4 years ago

Characterization of organic components in leachables from Bulgarian lignites by spectroscopy, chromatography and reductive pyrolysis

Lignites from Thrace- and Sofia- coal basins, i.e. “Maritsa-East” and “Stanjanci” mines, were subjected to aqueous sequential extraction at 25°C during 10weeks. Each 7days leachates were separated and pH and conductivity were measured. According to the extraction curves μS vs. time two portions were prepared, enriched in salts, extracts from the first two weeks (“head” of the elution) and in organic matter, extracts from the rest of time (“tail” of the elution curve). Combined freeze-dried extracts were characterized by yields, technical and elemental analyses. They were studied by X-ray photoelectron spectroscopy (XPS) and Infrared spectroscopy (IR). According to XPS spectra the main species on the leachate surfaces were carbon atoms in aromatic and aliphatic structures, 48–53at. % from the total C1s signal. The intensive N 1s signal at 400eV was assigned to pyrroles and amines (1–3at. %). The most abundant sulphur form was inorganic sulphates while intensities for the other ones were <1%. Respectively, the sulphatic sulphur content (13.6%) determined for Maritsa leachate was almost seven times higher than the same sulphur for Stanjanci leachate. FTIR spectra gave evidences for oxygen-containing functional groups, i.e. COOH groups in benzene carboxylic acids and their derivatives, in short-chain aliphatic fatty acids and for polyols. The appearance of mineral matter, mainly gypsum and kaolinite, made equivocal the IR spectra interpretation. Acetone soluble portions of “tail” leachates have represented relatively small parts of the organic matter (340mg/kg Maritsa East and 80mg/kg Stanjianci lignite) but have assigned reliable evidences for the polar constituents of leachates. Linear fatty acids, nC12nC32, nC16 max, n-alcohols, benzoic acids, i.e. hydroxy-, methoxy-, phthalic acids, were highly abundant. Sterols, stanols, ketosterols were present in both extracts. Phthalates were recognizable as well. AP-TPR-TD-GC/MS technique has proved the presence of phenols, PAHs and heteroatom containing components in leachates flue gases. From an environmental viewpoint it seems that the identified compounds do not represent an acute toxic risk. However, N-containing compounds could raise concerns and further attention is needed to be focused on them.

Publisher URL: www.sciencedirect.com/science

DOI: S0166516217305244

You might also like
Discover & Discuss Important Research

Keeping up-to-date with research can feel impossible, with papers being published faster than you'll ever be able to read them. That's where Researcher comes in: we're simplifying discovery and making important discussions happen. With over 19,000 sources, including peer-reviewed journals, preprints, blogs, universities, podcasts and Live events across 10 research areas, you'll never miss what's important to you. It's like social media, but better. Oh, and we should mention - it's free.

  • Download from Google Play
  • Download from App Store
  • Download from AppInChina

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.