Mineral oils and coal tars are complex nonaqueous phase liquids (NAPLs), which can serve as long-term sources of ground water contamination. Very limited data are available on mineral oil and coal tar entrapment in and removal from porous media. Thus, the objectives of this research were to evaluate the behavior of these NAPLs in porous media, and investigate the mechanisms governing NAPL entrapment in and recovery from porous media. Quantification of properties of three commercial mineral oils and six MGP coal tars reveals that mineral oils are slightly viscous LNAPLs (density: ~0.88 g/cm3; viscosity: 10-20 cP), whereas coal tars are highly viscous DNAPLs (density: 1.052-1.104 g/cm3; viscosity: 32-425 cP). Measured oil (tar)-water interfacial tensions (IFT) were lower than that of pure NAPLs. Properties of 16 field soil samples (soil particle size distribution, specific surface area, total carbon content, cationic exchange capacity and soil moisture release curves) were characterized. Correlations between residual NAPL saturation and NAPL and soil properties were developed, and show that the entrapment of NAPL dependent upon soil particle size distribution, total carbon content, NAPL viscosity and NAPL-water IFT. Aqueous pH and ionic strength were found to influence the interfacial properties in tar-water-silica systems. At pHs greater than 7.0, observed reduction in contact angle were attributed to the repulsive electrostatic force between coal tar and solid surface. When pH less than 4, hydration forces played a role on the contact angle decrease. The IFT reduction was resulted from the accumulation of surface-active molecules at the tar-water interface. The effect of ionic strength on interfacial properties was not significant below 0.5 M. The effects of temperature and surfactant or surfactant/polymer addition on coal tar removal was investigated by conducting coal tar displacement experiments at three different temperatures (22, 35, and 50??with sequential flushing of water, surfactant and surfactant/polymer. Coal tar removal from porous media was enhanced by elevating temperature and surfactant flushing due to the viscosity and IFT reduction, respectively. Xanthan gum was used as the polymer to increase the viscosity of the displacing fluid. In summary, these results provide tools for the prediction of NAPL entrapment in porous media, and for the selection of remediation strategies for coal tar contaminated source zone.

The possible benefits of thermal remediation of NAPL-contaminated subsurface were analyzed at pore-scale. Force balance analysis was performed to provide the insight and information on the critical conditions for the blob mobilization. First, the critical blob radius for blob mobilization was calculated in terms of blob radius, temperature, and water velocity. Temperature increase enhanced the blob mobilization along with the decrease of interfacial tension. Water velocity increase also enhanced the blob mobilization. Critical water velocity provided the critical condition for the initiation of blob mobilization to distinguish singlet and doublet in blob size. Second, the terminal (or steady state) blob velocity at the steady state blob motion was determined. Increases of temperature and water velocity raised the terminal blob velocity. When the observation of blob mobilization moved from REV scale (macroscale) to pore-scale, terminal blob velocity showed the different phenomena according to the change of oil saturation. At macro-scale, the terminal blob velocity was smaller than water velocity by an order or two. However, the terminal blob velocity reached to water velocity at pore-scale. This investigation would provide the better understanding on the pore-scale analysis of residual NAPL blob mobilization by thermal remediation. Additionally, the pore-scale analysis developed in this study would be incorporated into a general conservation equation in terms of the accumulation of multiple blobs. It would derive continuumaveraged equations that accurately represent pore-level physics. In conclusion, the study on the critical conditions for the initiation of blob mobilization as a single discrete blob would have some contribution to the transport and fate of NAPL contaminant and the desired subsurface remediation.

