Browsing by Author "Ilieva D."

Now showing 1 - 8 of 8
  • No Thumbnail Available
    Item
    Characterization of Bulgarian Copper Mine Tailing as a Precursor for Obtaining Geopolymers
    (2024-02-01) Ilieva D.; Angelova L.; Radoykova T.; Surleva A.; Chernev G.; Vizureanu P.; Burduhos-Nergis D.D.; Sandu A.V.
    Valorization of high-volume mine tailings could be achieved by the development of new geopolymers with a low CO2 footprint. Materials rich in aluminum and silicon with appropriate solubility in an alkaline medium can be used to obtain a geopolymer. This paper presents a study of copper mine tailings from Bulgaria as precursors for geopolymers. Particle size distribution, chemical and mineralogical composition, as well as alkaline reactivity, acidity and electroconductivity of aqueous slurry are studied. The heavy metal content and their mobility are studied by leaching tests. Sequential extraction was applied to determine the geochemical phase distribution of heavy metals. The studied samples were characterized by high alkalinity, which could favor the geopolymerization process. The water-soluble sulphates were less than 4%. The Si/Al ratio in mine tailing was found to be 3. The alkaline reactivity depended more so on the time of extraction than on the concentration of NaOH solution. The main part of the heavy metals was found in the residual fraction; hence, in high alkaline medium during the geopolymerization process, they will stay fixed. Thus, the obtained geopolymers could be expected to exert low environmental impact. The presented results revealed that studied copper mine tailing is a suitable precursor for geopolymerization.
  • No Thumbnail Available
    Item
    Comparative study of soil test methods for determination of plant available potassium in Bulgarian arable soils
    (2021-01-01) Angelova L.; Genova N.; Stoyanova S.; Surleva O.; Nekov I.H.; Ilieva D.; Surleva A.
    This comparative study was aimed at estimating analytical behavior of methods for determination of plant available potassium applied to Bulgarian arable soils and to reveal the relationship between the amount of extractable K. Twenty-four samples from two traditional agricultural regions in Bulgaria were studied. Soil potassium was extracted by NH4OAc/HOAc pH 4.5 (AA), diluted double acid (Mehlich 1), CaCl2, BaCl2 and a modified acetate/lactate method (ALM) and determined by Flame AES. The factors influencing the methods accuracy were identified and uncertainty was estimated. The expanded uncertainty was (in mg K2O (100 g dry soil)-1): 0.10 (ALM), 0.64 (Mehlich 1), 0.17 (CaCl2) and 1.1 (AA). The study revealed that the factor which mainly influence the uncertainty of the applied analytical methods for plant available potassium in soil was the calibration of Flame AES determination. The obtained results showed that extractable potassium lowered in the following order KALM ≥ KAA > KMechlich1 > KBaCl2 > KCaCl2. Soil potassium extracted by ALM procedure correlated with AA, BaCl2-K, CaCl2 –K and Mehlich 1 - K at 0.05 level of significance. ALM extracted between 1.2 to 5.8 times more soil K than other methods did. The obtained results provided a base for further study on correlation between extractable K and soil fertility indices for particular soil types and climatic regions in Bulgaria.
  • No Thumbnail Available
    Item
    CONTRIBUTION TO MINE TAILINGS TOXICITY ASSESSMENT
    (2026-01-01) Angelova L.; Ilieva D.; Surleva A.
    Various chemical, biological, and biochemical assays are currently employed to evaluate the state of mine tailing dumps. However, some chemical approaches could overestimate the environmental footprint. This study presents an assessment of the current state of the inactive mine tailing dump area, employing a sequential chemical extraction procedure (SEP) to study heavy metal fractionation and contamination indices, thereby assessing the mobility and potential bioavailability. The studied samples contained elevated concentrations of As, Cu, Pb, and Zn, of which Pb was the most abundant element. The results showed that although high total heavy metal content in soil and mine tailing was observed, the mobility factors rarely exceeded 10 %. Moreover, the values of contamination factors, individual and global, were below 1 and 6, respectively. Thus, the mine tailings and surrounding soils could be classified as sources with low contamination potential. The applied approach could benefit the ongoing efforts toward the sustainable management and conservation of post-mining landscapes.
  • No Thumbnail Available
    Item
    Determination of Alkaline Reactivity of Geopolymer’s Raw Materials: Practical Aspects
    (2025-01-01) Surleva A.; Ilieva D.; Angelova L.
    Alkaline reactivity characterizes the dissolution and reactive capacity of a solid material in alkaline media. The results are of significance in the development of technology for geopolymers obtaining based on the studied raw materials. However, no validated analytical procedure for estimation of alkaline reactivity of coal combustion by-products and mine tailing exists. It imposed the development of specific procedure for analysis and its verification. This report presents a procedure based on ICP-OES measurement of the concentration of Al, Si and Ca in alkali solution. Some problems of the analysis were successfully addressed, as a high salt content of leachates, and the procedure was verified applying a reference laboratory approach. The alkaline reactivity was studied as a function of time at 6.5 M NaOH during 48 h. Additionally, to reactive silica determination, the study was extended to reactive alumina and calcium, as these components contribute to the development of geopolymer matrix. To estimate the percentage of dissolved Al, Si and Ca detailed precise data about chemical composition of raw materials were required. To achieve it, samples components were determined by ICP-OES after digestion in acid oxidizing medium, combined with alkali fusion for silica determination, as well as loss of ignition and humidity determination. In contrast to the approach, usually reported in the literature, presenting the alkaline reactivity as a concentration of dissolved ions in the alkaline solution, in this study we proposed a new procedure. Alkaline reactivity was estimated: by a percentage of dissolved component in mg per kg dry sample. This approach allowed comparability of the data between various laboratories, procedures or raw materials. Moreover, the approach allowed the relative ratio between reactive components to be calculated.
