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Effects of temperature and soil components on emissions from pyrolysis of pyrene-contaminated soil [An article from: Journal of Hazardous Materials]
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This digital document is a journal article from Journal of Hazardous Materials, published by Elsevier in . The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.
Description:
Effects of temperature and soil on yields and identities of light gases (H"2, CH"4, C"2H"2, C"2H"4, C"2H"6, CO, and CO"2) and polycyclic aromatic hydrocarbons (PAH) from thermal treatment of a pyrene-contaminated (5wt%) soil in the absence of oxygen were determined for a U.S. EPA synthetic soil matrix prepared to proxy U.S. Superfund soils. Shallow piles (140-170mg) of contaminated soil particles and as controls, neat (non-contaminated) soil (140-160mg), neat pyrene (10-15mg), neat sand (230mg), and pyrene-contaminated sand (160mg), were heated in a ceramic boat inside a 1.65cm i.d. pyrex tube at temperatures from 500 to 1100^oC under an axial flow of helium. Volatile products spent 0.2-0.4s at temperature before cooling. Light gases, PAH and a dichloromethane extract of the residue in the ceramic boat, were analyzed by gas chromatography or high pressure liquid chromatography (HPLC). Over 99% pyrene removal was observed when heating for a few tens of seconds in all investigated cases, i.e., at 500, 650, 750, 1000, and 1100^oC for soil, and 750 and 1000^oC for sand. However, each of these experiments gave significant yields (0.2-16wt% of the initial pyrene) of other PAH, e.g., cyclopenta[cd]pyrene (CPP), which mutates bacterial cells and human cells in vitro. Heating pyrene-polluted soil gave pyrene conversions and yields of acetylene, CPP, and other PAH exceeding those predicted from similar, but separate heating of neat soil and neat pyrene. Up to 750^oC, recovered pyrene, other PAH, and light gases accounted for all or most of the initial pyrene whereas at 1000 and 1100^oC conversion to soot was significant. A kinetic analysis disentangled effects of soil-pyrene interactions and vapor phase pyrolysis of pyrene. Increase of residence time was found to be the main reason for the enhanced conversion of pyrene in the case of the presence of a solid soil or sand matrix. Light gas species released due to the thermal treatment, such as acetylene and methane, lead the formation of other, pyrene-derived PAH, e.g., methylpyrenes, cyclopenta[cd]pyrene, and benzo[a]pyrene. Implications of these findings for the chemistry of soil thermal decontamination and for diagnosing potential defects in soil thermal cleaning, e.g., incomplete elimination of targeted pollutants and formation of adverse by-products, are discussed. aning, e.g., incomplete elimination of targeted pollutants and formation of adverse by-products, are discussed.
Description:
Effects of temperature and soil on yields and identities of light gases (H"2, CH"4, C"2H"2, C"2H"4, C"2H"6, CO, and CO"2) and polycyclic aromatic hydrocarbons (PAH) from thermal treatment of a pyrene-contaminated (5wt%) soil in the absence of oxygen were determined for a U.S. EPA synthetic soil matrix prepared to proxy U.S. Superfund soils. Shallow piles (140-170mg) of contaminated soil particles and as controls, neat (non-contaminated) soil (140-160mg), neat pyrene (10-15mg), neat sand (230mg), and pyrene-contaminated sand (160mg), were heated in a ceramic boat inside a 1.65cm i.d. pyrex tube at temperatures from 500 to 1100^oC under an axial flow of helium. Volatile products spent 0.2-0.4s at temperature before cooling. Light gases, PAH and a dichloromethane extract of the residue in the ceramic boat, were analyzed by gas chromatography or high pressure liquid chromatography (HPLC). Over 99% pyrene removal was observed when heating for a few tens of seconds in all investigated cases, i.e., at 500, 650, 750, 1000, and 1100^oC for soil, and 750 and 1000^oC for sand. However, each of these experiments gave significant yields (0.2-16wt% of the initial pyrene) of other PAH, e.g., cyclopenta[cd]pyrene (CPP), which mutates bacterial cells and human cells in vitro. Heating pyrene-polluted soil gave pyrene conversions and yields of acetylene, CPP, and other PAH exceeding those predicted from similar, but separate heating of neat soil and neat pyrene. Up to 750^oC, recovered pyrene, other PAH, and light gases accounted for all or most of the initial pyrene whereas at 1000 and 1100^oC conversion to soot was significant. A kinetic analysis disentangled effects of soil-pyrene interactions and vapor phase pyrolysis of pyrene. Increase of residence time was found to be the main reason for the enhanced conversion of pyrene in the case of the presence of a solid soil or sand matrix. Light gas species released due to the thermal treatment, such as acetylene and methane, lead the formation of other, pyrene-derived PAH, e.g., methylpyrenes, cyclopenta[cd]pyrene, and benzo[a]pyrene. Implications of these findings for the chemistry of soil thermal decontamination and for diagnosing potential defects in soil thermal cleaning, e.g., incomplete elimination of targeted pollutants and formation of adverse by-products, are discussed. aning, e.g., incomplete elimination of targeted pollutants and formation of adverse by-products, are discussed.
