UV-C photon integrated surface dielectric barrier discharge hybrid reactor: A novel and energy-efficient route for rapid mineralisation of aqueous azo dyes

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

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 TiO2/H2O2. A new process is developed in which one electrode of excilamp is coated with TiO2 nanoparticles that improves the efficiency of the dye degradation. Additionally, the effects of varying TiO2 loading concentrations, XeI*-excimer light intensity, starting dye concentration, suspension pH, and H2O2 addition are examined. The outcomes of this study confirm 13 times faster degradation in XeI*-excimer/H2O2 than in XeI*-excimer/TiO2, attributed to an abundance of hydroxyl radicals generated by the modified XeI*-excimer/H2O2. Also, the degradation of RB5 in the modified XeI*-excimer/H2O2 is 2.3 times faster as compared to that of the bare electrode XeI*-excimer/H2O2. A more than 95% reduction in chemical oxygen demand has been achieved in 40 min in the case of XeI*-excimer/H2O2. 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.

A novel DBD/VUV/PMS process for efficient sulfadiazine degradation in wastewater: Singlet oxygen-dominated nonradical oxidation

In this study, a novel process of dielectric barrier discharge plasma/vacuum ultraviolet/peroxymonosulfate (DBD/VUV/PMS) for the nonradical-dominated degradation of sulfadiazine (SDZ) was investigated. The hybrid system has significant synergistic effects, with 95.5% SDZ and 68.3% TOC removal within 10 min. The activation efficiency of DBD/VUV (69.0%) on PMS via multipath was 2.07 times higher than that of single DBD (33.3%) under alkaline conditions. Electron paramagnetic resonance analyses and trapping experiments showed 1O2 was the primary active substance in the DBD/VUV/PMS process. The predominant role of 1O2 revealed that SDZ removal mainly followed the nonradical reaction pathway, contrary to the previously reported non-thermal plasma (NTP)-based radical-dominated process. Multiple spectroscopy analysis showed the efficient degradation process of SDZ. Unlike the radical attack sites, the SDZ transformation pathway by nonradical 1O2 was probably initiated by an aniline ring site attack based on density functional theory (DFT) calculations and product analyses. The DBD/VUV/PMS process reduced energy consumption by 69% compared to DBD. Finally, the evaluation of ecotoxicity and PMS utilization demonstrated the advantages and application prospects of the DBD/VUV/PMS process. This research developed a new nonradical-dominated pathway for antibiotic degradation by the photo/plasma/persulfate process.

Enhanced degradation of oxytetracycline in aqueous solution by DBD plasma-coupled vacuum ultraviolet/ultraviolet (VUV/UVC) system

A systematic investigation of coupling dielectric barrier discharge (DBD) plasma and different ultraviolet bands (UVA, UVB, UVC, and VUV) was constructed for antibiotic-contaminant wastewater treatment. Compared with DBD, UV, or other combined DBD/UV systems, the DBD/VUV/UVC system exhibited excellent degradation and mineralization efficiencies for oxytetracycline (OTC), achieving 93.2% removal rate (reaction rate constant 1.05 min^-1) and higher decarbonization efficiency (mineralization rate 0.47 mg C min^-1) within 2.5 min treatment. The radical quenching tests revealed that HO⋅, [Formula: see text] , and ¹O₂ were all involved in the decomposition of OTC in the DBD/VUV/UVC system, among which [Formula: see text] played a dominant role. Possible degradation pathways of OTC in the DBD/VUV/UVC process were proposed using density functional theory and detected intermediates. Four indexes were used to assess the toxicity of OTC and its degraded intermediates. The inorganic anions and HA slightly reduced the degradation efficiency of the DBD/VUV/UVC system. This research provides new ideas to broaden the application of plasma and alleviate the water environment crisis.