Significance of non-DLVO interactions on the co-transport of functionalized multiwalled carbon nanotubes and soil nanoparticles in porous media

Authors: ZHANG, MIAOYUE - Sun Yat-Sen University; Bradford, Scott; KLUMPP, ERWIN - Agrosphere Institute; ŠIMUNEK, JIRKA - University Of California; WANG, SHIZHONG - Sun Yat-Sen University; WAN, QUAN - South China Agricultural Univerisity; JIN, CHAO - Sun Yat-Sen University; QIU, RONGLIANG - Sun Yat-Sen University

Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2022
Publication Date: 6/8/2022
Citation: Zhang, M., Bradford, S.A., Klumpp, E., Šimunek, J., Wang, S., Wan, Q., Jin, C., Qiu, R. 2022. Significance of non-DLVO interactions on the co-transport of functionalized multiwalled carbon nanotubes and soil nanoparticles in porous media. Environmental Science and Technology. https://doi.org/10.1021/acs.est.2c00681.
DOI: https://doi.org/10.1021/acs.est.2c00681

Interpretive Summary: Engineered nanoparticles (ENPs), like multi-walled carbon nanotubes (MWCNTs), are increasing being used in commercial products and will eventually be released into soil and aquifer environments with soil colloids. This study examines the transport and retention behavior of MWCNTs in sand in the presence of representative positively charged (goethite) and negatively charged (bentonite) soil colloids. Results demonstrate that interactions between MWCNT and soil colloids will either enhance (bentonite) or diminish (goethite) their transport potential transport, and that co-interactions should be considered when assessing the environmental risk of ENPs. These results will be of interest to scientists and engineers concerned with managing MWCNT pollution in soils and aquifers.

Technical Abstract: Derjaguin–Landau–Verwey–Overbeek (DLVO) theory is typically used to quantify surface interactions between engineered nanoparticles (ENPs), soil nanoparticles (SNPs), and/or porous media, which are used to assess environmental risk and fate of ENPs. This study investigates the co-transport behavior of functionalized multiwalled carbon nanotubes (MWCNTs) with positively (goethite nanoparticles, GNPs) and negatively (bentonite nanoparticles, BNPs) charged SNPs in quartz sand (QS). The presence of BNPs increased the transport of MWCNTs, but GNPs inhibited the transport of MWCNTs. In addition, we, for the first time, observed that the transport of negatively (BNPs) and positively (GNPs) charged SNPs was facilitated by the presence of MWCNTs. Traditional mechanisms associated with competitive blocking, heteroaggregation, and classic DLVO calculations cannot explain such phenomena. Direct examination using batch experiments and Fourier transform infrared (FTIR) spectroscopy, asymmetric flow field flow fractionation (AF4) coupled to UV and inductively coupled plasma mass spectrometry (AF4-UV-ICP-MS), and molecular dynamics (MD) simulations demonstrated that MWCNTs-BNPs or MWCNT-GNPs complexes or aggregates can be formed during co-transport. Non-DLVO interactions (e.g., H-bonding and Lewis acid–base interaction) helped to explain observed MWCNT deposition, associations between MWCNTs and both SNPs (positively or negatively), and co-transport. This research sheds novel insight into the transport of MWCNTs and SNPs in porous media and suggests that (i) mutual effects between colloids (e.g., heteroaggregation, co-transport, and competitive blocking) need to be considered in natural soil; and (ii) non-DLVO interactions should be comprehensively considered when evaluating the environmental risk and fate of ENPs.