Journal of the University of Chemical Technology and Metallurgy, 39, Book 4, 2004

EDITOR-IN- CHIEF
Prof. DSc Rumen I. Dimitrov
Department of Fundamentals of ChemicalTechnology,
Tel: (+ 359 2) 62 54 485
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski ., 1756 Sofia, Bulgaria
E-mail: rumen@uctm.edu

Chapters:

 

Review
NON-STEROIDAL ANTI-INFLAMMATORY DRUGS AND CONTEMPORARY TENDENCIES IN THEIR DEVELOPMENT AND ELABORATION
A. Bijev, S. Vladimirova, D. Yaneva, P. Petrov
METHODS AND INDICATOR ELECTRODES IN POLAROGRAPHIC MEASUREMENTS IN MOLTEN SALT ENVIRONMENT
A. Girginov
Chemical Technology
ON THE PHOTOSTABILITY OF SOME TRIAZINE AZODYES AND THEIR COPOLYMERS WITH ACRYLAMIDE AND ACRYLONITRILE
P. Petrova-Miladinova, T. Konstantinova
UTILIZATION OF COBALT – MANGANESE CATALYSTS DISCHARGED FROM THE SYNTHETIC FIBRES PRODUCTION
L. Angelov
EFFECT OF CADMIUM ON THE GROWTH AND THE BIOACCUMULATION ABILITY OF TRICHOSPORON CUTANEUM R 57
N. Georgieva, R. Popova, D. Nikolova
Chemical Engineering
 ESTIMATION OF SO2 ADSORPTION EQUILIBRIUM ON NATURAL CLINOPTILOLITE IN PRESENCE OF WATER
E. Ivanova, M. Christov, M. Kostova
Metallurgy
KINETICS OF MINERAL BORNITE OXIDATION PROCESS
N. Štrbac, I. Mihajlovic, Ž. Živkovic, D. Živkovic
DISSOLUTION STUDIES ON A POLYMETALLIC ALLOY
V. Stefanova, P. Iliev, A. Avramov
Chemistry
 SOLVENT EXTRACTION AND SEPARATION OF Pr(III), Gd(III) AND Yb(III) IONS WITH MIXTURES OF THENOYLTRIFLUOROACETONE AND
1-(2-PYRIDYLAZO)-2-NAPHTHOL
M. Atanassova, I. Dukov
PHASE EQUILIBRIA IN THE Bi2O3-Bi2S3 SYSTEM
V. Vassilev1, S. Parvanov1, V. Vachkov2, L. Aljihmani1
MECHANISM OF THE PASSIVE FILM FORMATION ON Ni-Cr AND Fe-Cr ALLOYS IN MOLTEN NaOH
Tz. Tzvetkoff
Chemical Sciences
OPTICAL PROPERTIES OF STRONTIUM SULPHIDE (SrS) THIN FILMS PREPARED BY SOLUTION GROWTH TECHNIQUE
F.I. Ezema
A DESIGN FOR PULSE WIDTH MODULATION CONTROL OF A GREAT NUMBER OF HEATERS
A. Mirev, R. Bachvarsky
Economics
MERCHANDISING AS A WAY TO RAISE THE COMPETITIVE POWER
G. Kondev, D. Tenchev



NON-STEROIDAL ANTI-INFLAMMATORY DRUGS AND CONTEMPORARY TENDENCIES IN THEIR DEVELOPMENT AND ELABORATION
A. Bijev, S. Vladimirova, D. Yaneva, P. Petrov

University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: a.bijev@uctm.edu
 Received 20 July 2004
Accepted 26 November 2004

In spite of the notable success achieved by the corticosteroids, their observed unfavorable side effects have provoked the search for alternative synthetic products within various chemical classes, as a result of which a new group of drugs has been differentiated – the non-steroidal anti-inflammatory drugs (NSAIDs). Their efficiency has popularized them as the most often prescribed drugs in the world. Unfortunately their high anti-inflammatory activity was often associated with serious gastrointestinal disorders such as ulcers and hemorrhages, which set new challenges in front of the researchers. The first world wide success is the release on the market of Celebrex (at the end of 1998), a representative of a new generation of highly active NSAIDs, free from adverse effects.
The current survey is an introduction to the role and importance of the NSAIDs and the new tendencies of their development and elaboration. The role of the cyclooxygenase enzymes has been commented concerning on one hand the inflammatory processes and on the other - the unfavorable effects on the gastrointestinal secretion. This survey also summarizes the major groups of NSAIDs and the principles of their interaction with the biological targets as a base for the design of new and improved drugs during the past several years. Some prospective strategies, allowing the design and synthesis of new heterocyclic compounds with previously defined chemical architecture as potent active and harmless NSAIDs have been mapped out.
Keywords: anti-inflammatory agents, COX-1/COX-2 inhibitors, NSAIDs.

