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Rapid and versatile pre-treatment for quantification of multi-walled carbon nanotubes in the environment using microwave-induced heating
Citation:
He, Y., S. Al-Abed, P. Potter, AND D. Dionysios. Rapid and versatile pre-treatment for quantification of multi-walled carbon nanotubes in the environment using microwave-induced heating. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH. Ecomed Verlagsgesellschaft AG, Landsberg, Germany, 26(14):13999-14012, (2019). https://doi.org/10.1007/s11356-019-04229-8
Impact/Purpose:
The concerns regarding potential environmental release and ecological risks of multi-walled carbon nanotubes (MWCNTs) rise with their increased production and use. Therefore, it is necessary to determine the environmental concentration of the MWCNTs. Several analytical approaches have been demonstrated to quantify MWCNTs in environmental and biological samples based on their optical or thermal-stability, but most methods are most likely affected by the change of the characteristic properties of MWCNTs (e.g. length, diameter, aggregation). The characteristics information of the MWCNTs is usually missing for environmental samples, leading to the measurements inaccurate. In this paper, our recently developed microwave induced heating method was further studied for the feasibility of quantifying MWCNTs in environmental samples. Our findings indicated that the suppliers, length and diameter of the MWCNTs did not affect the microwave responses due to the unique dielectric heating of MWCNTs with the microwave energy. Although the aggregated MWCNTs were observed not to be active in absorbing and converting the microwave energy to heat, a 2-step pre-treatment procedure (high temperature exposure and acetone based surfactant solution addition) was proposed to disperse bundled MWCNTs that deposited in field samples, making the microwave method applicable. The presented microwave induced heating method with pre-treatment process could provide a solution to the environmental quantification of CNTs and it can be further leveraged to study ecotoxicity of CNTs and to assess risks of using nanomaterials in our everyday life.
Description:
The concerns regarding potential environmental release and ecological risks of multi-walled carbon nanotubes (MWCNTs) rise with their increased production and use. As a result, there is the need for an analytical method to determine the environmental concentration of MWCNTs. Although several methods have been demonstrated for the quantification of well-characterized MWCNTs, applying these methods to field samples is still a challenge due to interferences from unknown characteristics of MWCNTs and environmental media. To bridge this gap, a recently developed microwave-induced heating method was investigated for the quantification of MWCNTs in field samples. Our results indicated that the microwave response of MWCNTs was independent of the sources, length, and diameter of MWCNTs; however, the aggregated MWCNTs were not able to convert the microwave energy to heat, making the method inapplicable. Thus, a pre-treatment process for dispersing bundled MWCNTs in field samples was crucial for the use of the microwave method. In the present paper, a two-step pre-treatment procedure was proposed: the aggregated MWCNTs loaded environmental samples were first exposed to high temperature (500 °C) and then dispersed by using an acetone-surfactant solution. A validation study was performed to evaluate the effectiveness of the pre-treatment process, showing that an 80–120% recovery range of true MWCNT loading successfully covered the microwave-measured MWCNT mass.
URLs/Downloads:
DOI: Rapid and versatile pre-treatment for quantification of multi-walled carbon nanotubes in the environment using microwave-induced heating
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