Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

A rapid increase in the application of engineered nanoparticles (ENPs) in science, technology, medicine and every day life is anticipated. Currently, there is still relatively little knowledge on the behaviour of ENPs in the aquatic environment. Our study was aimed at gaining information on the behaviour of carbon nanotubes (CNTs) as potential carriers of pollutants in the case of accidental CNT release to the environment. The experiments showed that pristine CNTs possess little colloidal stability in aquatic suspensions. Also the sorption capacity of the pristine CNTs for uranium is low. However, modification of the CNTs by surface oxidation with HNO3/H2SO4 increased the colloidal stability of the CNTs in near-neutral waters dramatically. Moreover, also the sorption capacity for uranium, which served as an example of a toxic heavy metal, was strongly increased by the surface treatment. Uranium sorption data could best be fit by a Langmuir adsorption isotherm. The increase in colloidal stability and in sorption capacity was due to the generation of new sorption sites (carboxylic groups) on the surface of CNTs by surface oxidation. These groups could also be detected by FTIR. Another way to elevate colloidal stability is to add small amounts of humic acid to suspensions of the pristine