Sorption is a proven and reliable technology, but existing materials, e.g. granular activated carbon (GAC) are not well suited to remove low level contaminants from high background conditions of organic matter or cations. A novel sorbent membrane, activated carbon nanofiber nonwoven (ACNFN), takes advantage of nanoscale fabrication to reduce mass transfer limitations while functionalizing the surface through chemical means enhances the specificity of the sorption interaction. Mass transfer limitations were observed to decrease as the kinetic rate constant (�g g-1 h-1) for sorption of pyrene on ACNFN was up to 10-fold higher than that of GAC. In addition, the equilibrium capacity was at least double that of GAC. In our efforts to find more effective ways of functionalizing ACNFN, we have focused on novel reactions that limit material degradation.  We have added carboxylic acid groups on activated carbon with either traditional HNO3 surface oxidation or osmylation reactions. Osmylation is a novel pathway, less aggressive than HNO3, and results in a dicarboxylic acid to which other moieties can be linked.   Subsequently, ethylenediamine (EDA) was attached using coupling agents familiar to protein chemistry, to form stronger ligand interactions with metals. Both pathways generated the same diagnostic nC=O in the 1600-1700 cm-1 IR spectra range that indicates carboxylic acid functionality. However, later experiments that applied the two pathways to ACNFN showed that while HNO3 destroyed the nanofiber structure, the osmylation pathway kept the inherent structure. In addition, after EDA modification, the IR spectrum showed a decrease in carbonyl stretching and an increase in C-N bond stretching at 1180 cm-1.  Titrations showed increased basic functionality indicative of EDA attachment, and the overall sorption capacity for Ni was higher than the unmodified activated carbon. The results show promise that functional groups can be added to the surface of nanofibrous activated carbons via this novel mechanism.

Tuning an activated carbon nanofiber membrane material for specific sorption in water treatment systems

248th National Meeting (2014)

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