Non-monotonic contribution of nonionic surfactant on the retention of functionalized multi-walled carbon nanotubes in porous media

Authors: ZHANG, MIAOYUE - Sun Yat-Sen University; Bradford, Scott; KLUMPP, ERWIN - Forschungszentrum Juelich Gmbh; ŠIMUNEK, JIRKA - University Of California; JIN, CHAO - Sun Yat-Sen University; QIU, RONGLIANG - Sun Yat-Sen University

Submitted to: Journal of Hazardous Materials
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/2020
Publication Date: 12/17/2020
Citation: Zhang, M., Bradford, S.A., Klumpp, E., Šimunek, J., Jin, C., Qiu, R. 2020. Non-monotonic contribution of nonionic surfactant on the retention of functionalized multi-walled carbon nanotubes in porous media. Journal of Hazardous Materials. 407. Article 124874. https://doi.org/10.1016/j.jhazmat.2020.124874.
DOI: https://doi.org/10.1016/j.jhazmat.2020.124874

Interpretive Summary: Multi-walled carbon nanotubes (MWCNTs) are increasingly used in industrial applications and may be discharged with detergent residuals in sewage and wastewater. Experimental and modeling studies were therefore undertaken to assess the impact of a detergent residue TX100 on the environmental fate of MWCNTs. The maximum transport of MWCNTs was found to occur at intermediate TX100 concentrations because of differences in the strength of interactions between MWCNTs and TX100s. These results will be of interest to scientist, engineers, government regulators, and health care professions concerned with the fate of MWCNTs in the environment.

Technical Abstract: The concentration of nonionic surfactants like Triton X-100 (TX100) can influence the transport and fate of emerging contaminants (e.g., carbon nanotubes) in porous media, but limited research has previously addressed this issue. This study investigates the co-transport of functionalized multi-walled carbon nanotubes (MWCNTs) and various concentrations of TX100 in saturated quartz sand (QS). Batch experiments and molecular dynamics simulations were conducted to investigate the interactions between TX100 and MWCNTs. Results indicated that the concentration ratio of MWCNTs and TX100 strongly influences the dispersion of MWCNTs and interaction forces between MWCNTs and QS during the transport. Breakthrough curves of MWCNTs and TX100 and retention profiles of MWCNTs were determined and simulated in column studies. MWCNTs strongly enhanced the retention of TX100 in QS due to the high affinity of TX100 for MWCNTs. Conversely, the concentration of TX100 had a non-monotonic impact on MWCNT retention. The maximum transport of MWCNTs in the QS occurred at an input concentration of TX100 that was lower than the critical micelle concentration. This suggests that the relative importance of factors influencing MWCNTs changed with TX100 sorption. Results from interaction energy calculations and modeling of competitive blocking indicate that TX100 mainly altered intermolecular forces. This study provides new insights into the co-transport of surfactants and MWCNTs in porous media, which can be useful for environmental applications and risk management.