Abstract A novel process of combining electrokinetic remediation and nano-sized iron wall was used for studying its effectiveness of treating nitrate-containing soil. Nitrates and nitrites are commonly found in surface water and groundwater. These substances, in general, could pose a threat to both organisms in the water bodies and human health. Traditionally, nitrogen oxides in various water bodies are treated by biological denitrification processes. However, it would take a longer time to yield a satisfactory result as compared with physicochemical processes. In recent years, permeable reactive barriers (PRBs) using zero-valent iron have been successfully used for degradation of various compounds including nitrates. Electrokinetic processing (EK) also is considered as an effective in-situ technology for removing both inorganic and organic substances from the treatment zone. In this work, the synthesized nano-scale iron particles were incorporated into a PRB, which was further combined with EK to form a novel process for the degradation of nitrates. Various operating parameters were studied in this work. The nano-sized iron particles were determined to be ranging from 50-80nm in size and having specific surface area of 37.83m2. The isoelctric point of these nanoparticles was found to be at pH 7.3. Experimental results have shown that the best location of the iron wall was 5cm from the anode reservoir. Also, the optimal treatment time would be six days in this study. The treatment efficiency was found to increase with increasing dose of nano-sized iron particles in the PRB. Operating with the polarity reverse would slightly increase the overall treatment efficiency as compared with the case of no polarity reverse (92.38% versus 88.34%). An electric gradient of 1.5V/cm was determined to be the optimal electric field strength in this study. In this work, it was also found that 2.5g nano-scale iron particles outperformed 20g micro-scale iron particles (75-150µm) in terms of nitrate degradation. In a study of using an extended treatment time up to 20 days, the black colored iron wall would fade away becoming a rusty plume toward the cathode as the treatment time elapsed. Furthermore, the Fe2+ concentration was elevated throughout the soil column after the 20-day treatment. Therefore, it is evident that nano-sized iron particles would migrate when they are subjected to EK. Based on the research findings obtained, the novel process employed in this study was found to be an effective one for in-situ treatment of nitrate-containing soil.

The objective of this research was to evaluate the treatment efficiency of a trichloroethylene (TCE) contaminated soil by combined technologies of the suspension of palladized nanoiron and electrokinetic remediation process. First, nanoiron and palladized nanoiron were prepared using the chemical reduction method. Then they were characterized by various methods. Micrographs of scanning electron microscopy have shown that a majority of these nanoparticles were in the range of 50-80 nm. Specific surface areas were determined to be 76.88 m2/g and 100.61 m2/g for the former and latter, respectively. Results of X-ray diffractometry have shown that both types of nanoiron were poor in crystallinity. Three anionic dispersants were employed for evaluating their performance in stabilizing various nanoiron. Results have demonstrated that an addition of 1 wt% of Dispersant E during nanoiron preparation would result in a good stabilization of nanoiron. If the system pH was adjusted to 2.99, nanoparticles would settle rapidly. Batch tests were carried out to investigate the effects of various operating parameters on degradation of TCE in aqueous solutions. Experimental results have indicated that palladized nanoiron outperformed nanoiron in treatment of TCE in this study. The employment of Dispersant E would enhance the treatment efficiency further. Test results also showed that a linear increase of reaction rate constant was found with an increasing dose of palladium from 0.05 wt% to 1 wt% based on the mass of nanoiron. Further, an exponential increase of reaction rate constant would be obtained with an increasing pH. As for mixing intensity, it was found to be insignificant to the treatment efficiency of TCE in aqueous solutions. The final stage of this study was to evaluate the treatment efficiency of combined technologies of the suspension of palladized nanoiron and electrokinetic remediation process in treating a TCE-contaminated soil. Test conditions used were given as follows: (1) initial TCE concentration: 160-181 mg/kg; (2) electric potential gradient: 1 V/cm; (3) daily addition of 20 mL of suspension of palladized nanoiron (2.5 g/L) to the electrode reservoir; and (4) reaction time: 6 days. Test results have shown that addition of palladized iron suspension to the cathode reservoir yielded the lowest residual TCE concentration in soil. Namely, about 92.5% removal of TCE from soil. On the other hand, addition of palladized iron suspension to the anode reservoir would enhance the degradation of TCE therein. Based on the above findings, the treatment method employed in this work was proven to be a novel and efficient one in treating TCE-contaminated soil.

Thesis (Ph. D.)--Florida State University, 2004. / Advisor: Dr. Andrew Dzurik, Florida State University, College of Engineering, Dept. of Civil and Environmental Engineering. Title and description from dissertation home page (June 18, 2004). Includes bibliographical references.

Thesis (M.S.)--University of Tennessee, Knoxville, 2003. / Title from title page screen (viewed Mar. 25,2004). Thesis advisor: Daniel B. Koch. Document formatted into pages (viii, 113 p. : ill.). Vita. Includes bibliographical references (p. 58-61).

