Browsing by Author "Kapralova V."

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    CORROSION BEHAVIOR OF MILD STEEL IN SODIUM SULFATE SOLUTION IN PRESENCE OF PHOSPHATES OF DIFFERENT COMPOSITION
    (2024-01-01) Raimbekova A.; Kapralova V.; Popova A.; Kubekova S.; Dalbanbay A.; Kalenova A.; Mustahimov B.; Yermekbayeva S.; Myrzabekova S.
    Corrosion of mild steel in sodium sulfate solutions (1000 mg SO4 2- L-1) in the presence of various phosphate inhibitors was studied gravimetrically. Studies were performed under static conditions at room temperature. The known sodium polyphosphate inhibitor has been found to have low efficacy under these conditions. The inhibitor efficiency of its does not exceed 30.5 % at a concentration of 100 mg P2O5 L-1. It has been shown that a more effective inhibitor is calcium-manganese polyphosphate (Са, Mn)(PO3)2 obtained on the basis of manganese ore enrichment wastes of the Zhayrem deposit. The inhibitor efficiency of its already at a concentration of 20 mgP2O5 L-1 is 47.3 %. At a concentration of 100 mgP2O5 L-1, the inhibitor efficiency (Са, Mn)(PO3)2 is 96.2 %. Electrochemical tests confirmed the results of the gravimetric study. Infrared spectroscopic analysis showed that phosphate protective coatings were formed on the steel surface in solutions of sodium sulfate with additives of calcium-manganese polyphosphate.
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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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    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.