the heat-treatment temperature effect.
Keywords: infrared spectra, CoxByHz nanoparticles,composites , AlN additive

SPECTROPHOTOMETRIC DETERMINATION OF OXYGEN STOICHIOMETRY IN YBCO SUPERCONDUCTING MATERIALS
T. Nedeltcheva, L. Vladimirova

University of Chemical Technology and Metallurgy, 8 Kl. Ohridski, 1756 Sofia, Bulgaria e-mail: lkv@uctm.edu

Received 28 April 2001 Accepted 7 May 2001

ABSTRACT
The spectrophotometric method (Anal. Chim. Acta, 336 (1996) 223) for the determination of the non-stoichiometric oxygen in YBa2Cu3O6.5 + d superconducting materials by measuring the absorbance at wave length of 355 nm is discussed. Considerable improvements in the experimental conditions of the procedure for the film analyses are made, and a sensitive method for the spectrophotometric determination of the non-stoichiometric oxygen in superconducting bulk samples and films is proposed. The main changes of the method are two: (1) a substitution of the ligand ethylene-diamine tetraacetic acid with a,a¢,a²-trimethilamine-tricarboxylic acid or amino-etanoic acid and (2) five times decrease of the concentrations of the sodium acetate - acetic acid buffer. The other improvements are related to the way of the introduction of the potassium iodide, of the preparation of the blank sample solution and the solutions for measurement of the analytical signal, as well as to the way of the absorbance measurement.. The monophase superconducting bulk samples and two superconducting films are analyzed by the proposed method. The analytical results are in good coincidence with the results obtained both by coulometry and the spectrophotometric method for the bulk sample analysis by measurement the absorbance at wave length of 430 nm.
Keywords: Spectrophotometry; Oxygen; YBCO superconducting materials

ENLARGEMENT OF THE SPECTROPHOTOMETRIC METHOD FOR THE DETERMINATION OF OXYGEN STOICHIOMETRY IN YBCO SUPERCONDUCTING MATERIALS
L. Vladimirova, T. Nedeltcheva, R. Chavdarova

University of Chemical Technology and Metallurgy, 8 Kl. Ohridski, 1756 Sofia, Bulgaria e-mail: lkv@uctm.edu

Received 28 April 2001 Accepted 7 May 2001

ABSTRACT
The spectrophotometric method for the determination of the oxygen stoichiometry in YBCO superconducting materials, based on measurement of the absorbance of I3- complex in solutions with and without ligand for Cu(II) (glycine or nitrile triacetic acid) is discussed, and its boundaries of applicability are extended. Two procedures are suggested. It has been proved, that the procedure with measuring the absorbance at wave length of 355 nm is suitable for the determination of the oxygen stoichiometry in YBCO superconducting materials without limitation of the oxygen content. The procedure with measuring the absorbance at 430 nm is applicable only to the determination of oxygen stoichiometry in superconducting oxides, whose coefficient of non-stoichiometric oxygen is close to 0.5. The accuracy of the results is confirmed by known spectrophotometric and coulometric methods. The reproducibiliy, estimated by the relative standard deviation, is ±0.01.
Keywords: YBCO superconducting materials, oxygen stoichiometry, spectrophotometry

 

SPECTROPHOTOMETRIC STUDY ON THE KINETICS OF SYNTHESIS OF SOME BIOLOGICALLY ACTIVE AMIDINO DERIVATIVES OF 6?-AMINOPENICILLANIC ACID
A. Zwetanova, N. Kaloyanov and R. Stoyanova

University of Chemical Technology and Metallurgy, 8 Kl. Ohridski, 1756 Sofia, Bulgaria e-mail: alz@uctm.edu

RReceived 26 April 2001 Accepted 27 May 2001

ABSTRACT
The process of obtaining the two derivatives of 6ß-aminopenicillanic acid (6APA), denoted as I and II was studied spectrophotometrically. For the two substances antibacterial activity was proved [1]. The conditions for the synthesis and the isolation of the products as well as their characterization have been published elsewhere [1]. The initial substances for the synthesis, namely 6APA, 5-nitrofurfural (5NF) and 3-methoxy-2-nitrobenzaldehyde (3M2NB), as well as the products - I and II - absorb light in the near UV and VIS spectral regions. This fact enables us to develop a method for studying the process of synthesis as a function of time. On the basis of a mechanism, proposed in the literature [2] and proven by us for the reactions studied, the rate constants of the overall processes were calculated. The effect of the substi-tuents is also discussed.
Keywords: kinetics, ß-lactam antibiotics, mechanism

INDOLE DERIVATIVES OF THIOBARBITURIC ACID OF PHARMACEUTICAL INTEREST
A Bijev, P. Prodanova

University of Chemical Technology and Metallurgy, 8 Kl. Ohridski, 1756 Sofia, Bulgaria e-mail: a.bijev@uctm.edu

