LIQUID FERTILIZERS FROM DOLOMITE
R. Šlinkšiene, A. Sviklas
SPECIAL LIQUID FERTILIZERS FROM POTASSIUM PHOSPHATES
R. Paleckiene, A. Sviklas
THE POSSIBILITIES AND PROBLEMS OF SEMI-HYDRATE PHOSPHOGYPSUM
USE FOR PRODUCTION OF BINDER MATERIALS IN LITHUANIA
N. Kybartiene, V. Leskeviciene, D. Nizeviciene, Z. Valancius
ON THE PROPERTIES OF SOME NAPHTHALIMIDE DYES AND THEIR COPOLYMERS
WITH METHYLMETHACRYLATE
T. Konstantinova, R. Lazarova
DEACTIVATION OF ALUMINA SUPPORTED COPPER AND COBALT CATALYSTS
A. Naydenov, P. Konova, D. Mehandjiev
PREPARATION OF VANADIUM - TITANIUM CATALYST ALUMINIUM OXIDE
PROMOTED
N. Nikolov, M. Moskovkina
CORDIERITE-LIKE SUPPORTS OF CATALYSTS
D. Stoyanova1, D. Vladov2, N. Kassabova2, D. Mehandjiev1
KINETIC AND HYDRODYNAMIC INVESTIGATIONS DURING THE REDUCTION
OF A NICKEL CATALYST UNDER THE EFFECT OF AN EXTERNAL MAGNETIC FIELD /PART
I/
I. Krastev, T. Popova
POTENTIODYNAMIC AND ELECTRON-MICROSCOPY INVESTIGATIONS OF NEW
ANODIC MATERIALS
Y. Stefanov, T. Dobrev
INVESTIGATION OF THE BEHAVIOUR OF Sn, Pb AND ITS INTERMETALLIC
COMPOUNDS DURING REVERSIBLE LITHIUM ELECTROCHEMICAL INTERCALATION
A. Momchilov 1, S. Uzunova1, B. Banov1, S. Balova2, I. Abrahams3
ELECTROCHEMICAL BEHAVIOUR OF LOW-TEMPERATURE LiFexMn2-xO4 SPINELS
SYNTHESIZED IN A FLUIDIZED BED
S. Uzunova1, A. Momchilov1, B. Banov1, I. Uzunov 2, B. Puresheva1
ELECTROLESS DEPOSITION OF COPPER COMPOSITE COATINGS
M. Petrova, Z. Noncheva
FORMATION OF OXIDE FILMS ON ALUMINIUM IN SOLUTION OF PHOSPHORIC
ACID
E. Stoyanova, D. Stoychev
ELECTROCHEMICAL CORROSION BEHAVIOUR OF AMORPHOUS AND CRYSTALLINE
Fe-Co-Si-B ALLOYS
E. Petrova, V. Zaprianova, R. Raicheff, S. Vasilev
ELECTROCHEMICAL PREPARATION OF ANODE MATERIALS
L. Petkov1, A. Alexandrova2, I. Valov2, D. Kostova1, I. Gadjov1
NANOSIZED LixCu6Sn5B PARTICLES PREPARED BY BOROHYDRIDE REDUCTION
FOR SECONDARY LITHIUM BATTERIES
M. Mladenov, P. Zlatilova, E. Lefterova, I. Dragieva
IMPROVED CYCLING STABILITY OF SURFACE MODIFIED LiNi/CoO2 ELECTRODES
FOR LITHIUM-ION BATTERIES
M. Mladenov 1, E. Zhecheva 2, R. Stoyanova 2, S.Vassilev 1
AN ELECTROCHEMICAL METHOD FOR DECREASING SULFATES CONCENTRATION
IN WASTEWATER
V. Panayotov, M. Panayotova
REGENERATION OF DEACTIVATED Pd-CONTAINING CATALYST FOR HIGH
THERMAL DEGRADATION OF NOx
D. Shishkov, T. Velinova, D. Vladov, N. Kasabova
APPLICATION OF LIQUID INERT ABSORBENTS FOR DECREASING NITROGEN
OXIDES ( NOx ) EMISSIONS IN NITRIC ACID PRODUCTION
N. Georgieva1, I. Gruncharov2
MAGNETIC SEPARATION OF COAL FLY ASH
S. Shumkov, A. Shoumkova
REPROCESSING OF PYRITE CINDERS TO RED IRON OXIDE PIGMENT
A. Shoumkova
CHARACTERISTICS OF HEAVY METALS RELEASE FROM SEWAGE SLUDGE,
ITS ASH AND RE-PRODUCTS
E. Alexandrova, J. Balgaranova, A.Petkov, L.Pavlova
POSSIBILITIES FOR UTILIZATION OF MUNICIPAL SOLID WASTE ASHES
IN THE PRODUCTION OF BUILDING CERAMICS
B. Zdravkov, L. Pavlova, Y. Pelovski
LIQUID
FERTILIZERS FROM DOLOMITE
R. Šlinkšiene, A. Sviklas
Kaunas University of Technology
Radvilenu str. 19, LT-3028 Kaunas, Lithuania
E-mail: alfredas.sviklas@ktu.lt
|
