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Tampa, FL, United States

Wee H.-Y.,Doosan Hydro Technology Inc. | Cunningham J.,University of South Florida
Environmental Progress and Sustainable Energy | Year: 2011

Halogenated hydrophobic organic contaminants (HHOCs), such as chlorinated benzenes and polychlorinated biphenyls, are common soil contaminants. We propose a new method for treating soils contaminated by HHOCs by extracting the contaminants with a solvent, then destroying the contaminants catalytically, enabling the solvent to be reused. Here, we report on the assessment of this technology at the lab scale, operating in a semicontinuous mode where the solvent is recycled in a closed loop. The solvent employed was a mixture of water and ethanol, the catalyst was 1% palladium (Pd) on porous alumina, and hydrogen gas was used as the reductant. We tested the process on two soils: Texas sandy loam contaminated in the laboratory, and Florida sandy clay loam collected from a contaminated field site. The technology worked successfully on the Texas soil: over 90% of the contamination (pentachlorophenol and 1,2,4,5-tetrachlorobenzene) could be extracted and destroyed within 1 week using a solvent flow rate of 0.005 L/(min-kg soil) and a residence time of ∼3.5 min in the catalytic reactor. Seven batches of soil were treated (one week each) without needing to replace the solvent. Catalyst activity decreased over time but was recovered by cleaning the catalyst with a dilute solution of hypochlorite. However, the process was unsuccessful at treating the Florida soil because of rapid catalyst deactivation. We believe that the proposed technology (called remedial extraction and catalytic hydrodehalogenation, or REACH) is a promising "green" technology if we can protect the catalyst from deactivation; possible methods for achieving this are discussed. © 2010 American Institute of Chemical Engineers.

Park S.H.,Energy and Environmental Research Center | Batchelor B.,Texas A&M University | Lee C.,Doosan Hydro Technology Inc. | Han D.S.,Texas A&M University at Qatar | Abdel-Wahab A.,Texas A&M University at Qatar
Journal of Colloid and Interface Science | Year: 2012

In this study, chemical degradation of perchlorate was investigated using partially oxidized titanium ions (Ti(II) and Ti(III)). Results of UV spectra showed that the patterns of absorbance at all ratios of F/Ti(0) were similar each other, except the lowest F/Ti(0) of 0.5 (25mMF -) where mixture of Ti(II) and Ti(III) might be present, resulted in shift of the peak to wavelength of 480nm. The rate of perchlorate degradation was fastest at lowest F/Ti(0) ratio. Among catalysts investigated, only rhenium enhanced the perchlorate degradation in the presence of Ti(II), but no effect of catalysts in Ti(III). In addition, high ionic strength did not enhance the perchlorate-Ti(III) reaction, but high acid concentration did. Addition of solid acid catalysts (SACs) to Ti(III) solution showed slower perchlorate degradation, probably due to decrease in Ti(III) concentration by adsorption onto SAC. Rate constants for perchlorate degradation in Ti(III) were twofold higher than in Ti(II) when 5N HCl used. © 2012 Elsevier Inc.

Lee C.,Doosan Hydro Technology Inc. | Batchelor B.,Texas A&M University | Park S.H.,Korea Institute of Energy Research | Han D.S.,Texas A&M University at Qatar | And 2 more authors.
Journal of Colloid and Interface Science | Year: 2012

The kinetics of perchlorate reduction by zero-valent titanium (ZVT) undergoing electrical pitting corrosion was described by interactions of two domains (pit and solution). Two kinetic models were developed based on two possible inhibition mechanisms. A competitive adsorption model was developed based on surface coverage of perchlorate and chloride on bare ZVT, and a Ti(II) consumption model was developed based on Ti(II) oxidation by electrochemically developed chlorine. Both models well predicted perchlorate concentration changes in the solution. The competitive adsorption model showed that chloride has a higher adsorption affinity on both sites where oxidative dissolution of ZVT occurs and where chloride oxidation occurs. Also, the rates of perchlorate removal and chloride oxidation were directly proportional to current applied. For the Ti(II) consumption model, the rate constant of Ti(II) production was dependent on current. The rate of chloride oxidation is also believed to be proportional to current, but this conclusion cannot be made with confidence. Both kinetic models described changes in perchlorate concentration well. However, the Ti(II) consumption model was limited in its ability to predict chloride concentration. This limitation was probably caused by a lack of available information like electrochemical oxidation of chloride on bare ZVT and Ti(II) oxidation by chlorine. © 2012 Elsevier Inc.

Park S.H.,Korea Institute of Energy Research | Batchelor B.,Texas A&M University | Lee C.,Doosan Hydro Technology Inc. | Han D.S.,Texas A&M University at Qatar | Abdel-Wahab A.,Texas A&M University at Qatar
Journal of Membrane Science | Year: 2012

Perchlorate was reduced without adding high concentrations of acid into the contaminated water using a titanium membrane hybrid (TMH) system. The TMH treatment system was developed and a physicochemical model was built to describe transport and degradation of perchlorate in this system. A critical part of the TMH system is an anion permeable membrane that separates a degradation zone that contains Ti(III) from a contaminated zoned that contains perchlorate. The membrane adsorbs anions such as perchlorate and allows them to be transported to the other zone. Adsorption capacities of three membranes (AMX, ACS, ACM) for perchlorate were evaluated and found to be comparable and their adsorption behaviors followed the Freundlich model well. The ACM membrane showed more rapid transport of perchlorate initially (4. h), but the difference is negligible at later times (1 day). The AMX membrane allowed more hydrogen ions and Ti(III) to diffuse into the contamination zone than did other membranes. The proposed mathematical model predicts the performance and behavior of the TMH system for different physical and chemical conditions. It successfully described adsorption, diffusion and reduction of perchlorate in the system. © 2011 Elsevier B.V.

Park S.H.,Energy and Environmental Research Center | Batchelor B.,Texas A&M University | Lee C.,Doosan Hydro Technology Inc. | Han D.S.,Texas A&M University at Qatar | Abdel-Wahab A.,Texas A&M University at Qatar
Chemical Engineering Journal | Year: 2012

In this work, a new method to rapidly degrade perchlorate using aqueous Ti(II) as the reductant has been developed. To investigate the fundamental chemistry of Ti(II), the basic characteristics of Ti(II) solutions were examined and methods to optimize its production were developed. Then, its ability to reduce perchlorate was evaluated and a kinetic model was proposed to predict the rate of perchlorate reduction. Low pH is needed to produce Ti(II) from Ti(0) and the amounts produced using HCl and H2SO4 increased as the concentration of Ti(0) increased. Kinetic data show that HCl was more effective than H2SO4 in promoting the ability of those solutions to degrade perchlorate, possibly by producing lower pH. Higher concentrations of Ti(0) produced higher concentrations of Ti(II), which resulted in more rapid perchlorate destruction. © 2012 Elsevier B.V.

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