Eco-friendly filtration of microplastics using iron oxide NPs

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It is difficult to filter microplastics from water as they can bypass most filtration systems due to their microscopic size. In a study published in the journal Chemospheremagnetic iron oxide (Fe3O4) nanoparticles have been evaluated as potential candidates for adsorption removal of microplastics.

Study: Adsorption removal of micron-sized polystyrene particles using magnetic iron oxide nanoparticles. Image Credit: chayanuphol/Shutterstock.com

Harmful effects of plastic pollution

The increase in demand for plastic leads to an increase in plastic pollution, which can have significant consequences for natural ecosystems as well as human health and safety. Improper recycling and mishandling of plastic worsen plastic pollution.

Plastics have extended degradation times and are susceptible to accumulation in the ecosystem due to their high stability and durability. Rising levels of plastic in the environment, especially in marine ecosystems, are leading to growing concern for the environment. Plastic is carried to bodies of water by wind and ocean currents, and it breaks down into micro and nanoplastics over time.

It is difficult for living organisms to avoid consuming plastic waste due to the universal nature of microplastics. Once consumed, these microplastics move up the food chain and can ultimately have a negative impact on human health.

How to remove microplastics from water?

To remove microplastics from wastewater and drinking water, magnetic extraction, electrocoagulation and membrane separation technologies are suggested. However, it is difficult to remove microplastics with diameters less than 1 μm. Thus, these microplastics are common in wastewater treatment facilities.

To successfully remove microplastics from water, a consistent, simple, fast and repeatable technique must be developed.

Removing pollutants with iron oxide nanoparticles

As nanoparticles tend to have high specific surface areas, a cluster of iron oxide (Fe3O4) nanoparticles have a relatively high density of adsorption sites. Therefore, iron oxide nanoparticles have been used in various fields, including the removal of contaminants in the environment.

The magnetic effects of iron oxide allow faster removal of contaminating nanoparticles compared to centrifuges and filtering procedures.

Once the magnetic separation and regeneration processes are complete, the iron oxide nanoparticles can be reused, making it a viable adsorption material to remove environmental contaminants.

What did the researchers do?

The team investigated the use of magnetic Fe3O4 nanoparticles to filter microplastics from water by adsorption. To model the behavior of microplastics, polystyrene (PS) microparticles were used.

The researchers examined the kinetics of the process and the characteristics of isothermal adsorption of polystyrene microparticles on Fe3O4 nanoparticles.

They also performed adsorption tests for different groups of polystyrene microparticles with different average diameters to examine the adsorption efficiency of Fe3O4 nanoparticles. The hydrophobic and electrostatic dynamics involved in the Fe adsorption process3O4 and polystyrene microparticles have also been studied.

The team also determined the reusability of Fe3O4 nanoparticles by desorbing them from Fe3O4-polystyrene complexes (Fe3O4-PS).

Main research results

In this study, the team was able to successfully extract polystyrene microparticles from liquid environments using the combined effect of Fe3O4 nanoparticles and a magnet. The attachment of polystyrene microparticles to Fe3O4 nanoparticles enabled this process.

It has been observed in TEM imaging that Fe3O4 nanoparticles encompassed and brought together the polystyrene microparticles, allowing the use of a magnet to extract the resulting Fe3O4– fluid polystyrene complexes.

It has been established that the agglomeration of Fe3O4 with polystyrene microparticles was mainly due to a hydrophobic interaction between them. When an actual water sample was analyzed, suspended solids and coincident ions present in the sample prevented the deposition of polystyrene microparticles on Fe3O4 nanoparticles. Nevertheless, the adsorption efficiency can be improved by incorporating larger amounts of Fe adsorbent3O4 nanoparticles.

Fe3O4 nanoparticles were separated from Fe3O4-polystyrene complexes using a simple sonication procedure. Research has highlighted the potential for the employment of Fe3O4 nanoparticles to effectively remove microplastics from the ecosystem.

References

Heo, Y., Lee, E.-H., & Lee, S.-W. (2022). Adsorption removal of micron-sized polystyrene particles using magnetic iron oxide nanoparticles. Chemosphere. Available at: https://doi.org/10.1016/j.chemosphere.2022.135672

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