Application of UV-C LED activated PMS for the degradation of anatoxin-a

Abstract

The present study explores the application of sulfate radical based advanced oxidation process for the degradation of anatoxin-a. Peroxymonosulfate (PMS) was used as the source of sulfate radicals. λ=260nm was found to be the most effective wavelength for the activation of PMS. At pH=6.4, initial conc. of anatoxin-a=1.5μM, λ=260nm, [PMS]/[anatoxin-a]=100:1 and temperature=ambient, the degradation of anatoxin-a was found to be 98.6%. Radical scavenging study revealed that sulfate radicals were the dominant oxidative radicals in the degradation of anatoxin-a. The presence of carbonate and bicarbonate ions in the solution mixture had negative effect on the degradation of anatoxin-a. At low concentrations (0.2 and 2mg/L), humic acid enhanced the degradation of anatoxin-a through photosensitization effect. However at higher concentration of humic acid, the degradation of anatoxin-a was hampered. UV/PMS/Cu2+ system was found to be more efficient in degradation of anatoxin-a in comparison to UV/PMS/Fe3+ system. With UV/PMS/Cu2+ system, the degradation of anatoxin-a reached more that 99% in 10min of irradiation time. Due to the presence of high concentration of transition metal ions and humic substance in lake water, the degradation of anatoxin-a was more in lake water in comparison to tap water. The results of this study suggests that UV-C/PMS advanced oxidation process is very efficient in the degradation of anatoxin-a, even in natural water bodies.