Water activated by air discharges for applications in biodecontamination, agriculture and food processing
Machala Z., Tarabová B., Kučerová K., Sersenová D., Ndiiffo-Yemeli G. B., Žilková A., Henselová M., Tampieri F., Marotta E., Paradisi C., Hensel K.
11th International Symposium on Non-thermal Plasma Technology for Pollution Control and Sustainable Energy ISNTP-11, Montegrotto Terme (Italy), July 1-5, p. 32 (2018)
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Abstrakt: Non-thermal plasmas generated by electrical discharges in atmospheric pressure air are sources of various reactive species. When generated in contact with water, they enable the transfer of reactive oxygen and nitrogen species (RONS) formed in the gas-phase plasma into the water or aqueous solutions and so generate the plasma activated water (PAW). PAW is typically a strong antibacterial agent and besides multiple uses in medicine for disinfection it has the potential for food processing or agriculture applications.
We prepare PAW by a DC-driven streamer corona (SC) and transient spark (TS) discharges operated in air with water electrospray. The production of active species (e.g. O3, NO, NO2 and OH) in the gas and consequently the PAW properties can be controlled by the discharge regime and gas-flow and liquid-flow parameters. In low power air corona discharge, water electrospray increased O3 production, which enhanced the biocidal effects. In the higher power TS, dominant gaseous products are NOx that lead to significant NO2- and NO3- in the PAW and practically no O3. The bactericidal action is then mainly due to the synergy of H2O2, NO2- and acidic milieu (via ONOOH formation) and typically decays in time within several hours post plasma activation, depending on temperature and pH [1,2]. We use UV-VIS colorimetric and fluorescence methods for the analysis of RONS in the PAW.
PAW produced by TS air discharge has been tested for agriculture applications, such as enhanced plant growth (lettuce, radish, tomato, wheat) or seed germination rate. Testing various medical applications of PAW or plasma activated media in dentistry (periodontal biofilms, endodontics), wound disinfection, urinary tract infections, or cancer cells are under way.
In a similar concept, TS air discharge was successfully demonstrated to induce antimicrobial effects in fresh apple juice to extend its shelf lifetime up to 26 days without thermal pasteurization and without reducing its composition and nutrition/vitamin qualities.
This work was supported by Slovak Grant Agency VEGA 1/0419/18 and Slovak Research and Development Agency APVV-0134-12 and APVV-17-0382.
[1] P. Lukeš et al. : Plasma Sources Sci. Technol. 23, 015019 (2014).
[2] Z. Machala et al.: Plasma Process. Polym. 10, 649 (2013).
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