Mechanistic and
Kinetic Consideration of the Photochemically
Generated Oxidative Organic Radicals in Dissolved Black Carbon Solutions
under Simulated Solar Irradiation
posted on 2023-12-27, 14:34authored byHongyu Jiang, Mengzhe Zhao, Wenjie Hong, Weihua Song, Shuwen Yan
The photochemically generated oxidative organic radicals
(POORs)
in dissolved black carbon (DBC) was investigated and compared with
that in dissolved organic matter (DOM). POORs generated in DBC solutions
exhibited higher one-electron reduction potential values (1.38–1.56
V) than those in DOM solutions (1.22–1.38 V). We found that
the photogeneration of POORs from DBC is enhanced with dissolved oxygen
(DO) increasing, while the inhibition of POORs is observed in reference
to DOM solution. The behavior of the one-electron reducing species
(DBC•–/DOM•–) was
employed to explain this phenomenon. The experimental results revealed
that the DO concentration had a greater effect on DBC•– than on DOM•–. Low DO levels led to a substantial
increase in the steady-state concentration of DBC•–, which quenched the POORs via back-electron reactions. Moreover,
the contribution of POORs to the degradation of 19 emerging organic
contaminants (EOCs) in sunlight-exposed DBC and DOM solutions was
estimated. The findings indicate that POORs play an important role
in the photodegradation of EOCs previously known to react with triplets,
especially in DBC solutions. Compared to DOM solutions, POOR exhibits
a lower but considerable contribution to EOC attenuation. This study
enhances the understanding of pollutant fate in aquatic environments
by highlighting the role of DBC in photochemical pollutant degradation
and providing insights into pollutant transformation mechanisms involving
POORs.