Date of Award

8-2014

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Environmental Engineering

Advisor

Karanfil, Tanju

Committee Member

Lee , Cindy

Committee Member

Ladner , David

Abstract

Graphene nanomaterials are two-dimensional single layer sp2 hybridized carbon atoms densely packed in a hexagonal honeycomb lattice and can be visualized as basic building blocks for fullerenes, carbon nanotubes (CNTs), and graphite. In addition, they are hydrophobic nanomaterials and possess a large specific surface area (SSA), thus they have been evaluated as promising adsorbents to remove synthetic organic compounds (SOCs) from water. As with granular activated carbons (GACs) and CNTs, adsorption behavior of SOCs on graphene depends on the physicochemical properties of the adsorbents (e.g., specific surface area, pore size distribution and surface chemistry), SOCs (e.g., hydrophobicity, molecular size and substituent groups), and the condition of background solutions (e.g., pH, ionic strength and presence of NOM). Thus, simultaneously, multiple factors, which have varying relative contributions, can affect overall adsorption of SOCs on graphenes. Therefore, in this study, the overall goal was to investigate the roles of selected factors in the adsorption of aliphatic SOCs on graphenes and compare the adsorption behavior of graphenes with those of single-walled carbon nanotube (SWCNT) and granular activated carbon (HD3000). The study had three sub-objectives. First of all, the effect of selected carbonaceous adsorbents properties (i.e., specific surface area, pore size distribution and oxygen-containing functional groups) on the adsorption of aliphatic SOCs was investigated. The aqueous phase adsorption results indicated HD3000 and SWCNT exhibited higher adsorption capacities due to their microporous structures for the selected SOCs than graphene nanomaterials. Among selected four carbonaceous adsorbents, graphene oxides (GO) showed the lowest adsorption affinity for aliphatic SOCs, indicating that surface functionalization of pristine graphene nanosheets (GNS) decreased their adsorption capacities for the SOCs due to the formation of water clusters around the oxygen-containing functional groups of carbon surface. Second, the role of selected properties of aliphatic SOC on the adsorption was examined using ten aliphatic compounds that were specifically selected, including trichloroethylene (TCE), tetrachloroethylene (TeCE), 1,1,1-trichloroethane (111TCA), 1,1,2-trichloroethane (112TCA), carbon tetrachloride (CCl4), 1,1-dichloroethylene (11DCE), 1,2-dichloropropane (12DCP), 1,2-dibromoethane (12DBE), 1,1,1,2-tetrachloroethane (1112TeCA) and 1,2-dibromo-3-chloropropane (DBCP). Solubility normalized isotherm results demonstrated that although hydrophobicity of the SOCs was influential, it was not the only factor controlling their adsorption behavior. Through the analysis of the solubility normalized isotherms of selected aliphatic SOCs, polarizability, carbon double bonds and substituent groups were found to also affect the adsorption of aliphatic SOCs to different extents. Third, the impact of background solution chemistry (i.e., pH, ionic strength and presence of NOM) on the adsorption of aliphatic SOCs by different adsorbents was investigated. Among the three background components examined, natural organic matter (NOM) showed the most influential effect on the adsorption of the selected aliphatic SOCs. The impact of NOM on the adsorption of aliphatic SOCs was smaller on graphene nanomaterials than SWCNT. In addition, solution pH and ionic strength (IS) had a negligible effect on the adsorption of aliphatic SOCs by graphene nanomatierals.

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