Received:2 October 2003
Accepted 10 October 2003
|
The optimum
conditions of the decomposition of Lithuanian dolomite by nitric acid are
investigated. The function of decomposition degree as concentration of the
nitric acid, the acidulation duration and temperature as well as the ratio
of dolomite and nitric acid was determined. The phase diagrams of the systems
Ca(NO3)2 – Mg(NO3)2 – NH4NO3 – H2O and Ca(NO3)2 –
Mg(NO3)2 – CO(NO2)2 – H2O was examined. On the basis of these
results liquid fertilizers containing nitrogen, calcium and magnesium were
formulated for production. It was found that the manufacture of liquid fertilizers
of grade 16 % N, 6 % CaO and 4 % MgO using ammonium nitrate and 26 % N, 3
% CaO and 2 % MgO using urea are possible.
Keywords: decomposition of dolomite, calcium and magnesium
nitrates, liquid fertilizers, solubility of the systems, physico – chemical
properties.
SPECIAL
LIQUID FERTILIZERS FROM POTASSIUM PHOSPHATES
R. Paleckiene, A. Sviklas
Kaunas University of Technology
Radvilenu str. 19, LT-3028 Kaunas, Lithuania
E-mail: alfredas.sviklas@ktu.lt
|
Received:2 October 2003
Accepted 10 October 2003
|
The solubility of (NH4)2HPO4–K2HPO4–CO(NH2)2–H2O
and (NH4)2HPO4–KH2PO4–CO(NH2)2–H2O systems was investigated.
Solubility diagrams of these systems were investigated by the visual polythermic
method. The solid and liquid phases were analyzed and interaction between
solution components was determined.
These results form the theoretical basis, which allows the formulation of
the composition of liquid fertilizers containing nitrogen, phosphorus and
potassium.
The results obtained from 0?C solubility isotherms were used to set the maximum
feasible concentrations of nutrients.
On the basis of these results 21 grades of liquid fertilizers, differing in
both concentration and nutrient ratios were formulated.
Keywords: liquid complex fertilizers, ammonium phosphate,
potassium phosphate, urea, solubility diagrams, physical–chemical properties.
THE
POSSIBILITIES AND PROBLEMS OF SEMI-HYDRATE PHOSPHOGYPSUM USE FOR PRODUCTION
OF BINDER MATERIALS IN LITHUANIA
N. Kybartiene, V. Leskeviciene, D. Nizeviciene, Z. Valancius
Kaunas University of Technology
Radvilenu str. 19, LT-3028 Kaunas, Lithuania
E-mail: zenonas.valancius@ktu.lt
|
Received:30 September 2003
Accepted 10 October 2003 |
In present study it was investigated the
possibilities of use a waste material - semi-hydrate phosphogypsum for production
of gypsum binding materials. This phosphogypsum is a by-product of phosphorus
fertilizers production in the JSC “Lifosa” Lithuania. It was investigated
the chemical, physical, mechanical properties and crystalline structure of
semi-hydrate phosphogypsum and its dependence on the chemical and mineralogical
composition of apatites (Kola Peninsula Kirov and Kovdor site). A method for
neutralization of acid in semi-hydrate phosphogypsum with lime suspension
in a high temperature was presented. After this neutralization a compressive
strength of such dry samples was 18 28 MPa.
