Browsing by Author "Zahariev A."

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    Formation of complex anodic films on porous alumina matrices
    (2003-01-01) Zahariev A.; Girginov A.
    The kinetics of growth of complex anodic alumina films was investigated. These films were formed by filling porous oxide films (matrices) having deep pores. The porous films (matrices) were obtained voltastatically in (COOH)2 aqueous solution under various voltages. The filling was done by re-anodization in an electrolyte solution not dissolving the film. Data about the kinetics of re-anodization depending on the porosity of the matrices were obtained. On the other hand, the slopes of the kinetic curves during re-anodization were calculated by two equations expressing the dependence of these slopes on the ionic current density. A discrepancy was ascertained between the values of the calculated slopes and those experimentally found. For this discrepancy a possible explanation is proposed, related to the temperature increase in the film, because of that the real current density significantly increases during re-anodization.
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    METHANE PRODUCTION FROM COW MANURE IN THE PRESENCE OF Bi(III) COMPLEX OF SULFAMIC ACID
    (2024-01-01) Tzanova A.; Kaloyanov N.; Ruskova K.; Zahariev A.
    The present study examines the process of biomethanization of cow manure in an anaerobic environment, in the presence of small amounts of Bi(III) complex of sulfamic acid. Since this complex has good antimicrobial activity, the purpose of adding the complex is to determine its effect on biogas and methane production. The reference samples (cow manure only) and mixtures of cow manure + 10 mg and cow manure + 20 mg of bismuth complex with a composition [Bi6O4(OH)4](NH2SO3)6 are subjected to biodegradation under the following conditions – duration of 33 days, nitrogen atmosphere and temperature of 34.5 ± 1°C. During the process, the volume of biogas and the percentage content of methane in biogas are measured in 2 - 3 days as well. The analyses performed reveal that until the 10th day, the amount of biogas produced increases constantly and is comparable both for the control samples and for the mixtures. Further, until the end of the experiment, a significant and constant increase in the volume of biogas produced by the mixtures is observed compared to the control samples. Regarding the percentage of methane produced by the reference samples and the mixtures, comparable relative amounts are found by the 7th day. From the 8th day to the 33rd day, the percentage of methane released by the mixtures is visibly greater than that by the reference samples.
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    Synthesis of new complex [Bi6O6(OH)2](ClC6H4SO3)4and investigation of its thermal decomposition
    (2023-05-01) Kaloyanov N.; Zahariev A.; Parvanova V.; Avdeev G.; Girginov C.
    A new [Bi6O6(OH)2](ClC6H4SO3)4complex is synthesized through a reaction of Bi2O3 with aqueous 4-chlorobenzenesulfonic acid at elevated temperature. The product composition is elucidated by elemental analysis, ICP-OES and FTIR techniques. By means of XRD analysis, the compound s indexation, monoclinic P2(3) space group and unit cell parameters: A=31.25(3) A, b=19.78(1) A, c=8.795(8) A, γ = 94.33(4)o as well as a cell volume = 5424.21 A3 are determined. Based on DTA-TG technique, three specific temperatures aimed at studying product s thermal decomposition are determined. The compositions of solid residues after isothermal heating are proved following the XRD and FTIR data.