Oxidation and molecular properties of microcystin-LR, microcystin-RR and anatoxin-a using UV-light-emitting diodes at 255 nm in combination with H 2 O 2

Jeong Ann Park, Boram Yang, Mi Jang, Jae Hyun Kim, Song Bae Kim, Hee Deung Park, Hyun Mee Park, Sang Hyup Lee, Jae Woo Choi

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4 Citations (Scopus)

Abstract

On the use of UV light emitting diodes (UV-LEDs), emitting at 260–290 nm, has attracted attention for treating cyanotoxins, although most previous studies related with UV/H 2 O 2 process have been used conventional mercury UV lamp (λ = 254 nm). Therefore, the aim of the study was to investigate the UV-LEDs, having a wavelength of 255 nm, coupled with H 2 O 2 process for the removal of microcystin-LR (MC-LR), microcystin-RR (MC-RR), and anatoxin-a (ANTX) and to verify the degradation kinetics, mechanism and impact of water quality parameters in relation to their molecular properties. Among three UV-LEDs (λ = 255, 266, and 280 nm), the shortest one was the most effective to remove MC-LR coincided with its decadic molar absorption coefficient. The degradation rate constants of MC-LR, MC-RR, and ANTX were 0.0644, 0.0241, and 0.0076 cm 2 mJ −1 , respectively, during the UV-LED/H 2 O 2 process. For MC-LR and MC-RR degradation, reaction with [rad]OH is a major mechanism along with direct photolysis as a minor factor. ANTX degradation is predominantly attributed to [rad]OH. The second-order rate constant for ANTX is one order of magnitude lower than others because ANTX is recalcitrant to oxidation. The MC-LR degradation occurred at the diene and aromatic ring of Adda, Mdha, and amide bond and the main reactive oxidation site of MC-RR was the Adda chain. In contrast, photo-oxidation transformed ANTX to higher molecular weight compounds via polymerization instead of degradation. When MC-LR, MC-RR, and ANTX were co-present, lower concentration of dissolved organic carbon and higher acidity with bicarbonate was favorable to remove MC-LR and MC-RR according to their scavenging factors and reaction with CO [rad]− 3 . However, ANTX is relatively resistant to degradation at pH 3.2.

Original languageEnglish
Pages (from-to)423-432
Number of pages10
JournalChemical Engineering Journal
Volume366
DOIs
Publication statusPublished - 2019 Jun 15

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Keywords

  • Cyanotoxins
  • Hydrogen peroxides
  • Molecular property
  • Transformation products
  • UV-LED
  • Water quality parameters

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry
  • Chemical Engineering(all)
  • Industrial and Manufacturing Engineering

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