the degree of degradation depending on the type of antibiotic. Regarding the degree
of degradation depending on the type of antibiotic presented in Fig. 13.7, ampicillin
and tetracycline show after 120 minutes of reaction approximately the same degree
of degradation, but, for the same reaction time, the degree of degradation of
erythromycin is slightly lower. In this respect, after 120 minutes, the degree of
degradation for ampicillin is 98% for 300 mg O 2 /L and 96% for 900 mg O 2 /L, for
tetracycline is 95% for 300 mg O 2 /L and 96% for 900 mg O 2 /L, and for erythromycin is 90% for 300 mg O 2 /L and 86% for 900 mg O 2 /L.
The experimental results also revealed that the overall oxidation process follows
two successive stages. Thus, in the first stage, which is represented by the interval of
0–15 minutes of reaction, the oxidation of the antibiotics takes place with a high
reaction rate, being minimum in the case of erythromycin, for which an oxidation
degree of 60% for 300 mg O 2 /L and 50% for 900 mg O 2 /L was obtained. In the
second stage, which is represented by the interval of 15–120 minutes of reaction, the
reaction rate is much lower. This behavior can be attributed to organic intermediates
formed as a result of the oxidation, which are more resistant, especially in the final
phase of the oxidation process. In general, it can be concluded that the degree of
oxidation decreases in the following order: ampicillin>tetracycline> > erythromycin.
This behavior can be explained by the fact that the latter has a more complex
structure and a higher molecular mass as it was presented in Table 13.1. The
examination of the membrane after the tests indicates a small deterioration of the
sisal fiber substrate or the TiO 2 layer, the shape and general appearance remaining
largely the same as the original support.
13.5 Conclusions
The advanced oxidation processes can be applied to remove a large spectrum of
refractory compounds due to the high oxidation potential they have. The oxidation
potential can be considerably intensified by various combinations between oxidants
and catalysts. One of the promising emerging advanced oxidation process technologies that can be effectively used for industrial applications, including wastewater
treatment, is photocatalysis. Choosing the right photocatalyst as well as establishing
optimal working conditions can lead to the achievement of high degradation efficiencies of refractory organic contaminants from wastewater.
The experimental results obtained in this work on the photocatalytic degradation
of refractory compounds from the class of chlorophenols and antibiotics have
highlighted that the degradation rate of 4-chlorphenol is higher than that of
2,4-dichlorophenol. It is also revealed that, in the case of photocatalytic degradation
of the antibiotics, the degree of oxidation decreases in the following order: ampicillin
> tetracycline > > erythromycin. The rate of the photocatalytic oxidation process of
both 4-chlorphenol and 2,4-dichlorophenol is higher for the cobalt (Co)-doped TiO 2 /
polymer membrane than that of TiO 2 /Ti. The new obtained TiO 2 /sisal fiber
13 Photocatalytic Degradation of Chlorophenols and Antibiotics from Wastewater
425
of degradation depending on the type of antibiotic presented in Fig. 13.7, ampicillin
and tetracycline show after 120 minutes of reaction approximately the same degree
of degradation, but, for the same reaction time, the degree of degradation of
erythromycin is slightly lower. In this respect, after 120 minutes, the degree of
degradation for ampicillin is 98% for 300 mg O 2 /L and 96% for 900 mg O 2 /L, for
tetracycline is 95% for 300 mg O 2 /L and 96% for 900 mg O 2 /L, and for erythromycin is 90% for 300 mg O 2 /L and 86% for 900 mg O 2 /L.
The experimental results also revealed that the overall oxidation process follows
two successive stages. Thus, in the first stage, which is represented by the interval of
0–15 minutes of reaction, the oxidation of the antibiotics takes place with a high
reaction rate, being minimum in the case of erythromycin, for which an oxidation
degree of 60% for 300 mg O 2 /L and 50% for 900 mg O 2 /L was obtained. In the
second stage, which is represented by the interval of 15–120 minutes of reaction, the
reaction rate is much lower. This behavior can be attributed to organic intermediates
formed as a result of the oxidation, which are more resistant, especially in the final
phase of the oxidation process. In general, it can be concluded that the degree of
oxidation decreases in the following order: ampicillin>tetracycline> > erythromycin.
This behavior can be explained by the fact that the latter has a more complex
structure and a higher molecular mass as it was presented in Table 13.1. The
examination of the membrane after the tests indicates a small deterioration of the
sisal fiber substrate or the TiO 2 layer, the shape and general appearance remaining
largely the same as the original support.
13.5 Conclusions
The advanced oxidation processes can be applied to remove a large spectrum of
refractory compounds due to the high oxidation potential they have. The oxidation
potential can be considerably intensified by various combinations between oxidants
and catalysts. One of the promising emerging advanced oxidation process technologies that can be effectively used for industrial applications, including wastewater
treatment, is photocatalysis. Choosing the right photocatalyst as well as establishing
optimal working conditions can lead to the achievement of high degradation efficiencies of refractory organic contaminants from wastewater.
The experimental results obtained in this work on the photocatalytic degradation
of refractory compounds from the class of chlorophenols and antibiotics have
highlighted that the degradation rate of 4-chlorphenol is higher than that of
2,4-dichlorophenol. It is also revealed that, in the case of photocatalytic degradation
of the antibiotics, the degree of oxidation decreases in the following order: ampicillin
> tetracycline > > erythromycin. The rate of the photocatalytic oxidation process of
both 4-chlorphenol and 2,4-dichlorophenol is higher for the cobalt (Co)-doped TiO 2 /
polymer membrane than that of TiO 2 /Ti. The new obtained TiO 2 /sisal fiber
13 Photocatalytic Degradation of Chlorophenols and Antibiotics from Wastewater
425