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Honolulu, HI, United States, 2006/08/30 - Carbon nanomaterials have been studied as superior sorbents for their potential environmental applications to remove pollutants such as organic pollutants, metals, fluorides and radionuclides..
Most of these studies focused on the adsorption process and few dealt with the interfacial interactions of organic contaminants with carbon nanomaterials in aqueous media. However, understanding their desorption behavior as well is critical to evaluating environmental and health impacts of carbon nanomaterials. New research looks at the high adsorption capacity and reversible adsorption of PAHs (polycyclic aromatic hydrocarbons), many of which are suspected carcinogens, on CNTs. The findings imply the potential release of PAHs if PAH-adsorbed CNTs are inhaled by animals and humans, leading to a high environmental and public health risk.
It was suggested that the toxicity of carbon nanomaterials is not only from their own potentially harmful nature but also from the toxic substances sorbed by them. Therefore, knowledge of toxic compound adsorption by carbon nanomaterials is critical and useful for risk assessment of these nanomaterials. This knowledge is also important for understanding the effect of the nanomaterials on the fate and transport of toxic pollutants in the environment, similar to other carbon materials such as soot and charcoal.
Adsorption - desorption hysteresis is widely observed for the sorption of organic compounds by soils, sediments and charcoals. Such compounds include pesticides, chlorinated benzenes, and PAHs. Two types of hysteresis are often observed: reversible and irreversible hysteresis.
So far, the desorption of organic contaminants by carbon nanomaterials, addressed only by limited research, shows significant desorption hysteresis of naphthalene and 1,2-dichlorobenzene from fullerene (C60). However, the mechanisms of desorption hysteresis for fullerene are still unclear. Furthermore, desorption from carbon nanotubes has not been investigated as yet.
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By Michael Berger, Copyright 2006 Nanowerk LLC