 

METHODS AND INDICATOR ELECTRODES IN POLAROGRAPHIC MEASUREMENTS IN MOLTEN SALT ENVIRONMENT
A. Girginov

University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: assen@uctm.edu
 Received 02 November 2004
Accepted 26 November 2004

A review of the methods and indicator electrodes used in polarography of molten salts is presented. The applications of conventional and convective as well as differential and pulse methods are discussed. A review of the some metal ions (depolarizers) investigated in molten salt environments is also made. The application of different metal dropping electrodes together with a variety of solid electrodes (stationary, vibrating, rotating and self-cleaning) is considered. A special attention is paid on the application of polarography in determination of the concentration of electrochemically active ions and a number of kinetic parameters: diffusion coefficient, diffusion layer thickness, exchange current, etc. The polarographic measurements in ionic melts give information on the electrode reaction mechanism as well as on complex formation processes.
Keywords: polarography, indicator electrodes, molten salts, analytical measurements.

 

ON THE PHOTOSTABILITY OF SOME TRIAZINE AZODYES AND THEIR COPOLYMERS WITH ACRYLAMIDE AND ACRYLONITRILE
P. Petrova-Miladinova, T. Konstantinova

University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: ppolya@uctm.edu, konst@uctm.edu
 Received 20 October 2004
Accepted 26 November 2004

The photostability of 6 triazine azodyes, four of them polymerizable and three of them containing a tetramethylpiperidine (???) fragment in their molecule, was investigated. It was found that the presence of a TMP fragment in the molecule increased the photostability. The copolymers of 4 of them with acrylamide (ACA) and acrylonitrile (AN) with an intense colour stable to solvents were obtained. An increasing of the photostability of dyes in polymer was observed. The influence of the dye on the photostability of copolymers was studied as well and it was found that two of the dyes had good stabilizing effect and can be recommended.
Keywords: triazine azodyes, 2, 2, 6, 6-tetramethylpiperidine stabilizer, coloured PACA and PAN, photostability.

UTILIZATION OF COBALT – MANGANESE CATALYSTS DISCHARGED FROM THE SYNTHETIC FIBRES PRODUCTION
L. Angelov

University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: kangelov@uctm.edu
 Received 16 August 2004
Accepted 26 November 2004

The modern society uses a large number of synthetic materials, including synthetic fibres, such as polyester fibres– cable and staple fibres, polyester viscose, etc. Their manufacture employs catalytic processes and catalysts, such as Sb2O3, cobalt and manganese compounds and their mixtures. The latter defines the problems of their utilization and recycling. The subject of the present study is utilization of the discharged cobalt-manganese catalysts. A technological sequence with positive results was developed.
Keywords: polyester fibres, Co–Mn catalysts, utilization, recycling.

EFFECT OF CADMIUM ON THE GROWTH AND THE BIOACCUMULATION ABILITY OF TRICHOSPORON
CUTANEUM R 57
N. Georgieva, R. Popova, D. Nikolova

University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: neli@uctm.edu
 Received 13 October 2004
Accepted 26 November 2004

One of the promising ways of the bioremediation of polluted media with toxic quantity of cadmium is to use appropriate strains of microorganisms as bioremediation tools such as yeasts. The filamentous yeast Trichosporon cutaneum strain R57 was cultivated as batch culture on a liquid medium in the presence of various concentrations of Cd2+ from 0 to 2 mM. The uptake and the accumulation of Cd2+ ions by Tr.cutaneum cells depending on the concentration of Cd2+ in the medium were studied. The putative mechanism of cadmium stress tolerance of strain representing different ratio of passive and active uptake and release of Cd2+ was discussed.
Keywords: metal accumulation, cadmium, yeast, Tr.cutaneum.

 

 

DISSOLUTION STUDIES ON A POLYMETALLIC ALLOY
V. Stefanova, P. Iliev, A. Avramov

University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail:vps@uctm.edu
 Received 29 October2004
Accepted 15 November 2004

The polymetallic alloy with composition, in mass. %: 65.95 Fe, 12.81 Ni, 12.10 Cu, 5.33 Mn, 1.33 Co and 2.48 others was obtained after pyrometallurgical treatment of Manganese Nodules. Two approaches for dissolving of the alloy in sulphuric acid solution were studied: in a thermostat in the presence of a gaseous oxidizer and in an autoclave – without oxidizer. It was observed, that complete dissolution of the alloy in presence of oxygen was achieved after 5 hours at temperature-750C and initial quantity of sulphuric acid for gram alloy 2.64 g H2SO4 /g alloy. When air was used at the same conditions only 65 % of the alloy was dissolved for 8 hours. Experiments on autoclave dissolution showed that at temperature 1450C and 1.76 g H2SO4 /g alloy 60.5 % of the alloy was dissolved. It can be expected, that further increase of temperature and initial sulphuric acid quantity will lead to full dissolution of Fe, Ni, Co and Mn from the alloy and concentration of copper in the residue.
Keywords: polymetallic alloy, dissolution, sulphuric acid, autoclave.