Keywords: semi-hydrate phosphogypsum, apatite, phosphorus
fertilizers, neutralization.
ON
THE PROPERTIES OF SOME NAPHTHALIMIDE DYES AND THEIR COPOLYMERS WITH METHYLMETHACRYLATE
T. Konstantinova, R. Lazarova
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: kost@uctm.edu
|
Received:30 September 2003
Accepted 15 October 2003
|
Nine polymerizable dyes, derivatives of
N-allylnaphthalimide were investigated. On the basis of the spectrophotometric
investigations of the dyes in different solvents it can be concluded that
the charge transfer transition is ?? ?*. Textile samples of polyamide were
dyed in bright fluorescent yellow-greenish colours. At radical copolymerization
of the dyes with MMA, intensively coloured, highly fluorescent copolymers
were obtained. The chemical bond dye-polymer was proved. It was determined
that over 50 % of the initial quantity of the dye was incorporated in the
polymer chain. Photostability of the dyes in solution and in the copolymer
was investigated during irradiation with UV ligth and the connection between
this property and the dye structure was discussed.
Keywords: polymerizable dyes, naphthalimide derivatives,
photostability.
DEACTIVATION
OF ALUMINA SUPPORTED COPPER AND COBALT CATALYSTS
A. Naydenov, P. Konova, D. Mehandjiev
Institute of General and Inorganic Chemistry, BAS,
“Acad. G. Bonchev” str., bl. 11, 1113 Sofia, Bulgaria,
E-mail: naydenov@svr.igic.bas.bg
|
Received:30 September 2003
Accepted: 15 October 2003
|
The change in activity of alumina-supported
copper and cobalt oxide catalysts during ozone decomposition and the role
of the metal participating in the active phase were investigated. Two kinds
of samples with respect to their anionic composition were chosen: nitrates
and oxides. The observed loss of activity was attributed to the formation
of stable O3- - type groups, which stops the reaction process. As a result,
there is a sharp drop of the catalytic activity of the beginning of the process.
It was established that this deactivation is reversible. The second reason
for the deactivation is the presence of nitrogen oxides in the gas when ozone
is produced in air and this deactivation is not reversible below a given temperature,
specific for the stability of the corresponding surface nitrates.
Keywords: oxide catalysts, ozone decomposition, deactiva-tion.
PREPARATION
OF VANADIUM - TITANIUM CATALYST ALUMINIUM OXIDE PROMOTED
N. Nikolov, M. Moskovkina
Konstantin Preslavski University Shumen,
9712 Shumen, Universitetska Str, 115
E-mail: marinam@shu-bg.net
|
Received:30 September 2003
Accepted 15 October 2003
|
The V2O5-TiO2 (anatase) covered catalyst
for partial oxidation of o-xelene to phthalic anhydride was prepared. The
promoting action of Al2O3 upon the catalyst selectivity was investigated.
The optimal quantity of the promoting doping was estimated. The catalyst quality
under various space velocities was checked. The products of the catalytical
oxidation were analysed gaschromatographically. The results were compared
with that of the industrial catalysts.
Keywords: V2O5-TiO2 (anatase) catalyst, aluminium oxide,
o-xelene, oxidation, phtalyc anhydride.
CORDIERITE-LIKE
SUPPORTS OF CATALYSTS
D. Stoyanova1, D. Vladov2, N. Kassabova2, D. Mehandjiev1
1Institute of General and Inorganic Chemistry, BAS,
“Acad.G.Bonchev” str., bl. 11, Sofia 1113, Bulgaria
2University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: nikoletakasabova@yahoo.co.uk
|
Received:30 September 2003
Accepted 15 October 2003
|
Catalytic methods permit the establishment
of efficient processes for neutralizing the toxic components discharged into
the atmosphere. The catalysts used for this purpose comprise a support and
an active component. Beside the pure aluminium oxides, the alumina-silicate
cordierite-like ceramic supports are especially promising as high-temperature
catalysts. Clay, bentone, diatomite (kieselguhr) and MgO have been used as
the initial components. MgO has been added as a firing additive to all the
masses, both the precipitated ones and the mechanical mixtures, in such ratios
in relation to the other components that would ensure the formation of a cordierite-like
structure. The established physical-chemical and mechanical parameters of
the synthesized carriers give the possibility for active phase impregnation.