  • No Thumbnail Available
    Item
    Ensuring the Quality of the Analytical Process in a Research Laboratory
    (2024-04-01) Surleva A.; Angelova L.; Ilieva D.; Ivanova V.; Surleva O.; Chavdarova K.
    Featured Application: The approaches for estimation of the analytical behavior of measuring methods could be applied in a research laboratory aiming at the characterization of new materials or a new method for analysis. The limitations of well-known approaches are described, and the alternatives are discussed. This paper discusses approaches for verification of methods of measurements of chemical and physical characteristics of specific samples. The limitations of well-known approaches are discussed. Some examples of alternatives are given to demonstrate specific issues encountered in the research laboratory analyzing new materials or characterizing new properties of materials. Application of sequential procedure using lower quantities of samples and reagents is presented. A standard addition to solid samples is discussed. The approach of control charts for estimation of method uncertainty for determination of plant available phosphorus is presented. The method comparison is applied as an approach to verification of alkaline reactivity by inductively coupled plasma–optical emission spectroscopy (ICP-OES) measurement, as well as density of newly synthesized chalcogenide glass materials. The presented examples demonstrated that alternative approaches are needed in order to verify the methods applied due to the great variety of activities and corresponding tasks in a research laboratory.
  • No Thumbnail Available
    Item
    Estimation of soil and tailing dump toxicity: Development and validation of a protocol based on bioindicators and ICP-OES
    (2019-08-02) Ilieva D.; Angelova L.; Drochioiu G.; Murariu M.; Surleva A.
    A protocol for estimation of soil toxicity based on germination test, open acid sample digestion and ICP-OES determination of heavy metals and metalloids was proposed. Triticum aestivum was used as a bioindicator and germinated on contaminated soils. After estimation of the state of the plantlets, the accumulated heavy metals and metalloids content were determined. The sample digestion procedure and ICP-OES measurement were validated by analysing plant certified reference material. Additionally, standard addition before sample pretreatment was applied for estimation of method recovery at the levels of heavy metals found in plants from contaminated region. The recovery obtained was between 97 and 105 %. The precisions of the complete protocol (RSD), which included germination tests, sample digestion and ICP-OES measurements, ranged between 4.7% for Mn and 11 % for As. The expanded uncertainty was estimated. The proposed protocol was applied for estimation of soil toxicity and heavy metals bioavailability of tailing dump material and surrounding soils from an abandoned barite mine in Tarnita, Suceava, Romania. The coltsfoot used for remediation of the soil in the studied region was analysed. Cu, Ni, Zn, Mn, Pb, Fe and Al were found in the sample harvested nearby the tailing dump.
  • No Thumbnail Available
    Item
    INTEGRATED ALGORITHM FOR TOXICITY ASSESSMENT OF MINE TAILINGS AND SURROUNDING SOILS BASED ON CHEMICAL AND GERMINATION ASSAYS
    (2026-01-01) Angelova L.; Ilieva D.
    The evaluation of the environmental impact arising from mine tailing toxicity can be accomplished by chemical and biological assays. Several research groups and environmental agencies established working protocols for heavy metal determination and risk assessment. Nevertheless, there is no standardized methodology that integrates chemical and biological approaches for the toxicity assessment of soils and waters contaminated with heavy metals and metalloids. This study presents a comprehensive algorithm designed to assess the environmental toxicity of mine tailings and surrounding soils by applying a germination assay. Therefore, wheat germination bioassays and evaluation of bioconcentration of As, Pb, Cu, Zn, Cd, Ag, Fe, Mn, Ni, and Cr in contaminated environmental samples are carried out. The germination index showed results greater than 80 % classified as “excellent” in soil samples P1 and P2, and less than 40 % in soil sample P3 due to high Pb toxicity. The capability of plant species to remediate soils was evaluated by the Bioconcentration factor (BCF) and the Translocation factor (TF). The average results for BCF, based on Pb, As, Zn, and Cu, were 0.25, and a low TF was obtained, with values ranging between 0.05 and 0.2.
  • No Thumbnail Available
    Item
    Tarnita polluted area: Accumulation of heavy metals and nutrients from the soil by woody species
    (2019-03-01) Iacoban C.; Risca I.M.; Roibu C.; Ciornea E.T.; Necula R.; Ilieva D.; Sandu I.; Drochioiu G.
    Heavy metals are destructive environmental stressors that greatly reduce plant growth and productivity. Here, the content of some heavy metals (Fe, Cu, Zn and Mn) and mineral nutrients (Ca, Mg and K) in silver fir (Abies alba Mill.) and European beech (Fagus sylvatica L.) wood from two sites in the Tarniþa mining area (North-Est Romania) was analyzed. The first site (no. 1) is located near a big tailings dump, whereas the other one (no. 2) is situated 6 km South, in a less polluted area. The purpose of this work was to evaluate the present-date levels of such elements in the investigated biological materials and to compare them. Measurements of heavy metal content in wood were performed with an AAS flame spectrometer, whereas an ICP-OES spectrometer was used for soil and tailings dump samples. The Mn content was higher in the site no. 1 located near the dump, for both species, but the difference was statistically significant only for the European beech trees. The Zn content of samples from the site no. 1 was lower than that corresponding to the second one (no. 2) for both species, but significant for the silver fir only. However, there was not found a significant difference in respect to both iron and copper in the samples collected from the two species and two different sites. Furthermore, the content of Ca and Mg of both species was found higher for the site no. 2, suggesting a better state of nutrition of the investigated trees than of those located near the tailings dump. The content of calcium and magnesium of silver fir was negatively correlated with the diameter of the trees collected from both sites.