Advanced Non-equilibrium Cold Plasma Technologies for Water Purification

Ultraviolet (UV) light is highly effective in inactivating microorganisms and treating water contaminants [1]. Among UV spectral bands, UV-C (200–280 nm) is particularly effective due to its strong DNA absorption and potential for generating hydroxyl radicals (•OH) in advanced oxidation processes (AOPs). Industrial wastewater, especially from the textile and medical sectors, contains persistent azo dyes and organic micropollutants (OMPs), posing severe environmental risks. In recent developments, dielectric barrier discharge (DBD) plasma-based excilamps emitting far UV-C (KrCl*, 222 nm) and broad UV-C (XeI*, 253 nm) have been designed, developed and optimized for water treatment [2-4]. Electrical and optical characterizations ensured application-specific efficiency. These excilamps, applied via direct photolysis and AOPs (e.g., excilamp/TiO₂ and excilamp/H₂O₂), demonstrated enhanced degradation performance. A novel design, incorporating a photocatalyst-coated electrode in the XeI* excilamp showed 13 times faster degradation in XeI*-excimer/H₂O₂ than XeI*-excimer/TiO₂, attributed to an abundance of •OH generated by the modified XeI*-excimer/H₂O₂. A maximum energy yield of 5712 mg/kWh is obtained in the case of XeI*-excimer/H₂O₂. Compared with 254 nm, RB5 shows 1.26 times higher molar absorption at 222 nm. The obtained energy yield (6565 mg/kWh) for excimer-222/H₂O₂ demonstrates that the process is efficient in terms of energy consumption. Additionally, a non-thermal plasma (NTP) system was integrated with the KrCl* excilamp to eliminate chemical use and enhance OMP degradation. Plasma-generated NO₃⁻ and H₂O₂, activated by KrCl*, yielded a significantly higher •OH generation rate (46.7 × 10⁻⁸ M s⁻¹) than plasma plus Low Pressure UV (LPUV) lamp, due to better absorption at 222 nm. This plasma plus KrCl* system outperformed other methods in degrading various OMPs. These results highlight the potential of optimized excilamp and plasma-assisted UV-C systems for energy-efficient, chemical-free wastewater treatment. The efforts of these results will be presented.