Gaseous mercury released from aerated concrete during both presteam curing at 25 degrees C and steam curing at 80 degrees C was measured in controlled laboratory experiments. Mercury release originated from two major components in the concrete mixture: (1) class F coal fly ash and (2) a mixture of the fly ash and powdered activated carbon onto which elemental mercury was adsorbed. Mercury emitted during each curing cycle was collected on iodated carbon traps in a purge-and-trap arrangement and subsequently measured by cold-vapor atomic fluorescence spectrometry. Through 3 h of presteam curing, the release of mercury from the freshly prepared mixture was less than 0.03 ng/kg of concrete. Releases of total mercury over the 21 h steam curing process ranged from 0.4 to 5.8 ng of mercury/kg of concrete and depended upon mercury concentrations in the concrete. The steam-cured concrete had a higher mercury release rate (ng kg(-1) h(-1)) compared to air-cured concrete containing fly ash, but the shorter curing interval resulted in less total release of mercury from the steam-cured concrete. The mercury flux from exposed concrete surfaces to mercury-free air ranged from 0.77 to 11.1 ng m(-2) h(-1), which was similar to mercury fluxes for natural soils to ambient air of 4.2 ng m(-2) h(-1) reported by others. Less than 0.022% of the total quantity of mercury present from all mercury sources in the concrete was released during the curing process, and therefore, nearly all of the mercury was retained in the concrete.

Two novel sorbents (i.e. “regenerated sorbent” and “supersorbent”) for dry flue gas desulfurization were tested, and by-products characterized, using a pilot-scale version of the Ohio State Carbonation and Ash Reactivation (OSCAR) process. The main elements of the process consisted of sorbent production, a riser reactor, cyclone and baghouse. Trace elements, including As, Se and Hg, were found at higher levels in the OSCAR solid by-products (in both the cyclone and baghouse) compared to traditional lime spray dryer (LSD) ash. Polycyclic aromatic hydrocarbons (PAHs) detected on solid by-products were primarily small molecular weight compounds at low concentration (e.g., μg/kg). Small particulates (⩽3μm) that escaped from the cyclone and were captured by the baghouse showed higher trace element concentrations, possibly due to the lower operating temperature and greater specific surface area of solids in the baghouse. Operating conditions including flue gas flow rate and sorbent injection rate influenced the levels of trace elements and PAHs in OSCAR by-product material. Capture of PAHs was observed to increase with Ca concentration in experiments using supersorbent injection. However, possible release of PAHs occurred with regenerated sorbent injection. The concentrations of trace elements in leachate for all OSCAR cyclone samples tested were below Resource Conservation and Recovery Act limits. The concentrations of most trace elements in OSCAR by-product were also below the limits regulated in the EPA 503 Rule except As and Se. The similarity in the physical and engineering properties of OSCAR cyclone samples to natural cohesive soils suggests that this material can be utilized in a variety of construction, reclamation, and agricultural applications.

To evaluate possible mercury emissions during steam curing of cellular concretes containing fly ash and mercury-loaded PAC, we collected and measured gaseous mercury released during curing for concretes that contained different quantities of fly ash and mercury-loaded PAC (HgPAC). All experiments were conducted in a laboratory and were configured to enable estimation of an upper limit on the potential gaseous mercury release from steam-curing concretes that contain fly ash and mercury sorbent material. The observed emissions of mercury for the complete curing process generally increased with rising mercury concentrations in the concrete, where fly ash and fly ash– HgPAC by-products were the principal sources of mercury. However, release of mercury from concretes that contain these byproducts was less than 0.022% of the total quantity of mercury present in the concrete from all sources. Therefore, the steamcuring of cellular concrete containing fly ash and mercury-laden PAC does not result in a significant release of the mercury captured following coal combustion.