The obtained catalysts are suitable and can be applied for neutralization
of waste gases in the industrial practice. The applied methods for precipitation
of the carriers create conditions for synthesis of molito-cordierite type
structure at lower temperature of firing in comparison with the classic ceramic.
Keywords: precipitation, catalyst, support, spinel structure,
mechanical strength.
KINETIC
AND HYDRODYNAMIC INVESTIGATIONS DURING THE REDUCTION OF A NICKEL CATALYST
UNDER THE EFFECT OF AN EXTERNAL MAGNETIC FIELD /PART I/
I. Krastev, T. Popova
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: tfp@uctm.edu
|
Received:30 September 2003
Accepted 15 October 2003
|
The aim of the present work was to study
the kinetics of reduction of a nickel catalyst, designed for methanation and
its hydrodynamic behaviour under the effect of an external magnetic field
during the reduction process and after it. It has been proven that the reduction
of nickel oxide in a magnetically structured bed (MSB) is occurring at a greater
rate, compared to the rate in a free fluidized bed (FB). It is not always
possible to register the stage of germ nucleus formation. An effective reduction
of the NiO and the catalyst under the conditions of MSB could be realized
in a non-stationary regime in regard to the linear velocity and the intensity
of the external magnetic field.
Keywords: nickel catalyst, reduction, magnetic field, structure.
POTENTIODYNAMIC
AND ELECTRON-MICROSCOPY INVESTIGATIONS OF NEW ANODIC MATERIALS
Y. Stefanov, T. Dobrev
Institute of Physical Chemistry, Bulgarian Academy of Sciences, 1113 Sofia,
Bulgaria
E-mail: stefanov@ipchp.ipc.bas.bg
|
Received:30 September 2003
Accepted 15 October 2003 |
The mechanism of the anodic processes taking
place on the surface of the lead-cobalt composite electrodes during the zinc
electrowinning from model sulphate electrolytes have been established by potentiodynamic
investigations. On the basis of the obtained cyclic voltammograms information
about the corrosion rate of the composite anodes in the lead dioxide region
is obtained. The influence of the preprocessing of the lead plate and of the
organic additives in the electrolyte for deposition of lead-cobalt coatings
on this process is studied. SEM observations showed a nucleus typical „ear“
structure on the lead-cobalt composite coatings. The presence of such a structure
provides larger surface and leads to depolarization of the oxygen evolution
reaction respectively.
Keywords: zinc; electrowinning; lead-cobalt; composite coatings.
INVESTIGATION
OF THE BEHAVIOUR OF Sn, Pb AND ITS INTERMETALLIC COMPOUNDS DURING REVERSIBLE
LITHIUM ELECTROCHEMICAL INTERCALATION
A. Momchilov 1, S. Uzunova1, B. Banov1, S. Balova2, I. Abrahams3
1 CLEPS - BAS, G. Bonchev str., bl. 10, Sofia, Bulgaria 2University of
Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
3 Structural Chemistry Group, Dept. of Chemistry, Queen Mary College,
Mile End Road, London EI 4NS, UK
E-mail: aamomch@cleps.bas.bg
|
Received:30 September 2003
Accepted 15 October 2003
|
Tin, lead and their intermetalites are lithiated
electrochemi-cally. The difference between the initial and next lithiations
and delithiations is established. The phase changes in the materials are studied
and a possible explanation of this phenomenon is given. Sn, Pb and their intermetalites
are characterized as active anode material for Li-ion batteries.
Keywords: alloys, anode material, phase transition, Li-ion
battery.
