Oxidation and molecular properties of microcystin-LR, microcystin-RR and anatoxin-a using UV-light-emitting diodes at 255 nm in combination with H2O2

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

Research output: Contribution to journalArticlepeer-review

12 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/H2O2 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 H2O2 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 cm2 mJ−1, respectively, during the UV-LED/H2O2 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

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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