Adsorption Of Organic Contaminants To Surface Functionalized Carbon Nanomaterials

With surface functionalized carbon nanomaterials showing more and more potential applications in biomedical science, materials science, electronics, environmental protection and other fields, fully understanding the effect of surface functionalized carbon nanomaterials on transport and fate of organic contaminants is of critical importance to the effective environmental risk assessment of surface functionalized carbon nanomaterialsIn this thesis, chlorobenzenes, phenols and aromatic amines were chosen as adsorbates, and carbon nanomaterials with different surface functional groups were chosen as adsorbents. Batch experiments and shake flask experiments were conducted to systematically study the adsorption/desorption behavior of organic contaminants to/from carbon nanomaterials, and the effect of heavy metal ions. Our study shows that due to the different surface functional groups, the hydrophobicity and the adsorption mechanisms of carbon nanomaterials are different. For chlorobenzenes and phenols, adsorption to functionalized carbon nanotubes is weaker than the original ones. This was likely because the introduction of the surface functional group results in the increase of carbon nanotubes surface hydrophobicity and therefore weakens the adsorption of these compounds. However, for aromatic amines, adsorption to functionalized carbon nanotubes is stronger than the original ones. This is because the acid functional groups of carbon nanomaterials could interact with the amino group of aromatic amines through Lewis acid-base effect. Most organic contaminants could reach the adsorption-desorption equilibrium quickly and show reversible sorption behavior.In order to reflect more real effect of carbon nanomaterials on adsorption behavior of organic contaminants, the common environmental heavy metal ions Cu (II) was chosen to study. Its effect on the adsorption of organic contaminants to carbon nanomaterials was studied. Cu(II) has strong complex capability. It could serves as a bridging agent between organic contaminanst and the functional groups on CNT surfaces. The adsorption of phenols and aromatic amines to functionalized carbon nanotubes is significantly enhanced.Since carbon nanomaterials may exist in different forms in different environmental conditions, the colloidal graphene oxide (GONPs) was chosen for the study. A negligible depletion-solid-phase microextraction (nd-SPME) method was used to study adsorption mechanism of organic contaminants to colloidal carbon nanomaterials. It was found that the adsorption behavior on GONPs is significantly different with other carbon nanomaterials. Graphene oxide can disperse well in water phase, and in the presence of a single sheet structure. Its adsorption energy is more uniform compared with other carbon nanomaterials. So the linearity of the adsorption isotherms is stronger. Secondly, for phenolic aromatic compounds, the hydrogen bond effect is stronger than π-π electron donor acceptor (EDA) interaction effect. This is significantly different with the adsorption on carbon nanotubes. But the main mechanism for the adsorption of hydrophobic compounds to GONPs and other carbon nanomaterials is π-π EDA interaction. For adsorption of amino aromatics to GONPs, the main mechanism is likely Lewis acid-base interactions between amino groups on the contaminants and the O-functional groups on GONPs.This thesis shows that adsorption properties of carbon nanomaterials for organic contaminants could be effectively changed by surface functionalized groups. Surface functionalized carbon nanomaterials can be used as potential adsorbents which could be applied in environmental management/remediation and drug carriers and so on. This study could provide theoretical support. Research on adsorption properties of carbon nanomaterials in different forms in different water chemistry conditions could help us to evaluate the risk of carbon nanomaterials released into the environment. This study provides important technical reference and plays an important role on evaluation of environmental risks of carbon nanomaterials.