While in aquatic environments microplastics can be filtered out relatively easily, in soil it’s much harder to get to these microscopic particles. While you can certainly strip mine an entire area to process its soil, a less invasive method would involve something like the magnetic flakes proposed and demonstrated by [Jeonghyo Kim] et al. in a recent article in npg asia materials.
The Ti3C2Tx flakes, referred to as MXene microparticles, were designed to attract target microplastics. These were then combined with ferromagnetic nickel nanoparticles to make structures that can be propelled through soil using an external magnetic field.
During tests under laboratory conditions the researchers managed to remove about 81% of polystyrene and 72% of PET particles this way from soil, with a correspondingly higher percentage in water. After having the flakes rummage about for a while through the target material, they are removed with a strong magnetic field, which should recover most of them.
Naturally, the question with any such system is how it’ll perform once exposed to real world conditions and its myriad of soil types and conditions.
The amount of microplastics involved in the infrastructure required to manufacture these magnetic flakes far exceeds the amount of microplastics said flakes will ever remove from the soil. Just like keeping carbon out of the atmosphere, the best way to keep plastic out of the soil is to never put it there in the first place.