Divalent cation contributions to the co-transport and deposition of functionalized multi-walled carbon nanotubes and soil nanoparticles in porous media in the presence of bentonite or geothite nanoparticles: Experiment and

Authors: ZHANG, MIAOYUE - Sun Yat-Sen University; Bradford, Scott; KLUMPP, ERWIN - Forschungszentrum Juelich Gmbh; ŠIMUNEK, JIRÍ - University Of California, Riverside; MO, YIJUN - Sun Yat-Sen University; DING, KENGBO - Sun Yat-Sen University; WAN, QUAN - South China Agricultural Univerisity; WANG, SHIZHONG - Sun Yat-Sen University; JIN, CHAO - Sun Yat-Sen University; QIU, RONGLIANG - Sun Yat-Sen University

Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2023
Publication Date: 7/7/2023
Citation: Zhang, M., Bradford, S.A., Klumpp, E., Šimunek, J., Mo, Y., Ding, K., Wan, Q., Wang, S., Jin, C., Qiu, R. 2023. Divalent cation contributions to the co-transport and deposition of functionalized multi-walled carbon nanotubes and soil nanoparticles in porous media in the presence of bentonite or geothite nanoparticles: Experiment and. Journal of Hydrology. 625(Part A). Article 129909. https://doi.org/10.1016/j.jhydrol.2023.129909.
DOI: https://doi.org/10.1016/j.jhydrol.2023.129909

Interpretive Summary: Engineered nanoparticles, like multi-walled carbon nanotubes (MWCNTs), are increasingly used in commercial products and will eventually be released into groundwater with soil particles. This study examines the transport of MWCNTs with positively or negatively charged soil particles in sand under the presence of different solution chemistries. Results demonstrate that the environmental fate of MWCNT and soil particles is highly dependent on the charge of ions in solutions, competitive interactions with surfaces, and retention in soil pores. The presence of calcium ions had a larger influence on co-transport processes and interactions than potassium ions. These results will be of interest to scientists and engineers concerned with managing MWCNT pollution in soils and aquifers, and demonstrates that conventional theory to describe MWCNT fate and interactions is inaccurate in many situations.

Technical Abstract: This work investigates the influence of cation type (Ca2+ as compared to K+) on the co-transport and deposition of functionalized multi-walled carbon nanotubes (MWCNTs) with negatively (bentonite nanoparticles, BNPs) or positively (goethite nanoparticles, GNPs) charged natural nanoparticles under the same ionic strength (IS = 1 mM) conditions. In packed column tests with quartz sand (QS), the co-transport of MWCNTs was slightly increased by BNPs and inhibited by GNPs in both CaCl2 and KCl solutions, whereas the co-transport of BNPs or GNPs was facilitated by MWCNTs in both solutions. However, the co-transport of MWCNTs in the presence of BNPs or GNPs exhibited a different dependency on the cation type in quartz crystal microbalance with dissipation (QCM-D) tests. No deposition of MWCNTs and BNPs was observed in QCM-D studies in the presence of KCl, while enhanced deposition of MWCNTs and GNPs occurred in this same solution. In contrast, the deposition of both MWCNTs and BNPs or MWCNTs and GNPs increased in QCM-D in the presence of CaCl2. In both column and QCM-D studies, Ca2+ exhibited a more significant impact on co-transport than K+, especially for MWCNTs with GNPs than BNPs. Results from molecular dynamic simulations, aggregation studies, and interaction energy calculations indicate that non-DLVO interactions (e.g., H-bonding and cation-p interaction) between two nanoparticles (MWCNTs with BNPs or GNPs) played a non-negligible role in interpreting the deposition and cotransport in the presence of the divalent cation Ca2+. Mathematical modeling of breakthrough curves and retention profiles and aggregation results suggest that both straining and competitive blocking were enhanced and played dominant roles in the co-transport of MWCNTs in the presence of BNPs or GNPs in QS, especially in the presence of Ca2+. This work sheds novel insights on the contribution of divalent cations to interactions between two colloids and their co-transport in porous media. This information is needed to assess the environmental fate and risks of engineered nanoparticles (ENPs) and natural nanoparticles in aquatic and soil environments with abundant divalent cations.