Bratkova S.,University of Mining and Geology St Ivan Rilski |
Koumanova B.,University of Chemical Technology and Metallurgy of Sofia |
Beschkov V.,Bulgarian Academy of Science
Bioresource Technology | Year: 2013
Acid wastewaters contaminated with Fe - 1000mgL-1 and Cu - 100mgL-1 were remediated by microbial sulfate-reduction at high organic loading (theoretical TOC/SO42- ratio 1.1) in a laboratory installation. The installation design includes a fixed-bed anaerobic bioreactor for sulfate-reduction, a chemical reactor, a settler and a three-sectional bioreactor for residual organic compounds and hydrogen sulfide removal. Sulfate-reducing bacteria are immobilized on saturated zeolite in the fixed-bed bioreactor. The source of carbon and energy for bacteria was concentrated solution, containing ethanol, glycerol, lactate and citrate. Heavy metals removal was achieved by produced H2S at sulfate loading rate 88mgL-1h-1. The effluent of the anaerobic bioreactor was characterized with high concentrations of acetate and ethanol. The design of the second bioreactor (presence of two aerobic and an anoxic zones) makes possible the occurrence of nitrification and denitrification as well as the efficiently removal of residual organic compounds and H2S. © 2013 Elsevier Ltd.
Iotov P.I.,University of Chemical Technology and Metallurgy of Sofia |
Kalcheva S.V.,University of Chemical Technology and Metallurgy of Sofia |
Kanazirski I.A.,University of Mining and Geology St Ivan Rilski
Electrochimica Acta | Year: 2013
The initial steps of sodium borohydride oxidation are studied at PtAu alloy electrodes of Au bulk contentof 20, 40, 60 and 80 at.%. Linear sweep voltammetry is applied in 0.01 M NaBH4in 1.00 M NaOH varyingthe scan rate applied. The experiments are performed at four temperature values in the interval from293.2 K to 323.2 K. The data obtained are compared to those referring to Pt and Au as well. The values of the standard rate constant characterizing the first anodic peak are determined. The apparent activationenergy of the process studied is evaluated and its dependence on the alloys bulk and surface compositionis followed. It is found that the lowest apparent activation energy is expected in case of an alloy of Aubulk content of ca 45 at.%. The total number of electrons exchanged during the process is found. It isca 1 for Pt and most of the alloys indicating that borohydride anion adsorption determines the peakconsidered. For Au and the alloy of Au bulk content of 20 at.% it is 1.2 and 1.3, respectively. The lattervalues point to the fact that the anodic process on Au refers to borohydride anion adsorption followedby electrooxidation with the participation of the supporting electrolyte's hydroxide anions, while thaton the alloy can be attributed to two-step formation of adsorbed species containing BOH and H. Theenhanced electrocatalytic performance of PtAu alloys when compared to that of Pt and Au is ascribed toan electronic effect resulting in decrease of B H bonding strength when compared to that of unalloyedPt. Experimental evidence is provided by finding that weakly adsorbed species participate in the reactiondetermining the first anodic peak at the alloy of Au bulk content of 60 at.%. © 2013 Elsevier Ltd. All rights reserved.
Stambolova I.,Bulgarian Academy of Science |
Shipochka M.,Bulgarian Academy of Science |
Blaskov V.,Bulgarian Academy of Science |
Loukanov A.,University of Mining and Geology St Ivan Rilski |
Vassilev S.,Bulgarian Academy of Science
Journal of Photochemistry and Photobiology B: Biology | Year: 2012
Spray pyrolysis procedure for preparation of nanostructured TiO2 films with higher photocatalytic effectiveness and longer exploitation life is presented in this study. Thin films of active nanocrystalline TiO2 were obtained from titanium isopropoxide, stabilized with acetyl acetone and characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The activity of sprayed nanostructured TiO2 is tested for photocatalytic degradation of Reactive Black 5 dye with concentrations up to 80 ppm. Interesting result of the work is the reduction of toxicity after photocatalytic treatment of RB5 with TiO2, which was confirmed by the lower percentage of mortality of Artemia salina. It was proved that the film thickness, conditions of post deposition treatment and the type of the substrate affected significantly the photocatalytic reaction. Taking into account that the parameters are interdependent, it is necessary to optimize the preparation conditions in order to synthesize photocatalytic active films. © 2012 Elsevier B.V. All rights reserved.
