A. James Clark School of Engineering

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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.

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    Characterization of Trace Metal Leaching from Maryland Coal Fly Ashes
    (2011) Ozkok, Enes; Aydilek, Ahmet H; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Three coal fly ashes with different acid-base characteristics and their mixtures with an embankment soil were analyzed for arsenic, copper, and chromium leaching as function of pH using batch-type water leach tests (pH 4-10). Leach tests results showed that significant Cu release occurred only at pH ~4.3 and dissolved Cr concentrations typically increased with increasing pH. Cr(VI) was determined as the predominant oxidation state in leachates and results from WLTs spiked with Cr(VI) suggest that Cr was strongly sorbed below pH 7. Sorption affinity of fly ashes for Cr(VI) seemed to be to correlated to their oxalate-extractable Fe content, which is presumably a surrogate for amorphous iron (hydr)oxide content. Arsenic release typically followed a similar leaching pattern observed for Cr, with the exception of 100% alkaline fly ash; decreased As release above pH 9 for this sample was attributed to precipitation of Ca-As phases due to its high CaO content.
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    Release of inorganic and organic contaminants from fly ash amended permeable reactive barriers
    (2008-01-25) Morar, Doina Lorena; Aydilek, Ahmet H.; Seagren, Eric A.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Large quantities of fly ash are generated in the United States via coal combustion, most of which is disposed of in lagoons or landfills. The overall goal of this research was to assess the feasibility of using high carbon content (HCC) fly ashes as a reactive medium in permeable reactive barriers (PRBs) for remediation of petroleum hydrocarbon contaminated groundwater. A series of column and batch tests were performed to evaluate the leaching of selected metals from the fly ash, and adsorption/desorption of two target hydrocarbons (naphthalene and o-xylene) onto/from this PRB medium. Leaching of metals in the column experiments exhibited a first-flush, followed by a tailing slope elution pattern for all fly ashes. The naphthalene and o-xylene adsorption/desorption on/from the fly ashes were directly correlated with the organic carbon of the fly ash as measured by loss in ignition. Adsorption/desorption hysteresis was obvious in column and batch tests, suggesting that the adsorption/desorption was not completely reversible during the testing.