Plasma, often referred to as the fourth state of matter, is an ionized gas containing a mix of electrons, ions, atoms, molecules, radicals, and photons. Its ubiquitous presence extends from the fluorescent tubes illuminating kitchens to the technological miniaturization seen in mobile phones.
In the realm of technology, plasma has sparked a revolution. Previously, the engraving of circuits on silicon plates for electronic devices involved the use of environmentally harmful chemical products. The advent of plasma technology has ushered in a cleaner and more precise method, enabling the fabrication of smaller and more sophisticated devices.
Beyond its impact on electronics, plasma finds diverse applications, including water treatment. Collaborative research by the FQM-136 Physics of Plasmas and FQM-346 Organic Catalysis and Nanostructured Materials groups at the University of Córdoba delves into the potential of plasma for eliminating contaminants in water through chemical processes.
Their findings, detailed in the journal Chemosphere, address the escalating issue of organic pollutants in water, emanating from sources like dyes and compounds associated with agricultural and industrial activities. The researchers harnessed the power of plasma to combat this challenge.
In 2017, they demonstrated the ability of argon plasmas, induced by microwaves and open to the air, to generate reactive species containing oxygen and nitrogen when applied to water. These species, including hydroxyl radicals and nitrogen radicals, proved effective in decontaminating water.
Now, researchers Juan Amaro Gahete, Francisco J. Romero Salguero, and María C. García have elevated this approach. They designed a plasma reactor and significantly increased the production of active species in water, enabling the rapid destruction of high concentrations of dyes, such as methylene blue, in just minutes.
Their innovation involved modifying the surfatron, a metal device that blends microwave energy with plasma. By placing a small piece of silicon in the quartz discharge tube, the researchers created a different, more efficient plasma that interacts effectively with water.
Professor María C. García explained, “What we've done is to place a small piece of silicon in the quartz discharge tube, allowing a different plasma to be generated, one that is not filamentary and is more efficient at creating active species when interacting with water.”
The resulting plasma, when interacting with water, generates oxidizing species capable of degrading organic compounds and eliminating microorganisms. This breakthrough extends the potential applications of plasma reactors to water remediation.
The altered design of the electromagnetic field generated by the surfatron not only enhances the efficiency of the plasma but also eliminates the problem of filamentation, stabilizing the process. Professor Francisco J. Romero emphasized, “Those oxidizing species generated due to the action of plasma are very reactive and make it possible to destroy the organic matter inside the water.”
Crucially, the plasma is not directly introduced into the water; instead, it acts remotely. In the zone of air between the water and the plasma, numerous reactions occur due to collisions between excited species and oxygen, nitrogen, and water vapor molecules. This results in the generation of reactive species that diffuse into the liquid, effectively eliminating contaminants and showcasing the potential of plasma technology in advancing water purification methods.
Source: University of Córdoba