Influence of humic substances on the riboflavin photosensitized transformation of 2,4,6-trimethylphenol

TiO2 Photocatalysis of the Organophosphorus Fenamiphos: Insight into the Degradation Mechanism

“…The presence of humic substances (HS) at very low concentration slightly (<0.5%) permitted an increase in the disappearance rate constant while at high concentration it was mainly detrimental for FN disappearance. Two important factors are more likely involved in the presence of HS (i) they may partially absorb the excitation light by producing reactive species and thus participate in the degradation process of FN through the formation of oxygen reactive species (ROS) [6,9] and (ii) they may also play the role of hydroxyl radical scavenger and thus reducing their stationary concentration during irradiation. These two factors are of course dominant at high concentrations of HS.…”

“…Within the former process, photochemical reactions such as dissociations, oxidation, and hydrolysis are observed and may lead to the generation of various byproducts that, in some cases, may be more harmful than the parent compound. In natural waters, indirect processes may be also observed via the excitation of substances such as Natural Organic Matters (NOM) [6][7][8]. The solar light excitation of these substances leads to the formation of several reactive species such as triplet excited states or/and reactive oxygen species (ROS).…”

“…The solar light excitation of these substances leads to the formation of several reactive species such as triplet excited states or/and reactive oxygen species (ROS). Among these latter species, singlet oxygen 1 O 2 , superoxide anion O 2 •− , and hydroxyl radical • OH represent the main reactive ones [6,9].…”

Photosensitizing and antioxidant activities of humic substances: A case study of β2-adrenoceptor agonist terbutaline

“…The mentioned antioxidant properties of HS have been documented in the case of compounds such as aniline and sulfonamide antibiotics [9][10][11]. They are linked to H-atom donor properties, and mainly attributed to HS phenolic and polyphenolic moieties [12,13,23].…”

“…They are generally proposed to abstract electrons or H atoms from micropollutants and lead to their oxidation. However, it has been also reported that the sensitizedphotodegradation of chemicals such as aniline and sulfonamide antibiotics can be inhibited by HS [9][10][11]. HS that contain phenolic/polyphenolic moieties in their complex structures [12,13] could act as antioxidants, regenerating the starting micro-pollutants (reaction 1).…”