Browsing by Author "Lavrova S."

Now showing 1 - 7 of 7
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    Drug mass transfer mechanism, thermodynamics, and in vitro release kinetics of antioxidant-encapsulated zeolite microparticles as a drug carrier system
    (2018-10-01) Yaneva Z.; Georgieva N.; Bekirska L.; Lavrova S.
    The aim of the present study was to develop a new vitamin E-zeolite drug carrier system, and investigate the mass transfer mechanism of the antioxidant encapsulation and release on/from the mineral matrix by thermodynamic and kinetics sorption/desorption experiments and mathematical modelling of the experimental data. The surface, morphological and spectral characteristics of the vitamin and the zeolite were determined by Boehm titration, SEM, FTIR and UV/Vis spectrophotometric analyses. Intraparticle diffusion was not the only rate-limiting mechanism, as the mixed-order kinetics model gave the highest regression coefficient (R2) and lowest SSE, MSE, RMSE, and AICC values. The thermodynamic study confirmed the endothermic nature of the spontaneous encapsulation process and increased degrees of randomness at the solid-liquid interface. The in vitro release results were best modelled by the zero-order and sigmoidal models. The results obtained are essential for the development of innovative vitamin E-carrier systems for application in human and veterinary medicine.
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    EXPONENTIAL MOVING AVERAGE FOR AIR POLLUTION DATA: ASSESSING ITS ROLE IN PM10 MONITORING ACCURACY
    (2025-11-02) Stoyanova K.; Metodiev V.; Lavrova S.
    Accurate estimation of particulate matter (PM10) concentrations is critical for assessing air quality and mitigating public health risks. Traditional monitoring data processing methods, such as simple moving averages (MA), often struggle to capture rapid fluctuations in pollutant levels due to their uniform weighting of historical data, potentially compromising real - time decision - making. This study evaluates the efficiency of the Exponential Moving Average (EMA) algorithm, which prioritizes recent observations through exponential weighting, to improve PM10 concentration estimates. Using data from urban air quality monitoring stations, EMA was applied across varying time windows and compared against conventional MA approaches. Performance was assessed against ground - truth measurements. Results demonstrated that EMA significantly reduced estimation errors. The algorithm exhibited enhanced responsiveness to abrupt PM10 spikes, attributed to its dynamic weighting mechanism. Sensitivity analysis revealed that optimal smoothing factors depended on the selected time window, balancing noise reduction and trend detection. These findings underscore EMA’s potential as a robust tool for air pollution monitoring data analyses, offering superior adaptability to temporal variability. Implementation of EMA in regulatory and public health frameworks could enhance early warning systems and pollution control strategies. Future research should explore integrating EMA with machine learning models and low - cost sensor networks to further optimize real - time air quality management.
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    FEASIBILITY STUDY INTO THE POSSIBILITY OF MANGANESE ORE ENRICHMENT WASTE USE FOR SORBENT MATERIAL DEVELOPMENT
    (2026-01-01) Kalymbet A.; Kubekova S.; Kapralova V.; Lavrova S.
    This study explores the synthesis of sorption-active phosphate materials from manganese ore enrichment tailings of the Zhairem deposit. The initial tailings, predominantly composed of calcite (76.4 %), quartz (16.4 %), and braunite, were characterized by XRD and EPMA. Acid-thermal treatment with phosphoric acid followed by calcination at 200-800°C yielded calcium - manganese phosphate materials. Phase transformations were monitored via XRD, showing formation of crystalline phosphates at 200-600°C and a glassy phase at 800°C. The product synthesized at 600°C demonstrated the lowest water solubility (9.91 %), highest pore volume (0.175 cm3 g-1), and optimal sorption capacity for Ni2+ (0.2934 mg-eq g-1), which increased to 0.4697 mg-eq g-1 after 0.4 wt. % of HCl activation. The enhanced performance is attributed to the formation of low-solubility polyphosphates and well-developed porous structures. SEM confirmed porous morphology at 600°C and denser, glassy structure at 800°C. The synthesized material showed no toxic elements such as Pb, Cd, or As, making it suitable for environmental applications. The findings indicate that Zhairem tailings are a promising raw material for producing effective sorbents for heavy metal removal, especially after acid activation. The optimal product is the calcium-manganese phosphate synthesized at 600°C.
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    ORE ENRICHMENT WASTE AS RAW MATERIAL FOR HEAVY METAL SORBENTS
    (2025-01-01) Kalymbet A.; Kubekova S.; Lavrova S.
