Effectiveness and intermediates of microcystin-LR degradation by UV/H2O2 via 265 nm ultraviolet light-emitting diodes

• Published in: Environmental science and pollution research international Vol. 24; no. 5; pp. 4676 - 4684
• Main Authors: Liu, Juan, Ye, Jin-shao, Ou, Hua-se, Lin, Jialing
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.02.2017; Springer Nature B.V
• Subjects: Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Bonding strength; Chemical bonds; Degradation; Earth and Environmental Science; Ecotoxicology; Efficiency; Environment; Environmental Chemistry; Environmental Health; Environmental science; Hydrogen peroxide; Hydroxyl radicals; Intermediates; Light emitting diodes; Microcystin-LR; Mineralization; Molecular weight; Organic light emitting diodes; Oxidation; Qualitative analysis; Rate constants; Research Article; Toxicity; Ultraviolet radiation; Waste Water Technology; Water Management; Water Pollution Control; Wavelengths; Drinking water treatment; Organic matter; Toxicology; Photocatalysis; Hydroxyl radical; Cyanotoxin
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-016-8148-1

Although the degradation of cyanotoxins by 254 nm UV/H 2 O 2 has been well elucidated, the efficiency and mechanism involved are not necessarily true for other UV wavelengths. The degradation of microcystin-LR (MC-LR), a representative cyanotoxin, was explored by UV/H 2 O 2 using 265 nm ultraviolet light-emitting diode (UV-LED). The results indicated that 265 nm UV/H 2 O 2 treatment had a high removal efficiency of MC-LR ([MC-LR] = 0.1 μM, apparent rate constants reached 0.2077 min −1 , half-time at 3.3 min). The qualitative analyses demonstrated that three novel intermediates, C 48 H 74 N 10 O 15 (molecular weight = 1030.5335), C 36 H 58 N 10 O 14 (854.4134), and C 33 H 54 N 10 O 14 (814.3821), were generated in 265 nm UV/H 2 O 2 . Five published intermediates were also confirmed. The generative pathway of these products mainly involved free hydroxyl radical oxidation, resulting in consecutive hydroxyl substitutions and hydroxyl additions of unsaturated bonds in MC-LR. The toxicity of MC-LR was weaken with a relative low mineralization. The electrical energy per order values were calculated to be in the range of 0.00447 to 0.00612 kWh m −3  order −1 for 100–5000 μg L −1 MC-LR. Overall, 265 nm UV-LED/H 2 O 2 can be used as an alternative effective technology to improve the removal efficiency of MC-LR in water.