ELECTROCHEMICAL
BEHAVIOUR OF LOW-TEMPERATURE LiFexMn2-xO4 SPINELS SYNTHESIZED IN A FLUIDIZED
BED
S. Uzunova1, A. Momchilov1, B. Banov1, I. Uzunov 2, B. Puresheva1
1CLEPS–BAS, Acad. G.Bonchev Str.,bl.10, 1113 Sofia, Bulgaria,
2IGIC-BAS, Acad. G.Bonchev Str , bl.10, 1113 Sofia, Bulgaria
E-mail: s_uzunova@abv.bg
|
Received:30 September 2003
Accepted 15 October 2003
|
The fluidized bed method was used for synthesizing
LiFexMn2-xO4 (0 < x = 1.0) spinels. The structure of the spinels obtained
at 300oC was established by X-ray diffraction. The electrochemical behaviour
of LiFexMn2-xO4 (0 < x = 0.6) was investigated at voltages of 3.5 –5.2
V with a C/3 charge-discharge current. The iron-doped spinels with 0 <
x < 0.6 were found to possess a normal spinel structure, the iron ions
being positioned in octahedral sites only. When x rises up to 0.6, the percentage
of the 4 V plateau decreases to 67 with respect to the discharge capacity
whereas with the 5 V plateau an increase up to 33 is observed, the capacity
losses showing a twofold decrease as compared to the undoped spinel.
Keywords: lithium ion cells, doped spinels, cathode materials.
ELECTROLESS
DEPOSITION OF COPPER COMPOSITE COATINGS
M. Petrova, Z. Noncheva
Institute of Physical Chemistry, BAS,
“Acad. G. Bonchev” str., bl. 11, 1113 Sofia, Bulgaria,
E-mail: mpetrova@ipchp.ipc.bas.bg
|
Received:30 September 2003
Accepted 15 October 2003
|
The deposition of copper composite coatings
on ABS polymers from alkaline electrolytes has been studied. SiC and PA with
particle size of about 1 µm and nanosized SiO2 particles are used as
dispersoids. It is established that in all cases studied the deposition rate
of composite coatings is lower as compared to that of pure metal coatings.
The reason is that the micro- and nanosized particles of the dispersoid incorporating
in the metal matrix cause local blocking of the active sites on the metal
matrix thus preventing autocatalytic reduction of copper ions. The thickness
of produced copper composite coatings is quickly reduced with the increase
in dispersoid concentration. Hence, dispersoid particles incorporating in
the copper matrix strongly effect the kinetics of electroless copper plating.
The thickness of the corresponding composite coatings depends both on the
concentration of the basic components in the electrolyte and on the temperature.
Keywords: composite coatings, electroless copper plating.
FORMATION
OF OXIDE FILMS ON ALUMINIUM IN SOLUTION OF PHOSPHORIC ACID
E. Stoyanova, D. Stoychev
Institute of Physical Chemistry, BAS
Str.”Acad. G. Bonchev”, block 11, Sofia 1113
E-mail: emistoyan@yahoo.com
|
Received:30 September 2003
Accepted 15 October 2003
|
The kinetics of formation of oxide layers
on aluminium AD-1 has been studied in solutions of 0.5 M H3PO4. It has been
established that the rate of growth, respectively the thickness of the formed
oxide layers, increases with the increases forming voltage and the temperature.
The share of the basic secondary processes, accompanying the anodic oxidation
has been determined on the basis of the mass balance of the anodic reaction:
liberation of oxygen and dissolving of the oxide film already formed. Values
of the current efficiency in the process have been determined to be 65 -85
%, depending on the regime of anodization. A correlation has been established
between the ratio of the mass of the dissolved oxide/mass of formed oxide,
on one hand, and the porosity of the prepared layers, on the other hand.
Keywords: aluminium, oxide layers, anodic oxidation, growth
kinetics.
ELECTROCHEMICAL
CORROSION BEHAVIOUR OF AMORPHOUS AND CRYSTALLINE Fe-Co-Si-B ALLOYS
E. Petrova, V. Zaprianova, R. Raicheff, S. Vasilev
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: veselka@uctm.edu
|
Received:30 September 2003
Accepted 15 October 2003
|
The electrochemical and corrosion behaviour
of amorphous Fe71Co10B14Si5 alloy is studied and compared to the behaviour
of its microcrystalline and crystalline counterparts using weight-loss and
electrochemical potential sweep measurements. As model corrosive environments
1N H2SO4, 1N Na2SO4 and 1N NaOH solutions are used. DTA, SEM, and XRD techniques
are applied to characterized the alloy structure. It is found that the crystalline
alloy is a heterogeneous structure composed by ?-Fe and crystalline Fe3(Si,B)
phases. The last phases are also detected (as microcrystals) in the amorphous
matrix of the microcrystalline alloy. It is established that the microcrystalline
alloy possesses practically the same corrosion resistance as that of the alloy
in amorphous state, both showing however much higher resistance than the crystalline
one. It is also shown that the structure affects the rates of both partial
corrosion reactions but its effect on the anodic dissolution reaction is much
stronger.
