Dual roles of Goethite coating on the retention and release of plastic nanoparticles in porous media: The significance of collector surface heterogeneity

Authors: DONG, PENCHENG - Guangxi University; LIANG, YAN - Guangxi University; SHEN, CHONGYANG - China Agriculture University; LIU, JINXING - Guangxi University; Bradford, Scott

Submitted to: Journal of Hazardous Materials
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2024
Publication Date: 3/28/2024
Citation: Dong, P., Liang, Y., Shen, C., Liu, J., Bradford, S.A. 2024. Dual roles of Goethite coating on the retention and release of plastic nanoparticles in porous media: The significance of collector surface heterogeneity. Journal of Hazardous Materials. 470. https://doi.org/10.1016/j.jhazmat.2024.134153.
DOI: https://doi.org/10.1016/j.jhazmat.2024.134153

Interpretive Summary: Plastic nanoparticles (PSNPs) have attracted global concern as emerging contaminants due to their potential adverse effects on ecosystems. This study investigated how iron coatings on sand grains influence the mobility of different types of PSNPs in groundwater. The fate of PSNPs was found to depend on the their surface charge, the solution ionic strength and pH, the sand roughness, and the amount of iron coating on the sand. Removal of PSNPs by sand grains changed in a nonlinear fashion with the iron coating due to modification of the grain surface roughness and charge. This finding implies that surface roughness modification by minerals or colloids in the environment will significantly influence the removal of PSNPs and other colloidal contaminants. This research will be of interest to health professional and government regulators that are concerned about the risks of PSNPs in the environment.

Technical Abstract: The present study investigates the retention and release of different functionalized (blank, -COOH, and -NH2) plastic nanoparticles (PSNPs) in quartz sand without or with goethite coating. Systematic batch and column experiments and XDLVO calculations were performed to deduce the reversible-irreversible interactions of PSNPs with relatively smooth and rough sand that were coated by various goethite fractions. This study provides the first evidence of the dual roles of goethite coatings (e.g., modification of surface charge and roughness) on the transport and release of colloidal contaminants. It has been well acknowledged that the retention of negatively charged colloids tends to be enhanced in the presence of goethite coatings due to increased surface roughness and chemical heterogeneity. However, nonmonotonic retention was observed to be contingent on the PSNP functionalization, the solution ionic strength (IS), the collector surface roughness, and the goethite coating. The release of PSNPs with IS decrease and pH increase also differed with PSNP functionalization, collector surface roughness, and the goethite coating due to various energy barriers to detachment. In particular, the presence of goethite coating reduced the release of PSNPs without functional groups due to the increased detachment energy barrier arisen from charge heterogeneity, while the presence of -COOH and -NH2 on PSNP surfaces enhanced both the retention and release from goethite coated smooth sands. Findings of this study provide innovative insight into the transport mechanisms for colloidal contaminants.