STP720: Determination of Polynuclear Aromatic Hydrocarbons in Wastewater from Coal Liquefaction Processes by the Gas Chromatography-Ultraviolet Spectrometry Technique

    Robbins, WK
    Staff chemist and research associate, Exxon Research and Engineering Co., Linden, N.J.

    Searl, TD
    Staff chemist and research associate, Exxon Research and Engineering Co., Linden, N.J.

    Wasserstrom, DH
    Staff engineer and project engineer, Exxon Research and Engineering Co., Florham Park, N.J.

    Boyer, GT
    Staff engineer and project engineer, Exxon Research and Engineering Co., Florham Park, N.J.

    Pages: 18    Published: Jan 1980


    Abstract

    One of the classes of compounds that may be present in wastewater from coal conversion plants is polynuclear aromatic hydrocarbons (PAH). Since 13 PAHs containing from three to six condensed rings are on the U.S. Environmental Protection Agency (EPA) list of priority pollutants, an analytical method has been developed for the determination of PAHs in process waters from coal liquefaction processes. This method utilizes the well-established gas chromatography-ultraviolet spectrometry (GC-UV) technique to determine the 13 at the 0.1 ppb (micrograms per litre) level and higher. Isomers and twelve additional PAHs are routinely measured, and the technique may be extended as necessary to cover other compounds as well.

    In the method, each wastewater sample is spiked with [14C]phenanthrene, [14C]benz[a]anthracene, and [14C]benzo[a]pyrene prior to extraction with methylene chloride. The methylene chloride phase is then washed with aqueous acid and base to remove phenols, organic acids, and basic nitrogen compounds. The methylene chloride neutrals are then solvent exchanged into cyclohexane, and the cyclohexane phase is extracted with N-methylpyrrolidone (NMP). A PAH-rich fraction suitable for GC-UV measurement is obtained by dilution of the NMP with water and back extraction into isooctane. In the GC-UV measurement step, the PAHs are separated by gas chromatography and the component fractions trapped. After dissolution of the PAHs from the traps, ultraviolet absorption measurements are made for the individual PAHs. Peaks containing the carbon-14 internal standards are assayed for radioactivity, and the ratio of the final to the initial radioactivity is used to quantitate the data.

    With this technique, the effect of the coal type and the reaction conditions can be determined. Polynuclear aromatic hydrocarbon analyses of several raw wastewaters obtained from coal liquefaction pilot plants are presented and discussed.

    Keywords:

    polynuclear aromatic hydrocarbons (PAHs), wastewater, coal liquid, analysis, water, alternative fuels, aquatic toxicology


    Paper ID: STP27549S

    Committee/Subcommittee: D19.04

    DOI: 10.1520/STP27549S


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