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 292-310). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph.D)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2010. / Committee Chair: Taillefert, Martial; Committee Member: DiChristina, Thomas; Committee Member: Sobecky, Patricia; Committee Member: Van Cappellen, Philippe; Committee Member: Webb, Samuel. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Halogenated hydrophobic organic compounds (HHOCs) such as 1,2,4,5-tetrachlorobenzene (TeCB) present a threat to both human health and the environment. The common occurrence and recalcitrant nature of HHOCs as soil contaminants necessitate an effective soil remediation method. Wee and Cunningham (2008, 2011, 2013) proposed a clean-up technology called Remedial Extraction and Catalytic Hydrodehalogenation (REACH), which pairs solvent extraction of HHOC contaminants from soil with catalytic hydrodehalogenation to destroy contaminants. Wee and Cunningham (2008, 2011, 2013) utilized a palladium (Pd) catalyst to hydrodehalogenate TeCB to benzene. However, benzene is still a toxic contaminant. Prior research has demonstrated that Pd-catalyzed hydrodehalogenation (HDH) can be paired with Rh-catalyzed hydrogenation to transform TeCB to cyclohexane, which is a less toxic end product (Osborn 2011; Ticknor 2012). However, there remains a need to quantify the effects of different operating conditions on the catalytic reaction rates upon which the technology relies. It was hypothesized that (1) an increased ratio of water to ethanol in water/ethanol solvents would increase the reaction rates of both Pd-catalyzed HDH and Rh-catalyzed hydrogenation, and (2) catalytic reaction rates would be constant above a hydrogen pressure threshold, but would decrease with decreasing hydrogen pressure beneath the threshold. Thus, the objective of this thesis was to contribute to the development of optimal operating parameters for the REACH technology by quantifying the effects of solvent composition and hydrogen pressure on the catalytic conversion of TeCB to cyclohexane in water/ethanol solvents in a batch reactor. Complete conversion of TeCB to cyclohexane was achieved at all experimental conditions tested. The data were consistent with an apparent first-order kinetics model where Pd-catalyzed HDH and Rh-catalyzed hydrogenation occur in series. The effects of three water/ethanol solvent compositions (33:67, 50:50, 67:33) were investigated at 50 psi hydrogen pressure. HDH rate coefficients increased monotonically with an increasing fraction of water in the solvent. When the water fraction in the solvent was increased from 50% to 67%, a larger HDH rate coefficient increase was observed than when the water fraction was increased from 33% to 50%. In both cases, the observed increases were statistically significant at a 95% confidence level. For hydrogenation, rate coefficients at 33% and 50% water were approximately equal. The hydrogenation rate coefficient at 67% water was much greater than the rate coefficients at 50% and 33% water, but the increase was not statistically significant at a 95% confidence level. The observed time for complete conversion of TeCB to cyclohexane decreased with an increasing fraction of water in the solvent, from 12-18 hours with a 33% water solvent to 8-12 hours with a 50% water solvent, and to 1-1.5 hours with a 67% water solvent. The effects of three hydrogen pressures (50 psi, 30 psi, 10 psi) were investigated with a 50:50 water/ethanol solvent. HDH rate coefficients increased monotonically with decreasing hydrogen pressure, though the trend was not statistically significant at a 95% confidence level until the pressure was decreased from 30 psi to 10 psi. This trend can be attributed to the displacement of TeCB by hydrogen on the catalyst surface at higher hydrogen pressures. For hydrogenation, the data suggest that rate coefficients are independent of hydrogen pressure in the pressure range of 10-50 psi, since no statistically significant hydrogen pressure effect was observed. Complete conversion of TeCB to cyclohexane was achieved at hydrogen pressures as low as 5 psi. These findings suggest that a greater fraction of water in the solvent should be utilized in the REACH system when feasible to maximize catalytic reaction rates. These findings also suggest that the REACH system could be operated at hydrogen pressures as low as 5 psi, which would further improve the safety of the technology.

This research identifies the well components, operation factors, and the soil and hydrogeological parameters that influence the recovery of Light-Non-Aqueous-Phase-Liquids (LNAPL) in an heterogeneous environment using pumping wells. The purpose of this research is to improve the analysis of sites contaminated by LNAPLs to efficiently recover the feasible amounts of LNAPL in the sites. The focus is on heterogeneous soil environments. The model adapted to analyze the recovery of LNAPL from the contaminated sites was improved to account for a high degree of vertical heterogeneity, including the vertical variation of one or several of the soil properties within the same layer. This research also studies the optimization of the recovery of LNAPL for the system of wells both at the level of one well and a system of wells. The developed model and method are applied to a real site. Thus, the model’s ability to estimate the performance of a system of recovery wells is evaluated using real soil data and performance measurements. This research constitutes a robust background regarding the design, operation, analysis, and optimization of a system of recovery wells in a heterogeneous soil environment. / text