Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

Browse

Filters

2011 - 20152

Settings

Author: search.filters.author.Ozkok, EnesSubject: search.filters.subject.Environmental engineering

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Mitigation of High Alkalinity in Leachates of Aged Steel Slag
    (2015) Ozkok, Enes; Davis, Allen P; Aydilek, Ahmet H; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Steel slag, an abundant by-product of the steel-making industry, after it is aged, has a huge potential for use as an aggregate in road construction. However, the high pH of steel slag seepage (pH≥12) is a major impediment in its beneficial use. Analyses on aged steel slag samples demonstrated that the alkalinity producing capacity of aged steel slag samples strongly correlated to Ca(OH)2 dissolution and that prolonged aging periods have marginal effects on overall alkalinity. Treatment methods that included bitumen-coating, bathing in Al(III) solutions and addition of an alum-based drinking water treatment residual (WTR) were evaluated based on reduction in pH levels and leachate alkalinity. 10% (wt./wt.) alum-based drinking water treatment residual (WTR) addition to slag was determined to be the most successful mitigation method, providing 65−70% reduction in alkalinity both in batch-type and column leach tests, but final leachate pH was only 0.5−1 units lower and leachates were contaminated by dissolved Al(+III) (≥3−4 mM). Based on the interpretation of calculated saturation indices and SEM and EDX analyses, formation of calcium sulfoaluminate phases (i.e., ettringite and monosulfate) was suggested as the mechanism behind alkalinity mitigation upon WTR-modification. The residual alkalinity in WTR-amended slag leachates was able to be completely eliminated utilizing a biosolids compost with high base neutralization capacity. In column leach tests, effluent pH levels below 7 were maintained for 58−74 pore volumes worth of WTR-amended slag leachate using 0.13 kg compost (dry wt.) per 1 kg WTR-amended slag on average; also, dissolved Al(+III) was strongly retained on the compost.
  • Thumbnail Image
    Item
    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.