Dispersion State and Humic
Acids Concentration-Dependent
Sorption of Pyrene to Carbon Nanotubes
- Publication date
- Publisher
Abstract
Sonication and humic acids (HA) are known to disperse
carbon nanotube
(CNT) suspensions, but potential effects on sorption of chemicals
to CNTs remain poorly understood. We applied a passive sampling method
to investigate the influence of dispersion/aggregation on sorption
of pyrene to CNTs. Sonication broke down CNT aggregates and increased
pyrene sorption affinity by up to 1.39 orders of magnitude. Sorption
surfaces newly exposed by sonication remained available to pyrene
even after reaggregation occurred, suggesting an irreversible effect
of sonication. The presence of HA decreased sorption of pyrene to
CNTs, but at the highest HA concentration investigated (200 mg/L),
sorption affinity was still 1.90 orders of magnitude larger than sorption
of pyrene to HA alone. Specific interactions between pyrene and CNTs
were thus still taking place, in spite of the presence of a HA coating
on the CNTs’ surface. A greater suppression of sorption by
CNTs occurred when the HA addition was combined with a sonication
pretreatment. Sorption isotherm fitting indicated that the maximum
sorption capacity, sorption affinity, and heterogeneity of the CNT
surface were all affected by sonication and the presence of HA at
a concentration as low as 1 mg/L. The present results contribute to
an improved understanding of the sorption behavior of CNTs in both
natural and wastewater systems