Citation:

He, Y., S. Al-Abed, AND D. Dionysiou. Quantification of Carbon Nanotubes in Different Environmental Matrices by a Microwave Induced Heating Method. D. Barceló, and Jay Gan (ed.), SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, Netherlands, 580:509-517, (2017). https://doi.org/10.1016/j.scitotenv.2016.11.205

Impact/Purpose:

The main objective of the study is to make use of this microwave induced heating system to quantitatively detect CNTs in three matrices of environmental relevance including sand, soil and anaerobic sludge. To meet the objective, linear mass-heat relationships were developed for SWCNTs, MWCNTs and carboxylated MWCNTs in the three environmental samples.

Description:

Carbon nanotubes (CNTs) have been incorporated into numerous consumer products, and have also been employed in various industrial areas because of their extraordinary properties. The large scale production and wide applications of CNTs make their release into the environment a major concern. Therefore, it is crucial to determine the degree of potential CNT contamination in the environment, which requires a sensitive and accurate technique for selectively detecting and quantifying CNTs in environmental matrices. In this study, a simple device based on utilizing heat generated/temperature increase from CNTs under microwave irradiation was built to quantify single-walled CNTs (SWCNTs), multi-walled CNTs (MWCNTs) and carboxylated CNTs (MWCNT-COOH) in three environmentally relevant matrices (sand, soil and sludge). Linear temperature vs CNT mass relationships were developed for the three environmental matrices spiked with known amounts of different types of CNTs that were then irradiated in a microwave at low energies (70-149 W) for a short time (15-30 s). MWCNTs had a greater microwave response in terms of heat generated/temperature increase than SWCNTs and MWCNT-COOH. An evaluation of microwave behavior of different carbonaceous materials showed that the microwave measurements of CNTs were not affected even with an excess of other organic, inorganic carbon or carbon based nanomaterials (fullerene, granular activated carbon and graphene oxide) mainly because microwave selectively heats materials such as CNTs that have a higher dielectric loss factor. Quantification limits using this technique for the sand, soil and sludge were determined as low as 18.61, 27.92, and 814.4 µg/g for MWCNTs at a microwave power of 133 W and exposure time of 15 s.

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