# Transport and retention of engineered Al2O3, TiO2, and SiO2 nanoparticles through various sedimentary rocks

## TL;DR

This study examines how different nanoparticles move and get retained in various types of sedimentary rocks, showing that their movement depends on surface charges and rock properties.

## Contribution

The study provides new insights into NP transport mechanisms in different porous media using experimental and theoretical approaches.

## Key findings

- Al2O3 and TiO2 NPs are more mobile in limestone and dolomite than in quartz-sand.
- SiO2 NPs show highest recovery in quartz-sand and lowest in limestone.
- NP mobility is influenced by surface charge, suspension stability, and medium roughness.

## Abstract

Engineered aluminum oxide (Al2O3), titanium dioxide (TiO2), and silicon dioxide (SiO2) nanoparticles (NPs) are utilized in a broad range of applications; causing noticeable quantities of these materials to be released into the environment. Issues of how and where these particles are distributed into the subsurface aquatic environment remain as major challenges for those in environmental engineering. In this study, transport and retention of Al2O3, TiO2, and SiO2 NPs through various saturated porous media were investigated. Vertical columns were packed with quartz-sand, limestone, and dolomite grains. The NPs were introduced as a pulse suspended in aqueous solutions and breakthrough curves in the column outlet were generated using an ultraviolet-visible spectrophotometer. It was found that Al2O3 and TiO2 NPs are easily transported through limestone and dolomite porous media whereas NPs recoveries were achieved two times higher than those found in the quartz-sand. The highest and lowest SiO2-NPs recoveries were also achieved from the quartz-sand and limestone columns, respectively. The experimental results closely replicated the general trends predicted by the filtration and DLVO calculations. Overall, NPs mobility through a porous medium was found to be strongly dependent on NP surface charge, NP suspension stability against deposition, and porous medium surface charge and roughness.