Polycyclic aromatic hydrocarbon (PAH) content of Malkara lignite and its ex-situ underground coal gasification (UCG) char residues

Although underground coal gasification (UCG) is described and introduced as a clean coal technology, side effects of gasification process and its residues should be well examined for protection of surface water and groundwater systems. PAHs are one of the typical organic pollutants rising from UCG process, which are highly mutagenic, carcinogenic and toxic compounds. Due to reported environmental and health hazards of PAHs, PAH content of Malkara lignite and its UCG char residue has been investigated in this study. 16 PAHs listed by the United States Environmental Protection Agency (EPA) and DIN CEN/TS 15439 (Tar Protocol) are the main focus. Three different solvents with different polarity and composition have been used to understand the extraction mechanism in lignite and char samples and research data have been presented based on GC/MS, FT-IR and thermogravimetric analyses of samples. Malkara lignite and its UCG char contain 7.159 mg/kg and 2.758 mg/kg of EPA PAHs, respectively. Besides, lignite is rich with high molecular weight, whereas its char is abundant in low molecular weight PAHs and PAH derivatives according to data evaluation based on Tar Protocol. In addition to GC/MS data, FT-IR and thermogravimetric analyses also provide valuable information on organic content distribution in samples. The presented data in this paper provide PAH and PAH derivative compositions of Malkara lignite (Tekirdağ, Turkey) and its UCG char residue in detail, together with discussions on organic content distributions in samples.