Understanding the sorption interactions between nanoparticles and soils or sediments is a critical factor in determining their fate in environmental systems. As such, we examined the interactions of 14C-labeled multi-walled carbon nanotubes (MWNTs) in aqueous systems with peat as a model solid organic material. The presence of peat and the aqueous conditions significantly impacted the solid phase distribution of MWNTs. In the absence of peat, MWNTs began aggregating when the concentration of sodium cations in the solution increased above 4.0 mM or when pH of the solution dropped to 4.0. Dissolved organic matter (DOM) from peat effectively stabilized MWNTs in solution. Such stabilization effects, likely stemming from the steric hindrance of DOM adsorbed onto the MWNT surface, appeared to be less sensitive to changes in sodium concentrations or solution pH. Direct sorption interactions between MWNTs and solid peat were not observed in the absence of sodium cations, whereas sorption became apparent when the ionic strength was sufficiently high to reduce charge repulsion between the negatively charged peat and MWNTs. Moreover, the phase distribution of MWNTs appeared to be dependent on their sizes, with the smaller ones having a greater tendency to enter the solid phase, a result likely attributable to their relatively larger specific surface areas.
Citation: Environmental Science & Technology
Pub Type: Journals
Nanotoxicology, carbon nanotubes, sorption