Soil Remediation Using Solvent Extraction with Hydrodehalogenation and Hydrogenation in a Semicontinuous System.

摘要

The objective of this thesis is to aid in the development of Remedial Extraction And Catalytic Hydrodehalogenation (REACH), a green remediation technology used to remove and destroy halogenated hydrophobic organic compounds from soil. REACH has no secondary waste streams, uses an environmentally benign solvent, and aims to catalytically destroy rather than transfer the organic contaminants into a different phase. In this thesis, a bench-top semicontinuous model of the proposed remediation technology was constructed and used to extract the model contaminant, 1,2,4,5-tetrachlorobenzene, from soil and to convert it to an acceptable end product, cyclohexane. Palladium was used as a catalyst for hydrodehalogenation, which converted the tetrachlorobenzene to benzene. Rhodium was used to catalyze the hydrogenation of benzene to cyclohexane.;A novel method, ultraviolet solvent treatment, was proposed to mitigate catalyst deactivation that occurs because of extracted chemicals contained in the contaminated soil. The goal of this treatment is to degrade organic matter that is suspected of causing catalyst deactivation.;The REACH process was found to successfully extract TeCB from the soil, but only partial conversion from TeCB to cyclohexane occurred. Catalyst deactivation was the suspected cause of the low amount of conversion observed. Hydrogen limitation was also tested as a cause of limited conversion, but was not found to be a contributor. Ultraviolet solvent treatment was tested as a means of mitigating catalyst deactivation. However, the treatment was not effective in making a profound difference in stopping the catalyst from deactivating.;The experiments conducted in this research show that REACH has the potential to become a viable technology for cleaning soil contaminated with halogenated organic compounds. However, future research needs to be done to greatly reduce the severity of catalyst deactivation and to determine with which other halogenated organic compounds the technology works well.