Keywords: corrosion, electrochemistry, iron-based alloys,
amorphous, crystalline.
ELECTROCHEMICAL
PREPARATION OF ANODE MATERIALS
L. Petkov1, A. Alexandrova2, I. Valov2, D. Kostova1, I. Gadjov1
1University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: l.petkovv@uctm.edu
2Institute of Physical Chemistry, BAS,
Acad. G.Bonchev 1113,Sofia,Bulgaria
|
Received:30 September 2003
Accepted 15 October 2003
|
The possibility of electrochemical preparation
of insoluble anodes was studied. Different oxides: RuO2, ZrO2, CoxOy, RuO2
+ ZrO2, RuO2 + ZrO2 + CoxOy were deposited on Ti-substrate and were characterized
by XPS, EMS and CVA. The experiments show, that the electrolytic RuO2 has
lower overpotential for chorine evolution in comparsion with the same, but
prepared by thermal method.
Keywords: electrochemical preparation, insoluble anodes,
electrodeposition, oxides.
NANOSIZED
LixCu6Sn5B PARTICLES PREPARED BY BOROHYDRIDE REDUCTION FOR SECONDARY LITHIUM
BATTERIES
M. Mladenov, P. Zlatilova, E. Lefterova, I. Dragieva
CLEPS , BAS, 1113 Sofia, Bulgaria
E-mail: mladen47@bas.bg
|
Received:30 September 2003
Accepted 15 October 2003 |
The electrochemical characteristics of the
anode battery materials based on tin alloys depend on the structure and size
of the building lithium particles. The use of an improved borohydride method
(BH) for synthesis of nanosize Sn-containing particles, characterized as an
active material in the composition of a negative lithium-ion electrode is
proposed in this publication. The aim of the present work is to investigate
the possibility of nanoparticles synthesis with Cu6Sn5 content by borohydride
reduction, which to be used as an alternative anode material for secondary
lithium batteries . The optimum ratio between the concentrations of the precursor
metal salts used in the nanoparticles synthesis has been found. The changes
in the phase content of the alloy after electrochemical interactions have
been proven. The results from the performed cycling tests of model electrodes
in lithium-ion cells show a significantly higher discharge capacity (200 mAh/g)
for electrodes of the nanosize copper-tin alloy compared to that of nanosize
pure tin samples. During 70 cycles a better cycling stability is observed
for the electrodes with nanosize composite material CuxSny. An optimal alloy
composition of nanoparticles has been synthesized. Its main content is the
intermetal Li-compound Cu6Sn5, synthesized with the use of a complex-forming
agent in the precursor salts solution. The electrochemical lithiation process
of this alloy follows the mechanism of “replacement” of Cu from
the alloy, and interaction of the lithium with the tin till the formation
of the phase Li4.4Sn and a following liberation of the atomic Cu from the
initial alloy are observed.
Keywords: nanoparticles, electrode materials, Li batteries.
IMPROVED
CYCLING STABILITY OF SURFACE MODIFIED LiNi/CoO2 ELECTRODES FOR LITHIUM-ION
BATTERIES
M. Mladenov 1, E. Zhecheva 2, R. Stoyanova 2, S.Vassilev 1
1CLEPS , BAS, 1113 Sofia, Bulgaria
2IGIC , BAS, 1113 Sofia, Bulgaria
E-mail: mladen47@bas.bg
|
Received:30 September 2003
Accepted 15 October 2003
|
The coating technique was shown to be especially
effective for improving the cycling stability of cathode materials based on
layered LiNi/CoO2. The main concept of this technique is the specific treatment
of the surface of LiNi0.8Co0.2O2 with MgO, which do not take part in the electrochemical
reactions. In the potential range of 3.0–4.1 V charge/discharge curves
demonstrate a similar electro-chemical behavior of bare and treated oxides.
For an upper cut-off voltage higher than 4.2 V, surface treatment with MgO
causes a decrease in the initial capacity at the expense of improved cycling
stability. Based on ex-situ XRD, EPR of Ni3+ and IR spectroscopy of cycled
compositions, the electrochemical properties of Mg-treated oxides are discussed
taking into account the composition and structure of the Mg-coating.
