A review on nanoparticles for in situ remediation of soils and groundwater

by Virginia Greco

The unique properties of materials at the nanoscale offer opportunities for developing novel techniques to decontaminate polluted areas, which would reduce the impact of the process, while increasing its efficacy and penetrability. The state-of-the art and future perspectives of research in nano-remediation, balancing risks and benefits, is presented in a review recently published in “Science of Total Environment”.

Specifically engineered nanoparticles could provide solutions to some environmental challenges, such as remediation (i.e. decontamination) of polluted media –soils, surface and ground waters, sediments, air. Various studies have indeed proven that some nanoparticles are able to degrade, transform and/or immobilize contaminants; in addition, they can penetrate deeper and reach potentially inaccessible areas thanks to their reduced dimensions. New remediation techniques are being developed based on these unique properties of nanoparticles, nevertheless much research is still required, including the investigation of possible toxicities of the processes’ by-products.

A review recently published in the Elsevier’s journal Science of Total Environment and authored by Dr Lionel Marcon, from the Sorbonne University, CNRS and the Observatoire Océanologique de Banyuls sur Mer (France), and Jana Oliveras and group leader ICREA Prof. Víctor F. Puntes, from the ICN2 Inorganic Nanoparticles Group, discusses the use of tailored nanoparticles for in situ remediation, in particular of soil and groundwater, examining the progress made in research and application in this field since early 2000’s.

Various techniques exist that allow cleaning up areas contaminated by toxic substances –such as heavy metals, radionuclides, aliphatic hydrocarbons and halogenated organics– coming from industrial and pharmaceutical processes, agricultural practices and consumer products. Some of them, though, require excavation in the site and removal of the polluted medium, which is treated aboveground and put back in place. This procedure is not only very energy-consuming and costly, but also considerably disruptive of the natural environment. On the contrary, in situ techniques exploit biological, chemical or physical processes to remove pollutants, without the need for displacing the medium to be cleaned. This is where nanoparticles can play a determinant role, as explained in the highlighted paper.

The review provides, first of all, a general background about the main groups of target pollutants and the existing in situ techniques that are conventionally used. Then, different mechanisms through which nanoparticles can clean those pollutants in contaminated soils and ground waters are illustrated, as well as the properties of some of the materials that can be employed, such as iron (precisely, nanoscale zero-valent iron) and other nano-oxides. Current pilot- and field-scale applications are examined, considering advantages and limitations. Very important is also the study of the ecotoxicity of these nanoremediators, including their impact on microbiota (bacteria and fungi) and higher living organisms. Finally, perspectives and needs that will drive future research in this field are discussed.

Reference article:

Lionel Marcon, Jana Oliveras, Víctor F. Puntes, In situ nanoremediation of soils and groundwaters from the nanoparticle's standpoint: A review. Science of The Total Environment, vol. 791, 2021, 148324. DOI: 10.1016/j.scitotenv.2021.148324