Loukanov A.R.,University of Mining and Geology St Ivan Rilski |
Gagov H.,Sofia University
Microscopy Research and Technique | Year: 2012
In this study, we aimed to increase the sensitivity of protein labeling using 1.4 nm gold nanoparticles and glutamate δ2 receptor (GluD2) from the postsynaptic membrane of the Purkinje cells. The very small marker size of the particles reduces the steric hindrance between antibodies leading to a higher labeling efficiency of more than one subunit per single receptor molecule. The nanoparticles are visible in 200 kV dark-field scanning transmission electron microscope on freeze-fractured carbon replica of nervous tissue after plasma cleaning treatment. The different elemental composition of nanoparticles as Au nanogold or CdS quantum dot can be distinguished by energy dispersive X-ray spectroscopy. This method ensures detection of an average of three subunits per GluD2 and often labels all four of them with 1.4 nm Au nanoparticles. It is concluded that this high-resolution microscopic method is useful for exploring the quaternary structure of membrane proteins. © 2012 Wiley Periodicals, Inc.
Angelov A.,University of Mining and Geology St Ivan Rilski |
Bratkova S.,University of Mining and Geology St Ivan Rilski |
Loukanov A.,University of Mining and Geology St Ivan Rilski
Energy Conversion and Management | Year: 2013
A two chambered laboratory scale microbial fuel cell (MFC) has been developed, based on natural sulfate-reducing bacterium consortium in electroactive biofilm on zeolite. The MFC utilizes potassium ferricyanide in the cathode chamber as an electron acceptor that derives electrons from the obtained in anode chamber H2S. The molecular oxygen is finally used as a terminal electron acceptor at cathode compartment. The generated power density was 0.68 W m-2 with current density of 3.2 A m-2 at 150 Ω electrode resistivity. The hydrogen sulfide itself is produced by microbial dissimilative sulfate reduction process by utilizing various organic substrates. Finally, elemental sulfur was identified as the predominant final oxidation product in the anode chamber. It was removed from MFC through medium circulation and gathering in an external tank. This report reveals dependence relationship between the progress of general electrochemical parameters and bacterial sulfate-reduction rate. The presented MFC design can be used for simultaneous sulfate purification of mining drainage wastewater and generation of renewable electricity. © 2012 Elsevier Ltd. All rights reserved.
Boteva A.,University of Mining and Geology St Ivan Rilski
26th International Mineral Processing Congress, IMPC 2012: Innovative Processing for Sustainable Growth - Conference Proceedings | Year: 2012
A significant part of the currently production of the non-ferrous and precious metals is from sulfide ores. Character feature of sulfide ores is the presence in them always pyrite and wide range of different sulfide minerals else. These minerals are the carriers of valuable for industry metals. Due to the low content of the main components, very often call on the use of collective- selective flow-sheets. The extraction of minerals in the collective concentrates determined in a large extent the effectiveness of the collective-selective sheets. In conditions of bulk flotation kinetics to floatate of the various minerals is different. Due to why it is and how it can be used for a more effective selection of minerals -this is the main task of this report. For this purpose are used results from the bulk flotation of pyrite, copper sulfides, molybdenite, galena, blenda. It is separated and place of host rocks. Base it of large experimentation material, including both electro-kinetic measurements of mineral systems, as well as laboratory flotation tests and factories monitoring it is established kinetics of flotation of mineral particles in conditions of collective flotation. Made an effort to clarify the effect as of the species and the proportion of different sulfide minerals involved in flotation pulp else. Traced was the impact of the density and aeration of the flotation pulp on deferens in kinetics of mineral flotation in condition of balk flotation. The obtained results are used to increase the efficiency of the diffraction flotation of the complex sulfide ores containing precious metals. In the schemes, it is possible precious metals to fall in the most appropriate for the next processing products.
Gicheva G.,University of Mining and Geology St Ivan Rilski |
Yordanov G.,Sofia University
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2013
This article describes studies on the efficiency of activated carbon as adsorbent for water-dispersible silver nanoparticles. Nanoparticles of average size around 60nm and negative zeta-potential were synthesized by reduction of Ag(I) ions with sodium citrate in aqueous medium. Activated carbon (Norit® CA1) intended for water purification was found to be an efficient adsorbent for silver nanoparticles. It was found that nanoparticle adsorption on activated carbon could be described by Freundlich and Langmuir isotherms. The presence of electrolytes favored nanoparticle deposition on the surface of activated carbon. When electrolytes were used above their critical coagulation concentration aggregated nanoparticles were settling down along with the carbon particles, where carbons were acting as filter aid. This allowed complete removal of nanoparticles from the aqueous dispersions. It is expected that these studies could be important for better understanding of the interactions between nanoparticles and solid-liquid interfaces, for preparation of nanoparticle/carbon composite materials, as well as for designing of methods for removal of metal nanoparticles from contaminated water during treatment of nanowastes. © 2013 Elsevier B.V.