Received 10 May 2001 Accepted 16 May 2001

ABSTRACT
Five new indole compounds comprising two heterocycles of recognized pharmaceutical interest have been synthesized by condensation of 1-acetylindole-3-carbaldehyde with thiobarbituric acid and its N,N'-bis-methyl-, -bis-ethyl-, -bis-n-butyl and -bis-phenyl-derivatives. An insufficient carbonyl activity of N-unsubstituted indole-3-carbaldehyd has been observed and overcome by a preliminary N-acethylation.
The purity of the new compounds is confirmed by their TLC characteristics. The structure elucidation is based on 1H-NMR and IR spectral data.
Keywords: Thiobarbituric acids, Condensation, Heterocycles, Pyrroles, Synthetic methods

 

SPECTROPHOTOMETRIC INVESTIGATION OF BERYLLIUM (II) COMPLEXES WITH ERIOCHROME CYANINE R IN THE PRESENCE OF CATIONIC SURFACTANTS
Chr. Ivanova

University of Chemical Technology and Metallurgy, 8 Kl. Ohridski, 1756 Sofia, Bulgaria e-mail: christina@uctm.edu

Received 21 May 2001 Accepted 06 June 2001

ABSTRACT
The formation of complex-associates of beryllium(II) with Eriochrome Cyanine R (ECR) in the presence of the cationic surfactants (CS) - benzyldimethyltetradecylammonium chloride (BDTA) and benzyldimethylcethylammonium chloride (BDCA) at pH 5.5-6.5 (acetate buffer solutions; m = 0.1) has been investigated. The established ratio of the components in the complex-associates Be-ECR-BDTA (BDCA)
is 1:2:2.
A sensitive spectrophotometric method for determination of beryllium (e = 5.0x104 l mol-1 cm-1; <0.15 mg Be(II)/cm3 ) based on the significant batochromic and hyperchromic effects in the presence of BDTA is proposed. The main interfering cations - Al(III), Fe(III) and Cu(II) are masked with EDTA and Ca-EDTA respectively. The method is used for determination of beryllium in bronze.
Keywords: spectrophotometry, complex-associates, beryllium, Eriochrome Cyanine R, benzyldimethyltetradecylammonium chloride

 

SPECTRAL INVESTIGATION OF 1,10-PHENANTHROLINE COMPLEXES PREPARED IN THE PRESENCE OF TWO METAL IONS
M. Atanassova, G. Dimitrov

University of Chemical Technology and Metallurgy, 8 Kl. Ohridski, 1756 Sofia, Bulgaria e-mail: gdd@uctm.edu

Received 21 May 2001 Accepted 03 June 2001

ABSTRACT
The mixture FeCl3-1,10-phenanthroline and the systems formed by interaction of 1,10-phenanthroline with two metal ions (Fe3+, Cu2+; Fe3+, Co2+; Cu2+, Co2+) were studied by their electronic spectra and IR-spectra. The UV-spectra of the aqueous solutions of the systems showed maxima at 224-225 nm and 265-269 nm as well as a shoulder at 295 nm. A second shoulder at 282 nm is characteristic only of the system 1,10-phenanthroline-FeCl3, CoCl2. The visible spectrum of this system demonstrated that an electron transfer from Co2+ to Fe3+ took place thus forming the mixture tris(1,10-phenanthroline)Fe2+-tris(1,10-phenanthroline)Co3+. The IR-spectrum indicated an interaction between the phenanthroline molecule and FeCl3 which probably contributed to realization of the electron transfer creating the required steric conditions.
Keywords: 1,10-phenanthroline, FeCl3, two metal ions, electronic spectra, IR spectra, electron transfer

 

STUDY ON THE EQUILIBRIUM ADSORPTION OF CHLOROPHENOLS FROM AQUEOUS SOLUTIONS ON ACTIVATED CARBON PRODUCED FROM APRICOTE STONES
P. Peeva-Antova, B. Koumanova

University of Chemical Technology and Metallurgy, 8 Kl. Ohridski, 1756 Sofia, Bulgaria e-mail: bogdana@uctm.edu

Received 31 May 2001 Accepted 06 June 2001

ABSTRACT
The adsorption of chlorinated phenols from aqueous solutions on granular and powdered activated carbon produced through an one-stage method from apricot stones was studied in a batch reactor. Equilibrium measurements were conducted at pH 7.0. The adsorption isotherms of p-chlorophenol (p-CP), 2,4-dichlorophenol (2,4-DCP) and 3,5-dichlorophenol (3,5-DCP) on granular activated carbon (GAC) and the isotherm of 2,3,6-trichlorophenol (2,3,6-TCP) on powdered activated carbon (PAC) have been determined. The adsorptive capacities for GAC follow the order:
2,4-DCP > p-CP > 3,5-DCP.
Single-component equilibrium adsorption data for the studied compounds in the concentration range of 10-50 mg/l and GAC as adsorbent were fit well by the Langmuir equation. Both the Langmuir and Freundlich equations are suitable for the description of the adsorption equilibrium on PAC in the concentration range of 2,3,6-TCP 20-40 mg/l.
Keywords: adsorption, chlorophenols, activated carbon, adsorptive capacity, isotherms.