Two research groups at the University of Copenhagen have designed a microwave-sustained plasma (an ionized gas) reactor that can decontaminate water containing high concentrations of dyes. Plasma is an ionized gas that contains electrons, ions, atoms, molecules, free radicals and photons. It is often called the fourth state of matter, and it permeates all things. Plasma, which is artificially created by transferring energy to a gas, is found in fluorescent tubes used in kitchen lighting and is also making mobile phones smaller.
Plasma is a veritable revolution in technology. In the past, to carve circuits on silicon boards used in electronic devices such as mobile phones, environmentally polluting chemical products had to be used. Now, using plasma can do the job cleaner and more precisely, making the gaps smaller and smaller, and with them, the devices.
But plasmas also have other applications, such as water treatment. The FQM-136 Plasma Physics Group and the FQM-346 Organocatalysis and Nanostructured Materials Group of the University of Córdoba collaborated on a study aimed at eliminating pollutants in water by applying plasma to promote chemical processes.
To address the growing problem of organic pollutants in water bodies, such as dyes and other compounds from agricultural and industrial activities that can destabilize ecosystems, these researchers turned to the application of plasma.
A breakthrough in water purification
In 2017, the research team demonstrated for the first time that when argon plasma induced by microwaves open to the air acts on water, it will produce active species containing oxygen and nitrogen (such as hydroxyl radicals, hydrogen peroxide, nitrogen radicals) in the water, which can eliminate water pollution. Now, researchers Juan Amaro Gaget, Francisco J. Romero Salguero and Maria C. Garcia have successfully designed a reactor for this plasma and greatly increased the amount of these active species produced in water, making it possible to destroy high concentrations of dyes (in this case, methylene blue) in just a few minutes.
This was achieved by changing the design of the surfatron, a metal device that mixes energy from a microwave generator with the plasma to sustain it. Professor Maria-Garcia explains: "What we do is put a small piece of silicon in a quartz discharge tube, which allows us to create a different plasma, which is not filamentous and is more efficient in generating active species when interacting with water. The above plasma composition can produce oxidative species when interacting with water, thereby degrading organic compounds and killing microorganisms, which makes this plasma reactor useful in applications related to water remediation."
This new configuration therefore expands the applicable range of this type of plasma. "This design completely changes the configuration of the surface accelerator that generates the electromagnetic field to create the plasma, giving the plasma different and more efficient properties while also eliminating the problem of filamentation (the separation of a plasma column into many filaments) that destabilizes the plasma," explains Professor Garcia.
The future of plasma decontamination
Professor Francisco J. Romero continued: "The oxides produced under the action of plasma are highly reactive and can destroy organic matter in the water. To do this, the plasma is not introduced into the water. On the contrary, the plasma acts remotely, so there is an air zone between the water and the plasma, in which many reactions occur due to collisions between excited species and oxygen, nitrogen and water vapor molecules and produce active species that diffuse into the liquid and eventually combine with pollutants."
Researcher Juan Amaro said: "The decontamination potential of the plasma generated by this novel design has been tested to reduce high concentrations of methylene blue dye in water, achieving very efficient results in terms of energy, achieving complete elimination of the dye while shortening the treatment time."
Plasma is a "fourth state of matter" created by supplying energy to a stable gas and converting it into an ionized gas, and it has applications in almost everything: making microchips, sterilizing surfaces, healing wounds, depositing anti-reflective coatings on glasses, improving seed germination rates, recycling waste, activating plastic surfaces to improve paint adhesion, and countless other applications.
Compiled source: ScitechDaily