Stavrev P.,University of Mining and Geology St Ivan Rilski |
Reid A.,University of Leeds
Geophysics | Year: 2010
The concept of extended Euler homogeneity of potential fields is examined with respect to all variables of length dimension in their analytical expressions. This reveals the possible existence of positive degrees of homogeneity or corresponding negative structural indices considered as extensions of the Thompson's structural indices in Euler deconvolution. This approach is implemented for a contact gravity model, represented by a 2D semi-infinite slab with large thickness relative to its depth. Applying Euler deconvolution on synthetic and field data indicates that the positive degree of homogeneity, i.e., the extended negative structural index, is the appropriate one for the inversion of gravity anomalies from contact structures. © 2010 Society of Exploration Geophysicists.
Anguelov K.,University of Mining and Geology St Ivan Rilski
Global View of Engineering Geology and the Environment - Proceedings of the International Symposium and 9th Asian Regional Conference of IAEG | Year: 2013
Structural bonds among clayey particles were investigated by a number of scientists, predominantly based on results of physical and mechanical studies [Terzaghi K., 1925; Rehbinder, 1966; Derjaguin, 1986; Shtukin, 1965; Osipov, 2012; V.N. Sokolov, 1991]. The most recent comprehensions of academician V. I. Osipov revealed that the main types of structural bonds (contacts) in clays are as follows: phase, transitional, short range coagulation and long range coagulation contacts. Nevertheless of those physical-chemical concepts, which define the significant differences in the nature of contact interactions, all the types of clays are described by the same strength parameters-angle of internal friction (φ) and cohesion (c). Those parameters (φ and c) are convincing for clays with phase and transient contacts, where contacts between the particles are direct. What, however, may be said about clays with coagulation contacts, where hybrid coatings of bound water are available among the particles? Those kinds of contacts are present in the sliding surfaces of landslides. The present report will show which strength properties may be used instead of the traditional ones "φ" and "c" for defining the stability factor. © 2013 Taylor & Francis Group, London.
Zdravkov A.,University of Mining and Geology St Ivan Rilski |
Bechtel A.,University of Leoben |
Sachsenhofer R.F.,University of Leoben |
Kortenski J.,University of Mining and Geology St Ivan Rilski |
Gratzer R.,University of Leoben
Organic Geochemistry | Year: 2011
During the Miocene numerous sedimentary basins formed on the territory of Bulgaria as a result of the extensional tectonic settings related to the post-orogenic development of the late Alpine orogen. In this study, we review the petrographic composition and biomarker assemblage of two adjacent basins in western Bulgaria, i.e. Beli Breg and Staniantsi basins. Both contain lignite formed during late Miocene (c. 6. Ma). Despite similar tectonic settings and depositional environments, the lignite seams possess different petrographic and organic geochemical characteristics, reflecting differences in the peat forming palaeo-communities and facies variations. The peat-forming vegetation in Beli Breg Basin was dominated by decay resistant coniferous plants, as indicated by abundant fossil wood remains, very good tissue preservation and a biomarker assemblage dominated by diterpenoids. In contrast, Staniantsi lignite is poor in fossil wood and contains a significant amount of triterpenoid biomarkers, suggesting the predominance of angiosperm plants in the swamp. The results of the biomarker analyses are consistent with palaeobotanical and palynological data from the literature.The lignite seams in both basins formed under frequently changing Eh conditions, as indicated by the severe degradation of the non-gymnosperm tissues, the low gelification index values and the variations in pristane/phytane ratio, probably as a result of seasonal drying of the swamps and changes of the ground water table. Hopanoid contents in Beli Breg lignite are very low and are consistent with the abundance of decay-resistant vegetation. In contrast, bacterial activity was obviously higher in the Staniantsi swamp, however, resulting only in slightly enhanced gelification of plant tissues. The geochemical data suggest that the diagenetic changes of the organic matter were mainly governed by thermal degradation, rather than bacterial activity. © 2010 Elsevier Ltd.