Use of Carbon Nanofibers in the Removal of Organic Solvents from Water

Catalytically grown carbon nanofibers are a set of novel structures that are produced by the decomposition of selected carbon-containing gases over metal particles. These conformations consist of nanosized graphite platelets separated a distance of at least 0.34 nm and stacked in various orientations with respect to the fiber axis. Such an arrangement results in a unique structure that is composed of an infinite number of extremely short and narrow pores, suitable for the sequestering of small molecules. We have attempted to capitalize on this blend of properties by using such structures for the selective removal of organic contaminants from aqueous streams. Experimental results indicate that nanofibers possessing a structure in which the graphite platelets are aligned perpendicular to the fiber axis and possessing a high degree of structural perfection exhibit superior selective adsorption properties with respect to removal of alcohols from aqueous media over those displayed by active carbon. Adsorption was enhanced when the carbon nanofibers were initially subjected to a treatment in 1 M hydrochloric acid. In contrast, when this step was carried out in the presence of 1 M nitric acid, the beneficial properties of the nanofibers were effectively suppressed. An analogous series of experiments carried out with nanofibers possessing a structure in which the graphene layers were oriented at an angle with respect to the fiber axis did not result in the same degree of selective capture of the alcohols. A rationale is presented to account for this diverse pattern of behavior.