 

The solvent extraction of trivalent lanthanoids Pr, Gd and Yb with thenoyltrifluoroacetone (HTTA) and 1-(2-pyridylazo)-2-naphthol in C6H6 has been studied. It was found that in the presence of a 1-(2-pyridylazo)-2-naphthol (S) the lanthanoids have been extracted as Ln(TTA)3•S. On the basis of the experimental data, the values of the equilibrium constants have been calculated. The addition of a synergist to the chelating extractant has produced moderate synergistic effects and the selectivity among the lanthanoids has been changed significantly.
Keywords: synergistic extraction, thenoyltrifluoroacetone, 1-(2-pyridylazo)2-naphtol, lanthanoids separation factors.

PHASE EQUILIBRIA IN THE Bi2O3-Bi2S3 SYSTEM
V. Vassilev1, S. Parvanov1, V. Vachkov2, L. Aljihmani1

1University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: venciv@uctm.edu
2South West University ,,Neofit Rilski“,
66 Ivan Michailov Str., 2700 Blagoevgrad, Bulgaria
Received 29 October 2004
Accepted 11 November 2004

With the help of the differential thermal and x-ray diffraction analyses and the density measurement work out a phase diagram of the system Bi2O3-Bi2S3. As a result of the peritectic reaction a melting intermediate phase with a composition Bi2O2S is formed. It exists in the three polymorphic forms with temperatures of the phase transition respectively T??? = 275°C and T??? = 600°C. The unit-cell parameters of the intermediate phase Bi2O2S are determined as follows: a=12,326 Å, b=8,148 Å, c=4,360 Å, a=126,13°, ß=59,57°, ?=149,20°.
The oxychalcogenide system (Bi2O3)100-x(Bi2S3)x is also characterized by the border solid solutions on the base of a-Bi2O3, ß-Bi2O3 and Bi2S3 as well as the three nonvariant equilibria: peritectic, eutectoidal and eutectic. The coordinates (T [°?], x [mol % ?i2S3]) of the peritectic, eutectoidal and eutectic points are respectively: (? = 675, ? ˜ 37); (T = 650, ? = 20) and (? = 520, ? = 60). As a result of different physical chemical interactions in solid and liquid state and polymorphic Bi2O3 and of the intermediate phase Bi2O2S in the system 15 phasic fields exist, four of which are mono-phasic.
Keywords: differential thermal analysis, phase diagram, phase equilibria, X-ray diffraction.

MECHANISM OF THE PASSIVE FILM FORMATION ON Ni-Cr AND Fe-Cr ALLOYS IN MOLTEN NaOH
Tz. Tzvetkoff

University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: tzvetkof@uctm.edu
 Received 02 November 2004
Accepted 26 November 2004

A study of the corrosion kinetics of Ni-10 %Cr and Fe-18 %Cr alloys in molten NaOH is presented, investigating the effect of Cr addition on the corrosion behaviour of those wide spread construction materials. Impedance measurements were performed to elucidate the conductivity mechanism of the surface films formed. Data on surface composition are also obtained by XPS analysis.
A tentative kinetic model of the conductivity mechanism of the alloy/film/melt system for both alloys is proposed at the beginning of the paper, whereupon proved with experimental results.
Keywords: iron alloy, nickel alloy, ionic melt, passive film, impedance spectroscopy.

 

Chalcogenide thin films of SrS on glass slides were successfully grown, characterized and optimized, using cheap and simple solution growth techniques. The composition of the films were obtained using Energy Dispersive X-Ray Flourenscence (EDXRF) and Fourier transform infrared (FTIR) spectroscopy. The spectral analysis reveals that some of the SrS thin films transmit highly between 75 and 99 % in the UV-VIS-NIR regions. The refractive index ranges between 1.35 and 2.30 while the band gap ranges between 2.65 and 3.20 eV. The thickness of the films ranges between 0.068µm and 0.151 µm. The characterization shows that the films have high potentials for thermal control and antireflection coatings applications.
Keywords: solution growth technique, SrS thin films, optical properties, thermal and antireflection coatings.

A DESIGN FOR PULSE WIDTH MODULATION CONTROL OF A GREAT NUMBER OF HEATERS
A. Mirev, R. Bachvarsky

 

University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: mirev@uctm.edu
 Received 21 October 2004
Accepted 26 November 2004

Alternative variants for power control of a great number of heating elements by the Pulse Width Modulation (PWM) method are considered. The electromagnetic distortions, generated at this control are analyzed and a criterion for choice of control strategy with minimum disturbance is worked out. A design for low disturbance control and architecture of this control system are proposed.
Keywords: PWM, control, commutation, commutation disturbances.

Today in our constantly changing world businesses invest enormous resources to satisfy all requirements and preferences of their customers. At the same time they keep watching their competitors’ operations and undertakings. Every product is designed for giving satisfaction to particular needs. Along with marketologists, designers, financiers and engineers, merchandisers contribute a lot to raising the competitive power of the firm they work for. Merchandisers establish contacts with clients, i.e. retailers, as well as with buyers when it is their direct duty. The identification of the customers’ demands and expectations is of great importance for the firm but important is also the process of the implementation of their products and services in the market.
Building up of the firm’s competitive power is a long-lasting process, covering all phases and operations. From the point of view of their direct contacts with buyers, merchandisers are the people who contribute most to making the positive characteristics of a product and its benefits clear.
Keywords: merchandising, competitive power.