This study reports on the propranolol (PRO) degradation performance and product toxicity of an ultraviolet light-emitting diode (UV-LED)/chlorine process. The effects of experimental parameters including solution pH, chlorine dosage, and water matrix constituents on PRO removal were evaluated. Up to 94.5% of PRO could be eliminated within 15 min at a PRO-to-chlorine molar ratio of 1:4. The overall removal efficiency of PRO was non-pH dependent in the range of 5–9, while the initial rate was accelerated under alkaline conditions. The presence of Cl − /HCO 3 − had little influence on the PRO degradation, whereas either humic acid or NO 3 − had an obvious inhibitory effect. Radical scavenger experiments showed that both HO and Cl primarily contributed to the PRO degradation, and electron paramagnetic resonance data demonstrated the generation of 1 O 2 . The transformation of PRO during this process led to five detected products, which exhibited a higher acute toxicity than the parent compound according to the bright luminescent bacillus T3 method. It is worth mentioning that under the same ultraviolet illumination intensity, the degradation of PRO under UV-LED/chlorine gave a better performance than UV 254 /chlorine, but the EEO of the former is obviously higher than the latter. So further research is required on improving the electric current to photon conversion efficiency for UV-LED. Additionally, the UV-LED/chlorine system was effective in the degradation of other drugs including sulfamethoxazole, oxytetracycline hydrochloride, and gatifloxacin, suggesting the possible application of the UV-LED/chlorine process for the removal of pharmaceuticals during wastewater treatment .
Development of efficient and stable photocatalysts is of essential for photocatalytic degradation of refractory organics in wastewaters. Herein, the novel S-scheme MoSe 2 /AgBr (MS/AB) heterojunctions were synthesized for antibiotics degradation. Various characterization results showed that the S-scheme MS/AB photocatalysts exhibited efficient carriers’ separation and strong redox potential. Tetracycline (TC) (20 mg/L) degradation efficiency of 81.4% was achieved using the 5MS/AB within 90 min at pH of 9, superior to those of the counterparts. Photogenerated carriers' transfer and photocatalytic reaction mechanism of the S-scheme MoSe 2 /AgBr heterojunction were deduced by DFT calculation, in-situ XPS and work function calculation. Moreover, possible degradation pathways of TC were proposed based on identified intermediates, and most of the intermediates showed lower toxicity than that of TC. The 5MS/AB photocatalyst also showed great stability and excellent antibacterial effect. This study advances the design of efficient photocatalysts and enriches related mechanisms.
This study developed a long-wave ultraviolet (UVA)/nitrite (NO 2 - ) system to degrade antibiotics in aquaculture wastewater, using NO 2 - as a treatment agent in line with the “waste-to-treat-waste” approach. It further advanced the understanding of reactive nitrogen species (RNSs)-mediated oxidation by quantifying radical dynamics, assessing transformation product ecotoxicity, and evaluating system performance under varying environmental conditions. The degradation of sulfamethoxazole (SMX), a model antibiotic, was primarily driven by RNSs, with nitric oxide radicals (NO•) emerging as the most impactful species. Steady-state analysis revealed that the RNSs concentration ([RNSs] SS = 1.79 × 10 −13 M) was significantly higher than that of hydroxyl radical (•OH) ([•OH] SS = 2.25 × 10 −14 M). Among RNSs, NO• was dominant ([NO•] SS = 1.51 × 10 −13 M), followed by nitrogen dioxide radicals (NO 2 •, [NO 2 •] SS = 2.76 × 10 −14 M) and peroxynitrite (ONOO⁻, [ONOO⁻] SS = 4.19 × 10 −18 M). RNSs contributed 55.97 % to SMX degradation, surpassing UVA (3.23 %) and •OH (40.80 %). Furthermore, ten transformation products were identified, showing relatively low toxicity and minimal ecological impact. Additionally, the UVA/NO 2 ⁻ system remained stable across varying temperatures and anion concentrations, making it promising for real-world wastewater treatment. This study establishes a quantified methodology for RNSs, providing critical insights into their kinetic behavior and role in antibiotic degradation.
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