Mechanisms of increased small nanoplastic particle retention in water-saturated sand media with montmorillonite and diatomite: Particle sizes, water components, and modelling

Xiangrong Yang; Nan Xu; Xuelian Wang; Li Yang; Siyi Sun

doi:10.1016/j.jhazmat.2023.133056

Mechanisms of increased small nanoplastic particle retention in water-saturated sand media with montmorillonite and diatomite: Particle sizes, water components, and modelling

J Hazard Mater. 2024 Mar 5:465:133056. doi: 10.1016/j.jhazmat.2023.133056. Epub 2023 Nov 22.

Authors

Xiangrong Yang¹, Nan Xu², Xuelian Wang³, Li Yang⁴, Siyi Sun³

Affiliations

¹ School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215009, China; Jiangsu Key Laboratory of Environmental Functional Materials, Suzhou University of Science and Technology, Suzhou 215009, China.
² School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215009, China; Jiangsu Key Laboratory of Environmental Functional Materials, Suzhou University of Science and Technology, Suzhou 215009, China. Electronic address: nanxu@mail.usts.edu.cn.
³ School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215009, China.
⁴ Jiangsu Key Laboratory of Environmental Functional Materials, Suzhou University of Science and Technology, Suzhou 215009, China.

PMID: 38008050
DOI: 10.1016/j.jhazmat.2023.133056

Abstract

The processes by which small nanoplastics (NPs) accumulate in soil are unclear. To clarify the different deposition processes that affect small NPs (< 30 nm) compared to larger NPs in the soil environment, due to their interaction with clays as major soil components, the transport behavior of two-sized NPs (20 and 80 nm) with two clays (diatomite (Diat) and montmorillonite (Mont)) in NaCl and CaCl₂ solutions were investigated in water-saturated quartz sand columns. The experimental results showed that more 20 nm NPs could enter the lattice structure of Diat than Mont in NaCl solution. This contributed to the stronger deposition of 20 nm NPs by Diat on sand, which was associated with a lower k_1d/_k1 value (obtained from two-site kinetic attachment model). In contrast, 80 nm NPs had a stronger reversible retention than 20 nm NPs with Mont, even though both sizes of NPs-Mont displayed a similar transportability. In CaCl₂ solution, the larger NPs-Mont hetero-aggregates formed with a stronger suppressed depth of φ_max based on Derjaguin-Landau-Verwey-Overbeek theory. Thus, Mont had a stronger transport inhibition than Diat for both NPs sizes, with a lower k_1d/k₁. These findings could benefit in predicting the size-based deposition of NPs in a heterogenous soil environment.

Keywords: Diatomite; Model; Montmorillonite; Nanoplastics; Particle size; Transport.