while triclosan concentrations rapidly decreased in 44.2% in the photocatalytic
process during the same time. The 2,4-dichlorophenol photocatalysis indicated
34.6% degradation after 1 h. The intermediates identified in that study were
2,8-dichlorodibenzo-p-dioxin, quinone, and the hydroquinone structure of triclosan.
In addition to analytical instruments for intermediate product determination after
photocatalysis, toxicity evaluations can also be used as a powerful tool. Organisms
display either positive or negative responses when in contact with different compounds during photodegradation. In this way, Stamatis et al. (2014) identified
intermediate products and performed toxicity assays using Vibrio fischeri. Six
intermediate compounds were identified, mainly hydroxyl-triclosan derivatives via
single or multiple HO
• radical electrophilic attacks. The luminescent marine bacteria
showed low toxicity at an initial concentration (6% inhibition), while at 5-min
irradiation, toxicity increased inhibition in 20%, due the simultaneous generation
of photocatalysis transformation products. After this period, toxicity quickly
decreased (5% at 10 min of reaction) and reached nontoxicity in 30 min.
In order to enhance degradation, the Fenton-like process can be applied as a
heterogeneous photocatalysis. In this context, Song et al. (2012) investigated triclosan oxidation using magnetic BiFeOzone nanoparticles as a catalyst at pH 6.0. It
demonstrated that the hydrogen peroxide-BiFeOzone system removed 82.7% of
triclosan within 180 min, whereas the addition of ethylenediamine tetracetic acid
not only accelerated triclosan degradation (96.1% at 30 min) but also significantly
promoted the degradation of the toxic 2,4-dichlorophenol transformation products.
This fact is due to formation of the large cave at the BiFe-Ozone surface by
ethylenediamine tetracetic acid absorbed. Consequently, the local hydrogen peroxide concentrations are improved with
●
OH radical generation. Klamerth et al. (2009)
compared the degradation of nine different pharmaceuticals and personal care
products through two different approaches as mild solar Photo-Fenton and TiO 2
photocatalysis at solar compound parabolic collector pilot plant. The Photo-Fenton
process was more effective than TiO 2 regarding several pharmaceuticals and personal care products employed (i.e., triclosan, acetaminophen, caffeine, diclofenac,
progesterone, sulfamethoxazole).
Furthermore, a major challenge regarding photocatalysis when using the catalyst
in slurry form is that this process requires a further treatment step to remove the
catalyst from aqueous solution. In this sense, Miranda-García et al. (2011) explored
heterogeneous photocatalysis employing immobilized-TiO 2 on glass spheres
(Fig. 10.2) for 15 micropollutants removal, including triclosan, in a solar compound
parabolic collector pilot plant (10 L). The authors investigated different water
matrices, and the stability and activity on catalyst were evaluated after five times
with the same immobilized photocatalyst. The results indicate that diclofenac,
ibuprofen, progesterone, triclosan, acetaminophen, and caffeine were degraded in
the first cycle in the first 60 min reaction time, while the fifth degradation cycle of the
compounds was slower.
Ding et al. (2013) wrote the only research article about photocatalysis involving
triclocarban, applying photodegradation under two different artificial irradiation
sources such as ultraviolet and xenon light source, varying pH, initial triclocarban
314
E. M. Saggioro
process during the same time. The 2,4-dichlorophenol photocatalysis indicated
34.6% degradation after 1 h. The intermediates identified in that study were
2,8-dichlorodibenzo-p-dioxin, quinone, and the hydroquinone structure of triclosan.
In addition to analytical instruments for intermediate product determination after
photocatalysis, toxicity evaluations can also be used as a powerful tool. Organisms
display either positive or negative responses when in contact with different compounds during photodegradation. In this way, Stamatis et al. (2014) identified
intermediate products and performed toxicity assays using Vibrio fischeri. Six
intermediate compounds were identified, mainly hydroxyl-triclosan derivatives via
single or multiple HO
• radical electrophilic attacks. The luminescent marine bacteria
showed low toxicity at an initial concentration (6% inhibition), while at 5-min
irradiation, toxicity increased inhibition in 20%, due the simultaneous generation
of photocatalysis transformation products. After this period, toxicity quickly
decreased (5% at 10 min of reaction) and reached nontoxicity in 30 min.
In order to enhance degradation, the Fenton-like process can be applied as a
heterogeneous photocatalysis. In this context, Song et al. (2012) investigated triclosan oxidation using magnetic BiFeOzone nanoparticles as a catalyst at pH 6.0. It
demonstrated that the hydrogen peroxide-BiFeOzone system removed 82.7% of
triclosan within 180 min, whereas the addition of ethylenediamine tetracetic acid
not only accelerated triclosan degradation (96.1% at 30 min) but also significantly
promoted the degradation of the toxic 2,4-dichlorophenol transformation products.
This fact is due to formation of the large cave at the BiFe-Ozone surface by
ethylenediamine tetracetic acid absorbed. Consequently, the local hydrogen peroxide concentrations are improved with
●
OH radical generation. Klamerth et al. (2009)
compared the degradation of nine different pharmaceuticals and personal care
products through two different approaches as mild solar Photo-Fenton and TiO 2
photocatalysis at solar compound parabolic collector pilot plant. The Photo-Fenton
process was more effective than TiO 2 regarding several pharmaceuticals and personal care products employed (i.e., triclosan, acetaminophen, caffeine, diclofenac,
progesterone, sulfamethoxazole).
Furthermore, a major challenge regarding photocatalysis when using the catalyst
in slurry form is that this process requires a further treatment step to remove the
catalyst from aqueous solution. In this sense, Miranda-García et al. (2011) explored
heterogeneous photocatalysis employing immobilized-TiO 2 on glass spheres
(Fig. 10.2) for 15 micropollutants removal, including triclosan, in a solar compound
parabolic collector pilot plant (10 L). The authors investigated different water
matrices, and the stability and activity on catalyst were evaluated after five times
with the same immobilized photocatalyst. The results indicate that diclofenac,
ibuprofen, progesterone, triclosan, acetaminophen, and caffeine were degraded in
the first cycle in the first 60 min reaction time, while the fifth degradation cycle of the
compounds was slower.
Ding et al. (2013) wrote the only research article about photocatalysis involving
triclocarban, applying photodegradation under two different artificial irradiation
sources such as ultraviolet and xenon light source, varying pH, initial triclocarban
314
E. M. Saggioro