    The study considered ore enrichment waste from the Ashiktas, Akbakai, and Maikain deposits to create sorbents based on silicophosphates. X-ray phase and electron probe elemental analysis were carried out, which confirmed the presence of silicon, aluminosilicate, and other valuable components suitable for the sorbent’s synthesis. The optimal synthesis temperature (600°C) contributes to the sorbents’ porous structure development and a sorption capacity increase concerning Ni2+ ions, allowing them to be used to purify industrial wastewater from heavy metals, which was proven using zeta potential measurements and SEM images.
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    Treatment of landfill leachate in two stage vertical-flow wetland system with/without addition of carbon source
    (2016-01-01) Lavrova S.
    The aim of this study was to investigate the treatment efficiency of two laboratory scale vertical-flow wetland systems (VFWS) with/without additional carbon source to affect the denitrification of landfill leachate, taken from an active 15 years old landfill for municipal solid wastes. The BOD/COD ratio of the leachate was 0.26, which means predominance of slowly biodegradable substances. During the experiments the parameters COD, BOD, [NH4-N], [NO2-N], [NO3-N] and total phosphorus were determined. Significant removal efficiency according to COD (94.69 ± 2.5 %) and BOD (95.96 ± 2.5 %) was achieved. Complete nitrification of ammonium nitrogen into nitrite and nitrate occurred in both systems. Denitrification occurred only in the wetland system when methanol was added.
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    Treatment of wastewaters containing Fe, Cu, Zn and as by microbial hydrogen sulfide and subsequent emoval of COD, N and P
    (2018-01-01) Bratkova S.; Lavrova S.; Angelov A.; Nikolova K.; Ivanov R.; Koumanova B.
    Acid drainage wastewaters (pH 2.6 - 2.8) contaminated with Fe 200 mg/l, Cu 25 mg/l, Zn 25 mg/l, and As 15 mg/l were treated in a laboratory-scale installation. The installation design includes an anaerobic sulfidogenic bioreactor, a chemical reactor, an aerobic activated sludge reactor, an anaerobic biofilter and a vertical flow constructed wetland reactor, connected in series. Sulfate-reducing bacteria were adhered in biofilm, which is immobilized on zeolite particles in the anaerobic bioreactor. The bacteria were cultivated on a medium containing lactate as a source of carbon and energy. The influence of TOC/SO42- ratios 0.43, 0.54 0.64 on the rate of the microbial sulfate-reduction was determined. Pollutants removal was achieved in a chemical reactor by sedimentation with microbially produced H2S. SEM/EDS data and X-ray diffraction analyses proved that the precipitated heavy metals are mainly in forms of relevant insoluble sulfides. The design of the lab-scale installation makes possible efficient removal of the residual organic compounds and hydrogen sulfide as well as the processes of nitrification and denitrification to occur. The reported treating method allows the removal of heavy metals, COD, N and P from wastewaters below the permeable level for water intended for use in the agriculture and/or industry.
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    Valorization of Manganese Ore Tailings from the Borly Deposit into Functional Sorbents
    (2025-10-01) Kalymbet A.; Kubekova S.; Kapralova V.; Rysbekov K.; Lavrova S.
    This study reports the synthesis and characterization of a novel sorbent from manganese ore beneficiation tailings (Borly deposit, Kazakhstan), activated with 20% phosphoric acid and thermally treated at 600 °C. Compared to the raw material, the sorbent showed reduced BET surface area (6.05→3.02 m2/g) but increased average pore diameter (13.2→21.8 nm), more negative zeta potential (−4.1→−18.9 mV), and lower water solubility (0.82%). Equilibrium tests revealed ≥99% Cu2+ removal and a maximum capacity of 1.329 mg/g, with a type V isotherm indicating cooperative adsorption on heterogeneous sites. Among tested models, the RALF (Redlich–Anderson–Langmuir–Freundlich) isotherm provided the best fit (R2=0.999), confirming structured and energetically diverse adsorption sites. Kinetics followed a pseudo-second-order model (R2≈1), suggesting chemisorption with mixed physisorption contributions, while intraparticle diffusion was not the sole rate-limiting step. Fixed-bed tests showed a dynamic capacity of 0.68 mg/g. The results highlight a sustainable approach to valorizing manganese tailings for efficient copper removal. This work demonstrates a sustainable approach to valorizing mining waste into functional sorbents for heavy metal removal. Despite their modest adsorption capacity, the materials show high removal efficiency and low cost, making them promising for polishing treatment and other cost-sensitive applications.