Environmentally Friendly UV-C Excimer Light Source with Advanced Oxidation Process for Rapid Mineralization of Azo Dye in Wastewater

Abstract

Wastewater discharged from the textile industry contains approximately 15% unfixed dyes, predominantly 60−70% azo dyes. These unfixed dyes are a major environmental concern due to their persistence and potential toxicity. In this paper, an environmentally friendly mercury-free XeI* excilamp emitting 253 nm UV light is reported, and the same has been utilized for the degradation of azo dyes using the advanced oxidation process (AOP) with TiO 2 /H 2 O 2 . A new process is developed in which one electrode of excilamp is coated with TiO 2 nanoparticles that improves the efficiency of the dye degradation. Additionally, the effects of varying TiO 2 loading concentrations, XeI*-excimer light intensity, starting dye concentration, suspension pH, and H 2 O 2 addition are examined. The outcomes of this study confirm 13 times faster degradation in XeI*-excimer/H 2 O 2 than in XeI*excimer/TiO 2 , attributed to an abundance of hydroxyl radicals generated by the modified XeI*-excimer/H 2 O 2 . Also, the degradation of RB5 in the modified XeI*-excimer/H 2 O 2 is 2.3 times faster as compared to that of the bare electrode XeI*-excimer/H 2 O 2 . A more than 95% reduction in chemical oxygen demand has been achieved in 40 min in the case of XeI*-excimer/H 2 O 2 . In this study, a maximum energy yield of 5712 mg/kWh is reported. Furthermore, a high degree of degradation is found in the alkaline medium (pH 10). Because textile effluent is highly alkaline, this result is significant, and direct treatment of azo dyes is possible. The use of the developed source in industrial applications appears to be highly promising based on testing on a real wastewater matrix. The treated effluent has been utilized to study its reusability for agricultural purposes on the germination of radish seeds in soil, and ∼26% enhanced germination has been observed compared to dye wastewater.