(Invited) the Removal of Bisphenols from Wastewaters with Atmospheric Pressure Plasma
Authors: Hojnik Nataša , Kovačič Ana , Modic Martina , Štampar Martina , Gulin Martin Rafael , Nannou Christina , Koronaiou Lelouda-Athanasia , Heath David , Walsh James Leon , Žegura Bojana , Lambropoulou Dimitra , Cvelbar Uros , Heath Ester 
Published: February 2024

Bisphenols represent one of the most recognised harmful contaminants found in environment as a result of their extensive use for the industrial production of polycarbonate, epoxy resins, and thermal paper. They are known for their ability to act as endocrine disruptors, as well as for their potential to cause genotoxicity and cytotoxicity. 1. Although the awareness of their toxicity is high and the use of some of their representatives already limited or restricted in EU 2, they still represent a potential threat for public health. Due to their insufficient elimination with standard water treatment methods, the effluent from the wastewater treatment plants continues to be the major source of bisphenol environmental contamination. Thus, it is necessary to develop a new more efficient method.

Cold atmospheric pressure plasma (CAP) is a promising technology with tremendous potential in removal of various hazardous contaminants from wastewater 3. Essentially, plasma is the fourth state of matter, created by introducing gas into a strong electrical field resulting in ionisation, dissociation, and excitation of gaseous molecules. CAP, which is produced by using air and electricity, is a source of high concentration of reactive oxygen and nitrogen species (RONS). This property makes it a highly promising, cost-effective, and environmentally-friendly method for decontamination 4.

To demonstrate its potential, we investigated the application of air CAP for the removal of bisphenol A (BPA) and bisphenol S (BPS) from aqueous systems. Plasma was generated with surface barrier discharge systems, using different exposure times and discharge operating powers, which led to the formation of different plasma chemistries. Additionally, radical scavenger methanol was used to simulate environmental conditions. The highest degradation efficacies were observed at longest exposure time (480 s) and at high discharge power and was significantly affected by the presence of methanol. Moreover, radical scavenger influenced the formation of CAP generated RONS in liquid as well, resulting in lower concentrations of ˙OH, H2O2, and NO2
-. With non-target approach, we were able to identify 11 BPA and 5 BPS transformation products (TPs) and propose transformation pathways of both compounds. The toxicological examination performed with in vitro HepG2 cell model demonstrated that the mixture of transformation products formed during CAP treatment is less toxic than BPA and BPS. According to these results it was suggested that CAP is an effective and safe method for degradation of bisphenols.

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