Date of Award

12-1-2010

Degree Name

Master of Science

Department

Civil Engineering

First Advisor

Ma, Xingmao

Abstract

The release of carbon-based nanomaterials into the environment is causing great concern among environmental scientists and engineers due to their potential impacts on the fate and transport of environmental contaminants, deriving from their superior adsorption capacities. Chlorinated compounds are one of the most prevalent environmental contaminants in the United States, yet systematic studies concerning the adsorption and desorption mechanisms of chlorinated compounds on carbon nanotubes (CNTs) are scant. The objective of this study was to investigate the adsorption and desorption mechanisms of three chlorinated compounds with different molecular structures on multi-wall carbon nanotubes (MWCNTs) using a wide range of isotherms that were used as models to predict the adsorptive capacity of the MWCNT's. The results indicated that sorption capacities of chlorinated compounds to MWCNTs are greatly affected by the molecular structures and follows an order of 1,1,1-TCA < TCE < 1,3,5-TCB. Hysteresis was observed for all compounds on pristine MWCNTs. After thermal treatment of MWCNTs, sorption capacity of all three compounds was enhanced and sorption hysteresis was considerably reduced. The results highlighted the role of disorderly amorphous carbon in the adsorption and desorption process. We also conducted a study on how nano-texturing of sand surfaces using carbon nanotubes (CNT) can efficiently control the mobility and bioavailability of contaminants found in aquatic sediments. The CNT textured sand can be used as viable in-situ capping (ISC) materials to physically separate contaminated sediments from overlying water. Adsorption measurements of several common contaminants (chlorinated aliphatics) found in aquatic environment performed on CNT textured sand showed at least an order of magnitude increase in their sorption coefficients compared to traditional capping materials such as sand. It was also demonstrated that CNT textured sand can significantly reduce the migration of contaminants from sediments to overlying water and possess suitable geotechnical parameters needed for contaminant sequestration and sediment remediation technologies which can lead to clean and healthy aquatic environment.

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