Sulfate radical anion: Laser flash photolysis study and application in water disinfection and decontamination
Ilaria Berruti, María Inmaculada Polo-López, I. Oller, Jenny Flores, M. Luisa Marín, Francisco Boscá
Abstract
Sulfate radicals (SO4•-) reactivity against gram-negative (E. coli) and gram-positive (E. faecalis) bacteria and Contaminants of Emerging Concern (CECs) (Diclofenac-DCF, Sulfamethoxazole-SMX and Trimethoprim-TMP) was investigated through laser flash photolysis (LFP) technique. Analysis of the lifetime of SO4•- in presence of cell-wall compounds of bacteria and CECs allowed determining reactivity of SO4•- towards these compounds. Results showed that SO4•- reacts with common cell-wall components through H-abstraction mechanism (kSO4•− < 108 M-1s-1). By contrast, kSO4•− > 109 M-1s-1 were found using aromatic amino acids (AAA) only present in Porins of the gram-negative outer-membrane. The intermediates detected from the reaction of SO4•- with the AAA confirmed the involvement of electron transfer processes. Moreover, kSO4•− values determined for DCF, TMP and SMX also agreed with an electron transfer mechanism. Interestingly, bacteria and CECs removal at pilot plant scale by UV-C/SO4•- is in accordance with the kSO4•− obtained using the LFP: E. coli > E. faecalis and DCF > TMP ≅ SMX.