Assessment of the Enrichment of Heavy Metals in Coal and Its Combustion Residues

Abstract

Coal-fired thermal power plants remain one of the main sources of electricity generation in Turkey. Combustion of coal creates coal ash and slag, which are often stored in landfills located near residential and agricultural fields, increasing the potential for high environmental contamination and health risks. This study investigates the content and enrichment factor (EF) of heavy metals in pulverized lignite coal and its combustion residues from the Kangal lignite coal-fired thermal power plant situated in the Central Anatolian Region of Turkey. The concentration of heavy metals (Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Sr, Zr, Cd, Hg, and Pb) in lignite coal, slag, and fly ash samples were analyzed using an energy dispersive X-ray fluorescence technique. The concentration of Fe is highest while Hg concentration is lowest in the samples. The concentrations of heavy metals are higher in slag and fly ash samples than in lignite coal. Average values of EF (related to Earth’s crust average) revealed that extreme enrichment has been shown by arsenic and mercury in lignite coal and fly ash samples while very high enrichment has been shown in slag samples.

Assessment of the Levels of Potentially Toxic Elements Contained in Natural Bentonites Collected from Quarries in Turkey

“…After the samples were kept in the open air in the laboratory for a while, they were dried in a furnace at 110 °C for 5–10 h to remove moisture . The dry samples were grounded and powdered to make them fit the calibrated powder geometry in the energy-dispersive XRF (EDXRF) spectrometer. , Each powder sample was homogenized with an agate pestle and made ready for elemental analysis …”

“…EDXRF and wavelength-dispersive XRF spectroscopy are used for qualitative and quantitative multi-element analysis of major, minor, and trace elements in archeological, geological, biological, industrial, food, and environmental samples and require minimal sample preparation. ,− The analysis of PTEs in the bentonite samples was performed with the help of the EDXRF spectrometer (Spectro Xepos, Ametek). The EDXRF spectrometer is equipped with an anode X-ray tube (50 W, 60 kV) consisting of a dual thick Pd/Co mixture. ,,,, The EDXRF spectrometer’s target modifier, which optimizes excitation by using polarization and secondary targets, has many different excitation conditions that guarantee the best detection of all elements from Na to U. Analyses are performed in the He gas environment.…”

“…The enrichment factor (EF) is an effective normalization tool widely used to separate PTEs of natural variability from element fractions associated with anthropogenic activities. ,, In this study, the EF to Earth’s crustal average was used to evaluate the degree of PTEs in the bentonite samples. EFs for Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Zr, and Pb in the bentonite samples in all sampling areas were calculated as follows: , EF = false( true C PTE C R e normalf false) Bentonite false( true C PTE C R e normalf false) Earth ′ normals 0.25em crust where C PTE and C Ref are the concentration of PTEs and reference element in the bentonite sample and Earth’s crust, respectively. When the relevant literature is examined, it is seen that elements such as Al, Mn, Fe, Ca, Zr, Sc, Sr, and Ti are used as references based on different reasons in the calculation of the EF. ,− In this study, Sr was used as a reference element due to its low occurrence.…”

“…It uses sophisticated calibration techniques such as “no-standard” calibration, often based on the basic parameters method. Soil-certified reference material (NIST SRM 2709) was used for quality assurance of the EDXRF system. ,,,, Sample containers prepared for each bentonite sample were placed in an automatic sampler, and the analysis procedures were completed by counting for 2 h. The total uncertainty of the analytical procedure is between 2 and 15%. The XRF spectrum of each bentonite sample obtained was evaluated with the help of the software installed in the system.…”

“…4,37,45 In this study, the EF to Earth's crustal average was used to evaluate the degree of PTEs in the bentonite samples. EFs for Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Zr, and Pb in the bentonite samples in all sampling areas were calculated as follows: 34,37 = EF ( )…”