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Enhancing photocatalytic degradation of the cyanotoxin microcystin-LR with the addition of sulfate-radical generating oxidants.

Antoniou, M.G.; Boraei, I.; Solakidou, M.; Deligiannakis, Y.; Abhishek, M.; Lawton, L.A.; Edwards, C.

Authors

M.G. Antoniou

I. Boraei

M. Solakidou

Y. Deligiannakis

M. Abhishek



Abstract

This study investigated the coupling of sulfate radical generating oxidants, (persulfate, PS and peroxymonosulfate, PMS) with TiO2 photocatalysis for the degradation of microcystin-LR (MC-LR). Treatment efficiency was evaluated by estimating the electrical energy per order (EEO). Oxidant addition at 10 mg/L reduced the energy requirements of the treatment by 60% and 12% for PMS and PS, respectively compared with conventional photocatalysis. Quenching studies indicated that both sulfate and hydroxyl radicals contributed towards the degradation of MC-LR for both oxidants, while Electron Paramagnetic Resonance (EPR) studies confirmed that the oxidants prolonged that lifetime of both radicals (concentration maxima shifted from 10 to 20min), allowing for bulk diffusion and enhancing cyanotoxin removal. Structural identification of transformation products (TPs) formed during all treatments, indicated that early stage degradation of MC-LR occurred mainly on the aromatic ring and conjugated carbon double bonds of the ADDA amino acid. In addition, simultaneous hydroxyl substitution of the aromatic ring and the conjugated double carbon bonds of ADDA (m/z= 1027.5) are reported for the first time. Oxidant addition also increased the rates of formation/degradation of TPs and affected the overall toxicity of the treated samples. The detoxification and degradation order of the treatments was UVA/TiO2/PMS > UVA/TiO2/PS>> UVA/TiO2.

Journal Article Type Article
Publication Date Oct 15, 2018
Journal Journal of hazardous materials
Print ISSN 0304-3894
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 360
Pages 461-470
Institution Citation ANTONIOU, M.G., BORAEI, I., SOLAKIDOU, M., DELIGIANNAKIS, Y., ABHISHEK, M., LAWTON, L.A. and EDWARDS, C. 2018. Enhancing photocatalytic degradation of the cyanotoxin microcystin-LR with the addition of sulfate-radical generating oxidants. Journal of hazardous materials [online], 360, pages 461-470. Available from: https://doi.org/10.1016/j.jhazmat.2018.07.111
DOI https://doi.org/10.1016/j.jhazmat.2018.07.111
Keywords Cyanotoxins; Intermediates; TiO2 photo catalysis; Peroxymonosulfate; Persulfate

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