Efficacy and mechanism of chemical-free VUV/UV process for oxytetracycline degradation: Continuous-flow experiment and CFD modeling

• Published in: Chemical engineering journal advances Vol. 4; p. 100059
• Main Authors: Yan, Hanlu, Luo, Minghan, Chen, Qiuwen, Jeong, Taeseop, Zhang, Jianyun, Wang, Li
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.12.2020; Elsevier
• Subjects: Computational fluid dynamics; Degradation; Oxytetracycline; Photoreactor; VUV/UV; Oxytetracycline; Degradation; Computational fluid dynamics; Photoreactor; VUV/UV
• ISSN: 2666-8211; 2666-8211
• DOI: 10.1016/j.ceja.2020.100059

•The photoreactor with tangential inlet and outlet showed improved hydraulic property.•The VUV process generated less OTC degradation byproducts than the H2O2/UV process.•The formed bidirectional spiral flows improved mixing efficiency of fluids.•Reducing internal diameter of photoreactor may increase OTC degradation efficiency. Eliminating tetracycline antibiotics from waste streams by conventional water treatment techniques remains challenging. Vacuum-ultraviolet/ultraviolet (VUV/UV)-based advanced oxidation technique is a promising, environment-friendly alternative to remove micropollutants from wastewater without adding chemicals. This study carried out flow-through experiments and numerical modeling to determine the efficiency and mechanism of VUV/UV process in degrading oxytetracycline (OTC) via a newly developed photoreactor with tangential inlet and outlet. OTC degradation pathway and reaction rate constant were identified through semi-batch experiments at various initial OTC concentrations in different water matrices. The decomposition of OTC by the VUV/UV process was as effective as that by the H2O2/UV approach but generated less byproducts and thus could be beneficial for process control. Removal of organic matter and inorganic ions were suggested before VUV/UV process to improve the treatment efficiency. Flow characteristics simulated by computational fluid dynamics (CFD) revealed that a special bidirectional spiral flow was formed in the new reactor, which improved the mixing efficiency of fluids and thus enhanced the contact between hydroxyl radicals and the contaminant. The distribution profiles of OTC and hydroxyl radicals confirmed that the target contaminant was decomposed following the flow direction, and the degradation efficiency could be further increased by decreasing the internal diameter of the photoreactor. The electrical energy-per-order analysis of the photoreactor proved the high-energy utilization efficiency and cost-effectiveness of the VUV/UV process.