Degradation of carbamazepine and sulfamethoxazole in water by dielectric barrier discharge plasma coupled with a far UV-C (222 nm) system†

Abstract

Organic micropollutants (OMPs) are now frequently found in wastewater and pose a risk to human and environmental health. This study utilizes an in-house developed plasma source and KrCl* excilamp (far UV-C at 222 nm), a conventional UV (LPUV at 254 nm) lamp and the combinations of plasma with LPUV/far UV-C for the degradation of sulfamethoxazole (SMX) and carbamazepine (CBZ). At first, the concentrations of plasma-produced long-lived (such as H₂O₂, NO₃⁻, NO₂⁻) and short-lived (such as ·HO) reactive species have been quantified. Accordingly, the role of plasma-produced reactive species in the degradation of CBZ and SMX under UV 222 has been reported. In the case of DIW/plasma + UV 222, the complete degradation of CBZ and SMX only takes 15 and 10 minutes, respectively. Furthermore, the degradation rate considerably accelerated in TW, and CBZ and SMX completely degraded in just 12 and 8 minutes, respectively. Moreover, the degradation rate of CBZ in DIW is found to be 25 times higher when using plasma + UV 222 compared to using plasma + LPUV and 114 times higher compared to LPUV alone. This is due to the abundance of ·OH (46.7 × 10⁻⁸ M s⁻¹) generated under UV 222 from plasma-produced reactive species. The required electrical energy per order for the OMP degradation from this hybrid process is relatively low (73.38 kW h m⁻³), which makes it an energy-efficient approach. This study provides a fresh perspective to broaden the application of plasma coupling with UV 222 for treating wastewater containing numerous OMPs.