Modeling the Transport of Aggregating Nanoparticles in Porous Media

Abstract

Nanoparticle aggregation is an important process for particle attachment during transport in porous media. However, the available mathematical models for particle transport, which are based on colloid filtration theory (CFT), depth-dependent retention and blocking, despite their success in fitting relatively Abstract A novel mathematical model was developed to describe the transport of nanoparticles in water saturated, homogeneous porous media with uniform flow. The model accounts for the simultaneous migration and aggregation of nanoparticles. The nanoparticles are assumed to be found suspended in the aqueous phase or attached reversibly or irreversibly onto the solid matrix. The Derjaguin-Landau-Verwey-Overbeek theory was used to account for possible repulsive interactions between aggregates. Nanoparticle aggregation was represented by the Smoluchowski population balance equation (PBE). Both reaction-limited aggregation and diffusion-limited aggregation were considered. Particle-size dependent dispersivity was accounted for. In order to overcome the substantial difficulties introduced by the PBE, the governing coupled partial differential equations were solved by employing adaptive operator splitting methods, which decoupled the reactive transport and aggregation into distinct physical processes. The results from various model simulations showed that the transport of nanoparticles in porous media is substantially different than the transport of conventional biocolloids. In particular, aggregation was shown to either decrease or increase nanoparticle attachment onto the solid matrix, depending on particle size, and to yield early or late breakthrough, respectively. Finally, useful conclusions were drawn regarding possible erroneous results generated when aggregation, particle-size dependent dispersivity or nanoparticle surface charges are neglected.

Effect of Agricultural Organic Inputs on Nanoplastics Transport in Saturated Goethite-Coated Porous Media: Particle Size Selectivity and Role of Dissolved Organic Matter

“…Transport experiment data were simulated using a one-dimensional nanoparticle transport model considering attachment/detachment and chemical nonequilibrium with two-site (reversible and irreversible) kinetic retention. 44 Although the nanoparticle (reaction-limited and diffusionlimited) aggregation 45 was not considered, the proposed model can reflect the characteristics of NPs transport. Details of the transport model are shown in SI S5.…”

Significance of Non-DLVO Interactions on the Co-Transport of Functionalized Multiwalled Carbon Nanotubes and Soil Nanoparticles in Porous Media

“…The transport behavior of colloids can sometimes be reasonably described by quantifying these interactions. 22,32,33 For example, heteroaggregation between carbon nanoparticles and mineral colloids resulted in sedimentation of carbon nanoparticles due to reduced electrostatic repulsion. 26,34 However, some recent studies indicated that ENPs (e.g., CNTs) could exhibit different transport behavior from classic colloid filtration theory (CFT) and DLVO theory.…”

“…27,35 For example, Katzourakis and Chrysikopoulos indicated that aggregation could contribute to the attachment of ENPs in porous media. 33 Liu et al 27 and Yang et al 28 indicated that chemical bonds were formed between carbon dots and minerals, as well as biochar and bentonite, in batch and aggregation experiments, respectively. Soil colloids and ENPs were also found to be strongly associated during transport experiments, even under variable flow conditions.…”

“…DLVO theory assumes that colloid aggregation and retention are mainly controlled by interactions that arise from VDW and EDL forces. The transport behavior of colloids can sometimes be reasonably described by quantifying these interactions. ,, For example, heteroaggregation between carbon nanoparticles and mineral colloids resulted in sedimentation of carbon nanoparticles due to reduced electrostatic repulsion. , However, some recent studies indicated that ENPs (e.g., CNTs) could exhibit different transport behavior from classic colloid filtration theory (CFT) and DLVO theory. , For example, Katzourakis and Chrysikopoulos indicated that aggregation could contribute to the attachment of ENPs in porous media . Liu et al and Yang et al indicated that chemical bonds were formed between carbon dots and minerals, as well as biochar and bentonite, in batch and aggregation experiments, respectively.…”

Biosurfactant-mediated mobility of graphene oxide nanoparticles in saturated porous media

“…Notably, the mathematical model selected in this study does not account for GO and biosurfactant interactions. 92 To accurately describe the interaction between sand and GO in the presence of biosurfactant, additional co-transport models are needed to further illustrate the transport behaviors of GO in the presence of bio-surfactant. 93,94 In summary, the ndings presented in this study provide valuable insights into the mechanisms controlling the enhanced mobility of carbon-based nanomaterials in groundwater systems containing biosurfactants.…”