Comparison of UV and UV-LED activated sodium percarbonate for the degradation of O-desmethylvenlafaxine

Removal of tetracycline by ultraviolet/sodium percarbonate (UV/SPC)advanced oxidation process in water

Tetracycline (TC) was widely used and frequently detected in various water bodies, where the presence of TC posed a significant threat to the health of aquatic organisms. Furthermore, antibiotics were hardly degraded by biological treatment. Thus, in order to enhance the removal of TC, we proposed the use of a novel ultraviolet/sodium percarbonate (UV/SPC) advanced oxidation process and initiated an in-depth study. The study investigated the influence of oxidant dosage, initial pH, UV intensity, and TC concentration on the removal of TC. The results demonstrated that the UV/SPC system efficiently removed TC, with removal efficiency increasing as the SPC concentration increased. Within the pH range of 3-11, TC degradation exhibited minimal variation, indicating the UV/SPC system's strong adaptability to pH variations. The research on the impact of the water matrix on TC removal revealed that HCO3- had an inhibitory effect on TC degradation, while NO3- promoted TC degradation. Additionally, the presence of free radical species (·OH, ·CO3-, ·O2-) were detected and rate constants for the secondary reactions (k·OH,TC = 6.3 × 109 L mol-1·s-1, k·CO3-,TC = 3.4 × 108 L mol-1·s-1) were calculated, indicating that ·OH exhibited a stronger oxidative performance compared to ·CO3-. This study did not only present a novel strategy via UV/SPC to remove TC but also uncovered the unique role of ·CO3- for contaminant removal.

Hydroxyl radical dominated ibuprofen degradation by UV/percarbonate process: Response surface methodology optimization, toxicity, and cost evaluation

Ibuprofen (IBP) is a typical nonsteroidal anti-inflammatory drug with a wide range of applications, large dosages, and environmental durability. Therefore, ultraviolet-activated sodium percarbonate (UV/SPC) technology was developed for IBP degradation. The results showed that IBP could be efficiently removed using UV/SPC. The IBP degradation was enhanced with prolonged UV irradiation time, with the decreasing IBP concentration and the increasing SPC dosage. The UV/SPC degradation of IBP was highly adaptable to pH ranging from 4.05 to 8.03. The degradation rate of IBP reached 100% within 30 min. The optimal experimental conditions for IBP degradation were further optimized using response surface methodology. IBP degradation rate reached 97.3% under the optimal experimental conditions: 5 μM of IBP, 40 μM of SPC, 7.60 pH, and UV irradiation for 20 min. Humic acid, fulvic acid, inorganic anions, and natural water matrix inhibited the IBP degradation to varying degrees. Scavenging experiments of reactive oxygen species indicated that hydroxyl radical played a major role in the UV/SPC degradation of IBP, while carbonate radical played a minor role. Six IBP degradation intermediates were detected, and hydroxylation and decarboxylation were proposed as the primary degradation pathways. An acute toxicity test, based on the inhibition of luminescence in Vibrio fischeri, indicated that the toxicity of IBP during UV/SPC degradation decreased by 11%. An electrical energy per order value of 3.57 kWh m^-3 indicated that the UV/SPC process was cost-effective in IBP decomposition. These results provide new insights into the degradation performance and mechanisms of the UV/SPC process, which can potentially be used for practical water treatment in the future.

Photodegradation of oxytetracycline by UV-assisted persulfate and percarbonate processes: kinetics, influencing factors, anion effect, and radical species

In this study, the performance of ultraviolet (UV)-assisted persulfate (PS) and percarbonate (PC) oxidation processes in oxytetracycline (OTC) removal was investigated. UVC lamps were used for the photolysis process and the effect of operating parameters (initial pH, oxidant dose, initial OTC concentration, UV intensity) on OTC removal efficiency was determined. Control experiments were carried out at pH 5.5 and 32 W UV power for 60 min by adding a 4 mM oxidant with 10 mg/L initial OTC concentration. The OTC removal efficiency obtained as a result of only photolysis was 17.3% and the removal efficiency obtained by PS and PC oxidation alone was 18.3% and 12.7%, respectively. The OTC removal efficiencies increased in the combined processes and reached 58.1% and 69.9% for the UV-PS and UV-PC processes, respectively. The reaction rates of the processes were ranked as UV-PC > UV-PS > PS > UV > PC. In the UV-PS and UV-PC processes, the highest removal efficiencies were achieved at alkaline pH values. The OTC removal efficiency was increased with the increase in oxidant dose; however, the efficiency decreased after a certain dose due to the scavenging effect. The removal efficiency also increased as the initial OTC concentration decreased. The UV intensity had a positive effect on OTC removal efficiency. The effect of the water matrix on OTC removal efficiency was investigated while the dominant radical types were determined in UV-assisted processes. The EE/O values for the UV-PS and UV-PC processes were calculated as 211 kWh/m³ and 153 kWh/m³, respectively for 60 min of reaction time. Although similar removal efficiencies were obtained with both UV-assisted processes, the UV-PC process steps forward in terms of being a novel, environmentally friendly, more economic, and promising technology for OTC removal.