Recycling and disposal of carbon nanotubes

Abstract

Nanoparticles may be released throughout the lifecycle of products. Information on the handling, treatment, toxicity and mobility of carbon nanotubes (CNTs) is currently minimal. The objectives of the study were to determine the practices employed by nano-organisations for recycling and disposal of CNTs, identify quality management tools to aid responsible development and observe the behaviour, toxicity and leaching potential of CNTs. These objectives would support the development of a strategy for managing the potential environmental risks associated with the recycling and disposal of CNT. A mixed method tactic was adopted for this study. In addition to validated protocols based on OECD guidelines for validity and reliability in experimental work, the validity of the review was achieved by obtaining expert knowledge through scholarly articles and the internal consistency. While the reliability of the review was achieved by monitoring the repetitive information from literature sources and Cronbach alpha. Respondents participating in the survey indicated that there are differing practices for the recycling and disposal of engineered materials (ENMs). The toxicity studies revealed that while the nano-clay had a lethal response to earthworms during the pilot toxicity study, the main toxicity study showed that carbon nanotubes did not have a lethal response to earthworms in soil. However, worms were observed to be highly sensitised to increased concentrations of carbon nanotubes. The leaching in a soil column test showed that the movement of carbon nanotubes was inhibited with the largest portion of carbon nanotubes remaining on the surface and in the topmost layers of the soil. Results pointed to contradicting views with regards to environmental risks amongst people working in the field of nanotechnology. For this reason a continued precautionary approach is suggested until standardised legislation has been enforced for nanotechnology. Future work requires a more detailed understanding of the fate, behaviour, uptake and distribution of CNT in the environment. This can be achieved through the sharing of knowledge between nano-facilities.