Complex interplay between formation routes and natural organic matter modification controls capabilities of C nanoparticles (nC) to accumulate organic contaminants.

Accumulation of organic contaminants on fullerene nanoparticles (nC) may significantly affect the risks of C in the environment. The objective of this study was to further understand how the interplay of nC formation routes and humic acid modification affects contaminant adsorption of nC. Specifically, adsorption of 1,2,4,5-tetrachlorobenzene (a model nonionic, hydrophobic organic contaminant) on nC was greatly affected by nC formation route - the formation route significantly affected the aggregation properties of nC, thus affecting the available surface area and the extent of adsorption via the pore-filling mechanism. Depending on whether nC was formed via the "top-down" route (i.e., sonicating C powder in aqueous solution) or "bottom-up" route (i.e., phase transfer from an organic solvent) and the type of solvent involved (toluene versus tetrahydrofuran), modification of nC with Suwannee River humic acid (SRHA) could either enhance or inhibit the adsorption affinity of nC. The net effect depended on the specific way in which SRHA interacted with C monomers and/or C aggregates of different sizes and morphology, which determined the relative importance of enhanced adsorption from SRHA modification via preventing C aggregation and inhibited adsorption through blocking available adsorption sites. The findings further demonstrate the complex mechanisms controlling interactions between nC and organic contaminants, and may have significant implications for the life-cycle analysis and risk assessment of C.