Keywords: lithium nickel/cobalt oxide, surface interaction,
cathode materials, lithium-ion batteries.
AN
ELECTROCHEMICAL METHOD FOR DECREASING SULFATES CONCENTRATION IN WASTEWATER
V. Panayotov, M. Panayotova
University of Mining and Geology, Sofia 1700, Bulgaria,
E-mail: marichim@mgu.bg
|
Received:30 September 2003
Accepted 15 October 2003
|
Wastewater from sulfide ores processing
plants is often heavily polluted with sulfates. In spite of the fact that
sulfates are not classified as hazardous pollutant, concentrations higher
than 600 – 800 mg/l are unacceptable from environmental point of view,
even for discharge of industrial wastewater. Paper presented describes an
electrochemical method for treating acidic (pH 2.0-2.5) wastewater containing
high sulfate concentrations (1-1.5 g/l). Pollutants removal is mainly based
on electromigration. Passing the water through diaphragm electrolysis cells
with indissoluble electrodes carries out the treatment. Additional chemicals
are not introduced and voluminous sludge is not formed. Influence of some
process parameters (inlet water flow, current density) and cell design on
the sulfates removal efficiency and cost was studied. Concentration of sulfates
can be decreased to 500-600 mg/l and water pH value increased to pH 7.5-8.5
at treatment cost of 0.15-0.25 USD per m3.
Keywords: wastewater, sulfates, electrochemical treatment.
REGENERATION
OF DEACTIVATED Pd-CONTAINING CATALYST FOR HIGH THERMAL DEGRADATION OF NOx
D. Shishkov, T. Velinova, D. Vladov, N. Kasabova
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: bojinova@uctm.edu
|
Received 30 September 2003
Accepted 15 October 2003
|
Chemical productions generate much waste,
with varying effects on the environment. A great part of them use catalytic
processes, which results to the accumulation of deactivated catalysts that
are themselves a potential source of emissions and solid waste. Most of the
catalysts can be recycled and returned to production or used as raw material
in order to obtain precious metals.
Because of the high price of Pd as well as the price of the Pd catalyst used
for the high thermal degradation of NOx, it is worth to study the possibility
of regenerating the catalyst set aside from production and its second use.
Pd is extracted from the solid remnant formed of the available pieces and
dust. When the process is under control, the remnant carrier can be directed
to other catalytic systems.
Keywords: catalytic decomposition of NOx, Pd-containing catalyst,
regeneration.
APPLICATION
OF LIQUID INERT ABSORBENTS FOR DECREASING NITROGEN OXIDES ( NOx ) EMISSIONS
IN NITRIC ACID PRODUCTION
N. Georgieva1, I. Gruncharov2
1Technical University, Varna,
E-mail: geogievi@triada.bg
2University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
|
Received:30 September 2003
Accepted 15 October 2003 |
The quantity of nitrogen oxide gas emissions
in nitric acid production depends on the apparatus and methods used, as well
as on the applied treatment of the exhaust gas.
A brief review is made of a large number of methods used in nitric acid production
and removal of nitrogen oxides, as well as assessment of their economic and
technological aspects. A NOx abatement method is proposed, based on "Continuous
absorption-desorption nitrogen of NOx" in liquid inert absorbents with
subsequent management in a technological scheme. The laboratory embodiment
and work conditions are described in details. Data for six absorbents are
given. The absorption degrees are also determined as a function of the pressure
and gas flow rate. By using the absorbents proposed, an abatement of NOx to
50 ppm is achieved.
Keywords: Nitric acid, absorption, emissions, nitrogen oxides.
MAGNETIC
SEPARATION OF COAL FLY ASH
S. Shumkov, A. Shoumkova
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: annnie@abv.bg
|
Received:30 September 2003
Accepted 15 October 2003
|
A laboratory size High Gradient Magnetic
Separator (HGMS) system capable of producing fields of 2.2 Tesla was used
to separate the iron containing magnetic fraction from coal fly ashes. The
ash samples were taken from the electrostatic precipitator system of the carboelectric
power stations at “Maritza Istock” burning local coals.
