Antibiotics are commonly found in environmental compartments like surface water and groundwater,
and are classified as emerging contaminants due to their persistence and contribution to antibiotic
resistance, a critical global health issue. In recent years, plasma discharge in liquids has attracted
significant attention, largely due to its broad potential in areas like chemical processing, biotechnology,
environmental solutions, and medical advancements [1-3]. Plasma-liquid interactions represent a novel
tool to efficiently activate and decontaminate water based on the unique reactivity of the plasma
medium. These interactions of plasma with liquid induce a cascade of physical and chemical effects.
Plasma-liquid interaction reactions produce a considerable amount of chemically active species that
form at the plasma-liquid interface. These species are then transferred from the interface into the bulk
liquid, where they can initiate desirable reactions in biological samples. Among the most important
species [4] identified within bulk liquids are OH, O, O3, NO, H, H2O2, NO2 -, O2 -, NO3 -, and OH-.
These compounds (also called Reactive Oxygen Nitrogen Species – RONS) have been proven to be
efficient in destruction of organic pollutants [5,6].
Over time, atmospheric pressure plasma sources such as dielectric barrier discharges (DBD) have been
studied as potential processes that can be used for wastewater treatment [5]. For example, Karoui et al.
[7] have used a combination of plasma and photocatalytic methods to treat Ciprofloxacin (CIP). They
showed that the concentration of Ciprofloxacin decreases by more than 45% after 70 minutes of
treatment with an initial concentration of Ciprofloxacin of 6 mg/L (voltage 18 kV; frequency 350 Hz
and air flow rate 240 L/h). In an interdisciplinary collaboration, scientists from Romania and France
(GREMI) [8] used the DBD plasma method to treat water mixed with two antibiotic compounds,
amoxicillin (AMX), and sulfamethoxazole (SMX). They showed that by using the non-thermal plasma
method, the antibiotics are completely removed within 40 minutes with an applied voltage of 13-
15 kV at frequencies of 1000 Hz and 600 Hz.
While plasma treatment has proven its effectiveness in removing a wide range of contaminants, there
are still many challenges. For instance, pollutants are not always completely removed, the processes
are energy- and time-consuming, and the treatment capacities and contaminant concentrations
addressed remain quite limited. There is also a lack of suitable configurations for easy scale-up.
Moreover, understanding the mechanisms involved in plasma-liquid interactions remains a major focus of ongoing research, requiring more comprehensive investigation. Specifically, the formation
and interaction of reactive species in the plasma media, and their transport across the plasma-liquid
boundary, are critical areas that needs deepened investigations.
References:
[1] F. Rezaei et al., Materials 12:17 (2019) 2751
[2] Y. Yong et al., Plasma discharge in liquid: water treatment and applications. CRC press (2017)
[3] Metelmann et al., Comprehensive clinical plasma medicine: cold physical plasma for medical
application. Springer (2018)
[4] P. J. Bruggeman et al., Plasma Sources Sci. Technol. 25 (2016) 053002
[5] Y. He et al., Water 14 (2022) 1351
[6] R. A. Priatama et al., Int. J. Mol. Sci. 23 (2022) 4609
[7] S. Karoui et al., Journal of Water Process Engineering 50 (2022) 103207
[8] B. Florin, et al., Plasma Processes and Polymers 20 (2023) 2300020.