Abstract
Although the degradation of cyanotoxins by 254nm UV/H2O2 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/H2O2 using 265nm ultraviolet light-emitting diode (UV-LED). The results indicated that 265nm UV/H2O2 treatment had a high removal efficiency of MC-LR ([MC-LR]=0.1μM, apparent rate constants reached 0.2077min-1, half-time at 3.3min). The qualitative analyses demonstrated that three novel intermediates, C48H74N10O15 (molecular weight=1030.5335), C36H58N10O14 (854.4134), and C33H54N10O14 (814.3821), were generated in 265nm UV/H2O2. 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 0.00612kWhm-3order-1 for 100-5000μgL-1 MC-LR. Overall, 265nm UV-LED/H2O2 can be used as an alternative effective technology to improve the removal efficiency of MC-LR in water.
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