The exponential increase in fossil energy production from Devonian-age shale in the Northeastern United States has highlighted the management challenges for produced waters from hydraulically fractured wells. Confounding these challenges is a scant availability of critical water quality parameters for this wastewater. Chemical analyses of 160 flowback and produced water samples collected from hydraulically fractured Marcellus Shale gas wells in Pennsylvania were correlated with spatial and temporal information to reveal underlying trends. Chloride was used as a reference for the comparison as its concentration varies with time of contact with the shale. Most major cations (i.e., Ca, Mg, Sr) were well-correlated with chloride concentration while barium exhibited strong influence of geographic location (i.e., higher levels in the northeast than in southwest). Comparisons against brines from adjacent formations provide insight into the origin of salinity in produced waters from Marcellus Shale. Major cations exhibited variations that cannot be explained by simple dilution of existing formation brine with the fracturing fluid, especially during the early flowback water production when the composition of the fracturing fluid and solid-liquid interactions influence the quality of the produced water. Water quality analysis in this study may help guide water management strategies for development of unconventional gas resources.

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Novel sulfur-impregnated activated carbons for vapor phase mercury uptake (BPL-S series) were designed and developed in this study. Temperature and the initial sulfur to carbon ratio (SCR) during impregnation were the two control parameters for the impregnation procedure. By adjusting these two variables, a series of sulfurimpregnated carbons was created. These new materials together with commercially available sulfur-impregnated activated carbon (HGR) and coal samples were evaluated for the uptake of vapor phase elemental mercury using nitrogen as a carrier gas. The results showed that carbons impregnated with sulfur at high temperature exhibited the highest efficiency for mercury removal. As the impregnation temperature decreased, the performance of the carbons deteriorated. When SCR was varied from 4:1 to 1:2, the sulfur content decreased only slightly, which resulted in a small decrease in mercury uptake capacity. Therefore, the impregnation temperature is the most important factor influencing the efficiency of these sorbents for mercury uptake. Because the impregnation temperature dictates the predominant form of sulfur allotropes, it can be concluded that the actual form of sulfur rather than the total sulfur content is a crucial parameter governing the chemisorption process. Stronger bonding between sulfur and carbon surface was found for carbons impregnated at higher temperatures. This prevents sulfur from agglomerating and clogging the carbon pores during column runs at elevated temperatures. Large surface areas and large fractions of mesopores in these new sorbents also contributed to excellent mercury removal efficiencies.

Previously reported results by the authors revealed that the presence of molecular oxygen (oxic conditions) in the test environment can, in some instances, cause up to a 3-fold increase in the adsorptive capacity of granular activated carbon (GAC) for phenolic compounds. It was discovered that these compounds undergo oxidative coupling on the carbon surface under oxic conditions. The polymers formed as a result of these chemical reactions are very difficult to desorb from the surface of GAC. This led to significant irreversible adsorption in the presence of molecular oxygen. On the other hand, when the same compounds are adsorbed on the carbon surface under anoxic conditions, essentially all of the adsorbate can be recovered from the carbon surface by solvent extraction. The ionized species of phenolic compounds showed even higher susceptibility toward polymerization on the surface of GAC than the parent neutral molecules. GAC particle size did not influence the extent of polymerization. Oxygen uptake measurements revealed significant consumption of molecular oxygen during the adsorption of phenolic compounds. The amount of molecular oxygen consumed in these experiments was found to be linearly proportional to the amount of irreversibly adsorbed compound.

Parameters affecting the adsorptive capacity of granular activated carbon (GAC) for o-cresol, phenol, o-chlorophenol, 3-ethylphenol, trichloroethylene, and natural organic matter are investigated in this study. Experimental results prove that the presence of molecular oxygen significantly increases the adsorptive capacity of GAC for five of these six compounds. The oxic GAC adsorptive capacity for o-cresol, for example, can be up to 2.6-fold the capacity that is attainable under anoxic conditions. Experimental data also prove that there was no biological degradation of these compounds in the presence of oxygen; consequently, biological activity was not responsible for the increased adsorbate removal from the liquid phase. Presumably, the increase in the adsorptive capacity under oxic conditions is due to some polymerization of adsorbate on the surface of the carbon. Naturally occurring organic matter was also adsorbed to a greater extent when molecular oxygen was present in the test environment. However, the adsorptive capacity of GAC for aliphatic organic compounds, such as trichloroethylene, is not significantly influenced by the presence of molecular oxygen.