Browsing by Author "Minkova K."

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    Incorporation of Synechocystis salina in hybrid matrices. Effect of UV-B radiation on the copper and cadmium biosorption
    (2010-10-14) Toncheva-Panova T.; Pouneva I.; Chernev G.; Minkova K.
    The isolated Antarctic cyanobacterium Synechocystis salina was embedded in silica hybrid matrices. The ability of the cyanobacterium to remove copper (about 7.6 mg.g-1 biomass) and cadmium (about 9.0 mg.g-1 biomass) was shown. UV-B treatment of cells prior to their immobilization decreased the percentage of viable cells to 4.5. At the same time it increased the copper sorption to 18.8 mg.g-1 biomass without influencing too much the sorption of cadmium (9.0-8.6 mg.g-1 biomass). The addition of carrageenan to the matrices containing viable UV-B non-irradiated cells increased the accumulation of copper and cadmium by about 2.9 and 3.9 fold, respectively. Results indicate that immobilized in hybrid matrices viable and dead Synechocystis salina cells could be used as an active copper and cadmium removing biocomponent for bioremediation of wastewaters and/or soils.
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    OPTIMIZATION OF THE EXTRACTION CONDITIONS FOR THE Hg2+ - DITHIZONE COMPLEX IN CHLOROFORM AND ITS DETERMINATION BY UV-VIS SPECTROPHOTOMETRY
    (2026-01-01) Ivanova V.; Minkova K.; Chakarov K.
    This study aimed to optimize a UV- Vis spectrophotometric method for determining mercury based on its extraction with dithizone in chloroform. In the present work, the effects of pH, reagent concentration, stoichiometry of the complex were investigated. In addition, the sensitivity of the method was determined by calculating the molar absorbance, assessing the linearity and shaking time. Optimal conditions were established at pH ≈ 1.0 ± 0.1, using 4.00 mL of 5.00 mg L-1 dithizone and 1.00 min shaking. Under these parameters, the method showed stable absorbance and reproducible results. The calibration was linear within 0.80 - 1.10 mg L-1 Hg, and recovery tests yielded 71 - 74 % for spiked tap and deionized water samples. The optimized procedure provides reliable preliminary mercury determination and can be further adapted for complex matrices such as sediment, soil, or coal after microwave digestion.