The partitioning of As and Hg in various components of lime spray dryer (LSD) ash samples from a coal-fired boiler was characterized to better understand the form and fate of these elements in flue gas desulfurization byproducts. LSD ash samples, collected from the McCracken Power Plant on the Ohio State University campus, were separated by a 140-mesh (106 mu m) sieve into two fractions: a fly-ash-/unburned-carbon-enriched fraction (> 106 mu m) and a calcium-enriched fraction (< 106 mu m). Unburned carbon and fly ash in the material > 106 Am were subsequently separated by density using a lithium heteropolytungstate solution. The concentrations of As and Hg were significant in all fractions. The level of As was consistently greater in the calcium-enriched fraction, while Hg was evenly distributed in all components of LSD ash. Specific surface area was an important factor controlling the distribution of Hg in the different components of LSD ash, but not for As. Comparing the LSD ash data to samples collected from the economizer suggests that As was effectively captured by fly ash at 600 degrees C, while Hg was not. Leaching tests demonstrated that As and Hg were more stable in the calcium-enriched fraction than in the fly-ash- or carbon-enriched fractions, potentially because of the greater pH of the leachate and subsequently greater stability of small amounts of calcium solids containing trace elements in these fractions.

Ultrasonic extraction is a common method used to extract semi-volatile and nonvolatile organic compounds such as polycyclic aromatic hydrocarbons (PAHs) from solid matrices. However, ultrasonic energy has been suspected to lead to undesired reactions of the solute and thus affect qualitative and quantitative results. In this paper, sonolytic reactions of phenanthrene in common organic extraction solutions were examined using a 20kHz ultrasonic probe under conditions commonly used for ultrasonic extraction. Extraction parameters including phenanthrene concentration, solvent type, pulse length, and sonication time were investigated. Hexane:acetone (1:1 V/V) resulted in less phenanthrene degradation than dichloromethane (DCM):acetone (1:1 V/V). Initial solute concentration, length of sonication time, and solvent type affected the degradation of phenanthrene. Reaction byproducts including methylphenanthrene and methylnaphthalene detected after sonication indicate that phenanthrene reacts by both direct pyrolysis and reaction with methyl or ethyl radicals formed from solvent pyrolysis.

Ohio state carbonation and ash reactivation (OSCAR) process was installed as a slip-stream at the McCracken Power Plant located on the Ohio State University main campus to test the efficiency of a new dry FGD system to remove SO2. In this study, the chemical composition including heavy metals and polycyclic aromatic hydrocarbons (PAHs), leaching characteristics, and physical and engineering properties of solid by-product samples collected during the testing of the OSCAR process were examined to assess potential re-use opportunities for this material. Generally, trace element (i.e., arsenic, selenium, and mercury) concentrations were detected in mg/kg level. Measurement results for polycyclic aromatic hydrocarbons (PAHs) on selected cyclone and baghouse samples showed low concentrations (e.g. µg/kg). From the results, trace element concentrations in OSCAR samples were enriched compared to LSD ash. However leachate results indicated that ashes collected from the cyclone were not hazardous material. Arsenic concentration in cyclone ash was as much as 95 mg/kg, which is above the limit at 75 mg/kg for land application (EPA 503 Rule). For baghouse ash, arsenic and selenium concentrations were above the land application limits especially arsenic which was as high as 673 mg/kg. Bulk chemical and engineering properties indicated that OSCAR ash can be utilized in construction, agricultural and other civil engineering applications.

Current research is investigating the feasibility of utilizing lime spray dryer by- product in different engineering applications. However, concerns about the release of trace elements, in particular Hg, As and Se, from lime spray dryer by- product potentially limit re-use applications. In this study, lime spray dryer samples as well as feed coal and lime were collected from the McCracken Power Plant located on the Ohio State University main campus. Concentrations and leaching properties of Hg, As and Se were monitored over two years and compared to a previous study performed in 1991-1992. Distributions of Hg, As and Se in unburned carbon (>140 mesh, <1.87 g/cm3), fly ash-rich (>140 mesh, >1.87 g/cm3), and calcium-rich (<140 mesh) fractions were also investigated. Results indicated that the levels of Hg, As and Se in lime spray dryer by-product were constant within a factor of two; and the leaching properties were constant within an order of magnitude over the 11-year time period of the study. Fractionation of the lime spray dryer by-product indicated that the As concentration was highest in the calcium-rich fraction, accounting for 94% of the total As. The Se concentration was highest in the unburned carbon fraction, accounting for 32% of total Se. More Se (42%) on a mass basis, however, was found in calcium-rich fraction due to greater mass fraction of residual lime. The concentration of Hg was found to be similar in both unburned carbon and calcium-rich fractions; however, approximately 78% of the Hg mass was present in the calcium-rich fraction.