Increasing the reaction time to a complete mineralization in the case of
2,4-dichlorophenol, regardless of its concentration in the initial solution, compared
to that of 4-chlorophenol (Fig.13.3), can be correlated with the difference between
the characteristics of the two organic compounds. As can be seen from Fig. 13.3, for
a complete mineralization of 4-chlorophenol of 100 mg O 2 /L equivalent concentration in the initial solution, approximately 250 minutes of irradiation is required,
while for the same equivalent concentration, approximately 300 minutes of irradiation is required for 2,4-dichlorophenol. At an equivalent concentration of 300 mg
O 2 /L, approximately 500 minutes of irradiation is necessary for 4-chlorophenol and
approximately 600 minutes of irradiation for 2,4-dichlorophenol.
It is known that for the chlorinated phenols, the oxidation efficiency is different as
a function of the number and the position on aromatic ring of the chlorine atoms. In
this respect, it is expected that the oxidation rate, and subsequently the degradation
efficiency, decreases with the increase of the number of chlorine atoms on the
aromatic ring. This decrease may be associated with the decrease in the number of
favorable positions in which the attack of the hydroxyl radicals could have occurred
most probably due to their occupation by the chlorine atoms.
Photocatalytic Degradation of Antibiotics
The sisal fiber used to prepare the new photocatalytic membrane TiO 2 /sisal fiber has
been tested to determine whether it has its own catalytic activity. The tests were
performed by using an ampicillin solution at a chemical oxygen demand equivalent
concentration of 300 mg O 2 /L. In this respect, the reactor was operated first by using
only ampicillin solution at pH 3 and at a H 2 O 2 /ampicillin molar ratio of 1.5, and
then, it was operated by using the same solution of ampicillin and the sisal fiber
material without any impregnation with TiO 2 . As can be seen from Fig. 13.4, there is
no clear distinction between the results obtained with and without sisal fiber. These
results indicate that the degradation degree of approximately 50% after 120 minutes
of reaction obtained for ampicillin in the two experiments was due solely to the
oxidizing action of the H 2 O 2 introduced into the reaction medium.
The photocatalytic activity of the TiO 2 /sisal fiber membrane was tested for the
same ampicillin solution, the results being presented in Fig. 13.5 comparative to
those obtained in the experiments in which sisal fiber was used without any
impregnation with TiO 2 . As can be seen in Fig. 13.5, there is a clear distinction
between the results obtained with TiO 2 /sisal fiber membrane and those obtained with
sisal fiber without any impregnation with TiO 2 . In this respect, after 120 minutes of
reaction, the degradation degree of ampicillin in the presence of TiO 2 /sisal fiber
membrane is 100%, whereas, for the same reaction time, the degradation degree of
ampicillin in the presence of only sisal fiber is 49%. These results confirm the
photocatalytic role of the TiO 2 deposited on the sisal fiber.
The new photocatalytic TiO 2 /sisal fiber membrane, whose photocatalytic activity
was demonstrated in the experiments presented above, was used for degradation of
different types of antibiotics, namely, ampicillin, erythromycin, and tetracycline, at
422
C. Orbeci et al.
2,4-dichlorophenol, regardless of its concentration in the initial solution, compared
to that of 4-chlorophenol (Fig.13.3), can be correlated with the difference between
the characteristics of the two organic compounds. As can be seen from Fig. 13.3, for
a complete mineralization of 4-chlorophenol of 100 mg O 2 /L equivalent concentration in the initial solution, approximately 250 minutes of irradiation is required,
while for the same equivalent concentration, approximately 300 minutes of irradiation is required for 2,4-dichlorophenol. At an equivalent concentration of 300 mg
O 2 /L, approximately 500 minutes of irradiation is necessary for 4-chlorophenol and
approximately 600 minutes of irradiation for 2,4-dichlorophenol.
It is known that for the chlorinated phenols, the oxidation efficiency is different as
a function of the number and the position on aromatic ring of the chlorine atoms. In
this respect, it is expected that the oxidation rate, and subsequently the degradation
efficiency, decreases with the increase of the number of chlorine atoms on the
aromatic ring. This decrease may be associated with the decrease in the number of
favorable positions in which the attack of the hydroxyl radicals could have occurred
most probably due to their occupation by the chlorine atoms.
Photocatalytic Degradation of Antibiotics
The sisal fiber used to prepare the new photocatalytic membrane TiO 2 /sisal fiber has
been tested to determine whether it has its own catalytic activity. The tests were
performed by using an ampicillin solution at a chemical oxygen demand equivalent
concentration of 300 mg O 2 /L. In this respect, the reactor was operated first by using
only ampicillin solution at pH 3 and at a H 2 O 2 /ampicillin molar ratio of 1.5, and
then, it was operated by using the same solution of ampicillin and the sisal fiber
material without any impregnation with TiO 2 . As can be seen from Fig. 13.4, there is
no clear distinction between the results obtained with and without sisal fiber. These
results indicate that the degradation degree of approximately 50% after 120 minutes
of reaction obtained for ampicillin in the two experiments was due solely to the
oxidizing action of the H 2 O 2 introduced into the reaction medium.
The photocatalytic activity of the TiO 2 /sisal fiber membrane was tested for the
same ampicillin solution, the results being presented in Fig. 13.5 comparative to
those obtained in the experiments in which sisal fiber was used without any
impregnation with TiO 2 . As can be seen in Fig. 13.5, there is a clear distinction
between the results obtained with TiO 2 /sisal fiber membrane and those obtained with
sisal fiber without any impregnation with TiO 2 . In this respect, after 120 minutes of
reaction, the degradation degree of ampicillin in the presence of TiO 2 /sisal fiber
membrane is 100%, whereas, for the same reaction time, the degradation degree of
ampicillin in the presence of only sisal fiber is 49%. These results confirm the
photocatalytic role of the TiO 2 deposited on the sisal fiber.
The new photocatalytic TiO 2 /sisal fiber membrane, whose photocatalytic activity
was demonstrated in the experiments presented above, was used for degradation of
different types of antibiotics, namely, ampicillin, erythromycin, and tetracycline, at
422
C. Orbeci et al.