Photo-plasma: A new approach for efficient and enhanced mineralization of organic molecules*

Water contamination from complex organic molecules has become a significant cause of worry due to conventional treatment systems' poor response to their removal. Therefore, developing an improved and environmentally friendly treatment system is critical to achieving water quality objectives and protecting human health. The present work develops a novel and chemical-free treatment system by coupling surface dielectric barrier discharge (SDBD) with high energetic UV-C source. The improved ability of the hybrid reactor (photo-SDBD) to degrade and mineralize complex organic molecules is demonstrated by taking brilliant red 5B (C₁₂H₁₈N₃Na₃O₁₄S) as the model pollutant. The influence of pollutant feed concentration, solution pH, and background salts on brilliant red 5B degradation is studied. The photo-SDBD reactor showed unprecedented improvement in mineralizing brilliant red 5B compared to SDBD and UV-C.

Notably, Glauber's salts and solution pH did not influence the photo-SDBD performance. The data reveals that the new system could overcome the quenching of hydroxyl radicals due to background salts and recombination of hydroxyl radicals (•OH) and their conversion to hydrogen peroxide (H₂O₂). The analysis of reactive chemical species confirms a five-fold increase in the generation of hydroxyl radicals in photo-SDBD compared to SDBD. The system also showed a 2 to 10 times reduction in degradation time than SDBD or UV-C. This is attributed to breakdown of H₂O₂ in the presence of UV-C to •OH and possibly increased contact of reactive chemical species with the target contaminant. We believe that the present study would open pathways for developing a more efficient and green advanced treatment system to remove complex and recalcitrant organic molecules.