Effects Of Typical Colloidal Carbon Nanomaterials On The Environmental Behavior Of Organic Contaminants:Role Of Natural Organic Matter

The thesis is constructed on the basis of summarizing the research status of adsorption of organic contaminants on typical carbon nanomaterials (such as carbon nanotubes and fullerene), and analyzing limitations or unsolved problems of the existing researches. In order to complete the knowledge on the adsorption of organic contaminants to carbon nanomaterials, we started the research from the adsorption behaviors, rules and mechanisms of aromatic organic contaminants to colloidal carbon nanotubes which hadn’t been fully concerned, and we intended to consider the influencing mechanism of natural organic matter on the adsorption interaction between aromatic organic contaminants and carbon nanomaterials. Finally we focused on the effect of natural organic matter on the transport of colloidal fullerene nanoparticles, the adsorption mechanisms between organic contaminants and fullerene nanoparticles, and the organic contaminants mobilizing capacity by fullerene nanoparticles in the environment.In this research, two systems were selected to study the effect of natural organic matter on the adsorption mechanisms of organic contaminants on colloidal carbon nanomaterials, and to further study the role of organic matter in the influence of colloidal carbon nanomaterials on the fate and transport of organic contaminants in the environment. One is to study the effect of natural organic matter on the adsorption mechanism of organic contaminants to colloidal carbon nanomaterials. The other is to study the effect of natural organic matter on the transport of colloidal carbon nanomaterials and facilitated transport of organic contaminants by colloidal carbon nanomaterials in the porous media in the environment.Batch method was firstly conducted in the experiment in order to study the adsorption behaviors of phenanthrene,2-naphthol, and1-naphthylamine to three colloidal CNTs, including a stable suspension of oxidized multiwalled carbon nanotubes (O-MWNT), a humic acid (HA)-modified colloidal O-MWNT, and a sodium dodecyl sulfate (SDS)-modified colloidal O-MWNT. All the three colloidal O-MWNTs exhibit strong adsorption affinities to the three test compounds (with Koc values orders of magnitude greater than those of natural organic matter), likely resulting from strong non-hydrophobic interactions such as π-π electron donor-acceptor interactions and Lewis acid-base interactions. When thoroughly mixed, HA and SDS significantly affected the aggregation properties of O-MWNT, causing individually dispersed tubes to form a loosely entangled network. The effects of HA or SDS modification on adsorption are twofold. Adsorption of HA/SDS significantly reduces surface areas of O-MWNT; however, the entangled network allows adsorbate molecules to interact simultaneously with multiple tubes. An important implication is that humic substances and surfactant-like materials not only facilitate the formation of colloidal carbon nanoparticles but also affect how these colloidal carbon nanoparticles adsorb organic contaminants.Fullerene nanoparticles which could transport very well in the environment were also selected as the research object. We started from considering the effect of humic acid modification on the morphology and physicochemical properties of fullerene nanoparticles prepared by different methods. Batch method and non-depletion solid-phase microextraction technology were used to examine the adsorption affinity of hydropobic organic contaminants (1,2,4,5-tetrachlorobenzene) on different fullerene nanoparticles. Then column (packed with soil) experiment was conducted to study the transport and contaminant (2,2’,5,5’-polychlorinated biphenyl) mobilizing capacity of these fullerene nanoparticles. It was found that different humic acid modification had totally different effect on the morphology and physicochemical properties of fullerene nanoparticles prepared by different methods, on the adsorption behavior of organic contaminants to these fullerene nanoparticles, and also on the transport and contaminant mobilizing capacity of these fullerene nanoparticles. The fundamental mechanism was related to different forming approaches of fullerene nanoparticles and also to how and to what extent humic acid had affected the aggregation/packing of C6o monomers. An important environmental implication is that nC60formed under different environmental conditions might have vastly different effects on contaminant transport and risks.