Carbon nanotube-coated Al₂O₃ materials for removing N-nitrosamines, 2-methylisoborneol and geosmin from water

Abstract

Concern over safe drinking water has increased. In this study, aluminum oxide was coated with carbon nanotubes by chemical vapor deposition using ethanol or methanol as precursors to remove N-nitrosamines, 2-methylisoborneol (MIB) and geosmin from water. Seven types of N-nitrosamines were investigated. The differences in the surface of the carbon nanotubes were attributed to the carbon precursors ethanol and methanol. Despite the high concentration of analytes, the adsorption capacity of both carbon nanotubes (CNTs) was around 19 mg/mg for MIB and geosmin. Against approximately 0.9 ng/mg for activated carbon. For N-nitrosamines, the adsorption capacity of CNTs reached 50 ng/mg for NDBA, N-nitrosamines with the highest molecular weight, while activated carbon had values below 6.0 ng/mg. The results showed π-π interactions play a dominant role in the adsorption of MIB and geosmin under the investigated conditions. On the other hand, for N-nitrosamines, both dipole-dipole and π-π interactions come into play, with the latter becoming more prominent as the molecular weight of N-nitrosamines increases. The removal efficiencies of CNT-coated aluminum oxide reached 84,0%. The analytes with longer carbon chains were removed more efficiently and CNT-coated aluminum oxide grown from ethanol or methanol had no statistical difference between the removal efficiencies of all evaluated analytes.

Keywords:

• Carbon nanotube
• N-nitrosamine
• 2-methylisoborneol
• geosmin
• water purification

Author contributions

Ana Isabela Pianowski Salussoglia: conceptualization, investigation, writing, review, editing; Gabriel Matias Silva: investigation, adsorption data analysis, writing, review; Gustavo Guerreiro Candido Soares and Maria Eduarda de Lima: production of CNT-coated Al₂O₃; José Mauricio Rosolen: conceptualization, design of micro/nanostructured materials, supervision, writing, review, editing; Luiz Alberto Beraldo de Moraes: conceptualization, investigation, supervision, review.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was funded by São Paulo Research Foundation (FAPESP) grant #2020/12204-3. JMR thanks National Council for Scientific and Technological Development (CNPq) grant #311647/2021-9.