Experiments determining the effect of the main parameters, which control the
wet magnetic separation, were carried out. Three types of magnetic filters
were used: stainless steel wool (SS430), steel balls and “cell configuration”
matrix.
The iron enrichment in the mags is possible at low magnetic field due to the
high capture efficiency. The “cell configuration” filter was found
to be the most suitable matrix for this application. The data show that the
part of magnetic particles being associated with the alumosilicate compounds
prevents a complete separation. At optimum separation conditions the magnetic
fraction in the mags is almost three times higherthan that in the feed.
Keywords: coal fly ash, magnetic separation, magnetic recovery,
waste utilization.
REPROCESSING
OF PYRITE CINDERS TO RED IRON OXIDE PIGMENT
A. Shoumkova
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: annnie@abv.bg
|
Received:8 October 2003
Accepted 15 October 2003
|
A method including a combination of magnetic
and thermo-chemical reprocessing of pyrite cinders to red iron oxide pigments
was elaborated. It consists of three basic stages: wet magnetic separation
of pyrite cinders for obtaining a magnetic concentrate with higher quantity
of iron, thermal oxidation of the concentrate and micronizing the synthesized
pigment.
Pyrite cinders from the mechanical and electrocleaning equipment in sulfuric
acid production plants were treated and the influence of the main working
parameters such as magnetic field strength, linear velocity of the suspension,
particle size and firing conditions on the quality of the final product was
researched. It was found that at optimum operating conditions a considerable
increasing of the concentration of iron oxides - up to 91 wt % Fe2O3 in magnetic
concentrate was obtained. After firing at temperatures from 873 to 1273 K
and milling red iron oxide pigments with very good spectral characteristics
were synthesized.
Keywords: pyrite cinders, magnetic separation, waste utilization,
iron oxide pigment.
CHARACTERISTICS
OF HEAVY METALS RELEASE FROM SEWAGE SLUDGE, ITS ASH AND RE-PRODUCTS
E. Alexandrova, J. Balgaranova, A.Petkov, L.Pavlova
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: petkov@uctm.edu
|
Received:30 September 2003
Accepted 15 October 2003 |
During the municipal wastewater treatment
considerable amount of sludge is generated. Such sludge contains pollutions
– heavy metals, toxic substances and constitutes a real environmental
risk. Thermal solidification of the sewage sludge leads to production of ash
defined by the EU regulations as waste. A perspective method for utilization
of these wastes is their use as raw materials in the brick industry. However
there is no standardized method in the literature for the control of heavy
metals release from these materials. Several leaching tests were conducted
for sewage sludge, its ash and re-products to investigate the characteristics
of heavy metals release. Sintering was applied for re-product stabilization.
The amount of heavy metal extraction varied according to the leaching test
method. Cd and Cr were not detected as trace metal released from incinerated
ash. The lower pH value of the leachate after the leaching test, the higher
the concentration of Cd and Cr was detected after re-product treatment.
Keywords: leaching test, heavy metals, sewage sludge.
POSSIBILITIES
FOR UTILIZATION OF MUNICIPAL SOLID WASTE ASHES IN THE PRODUCTION OF BUILDING
CERAMICS
B. Zdravkov, L. Pavlova, Y. Pelovski
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: pelovsky@ uctm.ed
|
Received:30 September 2003
Accepted 15 October 2003
|
Recent study represents experimental results
evaluating the possibilities for utilization of ashes obtained from incineration
of the municipal solid wastes (MSW) for production of ceramic building products.
The generated ash residues are analyzed by chemical analysis, X-ray phase
analysis (RPA) and differential thermal analysis (TG-DTA). Data show that
basic ash components are SiO2 and CaO, while the dominated phases are quartz
and plagioclases. Different composite mixtures of the plastic clay and ash
are worked out for defining maximum allowable ash content, which is varied
between 10 to 30 % wt. The products are dried and after that fired at temperatures
of 1173, 1223 and 1273K. The most important properties are defined on fired
products - a mechanical strength, shrinkage, water adsorption, etc. Analyses
performed prove that MSW ashes are suitable for production of bricks if their
content does not exceed 10 % wt. The optimal fired temperature is 1223K.
Keywords: municipal solid wastes, ashes, extrusion, firing,
ceramic building products.
