Carbon nanotube-impeded transport of non-steroidal anti-inflammatory drugs in Xiangjiang sediments

Carbon nanotubes (CNTs), usually with a superior affinity with organic chemicals, are expected to ultimately released to the environment through their manufacturing, usage, and eventual disposal, which will influence the mobility and environmental risk of nonsteroidal anti-inflammatory drugs (NSAIDs). In this study, batch and column experiments were performed to examine the effects of two kinds of multi-walled carbon nanotubes (MWCNTs: MWCNT2040, MWCNT0815) and one kind of single-walled carbon nanotubes (SWCNTs) on the environmental fate of two NSAIDs, paracetamol (PA) and diclofenac sodium (DS), in sediments. Impact ways of CNTs including addition in inflow and mixing with sediments were investigated. The adsorption capacity of NSAIDs on sediments increased with increasing CNTs/sediments ratios and in an order of MWCNT2040<MTWCNT0815<SWCNT. In column tests, PA showed a higher mobility than DS. With CNTs in inflow, the amounts of NSAIDs leached from sediment columns reduced because of the association with CNTs. For the sediment columns mixed with CNTs, breakthrough of the two NSAIDs was dramatically retarded, and the NSAIDs were hard to separate from CNT-polluted sediments. Our work provides useful insights into fate, transport and risk assessment of NSAIDs in the presence of CNTs.