Induced Sequestration of Phenolic Compounds in Natural SorbentsEPA Grant Number: U915351
Title: Induced Sequestration of Phenolic Compounds in Natural Sorbents
Investigators: Keinath, Thomas Michael
Institution: University of Michigan
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 1998 through August 1, 2001
Project Amount: $100,692
RFA: STAR Graduate Fellowships (1998) RFA Text | Recipients Lists
Research Category: Fellowship - Environmental Engineering , Engineering and Environmental Chemistry , Academic Fellowships
The objective of this research project is to evaluate the effects of enzyme- and metal oxide-induced coupling reactions of phenolic compounds on sorption/desorption/ sequestration behavior in natural geosorbents. This research project aims to evaluate the feasibility of artificially inducing coupling reactions in the subsurface, and immobilizing phenolics on the soil organic matter.
To quantify the effects of the coupling reactions in natural systems, an experimental matrix of three target 14C-labeled phenolics—phenol, o-cresol, and p-chlorophenol—and five natural sorbents with varying organic carbon content and degrees of diagenetic alteration was established. To determine the fraction of the target compound that is nonextractable, nonequilibrium flow-through column systems with both catalyst-amended and nonamended sorbents have been constructed. With the manganese oxide (birnessite) amendment, the catalyst is placed in a reactive barrier configuration at the entrance of the column. Immobilization of the enzyme (horseradish peroxidase) on porous agarose beads and the subsequent efficacy of this reactor configuration will be investigated to ensure that enzyme additions can be used in the same reactive barrier configuration. These column studies involve four phases of operations—adsorption to exhaustion, aqueous desorption, methanol extraction, and combustion of residual. An analysis of the effluent profiles yields the fraction of phenolic that is not methanol extractable. A comparison between catalyst-amended and nonamended sorbent profiles gives an indication of the efficacy of artificially inducing this nonextractable fraction. It is important to determine, however, what actually is being measured in the nonextractable fraction, and whether this fraction can be considered sequestered. Instead of forming covalent linkages to the soil matrix, coupling reactions can form phenolic polymers that either sorb more favorably or are large enough to precipitate out of solution, although solvent extraction should remove precipitated polymers. The characterization of polymers under experimental conditions will aid in the understanding of coupling in natural sorbents. In addition, for practical application, the efficacy of the catalyst in a flow-through system will be determined.