Floating nanoparticles to remove contaminants from water

A team from the Madrid Institute of Materials Science (ICMM-CSIC), an entity dependent on the Ministry of Science, Innovation and Universities, has developed a method for decontaminating water based on the use of nanoparticles (the size of one billionth of a meter). This not only adsorbs contaminants but also allows for simple recovery of the nanoparticles used after the process, thus reducing costs.

"The presence of contaminants in aqueous media is a problem that today's society and industry must address," says Javier Pérez-Carvajal, a researcher at ICMM-CSIC and one of the creators of this new formula.

Currently, various methods are being used to decontaminate water using nanoparticles. In these processes, the removal or recovery of particles is key to preventing their release into the environment. However, their nanometric size makes it difficult for them to settle easily for recovery or to retain them using conventional processes. "The methods used involve recovery or filtration processes, the cost of which increases the smaller the contaminant," adds Pilar Aranda, also a researcher at ICMM-CSIC and creator of the method.

This team's solution involves the use of nano- and microcrystalline particles of an MOF network (an acronym for a type of material that combines organic molecules with metal atoms) with many pores just a few nanometers (one millionth of a millimeter) in size, which trap organic contaminants in the water. "These particles interact with each other and form micro-objects that tend to float on the surface of the water, making them easy to remove once they have fulfilled their function," explains Pérez-Carvajal.

Compared to this process, traditional methods employ physical properties to separate nanoparticles from water, such as centrifugation, which uses centrifugal force to accelerate their sedimentation, or ultrafiltration, in which water is pumped through membranes that trap nanoparticles larger than the pores of these membranes. However, their application requires an external source of energy.

"Traditionally, nanoparticles require a lot of energy to recover from the environment, so although they are very efficient at removing organic contaminants, their removal can be problematic or require the use of processes that are too costly," Aranda explains.

This new development is sustainable because "it reduces the cost of recovering adsorbent micro- and nanoparticles by eliminating the need for centrifugation systems or other common methods, and it also prevents the formation of sludge," the researcher adds. This technology has already been granted a priority European patent and is available for laboratory demonstration.

Furthermore, the floating membranes formed when nanoparticles coalesce can not only adsorb contaminants but can also have catalytic effects, acting, for example, to degrade some contaminating dyes. Pérez-Carvajal explains that this system is "fast and comparable to the ultrafiltration process, but with the advantage of not requiring an external energy input."