Degradability of aged aquatic suspensions of C60 nanoparticles

In this study, aged aqueous suspensions of C 60 (nC 60 ) were investigated in the respirometric OECD test for ready biodegradability. Two suspensions of nC 60 were prepared by stirring and aged under indirect exposure to sunlight for 36 months. ATR-FTIR analyses confirmed the presence of C 60 -structures in the suspensions. Samples of the nC 60 suspensions (20 mg/l) were inoculated with activated sludge (30 mgTSS/L) and incubated in a mineral medium under aerobic conditions. Since no mineralisation of nC 60 was observed after 28 days of incubation, 5 mg/l sodium acetate was added to the media. After additional 20 days, no mineralisation of nC 60 was observed. However, within a few days sodium acetate was completely mineralised, showing that the biomass was not inhibited by the presence of nC 60 . Based on results from this simple approach, aged nC 60 can be classified as not ready biodegradable according to the standard OECD test procedure.