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Abstract

Hua, B., B. Deng and J. Yang. 2008. Characterization and dissolution of metal impurities in multi-walled carbon nanotubes. JEMREST 5:00-00

Carbon nanotubes (CNT) containing heavy metals such as iron (Fe), nickel (Ni), and chromium (Cr) have been reported toxic to aquatic life and are environmentally concerned. Understanding the mechanisms of CNT toxicity to aquatic organisms is critical for assessing their potential impacts on human health and environments. This study was conducted to fully characterize the metals in CNT and evaluate their dissolution kinetics from a multi-walled carbon nanotubes (MWCNT). Characterization by scanning microscopy and microprobe (SEM-EDS) indicated that Ni, Fe, and Cr were major metal impurities of MWCNT. Extraction study by 3.5 M HNO₃ showed that 3.78 mg Ni and 0.779 mg Fe g^-1 CNT were extractable, while only 1.12 mg Ni and 0.00634 mg Fe g^-1 CNT by deionized water (18.2 MΩ cm^-1). In both cases, extractable Cr was always below the detection limit of 0.001 mg g^-1. Burning of MWCNT at 950°C followed by 3.5 M HNO₃extraction resulted in extractable 7.42 mg Ni and 2.31 mg Fe g^-1. Results demonstrate that about 49% of Ni, 66% of Fe, and 100% of Cr may reside inside MWCNT and are non-extractable or non-releasable to aqueous phase.